AVIRON
S-1, 1996-06-05
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<PAGE>
   
      AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 5, 1996
    
 
                                                      REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
                                     AVIRON
             (Exact name of registrant as specified in its charter)
 
<TABLE>
<S>                        <C>                                            <C>
       CALIFORNIA                              2836                            77-0306986
     (State or other               (Primary Standard Industrial             (I.R.S. Employer
     jurisdiction of                Classification Code Number)           Identification No.)
    incorporation or
      organization)
</TABLE>
 
                            ------------------------
                           297 NORTH BERNARDO AVENUE
                        MOUNTAIN VIEW, CALIFORNIA 94043
                                 (415) 919-6500
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)
                            ------------------------
                             J. LEIGHTON READ, M.D.
                      CHAIRMAN AND CHIEF EXECUTIVE OFFICER
                                     AVIRON
                           297 NORTH BERNARDO AVENUE
                        MOUNTAIN VIEW, CALIFORNIA 94043
                                 (415) 919-6500
           (Name, address and telephone number of agent for service)
                            ------------------------
                                   COPIES TO:
 
<TABLE>
<S>                                              <C>
            ALAN C. MENDELSON, ESQ.                           ALAN K. AUSTIN, ESQ.
            ROBERT J. BRIGHAM, ESQ.                         ELIZABETH R. FLINT, ESQ.
    Cooley Godward Castro Huddleson & Tatum                  ELIZABETH M. KURR, ESQ.
             Five Palo Alto Square                     Wilson, Sonsini, Goodrich & Rosati
              3000 El Camino Real                              650 Page Mill Road
          Palo Alto, California 94306                      Palo Alto, California 94304
</TABLE>
 
                            ------------------------
                APPROXIMATE DATE OF PROPOSED SALE TO THE PUBLIC:
AS SOON AS PRACTICABLE AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.
                            ------------------------
 
    If  any of the Securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to  Rule 415 under the Securities Act  of
1933, check the following box.  / /
 
    If  this Form  is filed  to register  additional securities  for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list  the  Securities  Act  registration statement  number  of  the  earlier
effective registration statement for the same offering.  / /
 
    If  this Form  is a post-effective  amendment filed pursuant  to Rule 462(c)
under the Securities Act,  check the following box  and list the Securities  Act
registration  statement number  of the earlier  effective registration statement
for the same offering.  / /
 
    If delivery of the Prospectus is expected  to be made pursuant to Rule  434,
please check the following box.  / /
 
                        CALCULATION OF REGISTRATION FEE
 
   
<TABLE>
<CAPTION>
                                                                        PROPOSED MAXIMUM    PROPOSED MAXIMUM
                                                      AMOUNT TO BE     OFFERING PRICE PER  AGGREGATE OFFERING      AMOUNT OF
      TITLE OF SECURITIES TO BE REGISTERED           REGISTERED (1)        SHARE (2)           PRICE (2)        REGISTRATION FEE
<S>                                                <C>                 <C>                 <C>                 <C>
Common Stock, $0.001 par value...................      3,450,000             $13.00           $44,850,000           $15,466
</TABLE>
    
 
(1)  Includes  450,000 shares  of  Common Stock  issuable  upon exercise  of the
    Underwriters' over-allotment option.
 
(2)  Estimated  solely  for  the  purpose  of  calculating  the  amount  of  the
    registration  fee in  accordance with Rule  457 under the  Securities Act of
    1933.
                            ------------------------
    THE REGISTRANT HEREBY  AMENDS THIS  REGISTRATION STATEMENT ON  SUCH DATE  OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE  A  FURTHER  AMENDMENT  THAT  SPECIFICALLY  STATES  THAT  THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE  IN ACCORDANCE WITH SECTION 8(a)  OF
THE  SECURITIES ACT  OF 1933  OR UNTIL  THE REGISTRATION  STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION  8(a),
MAY DETERMINE.
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
                                     AVIRON
 
                             CROSS-REFERENCE SHEET
 
                   PURSUANT TO ITEM 501(b) OF REGULATION S-K
                 SHOWING LOCATION IN PROSPECTUS OF INFORMATION
                         REQUIRED BY ITEMS OF FORM S-1
 
<TABLE>
<CAPTION>
                   ITEM NUMBER AND HEADING
             IN FORM S-1 REGISTRATION STATEMENT                                 LOCATION IN PROSPECTUS
- -------------------------------------------------------------  --------------------------------------------------------
<C>        <S>                                                 <C>
       1.  Forepart of the Registration Statement and Outside
            Front Cover Page of Prospectus...................  Outside Front Cover Page
       2.  Inside Front and Outside Back Cover Pages of
            Prospectus.......................................  Inside Front and Outside Back Cover Pages
       3.  Summary Information; Risk Factors; and Ratio of
            Earnings to Fixed Charges........................  Inside Front Cover Page; Prospectus Summary; Risk
                                                                Factors
       4.  Use of Proceeds...................................  Use of Proceeds
       5.  Determination of Offering Price...................  Outside Front Cover Page; Underwriting
       6.  Dilution..........................................  Dilution
       7.  Selling Security Holders..........................  Not Applicable
       8.  Plan of Distribution..............................  Outside Front Cover Page; Underwriting
       9.  Description of Securities to be Registered........  Prospectus Summary; Capitalization; Description of
                                                                Capital Stock
      10.  Interests of Named Experts and Counsel............  Legal Matters; Experts
      11.  Information with Respect to the Registrant........  Outside Front and Inside Front Cover Pages; Prospectus
                                                                Summary; Risk Factors; Dividend Policy; Capitalization;
                                                                Selected Financial Data; Management's Discussion and
                                                                Analysis of Financial Condition and Results of
                                                                Operations; Business; Management; Certain Transactions;
                                                                Principal Stockholders; Description of Capital Stock;
                                                                Shares Eligible for Future Sale; Financial Statements
      12.  Disclosure of Commission Position on
            Indemnification for Securities Act
            Liabilities......................................  Not Applicable
</TABLE>
<PAGE>
INFORMATION   CONTAINED  HEREIN  IS  SUBJECT   TO  COMPLETION  OR  AMENDMENT.  A
REGISTRATION STATEMENT  RELATING TO  THESE SECURITIES  HAS BEEN  FILED WITH  THE
SECURITIES  AND EXCHANGE  COMMISSION. THESE SECURITIES  MAY NOT BE  SOLD NOR MAY
OFFERS TO BUY BE ACCEPTED PRIOR  TO THE TIME THE REGISTRATION STATEMENT  BECOMES
EFFECTIVE.  THIS  PROSPECTUS  SHALL  NOT  CONSTITUTE AN  OFFER  TO  SELL  OR THE
SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE  SECURITIES
IN  ANY STATE IN WHICH SUCH OFFER,  SOLICITATION OR SALE WOULD BE UNLAWFUL PRIOR
TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE.
<PAGE>
   
                   SUBJECT TO COMPLETION, DATED JUNE 5, 1996
    
 
   
                                     [LOGO]
    
                                3,000,000 SHARES
                                  COMMON STOCK
    All of the 3,000,000 shares of Common Stock offered hereby are being  issued
and  sold by Aviron  (the "Company"). Prior  to this offering  there has been no
public market for  the Common Stock  of the Company.  It is currently  estimated
that  the initial  public offering  price of  the Common  Stock will  be between
$11.00 and $13.00 per share. See "Underwriting" for a discussion of the  factors
considered in determining the initial public offering price.
 
   
    Concurrent with this offering, the Company intends to sell 333,333 shares of
its Common Stock to Sang-A Pharm. Co., Ltd. ("Sang-A") in a private placement at
the  initial public  offering price  (the "Sang-A  Shares"), with  the number of
shares to be sold to Sang-A subject to adjustment under certain conditions.  See
"Business -- Collaborative Agreements" and "Underwriting."
    
 
                                ----------------
 
        THE COMMON STOCK OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
                    SEE "RISK FACTORS" BEGINNING ON PAGE 7.
                                ---------------
   
 THESE  SECURITIES  HAVE NOT  BEEN APPROVED  OR  DISAPPROVED BY  THE SECURITIES
    AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS  THE
     COMMISSION  OR  ANY  STATE  SECURITIES  COMMISSION  PASSED  UPON THE
       ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY  REPRESENTATION TO
                      THE CONTRARY IS A CRIMINAL OFFENSE.
    
 
<TABLE>
<CAPTION>
                                                                            UNDERWRITING
                                                          PRICE TO         DISCOUNTS AND        PROCEEDS TO
                                                           PUBLIC           COMMISSIONS         COMPANY (1)
<S>                                                  <C>                 <C>                 <C>
Per Share..........................................          $                   $                   $
Total (2)..........................................          $                   $                   $
</TABLE>
 
(1) Before deducting expenses payable by the Company estimated at $600,000.
 
   
(2) The Company has granted the Underwriters  a 30-day option to purchase up  to
    an   additional   450,000  shares   of   Common  Stock,   solely   to  cover
    over-allotments, if any. See "Underwriting." If such option is exercised  in
    full,  the total Price to Public, Underwriting Discounts and Commissions and
    Proceeds to Company will be $      , $      and $      , respectively.
    
 
                                ----------------
 
   
    The Common Stock is offered by the Underwriters as stated herein, subject to
receipt and acceptance by them and subject to their right to reject any order in
whole or in part and certain other  conditions. It is expected that delivery  of
such  shares will be made  through the offices of  Robertson, Stephens & Company
LLC ("Robertson, Stephens  & Company"),  San Francisco, California  on or  about
         , 1996.
    
 
ROBERTSON, STEPHENS & COMPANY
 
                            BEAR, STEARNS & CO. INC.
 
                                                               HAMBRECHT & QUIST
 
                The date of this Prospectus is            , 1996
<PAGE>
   
          AVIRON USES BOTH ITS RATIONAL VACCINE DESIGN TECHNOLOGY AND
                  CLASSICAL METHODS OF LIVE VACCINE DISCOVERY
    
 
   
                       RATIONAL VACCINE DESIGN TECHNOLOGY
    
 
   
                  [Virus particle containing genetic
                  information; three segments are highlighted
                  to correspond with methods of modifying the
                  virus' genetic information.]
    
 
   
  DELETE VIRULENCE                                  ADD GENETIC INFORMATION
  PROTEINS                                          Insert genes to enhance
  Remove genes for viral components                 the virus'
  thought to be important in disease                stimulation of the
  mechanism                                         immune system
 
  [Virus particle containing genetic                [Virus particle
  information; one segment of genetic               containing genetic
  information being removed.]                       information; one
                                                    segment of genetic
                                                    information being
                                                    added.]
 
    
   
                                 DOWN-REGULATE
                                  REPLICATION
                         Alter genetic information used
                  by the virus in controlling its replication
    
 
   
                  ["Tree" structure comprised of 15 dots
                  symbolizing virus replication; second
                  structure comprised of 3 dots symbolizing
                  virus' reduced ability to replicate.]
    
 
   
                               VACCINE CANDIDATES
    
 
   
SPECIES SELECTION          FOREIGN CELL               ADAPTION TO PHYSICAL
Strains originate from     PASSAGE                    CONDITIONS
non-human species          Human virus mutates as it  Human virus mutates as it
                           is propagated in cells     is propagated in cells
                           from non-human species     under unusual conditions,
                                                      e.g., cold temperature
 
[Graphic of a chicken and  [Graphic of cells (3)      [Petri dishes (2), each
a cow.]                    sequentially connected by  with a corresponding
                           arrows.]                   graphic representation of
                                                      a thermometer. One
                                                      thermometer shows a higher
                                                      temperature than the
                                                      other.]
 
    
 
   
                               CLASSICAL METHODS
    
 
                                ----------------
 
    IN  CONNECTION WITH THIS OFFERING, THE UNDERWRITERS MAY OVER-ALLOT OR EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE COMMON STOCK OF
THE COMPANY AT  A LEVEL ABOVE  THAT WHICH  MIGHT OTHERWISE PREVAIL  IN THE  OPEN
MARKET.  SUCH TRANSACTIONS MAY  BE EFFECTED ON THE  NASDAQ NATIONAL MARKET. SUCH
STABILIZING, IF COMMENCED, MAY BE DISCONTINUED AT ANY TIME.
 
                                ----------------
 
    "Aviron" is a  trademark of  the Company.  Certain other  trademarks of  the
Company and other companies are used in this Prospectus.
<PAGE>
   
                         AVIRON'S PROPOSED NASAL SPRAY
                             VACCINE FOR INFLUENZA
    
 
   
                                 Genes from             Genes from cold
                            naturally-occurring          adapted master
                            influenza viruses as     influenza virus strain
                             selected by public
                             health authorities
 
[Silhouette of human      [Virus particle with box  [Virus particle with box
head with lines coming    around 2 of 8 segments    around 6 of 8 segments
from nasal area leading   of genetic information.   of genetic information.]
to virus particle to the  ------------------------
right.]                   Dashed lines connecting
                          to second virus particle
                          with box around 6 of 8
                          segments.]
 
                                                    [Virus particle
                                                    containing 8 segments of
                                                    genetic information; six
                                                    segments of the same
                                                    color, two segments of
                                                    different colors.]
 
    
 
   
                           AVIRON'S INFLUENZA VACCINE
                              COMBINES GENES FROM
                          NATURALLY OCCURRING VIRUSES
                            WITH GENES FROM THE COLD
                             ADAPTED MASTER STRAIN
    
 
   
             [Photograph of a human hand holding a device
             which is used to administer a vaccine in an
             aerosol spray (to the upper respitory
             tract-not shown). A spray effect is shown
             which serves as the backdrop for an image of
             a virus particle to the upper right.]
    
 
   
               THE POTENTIAL IMPACT OF INFLUENZA IN THE COMMUNITY
    
 
   
 [Photo of five young      [Photo of one child from   [Photo of woman from
 children playing with     previous picture in bed    previous picture now in
 blocks in a pre-school    at home with mother at     an office setting with 5
 setting. Lines            bedside. Child is ill,     other adults. Lines
 symbolically show how a   and is shown with          symbolically show how the
 virus spreads from one    thermometer in mouth,      virus might spread to
 child to the next.]       mother touching forehead,  others in the room.]
                           tissues and medication
                           bottle by bedside. Mother
                           is on the telephone.
                           Lines symbolically show
                           virus spreading from
                           child to mother.]
 
AGE GROUP:                               Children 1-18
ESTIMATED INFLUENZA ATTACK RATE:         37 per 100
BURDEN OF ILLNESS:                       illness, doctor visits, middle ear
                                         infections, school absenteeism,
                                         parents' lost work
ESTIMATED UNITED STATES POPULATION:      69 million
AVIRON PRODUCT STATUS:                   Phase I/II studies conducted
 
    
<PAGE>
   
THE  COMPANY'S COLD ADAPTED  NASAL SPRAY VACCINE  IS AN INVESTIGATIONAL BIOLOGIC
AND HAS  NOT  BEEN APPROVED  FOR  SALE IN  ANY  COUNTRY. THE  COMPANY  DOES  NOT
ANTICIPATE  APPLYING FOR REGULATORY APPROVAL TO MARKET THIS PROPOSED VACCINE FOR
SEVERAL YEARS, IF EVER, AND WILL  BE REQUIRED TO SUCCESSFULLY COMPLETE  CLINICAL
TRIALS  TO DEMONSTRATE  ITS SAFETY AND  EFFICACY PRIOR TO  FILING FOR REGULATORY
APPROVAL. SEE "RISK FACTORS."
    
 
   
                       IMMUNE RESPONSE TO INFLUENZA VACCINES
 
     [Silhouette of human head and torso   [Silhouette of human head and torso
     within which is visible the           within which is visible the
     circulatory system (red). The figure  circulatory system (red) and the
     is receiving an injection in the      upper respiratory tract (blue). The
     upper arm by syringe. The injected    figure is receiving an aerosol spray
     vaccine forms a small pool of liquid  directed into the nasal passages and
     at the site of injection.]            upper respiratory tract by nasal
                                           spray administration.]
 
     INJECTABLE INACTIVATED                NASAL SPRAY
     VACCINE                               VACCINE
 
     - Strongly stimulates                 - Stimulates mucosal
       circulating antibodies                immunity in
                                             respiratory tract
 
                                           - Stimulates cell-mediated
                                             immunity
 
                                           - Stimulates circulating
                                             antibodies
 
     [Photo of man from previous picture   [The elderly woman from the previous
     (presumably infected with the virus)  picture is shown ill in bed in a
     visiting with his elderly mother in   hospital setting. Some medical
     her home. He is kneeling beside a     equipment is visible to the left; a
     chair in which she is sitting and he  healthcare worker or nurse is at her
     is presenting her with a gift. A      bedside. She appears awake and
     line symbolically shows the virus     alert.]
     being passed between them.]
 
    
 
   
     Adults 19-65                         Elderly over 65
     10-22 per 100                        10 per 100
     illness, doctor visits, lost         illness, doctor visits,
     work                                 hospitalization, death
     159 million                          32 million
     Phase II studies conducted           Clinical trials planned for
                                          co-administration with
                                          injectable inactivated vaccine
    
<PAGE>
   
    No  dealer,  salesperson or  other person  has been  authorized to  give any
information or to make  any representations other than  those contained in  this
Prospectus  and, if given or made, such information and representations must not
be relied upon  as having been  authorized by the  Company or the  Underwriters.
This  Prospectus does not constitute an offer to sell, or the solicitation of an
offer to buy, any  securities other than the  registered securities to which  it
relates  or an offer to,  or solicitation of, any  person in any jurisdiction in
which such offer or solicitation would be  unlawful or to any person to whom  it
is  unlawful. Neither the delivery of this Prospectus nor any offer or sale made
hereunder shall, under any circumstances, create any implication that there  has
been  no change in the affairs of the  Company since the date hereof or that the
information contained herein is  correct as of any  time subsequent to the  date
hereof.
    
 
   
    Until               , 1996 (25 days after  the date of this Prospectus), all
dealers effecting transactions in the Common Stock, whether or not participating
in the distribution,  may be  required to  deliver a  Prospectus. This  delivery
requirement  is in addition to the obligation of dealers to deliver a Prospectus
when acting  as Underwriters  and with  respect to  their unsold  allotments  or
subscriptions.
    
 
                              -------------------
 
                               TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
Prospectus Summary........................................................     4
Risk Factors..............................................................     7
Use Of Proceeds...........................................................    18
Dividend Policy...........................................................    18
Capitalization............................................................    19
Dilution..................................................................    20
Selected Financial Data...................................................    21
Management's Discussion and Analysis of Financial Condition and Results of
 Operations...............................................................    22
Business..................................................................    26
Management................................................................    51
Certain Transactions......................................................    58
Principal Stockholders....................................................    60
Description Of Capital Stock..............................................    63
Shares Eligible For Future Sale...........................................    66
Underwriting..............................................................    68
Legal Matters.............................................................    69
Experts...................................................................    69
Additional Information....................................................    69
</TABLE>
    
 
                                       3
<PAGE>
                                    SUMMARY
 
   
    THIS  PROSPECTUS CONTAINS FORWARD-LOOKING STATEMENTS WHICH INVOLVE RISKS AND
UNCERTAINTIES. THE COMPANY'S ACTUAL RESULTS  COULD DIFFER MATERIALLY FROM  THOSE
ANTICIPATED  IN THESE FORWARD-LOOKING STATEMENTS AS A RESULT OF CERTAIN FACTORS,
INCLUDING THOSE SET FORTH UNDER "RISK FACTORS" AND ELSEWHERE IN THIS PROSPECTUS.
    
 
    THE FOLLOWING SUMMARY  IS QUALIFIED IN  ITS ENTIRETY AND  SHOULD BE READ  IN
CONJUNCTION WITH THE MORE DETAILED INFORMATION, INCLUDING "RISK FACTORS" AND THE
FINANCIAL STATEMENTS AND NOTES THERETO, APPEARING ELSEWHERE IN THIS PROSPECTUS.
 
                                  THE COMPANY
 
   
    Aviron  is  a  biopharmaceutical  company  whose  strategy  is  to  focus on
prevention of  disease.  The  Company's  goal  is to  become  a  leader  in  the
discovery,  development, manufacture and marketing  of live virus vaccines which
are sufficiently cost effective  to justify their  use in immunization  programs
targeting  the  general  population.  Live virus  vaccines,  such  as  those for
smallpox, polio, measles, mumps and rubella,  have had a long record of  success
in  preventing, and in some cases eliminating, disease. The Company currently is
analyzing data from Phase I and Phase II clinical trials in children and  adults
of  its  live cold  adapted intranasal  vaccine for  influenza. The  Company has
recently in-licensed a live  intranasal vaccine for  Parainfluenza Virus Type  3
("PIV-3")  which has been  tested by others  in Phase I/II  clinical trials. The
Company also is developing a subunit vaccine for Epstein-Barr Virus ("EBV").  In
addition,  Aviron is using its  proprietary "Rational Vaccine Design" technology
to discover  new  live virus  vaccines.  Rational Vaccine  Design  involves  the
deletion  or modification of  virulence proteins, changes  to the virus' genetic
control signals to  slow down  its replication,  or addition  of information  to
enhance  the virus'  stimulation of the  immune system. The  Company is applying
this technology to develop candidates for the prevention of influenza in elderly
persons  and  diseases  caused   by  Cytomegalovirus  ("CMV"),  Herpes   Simplex
Virus-Type 2 ("HSV-2") and Respiratory Syncytial Virus ("RSV").
    
 
   
    Aviron's  age-specific influenza programs  address three distinct population
groups: children, adults  and the elderly.  Influenza affects 20  to 50  million
Americans each year resulting in approximately 20,000 deaths annually, primarily
in  the elderly, despite  the availability of  an injectable inactivated vaccine
that has been reported to  be 60% to 80% effective.  The United States Food  and
Drug Administration (the "FDA") estimates that approximately 75 million doses of
influenza  vaccine  were manufactured  for  use in  the  United States  in 1995.
Experts suggest  that,  although  over  half  of  Americans  at  high  risk  for
complications  from influenza  receive the annual  influenza vaccine, relatively
few of the 70 million children under the age of 18 are vaccinated.
    
 
   
    To address the need for  more convenient influenza prophylaxis, the  Company
has  in-licensed  the  rights  to  a cold  adapted  influenza  vaccine  from the
University of  Michigan and  the National  Institute of  Allergy and  Infectious
Disease  ("NIAID"), a division of the National Institutes of Health (the "NIH").
Formulations of this vaccine were tested in over 7,000 persons prior to Aviron's
acquisition of  the vaccine,  and  subsequently have  been studied  in  clinical
trials conducted by the Company involving over 700 children and adults. The cold
adapted  influenza vaccine  elicits an  immune response  similar to  that of the
natural  infection  by  stimulating  mucosal  immunity  in  the  nose,  cellular
components  of the immune  system and circulating  antibodies. Aviron intends to
develop the cold adapted influenza vaccine for widespread annual use in children
and adults, and for co-administration with the inactivated vaccine for  improved
protection  in  the elderly.  In addition,  Aviron  is developing  a genetically
engineered influenza vaccine that is intended to be a better immune stimulus  in
the  elderly than  either the  cold adapted  vaccine or  the inactivated vaccine
alone, and therefore  more suitable  for use as  a single-dose  vaccine in  this
population.
    
 
   
    Aviron  also is  conducting research  and development  on additional vaccine
targets, including:
    
 
   
        PARAINFLUENZA VIRUS TYPE  3.   PIV-3 is  a common  respiratory virus  of
    childhood  which  causes  croup, cough,  fever  and pneumonia.  Over  80% of
    children have been  infected by  age four, many  having experienced  several
    cases of PIV-3 infection. The Company has in-licensed the rights to a bovine
    PIV-3  ("bPIV-3") vaccine  from the  NIH which has  been tested  in over 100
    infants and adults. Aviron intends to develop the bPIV-3 vaccine for use  in
    preventing childhood PIV-3 illness.
    
 
                                       4
<PAGE>
   
        EPSTEIN-BARR  VIRUS.   EBV infects  most people  at some  point in their
    lifetime. Half or more of the approximately 10% of students who first become
    infected with  the  virus in  high  school and  college  develop  infectious
    mononucleosis.  EBV also has been  shown to be a  contributing factor in the
    development of  certain  types  of  cancer  and  lymphoma.  The  Company  is
    conducting  preclinical  evaluation of  a subunit  EBV vaccine  candidate in
    conjunction with SmithKline Beecham Biologicals S.A. ("SmithKline Beecham").
    
 
   
        CYTOMEGALOVIRUS.  Most people also become infected with CMV at some time
    in their lives,  but the  resulting disease  is typically  serious only  for
    those  with impaired immune systems  or for babies of  women infected in the
    first trimester of pregnancy. The  Company is developing and evaluating  its
    engineered vaccine candidates in preclinical models to create a prophylactic
    vaccine.
    
 
   
        HERPES  SIMPLEX VIRUS-TYPE  2.  Genital  herpes is  an incurable disease
    characterized by recurrent, often painful  genital sores, with over  700,000
    new cases estimated in the United States each year. The Company currently is
    developing and evaluating vaccine candidates in preclinical models to create
    a prophylactic vaccine.
    
 
        RESPIRATORY   SYNCYTIAL  VIRUS.    RSV  is  the  major  cause  of  lower
    respiratory tract illness  in the  very young, responsible  for over  90,000
    hospitalizations  and more than 4,000 deaths  per year in the United States.
    Aviron is using its proprietary  technology to create candidate vaccines  to
    prevent RSV disease.
 
   
    Aviron  intends  to enter  into  selected collaborative  agreements  to gain
access to complementary technologies, capabilities and financial support for its
programs. In addition  to acquiring  rights from  third parties  to augment  its
Rational  Vaccine  Design  technology  and the  cold  adapted  influenza vaccine
technology,  the  Company  has  entered  into  a  collaborative  agreement  with
SmithKline  Beecham  covering  worldwide  rights  to  its  EBV  vaccine,  and  a
collaboration with Sang-A involving  certain marketing and manufacturing  rights
to its products in Korea.
    
 
   
    The  Company was  incorporated in California  in April 1992,  and intends to
reincorporate in  Delaware in  June 1996.  The Company's  executive offices  are
located  at 297 North Bernardo Avenue,  Mountain View, California 94043, and its
telephone number is (415) 919-6500.
    
 
                                       5
<PAGE>
                                  THE OFFERING
 
   
<TABLE>
<S>                                   <C>
Common Stock Offered by the           3,000,000 shares
 Company............................
Common Stock Outstanding After the    12,285,990 shares (1)
 Offering...........................
Use of Proceeds.....................  For research  and  development,  including
                                      preclinical  testing and  clinical trials;
                                      capital expenditures; and working  capital
                                      and  general corporate  purposes. See "Use
                                      of Proceeds."
Proposed Nasdaq National Market       AVIR
 Symbol.............................
</TABLE>
    
 
                             SUMMARY FINANCIAL DATA
                     (in thousands, except per share data)
 
   
<TABLE>
<CAPTION>
                                           FOR THE PERIOD FROM                                            THREE MONTHS ENDED
                                             APRIL 15, 1992            YEAR ENDED DECEMBER 31,                MARCH 31,
                                             (INCEPTION) TO      ------------------------------------  ------------------------
                                            DECEMBER 31, 1992       1993         1994         1995        1995         1996
                                          ---------------------  -----------  -----------  ----------  -----------  -----------
<S>                                       <C>                    <C>          <C>          <C>         <C>          <C>
STATEMENT OF OPERATIONS DATA:
Total revenues..........................        $      --          $      --    $      --   $   1,707    $ --         $     188
Operating expenses:
  Research and development..............              320              2,073        4,216      10,220        3,088        3,044
  General and administrative............              470              1,874        2,493       3,252          701        1,063
                                                    -----        -----------  -----------  ----------  -----------  -----------
    Total operating expenses............              790              3,947        6,709      13,472        3,789        4,107
                                                    -----        -----------  -----------  ----------  -----------  -----------
Loss from operations....................             (790)            (3,947)      (6,709)    (11,765)      (3,789)      (3,919)
Interest income, net of interest
 expense................................               37                175          207         362           32          183
                                                    -----        -----------  -----------  ----------  -----------  -----------
Net loss................................        $    (753)         $  (3,772)   $  (6,502)  $ (11,403)   $  (3,757)   $  (3,736)
                                                    -----        -----------  -----------  ----------  -----------  -----------
                                                    -----        -----------  -----------  ----------  -----------  -----------
Pro forma net loss per share (2)........                           $   (0.56)   $   (0.73)  $   (1.24)   $   (0.41)   $   (0.41)
                                                                 -----------  -----------  ----------  -----------  -----------
                                                                 -----------  -----------  ----------  -----------  -----------
Shares used in computing pro forma net
 loss per share (2).....................                               6,696        8,948       9,183        9,062        9,223
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                                                                           MARCH 31, 1996
                                                                                      -------------------------
                                                                                       ACTUAL    AS ADJUSTED(3)
                                                                                      ---------  --------------
<S>                                                                                   <C>        <C>
BALANCE SHEET DATA:
Cash, cash equivalents and short-term investments...................................  $  14,494    $   51,374
Working capital.....................................................................     12,804        49,684
Total assets........................................................................     17,275        54,155
Accumulated deficit.................................................................    (26,192)      (26,192)
Total stockholders' equity..........................................................     14,167        51,047
</TABLE>
    
 
- ------------------------
   
(1) Includes the estimated  333,333 shares intended  to be sold  to Sang-A in  a
    private placement concurrent with this offering. Excludes (i) 643,480 shares
    of  Common Stock issuable upon exercise of options outstanding as of June 1,
    1996, at a weighted average exercise price of approximately $1.22 per share,
    (ii) an  aggregate  of  1,556,520  shares  reserved  for  future  grants  or
    purchases  pursuant to  the Company's  1996 Equity  Incentive Plan, Employee
    Stock Purchase  Plan  and Non-Employee  Director  Stock Option  Plan,  (iii)
    118,395  shares issuable upon exercise of warrants outstanding as of June 1,
    1996 at  a weighted  average exercise  price of  $6.65 per  share, and  (iv)
    warrants  to purchase 29,750 shares which become exercisable at the close of
    the offering at 125% of the initial public offering price.
    
 
(2) See Note 1 of Notes to Financial Statements for an explanation of the method
    used to determine the number of shares  used to compute pro forma per  share
    amounts.
 
   
(3)  As adjusted to give effect to the  sale of 3,000,000 shares of Common Stock
    at an assumed  initial public  offering price of  $12.00 per  share and  the
    estimated  333,333  shares  intended  to  be sold  to  Sang-A  in  a private
    placement concurrent  with this  offering  and the  application of  the  net
    proceeds therefrom. See "Use of Proceeds" and "Capitalization."
    
 
   
    UNLESS  OTHERWISE INDICATED, ALL  INFORMATION IN THIS  PROSPECTUS REFLECTS A
ONE-FOR-FIVE REVERSE SPLIT OF  THE COMPANY'S COMMON STOCK  EFFECTED IN MAY  1996
AND  ASSUMES  (I)  REINCORPORATION  OF  THE COMPANY  IN  DELAWARE  PRIOR  TO THE
OFFERING, (II) THE CONVERSION OF ALL  OUTSTANDING SHARES OF ITS PREFERRED  STOCK
INTO  SHARES OF COMMON STOCK UPON THE CLOSING  OF THIS OFFERING AT A RATE OF ONE
SHARE OF COMMON STOCK FOR FIVE SHARES OF PREFERRED STOCK, AND (III) NO  EXERCISE
OF THE UNDERWRITERS' OVER-ALLOTMENT OPTION.
    
 
                                       6
<PAGE>
                                  RISK FACTORS
 
   
    This  Prospectus contains forward-looking statements which involve risks and
uncertainties. The Company's actual results  could differ materially from  those
anticipated  in these forward-looking statements as a result of certain factors,
including those set forth  in the following risk  factors and elsewhere in  this
Prospectus.
    
 
   
    The  following risk factors should be considered carefully in evaluating the
Company and its business  before purchasing shares of  the Common Stock  offered
hereby.
    
 
UNCERTAINTIES RELATED TO CLINICAL TRIALS
 
   
    Before  obtaining required regulatory  approvals for the  commercial sale of
any of  its products  under development,  the Company  must demonstrate  through
preclinical  testing and clinical trials that each product is safe and effective
for use in  each target  indication. The  results from  preclinical testing  and
early  clinical  trials  may not  be  predictive  of results  obtained  in later
clinical trials  and  large-scale  testing.  Companies  in  the  pharmaceutical,
biopharmaceutical   and  biotechnology  industries   have  suffered  significant
setbacks in various stages of clinical trials, even in advanced clinical  trials
after  promising  results had  been obtained  in  earlier trials.  The Company's
vaccines are  intended  for use  primarily  in healthy  individuals.  To  obtain
regulatory approval, the Company must demonstrate safety and efficacy in healthy
people which likely will require a lengthier process and involve a larger number
of  trials  and  patients  than  would  be  customary  for  clinical  trials  of
therapeutics for  disease  management.  There  can  be  no  assurance  that  the
Company's  clinical trials  will demonstrate  sufficient safety  and efficacy to
obtain the requisite regulatory approvals or will result in marketable products.
The Company recently completed  a Phase II challenge  study of its cold  adapted
influenza  vaccine in  adults. Preliminary analysis  of the  results indicated a
very low  level of  illness in  both the  placebo and  treated groups,  and  the
Company  believes that this study is  unlikely to show statistically significant
efficacy in preventing influenza. Regardless of  the results of this study,  the
Company  intends to discuss with the FDA  its plans to proceed directly to Phase
III clinical trials  in adults and  does not intend  to conduct other  challenge
studies. If the Company's cold adapted influenza vaccine is not shown to be safe
and  effective in Aviron's  clinical trials, the  resulting delays in developing
this and other vaccine candidates and conducting related preclinical testing and
clinical trials, as  well as  the need for  additional financing,  would have  a
material  adverse  effect on  the  Company's business,  financial  condition and
results of operations.
    
 
   
    The Company's cold adapted influenza vaccine is based on technology licensed
from  the  NIH  and  the  University  of  Michigan.  Wyeth-Ayerst   Laboratories
("Wyeth-Ayerst"),  a division  of American  Home Products  Corporation, licensed
certain rights  to  the vaccine  in  1989 and  was  developing it  for  sale  in
collaboration  with the NIH until relinquishing its rights in 1993. In addition,
Kaketsuken, a  Japanese  research foundation  ("Kaketsuken"),  licensed  certain
rights  to the  vaccine in 1993  and was developing  it for sale  in Japan until
relinquishing such rights  in 1996. Formulations  of the vaccine  have been  the
subject  of a number of clinical trials  performed by Wyeth-Ayerst, the NIAID of
the NIH and Kaketsuken. The Company has reviewed the data from these trials  and
believes  that it can submit such data in partial support of its application for
regulatory approval  from the  FDA. The  Company did  not participate  in  these
trials and cannot be confident in the accuracy of the data collected. Although a
large  proportion of this data was positive, a number of trials included results
that were not.  Very few of  the trials involved  a trivalent vaccine  delivered
through  nasal spray. The Company will need  to perform additional trials of its
vaccine candidate  to  support its  application  to the  FDA.  There can  be  no
assurance  that the  data from  these third-party  trials is  accurate, that the
Company will be able to  obtain favorable results from  its own trials, or  that
the  Company  can  complete these  trials  on a  timely  basis, or  at  all. See
"Business -- Influenza Clinical Trials."
    
 
   
    The rate of completion  of the Company's clinical  trials may be delayed  by
many  factors. For example, delays may  be encountered in enrolling a sufficient
number of patients fitting the appropriate trial profile, preparing the modified
vaccine strain for certain influenza seasons or in manufacturing clinical  trial
materials.  The  Company's  late-stage  clinical  trials  of  its  cold  adapted
influenza vaccine must  be conducted  during the  influenza season  and must  be
commenced  early enough in the approximately  five-month season so that subjects
may be  vaccinated  well in  advance  of a  challenge  by the  wild-type  virus.
Additionally, there is a risk that there will not be enough natural influenza in
the  community in a given influenza  season to achieve statistically significant
results
    
 
                                       7
<PAGE>
   
from clinical trials.  As a result,  if the  Company is unable  to commence  its
clinical  trials on a  timely basis it will  be required to  wait until the next
influenza season, which will not occur  for another year in that country.  There
can  be no assurance that delays in, or termination of, clinical trials will not
occur. Any delays in,  or termination of, the  Company's clinical trial  efforts
would  have  a  material adverse  effect  on the  Company's  business, financial
condition and results of operations.
    
 
   
    There can  be no  assurance  that Aviron  will  be permitted  by  regulatory
authorities  to  undertake  additional  clinical  trials  for  its  cold adapted
influenza vaccine or initiate clinical trials for its other programs or, if  any
such  trials are  conducted, that any  of the Company's  product candidates will
prove to  be  safe and  effective  or  will receive  regulatory  approvals.  See
"Business -- Vaccine Products Under Development."
    
 
UNCERTAINTIES RELATED TO EARLY STAGE OF DEVELOPMENT; TECHNOLOGICAL UNCERTAINTY
 
   
    Aviron  commenced  its operations  in April  1992 and  until recently  was a
development stage company. All  of the Company's product  candidates are in  the
research  or development  stage. With the  exception of  two in-licensed product
candidates, none of the  Company's proposed products has  yet been approved  for
clinical  trials. To date, the Company has had no revenue from product sales and
all of its resources have been  dedicated to the development of vaccines.  There
can be no assurance that product revenues will be realized on a timely basis, if
ever.
    
 
   
    The  development of safe and effective  vaccines for the prevention of viral
diseases such as influenza, herpes simplex  and other target diseases is  highly
uncertain  and subject to  numerous risks. Potential products  that appear to be
promising at early stages of development may  not reach the market for a  number
of  reasons. Potential products  may be found ineffective  or cause harmful side
effects during preclinical testing or clinical trials, fail to receive necessary
regulatory  approvals,  be  difficult  to  manufacture  on  a  large  scale,  be
uneconomical,   fail  to  achieve   market  acceptance  or   be  precluded  from
commercialization by proprietary  rights of  third parties. Aviron  has not  yet
requested  or received the regulatory approvals  that are required to market its
products. Aviron does not expect that any of its proposed products will be ready
for commercialization  for  the  next  several years,  if  at  all.  To  achieve
profitability,  the Company, alone  or with others,  must successfully identify,
develop, test, manufacture and  market its products. There  can be no  assurance
that  Aviron will succeed in  the development and marketing  of any product. Any
potential product will require  significant additional investment,  development,
preclinical  testing and clinical trials  prior to potential regulatory approval
and commercialization.
    
 
   
    The Company's cold adapted influenza vaccine involves a complex  development
process.  If the Company were to  successfully develop an influenza vaccine, its
composition would require  annual modification.  Influenza viruses  have a  high
mutation  rate  and  the  surface  antigens  of  influenza  viruses  that induce
protective immunity are variable from year to year. Each spring, the FDA and the
United States  Centers for  Disease Control  and Prevention  (the "CDC")  select
circulating  influenza strains that  will be included  in the following season's
influenza vaccines. As  a result,  manufacturers of vaccines  must modify  their
influenza  vaccines each  year to  include the selected  strains in  a form that
meets FDA guidelines within an approximately  six-month period in order to  make
it  available before  the influenza  season. On  one occasion  in the  past, the
Company experienced difficulty in preparing modified vaccine strains in time  to
conduct clinical trials during the influenza season. Even if the Company is able
to  develop an influenza vaccine for a particular year, it must also establish a
dependable process by which  the vaccine may be  modified and manufactured on  a
timely basis to include additional strains each year. If the Company were unable
to  develop an influenza vaccine for a particular year that meets FDA guidelines
and establish a manufacturing process  for the vaccine, its business,  financial
condition  and results of operations would  be materially adversely affected. No
assurance can be  given that delays  in preparing vaccines  for use in  clinical
trials or commercial sales will not be encountered. In addition, there can be no
assurance  that  the  Company's  development efforts  will  be  successful, that
required regulatory approvals, including  those with respect to  Investigational
New  Drug  ("IND")  applications, will  be  obtained  or that  any  products, if
introduced, will be  successfully marketed.  See "Business  -- Vaccine  Products
Under Development."
    
 
                                       8
<PAGE>
   
NEED FOR FUTURE FUNDING; UNCERTAINTY OF ACCESS TO CAPITAL
    
 
   
    The  Company's operations to  date have consumed  substantial and increasing
amounts of cash. The negative cash flow from operations is expected to  continue
and  to accelerate in  the foreseeable future. The  development of the Company's
technology and proposed products will require a commitment of substantial  funds
to  conduct  the costly  and  time-consuming research,  preclinical  testing and
clinical trials necessary to develop  and optimize such technology and  proposed
products, to establish manufacturing and marketing capabilities and to bring any
such  products to market. The Company's  future capital requirements will depend
upon many factors, including continued  scientific progress in the research  and
development  of  the Company's  technology and  vaccine  programs, the  size and
complexity of  these programs,  the  ability of  the  Company to  establish  and
maintain  collaborative  arrangements,  progress  with  preclinical  testing and
clinical trials, the time and costs involved in obtaining regulatory  approvals,
the  cost involved in preparing,  filing, prosecuting, maintaining and enforcing
patent claims or trade secrets, and product commercialization activities.
    
 
   
    The Company anticipates that  the proceeds of  this offering, together  with
the  interest thereon,  and existing  capital resources,  revenues from existing
collaborations, cash equivalents  and short-term investments  will enable it  to
maintain  its current and planned operations  at least through 1997. The Company
is actively seeking additional collaborative agreements with corporate  partners
and  may  seek  additional funding  through  public  or private  equity  or debt
financing.  There  can  be  no  assurance  that  any  additional   collaborative
agreements  will be entered into or  that additional financing will be available
on acceptable terms, if at all. If additional funds are raised by issuing equity
securities, further dilution to stockholders  may result. If adequate funds  are
not  available, the Company  may be required  to delay, reduce  the scope of, or
eliminate one or more of its research or development programs or to obtain funds
through collaborative arrangements with others  that may require the Company  to
relinquish rights to certain of its technologies, product candidates or products
that  the Company would  otherwise seek to develop  or commercialize itself. See
"Management's Discussion  and Analysis  of Financial  Condition and  Results  of
Operations -- Liquidity and Capital Resources."
    
 
LACK OF MANUFACTURING EXPERIENCE; RELIANCE ON CONTRACT MANUFACTURERS
 
   
    The  Company currently does not have  the facilities to manufacture products
for  large-scale  clinical  trials  or  in  commercial  quantities  and  has  no
experience  in commercial-scale  manufacturing. To manufacture  its products for
large-scale clinical trials or on a  commercial scale, the Company will have  to
build  or gain access to a large-scale manufacturing facility which will require
a significant amount of funds. The Company currently is evaluating the costs and
benefits of developing internal  manufacturing capabilities or contracting  with
third-party   manufacturers.  The  production  of  the  Company's  cold  adapted
influenza  vaccine  is  subject  to  the  availability  of  a  large  number  of
pathogen-free  hen  eggs, for  which  there are  currently  a limited  number of
suppliers. Contamination or disruption of this source of supply would  adversely
affect  the ability to manufacture the Company's cold adapted influenza vaccine.
In addition, to  make the vaccine  available for clinical  trials or  commercial
sales  before the  influenza season,  the Company  must successfully  modify the
vaccine within a six-month period to  include selected strains for a  particular
year  in  time  for manufacturing  and  distribution. The  Company  currently is
considering whether to construct  manufacturing facilities capable of  producing
both pilot-scale and commercial quantities of its potential vaccine products and
is presently building a pilot manufacturing facility. This scale-up process will
require  the Company to  develop advanced manufacturing  techniques and rigorous
process controls.  Furthermore, the  Company will  be required  to register  its
facility  with the FDA and with the California Department of Health Services and
will be  subject  to state  and  federal inspections  confirming  the  Company's
compliance  with  current  Good  Manufacturing  Practices  ("cGMP")  regulations
established by the  FDA. No  assurance can  be given as  to the  ability of  the
Company to produce commercial quantities of its potential products in compliance
with applicable regulations or at an acceptable cost, if at all.
    
 
   
    The  Company is alternatively considering  the use of contract manufacturers
for the commercial production of  its potential products. The Company  currently
relies  on Evans Medical Limited, a subsidiary  of Medeva plc ("Evans"), for the
manufacture of its influenza vaccine for  clinical trials. The Company is  aware
of only a limited number of manufacturers which it believes have the ability and
capacity  to  manufacture its  potential  products, including  the  cold adapted
influenza vaccine,  in a  timely manner.  There  can be  no assurance  that  the
Company  would  be able  to contract  with  any of  these manufacturers  for the
manufacture of its products on acceptable
    
 
                                       9
<PAGE>
terms, if at all.  If the Company  enters into an  agreement with a  third-party
manufacturer,  it will  be required to  relinquish control  of the manufacturing
process, which  might  adversely affect  the  Company's results  of  operations.
Furthermore, a third-party manufacturer also will be required to manufacture the
Company's  products in compliance with state and federal regulations. Failure of
any such third-party manufacturer to  comply with state and federal  regulations
and  to deliver the  required quantities on  a timely basis  and at commercially
reasonable prices  would materially  adversely  affect the  Company's  business,
financial  condition and results  of operations. No assurance  can be given that
the Company, alone or with a third party, will be able to make the transition to
commercial-scale production of its potential  products successfully, if at  all,
or that if successful, the Company will be able to maintain such production. See
"Business -- Manufacturing" and "-- Government Regulation."
 
UNCERTAINTY OF FUTURE PROFITABILITY; ACCUMULATED DEFICIT
 
   
    The  Company  has experienced  significant  and increasing  operating losses
since its inception  in April 1992.  As of March  31, 1996, the  Company had  an
accumulated  deficit of approximately $26.2 million. Aviron has not received any
product revenue to date and does not  expect to generate revenues from the  sale
of  products  for  several  years,  if at  all.  The  Company  expects  to incur
significant and increasing operating losses over at least the next several years
as the Company's research  and development efforts  and preclinical testing  and
clinical trial activities expand. The Company's ability to achieve profitability
depends  in part upon its ability, alone or with others, to complete development
of its  proposed  products,  to  obtain required  regulatory  approvals  and  to
successfully  manufacture  and  market such  products.  To the  extent  that the
Company is  unable  to obtain  third-party  funding for  expenses,  the  Company
expects  that  its  increased  expenses will  result  in  increased  losses from
operations.  There  can  be  no  assurance  that  Aviron  will  obtain  required
regulatory  approvals or  successfully identify, develop,  test, manufacture and
market any product  candidates, or that  the Company will  ever achieve  product
revenues   or  profitability.  See  "Management's  Discussion  and  Analysis  of
Financial Condition and Results of Operations."
    
 
UNCERTAINTY OF PROTECTION OF PATENTS AND PROPRIETARY RIGHTS; DEPENDENCE ON TRADE
SECRETS
 
   
    The Company's success  will depend in  part on its  ability to maintain  its
technology  licenses, maintain trade secrets, obtain patents and operate without
infringing the proprietary rights  of others, both in  the United States and  in
other  countries. Since patent applications in  the United States are maintained
in secrecy  until patents  issue and  since publication  of discoveries  in  the
scientific or patent literature often lag behind actual discoveries, the Company
cannot  be certain that it was the first  to make the inventions covered by each
of its pending  patent applications  or that  it was  the first  to file  patent
applications  for  such inventions.  The patent  positions of  biotechnology and
pharmaceutical companies can be highly  uncertain and involve complex legal  and
factual  questions, and therefore the breadth of claims allowed in biotechnology
and pharmaceutical patents, or their enforceability, cannot be predicted.  There
can  be no assurance  that any of  the Company's patents  or patent applications
will issue or, if issued, will  not be challenged, invalidated or  circumvented,
or  that the  rights granted thereunder  will provide  proprietary protection or
competitive advantages to the Company.
    
 
   
    The commercial  success  of Aviron  also  will  depend, in  part,  upon  the
Company's  not infringing patents  issued to others.  A number of pharmaceutical
companies, biotechnology companies, universities and research institutions  have
filed  patent applications  or received  patents in  the areas  of the Company's
programs. Some  of these  applications  or patents  may  limit or  preclude  the
Company's  applications, or conflict in certain  respects with claims made under
the Company's applications.
    
 
   
    On May  22,  1996,  the  Company received  notice  from  Chiron  Corporation
("Chiron") that Chiron intends to file a lawsuit against Aviron, unless a prompt
negotiated  settlement can be reached, alleging  that certain of Aviron's patent
applications relating  to  its  EBV  program are  based  on  Chiron  proprietary
information which was improperly conveyed to Aviron by a former Chiron employee.
Aviron  believes that Chiron's allegations are without merit and, if a complaint
is filed, intends to  vigorously defend itself against  any such action.  Aviron
does not utilize the alleged proprietary information in any of its programs. The
Company  has  received terms  of a  proposed  settlement from  Chiron and  is in
discussions with  Chiron regarding  a  possible settlement  of the  dispute.  No
assurance can be given that litigation will not ensue, which could be costly and
time-consuming.
    
 
                                       10
<PAGE>
   
    The  Company is aware of pending patent applications that have been filed by
others that may  pertain to  certain aspects of  the Company's  programs or  its
issued  or pending patent  applications. If patents  have been or  are issued to
others  containing  preclusive  or  conflicting  claims  and  such  claims   are
ultimately  determined  to  be valid,  the  Company  may be  required  to obtain
licenses to these  patents or to  develop or obtain  alternative technology.  No
assurance can be given that patents have not been issued, or will not be issued,
to  third parties that contain preclusive  or conflicting claims with respect to
the cold adapted influenza vaccine or  any of the Company's other programs.  The
Company's  breach  of an  existing license  or  failure to  obtain a  license to
technology required to commercialize  its products may  have a material  adverse
effect on the Company's business, financial condition and results of operations.
Litigation,  which could result in substantial costs to the Company, may also be
necessary to enforce any patents issued to the Company or to determine the scope
and validity of third-party  proprietary rights. If  competitors of the  Company
prepare  and file patent applications in the United States that claim technology
also claimed by the Company, the Company may have to participate in interference
proceedings declared  by  the  United  States Patent  and  Trademark  Office  to
determine  priority of invention, which could  result in substantial cost to the
Company, even if the  eventual outcome is favorable  to the Company. An  adverse
outcome  could subject the  Company to significant  liabilities to third parties
and require the  Company to  license disputed rights  from third  parties or  to
cease using such technology.
    
 
   
    The  Company has  no issued  patents on the  technology related  to its cold
adapted influenza vaccine. The Company's rights to this technology are based  on
a  license of materials and know-how from the University of Michigan, which owns
the master  strains from  which the  vaccine is  derived, and  on a  license  of
know-how  and clinical trial data from the NIH. There can be no assurance that a
third party will not reproduce the  Company's cold adapted influenza vaccine  or
that  a third party will not  develop another live-virus influenza vaccine which
might be comparable to Aviron's in terms of safety and effectiveness.
    
 
    The Company  also  relies  on  trade  secrets  to  protect  its  technology,
especially  where  patent  protection  is  not  believed  to  be  appropriate or
obtainable. Certain of  the Company's licensors  also rely on  trade secrets  to
protect  technology which  has been  licensed to  Aviron, and  as a  result, the
Company is dependent  on the  efforts of such  licensors to  protect such  trade
secrets.  For  example, the  University of  Michigan relies,  in part,  on trade
secrets to protect the master strains  of the cold adapted influenza virus  used
by  the Company.  Aviron protects its  proprietary technology  and processes, in
part,  by   confidentiality   agreements  with   its   employees,   consultants,
collaborators  and certain  contractors. There  can be  no assurance  that these
agreements will not be breached, that  the Company would have adequate  remedies
for  any breach, or that  the Company's trade secrets  or those of its licensors
will not otherwise become known  or be independently discovered by  competitors.
To  the  extent that  Aviron or  its consultants  or research  collaborators use
intellectual property owned by  others in their work  for the Company,  disputes
may also arise as to the rights in related or resulting know-how and inventions.
See "Business -- Patents and Proprietary Rights."
 
GOVERNMENT REGULATION; NO ASSURANCE OF REGULATORY APPROVALS
 
   
    The  production  and marketing  of the  Company's  products and  its ongoing
research and  development  activities are  subject  to extensive  regulation  by
numerous  government authorities in the United States and other countries. Prior
to marketing in  the United States,  any product developed  by the Company  must
undergo  rigorous  preclinical  testing  and clinical  trials  and  an extensive
regulatory approval process  implemented by  the FDA  under the  Food, Drug  and
Cosmetic  Act.  Satisfaction  of such  regulatory  requirements,  which includes
demonstrating that  the product  is  both safe  and effective,  typically  takes
several  years or more  depending upon the  type, complexity and  novelty of the
product and requires the expenditure of substantial resources. This process  may
be  more demanding for vaccines  intended for use in  healthy people compared to
therapeutics used for  treatment of  people with  diseases. Preclinical  studies
must  be conducted in compliance with the FDA's Good Laboratory Practice ("GLP")
regulations. Clinical testing  must meet requirements  for Institutional  Review
Board  ("IRB")  oversight and  informed consent,  as well  as FDA  prior review,
oversight and  good  clinical practice  requirements.  The Company  has  limited
experience  in conducting and  managing the clinical  trials necessary to obtain
regulatory approval. Furthermore, the  Company or the  FDA may suspend  clinical
trials at any time if it believes that the subjects participating in such trials
are being exposed to unacceptable health risks.
    
 
                                       11
<PAGE>
    Before  receiving FDA approval to market a product, the Company will have to
demonstrate that the product  is safe and effective  and represents an  improved
form  of health management  compared to existing  approaches. Data obtained from
preclinical  testing   and   clinical   trials  are   susceptible   to   varying
interpretations  which could  delay, limit  or prevent  regulatory approvals. In
addition,  delays  or  rejections  may  be  encountered  based  upon  additional
government  regulation  from  future  legislation  or  administrative  action or
changes in FDA policy during the period of product development, clinical  trials
and  FDA regulatory  review. Similar delays  may also be  encountered in foreign
countries. There can be no assurance that even after such time and expenditures,
regulatory approval will be obtained for any products developed by the  Company.
If regulatory approval of a product is granted, such approval will be limited to
those specific segments of the population for which the product is effective, as
demonstrated  through clinical trials. Furthermore,  approval may entail ongoing
requirements for post-marketing  studies. Even  if such  regulatory approval  is
obtained,  a marketed product, its manufacturer and its manufacturing facilities
are subject  to  continual  review  and  periodic  inspections.  The  regulatory
standards  for manufacturing are currently being applied stringently by the FDA.
Discovery of  previously  unknown  problems  with  a  product,  manufacturer  or
facility  may result in restrictions on  such product or manufacturer, including
costly recalls or even withdrawal of the  product from the market. There can  be
no  assurance that any product developed by  the Company alone or in conjunction
with others will prove to  be safe and efficacious  in clinical trials and  will
meet  all of the applicable regulatory  requirements needed to receive marketing
approval.
 
    Outside the United  States, the  Company's ability  to market  a product  is
contingent   upon  receiving   marketing  authorization   from  the  appropriate
regulatory authorities.  The  requirements  governing the  conduct  of  clinical
trials,  marketing  authorization, pricing  and  reimbursement vary  widely from
country to country. At present, foreign marketing authorizations are applied for
at a national level, although within  the European Union (the "EU"),  procedures
are  available to  companies wishing  to market  a product  in more  than one EU
member state. If the regulatory authorities are satisfied that adequate evidence
of safety, quality and  efficacy has been  presented, a marketing  authorization
will  be granted. This  foreign regulatory approval process  includes all of the
risks associated with FDA approval set forth above. See "Business --  Government
Regulation."
 
INTENSE COMPETITION AND RISK OF TECHNOLOGICAL OBSOLESCENCE
 
   
    The  Company operates in a rapidly  evolving field. Any product developed by
the Company would compete with existing and new drugs and vaccines being created
by pharmaceutical, biopharmaceutical and biotechnology companies. If the Company
were able  to successfully  develop its  vaccines, it  would be  competing  with
larger  companies that have  already introduced vaccines  and have significantly
greater  marketing,  manufacturing,  financial  and  managerial  resources.  For
example, with respect to its cold adapted influenza vaccine, the Company will be
competing   against  larger   companies  such  as   Pasteur  Merieux  Connaught,
Wyeth-Ayerst,  Parke-Davis  Group,  a   subsidiary  of  Warner-Lambert   Company
("Parke-Davis")   and  Evans.  Each  of  these  companies  sell  the  injectable
inactivated influenza vaccine in the  United States, have significantly  greater
financial  resources than Aviron and have established marketing and distribution
channels for such products. The Company is also aware of several companies  that
are marketing or are in late-stage development of products to prevent CMV or HSV
disease,  including Glaxo Wellcome plc  ("Glaxo"), SmithKline Beecham and Chiron
Biocine Corporation. In addition, the Company is aware of the use in Russia of a
cold adapted influenza  vaccine, research  programs by some  of the  competitors
listed  above, among others, to develop  more effective influenza vaccines and a
cold adapted PIV-3 vaccine developed with NIH support which may be licensed to a
large vaccine company.
    
 
    New developments are  expected to  continue in both  the pharmaceutical  and
biotechnology  industries  and  in  academia.  Other  companies  may  succeed in
developing products that are safer, more effective or less costly than any  that
may  be developed by the Company. Such companies may also be more effective than
the Company  in the  production and  marketing of  their products.  Furthermore,
rapid  technological  development by  competitors  may result  in  the Company's
products becoming obsolete before the Company  is able to recover its  research,
development  or commercialization expenses incurred  in connection with any such
product.  Many  potential  competitors  have  substantially  greater  financial,
technical and marketing resources than the Company. Some of these companies also
have  considerable experience in preclinical  testing, clinical trials and other
 
                                       12
<PAGE>
regulatory  approval  procedures.   Moreover,  certain  academic   institutions,
government  agencies and other research organizations are conducting research in
areas  in  which  the  Company  is  working.  These  institutions  are  becoming
increasingly  aware of the  commercial value of their  findings and are becoming
more active in seeking patent  protection and licensing arrangements to  collect
royalties for the use of technology that they have developed. These institutions
may  also market competitive  commercial products on their  own or through joint
ventures.
 
    Aviron believes  that  competition in  the  markets it  is  addressing  will
continue  to be intense. The vaccine  industry is characterized by intense price
competition, and the Company anticipates that it will face this and other  forms
of competition. There can be no assurance that pharmaceutical, biopharmaceutical
and  biotechnology companies will not develop more effective products than those
of the Company or will not market and sell their products more effectively  than
the  Company,  which  would have  a  material  adverse effect  on  the Company's
business, financial  condition  and  results of  operations.  See  "Business  --
Competition."
 
DEPENDENCE ON COLLABORATIVE AGREEMENTS
 
    The  Company's strategy for the  development, clinical trials, manufacturing
and commercialization  of  certain  of its  products  includes  maintaining  and
entering   into  various  collaborations  with  corporate  partners,  licensors,
licensees and others. There can be no assurance that the Company will be able to
maintain existing collaborative agreements, negotiate collaborative arrangements
in the future on  acceptable terms, if  at all, or  that any such  collaborative
arrangements  will be successful. To the extent  that the Company is not able to
maintain or  establish  such arrangements,  the  Company would  be  required  to
undertake  product  development  and  commercialization  activities  at  its own
expense, which would increase the Company's capital requirements or require  the
Company  to limit the scope of its development and commercialization activities.
In addition, the  Company may  encounter significant delays  in introducing  its
products  into certain markets or find that the development, manufacture or sale
of its products in  such markets is  adversely affected by  the absence of  such
collaborative agreements.
 
   
    The  Company cannot  control the  amount and  timing of  resources which its
collaborative partners devote to the  Company's programs or potential  products,
which may vary because of factors unrelated to the potential products. If any of
the  Company's collaborative partners breach  or terminate their agreements with
the Company or  otherwise fail to  conduct their collaborative  activities in  a
timely  manner, the preclinical or  clinical development or commercialization of
product candidates or research programs will  be delayed, and the Company  would
be   required  to  devote  additional   resources  to  product  development  and
commercialization,   or   terminate   certain   development   programs.    These
relationships  generally may  be terminated at  the discretion  of the Company's
collaborative partners, in some cases with  only limited notice to the  Company.
The  termination  of collaborative  arrangements could  have a  material adverse
effect on the Company's business, financial condition and results of operations.
There also can be no assurance that  disputes will not arise in the future  with
respect  to  the ownership  of  rights to  any  technology developed  with third
parties. These and  other possible disagreements  between collaborators and  the
Company  could  lead to  delays in  the  collaborative research,  development or
commercialization of certain product candidates,  or could result in  litigation
or  arbitration, which would be  time consuming and expensive,  and would have a
material adverse  effect  on the  Company's  business, financial  condition  and
results of operations.
    
 
    In  addition, Aviron's collaborative  partners may develop,  either alone or
with others, products  that compete with  the development and  marketing of  the
Company's  products. Competing products of  the Company's collaborative partners
may result in their withdrawal  of support with respect to  all or a portion  of
the  Company's technology,  which would  have a  material adverse  effect on the
Company's business, financial condition and results of operations. See "Business
- -- Collaborative Agreements."
 
UNCERTAINTY OF MARKET ACCEPTANCE
 
    Even if the requisite  regulatory approvals are  obtained for the  Company's
potential  products,  uncertainty exists  as to  whether  such products  will be
accepted in United States or foreign markets. The Company believes, for example,
that widespread use of the Company's  proposed vaccines in the United States  is
unlikely without
 
                                       13
<PAGE>
   
positive  recommendations from the Advisory  Committee on Immunization Practices
(the "ACIP") of  the CDC,  the American Academy  of Pediatrics  or the  American
College  of Physicians.  There can  be no  assurance that  such authorities will
recommend the  use  of  the  Company's  proposed  products.  The  lack  of  such
recommendations  would have a material adverse effect on the Company's business,
financial condition and results of operations.
    
 
   
    A number  of additional  factors  may affect  the  rate and  overall  market
acceptance  of Aviron's  cold adapted influenza  vaccine and  any other products
which may  be  developed by  the  Company, including  the  rate of  adoption  of
Aviron's  vaccines by health care practitioners,  the rate of vaccine acceptance
by the target  population, the timing  of market entry  relative to  competitive
products,  the  availability  of  alternative  technologies,  the  price  of the
Company's products  relative to  alternative technologies,  the availability  of
third-party  reimbursement and the  extent of marketing  efforts by the Company,
collaborative partners and  third-party distributors or  agents retained by  the
Company.  Side effects or unfavorable  publicity concerning Aviron's products or
any product incorporating live  virus vaccines could have  an adverse effect  on
the  Company's  ability  to  obtain  physician,  patient  or  third-party  payor
acceptance and efforts  to sell  the Company's products.  The Company's  current
formulation  of the cold adapted influenza  vaccine for clinical trials requires
frozen storage, which may adversely affect market acceptance in certain  foreign
countries  where adequate refrigeration is not  commonly available. There can be
no assurance that  physicians, patients  or third-party payors  will accept  new
live virus vaccine products or any of the Company's products as readily as other
types  of  vaccines,  or  at  all.  See  "Business  --  Vaccine  Products  Under
Development."
    
 
LACK OF MARKETING EXPERIENCE; DEPENDENCE ON THIRD PARTIES
 
    The Company currently has no sales, marketing or distribution capability. To
market any products, Aviron must either  obtain the assistance of a third  party
with  a suitable distribution system, develop a direct sales and marketing staff
of its own or combine the efforts of  a third party with its own efforts.  Other
than  SmithKline Beecham and Sang-A,  the Company to date  has no agreements for
marketing or distributing its potential products.
 
   
    The success and commercialization of the Company's products is dependent  in
part  upon the  ability of  the Company  to maintain  and enter  into additional
collaborative agreements with  corporate partners for  the development,  testing
and  marketing of certain  of its vaccines  and upon the  ability of these third
parties to perform their responsibilities. Although Aviron believes that parties
to any  such  arrangements would  have  an  economic motivation  to  succeed  in
performing   their  contractual  responsibilities,  the  amount  and  timing  of
resources devoted to  these activities  will not be  within the  control of  the
Company. There can be no assurance that any such agreements or arrangements will
be  available on  terms acceptable to  the Company,  if at all,  that such third
parties would perform their obligations as  expected, or that any revenue  would
be  derived from  such arrangements. If  Aviron is  not able to  enter into such
agreements or  arrangements,  it  could  encounter  delays  in  introducing  its
products   into  the   market  or   be  forced  to   limit  the   scope  of  its
commercialization activities. If the Company  were to market products  directly,
significant  additional  expenditures, management  resources  and time  would be
required to develop a sales and marketing staff within the Company. In addition,
the Company would  also be competing  with other companies  that currently  have
experienced  and well-funded  marketing and  sales operations.  There can  be no
assurance that the Company will be able to establish its own sales and marketing
force or that any such force, if established, would be successful. See "Business
- -- Marketing and Sales" and "-- Collaborative Agreements."
    
 
VOLATILITY OF COMMON STOCK PRICE
 
    The market prices  for securities of  pharmaceutical, biopharmaceutical  and
biotechnology  companies have historically been  highly volatile. The market has
from time to time experienced significant price and volume fluctuations that are
unrelated to the  operating performance  of particular  companies. In  addition,
factors such as fluctuations in the Company's operating results, future sales of
Common  Stock,  announcements of  technological  innovations or  new therapeutic
products by  the Company  or its  competitors, announcements  of  collaborators,
clinical  trial results, government regulation,  developments in patent or other
proprietary rights, public concern  as to the safety  of drugs developed by  the
Company   or  others,   comments  made   by  securities   analysts  and  general
 
                                       14
<PAGE>
market conditions can have an adverse effect  on the market price of the  Common
Stock.  In particular, the  realization of any  of the risks  described in these
"Risk Factors" could have a significant and adverse impact on such market price.
 
RISK OF PRODUCT LIABILITY; UNCERTAINTY OF AVAILABILITY OF INSURANCE
 
   
    The Company's business exposes it to potential product liability risks  that
are  inherent  in  the testing,  manufacturing  and marketing  of  vaccines. The
Company has obtained clinical trial liability insurance for its clinical trials,
but there  can  be no  assurance  that it  will  be able  to  maintain  adequate
insurance  for its  clinical trials.  The Company  also intends  to seek product
liability insurance in the future for  products approved for marketing, if  any.
However,  no assurance can be given that the  Company will be able to acquire or
maintain insurance  or  that  insurance  can be  acquired  or  maintained  at  a
reasonable cost or in sufficient amounts to protect the Company. There can be no
assurance  that insurance  coverage and  the resources  of the  Company would be
sufficient to satisfy any liability  resulting from product liability claims.  A
successful  product  liability claim  or series  of  claims brought  against the
Company could  have  a  material  adverse  effect  on  its  business,  financial
condition  and results of  operations. The Company intends  to seek inclusion of
certain  of  its  products  in   the  United  States  National  Vaccine   Injury
Compensation Program, a no-fault compensation program for claims against vaccine
manufacturers,  which administers  a trust  funded by  excise taxes  on sales of
certain recommended  childhood vaccines.  There can  be no  assurance that  this
government program will continue or that the Company's proposed vaccines will be
included in the program.
    
 
UNCERTAINTY RELATED TO PHARMACEUTICAL PRICING AND REIMBURSEMENT
 
   
    Political, economic and regulatory influences are subjecting the health care
industry  in  the United  States to  fundamental  change. Recent  initiatives to
reduce the federal  deficit and to  reform health care  delivery are  increasing
cost-containment   efforts.  The   Company  anticipates   that  Congress,  state
legislatures  and  the  private  sector  will  continue  to  review  and  assess
alternative  benefits, controls on  health care spending  through limitations on
the growth  of  private health  insurance  premiums and  Medicare  and  Medicaid
spending,  the creation of large insurance  purchasing groups, price controls on
pharmaceuticals and  other  fundamental  changes to  the  health  care  delivery
system.  Any such  proposed or  actual changes  could cause  the Company  or its
collaborative partners to limit or  eliminate spending on development  projects.
Legislative  debate is expected to continue in the future, and market forces are
expected to demand reduced costs. Aviron cannot predict what impact the adoption
of any federal  or state health  care reform measures  or future private  sector
reforms may have on its business.
    
 
    In  both  domestic  and foreign  markets,  sales of  the  Company's proposed
vaccines will  depend  in  part  upon the  availability  of  reimbursement  from
third-party  payors,  such  as  government  health  administration  authorities,
managed care  providers, private  health insurers  and other  organizations.  In
addition,  other third-party payors  are increasingly challenging  the price and
cost effectiveness  of medical  products and  services. Significant  uncertainty
exists  as to the  reimbursement status of newly  approved health care products.
There can  be  no  assurance  that  the  Company's  proposed  products  will  be
considered  cost effective  or that  adequate third-party  reimbursement will be
available to enable  Aviron to maintain  price levels sufficient  to realize  an
appropriate  return on  its investment  in product  development. Legislation and
regulations affecting  the  pricing of  pharmaceuticals  may change  before  the
Company's  proposed  products  are  approved  for  marketing.  Adoption  of such
legislation could further limit reimbursement for medical products. If  adequate
coverage  and  reimbursement  levels  are not  provided  by  the  government and
third-party payors for the  Company's products, the  market acceptance of  these
products would be adversely affected, which would have a material adverse effect
on the Company's business, financial condition and results of operations.
 
NEED TO ATTRACT AND RETAIN KEY EMPLOYEES AND CONSULTANTS
 
    The  Company is highly dependent on  the principal members of its scientific
and management  staff.  In  addition,  the Company  relies  on  consultants  and
advisors,   including  its  scientific  advisors,   to  assist  the  Company  in
formulating its  research and  development  strategy. Attracting  and  retaining
qualified  personnel, consultants and advisors will be critical to the Company's
success.   To   pursue   its   product   development   and   marketing    plans,
 
                                       15
<PAGE>
the  Company will be required to  hire additional qualified scientific personnel
to perform research  and development,  as well  as personnel  with expertise  in
conducting  clinical trials, government  regulation, manufacturing and marketing
and sales. Expansion in  product development and marketing  is also expected  to
require  the addition of management personnel  and the development of additional
expertise by existing  management personnel. The  Company faces competition  for
qualified   individuals  from  numerous  pharmaceutical,  biopharmaceutical  and
biotechnology companies, universities and other research institutions. There can
be no  assurance that  the  Company will  be able  to  attract and  retain  such
individuals.
 
   
    In  addition,  a  portion  of  the  Company's  research  and  development is
conducted under  sponsored  research  programs  with  several  universities  and
research  institutions. The Company  depends on the  availability of a principal
investigator for each  such program, and  the Company cannot  assure that  these
individuals  or their research staffs will  be available to conduct research and
development for Aviron. The Company's  academic collaborators are not  employees
of  the  Company.  As a  result,  the  Company has  limited  control  over their
activities and  can expect  that only  limited  amounts of  their time  will  be
dedicated  to Company activities. The  Company's academic collaborators may have
relationships with other commercial entities,  some of which could compete  with
the Company. See "Business -- Scientific Advisory Board" and "Management."
    
 
RISKS ASSOCIATED WITH HAZARDOUS MATERIALS
 
    The  Company's  research  and  development involves  the  controlled  use of
hazardous materials,  chemicals,  various radioactive  substances  and  viruses.
Although  the  Company  believes that  its  safety procedures  for  handling and
disposing of such materials  comply with the standards  prescribed by state  and
federal  regulations, the risk of accidental  contamination or injury from these
materials cannot be completely eliminated. In the event of such an accident, the
Company could be held liable for any damages that result and any such  liability
could  exceed the  resources of the  Company. The Company  may incur substantial
costs  to  comply  with  environmental  regulations  if  the  Company   develops
manufacturing capacity.
 
DILUTION
 
   
    The  assumed initial public offering price  is substantially higher than the
pro forma  net tangible  book value  per share  of the  Company's Common  Stock.
Investors  purchasing shares  of Common  Stock in  this offering  and the Sang-A
Shares will  therefore incur  immediate, substantial  dilution of  approximately
$7.82  per share.  In addition, investors  purchasing shares of  Common Stock in
this offering will incur additional  dilution to the extent outstanding  options
and warrants are exercised. See "Dilution."
    
 
NO PRIOR PUBLIC MARKET
 
    Prior  to this offering, there  has been no public  market for the Company's
Common Stock, and there can be no  assurance that a regular trading market  will
develop  and continue after this offering or that the market price of the Common
Stock will not  decline below  the initial  public offering  price. The  initial
public  offering  price  will  be determined  through  negotiations  between the
Company and the Representatives of the Underwriters and may not be indicative of
the market price of the Common Stock following this offering. Among the  factors
considered  in such negotiations  will be prevailing  market conditions, certain
financial information of the Company, market valuations of other companies  that
the Company and the Representatives of the Underwriters believe to be comparable
to  the Company, estimates of the business potential of the Company, the present
state of  the  Company's development  and  other factors  deemed  relevant.  See
"Underwriting."
 
POTENTIAL ADVERSE EFFECTS OF SHARES ELIGIBLE FOR FUTURE SALE
 
   
    Sales of a substantial amount of Common Stock in the public market following
this  offering could adversely affect the  market price for the Company's Common
Stock. Upon completion of this offering and  the sale of the Sang-A Shares,  the
Company  will have 12,285,990 shares of Common Stock outstanding. In addition to
the 3,000,000  shares  of Common  Stock  offered hereby,  approximately  149,329
shares  will be available for sale in  the public market upon the effective date
of the Registration Statement pursuant to subsection (k) of Rule 144 promulgated
under the Securities Act of 1933,  as amended (the "Act"). Approximately  37,395
shares of Common
    
 
                                       16
<PAGE>
   
Stock  will be available for  sale in the public market  pursuant to Rule 144 or
Rule 701 under  the Act beginning  90 days  after the date  of this  Prospectus,
subject in certain cases to volume and manner of sale restrictions. In addition,
283,160  shares subject  to vested  options will be  available for  sale 90 days
after the date of this Prospectus pursuant to Rule 701. Beginning 180 days  from
the  date of this Prospectus, 5,311,881  shares of outstanding and 33,726 shares
subject to additional  vested options  will be  available for  sale, subject  in
certain  cases to volume  limitations, upon the expiration  of agreements not to
sell such  outstanding shares  or  shares subject  to such  options.  Robertson,
Stephens  & Company may, in its sole  discretion and at any time without notice,
release all  or  any  portion  of the  shares  subject  to  lock-up  agreements.
Additional  shares held by  existing shareholders will  become eligible for sale
from  time  to  time  in  the  future.  After  this  offering,  the  holders  of
approximately  7,833,659  shares  of  Common  Stock  and  warrants  to  purchase
approximately 148,145 shares of Common Stock will be entitled to certain  demand
and  piggyback registration rights  with respect to  registration of such shares
under the  Act.  If  such  holders, by  exercising  their  demand  or  piggyback
registration  rights, cause  a large number  of securities to  be registered and
sold in the public market, such sales could have an adverse effect on the market
price for  the Company's  Common Stock.  If the  Company were  to include  in  a
Company-initiated  registration  shares held  by  such holders  pursuant  to the
exercise of their piggyback registration rights, such sales may have an  adverse
effect  on the Company's  ability to raise needed  capital. See "Shares Eligible
for Future Sale" and "Underwriting."
    
 
ANTI-TAKEOVER EFFECTS OF DELAWARE LAW AND CERTAIN CHARTER PROVISIONS
 
    The Company's Board of Directors has the authority to issue up to  5,000,000
shares  of Preferred Stock  and to determine the  price, rights, preferences and
privileges of those shares without any  further vote or action by the  Company's
stockholders.  The rights of the holders of Common Stock will be subject to, and
may be adversely affected by, the rights  of the holders of any Preferred  Stock
that  may be issued in the future. While the Company has no present intention to
issue shares  of  Preferred  Stock, such  issuance,  while  providing  desirable
flexibility  in  connection  with  possible  acquisitions  and  other  corporate
purposes, could have the effect of making it more difficult for a third party to
acquire a majority of the outstanding voting stock of the Company. In  addition,
the  Company is subject  to the anti-takeover  provisions of Section  203 of the
Delaware General Corporation Law, which prohibits the Company from engaging in a
"business combination" with an  "interested stockholder" for  a period of  three
years after the date of the transaction in which the person became an interested
stockholder, unless the business combination is approved in a prescribed manner.
The application of Section 203 could have the effect of delaying or preventing a
change  of control  of the Company.  The Company's  Certificate of Incorporation
provides for staggered  terms for  the members of  the Board  of Directors.  The
staggered  Board  of Directors  and certain  other  provisions of  the Company's
Certificate of  Incorporation and  Bylaws may  have the  effect of  delaying  or
preventing  changes  in  control  or  management  of  the  Company,  which could
adversely  affect  the  market  price   of  the  Company's  Common  Stock.   See
"Description  of Capital Stock -- Delaware Anti-Takeover Law and Certain Charter
Provisions."
 
                                       17
<PAGE>
                                USE OF PROCEEDS
 
    The net proceeds  to the Company  from the  sale of shares  of Common  Stock
offered  hereby  are  estimated  to  be  $32.9  million  ($37.9  million  if the
Underwriters' over-allotment option  is exercised in  full) after deducting  the
estimated  underwriting discounts and commissions  and offering expenses payable
by the Company. In addition,  the net proceeds to the  Company from the sale  of
the Sang-A Shares are estimated to be $4.0 million.
 
   
    The  Company  anticipates  using  approximately  $24.0  million  of  the net
proceeds from this offering and from the  sale of the Sang-A Shares for  product
research  and development, including preclinical testing and clinical trials and
approximately $8.0  million for  capital expenditures.  The balance  of the  net
proceeds  will be used  for working capital and  general corporate purposes. The
amounts and timing of the expenditures for these purposes may vary significantly
depending on numerous factors, such as the status of the Company's research  and
development  efforts, the  regulatory approval  process, technological advances,
determinations as to commercial potential, the terms of collaborative agreements
entered into  by  the  Company,  the status  of  competitive  products  and  the
possibility  of the  Company's construction of  a commercial-scale manufacturing
facility for its  potential products.  In addition, the  Company's research  and
development expenditures will vary as projects are added, extended or terminated
and  as a result of variations in  funding from existing or future collaborative
agreements. The Company may also use a  portion of such net proceeds to  acquire
or  invest in  businesses, products and  technologies that  are complementary to
those of  the  Company, although  no  such  acquisitions are  planned  or  being
negotiated as of the date of this Prospectus, and no portion of the net proceeds
has been allocated for any specific acquisition.
    
 
    The   Company  believes  that  its  available  cash,  cash  equivalents  and
short-term investments, together with the net proceeds of this offering and from
the sale of the Sang-A Shares, and  the interest thereon, will be sufficient  to
meet  its capital requirements at least through 1997. Pending application of the
net proceeds as described above, the Company intends to invest the net  proceeds
in short-term, interest-bearing, investment-grade securities.
 
                                DIVIDEND POLICY
 
    The  Company has  not declared  or paid cash  dividends on  its Common Stock
since inception and does not intend to pay any cash dividends in the foreseeable
future. Future  cash dividends,  if any,  will  be determined  by the  Board  of
Directors.
 
                                       18
<PAGE>
                                 CAPITALIZATION
 
   
    The  following table  sets forth, as  of March  31, 1996, (i)  the pro forma
capitalization  of  the  Company,  giving  effect  to  the  conversion  of   all
outstanding shares of Preferred Stock of the Company into Common Stock, and (ii)
the pro forma capitalization as adjusted to reflect the receipt of the estimated
net  proceeds from the sale  of 3,000,000 shares of  Common Stock offered by the
Company hereby at an assumed initial public offering price of $12.00 per  share,
after  deducting  the  estimated  underwriting  discounts  and  commissions  and
offering expenses payable by  the Company, and the  estimated proceeds from  the
sale of the Sang-A Shares:
    
 
   
<TABLE>
<CAPTION>
                                                              MARCH 31, 1996
                                                         ------------------------
                                                          PRO FORMA   AS ADJUSTED
                                                         -----------  -----------
                                                              (in thousands)
<S>                                                      <C>          <C>
Capital lease obligations, noncurrent..................   $     545    $     545
                                                         -----------  -----------
Stockholders' equity:
  Preferred Stock, $0.001 par value; 5,000,000 shares
   authorized; none issued and outstanding.............          --           --
  Common Stock, $0.001 par value; 30,000,000 shares
   authorized; 8,874,456 shares issued and outstanding
   pro forma, and 12,207,789 shares issued and
   outstanding as adjusted (1).........................           9           12
  Additional paid-in capital...........................      41,598       78,475
  Notes receivable from stockholders...................        (310)        (310)
  Deferred compensation................................        (938)        (938)
  Accumulated deficit..................................     (26,192)     (26,192)
                                                         -----------  -----------
        Total stockholders' equity.....................      14,167       51,047
                                                         -----------  -----------
          Total capitalization.........................   $  14,712    $  51,592
                                                         -----------  -----------
                                                         -----------  -----------
</TABLE>
    
 
- -------------------
   
(1)  Excludes (i) 78,201 shares  of Common Stock issued  subsequent to March 31,
    1996 upon exercise  of stock options,  (ii) 643,480 shares  of Common  Stock
    issuable  upon  exercise of  options outstanding  as  of June  1, 1996  at a
    weighted average exercise price of  approximately $1.22 per share, (iii)  an
    aggregate  of  1,556,520  shares  reserved for  future  grants  or purchases
    pursuant to  the  Company's  1996  Equity  Incentive  Plan,  Employee  Stock
    Purchase  Plan  and Non-Employee  Director Stock  Option Plan,  (iv) 118,395
    shares issuable upon exercise of warrants outstanding as of June 1, 1996  at
    a  weighted average exercise price  of $6.65 per share,  and (v) warrants to
    purchase 29,750 shares which become exercisable at the close of the offering
    at 125% of the initial public offering price.
    
 
                                       19
<PAGE>
                                    DILUTION
 
   
    The pro forma net tangible book value of the Company, as of March 31,  1996,
was  $14,167,000 or $1.60 per share of Common Stock. Pro forma net tangible book
value per share is determined by dividing the pro forma net tangible book  value
(pro  forma tangible assets less total liabilities) of the Company by the number
of shares of Common Stock outstanding  at that date, including shares of  Common
Stock  to be issued upon conversion of  the Preferred Stock immediately prior to
the consummation of this offering. After giving effect to the receipt of the net
proceeds from the sale of  the 3,000,000 shares of  Common Stock offered by  the
Company  at an assumed initial public offering price of $12.00 per share and the
estimated proceeds  from  the sale  of  the Sang-A  Shares,  the pro  forma  net
tangible  book  value  of the  Company  as of  March  31, 1996  would  have been
$51,047,000 or $4.18 per  share. This represents an  immediate increase in  such
pro  forma net tangible book  value of $2.58 per  share to existing stockholders
and an immediate dilution of $7.82 per share to new public investors and Sang-A.
The following table illustrates this per share dilution:
    
 
   
<TABLE>
<S>                                                      <C>        <C>
Assumed initial public offering price..................             $   12.00
  Pro forma net tangible book value before offering....  $    1.60
  Increase attributable to new investors...............       2.58
                                                         ---------
Pro forma net tangible book value after offering.......                  4.18
                                                                    ---------
Dilution to new investors..............................             $    7.82
                                                                    ---------
                                                                    ---------
</TABLE>
    
 
   
    The following table summarizes, on a pro forma basis, as of March 31,  1996,
the  difference between the number of shares  of Common Stock purchased from the
Company, the total consideration  paid and the average  price per share paid  by
existing  stockholders  and  by  the new  investors  purchasing  shares  in this
offering and purchasing the Sang-A Shares at an assumed initial public  offering
price  of  $12.00  per share  and  before deducting  underwriting  discounts and
estimated offering expenses:
    
 
   
<TABLE>
<CAPTION>
                                                  SHARES PURCHASED         TOTAL CONSIDERATION       AVERAGE
                                              ------------------------  -------------------------   PRICE PER
                                                 NUMBER      PERCENT       AMOUNT       PERCENT       SHARE
                                              ------------  ----------  -------------  ----------  -----------
<S>                                           <C>           <C>         <C>            <C>         <C>
Existing stockholders.......................     8,874,456       72.7%  $  41,454,000       50.9%   $    4.67
New investors...............................     3,333,333       27.3      40,000,000       49.1        12.00
                                              ------------      -----   -------------      -----
    Total...................................    12,207,789      100.0%  $  81,454,000      100.0%
                                              ------------      -----   -------------      -----
                                              ------------      -----   -------------      -----
</TABLE>
    
 
   
    The foregoing  table  excludes (i)  78,201  shares of  Common  Stock  issued
subsequent to March 31, 1996 upon exercise of stock options, (ii) 643,480 shares
of  Common Stock  issuable upon  exercise of options  outstanding as  of June 1,
1996, at a  weighted average exercise  price of approximately  $1.22 per  share,
(iii)  an aggregate of 1,556,520 shares  reserved for future grants or purchases
pursuant to the Company's  1996 Equity Incentive  Plan, Employee Stock  Purchase
Plan  and Non-Employee Director Stock Option  Plan, (iv) 118,395 shares issuable
upon exercise of warrants outstanding as of  June 1, 1996 at a weighted  average
exercise  price of $6.65 per  share, and (v) warrants  to purchase 29,750 shares
which become exercisable at  the close of  the offering at  125% of the  initial
public offering price.
    
 
                                       20
<PAGE>
                            SELECTED FINANCIAL DATA
 
   
    The  selected financial data  set forth below should  be read in conjunction
with "Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the Financial Statements and Notes thereto included elsewhere in
this Prospectus. The statement of operations  data for the years ended  December
31,  1993, 1994 and  1995, and the balance  sheet data at  December 31, 1994 and
1995, are  derived  from  the  financial  statements  of  the  Company  included
elsewhere  in this  Prospectus which  have been  audited by  Ernst &  Young LLP,
independent auditors, whose report is included elsewhere in this Prospectus. The
statement of operations data  from inception (April  15, 1992) through  December
31,  1992 and  the balance  sheet data  as of  December 31,  1992 and  1993, are
derived from audited financial statements not included herein. Financial data as
of March 31, 1996 and for the three-month periods ended March 31, 1995 and 1996,
is derived from unaudited financial  statements included elsewhere herein,  and,
in the opinion of management, includes all normal recurring adjustments that the
Company   considers  necessary  for  a  fair  presentation  of  its  results  of
operations.  The  results  of  operations  for  the  interim  periods  are   not
necessarily  indicative of  results to  be expected  for any  future period. The
Company has  not declared  or paid  cash  dividends on  its Common  Stock  since
inception  and does  not intend  to pay  any cash  dividends in  the foreseeable
future.
    
 
   
<TABLE>
<CAPTION>
                                        FOR THE PERIOD FROM                                            THREE MONTHS ENDED
                                          APRIL 15, 1992            YEAR ENDED DECEMBER 31,                MARCH 31,
                                        (DATE OF INCEPTION)   ------------------------------------  ------------------------
                                       TO DECEMBER 31, 1992      1993         1994         1995        1995         1996
                                       ---------------------  -----------  -----------  ----------  -----------  -----------
                                                               (in thousands, except per share data)
<S>                                    <C>                    <C>          <C>          <C>         <C>          <C>
STATEMENTS OF OPERATIONS DATA:
Total revenue........................        $      --          $      --    $      --   $   1,707    $      --    $     188
Operating expenses:
  Research and development...........              320              2,073        4,216      10,220        3,088        3,044
  General and administrative.........              470              1,874        2,493       3,252          701        1,063
                                                 -----        -----------  -----------  ----------  -----------  -----------
    Total operating expenses.........              790              3,947        6,709      13,472        3,789        4,107
                                                 -----        -----------  -----------  ----------  -----------  -----------
Loss from operations.................             (790)            (3,947)      (6,709)    (11,765)      (3,789)      (3,919)
                                                 -----        -----------  -----------  ----------  -----------  -----------
Interest income, net of interest
 expense.............................               37                175          207         362           32          183
                                                 -----        -----------  -----------  ----------  -----------  -----------
Net loss.............................        $    (753)         $  (3,772)   $  (6,502)  $ (11,403)   $  (3,757)   $  (3,736)
                                                 -----        -----------  -----------  ----------  -----------  -----------
                                                 -----        -----------  -----------  ----------  -----------  -----------
Pro forma net loss per share (1).....                           $   (0.56)   $   (0.73)  $   (1.24)   $   (0.41)   $   (0.41)
                                                              -----------  -----------  ----------  -----------  -----------
                                                              -----------  -----------  ----------  -----------  -----------
Shares used in computing pro forma
 net loss per share (1)..............                               6,696        8,948       9,183        9,062        9,223
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                                                               DECEMBER 31,                    MARCH 31,
                                                             ------------------------------------------------  ----------
                                                                 1992         1993        1994        1995        1996
                                                             ------------  ----------  ----------  ----------  ----------
                                                                              (in thousands)
<S>                                                          <C>           <C>         <C>         <C>         <C>
BALANCE SHEET DATA:
Cash, cash equivalents and short-term investments..........     $   1,492   $  12,410   $   6,449   $  17,819   $  14,494
Working capital............................................         1,355      12,155       5,877      16,775      12,804
Total assets...............................................         1,901      13,206       7,789      19,878      17,275
Capital lease obligations, noncurrent......................            --          --        (750)       (618)       (545)
Deferred compensation (2)..................................            --          --          --         180         938
Accumulated deficit........................................          (753)     (4,525)    (11,060)    (22,444)    (26,192)
Total stockholders' equity.................................         1,722      12,893       6,362      17,537      14,167
</TABLE>
    
 
- --------------
(1) See Note 1 of Notes to Financial Statements for an explanation of the method
    used to determine the number of shares  used to compute pro forma per  share
    amounts.
 
   
(2)  In  May  1996,  the Company  recorded  approximately  $463,000  of deferred
    compensation related to  grants of  employee stock  options. See  Note 7  of
    Notes to Financial Statements.
    
 
                                       21
<PAGE>
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
   
    The  following Management's  Discussion and Analysis  of Financial Condition
and Results  of Operations  contains  forward-looking statements  which  involve
risks  and uncertainties. The  Company's actual results  could differ materially
from those  anticipated  in these  forward-looking  statements as  a  result  of
certain factors, including those set forth under "Risk Factors" and elsewhere in
this Prospectus.
    
 
OVERVIEW
 
   
    Since  its inception in April 1992,  Aviron has devoted substantially all of
its resources to its research and development programs. To date, Aviron has  not
generated any revenues from the sale of products and does not expect to generate
any  such revenues for  at least several  years, if at  all. Aviron has incurred
cumulative net losses of approximately $26.2  million as of March 31, 1996,  and
it expects to incur increasing operating losses for a number of years.
    
 
    Aviron  has financed its operations through proceeds from private placements
of  Preferred  Stock,  revenue  from  its  collaborative  agreements,  including
reimbursement   of  certain  of  Aviron's  research  and  development  expenses,
equipment lease  financing and  investment income  earned on  cash balances  and
short-term investments.
 
   
    The  Company expects its  research and development  expenditures to increase
substantially over the next  several years as the  Company expands its  research
and development efforts and preclinical testing and clinical trials with respect
to certain of its programs. In addition, general and administrative expenses are
expected  to  continue to  increase as  the Company  expands its  operations and
incurs the additional expenses associated with operating as a public company.
    
 
   
    In October 1995,  the Company  signed an agreement  with SmithKline  Beecham
defining  a  collaboration  on the  Company's  EBV vaccine  technology  (the "SB
Agreement"). Under the terms of the SB Agreement, the Company granted SmithKline
Beecham an exclusive  license to  produce, use  and sell  non-live EBV  vaccines
incorporating  the Company's technology for prophylactic and therapeutic uses on
a worldwide basis,  except in  South and  North Korea  (together, "Korea").  The
Company  has retained the right to co-distribute a monovalent formulation of the
vaccine in certain markets in the  United States and to have SmithKline  Beecham
supply  such  vaccine.  SmithKline  Beecham  has  agreed  to  fund  research and
development at the  Company related  to the  EBV vaccine,  in specified  minimum
amounts, during the first two years of the SB Agreement. SmithKline Beecham made
an initial upfront payment to the Company and agreed to make additional payments
upon  the achievement of certain product  development milestones. The Company is
entitled to royalties from SmithKline Beecham based on net sales of the vaccine.
No assurance can be given, however, that the Company will receive any additional
payments from SmithKline Beecham or  that SmithKline Beecham will not  terminate
its agreement with the Company. See "Business -- Collaborative Agreements."
    
 
   
    In  May 1995, the  Company entered into a  Development and License Agreement
with Sang-A.  The  Company granted  to  Sang-A exclusive  clinical  development,
manufacturing  and marketing rights in Korea for specified products developed by
Aviron, including vaccines  for influenza (cold  adapted and recombinant),  EBV,
CMV,  HSV-2 and RSV. However, the Company  is under no obligation to develop any
product. Sang-A  also will  make  payments to  the  Company upon  the  Company's
meeting  certain regulatory milestones for each product  in Korea and will pay a
royalty to the Company on net sales of such products in Korea. No assurance  can
be  given, however, that  the Company will  receive any payments  from Sang-A or
that Sang-A will not terminate its agreement with the Company. See "Business  --
Collaborative Agreements."
    
 
   
    The  Company currently  is evaluating the  costs and  benefits of developing
internal   manufacturing   capabilities   or   contracting   with    third-party
manufacturers.  The Company presently  is funding the  construction of its pilot
manufacturing facility through a capital lease  line of credit, however, if  the
Company decides to establish its own commercial-scale manufacturing facility, it
would require a significant amount of funds. See "Business -- Manufacturing."
    
 
                                       22
<PAGE>
   
    The  Company's business is  subject to significant  risks, including but not
limited to the risks inherent in its research and development efforts, including
preclinical testing  and clinical  trials,  uncertainties associated  both  with
obtaining  and enforcing its patents  and with the patent  rights of others, the
lengthy, expensive  and  uncertain  process  of  seeking  regulatory  approvals,
uncertainties regarding government reforms and product pricing and reimbursement
levels,  technological change  and competition,  manufacturing uncertainties and
dependence on third  parties. Even  if the Company's  product candidates  appear
promising  at an early stage  of development, they may  not reach the market for
numerous reasons. Such reasons include the possibilities that the products  will
be  found unsafe  or ineffective  during clinical  trials, will  fail to receive
necessary regulatory  approvals, will  be difficult  to manufacture  on a  large
scale,   will   be   uneconomical  to   market   or  will   be   precluded  from
commercialization by proprietary rights of third parties.
    
 
RESULTS OF OPERATIONS
 
   
  THREE MONTHS ENDED MARCH 31, 1996 AND 1995
    
 
   
    REVENUES
    
 
   
    Total revenue for the three months ended March 31, 1996 was $188,000, and no
revenue was earned for  the three months  ended March 31,  1995. Revenue in  the
three  months ended March 31, 1996 resulted primarily from the Company's license
and  development   agreement  with   SmithKline   Beecham.  See   "Business   --
Collaborative Agreements -- SmithKline Beecham Biologicals S.A."
    
 
   
    OPERATING EXPENSES
    
 
   
    Research  and development  expenses were $3.0  million for  the three months
ended March 31, 1996 and $3.1 million for the three months ended March 31, 1995.
Included in research and development expenses  for the three months ended  March
31,  1995 is a  one-time charge of  $1.6 million relating  to Aviron's agreement
with the University of Michigan (see  Note 2 of Notes to Financial  Statements).
Without  the one-time charge,  research and development  expenses increased 103%
between the three  months ended March  31, 1996 and  1995. These increases  were
primarily due to increases in research and development staffing, licensing fees,
expenses associated with clinical trials of the Company's cold adapted influenza
vaccine and preclinical testing associated with other programs.
    
 
   
    General  and administrative  expenses increased 52%  to $1.1  million in the
three months ended March 31, 1996 from $701,000 in the three months ended  March
31,  1995.  These  increases were  incurred  to support  the  Company's expanded
research and development efforts and facilities, patent and legal expenses,  and
corporate development activities.
    
 
   
    NET INTEREST INCOME
    
 
   
    The  Company's net interest income increased to $183,000 in the three months
ended March 31, 1996, from $32,000 in the three months ended March 31, 1995. The
increase reflects  the effect  of  the Comany's  higher  average cash  and  cash
equivalents and short-term investment balances.
    
 
  YEARS ENDED DECEMBER 31, 1995 AND 1994
 
    REVENUES
 
    Total  revenue for 1995 was  $1.7 million, and no  revenue was earned in the
year ended  December 31,  1994. Revenue  in  the year  ended December  31,  1995
resulted  primarily from  the Company's  license and  development agreement with
SmithKline Beecham.  See "Business  --  Collaborative Agreements  --  SmithKline
Beecham Biologicals S.A."
 
    OPERATING EXPENSES
 
   
    Research  and development  expenses increased 142%  to $10.2  million in the
year ended December 31, 1995  from $4.2 million in  the year ended December  31,
1994.   These  increases  were  primarily  due  to  increases  in  research  and
development staffing, licensing fees (including the one-time charge relating  to
Aviron's  agreement  with  the  University  of  Michigan  discussed  above), and
expenses associated primarily with clinical trials of its cold adapted influenza
vaccine and  preclinical  testing  associated  with  the  herpes  simplex  virus
program.  General and administrative  expenses increased 30%  to $3.3 million in
the year ended December 31, 1995 from
    
 
                                       23
<PAGE>
$2.5 million in the year ended December 31, 1994. These increases were  incurred
to   support  the  Company's  expanded  research  and  development  efforts  and
facilities, patent and legal expenses, and corporate development activities.
 
    NET INTEREST INCOME
 
    The Company's net  interest income  increased 75%  to $362,000  in the  year
ended  December 31, 1995, from $207,000 in the year ended December 31, 1994. The
increase in 1995 reflects  the effect of the  Company's higher average cash  and
cash  equivalents  and  short-term  investment  balances,  offset  by  increased
interest expense related to capital lease obligations.
 
  YEARS ENDED DECEMBER 31, 1994 AND 1993
 
    OPERATING EXPENSES
 
    Research and development expenses increased 103% to $4.2 million in the year
ended December 31, 1994, from $2.1 million in the year ended December 31,  1993.
These  increases were  primarily due  to increases  in research  and development
staffing and preclinical testing. General and administrative expenses  increased
33%  from $2.5 million in the year ended December 31, 1994, from $1.9 million in
the year ended December 31, 1993.  These increases were incurred to support  the
Company's  expanded research and  development efforts and  facilities and patent
and legal expenses.
 
    NET INTEREST INCOME
 
    The Company's net  interest income  increased 18%  to $207,000  in the  year
ended  December 31, 1994, from $175,000 in the year ended December 31, 1993. The
increase reflected the  effect of  the Company's  higher average  cash and  cash
equivalents  and  short-term  investment balances,  offset  by  interest expense
related to capital lease obligations in 1994.
 
   
  NET OPERATING LOSS CARRYFORWARD
    
 
    As of  December 31,  1995, the  Company  had a  federal net  operating  loss
carryforward  of approximately $20.0 million  available to offset future taxable
income, if any. The net operating loss carryforward will expire at various dates
beginning from  2007 through  2010,  if not  utilized.  Utilization of  the  net
operating losses and credits may be subject to substantial annual limitation due
to the "change in ownership" provisions of the Internal Revenue Code of 1986 and
similar  state provisions. The annual limitation may result in the expiration of
net operating losses  and credits  before utilization. See  Note 8  of Notes  to
Financial Statements.
 
LIQUIDITY AND CAPITAL RESOURCES
 
   
    Aviron  had cash, cash  equivalents and short-term  investments at March 31,
1996 of approximately $14.5 million. In order to preserve principal and maintain
liquidity,  the  Company's  funds  are   invested  in  United  States   Treasury
obligations,   highly-rated   corporate   obligations   and   other   short-term
investments.
    
 
   
    The Company has  financed its operations  since inception primarily  through
private  placements of Preferred Stock. Through  March 31, 1996, the Company had
raised approximately $38.4  million from  such sales net  of offering  expenses.
Cash  used in operations was  $3.4 million, $6.1 million,  $8.9 million and $3.0
million in 1993, 1994,  1995 and the first  quarter of 1996, respectively.  Cash
expended  for  capital  additions  and  to  repay  lease  financing arrangements
amounted to approximately  $593,000, $472,000,  $622,000 and  $659,000 in  1993,
1994  and 1995 and the first quarter  of 1996, respectively. The Company expects
expenditures for capital  additions will  increase in 1996  as a  result of  the
construction of a pilot manufacturing facility. The Company expects expenditures
for  research  and  development,  clinical  trials  and  general  administrative
expenditures will  continue to  increase in  1996 as  the Company  develops  its
products and expands its clinical trials.
    
 
   
    The  Company anticipates that  the proceeds of  this offering, together with
the interest  thereon and  existing capital  resources, revenues  from  existing
collaborations,  cash equivalents and short-term  investments, will enable it to
maintain its current and planned operations at least through 1997. The Company's
future cash requirements  will depend on  numerous factors, including  continued
scientific  progress in the research and development of the Company's technology
and vaccine programs, the size and complexity of these programs, the ability  of
the  Company to establish and maintain collaborative arrangements, progress with
preclinical
    
 
                                       24
<PAGE>
testing and clinical trials, the time and costs involved in obtaining regulatory
approvals, the cost involved in preparing, filing, prosecuting, maintaining  and
enforcing  patent claims, and product  commercialization activities. The Company
is seeking additional collaborative agreements  with corporate partners and  may
seek  access to the public or private equity markets. There can be no assurance,
however, that any such agreements will be entered into or that they will  reduce
the Company's funding requirements or that additional funding will be available.
The  Company expects that additional equity  or debt financings will be required
to fund  its operations.  There can  be no  assurance that  such funds  will  be
available  on favorable terms, if  at all. If adequate  funds are not available,
the Company may be required to delay,  reduce the scope of, or eliminate one  or
more  of  its  research  or  development programs  or  to  obtain  funds through
collaborative agreements with others that may require the Company to  relinquish
rights  to certain of its technologies,  product candidates or products that the
Company would otherwise  seek to  develop or commercialize  itself, which  would
materially  adversely  affect the  Company's  business, financial  condition and
results of operations.
 
                                       25
<PAGE>
                                    BUSINESS
 
   
    The  following  Business section  contains forward-looking  statements which
involve risks  and  uncertainties. The  Company's  actual results  could  differ
materially  from  those anticipated  in  these forward-looking  statements  as a
result of certain factors,  including those set forth  under "Risk Factors"  and
elsewhere in this Prospectus.
    
 
OVERVIEW
 
   
    Aviron  is  a  biopharmaceutical  company  whose  strategy  is  to  focus on
prevention of  disease.  The  Company's  goal  is to  become  a  leader  in  the
discovery,  development, manufacture and marketing  of live virus vaccines which
are sufficiently cost effective  to justify their  use in immunization  programs
targeting  the  general  population.  Live virus  vaccines,  such  as  those for
smallpox, polio, measles, mumps and rubella,  have had a long record of  success
in  preventing, and in some cases eliminating, disease. The Company currently is
analyzing data from Phase I and Phase II clinical trials in children and  adults
of  its  live cold  adapted intranasal  vaccine for  influenza. The  Company has
recently in-licensed a live  intranasal vaccine for  Parainfluenza Virus Type  3
("PIV-3")  which has been  tested by others  in Phase I/II  clinical trials. The
Company also  is  developing  a  vaccine  for  Epstein-Barr  virus  ("EBV").  In
addition,  Aviron is using its  proprietary "Rational Vaccine Design" technology
to discover  new  live virus  vaccines.  Rational Vaccine  Design  involves  the
deletion  or modification of  virulence proteins, changes  to the virus' genetic
control signals to  slow down  its replication,  or addition  of information  to
enhance  the virus'  stimulation of the  immune system. The  Company is applying
this technology to develop candidates for the prevention of influenza in elderly
persons  and  diseases  caused   by  Cytomegalovirus  ("CMV"),  Herpes   Simplex
Virus-Type 2 ("HSV-2") and Respiratory Syncytial Virus ("RSV").
    
 
BACKGROUND
 
  PREVENTION TECHNOLOGY IN THE ERA OF MANAGED CARE AND COST CONTAINMENT
 
   
    Market-based  changes  already underway  in  the United  States  health care
system are dramatically altering prospects for technologies which can be used to
manage disease or lower the cost of  health care for patients in managed  health
plans.  Medical cost-containment efforts and the reorganization of United States
health care  delivery  into managed  care  systems  are changing  the  basis  of
competition   for  producers   of  health  care   products.  Health  maintenance
organization enrollment was  approximately 54  million in the  United States  in
1995  and is growing rapidly. Decision makers  in the United States, such as HMO
medical  directors,  clinical   practice  committees,   and  government   health
authorities,  are  increasingly evaluating  whether preventive  technologies are
more cost  effective than  treating disease  once it  is present.  For  example,
vaccinations  are widely  used by managed  care organizations  and in government
programs. In determining whether to use an FDA-approved vaccine, decision makers
consider  whether  it  has  been  recommended  by  the  Advisory  Committee   on
Immunization Practices (the "ACIP") of the CDC and whether it is cost effective.
    
 
    Health  care  cost  containment efforts  are  also  evident in  many  of the
developed economies outside the United  States. These efforts include  physician
budgets  in Germany  and general practice  schemes in the  United Kingdom, where
doctors are given responsibility for the cost of their patients' overall care.
 
  THE IMMUNE SYSTEM AND VACCINES
 
   
    Infections occur  when  a  pathogenic  microorganism, such  as  a  virus  or
bacterium, invades body tissues and begins to replicate. The human immune system
responds  with a battery of resources to  contain and eliminate this threat. The
process begins when specialized cells recognize that molecules on the surface of
invading pathogens  are  foreign (antigens).  Immune  responses to  contain  and
eliminate the threat include:
    
 
    - ANTIBODIES:  Antigens  stimulate  the immune  system  to  produce specific
      molecules  (antibodies)  which  bind  to  and  neutralize  the  virus   or
      bacterium.
 
    - CELL-MEDIATED  RESPONSE: An effective immune response typically also leads
      to  the  multiplication  of  specific  types  of  white  blood  cells   (a
      cell-mediated  response) which have the ability to inactivate the pathogen
      or to destroy infected cells, thereby limiting replication of the virus or
      bacterium.
 
                                       26
<PAGE>
   
    - MUCOSAL  IMMUNITY:  In   addition  to  circulating   antibodies  and   the
      cell-mediated  response, antibodies are produced  in the mucous membranes,
      such as  those  which  line  the nose  and  throat.  Mucosal  immunity  is
      important  in  protecting against  pathogens  which cause  disease  in the
      respiratory, gastrointestinal and  genitourinary systems,  or which  enter
      the body through these portals.
    
 
   
    Vaccines  are designed to stimulate a  person's immune system through one or
more of the above mechanisms to induce memory of specific antigens prior to  the
invasion  of a  pathogen. This memory  primes the  immune system so  that it can
inactivate the  specific pathogen  if encountered  again. This  may be  achieved
through  one of several techniques, including  introduction of a live attenuated
(weakened)  virus  or  bacterium,  administration  of  an  antigen  fragment  (a
subunit), or administration of an inactivated (killed) virus.
    
 
  HISTORY OF VACCINES
 
   
    The  first successful vaccine  against an infectious  disease was created by
Edward Jenner who, in 1796, demonstrated that introduction of infected  material
from  a diseased cow  could be used  to protect humans  from the deadly smallpox
virus. Smallpox  vaccination programs  based  on this  live virus  vaccine  were
gradually  adopted by industrialized countries, and a concerted global effort by
public health authorities in this century succeeded in eradicating smallpox from
the human population in the 1970s.
    
 
   
    Vaccines against  two life-threatening  bacterial diseases,  diphtheria  and
tetanus,  came  into  use  early  in this  century.  These  vaccines  consist of
bacterial toxins  which  have  been  chemically  inactivated.  These  are  often
administered  in combination with an  inactivated pertussis bacterium vaccine to
prevent whooping cough.  This combination is  known as the  "DTP" vaccine.  Just
prior  to World War  II, a live  attenuated virus vaccine  was developed against
yellow  fever,  used  primarily  in  protecting  military  personnel  and  those
traveling  to areas where  this disease is  endemic. In the  years after the war
following several  widespread  polio epidemics,  Jonas  Salk created  the  first
successful  polio vaccine  by growing  the wild-type  virus and  inactivating it
before injection. Salk's vaccine was introduced into widespread use in the early
1950s, but was supplanted in the United  States and many other countries by  the
orally  administered  live attenuated  polio virus  vaccine developed  by Albert
Sabin and first  introduced in  1961. In the  1960s and  1970s, live  attenuated
virus  vaccines  against  measles,  mumps  and  rubella  (German  measles)  were
successfully developed and recommended by the  ACIP to be included in  childhood
immunization programs.
    
 
   
    After  a period of almost two decades during which no new vaccines came into
widespread use, a  genetically engineered  subunit vaccine for  hepatitis B  was
introduced  in the mid-1980s  and is now part  of the ACIP-recommended childhood
immunization program. In 1990, a vaccine for bacterial meningitis was also added
to this program.  Two inactivated vaccines  against the hepatitis  A virus  were
approved  in  the  United  States in  1995  and  1996. In  1995,  the  ACIP also
recommended that children be vaccinated against  chicken pox using a live  virus
vaccine recently approved by the FDA.
    
 
    Current  challenges  for  vaccine  innovation  include  providing  effective
protection against  the major  infectious  diseases for  which no  vaccines  are
currently available and improving on current vaccines to achieve higher efficacy
or greater ease of administration.
 
  TYPES OF VACCINES
 
    LIVE VIRUS VACCINES
 
   
    Live  virus vaccines expose the  immune system to an  attenuated form of the
virus which is sufficiently infectious to stimulate a lasting immune response to
the natural (or wild-type) virus.  All of the live  virus vaccines in use  today
are  strains  derived from  natural infections  of  humans. Attenuation  of live
viruses, including polio, yellow fever, measles, mumps and rubella, and  chicken
pox  vaccines  was  accomplished  by  "passaging,"  or  propagating,  the  virus
repeatedly in non-human cells. As a result of this process, viruses may  acquire
mutations  that decrease the  ability of the  virus to cause  disease in humans.
After an  arbitrary  number  of  passages, the  mutated  strain  is  tested  for
attenuation  in  animal models,  if available,  or  directly in  human subjects.
Following assessment  of safety  and immunogenicity  (stimulation of  an  immune
response) in a limited number of human subjects, larger-scale trials are used to
demonstrate efficacy in preventing naturally acquired infections.
    
 
                                       27
<PAGE>
   
    Live   virus  vaccines  mimic  the  natural  disease-causing  infection  and
therefore may activate the same protective mechanisms of the human immune system
as the  disease itself.  This  process results  in  a balanced  immune  response
activating  all  parts  of  the  immune  system  including  systemic  and  local
antibodies as well  as cell-mediated  immunity. As  a result,  live viruses  are
often  considered to be more effective than other types of vaccines in providing
immunity to natural variations in the wild-type viruses which cause disease. For
example, the live polio vaccine is believed to be more effective in  eliminating
wild-type  polio  virus  than inactivated  polio  vaccines. The  basis  of these
advantages is  that live  vaccines  typically present  all  of the  surface  and
internal  antigens associated with the natural pathogen. Live virus vaccines may
also  be  easier  to  administer  through  their  natural  route  of  infection,
intranasally or orally, as in the case of the oral polio vaccine.
    
 
   
    However,  an attenuated live vaccine  could cause disease resembling natural
infection, as  might  occur  in people  with  an  immune system  impaired  by  a
congenital  disease,  HIV  infection  or  drug  treatment  for  cancer  or organ
transplantation. To date, the live virus vaccines in widespread use rarely  have
been  associated with  significant adverse events.  For example,  the 19 million
doses of  live attenuated  polio  vaccine administered  annually in  the  United
States  are thought  to be responsible  for only  eight to 10  cases of clinical
polio per  year. To  further  reduce the  number of  these  cases, the  ACIP  is
recommending  that the inactivated polio vaccine be given for the initial infant
dose, now  that wild-type  polio has  been virtually  eradicated in  the  United
States.
    
 
    Live  virus strains can change  as they replicate in  human hosts, and it is
possible that a  vaccine virus  could revert to  the wild-type  characteristics.
This  reversion potential  is a  small but  recognized problem  for some  of the
current live  vaccines,  including polio.  Finally,  there are  two  theoretical
concerns  regarding live attenuated viruses.  First, an attenuated vaccine virus
may exchange genetic information with wild-type strains after immunization, with
the resulting strain being more dangerous than either alone. Second, the DNA  of
a  live virus  vaccine could  integrate into  the genome  of the  host and cause
cancer or other problems in the future.
 
    INACTIVATED AND SUBUNIT VIRUS VACCINES
 
    Inactivated virus vaccines are produced by killing a virus using  chemicals.
Some  vaccines,  such  as the  hepatitis  A  vaccine, are  based  on  the whole,
inactivated  virus.  Other  vaccines  are  the  result  of  various  degrees  of
purification  to  concentrate  certain  surface  glycoproteins  (subunits)  most
responsible for producing  immunity. A different  approach is used  to make  the
current  hepatitis B vaccine, the  first successful recombinant subunit vaccine.
For this  vaccine, the  tools of  molecular biology  were applied  to clone  and
express  the  dominant  hepatitis  surface glycoprotein  in  a  yeast production
system. Inactivated and  subunit vaccines offer  the advantage of  little or  no
risk  of  infection  from  the  vaccine  itself,  assuming  the  virus  has been
adequately  inactivated.  Good  manufacturing   techniques  also  minimize   the
possibility  of contamination with other viruses or fragments of DNA which could
integrate into the recipient's genes.
 
   
    The principle  disadvantage of  inactivated and  subunit vaccines  for  many
viruses has been a lack of success in creating protective immunity. A successful
subunit  vaccine requires knowledge  of which specific  antigens are responsible
for  providing  protection.  Subunit   and  inactivated  vaccines  may   produce
reasonable  levels of  circulating antibodies,  but are  less able  to stimulate
antibodies in  the mucosal  sites of  viral entry,  such as  the lining  of  the
respiratory, gastrointestinal or genitourinary tracts. To improve stimulation of
the  cellular components  of the  immune system,  adjuvants (non-specific immune
stimulants) are typically added  to inactivated or  subunit vaccines. Only  alum
(an  aluminum salt preparation) is approved for use as an adjuvant in the United
States. Several  new adjuvants  are in  clinical testing  and show  promise  for
boosting  the  immune  response  to subunit  antigens.  The  mechanism  by which
adjuvants work is still poorly understood, so each vaccine-adjuvant  combination
must  be evaluated in  a trial and  error process in  animal models and clinical
trials. Finally, certain inactivated vaccines in clinical trials left recipients
more vulnerable  to  disease after  vaccination,  due to  an  unbalanced  immune
response.  For example, in  trials of experimental  inactivated vaccines against
RSV and measles, some  children were shown to  experience more severe,  atypical
disease   when  they  later  acquired  the  natural  viral  infection  following
vaccination.
    
 
    EMERGING VACCINE TECHNOLOGIES
 
   
    Several  companies  and  academic  scientists  have  reported  that   direct
injection  of DNA  encoding viral  antigens can be  used to  stimulate an immune
response.  Although   at  an   early  stage,   this  approach   shows   promise.
    
 
                                       28
<PAGE>
However,  it is  not clear  whether the  sustained expression  of viral antigens
obtainable by  this  approach  is  advantageous in  eliciting  a  better  immune
response.  In addition, it  is possible that the  administered DNA may integrate
into the genes of the recipient and cause potential unwanted effects.
 
    Another new technology for  vaccination is based  on genetic engineering  to
modify  one virus  so that  it carries  antigens which  may stimulate  an immune
response to  protect against  other  pathogens. For  example, pox  virus  vector
strains,  related to  the virus  used successfully  to eradicate  smallpox, have
shown usefulness in  protecting dogs and  cats against rabies.  Other pox  virus
vectors  are being evaluated  in experimental models  of human malaria  and in a
hybrid regimen  combining doses  of a  modified live  virus with  a subunit  HIV
vaccine to protect high-risk individuals.
 
AVIRON'S TECHNOLOGY
 
    Aviron's  vaccine programs  are based on  both classical  live virus vaccine
attenuation  techniques  and  the  Company's  proprietary  genetic   engineering
technology.
 
  COLD ADAPTED INFLUENZA TECHNOLOGY
 
    The  Company is applying its expertise in the molecular biology of influenza
to develop  a  live  virus  vaccine  discovered  using  classical  cold-adaption
techniques.  This cold adapted influenza  vaccine technology was first developed
by Dr. H.F. Maassab at the University  of Michigan in 1967. Dr. Maassab  created
attenuated  influenza strains by  propagating the virus  in progressively colder
conditions until these strains had lost the  ability to grow well at human  body
temperature.  The Company  has obtained  exclusive rights  to this  cold adapted
influenza vaccine technology.
 
   
    The cold adapted  influenza vaccine technology  includes the master  strains
for  influenza A and  B, as well  as techniques useful  for updating the vaccine
each year according to recommendations of  the CDC and the FDA. Updated  strains
are made by mating the master strains with recent strains to obtain viruses with
the  attenuated properties of  the cold adapted master  strain and the antigenic
properties of  the current  wild-type  strain. This  process is  called  genetic
reassortment.  After cultured cells  are infected with  two different strains of
virus, the eight RNA  genes of influenza mix  at random in the  cells and it  is
possible  to select  the two  genes for  the antigens  of the  expected epidemic
strain and the six  remaining genes from the  cold adapted master donor  strain.
The  Company has  received the technology  for updating the  cold adapted master
strains from the University  of Michigan and has  extended this approach by  the
introduction  of  Aviron's proprietary  techniques,  including those  of reverse
genetics, which  may facilitate  the  annual process  of creating  a  reassorted
vaccine.
    
 
  RATIONAL VACCINE DESIGN
 
   
    Since  the Company's founding, its core  vaccine discovery strategy has been
to apply genetic engineering techniques to create live attenuated virus  vaccine
candidates   for  targets  where  traditional  discovery  techniques  have  been
inadequate. The Company believes that this "Rational Vaccine Design" approach is
more flexible and systematic than traditional methods of live vaccine  discovery
and is a platform that can be applied to many viral targets and, potentially, to
the  creation  of viruses  used in  gene  therapy and  the treatment  of cancer.
Furthermore, Aviron believes  that a  particular advantage  of Rational  Vaccine
Design  is that engineered viruses can be  designed so that they are less likely
to revert to wild-type characteristics than classically derived vaccines.  Three
ways of implementing this approach are:
    
 
    - DELETING   OR  MODIFYING  SPECIFIC  VIRAL  GENES  WHICH  ENCODE  VIRULENCE
      PROTEINS.  Virulence  proteins   are  viral  components   thought  to   be
      particularly  important in  the mechanism  of disease,  but which  are not
      required for  the  virus  to  replicate  and  stimulate  a  strong  immune
      response. An example of this strategy is the Company's program to create a
      live  attenuated  vaccine against  the  HSV-2 virus  which  causes genital
      herpes. One of the Company's  founders, Dr. Bernard Roizman, discovered  a
      particular  protein important  in the  ability of  HSV-2 to  grow in nerve
      cells. Since  nerve ganglia  are the  reservoir from  which HSV-2  reseeds
      itself  to cause painful skin lesions,  deletion of the gene encoding this
      protein is the basis of the Company's Rational Vaccine Design program  for
      development of a vaccine for this target.
 
    - ALTERING  THE GENETIC  INFORMATION USED  BY THE  VIRUS IN  CONTROLLING ITS
      REPLICATION. An example of this strategy is work by Company scientists  to
      create  live attenuated vaccine candidates  for influenza. Until recently,
      it
 
                                       29
<PAGE>
   
      was impossible  to  genetically  engineer  vaccine  strains  of  influenza
      because  influenza genes are  composed of negative-strand  RNA rather than
      DNA or  positive-strand  RNA.  Dr.  Peter Palese,  one  of  the  Company's
      founders, discovered how to create recombinant negative-strand RNA viruses
      using  reverse  genetics. Company  scientists  have employed  this reverse
      genetics technology  to  engineer  mutations  into  a  gene  used  by  the
      influenza  virus  to  make copies  of  itself. The  resulting  strains are
      attenuated in animal models and at least one strain has been identified as
      a potential candidate for clinical trials.
    
 
   
    - ADDING ANTIGENIC INFORMATION DISPLAYED BY THE VACCINE VIRUS. An example of
      this strategy  is  the  Company's  approach to  the  creation  of  a  live
      attenuated  CMV vaccine, which begins with  a vaccine candidate thought to
      be over-attenuated and  thus insufficiently  immunogenic. Aviron  recently
      discovered  genes for certain antigen  structures present in wild-type CMV
      viruses. These genes are being engineered into an over-attenuated  vaccine
      candidate  to create a  potentially more immunogenic  vaccine. The Company
      believes this  technique  of  adding antigen  structures  may  enable  the
      Company  to create combination  vaccines expressing antigens  of more than
      one virus in a single vaccine strain.
    
 
BUSINESS STRATEGY
 
    Aviron's objective  is to  become a  leader in  the discovery,  development,
manufacture  and marketing  of live virus  vaccines which  are sufficiently cost
effective to justify their  use in immunization  programs targeting the  general
population. The Company's strategy is to:
 
    ADDRESS    INFECTIOUS   DISEASES   WHICH   MERIT   WIDESPREAD   IMMUNIZATION
PROGRAMS.  The concept of universal immunization is well established for certain
infectious diseases where  safe and  effective vaccines  are already  available,
including  immunization against pathogens such as polio, measles, mumps, rubella
and hepatitis B. For each of its potential products, the Company's objective  is
to  produce vaccine  strains which are  sufficiently safe and  cost effective to
obtain official recommendations for universal use in childhood vaccine  regimens
or, in the case of influenza, annual use in the general population.
 
    APPLY   RATIONAL   VACCINE   DESIGN   TECHNOLOGY  TO   A   RANGE   OF  VIRAL
TARGETS.  Aviron believes that its proprietary genetic engineering  technologies
may  be  used to  create  live attenuated  vaccines for  a  wide range  of viral
targets, such as viruses related to influenza and herpes viruses.
 
   
    SELECT PROGRAMS AND MARKET VACCINES BASED ON PHARMACOECONOMIC DATA.   Public
health  agencies and  managed care systems  are increasingly  concerned with the
economic impact of potential new mandates for vaccines. In setting its  internal
product  development priorities, the Company considers the costs of implementing
widespread vaccine programs based on its products in relation to potential  cost
savings to the government and managed health care systems and intends to perform
rigorous cost-effectiveness analyses on its products.
    
 
   
    IN-LICENSE  PROMISING  VACCINE  TECHNOLOGY.   Aviron  evaluates in-licensing
opportunities and intends to  add programs which  complement the Company's  core
technologies  and  capabilities.  For example,  the  Company  obtained exclusive
rights to the cold adapted influenza  vaccine technology from the University  of
Michigan and the NIH, and to the PIV-3 vaccine from the NIH.
    
 
   
    ESTABLISH   COLLABORATIVE  ARRANGEMENTS   TO  ENHANCE   PRODUCT  DEVELOPMENT
EFFORTS.  Aviron intends to enter into collaborative arrangements to gain access
to specific technologies and skills which may accelerate product development and
provide additional financial resources to  support its research and  development
and  commercialization efforts, particularly  outside of the  United States. The
Company has entered into collaborative arrangements with SmithKline Beecham  for
development  of  an  EBV vaccine  and  with  Sang-A for  certain  rights  to the
Company's products in Korea.
    
 
                                       30
<PAGE>
VACCINE PRODUCTS UNDER DEVELOPMENT
 
    The following  table summarizes  Aviron's most  advanced potential  products
under  research  and development.  This table  is qualified  in its  entirety by
reference  to  the  more  detailed  descriptions  appearing  elsewhere  in  this
Prospectus.
 
   
<TABLE>
<CAPTION>
                                                                                                  COMMERCIAL
      PROGRAM                       VACCINE TYPE                              STATUS (1)          RIGHTS (2)
      ----------------------------  ----------------------------------------  ------------------  --------------
      <S>                           <C>                                       <C>                 <C>
      Influenza
 
        Adults                      Cold adapted live virus                   Phase II Conducted  Aviron
 
        Children                    Cold adapted live virus                   Phase I/II          Aviron
                                                                              Conducted
 
        Elderly                     Cold adapted live virus                   Clinical Trials     Aviron
                                     (co-administered with inactivated        Planned
                                     vaccine)
                                    Genetically engineered live virus         Preclinical         Aviron
 
      Parainfluenza Virus Type 3    Bovine live virus                         IND Planned         Aviron
 
      Epstein-Barr Virus            Recombinant subunit glycoprotein          Preclinical         SmithKline
                                                                                                  Beecham/
                                                                                                  Aviron (3)
 
      Cytomegalovirus               Genetically engineered live virus         Preclinical         Aviron
 
      Herpes Simplex Virus-Type 2   Genetically engineered live virus         Preclinical         Aviron
 
      Respiratory Syncytial Virus   Genetically engineered live virus         Research            Aviron
      ----------------
      (1)     "Phase  II   Conducted"  means  Aviron   is  evaluating  data   from  multi-center,  double-blind,
           placebo-controlled clinical trials for safety, immunogenicity and efficacy and the Company intends to
           proceed directly to Phase III clinical trials.
          "Phase  I/II   Conducted"  means   Aviron  is   evaluating  data   from  multi-center,   double-blind,
          placebo-controlled  clinical trials for safety and immunogenicity  in a limited patient population and
          the Company intends to proceed directly to Phase III clinical trials.
          "Clinical Trials Planned" indicates  that no clinical  trials have been conducted  by Aviron to  date.
          Aviron intends to discuss with the FDA its plans to proceed directly to Phase III clinical trials.
          "Preclinical" includes assessment of specific vaccine candidates for growth properties in cell culture
          and for attenuation and immunogenicity in animal models.
          "IND  Planned" indicates that no clinical trials have been conducted by Aviron to date. The Company is
          evaluating the timing and level of commitment for Aviron-sponsored clinical trials.
          "Research" includes  identification of  vaccine  candidates and  approaches  to create  new  candidate
          strains. See "Government Regulation."
      (2)   Commercial rights for Korea  for most listed programs are  licensed to Sang-A. See "-- Collaborative
           Agreements."
      (3)  Worldwide rights licensed to SmithKline Beecham; Aviron retains certain United States co-promotion
           rights.
</TABLE>
    
 
                                       31
<PAGE>
INFLUENZA
 
   
    Every year  in mid-  to  late-winter, influenza  spreads across  the  globe,
infecting  an  average  of  approximately  10%  to  20%  of  the  United  States
population. In the  United States,  20 to 50  million cases  of influenza  occur
annually.  Influenza cases  are associated  with symptoms  lasting for  at least
three to five  days, an  average of  approximately three  days of  lost work  or
missed school, and approximately 20,000 deaths each year. Field studies indicate
the attack rate ranges from a low of 10% in persons over age 65 to a high of 37%
in  children  aged one  to 18.  Children are  also a  major factor  in spreading
influenza to  other  population  segments,  including  those  at  high  risk  of
contracting the disease. At the peak of a typical epidemic, reportedly 9% to 22%
of  all  physician  office  visits  are  for  flu-like  symptoms.  Over  90%  of
influenza-related deaths occur  in people over  age 65, but  children under  age
five  and women in the third trimester of  pregnancy are also at higher risk for
serious complications. Several times this  century, influenza has appeared as  a
much more serious pandemic. These major pandemics occur when the influenza virus
undergoes  "antigenic shift"  in which  one influenza  subtype is  replaced by a
different strain  for which  the population  has not  developed antibodies  and,
therefore, for which it is extremely susceptible to infection.
    
 
   
    The  variability of certain components of  the influenza virus requires that
the influenza  vaccine  be modified  annually.  The  CDC and  the  World  Health
Organization (the "WHO") maintain a global network which generates data required
to  select strains  for the  coming influenza  season's vaccine  and monitor the
occurrence of especially severe epidemics. Based on these data, the FDA and  the
CDC  discuss circulating influenza strains which are candidates for inclusion in
the following season's  influenza vaccine.  A similar process  is undertaken  in
Europe  by  the  WHO  and  various  national  authorities.  Currently  available
inactivated influenza vaccines  contain three  strains of  influenza virus  (two
strains  of influenza A and one strain  of influenza B) and are therefore called
trivalent vaccines.  Typically one  or sometimes  two of  the strains  in  these
trivalent  vaccines are recommended for updating annually. Current vaccines have
been variously  reported to  be  60% to  80%  effective in  preventing  illness,
pneumonia, hospitalization and death due to complications from influenza.
    
 
   
    The  ACIP  has  identified  the  principal  target  groups  for  the current
influenza  vaccine   as   those   at  increased   risk   for   influenza-related
complications:  persons age 65  or older, residents  of chronic-care facilities,
adults and children with  chronic disorders of  the pulmonary or  cardiovascular
system,  adults  and children  who have  required  regular medical  follow-up or
hospitalization during the preceding year because of chronic metabolic  diseases
or  immunosuppression, and  children and  teenagers receiving  long-term aspirin
therapy and therefore at risk of  developing Reye's syndrome. The next level  of
priority for vaccination identified by the ACIP includes certain groups, such as
health  care  personnel and  household  members (including  children),  that may
transmit influenza to high-risk persons.  Furthermore, the ACIP recommends  that
physicians  administer influenza vaccine to any  person who wishes to reduce the
chance of becoming ill with influenza.
    
 
   
    The FDA  estimates  that  over  75  million  influenza  vaccine  doses  were
manfactured  for use in  the United States  in 1995. According  to the CDC, over
half of  the 34  million Americans  over age  65 received  the annual  influenza
vaccine for the 1993 influenza season, up from less than approximately 25% a few
years ago. The Company believes that a lower percentage of high-risk individuals
under  age 65 were vaccinated in 1994,  and that the majority of influenza doses
used in the United States are being administered to healthy adults under age 65,
many of whom participate in voluntary work place immunization programs.  Experts
suggest that very few of the 70 million children under age 18 receive the annual
influenza vaccine.
    
 
   
    In  addition  to  the  currently  available  vaccines,  two  oral  drugs are
currently approved  for use  in the  prevention and  treatment of  influenza  A:
amantadine,  which has  been on  the market for  many years,  and rimantidine, a
closely related compound  which produces  fewer side effects.  Both agents  have
been  shown to be effective in reducing  the severity of influenza A disease and
the number of  days of disability,  but are not  effective against influenza  B.
Both  are also recommended for daily use  during the influenza season by certain
high-risk persons for  whom the influenza  vaccine is contraindicated.  However,
there  is a concern that widespread prophylactic  use could lead to emergence of
drug-resistant strains.
    
 
   
    AVIRON'S COLD  ADAPTED  INFLUENZA  VACCINE.   The  Company's  most  advanced
program  is based on the live cold adapted influenza vaccine technology licensed
from the University of  Michigan and on a  Cooperative Research and  Development
Agreement  ("CRADA")  with  the  NIH.  The  cold  adapted  influenza  vaccine is
    
 
                                       32
<PAGE>
   
currently undergoing  extensive clinical  trials  by Aviron  with a  network  of
NIH-sponsored  investigators.  Prior to  Company-initiated  trials, at  least 65
clinical trials  of the  cold  adapted influenza  vaccine technology  have  been
performed  since 1977, involving more than 15,000 volunteers, of whom over 7,000
received the cold adapted influenza vaccine. See "-- Influenza Clinical Trials."
    
 
   
    The Company  intends  to develop  the  cold adapted  influenza  vaccine  for
widespread annual use in children and adults, and for co-administration with the
inactivated  vaccine for improved protection in  the elderly. The quality of the
immune response  induced by  cold adapted  influenza vaccine  differs from  that
induced  by inactivated influenza  vaccines. The cold  adapted influenza vaccine
elicits an  immune response  to multiple  viral proteins  mimicking the  natural
immunobiology  of influenza, whereas  the response to  the classical inactivated
vaccine is directed primarily  to one component of  the virus. Because the  cold
adapted influenza vaccine is delivered as a nasal spray, the Company believes it
would  provide the first practical way to  immunize children on an annual basis.
Children are  an important  target  because, while  the elderly  experience  the
greatest mortality from the annual influenza epidemic, much of the morbidity and
illness  occurs in young children. Children are  also thought to be important in
the spread of influenza in  the population. In addition  to its proposed use  in
physician's  offices,  Aviron believes  that the  nasal  spray delivery  of this
vaccine will enable  it to  be administered  by adults  without special  medical
training,  so that  it will  be practical  to consider  delivery via pharmacies,
schools, day care centers, and possibly in the home.
    
 
   
    Aviron also is  targeting healthy  adults, many  of whom  are being  offered
influenza  prophylaxis by their employer and  who may prefer Aviron's intranasal
administration to injection. The Company believes that many adults who regularly
receive the inactivated influenza vaccine will select the intranasal vaccine  if
given  the choice, and that people who have avoided "flu shots" in the past will
receive a vaccination if the  intranasal alternative is available. In  addition,
the  Company is developing its vaccine for co-administration by nasal spray with
the inactivated influenza vaccine injection  for the elderly. While efficacy  in
the elderly has not been conclusively demonstrated, nursing home studies suggest
that  simultaneous  administration  of  the  intranasal  cold  adapted influenza
vaccine with an  injection of  the inactivated vaccine  offers added  protection
compared  to administration of the inactivated  vaccine alone. Aviron intends to
seek recommendations from the  ACIP and the American  Academy of Pediatrics  for
use of the cold adapted influenza vaccine in the appropriate population.
    
 
   
    The  Company  has completed  enrollment of  259 adults  and 356  children in
multicenter Phase I/II clinical trials designed to show that Aviron's  trivalent
formulation  and nasal spray delivery system  are generally safe, well tolerated
and immunogenic. These studies were followed by a Phase II challenge study in 92
adults. Data  from  these studies  are  under analysis.  Additional  large-scale
clinical  trials are planned for the influenza  seasons of 1996 through 1998. In
addition, the Company intends to  discuss with the FDA  its plans for Phase  III
clinical  trials  to  demonstrate  efficacy of  the  co-administration  with the
inactivated influenza vaccine in  the elderly. No assurances  can be given  that
the Company will commence clinical trials as planned, or that if commenced, such
trials  can be  successfully completed  on a  timely basis,  if at  all. See "--
Clinical Trials."
    
 
   
    AVIRON'S NEXT-GENERATION  GENETICALLY  ENGINEERED INFLUENZA  VACCINE.    The
Company  is using its proprietary reverse genetics technology to engineer future
generations of influenza vaccines which are designed to the needs of various age
groups in the  population. The Company's  first priority is  to develop  strains
which  offer  improved  protection  in the  elderly  compared  to  the currently
available inactivated vaccines. Since most  elderly persons have had  experience
with several influenza infections in their lifetime, pre-existing antibodies may
prevent  the cold adapted virus  from multiplying sufficiently to  be used as an
alternative to the currently available vaccines in the elderly. To address  this
problem,  Aviron  scientists  have  created  new  strains  of  influenza vaccine
candidates which have been evaluated and  shown to be attenuated in ferrets,  an
animal  model for influenza.  Vaccinated animals were  protected from subsequent
challenge with a virulent strain of influenza. Some of the Company's genetically
engineered strains have been found to better replicate in the upper  respiratory
tract  of these animals than the cold adapted influenza vaccine, while retaining
the property of restricted growth in the lower respiratory tract. Work with  the
cold adapted influenza vaccine has shown that these features are associated with
desirable  characteristics  of  attenuation  in  humans.  However,  animal model
results are  not  necessarily  predictive  of results  in  humans.  The  Company
believes that these strains may be more
    
 
                                       33
<PAGE>
immunogenic  than the cold adapted vaccine and, therefore, more suitable for use
as a single-dose vaccine  for the elderly.  No assurance can  be given that  the
Company  will be able to commence or  successfully complete clinical trials on a
timely basis, if at all.
 
   
PARAINFLUENZA VIRUS TYPE 3
    
 
   
    PIV-3 is a common respiratory virus of childhood which causes croup,  cough,
fever  and pneumonia. Every year, primarily during the spring and summer months,
PIV-3 infects infants, children and adults.  In the United States, at least  60%
of  children are infected  by the time they  reach two years of  age, and 80% by
four years of age. These cases  are associated with symptoms lasting from  three
to  eight days and approximately 17,000  hospitalizations per year. Children are
also a major  factor in  introducing PIV-3  infection into  the family  setting.
PIV-3  frequently  reoccurs  and  children  typically  experience  two  to three
infections of decreasing severity. Unlike influenza, PIV-3 undergoes only a very
minor degree of variation in the surface proteins from year to year;  therefore,
a PIV-3 vaccine will not require annual updates.
    
 
   
    Both  serum and nasal  antibodies directed to PIV-3  surface proteins play a
role in protection against PIV-3 disease.  It is thought that protection of  the
lower  respiratory tract from PIV-3 replication  and disease requires high serum
antibody levels, whereas resistance to infection and protection against  disease
in the upper respiratory tract requires mucosal antibodies in the nose. There is
currently  no available vaccine to protect  against PIV-3 infection, and no drug
for treatment of PIV-3 disease.
    
 
   
    AVIRON'S LIVE PARAINFLUENZA VIRUS TYPE 3 VACCINE.  The Company's live  PIV-3
vaccine  program utilizes  bovine PIV-3  ("bPIV-3") vaccine  technology licensed
from the NIH. Use of bPIV-3 as  a vaccine to protect humans against human  PIV-3
strains  is based on the  successful strategy first used  by Jenner for smallpox
vaccination, in  which  an animal  virus  is used  to  protect humans  from  the
analogous  human virus. It is thought that the attenuation of bPIV-3 in primates
is due to mutations sustained throughout its genome during its long evolutionary
adaptation to the bovine host.
    
 
   
    Prior to  the Company's  in-licensing of  the bPIV-3  vaccine, it  had  been
tested in Phase I/II clinical trials in adults, children and infants. In all age
groups,   the  bPIV-3  vaccine  appeared  satisfactorily  attenuated,  safe  and
genetically stable.  Eighty-five percent  of seronegative  children (six  to  60
months  of age) were infected  by the tested dose,  and 61% of bPIV-3 recipients
developed a level  of antibody  to PIV-3 previously  associated with  protection
from disease. The vaccine strain infected 92% of infants younger than six months
of  age, even in the presence  of maternally-derived PIV-3 antibodies. Infection
with the bPIV-3 vaccine stimulated an immune  response to PIV-3 in 42% of  these
young  infants. The Company is evaluating the timing and level of commitment for
Aviron-sponsored Phase II clinical  trials of bPIV-3  using the existing  bPIV-3
vaccine supply produced and tested for the NIAID. There can be no assurance that
this  vaccine supply will be  suitable for clinical trials  or that these or any
additional  clinical  trials  will  be  commenced  or,  if  commenced,  will  be
successful,  or  that  the Company  will  develop successfully  and  receive FDA
approval of its bPIV-3 vaccine.
    
 
   
EPSTEIN-BARR VIRUS
    
 
   
    Epstein-Barr virus,  a herpes  virus that  causes infectious  mononucleosis,
infects  most people at some  point in their lifetime.  Infection at a young age
may  cause  mild   symptoms,  but  the   debilitating  syndrome  of   infectious
mononucleosis  is most  common where  infection first  occurs in  adolescence or
young adulthood via exchange of saliva. Sore throat and swollen neck glands  are
followed  by a period of  fatigue and lethargy which can  last for weeks or even
months. Approximately 10% of  high school and  college students become  infected
with  EBV each  year in  the United States,  of which  half or  more may develop
infectious  mononucleosis.  The   disease  usually  runs   its  course   without
significant  medical  intervention;  however, the  long  duration  of infectious
mononucleosis can be a serious problem for high school and college students  and
workers.  Enlargement  of  the liver  and  spleen  are also  common,  so doctors
typically prohibit  participation  in  athletic activities  to  prevent  serious
injuries. EBV is one of the viruses implicated as a contributing cause of cancer
in  humans, including  Hodgkin's disease,  post-transplant and  other lymphomas,
nasopharyngeal carcinoma (the most common head and neck cancer in large  regions
of Asia) and Burkitt's lymphoma (a significant disease in Africa).
    
 
                                       34
<PAGE>
   
    The  Company is  developing a  subunit vaccine for  EBV based  on the single
surface antigen responsible for most  of the neutralizing antibodies  stimulated
by  EBV infection. Quantities of this  antigen have been expressed, purified and
evaluated in a rabbit model, where preliminary results indicate that the antigen
is immunogenic when combined with an adjuvant. In 1995, the Company entered into
a collaboration with  SmithKline Beecham, whereby  SmithKline Beecham will  fund
the  development  of  Aviron's EBV  vaccine  in exchange  for  certain marketing
rights. See "-- Collaborative Agreements."
    
 
   
CYTOMEGALOVIRUS
    
 
   
    Most people become  infected with CMV,  another member of  the herpes  virus
family,  at some  time in their  life, and  in the United  States 40%  to 60% of
infections occur in  childhood. These infections  are typically asymptomatic  or
result  in mild illness with sore  throat, headache, fatigue and swollen glands.
CMV  also   can   cause   an  infectious   mononucleosis   syndrome   clinically
indistinguishable  from  that associated  with EBV  infection. More  serious CMV
disease is also  often associated  with a weakened  immune system,  as is  often
found  in AIDS, cancer and transplant patients, which may be due to reactivation
of CMV acquired early in life or a primary infection. In addition, if a woman is
first exposed to  this virus  early in  pregnancy, the  resulting infection  can
cause  serious fetal abnormalities.  Approximately 40,000 infants  in the United
States are infected each  year, resulting in varying  levels of brain damage  or
deafness  in  over 10%  of  these infants.  Congenital  CMV syndrome  results in
significant expenditures for neonatal intensive care.
    
 
   
    No vaccine currently is available for CMV. Antibodies from persons with high
levels of  immunity are  available  in the  form  of hyperimmune  globulins  for
certain  high-risk patients,  but use  of these  products can  be costly  and of
limited efficacy. The Company believes  that widespread vaccination of  children
with a safe effective CMV vaccine is justified for the same reason that children
in  the United States are vaccinated against rubella: to protect unborn children
from birth defects  by reducing the  risk that mothers  are exposed to  infected
children.
    
 
   
    A live attenuated CMV vaccine candidate, known as the Towne strain, has been
tested  by third parties in several hundred  people. This strain was reported to
be well tolerated, but did not provide sufficient protection in pregnant mothers
of children in day care  who were at risk for  congenital CMV, or in  transplant
recipients  at risk  of acquiring CMV  from the donor  organs. Aviron scientists
have discovered differences between the genome  of the Towne strain and that  of
wild-type  CMV.  Based on  this  knowledge, the  Company  has used  its Rational
Vaccine Design approach to create new  recombinant CMV vaccine candidates in  an
attempt  to strike the  appropriate balance between  attenuation and protection.
Some of  these vaccine  candidates have  been made  and tested  by Aviron  in  a
specialized  animal model. The Company expects  to select a vaccine candidate to
prevent CMV infection for testing in clinical trials. However, no assurance  can
be  given  that the  Company will  be  successful in  identifying a  CMV vaccine
candidate.
    
 
   
HERPES SIMPLEX VIRUS-TYPE 2
    
 
   
    It is estimated that HSV-2, the cause of genital herpes, infects one out  of
five  persons in the United States.  Only one-third of those infected experience
symptoms, but a significant portion of new infections are caused by transmission
from asymptomatic  individuals. Genital  herpes is  a non-lethal  but  incurable
disease  that  invades  the body  once  and  settles in  for  a  lifetime, often
manifesting its presence several times a year with painful sores in the  genital
area.  It is estimated that  there are over 700,000  new cases of genital herpes
per year in  the United States,  and that  the disease is  responsible for  over
500,000 physician visits per year.
    
 
   
    Genital  herpes also can be acquired by  newborn babies as they pass through
the birth  canal of  infected  mothers. Neonatal  herpes simplex  infection  can
result  in serious damage to the brain and many other organs. Even with therapy,
over 20% of the 1,500 infants infected  each year in the United States die,  and
many  of the survivors  are seriously impaired. In  addition, efforts to prevent
neonatal herpes contribute significantly to  the cost of the disease.  Thousands
of  women in the United  States with a history of  genital herpes are advised to
undergo a  Cesarean section  when prenatal  cultures or  examinations suggest  a
recurrence  near the time of delivery. HSV-2  infection can also lead to serious
and fatal complications in  adults with impaired immune  systems due to AIDS  or
drug therapy for organ transplants.
    
 
                                       35
<PAGE>
   
    The  most widely used drug therapy for HSV-2 disease is acyclovir (Zovirax),
which has been shown  to reduce the severity  and duration of herpetic  lesions,
although  most patients treated still experience symptoms for several days. When
taken several times a day  as a prophylaxis for  HSV-2, acyclovir also has  been
shown  to reduce the  frequency of recurrences.  Several additional therapeutics
are available  or  are  in the  late  stages  of clinical  trials,  and  several
prophylactic  vaccines are in clinical trials;  however, no vaccine currently is
available to prevent  genital herpes. At  least two companies  are in Phase  III
clinical  trials  of  subunit vaccines  for  the primary  prevention  of genital
herpes.
    
 
   
    Aviron is using its Rational Vaccine Design approach to create an injectable
live attenuated vaccine to  be used in uninfected  children and young adults  to
prevent  genital herpes. Two of the  Company's founders, Dr. Bernard Roizman and
Dr. Richard Whitley, in  collaboration with Pasteur  Merieux Serums et  Vaccins,
developed  a prototype live herpes vaccine based on an oral herpes virus (HSV-1)
backbone. After extensive preclinical testing,  the virus was tested in  humans;
however, the immune response following vaccination was deemed insufficient. This
insufficiency  was attributed to  the use of  the HSV-1 backbone  from which too
many important genes had been deleted, thus rendering the virus over-attenuated.
Aviron has licensed this technology, along with patents covering strategies  for
more specific deletions, from ARCH Development Corporation. Aviron has used this
technology  to create live vaccine candidates  using an HSV-2 backbone, which it
currently is evaluating  in preclinical  models. Several  candidates have  shown
attenuation  in various rodent models, as  well as efficacy in protecting guinea
pigs and primates  from challenge  with a lethal  dose of  wild-type HSV-2.  The
Company  intends to use the  results of animal studies  to select these or other
strains under development  for evaluation in  clinical trials. There  can be  no
assurance,  however,  that the  Company will  commence or  successfully complete
clinical trials on a timely basis, if at all.
    
 
   
    Aviron is currently in discussions with a third party to license certain  of
Aviron's patent rights covering or related to the use of HSV for cancer and gene
therapy (excluding vaccines).
    
 
RESPIRATORY SYNCYTIAL VIRUS
 
   
    RSV is the major cause of lower respiratory tract illness in the very young,
responsible  for over 90,000 hospitalizations and  more than 4,000 deaths a year
in the United States. Infection  is manifested as cough  and fever and, in  some
cases,  pneumonia. While RSV infection can occur  at any time of year, epidemics
generally occur in the winter. Most cases  are in children under age four,  with
the peak of severe illness under six months of age, particularly in infants with
pre-existing  heart and lung disease. No vaccine for RSV currently is available,
although certain third parties  are testing a cold  adapted live attenuated  RSV
vaccine  in infants.  Available drug  therapy is  reserved for  the most serious
cases as it  has significant side  effects. Aviron is  developing a  genetically
engineered  live attenuated virus vaccine for  RSV using its proprietary reverse
genetics technology. Aviron's objective  is to use this  technology to create  a
number  of live virus  vaccine candidates which  can be tested  in animal models
before selecting a candidate for testing in humans. However, no assurance can be
given that the Company will be successful in identifying a vaccine candidate.
    
 
INFLUENZA CLINICAL TRIALS
 
CLINICAL TRIALS CONDUCTED BY OTHERS
 
   
    The Company's most  advanced vaccine product  is based on  the cold  adapted
influenza  vaccine technology licensed  from the University  of Michigan and the
NIH. The  Company has  obtained from  the  NIH and  the University  of  Michigan
exclusive  rights  to  trial results  and  data  from the  work  at  the Vaccine
Treatment Evaluation Units (the "VTEUs")  and Wyeth-Ayerst. Aviron has  reviewed
the  data from  over 65  previous clinical  trials of  influenza vaccine viruses
derived from the University of Michigan master strains. These studies, performed
since 1976, involved more  than 15,000 volunteers, of  whom over 7,000  received
the  cold  adapted influenza  vaccine. Most  of these  trials were  conducted by
academic investigators  to explore  the biology  of the  vaccines and  were  not
designed  to support an application to the FDA for approval to market a product.
Each of the 15  vaccine strains that  were tested were  derived from the  master
strains  and typically corresponded to the contemporaneous inactivated influenza
vaccine for the year of testing.
    
 
                                       36
<PAGE>
   
    Those who received the cold adapted vaccine ranged in age from two months to
over 80 years.  More than  50 of  these trials  studied strains  of influenza  A
vaccine,  involving more  than 13,000 volunteers,  and 15 of  the trials studied
strains of influenza  B vaccines, involving  approximately 2,200 volunteers.  In
the aggregate, these clinical trials involved over 2,000 children. Nearly all of
these   trials  used   monovalent  (one   strain)  or   bivalent  (two  strains)
formulations, containing only one or two  of the three strains usually found  in
the  current trivalent inactivated vaccine. These  trials used either placebo or
an inactivated virus vaccine  as controls. In  these clinical trials,  trivalent
formulations  were administered to  about 350 adults and  200 children. The cold
adapted influenza vaccine  was given in  most of these  clinical trials as  nose
drops, although in some instances it was given as a nasal spray.
    
 
   
    The  effectiveness  of  the  cold adapted  influenza  vaccine  in preventing
influenza infection in adults and children has been evaluated in seven adult and
three pediatric challenge  studies. Six  of these adult  challenge studies  were
placebo-controlled and involved 254 seronegative (relatively low levels of prior
antibodies  to  the  influenza  strains  used  in  the  study)  adults  who were
challenged within six  months of vaccination.  A challenge study  is a  clinical
trial  in  which,  typically, 20  to  30  adult volunteers  are  given wild-type
influenza by  nose drops,  one to  two months  following immunization  with  the
experimental or control vaccine preparation. Compared to placebo rates, the cold
adapted  influenza strains  resulted in significant  reduction (66%  to 100%) in
systemic illness compared to the placebo group and a reduction (17% to 100%)  in
infection  as  measured by  evidence of  challenge  virus replication,  or virus
shedding, in the  nose of the  recipient. Two  of these six  studies included  a
comparison  group of subjects treated with the inactivated virus vaccines. While
these studies  did  not  have  a  sufficient number  of  patients  to  detect  a
statistical  difference between the  cold adapted and  inactivated vaccines, the
cold adapted vaccine protection rates were  equal or better than those seen  for
the  inactivated vaccine in each of the  five studies. In one study where adults
were challenged seven  months after  immunization, less protection  was seen  as
measured  by  infection or  any illness  for both  inactivated and  cold adapted
vaccines. However, protection  rates against  systemic illness,  such as  fever,
were 79% to 100% for the cold adapted vaccine and 67% to 84% for the inactivated
vaccine.
    
 
   
    Children  are challenged  in such studies  using the  cold adapted influenza
vaccine as  the  challenge  virus  rather than  virulent  wild-type  virus.  The
endpoint  measured in children is protection  from infection, defined as vaccine
virus growth  in  the nose  after  challenge. Of  the  three  placebo-controlled
studies  in  86 children,  prior immunization  with  the cold  adapted influenza
vaccine was associated with a significant reduction (52% to 100%) in the percent
of children infected with the challenge  virus compared to placebo. In the  only
children's  study that  included a comparison  to inactivated  vaccine, the cold
adapted vaccine  resulted in  a 52%  reduction in  virus shedding,  whereas  the
inactivated vaccine reduced shedding by 6% compared to the placebo.
    
 
   
    Cold  adapted influenza vaccines also have been tested in field trials where
children and adults were  vaccinated before the influenza  season, and are  then
followed  during  the next  six  months in  order  to assess  protection against
influenza disease.  The  largest  study  was  conducted  over  four  consecutive
influenza seasons. Approximately 1,500 children and adults from ages three to 65
were  randomly  assigned to  each arm  of this  double-blind, placebo-controlled
study. This study  design only allowed  comparison of the  inactivated and  cold
adapted   influenza  A   components.  Both   vaccines  were   considered  to  be
well-tolerated, with slightly increased redness and tenderness at the  injection
site  in those  receiving the  inactivated vaccine  and slightly  increased sore
throat or runny  nose, lethargy and  aches in those  receiving the vaccine  nose
drops.  This  study  showed that  both  cold adapted  and  inactivated influenza
vaccines were  well  tolerated  and  reduced  infection  and  morbidity  due  to
influenza  A.  The  relative efficacy  of  the  two vaccines  differed  from one
epidemic year to another and according  to which measurement was used to  assess
efficacy.  As measured by  rises in circulating  antibodies during the influenza
season  (seroconversion),  the  inactivated  vaccine  appeared  more  effective.
However, it is not clear how well this correlates with actual protection, as the
cold   adapted  and   inactivated  vaccines   both  protected   recipients  from
culture-positive disease at rates  which did not differ  by an amount which  was
statistically significant.
    
 
CLINICAL TRIALS BY AVIRON
 
   
    The  Company intends  to conduct  additional clinical  trials to demonstrate
safety and efficacy  of its cold  adapted influenza vaccine.  While the  Company
believes  that it can use  the previous data to  support its regulatory filings,
the Company's use of the previous trial data to establish safety and efficacy of
its proposed
    
 
                                       37
<PAGE>
   
vaccine is limited because very few of the clinical trials involved a  trivalent
vaccine  delivered through a nasal spray.  The additional studies will relate to
the safety  of  the  formulation as  well  as  the safety  of  its  delivery  by
intranasal spray. Aviron enrolled a total of 615 patients in Phase I/II clinical
trials  and 92 patients in a  Phase II challenge study in  five VTEUs as part of
the Company's CRADA with the NIH.
    
 
   
    The first study, conducted at three university research laboratories, was  a
safety  and  immunogenicity study  involving 259  healthy adults.  Patients were
randomly assigned to  receive either Aviron's  trivalent cold adapted  influenza
vaccine  by nasal spray or nose drops, or  placebo by nasal spray or nose drops.
No serious adverse events were seen  in any subjects. In a preliminary  analysis
based on approximately 80% of the patients enrolled, there were no statistically
significant  differences in  the occurrence of  fever, sore  throat, runny nose,
cough, headache or any  other potential reaction assessed  in the study  between
the  vaccine or  placebo or between  the different types  of administration. The
Company is in the process of assessing additional safety and immunogenicity data
from this study.
    
 
   
    Two hundred thirty-eight  children between the  ages of 18  months and  five
years  were enrolled at four VTEUs and  118 children were enrolled at the Center
for  Vaccine  Development  in  Santiago,  Chile,  in  a  Phase  I/  II   safety,
immunogenicity  and dose-escalation study.  The study design  and endpoints were
similar to the adult  study, except that  the initial phases  used a dose  lower
than  that given to adults. No serious  adverse events were seen in any subjects
in any  of the  three phases  of the  dose escalation.  Based on  a  statistical
analysis of safety data by an NIH-appointed data monitoring and safety committee
following  each  of the  escalating  dose phases  of  the children's  study, the
Company received notification from the committee that it had no objection to the
Company proceeding with a  larger-scale Phase III pivotal  trial in children  at
the  highest dose  tested. The  Company intends  to initiate  such a large-scale
field trial in the second  half of the year. However,  the FDA must review  data
from  its completed Phase I/II trials before  the Company can enroll subjects in
the pivotal trial. The Company intends to enroll approximately 900 children  who
will  be vaccinated with either the cold  adapted influenza vaccine or a placebo
and observed for evidence of illness or infection during the 1996-1997 influenza
season  and,  if  required,  revaccinated  and  observed  during  the  1997-1998
influenza season.
    
 
   
    Aviron's   trivalent  intranasal  spray  formulation  of  the  cold  adapted
influenza vaccine also  has been tested  in a  Phase II challenge  study at  two
VTEUs  involving ninety-two  healthy young  adults. Subjects  were randomized to
receive either  the trivalent  cold adapted  intranasal vaccine,  the  trivalent
inactivated vaccine injection or a placebo. There were no serious adverse events
attributed  to the  study vaccine seen  in any  subjects. The Company  is in the
process of  analyzing safety  and  efficacy data  from this  study.  Preliminary
analysis  of  clinical  illness and  viral  shedding following  exposure  to the
challenge virus indicates that a lower  than expected percentage of subjects  in
the  placebo  group experienced  influenza-like illness  than  had been  seen in
previous challenge studies. The Company believes that this may have been due  to
a  problem with the challenge virus used to produce influenza in the subjects or
to a  problem  with selection  of  subjects based  on  their prior  exposure  to
influenza.  Therefore, the Company believes that the challenge study is unlikely
to show statistically significant efficacy on the primary endpoint of preventing
laboratory-confirmed influenza. Regardless  of the  results of  this study,  the
Company  intends to discuss with the FDA  its plans to proceed directly to Phase
III clinical trials  in adults and  does not intend  to conduct other  challenge
studies.
    
 
    Additional  trials in children,  adults and the elderly  will be required to
assess the safety and efficacy of the Company's cold adapted influenza  vaccine.
There can be no assurance that these or any additional trials will be successful
or  that the Company will  successfully develop and receive  FDA approval of its
cold adapted influenza vaccine.
 
ADDITIONAL RESEARCH PROGRAMS
 
LIVE VIRUSES AS VECTORS
 
   
    Aviron believes that its virus engineering technology may be used to  create
strains which carry "foreign" genes and are able to deliver genetic or antigenic
information  to specific  tissues in  the host. For  example, it  is possible to
engineer antigens  from  other  viruses  into influenza,  as  has  already  been
demonstrated  for small antigenic  regions from agents such  as HIV and malaria.
RSV and PIV-3 are two other  important causes of childhood infections which  may
be targeted by using the influenza virus as a vector to deliver antigens.
    
 
                                       38
<PAGE>
   
    Members  of the  herpes virus  family may also  serve as  vectors to deliver
antigens to  make vaccines  which  protect against  other  viruses. Due  to  the
natural  properties  of  this  virus,  it  may  be  useful  to  delivery genetic
information to the central nervous system. Aviron is considering entering into a
collaboration to develop  the Company's  proprietary technology for  the use  of
herpes simplex virus as a vector in gene therapy. There can be no assurance that
the  Company will  be able to  enter into  a collaboration or  that the Company,
alone or with others, will be successful in developing this technology.
    
 
MODIFIED HERPES SIMPLEX VIRUSES TO TREAT BRAIN CANCER
 
   
    The Company's proprietary  technology to modify  herpes simplex viruses  has
been  evaluated by others  in animal models  for the treatment  of brain cancer.
Malignant glioma is  the most  lethal of the  common tumors  originating in  the
brain.  In spite of  surgical therapy, radiotherapy  and chemotherapy, five-year
survival rates  of approximately  5%  are seen.  Many  new therapies  have  been
investigated,  including  radiation, hyperthermia,  phototherapy, immunotherapy,
novel drug delivery for chemotherapy and gene therapy. Two of Aviron's founders,
Dr. Richard Whitley and Dr. Bernard  Roizman, modified the herpes simplex  virus
using  genetic engineering  and have  tested this  virus in  an animal  model of
malignant glioma. Preliminary results  show that tumor size  was reduced by  the
modified  viruses,  resulting in  a survival  benefit  for the  treated animals.
However, no  assurance can  be given  that  the Company  will be  successful  in
developing this technology.
    
 
MANUFACTURING
 
   
    All  of the  vaccine material being  used in the  Company's current clinical
trials is being supplied  by Evans Medical Limited,  a subsidiary of Medeva  plc
("Evans").  Evans is one  of the four  companies licensed by  the FDA to produce
influenza vaccine for sale in the United States. Evans has also agreed to supply
clinical vaccine  material  for  the 1996-1997  influenza  season.  The  Company
currently  does  not have  facilities  to manufacture  products  for large-scale
clinical  trials  or  in  commercial   quantities  and  has  no  experience   in
commercial-scale  manufacturing.  To  manufacture its  products  for large-scale
clinical trials or on a commercial scale, the Company will have to build or gain
access to a large-scale manufacturing facility which will require a  significant
amount  of funds. The production of the Company's cold adapted influenza vaccine
is subject to the availability of a large number of pathogen-free hen eggs,  for
which  there  are  currently a  limited  number of  suppliers.  Contamination or
disruption of  this source  of  supply would  adversely  affect the  ability  to
manufacture  the Company's cold adapted influenza  vaccine. In addition, to make
the vaccine  available  for  clinical  trials or  commercial  sales  before  the
influenza  season, the  Company must  successfully modify  the vaccine  within a
six-month period to include selected strains for a particular year.
    
 
   
    The Company  currently is  considering  whether to  construct  manufacturing
facilities  capable of producing  both pilot-scale and  commercial quantities of
its potential vaccine products and  is presently building a pilot  manufacturing
facility  for its potential vaccine  products other than cold-adapted influenza.
This scale-up process will require the Company to develop advanced manufacturing
techniques and  rigorous  process controls.  Furthermore,  the Company  will  be
required  to  register  its  facility  with  the  FDA  and  with  the California
Department of  Health  Services  and  will  be  subject  to  state  and  federal
inspections   confirming   the  Company's   compliance  with   cGMP  regulations
established by the FDA. However, no assurance can be given as to the ability  of
the  Company  to  produce commercial  quantities  of its  potential  products in
compliance with applicable regulations or at an acceptable cost, or at all.
    
 
   
    The Company is alternatively considering  the use of contract  manufacturers
for the commercial production of its potential products. The Company is aware of
only  a limited number of  manufacturers which it believes  have the ability and
capacity to  manufacture  its potential  products,  including the  cold  adapted
influenza  vaccine,  in a  timely manner.  There  can be  no assurance  that the
Company would  be  able  to  contract  with  any  of  these  companies  for  the
manufacture  of its  products on  acceptable terms,  if at  all. If  the Company
enters into an agreement with a third-party manufacturer, it will be required to
relinquish control of  the manufacturing process,  which might adversely  affect
the  Company's results  of operations.  Furthermore, a  third-party manufacturer
also will be required to manufacture  the Company's products in compliance  with
state  and federal regulations. Failure of  any such third-party manufacturer to
comply with state and federal regulations and to deliver the required quantities
on a  timely  basis  and  at commercially  reasonable  prices  would  materially
    
 
                                       39
<PAGE>
adversely  affect  the Company's  business, financial  condition and  results of
operations. No assurance can be  given that the Company,  alone or with a  third
party, will be able to make the transition to commercial-scale production of its
potential  products successfully, if at all,  or that if successful, the Company
will be able to maintain such production.
 
   
    In November 1995,  the Company and  Evans entered into  a manufacturing  and
development  agreement (the  "Evans Agreement").  Under the  terms of  the Evans
Agreement, Evans is performing  the development of  a manufacturing process  for
production  of a cold adapted influenza vaccine and will produce such vaccine in
sufficient quantities to enable the Company to conduct its planned field  trials
and  large-scale clinical trials of the vaccine, subject to certain limitations.
In addition, in the event that  the Company seeks to offer manufacturing  rights
to  a third party, Evans has a right of first negotiation to supply a portion of
the Company's  commercial  requirements  for the  vaccine  in  certain  European
markets.  The  Company also  granted  Evans a  right  of first  negotiation with
respect to distribution  rights for the  vaccine in Europe.  After December  31,
1996,  either party may terminate the Evans  Agreement upon six months notice to
the other party.
    
 
MARKETING AND SALES
 
   
    The current purchasers  of vaccines are  principally physicians, large  HMOs
and  state and  federal government agencies.  However, the  United States health
care system is undergoing significant  changes and the relative proportion  that
each  group  will  represent  in  the future  will  depend  on  factors  such as
legislative changes and the  economy. The Company intends  to sell its  products
directly to HMOs and state and federal health care agencies, and to other buyers
through  partners with strong capabilities in  local markets. Outside the United
States, the Company plans to  sell its potential products through  collaborative
agreements   with   strategic   partners.  Aviron   intends   to   use  rigorous
cost-effectiveness analysis as a guide for  its pricing strategy and in  support
of its marketing plans.
    
 
   
    The  Company currently has no marketing, sales or distribution capabilities.
To market any  products, Aviron  must either obtain  the assistance  of a  third
party  with a suitable distribution system, develop a direct sales and marketing
staff of its own or combine the efforts  of a third party with its own  efforts.
Other  than SmithKline Beecham and Sang-A, the Company to date has no agreements
for marketing or distributing its potential products.
    
 
   
    The success and commercialization of the Company's products is dependent  in
part  upon the  ability of  the Company  to maintain  and enter  into additional
collaborative agreements with  corporate partners for  the development,  testing
and  marketing of certain  of its vaccines  and upon the  ability of these third
parties to perform their responsibilities. Although Aviron believes that parties
to any  such  arrangements would  have  an  economic motivation  to  succeed  in
performing   their  contractual  responsibilities,  the  amount  and  timing  of
resources devoted to  these activities  will not be  within the  control of  the
Company.  There can  be no  assurance that  any such  agreements or arrangements
would be available  on terms acceptable  to the  Company, if at  all, that  such
third  parties would perform their obligations  as expected, or that any revenue
would be derived from  such arrangements. If  Aviron is not  able to enter  into
such  agreements or arrangements,  it could encounter  delays in introducing its
potential products  into the  market or  be forced  to limit  the scope  of  its
commercialization  activities. If the Company  were to market products directly,
significant additional  expenditures, management  resources  and time  would  be
required to develop a marketing and sales staff within the Company. In addition,
the  Company would  also be competing  with other companies  that currently have
experienced and  well-funded marketing  and sales  operations. There  can be  no
assurance that the Company will be able to establish its own marketing and sales
force or that any such force, if established, would be successful.
    
 
COLLABORATIVE AGREEMENTS
 
    The  Company's strategy for the  development, clinical trials, manufacturing
and commercialization  of  certain  of its  products  includes  maintaining  and
entering   into  various  collaborations  with  corporate  partners,  licensors,
licensees and others. There can be no assurance that the Company will be able to
maintain existing
 
                                       40
<PAGE>
collaborative agreements, negotiate collaborative arrangements in the future  on
acceptable terms, if at all, or that any such collaborative arrangements will be
successful.  To date  the Company has  entered into  the following collaborative
agreements.
 
   
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES -- PARAINFLUENZA VIRUS
TYPE 3
    
 
   
    In May 1996, the Company obtained exclusive rights from the NIAID of the NIH
to certain biological materials and clinical  trial data for its PIV-3  program.
The  NIH granted to the  Company exclusive rights in  specific strains of bovine
parainfluenza virus (the  "Licensed Materials") to  develop, test,  manufacture,
use  and sell  products for  vaccination against  human parainfluenza  virus and
other human and animal diseases ("Licensed Products"). In addition, the  Company
obtained  from the NIAID the right to reference an existing IND and certain data
relating to  the Licensed  Materials. The  NIH retained  certain rights  to  the
Licensed Materials on behalf of the United States Government to conduct research
and  to grant research licenses to third parties under certain circumstances. In
return for the rights granted by NIH,  the Company will make payments to NIH  on
the  achievement of specified milestones and  will make certain royalty payments
to NIH. Unless otherwise terminated,  the Agreement will terminate on  cessation
of  commercial sales of Licensed Products by the Company or its sublicensee. The
Company has the unilateral right to terminate the Agreement in any country  upon
providing 60 days notice to NIH.
    
 
SMITHKLINE BEECHAM BIOLOGICALS S.A.
 
   
    In  October 1995,  the Company signed  an agreement  with SmithKline Beecham
defining a  collaboration  on the  Company's  EBV vaccine  technology  (the  "SB
Agreement"). Under the terms of the SB Agreement, the Company granted SmithKline
Beecham  an exclusive  license to  produce, use  and sell  non-live EBV vaccines
incorporating the Company's technology for prophylactic and therapeutic uses  on
a  worldwide basis,  except in  South and  North Korea  (together, "Korea"). The
Company has retained the right to co-distribute a monovalent formulation of  the
vaccine  in certain markets in the United  States and to have SmithKline Beecham
supply such vaccine. In addition, SmithKline  Beecham obtained a right of  first
refusal to an exclusive, worldwide (except Korea) license under any intellectual
property  rights  relating  to  any live  EBV  vaccine  technology  developed or
controlled by the Company during the term of the SB Agreement.
    
 
   
    SmithKline Beecham  has  agreed to  fund  research and  development  at  the
Company  related to  the EBV vaccine,  in specified minimum  amounts, during the
first two years of the SB Agreement. SmithKline Beecham made an initial  upfront
payment  to  the  Company  and  agreed  to  make  additional  payments  upon the
achievement of certain product development  milestones. The Company is  entitled
to  royalties from SmithKline Beecham based on  net sales of the vaccine. Unless
otherwise terminated,  the SmithKline  Beecham Agreement  will expire  upon  the
expiration  or  invalidation of  the  last remaining  patent  covered by  the SB
Agreement or 10 years  from the date  of first commercial  sale of the  vaccine,
whichever  is later.  The SB Agreement  may be terminated  by SmithKline Beecham
with respect to any country at any time.
    
 
SANG-A PHARM. CO., LTD.
 
   
    In May 1995, the  Company entered into a  Development and License  Agreement
with  Sang-A.  The Company  granted  to Sang-A  exclusive  clinical development,
manufacturing and marketing rights in Korea for specified products developed  by
Aviron,  including vaccines for  influenza (cold adapted  and recombinant), EBV,
CMV, HSV-2 and RSV. However, the Company  is under no obligation to develop  any
product.  Sang-A  also will  make  payments to  the  Company upon  the Company's
meeting certain regulatory milestones for each  product in Korea and will pay  a
royalty to the Company on net sales of such products in Korea.
    
 
    Sang-A also is obligated to establish a manufacturing facility with at least
enough  capacity to  meet demand  for all  Korean product  requirements for each
product that  reaches commercialization,  if  any. In  the event  that  Sang-A's
manufacturing  capabilities satisfy certain objective criteria and subject to an
obligation to cooperate  with the  Company's future corporate  partners for  any
given    products,    Sang-A    has    a    right    of    first    refusal   to
 
                                       41
<PAGE>
manufacture a portion of the total  requirements of the Company, its  affiliates
and  sublicensees  for the  specified products,  with the  exception of  the EBV
vaccine, in specified countries, including  the United States, provided that  it
can do so at a competitive price, quality and timeline.
 
    The  term of this agreement extends, on a product-by-product basis, until 10
years from the date of  first commercial sale of each  product in Korea. At  the
conclusion  of  the term,  Sang-A has  an option  to extend  the agreement  on a
product-by-product basis,  for the  longer  of an  additional  10 years  or  the
expiration  of the  patents covering  such product.  During any  such extension,
Sang-A will  have either  no royalty  obligation  to the  Company or  a  reduced
royalty obligation, depending on the product. Aviron may terminate the Agreement
on  a  product-by-product  basis  for  material  breach  by  Sang-A  of  certain
provisions of the Agreement, and may terminate the agreement in its entirety for
material breach of certain other provisions.
 
   
    In return for the rights granted to Sang-A, Sang-A made an equity investment
in the Company in  May 1995 of approximately  $4.0 million. Sang-A  subsequently
made  an  additional  equity investment  of  approximately $1.6  million  in the
Company's private  placement of  Series  C Preferred  Stock and  currently  owns
4,265,480  shares of  the Company's Series  C Preferred  Stock, convertible into
853,096 shares of the Company's  Common Stock, representing approximately 9%  of
the  Company's Common Stock (on an as-converted basis) outstanding prior to this
offering. In addition, Sang-A has agreed to purchase, if so requested by Aviron,
10% of any subsequent  offerings by the  Company of new  securities at the  same
price offered to other purchasers in any such offering. This purchase obligation
expires  following the closing of the  first firmly underwritten public offering
of the Company's Common Stock. Concurrent with this offering, Aviron intends  to
sell  to Sang-A in a private placement,  at the initial public offering price, a
number of shares of Common Stock equal to 10% of the aggregate number of  shares
sold  in the offering and  in the private placement,  provided however, that the
total number of  shares to  be purchased by  Sang-A will  not exceed  $5,000,000
divided by the initial public offering price.
    
 
   
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES -- COLD ADAPTED INFLUENZA
VACCINE
    
 
    Following  a  competitive application  process, the  Company entered  into a
CRADA in  March 1995  with  the National  Institute  of Allergy  and  Infectious
Diseases  of the NIH  to conduct clinical  trials of the  Company's cold adapted
influenza vaccine. Wyeth-Ayerst licensed certain rights to the vaccine from  the
NIH  in 1989 and was developing it for  sale in collaboration with the NIH until
relinquishing its  rights in  1993. Aviron  has obtained  from the  NIH and  the
University  of Michigan exclusive rights to trial results and data from the work
at the VTEUs  and Wyeth-Ayerst.  The NIH  has agreed  to support  the trials  by
enrolling  subjects in its  network of VTEUs. In  addition, the Company acquired
exclusive commercial rights to data generated from all previous clinical  trials
conducted  by the NIH and Wyeth-Ayerst using  the vaccine. The term of the CRADA
will not exceed five  years without a written  amendment by the parties.  Either
party may terminate the CRADA for material breach.
 
UNIVERSITY OF MICHIGAN
 
   
    In  February  1995,  the  Company  entered  into  a  materials  transfer and
intellectual property agreement (the  "Michigan Agreement") with the  University
of  Michigan. Pursuant  to the  Michigan Agreement,  the University  of Michigan
granted the  Company  exclusive  rights to  certain  intellectual  property  and
technology  relating to a  cold adapted influenza  vaccine and proprietary donor
strains  of  influenza  viruses  useful  in  the  production  of  products   for
vaccination  against influenza and  potentially for gene  therapy and other uses
(the "Master Strains"). Specifically, the  Company obtained the exclusive  right
to  develop, manufacture, use,  market and sell  products incorporating any such
intellectual property or utilizing  the Master Strains in  all countries of  the
world  except Japan. Aviron is  in the process of  acquiring the Japanese rights
from  the  University   of  Michigan   for  no   additional  consideration.   In
consideration  for the rights  granted to the  Company, the Company  (i) made an
initial cash payment to the University of Michigan; (ii) agreed to pay a royalty
to the University of Michigan on net  sales of products subject to the  license;
(iii)  entered  into  a  sponsored research  agreement  with  the  University of
Michigan for a period of at least  two years; and (iv) issued to the  University
of  Michigan  1,323,734 shares  of Series  B  Preferred Stock,  convertible into
264,746 shares of the Company's  Common Stock, representing approximately 3%  of
the  Company's Common Stock (on an as-converted basis) outstanding prior to this
offering.
    
 
                                       42
<PAGE>
In addition, in the event that Aviron receives approval to commercially market a
product based on the University of  Michigan technology, the Company has  agreed
to  issue a  warrant to  the University  of Michigan  to purchase  shares of the
Company's Common Stock,  for a  number of  shares to be  based on  1.25% of  the
Common Stock outstanding on the date of the first commercial sale of the product
incorporating the University of Michigan technology. See "Description of Capital
Stock -- Warrants."
 
   
    Pursuant  to the Michigan Agreement, the Company is required to grant to the
University  of  Michigan  an  irrevocable,  royalty-free  license  for  research
purposes, or for transfer to a subsequent licensee should the Michigan Agreement
be  terminated, to (i) all improvements developed by the Company, its affiliates
or sublicensees, whether or not patentable, relating to delivery mechanisms  and
processes   for  administration  and  manufacturing  of  products,  as  well  as
packaging, storage and preservation processes  for the Master Strains, and  (ii)
all  new  technical  information  acquired by  the  Company,  its  affiliates or
sublicensees relating to the Master Strains and products.
    
 
    The term of the Michigan Agreement is until the later of the last to  expire
of  the the University of  Michigan patents licensed to  the Company or 20 years
from the date of first commercial  sale of a product incorporating the  Michigan
technology.  The Company has the further right  to terminate for any reason upon
12 months notice to the University of Michigan.
 
   
THE MOUNT SINAI SCHOOL OF MEDICINE
    
 
   
    In February 1993, the Company  entered into a technology transfer  agreement
with  The Mount  Sinai School  of Medicine  of the  City University  of New York
("Mount Sinai"). Under this agreement, Mount  Sinai assigned to the Company  all
of  its  rights,  title  and  interest in  and  to  certain  patents  and patent
applications,  as  well   as  all  associated   know-how  and  other   technical
information,  relating  to  recombinant  negative  strand  RNA  virus expression
systems and vaccines, attenuated influenza viruses and certain other technology.
Mount Sinai also granted the Company  (i) an option to acquire any  improvements
to  the inventions  disclosed in  the assigned  patents and  patent applications
thereafter developed by Mount Sinai and (ii) a right of first negotiation for  a
license or assignment to certain additional related technology. In consideration
for  the rights granted to the Company, the Company issued to Mount Sinai 35,000
shares of the  Company's Common Stock.  The Company also  issued to Mount  Sinai
three  warrants to  purchase up to  a total  of 225,000 shares  of the Company's
Series A Preferred Stock, each exercisable  for a term of five years  commencing
upon  the  occurrence  of certain  milestone  events which  accelerate  upon the
effectiveness of this  offering. Warrants to  purchase 45,000 of  the shares  of
Series  A Preferred  Stock (convertible into  9,000 shares of  Common Stock) are
exercisable at a purchase price of $4.50 per share of Common Stock. Warrants  to
purchase  148,750 shares  of Series A  Preferred Stock  (convertible into 29,750
shares of Common Stock), will become  exercisable at the effective date of  this
offering  at a  price per share  of Common Stock  of 125% of  the initial public
offering price  of the  Company's  Common Stock.  The  warrant to  purchase  the
remaining  31,250 shares of  Series A Preferred  Stock will be  cancelled on the
effective date of this offering. See "Capital Stock -- Warrants."
    
 
ARCH DEVELOPMENT CORPORATION
 
   
    In July  1992,  the Company  entered  into  a license  agreement  with  ARCH
Development   Corporation  ("ARCH"),  an   Illinois  not-for-profit  corporation
associated with  the  University  of  Chicago, pursuant  to  which  the  Company
obtained  an exclusive, worldwide  commercialization license, with  the right to
sublicense, to  certain  patent rights  and  related intellectual  property  and
materials  pertaining to the herpes simplex viruses, EBV and various recombinant
methods and materials.  In return for  the rights granted  to the Company  under
this  agreement, the Company will make payments  to ARCH upon the achievement of
certain milestones in  the development of  products covered by  the license  and
will  pay royalties to ARCH on net sales of such products. ARCH also granted the
Company certain rights  to improvements and  additional related technology.  The
term of this agreement extends until the expiration of the last-to-expire patent
rights  covered  under  the license.  In  connection with  this  agreement, ARCH
purchased 40,000  shares  of the  Company's  Common Stock.  Subsequent  to  this
agreement,  affiliates  of ARCH  made equity  investments in  Aviron, purchasing
700,000, 300,000 and 113,999 shares of the Company's Series A, B and C Preferred
Stock, respectively, convertible into a total of
    
 
                                       43
<PAGE>
   
222,799 shares of the Company's Common  Stock. ARCH and its affiliates  together
own  shares representing approximately 2.5% of the Company's Common Stock (on an
as-converted basis) outstanding prior to this offering.
    
 
PATENTS AND PROPRIETARY RIGHTS
 
   
    Aviron believes that patent and trade secret protection is important to  its
business  and that its future will depend in part on its ability to maintain its
technology licenses,  maintain  trade  secret  protection,  obtain  patents  and
operate without infringing the proprietary rights of others. The Company owns or
has licensed rights to United States and foreign patents and patent applications
covering  aspects of technology relating to  herpes viruses, including EBV, CMV,
and  HSV-2  and  negative  strand  RNA  viruses,  such  as  influenza  and   RSV
technologies.
    
 
   
    The  Company has  no issued  patents on the  technology related  to its cold
adapted influenza vaccine. The Company's rights to this technology are based  on
a  license of materials and know-how from the University of Michigan, which owns
the master  strains from  which the  vaccine is  derived, and  on a  license  of
know-how and clinical trial data from the NIH. There can be no assurance, that a
third  party will not reproduce the  Company's cold adapted influenza vaccine or
that a third party will not  develop another live-virus influenza vaccine  which
might be comparable to Aviron's in terms of safety and efficacy.
    
 
   
    The  Company  also  relies  on  trade  secrets  to  protect  its technology,
especially where  patent  protection  is  not  believed  to  be  appropriate  or
obtainable.  Certain of  the Company's licensors  also rely on  trade secrets to
protect technology  which has  been licensed  to Aviron,  and as  a result,  the
Company  is dependent on  the efforts of  these licensors to  protect such trade
secrets. For example, the University of Michigan relies in part on trade secrets
to protect the master strains  of the cold adapted  influenza virus used by  the
Company  and  the NIH  relies in  part on  trade secrets  to protect  the master
strains of  the bPIV-3  virus. Aviron  protects its  proprietary technology  and
processes,   in  part,   by  confidentiality  agreements   with  its  employees,
consultants, collaborators and  certain contractors. There  can be no  assurance
that these agreements will not be breached, that the Company would have adequate
remedies  for any breach,  or that the  Company's trade secrets  or those of its
licensors will  not otherwise  become known  or be  independently discovered  by
competitors.   To  the  extent  that  Aviron  or  its  consultants  or  research
collaborators use intellectual property  owned by others in  their work for  the
Company,  disputes  may also  arise as  to  the rights  in related  or resulting
know-how and inventions.
    
 
   
    The Company's success  also will  depend in part  on its  ability to  obtain
patents,  both  in  the  United  States and  in  other  countries.  Since patent
applications in the United States are maintained in secrecy until patents  issue
and  since publication  of discoveries  in the  scientific or  patent literature
often lag behind actual discoveries, the  Company cannot be certain that it  was
the  first  to  make  the  inventions covered  by  each  of  its  pending patent
applications or  that it  was the  first to  file patent  applications for  such
inventions.  The patent positions of  biotechnology and pharmaceutical companies
can be highly  uncertain and involve  complex legal and  factual questions,  and
therefore  the  breadth of  claims allowed  in biotechnology  and pharmaceutical
patents or  their  enforceability  cannot  be  predicted.  Although  Aviron  has
acquired  or licensed rights to over a  dozen patent applications pending in the
United States, and seven issued United States patents, there can be no assurance
that any  of the  Company's patents  or patent  applications will  issue, or  if
issued,  will not be challenged, invalidated or circumvented, or that the rights
granted thereunder will provide proprietary protection or competitive advantages
to the Company.
    
 
   
    The commercial success of Aviron additionally will depend, in part, upon the
Company's not infringing patents  issued to others.  A number of  pharmaceutical
companies,  biotechnology companies, universities and research institutions have
filed patent applications  or received  patents in  the areas  of the  Company's
programs.  Some  of these  applications  or patents  may  limit or  preclude the
Company's applications, or conflict in  certain respects with claims made  under
the Company's applications.
    
 
    The  Company is aware of pending patent applications that have been filed by
others that may pertain to certain aspects of the Company's programs,  including
a  genetically engineered influenza vaccine,  the Company's herpes virus program
or other of its issued or pending patent applications. If patents are issued  to
others   containing  preclusive  or  conflicting  claims  and  such  claims  are
ultimately determined to be valid, the Company
 
                                       44
<PAGE>
may be required  to obtain licenses  to these  patents or to  develop or  obtain
alternative  technology. The Company's breach of  an existing license or failure
to obtain a  license to technology  required to commercialize  its products  may
have  a material adverse  effect on the  Company's business, financial condition
and results of operations. Litigation,  which could result in substantial  costs
to  the Company,  may also  be necessary  to enforce  any patents  issued to the
Company or  to  determine the  scope  and validity  of  third-party  proprietary
rights.  If competitors of  the Company prepare and  file patent applications in
the United States that claim technology also claimed by the Company, the Company
may have  to participate  in  interference proceedings  declared by  the  United
States  Patent and  Trademark Office to  determine priority  of invention, which
could result in substantial cost to the Company, even if the eventual outcome is
favorable to  the Company.  An  adverse outcome  could  subject the  Company  to
significant  liabilities to  third parties  and require  the Company  to license
disputed rights from third parties or to cease using such technology.
 
   
    On May 22, 1996, the Company received notice from Chiron that Chiron intends
to file a lawsuit against Aviron,  unless a prompt negotiated settlement can  be
reached,  alleging that certain of Aviron's  patent applications relating to its
EBV program are  based on  Chiron proprietary information  which was  improperly
conveyed  to Aviron by  a former Chiron employee.  Aviron believes that Chiron's
allegations are  without  merit  and,  if  a  complaint  is  filed,  intends  to
vigorously  defend itself against  any such action. Aviron  does not utilize the
alleged proprietary information in any of its programs. The Company has received
terms of a  proposed settlement from  Chiron and is  in discussions with  Chiron
regarding  a possible settlement of the dispute.  No assurance can be given that
litigation will not ensue, which could be costly and time-consuming.
    
 
GOVERNMENT REGULATION
 
    Regulation  by  government  authorities  in  the  United  States  and  other
countries will be a significant factor in the manufacturing and marketing of any
products  that may be  developed by the  Company. All of  the Company's products
will   require   regulatory   approval   by   government   agencies   prior   to
commercialization.  The  Company's  vaccine  products  are  subject  to rigorous
preclinical testing and clinical trial and other approval procedures by the  FDA
and  similar health authorities  in foreign countries.  Various federal statutes
and regulations also  govern or influence  the manufacturing, safety,  labeling,
storage, record keeping and marketing of such products.
 
   
    The Company believes that its vaccine products will be classified by the FDA
as  "biologic products,"  as opposed  to "drug  products." The  steps ordinarily
required before  a drug  or biological  product may  be marketed  in the  United
States  include (a) preclinical testing and  clinical trials; (b) the submission
to the FDA of  an IND, which  must become effective  before clinical trials  may
commence;  (c)  adequate and  well-controlled clinical  trials to  establish the
safety and efficacy  of the drug;  (d) the submission  to the FDA  of a  Product
License  Application ("PLA") together with  an Establishment License Application
("ELA"); and (e)  FDA approval  of the  application, including  approval of  all
product labeling and, in some instances, advertising.
    
 
   
    Preclinical  testing  includes laboratory  evaluation of  product chemistry,
formulation and stability,  as well as  animal studies to  assess the  potential
safety  and efficacy of each product. Preclinical safety tests must be conducted
by laboratories  that  comply with  FDA  regulations regarding  Good  Laboratory
Practice.  The results of the preclinical tests are submitted to the FDA as part
of an  IND and  are reviewed  by the  FDA before  the commencement  of  clinical
trials.  Unless the FDA objects to an IND, the IND will become effective 30 days
following its receipt by the FDA. There  can be no assurance that submission  of
an  IND will result in FDA authorization to commence clinical trials or that the
lack of an objection means that  the FDA will ultimately approve an  application
for marketing approval.
    
 
   
    Clinical trials involve the administration of the investigational product to
humans  under the  supervision of  a qualified  principal investigator. Clinical
trials must  be  conducted in  accordance  with Good  Clinical  Practices  under
protocols  submitted to the FDA  as part of the  IND. In addition, each clinical
trial must  be approved  and conducted  under the  auspice of  an  Institutional
Review  Board and with patient informed  consent. The Institutional Review Board
will consider, among other things, ethical factors, the safety of human subjects
and the possible liability of the institution conducting the clinical trial.
    
 
    Phase I clinical trials are  generally performed in healthy human  subjects.
The  goal of  the Phase  I clinical  trials is  to establish  initial data about
safety and tolerance  of the  vaccine in humans.  Also, the  data regarding  the
 
                                       45
<PAGE>
immune  response to  a vaccine  may be  obtained. In  Phase II  clinical trials,
evidence is sought about the desired therapeutic efficacy of a drug or antibody,
or the immune response to  a vaccine, in limited  studies with small numbers  of
carefully selected subjects. Efforts are made to evaluate the effects of various
dosages and to establish an optimal dosage level and dosage schedule. Additional
safety  data are also gathered from these  studies. The Phase III clinical trial
program consists of  expanded, large-scale, multicenter  studies of persons  who
are  susceptible  to  the  disease.  The goal  of  these  studies  is  to obtain
definitive statistical  evidence of  the  efficacy and  safety of  the  proposed
product and dosage regimen.
 
    All  data obtained from this comprehensive development program are submitted
as a PLA to the FDA and the corresponding agencies in other countries for review
and approval. FDA approval of the PLA and the associated ELA is required  before
marketing  may begin in the  United States. The FDA  will present to the Vaccine
and Related  Biological Products  Advisory Committee  documentation on  most  of
Aviron's  products for review  and recommendation before  PLA approval. Although
the FDA's policy  is to review  priority applications within  180 days of  their
filing,  in practice longer  times may be required.  The FDA frequently requests
that additional information be submitted requiring significant additional review
time. All proposed  products of  the Company will  be subject  to demanding  and
time-consuming  PLA or  similar approval procedures  in the  countries where the
Company intends to market  its products. These regulations  define not only  the
form  and content of the  development of safety and  efficacy data regarding the
proposed product, but also impose specific requirements regarding manufacture of
the product,  quality assurance,  packaging, storage,  documentation and  record
keeping,   labelling  and  advertising,   and  marketing  procedures.  Effective
commercialization also requires inclusion of the Company's products in national,
state, provincial, or institutional formularies or cost reimbursement systems.
 
    FDA  approval  of  the  Company's  products,  including  a  review  of   the
manufacturing  processes and facilities  used to produce  such products, will be
required before such products may be marketed in the United States. The  process
of obtaining approvals from the FDA can be costly, time consuming and subject to
unanticipated  delays.  The  FDA may  refuse  to  approve an  application  if it
believes that applicable regulatory criteria are not satisfied. The FDA may also
require additional testing  for safety and  efficacy of the  drug. Moreover,  if
regulatory  approval of a drug product is  granted, the approval will be limited
to specific  indications.  There can  be  no  assurance that  approvals  of  the
Company's proposed products, processes or facilities will be granted on a timely
basis,  if at all.  Any failure to  obtain or delay  in obtaining such approvals
would have  a  material adverse  effect  on the  Company's  business,  financial
condition  and results of  operations. Moreover, even  if regulatory approval is
granted, such approval may include significant limitations on indicated uses for
which a product could be marketed.
 
    In addition to regulations enforced by the FDA, the Company also is  subject
to  regulation under the  Occupational Safety and  Health Act, the Environmental
Protection Act,  the  Toxic  Substances  Control  Act,  the  Nuclear  Regulatory
Commission,  the Resource  Conservation and Recovery  Act and  other present and
potential future federal, state or local regulations. The Company's research and
development involves the  controlled use of  hazardous materials and  chemicals.
Although  the  Company  believes that  its  safety procedures  for  handling and
disposing of such materials  comply with the standards  prescribed by state  and
federal  regulations, there can be no assurance that accidental contamination or
injury from these materials will  not occur. In the  event of such an  accident,
the  Company  could be  held liable  for any  damages that  result and  any such
liability could exceed the resources of the Company.
 
    Whether or not  FDA approval  has been obtained,  approval of  a product  by
comparable regulatory authorities may be necessary in foreign countries prior to
the  commencement of  marketing of the  product in such  countries. The approval
procedure varies among countries, can  involve additional testing, and the  time
required may differ from that required for FDA approval. Although there is now a
centralized  European Union approval  mechanism in place,  each European country
may nonetheless impose its  own procedures and requirements,  many of which  are
time consuming and expensive. Thus, there can be substantial delays in obtaining
required  approvals from both  the FDA and  foreign regulatory authorities after
the relevant applications are  filed. The Company expects  to rely on  corporate
partners  and licensees,  along with  Company expertise,  to obtain governmental
approval in foreign countries of drug formulations utilizing its candidates.
 
                                       46
<PAGE>
    The Company believes that  the approval process for  vaccines may be  longer
than  for other  therapeutic products. In  addition, regulatory  scrutiny may be
particularly intense for  products, such as  Aviron's cold-attenuated  influenza
vaccine, which are designed to be given to otherwise healthy children.
 
COMPETITION
 
   
    The  Company operates in a rapidly  evolving field. Any product developed by
the Company would compete with existing and new drugs and vaccines being created
by pharmaceutical, biopharmaceutical and biotechnology companies. If the Company
were able  to successfully  develop its  vaccines, it  would be  competing  with
larger  companies that have  already introduced vaccines  and have significantly
greater  marketing,  manufacturing,  financial  and  managerial  resources.  For
example, with respect to its cold adapted influenza vaccine, the Company will be
competing   against  larger   companies  such  as   Pasteur  Merieux  Connaught,
Wyeth-Ayerst,  Parke-Davis  and  Evans.  Each  of  these  companies  sells   the
inactivated injectable influenza vaccine in the United States, has significantly
greater  financial  resources  than  Aviron and  has  established  marketing and
distribution channels for such  products. The Company is  also aware of  several
companies  that are  marketing or are  in late-stage development  of products to
prevent HSV  disease, including  Glaxo, SmithKline  Beecham and  Chiron  Biocine
Corporation.  In addition, the Company  is also aware of the  use in Russia of a
cold adapted influenza  vaccine, research  programs by some  of the  competitors
listed  above, among others, to develop  more effective influenza vaccines and a
cold adapted PIV-3 vaccine developed with NIH support which may be licensed to a
large vaccine company.
    
 
    New developments are  expected to  continue in both  the pharmaceutical  and
biotechnology  industries  and  in  academia.  Other  companies  may  succeed in
developing products that are safer, more effective or less costly than any  that
may  be developed by the Company. Such companies may also be more effective than
the Company  in the  production and  marketing of  their products.  Furthermore,
rapid  technological  development by  competitors  may result  in  the Company's
products becoming obsolete before the Company  is able to recover its  research,
development  or commercialization expenses incurred  in connection with any such
product.  Many  potential  competitors  have  substantially  greater  financial,
technical and marketing resources than the Company. Some of these companies also
have  considerable experience in preclinical  testing, clinical trials and other
regulatory  approval  procedures.   Moreover,  certain  academic   institutions,
government  agencies and other research organizations are conducting research in
areas  in  which  the  Company  is  working.  These  institutions  are  becoming
increasingly  aware of the  commercial value of their  findings and are becoming
more active in seeking patent  protection and licensing arrangements to  collect
royalties for the use of technology that they have developed. These institutions
may  also market competitive  commercial products on their  own or through joint
ventures.
 
    Aviron believes  that  competition in  the  markets it  is  addressing  will
continue  to be intense. The vaccine  industry is characterized by intense price
competition, and the Company anticipates that it will face this and other  forms
of competition. There can be no assurance that pharmaceutical, biopharmaceutical
and  biotechnology companies will not develop more effective products than those
of the Company or will not market and sell their products more effectively  than
the  Company,  which  would have  a  material  adverse effect  on  the Company's
business, financial condition and results of operations.
 
   
PHARMACEUTICAL PRICING AND REIMBURSEMENT
    
 
   
    Political, economic and regulatory influences are subjecting the health care
industry in  the United  States  to fundamental  change. Recent  initiatives  to
reduce  the federal  deficit and to  reform health care  delivery are increasing
cost-containment  efforts.  The   Company  anticipates   that  Congress,   state
legislatures  and  the  private  sector  will  continue  to  review  and  assess
alternative benefits, controls  on health care  spending through limitations  on
the  growth  of  private health  insurance  premiums and  Medicare  and Medicaid
spending, the creation of large  insurance purchasing groups, price controls  on
pharmaceuticals  and  other  fundamental  changes to  the  health  care delivery
system. Any  such proposed  or actual  changes could  cause the  Company or  its
collaborative  partners to limit or  eliminate spending on development projects.
Legislative debate is expected to
    
 
                                       47
<PAGE>
continue  in the future, and market forces are expected to demand reduced costs.
Aviron cannot predict what  impact the adoption of  any federal or state  health
care reform measures or future private sector reforms may have on its business.
 
    In  both  domestic  and foreign  markets,  sales of  the  Company's proposed
vaccines will  depend  in  part  upon the  availability  of  reimbursement  from
third-party  payors,  such  as  government  health  administration  authorities,
managed care  providers, private  health insurers  and other  organizations.  In
addition,  other third-party payors  are increasingly challenging  the price and
cost effectiveness  of medical  products and  services. Significant  uncertainty
exists  as to the  reimbursement status of newly  approved health care products.
There can  be  no  assurance  that  the  Company's  proposed  products  will  be
considered  cost effective  or that  adequate third-party  reimbursement will be
available to enable  Aviron to maintain  price levels sufficient  to realize  an
appropriate  return on  its investment  in product  development. Legislation and
regulations affecting  the  pricing of  pharmaceuticals  may change  before  the
Company's  proposed  products  are  approved  for  marketing.  Adoption  of such
legislation could further limit reimbursement for medical products. If  adequate
coverage  and  reimbursement  levels  are not  provided  by  the  government and
third-party payors for the  Company's products, the  market acceptance of  these
products would be adversely affected, which would have a material adverse effect
on the Company's business, financial condition and results of operations.
 
   
    Several of the Company's proposed vaccines are intended for use in children.
Widespread  use of these  proposed vaccines is  unlikely without recommendations
for their use in  childhood immunization programs from  authorities such as  the
ACIP, the American Academy of Pediatrics and the American College of Physicians.
The  ACIP has a role in making recommendations which affect the market for most,
if  not  all,  of  the  products  Aviron  intends  to  make.  The  CDC  develops
epidemiologic  data in support of the need for new vaccines and monitors vaccine
usage and changes in disease incidence. In addition, CDC staff frequently act as
key advisors to the FDA in their review process. There can be no assurance  that
such  authorities will  recommend the  use of  the Company's  proposed products,
which would have a material adverse effect on the Company's business,  financial
condition and results of operations.
    
 
EMPLOYEES
 
   
    As  of June 1, 1996, the Company had 70 full-time employees. Thirty-eight of
the Company's employees were in research  and development 16 were in  regulatory
affairs,  quality assurance and quality control,  and 16 were in administration.
No Company employee is  represented by a  labor union, and  the Company has  not
experienced  any work stoppages. The Company considers its employee relations to
be good.
    
 
FACILITIES
 
    Aviron occupies approximately  52,800 square feet  of office and  laboratory
space in Mountain View, California. The Company has leased this facility through
October  2005 and has two  options to extend the  lease for successive five-year
terms. The Company currently subleases approximately 15,000 square feet of space
to three subtenants. The subleases run through June 1996 and may be extended  at
Aviron's discretion. The Company believes that this facility is adequate to meet
its needs for the foreseeable future.
 
LEGAL PROCEEDINGS
 
   
    The  Company is not a  party to any material  legal proceedings. However, on
May 22, 1996,  the Company received  notice from Chiron  that Chiron intends  to
file  a lawsuit  against Aviron,  unless a  prompt negotiated  settlement can be
reached, alleging that certain of  Aviron's patent applications relating to  its
EBV  program are  based on Chiron  proprietary information  which was improperly
conveyed to Aviron by  a former Chiron employee.  Aviron believes that  Chiron's
allegations  are  without  merit  and,  if  a  complaint  is  filed,  intends to
vigorously defend itself against  any such action. Aviron  does not utilize  the
alleged proprietary information in any of its programs. The Company has received
terms  of a possible  settlement from Chiron  and is in  discussions with Chiron
regarding a proposed settlement of the  dispute. No assurance can be given  that
litigation will not ensue, which could be costly and time-consuming.
    
 
                                       48
<PAGE>
SCIENTIFIC ADVISORY BOARD
 
   
    Aviron's  scientific advisors are consultants who  devote six to 20 days per
year to the  Company. Some  meet frequently  with Company  employees to  discuss
specific  projects and others participate primarily via the Company's two annual
meetings of the Scientific Advisory Board.
    
 
   
    ANN ARVIN, M.D., Professor of Pediatrics, Microbiology and Immunology at the
Stanford University  School of  Medicine, has  been a  member of  the  Company's
Scientific  Advisory Board since  1992. Dr. Arvin has  conducted research on the
epidemiology of maternal-to-infant transmission of HSV-2 and she directs one  of
the  leading laboratories in  the study of  the interaction of  the human immune
system with the  varicella zoster  (chicken pox)  virus in  natural and  vaccine
infections.
    
 
   
    HARRY  GREENBERG, M.D.,  Professor of Medicine,  Microbiology and Immunology
and Chief  of  the  Division  of Gastroenterology  and  Associate  Chairman  for
Academic  Affairs, Department of  Medicine at the  Stanford University School of
Medicine, has been  a member of  the Company's Scientific  Advisory Board  since
1992. Dr. Greenberg's research deals with the immunology and pathogenesis of the
principal viruses which cause infectious diarrhea and hepatitis.
    
 
   
    ELLIOT  KIEFF, M.D.,  PH.D., Albee  Professor of  Medicine, Microbiology and
Molecular Genetics and Chairman of  the Virology Program at Harvard  University,
and Director of Infectious Disease at the Brigham and Women's Hospital, has been
a  member of  the Company's  Scientific Advisory  Board since  1992. Dr. Kieff's
laboratory conducts  research  on the  molecular  mechanisms  of how  EBV  is  a
contributory cause of cancer in humans.
    
 
    JOSHUA  LEDERBERG, PH.D., the Raymond and Beverly Sackler Foundation Scholar
and former President  of The Rockefeller  University, has been  a member of  the
Company's  Scientific Advisory Board since 1992.  He received the Nobel Prize in
Physiology or Medicine for his  discovery of genetic recombination in  bacteria.
His  laboratory at the Rockefeller University  studies molecular genetics and he
is active in formulation of national policy concerning emerging infections.
 
    HUNEIN F. MAASSAB, PH.D., Chairman of the Department of Epidemiology, School
of Public  Health, at  the University  of Michigan,  has been  a member  of  the
Company's  Scientific Advisory Board since 1995. He  is the inventor of the cold
adapted influenza vaccine licensed to the Company by the University of  Michigan
and  has published numerous  papers on this subject.  His laboratory is studying
the  molecular  basis  of  influenza  virus  attenuation  and  is  involved   in
development of new vaccines for other respiratory viruses.
 
    EDWARD  MOCARSKI, JR.,  PH.D., Professor and  Chairman of  the Department of
Microbiology and Immunology at the  Stanford University School of Medicine,  has
been  a  member  of the  Company's  Scientific  Advisory Board  since  1992. His
laboratory  engineered   the  first   recombinant   CMV  providing   the   first
demonstration  of  this virus  as  a vector  and is  one  of the  leading groups
conducting research on CMV gene regulation.
 
   
    PETER PALESE, PH.D., a founder of  the Company and member of the  Scientific
Advisory  Board  since 1992,  is  Professor and  Chairman  of the  Department of
Microbiology at The Mount Sinai School of Medicine of the City University of New
York.  His  laboratory  developed  the  first  successful  strategy  for  making
genetically  engineered influenza  viruses. This invention  is the  subject of a
United States patent issued in 1992 covering the genetic engineering of negative
strand RNA viruses rights to which patent have been acquired by the Company. Dr.
Palese's research group has  been responsible for developing  a genetic map  for
influenza virus, elucidating the function of viral proteins, and the creation of
recombinant  influenza  strains which  demonstrate the  use of  this virus  as a
vector.
    
 
   
    GERALD V. QUINNAN, JR., M.D., Professor of Preventive Medicine, Medicine and
Microbiology, Department of Preventive Medicine and Biometrics at the  Uniformed
Services  University of  the Health Sciences  in Bethesda, Maryland,  has been a
member of the Company's  Scientific Advisory Board since  1995. Dr. Quinnan  was
employed  by the FDA from 1977 until 1993. From 1980 to 1988, he was Director of
the Virology  Division,  subsequently  serving as  Deputy  Director  and  Acting
Director,  of the  Center for Biologics  Evaluation and  Research. Dr. Quinnan's
research concerns aspects of HIV immunology related to vaccine development.
    
 
    BERNARD ROIZMAN, SC.D., a founder and director of the Company and member  of
the Scientific Advisory Board since 1992, is the Joseph Regenstein Distinguished
Service Professor of the Departments of Molecular
 
                                       49
<PAGE>
Genetics  and  Cell Biology  and of  Biochemistry and  Molecular Biology  at The
University of  Chicago.  His laboratory  is  a  leading center  of  research  on
neurovirulence  of the  herpes simplex viruses,  created the first  example of a
large DNA virus  which had been  genetically engineered and  provided the  first
demonstration  of herpes simplex virus  as a vector. Dr.  Roizman is a member of
the United  States National  Academy of  Sciences. The  Company's HSV-2  vaccine
program is based on his patented technology, licensed to Aviron.
 
    JOHN  SKEHEL,  PH.D., FRS,  Director of  the  National Institute  of Medical
Research of  the Medical  Research Council  and the  WHO Influenza  Surveillance
Center  in Mill Hill near London, has  been a member of the Company's Scientific
Advisory Board since 1992. His laboratory  has contributed new knowledge on  the
structure  of the influenza virus as well  as the molecular epidemiology of this
virus.
 
   
    RICHARD WHITLEY, M.D., a founder of the Company and member of the Scientific
Advisory Board  since  1992,  is  Professor  of  Pediatrics,  Microbiology,  and
Medicine  and Vice Chairman of the Department of Pediatrics at the University of
Alabama School of  Medicine in  Birmingham. He has  conducted pharmacologic  and
clinical  studies on many antiviral drugs and his laboratory is a leading center
of research on the mechanism by  which herpes simplex virus causes disease,  and
he  is studying the  use of modified  herpes viruses to  treat brain cancer. Dr.
Whitley is former Chairman of the  NIH Data Monitoring and Safety Committee  for
AIDS Therapy and a member of the Committee on Infectious Disease of the American
Academy of Pediatrics (The Redbook Committee).
    
 
    MAX  WILHELM, PH.D., is  a consultant to the  biotechnology industry and has
been a member  of the  Company's Scientific Advisory  Board since  1993. He  has
retired  from a 35-year career at Ciba-Geigy where he was most recently a member
of the  Pharmaceuticals Division  Committee  overseeing worldwide  research  and
development operations. He was involved in the formation of The Biocine Company,
a joint venture vaccine company between Ciba-Geigy and Chiron, serving as one of
its  original directors, and is currently Chairman  of the Board of Directors of
Genelabs Technologies, Inc.
 
                                       50
<PAGE>
                                   MANAGEMENT
 
   
EXECUTIVE OFFICERS AND DIRECTORS
    
 
   
    The executive officers and directors  of the Company as  of June 1, 1996  is
set forth below:
    
 
   
<TABLE>
<CAPTION>
                NAME                 AGE               POSITION
  ---------------------------------  ---  -----------------------------------
  <S>                                <C>  <C>
  J. Leighton Read, M.D............  45   Chairman, Chief Executive Officer
                                          and Chief Financial Officer
  Martin L. Bryant, M.D., Ph.D.....  47   Vice President, Research
  Victor Jegede, Ph.D..............  51   Vice President, Technical Affairs
  Vera Kallmeyer, M.D., Ph.D.......  37   Vice President, Corporate
                                          Development
  Paul M. Mendelman, M.D...........  48   Vice President, Clinical Research
  Eric J. Patzer, Ph.D.............  47   Vice President, Development
  Reid W. Dennis (1)(2)............  70   Director
  Paul H. Klingenstein (1)(2)......  40   Director
  Jane E. Shaw, Ph.D...............  57   Director
  L. James Strand, M.D. (1)(2).....  54   Director
  Bernard Roizman, Sc.D............  67   Director
  Alan C. Mendelson................  48   Secretary
</TABLE>
    
 
- -------------------
(1) Member of the Compensation Committee.
 
(2) Member of the Audit Committee.
 
   
    J.  LEIGHTON READ, M.D., a founder of  the Company, has been Chairman, Chief
Executive Officer and  Chief Financial  Officer of  the Company  since 1992.  In
1989, he co-founded Affymax N.V. with Dr. Alejandro Zaffaroni, serving initially
as its Executive Vice President and Chief Operating Officer and later, from 1990
to  1991, as President of the Pharma Division  and as a Managing Director of the
parent company. From  1991 to 1993,  Dr. Read was  a principal with  Interhealth
Limited, an investment partnership. Prior to 1989, Dr. Read held appointments at
the Harvard Medical School and School of Public Health, where his research dealt
with techniques for assessing the cost effectiveness of pharmaceutical products.
He  has served on the boards of  a number of private biotechnology companies and
is currently on the board of a  private biotechnology company. Dr. Read holds  a
B.S.  in  Biology and  Psychology  from Rice  University  and an  M.D.  from the
University of Texas Health Science Center at San Antonio.
    
 
   
    MARTIN L. BRYANT,  M.D., PH.D.,  has been  Vice President,  Research of  the
Company  since 1995. Dr. Bryant also currently is Consulting Associate Professor
of Pediatrics, Microbiology and Immunology at the Stanford University School  of
Medicine  and  Adjunct  Associate  Professor of  Molecular  Microbiology  at the
Washington University School of  Medicine. From 1991 to  1995, he was  Director,
Infectious  Disease Research for  G. D. Searle  & Co./Monsanto, a pharmaceutical
company. From  1990  to 1991,  he  was  an Instructor  in  Pediatric  Infectious
Diseases  at the  Washington University School  of Medicine. Dr.  Bryant holds a
B.A. in Chemistry  from Duke  University, an M.A.  in Chemistry  from San  Diego
State  University,  and an  M.D. and  a  Ph.D. from  the University  of Southern
California.
    
 
    VICTOR JEGEDE,  PH.D., has  been Vice  President, Technical  Affairs of  the
Company since 1995. From 1992 to 1994, Dr. Jegede was Vice President, Regulatory
Affairs  and  Quality  for  Creative  BioMolecules,  Inc.,  a biopharmaceuticals
company, and from 1989 to 1992, he was Director, Regulatory Affairs and  Quality
for  WelGen Manufacturing  Partnership (BW  Manufacturing, Inc.),  a division of
Burroughs Welcome Manufacturing, Inc., a pharmaceutical manufacturer. Dr. Jegede
holds a B.S. and  an M.S. in  Biology, and a Ph.D.  in Bacteriology from  Boston
College.
 
                                       51
<PAGE>
   
    VERA  KALLMEYER, M.D., PH.D., has been Vice President, Corporate Development
of the Company since 1994. From 1993 to 1994, Dr. Kallmeyer was Vice  President,
Healthcare  Banking/Biotech at Flemings, a London-based merchant bank. From 1990
to 1993, she was an Associate  in Investment Banking at Wasserstein Perella  and
Company.  In  1994,  she  co-founded  Pacific  Futures,  an  investment advisory
business located in Hong Kong, for which she currently serves as Senior Advisor.
Dr.  Kallmeyer  holds  an  M.D.  and  a  Ph.D.  in  Pediatric  Cardiology   from
Ludwig-Alexander  University in Erlangen,  Germany, and an  M.B.A. from Stanford
University. She has  also studied at  the Harvard Medical  School and the  Royal
Postgraduate Medical School in London.
    
 
   
    PAUL  M. MENDELMAN, M.D., has been  Vice President, Clinical Research of the
Company since  May  1996.  Prior  to joining  the  Company,  Dr.  Mendelman  was
Director,   Clinical   Research,   Infectious   Diseases   for   Merck  Research
Laboratories, a pharmaceutical company, since September 1991. From 1983 to 1991,
Dr. Mendelman was  Clinical Instructor, Assistant  Professor and then  Associate
Professor  of Pediatrics at the University  of Washington. Dr. Mendelman holds a
B.S. and an  M.D. from Ohio  State University and  is a fellow  of the  American
Academy of Pediatrics.
    
 
   
    ERIC  J. PATZER, PH.D., has been  Vice President, Development of the Company
since 1996. Prior to joining the Company, Dr. Patzer had held various  positions
with  Genentech, Inc.,  a pharmaceutical company,  since 1981,  most recently as
Vice President, Development. Dr. Patzer  holds a B.S. in Mechanical  Engineering
from  The Pennsylvania  State University  and a  Ph.D. in  Microbiology from the
University of Virginia.
    
 
    REID W. DENNIS has been a director of the Company since 1992. Mr. Dennis has
been active in venture capital investments since 1952. He founded  Institutional
Venture  Partners ("IVP"),  a venture  capital firm, in  1980, and  has acted as
general partner of IVP since that time.  He is currently a director of  Collagen
Corporation,  as well as several  private companies. Mr. Dennis  holds a B.S. in
Electrical Engineering and an M.B.A. from Stanford University.
 
    PAUL H. KLINGENSTEIN  has been  a director of  the Company  since 1993.  Mr.
Klingenstein  has been associated  with Accel Partners,  a venture capital firm,
since 1986, where he has been a General Partner since 1988. He is a director  of
several  private health  care and biopharmaceutical  companies. Mr. Klingenstein
holds an A.B. from Harvard University and an M.B.A. from Stanford University.
 
    BERNARD ROIZMAN, SC.D., has been a  director of the Company since 1992.  Dr.
Roizman  has  been  the  Joseph Regenstein  Distinguished  Service  Professor of
Virology at the University of Chicago since 1984. He holds B.A. and M.S. degrees
from Temple  University and  an Sc.D.  from The  Johns Hopkins  University.  Dr.
Roizman is also a member of the Company's Scientific Advisory Board.
 
   
    JANE  E. SHAW, PH.D., has been a Director of the Company since May 1996. Dr.
Shaw has been associated with The Stable Network, a biopharmaceutical consulting
company, since she founded it in 1995. From 1987 to 1994, Dr. Shaw was President
and Chief Operating Officer of ALZA Corporation, a pharmaceutical company, where
she began  her career  as a  research  scientist in  1970. Dr.  Shaw is  also  a
director   of  Intel   Corporation,  McKesson  Corporation   and  Boise  Cascade
Corporation. Dr. Shaw holds  a B.Sc. and a  Ph.D. in physiology from  Birmingham
University,  England,  and  an honorary  Doctorate  of Science  degree  from the
Worcester Polytechnic Institute.
    
 
   
    L. JAMES STRAND, M.D., has  been a director of  the Company since 1992.  Dr.
Strand began consulting for IVP, a venture capital firm, in 1986, was named Life
Sciences Venture Partner of IVP in 1993 and a General Partner in 1994. From 1983
to  1993, Dr. Strand was President of Advanced Marketing Decisions, a biomedical
marketing and product development consulting  company. Dr. Strand is a  director
of  Microcide Pharmaceuticals, Inc.  and several privately-held  health care and
biomedical companies. He holds B.S., M.A.  and M.D. degrees from the  University
of  California at San Francisco and an M.B.A. from Santa Clara University and is
a fellow of the American College of Physicians.
    
 
   
    ALAN C. MENDELSON has served as Secretary of the Company since 1992. He  has
been  a  partner of  Cooley Godward  Castro  Huddleson &  Tatum, counsel  to the
Company, since 1980 and served as Managing Partner of its Palo Alto office  from
1990  to 1995. Mr. Mendelson also served as Secretary and Acting General Counsel
of Amgen Inc.,  a biopharmaceutical company,  from 1990 to  1991, and served  as
Acting General Counsel at
    
 
                                       52
<PAGE>
   
Cadence  Design Systems, Inc., an electronic design automation software company,
from 1995  to 1996.  He is  a director  of Acuson  Corporation, CoCensys,  Inc.,
Elexsys International, Inc. and Isis Pharmaceuticals, Inc. Mr. Mendelson holds a
B.A.  from the University of California at Berkeley, and a J.D. from the Harvard
Law School.
    
 
    The Board of  Directors has  an Audit  Committee which  consists of  Messrs.
Dennis,  Klingenstein and Strand.  The Audit Committee  makes recommendations to
the Board  regarding  the  selection of  independent  accountants,  reviews  the
results  and scope  of the  audit and other  services provided  by the Company's
independent  accountants,  and  reviews  and  evaluates  the  Company's  control
functions. The Board of Directors has a Compensation Committee which consists of
Messrs.  Dennis,  Klingenstein  and  Strand.  The  Compensation  Committee makes
recommendations to the Board concerning salaries and incentive compensation  for
employees and consultants of the Company.
 
    The  Board of  Directors presently consists  of six members  who hold office
until the annual meeting of stockholders  and until a successor is duly  elected
and  qualified. Effective upon the  Company's reincorporation into Delaware, the
Board of Directors will be divided into  three classes of equal size. One  class
of  directors will be  elected annually and  its members will  hold office for a
three year term  or until their  successors are duly  elected and qualified,  or
until  their  earlier  removal  or resignation.  The  number  of  directors will
initially be six and may be changed  by a resolution of the Board of  Directors.
Executive  officers are elected by  the Board of Directors.  There are no family
relationships among any of the directors and executive officers of the Company.
 
DIRECTOR COMPENSATION
 
    Directors currently receive no cash compensation from the Company for  their
services  as members of the Board of  Directors. They are reimbursed for certain
expenses in connection with attendance at Board and Committee meetings.
 
    All  of   Aviron's   non-employee   directors  are   entitled   to   receive
non-discretionary   annual  stock   option  grants  under   the  Company's  1996
Non-Employee Directors' Stock Option Plan  (the "Directors' Plan"). Each  option
granted  pursuant to the Directors' Plan has an exercise price equal to the fair
market value  of the  Common Stock  on  the date  of grant,  and is  subject  to
three-year  vesting in equal  annual installments. The  Directors' Plan provides
for initial grants of  options to purchase 15,000  shares for each  non-employee
director  who  joins the  Board following  the offering,  plus annual  grants of
options to purchase 3,000 shares.
 
EXECUTIVE COMPENSATION
 
    The following table sets forth certain  compensation awarded or paid by  the
Company  during the  fiscal year  ended December 31,  1995 to  its President and
Chief Executive Officer and four of  the Company's other executive officers  who
earned more than $100,000 during the year ended December 31, 1995 (collectively,
the "Named Executive Officers"):
 
   
                           SUMMARY COMPENSATION TABLE
    
 
   
<TABLE>
<CAPTION>
                                                                                  ALL OTHER
                                                      ANNUAL COMPENSATION      COMPENSATION (1)
                                                    ------------------------   ----------------
                                                               OTHER ANNUAL
NAME AND PRINCIPAL POSITION                          SALARY    COMPENSATION
- --------------------------------------------------  --------  --------------
<S>                                                 <C>       <C>              <C>
J. Leighton Read, M.D. ...........................  $210,000  $  --                $   743
  Chairman, Chief Executive Officer and Chief
  Financial Officer
Francis R. Cano, Ph.D. (2) .......................   222,500     --                 20,381
  President and Chief Operating Officer
Martin L. Bryant, M.D., Ph.D. (3) ................   153,333   121,351(4)(5)           940
  Vice President, Research
Victor Jegede, Ph.D. (6) .........................   156,667    94,195(4)            1,555
  Vice President, Technical Affairs
Vera Kallmeyer, M.D., Ph.D. ......................   148,167     --                    304
  Vice President, Corporate Development
</TABLE>
    
 
                                       53
<PAGE>
- -------------------
(1)  Includes group term life insurance paid by the Company and reimbursement by
    the Company of $18,120 paid  by Dr. Cano as a  premium payment on his  split
    dollar life insurance policy.
 
   
(2)  Dr. Cano  resigned as a  director, officer  and employee of  the Company in
    April 1996.
    
 
   
(3) Dr. Bryant began his employment with the Company on January 16, 1995.
    
 
   
(4) Includes reimbursement  of moving,  housing and other  expenses incurred  in
    connection with relocating to California as follows: for Dr. Bryant, $45,308
    in direct reimbursement, $16,000 in relocation assistance, $8,000 in monthly
    housing  assistance, and  $25,953 in  federal income  tax gross-up;  for Dr.
    Jegede, $47,042 in direct  reimbursement, $16,000 in relocation  assistance,
    $6,500  in monthly  housing assistance,  and $23,097  in federal  income tax
    gross-up.
    
 
   
(5) Includes $25,000 paid  to Dr. Bryant  in March 1995  as reimbursement for  a
    bonus forfeited upon Dr. Bryant's leaving his former employer.
    
 
   
(6) Dr. Jegede began his employment with the Company on January 9, 1995.
    
 
   
                       OPTION GRANTS IN LAST FISCAL YEAR
    
 
   
<TABLE>
<CAPTION>
                                           INDIVIDUAL GRANTS
                                     -----------------------------
                                      NUMBER OF           %                                  POTENTIAL REALIZABLE VALUE AT ASSUMED
                                      SECURITIES      OF TOTAL                                    ANNUAL RATES OF STOCK PRICE
                                      UNDERLYING   OPTIONS GRANTED   EXERCISE                   APPRECIATION FOR OPTION TERM (3)
                                       OPTIONS     TO EMPLOYEES IN   PRICE PER   EXPIRATION  --------------------------------------
NAME                                   GRANTED     FISCAL YEAR (1)   SHARE (2)      DATE         0%           5%           10%
- -----------------------------------  ------------  ---------------  -----------  ----------  ----------  ------------  ------------
<S>                                  <C>           <C>              <C>          <C>         <C>         <C>           <C>
J. Leighton Read, M.D..............      60,000            19.4%     $    0.50     05/08/05  $  690,000  $  1,124,700  $  1,787,100
                                         20,000(4)          6.5           0.50     05/08/05     230,000       374,900       595,700
                                         20,000(4)          6.5           1.25     12/12/05     215,000       350,450       556,850
Francis R. Cano, Ph.D. (5).........      40,000            12.9           0.50     05/08/05     460,000       749,800     1,191,400
Martin L. Bryant, Ph.D.............      24,000             7.8           0.50     03/14/05     276,000       449,880       714,840
Victor Jegede, Ph.D................      24,000             7.8           0.50     03/14/05     276,000       449,880       714,840
Vera Kallmeyer, M.D., Ph.D.........       4,000             1.3           0.50     05/08/05      46,000        74,980       119,140
                                          5,000             1.6           0.50     05/08/05      57,500        93,725       148,925
                                         15,000             4.9           0.50     05/08/05     172,500       281,175       446,775
                                         20,000             6.5           1.25     12/12/05     215,000       350,450       556,850
</TABLE>
    
 
- -------------------
(1)  Based on an aggregate of 309,000 options granted to employees and directors
    of the Company in  fiscal 1995, including the  Named Executive Officers  set
    forth  in the "Summary Compensation Table"  above and directors set forth in
    "Director Compensation" above.
 
(2) The exercise price is equal to 100%  of the fair market value of the  Common
    Stock at the date of grant.
 
(3) The potential realizable value is calculated based on the term of the option
    at  the time of grant (ten years).  Stock price appreciation of five percent
    and ten percent is assumed pursuant  to rules promulgated by the  Securities
    and  Exchange Commission and does not  represent the Company's prediction of
    its  stock  price  performance.  The   potential  realizable  value  of   0%
    appreciation  measures the value of the option at effectiveness based on the
    assumed initial public offering price per share of $12.00 less the  exercise
    price.  The  potential  realizable  value  at  5%  and  10%  appreciation is
    calculated by  assuming  that  the assumed  initial  public  offering  price
    appreciates at the indicated rate for the entire term of the option and that
    the  option is exercised at  the exercise price and sold  on the last day of
    its term at the appreciated price.
 
(4) Options granted outside of the 1996 Equity Incentive Plan.
 
   
(5) Dr. Cano  resigned as a  director, officer  and employee of  the Company  in
    April 1996.
    
 
                                       54
<PAGE>
   
                AGGREGATED OPTION EXERCISES IN LAST FISCAL YEAR
                       AND FISCAL YEAR-END OPTION VALUES
    
 
   
<TABLE>
<CAPTION>
                                                             NUMBER OF SECURITIES
                                                                  UNDERLYING              VALUE OF UNEXERCISED
                                                             UNEXERCISED OPTIONS          IN-THE-MONEY OPTIONS
                                   SHARES                    AT DECEMBER 31, 1995         AT DECEMBER 31, 1995
                                 ACQUIRED ON     VALUE    --------------------------  -----------------------------
NAME                              EXERCISE     REALIZED   EXERCISABLE  UNEXERCISABLE  EXERCISABLE   UNEXERCISABLE (1)
- ------------------------------  -------------  ---------  -----------  -------------  ------------  ---------------
<S>                             <C>            <C>        <C>          <C>            <C>           <C>
J. Leighton Read, M.D.........      60,000(2)  $  15,000      40,000        --        $    445,000    $   --
Francis R. Cano, Ph.D.........       --           --         110,000        30,000       1,282,500        352,500
Martin L. Bryant, Ph.D........       --           --          --            24,000         --             276,000
Victor Jegede, Ph.D...........       --           --          --            24,000         --             276,000
Vera Kallmeyer, M.D., Ph.D....       --           --          14,780        49,220         169,970        551,030
</TABLE>
    
 
- -------------------
(1)  Based on  the assumed  initial public offering  price of  $12.00 per share,
    minus the exercise price, multiplied by the number of shares underlying  the
    option.
 
   
(2) As of June 1, 1996, 34,200 of the shares acquired upon exercise were subject
    to repurchase by the Company.
    
 
EMPLOYMENT CONTRACTS
 
   
    The  Company's offer of employment to Martin L. Bryant, Ph.D., the Company's
Vice President,  Research, in  December  1994, provided  for an  initial  annual
salary of $160,000 and payment of $25,000 as reimbursement for a bonus forfeited
by Dr. Bryant when he left his previous employer. The Company also agreed to pay
certain  relocation expenses and to  loan Dr. Bryant up  to $50,000 in aggregate
principal amount, at 7.75% simple interest, to  assist him in the purchase of  a
home.  Interest on this  loan will be  forgiven annually, and  principal will be
forgiven annually at the rate of 20% per year as long as Dr. Bryant remains with
the Company.
    
 
   
    The Company's offer of employment to Victor A. Jegede, Ph.D., the  Company's
Vice  President, Technical  Affairs, in December  1994, provided  for an initial
annual salary of  $160,000. The Company  also agreed to  pay certain  relocation
expenses  and to loan Dr. Jegede up to $50,000 in aggregate principal amount, at
7.75% simple interest, to assist him in the purchase of a home. Interest on this
loan will be forgiven annually, and  principal will be forgiven annually at  the
rate of 20% per year as long as Dr. Jegede remains with the Company.
    
 
   
    The  Company's offer of  employment to Eric J.  Patzer, Ph.D., the Company's
Vice President, Development, in  December 1995, provided  for an initial  annual
salary  of $185,000 and a bonus payment of $25,000 upon signing of the agreement
and $25,000 after the completion of one year of service. The Company also agreed
to pay certain  relocation expenses and  to loan  Dr. Patzer up  to $100,000  in
aggregate  principal  amount, at  7.75% simple  interest, to  assist him  in the
purchase of a home. Interest on this loan, when made, will be forgiven annually,
and principal will be forgiven annually at the  rate of 20% per year as long  as
Dr. Patzer remains with the Company.
    
 
   
    The  Company's offer of employment to Paul M. Mendelman, M.D., the Company's
Vice President, Clinical Research, in April 1996, provided for an initial annual
salary of  $185,000  and  a  bonus  payment  of  $25,000  upon  Dr.  Mendelman's
acceptance  of the offer. The Company also agreed to reimburse Dr. Mendelman for
certain relocation  expenses  and  to  loan Dr.  Mendelman  up  to  $100,000  in
aggregate  principal  amount, at  7.75% simple  interest, to  assist him  in the
purchase of a home. Interest on this loan, when made, will be forgiven  annually
at the rate of 20% per year as long as Dr. Mendelman remains with the Company.
    
 
   
    Francis  R. Cano, Ph.D. resigned as  Director, President and Chief Operating
Officer of  the Company  effective  April 19,  1996.  Pursuant to  an  agreement
between  Dr. Cano and  the Company, Dr. Cano  will continue to  be employed as a
consultant by the Company until April 18, 1997. In consideration for Dr.  Cano's
consulting  services, the  Company will  continue to  pay Dr.  Cano's salary and
benefits during the consulting period.
    
 
                                       55
<PAGE>
STOCK OPTION PLANS
 
    EQUITY  INCENTIVE PLAN.   In March 1996,  the Board adopted  the 1996 Equity
Incentive Plan (the  "Incentive Plan") as  an amendment and  restatement of  its
1992  Stock Option Plan and increased the number of shares reserved for issuance
under the Incentive Plan  to 1,750,000 shares. The  Incentive Plan provides  for
grants  of incentive stock options to employees (including officers and employee
directors) and  nonstatutory stock  options, restricted  stock purchase  awards,
stock bonuses and stock appreciation rights to employees (including officers and
employee  directors) and  consultants of  the Company.  It is  intended that the
Incentive Plan  will  be  administered  by  the  Compensation  Committee,  which
determines  recipients and types of awards to be granted, including the exercise
price, number of shares subject to the award and the exercisability thereof.
 
    The term of a  stock option granted under  the Incentive Plan generally  may
not  exceed 10 years. The exercise price  of options granted under the Incentive
Plan is determined by the Board of  Directors, but, in the case of an  incentive
stock  option, cannot be less  than 100% of the fair  market value of the Common
Stock on the date of  grant or, in the case  of 10% stockholders, not less  than
110%  of the fair market value of the Common Stock on the date of grant. Options
granted under the Incentive Plan to new employees and consultants generally will
vest at the  rate of of  the shares subject  to the option  on the first  annual
anniversary  of the date  of hire and 1/48th  of such shares at  the end of each
calendar month thereafter. No  option may be transferred  by the optionee  other
than  by will  or the  laws of  descent or  distribution or,  in certain limited
instances, pursuant to a qualified  domestic relations order. An optionee  whose
relationship  with the Company or any  related corporation ceases for any reason
(other than by death or permanent and total disability) may exercise options  in
the  three-month period following such  cessation (unless such options terminate
or expire sooner by their terms) or  in such longer period as may be  determined
by the Board of Directors.
 
    Shares  subject  to options  which have  lapsed or  terminated may  again be
subject to options granted under the  Incentive Plan. Furthermore, the Board  of
Directors  may  offer to  exchange new  options for  existing options,  with the
shares subject to the existing options again becoming available for grant  under
the  Incentive Plan.  In the event  of a decline  in the value  of the Company's
Common Stock, the Board  of Directors has the  authority to offer optionees  the
opportunity  to replace outstanding higher priced  options with new lower priced
options.
 
    Restricted stock purchase  awards granted  under the Incentive  Plan may  be
granted  pursuant to a repurchase  option in favor of  the Company in accordance
with a vesting  schedule determined  by the Board.  The purchase  price of  such
awards  will be at least 85% of the fair market value of the Common Stock on the
date of grant. Stock bonuses may  be awarded in consideration for past  services
without  a purchase payment.  Stock appreciation rights  authorized for issuance
under the Incentive  Plan may  be tandem stock  appreciation rights,  concurrent
stock appreciation rights or independent stock appreciation rights.
 
    Upon  any merger or consolidation in which  the Company is not the surviving
corporation, all outstanding  awards under  the Incentive Plan  shall either  be
assumed  or  substituted  by  the  surviving  entity.  If  the  surviving entity
determines not to assume or substitute  such awards, the time during which  such
awards  may be exercised shall  be accelerated and the  awards terminated if not
exercised prior to the merger or consolidation.
 
   
    As of June  1, 1996, 643,480  options were outstanding  under the  Incentive
Plan,  with  1,106,520  shares  reserved for  future  grants  or  purchases. The
Incentive Plan will terminate in January  2006, unless terminated sooner by  the
Board of Directors. See Note 7 of Notes to Financial Statements.
    
 
    EMPLOYEE STOCK PURCHASE PLAN.  In March 1996, the Board adopted the Employee
Stock  Purchase  Plan (the  "Purchase Plan")  covering  an aggregate  of 250,000
shares of Common Stock. The Purchase Plan is intended to qualify as an  employee
stock  purchase plan within  the meaning of  Section 423 of  the Code. Under the
Purchase Plan, the Board  of Directors may  authorize participation by  eligible
employees,  including officers, in periodic  offerings following the adoption of
the Purchase Plan. The offering period for any offering will be no more than  27
months.
 
    Employees  are eligible to participate if  they are employed by the Company,
or an affiliate  of the Company  designated by  the Board of  Directors, for  at
least  20 hours per week and are employed by the Company, or an affiliate of the
Company designated by  the Board, for  at least five  months per calendar  year.
Employees who
 
                                       56
<PAGE>
participate  in  an offering  can  have up  to  15% of  their  earnings withheld
pursuant to the Purchase Plan. The amount withheld will then be used to purchase
shares of  the  Common Stock  on  specified dates  determined  by the  Board  of
Directors.  The price of Common Stock purchased  under the Purchase Plan will be
equal to 85% of the lower  of the fair market value  of the Common Stock on  the
commencement  date of  each offering period  or on the  specified purchase date.
Employees may end  their participation in  the offering at  any time during  the
offering  period. Participation ends automatically  on termination of employment
with the Company.
 
   
    In the  event  of a  merger,  reorganization, consolidation  or  liquidation
involving  the Company, in  which the Company is  not the surviving corporation,
the Board of  Directors has discretion  to provide that  each right to  purchase
Common Stock will be assumed or an equivalent right substituted by the successor
corporation,  or the Board may  shorten the offering period  and provide for all
sums collected by payroll deductions to be applied to purchase stock immediately
prior to such merger or other  transaction. The Purchase Plan will terminate  at
the  Board's discretion. The Board  has the authority to  amend or terminate the
Purchase Plan,  subject to  the limitation  that no  such action  may  adversely
affect  any outstanding rights to purchase Common  Stock. See Note 7 of Notes to
Financial Statements.
    
 
    1996 NON-EMPLOYEE DIRECTORS' STOCK  OPTION PLAN.  In  March 1996, the  Board
adopted  the  1996 Non-Employee  Directors' Stock  Option Plan  (the "Directors'
Plan") to  provide for  the automatic  grant of  options to  purchase shares  of
Common  Stock to non-employee  directors of the Company.  The Directors' Plan is
administered  by   the  Board   of  Directors,   unless  the   Board   delegates
administration to a committee comprised of members of the Board.
 
   
    The  maximum number of shares of Common Stock that may be issued pursuant to
options granted under the Directors' Plan  is 200,000. Pursuant to the terms  of
the  Directors' Plan, each director of the Company not otherwise employed by the
Company and who is first elected as a non-employee director after the completion
of this offering  automatically will  be granted  an option  to purchase  15,000
shares  of Common Stock upon such election. Finally, each director who continues
to serve as a non-employee director of the Company will be granted an additional
option to purchase 3,000 shares of Common Stock on December 31 of each year. All
such options vest one-third on  the first anniversary of  the date of grant  and
one-third per year thereafter.
    
 
    In   the  event   of  a   merger,  consolidation,   reverse  reorganization,
dissolution, sale of substantially all of the assets of the Company, or  certain
changes  in the beneficial ownership of the Company's securities representing at
least a  50%  change of  such  ownership,  then options  outstanding  under  the
Directors' Plan will automatically become fully vested and will terminate if not
exercised prior to such event.
 
   
    No  option  granted under  the Directors'  Plan may  be exercised  after the
expiration of ten  years from the  date it  was granted. The  exercise price  of
options under the Directors' Plan will equal the fair market value of the Common
Stock  on the date of grant. The Directors' Plan will terminate in January 2006,
unless earlier  terminated  by the  Board.  See Note  7  of Notes  to  Financial
Statements.
    
 
                                       57
<PAGE>
                              CERTAIN TRANSACTIONS
 
    In  June and  July 1992,  14 investors  purchased an  aggregate of 5,000,000
shares of the Company's Series A Preferred Stock at a per share price of  $0.50.
Institutional  Venture Partners V  and Institutional Venture  Management V, each
affiliated with Institutional Venture Partners ("IVP"), purchased 2,955,000  and
45,000  shares,  respectively,  of  Series  A  Preferred  Stock.  IVP  is  a  5%
stockholder of the Company, and Reid W. Dennis and L. James Strand, directors of
the Company, are each General Partners of IVP. J. Leighton Read, M.D.,  Chairman
of  the Board of Directors, Chief  Executive Officer and Chief Financial Officer
of the  Company, and  Bernard  Roizman, a  director  of the  Company,  purchased
500,000 and 100,000 shares, respectively, of Series A Preferred Stock. Albert L.
Zesiger, a member of Zesiger Capital Group LLC, a 5% stockholder of the Company,
purchased  300,000 shares of Series A  Preferred Stock. Peter Palese and Richard
Whitley, two  of the  founders  of the  Company,  purchased 100,000  and  10,000
shares,  respectively, of Series A Preferred Stock. The Series A Preferred Stock
purchased by the IVP  affiliates and by Drs.  Read, Roizman, Palese and  Whitley
were  purchased on  the same  terms and conditions  as Series  A Preferred Stock
purchased by other investors. The Series  A Preferred Stock is convertible  into
Common  Stock of the Company at  the rate of one share  of Common Stock for each
five shares of Series A Preferred Stock owned.
 
    In September 1993, 34 investors purchased an aggregate of 16,666,667  shares
of  the  Company's Series  B  Preferred Stock  at a  per  share price  of $0.90.
Institutional  Venture  Partners  V  and  Institutional  Venture  Management   V
purchased  1,361,667  and 27,767  shares,  respectively, of  Series  B Preferred
Stock. In addition, Institutional Venture  Partners V and Institutional  Venture
Management  V  received 1,633,333  shares  and 33,333  shares,  respectively, of
Series B Preferred Stock upon  conversion of promissory notes, bearing  interest
at  a 4% annualized rate and aggregating $1,500,000, which the Company issued to
these entities in connection with bridge  loan financing in June 1993.  Entities
affiliated  with  Accel Partners,  a 5%  stockholder  of the  Company, purchased
shares of Series B Preferred Stock  as follows: Accel IV L.P., 2,811,111  shares
and  Accel Japan L.P., 244,444  shares. Paul H. Klingenstein,  a director of the
Company, is a General Partner of Accel Partners. Entities controlled by  Zesiger
Capital  Group  LLC, an  affiliate  of Abingworth  Bioventures  SICAV, purchased
2,065,000 shares  of Series  B  Preferred Stock.  Abingworth Bioventures,  a  5%
stockholder  of the  Company, purchased 2,777,778  shares of  Series B Preferred
Stock. Entities affiliated with Brinson Partners, Inc., a 5% stockholder of  the
Company,  purchased shares of Series B Preferred Stock as follows: Brinson Trust
Company as trustee of the Brinson MAP Venture Capital Fund III, 311,598  shares,
and  Brinson  Venture  Capital Fund  III,  1,910,624 shares.  Peter  Palese also
purchased 55,556 shares  of Series  B Preferred  Stock. The  Series B  Preferred
Stock  purchased by the affiliates of 5%  stockholders of the Company and by Dr.
Palese were purchased on the same terms and conditions as the Series B Preferred
Stock purchased by other investors. The Series B Preferred Stock is  convertible
into  Common Stock of the Company  at the rate of one  share of Common Stock for
each five shares of Series B Preferred Stock owned.
 
    In September 1993, the Company issued warrants to purchase 400,000 shares of
its Series B Preferred Stock at an exercise price of $1.25 per share to entities
affiliated with IVP. The warrants expired unexercised in June 1995.
 
    In May  1995, Sang-A  Pharm. Co.,  Ltd., a  5% stockholder  of the  Company,
purchased  2,941,863 shares of Series C Preferred  Stock at $1.35 per share. The
Series C Preferred Stock is convertible into Common Stock of the Company at  the
rate  of one share  of Common Stock for  each five shares  of Series C Preferred
Stock owned.
 
    From July  through November  1995, 66  investors purchased  an aggregate  of
13,099,707 shares of the Company's Series C Preferred Stock at a per share price
of  $1.35. Dr.  Bernard Roizman  purchased 20,000  shares of  Series C Preferred
Stock. Institutional Venture Partners V  and Institutional Venture Management  V
purchased  653,332 and 13,335 shares, respectively, of Series C Preferred Stock.
Various entities affiliated  with Accel  Partners purchased shares  of Series  C
Preferred  Stock as follows:  Accel Investors '93 L.P.,  41,112 shares; Accel IV
L.P., 930,000  shares; Accel  Japan L.P.,  88,890 shares;  Accel Keiretsu  L.P.,
20,000  shares;  Ellmore  C.  Patterson  Partners,  24,444  shares;  and Prosper
Partners, 6,666 shares. Sang-A  Pharm. Co., Ltd.  purchased 1,187,295 shares  of
Series C Preferred Stock. Orefund, whose investment in the Company is controlled
by  Zesiger Capital Group LLC, purchased  1,481,400 shares of Series C Preferred
Stock. Abingworth  Bioventures  SICAV  purchased  370,370  shares  of  Series  C
Preferred Stock. Biotech Growth, a 5% stockholder of the
 
                                       58
<PAGE>
Company,  purchased  3,000,000  shares  of Series  C  Preferred  Stock. Entities
affiliated with Brinson Partners,  Inc. purchased shares  of Series C  Preferred
Stock  as follows: First National  Bank of Chicago, as  custodian to the Brinson
MAP Venture Capital Fund III, 36,872 shares, and First National Bank of Chicago,
as custodian to  the Brinson  Venture Capital  Fund III,  226,091 shares.  Sally
Whitley,  wife of Richard Whitley purchased  10,000 shares of Series C Preferred
Stock. The Series  C Preferred shares  purchased by the  5% stockholders of  the
Company  and their affiliates and by Dr. Roizman and Mrs. Whitley were purchased
on the same terms and conditions as Series C Preferred shares purchased by other
investors. The Series C Preferred Stock is convertible into Common Stock of  the
Company  at the rate of one share of Common Stock for each five shares of Series
C Preferred Stock owned.
 
   
    In March 1996, Sang-A Pharm Co.,  Ltd. purchased 136,326 shares of Series  C
Preferred  Stock, at a price of $1.35 per share. The Series C Preferred Stock is
convertible into Common Stock of the Company at the rate of one share of  Common
Stock for each five shares of Series C Preferred Stock owned.
    
 
    Vera  Kallmeyer, Vice President, Corporate Development  of the Company, is a
founder, senior  advisor,  and  15% shareholder  of  Pacific  Futures  (formerly
Pacific  Century),  a  Hong  Kong-based  investment  advisory  business. Pacific
Futures received a sales commission on the  sale of Series C Preferred Stock  to
Sang-A,  in an aggregate amount of  $334,462 during 1995. Dr. Kallmeyer received
no portion of such sales commission,  and is currently receiving no salary  from
Pacific Futures.
 
   
    Pursuant  to certain  offer letters to  certain of its  senior officers, the
Company made loans to  these officers to facilitate  home purchases and  certain
other commitments. As of June 1, 1996, the amounts outstanding for principal and
interest on these loans was $40,388 to Martin L. Bryant and $40,388 to Victor A.
Jegede. See "Management -- Employment Contracts."
    
 
    In  January 1996, the  Company extended loans to  certain senior officers to
facilitate the early  exercise of options  to purchase shares  of Common  Stock,
including  loans of $70,000 to Dr. Patzer; $65,000 to Dr. Bryant; $65,000 to Dr.
Jegede; $70,000 to Dr. Cano; and $40,000 to Dr. Kallmeyer. The loans bear simple
interest at a  rate of  5.73% per year.  Principal on  each loan is  due on  the
earlier of 50 months from the date of the underlying option grant or the date of
employment termination.
 
   
    See also "Management -- Employment Contracts."
    
 
                                       59
<PAGE>
                             PRINCIPAL STOCKHOLDERS
 
   
    The  following  table sets  forth  certain information  regarding beneficial
ownership of the  Company's Common Stock  as of June  1, 1996 held  by (i)  each
person  who is  known by  the Company to  own beneficially  more than  5% of the
outstanding shares  of Common  Stock,  (ii) each  director and  Named  Executive
Officer  of the Company, and  (iii) all directors and  executive officers of the
Company as a group.  Unless otherwise indicated below,  to the knowledge of  the
Company,  all persons  listed below have  sole voting and  investment power with
respect to  their shares  of Common  Stock, except  to the  extent authority  is
shared  by spouses  under applicable law.  Except as otherwise  noted below, the
address of  each person  listed below  is c/o  the Company,  297 North  Bernardo
Avenue, Mountain View, California 94043.
    
 
   
<TABLE>
<CAPTION>
                                                                                                PERCENTAGE OF
                                                                                             SHARES BENEFICIALLY
                                                                                                  OWNED (1)
                                                                                 SHARES      -------------------
                                                                              BENEFICIALLY   PRIOR TO    AFTER
BENEFICIAL OWNER                                                               OWNED (1)     OFFERING   OFFERING
- ----------------------------------------------------------------------------  ------------   --------   --------
<S>                                                                           <C>            <C>        <C>
Entities affiliated with Institutional Venture Partners (2) ................   1,344,553      15.02%     10.94%
  3000 Sand Hill Road
  Building 2, Suite 290
  Menlo Park, CA 94025
Sang-A Pharm. Co., Ltd. (3) ................................................     853,096       9.53%      9.66%
  640-9 Deung Chon Dung
  Kangseo-Ku
  Seoul, South Korea
Entities affiliated with Accel Partners (4) ................................     833,330       9.31%      6.78%
  One Embarcadero Center, Suite 3820
  San Francisco, CA 94111
Entities controlled by Zesiger Capital Group LLC (5) .......................     769,280       8.59%      6.26%
  320 Park Avenue
  New York, NY 10022
Abingworth Bioventures SICAV ...............................................     629,629       7.03%      5.12%
  26 St. James's Street
  London SW1A 1HA England
Biotech Growth .............................................................     600,000       6.70%      4.88%
  Bellevue Asset Management
  Grundstrasse 12
  CH-6343 Rotkreuz
  Switzerland
Entities affiliated with Brinson Partners, Inc. (6) ........................     497,035       5.55%      4.05%
  209 South LaSalle Street, Suite 114
  Chicago, IL 60604-1295
J. Leighton Read, M.D. (7)..................................................     395,000       4.41%      3.22%
Martin L. Bryant, M.D., Ph.D. (8)...........................................      34,640       *          *
Victor Jegede, Ph.D. (9)....................................................      34,640       *          *
Vera Kallmeyer, M.D., Ph.D. (10)............................................      45,673       *          *
Eric J. Patzer, Ph.D. (11)..................................................      40,000       *          *
Reid W. Dennis (2)..........................................................   1,344,553      15.02%     10.94%
Paul H. Klingenstein (4)....................................................     833,330       9.31%      6.78%
Bernard Roizman, Sc.D. (12).................................................     175,200       1.96%      1.43%
Jane E. Shaw, Ph.D. (13)....................................................       4,000       *          *
L. James Strand, M.D. (14)..................................................   1,354,553      15.12%     11.02%
All directors and executive officers as a group
  (11 persons) (15).........................................................   2,917,036      32.38%     23.63%
</TABLE>
    
 
- -------------------
   
*   Represents beneficial ownership of less than 1% of the outstanding shares of
    the Company's Common
    Stock.
    
 
                                       60
<PAGE>
   
(1)  Calculated  as  if all  outstanding  shares  of Preferred  Stock  have been
    converted into Common Stock at a ratio of five shares of Preferred Stock for
    one share of Common Stock. Beneficial ownership is determined in  accordance
    with  the  rules of  the Securities  and  Exchange Commission  and generally
    includes voting or investment power  with respect to securities.  Beneficial
    ownership  also includes  shares of  stock subject  to options  and warrants
    currently exercisable or convertible,  or exercisable or convertible  within
    60  days of the  date of this  table. Percentage of  beneficial ownership is
    based on 8,952,657 shares  of Common Stock outstanding  as of June 1,  1996,
    and  12,285,990 shares of Common Stock  outstanding after completion of this
    offering and the concurrent sale of the Sang-A Shares.
    
 
   
(2) Includes  1,320,666 shares  held  by Institutional  Venture Partners  V  and
    23,887  shares  held by  Institutional Venture  Management  V, of  which Mr.
    Dennis, a  Director  of the  Company  is a  general  partner.  Institutional
    Venture  Management  V  is  the  general  partner  of  Institutional Venture
    Partners V. Mr. Dennis disclaims beneficial ownership of the shares held  by
    Institutional  Venture Partners  V and  Institutional Venture  Management V,
    except to the extent of his pecuniary interests therein.
    
 
   
(3)  Percentage  of  shares  beneficially  owned  after  offering  includes  the
    estimated  333,333  shares Sang-A  intends to  purchase concurrent  with the
    offering.
    
 
   
(4) Includes 697,500 shares held by Accel IV, L.P., 66,666 shares held by  Accel
    Japan,  L.P., 30,833 shares held by Accel Investors '93, L.P., 18,332 shares
    held by Ellmore C. Patterson Partners, 15,000 shares held by Accel Keiretsu,
    L.P. and 4,999 shares held by Prosper Partners. Mr. Klingenstein, a Director
    of the Company  is a  general partner  of Accel  Partners. Mr.  Klingenstein
    disclaims  beneficial ownership of the shares  held by Accel IV, L.P., Accel
    Japan, L.P.,  Accel  Investors '93,  L.P.,  Ellmore C.  Patterson  Partners,
    Prosper  Partners  and Accel  Keiretsu, L.P.,  except to  the extent  of his
    pecuniary interests therein.
    
 
   
(5) Includes  8,000 shares  held by  A. Carey  Zesiger Revocable  Trust,  22,000
    shares  held by  Atwell & Co.,  11,000 shares  held by Batrus  & Co., 11,000
    shares held by Booth  & Co., 11,000  shares held by  Calmont & Co.,  100,000
    shares held by Comply & Co., 33,000 shares held by Daly & Co., 28,000 shares
    held by Heil & Co., 17,000 shares held by J.C. Orr & Co., 90,000 shares held
    by  Kane & Co., 17,000 shares held  by Domenic Mizio, 296,280 shares held by
    Orefund, 28,000 shares held by Sigler & Co., 60,000 shares held by Albert L.
    Zesiger, 7,000 shares held by Alexa L. Zesiger, 22,000 shares held by  Barry
    Ramsay  Zesiger and 8,000 shares held  by Nicola L. Zesiger. Zesiger Capital
    Group LLC disclaims beneficial ownership of all such shares.
    
 
   
(6) Includes 427,342 shares held by  Brinson Venture Capital Fund III, L.P.  and
    69,693  shares held by Brinson  Trust Company as Trustee  of The Brinson MAP
    Venture Capital Fund III.
    
 
   
(7) Includes 40,000 shares Dr. Read  acquired pursuant to the exercise of  stock
    options.  Also includes an aggregate of  110,000 shares acquired pursuant to
    an early exercise of stock options, of which an aggregate of 76,400 will  be
    subject  to repurchase by the Company as  of July 31, 1996. Also includes an
    aggregate of 32,000 shares held by The Travis Read 1993 Trust and The  Haley
    Read  1993 Trust (the  "Trusts") of which Robert  Fitzwilson is the trustee.
    Dr. Read disclaims beneficial ownership of the shares held by the Trusts.
    
 
   
(8) Includes  26,000 shares  acquired pursuant  to an  early exercise  of  stock
    options,  of which 22,880 will be subject to repurchase by the Company as of
    July 31,  1996. Also  includes 8,640  shares  Dr. Bryant  has the  right  to
    acquire pursuant to options exercisable as of July 31, 1996.
    
 
   
(9)  Includes  26,000 shares  acquired pursuant  to an  early exercise  of stock
    options, of which 22,880 will be subject to repurchase by the Company as  of
    July  31,  1996. Also  includes 8,640  shares  Dr. Jegede  has the  right to
    acquire pursuant to options exercisable as of July 31, 1996.
    
 
   
(10) Includes 16,000  shares acquired  pursuant to  an early  exercise of  stock
    options,  of which 14,080 will be subject to repurchase by the Company as of
    July 31, 1996. Also  includes 29,673 shares Dr.  Kallmeyer has the right  to
    acquire pursuant to options exercisable as of July 31, 1996.
    
 
   
(11)  Includes 40,000  shares acquired  pursuant to  an early  exercise of stock
    options, all of which are subject to repurchase by the Company.
    
 
                                       61
<PAGE>
   
(12) Includes 12,000 shares which are  subject to repurchase by the Company  and
    1,200  shares  Dr. Roizman  has  the right  to  acquire pursuant  to options
    exercisable as of July 31, 1996.
    
 
   
(13) Includes 4,000 shares Dr. Shaw has the right to acquire pursuant to options
    exercisable as of July 31, 1996.
    
 
   
(14) Includes 1,320,666 shares  held by Institutional  Venture Partners V  ("IVP
    V"),  of which Dr.  Strand is a  limited partner, and  23,887 shares held by
    Insitutional Venture Management V,  which is the general  partner of IVP  V,
    and  5,000 shares Dr.  Strand has the  right to acquire  pursuant to options
    exercisable as of July 31,  1996. Dr. Strand disclaims beneficial  ownership
    of the shares held by IVP V and Institutional Venture Management V.
    
 
   
(15)  Includes  2,177,883  shares  held  by  entities  affiliated  with  certain
    directors of the Company as described in footnotes 2 and 3 above and  57,153
    shares subject to options exercisable as of July 31, 1996.
    
 
                                       62
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK
 
    The  following description of  the capital stock of  the Company and certain
provisions of  the  Company's Certificate  of  Incorporation and  Bylaws  to  be
effective  upon completion of this offering is a summary and is qualified in its
entirety by the provisions of the Certificate of Incorporation and Bylaws, which
have been filed as  exhibits to the Company's  Registration Statement, of  which
this Prospectus is a part.
 
    Upon  the  closing of  this offering,  the authorized  capital stock  of the
Company will consist of 30,000,000 shares of Common Stock, par value $0.001  and
5,000,000 shares of Preferred Stock, par value $0.001.
 
COMMON STOCK
 
   
    Upon  completion of this offering, there will be 12,285,990 shares of Common
Stock outstanding (plus up to 38,888 shares that may be issued upon exercise  of
outstanding  warrants). The holders of Common Stock are entitled to one vote for
each  share  held  of  record  on  all  matters  submitted  to  a  vote  of  the
stockholders.  The holders of Common Stock are not entitled to cumulative voting
rights with respect to the election of directors, and as a consequence, minority
stockholders will not be  able to elect  directors on the  basis of their  votes
alone.
    
 
    Subject to preferences that may be applicable to any then outstanding shares
of Preferred Stock, holders of Common Stock are entitled to receive ratably such
dividends  as may  be declared by  the Board  of Directors out  of funds legally
available therefore.  See  "Dividend  Policy."  In  the  event  of  liquidation,
dissolution  or  winding up  of the  Company,  holders of  the Common  Stock are
entitled to share ratably in all  assets remaining after payment of  liabilities
and  the  liquidation preference  of any  then  outstanding shares  of Preferred
Stock. Holders of Common Stock have no preemptive rights and no right to convert
their Common Stock into any other securities. There are no redemption or sinking
fund provisions applicable to the Common Stock. All outstanding shares of Common
Stock are, and all shares of Common  Stock to be outstanding upon completion  of
this offering will be, fully paid and nonassessable.
 
PREFERRED STOCK
 
    Upon  the closing of  this offering, all outstanding  Preferred Stock of the
Company will be converted  into Common Stock. The  Board of Directors will  have
the  authority,  without further  action  by the  stockholders,  to issue  up to
5,000,000 shares of Preferred Stock in one or more series and to fix the rights,
preferences, privileges  and restrictions  thereof, including  dividend  rights,
conversion  rights, voting rights, terms of redemption, liquidation preferences,
sinking fund  terms and  the number  of shares  constituting any  series or  the
designation  of  such  series,  without  any  further  vote  or  action  by  the
stockholders. The issuance of Preferred Stock could adversely affect the  voting
power  of holders  of Common  Stock and  the likelihood  that such  holders will
receive dividend payments and payments upon  liquidation may have the effect  of
delaying,  deferring or  preventing a  change in  control of  the Company, which
could have  a depressive  effect on  the market  price of  the Company's  Common
Stock. The Company has no present plan to issue any shares of Preferred Stock.
 
WARRANTS
 
   
    In February 1993, the Company entered into an agreement with The Mount Sinai
School  of Medicine of  the City University  of New York  ("Mount Sinai"), under
which Mount Sinai transferred to the  Company rights to certain patents,  patent
applications,  and associated  know-how and  other technical  information. Mount
Sinai also granted the Company (i) an option to acquire any improvements to  the
inventions  disclosed in the licensed patents and patent applications thereafter
developed by Mount Sinai and (ii) a right of first negotiation for a license  or
assignment  to certain related technology.  In connection with these agreements,
the Company  issued to  Mount Sinai  warrants (the  "Mount Sinai  Warrants")  to
purchase,  in the aggregate, 225,000 shares  of the Company's Series A Preferred
Stock (45,000 shares of Common Stock  upon conversion of the Series A  Preferred
Stock).  Each Mount  Sinai Warrant  is exercisable  for a  period of  five years
commencing upon the occurrence of  specified milestone events, which  accelerate
upon  the effectiveness  of this  offering. Warrants  to purchase  45,000 of the
shares are exercisable at a purchase price of $0.90 per share (convertible  into
9,000  shares of Common Stock) issuable  upon exercise of the warrants. Warrants
to purchase 148,750  of the shares  will become exercisable  upon the  effective
date  of this offering, at a purchase price per share of Common Stock receivable
upon
    
 
                                       63
<PAGE>
   
conversion of  the  Series A  Preferred  Stock  issuable upon  exercise  of  the
warrants  equal to  125% of the  per share  price of this  offering. Warrants to
purchase the remaining 31,250 shares will  be canceled on the effective date  of
this  offering. See  "Business --  Collaborative Agreements  -- The  Mount Sinai
School of Medicine of the City University of New York."
    
 
    In connection  with an  agreement entered  into in  February 1995  with  the
University  of Michigan  ("Michigan"), under  which Michigan  transferred to the
Company certain  intellectual  property  rights and  technology  (the  "Michigan
Technology"),  the Company agreed to issue  to Michigan a warrant (the "Michigan
Warrant") to purchase shares of its Common Stock upon the first commercial  sale
of a product incorporating the Michigan Technology, for a number of shares equal
to  1.25% of  the total  issued and outstanding  shares of  the Company's Common
Stock as of  the date of  such first  commercial sale (excluding  shares of  the
Company's  Common Stock issued by the Company in connection with its acquisition
of another company,  in connection  with any  corporate partnering  transaction,
issued  in connection with other technology transfers not involving the Michigan
Technology, or unvested  employee or  director option  shares), at  a per  share
exercise  price equal to  125% of the  price of this  Offering. See "Business --
Collaborative Agreements -- University of Michigan."
 
   
    In connection with  a private  placement of  Series C  Preferred Stock,  the
Company  issued to the placement  agent a warrant to  purchase 352,536 shares of
its  Series  C  Preferred  Stock  at  an  exercise  price  of  $1.62  per  share
(convertible  into  70,507  shares of  Common  Stock), exercisable  at  any time
through November 9, 2000.
    
 
REGISTRATION RIGHTS
 
   
    The holders (or  their permitted transferees)  ("Holders") of  approximately
7,833,634  shares of Common Stock and warrants to purchase approximately 148,145
shares of  Common Stock  are entitled  to  certain rights  with respect  to  the
registration of such shares under the Securities Act. If the Company proposes to
register  any of  its securities  under the Securities  Act, either  for its own
account or for the account of  other security holders, the Holders are  entitled
to  notice of  the registration  and are entitled  to include,  at the Company's
expense, such shares therein.  In addition, certain of  the Holders may  require
the Company at its expense on not more than two occasions to file a Registration
Statement  under  the Securities  Act, with  respect to  their shares  of Common
Stock, and  the Company  is  required to  use its  best  efforts to  effect  the
registration,  subject  to  certain  conditions  and  limitations.  Further, the
Holders may require the Company at its expense to register their shares on  Form
S-3  when  such  form  becomes  available to  the  Company,  subject  to certain
conditions and limitations.
    
 
DELAWARE ANTI-TAKEOVER LAW AND CERTAIN CHARTER PROVISIONS
 
    Upon completion of  the Company's reincorporation  in Delaware, the  Company
will  be  subject to  the  provisions of  Section  203 of  the  Delaware General
Corporation Law  (the "Delaware  Law"), an  anti-takeover law.  In general,  the
statute  prohibits  a  publicly-held  Delaware corporation  from  engaging  in a
"business combination" with an  "interested stockholder" for  a period of  three
years after the date of the transaction in which the person became an interested
stockholder, unless the business combination is approved in a prescribed manner.
A  "business combination"  includes a  merger, asset  sale or  other transaction
resulting in a  financial benefit to  the stockholder. For  purposes of  Section
203,  an "interested stockholder" is a  person who, together with affiliates and
associates, owns (or  within three  years prior,  did own)  15% or  more of  the
corporation's voting stock.
 
    Upon  completion of the Company's reincorporation in Delaware, the Company's
Certificate of Incorporation will  provide that each director  will serve for  a
three-year  term, with  approximately one-third of  the directors  to be elected
annually. Candidates  for  director  may  be nominated  only  by  the  Board  of
Directors  or by a stockholder who gives  written notice to the Company at least
20 days before the annual meeting. The Company may have the number of  directors
as  determined from time to time to pursuant to a resolution of the Board, which
currently consists of six members.  Between stockholder meetings, the Board  may
appoint  new directors  to fill  vacancies or  newly created  directorships. The
Certificate will not provide for  cumulative voting at stockholder meetings  for
election  of directors. As  a result, stockholders controlling  more than 50% of
the outstanding Common  Stock can  elect the  entire Board  of Directors,  while
stockholders  controlling 49% of the outstanding Common Stock may not be able to
elect any directors. A director may be removed from office only for cause by the
affirmative vote  of  a  majority of  the  combined  voting power  of  the  then
outstanding  shares  of stock  entitled  to vote  generally  in the  election of
directors.
 
                                       64
<PAGE>
    Upon completion of the Company's reincorporation in Delaware, the  Company's
Certificate  of Incorporation will require that any action required or permitted
to be taken by  stockholders of the  Company must be effected  at a duly  called
annual  or special meeting of stockholders and  may not be effected by a consent
in writing. The Company's  Certificate of Incorporation  also provides that  the
authorized number of directors may be changed only by resolution of the Board of
Directors.  See "Management --  Directors and Executive  Officers." Delaware Law
and these charter provisions may have the effect of deterring hostile  takeovers
or  delaying changes in control or management of the Company, which could have a
depressive effect on the market price of the Company's Common Stock.
 
LIMITATION OF LIABILITY AND INDEMNIFICATION
 
    Upon completion of the Company's reincorporation in Delaware, the  Company's
Certificate  of Incorporation  will contain  certain provisions  permitted under
Delaware Law relating to the liability of directors. These provisions  eliminate
a  director's personal liability for monetary damages resulting from a breach of
fiduciary duty, except in certain circumstances involving certain wrongful acts,
such as (i) for any breach of the  director's duty of loyalty to the Company  or
its  stockholders, (ii) for acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) under Section 174 of
the Delaware General Corporation Law, or (iv) for any transaction from which the
director derives an improper personal benefit. These provisions do not limit  or
eliminate  the rights  of the  Company or  any stockholder  to seek non-monetary
relief, such  as an  injunction  or rescission,  in the  event  of a  breach  of
director's fiduciary duty. These provisions will not alter a directors liability
under  federal securities laws. The  Company's Certificate of Incorporation also
contains provisions indemnifying the  directors and officers  of the Company  to
the  fullest extent permitted  by Delaware General  Corporation Law. The Company
believes that  these  provisions  will  assist the  Company  in  attracting  and
retaining qualified individuals to serve as directors.
 
TRANSFER AGENT
 
    The transfer agent for the Common Stock of the Company is The First National
Bank of Boston.
 
                                       65
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE
 
    Prior  to this offering, there has not been any public market for the Common
Stock of the Company.  Further sales of substantial  amounts of Common Stock  in
the  open  market may  adversely affect  the  market price  of the  Common Stock
offered hereby.
 
   
    Upon completion of this offering, based on the number of shares  outstanding
as of June 1, 1996, the Company will have outstanding an aggregate of 12,285,990
shares  of Common Stock  assuming (i) the  issuance by the  Company of 3,000,000
shares of Common Stock offered hereby,  (ii) the issuance of the 333,333  Sang-A
Shares,  (iii)  no  issuance  of  148,145 shares  of  Common  Stock  relating to
outstanding warrants to purchase Common  Stock, (iv) no exercise of  outstanding
options  exercisable  to purchase  643,480 shares  of Common  Stock, and  (v) no
exercise of the Underwriters' over-allotment  option to purchase 450,000  shares
of Common Stock. Of these shares, 3,000,000 shares sold in this offering will be
freely tradable without restriction or further registration under the Securities
Act,  except for  shares held  by "affiliates"  of the  Company as  that term is
defined in Rule 144 under  the Securities Act (whose  sales would be subject  to
certain  limitations  and  restrictions  described  below)  and  the regulations
promulgated thereunder.
    
 
   
    The remaining  8,952,657  shares  held by  officers,  directors,  employees,
consultants  and other shareholders of  the Company were sold  by the Company in
reliance on exemptions from the registration requirements of the Securities  Act
and  are  "restricted"  securities within  the  meaning  of Rule  144  under the
Securities Act. Approximately 149,329  of these shares of  Common Stock will  be
eligible  for  sale  in  the  public  market  upon  the  effective  date  of the
Registration Statement of which this Prospectus is a part (the "Effective Date")
in reliance on Rule 144(k) under the Securities Act. Beginning 90 days after the
Effective Date, an additional  37,395 of these shares  will become eligible  for
sale  subject to the provisions of Rule 144  and Rule 701 of the Securities Act.
Beginning 180 days after  the Effective Date, an  additional 5,311,881 of  these
shares  will become eligible for  sale subject to the  provisions of Rule 144 or
Rule 701 upon the expiration of agreements not to sell such shares. In addition,
90 days after the Effective Date, 283,160 shares subject to vested options  will
be  available for sale, subject  to compliance with Rule  701, and an additional
33,726 shares subject to  additional vested options will  be available for  sale
upon the expiration of the Lock-Up Period described below.
    
 
    Each  officer, director and certain stockholders  of the Company have agreed
with the representatives of the Underwriters for a period of 180 days after  the
effective  date of  this Prospectus (the  "Lock-Up Period"),  subject to certain
exceptions, not to offer to sell,  contract to sell, or otherwise sell,  dispose
of, loan, pledge or grant any rights with respect to any shares of Common Stock,
any  options  or  warrants  to  purchase any  shares  of  Common  Stock,  or any
securities convertible into or exchangeable for shares of Common Stock owned  as
of  the date of this Prospectus or  thereafter acquired directly by such holders
or  with  respect  to  which  they  have  or  hereafter  acquire  the  power  of
disposition, without the prior written consent of Robertson, Stephens & Company.
However,  Robertson, Stephens & Company  may, in its sole  discretion and at any
time without notice,  release all or  any portion of  the securities subject  to
lock-up  agreements. In addition, the Company has agreed that during the Lock-Up
Period, the Company will  not, without the prior  written consent of  Robertson,
Stephens  & Company,  subject to  certain exceptions,  issue, sell,  contract to
sell, or  otherwise dispose  of, any  shares  of Common  Stock, any  options  or
warrants  to purchase any  shares of Common Stock  or any securities convertible
into, exercisable for or exchangeable for shares of Common Stock.
 
   
    In general, under  Rule 144  as currently in  effect, a  person (or  persons
whose shares are aggregated), including an affiliate, who has beneficially owned
shares for at least two years is entitled to sell, within any three-month period
commencing  90 days after the  Effective Date, a number  of shares that does not
exceed the greater  of (i) 1%  of the  then outstanding shares  of Common  Stock
(approximately  122,860 shares  outstanding immediately after  this offering) or
(ii) the  average weekly  trading volume  in the  Common Stock  during the  four
calendar  weeks preceding such  sale, subject to  the filing of  a Form 144 with
respect to  such  sale  and  certain  other  limitations  and  restrictions.  In
addition, a person who is not deemed to have been an affiliate of the Company at
any  time during  the three  months preceding a  sale, and  who has beneficially
owned the shares proposed to be sold for at least three years, would be entitled
to   sell   such   shares   under   Rule   144(k)   without   regard   to    the
    
 
                                       66
<PAGE>
requirements  described above. To  the extent that shares  were acquired from an
affiliate of the Company, such stockholder's  holding period for the purpose  of
effecting  a sale  under Rule  144 commences  on the  date of  transfer from the
affiliate.
 
    Any employee,  officer or  director  of or  consultant  to the  Company  who
purchased shares or was granted options to purchase shares pursuant to a written
compensatory  plan or contract  ("Rule 701 Shares")  is entitled to  rely on the
resale provisions of  Rule 701. Rule  701 permits non-affiliates  to sell  their
Rule   701  Shares  without  having   to  comply  with  the  public-information,
holding-period, volume-limitation or notice provisions  of Rule 144 and  permits
affiliates  to sell  their Rule  701 Shares  without having  to comply  with the
holding period restrictions of Rule 144,  in each case commencing 90 days  after
the  Effective  Date.  However, all  officers  and directors  and  certain other
stockholders have agreed not to sell or otherwise dispose of Common Stock of the
Company  during  the  Lock-Up  Period  without  the  prior  written  consent  of
Robertson, Stephens & Company. See "Underwriting."
 
    The  Company intends to  file a registration  statement under the Securities
Act to register shares  of Common Stock reserved  for issuance under the  Option
Plan,  thus permitting the resale of such shares by non-affiliates in the public
market without restriction under the Securities Act. Such registration statement
will become effective immediately upon filing.
 
                                       67
<PAGE>
                                  UNDERWRITING
 
   
    The  Underwriters  named   below,  acting   through  their   representatives
Robertson,  Stephens & Company  LLC, Bear, Stearns  & Co. Inc.,  and Hambrecht &
Quist LLC (the "Representatives"), have  severally agreed, subject to the  terms
and  conditions of the Underwriting Agreement,  to purchase from the Company the
number of  shares of  Common Stock  set forth  opposite their  names below.  The
Underwriters  are committed to purchase and pay  for all such shares, if any are
purchased.
    
 
   
<TABLE>
<CAPTION>
                                                                   NUMBER OF
                           UNDERWRITER                               SHARES
- -----------------------------------------------------------------  ----------
<S>                                                                <C>
Robertson, Stephens & Company LLC................................
Bear, Stearns & Co. Inc..........................................
Hambrecht & Quist LLC............................................
 
                                                                   ----------
    Total........................................................   3,000,000
                                                                   ----------
                                                                   ----------
</TABLE>
    
 
   
    The Representatives have advised the  Company that the Underwriters  propose
to offer the shares of Common Stock to the public at the initial public offering
price  set forth on the cover page of  this Prospectus and to certain dealers at
such price less a  concession of not  more than $           per share, of  which
$         may be  reallowed to other dealers. After the initial public offering,
the public offering price, concession and reallowance to dealers may be  reduced
by the Representatives. No such reduction shall change the amount of proceeds to
be received by the Company as set forth on the cover page of this Prospectus.
    
 
   
    The  Company has granted  to the Underwriters  an option, exercisable during
the 30-day period after the date of  this Prospectus, to purchase up to  450,000
additional  shares of Common  Stock at the  same price per  share as the Company
will receive  for the  3,000,000 shares  that the  Underwriters have  agreed  to
purchase.  To the extent that the Underwriters exercise such option, each of the
Underwriters will  have a  firm commitment  to purchase  approximately the  same
percentage  of such additional shares that the  number of shares of Common Stock
to be purchased by it shown in the above table represents as a percentage of the
3,000,000 shares offered hereby.  If purchased, such  additional shares will  be
sold  by the  Underwriters on  the same  terms as  those on  which the 3,000,000
shares are being sold.
    
 
   
    The  Underwriting  Agreement  contains  covenants  of  indemnity  among  the
Underwriters  and  the  Company  against  certain  civil  liabilities, including
liabilities under the Securities  Act and liabilities  arising from breaches  of
representations and warranties contained in the Underwriting Agreement.
    
 
   
    Each  executive officer and  director and certain  other shareholders of the
Company have agreed with the Representatives for the Lock-Up Period not to offer
to sell, contract to sell, or otherwise sell, dispose of, loan, pledge or  grant
any  rights with respect to any shares  of Common Stock, any options or warrants
to purchase any shares  of Common Stock, or  any securities convertible into  or
exchangeable  for shares of Common Stock owned as of the date of this Prospectus
or thereafter acquired directly  by such holders or  with respect to which  they
have  or hereinafter acquire the power of disposition, without the prior written
consent of Robertson,  Stephens &  Company LLC. However,  Robertson, Stephens  &
Company  LLC may,  in its  sole discretion  at any  time or  from time  to time,
without notice, release  all or  any portion of  the securities  subject to  the
lock-up  agreements. Approximately 5,311,881 of such shares will be eligible for
immediate public sale following expiration of the Lock-Up Period, subject to the
provisions of Rule  144. In  addition, the Company  has agreed  that during  the
Lock-Up  Period, it  will not, without  the prior written  consent of Robertson,
Stephens & Company LLC,  issue, sell, contract to  sell or otherwise dispose  of
any  shares of Common Stock,  any options or warrants  to purchase any shares of
Common Stock or any securities convertible into, exercisable for or exchangeable
for shares of  Common Stock other  than the  issuance of Common  Stock upon  the
exercise  of outstanding options and under  the existing employee stock purchase
plan and the Company's issuance of options under existing employee stock  option
plans. See "Shares Eligible For Future Sale."
    
 
                                       68
<PAGE>
   
    The  Underwriters do not intend to confirm  sales to any accounts over which
they exercise discretionary authority in excess of 5% of the number of shares of
Common Stock offered hereby.
    
 
   
    Prior to this offering, there has been no public market for the Common Stock
of the Company. Consequently, the initial  public offering price for the  Common
Stock  offered hereby was determined through  negotiations among the Company and
the Representatives.  Among the  factors considered  in such  negotiations  were
prevailing  market  conditions, certain  financial  information of  the Company,
market valuations of other  companies that the  Company and the  Representatives
believe  to be comparable to the Company, estimates of the business potential of
the Company, the present  state of the Company's  development and other  factors
deemed relevant.
    
 
   
    In  addition  to the  3,000,000 shares  of Common  Stock to  be sold  by the
Company in this offering, concurrent with  this offering the Company intends  to
sell  in a private placement a number of  shares of Common Stock equal to 10% of
the aggregate  number  of  shares sold  in  this  offering and  in  the  private
placement  at  the  initial  public offering  price  per  share  (333,333 shares
assuming a purchase price of $12.00 per share); provided however, that the total
number of shares to be purchased by Sang-A will not exceed $5,000,000 divided by
the initial public  offering price.  Such sale will  be effected  pursuant to  a
separate agreement with Sang-A and not pursuant to the Underwriting Agreement.
    
 
   
    An  individual associated  with Bear, Stearns  & Co.  Inc. beneficially owns
10,000 shares of the Company's Common Stock.
    
 
                                 LEGAL MATTERS
 
   
    The validity of  the shares of  Common Stock offered  hereby will be  passed
upon  for the  Company by  Cooley Godward Castro  Huddleson &  Tatum, Palo Alto,
California. GC&H Investments,  an entity affiliated  with Cooley Godward  Castro
Huddleson  &  Tatum, beneficially  owns 22,000  shares  of the  Company's Common
Stock. Certain legal matters will be passed upon for the Underwriters by  Wilson
Sonsini Goodrich & Rosati, Palo Alto, California.
    
 
                                    EXPERTS
 
   
    The  financial statements of Aviron as of December 31, 1994 and 1995 and for
each of the three years in the period ended December 31, 1995 appearing in  this
Prospectus  and Registration Statement  have been audited by  Ernst & Young LLP,
independent auditors, as set  forth in their  report theron appearing  elsewhere
herein  and are included in reliance upon  such report given on the authority of
such firm as experts in accounting and auditing.
    
 
                             ADDITIONAL INFORMATION
 
    A Registration Statement on Form S-1, including amendments thereto, relating
to the  Common Stock  offered hereby  has been  filed by  the Company  with  the
Securities  and Exchange Commission. This Prospectus does not contain all of the
information set  forth  in  the  Registration Statement  and  the  exhibits  and
schedules thereto. Statements contained in this Prospectus as to the contents of
any  contract or other document referred to  are not necessarily complete and in
each instance reference is made to the  copy of such contract or other  document
filed  as an  exhibit to the  Registration Statement, each  such statement being
qualified in  all  respects by  such  reference. For  further  information  with
respect to the Company and the Common Stock offered hereby, reference is made to
such  Registration Statement, exhibits and schedules. A copy of the Registration
Statement may  be  inspected  by  anyone  without  charge  at  the  Commission's
principal  office located at 450 Fifth Street, N.W., Washington, D.C. 20549, the
New York Regional Office located at 7 World Trade Center, 13th Floor, New  York,
New  York 10048, and the Chicago  Regional Office located at Northwestern Atrium
Center, 500 West Madison Street, Chicago, Illinois 60661-2511, and copies of all
or any part  thereof may be  obtained from  the Public Reference  Branch of  the
Commission upon the payment of certain fees prescribed by the Commission.
 
                                       69
<PAGE>
                                     AVIRON
 
                         INDEX TO FINANCIAL STATEMENTS
 
   
<TABLE>
<S>                                                                         <C>
Report of Ernst & Young LLP, Independent Auditors.........................   F-2
 
Audited Financial Statements
 
Balance Sheets............................................................   F-3
Statements of Operations..................................................   F-4
Statement of Stockholders' Equity.........................................   F-5
Statements of Cash Flows..................................................   F-7
Notes to Financial Statements.............................................   F-7
</TABLE>
    
 
                                      F-1
<PAGE>
               REPORT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
The Board of Directors
Aviron
 
    We have audited the accompanying balance sheets of Aviron as of December 31,
1994  and 1995, and the related  statements of operations, stockholders' equity,
and cash flows  for each of  the three years  in the period  ended December  31,
1995.  These  financial  statements  are  the  responsibility  of  the Company's
management. Our  responsibility is  to  express an  opinion on  these  financial
statements based on our audits.
 
    We  conducted  our audits  in  accordance with  generally  accepted auditing
standards. Those standards require that we plan and perform the audit to  obtain
reasonable assurance about whether the financial statements are free of material
misstatement.  An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also  includes
assessing  the  accounting principles  used  and significant  estimates  made by
management, as well as evaluating the overall financial statement  presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
    In  our opinion, the financial statements  referred to above present fairly,
in all material respects, the financial position of Aviron at December 31,  1994
and  1995, and the results of its operations  and its cash flows for each of the
three years in the period ended December 31, 1995, in conformity with  generally
accepted accounting principles.
 
                                             ERNST & YOUNG LLP
 
   
Palo Alto, California
January 26, 1996,
except as to the first paragraph of Note 1 and
Note 10, for which the date is May 30, 1996
    
 
                                      F-2
<PAGE>
                                     AVIRON
 
                                 BALANCE SHEETS
 
                       (in thousands, except share data)
 
   
<TABLE>
<CAPTION>
                                                                DECEMBER 31,
                                                            --------------------
                                                              1994       1995
                                                            ---------  ---------
                                                                                   MARCH 31,    UNAUDITED
                                                                                     1996       PRO FORMA
                                                                                  -----------  STOCKHOLDERS'
                                                                                                EQUITY AT
                                                                                  (UNAUDITED)   MARCH 31,
                                                                                                  1996
                                                                                               -----------
                                                                                                (NOTE 10)
                                                  ASSETS
<S>                                                         <C>        <C>        <C>          <C>
Current assets:
  Cash and cash equivalents...............................  $     952  $  11,532   $  10,000
  Short-term investments..................................      5,497      6,287       4,494
  Prepaid expenses and other current assets...............        105        679         873
                                                            ---------  ---------  -----------
Total current assets......................................      6,554     18,498      15,367
Property and equipment, net...............................      1,216      1,275       1,816
Deposits and other assets.................................         19        105          92
                                                            ---------  ---------  -----------
  Total assets............................................  $   7,789  $  19,878   $  17,275
                                                            ---------  ---------  -----------
                                                            ---------  ---------  -----------
 
                                   LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable........................................  $     101  $     312   $     703
  Accrued compensation....................................         68        130         149
  Accrued clinical trial costs............................         --        545         470
  Accrued expenses and other liabilities..................        201        108         319
  Deferred revenue........................................         --        208         437
  Current portion of capital lease obligations............        307        420         485
                                                            ---------  ---------  -----------
Total current liabilities.................................        677      1,723       2,563
Capital lease obligations, noncurrent.....................        750        618         545
Commitments
Stockholders' equity:
  Preferred Stock, no par value; 43,000,000 shares
   authorized, issuable in series; 21,666,667, 39,031,971
   and 39,168,297, convertible preferred shares issued and
   outstanding at December 31, 1994 and 1995 and March 31,
   1996 respectively, aggregate liquidation preference of
   $40,347,481 and $40,531,520 at December 31, 1995 and
   March 31, 1996, respectively (pro forma at March 31,
   1996 -- $0.001 par value, 5,000,000 shares authorized,
   none issued and outstanding)...........................     17,406     39,844      40,028    $      --
  Common Stock, no par value; 53,000,000 shares
   authorized; 695,414, 758,306 and 1,040,822 shares
   issued and outstanding at December 31, 1994 and 1995,
   and March 31, 1996 respectively (pro forma at March 31,
   1996 -- $0.001 par value 30,000,000 shares authorized,
   8,874,456 shares issued and outstanding)...............         16        317       1,579            9
  Additional paid-in capital..............................         --         --          --       41,598
  Notes receivable from stockholders......................         --         --        (310)        (310)
  Deferred compensation...................................         --       (180)       (938)        (938)
  Accumulated deficit.....................................    (11,060)   (22,444)    (26,192)     (26,192)
                                                            ---------  ---------  -----------
Total stockholders' equity................................      6,362     17,537      14,167       14,167
                                                            ---------  ---------  -----------  -----------
  Total liabilities and stockholders' equity..............  $   7,789  $  19,878   $  17,275    $  17,275
                                                            ---------  ---------  -----------  -----------
                                                            ---------  ---------  -----------  -----------
</TABLE>
    
 
                            See accompanying notes.
 
                                      F-3
<PAGE>
                                     AVIRON
                            STATEMENTS OF OPERATIONS
                (in thousands, except share and per share data)
 
   
<TABLE>
<CAPTION>
                                                                                              THREE MONTHS ENDED
                                                             YEAR ENDED DECEMBER 31,              MARCH 31,
                                                        ----------------------------------  ----------------------
                                                           1993        1994        1995        1995        1996
                                                        ----------  ----------  ----------  ----------  ----------
                                                                                                 (UNAUDITED)
<S>                                                     <C>         <C>         <C>         <C>         <C>
Revenues:
  License revenue.....................................  $       --  $       --  $    1,500  $       --  $       --
  Contract revenue....................................          --          --         207          --         188
                                                        ----------  ----------  ----------  ----------  ----------
Total revenues........................................          --          --       1,707          --         188
Operating expenses:
  Research and development............................       2,073       4,216      10,220       3,088       3,044
  General and administrative..........................       1,874       2,493       3,252         701       1,063
                                                        ----------  ----------  ----------  ----------  ----------
Total operating expenses..............................       3,947       6,709      13,472       3,789       4,107
                                                        ----------  ----------  ----------  ----------  ----------
Loss from operations..................................      (3,947)     (6,709)    (11,765)     (3,789)     (3,919)
Other income (expense):
  Interest income.....................................         175         306         520          71         220
  Interest expense....................................          --         (99)       (158)        (39)        (37)
                                                        ----------  ----------  ----------  ----------  ----------
Total other income, net...............................         175         207         362          32         183
                                                        ----------  ----------  ----------  ----------  ----------
Net loss..............................................  $   (3,772) $   (6,502) $  (11,403) $   (3,757) $   (3,736)
                                                        ----------  ----------  ----------  ----------  ----------
                                                        ----------  ----------  ----------  ----------  ----------
Pro forma net loss per share..........................  $    (0.56) $    (0.73) $    (1.24) $    (0.41) $    (0.41)
                                                        ----------  ----------  ----------  ----------  ----------
                                                        ----------  ----------  ----------  ----------  ----------
Shares used in computing pro forma net loss per
 share................................................   6,696,454   8,948,240   9,182,642   9,061,525   9,223,033
</TABLE>
    
 
                            See accompanying notes.
 
                                      F-4
<PAGE>
                                     AVIRON
                       STATEMENT OF STOCKHOLDERS' EQUITY
                       (in thousands, except share data)
   
<TABLE>
<CAPTION>
                                           PREFERRED STOCK           COMMON STOCK
                                        ----------------------  ----------------------      NOTES         DEFERRED
                                         SHARES      AMOUNT      SHARES      AMOUNT      RECEIVABLE     COMPENSATION
                                        ---------  -----------  ---------  -----------  -------------  ---------------
<S>                                     <C>        <C>          <C>        <C>          <C>            <C>
Balances at December 31, 1992.........  5,000,000   $   2,471     648,000   $       3            --       $      --
  Issuance of Series B Convertible
   Preferred Stock at $0.90 per share
   for cash and conversion of notes
   payable in September 1993, net of
   issuance costs of $65..............  16,666,667     14,935          --          --            --              --
  Issuance of Common Stock at $0.25
   per share in April 1993 for certain
   technology and patent rights.......         --          --      35,000           9            --              --
  Exercise of stock options at $0.25
   per share for cash.................         --          --       2,550           1            --              --
  Net loss............................         --          --          --          --            --              --
                                        ---------  -----------  ---------  -----------        -----           -----
Balance at December 31, 1993..........  21,666,667     17,406     685,550          13            --              --
  Exercise of stock options at $0.25
   to $0.50 per share for cash........         --          --       9,864           3            --              --
  Net unrealized loss on available-
   for-sale investments...............         --          --          --          --            --              --
  Net loss............................         --          --          --          --            --              --
                                        ---------  -----------  ---------  -----------        -----           -----
Balance at December 31, 1994..........  21,666,667     17,406     695,414          16            --              --
  Issuance of Series B Convertible
   Preferred Stock at $1.20 per share
   in February 1995 for certain
   in-process technology..............  1,323,734       1,588          --          --            --              --
  Issuance of Series C Convertible
   Preferred Stock at $1.35 per share
   for cash in June through November
   1995, net of issuance costs of
   $807...............................  16,041,570     20,850          --          --            --              --
  Exercise of stock options at $0.25
   to $0.50 per share for cash........         --          --      62,892          31            --              --
  Deferred compensation related to the
   grant of certain stock options.....         --          --          --         270            --            (270)
  Amortization of deferred
   compensation.......................         --          --          --          --            --              90
  Change in net unrealized loss on
   available-for-sale investments.....         --          --          --          --            --              --
  Net loss............................         --          --          --          --            --              --
                                        ---------  -----------  ---------  -----------        -----           -----
Balance at December 31, 1995..........  39,031,971  $  39,844     758,306   $     317            --       $    (180)
  Issuance of Series C Convertible
   Preferred Stock at $1.35 per share
   for cash in March 1996
   (unaudited)........................    136,326         184          --          --            --              --
  Exercise of stock options at $0.25
   to $2.50 per share for cash
   (unaudited)........................         --          --     114,516         168            --              --
  Exercise of stock options at $0.50
   to $2.50 per share for notes
   receivable (unaudited).............         --          --     168,000         310          (310)             --
  Deferred compensation related to the
   grant of certain stock options
   (unaudited)........................         --          --          --         784            --            (784)
  Amortization of deferred
   compensation (unaudited)...........         --          --          --          --            --              26
  Change in net unrealized gain on
   available-for-sale Investments
   (unaudited)........................         --          --          --          --            --              --
  Net loss (unaudited)................         --          --          --          --            --              --
                                        ---------  -----------  ---------  -----------        -----           -----
Balance at March 31, 1996
 (unaudited)..........................  39,168,297  $  40,028   1,040,822   $   1,579     $    (310)      $    (938)
                                        ---------  -----------  ---------  -----------        -----           -----
                                        ---------  -----------  ---------  -----------        -----           -----
 
<CAPTION>
                                                           TOTAL
                                         ACCUMULATED   STOCKHOLDERS'
                                           DEFICIT        EQUITY
                                        -------------  -------------
<S>                                     <C>            <C>
Balances at December 31, 1992.........    $    (753)     $   1,721
  Issuance of Series B Convertible
   Preferred Stock at $0.90 per share
   for cash and conversion of notes
   payable in September 1993, net of
   issuance costs of $65..............           --         14,935
  Issuance of Common Stock at $0.25
   per share in April 1993 for certain
   technology and patent rights.......           --              9
  Exercise of stock options at $0.25
   per share for cash.................           --              1
  Net loss............................       (3,772)        (3,772)
                                        -------------  -------------
Balance at December 31, 1993..........       (4,525)        12,894
  Exercise of stock options at $0.25
   to $0.50 per share for cash........           --              3
  Net unrealized loss on available-
   for-sale investments...............          (33)           (33)
  Net loss............................       (6,502)        (6,502)
                                        -------------  -------------
Balance at December 31, 1994..........      (11,060)         6,362
  Issuance of Series B Convertible
   Preferred Stock at $1.20 per share
   in February 1995 for certain
   in-process technology..............           --          1,588
  Issuance of Series C Convertible
   Preferred Stock at $1.35 per share
   for cash in June through November
   1995, net of issuance costs of
   $807...............................           --         20,850
  Exercise of stock options at $0.25
   to $0.50 per share for cash........           --             31
  Deferred compensation related to the
   grant of certain stock options.....           --             --
  Amortization of deferred
   compensation.......................           --             90
  Change in net unrealized loss on
   available-for-sale investments.....           19             19
  Net loss............................      (11,403)       (11,403)
                                        -------------  -------------
Balance at December 31, 1995..........    $ (22,444)     $  17,537
  Issuance of Series C Convertible
   Preferred Stock at $1.35 per share
   for cash in March 1996
   (unaudited)........................           --            184
  Exercise of stock options at $0.25
   to $2.50 per share for cash
   (unaudited)........................           --            168
  Exercise of stock options at $0.50
   to $2.50 per share for notes
   receivable (unaudited).............           --             --
  Deferred compensation related to the
   grant of certain stock options
   (unaudited)........................           --             --
  Amortization of deferred
   compensation (unaudited)...........           --             26
  Change in net unrealized gain on
   available-for-sale Investments
   (unaudited)........................          (12)           (12)
  Net loss (unaudited)................       (3,736)        (3,736)
                                        -------------  -------------
Balance at March 31, 1996
 (unaudited)..........................    $ (26,192)     $  14,167
                                        -------------  -------------
                                        -------------  -------------
</TABLE>
    
 
   
                            See accompanying notes.
    
 
                                      F-5
<PAGE>
                                     AVIRON
 
                            STATEMENTS OF CASH FLOWS
 
                                 (in thousands)
 
   
<TABLE>
<CAPTION>
                                                                                               THREE MONTHS ENDED
                                                                 YEAR ENDED DECEMBER 31,           MARCH 31,
                                                             -------------------------------  --------------------
                                                               1993       1994       1995       1995       1996
                                                             ---------  ---------  ---------  ---------  ---------
                                                                                                  (UNAUDITED)
<S>                                                          <C>        <C>        <C>        <C>        <C>
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss...................................................  $  (3,772) $  (6,502) $ (11,403) $  (3,757) $  (3,736)
Adjustments to reconcile net loss to net cash used in
 operating activities:
  Depreciation and amortization............................        223        416        544        127        110
  Acquired technology and patent rights....................          9         --      1,588      1,588         --
  Amortization of deferred compensation....................         --         --         90         --         26
  Changes in assets and liabilities:
    Prepaid expenses and other current assets..............        (16)       (46)      (574)       (66)      (194)
    Deposits and other assets..............................         (1)        (4)       (86)        --         13
    Accounts payable.......................................        (34)       (39)       211         61        391
    Accrued expenses and other liabilities.................        168         96        514        (19)       155
    Deferred revenue.......................................         --         --        208         --        229
                                                             ---------  ---------  ---------  ---------  ---------
Net cash used in operating activities......................     (3,423)    (6,079)    (8,908)    (2,066)    (3,006)
                                                             ---------  ---------  ---------  ---------  ---------
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of short-term investments........................     (7,854)    (9,755)    (9,493)      (441)    (3,147)
Maturities of short-term investments.......................      1,815     11,579      8,722      4,257      4,928
Expenditures for property and equipment....................       (593)      (260)      (238)       (75)      (545)
                                                             ---------  ---------  ---------  ---------  ---------
Net cash provided by (used in) investing activities........     (6,632)     1,564     (1,009)     3,741      1,236
                                                             ---------  ---------  ---------  ---------  ---------
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from capital lease line of credit.................         --        620         --         --         --
Principal payments on capital lease obligation.............         --       (212)      (384)       (85)      (114)
Proceeds from notes payable................................      1,500         --         --         --         --
Cash proceeds from issuance of:
  Series B Convertible Preferred Stock.....................     13,434         --         --         --         --
  Series C Convertible Preferred Stock.....................         --         --     20,850         --        184
  Common Stock.............................................          1          3         31          1        168
                                                             ---------  ---------  ---------  ---------  ---------
Cash flows provided by financing activities................     14,935        411     20,497        (84)       238
                                                             ---------  ---------  ---------  ---------  ---------
Net increase (decrease) in cash and cash equivalents.......      4,880     (4,104)    10,580      1,591     (1,532)
Cash and cash equivalents at beginning of year.............        176      5,056        952        952     11,532
                                                             ---------  ---------  ---------  ---------  ---------
Cash and cash equivalents at end of year...................  $   5,056  $     952  $  11,532  $   2,543  $  10,000
                                                             ---------  ---------  ---------  ---------  ---------
                                                             ---------  ---------  ---------  ---------  ---------
SUPPLEMENTAL SCHEDULE OF NONCASH FINANCING ACTIVITIES
Issuance of Common Stock and Preferred Stock for certain
 technology and patent rights..............................  $       9  $      --  $   1,588  $   1,588  $      --
                                                             ---------  ---------  ---------  ---------  ---------
                                                             ---------  ---------  ---------  ---------  ---------
Conversion of notes payable to Series B Preferred Stock....  $   1,500  $      --  $      --  $      --  $      --
                                                             ---------  ---------  ---------  ---------  ---------
                                                             ---------  ---------  ---------  ---------  ---------
Equipment acquired under line of credit....................  $      --  $     648  $     365  $     114  $     106
                                                             ---------  ---------  ---------  ---------  ---------
                                                             ---------  ---------  ---------  ---------  ---------
Deferred compensation related to the grant of certain stock
 options...................................................  $      --  $      --  $     270  $      --  $     784
                                                             ---------  ---------  ---------  ---------  ---------
                                                             ---------  ---------  ---------  ---------  ---------
</TABLE>
    
 
                            See accompanying notes.
 
                                      F-6
<PAGE>
                                     AVIRON
 
                         NOTES TO FINANCIAL STATEMENTS
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
ORGANIZATION AND BUSINESS
 
   
    Aviron  (the "Company") was incorporated in the State of California on April
15, 1992 and will be reincorporated in the State of Delaware in June, 1996.  The
Company  was  organized to  develop  and commercialize  cost-effective  forms of
disease prevention and treatment based on live virus vaccines. Prior to  October
1995, the Company was considered to be in the development stage.
    
 
    The  Company  anticipates  working  on  a  number  of  long-term development
projects which will involve experimental  and unproven technology. The  projects
may  require many years and substantial  expenditures to complete, and which may
ultimately  be  unsuccessful.  Therefore,  the  Company  will  need  to   obtain
additional  funds from outside sources to  continue its research and development
activities, fund  operating  expenses,  pursue regulatory  approvals  and  build
production,  sales and marketing capabilities, as necessary. Management believes
it has  sufficient  capital to  achieve  planned business  objectives  including
supporting preclinical development and clinical testing, through at least 1996.
 
   
INTERIM FINANCIAL INFORMATION
    
 
   
    The  financial information  at March  31, 1996,  for the  three months ended
March 31, 1995 and  1996 is unaudited but  includes all adjustments  (consisting
only  of normal recurring adjustments) which the Company considers necessary for
a fair presentation of the financial position at such date and of the  operating
results  and cash flows  for those periods.  Results of the  1996 period are not
necessarily indicative of results expected for the entire year.
    
 
USE OF ESTIMATES
 
    The preparation of  the financial  statements in  conformity with  generally
accepted  accounting  principles  requires  management  to  make  estimates  and
assumptions that affect  the amounts  reported in the  financial statements  and
accompanying notes. Actual results could differ from those estimates.
 
CASH AND CASH EQUIVALENTS
 
   
    The  Company  considers  all  highly  liquid  investments  with  an original
maturity of 90  days or less  to be cash  equivalents. Cash equivalents  include
$11,831,000  and $9,667,000 in money market funds at December 31, 1995 and March
31, 1996, respectively.
    
 
SHORT-TERM INVESTMENTS
 
    The Company  adopted the  provisions of  Statement of  Financial  Accounting
Standards  No.  115,  "Accounting for  Certain  Investments in  Debt  and Equity
Securities" ("SFAS  No. 115")  for  investments held  as  of or  acquired  after
January 1, 1994.
 
    The Company's entire short-term investment portfolio is currently classified
as available-for-sale and is carried at fair value based on quoted market prices
with  the  unrealized gains  and losses  included  in stockholders'  equity. The
amortized cost of debt securities  classified as available-for-sale is  adjusted
for  amortization  of  premiums and  accretion  of discounts  to  maturity. Such
amortization is  included  in interest  income.  Realized gains  or  losses  and
declines  in  value  judged to  be  other-than-temporary are  included  in other
income. The cost  of securities  sold is  based on  the specific  identification
method. The Company has not experienced any significant realized gains or losses
on its investments.
 
                                      F-7
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
PROPERTY AND EQUIPMENT
 
    Property  and equipment  is stated  at cost.  Depreciation is  provided on a
straight-line basis over  the estimated  useful lives of  the respective  assets
which range from three to seven years. Leasehold improvements are amortized on a
straight-line  basis over the shorter  of their useful lives  or the term of the
lease.
 
REVENUE RECOGNITION
 
    Collaborative  research  revenue  earned  is  based  on  research   expenses
incurred.  Amounts received in advance of  services to be performed are recorded
as deferred revenue until the related expenses are incurred. Milestone  payments
are recognized as revenue in the period earned.
 
STOCK COMPENSATION
 
    In  October 1995, the Financial  Accounting Standards Board issued Statement
No. 123,  "Accounting  for  Stock-Based  Compensation"  ("SFAS  No.  123").  The
Statement  is  effective  for Aviron  beginning  in  1996. Under  SFAS  No. 123,
stock-based compensation  expense  to employees  is  measured using  either  the
intrinsic-value  method as prescribed by  Accounting Principle Board Opinion No.
25 or the fair-value  method described in SFAS  No. 123. Companies choosing  the
intrinsic-value  method will be required to disclose but not actually record the
pro forma impact of the fair-value method on net income and earnings per  share.
The  Company plans to adopt  the SFAS No. 123  in 1996 using the intrinsic-value
method for stock awards to  employees. There will be  no effect of adopting  the
SFAS No. 123 on the Company's financial position or results of operations.
 
   
RECENT PRONOUNCEMENTS
    
 
   
    During March 1995, the Financial Accounting Standards Board issued Statement
No.  121 (SFAS 121), "Accounting for the Impairment of Long-Lived Assets and for
Long-Lived Assets to Be Disposed Of,"  which requires the Company to review  for
impairment  of  long-lived  assets.  SFAS  121  will  become  effective  for the
Company's  year  ending  December  31,   1996.  The  Company  has  studied   the
implications  of SFAS 121 and, based on  its initial evaluation, does not expect
it to have a material impact on the Company's financial condition or results  of
operations.
    
 
NET LOSS PER SHARE
 
    Except  as noted below, historical net loss  per share is computed using the
weighted average number of common  shares outstanding. Common equivalent  shares
from  stock options, convertible preferred stock  and warrants are excluded from
the computation as their  effect is antidilutive, except  that, pursuant to  the
Securities and Exchange Commission Staff Accounting Bulletins, common and common
equivalent  shares issued  during the  period beginning  12 months  prior to the
initial filing of the proposed public offering at prices substantially below the
assumed public offering price have been  included in the calculation as if  they
were  outstanding for all periods presented (using the treasury stock method and
the assumed  public  offering price  for  stock  options and  warrants  and  the
if-converted method for convertible preferred stock).
 
                                      F-8
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
    Historical net loss per share information is as follows:
 
   
<TABLE>
<CAPTION>
                                                                                THREE MONTHS ENDED
                                               YEAR ENDED DECEMBER 31,              MARCH 31,
                                          ----------------------------------  ----------------------
                                             1993        1994        1995        1995        1996
                                          ----------  ----------  ----------  ----------  ----------
<S>                                       <C>         <C>         <C>         <C>         <C>
Net loss per share......................  $    (0.82) $    (1.41) $    (2.47) $    (0.81) $    (0.81)
                                          ----------  ----------  ----------  ----------  ----------
                                          ----------  ----------  ----------  ----------  ----------
Shares used in computing net loss per
 share..................................   4,600,440   4,614,907   4,624,721   4,624,078   4,624,953
                                          ----------  ----------  ----------  ----------  ----------
                                          ----------  ----------  ----------  ----------  ----------
</TABLE>
    
 
    Pro  forma net loss per share has  been computed as described above and also
gives effect  to the  conversion of  convertible preferred  shares not  included
above  that will automatically convert upon  completion of the Company's initial
public offering  (using  the if-converted  method)  from the  original  date  of
issuance.
 
2.  LICENSE AGREEMENTS
 
ARCH DEVELOPMENT CORPORATION
 
   
    On  July 1,  1992, the Company  entered into an  exclusive license agreement
with ARCH  Development Corporation  ("ARCH") to  acquire the  rights to  use  or
sublicense  certain technology and make, use  or sell certain licensed products.
The agreement calls for the Company to make certain payments to ARCH totaling as
much as $2.6 million as certain  milestones are met. No benchmark payments  were
made  or were  due through 1995.  If commercialization is  achieved, the Company
will be  required to  pay ARCH  royalties based  on net  sales of  the  licensed
products. Further, if the Company were to sublicense the technology, it would be
required  to  pay ARCH  royalties on  net  sales of  the sublicensee  and, under
certain circumstances, up to 50% of the license fee paid by the sublicensee.  In
conjunction  with  this license  agreement, the  Company  sold 40,000  shares of
Common Stock to ARCH at $0.005 per share in 1992. Subsequent to this  agreement,
affiliates  of  ARCH  purchased  700,000,  300,000  and  113,999  shares  of the
Company's Series A, B and C Preferred Stock, respectively.
    
 
   
THE MOUNT SINAI SCHOOL OF MEDICINE
    
 
   
    In 1993, the Company entered into  a technology transfer agreement with  The
Mount  Sinai  School of  Medicine of  the  City University  of New  York ("Mount
Sinai") to acquire certain patent rights and technical information. Pursuant  to
the  agreement, the Company issued to Mount  Sinai 35,000 shares of Common Stock
which resulted in a  charge to research and  development expense of $8,750,  and
warrants  to purchase,  in the aggregate,  225,000 shares of  Series A Preferred
Stock.  The  warrants  become  exercisable  upon  the  occurrence  of   specific
milestones and expire five years from such date or on the day preceding the sale
of  the Company. Upon the closing of  an initial public offering by the Company,
warrants covering  148,750  shares  of  Series A  Preferred  Stock  will  become
exercisable  at a price per share of Common  Stock of 125% of the initial public
offering price of the Common Stock. The remaining warrants will be cancelled. At
December 31, 1995 and March 31, 1996, warrants covering 45,000 shares of  Series
A  Preferred  Stock are  exercisable at  $0.90  per share.  The Company  is also
required to reimburse  Mount Sinai  for costs  incurred in  connection with  the
maintenance and protection of certain patents.
    
 
UNIVERSITY OF MICHIGAN
 
   
    In February 1995, the Company signed a license agreement with the University
of  Michigan. The license agreement gives the Company a worldwide license to the
University of Michigan's inventions and discoveries
    
 
                                      F-9
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
2.  LICENSE AGREEMENTS (CONTINUED)
   
related to a cold adapted influenza  vaccine, including the ability to  develop,
use,  sublicense, manufacture  and sell  products and  processes claimed  in the
patent rights.  Under  the  arrangement,  the Company  paid  the  University  of
Michigan  and expensed a  $100,000 fee and  issued 1,323,734 shares  of Series B
Preferred Stock which resulted in a  charge to research and development  expense
of  $1,588,481.  Upon  commercialization  of the  vaccine  product,  the license
agreement provides that the Company will pay royalties based on net revenues  as
well  as  issuing  warrants  to  purchase  1.25%  of  the  Company's  then total
outstanding Common Stock at  an exercise price  equal to 125%  of the per  share
price  of Common Stock in the Company's initial public offering of Common Stock.
The warrant  will be  exercisable for  five years  after its  issuance date.  In
conjunction  with the license agreement, the Company signed a research agreement
with  the  University  of   Michigan  which  obligates   the  Company  to   fund
approximately  $530,000 of specific research projects.  As of December 31, 1996,
the Company had funded $184,000 for  research under this agreement. The  Company
had also paid the University of Michigan $67,000 for other research services.
    
 
3.  DEVELOPMENT AGREEMENTS
 
   
SMITHKLINE BEECHAM BIOLOGICALS S.A.
    
 
   
    In  October 1995,  the Company signed  an agreement  with SmithKline Beecham
Biologicals  S.A.  ("SmithKline  Beecham")   which  grants  SmithKline   Beecham
exclusive   worldwide  (excluding  Korea)  rights  to  produce  and  market  any
prophylactic and  therapeutic  Epstein-Barr  Virus ("EBV")  vaccines  under  the
Company's  patents. Under the  Agreement, SmithKline Beecham  paid the Company a
$1,500,000 nonrefundable  licensing  fee  and is  required  to  make  additional
benchmark  payments  as  certain  milestones  are  met.  Upon commercialization,
SmithKline Beecham  will  pay the  Company  a royalty  based  on net  sales  (by
country). In conjunction with the licensing rights, SmithKline Beecham will fund
the Company's development of the EBV vaccine for a minimum of two years based on
approved  budgeted amounts.  For the year  ended December 31,  1995, the Company
recognized $1,500,000 of  license revenue  and $125,000  of development  revenue
pursuant  to the agreement.  As of December  31, 1995, the  Company has recorded
$208,000 in deferred revenue relating to development that will be recognized  in
1996.
    
 
SANG-A PHARM. CO., LTD.
 
   
    In  May 1995, the Company signed  a development and licensing agreement with
Sang-A Pharm.  Co.,  Ltd.  ("Sang-A"),  a  Korean  pharmaceutical  company.  The
agreement  covers  a  wide  range  of vaccine  products  and  grants  Sang-A the
exclusive rights  and  licenses  to  such products  in  South  and  North  Korea
("Korea").  Under the terms  of the agreement, Sang-A  will conduct all clinical
development work necessary for approval in Korea at its expense, and is required
to make payments based on certain milestones and, upon commercialization of each
product, to pay royalties based on net revenues. The agreement also gives Sang-A
the first  right of  refusal to  supply  a percentage  of Aviron's  products  in
selected countries.
    
 
   
    In  connection  with this  agreement, Sang-A  purchased 2,941,863  shares of
Series C Preferred Stock for $3,971,515. Sang-A subsequently purchased 1,187,295
additional shares of  Series C Preferred  Stock for $1,602,848.  In the  future,
Sang-A  is  required to  purchase  10% of  any  offering of  new  securities (as
defined) of the Company, if  requested by the Company,  until the earlier of  36
months  following  Sang-A's initial  investment or  an initial  public offering.
During the three months ended March 31, 1996, Sang-A purchased 136,326 shares of
Series C Preferred Stock for $184,040.
    
 
                                      F-10
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
4.  SHORT-TERM INVESTMENTS
   
    At  December  31,  1994  and  1995,  the  Company's  short-term  investments
consisted  of the following debt securities, all  of which had maturities of one
year or less (in thousands):
    
 
<TABLE>
<CAPTION>
                                              AVAILABLE-FOR-SALE SECURITIES
                                       -------------------------------------------
                                                 GROSS        GROSS      ESTIMATED
                                               UNREALIZED   UNREALIZED     FAIR
                                        COST     GAINS        LOSSES       VALUE
                                       ------  ----------   ----------   ---------
<S>                                    <C>     <C>          <C>          <C>
As of December 31, 1994:
U.S. Treasury securities and
 obligations of U.S. government
 agencies............................  $2,261   $ --           $(22)      $2,239
U.S. corporate commercial paper......   2,983     --             (1)       2,982
U.S. corporate obligations...........     514     --             (1)         513
Foreign government securities........     520     --             (9)         511
                                       ------  ----------       ---      ---------
                                       $6,278   $ --           $(33)      $6,245
                                       ------  ----------       ---      ---------
                                       ------  ----------       ---      ---------
As of December 31, 1995:
U.S. Treasury securities and
 obligations of U.S. government
 agencies............................  $1,025   $     2        $ (4)      $1,023
U.S. corporate commercial paper......   3,705     --             --        3,705
U.S. corporate obligations...........   1,571     --            (12)       1,559
                                       ------  ----------       ---      ---------
                                       $6,301   $     2        $(16)      $6,287
                                       ------  ----------       ---      ---------
                                       ------  ----------       ---      ---------
</TABLE>
 
   
    Included in  the above  table as  of December  31, 1994  are corporate  debt
obligations  with a fair value of $748  which are classified as cash equivalents
in the accompanying balance sheet.
    
 
5.  PROPERTY AND EQUIPMENT
   
    Property and equipment consisted of the following (in thousands):
    
 
   
<TABLE>
<CAPTION>
                                                             DECEMBER 31,       MARCH 31,
                                                           1994       1995        1996
                                                         ---------  ---------  -----------
<S>                                                      <C>        <C>        <C>
Laboratory equipment...................................  $   1,220  $   1,512   $   1,601
Computer equipment.....................................        199        323         370
Office equipment.......................................         68         90         100
Leasehold improvements.................................        336         62         567
                                                         ---------  ---------  -----------
                                                             1,823      1,987       2,638
Less accumulated depreciation and amortization.........       (607)      (712)       (822)
                                                         ---------  ---------  -----------
                                                         $   1,216  $   1,275   $   1,816
                                                         ---------  ---------  -----------
                                                         ---------  ---------  -----------
</TABLE>
    
 
6.  LEASE ARRANGEMENTS
   
    In April 1994, the Company entered into a $2,500,000 equipment and leasehold
improvement lease line of credit that bears interest based on an average of  the
three-year  and five-year indices  of U.S. Treasury  bonds. Outstanding balances
under the line are  secured by the related  equipment purchased. The lease  line
was  extended and expires December 31, 1996.  At March 31, 1996, $761,000 of the
line was available. In connection  with this financing arrangement, the  Company
issued  warrants to purchase 116,667 shares  of the Company's Series B Preferred
Stock. These warrants are  exercisable at an exercise  price of $0.90 per  share
and will expire at the earlier of March 2000 or upon the initial public offering
of  the Company's  Common Stock. As  consideration for  extending the expiration
date of the lease line, the Company  issued warrants in 1995 to purchase  77,778
    
 
                                      F-11
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
6.  LEASE ARRANGEMENTS (CONTINUED)
   
shares of the Company's Series B Preferred Stock. These warrants are exercisable
at  an exercise price of $0.90  per share and will expire  at the earlier of May
2001 or upon the initial  public offering of the  Company's Common Stock. As  of
March 31, 1996, none of the warrants had been exercised.
    
 
   
    Included  in property and equipment at December  31, 1995 and March 31, 1996
are  assets  with  a  cost  of  $1,826,125  and  $2,032,532,  respectively,  and
accumulated amortization of $688,594 and $786,784, respectively, which have been
financed pursuant to the lease line of credit.
    
 
   
    The  Company has  entered into an  operating lease agreement  for office and
research facilities which expires  in 2005 and includes  an option allowing  the
Company  to extend the  lease for two additional  five-year terms. The agreement
requires  the  Company  to  pay  operating  costs,  including  property   taxes,
utilities,  insurance and maintenance. Rent expense for the years ended December
31, 1993, 1994 and 1995 was $130,400, $167,568 and $412,869, respectively.
    
 
    At  December  31,  1995,  the  Company's  aggregate  commitment  under  such
arrangements are as follows (in thousands):
 
<TABLE>
<CAPTION>
                                                         CAPITAL LEASE   OPERATING
                                                          OBLIGATIONS      LEASE
                                                         -------------  -----------
<S>                                                      <C>            <C>
Years ending December 31,
  1996.................................................    $     528     $     747
  1997.................................................          424           866
  1998.................................................          226           919
  1999.................................................           49           924
  2000.................................................       --               950
  Thereafter...........................................       --             4,910
                                                              ------    -----------
                                                               1,227     $   9,316
                                                                        -----------
                                                                        -----------
Less amounts representing interest.....................         (189)
                                                              ------
                                                               1,038
Less current portion...................................         (420)
                                                              ------
                                                           $     618
                                                              ------
                                                              ------
</TABLE>
 
7.  STOCKHOLDERS' EQUITY
 
    COMMON STOCK
 
   
    During June and July 1992, 648,000 shares of Common Stock were issued to the
Company's  founders,  consultants and  a licensor  of  technology at  $0.005 per
share. These shares  are subject  to certain transfer  restrictions. Certain  of
these  shares,  until vested,  are  subject to  repurchase  at $0.005  per share
(adjusted to reflect  any stock  splits or  stock dividends)  on termination  of
employment.  In addition,  certain shares of  Common Stock issued  to members of
management in 1995 and  1996 through exercises of  stock options are subject  to
repurchase  by the Company at $0.50-$2.50 per  share. The above shares vest over
periods specified by the Board of Directors. At December 31, 1995 and March  31,
1996,  101,700  and 268,480  shares  remain subject  to  the Company's  right of
repurchase, respectively.
    
 
    PREFERRED STOCK
 
    Preferred Stock  is issuable  in series.  Series A,  Series B  and Series  C
Preferred  Stock are convertible into 0.20 share  of Common Stock of the Company
at  the  option  of   the  holder,  and  carry   voting  rights  equivalent   to
 
                                      F-12
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
7.  STOCKHOLDERS' EQUITY (CONTINUED)
Common  Stock on a  share-for-share basis. The conversion  rate of the Preferred
Stock is subject to adjustment in the event of, among other things, stock splits
and stock dividends. Each share  of Preferred Stock automatically converts  into
0.20  shares of Common Stock  in the event of an  initial public offering of the
Company's Common Stock  in which  the gross  offering proceeds  equal or  exceed
$10.0  million or upon approval of the conversion by a majority of the preferred
stockholders voting  together as  a single  class. The  Series A,  Series B  and
Series  C preferred stockholders are entitled  to noncumulative dividends at the
rate of $0.05, $0.09 and $0.135 per share, respectively, when and if declared by
the board of directors. None have been declared.
 
    The Series  A, Series  B  and Series  C Preferred  Stock  are subject  to  a
liquidation  preference of $0.50, $0.90 and  $1.35 per share, respectively, plus
all declared but unpaid dividends.
 
   
    The Preferred Stock authorized, issued and outstanding at December 31,  1995
is as follows:
    
 
   
<TABLE>
<CAPTION>
                                                            SHARES      SHARES ISSUED    LIQUIDATION
                                                          AUTHORIZED   AND OUTSTANDING   PREFERENCE
                                                         ------------  ---------------  -------------
<S>                                                      <C>           <C>              <C>
Series A...............................................     5,225,000       5,000,000   $   2,500,000
Series B...............................................    18,650,000      17,990,401      16,191,361
Series C...............................................    18,000,000      16,041,570      21,656,120
Undesignated...........................................     1,125,000        --              --
                                                         ------------  ---------------  -------------
                                                           43,000,000      39,031,971   $  40,347,481
                                                         ------------  ---------------  -------------
                                                         ------------  ---------------  -------------
</TABLE>
    
 
   
    In  November 1995,  in conjunction  with the  private placement  of Series C
Preferred Stock, the Company issued to the placement agent warrants to  purchase
352,536 shares of the Company's Series C Preferred Stock. These warrants have an
exercise  price of $1.62 per share and will expire in November 2000. As of March
31, 1996, none of the warrants had been exercised.
    
 
   
    A total of 771,981 shares of Preferred Stock have been reserved for issuance
upon exercise of  outstanding warrants  as of December  31, 1995  and March  31,
1996.
    
 
    In  addition,  8,600,000  shares  of Common  Stock  have  been  reserved for
issuance upon the conversion of convertible Preferred Stock.
 
    STOCK OPTIONS
 
    On September 15, 1992, the board of directors adopted the 1992 Stock  Option
Plan  (the "1992 Plan"). The Company initially reserved 272,000 shares of Common
Stock for issuance under the 1992 Plan which was increased by 200,000 shares  in
1993 and 300,000 shares in 1994.
 
    The  1992 Plan provides for both incentive and nonqualified stock options to
be granted to employees, directors and consultants. The 1992 Plan provides  that
incentive  stock options will be  granted at no less than  the fair value of the
Company's Common Stock  (no less  than 85% of  the fair  value for  nonqualified
stock  options), as  determined by  the board  of directors  at the  date of the
grant. If, at the time the Company grants an option, the optionee owns more than
10% of  the total  combined voting  power of  all the  classes of  stock of  the
Company,  the option  price shall  be at least  110% of  the fair  value and the
option shall not be exercised more than five years after the date of grant.  The
options  vest and  become exercisable  over periods  determined by  the board of
directors. Except as noted above, options expire no more than 10 years after the
date of grant, or earlier if employment terminates.
 
                                      F-13
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
7.  STOCKHOLDERS' EQUITY (CONTINUED)
    Option activity under the Plan is as follows:
 
   
<TABLE>
<CAPTION>
                                                                                 OPTIONS OUTSTANDING
                                                                              --------------------------
                                                                    SHARES                   EXERCISE
                                                                   AVAILABLE   NUMBER OF     PRICE PER
                                                                   FOR GRANT    SHARES         SHARE
                                                                   ---------  -----------  -------------
<S>                                                                <C>        <C>          <C>
Balance at December 31, 1992.....................................    157,100     114,900    $      0.25
  Options authorized.............................................    200,000      --            --
  Options granted................................................   (235,117)    235,117    $0.25-$0.50
  Options exercised..............................................     --          (2,550)   $      0.25
  Options canceled...............................................      9,550      (9,550)   $      0.25
                                                                   ---------  -----------  -------------
Balance at December 31, 1993.....................................    131,533     337,917    $0.25-$0.50
  Options authorized.............................................    300,000      --            --
  Options granted................................................    (71,230)     71,230    $      0.50
  Options exercised..............................................     --          (9,864)   $0.25-$0.50
  Options canceled...............................................     29,996     (29,996)   $0.25-$0.50
                                                                   ---------  -----------  -------------
Balance at December 31, 1994.....................................    390,299     369,287    $0.25-$0.50
  Options granted................................................   (269,000)    269,000    $0.50-$1.25
  Options exercised..............................................     --         (62,892)   $0.50-$1.25
  Options canceled...............................................      2,357      (2,357)   $0.25-$0.50
                                                                   ---------  -----------  -------------
Balance at December 31, 1995.....................................    123,656     573,038    $0.25-$1.25
  Options granted (unaudited)....................................    (96,625)     96,625    $      2.50
  Options exercised (unaudited)..................................     --         (64,516)   $0.25-$0.50
  Options canceled (unaudited)...................................        735        (735)   $0.25-$2.50
                                                                   ---------  -----------  -------------
Balance at March 31, 1996 (unaudited)............................     27,766     604,412    $0.25-$2.50
                                                                   ---------  -----------  -------------
                                                                   ---------  -----------  -------------
</TABLE>
    
 
   
    In addition, during 1995  fully-vested non-qualified stock options  covering
40,000  shares  were issued  outside  of the  1992  Plan at  exercise  prices of
$0.50-$1.25 per share. During January 1996, 208,000 non-qualified stock  options
were  issued outside the 1992 Plan at  exercise prices of $1.75-$2.50 per share.
Of the  stock options  issued outside  of the  1992 Plan,  218,000 options  were
exercised  at exercise prices of $0.50-$2.50 per share during the quarter ending
March 31, 1996.
    
 
   
    During the  three months  ended  March 31,  1996,  officers of  the  Company
exercised  options for 168,000  shares by signing  promissory notes amounting to
$310,000 which bear interest at 5.73%.
    
 
   
    As of December 31, 1995 and March 31, 1996, options to purchase 347,893  and
291,491 shares of Common Stock were exercisable.
    
 
   
    For  certain options granted during 1995 and 1996, the Company recognized as
deferred compensation the  excess of  the deemed value  for financial  reporting
purposes of the Common Stock issuable upon the exercise of such options over the
aggregate  exercise  price  of  such  options.  Total  deferred  compensation of
$270,000 recorded through December 31, 1995 is being amortized over the  vesting
period  of  such options.  A portion  of these  options vested  immediately upon
grant. In January 1996, the Company  granted an additional 304,625 options  with
exercise  prices of $1.75 to $2.50 and recorded related deferred compensation of
approximately $784,000. In May 1996, the Company granted 102,950 options with an
exercise  price  of  $2.50  and   recorded  related  deferred  compensation   of
approximately $463,000.
    
 
                                      F-14
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
7.  STOCKHOLDERS' EQUITY (CONTINUED)
   
    In  March 1996, the Company  amended and restated the  1992 Plan as the 1996
Equity Incentive Plan (the "1996 Plan").  Total shares of Common Stock  reserved
for  future issuance under the  1996 Plan were increased  to 1,750,000. The 1996
Plan provides  for the  grant of  incentive and  nonstatutory stock  options  to
employees and consultants of the Company.
    
 
   
    In  March 1996, the  Company adopted the  1996 Non-Employee Directors' Stock
Option Plan (the "Directors' Plan") under  which 200,000 shares of Common  Stock
are reserved for issuance pursuant to nonstatutory stock options.
    
 
   
    In  March 1996,  the Company also  adopted the Employee  Stock Purchase Plan
(the "Purchase Plan"). A  total of 250,000 shares  of Common Stock are  reserved
for  issuance  under  the  Purchase Plan.  The  Purchase  Plan  permits eligible
employees to purchase Common Stock through  payroll deductions at a price  equal
to  the lower of 85% of  the fair market value of  the Company's Common Stock at
the beginning or end of the applicable offering period.
    
 
8.  INCOME TAXES
    As of  December 31,  1995, the  Company  had a  federal net  operating  loss
carryforward  of approximately $20,000,000. The  net operating loss carryforward
will expire at various dates beginning from 2007 through 2010, if not  utilized.
Utilization  of  the  net operating  losses  and  credits may  be  subject  to a
substantial annual limitation due  to the "ownership  change" provisions of  the
Internal Revenue Code of 1986.
 
    Significant components of the Company's deferred tax assets are as follows:
 
<TABLE>
<CAPTION>
                                                                                    DECEMBER 31,
                                                                           -------------------------------
                                                                             1993       1994       1995
                                                                           ---------  ---------  ---------
                                                                                   (in thousands)
<S>                                                                        <C>        <C>        <C>
Net operating loss carryforward..........................................  $   1,500  $   3,800  $   7,100
Capitalized research expenses............................................     --            200      1,060
Research tax credits (expires from 2007-2010)............................        100        300        550
Other....................................................................        200        100        140
                                                                           ---------  ---------  ---------
Net deferred tax assets..................................................      1,800      4,400      8,850
Valuation allowance......................................................     (1,800)    (4,400)    (8,850)
                                                                           ---------  ---------  ---------
                                                                           $  --      $  --      $  --
                                                                           ---------  ---------  ---------
                                                                           ---------  ---------  ---------
</TABLE>
 
    Because  of the  Company's lack  of earnings  history, the  net deferred tax
asset has been fully  offset by a valuation  allowance. The valuation  allowance
increased by approximately $1,500,000 in 1993.
 
9.  RELATED PARTY TRANSACTIONS
   
    In  1995, the  Company made unsecured  loans to  officers totalling $100,000
which bear interest at 7.75% and are due in April 2000.
    
 
   
    An officer  of  the Company  is  a  shareholder in  an  investment  advisory
business  which was paid  a commission by the  Company of approximately $334,000
during 1995 related to the Sang-A transaction (see Note 3). The officer received
no direct compensation from the transaction.
    
 
10. SUBSEQUENT EVENT -- PROPOSED PUBLIC OFFERING AND RELATED MATTERS
   
    On May 30, 1996, the board of directors authorized management of the Company
to file a  Registration Statement  with the Securities  and Exchange  Commission
offering  shares  of  its  Common  Stock  to  the  public.  If  the  offering is
consummated under the terms  presently anticipated, all  of the Preferred  Stock
outstanding will
    
 
                                      F-15
<PAGE>
                                     AVIRON
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                               DECEMBER 31, 1995
   
 (INFORMATION FOR THE THREE MONTHS ENDED MARCH 31, 1995 AND 1996 IS UNAUDITED)
    
 
10. SUBSEQUENT EVENT -- PROPOSED PUBLIC OFFERING AND RELATED MATTERS (CONTINUED)
   
automatically  convert into 7,833,634 shares of Common Stock upon the closing of
the offering. Unaudited pro forma stockholders'  equity as of December 31,  1995
as  adjusted for the assumed  conversion of the Preferred  Stock is set forth on
the accompanying balance sheet.
    
 
   
    In May  1996,  the  Company  filed restated  Articles  of  Incorporation  in
California  to  effect a  one-for-five reverse  stock  split of  all outstanding
shares of Common Stock, Common Stock options and warrants. The conversion  ratio
of all outstanding shares of Convertible Preferred Stock were adjusted such that
each  preferred share converts into .20 shares of common stock. All common share
and per share data  in the accompanying financial  statements has been  adjusted
retroactively to give effect to the reverse stock split. In conjunction with the
registration,  the board of directors also authorized the reincorporation of the
Company in Delaware.
    
 
                                      F-16
<PAGE>
   
                                     [LOGO]
    
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.
 
    The  following table  sets forth all  expenses, other  than the underwriting
discounts and commissions, payable by the Registrant in connection with the sale
of the Common Stock being registered.  All the amounts are estimates except  for
the registration fee and the NASD filing fee.
 
<TABLE>
<S>                                                         <C>
Registration fee..........................................  $  15,466
NASD filing fee...........................................      4,985
Blue sky qualification fees and expenses..................      5,000
Printing and engraving expenses...........................    125,000
Legal fees and expenses...................................    300,000
Accounting fees and expenses..............................    130,000
Transfer agent and registrar fees.........................     10,000
Miscellaneous.............................................      9,549
                                                            ---------
    Total.................................................  $ 600,000
                                                            ---------
                                                            ---------
</TABLE>
 
ITEM 14.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
    Under  Section 145 of  the Delaware General  Corporation Law, the Registrant
has broad powers  to indemnify  its directors and  officers against  liabilities
they  may incur in  such capacities, including  liabilities under the Securities
Act of 1933,  as amended (the  "Securities Act"). The  Registrant's Bylaws  also
provide  that the Registrant will indemnify its directors and executive officers
and may indemnify its other officers, employees and agents to the fullest extent
permitted by Delaware law.
 
    The Registrant's Certificate of  Incorporation provides for the  elimination
of liability for monetary damages for breach of the directors' fiduciary duty of
care  to the Registrant and its  stockholders. These provisions do not eliminate
the directors'  duty  of  care  and,  in  appropriate  circumstances,  equitable
remedies  such an injunctive  or other forms of  non-monetary relief will remain
available under Delaware  law. In addition,  each director will  continue to  be
subject  to  liability for  breach  of the  director's  duty of  loyalty  to the
Registrant, for acts  or omissions not  in good faith  or involving  intentional
misconduct,  for knowing violations  of law, for any  transaction from which the
director derived an improper personal benefit,  and for payment of dividends  or
approval  of stock repurchases  or redemptions that  are unlawful under Delaware
law. The provision does not affect a director's responsibilities under any other
laws, such as  the federal  securities laws  or state  or federal  environmental
laws.
 
    The  Underwriting  Agreement  filed  as  Exhibit  1.1  to  this Registration
Statement, will  provide  for  indemnification by  the  Underwriters  and  their
controlling  persons, on the one hand, and of the Registrant and its controlling
persons on the other hand, for certain liabilities arising under the  Securities
Act or otherwise.
 
ITEM 15.  RECENT SALES OF UNREGISTERED SECURITIES.
 
    Since   inception,  the  Registrant  has   sold  and  issued  the  following
unregistered securities (adjusted  to give  effect to  the one-for-five  reverse
stock split):
 
   
        (1)  From April  1992 through June  1, 1996, the  Registrant has granted
    stock options to purchase 889,822 shares of the Company's Common Stock at  a
    weighted average exercise price of $1.02 per share to employees, consultants
    and  directors pursuant  to its 1996  Equity Incentive  Plan, or predecessor
    plans (the "Plans").  Of these  options, 58,318 have  been canceled  without
    being exercised, 218,024 have been exercised and 613,480 remain outstanding.
    In  January 1996,  208,000 options were  issued outside the  Plan to certain
    senior executives and founders  of the Company,  at exercise prices  ranging
    from $1.75 to $2.50 per share.
    
 
                                      II-1
<PAGE>
        (2)  In June  and July 1992,  the Registrant issued  5,000,000 shares of
    Series A  Preferred  Stock to  14  purchasers at  $0.50  per share,  for  an
    aggregate  purchase price of $2,500,000. Shares  of Series A Preferred Stock
    are convertible into  shares of Common  Stock at  the rate of  one share  of
    Common Stock for each five shares of Series A Preferred Stock owned.
 
   
        (3)  In February  1993, the  Company issued  warrants to  purchase up to
    225,000 shares of  Series A  Preferred Stock to  The Mount  Sinai School  of
    Medicine  of the City  University of New York  ("Mount Sinai") in connection
    with the  transfer by  Mount  Sinai to  the  Company of  certain  technology
    rights. The shares of Series A Preferred Stock issuable upon exercise of the
    warrants  are convertible  into shares  of Common Stock  at the  rate of one
    share of  Common Stock  for each  five shares  of Series  A Preferred  Stock
    owned.
    
 
        (4) In September 1993, the Registrant issued 16,666,667 shares of Series
    B  Preferred Stock to  34 purchasers (including  two purchasers who received
    1,666,666 shares upon conversion of promissory notes aggregating $1,500,000)
    at $0.90 per share, for an  aggregate purchase price of $15,000,000.  Shares
    of  Series B Preferred Stock are convertible  into shares of Common Stock at
    the rate of  one share  of Common  Stock for each  five shares  of Series  B
    Preferred Stock owned.
 
   
        (5)  In  September  1993,  the Registrant  issued  warrants  to purchase
    400,000 shares of  its Series  B Preferred Stock,  at an  exercise price  of
    $1.25  per share,  to entitles affiliated  with IVP.  These warrants expired
    unexercised in June 1995.
    
 
   
        (6) In February 1995,  the Registrant entered  into a license  agreement
    with the University of Michigan under which, in return for certain rights to
    the  University of Michigan's  inventions and discoveries  related to a cold
    adapted influenza vaccine,  the Registrant  issued 1,323,734  shares of  the
    Registrant's  Series B  Preferred Shares, plus  a warrant to  purchase up to
    1.25% of the Registrant's outstanding Common Stock under certain conditions.
    Shares of Series  B Preferred Stock  are convertible into  shares of  Common
    Stock  at the  rate of  one share of  Common Stock  for each  five shares of
    Series B Preferred Stock owned.
    
 
   
        (7) In  April 1994  and  May 1995,  the  Registrant issued  warrants  to
    purchase  an aggregate of 194,445  shares of Series B  Preferred Stock at an
    exercise price of $0.90 per share to Lease Management Services, Inc.
    
 
   
        (8) In May 1995,  the Registrant entered into  a license agreement  with
    Sang-A Pharm Co., Ltd., ("Sang-A") under which, in return for certain rights
    to certain of the Registrant's products in Korea, Sang-A purchased 2,941,863
    of  the Registrant's Series  C Preferred Stock for  $3,971,575, or $1.35 per
    share. Shares of  Series C Preferred  Stock are convertible  into shares  of
    Common  Stock at the rate of one share  of Common Stock for each five shares
    of Series C Preferred Stock owned.
    
 
        (9) From July  through November 1995,  the Registrant issued  13,099,707
    shares  of Series C Preferred Stock to  66 purchasers at a purchase price of
    $1.35 per share  (including 1,187,295  shares to Sang-A),  for an  aggregate
    purchase  price  of  $17,684,604. Shares  of  Series C  Preferred  Stock are
    convertible into shares of Common Stock at  the rate of one share of  Common
    Stock for each five shares of Series C Preferred Stock owned.
 
   
        (10)  In  November 1995,  the Registrant  issued  a warrant  to purchase
    352,536 shares of the  Series C Preferred Stock  of the Company to  Raymond,
    James  &  Associates,  Inc.,  for  an  exercise  price  of  $1.62  per share
    (convertible into 70,507 shares of  Common Stock) issuable upon exercise  of
    the  warrant. Shares of Series C Preferred Stock are convertible into shares
    of Common Stock  at the  rate of  one share of  Common Stock  for each  five
    shares of Series C Preferred Stock owned.
    
 
        (11)  In March  1996, the Registrant  issued 136,315 shares  of Series C
    Preferred Stock  to  Sang-A Pharm  Co.,  Ltd. at  $1.35  per share,  for  an
    aggregate purchase price of $184,025. Shares of Series C Preferred Stock are
    convertible  into shares of Common Stock at  the rate of one share of Common
    Stock for each five shares of Series C Preferred Stock owned.
 
    The sales and issuances of securities described in paragraph (1) above  were
deemed to be exempt from registration under the Securities Act by virtue of Rule
701  of the Securities Act.  The sales and issuances  of securities described in
paragraphs (2) through  (9) above  were deemed  to be  exempt from  registration
under the
 
                                      II-2
<PAGE>
Securities  Act  by virtue  of Rule  4(2) of  the Securities  Act. The  sale and
issuance of  securities described  in paragraph  (10) above  were deemed  to  be
exempt  from registration under the Securities Act  by virtue of Rule 3(a)(9) of
the Securities Act.
 
    Appropriate legends  are affixed  to the  stock certificates  issued in  the
aforementioned transactions. Similar legends were imposed in connection with any
subsequent sales of any such securities. All recipients either received adequate
information  about the  Registrant or  had access,  through employment  or other
relationships, to such information.
 
ITEM 16. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.
 
    (a)   The  following  is  a  list  of exhibits  filed  as  a  part  of  this
Registration Statement:
 
   
<TABLE>
<CAPTION>
   EXHIBIT
   NUMBER                        DESCRIPTION OF DOCUMENT
- -------------  ------------------------------------------------------------
<C>            <S>
      *1.1     Form of Underwriting Agreement.
       3.1     Amended  and  Restated  Articles  of  Incorporation  of  the
                Registrant, as amended.
      *3.2     Amendment  to   the  Amended   and  Restated   Articles   of
                Incorporation of the Registrant.
       3.3     Bylaws of the Registrant.
      *3.4     Form of Certificate of Incorporation of the Registrant to be
                filed upon reincorporation in Delaware.
      *3.5     Form  of  Bylaws  of  the Registrant  to  be  effective upon
                reincorporation in Delaware.
      *3.6     Form  of  Restated  Certificate  of  Incorporation  of   the
                Registrant, to be filed after completion of this offering.
      *3.7     Form  of Restated Bylaws of  the Registrant, to be effective
                upon the completion of this offering.
       4.1     Reference is made to Exhibits  3.1, 3.2, 3.3, 3.4., 3.5  and
                3.6.
      *4.2     Specimen Stock Certificate.
       4.3     Warrant  for Series A  Preferred Stock, issued  to The Mount
                Sinai School of Medicine of the City of New York.
       4.4     Warrant for Series  A Preferred Stock,  issued to The  Mount
                Sinai School of Medicine of the City of New York.
      *4.5     Warrant  for Series A  Preferred Stock, issued  to The Mount
                Sinai School of Medicine of the City of New York.
      *4.6     Warrant for Series  A Preferred Stock,  issued to The  Mount
                Sinai School of Medicine of the City of New York.
      *4.7     Warrant  for Series  C Preferred  Stock, issued  to Raymond,
                James & Associates.
       4.8     Investors Rights Agreement, dated  July 18, 1995, among  the
                Registrant and the investors named therein.
       5.1     Opinion of Cooley Godward Castro Huddleson & Tatum.
     +10.1     License   Agreement   between   the   Registrant   and  ARCH
                Development Corporation, dated July 1, 1992.
     +10.2     Technology Transfer Agreement between the Registrant and The
                Mount Sinai School  of Medicine of  the City University  of
                New York, dated February 9, 1993.
     +10.3     Materials   Transfer  and  Intellectual  Property  Agreement
                between the Registrant and the Regents of the University of
                Michigan, dated February 24, 1995.
      10.4     Stock Transfer  Agreement  between the  Registrant  and  the
                Regents  of the University of  Michigan, dated February 24,
                1995.
</TABLE>
    
 
                                      II-3
<PAGE>
   
<TABLE>
<CAPTION>
   EXHIBIT
   NUMBER                        DESCRIPTION OF DOCUMENT
- -------------  ------------------------------------------------------------
<C>            <S>
     +10.5     Development and License Agreement between the Registrant and
                Sang-A Pharm. Co., Ltd., dated May 3, 1995.
     +10.6     Cooperative Research and  Development Agreement between  the
                Registrant and the National Institutes of Health, dated May
                30, 1995.
    *+10.7     Heads  of  Agreement between  the Registrant  and SmithKline
                Beecham Biologicals S.A., dated October 8, 1995.
     +10.8     Manufacturing  and   Development   Agreement   between   the
                Registrant  and  Evans Medical  Limited, dated  November 7,
                1995.
      10.9     1996 Equity Incentive Plan.
      10.10    1996 Non-Employee Directors' Stock Option Plan.
      10.11    1996 Employee Stock Purchase Plan.
      10.12    Industrial  Lease  between  the  Registrant  and  the  Vanni
                Business Park General Partnership, dated August 29, 1995.
      11.1     Statement  regarding Computation  of Pro Forma  Net Loss Per
                Share.
      23.1     Consent of Ernst & Young LLP.
      24.2     Consent  of  Cooley  Godward   Castro  Huddleson  &   Tatum.
                Reference is made to Exhibit 5.1.
      25.1     Power of Attorney. Reference is made to page II-5.
      27.1     Financial Data Schedules.
</TABLE>
    
 
- -------------------
*   To be filed by amendment.
+   Confidential treatment has been requested for portions of this exhibit.
 
ITEM 17. UNDERTAKINGS.
 
    The  Registrant hereby undertakes to provide the Underwriters at the closing
specified in the Underwriting Agreement  certificates in such denominations  and
registered  in  such names  as  required by  the  Underwriters to  permit prompt
delivery to each purchaser.
 
    Insofar as indemnification for liabilities arising under the Securities  Act
may  be  permitted  to  directors,  officers,  and  controlling  persons  of the
Registrant pursuant to  the provisions described  in Item 14  or otherwise,  the
Registrant  has been advised that in the  opinion of the Securities and Exchange
Commission such indemnification  is against  public policy as  expressed in  the
Securities  Act and is, therefore, unenforceable. In  the event that a claim for
indemnification  against  such  liabilities  (other  than  the  payment  by  the
Registrant  of expenses incurred or paid  by a director, officer, or controlling
person of  the Registrant  in the  successful defense  of any  action, suit,  or
proceeding)  is asserted  by such  director, officer,  or controlling  person in
connection with the securities being registered, the Registrant will, unless  in
the opinion of its counsel the matter has been settled by controlling precedent,
submit  to  a  court  of  appropriate  jurisdiction  the  question  whether such
indemnification by it is  against public policy as  expressed in the  Securities
Act and will governed by the final adjudication of such issue.
 
    The  undersigned Registrant undertakes that: (1) for purposes of determining
any liability under the Securities Act, the information omitted from the form of
prospectus filed as  part of the  registration statement in  reliance upon  Rule
430A and contained in the form of prospectus filed by the Registrant pursuant to
Rule  424(b)(1) or (4) or 497(h) under the  Securities Act shall be deemed to be
part of the registration statement as of the time it was declared effective, and
(2) for the purpose of determining any liability under the Securities Act,  each
post-effective  amendment that contains a form  of prospectus shall be deemed to
be a new registration statement relating to the securities offered therein,  and
the  offering of such securities at that time  shall be deemed to be the initial
bona fide offering thereof.
 
                                      II-4
<PAGE>
                                   SIGNATURES
 
   
    In  accordance  with the  requirements of  the Securities  Act of  1933, the
Registrant has duly caused this Registration Statement on Form S-1 to be  signed
on  its behalf by the undersigned, in the  City of Moutain View, County of Santa
Clara, State of California, on the 4th day of June, 1996.
    
 
                                          AVIRON
 
                                          By:    /s/ J. LEIGHTON READ
                                             -----------------------------------
                                               J. Leighton Read, M.D.
                                               CHAIRMAN, CHIEF EXECUTIVE OFFICER
                                               AND CHIEF FINANCIAL OFFICER
                                               (PRINCIPAL EXECUTIVE OFFICER)
 
                               POWER OF ATTORNEY
 
    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below constitutes and  appoints J. Leighton  Read, M.D. as  his true and  lawful
attorney-in-fact  and agent, with full power of substitution and resubstitution,
for him and in his name, place and stead, in any all capacities, to sign any and
all amendments (including post-effective amendments and registration  statements
filed  pursuant to  Rule 462)  to this Registration  Statement, and  to file the
same, with all exhibits  thereto, and other  documents in connection  therewith,
with the Securities and Exchange Commission, granting unto said attorney-in-fact
and  agent, full power  and authority to do  and perform each  and every act and
thing requisite and necessary  to be done in  connection therewith, as fully  to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming  all that  said attorney-in-fact and  agent, or  his substitutes, may
lawfully do or cause to be done by virtue hereof.
 
    IN ACCORDANCE WITH  THE REQUIREMENTS  OF THE  SECURITIES ACT  OF 1933,  THIS
REGISTRATION  STATEMENT  WAS  SIGNED  BELOW  BY  THE  FOLLOWING  PERSONS  IN THE
CAPACITIES AND ON THE DATES STATED.
 
   
<TABLE>
<C>                                               <S>                             <C>
                   SIGNATURE                                  TITLE                    DATE
- ------------------------------------------------  ------------------------------  --------------
                                                  Chairman, Chief Executive
                                                  Officer and Chief Financial
              /s/ J. LEIGHTON READ                Officer
     --------------------------------------       (PRINCIPAL EXECUTIVE OFFICER     June 4, 1996
             J. Leighton Read, M.D.               AND PRINCIPAL FINANCIAL AND
                                                  ACCOUNTING OFFICER)
 
               /s/ REID W. DENNIS
     --------------------------------------       Director                         June 4, 1996
                 Reid W. Dennis
 
            /s/ PAUL H. KLINGENSTEIN
     --------------------------------------       Director                         June 4, 1996
              Paul H. Klingenstein
 
              /s/ BERNARD ROIZMAN
     --------------------------------------       Director                         June 4, 1996
             Bernard Roizman, Sc.D.
 
              /s/ L. JAMES STRAND
     --------------------------------------       Director                         June 4, 1996
             L. James Strand, M.D.
 
                /s/ JANE E. SHAW
     --------------------------------------       Director                         June 4, 1996
              Jane E. Shaw, Ph.D.
</TABLE>
    
 
                                      II-5
<PAGE>
                                                                    EXHIBIT 23.1
 
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
   
    We consent  to  the reference  to  our  firm under  the  captions  "Selected
Financial  Data" and "Experts"  and to the  use of our  report dated January 26,
1996 (except as to  the first paragraph of  Note 1 and Note  10 as to which  the
date  is June   , 1996),  in the  Registration Statement (Form  S-1) and related
Prospectus of Aviron  for the  registration of  3,450,000 shares  of its  Common
Stock.
    
 
                                          ERNST & YOUNG LLP
Palo Alto, California
 
- --------------------------------------------------------------------------------
The  foregoing consent is in the form that will be signed upon the completion of
the restatement  of capital  accounts  described in  Note  10 to  the  financial
statements.
 
   
Palo Alto, California
June  , 1996
    
 
                                      II-6
<PAGE>
                                 EXHIBIT INDEX
 
   
<TABLE>
<CAPTION>
                                                                                                        SEQUENTIAL
 EXHIBIT                                                                                                   PAGE
 NUMBER                                      DESCRIPTION OF DOCUMENT                                      NUMBER
- ---------  -------------------------------------------------------------------------------------------  ----------
<C>        <S>                                                                                          <C>
    *1.1   Form of Underwriting Agreement.............................................................
     3.1   Amended and Restated Articles of Incorporation of the Registrant, as amended...............
    *3.2   Amendment to the Amended and Restated Articles of Incorporation of the Registrant..........
     3.3   Bylaws of the Registrant...................................................................
    *3.4   Form of Certificate of Incorporation of the Registrant to be filed upon reincorporation in
            Delaware..................................................................................
    *3.5   Form of Bylaws of the Registrant to be effective upon reincorporation in Delaware..........
    *3.6   Form of Restated Certificate of Incorporation of the Registrant, to be filed after
            completion of this offering...............................................................
    *3.7   Form of Restated Bylaws of the Registrant, to be effective upon the completion of this
            offering..................................................................................
     4.1   Reference is made to Exhibits 3.1, 3.2, 3.3, 3.4., 3.5 and 3.6.............................
    *4.2   Specimen Stock Certificate.................................................................
     4.3   Warrant for Series A Preferred Stock, issued to The Mount Sinai School of Medicine of the
            City of New York..........................................................................
     4.4   Warrant for Series A Preferred Stock, issued to The Mount Sinai School of Medicine of the
            City of New York..........................................................................
     4.5   Warrant for Series A Preferred Stock, issued to The Mount Sinai School of Medicine of the
            City of New York..........................................................................
     4.6   Warrant for Series A Preferred Stock, issued to The Mount Sinai School of Medicine of the
            City of New York..........................................................................
     4.7   Warrant for Series C Preferred Stock, issued to Raymond, James & Associates................
     4.8   Amended and Restated Investors Rights Agreement, dated July 18, 1995, among the Registrant
            and the investors named therein...........................................................
     5.1   Opinion of Cooley Godward Castro Huddleson & Tatum.........................................
   +10.1   License Agreement between the Registrant and ARCH Development Corporation, dated July 1,
            1992......................................................................................
   +10.2   Technology Transfer Agreement between the Registrant and The Mount Sinai School of Medicine
            of the City University of New York, dated February 9, 1993................................
   +10.3   Materials Transfer and Intellectual Property Agreement between the Registrant and the
            Regents of the University of Michigan, dated February 24, 1995............................
    10.4   Stock Transfer Agreement between the Registrant and the Regents of the University of
            Michigan, dated February 24, 1995.........................................................
   +10.5   Development and License Agreement between the Registrant and Sang-A Pharm. Co., Ltd., dated
            May 3, 1995...............................................................................
   +10.6   Cooperative Research and Development Agreement between the Registrant and the National
            Institutes of Health, dated May 30, 1995..................................................
  *+10.7   Heads of Agreement between the Registrant and SmithKline Beecham Biologicals S.A., dated
            October 8, 1995...........................................................................
   +10.8   Manufacturing and Development Agreement between the Registrant and Evans Medical Limited,
            dated November 7, 1995....................................................................
    10.9   1996 Equity Incentive Plan.................................................................
    10.10  1996 Non-Employee Directors' Stock Option Plan.............................................
    10.11  1996 Employee Stock Purchase Plan..........................................................
</TABLE>
    
<PAGE>
   
<TABLE>
<CAPTION>
                                                                                                        SEQUENTIAL
 EXHIBIT                                                                                                   PAGE
 NUMBER                                      DESCRIPTION OF DOCUMENT                                      NUMBER
- ---------  -------------------------------------------------------------------------------------------  ----------
<C>        <S>                                                                                          <C>
    10.12  Industrial Lease between the Registrant and the Vanni Business Park General Partnership,
            dated August 29, 1995.....................................................................
  *+10.13  First Amendment to License Agreement between the Registrant and ARCH Development
            Corporation, dated March 15, 1996.........................................................
  *+10.14  Biological Materials License Agreement between the Registrant and the National Institutes
            of Health, dated May 31, 1996.............................................................
    11.1   Statement regarding Computation of Pro Forma Net Loss Per Share............................
    23.1   Consent of Ernst & Young LLP...............................................................
    24.2   Consent of Cooley Godward Castro Huddleson & Tatum. Reference is made to Exhibit 5.1.......
    25.1   Power of Attorney. Reference is made to page II-5..........................................
    27.1   Financial Data Schedules...................................................................
</TABLE>
    
 
- -------------------
*   To be filed by amendment.
+   Confidential treatment has been requested for portions of this exhibit.

<PAGE>



                                 AMENDED AND RESTATED

                             ARTICLES OF INCORPORATION OF

                                        AVIRON


         J. Leighton Read and Alan C. Mendelson certify that:

         1.   They are the Chief Executive Officer and Secretary, respectively,
of Aviron, a California corporation (the "Corporation").

         2.   The Articles of Incorporation of this Corporation are amended and
restated as follows:

                                         "I.

         The name of this corporation is Aviron.

                                         II.

         The purpose of this corporation is to engage in any lawful act or
activity for which a corporation may be organized under the General Corporation
Law of California other than the banking business, the trust company business or
the practice of a profession permitted to be incorporated by the California
Corporations Code.

                                         III.

         A.   This corporation is authorized to issue two classes of stock to
be designated, respectively, "Common Stock" and "Preferred Stock."  The total
number of shares which the corporation is authorized to issue is Ninety-Six
Million (96,000,000) shares. Fifty-Three Million (53,000,000) shares shall be
Common Stock.  Forty-Three Million (43,000,000) shares shall be Preferred Stock.

              The Preferred Stock may be issued from time to time in one or
more series.  Subject to the protective provisions set forth in Section 5 below,
the Board of Directors is hereby authorized to fix or alter the dividend rights,
dividend rate, conversion rights, voting rights, rights and terms of redemption
(including sinking fund provisions), redemption price or prices, and the
liquidation preferences of any wholly unissued series of Preferred Stock, and
the number of shares


                                          1

<PAGE>

constituting any such series and the designation thereof, or any of them; and to
increase or decrease the number of shares of any series subsequent to the
issuance of shares of that series, but not below the number of shares of such
series then outstanding.  In case the number of shares of any series shall be so
decreased, the shares constituting such decrease shall resume the status that
they had prior to the adoption of the resolution originally fixing the number of
shares of such series.

         B.   Five million two hundred twenty-five thousand (5,225,000) of the
authorized shares of Preferred Stock are hereby designated "Series A Preferred
Stock."  Eighteen million six hundred fifty thousand (18,650,000) of the
authorized shares of Preferred Stock are hereby designated "Series B Preferred
Stock," and eighteen million (18,000,000) of the authorized shares of Preferred
Stock are hereby designated "Series C Preferred Stock."  The Series A Preferred
Stock, Series B Preferred Stock and Series C Preferred Stock are collectively
referred to as the "Preferred Stock."

         C.   The respective rights, preferences, privileges, restrictions and
other matters relating to the Preferred Stock are as follows:

         1.   DIVIDENDS.  The holders of the Preferred Stock shall be entitled
to receive, payable in preference and priority to the holders of Common Stock,
when and as declared by the Board of Directors, out of any assets at the time
legally available therefor, dividends at the rate of:

              (a)  with respect to the Series A Preferred Stock, $.05 per share
per annum (as appropriately adjusted for any combination, consolidation, stock
distribution, stock dividend, stock split or similar event with respect to such
shares (a "Recapitalization")); 

              (b)  with respect to the Series B Preferred Stock, $.09 per share
per annum (as adjusted for any Recapitalization); and

              (c)  with respect to the Series C Preferred Stock, $.135 per
share per annum (as adjusted for any Recapitalization).

Such dividends shall not be cumulative and no right to such dividends shall
accrue to holders of Preferred Stock unless declared by the Board of Directors. 
No dividends shall be declared or paid with respect to the Common Stock (other
than a dividend payable solely in Common Stock of the Corporation) unless a
dividend of equal or greater amount per share (on an as-if-converted to Common
Stock basis) is first declared and paid with respect to the Preferred Stock. 
Each share of Preferred Stock shall rank on parity with every other share of
Preferred Stock, irrespective of series, with regard to dividends, and no
dividends shall be paid, declared or set apart for payment


                                          2

<PAGE>

on the shares of any series of Preferred Stock unless at the same time a
dividend for the same percentage of the respective dividend rates shall also be
paid, declared or set apart for payment, as the case may be, on the shares of
Preferred Stock or each other series then outstanding.

So long as any shares of Preferred Stock shall be outstanding, no dividend,
whether in cash or property, shall be paid or declared, nor shall any other
distribution be made, on any Common Stock, nor shall any shares of the Common
Stock of the Corporation be purchased, redeemed, or otherwise acquired for value
by the Corporation (except for acquisitions of Common Stock by the Corporation
from the founders, directors, employees or consultants of the Corporation
pursuant to agreements which permit the Corporation to repurchase such shares
upon termination of an employment or consulting relationship or in exercise of
the Corporation's right of first refusal upon a proposed transfer) until all
accrued but unpaid dividends on the Preferred Stock shall have been paid or
declared and set apart.  In the event dividends are paid on any share of Common
Stock, an additional dividend shall be paid with respect to all outstanding
shares of Preferred Stock in an amount for each such share of Preferred Stock
equal to the aggregate amount of such dividends for all shares of Common Stock
into which each such share of Preferred Stock could then be converted.  The
provisions of this Section 1(b) shall not, however, apply to (i) a dividend
payable in Common Stock, (ii) the acquisition of shares of any Common Stock in
exchange for shares of any other Common Stock, or (iii) any repurchase of any
outstanding securities of the Corporation that is approved by the Corporation's
Board of Directors.  

         2.   LIQUIDATION PREFERENCE.  

              (a)  In the event of any liquidation, dissolution or winding up
of the Corporation, either voluntary or involuntary,  the holders of the Series
A Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock shall
be entitled to receive, prior and in preference to any distribution of any of
the assets or surplus funds of the Corporation to the holders of Common Stock by
reason of their ownership thereof, the amount of $.50, $.90, and $1.35 per
share, respectively (appropriately adjusted for any Recapitalization), plus all
declared but unpaid dividends on such share for each share of Series A Preferred
Stock, Series B Preferred Stock, or Series C Preferred Stock then held by them. 
If upon the occurrence of such event, the assets and funds thus distributed
among the holders of the Preferred Stock shall be insufficient to permit the
payment to such holders of the full aforesaid preferential amount, then the
entire assets and funds of the Corporation legally available for distribution
shall be distributed among the holders of the Preferred Stock in proportion to
the full amounts to which they would otherwise be entitled and in proportion to
the number of shares of Preferred Stock then held by them.  

              (b)  After payment to the holders of Preferred Stock of the
amount set forth in subparagraph (a) above, the entire remaining assets and
funds of the Corporation legally available for distribution, if any, shall be
distributed among the holders of the Preferred Stock and


                                          3

<PAGE>

Common Stock pro rata based on the number of shares of Common Stock held by them
(assuming conversion of all Preferred Stock).

              (c)  A consolidation or merger of the Corporation with or into
any other corporation or corporations, or a sale of all or substantially all of
the assets of the Corporation, other transaction or series of related
transactions resulting in a change of voting control shall be deemed a
liquidation, dissolution or winding up within the meaning of this Section 2 if
(a) more than 50% of the outstanding securities of each class of the surviving
entity, or (b) an interest in equity securities representing at least 50% of the
voting power or at least 50% of the equity interest in the surviving entity, is
not owned by persons who were holders of capital stock or securities convertible
into capital stock of the Corporation immediately prior to such merger,
consolidation or sale; provided, however, that the sale of Preferred Stock to
private investors pursuant to a Preferred Stock Purchase Agreement shall not
constitute a liquidation, dissolution or winding up within the meaning of this
section.

         3.   VOTING RIGHTS.  Except as otherwise expressly provided herein or
as required by law, the holder of each share of Preferred Stock shall be
entitled to the number of votes equal to the number of shares of Common Stock
into which such share of Preferred Stock could be converted on the record date
for the vote or the date of the solicitation of any written consent of
shareholders and shall have voting rights and powers equal to the voting rights
and powers of the Common Stock (except as otherwise expressly provided herein or
as required by law, voting together with the Common Stock as a single class) and
shall be entitled to notice of any stockholders' meeting in accordance with the
Bylaws of the Corporation.  Fractional votes shall not, however, be permitted
and any fractional voting rights resulting from the above formula (after
aggregating all shares into which shares of Preferred Stock held by each holder
could be converted) shall be rounded to the nearest whole number (with one-half
being rounded upward).

         4.   CONVERSION.  The holders of Preferred Stock shall have conversion
rights as follows (the "Conversion Rights"):

              (a)  RIGHT TO CONVERT.   Each share of Preferred Stock shall be
convertible, at the option of the holder thereof, at any time after the date of
issuance of such share, at the office of the Corporation or any transfer agent
for such stock.  The number of fully paid and nonassessable shares of Common
Stock to which a holder of Series A Preferred Stock shall be entitled upon
conversion shall be the product obtained by multiplying the "Series A Conversion
Rate" then in effect (determined as provided in Section 4(b)) by the number of
shares of Series A Preferred Stock being converted.  The number of fully paid
and nonassessable shares of Common Stock to which a holder of Series B Preferred
Stock shall be entitled upon conversion shall be the product obtained by
multiplying the "Series B Conversion Rate" then in effect (determined as
provided in Section 4(c)) by the number of shares of Series B Preferred being


                                          4

<PAGE>

converted. The number of fully paid and nonassessable shares of Common Stock to
which a holder of Series C Preferred Stock shall be entitled upon conversion
shall be the product obtained by multiplying the "Series C Conversion Rate" then
in effect (determined as provided in Section 4(d)) by the number of shares of
Series C Preferred being converted. 

              (b)  SERIES A CONVERSION RATE.  The conversion rate in effect at
any time for conversion of the Series A Preferred Stock (the "Series A
Conversion Rate") shall be the quotient obtained by dividing $.50 by the "Series
A Conversion Price," calculated as provided in Section 4(e). 

              (c)  SERIES B CONVERSION RATE.  The conversion rate in effect at
any time for conversion of the Series B Preferred Stock (the "Series B
Conversion Rate") shall be the quotient obtained by dividing $.90 by the "Series
B Conversion Price," calculated as provided in Section 4(e).

              (d) SERIES C CONVERSION RATE.  The conversion rate in effect at
any time for conversion of the Series C Preferred Stock (the "Series C
Conversion Rate") shall be the quotient obtained by dividing $1.35 by the
"Series C Conversion Price," calculated as provided in Section 4(e).

              (e)  CONVERSION PRICE.  The conversion price for the Series A
Preferred Stock shall initially be $.50 (the "Series A Conversion Price").  The
conversion price of the Series B Preferred Stock shall initially be $.90 (the
"Series B Conversion Price"). The conversion price of the Series C Preferred
Stock shall initially be $1.35 (the "Series C Conversion Price").   Such initial
Series A Conversion Price, Series B Conversion Price and Series C Conversion
Price (the "Conversion Prices") shall be adjusted from time to time in
accordance with this Section 4.  All references to the Conversion Prices herein
shall mean the Conversion Prices as so adjusted.  

              (f)  AUTOMATIC CONVERSION.  Each share of Preferred Stock shall
automatically be converted into shares of Common Stock at the then effective
Conversion Price immediately upon (i) the closing of the sale of the
Corporation's Common Stock in a firm commitment, underwritten public offering
registered under the Securities Act of 1933, as amended (other than a
registration relating solely to a transaction under Rule 145 under such Act (or
any successor thereto) or to an employee benefit plan of the Company), at a
public offering price equal to or exceeding $2.50 per share of Common Stock
(appropriately adjusted for any Recapitalization) and the aggregate net proceeds
to the Corporation (before deduction for underwriter commissions and expenses
relating to the issuance, including without limitation fees of the Corporation's
counsel) of which equal or exceed $10,000,000 or (ii) upon receipt by the


                                          5

<PAGE>

Corporation of the affirmative vote at a duly noticed shareholders meeting or
pursuant to a duly solicited written consent of approval of the holders of at
least a majority of the then outstanding shares of the Series A Preferred Stock,
the Series B Preferred Stock, and the Series C Preferred Stock, voting together
as a single class in favor of the conversion of all of the shares of Preferred
Stock into Common Stock.

              (g)  MECHANICS OF CONVERSION.  Before any holder of Preferred
Stock shall be entitled to convert the same into shares of Common Stock, the
holder shall surrender the certificate or certificates thereof, duly endorsed,
at the office of the Corporation or of any transfer agent for such stock, and
shall give written notice to the Corporation at such office that he elects to
convert the same and shall state therein the name or names in which he wishes
the certificate or certificates for shares of Common Stock to be issued.  The
Corporation shall, as soon as practicable thereafter, issue and deliver at such
office to such holder of Preferred Stock, a certificate or certificates for the
number of shares of Common Stock to which he shall be entitled as aforesaid. 
Such conversion shall be deemed to have been made immediately prior to the close
of business on the date of surrender of the shares of Preferred Stock to be
converted, except that in the case of an automatic conversion pursuant to
Section 4(f) hereof, such conversion shall be deemed to have been made (i)
immediately prior to the closing of the offering referred to in Section 4(f)(i)
or (ii) immediately upon the approval by vote or written consent referred to in
Section 4(f)(ii) above, and the person or persons entitled to receive the shares
of Common Stock issuable upon such conversion shall be treated for all purposes
as the record holder or holders of such shares of Common Stock on such date.  

              (h)  ADJUSTMENTS TO CONVERSION PRICE.  

                   (i)  SPECIAL DEFINITIONS.  For purposes of this Section 4(h)
`ORIGINAL ISSUE DATE' shall mean the date on which a share of Preferred Stock
was first issued.

                   (ii) ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF COMMON
STOCK.  In the event the Corporation at any time or from time to time after the
Original Issue Date shall declare or pay any dividend on the Common Stock
payable in Common Stock or in any right to acquire Common Stock, or shall effect
a subdivision of the outstanding shares of Common Stock into a greater number of
shares of Common Stock (by stock split, reclassification or otherwise), or in
the event the outstanding shares of Common Stock shall be combined or
consolidated, by reclassification or otherwise, into a lesser number of shares
of Common Stock, then the respective Conversion Prices of the Series A Preferred
Stock, Series B Preferred Stock and Series C Preferred Stock in effect
immediately prior to such event shall, concurrently with the effectiveness of
such event, be proportionately decreased or increased, as appropriate.  


                                          6

<PAGE>

              (i)  OTHER DISTRIBUTIONS.  In the event the Corporation shall at
any time or from time to time make or issue, or fix a record date for the
determination of holders of Common Stock entitled to receive, a dividend or
other distribution payable in securities of the Corporation or any of its
subsidiaries, then in each such event provision shall be made so that the
holders of Preferred Stock shall receive, upon the conversion thereof, the
securities of the Corporation or any of its subsidiaries which they would have
received had their stock been converted into Common Stock on the date of such
event.  

              (j)  NO IMPAIRMENT.  The Corporation will not, by amendment of
its Articles of Incorporation or through any reorganization, transfer of assets,
consolidation, merger, dissolution, issue or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed hereunder by the Corporation, but will at
all times in good faith assist in the carrying out of all the provisions of this
Section 4 and in the taking of all such action as may be necessary or
appropriate in order to protect the Conversion Rights of the holders of the
Preferred Stock against impairment.  

              (k)  CERTIFICATES AS TO ADJUSTMENTS.  Upon the occurrence of each
adjustment or readjustment of the Conversion Price pursuant to this Section 4,
the Corporation at its expense shall promptly compute such adjustment or
readjustment in accordance with the terms hereof and cause independent public
accountants selected by the Corporation to verify such computation and prepare
and furnish to each holder of Preferred Stock a certificate setting forth such
adjustment or readjustment and showing in detail the facts upon which such
adjustment or readjustment is based.  The Corporation shall, upon the written
request at any time of any holder of Preferred Stock, furnish or cause to be
furnished to such holder a like certificate setting forth (i) such adjustments
and readjustments, (ii) the Conversion Price at the time in effect, and (iii)
the number of shares of Common Stock and the amount, if any, of other property
which at the time would be received upon the conversion of Preferred Stock.  

              (l)  NOTICES OF RECORD DATE.  In the event of any taking by the
Corporation of a record of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend (other than a cash dividend) or other distribution, any security or
right convertible into or entitling the holder thereof to receive shares of
Common Stock, or any right to subscribe for, purchase or otherwise acquire any
shares of stock of any class or any other securities or property, or to receive
any other right, the Corporation shall mail to each holder of Preferred Stock at
least 20 days prior to the date specified therein, a notice specifying the date
on which any such record is to be taken for the purpose of such dividend,
distribution, security or right, and the amount and character of such dividend,
distribution, security or right.  


                                          7

<PAGE>

              (m)  ISSUE TAXES.  The Corporation shall pay any and all issue
and other taxes, excluding federal, state or local income taxes, that may be
payable in respect of any issue or delivery of shares of Common Stock on
conversion of shares of Preferred Stock pursuant hereto; provided, however, that
the Corporation shall not be obligated to pay any transfer taxes resulting from
any transfer requested by any holder in connection with any such conversion.  

              (n)  RESERVATION OF STOCK ISSUABLE UPON CONVERSION.  The
Corporation shall at all times reserve and keep available out of its authorized
but unissued shares of Common Stock, solely for the purpose of effecting the
conversion of the shares of the Preferred Stock, such number of its shares of
Common Stock as shall from time to time be sufficient to effect the conversion
of all outstanding shares of the Preferred Stock; and if at any time the number
of authorized but unissued shares of Common Stock shall not be sufficient to
effect the conversion of all then outstanding shares of the Preferred Stock, the
Corporation will take such corporate action as may, in the opinion of its
counsel, be necessary to increase its authorized but unissued shares of Common
Stock to such number of shares as shall be sufficient for such purpose,
including, without limitation, engaging in best efforts to obtain the requisite
shareholder approval of any necessary amendment to this Articles of
Incorporation.

              (o)  CONSENT TO CERTAIN DISTRIBUTIONS.    Each holder of
Preferred Stock shall be deemed to have consented for purposes of Sections 502,
503 and 506 of the General Corporation Law to distributions and payments made by
the Corporation and approved by the Board of Directors of the Corporation in
connection with the repurchases of shares of Common Stock issued or to held by
directors, board advisors and employees of, or consultants to, the Corporation
upon termination of their employment or services. 

              (p)  FRACTIONAL SHARES.  No fractional share shall be issued upon
the conversion of any share or shares of Preferred Stock.  All shares of Common
Stock (including fractions thereof) issuable upon conversion of more than one
share of Preferred Stock by a holder thereof shall be aggregated for purposes of
determining whether the conversion would result in the issuance of any
fractional share.  If, after the aforementioned aggregation, the conversion
would result in the issuance of a fraction of a share of Common Stock, the
Corporation shall, in lieu of issuing any fractional share, pay the holder
otherwise entitled to such fraction a sum in cash equal to the fair market value
of such fraction on the date of conversion (as determined in good faith by the
Board of Directors of the Corporation).  

              (q)  NOTICES.  Any notice required by the provisions of this
Section 4 to be given to the holders of shares of Preferred Stock shall be
deemed given if deposited in the United States mail, postage prepaid, and
addressed to each holder of record at its address appearing on the books of the
Corporation.  Notwithstanding the above, any notice or communication to an


                                          8

<PAGE>

address outside the United States shall be sent by telecopy and confirmed in
writing sent by courier guaranteeing delivery in no more than two (2) business
days.

              (r)  ADJUSTMENTS.  In case of any reorganization or any
reclassification of the capital stock of the Corporation, any consolidation or
merger of the Corporation with or into another corporation or corporations, or
the conveyance of all or substantially all of the assets of the Corporation to
another corporation, each share of Preferred Stock shall thereafter be
convertible into the number of shares of stock or other securities or property
(including cash) to which a holder of the number of shares of Common Stock
deliverable upon conversion of such share of Preferred Stock would have been
entitled upon the record date of (or date of, if no record date is fixed) such
reorganization, reclassification, consolidation, merger or conveyance; and, in
any case, appropriate adjustment (as determined by the Board of Directors) shall
be made in the application of the provisions herein set forth with respect to
the rights and interests thereafter of the holders of such Preferred Stock, to
the end that the provisions set forth herein shall thereafter be applicable, as
nearly as equivalent as is practicable, in relation to any shares of stock or
the securities or property (including cash) thereafter deliverable upon the
conversion of the shares of such Preferred Stock.

         5.   RESTRICTIONS AND LIMITATIONS.  So long as at least 5,000,000 of
the authorized shares of Preferred Stock remain outstanding, the Corporation
shall not, without the vote or written consent by the holders of majority of the
then outstanding shares of Series A Preferred Stock, Series B Preferred Stock,
and Series C Preferred Stock, voting together as a single class on an as-
converted basis:

              (a)  Amend, repeal or waive any provision of, or add any
provision to, the Corporation's Articles of Incorporation if such action would
alter or change in an adverse manner the preferences, rights, privileges or
powers of, or the restrictions provided for the benefit of, the Preferred Stock;

              (b)  Increase the total number of authorized shares of Common
Stock or Preferred Stock of the Corporation or the number of shares designated
as any series of Preferred Stock;

              (c)  Authorize or issue, or obligate itself to issue, any other
equity security senior to the Series A Preferred Stock Series B Preferred Stock
or Series C Preferred Stock as to dividend or redemption rights, liquidation
preferences, conversion rights, voting rights or otherwise, or create any
obligation or security convertible into or exchangeable for, or having any
option rights to purchase, any such equity security which is senior to the
Series A Preferred Stock, Series B Preferred Stock or Series C Preferred Stock;
provided, however, that an equity security issued subsequent to the issuance of
the Series A Preferred Stock, Series B Preferred Stock or


                                          9

<PAGE>

Series C Preferred Stock for a share price and corresponding liquidation price
higher than that of the Series A Preferred Stock, Series B Preferred Stock, or
Series C Preferred Stock shall not be deemed senior to the Series A Preferred
Stock, Series B Preferred Stock or Series C Preferred Stock solely by reason of
such share price and liquidation price;

              (d)  Do any act or thing which would result in taxation of the
holders of shares of the Preferred Stock under Section 305 of the Internal
Revenue Code of 1968, as amended (the "Code") (or any comparable provision of
the Code as hereafter from time to time amended);

              (e)  Effect any sale or other conveyance of all or substantially
all of the assets of the Corporation or any of its subsidiaries, or any
consolidation or merger involving the Corporation or any of its subsidiaries
with or into any other corporation, if more than 50% of the surviving entity is
not owned by persons who were holders of capital stock or securities convertible
into capital stock of the Corporation immediately prior to such merger,
consolidation or sale; or

              (f)  Set aside any amounts for or purchase, or declare or pay any
dividend or make any other distribution on, any shares of capital stock other
than the Series A Preferred Stock, Series B Preferred Stock or Series C
Preferred Stock, except for repurchases required by current agreements with
directors, consultants or employees.

         6.   NO REISSUANCE OF PREFERRED STOCK.  No share or shares of
Preferred Stock acquired by the Corporation by reason of redemption, purchase,
conversion or otherwise shall be reissued, and all such shares shall be returned
to the status of undesignated shares of Preferred Stock.

                                         IV.

         A.   The liability of the directors of this corporation for monetary
damages shall be eliminated to the fullest extent permissible under California
law.

         B.   This corporation is authorized to provide indemnification of
agents (as defined in Section 317 of the California Corporations Code) for
breach of duty to the corporation and its shareholders through bylaw provisions
or through agreements with the agents, or through shareholder resolutions, or
otherwise, to the fullest extent permitted by California law.

         C.   Any repeal or modification of this Article shall only be
prospective and shall not affect the rights under this Article in effect at the
time of the alleged occurrence of any act or omission to act giving rise to
liability or indemnification."


                                          10

<PAGE>

         3.  The foregoing Amended and Restated Articles of Incorporation has
been duly approved by the board of directors.

         4.   The foregoing Amended and Restated Articles of Incorporation has
been duly approved by the required vote of shareholders in accordance with
Sections 902 and 903 of the Corporations Code.  The total number of outstanding
shares of the corporation is 3,486,370 shares of Common Stock, 5,000,000 shares
of Series A Preferred Stock and 17,990,401 shares of Series B Preferred Stock. 
The number of shares voting in favor of the amendment equaled or exceeded the
vote required.  The percentage vote required was more than 50% of the Common
Stock, more than 50% of the Series A Preferred Stock and Series B Preferred
Stock voting together as a separate class and more than 50% of the Common Stock
and Preferred Stock voting together on an as-converted basis.


We further declare under penalty of perjury under the laws of the State of
California that the matters set forth in this certificate are true and correct
of our own knowledge.


DATE:                     , 1995
      --------------------



                                  -----------------------------------------
                                  J. Leighton Read, Chief Executive Officer



                                  -----------------------------------------
                                  Alan C. Mendelson, Secretary


                                          11


<PAGE>





                                     BYLAWS

                                       OF

                                     AVIRON,
                            A CALIFORNIA CORPORATION


                       As amended as of September 2, 1993


<PAGE>


                                TABLE OF CONTENTS

                                                                            PAGE
                                                                            ----

ARTICLE I - Offices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

     Section 1.  Principal Office. . . . . . . . . . . . . . . . . . . . . . . 1
     Section 2.  Other Offices . . . . . . . . . . . . . . . . . . . . . . . . 1

ARTICLE II - Corporate Seal. . . . . . . . . . . . . . . . . . . . . . . . . . 1

     Section 3.  Corporate Seal. . . . . . . . . . . . . . . . . . . . . . . . 1

ARTICLE III - Shareholders' Meetings and Voting Rights . . . . . . . . . . . . 1

     Section 4.   Place of Meetings. . . . . . . . . . . . . . . . . . . . . . 1
     Section 5.   Annual Meeting . . . . . . . . . . . . . . . . . . . . . . . 2
     Section 6.   Postponement of Annual Meeting . . . . . . . . . . . . . . . 2
     Section 7.   Special Meetings . . . . . . . . . . . . . . . . . . . . . . 2
     Section 8.   Notice of Meetings . . . . . . . . . . . . . . . . . . . . . 2
     Section 9.   Manner of Giving Notice. . . . . . . . . . . . . . . . . . . 3
     Section 10.  Quorum and Transaction of Business . . . . . . . . . . . . . 4
     Section 11.  Adjournment and Notice of Adjourned Meetings . . . . . . . . 4
     Section 12.  Waiver of Notice, Consent to Meeting or Approval
                    of Minutes . . . . . . . . . . . . . . . . . . . . . . . . 5
     Section 13.  Action by Written Consent Without a Meeting. . . . . . . . . 5
     Section 14.  Voting . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     Section 15.  Persons Entitled to Vote or Consent. . . . . . . . . . . . . 6
     Section 16.  Proxies. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     Section 17.  Inspectors of Election . . . . . . . . . . . . . . . . . . . 7

ARTICLE IV - Board of Directors. . . . . . . . . . . . . . . . . . . . . . . . 8

     Section 18.  Powers . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     Section 19.  Number of Directors. . . . . . . . . . . . . . . . . . . . . 8
     Section 20.  Election Of Directors, Term, Qualifications. . . . . . . . . 9
     Section 21.  Resignations . . . . . . . . . . . . . . . . . . . . . . . . 9
     Section 22.  Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     Section 23.  Vacancies. . . . . . . . . . . . . . . . . . . . . . . . . . 9
     Section 24.  Regular Meetings . . . . . . . . . . . . . . . . . . . . . .10
     Section 25.  Participation by Telephone . . . . . . . . . . . . . . . . .10
     Section 26.  Special Meetings . . . . . . . . . . . . . . . . . . . . . .10


                                       i.
<PAGE>


     Section 27.  Notice of Meetings . . . . . . . . . . . . . . . . . . . . .10
     Section 28.  Place of Meetings. . . . . . . . . . . . . . . . . . . . . .11
     Section 29.  Action by Written Consent Without a Meeting. . . . . . . . .11
     Section 30.  Quorum and Transaction of Business . . . . . . . . . . . . .11
     Section 31.  Adjournment. . . . . . . . . . . . . . . . . . . . . . . . .11
     Section 32.  Organization . . . . . . . . . . . . . . . . . . . . . . . .11
     Section 33.  Compensation . . . . . . . . . . . . . . . . . . . . . . . .11
     Section 34.  Committees . . . . . . . . . . . . . . . . . . . . . . . . .11

ARTICLE V - Officers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

     Section 35.  Officers . . . . . . . . . . . . . . . . . . . . . . . . . .12
     Section 36.  Appointment. . . . . . . . . . . . . . . . . . . . . . . . .13
     Section 37.  Inability to Act . . . . . . . . . . . . . . . . . . . . . .13
     Section 38.  Resignations . . . . . . . . . . . . . . . . . . . . . . . .13
     Section 39.  Removal. . . . . . . . . . . . . . . . . . . . . . . . . . .13
     Section 40.  Vacancies. . . . . . . . . . . . . . . . . . . . . . . . . .13
     Section 41.  Chairman of the Board. . . . . . . . . . . . . . . . . . . .13
     Section 42.  President. . . . . . . . . . . . . . . . . . . . . . . . . .13
     Section 43.  Vice Presidents. . . . . . . . . . . . . . . . . . . . . . .14
     Section 44.  Secretary. . . . . . . . . . . . . . . . . . . . . . . . . .14
     Section 45.  Chief Financial Officer. . . . . . . . . . . . . . . . . . .15
     Section 46.  Compensation . . . . . . . . . . . . . . . . . . . . . . . .15

ARTICLE VI - Contracts, Loans, Bank Accounts, Checks and Drafts. . . . . . . .16

     Section 47.  Execution of Contracts and Other Instruments . . . . . . . .16
     Section 48.  Loans. . . . . . . . . . . . . . . . . . . . . . . . . . . .16
     Section 49.  Bank Accounts. . . . . . . . . . . . . . . . . . . . . . . .16
     Section 50.  Checks, Drafts, Etc. . . . . . . . . . . . . . . . . . . . .16

ARTICLE VII - Certificates for Shares and Their Transfer . . . . . . . . . . .17

     Section 51.  Certificate for Shares . . . . . . . . . . . . . . . . . . .17
     Section 52.  Transfer on the Books. . . . . . . . . . . . . . . . . . . .17
     Section 53.  Lost, Destroyed and Stolen Certificates. . . . . . . . . . .17
     Section 54.  Issuance, Transfer and Registration of Shares. . . . . . . .18

ARTICLE VIII - Inspection of Corporate Records . . . . . . . . . . . . . . . .18

     Section 55.  Inspection by Directors. . . . . . . . . . . . . . . . . . .18
     Section 56.  Inspection by Shareholders . . . . . . . . . . . . . . . . .18
     Section 57.  Written Form . . . . . . . . . . . . . . . . . . . . . . . .19


                                       ii.
<PAGE>


ARTICLE IX - Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . .19

     Section 58.  Fiscal Year. . . . . . . . . . . . . . . . . . . . . . . . .19
     Section 59.  Annual Report. . . . . . . . . . . . . . . . . . . . . . . .19
     Section 60.  Record Date. . . . . . . . . . . . . . . . . . . . . . . . .20
     Section 61.  Bylaw Amendments . . . . . . . . . . . . . . . . . . . . . .20
     Section 62.  Construction and Definition. . . . . . . . . . . . . . . . .20

ARTICLE X - Indemnification. . . . . . . . . . . . . . . . . . . . . . . . . .21

     Section 63. Indemnification of Directors, Officers, Employees
                   And Other Agents. . . . . . . . . . . . . . . . . . . . . .21

ARTICLE XI - Right of First Refusal. . . . . . . . . . . . . . . . . . . . . .25

     Section 64.  Right of First Refusal . . . . . . . . . . . . . . . . . . .25

ARTICLE XII - Loans of Officers and Others . . . . . . . . . . . . . . . . . .27

     Section 65.   Certain Corporate Loans and Guaranties. . . . . . . . . . .27


                                      iii.
<PAGE>

                                     BYLAWS

                                       OF

                                     AVIRON,
                            A CALIFORNIA CORPORATION


                       As Amended as of September 2, 1993


                                    ARTICLE I

                                     OFFICES

     Section 1.  PRINCIPAL OFFICE.  The principal executive office of the
corporation shall be located at such place as the Board of Directors may from
time to time authorize.  If the principal executive office is located outside
this state, and the corporation has one or more business offices in this state,
the board of directors shall fix and designate a principal business office in
the State of California.

     Section 2.  OTHER OFFICES.  Additional offices of the corporation shall be
located at such place or places, within or outside the State of California, as
the Board of Directors may from time to time authorize.


                                   ARTICLE II

                                 CORPORATE SEAL

     Section 3.  CORPORATE SEAL.  If the Board of Directors adopts a corporate
seal such seal shall have inscribed thereon the name of the corporation and the
state and date of its incorporation.  If and when a seal is adopted by the Board
of Directors, such seal may be engraved, lithographed, printed, stamped,
impressed upon, or affixed to any contract, conveyance, certificate for shares,
or other instrument executed by the corporation.


                                   ARTICLE III

                    SHAREHOLDERS' MEETINGS AND VOTING RIGHTS

     Section 4.  PLACE OF MEETINGS.  Meetings of shareholders shall be held at
the principal executive office of the corporation, or at any other place, within
or outside the State of California,


                                       1.
<PAGE>


which may be fixed either by the Board of Directors or by the written consent of
all persons entitled to vote at such meeting, given either before or after the
meeting and filed with the Secretary of the Corporation.

     Section 5.  ANNUAL MEETING.  The annual meeting of the shareholders of the
corporation shall be held on any date and time which may from time to time be
designated by the Board of Directors.  At such annual meeting, directors shall
be elected and any other business may be transacted which may properly come
before the meeting.

     Section 6.  POSTPONEMENT OF ANNUAL MEETING.  The Board of Directors and the
President shall each have authority to hold at an earlier date and/or time, or
to postpone to a later date and/or time, the annual meeting of shareholders.

     Section 7.  SPECIAL MEETINGS.

            (a)  Special meetings of the shareholders, for any purpose or
purposes, may be called by the Board of Directors, the Chairman of the Board of
Directors, the President, or the holders of shares entitled to cast not less
than ten percent (10%) of the votes at the meeting.

            (b)  Upon written request to the Chairman of the Board of Directors,
the President, any vice president or the Secretary of the corporation by any
person or persons (other than the Board of Directors) entitled to call a special
meeting of the shareholders, such officer forthwith shall cause notice to be
given to the shareholders entitled to vote, that a meeting will be held at a
time requested by the person or persons calling the meeting, such time to be not
less than thirty-five (35) nor more than sixty (60) days after receipt of such
request.  If such notice is not given within twenty (20) days after receipt of
such request, the person or persons calling the meeting may give notice thereof
in the manner provided by law or in these bylaws. Nothing contained in this
Section 7 shall be construed as limiting, fixing or affecting the time or date
when a meeting of shareholders called by action of the Board of Directors may be
held.

     Section 8.  NOTICE OF MEETINGS.  Except as otherwise may be required by law
and subject to subsection 7(b) above, written notice of each meeting of
shareholders shall be given to each shareholder entitled to vote at that meeting
(see Section 15 below), by the Secretary, assistant secretary or other person
charged with that duty, not less than ten (10) (or, if sent by third class mail,
thirty (30)) nor more than sixty (60) days before such meeting.

     Notice of any meeting of shareholders shall state the date, place and hour
of the meeting and,

            (a)  in the case of a special meeting, the general nature of the
business to be transacted, and no other business may be transacted at such
meeting;


                                       2.
<PAGE>


            (b)  in the case of an annual meeting, the general nature of matters
which the Board of Directors, at the time the notice is given, intends to
present for action by the shareholders;

            (c)  in the case of any meeting at which directors are to be
elected, the names of the nominees intended at the time of the notice to be
presented by management for election; and

            (d)  in the case of any meeting, if action is to be taken on any of
the following proposals, the general nature of such proposal:

                    (1)  a proposal to approve a transaction within the
provisions of California Corporations Code, Section 310 (relating to certain
transactions in which a director has an interest);

                    (2)  a proposal to approve a transaction within the
provisions of California Corporations Code, Section 902 (relating to amending
the Articles of Incorporation of the corporation);

                    (3)  a proposal to approve a transaction within the
provisions of California Corporations Code, Sections 181 and 1201 (relating to
reorganization);

                    (4)  a proposal to approve a transaction within the
provisions of California Corporations Code, Section 1900 (winding up and
dissolution);

                    (5)  a proposal to approve a plan of distribution within the
provisions of California Corporations Code, Section 2007 (relating to certain
plans providing for distribution not in accordance with the liquidation rights
of preferred shares, if any).

            At a special meeting, notice of which has been given in accordance
with this Section, action may not be taken with respect to business, the general
nature of which has not been stated in such notice.  At an annual meeting,
action may be taken with respect to business stated in the notice of such
meeting, given in accordance with this Section, and, subject to subsection 8(d)
above, with respect to any other business as may properly come before the
meeting.

     Section 9.  MANNER OF GIVING NOTICE.  Notice of any meeting of shareholders
shall be given either personally or by first-class mail, or, if the corporation
has outstanding shares held of record by 500 or more persons (determined as
provided in California Corporations Code Section 605) on the record date for
such meeting, third-class mail, or telegraphic or other written communication,
addressed to the shareholder at the address of that shareholder appearing on the
books of the corporation or given by the shareholder to the corporation for the
purpose of notice.  If no such address appears on the corporation's books or is
given, notice shall be deemed to have been given if sent to that shareholder by
first-class mail or telegraphic or other written communication to the
corporation's principal executive office, or if published at least once in a


                                       3.
<PAGE>


newspaper of general circulation in the county where that office is located.
Notice shall be deemed to have been given at the time when delivered personally
or deposited in the mail or sent by telegram or other means of written
communication.

     If any notice addressed to a shareholder at the address of that shareholder
appearing on the books of the corporation is returned to the corporation by the
United States Postal Service marked to indicate that the United States Postal
Service is unable to deliver the notice to the shareholder at that address, all
future notices shall be deemed to have been duly given without further mailing
if these shall be available to the shareholder on written demand by the
shareholder at the principal executive office of the corporation for a period of
one year from the date of the giving of the notice.

     Section 10.  QUORUM AND TRANSACTION OF BUSINESS.

            (a)  At any meeting of the shareholders, a majority of the shares
entitled to vote, represented in person or by proxy, shall constitute a quorum.
If a quorum is present, the affirmative vote of the majority of shares
represented at the meeting and entitled to vote on any matter shall be the act
of the shareholders, unless the vote of a greater number or voting by classes is
required by law or by the Articles of Incorporation, and except as provided in
subsection (b) below.

            (b)  The shareholders present at a duly called or held meeting of
the shareholders at which a quorum is present may continue to do business until
adjournment, notwithstanding the withdrawal of enough shareholders to leave less
than a quorum, provided that any action taken (other than adjournment) is
approved by at least a majority of the shares required to constitute a quorum.

            (c)  In the absence of a quorum, no business other than adjournment
may be transacted, except as described in subsection (b) above.

     Section 11.  ADJOURNMENT AND NOTICE OF ADJOURNED MEETINGS. Any meeting of
shareholders may be adjourned from time to time, whether or not a quorum is
present, by the affirmative vote of a majority of shares represented at such
meeting either in person or by proxy and entitled to vote at such meeting.

     In the event any meeting is adjourned, it shall not be necessary to give
notice of the time and place of such adjourned meeting pursuant to Sections 8
and 9 of these bylaws; provided that if any of the following three events occur,
such notice must be given:

            (1)  announcement of the adjourned meeting's time and place is not
made at the original meeting which it continues or


                                       4.
<PAGE>


            (2)  such meeting is adjourned for more than forty-five (45) days
from the date set for the original meeting or

            (3)  a new record date is fixed for the adjourned meeting.

     At the adjourned meeting, the corporation may transact any business which
might have been transacted at the original meeting.

     Section 12.  WAIVER OF NOTICE, CONSENT TO MEETING OR APPROVAL OF MINUTES.

            (a)  Subject to subsection (b) of this Section, the transactions of
any meeting of shareholders, however called and noticed, and wherever held,
shall be as valid as though made at a meeting duly held after regular call and
notice, if a quorum is present either in person or by proxy, and if, either
before or after the meeting, each of the persons entitled to vote but not
present in person or by proxy signs a written waiver of notice or a consent to
holding of the meeting or an approval of the minutes thereof.

            (b)  A waiver of notice, consent to the holding of a meeting or
approval of the minutes thereof need not specify the business to be transacted
or transacted at nor the purpose of the meeting; provided that in the case of
proposals described in subsection (d) of Section 8 of these bylaws, the general
nature of such proposals must be described in any such waiver of notice and such
proposals can only be approved by waiver of notice, not by consent to holding of
the meeting or approval of the minutes.

            (c)  All waivers, consents and approvals shall be filed with the
corporate records or made a part of the minutes of the meeting.

            (d)  A person's attendance at a meeting shall constitute waiver of
notice of and presence at such meeting, except when such person objects at the
beginning of the meeting to transaction of any business because the meeting is
not lawfully called or convened and except that attendance at a meeting is not a
waiver of any right to object to the consideration of matters which are required
by law or these bylaws to be in such notice (including those matters described
in subsection (d) of Section 8 of these bylaws), but are not so included if such
person expressly objects to consideration of such matter or matters at any time
during the meeting.

     Section 13.  ACTION BY WRITTEN CONSENT WITHOUT A MEETING. Any action which
may be taken at any meeting of shareholders may be taken without a meeting and
without prior notice if written consents setting forth the action so taken are
signed by the holders of the outstanding shares having not less than the minimum
number of votes that would be necessary to authorize or take such action at a
meeting at which all shares entitled to vote thereon were present and voted.


                                       5.
<PAGE>


     Directors may not be elected by written consent except by unanimous written
consent of all shares entitled to vote for the election of directors; provided
that any vacancy on the Board of Directors (other than a vacancy created by
removal) which has not been filled by the Board of Directors may be filled by
the written consent of a majority of outstanding shares entitled to vote for the
election of directors.

     Any written consent may be revoked pursuant to California Corporations Code
Section 603(c) prior to the time that written consents of the number of shares
required to authorize the proposed action have been filed with the Secretary.
Such revocation must be in writing and will be effective upon its receipt by the
Secretary.

     If the consents of all shareholders entitled to vote have not been
solicited in writing, and if the unanimous written consent of all such
shareholders shall not have been received, the Secretary shall give prompt
notice of any corporate action approved by the shareholders without a meeting to
those shareholders entitled to vote on such matters who have not consented
thereto in writing.  This notice shall be given in the manner specified in
Section 8 of these bylaws.  In the case of approval of (i) a transaction within
the provisions of California Corporations Code, Section 310 (relating to certain
transactions in which a director has an interest), (ii) a transaction within the
provisions of California Corporations Code, Section 317 (relating to
indemnification of agents of the corporation), (iii) a transaction within the
provisions of California Corporations Code, Sections 181 and 1201 (relating to
reorganization), and (iv) a plan of distribution within the provisions of
California Corporations Code, Section 2007 (relating to certain plans providing
for distribution not in accordance with the liquidation rights of preferred
shares, if any), the notice shall be given at least ten (10) days before the
consummation of any action authorized by that approval.

     Section 14.  VOTING.  Voting at any meeting of shareholders need not be by
ballot; provided, however, that elections for directors must be by ballot if
balloting is demanded by a shareholder at the meeting and before the voting
begins.

     Every person entitled to vote at an election for directors may cumulate the
votes to which such person is entitled, i.e., such person may cast a total
number of votes equal to the number of directors to be elected multiplied by the
number of votes to which such person's shares are entitled, and may cast said
total number of votes for one or more candidates in such proportions as such
person thinks fit; provided, however, no shareholder shall be entitled to so
cumulate such shareholder's votes unless the candidates for which such
shareholder is voting have been placed in nomination prior to the voting and a
shareholder has given notice at the meeting, prior to the vote, of an intention
to cumulate votes.  In any election of directors, the candidates receiving the
highest number of votes, up to the number of directors to be elected, are
elected.

     Except as may be otherwise provided in the Articles of Incorporation or by
law, and subject to the foregoing provisions regarding the cumulation of votes,
each shareholder shall be entitled to one vote for each share held.


                                       6.
<PAGE>


     Any shareholder may vote part of such shareholder's shares in favor of a
proposal and refrain from voting the remaining shares or vote them against the
proposal, other than elections to office, but, if the shareholder fails to
specify the number of shares such shareholder is voting affirmatively, it will
be conclusively presumed that the shareholder's approving vote is with respect
to all shares such shareholder is entitled to vote.

     No shareholder approval, other than unanimous approval of those entitled to
vote, will be valid as to proposals described in subsection 8(d) of these bylaws
unless the general nature of such business was stated in the notice of meeting
or in any written waiver of notice.

     Section 15.  PERSONS ENTITLED TO VOTE OR CONSENT.  The Board of Directors
may fix a record date pursuant to Section 60 of these bylaws to determine which
shareholders are entitled to notice of and to vote at a meeting or consent to
corporate actions, as provided in Sections 13 and 14 of these bylaws.  Only
persons in whose name shares otherwise entitled to vote stand on the stock
records of the corporation on such date shall be entitled to vote or consent.

     If no record date is fixed:

            (1)  The record date for determining shareholders entitled to notice
of or to vote at a meeting of shareholders shall be at the close of business on
the business day next preceding the day notice is given or, if notice is waived,
at the close of business on the business day next preceding the day on which the
meeting is held;

            (2)  The record date for determining shareholders entitled to give
consent to corporate action in writing without a meeting, when no prior action
by the Board of Directors has been taken, shall be the day on which the first
written consent is given;

            (3)  The record date for determining shareholders for any other
purpose shall be at the close of business on the day on which the Board of
Directors adopts the resolution relating thereto, or the sixtieth (60th) day
prior to the date of such other action, whichever is later.

     A determination of shareholders of record entitled to notice of or to vote
at a meeting of shareholders shall apply to any adjournment of the meeting
unless the Board of Directors fixes a new record date for the adjourned meeting;
provided, however, that the Board of Directors shall fix a new record date if
the meeting is adjourned for more than forty-five (45) days from the date set
for the original meeting.

     Shares of the corporation held by its subsidiary or subsidiaries (as
defined in California Corporations Code, Section 189(b)) are not entitled to
vote in any matter.

     Section 16.  PROXIES.  Every person entitled to vote or execute consents
may do so either in person or by one or more agents authorized to act by a
written proxy executed by the person or such person's duly authorized agent and
filed with the Secretary of the corporation; provided


                                       7.
<PAGE>


that no such proxy shall be valid after the expiration of eleven (11) months
from the date of its execution unless otherwise provided in the proxy.  The
manner of execution, suspension, revocation, exercise and effect of proxies is
governed by law.

     Section 17.  INSPECTORS OF ELECTION.  Before any meeting of shareholders,
the Board of Directors may appoint any persons, other than nominees for office,
to act as inspectors of election at the meeting or its adjournment. If no
inspectors of election are so appointed, the chairman of the meeting may, and on
the request of any shareholder or a shareholder's proxy shall, appoint
inspectors of election at the meeting.  The number of inspectors shall be either
one (1) or three (3).  If inspectors are appointed at a meeting on the request
of one or more shareholders or proxies, the majority of shares represented in
person or proxy shall determine whether one (1) or three (3) inspectors are to
be appointed.  If any person appointed as inspector fails to appear or fails or
refuses to act, the chairman of the meeting may, and upon the request of any
shareholder or a shareholder's proxy shall, appoint a person to fill that
vacancy.

     These inspectors shall:

            (a)  Determine the number of shares outstanding and the voting power
of each, the shares represented at the meeting, the existence of a quorum, and
the authenticity, validity, and effect of proxies;

            (b)  Receive votes, ballots, or consents;

            (c)  Hear and determine all challenges and questions in any way
arising in connection with the right to vote;

            (d)  Count and tabulate all votes or consents;

            (e)  Determine when the polls shall close;

            (f)  Determine the result; and

            (g)  Do any other acts that may be proper to conduct the election or
vote with fairness to all shareholders.


                                   ARTICLE IV

                               BOARD OF DIRECTORS

     Section 18.  POWERS.  Subject to the provisions of law or any limitations
in the Articles of Incorporation or these bylaws, as to action required to be
approved by the shareholders or by the outstanding shares, the business and
affairs of the corporation shall be managed and all corporate


                                       8.
<PAGE>


powers shall be exercised, by or under the direction of the Board of Directors.
The Board of Directors may delegate the management of the day-to-day operation
of the business of the corporation to a management company or other person,
provided that the business and affairs of the corporation shall be managed and
all corporate powers shall be exercised under the ultimate direction of the
Board of Directors.

     Section 19.  NUMBER OF DIRECTORS.  The authorized number of directors of
the corporation shall be not less than a minimum of four (4) nor more than a
maximum of seven (7) (which maximum number in no case shall be greater than two
times said minimum, minus one) and the number of directors presently authorized
is six (6).  The exact number of directors shall be set within these limits from
time to time (a) by approval of the Board of Directors, or (b) by the
affirmative vote of a majority of the shares represented and voting at a duly
held meeting at which a quorum is present (which shares voting affirmatively
also constitute at least a majority of the required quorum) or by the written
consent of shareholders pursuant to Section 13 hereinabove.

     Any amendment of these bylaws changing the maximum or minimum number of
directors may be adopted only by the affirmative vote of a majority of the
outstanding shares entitled to vote; provided, an amendment reducing the minimum
number of directors to less than five (5), cannot be adopted if votes cast
against its adoption at a meeting or the shares not consenting to it in the case
of action by written consent are equal to more than 16-2/3 percent of the
outstanding shares entitled to vote.

     No reduction of the authorized number of directors shall remove any
director prior to the expiration of such director's term of office.

     Section 20.  ELECTION OF DIRECTORS, TERM, QUALIFICATIONS. The directors
shall be elected at each annual meeting of shareholders to hold office until the
next annual meeting.  Each director, including a director elected or appointed
to fill a vacancy, shall hold office either until the expiration of the term for
which elected or appointed and until a successor has been elected and qualified,
or until his death, resignation or removal.  Directors need not be shareholders
of the corporation.

     Section 21.  RESIGNATIONS.  Any director of the corporation may resign
effective upon giving written notice to the Chairman of the Board, the
President, the Secretary or the Board of Directors of the corporation, unless
the notice specifies a later time for the effectiveness of such resignation.  If
the resignation specifies effectiveness at a future time, a successor may be
elected pursuant to Section 23 of these bylaws to take office on the date that
the resignation becomes effective.

     Section 22.  REMOVAL.  The Board of Directors may declare vacant the office
of a director who has been declared of unsound mind by an order of court or who
has been convicted of a felony.


                                       9.
<PAGE>


     The entire Board of Directors or any individual director may be removed
from office without cause by the affirmative vote of a majority of the
outstanding shares entitled to vote on such removal; provided, however, that
unless the entire Board is removed, no individual director may be removed when
the votes cast against such director's removal, or not consenting in writing to
such removal, would be sufficient to elect that director if voted cumulatively
at an election at which the same total number of votes cast were cast (or, if
such action is taken by written consent, all shares entitled to vote were voted)
and the entire number of directors authorized at the time of such director's
most recent election were then being elected.

     Section 23.  VACANCIES.  A vacancy or vacancies on the Board of Directors
shall be deemed to exist in case of the death, resignation or removal of any
director, or upon increase in the authorized number of directors or if
shareholders fail to elect the full authorized number of directors at an annual
meeting of shareholders or if, for whatever reason, there are fewer directors on
the Board of Directors, than the full number authorized.  Such vacancy or
vacancies, other than a vacancy created by the removal of a director, may be
filled by a majority of the remaining directors, though less than a quorum, or
by a sole remaining director.  A vacancy created by the removal of a director
may be filled only by the affirmative vote of a majority of the shares
represented and voting at a duly held meeting at which a quorum is present
(which shares voting affirmatively also constitute at least a majority of the
required quorum) or by the written consent of shareholders pursuant to
Section 13 hereinabove.  The shareholders may elect a director at any time to
fill any vacancy not filled by the directors.  Any such election by written
consent, other than to fill a vacancy created by removal, requires the consent
of a majority of the outstanding shares entitled to vote. Any such election by
written consent to fill a vacancy created by removal requires the consent of all
of the outstanding shares entitled to vote.

     If, after the filling of any vacancy by the directors, the directors then
in office who have been elected by the shareholders constitute less than a
majority of the directors then in office, any holder or holders of an aggregate
of five percent (5%) or more of the shares outstanding at that time and having
the right to vote for such directors may call a special meeting of shareholders
to be held to elect the entire Board of Directors.  The term of office of any
director shall terminate upon such election of a successor.

     Section 24.  REGULAR MEETINGS.  Regular meetings of the Board of Directors
shall be held at such times, places and dates as fixed in these bylaws or by the
Board of Directors; provided, however, that if the date for such a meeting falls
on a legal holiday, then the meeting shall be held at the same time on the next
succeeding full business day.  Regular meetings of the Board of Directors held
pursuant to this Section 24 may be held without notice.

     Section 25.  PARTICIPATION BY TELEPHONE.  Members of the Board of Directors
may participate in a meeting through use of conference telephone or similar
communications equipment, so long as all members participating in such meeting
can hear one another.  Such participation constitutes presence in person at such
meeting.


                                       10.
<PAGE>


     Section 26.  SPECIAL MEETINGS.  Special meetings of the Board of Directors
for any purpose may be called by the Chairman of the Board or the President or
any vice president or the Secretary of the corporation or any two (2) directors.

     Section 27.  NOTICE OF MEETINGS.  Notice of the date, time and place of all
meetings of the Board of Directors, other than regular meetings held pursuant to
Section 24 above shall be delivered personally, orally or in writing, or by
telephone or telegraph to each director, at least forty-eight (48) hours before
the meeting, or sent in writing to each director by first-class mail, charges
prepaid, at least four (4) days before the meeting.  Such notice may be given by
the Secretary of the corporation or by the person or persons who called a
meeting. Such notice need not specify the purpose of the meeting.  Notice of any
meeting of the Board of Directors need not be given to any director who signs a
waiver of notice of such meeting, or a consent to holding the meeting or an
approval of the minutes thereof, either before or after the meeting, or who
attends the meeting without protesting prior thereto or at its commencement such
director's lack of notice.  All such waivers, consents and approvals shall be
filed with the corporate records or made a part of the minutes of the meeting.

     Section 28.  PLACE OF MEETINGS.  Meetings of the Board of Directors may be
held at any place within or without the state which has been designated in the
notice of the meeting or, if not stated in the notice or there is no notice,
designated in the bylaws or by resolution of the Board of Directors.

     Section 29.  ACTION BY WRITTEN CONSENT WITHOUT A MEETING. Any action
required or permitted to be taken by the Board of Directors may be taken without
a meeting, if all members of the Board of Directors individually or collectively
consent in writing to such action.  Such written consent or consents shall be
filed with the minutes of the proceedings of the Board of Directors.  Such
action by written consent shall have the same force and effect as a unanimous
vote of such directors.

     Section 30.  QUORUM AND TRANSACTION OF BUSINESS.  A majority of the
authorized number of directors shall constitute a quorum for the transaction of
business.  Every act or decision done or made by a majority of the authorized
number of directors present at a meeting duly held at which a quorum is present
shall be the act of the Board of Directors, unless the law, the Articles of
Incorporation or these bylaws specifically require a greater number.  A meeting
at which a quorum is initially present may continue to transact business,
notwithstanding withdrawal of directors, if any action taken is approved by at
least a majority of the number of directors constituting a quorum for such
meeting.  In the absence of a quorum at any meeting of the Board of Directors, a
majority of the directors present may adjourn the meeting, as provided in
Section 31 of these bylaws.

     Section 31.  ADJOURNMENT.  Any meeting of the Board of Directors, whether
or not a quorum is present, may be adjourned to another time and place by the
affirmative vote of a majority of the directors present.  If the meeting is
adjourned for more than twenty-four (24)


                                       11.
<PAGE>


hours, notice of such adjournment to another time or place shall be given prior
to the time of the adjourned meeting to the directors who were not present at
the time of the adjournment.

     Section 32.  ORGANIZATION.  The Chairman of the Board shall preside at
every meeting of the Board of Directors, if present. If there is no Chairman of
the Board or if the Chairman is not present, a Chairman chosen by a majority of
the directors present shall act as chairman.  The Secretary of the corporation
or, in the absence of the Secretary, any person appointed by the Chairman shall
act as secretary of the meeting.

     Section 33.  COMPENSATION.  Directors and members of committees may receive
such compensation, if any, for their services, and such reimbursement for
expenses, as may be fixed or determined by the Board of Directors.

     Section 34.  COMMITTEES.  The Board of Directors may, by resolution adopted
by a majority of the authorized number of directors, designate one or more
committees, each consisting of two (2) or more directors, to serve at the
pleasure of the Board of Directors.  The Board of Directors, by a vote of the
majority of authorized directors, may designate one or more directors as
alternate members of any committee, to replace any absent member at any meeting
of such committee.  Any such committee shall have authority to act in the manner
and to the extent provided in the resolution of the Board of Directors, and may
have all the authority of the Board of Directors in the management of the
business and affairs of the corporation, except with respect to:

            (a)  the approval of any action for which shareholders' approval or
approval of the outstanding shares also is required by the California
Corporations Code;

            (b)  the filling of vacancies on the Board of Directors or any of
its committees;

            (c)  the fixing of compensation of directors for serving on the
Board of Directors or any of its committees;

            (d)  the adoption, amendment or repeal of these bylaws;

            (e)  the amendment or repeal of any resolution of the Board of
Directors which by its express terms is not so amendable or repealable;

            (f)  a distribution to shareholders, except at a rate or in a
periodic amount or within a price range determined by the Board of Directors; or

            (g)  the appointment of other committees of the Board of Directors
or the members thereof.


                                       12.
<PAGE>


     Any committee may from time to time provide by resolution for regular
meetings at specified times and places.  If the date of such a meeting falls on
a legal holiday, then the meeting shall be held at the same time on the next
succeeding full business day.  No notice of such a meeting need be given.  Such
regular meetings need not be held if the committee shall so determine at any
time before or after the time when such meeting would otherwise have taken
place.  Special meetings may be called at any time in the same manner and by the
same persons as stated in Sections 25 and 26 of these bylaws for meetings of the
Board of Directors.  The provisions of Sections 24, 27, 28, 29, 30 and 31 of
these bylaws shall apply to committees, committee members and committee meetings
as if the words "committee" and "committee member" were substituted for the word
"Board of Directors", and "director", respectively, throughout such sections.


                                    ARTICLE V

                                    OFFICERS

     Section 35.  OFFICERS.  The corporation shall have a Chairman of the Board
or a President or both, a Secretary, a Chief Financial Officer and such other
officers with such titles and duties as the Board of Directors may determine.
Any two or more offices may be held by the same person.

     Section 36.  APPOINTMENT.  All officers shall be chosen and appointed by
the Board of Directors; provided, however, the Board of Directors may empower
the chief executive officer of the corporation to appoint such officers, other
than Chairman of the Board, President, Secretary or Chief Financial Officer, as
the business of the corporation may require.  All officers shall serve at the
pleasure of the Board of Directors, subject to the rights, if any, of an officer
under a contract of employment.

     Section 37.  INABILITY TO ACT.  In the case of absence or inability to act
of any officer of the corporation or of any person authorized by these bylaws to
act in such officer's place, the Board of Directors may from time to time
delegate the powers or duties of such officer to any other officer, or any
director or other person whom it may select, for such period of time as the
Board of Directors deems necessary.

     Section 38.  RESIGNATIONS.  Any officer may resign at any time upon written
notice to the corporation, without prejudice to the rights, if any, of the
corporation under any contract to which such officer is a party.  Such
resignation shall be effective upon its receipt by the Chairman of the Board,
the President, the Secretary or the Board of Directors, unless a different time
is specified in the notice for effectiveness of such resignation.  The
acceptance of any such resignation shall not be necessary to make it effective
unless otherwise specified in such notice.


                                       13.
<PAGE>


     Section 39.  REMOVAL.  Any officer may be removed from office at any time,
with or without cause, but subject to the rights, if any, of such officer under
any contract of employment, by the Board of Directors or by any committee to
whom such power of removal has been duly delegated, or, with regard to any
officer who has been appointed by the chief executive officer pursuant to
Section 36 above, by the chief executive officer or any other officer upon whom
such power of removal may be conferred by the Board of Directors.

     Section 40.  VACANCIES.  A vacancy occurring in any office for any cause
may be filled by the Board of Directors, in the manner prescribed by this
Article of the bylaws for initial appointment to such office.

     Section 41.  CHAIRMAN OF THE BOARD.  The Chairman of the Board, if there be
such an officer, shall, if present, preside at all meetings of the Board of
Directors and shall exercise and perform such other powers and duties as may be
assigned from time to time by the Board of Directors or prescribed by these
bylaws. If no President is appointed, the Chairman of the Board is the general
manager and chief executive officer of the corporation, and shall exercise all
powers of the President described in Section 42 below.

     Section 42.  PRESIDENT.  Subject to such powers, if any, as may be given by
the Board of Directors to the Chairman of the Board, if there be such an
officer, the President shall be the general manager and chief executive officer
of the corporation and shall have general supervision and control over the
business and affairs of the corporation, subject to the control of the Board of
Directors.  The President may sign and execute, in the name of the corporation,
any instrument authorized by the Board of Directors, except when the signing and
execution thereof shall have been expressly delegated by the Board of Directors
or by these bylaws to some other officer or agent of the corporation. The
President shall have all the general powers and duties of management usually
vested in the president of a corporation, and shall have such other powers and
duties as may be prescribed from time to time by the Board of Directors or these
bylaws.  The President shall have discretion to prescribe the duties of other
officers and employees of the corporation in a manner not inconsistent with the
provisions of these bylaws and the directions of the Board of Directors.

     Section 43.  VICE PRESIDENTS.  In the absence or disability of the
President, in the event of a vacancy in the office of President, or in the event
such officer refuses to act, the Vice President shall perform all the duties of
the President and, when so acting, shall have all the powers of, and be subject
to all the restrictions on, the President.  If at any such time the corporation
has more than one vice president, the duties and powers of the President shall
pass to each vice president in order of such vice president's rank as fixed by
the Board of Directors or, if the vice presidents are not so ranked, to the vice
president designated by the Board of Directors.  The vice presidents shall have
such other powers and perform such other duties as may be prescribed for them
from time to time by the Board of Directors or pursuant to Sections 35 and 36 of
these bylaws or otherwise pursuant to these bylaws.


                                       14.
<PAGE>


     Section 44.  SECRETARY.  The Secretary shall:

            (a)  Keep, or cause to be kept, minutes of all meetings of the
corporation's shareholders, Board of Directors, and committees of the Board of
Directors, if any.  Such minutes shall be kept in written form.

            (b)  Keep, or cause to be kept, at the principal executive office of
the corporation, or at the office of its transfer agent or registrar, if any, a
record of the corporation's shareholders, showing the names and addresses of all
shareholders, and the number and classes of shares held by each. Such records
shall be kept in written form or any other form capable of being converted into
written form.

            (c)  Keep, or cause to be kept, at the principal executive office of
the corporation, or if the principal executive office is not in California, at
its principal business office in California, an original or copy of these
bylaws, as amended.

            (d)  Give, or cause to be given, notice of all meetings of
shareholders, directors and committees of the Board of Directors, as required by
law or by these bylaws.

            (e)  Keep the seal of the corporation, if any, in safe custody.

            (f)  Exercise such powers and perform such duties as are usually
vested in the office of secretary of a corporation, and exercise such other
powers and perform such other duties as may be prescribed from time to time by
the Board of Directors or these bylaws.

     If any assistant secretaries are appointed, the assistant secretary, or one
of the assistant secretaries in the order of their rank as fixed by the Board of
Directors or, if they are not so ranked, the assistant secretary designated by
the Board of Directors, in the absence or disability of the Secretary or in the
event of such officer's refusal to act or if a vacancy exists in the office of
Secretary, shall perform the duties and exercise the powers of the Secretary and
discharge such duties as may be assigned from time to time pursuant to these
bylaws or by the Board of Directors.

     Section 45.  CHIEF FINANCIAL OFFICER.  The Chief Financial Officer shall:

            (a)   Be responsible for all functions and duties of the treasurer
of the corporation.

            (b)   Keep and maintain, or cause to be kept and maintained,
adequate and correct books and records of account for the corporation.

            (c)   Receive or be responsible for receipt of all monies due and
payable to the corporation from any source whatsoever; have charge and custody
of, and be responsible for, all monies and other valuables of the corporation
and be responsible for deposit of all such monies


                                       15.
<PAGE>


in the name and to the credit of the corporation with such depositaries as may
be designated by the Board of Directors or a duly appointed and authorized
committee of the Board of Directors.

            (d)   Disburse or be responsible for the disbursement of the funds
of the corporation as may be ordered by the Board of Directors or a duly
appointed and authorized committee of the Board of Directors.

            (e)   Render to the chief executive officer and the Board of
Directors a statement of the financial condition of the corporation if called
upon to do so.

            (f)   Exercise such powers and perform such duties as are usually
vested in the office of chief financial officer of a corporation, and exercise
such other powers and perform such other duties as may be prescribed by the
Board of Directors or these bylaws.

     If any assistant financial officer is appointed, the assistant financial
officer, or one of the assistant financial officers, if there are more than one,
in the order of their rank as fixed by the Board of Directors or, if they are
not so ranked, the assistant financial officer designated by the Board of
Directors, shall, in the absence or disability of the Chief Financial Officer or
in the event of such officer's refusal to act, perform the duties and exercise
the powers of the Chief Financial Officer, and shall have such powers and
discharge such duties as may be assigned from time to time pursuant to these
bylaws or by the Board of Directors.

     Section 46.  COMPENSATION.  The compensation of the officers shall be fixed
from time to time by the Board of Directors, and no officer shall be prevented
from receiving such compensation by reason of the fact that such officer is also
a director of the corporation.


                                   ARTICLE VI

               CONTRACTS, LOANS, BANK ACCOUNTS, CHECKS AND DRAFTS

     Section 47.  EXECUTION OF CONTRACTS AND OTHER INSTRUMENTS. Except as these
bylaws may otherwise provide, the Board of Directors or its duly appointed and
authorized committee may authorize any officer or officers, agent or agents, to
enter into any contract or execute and deliver any instrument in the name of and
on behalf of the corporation, and such authorization may be general or confined
to specific instances.  Except as so authorized or otherwise expressly provided
in these bylaws, no officer, agent, or employee shall have any power or
authority to bind the corporation by any contract or engagement or to pledge its
credit or to render it liable for any purpose or in any amount.

     Section 48.  LOANS.  No loans shall be contracted on behalf of the
corporation and no negotiable paper shall be issued in its name, unless and
except as authorized by the Board of Directors or its duly appointed and
authorized committee.  When so authorized by the Board of


                                       16.
<PAGE>


Directors or such committee, any officer or agent of the corporation may effect
loans and advances at any time for the corporation from any bank, trust company,
or other institution, or from any firm, corporation or individual, and for such
loans and advances may make, execute and deliver promissory notes, bonds or
other evidences of indebtedness of the corporation and, when authorized as
aforesaid, may mortgage, pledge, hypothecate or transfer any and all stocks,
securities and other property, real or personal, at any time held by the
corporation, and to that end endorse, assign and deliver the same as security
for the payment of any and all loans, advances, indebtedness, and liabilities of
the corporation. Such authorization may be general or confined to specific
instances.

     Section 49.  BANK ACCOUNTS.  The Board of Directors or its duly appointed
and authorized committee from time to time may authorize the opening and keeping
of general and/or special bank accounts with such banks, trust companies, or
other depositaries as may be selected by the Board of Directors, its duly
appointed and authorized committee or by any officer or officers, agent or
agents, of the corporation to whom such power may be delegated from time to time
by the Board of Directors.  The Board of Directors or its duly appointed and
authorized committee may make such rules and regulations with respect to said
bank accounts, not inconsistent with the provisions of these bylaws, as are
deemed advisable.

     Section 50.  CHECKS, DRAFTS, ETC.   All checks, drafts or other orders for
the payment of money, notes, acceptances or other evidences of indebtedness
issued in the name of the corporation shall be signed by such officer or
officers, agent or agents, of the corporation, and in such manner, as shall be
determined from time to time by resolution of the Board of Directors or its duly
appointed and authorized committee. Endorsements for deposit to the credit of
the corporation in any of its duly authorized depositaries may be made, without
counter-signature, by the President or any vice president or the Chief Financial
Officer or any assistant financial officer or by any other officer or agent of
the corporation to whom the Board of Directors or its duly appointed and
authorized committee, by resolution, shall have delegated such power or by
hand-stamped impression in the name of the corporation.


                                   ARTICLE VII

                   CERTIFICATES FOR SHARES AND THEIR TRANSFER

     Section 51.  CERTIFICATE FOR SHARES.  Every holder of shares in the
corporation shall be entitled to have a certificate signed in the name of the
corporation by the Chairman or Vice Chairman of the Board or the President or a
Vice President and by the Chief Financial Officer or an assistant financial
officer or by the Secretary or an assistant secretary, certifying the number of
shares and the class or series of shares owned by the shareholder.  Any or all
of the signatures on the certificate may be facsimile. In case any officer,
transfer agent or registrar who has signed or whose facsimile signature has been
placed upon a certificate shall have ceased to be such officer, transfer agent
or registrar before such certificate is issued, it may be issued by the


                                       17.
<PAGE>


corporation with the same effect as if such person were an officer, transfer
agent or registrar at the date of issue.

     In the event that the corporation shall issue any shares as only partly
paid, the certificate issued to represent such partly paid shares shall have
stated thereon the total consideration to be paid for such shares and the amount
paid thereon.

     Section 52.  TRANSFER ON THE BOOKS.  Upon surrender to the Secretary or
transfer agent (if any) of the corporation of a certificate for shares of the
corporation duly endorsed, with reasonable assurance that the endorsement is
genuine and effective, or accompanied by proper evidence of succession,
assignment or authority to transfer and upon compliance with applicable federal
and state securities laws and if the corporation has no statutory duty to
inquire into adverse claims or has discharged any such duty and if any
applicable law relating to the collection of taxes has been complied with, it
shall be the duty of the corporation, by its Secretary or transfer agent, to
cancel the old certificate, to issue a new certificate to the person entitled
thereto and to record the transaction on the books of the corporation.

     Section 53.  LOST, DESTROYED AND STOLEN CERTIFICATES.  The holder of any
certificate for shares of the corporation alleged to have been lost, destroyed
or stolen shall notify the corporation by making a written affidavit or
affirmation of such fact. Upon receipt of said affidavit or affirmation the
Board of Directors, or its duly appointed and authorized committee or any
officer or officers authorized by the board so to do, may order the issuance of
a new certificate for shares in the place of any certificate previously issued
by the corporation and which is alleged to have been lost, destroyed or stolen.
However, the Board of Directors or such authorized committee, officer or
officers may require the owner of the allegedly lost, destroyed or stolen
certificate, or such owner's legal representative, to give the corporation a
bond or other adequate security sufficient to indemnify the corporation and its
transfer agent and/or registrar, if any, against any claim that may be made
against it or them on account of such allegedly lost, destroyed or stolen
certificate or the replacement thereof. Said bond or other security shall be in
such amount, on such terms and conditions and, in the case of a bond, with such
surety or sureties as may be acceptable to the Board of Directors or to its duly
appointed and authorized committee or any officer or officers authorized by the
Board of Directors to determine the sufficiency thereof.  The requirement of a
bond or other security may be waived in particular cases at the discretion of
the Board of Directors or its duly appointed and authorized committee or any
officer or officers authorized by the Board of Directors so to do.

     Section 54.  ISSUANCE, TRANSFER AND REGISTRATION OF SHARES. The Board of
Directors may make such rules and regulations, not inconsistent with law or with
these bylaws, as it may deem advisable concerning the issuance, transfer and
registration of certificates for shares of the capital stock of the corporation.
The Board of Directors may appoint a transfer agent or registrar of transfers,
or both, and may require all certificates for shares of the corporation to bear
the signature of either or both.


                                       18.
<PAGE>


                                  ARTICLE VIII

                         INSPECTION OF CORPORATE RECORDS

     Section 55.  INSPECTION BY DIRECTORS.  Every director shall have the
absolute right at any reasonable time to inspect and copy all books, records,
and documents of every kind of the corporation and any of its subsidiaries and
to inspect the physical properties of the corporation and any of its
subsidiaries.  Such inspection may be made by the director in person or by agent
or attorney, and the right of inspection includes the right to copy and make
extracts.

     Section 56.  INSPECTION BY SHAREHOLDERS.

             (a)  INSPECTION OF CORPORATE RECORDS.

                  (i)  A shareholder or shareholders holding at least five
percent in the aggregate of the outstanding voting shares of the corporation or
who hold at least one percent of such voting shares and have filed a Schedule
14B with the United States Securities and Exchange Commission relating to the
election of directors of the corporation shall have an absolute right to do
either or both of the following:

                         (A)  Inspect and copy the record of shareholders' names
and addresses and shareholdings during usual business hours upon five business
days' prior written demand upon the corporation; or

                         (B)  Obtain from the transfer agent, if any, for the
corporation, upon five business days' prior written demand and upon the tender
of its usual charges for such a list (the amount of which charges shall be
stated to the shareholder by the transfer agent upon request), a list of the
shareholders' names and addresses who are entitled to vote for the election of
directors and their shareholdings, as of the most recent record date for which
it has been compiled or as of a date specified by the shareholder subsequent to
the date of demand.

                  (ii)  The record of shareholders shall also be open to
inspection and copying by any shareholder or holder of a voting trust
certificate at any time during usual business hours upon written demand on the
corporation, for a purpose reasonably related to such holder's interest as a
shareholder or holder of a voting trust certificate.

                  (iii)  The accounting books and records and minutes of
proceedings of the shareholders and the Board of Directors and of any committees
of the Board of Directors of the corporation and of each of its subsidiaries
shall be open to inspection, copying and making extracts upon written demand on
the corporation of any shareholder or holder of a voting trust certificate at
any reasonable time during usual business hours, for a purpose reasonably
related to such holder's interests as a shareholder or as a holder of such
voting trust certificate.


                                       19.
<PAGE>


                  (iv)   Any inspection, copying, and making of extracts under
this subsection (a) may be done in person or by agent or attorney.

            (b)   INSPECTION OF BYLAWS.  The original or a copy of these bylaws
shall be kept as provided in Section 44 of these bylaws and shall be open to
inspection by the shareholders at all reasonable times during office hours.  If
the principal executive office of the corporation is not in California, and the
corporation has no principal business office in the state of California, a
current copy of these bylaws shall be furnished to any shareholder upon written
request.

     Section 57.  WRITTEN FORM.  If any record subject to inspection pursuant to
Section 56 above is not maintained in written form, a request for inspection is
not complied with unless and until the corporation at its expense makes such
record available in written form.


                                   ARTICLE IX

                                  MISCELLANEOUS

     Section 58.  FISCAL YEAR.  Unless otherwise fixed by resolution of the
Board of Directors, the fiscal year of the corporation shall end on the 31st day
of December in each calendar year.

     Section 59.    ANNUAL REPORT.

          (a) Subject to the provisions of Section 59(b) below, the Board of
Directors shall cause an annual report to be sent to each shareholder of the
corporation in the manner provided in Section 9 of these bylaws not later than
one hundred twenty (120) days after the close of the corporation's fiscal year.
Such report shall include a balance sheet as of the end of such fiscal year and
an income statement and statement of changes in financial position for such
fiscal year, accompanied by any report thereon of independent accountants or, if
there is no such report, the certificate of an authorized officer of the
corporation that such statements were prepared without audit from the books and
records of the corporation.  When there are more than 100 shareholders of record
of the corporation's shares, as determined by Section 605 of the California
Corporations Code, additional information as required by Section 1501(b) of the
California Corporations Code shall also be contained in such report, provided
that if the corporation has a class of securities registered under Section 12 of
the United States Securities Exchange Act of 1934, that Act shall take
precedence.  Such report shall be sent to shareholders at least fifteen (15)
days prior to the next annual meeting of shareholders after the end of the
fiscal year to which it relates.

          (b)  If and so long as there are fewer than 100 holders of record of
the corporation's shares, the requirement of sending of an annual report to the
shareholders of the corporation is hereby expressly waived.


                                       20.
<PAGE>


     Section 60.  RECORD DATE.  The Board of Directors may fix a time in the
future as a record date for the determination of the shareholders entitled to
notice of or to vote at any meeting or entitled to receive payment of any
dividend or other distribution or allotment of any rights or entitled to
exercise any rights in respect of any change, conversion or exchange of shares
or entitled to exercise any rights in respect of any other lawful action.  The
record date so fixed shall not be more than sixty (60) days nor less than ten
(10) days prior to the date of the meeting nor more than sixty (60) days prior
to any other action or event for the purpose of which it is fixed.  If no record
date is fixed, the provisions of Section 15 of these bylaws shall apply with
respect to notice of meetings, votes, and consents and the record date for
determining shareholders for any other purpose shall be at the close of business
on the day on which the Board of Directors adopts the resolutions relating
thereto, or the sixtieth (60th) day prior to the date of such other action or
event, whichever is later.

     Only shareholders of record at the close of business on the record date
shall be entitled to notice and to vote or to receive the dividend, distribution
or allotment of rights or to exercise the rights, as the case may be,
notwithstanding any transfer of any shares on the books of the corporation after
the record date, except as otherwise provided in the Articles of Incorporation,
by agreement or by law.

     Section 61.  BYLAW AMENDMENTS.  Except as otherwise provided by law or
Section 19 of these bylaws, these bylaws may be amended or repealed by the Board
of Directors or by the affirmative vote of a majority of the outstanding shares
entitled to vote, including, if applicable, the affirmative vote of a majority
of the outstanding shares of each class or series entitled by law or the
Articles of Incorporation to vote as a class or series on the amendment or
repeal or adoption of any bylaw or bylaws; provided, however, after issuance of
shares, a bylaw specifying or changing a fixed number of directors or the
maximum or minimum number or changing from a fixed to a variable board or vice
versa may only be adopted by approval of the outstanding shares as provided
herein.

     Section 62.  CONSTRUCTION AND DEFINITION.  Unless the context requires
otherwise, the general provisions, rules of construction, and definitions
contained in the California Corporations Code shall govern the construction of
these bylaws.

     Without limiting the foregoing, "shall" is mandatory and "may" is
permissive.


                                    ARTICLE X

                                 INDEMNIFICATION

     Section 63.  INDEMNIFICATION OF DIRECTORS, OFFICERS, EMPLOYEES AND OTHER
AGENTS.


                                       21.
<PAGE>


          (a)  DIRECTORS AND EXECUTIVE OFFICERS.  The corporation shall
indemnify its directors and executive officers to the fullest extent not
prohibited by the California General Corporation Law; PROVIDED, HOWEVER, that
the corporation may limit the extent of such indemnification by individual
contracts with its directors and executive officers; and, PROVIDED, FURTHER,
that the corporation shall not be required to indemnify any director or
executive officer in connection with any proceeding (or part thereof) initiated
by such person or any proceeding by such person against the corporation or its
directors, officers, employees or other agents unless (i) such indemnification
is expressly required to be made by law, (ii) the proceeding was authorized by
the board of directors of the corporation or (iii) such indemnification is
provided by the corporation, in its sole discretion, pursuant to the powers
vested in the corporation under the California General Corporation Law.

          (b)  OTHER OFFICERS, EMPLOYEES AND OTHER AGENTS.  The corporation
shall have the power to indemnify its other officers, employees and other agents
as set forth in the California General Corporation Law.

          (c)  DETERMINATION BY THE CORPORATION.  Promptly after receipt of a
request for indemnification hereunder (and in any event within ninety (90) days
thereof) a reasonable, good faith determination as to whether indemnification of
the director or executive officer is proper under the circumstances because such
director or executive officer has met the applicable standard of care shall be
made by:

               (1)  a majority vote of a quorum consisting of directors who are
not parties to such proceeding;

               (2)  if such quorum is not obtainable, by independent legal
counsel in a written opinion; or

               (3)  approval or ratification by the affirmative vote of a
majority of the shares of this corporation represented and voting at a duly held
meeting at which a quorum is present (which shares voting affirmatively also
constitute at least a majority of the required quorum) or by written consent of
a majority of the outstanding shares entitled to vote; where in each case the
shares owned by the person to be indemnified shall not be considered entitled to
vote thereon.

          (d)  GOOD FAITH.

               (1)  For purposes of any determination under this bylaw, a
director or executive officer shall be deemed to have acted in good faith and in
a manner he reasonably believed to be in the best interests of the corporation
and its shareholders, and, with respect to any criminal action or proceeding, to
have had no reasonable cause to believe that his conduct was unlawful, if his
action is based on information, opinions, reports and statements, including
financial statements and other financial data, in each case prepared or
presented by:


                                       22.
<PAGE>


                    (i)  one or more officers or employees of the corporation
whom the director or executive officer believed to be reliable and competent in
the matters presented;

                    (ii)  counsel, independent accountants or other persons as
to matters which the director or executive officer believed to be within such
person's professional competence; and

                    (iii)  with respect to a director, a committee of the Board
upon which such director does not serve, as to matters within such committee's
designated authority, which committee the director believes to merit confidence;
so long as, in each case, the director or executive officer acts without
knowledge that would cause such reliance to be unwarranted.

               (2)  The termination of any proceeding by judgment, order,
settlement, conviction or upon a plea of nolo contendere or its equivalent shall
not, of itself, create a presumption that the person did not act in good faith
and in a manner which he reasonably believed to be in the best interests of the
corporation and its shareholders or that he had reasonable cause to believe that
his conduct was unlawful.

               (3)  The provisions of this paragraph (d) shall not be deemed to
be exclusive or to limit in any way the circumstances in which a person may be
deemed to have met the applicable standard of conduct set forth by the
California General Corporation Law.

          (e)  EXPENSES.  The corporation shall advance, prior to the final
disposition of any proceeding, promptly following request therefor, all expenses
incurred by any director or executive officer in connection with such proceeding
upon receipt of an undertaking by or on behalf of such person to repay said
amounts if it shall be determined ultimately that such person is not entitled to
be indemnified under this bylaw or otherwise.

     Notwithstanding the foregoing, unless otherwise determined pursuant to
paragraph (f) of this bylaw, no advance shall be made by the corporation if a
determination is reasonably and promptly made by the board of directors by a
majority vote of a quorum consisting of directors who were not parties to the
proceeding (or, if no such quorum exists, by independent legal counsel in a
written opinion) that the facts known to the decision making party at the time
such determination is made demonstrate clearly and convincingly that such person
acted in bad faith or in a manner that such person did not believe to be in the
best interests of the corporation and its shareholders.

          (f)  ENFORCEMENT.  Without the necessity of entering into an express
contract, all rights to indemnification and advances to directors and executive
officers under this bylaw shall be deemed to be contractual rights and be
effective to the same extent and as if provided for in a contract between the
corporation and the director or executive officer.  Any right to indemnification
or advances granted by this bylaw to a director or executive officer shall be
enforceable by or on behalf of the person holding such right in the forum in
which the proceeding


                                       23.
<PAGE>


is or was pending or, if such forum is not available or a determination is made
that such forum is not convenient, in any court of competent jurisdiction if (i)
the claim for indemnification or advances is denied, in whole or in part, or
(ii) no disposition of such claim is made within ninety (90) days of request
therefor.  The claimant in such enforcement action, if successful in whole or in
part, shall be entitled to be paid also the expense of prosecuting his claim.
The corporation shall be entitled to raise as a defense to any such action that
the claimant has not met the standards of conduct that make it permissible under
the California General Corporation Law for the corporation to indemnify the
claimant for the amount claimed.  Neither the failure of the corporation
(including its board of directors, independent legal counsel or its
shareholders) to have made a determination prior to the commencement of such
action that indemnification of the claimant is proper in the circumstances
because he has met the applicable standard of conduct set forth in the
California General Corporation Law, nor an actual determination by the
corporation (including its board of directors, independent legal counsel or its
shareholders) that the claimant has not met such applicable standard of conduct,
shall be a defense to the action or create a presumption that claimant has not
met the applicable standard of conduct.

          (g)  NON-EXCLUSIVITY OF RIGHTS.  To the fullest extent permitted by
the corporation's Articles of Incorporation and the California General
Corporation Law, the rights conferred on any person by this bylaw shall not be
exclusive of any other right which such person may have or hereafter acquire
under any statute, provision of the Articles of Incorporation, bylaws,
agreement, vote of shareholders or disinterested directors or otherwise, both as
to action in his official capacity and as to action in another capacity while
holding office.  The corporation is specifically authorized to enter into
individual contracts with any or all of its directors, officers, employees or
agents respecting indemnification and advances, to the fullest extent permitted
by the California General Corporation Law and the corporation's Articles of
Incorporation.

          (h)  SURVIVAL OF RIGHTS.  The rights conferred on any person by this
bylaw shall continue as to a person who has ceased to be a director or executive
officer and shall inure to the benefit of the heirs, executors and
administrators of such a person.

          (i)  INSURANCE.   The corporation, upon approval by the board of
directors, may purchase insurance on behalf of any person required or permitted
to be indemnified pursuant to this bylaw.

          (j)  AMENDMENTS.  Any repeal or modification of this bylaw shall only
be prospective and shall not affect the rights under this bylaw in effect at the
time of the alleged occurrence of any action or omission to act that is the
cause of any proceeding against any agent of the corporation.

          (k)  EMPLOYEE BENEFIT PLANS.   The corporation shall indemnify the
directors and officers of the corporation who serve at the request of the
corporation as trustees, investment managers or other fiduciaries of employee
benefit plans to the fullest extent permitted by the California General
Corporation Law.


                                       24.
<PAGE>


          (l)  SAVING CLAUSE.  If this bylaw or any portion hereof shall be
invalidated on any ground by any court of competent jurisdiction, then the
corporation shall nevertheless indemnify each director and executive officer to
the fullest extent permitted by any applicable portion of this bylaw that shall
not have been invalidated, or by any other applicable law.

          (m)  CERTAIN DEFINITIONS.   For the purposes of this bylaw, the
following definitions shall apply:

               (1)  The term "proceeding" shall be broadly construed and shall
include, without limitation, the investigation, preparation, prosecution,
defense, settlement and appeal of any threatened, pending or completed action,
suit or proceeding, whether civil, criminal, administrative, arbitrative or
investigative.

               (2)  The term "expenses" shall be broadly construed and shall
include, without limitation, court costs, attorneys' fees, witness fees, fines,
amounts paid in settlement or judgment and any other costs and expenses of any
nature or kind incurred in connection with any proceeding, including expenses of
establishing a right to indemnification under this bylaw or any applicable law.

               (3)  The term the "corporation" shall include, in addition to
the resulting corporation, any constituent corporation (including any
constituent of a constituent) absorbed in a consolidation or merger which, if
its separate existence had continued, would have had power and authority to
indemnify its directors, officers, and employees or agents, so that any person
who is or was a director, officer, employee or agent of such constituent
corporation, or is or was serving at the request of such constituent corporation
as a director, officer, employee or agent of another corporation, partnership,
joint venture, trust or other enterprise, shall stand in the same position under
the provisions of this bylaw with respect to the resulting or surviving
corporation as he would have with respect to such constituent corporation if its
separate existence had continued.

               (4)  References to a "director," "officer," "employee," or
"agent" of the corporation shall include, without limitation, situations where
such person is serving at the request of the corporation as a director, officer,
employee, trustee or agent of another corporation, partnership, joint venture,
trust or other enterprise.


                                   ARTICLE XI

                             RIGHT OF FIRST REFUSAL

     Section 64.  RIGHT OF FIRST REFUSAL.  No shareholder shall sell, assign,
pledge, or in any manner transfer any of the shares of stock of the corporation
or any right or interest therein,


                                       25.
<PAGE>


whether voluntarily or by operation of law, or by gift or otherwise, except by a
transfer which meets the requirements hereinafter set forth in this bylaw:

          (a)  If the shareholder desires to sell or otherwise transfer any of
his shares of stock, then the shareholder shall first give written notice
thereof to the corporation.  The notice shall name the proposed transferee and
state the number of shares to be transferred, the proposed consideration, and
all other terms and conditions of the proposed transfer.

          (b)  For thirty (30) days following receipt of such notice, the
corporation shall have the option to purchase all (but not less than all) of the
shares specified in the notice at the price and upon the terms set forth in such
notice; provided, however, that, with the consent of the shareholder, the
corporation shall have the option to purchase a lesser portion of the shares
specified in said notice at the price and upon the terms set forth therein.  In
the event of a gift, property settlement or other transfer in which the proposed
transferee is not paying the full price for the shares, and that is not
otherwise exempted from the provisions of this Section 64, the price shall be
deemed to be the fair market value of the stock at such time as determined in
good faith by the Board of Directors.  In the event the corporation elects to
purchase all of the shares or, with consent of the shareholder, a lesser portion
of the shares, it shall give written notice to the transferring shareholder of
its election and settlement for said shares shall be made as provided below in
paragraph (d).

          (c)  The corporation may assign its rights hereunder.

          (d)  In the event the corporation and/or its assignee(s) elect to
acquire any of the shares of the transferring shareholder as specified in said
transferring shareholder's notice, the Secretary of the corporation shall so
notify the transferring shareholder and settlement thereof shall be made in cash
within thirty (30) days after the Secretary of the corporation receives said
transferring shareholder's notice; provided that if the terms of payment set
forth in said transferring shareholder's notice were other than cash against
delivery, the corporation and/or its assignee(s) shall pay for said shares on
the same terms and conditions set forth in said transferring shareholder's
notice.

          (e)  In the event the corporation and/or its assignees(s) do not elect
to acquire all of the shares specified in the transferring shareholder's notice,
said transferring shareholder may, within the sixty-day (60-day) period
following the expiration of the option rights granted to the corporation and/or
its assignees(s) herein, transfer the shares specified in said transferring
shareholder's notice which were not acquired by the corporation and/or its
assignees(s) as specified in said transferring shareholder's notice.  All shares
so sold by said transferring shareholder shall continue to be subject to the
provisions of this bylaw in the same manner as before said transfer.

          (f)  Anything to the contrary contained herein notwithstanding, the
following transactions shall be exempt from the provisions of this bylaw:


                                       26.
<PAGE>


               (1)  A shareholder's transfer of any or all shares held either
during such shareholder's lifetime or on death by will or intestacy to such
shareholder's immediate family or to any custodian or trustee for the account of
such shareholder or such shareholder's immediate family. "Immediate family" as
used herein shall mean spouse, lineal descendant, father, mother, brother,
sister, brother-in-law or sister-in-law of the shareholder making such transfer.

               (2)  A shareholder's bona fide pledge or mortgage of any shares
with a commercial lending institution, provided that any subsequent transfer of
said shares by said institution shall be conducted in the manner set forth in
this bylaw.

               (3)  A shareholder's transfer of any or all of such
shareholder's shares to the corporation or to any other shareholder of the
corporation.

               (4)  A shareholder's transfer of any or all of such
shareholder's shares to a person who, at the time of such transfer, is an
officer or director of the corporation.

               (5)  A corporate shareholder's transfer of any or all of its
shares pursuant to and in accordance with the terms of any merger,
consolidation, reclassification of shares or capital reorganization of the
corporate shareholder, or pursuant to a sale of all or substantially all of the
stock or assets of a corporate shareholder.

               (6)  A corporate shareholder's transfer of any or all of its
shares to any or all of its shareholders.

               (7)  A transfer by a shareholder which is a limited or general
partnership (i) to any or all of its partners or former partners or (ii) to any
or all of its affiliated limited or general partnerships, which partnerships are
in a substantially similar line of business.

          In any such case, the transferee, assignee, or other recipient shall
receive and hold such stock subject to the provisions of this bylaw, and there
shall be no further transfer of such stock except in accord with this bylaw.

          (g)  The provisions of this bylaw may be waived with respect to any
transfer either by the corporation, upon duly authorized action of its Board of
Directors, or by the shareholders, upon the express written consent of the
owners of a majority of the voting power of the corporation (excluding the votes
represented by those shares to be transferred by the transferring shareholder).
This bylaw may be amended or repealed either by a duly authorized action of the
Board of Directors or by the shareholders, upon the express written consent of
the owners of a majority of the voting power of the corporation.

          (h)  Any sale or transfer, or purported sale or transfer, of
securities of the corporation shall be null and void unless the terms,
conditions, and provisions of this bylaw are strictly observed and followed.


                                       27.
<PAGE>


          (i)  The foregoing right of first refusal shall terminate on either of
the following dates, whichever shall first occur:

               (1)  On April 15, 2002; or

               (2)  Upon the date securities of the corporation are first
offered to the public pursuant to a registration statement filed with, and
declared effective by, the United States Securities and Exchange Commission
under the Securities Act of 1933, as amended.

          (j)  The certificates representing shares of stock of the corporation
shall bear on their face the following legend so long as the foregoing right of
first refusal remains in effect:

          "The shares represented by this certificate are subject to a right of
     first refusal option in favor of the corporation and/or its assignee(s), as
     provided in the bylaws of the corporation."


                                   ARTICLE XII

                          LOANS OF OFFICERS AND OTHERS


     Section 65.   CERTAIN CORPORATE LOANS AND GUARANTIES.  If the corporation
has outstanding shares held of record by 100 or more persons on the date of
approval by the Board of Directors, the corporation may make loans of money or
property to, or guarantee the obligations of, any officer of the corporation or
its parent or any subsidiary, whether or not a director of the corporation or
its parent or any subsidiary, or adopt an employee benefit plan or plans
authorizing such loans or guaranties, upon the approval of the Board of
Directors alone, by a vote sufficient without counting the vote of any
interested director or directors, if the Board of Directors determines that such
a loan or guaranty or plan may reasonably be expected to benefit the
corporation.


                                       28.


<PAGE>

                                                                Warrant No. PW-1

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.



                                     AVIRON

                         WARRANT TO PURCHASE SHARES OF
                            SERIES A PREFERRED STOCK



     This certifies that MOUNT SINAI SCHOOL OF MEDICINE, ("MOUNT SINAI") for
value received, is entitled to purchase from AVIRON, a California corporation
(the "COMPANY"), having a principal place of business at 1815 Old County Road,
Belmont, California 94002, at any time after the Eligibility Date (as defined
below) and prior to the Termination Date (as defined below), twenty-five
thousand (25,000) fully paid and nonassessable shares of Series A Preferred
Stock (the "Series A Stock") of the Company at the Purchase Price (as defined
below), subject to the provisions and upon the terms and conditions hereinafter
set forth.

     1.   EXERCISABILITY.  Until terminated pursuant to Section 2 below, and
except as otherwise provided in Section 11(c) and Section 12, the purchase
rights represented by this Warrant are exercisable at the option of the holder
of record hereof, at any time or from time to time after the date of initiation
by the Company, its affiliate, licensee or other transferee of the first animal
study of a Product (as defined in that certain Technology Transfer Agreement
between the Company and Mount Sinai of even date herewith) (the "ELIGIBILITY
DATE"), for all or any part of the Series A Stock (but not for a fraction of a
share) which may be purchased hereunder.  The Company shall deliver to the
holder of this Warrant notice of the occurrence of any Eligibility Date within
ten (10) days of such occurrence.

     2.   TERMINATION.  Where the Eligibility Date has occurred, this Warrant,
and all rights to exercise this Warrant in whole or in part, shall immediately
terminate at the earlier of (a) 5:00 p.m. (Pacific Time), on the fifth (5th)
anniversary of the Eligibility Date, or (b) 5:00 p.m. (Pacific Time), on the day
preceding the closing of the Company's sale of all or substantially all of its
assets or the acquisition of the Company by another entity by means of a merger
or consolidation or sale of stock resulting in the exchange of more than fifty
percent (50%) of the outstanding shares of the Company for securities or
consideration issued, or caused to be issued,

                                       1.
<PAGE>

by the acquiring entity (a "SALE OF THE COMPANY") (such earlier date herein
referred to as the "TERMINATION DATE").  Where the Eligibility Date has not yet
occurred and the events described in (b) above transpire, this Warrant shall
terminate as provided above, except that the Eligibility Date shall be
accelerated as provided in Section 11(c).

     3.   PURCHASE PRICE.  Except as otherwise provided in Section 11(c) and
Section 12, this Warrant shall be exercisable, on or after the Eligibility Date,
at a price per share (the "PURCHASE PRICE") equal to (a) the price per share
(the "PREFERRED SHARE PRICE") at which the most recent series of preferred stock
of the Company (the "PREFERRED STOCK") was sold in the most recent offering of
such Preferred Stock to investors of the Company prior to the Eligibility Date
(it being understood that the sale or issuance of Preferred Stock pursuant to a
transaction with a corporate partner at a price above or below that most
recently paid for such Preferred Stock by the Company's investors shall not
constitute such an "offering"), and, if such Preferred Stock was not Series A
Stock, adjusted as provided below to reflect any difference in the terms of the
dividends payable and paid on or the conversion rights of such Preferred Stock
from the corresponding terms of the Series A Stock, or (b) if the common stock
of the Company (the "COMMON STOCK") is traded on the public market on the date
immediately prior to the Eligibility Date, the average of the closing prices of
the Common Stock reported in the consolidated reporting system for the sixty
(60) trading-day period ending on the trading day immediately prior to the
Eligibility Date or such other shorter period in the event the Eligibility Date
transpires prior to the Common Stock having been traded for such sixty (60)
trading-day period.

     If, as of the Eligibility Date, each share of Preferred Stock is
convertible into more or less than one share of Common Stock, or if any
dividends have been paid on the Preferred Stock in additional shares of
Preferred Stock or shares of Common Stock, then the Preferred Share Price shall
be adjusted by dividing the Preferred Share Price by the number of shares of
Common Stock into which each original share of Preferred Stock converts (after
giving effect to any stock dividends).  If, as of the Eligibility Date, the
dividend terms of the Preferred Stock differ from those of the Series A Stock,
the Preferred Share Price shall be adjusted as agreed upon by the Company and
the holder of this Warrant, or if they fail to agree, by an investment banker
mutually acceptable to the Company and the holder (the fees of the investment
banker to be shared by the Company and Mount Sinai; provided, however, that
Mount Sinai shall not be required to remit its portion of such fees to the
Company until the exercise of this Warrant).

     4.   RESERVATION OF PREFERRED STOCK.  The Company shall at all times
reserve and keep available out of its authorized but unissued shares of
Preferred Stock and Common Stock, solely for the purpose of effecting the
exercise of this Warrant, such number of its shares of Series A Stock (and
Common Stock upon conversion of the Series A Stock) as shall from time to time
be sufficient to effect the exercise of the Warrants and the conversion of the
Series A Stock to Common Stock.

     5.   NO SHAREHOLDER RIGHTS.  Except as expressly provided herein, nothing
contained in this Warrant shall be construed as conferring upon the holder
hereof or any other person the right to vote or to consent or to receive notice
as a stockholder in respect of meetings of

                                       2.
<PAGE>

stockholders for the election of directors of the Company or any other matter or
any rights whatsoever as a stockholder of the Company; and no dividends or
interest shall be payable or accrued in respect of this Warrant or the interest
represented hereby or the shares purchasable hereunder until, and only to the
extent that, this Warrant shall have been exercised.

     6.   METHOD OF EXERCISE; PAYMENT; ISSUANCE OF NEW WARRANT.  Subject to
Section 2 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part, by the surrender of this
Warrant (with a duly executed notice of exercise in the form attached hereto as
Exhibit A) at the principal office of the Company and by the payment to the
Company, by check or wire transfer, of an amount equal to the then applicable
Purchase Price per share multiplied by the number of shares then being
purchased.  In the event of any exercise of the rights represented by this
Warrant, certificates for the shares of stock so purchased shall be in the name
of, and delivered to, the holder hereof, or as such holder may direct (subject
to the restrictions upon transfer contained herein and upon payment by such
holder hereof of any applicable transfer taxes).  Such delivery shall be made
within ten (10) business days after exercise of the Warrant and at the Company's
expense and, unless this Warrant has been fully exercised or has expired, a new
Warrant representing the number of shares of Series A Stock, if any, with
respect to which this Warrant shall not then have been exercised shall also be
issued to the holder hereof within ten (10) business days after exercise of the
Warrant.

     7.   EXCHANGE OF WARRANT FOR OTHER WARRANTS.  This Warrant, with or without
similar Warrants, when surrendered properly endorsed at the principal offices of
the Company may be exchanged for another Warrant or Warrants of different
denominations, of like tenor and representing in the aggregate the right to
purchase a like number of shares of Series A Stock of the Company; provided,
however, that the Company's obligations under this Section 7 shall be subject to
and conditioned upon the compliance of any such subdivision with applicable
state securities laws and with the Securities Act of 1933, as amended (the
"ACT").

     8.   CERTAIN RESTRICTIONS.

          a.   RESTRICTIONS ON TRANSFERABILITY.  The Warrant and the Series A
Stock (or such other securities at the time receivable upon exercise of this
Warrant) shall not be transferable except upon the conditions specified in this
Section 8, which conditions are intended to insure compliance with the
provisions of the Act and to assist in an orderly distribution.  Each holder of
this Warrant or the Series A Stock issuable hereunder will cause any proposed
transferee of the Warrant or Series A Stock to agree to take and hold such
securities subject to the provisions and upon the conditions specified in this
Section 8.

          b.   RESTRICTIVE LEGENDS.  Each certificate representing (a) this
Warrant, (b) the Series A Stock and (c) any other securities issued in respect
of the Series A Stock upon any stock split, stock dividend, recapitalization,
merger, consolidation or similar event, shall (unless otherwise permitted by the
provisions of Section 8.c or Section 9 below or unless such securities have been
registered under the Act or sold under Rule 144) be stamped or otherwise
imprinted

                                       3.
<PAGE>

with legends substantially in the following form (in addition to any legend
required under applicable state securities laws):

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.  COPIES OF THE WARRANT DATED APRIL 23, 1993, WHICH
CONTAINS RESTRICTIONS APPLICABLE TO THESE SECURITIES, MAY BE OBTAINED AT NO COST
BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD OF THE CERTIFICATE TO THE
SECRETARY OF THE CORPORATION.

THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST
REFUSAL OPTION IN FAVOR OF THE CORPORATION AND/OR ITS ASSIGNEE(S), AS PROVIDED
IN THE BYLAWS OF THE CORPORATION.

     In addition, the certificates shall bear all legends required pursuant to
state securities and blue sky laws.


          c.   RESTRICTIONS ON TRANSFER.  The holder of this Warrant and each
person to whom this Warrant is subsequently transferred represents and warrants
to the Company (by acceptance of such transfer) that it will not transfer the
Warrant (or securities issuable upon exercise hereof unless a registration
statement under the Act was in effect with respect to such securities at the
time of issuance thereof) except pursuant to (a) an effective registration
statement under the Act, (b) Rule 144 under the Act (or any other rule under the
Act relating to the disposition of securities), or (c) an opinion of counsel,
reasonably satisfactory to counsel for the Company, that an exemption from such
registration is available.

     9.   WARRANTS TRANSFERABLE.  Subject to the provisions of Section 8, this
Warrant and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes), upon surrender of this
Warrant properly endorsed; PROVIDED, HOWEVER, that the Company's Bylaws provide
for a right of first refusal in favor of the Company with respect to all sales,
assignments, pledges or transfers of shares of stock of the Company or any
interest therein.  The Company agrees, however, that transfers of this Warrant
to any person or entity listed on Schedule 1 (the "Permitted Transferees")
hereto shall not be subject to such right of first refusal and hereby waives any
such rights with respect thereto, provided that any subsequent transfer by any
of the Permitted Transferees shall nonetheless be subject to such right of first
refusal.  Each permitted taker and holder of this Warrant, by taking or holding
the same, consents and agrees that this Warrant, when endorsed in blank, shall
be deemed negotiable, and that the holder hereof, when this Warrant shall have
been so endorsed, may be treated by the Company and all other persons dealing
with this Warrant as the absolute owner hereof for any purpose and as the person
entitled to exercise the rights represented by this Warrant, or to the transfer
hereof on the books of the Company any notice to the contrary notwithstanding;
but until

                                       4.
<PAGE>

such transfer on such books, the Company may treat the registered owner hereof
as the owner for all purposes.

     10.  RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, contained in
Sections 8 and 9 shall survive the exercise of this Warrant.

     11.  ADJUSTMENT FOR CHANGES IN SERIES A STOCK.  The Purchase Price and the
number of shares purchasable upon the exercise of this Warrant, as well as the
date of exercisability of this Warrant, shall be subject to adjustment from time
to time upon the occurrence of certain events described in this Section 11.
Upon each adjustment of the Purchase Price, the holder of this Warrant shall
thereafter be entitled to purchase, at the Purchase Price resulting from such
adjustment, the number of shares obtained by multiplying the Purchase Price in
effect immediately prior to such adjustment by the number of shares purchasable
pursuant hereto immediately prior to such adjustment, and dividing the product
thereof by the Purchase Price resulting from such adjustment.

          a.   SUBDIVISION OR COMBINATION OF STOCK.  Should the Company at any
time subdivide its outstanding shares of Series A Stock into a greater number of
shares, the Purchase Price then in effect immediately prior to such subdivision
shall be proportionately reduced, and conversely, in case the outstanding shares
of Series A Stock shall be combined into a smaller number of shares, the
Purchase Price then in effect immediately prior to such combination shall be
proportionately increased.

          b.   DIVIDENDS IN SERIES A STOCK, OTHER STOCK, PROPERTY,
RECLASSIFICATION.  If at any time or from time to time the holders of Series A
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

               i.   Series A Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Series A Stock, or any rights or options to subscribe for, purchase or
otherwise acquire any of the foregoing by way of dividend or other distribution,

               ii.  Series A Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than shares of
Series A Stock issued as a stock split, adjustments in respect of which shall be
covered by the terms of Section 11(a) above),

then and in each such case, the holder hereof shall, upon the exercise of this
Warrant, be entitled to receive, in addition to the number of shares of Series A
Stock receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (i) and (ii) above) which such

                                       5.
<PAGE>

holder would hold on the date of such exercise had he been the holder of record
of such Series A Stock as of the date on which holders of Series A Stock
received or became entitled to receive such shares or all other additional stock
and other securities and property.

          c.   ACCELERATION OF EXERCISABILITY UPON SALE OF THE COMPANY.  If,
prior to the Eligibility Date, any Sale of the Company shall be effected, then
notwithstanding Section 1, the exercisability of this Warrant shall be
accelerated to a date ten (10) days prior to the closing of such Sale of the
Company (the "MERGER ELIGIBILITY DATE"), and thereupon shall become exercisable
with respect to the total number of shares purchasable hereunder, at a price
equal to the lesser of (i) the Purchase Price, or (ii) One and One-half Dollars
($1.50) per share.  The Company shall provide notice of the occurrence of such
Merger Eligibility Date pursuant to Section 14.

     12.  EVENTS UPON AN IPO.

          a.   If prior to the Eligibility Date the Company shall effect its
first public offering of any equity securities of the Company (an "IPO")
pursuant to a registration statement filed with, and declared effective by, the
Securities and Exchange Commission pursuant to the Act, then notwithstanding
Section 1, the exercisability of this Warrant shall be accelerated to the date
of the closing of such IPO (the "IPO ELIGIBILITY DATE"), and this Warrant shall
be exercisable with respect to the same amount of shares, and in the same
manner, as is set forth in subsection 11(c) above with respect to a Sale of the
Company, EXCEPT that the Warrant shall be exercisable at a purchase price equal
to one hundred twenty-five percent (125%) of the price at which the Common Stock
of the Company is to be sold in such IPO.  The Company shall provide notice of
the occurrence of such IPO Eligibility Date pursuant to Section 14.  Such
accelerated Warrant, and all rights to exercise such Warrant in whole or in
part, shall immediately terminate at 5:00 p.m. (Pacific Time), on the fifth
(5th) anniversary of the IPO Eligibility Date.  Any occurrence of the product
milestone event (i.e., the Eligibility Date) set forth in Section 1 following
such IPO shall have no effect upon such an accelerated Warrant.

          b.   If subsequent to the Eligibility Date the Company shall effect an
IPO, then this Warrant shall continue in full force and effect, and the holder
hereof shall have the right to purchase and receive upon the exercise of this
Warrant such shares of Series A Stock or Common Stock (assuming conversion of
the Series A Stock prior to such IPO) as is set forth in Section 1, at the
Purchase Price set forth in Section 3.

     13.  FRACTIONAL SHARES.  No fractional share shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share,
pay the holder entitled to such fraction a sum in cash equal to the fair market
value of such fraction on the date of exercise (as determined in good faith by
the Board of Directors of the Company).

     14.  NOTICE OF CERTAIN ACTIONS.  In the event of any reclassification or
recapitalization of the capital stock of the Company, any Sale of the Company,
any IPO, or any voluntary or involuntary dissolution, liquidation, or winding up
of the Company, the Company shall mail to

                                       6.
<PAGE>


the holder of this Warrant at least fifteen (15) days prior to the record date
specified therein, a notice specifying (a) the date on which any such record is
to be taken for the purpose of such dividend or distribution and a description
of such dividend or distribution, (b) the date on which any such
reclassification, recapitalization, Sale of the Company, IPO, dissolution,
liquidation, or winding up is expected to become effective, and (c) the time, if
any, that is to be fixed, as to when the holders of record of Common Stock (or
other securities) shall be entitled to exchange their shares of Common Stock (or
other securities) for securities or other property deliverable upon such
reclassification, recapitalization, Sale of the Company, IPO, dissolution,
liquidation, or winding up; provided, however, that the Company shall not be
required to provide any notice under this Section 14 unless and until the
occurrence of the Eligibility Date, except where required pursuant to Section
11(c) and Section 12.

     15.  MISCELLANEOUS.  This Warrant shall be governed by the laws of the
State of California, as applied to contracts entered into between California
residents and to be performed entirely within the State of California.  The
headings in this Warrant are for purposes of convenience and reference only, and
shall not be deemed to constitute a part hereof.  Neither this Warrant nor any
term hereof may be changed, waived, discharged or terminated orally but only by
an instrument in writing signed by the Company and the registered holder hereof.
All notices and other communications from the Company to the holder of this
Warrant shall be made by personal delivery (including confirmed telex or
telecopy) or shall be mailed by first-class registered or certified mail,
postage prepaid, to the address furnished to the Company in writing by the last
holder of this Warrant who shall have furnished an address to the Company in
writing.

     IN WITNESS WHEREOF the Company has caused this Warrant to be duly executed
by its officers thereunto duly authorized this 23rd day of April, 1993.


                              AVIRON



                              By
                                  -----------------------------
                                   J. Leighton Read, M.D.
                                   Chief Executive Officer





                                       7.
<PAGE>
                                    EXHIBIT A


                              FORM OF SUBSCRIPTION


                  (To be signed only upon exercise of Warrant)


To AVIRON:


     The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise the purchase right represented by such Warrant for, and to
purchase thereunder, __________________ _____________________ (___________)
shares of Series A Preferred Stock of AVIRON and herewith makes payment of ___
_______ _______________ DOLLARS ($__________) therefor, and requests the
certificates for such shares be issued in the name of, and delivered _________
to, whose address is__________________________________________________________.

     The undersigned represents that it is acquiring such Series A Preferred
Stock for its own account for investment and not with a view to or for sale in
connection with any distribution thereof.

     DATED:    __________________


                                   By:
                                       -----------------------------------------
                                   Title:
                                          --------------------------------------
                                   Address:
                                            ------------------------------------

                                   ---------------------------------------------



                                       1.
<PAGE>
                                   SCHEDULE 1

                              PERMITTED TRANSFEREES

                             Masayoshi Enami, Ph.D.
                             Reinhard Vlasak, Ph.D.
                              Thomas Muster, Ph.D.
                              Jeffrey Parvin, Ph.D.
                               Mark Krystal, Ph.D.
                             Michael Bergmann, M.D.



                                       2.

<PAGE>

                                                                Warrant No. PW-3

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.



                                     AVIRON

                         WARRANT TO PURCHASE SHARES OF
                            SERIES A PREFERRED STOCK



     This certifies that MOUNT SINAI SCHOOL OF MEDICINE, ("MOUNT SINAI") for
value received, is entitled to purchase from AVIRON, a California corporation
(the "COMPANY"), having a principal place of business at 1815 Old County Road,
Belmont, California 94002, at any time after the Eligibility Date (as defined
below) and prior to the Termination Date (as defined below), one hundred twenty-
five thousand (125,000) fully paid and nonassessable shares of Series A
Preferred Stock (the "SERIES A STOCK") of the Company at the Purchase Price (as
defined below), subject to the provisions and upon the terms and conditions
hereinafter set forth.

     1.   EXERCISABILITY.  Until terminated pursuant to Section 2 below, and
except as otherwise provided in Section 11(c) and Section 12, the purchase
rights represented by this Warrant are exercisable at the option of the holder
of record hereof, at any time or from time to time after the date of receipt by
the Company of written approval by the United States Food and Drug Adminstration
with respect to the Company's, its affiliate's, licensee's or other transferee's
first New Drug Application with respect to a Product (as defined in that certain
Technology Transfer Agreement between the Company and Mount Sinai of even date
herewith) (the "ELIGIBILITY DATE"), for all or any part of the Series A Stock
(but not for a fraction of a share) which may be purchased hereunder.  The
Company shall deliver to the holder of this Warrant notice of the occurrence of
any Eligibility Date within ten (10) days of such occurrence.

     2.   TERMINATION.  Where the Eligibility Date has occurred, this Warrant,
and all rights to exercise this Warrant in whole or in part, shall immediately
terminate at the earlier of (a) 5:00 p.m. (Pacific Time), on the fifth (5th)
anniversary of the Eligibility Date, or (b) 5:00 p.m. (Pacific Time), on the day
preceding the closing of the Company's sale of all or substantially all of its
assets or the acquisition of the Company by another entity by means of a merger
or

                                       1.
<PAGE>

consolidation or sale of stock resulting in the exchange of more than fifty
percent (50%) of the outstanding shares of the Company for securities or
consideration issued, or caused to be issued, by the acquiring entity (a "SALE
OF THE COMPANY") (such earlier date herein referred to as the "TERMINATION
DATE").  Where the Eligibility Date has not yet occurred and the events
described in (b) above transpire, this Warrant shall terminate as provided
above, except that the Eligibility Date shall be accelerated as provided in
Section 11(c).

     3.   PURCHASE PRICE.  Except as otherwise provided in Section 11(c) and
Section 12, this Warrant shall be exercisable, on or after the Eligibility Date,
at a price per share (the "PURCHASE PRICE") equal to (a) the price per share
(the "PREFERRED SHARE PRICE") at which the most recent series of preferred stock
of the Company (the "PREFERRED STOCK") was sold in the most recent offering of
such Preferred Stock to investors of the Company prior to the Eligibility Date
(it being understood that the sale or issuance of Preferred Stock pursuant to a
transaction with a corporate partner at a price above or below that most
recently paid for such Preferred Stock by the Company's investors shall not
constitute such an "offering"), and, if such Preferred Stock was not Series A
Stock, adjusted as provided below to reflect any difference in the terms of the
dividends payable and paid on or the conversion rights of such Preferred Stock
from the corresponding terms of the Series A Stock, or (b) if the common stock
of the Company (the "COMMON STOCK") is traded on the public market on the date
immediately prior to the Eligibility Date, the average of the closing prices of
the Common Stock reported in the consolidated reporting system for the sixty
(60) trading-day period ending on the trading day immediately prior to the
Eligibility Date or such other shorter period in the event the Eligibility Date
transpires prior to the Common Stock having been traded for such sixty (60)
trading-day period.

     If, as of the Eligibility Date, each share of Preferred Stock is
convertible into more or less than one share of Common Stock, or if any
dividends have been paid on the Preferred Stock in additional shares of
Preferred Stock or shares of Common Stock, then the Preferred Share Price shall
be adjusted by dividing the Preferred Share Price by the number of shares of
Common Stock into which each original share of Preferred Stock converts (after
giving effect to any stock dividends).  If, as of the Eligibility Date, the
dividend terms of the Preferred Stock differ from those of the Series A Stock,
the Preferred Share Price shall be adjusted as agreed upon by the Company and
the holder of this Warrant, or if they fail to agree, by an investment banker
mutually acceptable to the Company and the holder (the fees of the investment
banker to be shared by the Company and Mount Sinai; provided, however, that
Mount Sinai shall not be required to remit its portion of such fees to the
Company until the exercise of this Warrant).

     4.   RESERVATION OF PREFERRED STOCK.  The Company shall at all times
reserve and keep available out of its authorized but unissued shares of
Preferred Stock and Common Stock, solely for the purpose of effecting the
exercise of this Warrant, such number of its shares of Series A Stock (and
Common Stock upon conversion of the Series A Stock) as shall from time to time
be sufficient to effect the exercise of the Warrants and the conversion of the
Series A Stock to Common Stock.

                                       2.
<PAGE>


     5.   NO SHAREHOLDER RIGHTS.  Except as expressly provided herein, nothing
contained in this Warrant shall be construed as conferring upon the holder
hereof or any other person the right to vote or to consent or to receive notice
as a stockholder in respect of meetings of stockholders for the election of
directors of the Company or any other matter or any rights whatsoever as a
stockholder of the Company; and no dividends or interest shall be payable or
accrued in respect of this Warrant or the interest represented hereby or the
shares purchasable hereunder until, and only to the extent that, this Warrant
shall have been exercised.

     6.   METHOD OF EXERCISE; PAYMENT; ISSUANCE OF NEW WARRANT.  Subject to
Section 2 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part, by the surrender of this
Warrant (with a duly executed notice of exercise in the form attached hereto as
Exhibit A) at the principal office of the Company and by the payment to the
Company, by check or wire transfer, of an amount equal to the then applicable
Purchase Price per share multiplied by the number of shares then being
purchased.  In the event of any exercise of the rights represented by this
Warrant, certificates for the shares of stock so purchased shall be in the name
of, and delivered to, the holder hereof, or as such holder may direct (subject
to the restrictions upon transfer contained herein and upon payment by such
holder hereof of any applicable transfer taxes).  Such delivery shall be made
within ten (10) business days after exercise of the Warrant and at the Company's
expense and, unless this Warrant has been fully exercised or has expired, a new
Warrant representing the number of shares of Series A Stock, if any, with
respect to which this Warrant shall not then have been exercised shall also be
issued to the holder hereof within ten (10) business days after exercise of the
Warrant.

     7.   EXCHANGE OF WARRANT FOR OTHER WARRANTS.  This Warrant, with or without
similar Warrants, when surrendered properly endorsed at the principal offices of
the Company may be exchanged for another Warrant or Warrants of different
denominations, of like tenor and representing in the aggregate the right to
purchase a like number of shares of Series A Stock of the Company; provided,
however, that the Company's obligations under this Section 7 shall be subject to
and conditioned upon the compliance of any such subdivision with applicable
state securities laws and with the Securities Act of 1933, as amended (the
"ACT").

     8.   CERTAIN RESTRICTIONS.

          a.   RESTRICTIONS ON TRANSFERABILITY.  The Warrant and the Series A
Stock (or such other securities at the time receivable upon exercise of this
Warrant) shall not be transferable except upon the conditions specified in this
Section 8, which conditions are intended to insure compliance with the
provisions of the Act and to assist in an orderly distribution.  Each holder of
this Warrant or the Series A Stock issuable hereunder will cause any proposed
transferee of the Warrant or Series A Stock to agree to take and hold such
securities subject to the provisions and upon the conditions specified in this
Section 8.

          b.   RESTRICTIVE LEGENDS.  Each certificate representing (a) this
Warrant, (b) the Series A Stock and (c) any other securities issued in respect
of the Series A Stock upon any stock

                                       3.
<PAGE>

split, stock dividend, recapitalization, merger, consolidation or similar event,
shall (unless otherwise permitted by the provisions of Section 8.c or Section 9
below or unless such securities have been registered under the Act or sold under
Rule 144) be stamped or otherwise imprinted with legends substantially in the
following form (in addition to any legend required under applicable state
securities laws):

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.  COPIES OF THE WARRANT DATED APRIL 23, 1993 WHICH
CONTAINS RESTRICTIONS APPLICABLE TO THESE SECURITIES, MAY BE OBTAINED AT NO COST
BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD OF THE CERTIFICATE TO THE
SECRETARY OF THE CORPORATION.

THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST
REFUSAL OPTION IN FAVOR OF THE CORPORATION AND/OR ITS ASSIGNEE(S), AS PROVIDED
IN THE BYLAWS OF THE CORPORATION.

     In addition, the certificates shall bear all legends required pursuant to
state securities and blue sky laws.

          c.   RESTRICTIONS ON TRANSFER.  The holder of this Warrant and each
person to whom this Warrant is subsequently transferred represents and warrants
to the Company (by acceptance of such transfer) that it will not transfer the
Warrant (or securities issuable upon exercise hereof unless a registration
statement under the Act was in effect with respect to such securities at the
time of issuance thereof) except pursuant to (a) an effective registration
statement under the Act, (b) Rule 144 under the Act (or any other rule under the
Act relating to the disposition of securities), or (c) an opinion of counsel,
reasonably satisfactory to counsel for the Company, that an exemption from such
registration is available.

     9.   WARRANTS TRANSFERABLE.  Subject to the provisions of Section 8, this
Warrant and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes), upon surrender of this
Warrant properly endorsed; PROVIDED, HOWEVER, that the Company's Bylaws provide
for a right of first refusal in favor of the Company with respect to all sales,
assignments, pledges or transfers of shares of stock of the Company or any
interest therein.  The Company agrees, however, that transfers of this Warrant
to any person or entity listed on Schedule 1 (the "Permitted Transferees")
hereto shall not be subject to such right of first refusal and hereby waives any
such rights with respect thereto, provided that any subsequent transfer by any
of the Permitted Transferees shall nonetheless be subject to such right of first
refusal.  Each permitted taker and holder of this Warrant, by taking or holding
the same, consents and agrees that this Warrant, when endorsed in blank, shall
be deemed negotiable, and

                                       4.
<PAGE>

that the holder hereof, when this Warrant shall have been so endorsed, may be
treated by the Company and all other persons dealing with this Warrant as the
absolute owner hereof for any purpose and as the person entitled to exercise the
rights represented by this Warrant, or to the transfer hereof on the books of
the Company any notice to the contrary notwithstanding; but until such transfer
on such books, the Company may treat the registered owner hereof as the owner
for all purposes.

     10.  RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, contained in
Sections 8 and 9 shall survive the exercise of this Warrant.

     11.  ADJUSTMENT FOR CHANGES IN SERIES A STOCK.  The Purchase Price and the
number of shares purchasable upon the exercise of this Warrant, as well as the
date of exercisability of this Warrant, shall be subject to adjustment from time
to time upon the occurrence of certain events described in this Section 11.
Upon each adjustment of the Purchase Price, the holder of this Warrant shall
thereafter be entitled to purchase, at the Purchase Price resulting from such
adjustment, the number of shares obtained by multiplying the Purchase Price in
effect immediately prior to such adjustment by the number of shares purchasable
pursuant hereto immediately prior to such adjustment, and dividing the product
thereof by the Purchase Price resulting from such adjustment.

          a.   SUBDIVISION OR COMBINATION OF STOCK.  Should the Company at any
time subdivide its outstanding shares of Series A Stock into a greater number of
shares, the Purchase Price then in effect immediately prior to such subdivision
shall be proportionately reduced, and conversely, in case the outstanding shares
of Series A Stock shall be combined into a smaller number of shares, the
Purchase Price then in effect immediately prior to such combination shall be
proportionately increased.

          b.   DIVIDENDS IN SERIES A STOCK, OTHER STOCK, PROPERTY,
RECLASSIFICATION.  If at any time or from time to time the holders of Series A
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

               i.   Series A Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Series A Stock, or any rights or options to subscribe for, purchase or
otherwise acquire any of the foregoing by way of dividend or other distribution,

               ii.  Series A Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than shares of
Series A Stock issued as a stock split, adjustments in respect of which shall be
covered by the terms of Section 11(a) above),


                                       5.
<PAGE>

then and in each such case, the holder hereof shall, upon the exercise of this
Warrant, be entitled to receive, in addition to the number of shares of Series A
Stock receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (i) and (ii) above) which such holder would
hold on the date of such exercise had he been the holder of record of such
Series A Stock as of the date on which holders of Series A Stock received or
became entitled to receive such shares or all other additional stock and other
securities and property.

          c.   ACCELERATION OF EXERCISABILITY UPON SALE OF THE COMPANY.  If,
prior to the Eligibility Date, any Sale of the Company shall be effected, then
notwithstanding Section 1, the exercisability of this Warrant shall be
accelerated to a date ten (10) days prior to the closing of such Sale of the
Company (the "MERGER ELIGIBILITY DATE"), and thereupon shall become exercisable
with respect to (i) fifty percent percent (50%) of the shares purchasable
hereunder where the Company, its affiliate, licensee or other transferee has not
yet initiated the first animal study of a Product prior to the date of such
accelerated exercise, or (ii) seventy-five percent (75%) where the Company, its
affiliate, licensee or other transferee has initiated the first animal study of
a Product prior to the date of such accelerated exercise, or (iii) eighty
percent (80%) where the Company, its affiliate, licensee or other transferee has
received written acceptance by the United States Food and Drug Administration of
the Company's, its affiliate's, licensee's or other transferee's first
Investigational New Drug application with respect to a Product prior to the date
of such accelerated exercise.  In each such case the Warrant shall be
exercisable at a price equal to the lesser of (iv) the Purchase Price, or (v)
Four and One-half Dollars ($4.50) per share.  The Company shall provide notice
of such Merger Eligibility Date pursuant to Section 14.  This Warrant shall be
cancelled with respect to that percentage of shares as to which exercisability
is not accelerated under this Section 11(c).

     12.  EVENTS UPON AN IPO.

          a.   If prior to the Eligibility Date the Company shall effect its
first public offering of any equity securities of the Company (an "IPO")
pursuant to a registration statement filed with, and declared effective by, the
Securities and Exchange Commission pursuant to the Act, then notwithstanding
Section 1, the exercisability of this Warrant shall be accelerated to the date
of the closing of such IPO (the "IPO ELIGIBILITY DATE"), and this Warrant shall
be exercisable with respect to the same amount of shares, and in the same
manner, as is set forth in subsection 11(c) above with respect to a Sale of the
Company, EXCEPT that the Warrant shall be exercisable at a purchase price equal
to one hundred twenty-five percent (125%) of the price at which the Common Stock
of the Company is to be sold in such IPO.  The Company shall provide notice of
the occurrence of such IPO Eligibility Date pursuant to Section 14.  Such
accelerated Warrant, and all rights to exercise such Warrant in whole or in
part, shall immediately terminate at 5:00 p.m. (Pacific Time), on the fifth
(5th) anniversary of the IPO Eligibility Date.  Any occurrence of the product
milestone event (i.e., the Eligibility Date) set forth in Section 1 following
such IPO shall have no effect upon such an accelerated Warrant.


                                       6.
<PAGE>

          b.   If subsequent to the Eligibility Date the Company shall effect an
IPO, then this Warrant shall continue in full force and effect, and the holder
hereof shall have the right to purchase and receive upon the exercise of this
Warrant such shares of Series A Stock or Common Stock (assuming conversion of
the Series A Stock prior to such IPO) as is set forth in Section 1, at the
Purchase Price set forth in Section 3.

     13.  FRACTIONAL SHARES.  No fractional share shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share,
pay the holder entitled to such fraction a sum in cash equal to the fair market
value of such fraction on the date of exercise (as determined in good faith by
the Board of Directors of the Company).

     14.  NOTICE OF CERTAIN ACTIONS.  In the event of any reclassification or
recapitalization of the capital stock of the Company, any Sale of the Company,
any IPO, or any voluntary or involuntary dissolution, liquidation, or winding up
of the Company, the Company shall mail to the holder of this Warrant at least
fifteen (15) days prior to the record date specified therein, a notice
specifying (a) the date on which any such record is to be taken for the purpose
of such dividend or distribution and a description of such dividend or
distribution, (b) the date on which any such reclassification, recapitalization,
Sale of the Company, IPO, dissolution, liquidation, or winding up is expected to
become effective, and (c) the time, if any, that is to be fixed, as to when the
holders of record of Common Stock (or other securities) shall be entitled to
exchange their shares of Common Stock (or other securities) for securities or
other property deliverable upon such reclassification, recapitalization, Sale of
the Company, IPO, dissolution, liquidation, or winding up; provided, however,
that the Company shall not be required to provide any notice under this Section
14 unless and until the occurrence of the Eligibility Date, except where
required pursuant to Section 11(c) and Section 12.

     15.  MISCELLANEOUS.  This Warrant shall be governed by the laws of the
State of California, as applied to contracts entered into between California
residents and to be performed entirely within the State of California.  The
headings in this Warrant are for purposes of convenience and reference only, and
shall not be deemed to constitute a part hereof.  Neither this Warrant nor any
term hereof may be changed, waived, discharged or terminated orally but only by
an instrument in writing signed by the Company and the registered holder hereof.
All notices and other communications from the Company to the holder of this
Warrant shall be made by personal delivery (including confirmed telex or
telecopy) or shall be mailed by first-class registered or certified mail,
postage prepaid, to the address furnished to the Company in writing by the last
holder of this Warrant who shall have furnished an address to the Company in
writing.

     IN WITNESS WHEREOF the Company has caused this Warrant to be duly executed
by its officers thereunto duly authorized this 23rd day of April, 1993.


                              AVIRON

                                       7.
<PAGE>


                              By
                                  -----------------------------
                                   J. Leighton Read, M.D.
                                   Chief Executive Officer


                                       8.
<PAGE>
                                    EXHIBIT A


                              FORM OF SUBSCRIPTION


                  (To be signed only upon exercise of Warrant)


To AVIRON:


     The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise the purchase right represented by such Warrant for, and to
purchase thereunder, __________________ _____________________ (___________)
shares of Series A Preferred Stock of AVIRON and herewith makes payment of ____
_______ _______________ DOLLARS ($__________) therefor, and requests the
certificates for such shares be issued in the name of, and delivered __________
to, whose address is _________________________________________________________.

     The undersigned represents that it is acquiring such Series A Preferred
Stock for its own account for investment and not with a view to or for sale in
connection with any distribution thereof.

     DATED:
               ------------------

                                   By:
                                       -----------------------------------------
                                   Title:
                                          -------------------------------------
                                   Address:
                                           -------------------------------------

                                   ---------------------------------------------


                                       1.
<PAGE>
                                   SCHEDULE 1

                              PERMITTED TRANSFEREES

                             Masayoshi Enami, Ph.D.
                             Reinhard Vlasak, Ph.D.
                              Thomas Muster, Ph.D.
                              Jeffrey Parvin, Ph.D.
                               Mark Krystal, Ph.D.
                             Michael Bergmann, M.D.



                                       2.
<PAGE>




                                       1.

<PAGE>


                                                               Warrant No. PW-2B

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.



                                        AVIRON

                            WARRANT TO PURCHASE SHARES OF
                               SERIES A PREFERRED STOCK



    This certifies that MOUNT SINAI SCHOOL OF MEDICINE, ("MOUNT SINAI") for
value received, is entitled to purchase from AVIRON, a California corporation
(the "COMPANY"), having a principal place of business at 297 North Bernardo
Avenue, Mountain View, California 94043, at any time after the Eligibility Date
(as defined below) and prior to the Termination Date (as defined below), fifty-
five thousand 55,000 shares fully paid and nonassessable shares of Series A
Preferred Stock (the "SERIES A STOCK") of the Company at the Purchase Price (as
defined below), subject to the provisions and upon the terms and conditions
hereinafter set forth.


1.  EXERCISABILITY.  Until terminated pursuant to Section 2 below, and except
as otherwise provided in Section 11(c) and Section 12, the purchase rights
represented by this Warrant are exercisable at the option of the holder of
record hereof, at any time or from time to time after the date of receipt by the
Company of written acceptance by the United States Food and Drug Administration
of the Company's, its affiliate's, licensee's or other transferee's first
Investigational New Drug application with respect to a Product (as defined in
that certain Technology Transfer Agreement between the Company and Mount Sinai
dated February 9, 1993) (the "ELIGIBILITY DATE"), for all or any part of the
Series A Stock (but not for a fraction of a share) which may be purchased
hereunder.  The Company shall deliver to the holder of this Warrant notice of
the occurrence of any Eligibility Date within ten (10) days of such occurrence.

    2.   TERMINATION.  Where the Eligibility Date has occurred, this Warrant,
and all rights to exercise this Warrant in whole or in part, shall immediately
terminate at the earlier of (a) 5:00 p.m. (Pacific Time), on the fifth (5th)
anniversary of the Eligibility Date, or (b) 5:00 p.m. (Pacific Time), on the day
preceding the closing of the Company's sale of all or substantially all of its
assets or the acquisition of the Company by another entity by means of a merger
or consolidation or sale of stock resulting in the exchange of more than fifty
percent (50%) of the


                                          1.

<PAGE>

outstanding shares of the Company for securities or consideration issued, or
caused to be issued, by the acquiring entity (a "SALE OF THE COMPANY") (such
earlier date herein referred to as the "TERMINATION DATE").  Where the
Eligibility Date has not yet occurred and the events described in (b) above
transpire, this Warrant shall terminate as provided above, except that the
Eligibility Date shall be accelerated as provided in Section 11(c).

    3.   PURCHASE PRICE.  Except as otherwise provided in Section 11(c) and
Section 12, this Warrant shall be exercisable, on or after the Eligibility Date,
at a price per share (the "PURCHASE PRICE") equal to (a) the price per share
(the "PREFERRED SHARE PRICE") at which the most recent series of preferred stock
of the Company (the "PREFERRED STOCK") was sold in the most recent offering of
such Preferred Stock to investors of the Company prior to the Eligibility Date
(it being understood that the sale or issuance of Preferred Stock pursuant to a
transaction with a corporate partner at a price above or below that most
recently paid for such Preferred Stock by the Company's investors shall not
constitute such an "offering"), and, if such Preferred Stock was not Series A
Stock, adjusted as provided below to reflect any difference in the terms of the
dividends payable and paid on or the conversion rights of such Preferred Stock
from the corresponding terms of the Series A Stock, or (b) if the common stock
of the Company (the "COMMON STOCK") is traded on the public market on the date
immediately prior to the Eligibility Date, the average of the closing prices of
the Common Stock reported in the consolidated reporting system for the sixty
(60) trading-day period ending on the trading day immediately prior to the
Eligibility Date or such other shorter period in the event the Eligibility Date
transpires prior to the Common Stock having been traded for such sixty (60)
trading-day period.

    If, as of the Eligibility Date, each share of Preferred Stock is
convertible into more or less than one share of Common Stock, or if any
dividends have been paid on the Preferred Stock in additional shares of
Preferred Stock or shares of Common Stock, then the Preferred Share Price shall
be adjusted by dividing the Preferred Share Price by the number of shares of
Common Stock into which each original share of Preferred Stock converts (after
giving effect to any stock dividends).  If, as of the Eligibility Date, the
dividend terms of the Preferred Stock differ from those of the Series A Stock,
the Preferred Share Price shall be adjusted as agreed upon by the Company and
the holder of this Warrant, or if they fail to agree, by an investment banker
mutually acceptable to the Company and the holder (the fees of the investment
banker to be shared by the Company and Mount Sinai; provided, however, that
Mount Sinai shall not be required to remit its portion of such fees to the
Company until the exercise of this Warrant).

    4.   RESERVATION OF PREFERRED STOCK.  The Company shall at all times
reserve and keep available out of its authorized but unissued shares of
Preferred Stock and Common Stock, solely for the purpose of effecting the
exercise of this Warrant, such number of its shares of Series A Stock (and
Common Stock upon conversion of the Series A Stock) as shall from time to time
be sufficient to effect the exercise of the Warrants and the conversion of the
Series A Stock to Common Stock.

    5.   NO SHAREHOLDER RIGHTS.  Except as expressly provided herein, nothing
contained in this Warrant shall be construed as conferring upon the holder
hereof or any other


                                          2.

<PAGE>

person the right to vote or to consent or to receive notice as a stockholder in
respect of meetings of stockholders for the election of directors of the Company
or any other matter or any rights whatsoever as a stockholder of the Company;
and no dividends or interest shall be payable or accrued in respect of this
Warrant or the interest represented hereby or the shares purchasable hereunder
until, and only to the extent that, this Warrant shall have been exercised.

    6.   METHOD OF EXERCISE; PAYMENT; ISSUANCE OF NEW WARRANT.  Subject to
Section 2 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part, by the surrender of this
Warrant (with a duly executed notice of exercise in the form attached hereto as
Exhibit A) at the principal office of the Company and by the payment to the
Company, by check or wire transfer, of an amount equal to the then applicable
Purchase Price per share multiplied by the number of shares then being
purchased.  In the event of any exercise of the rights represented by this
Warrant, certificates for the shares of stock so purchased shall be in the name
of, and delivered to, the holder hereof, or as such holder may direct (subject
to the restrictions upon transfer contained herein and upon payment by such
holder hereof of any applicable transfer taxes).  Such delivery shall be made
within ten (10) business days after exercise of the Warrant and at the Company's
expense and, unless this Warrant has been fully exercised or has expired, a new
Warrant representing the number of shares of Series A Stock, if any, with
respect to which this Warrant shall not then have been exercised shall also be
issued to the holder hereof within ten (10) business days after exercise of the
Warrant.

    7.   EXCHANGE OF WARRANT FOR OTHER WARRANTS.  This Warrant, with or without
similar Warrants, when surrendered properly endorsed at the principal offices of
the Company may be exchanged for another Warrant or Warrants of different
denominations, of like tenor and representing in the aggregate the right to
purchase a like number of shares of Series A Stock of the Company; provided,
however, that the Company's obligations under this Section 7 shall be subject to
and conditioned upon the compliance of any such subdivision with applicable
state securities laws and with the Securities Act of 1933, as amended (the
"ACT").

    8.   CERTAIN RESTRICTIONS.

         a.   RESTRICTIONS ON TRANSFERABILITY.  The Warrant and the Series A
Stock (or such other securities at the time receivable upon exercise of this
Warrant) shall not be transferable except upon the conditions specified in this
Section 8, which conditions are intended to insure compliance with the
provisions of the Act and to assist in an orderly distribution.  Each holder of
this Warrant or the Series A Stock issuable hereunder will cause any proposed
transferee of the Warrant or Series A Stock to agree to take and hold such
securities subject to the provisions and upon the conditions specified in this
Section 8.

         b.   RESTRICTIVE LEGENDS.  Each certificate representing (a) this
Warrant, (b) the Series A Stock and (c) any other securities issued in respect
of the Series A Stock upon any stock split, stock dividend, recapitalization,
merger, consolidation or similar event, shall (unless otherwise permitted by the
provisions of Section 8.c or Section 9 below or unless such securities have been
registered under the Act or sold under Rule 144) be stamped or otherwise
imprinted


                                          3.

<PAGE>

with legends substantially in the following form (in addition to any legend
required under applicable state securities laws):

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.  COPIES OF THE WARRANT DATED DECEMBER 1, 1994, _____
WHICH CONTAINS RESTRICTIONS APPLICABLE TO THESE SECURITIES, MAY BE OBTAINED AT
NO COST BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD OF THE CERTIFICATE TO
THE SECRETARY OF THE CORPORATION.

THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST
REFUSAL OPTION IN FAVOR OF THE CORPORATION AND/OR ITS ASSIGNEE(S), AS PROVIDED
IN THE BYLAWS OF THE CORPORATION.

    In addition, the certificates shall bear all legends required pursuant to
state securities and blue sky laws.

         c.   RESTRICTIONS ON TRANSFER.  The holder of this Warrant and each
person to whom this Warrant is subsequently transferred represents and warrants
to the Company (by acceptance of such transfer) that it will not transfer the
Warrant (or securities issuable upon exercise hereof unless a registration
statement under the Act was in effect with respect to such securities at the
time of issuance thereof) except pursuant to (a) an effective registration
statement under the Act, (b) Rule 144 under the Act (or any other rule under the
Act relating to the disposition of securities), or (c) an opinion of counsel,
reasonably satisfactory to counsel for the Company, that an exemption from such
registration is available.

    9.   WARRANTS TRANSFERABLE.  Subject to the provisions of Section 8, this
Warrant and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes), upon surrender of this
Warrant properly endorsed; provided, however, that the Company's Bylaws provide
for a right of first refusal in favor of the Company with respect to all sales,
assignments, pledges or transfers of shares of stock of the Company or any
interest therein.  The Company agrees, however, that transfers of this Warrant
to any person or entity listed on Schedule 1 (the "Permitted Transferees")
hereto shall not be subject to such right of first refusal and hereby waives any
such rights with respect thereto, provided that any subsequent transfer by any
of the Permitted Transferees shall nonetheless be subject to such right of first
refusal.  Each permitted taker and holder of this Warrant, by taking or holding
the same, consents and agrees that this Warrant, when endorsed in blank, shall
be deemed negotiable, and that the holder hereof, when this Warrant shall have
been so endorsed, may be treated by the Company and all other persons dealing
with this Warrant as the absolute owner hereof for any purpose and as the person
entitled to exercise the rights represented by this Warrant, or to the transfer
hereof on the books of the Company any notice to the contrary notwithstanding;
but until


                                          4.

<PAGE>

such transfer on such books, the Company may treat the registered owner hereof
as the owner for all purposes.

    10.  RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, contained in
Sections 8 and 9 shall survive the exercise of this Warrant.

    11.  ADJUSTMENT FOR CHANGES IN SERIES A STOCK.  The Purchase Price and the
number of shares purchasable upon the exercise of this Warrant, as well as the
date of exercisability of this Warrant, shall be subject to adjustment from time
to time upon the occurrence of certain events described in this Section 11.
Upon each adjustment of the Purchase Price, the holder of this Warrant shall
thereafter be entitled to purchase, at the Purchase Price resulting from such
adjustment, the number of shares obtained by multiplying the Purchase Price in
effect immediately prior to such adjustment by the number of shares purchasable
pursuant hereto immediately prior to such adjustment, and dividing the product
thereof by the Purchase Price resulting from such adjustment.

         a.   SUBDIVISION OR COMBINATION OF STOCK.  Should the Company at any
time subdivide its outstanding shares of Series A Stock into a greater number of
shares, the Purchase Price then in effect immediately prior to such subdivision
shall be proportionately reduced, and conversely, in case the outstanding shares
of Series A Stock shall be combined into a smaller number of shares, the
Purchase Price then in effect immediately prior to such combination shall be
proportionately increased.

         b.   DIVIDENDS IN SERIES A STOCK, OTHER STOCK, PROPERTY,
RECLASSIFICATION.  If at any time or from time to time the holders of Series A
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

              i.   Series A Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Series A Stock, or any rights or options to subscribe for, purchase or
otherwise acquire any of the foregoing by way of dividend or other distribution,

              ii.  Series A Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than shares of
Series A Stock issued as a stock split, adjustments in respect of which shall be
covered by the terms of Section 11(a) above),

then and in each such case, the holder hereof shall, upon the exercise of this
Warrant, be entitled to receive, in addition to the number of shares of Series A
Stock receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (i) and (ii) above) which such


                                          5.

<PAGE>

holder would hold on the date of such exercise had he been the holder of record
of such Series A Stock as of the date on which holders of Series A Stock
received or became entitled to receive such shares or all other additional stock
and other securities and property.

         c.   ACCELERATION OF EXERCISABILITY UPON SALE OF THE COMPANY.  If,
prior to the Eligibility Date, any Sale of the Company shall be effected, then
notwithstanding Section 1, the exercisability of this Warrant shall be
accelerated to a date ten (10) days prior to the closing of such Sale of the
Company (the "MERGER ELIGIBILITY DATE"), at a price equal to the lesser of (i)
the Purchase Price or (ii) $3.00 per share.  The Company shall provide notice of
such Merger Eligibility Date pursuant to Section 14.

    12.  EVENTS UPON AN IPO.

         a.   If prior to the Eligibility Date the Company shall effect its
first public offering of any equity securities of the Company (an "IPO")
pursuant to a registration statement filed with, and declared effective by, the
Securities and Exchange Commission pursuant to the Act, then notwithstanding
Section 1, the exercisability of this Warrant shall be accelerated to the date
of the closing of such IPO (the "IPO ELIGIBILITY DATE"), and this Warrant shall
be exercisable with respect to the same amount of shares, and in the same
manner, as is set forth in subsection 11(c) above with respect to a Sale of the
Company, except that the Warrant shall be exercisable at a purchase price equal
to one hundred twenty-five percent (125%) of the price at which the Common Stock
of the Company is to be sold in such IPO.  The Company shall provide notice of
the occurrence of such IPO Eligibility Date pursuant to Section 14.  Such
accelerated Warrant, and all rights to exercise such Warrant in whole or in
part, shall immediately terminate at 5:00 p.m. (Pacific Time), on the fifth
(5th) anniversary of the IPO Eligibility Date.  Any occurrence of the product
milestone event (i.e., the Eligibility Date) set forth in Section 1 following
such IPO shall have no effect upon such an accelerated Warrant.

         b.   If subsequent to the Eligibility Date the Company shall effect an
IPO, then this Warrant shall continue in full force and effect, and the holder
hereof shall have the right to purchase and receive upon the exercise of this
Warrant such shares of Series A Stock or Common Stock (assuming conversion of
the Series A Stock prior to such IPO) as is set forth in Section 1, at the
Purchase Price set forth in Section 3.

    13.  FRACTIONAL SHARES.  No fractional share shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share,
pay the holder entitled to such fraction a sum in cash equal to the fair market
value of such fraction on the date of exercise (as determined in good faith by
the Board of Directors of the Company).

    14.  NOTICE OF CERTAIN ACTIONS.  In the event of any reclassification or
recapitalization of the capital stock of the Company, any Sale of the Company,
any IPO, or any voluntary or involuntary dissolution, liquidation, or winding up
of the Company, the Company shall mail to the holder of this Warrant at least
fifteen (15) days prior to the record date specified therein, a notice
specifying (a) the date on which any such record is to be taken for the purpose


                                          6.

<PAGE>

of such dividend or distribution and a description of such dividend or
distribution, (b) the date on which any such reclassification, recapitalization,
Sale of the Company, IPO, dissolution, liquidation, or winding up is expected to
become effective, and (c) the time, if any, that is to be fixed, as to when the
holders of record of Common Stock (or other securities) shall be entitled to
exchange their shares of Common Stock (or other securities) for securities or
other property deliverable upon such reclassification, recapitalization, Sale of
the Company, IPO, dissolution, liquidation, or winding up; provided, however,
that the Company shall not be required to provide any notice under this Section
14 unless and until the occurrence of the Eligibility Date, except where
required pursuant to Section 11(c) and Section 12.

    15.  MISCELLANEOUS.  This Warrant shall be governed by the laws of the
State of California, as applied to contracts entered into between California
residents and to be performed entirely within the State of California.  The
headings in this Warrant are for purposes of convenience and reference only, and
shall not be deemed to constitute a part hereof.  Neither this Warrant nor any
term hereof may be changed, waived, discharged or terminated orally but only by
an instrument in writing signed by the Company and the registered holder hereof.
All notices and other communications from the Company to the holder of this
Warrant shall be made by personal delivery (including confirmed telex or
telecopy) or shall be mailed by first-class registered or certified mail,
postage prepaid, to the address furnished to the Company in writing by the last
holder of this Warrant who shall have furnished an address to the Company in
writing.

    IN WITNESS WHEREOF the Company has caused this Warrant to be duly executed
by its officers thereunto duly authorized this ___ day of ___________, 1996.


                                  AVIRON



                                  By
                                    ------------------------------------
                                       J. Leighton Read, M.D.
                                       Chairman and Chief Executive Officer


                                          7.

<PAGE>

                                      EXHIBIT A


                                 FORM OF SUBSCRIPTION


                     (To be signed only upon exercise of Warrant)


To Aviron:


    The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise the purchase right represented by such Warrant for, and to
purchase thereunder, __________________ _____________________ (___________)
shares of Series A Preferred Stock of Aviron and herewith makes payment of
____________ _______________ DOLLARS ($__________) therefor, and requests the
certificates for such shares be issued in the name of, and delivered
____________________ to, whose address is                                      .

    The undersigned represents that it is acquiring such Series A Preferred
Stock for its own account for investment and not with a view to or for sale in
connection with any distribution thereof.

DATED:
         -----------------


                                       By:
                                          -----------------------------------

                                       Title:
                                             --------------------------------

                                       Address:
                                               ------------------------------


                                       --------------------------------------


                                          1.

<PAGE>

                                      SCHEDULE 1

                                PERMITTED TRANSFEREES



                                Masayoshi Enami, Ph.D.
                                Reinhard Vlasak, Ph.D.
                                 Thomas Muster, Ph.D.
                                Jeffrey Parvin, Ph.D.
                                 Mark Krystal, Ph.D.
                                Michael Bergmann, M.D.


                                          2.


<PAGE>


                                                               Warrant No. PW-2A

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.



                                        AVIRON

                            WARRANT TO PURCHASE SHARES OF
                               SERIES A PREFERRED STOCK



    This certifies that MOUNT SINAI SCHOOL OF MEDICINE, ("MOUNT SINAI") for
value received, is entitled to purchase from AVIRON, a California corporation
(the "COMPANY"), having a principal place of business at 297 North Bernardo
Avenue, Mountain View, California 94043, at any time after the Eligibility Date
(as defined below) and prior to the Termination Date (as defined below), twenty
thousand 20,000 shares fully paid and nonassessable shares of Series A Preferred
Stock (the "SERIES A STOCK") of the Company at the Purchase Price (as defined
below), subject to the provisions and upon the terms and conditions hereinafter
set forth.


1.  EXERCISABILITY.  Until terminated pursuant to Section 2 below, and except
as otherwise provided in Section 12, the purchase rights represented by this
Warrant are exercisable at the option of the holder of record hereof, at any
time or from time to time after May 1, 1995 (the "ELIGIBILITY DATE"), for all or
any part of the Series A Stock (but not for a fraction of a share) which may be
purchased hereunder.

    2.   TERMINATION.  This Warrant, and all rights to exercise this Warrant in
whole or in part, shall immediately terminate at the earlier of (a) 5:00 p.m.
(Pacific Time), on May 1, 2000, or (b) 5:00 p.m. (Pacific Time), on the day
preceding the closing of the Company's sale of all or substantially all of its
assets or the acquisition of the Company by another entity by means of a merger
or consolidation or sale of stock resulting in the exchange of more than fifty
percent (50%) of the outstanding shares of the Company for securities or
consideration issued, or caused to be issued, by the acquiring entity (a "SALE
OF THE COMPANY") (such earlier date herein referred to as the "TERMINATION
DATE").

    3.   PURCHASE PRICE.  Except as otherwise provided in Section 12, this
Warrant shall be exercisable, on or after the Eligibility Date, at $0.90 per
share (the "PURCHASE PRICE").


                                          1.

<PAGE>

    4.   RESERVATION OF PREFERRED STOCK.  The Company shall at all times
reserve and keep available out of its authorized but unissued shares of
Preferred Stock and Common Stock, solely for the purpose of effecting the
exercise of this Warrant, such number of its shares of Series A Stock (and
Common Stock upon conversion of the Series A Stock) as shall from time to time
be sufficient to effect the exercise of the Warrants and the conversion of the
Series A Stock to Common Stock.

    5.   NO SHAREHOLDER RIGHTS.  Except as expressly provided herein, nothing
contained in this Warrant shall be construed as conferring upon the holder
hereof or any other person the right to vote or to consent or to receive notice
as a stockholder in respect of meetings of stockholders for the election of
directors of the Company or any other matter or any rights whatsoever as a
stockholder of the Company; and no dividends or interest shall be payable or
accrued in respect of this Warrant or the interest represented hereby or the
shares purchasable hereunder until, and only to the extent that, this Warrant
shall have been exercised.

    6.   METHOD OF EXERCISE; PAYMENT; ISSUANCE OF NEW WARRANT.  Subject to
Section 2 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part, by the surrender of this
Warrant (with a duly executed notice of exercise in the form attached hereto as
Exhibit A) at the principal office of the Company and by the payment to the
Company, by check or wire transfer, of an amount equal to the then applicable
Purchase Price per share multiplied by the number of shares then being
purchased.  In the event of any exercise of the rights represented by this
Warrant, certificates for the shares of stock so purchased shall be in the name
of, and delivered to, the holder hereof, or as such holder may direct (subject
to the restrictions upon transfer contained herein and upon payment by such
holder hereof of any applicable transfer taxes).  Such delivery shall be made
within ten (10) business days after exercise of the Warrant and at the Company's
expense and, unless this Warrant has been fully exercised or has expired, a new
Warrant representing the number of shares of Series A Stock, if any, with
respect to which this Warrant shall not then have been exercised shall also be
issued to the holder hereof within ten (10) business days after exercise of the
Warrant.

    7.   EXCHANGE OF WARRANT FOR OTHER WARRANTS.  This Warrant, with or without
similar Warrants, when surrendered properly endorsed at the principal offices of
the Company may be exchanged for another Warrant or Warrants of different
denominations, of like tenor and representing in the aggregate the right to
purchase a like number of shares of Series A Stock of the Company; provided,
however, that the Company's obligations under this Section 7 shall be subject to
and conditioned upon the compliance of any such subdivision with applicable
state securities laws and with the Securities Act of 1933, as amended (the
"ACT").

    8.   CERTAIN RESTRICTIONS.

         a.   RESTRICTIONS ON TRANSFERABILITY.  The Warrant and the Series A
Stock (or such other securities at the time receivable upon exercise of this
Warrant) shall not be transferable except upon the conditions specified in this
Section 8, which conditions are intended to insure compliance with the
provisions of the Act and to assist in an orderly distribution.  Each holder


                                          2.

<PAGE>

of this Warrant or the Series A Stock issuable hereunder will cause any proposed
transferee of the Warrant or Series A Stock to agree to take and hold such
securities subject to the provisions and upon the conditions specified in this
Section 8.

         b.   RESTRICTIVE LEGENDS.  Each certificate representing (a) this
Warrant, (b) the Series A Stock and (c) any other securities issued in respect
of the Series A Stock upon any stock split, stock dividend, recapitalization,
merger, consolidation or similar event, shall (unless otherwise permitted by the
provisions of Section 8.c or Section 9 below or unless such securities have been
registered under the Act or sold under Rule 144) be stamped or otherwise
imprinted with legends substantially in the following form (in addition to any
legend required under applicable state securities laws):

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.  COPIES OF THE WARRANT DATED DECEMBER 1, 1994 WHICH
CONTAINS RESTRICTIONS APPLICABLE TO THESE SECURITIES, MAY BE OBTAINED AT NO COST
BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD OF THE CERTIFICATE TO THE
SECRETARY OF THE CORPORATION.

THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF FIRST
REFUSAL OPTION IN FAVOR OF THE CORPORATION AND/OR ITS ASSIGNEE(S), AS PROVIDED
IN THE BYLAWS OF THE CORPORATION.

    In addition, the certificates shall bear all legends required pursuant to
state securities and blue sky laws.

         c.   RESTRICTIONS ON TRANSFER.  The holder of this Warrant and each
person to whom this Warrant is subsequently transferred represents and warrants
to the Company (by acceptance of such transfer) that it will not transfer the
Warrant (or securities issuable upon exercise hereof unless a registration
statement under the Act was in effect with respect to such securities at the
time of issuance thereof) except pursuant to (a) an effective registration
statement under the Act, (b) Rule 144 under the Act (or any other rule under the
Act relating to the disposition of securities), or (c) an opinion of counsel,
reasonably satisfactory to counsel for the Company, that an exemption from such
registration is available.

    9.   WARRANTS TRANSFERABLE.  Subject to the provisions of Section 8, this
Warrant and all rights hereunder are transferable, in whole or in part, without
charge to the holder hereof (except for transfer taxes), upon surrender of this
Warrant properly endorsed; provided, however, that the Company's Bylaws provide
for a right of first refusal in favor of the Company with respect to all sales,
assignments, pledges or transfers of shares of stock of the Company or any
interest therein.  The Company agrees, however, that transfers of this Warrant
to any person or


                                          3.

<PAGE>

entity listed on Schedule 1 (the "Permitted Transferees") hereto shall not be
subject to such right of first refusal and hereby waives any such rights with
respect thereto, provided that any subsequent transfer by any of the Permitted
Transferees shall nonetheless be subject to such right of first refusal.  Each
permitted taker and holder of this Warrant, by taking or holding the same,
consents and agrees that this Warrant, when endorsed in blank, shall be deemed
negotiable, and that the holder hereof, when this Warrant shall have been so
endorsed, may be treated by the Company and all other persons dealing with this
Warrant as the absolute owner hereof for any purpose and as the person entitled
to exercise the rights represented by this Warrant, or to the transfer hereof on
the books of the Company any notice to the contrary notwithstanding; but until
such transfer on such books, the Company may treat the registered owner hereof
as the owner for all purposes.

    10.  RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, contained in
Sections 8 and 9 shall survive the exercise of this Warrant.

    11.  ADJUSTMENT FOR CHANGES IN SERIES A STOCK.  The Purchase Price and the
number of shares purchasable upon the exercise of this Warrant, as well as the
date of exercisability of this Warrant, shall be subject to adjustment from time
to time upon the occurrence of certain events described in this Section 11.
Upon each adjustment of the Purchase Price, the holder of this Warrant shall
thereafter be entitled to purchase, at the Purchase Price resulting from such
adjustment, the number of shares obtained by multiplying the Purchase Price in
effect immediately prior to such adjustment by the number of shares purchasable
pursuant hereto immediately prior to such adjustment, and dividing the product
thereof by the Purchase Price resulting from such adjustment.

         a.   SUBDIVISION OR COMBINATION OF STOCK.  Should the Company at any
time subdivide its outstanding shares of Series A Stock into a greater number of
shares, the Purchase Price then in effect immediately prior to such subdivision
shall be proportionately reduced, and conversely, in case the outstanding shares
of Series A Stock shall be combined into a smaller number of shares, the
Purchase Price then in effect immediately prior to such combination shall be
proportionately increased.

         b.   DIVIDENDS IN SERIES A STOCK, OTHER STOCK, PROPERTY,
RECLASSIFICATION.  If at any time or from time to time the holders of Series A
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

              i.   Series A Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Series A Stock, or any rights or options to subscribe for, purchase or
otherwise acquire any of the foregoing by way of dividend or other distribution,


                                          4.

<PAGE>

              ii.  Series A Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than shares of
Series A Stock issued as a stock split, adjustments in respect of which shall be
covered by the terms of Section 11(a) above),

then and in each such case, the holder hereof shall, upon the exercise of this
Warrant, be entitled to receive, in addition to the number of shares of Series A
Stock receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (i) and (ii) above) which such holder would
hold on the date of such exercise had he been the holder of record of such
Series A Stock as of the date on which holders of Series A Stock received or
became entitled to receive such shares or all other additional stock and other
securities and property.

    12.  EVENTS UPON AN IPO.  If the Company shall effect an IPO, then this
Warrant shall continue in full force and effect, and the holder hereof shall
have the right to purchase and receive upon the exercise of this Warrant such
shares of Series A Stock or Common Stock (assuming conversion of the Series A
Stock prior to such IPO) as is set forth in Section 1, at the Purchase Price set
forth in Section 3.

    13.  FRACTIONAL SHARES.  No fractional share shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share,
pay the holder entitled to such fraction a sum in cash equal to the fair market
value of such fraction on the date of exercise (as determined in good faith by
the Board of Directors of the Company).

    14.  NOTICE OF CERTAIN ACTIONS.  In the event of any reclassification or
recapitalization of the capital stock of the Company, any Sale of the Company,
any IPO, or any voluntary or involuntary dissolution, liquidation, or winding up
of the Company, the Company shall mail to the holder of this Warrant at least
fifteen (15) days prior to the record date specified therein, a notice
specifying (a) the date on which any such record is to be taken for the purpose
of such dividend or distribution and a description of such dividend or
distribution, (b) the date on which any such reclassification, recapitalization,
Sale of the Company, IPO, dissolution, liquidation, or winding up is expected to
become effective, and (c) the time, if any, that is to be fixed, as to when the
holders of record of Common Stock (or other securities) shall be entitled to
exchange their shares of Common Stock (or other securities) for securities or
other property deliverable upon such reclassification, recapitalization, Sale of
the Company, IPO, dissolution, liquidation, or winding up.

    15.  MISCELLANEOUS.  This Warrant shall be governed by the laws of the
State of California, as applied to contracts entered into between California
residents and to be performed entirely within the State of California.  The
headings in this Warrant are for purposes of convenience and reference only, and
shall not be deemed to constitute a part hereof.  Neither this Warrant nor any
term hereof may be changed, waived, discharged or terminated orally but only by
an instrument in writing signed by the Company and the registered holder hereof.
All notices and other communications from the Company to the holder of this
Warrant shall be made by


                                          5.

<PAGE>

personal delivery (including confirmed telex or telecopy) or shall be mailed by
first-class registered or certified mail, postage prepaid, to the address
furnished to the Company in writing by the last holder of this Warrant who shall
have furnished an address to the Company in writing.

    IN WITNESS WHEREOF the Company has caused this Warrant to be duly executed
by its officers thereunto duly authorized this ___ day of ___________, 1996.

                                  AVIRON



                                  By
                                    -----------------------------------------
                                       J. Leighton Read, M.D.
                                       Chairman and Chief Executive Officer


                                          6.

<PAGE>

                                      EXHIBIT A


                                 FORM OF SUBSCRIPTION


                     (To be signed only upon exercise of Warrant)


To Aviron:


    The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise the purchase right represented by such Warrant for, and to
purchase thereunder, __________________ _____________________ (___________)
shares of Series A Preferred Stock of Aviron and herewith makes payment of
____________ _______________ DOLLARS ($__________) therefor, and requests the
certificates for such shares be issued in the name of, and delivered
____________________ to, whose address is ____________________________________.

    The undersigned represents that it is acquiring such Series A Preferred
Stock for its own account for investment and not with a view to or for sale in
connection with any distribution thereof.

DATED:
          ------------------


                                  By:
                                     ----------------------------------------

                                  Title:
                                        -------------------------------------

                                  Address:
                                          -----------------------------------


                                  -------------------------------------------


                                          1.

<PAGE>

                                      SCHEDULE 1

                                PERMITTED TRANSFEREES



                                Masayoshi Enami, Ph.D.
                                Reinhard Vlasak, Ph.D.
                                 Thomas Muster, Ph.D.
                                Jeffrey Parvin, Ph.D.
                                 Mark Krystal, Ph.D.
                                Michael Bergmann, M.D.


                                          2.


<PAGE>


                                                                       No. PCW-1


THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "ACT").  THIS WARRANT WILL BE ACQUIRED FOR INVESTMENT AND NOT WITH
A VIEW TO, OR FOR RESALE IN CONNECTION WITH, ANY DISTRIBUTION THEREOF.  NO SUCH
SALE OR OTHER DISTRIBUTION MAY BE MADE WITHOUT AN EFFECTIVE REGISTRATION
STATEMENT UNDER THE ACT AND QUALIFICATION UNDER ANY APPLICABLE STATE SECURITIES
LAW RELATED THERETO OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
COMPANY, AND ITS COUNSEL, THAT SAID REGISTRATION AND QUALIFICATION ARE NOT
REQUIRED UNDER THE ACT AND ANY APPLICABLE STATE SECURITIES LAW, RESPECTIVELY.


                                 WARRANT TO PURCHASE
                          SERIES C PREFERRED STOCK OF AVIRON
                            (Void after November 9, 2000)

    WHEREAS, Raymond James & Associates, Inc. (the "Holder") has acted as
placement agent in the sale of 7,050,714 shares of the Series C Preferred Stock
of Aviron, a California corporation (the "Company"), having a place of business
at 297 North Bernardo Avenue, Mountain View, California  94043, pursuant to a
Placement Agent Agreement dated July 17, 1995 (the "Placement Agreement"); and

    WHEREAS, the parties intend to grant the Holder a right to purchase equity
securities of the Company in proportion to the number of shares sold;

    NOW, THEREFORE, it is agreed as follows:

1.  GRANT OF RIGHT.  This certifies that the Holder, or assigns, for value
received, is entitled to purchase at the Stock Purchase Price (as defined below)
from the Company Three Hundred Fifty-Two Thousand, Five Hundred Thirty-Six
(352,536) fully paid and nonassessable shares of the Company's Series C
Preferred Stock ("Series C Stock") at an exercise price of One Dollar and Sixty-
Two Cents ($1.62) (the "Stock Purchase Price"), at any time from the date
hereof, up to and including 5:00 p.m. (Pacific time) on November 9, 2000, such
day being referred to herein as the "Expiration Date," upon surrender to the
Company at its principal office (or at such other location as the Company may
advise the Holder in writing) of this Warrant properly endorsed with the Form of
Subscription attached hereto duly filled in and signed and, if applicable, upon
payment in cash or by check of the aggregate Stock Purchase Price for the number
of shares for which this Warrant is being exercised determined in accordance
with the provisions hereof.  The Stock Purchase Price and the number of shares
purchasable hereunder are subject to adjustment as provided in Section 4 of this
Warrant.

<PAGE>

2.  EXERCISE; ISSUANCE OF CERTIFICATES; PAYMENT FOR SHARES.

    2.1  GENERAL.  This Warrant is exercisable at the option of the holder of
record hereof, at any time or from time to time up to the Expiration Date, for
all or any part of the shares (but not for a fraction of a share) of Series C
Stock, or Common Stock issuable upon conversion of Series C Stock, which may be
purchased hereunder (the "Exercise Stock").  The Company agrees that the shares
of Exercise Stock purchased under this Warrant shall be and are deemed to be
issued to the Holder hereof as the record owner of such shares as of the close
of business on the date on which this Warrant shall have been surrendered,
properly endorsed, the completed, executed Subscription Form delivered and
payment made for such shares.  Certificates for the shares of Exercise Stock so
purchased, together with any other securities or property to which the Holder
hereof is entitled upon such exercise, shall be delivered to the Holder hereof
by the Company at the Company's expense within a reasonable time after the
rights represented by this Warrant have been so exercised.  In case of a
purchase of less than all the shares which may be purchased under this Warrant,
the Company shall cancel this Warrant and execute and deliver a new Warrant or
Warrants of like tenor for the balance of the shares purchasable under the
Warrant surrendered upon such purchase to the Holder hereof within a reasonable
time.  Each stock certificate so delivered shall be in such denominations of
Exercise Stock as may be requested by the Holder hereof and shall be registered
in the name of such Holder.

    2.2  NET ISSUE EXERCISE.  Notwithstanding any provisions herein to the
contrary, if the fair market value of one share of the Company's Exercise Stock
is greater than the Stock Purchase Price (at the date of calculation as set
forth below), in lieu of exercising this Warrant for cash, the Holder may elect
to receive shares equal to the value (as determined below) of this Warrant (or
the portion thereof being canceled) by surrender of this Warrant at the
principal office of the Company together with the properly endorsed Form of
Subscription and notice of such election, in which event the Company shall issue
to the Holder a number of shares of Exercise Stock computed using the following
formula:

         X = Y (A-B)
              -------
                A

    Where     X =  the number of shares of Exercise Stock to be issued to the
                   Holder

              Y =  the number of shares of Exercise Stock purchasable under the
                   Warrant or, if only a portion of the Warrant is being
                   exercised, the portion of the Warrant being canceled (at the
                   date of such calculation)

              A =  the fair market value of one share of the Company's Exercise
                   Stock (at the date of such calculation)

              B =  Stock Purchase Price (as adjusted to the date of such
                   calculation)


                                          2.

<PAGE>

For purposes of the above calculation, fair market value of one share of
Preferred Stock shall be determined by the Company's Board of Directors in good
faith; provided, however, that in the event the Company makes an initial public
offering of its Common Stock and (i) if the Exercise Stock is Common Stock, the
fair market value per share shall be the Current Market Price of the Company's
Common Stock on the date of exercise (the "Common Stock Price") or (ii) if the
Exercise Stock is Preferred Stock, the product of (x) the Common Stock Price,
and (x) the number of shares of Common Stock into which each share of Preferred
Stock is convertible at the time of such exercise.

For purposes of this Warrant, the "Current Market Price" of a share of Common
Stock is the last reported sales price of the Common Stock as reported by the
Nasdaq National Market, or the primary national securities exchange on which the
Common Stock is then quoted, on the last trading day prior to the exercise date;
PROVIDED, HOWEVER, that if the Common Stock is neither traded on the Nasdaq
National Market nor on a national securities exchange, the price referred to
above shall be the price reflected in the over-the-counter market as reported by
the National Quotation Bureau, Inc. or any organization performing a similar
function, and if the Common Stock is not so reported, the Current Market Price
shall be determined by the Company's Board of Directors.

3.  SHARES TO BE FULLY PAID; RESERVATION OF SHARES.  The Company covenants and
agrees that all shares of Exercise Stock which may be issued upon the exercise
of the rights represented by this Warrant will, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable and free from all
preemptive rights of any shareholder and free of all taxes, liens and charges
with respect to the issue thereof.  The Company further covenants and agrees
that, during the period within which the rights represented by this Warrant may
be exercised, the Company will at all times have authorized and reserved, for
the purpose of issue or transfer upon exercise of the subscription rights
evidenced by this Warrant, a sufficient number of shares of authorized but
unissued Exercise Stock, or other securities and property, when and as required
to provide for the exercise of the rights represented by this Warrant and the
conversion of the Exercise Stock.  The Company will take all such action as may
be necessary to assure that such shares of Exercise Stock may be issued as
provided herein without violation of any applicable law or regulation, or of any
requirements of any domestic securities exchange upon which the Exercise Stock
may be listed; provided, however, that the Company shall not be required to
effect a registration under Federal or State securities laws with respect to
such exercise.  The Company will not take any action which would result in any
adjustment of the Stock Purchase Price (as defined in Section 4 hereof) (i) if
the total number of shares of Exercise Stock issuable after such action upon
exercise of all outstanding warrants, together with all shares of Exercise Stock
then outstanding and all shares of Exercise Stock then issuable upon exercise of
all options and upon the conversion of all convertible securities then
outstanding, would exceed the total number of shares of Exercise Stock then
authorized by the Company's Articles of Incorporation, or (ii) if the total
number of shares of Common Stock issuable after such action upon the conversion
of all such shares of Exercise Stock, together with all shares of Common Stock
then issuable upon exercise of all options and upon the conversion of all such
shares of Exercise Stock, together with all shares of Common Stock then
outstanding and all shares of Common Stock then issuable upon exercise of all
options


                                          3.

<PAGE>

and upon the conversion of all convertible securities then outstanding would
exceed the total number of shares of Common Stock then authorized by the
Company's Articles of Incorporation.

4.  ADJUSTMENT OF STOCK PURCHASE PRICE AND NUMBER OF SHARES.  The Stock
Purchase Price and the number of shares purchasable upon the exercise of this
Warrant shall be subject to adjustment from time to time upon the occurrence of
certain events described in this Section 4.  Upon each adjustment of the Stock
Purchase Price, the Holder of this Warrant shall thereafter be entitled to
purchase, at the Stock Purchase Price resulting from such adjustment, the number
of shares obtained by multiplying the Stock Purchase Price in effect immediately
prior to such adjustment by the number of shares purchasable pursuant hereto
immediately prior to such adjustment, and dividing the product thereof by the
Stock Purchase Price resulting from such adjustment.

    4.1  SUBDIVISION OR COMBINATION OF STOCK.  In case the Company shall at any
time subdivide its outstanding shares of Exercise Stock into a greater number of
shares, the Stock Purchase Price in effect immediately prior to such subdivision
shall be proportionately reduced, and conversely, in case the outstanding shares
of Exercise Stock of the Company shall be combined into a smaller number of
shares, the Stock Purchase Price in effect immediately prior to such combination
shall be proportionately increased.

    4.2  DIVIDENDS IN PREFERRED STOCK, OTHER STOCK, PROPERTY, RECLASSIFICATION.
If at any time or from time to time the Holders of Exercise Stock (or any shares
of stock or other securities at the time receivable upon the exercise of this
Warrant) shall have received or become entitled to receive, without payment
therefor,

         (A)  Exercise Stock or any shares of stock or other securities which
are at any time directly or indirectly convertible into or exchangeable for
Exercise Stock, or any rights or options to subscribe for, purchase or otherwise
acquire any of the foregoing by way of dividend or other distribution,

         (B)  any cash paid or payable otherwise than as a cash dividend, or

         (C)  Exercise Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than (i) shares
of Exercise Stock issued as a stock split, adjustments in respect of which shall
be covered by the terms of Section 4.1 above or (ii) an event for which
adjustment is otherwise made pursuant to Section 4.4 below), then and in each
such case, the Holder hereof shall, upon the exercise of this Warrant, be
entitled to receive, in addition to the number of shares of Exercise Stock
receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (B) and (C) above) which such Holder would
hold on the date of such exercise had it been the holder of record of such
Exercise Stock as of the date on which holders of Exercise Stock received or
became entitled to receive such shares or all other additional stock and other
securities and property.


                                          4.

<PAGE>

    4.3  REORGANIZATION, RECLASSIFICATION, CONSOLIDATION, MERGER OR SALE.  If
any capital reorganization of the capital stock of the Company, or any
consolidation or merger of the Company with another corporation, or the sale of
all or substantially all of its assets to another corporation shall be effected
in such a way that holders of Exercise Stock shall be entitled to receive stock,
securities, or other assets or property, then, as a condition of such
reorganization, reclassification, consolidation, merger or sale, lawful and
adequate provisions shall be made whereby the holder hereof shall thereafter
have the right to purchase and receive (in lieu of the shares of the Exercise
Stock of the Company immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby) such shares of stock, securities or
other assets or property as may be issued or payable with respect to or in
exchange for a number of outstanding shares of such Exercise Stock equal to the
number of shares of such stock immediately theretofore purchasable and
receivable upon the exercise of the rights represented hereby; provided,
however, that in the event the value of the stock, securities or other assets or
property (determined in good faith by the Board of Directors of the Company)
issuable or payable with respect to one share of the Exercise Stock of the
Company immediately theretofore purchasable and receivable upon the exercise of
the rights represented hereby is in excess of the Stock Purchase Price hereof
effective at the time of the merger and securities received in such
reorganization, if any, are publicly traded, then this Warrant shall expire
unless exercised prior to the reorganization.  In any reorganization described
above, appropriate provision shall be made with respect to the rights and
interests of the Holder of this Warrant to the end that the provisions hereof
(including, without limitation, provisions for adjustments of the Stock Purchase
Price and of the number of shares purchasable and receivable upon the exercise
of this Warrant) shall thereafter be applicable, as nearly as may be, in
relation to any shares of stock, securities or assets thereafter deliverable
upon the exercise hereof.  The Company will not effect any such consolidation,
merger or sale unless, prior to the consummation thereof, the successor
corporation (if other than the Company) resulting from such consolidation or the
corporation purchasing such assets shall assume by written instrument, executed
and mailed or delivered to the registered Holder hereof at the last address of
such Holder appearing on the books of the Company, the obligation to deliver to
such Holder such shares of stock, securities or assets as, in accordance with
the foregoing provisions, such Holder may be entitled to purchase.

    4.4  ADJUSTMENT UPON CONVERSION OF SERIES C PREFERRED STOCK.  If at any
time after the date hereof, all of the Series C Preferred Stock of the Company
is converted to Common Stock, either as part of an initial public offering of
the Company's Common Stock or for any other reason, then the Exercise Stock of
this Warrant shall hereinafter be Common Stock.  The Holder of this Warrant
shall have the right to receive upon the exercise of this Warrant such shares of
Common Stock as it would have been entitled to had the Warrant been exercised
for Series C Preferred Stock immediately prior to such conversion.

    4.5  ADJUSTMENTS SET FORTH IN ARTICLES OF INCORPORATION.  In addition to
the foregoing adjustments, the conversion rate of the Exercise Stock into Common
Stock will be subject to adjustments as set forth in the Company's Articles of
Incorporation.  The Company represents that as of the date this Warrant was
first issued, the Company anticipates each share of Preferred Stock will be
convertible into one share of Common Stock.


                                          5.

<PAGE>

    4.6  NOTICE OF ADJUSTMENT.  Upon any adjustment of the Stock Purchase Price
or in the conversion ratio of the Preferred Stock or any increase or decrease in
the number of shares purchasable upon the exercise of this Warrant, the Company
shall give written notice thereof, by first class mail, postage prepaid,
addressed to the registered Holder of this Warrant at the address of such Holder
as shown on the books of the Company.  The notice shall be signed by the
Company's chief financial officer and shall state the Stock Purchase Price
resulting from such adjustment and the increase or decrease, if any, in the
number of shares purchasable at such price upon the exercise of this Warrant,
setting forth in reasonable detail the method of calculation and the facts upon
which such calculation is based.  Any written notice delivered pursuant to this
Section 4.5 shall be attached to this Warrant and incorporated herein by
reference.

    4.7  OTHER NOTICES.  If at any time:

         (1)  the Company shall declare any cash dividend upon its Exercise
Stock;

         (2)  the Company shall declare any dividend upon its Exercise Stock
payable in stock or make any special dividend or other distribution to the
holders of its Exercise Stock;

         (3)  the Company shall offer for subscription pro rata to the holders
of its Exercise Stock any additional shares of stock of any class or other
rights;

         (4)  there shall be any capital reorganization or reclassification of
the capital stock of the Company; or consolidation or merger of the Company
with, or sale of all or substantially all of its assets to, another corporation;

         (5)  there shall be a voluntary or involuntary dissolution,
liquidation or winding-up of the Company; or

         (6)  there shall be an initial public offering of Company securities;

then, in any one or more of said cases, the Company shall give, by first class
mail, postage prepaid, addressed to the Holder of this Warrant at the address of
such Holder as shown on the books of the Company, (a) at least thirty (30) days'
prior written notice of the date on which the books of the Company shall close
or a record shall be taken for such dividend, distribution or subscription
rights or for determining rights to vote in respect of any such reorganization,
reclassification, consolidation, merger, sale, dissolution, liquidation or
winding-up, and (b) in the case of any such reorganization, reclassification,
consolidation, merger, sale, dissolution, liquidation, winding-up or public
offering, at least thirty (30) days' prior written notice of the date when the
same shall take place; provided, however, that the Holder shall make a best
efforts attempt to respond to such notice as early as possible after the receipt
thereof.  Any notice given in accordance with the foregoing clause (a) shall
also specify, in the case of any such dividend, distribution or subscription
rights, the date on which the holders of Preferred Stock shall be entitled
thereto.  Any notice given in accordance with the foregoing clause (b) shall
also specify the date on which the holders of Exercise Stock shall be entitled
to exchange their Exercise Stock for securities or other property deliverable
upon such reorganization, reclassification, consoli-


                                          6.

<PAGE>

dation, merger, sale, dissolution, liquidation, winding-up, conversion or public
offering, as the case may be.

    4.8  CERTAIN EVENTS.  If any change in the outstanding Exercise Stock of
the Company or any other event occurs as to which the other provisions of this
Section 4 are not strictly applicable or if strictly applicable would not fairly
protect the purchase rights of the Holder of the Warrant in accordance with such
provisions, then the Board of Directors of the Company shall make an adjustment
in the number and class of shares available under the Warrant, the Stock
Purchase Price or the application of such provisions, so as to protect such
purchase rights as aforesaid.  The adjustment shall be such as will give the
Holder of the Warrant upon exercise for the same aggregate Stock Purchase Price
the total number, class and kind of shares as he would have owned had the
Warrant been exercised prior to the event and had it continued to hold such
shares until after the event requiring adjustment.

5.  REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

    The Company hereby represents and warrants to the Holder as follows:

    5.1  CORPORATE POWER.  The Company will have on the date hereof all
requisite corporate power to execute and deliver this Warrant and to carry out
and perform its obligations under the terms of this Warrant.
    5.2 AUTHORIZATION.  All corporate action on the part of the Company, its
directors and its stockholders necessary for the authorization, execution,
delivery and performance of this Warrant by the Company and the performance of
the Company's obligations hereunder, has been taken or will be taken prior to
the date hereof. This Warrant, when executed and delivered by the Company, shall
constitute a valid and binding obligation of the Company enforceable in
accordance with its terms, subject to laws of general application relating to
bankruptcy, insolvency, the relief of debtors and, with respect to rights to
indemnity, subject to federal and state securities laws.

    5.3  GOVERNMENTAL CONSENTS.  All consents, approvals, orders or
authorizations of, or registrations, qualifications, designations, declarations
or filings with, any governmental authority, required on the part of the Company
in connection with the offer, sale or issuance of this Warrant shall have been
obtained and will be effective on the date hereof, except for notices required
or permitted to be filed with certain state and federal securities commissions,
which notices will be filed on a timely basis.

    5.4  OFFERING.  Assuming the accuracy of the representations and warranties
of the Purchasers contained in Section 6 hereof, the offer, issue and sale of
this Warrant is and will be exempt from the registration and prospectus delivery
requirements of the Securities Act of 1933, as amended (the "1933 Act"), and has
been registered or qualified (or are exempt from registration and qualification)
under the registration, permit or qualification requirements of all applicable
state securities laws.


                                          7.


<PAGE>

6.  REPRESENTATIONS AND WARRANTIES OF THE HOLDER.

    6.1 PURCHASE FOR OWN ACCOUNT.  The Holder represents that it is acquiring
this Warrant and the Exercise Stock issuable upon exercise of this Warrant
(collectively, the "Securities") solely for its own account and beneficial
interest for investment and not for sale or with a view to distribution of the
Securities or any part thereof, has no present intention of selling (in
connection with a distribution or otherwise), granting any participation in, or
otherwise distributing the same, and does not presently have reason to
anticipate a change in such intention.

    6.2 INFORMATION AND SOPHISTICATION.  The Holder acknowledges that it has
received all the information it has requested from the Company and considers
necessary or appropriate for deciding whether to acquire the Warrant.  The
Holder represents that it has had an opportunity to ask questions and receive
answers from the Company regarding the terms and conditions of the offering of
the Warrant and to obtain any additional information necessary to verify the
accuracy of the information given the Holder.  The Holder further represents
that it has such knowledge and experience in financial and business matters that
it is capable of evaluating the merits and risk of this investment.

    6.3  FURTHER LIMITATIONS ON DISPOSITION.  Without in any way limiting the
representations set forth above, the Holder further agrees not to make any
disposition of all or any portion of the Securities unless and until:

         (a)  There is then in effect a registration statement under the 1933
Act covering such proposed disposition and such disposition is made in
accordance with such registration statement; or

         (b)  (i)  The Holder shall have notified the Company of the proposed
disposition and shall have furnished the Company with a detailed statement of
the circumstances surrounding the proposed disposition, and (ii) if reasonably
requested by the Company, the Holder shall have furnished the Company with an
opinion of counsel, reasonably satisfactory to the Company, that such
disposition will not require registration under the 1933 Act.

         (c)  Notwithstanding the provisions of paragraphs (a) and (b) above,
no such registration statement or opinion of counsel shall be necessary for a
transfer by the Holder to a stockholder or partner (or retired partner) of the
Holder, or transfers by gift, will or intestate succession to any spouse or
lineal descendants or ancestors, if all transferees agree in writing to be
subject to the terms hereof to the same extent as if they were the Holder
hereunder.

Each certificate for Warrant Shares issued upon exercise of this Warrant, unless
at the time of exercise such Warrant Shares are acquired pursuant to a
registration statement that has been declared effective under the Act, shall
bear a legend substantially in the following form:

    THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
    SECURITIES ACT OF 1933 (THE "ACT") AND


                                          8.

<PAGE>

    MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR
    HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE
    OPINION OF COUNSEL OR BASED ON OTHER WRITTEN EVIDENCE IN FORM AND
    SUBSTANCE SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER,
    SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

Any certificate for any Warrant Shares issued at any time in exchange or
substitution for any certificate for any Warrant Shares bearing such legend
(except a new certificate for any Warrant Shares issued after the acquisition of
such Warrant Shares pursuant to a registration statement that has been declared
effective under the Act) shall also bear such legend unless, in the opinion of
counsel for the Company, the Warrant Shares represented thereby need no longer
be subject to the restriction contained herein.  The provision of this Section
6.3(d) shall be binding upon all subsequent holders of certificates for Warrant
Shares bearing the above legend and all subsequent holders of this Warrant, if
any.

    6.4  ACCREDITED INVESTOR.  The Holder is an "accredited investor" as such
term is defined in Rule 501 under the Securities Act.

7.  ISSUE TAX.  The issuance of certificates for shares of Exercise Stock upon
the exercise of the Warrant shall be made without charge to the Holder of the
Warrant for any issue tax (other than any applicable income taxes) in respect
thereof; provided, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the issuance and
delivery of any certificate in a name other than that of the then Holder of the
Warrant being exercised.

8.  CLOSING OF BOOKS.  The Company will at no time close its transfer books
against the transfer of any warrant or of any shares of Exercise Stock issued or
issuable upon the exercise of any warrant in any manner which interferes with
the timely exercise of this Warrant.

9.  NO VOTING OR DIVIDEND RIGHTS; LIMITATION OF LIABILITY.  Nothing contained
in this Warrant shall be construed as conferring upon the holder hereof the
right to vote or to consent or to receive notice as a shareholder of the Company
or any other matters or any rights whatsoever as a shareholder of the Company.
No dividends or interest shall be payable or accrued in respect of this Warrant
or the interest represented hereby or the shares purchasable hereunder until,
and only to the extent that, this Warrant shall have been exercised.  No
provisions hereof, in the absence of affirmative action by the holder to
purchase shares of Exercise Stock, and no mere enumeration herein of the rights
or privileges of the holder hereof, shall give rise to any liability of such
holder for the Stock Purchase Price or as a shareholder of the Company, whether
such liability is asserted by the Company or by its creditors.

10. REGISTRATION RIGHTS.  The registration rights and related obligations of
the Holder with respect to this Warrant and the Exercise Stock will be the same
as those agreed to with certain holders of the Company's Preferred Stock under
Section 3 (but excluding Sections 3.1, 3.9 and


                                          9.

<PAGE>

3.11) of that certain Amended and Restated Investor's Rights Agreement among the
Company and certain of its investors dated as of July 18, 1995.

11. WARRANTS TRANSFERABLE.  Subject to compliance with applicable federal and
state securities laws and the transfer restrictions set forth Section 6.4 above,
this Warrant and all rights hereunder are transferable, in whole or in part,
without charge to the holder hereof (except for transfer taxes), upon surrender
of this Warrant properly endorsed and compliance with the provisions of this
Warrant.  Each taker and holder of this Warrant, by taking or holding the same,
consents and agrees that this Warrant, when endorsed in blank, shall be deemed
negotiable, and that the holder hereof, when this Warrant shall have been so
endorsed, may be treated by the Company, at the Company's option, and all other
persons dealing with this Warrant as the absolute owner hereof for any purpose
and as the person entitled to exercise the rights represented by this Warrant,
or to the transfer hereof on the books of the Company any notice to the contrary
notwithstanding; but until such transfer on such books, the Company may treat
the registered owner hereof as the owner for all purposes.

12. RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT.  The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Exercise Stock issued upon exercise of this Warrant, referred to in
Sections 10 and 11 shall survive the exercise of this Warrant.

13. MODIFICATION AND WAIVER.  This Warrant and any provision hereof may be
changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

14. NOTICES.  Any notice, request or other document required or permitted to be
given or delivered to the holder hereof or the Company shall be delivered or
shall be sent by certified mail, postage prepaid, to each such holder at its
address as shown on the books of the Company or to the Company at the address
indicated therefor in the first paragraph of this Warrant or such other address
as either may from time to time provide to the other.

15. BINDING EFFECT ON SUCCESSORS.  This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets.  All of the obligations of the
Company relating to the Exercise Stock issuable upon the exercise of this
Warrant shall survive the exercise and termination of this Warrant.  All of the
covenants and agreements of the Company shall inure to the benefit of the
successors and assigns of the holder hereof.

16. DESCRIPTIVE HEADINGS AND GOVERNING LAW.  The description headings of the
several sections and paragraphs of this Warrant are inserted for convenience
only and do not constitute a part of this Warrant.  This Warrant shall be
construed and enforced in accordance with, and the rights of the parties shall
be governed by, the laws of the State of California.

17. LOST WARRANTS.  The Company represents and warrants to the Holder hereof
that upon receipt of evidence reasonably satisfactory to the Company of the
loss, theft, destruction, or


                                         10.

<PAGE>

mutilation of this Warrant and, in the case of any such loss, theft or
destruction, upon receipt of an indemnity reasonably satisfactory to the
Company, or in the case of any such mutilation upon surrender and cancellation
of such Warrant, the Company, at its expense, will make and deliver a new
Warrant, of like tenor, in lieu of the lost, stolen, destroyed or mutilated
Warrant.
18. FRACTIONAL SHARES.  No fractional shares shall be issued upon exercise of
this Warrant.  The Company shall, in lieu of issuing any fractional share, pay
the holder entitled to such fraction a sum in cash equal to such fraction
multiplied by the then effective Stock Purchase Price.


    IN WITNESS WHEREOF, the Company has caused this Warrant to be duly executed
by its officers, thereunto duly authorized this 10th day of November, 1995.

                                       AVIRON
                                       a California corporation



                                       By:
                                          -----------------------------------

                                       Title:
                                             --------------------------------

ATTEST:



- -----------------------------------
Secretary


                                       RAYMOND JAMES & ASSOCIATES, INC.



                                       By:
                                          -----------------------------------

                                       Title:
                                             --------------------------------


                                         11.

<PAGE>

                                      EXHIBIT A

                                  SUBSCRIPTION FORM

                                                            Date:
                                                                  --------------

AVIRON
297 North Bernardo Avenue
Mountain View, California  94043
Attn:  Chief Executive Officer

Gentlemen:

/ / The undersigned hereby elects to exercise the warrant issued to it by
    AVIRON (the "Company") and dated November 10, 1995 Warrant No. PCW-1 (the
    "Warrant") and to purchase thereunder Three Hundred Fifty-Two Thousand,
    Five Hundred Thirty-Six (352,536) shares of the Series C Preferred Stock of
    the Company at a purchase price of One Dollar and Sixty-Two Cents ($1.62)
    per Share or an aggregate purchase price of Five Hundred Seventy-One
    Thousand, One Hundred Eight Dollars and Thirty-Two Cents ($571,108.32) (the
    "Purchase Price").

    FOR USE IN CONNECTION WITH A NET ISSUE EXERCISE:

/ / The undersigned hereby elects to convert _______________________ percent
    (____%) of the value of the Warrant pursuant to the provisions of Section
    2.2 of the Warrant.

    Pursuant to the terms of the Warrant the undersigned has delivered the
Purchase Price herewith in full in cash or by certified check or wire transfer.
The undersigned also makes the representations set forth on the attached Exhibit
B of the Warrant.


                                       Very truly yours,

                                       --------------------------------------


                                       By
                                          -----------------------------------

                                       Title
                                             --------------------------------


<PAGE>

                                      EXHIBIT B

                              INVESTMENT REPRESENTATIONS


THIS AGREEMENT MUST BE COMPLETED, SIGNED AND RETURNED TO AVIRON ALONG WITH THE
SUBSCRIPTION FORM BEFORE THE SERIES C PREFERRED STOCK ISSUABLE UPON EXERCISE OF
THE WARRANT CERTIFICATE DATED NOVEMBER 10, 1995, WILL BE ISSUED.


                                                  , 19
                             ---------------------    --


AVIRON
297 North Bernardo Avenue
Mountain View, California  94043
Attention:  Chief Executive Officer


    The undersigned, Raymond James & Associates, Inc. ("Purchaser"), intends to
acquire up to 352,536 shares of the Series C Preferred Stock (the "Stock") of
AVIRON (the "Company") from the Company pursuant to the exercise or conversion
of certain Warrants to purchase Stock held by Purchaser.  The Stock will be
issued to Purchaser in a transaction not involving a public offering and
pursuant to an exemption from registration under the Securities Act of 1933, as
amended (the "1933 Act") and applicable state securities laws.  In connection
with such purchase and in order to comply with the exemptions from registration
relied upon by the Company, Purchaser represents, warrants and agrees as
follows:

    Purchaser is acquiring the Stock for its own account, to hold for
investment, and Purchaser shall not make any sale, transfer or other disposition
of the Stock in violation of the 1933 Act or the General Rules and Regulations
promulgated thereunder by the Securities and Exchange Commission (the "SEC") or
in violation of any applicable state securities law.

    Purchaser has been advised that the Stock has not been registered under the
1933 Act or state securities laws on the ground that this transaction is exempt
from registration, and that reliance by the Company on such exemptions is
predicated in part on Purchaser's representations set forth in this letter.

    Purchaser has been informed that under the 1933 Act, the Stock must be held
indefinitely unless it is subsequently registered under the 1933 Act or unless
an exemption from such registration (such as Rule 144) is available with respect
to any proposed transfer or disposition by Purchaser of the Stock.  Purchaser
further agrees that the Company may refuse to permit Purchaser to sell, transfer
or dispose of the Stock (except as permitted under Rule 144) unless there is in
effect a registration statement under the 1933 Act and any applicable state
securities

<PAGE>

laws covering such transfer, or unless Purchaser furnishes an opinion of counsel
reasonably satisfactory to counsel for the Company, to the effect that such
registration is not required.

    Purchaser also understands and agrees that there will be placed on the
certificate(s) for the Stock, or any substitutions therefor, legends stating in
substance:

    "These securities have not been registered under the Securities Act of
1933.  They may not be sold, offered for sale, pledged or hypothecated in the
absence of an effective registration statement as to the securities under said
act or an opinion of counsel satisfactory to the Company that registration is
not required."

    Purchaser has carefully read this letter and has discussed its requirements
and other applicable limitations upon Purchaser's resale of the Stock with
Purchaser's counsel.

                                       Very truly yours,

                                       RAYMOND JAMES & ASSOCIATES, INC.



                                       By:
                                          --------------------------------

                                       Title:
                                             -----------------------------


<PAGE>




                                        AVIRON


                   AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT


                                    JULY 18, 1995

<PAGE>

                                        AVIRON

                   AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT


    THIS AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT (the "Agreement") is
entered into as of July 18, 1995 by and among AVIRON, a California corporation
(the "Company"), the parties listed on Exhibit A hereto (the "Investors"), the
parties listed on Exhibit B hereto (the "Series A Warrant Holders"), and the
parties listed on Exhibit C hereto (the "Series B Warrant Holders").

                                       RECITALS

    WHEREAS the Company proposes to issue and sell up to 11,111,111 shares of
its Series C Preferred Stock ("Series C Preferred") as more fully described in
the Private Placement Memorandum, dated as of May 1995 (the "Private
Placement"); 

    WHEREAS the Investors are the purchasers of the Company's Series A
Preferred Stock pursuant to that certain Series A Preferred Stock Purchase
Agreement, dated as of June 19, 1992, by and among the Company and the
purchasers named therein (the "Series A Agreement"); the purchasers of the
Company's Series B Preferred Stock pursuant to that certain Series B Preferred
Stock Purchase Agreement, dated as of September 3, 1993, by and among the
Company and the Purchasers named therein (the "Series B Agreement"); and the
purchasers of the Company's Series C Preferred Stock pursuant to the Private
Placement;

    WHEREAS the Series A Warrant Holders are the holders of either Series A
Preferred Stock or Warrants to purchase Series A Preferred Stock of the Company,
the Series B Warrant Holders are the holders of either Series B Preferred Stock
or Warrants to purchase Series B Preferred Stock of the Company, and the
Founders are Peter Palese, J. Leighton Read, Bernard Roizman and Richard J.
Whitley; and

     WHEREAS, in connection with the Private Placement, the prospective
purchasers have requested that the Company extend certain rights to them with
respect to the Series C Preferred.  The Company has requested and the existing
Holders are willing to amend the rights given to them under the Amended and
Restated Investor Rights Agreement, dated as of September 3, 1993 (the "Prior
Agreement"), as amended as of March 15, 1995 by replacing such rights in their
entirety with the rights set forth in this Agreement.

    NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants, and conditions set forth in this Agreement and in the
agreements pursuant to which the Investors acquired their securities in the
Company, the parties mutually agree as follows:


                                          1.

<PAGE>
                                           
I. GENERAL

    1.1  PRIOR AGREEMENT SUPERSEDED.  Effective upon the initial closing of the
Private Placement, the Prior Agreement is hereby terminated and superseded in
its entirety by this Agreement.

    1.2  DEFINITIONS.  As used in this Agreement, the following terms shall
have the following respective meanings:

         "COMMISSION" shall mean the Securities and Exchange Commission or any
other federal agency at the time administering the Securities Act.

         "COMMON STOCK" shall mean shares of the Company's Common Stock, no par
value.

         "HOLDER" shall mean any holder of outstanding Registrable Securities. 
For purposes of Sections 3.2 through 3.12 of this Agreement only, the definition
of "Holder" also includes Michigan.

         "INITIATING HOLDERS" shall mean any Holder or Holders of not less than
40% of the then outstanding Registrable Securities. 

         "MICHIGAN" refers to the Regents of the University of Michigan, a
constitutional corporation of the state of Michigan.

         "MICHIGAN SHARES" refers to shares of Series B Preferred Stock of the
Company issued to  Michigan, pursuant to the Stock Transfer Agreement, dated as
of February 24, 1995, between the Company and Michigan (the "Michigan
Agreement").

         "MICHIGAN WARRANT" refers to a warrant to purchase shares of Common
Stock  which the Company is obligated to issue to Michigan under certain
circumstances, as provided in the Michigan Agreement.

         "MICHIGAN WARRANT SHARES" refers to the shares of Common Stock issued
under the Michigan Warrant.

         "PREFERRED STOCK" shall mean shares of the Company's Preferred Stock.

         "REGISTRABLE SECURITIES" means (i) shares of Common Stock issued or
issuable pursuant to the conversion or exercise of the Shares  and (ii) shares
of Common Stock issued as a dividend or other distribution with respect to, or
in exchange or in replacement of, the Shares, excluding in all cases, however
(including exclusion from the calculation of the number of outstanding
Registrable Securities), any Registrable Securities sold by a person, (x) in a
transaction pursuant to Rule 144, or (y) pursuant to a registration statement
under this Agreement


                                          2.

<PAGE>

or (z) in a transaction in which his rights under this Agreement are not
transferred, including a transaction pursuant to a registration statement under
this Agreement.  For purposes of Sections 3.2 through 3.12 of this Agreement
only, the definition of "Registrable Securities" also includes the Michigan
Warrant Shares.

         The terms "REGISTER," "REGISTERED" and "REGISTRATION" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act, and the declaration or ordering of the
effectiveness of such registration statement by the Commission.

         "REGISTRATION EXPENSES" shall mean all expenses incurred by the
Company in complying with Sections 3.1, 3.2 and 3.9 hereof, including, without
limitation, all registration and filing fees, printing expenses, fees and
disbursements of counsel for the Company, fees and disbursements of a single
special counsel for the Holders not to exceed $20,000, blue sky fees and
expenses, and the expense of any special audits incident to or required by any
such registration (but excluding the compensation of regular employees of the
Company which shall be paid in any event by the Company).

         "RESTRICTED SECURITIES" shall mean the securities of the Company
required to bear the legend set forth in Section 2.2 hereof.  

         "SECURITIES ACT" shall mean the Securities Act of 1933, as amended, or
any similar federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

         "SELLING EXPENSES" shall mean all underwriting discounts and selling
commissions applicable to the sale.

         "SHARES" shall mean (i) the securities of the Company held by the
Investors and Founders as described on Exhibit A, (ii) the securities issuable
upon exercise of the Warrants to purchase Series A Preferred Stock held by the
Series A Warrant Holders as described on Exhibit B, or (iii) the securities
issuable upon exercise of the Warrants to purchase Series B Preferred Stock held
by the Series B Warrant Holders as described on Exhibit C.  For purposes of
Sections 3.2 through 3.12 of this Agreement only, the definition of "Shares"
also includes the Michigan Shares and the Michigan Warrant Shares. 


                                 II. TRANSFERABILITY

    2.1  RESTRICTIONS ON TRANSFERABILITY.   The Shares and any Preferred Stock
or Common Stock into which the Shares may be convertible or exercisable, shall
not be transferable except upon the conditions specified in this Agreement,
which conditions are intended to insure compliance with the provisions of the
Securities Act, or, in the case of Section 3.8 hereof, to assist in an orderly
distribution.  Each Investor will cause any proposed transferee of the Shares
(or of the Preferred Stock or Common Stock into which the Shares may be
convertible or


                                          3.

<PAGE>

exercisable) held by an Investor to agree to take and hold such securities
subject to the provisions and upon the conditions specified in this Agreement.

    2.2  RESTRICTIVE LEGEND.  Each certificate representing (i) the Shares, or
(ii) shares of the Company's Common Stock or Preferred Stock issued upon
conversion or exercise of the Shares and (iii) any securities issued in respect
of the Shares or such Common Stock or Preferred Stock, shall (unless otherwise
permitted by the provisions of Section 2.3 below) be stamped or otherwise
imprinted with a legend in substantially the following form (in addition to any
legend required under applicable state securities laws):

         THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE BEEN
         ACQUIRED FOR INVESTMENT UNDER AN EXEMPTION FROM THE
         REGISTRATION REQUIREMENTS OF THE SECURITIES ACT OF 1933. 
         SUCH SHARES MAY NOT BE OFFERED, SOLD OR TRANSFERRED IN THE
         ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT UNDER SAID
         ACT OR AN EXEMPTION THEREFROM OR IN CONTRAVENTION OF THE
         AGREEMENT COVERING THE PURCHASE OF THESE SHARES AND
         RESTRICTING THEIR TRANSFER.  COPIES OF THE AGREEMENT MAY BE
         OBTAINED AT NO COST BY WRITTEN REQUEST MADE BY THE HOLDER OF
         RECORD OF THIS CERTIFICATE TO THE SECRETARY OF THE
         CORPORATION AT ITS PRINCIPAL OFFICE.

    2.3  NOTICE OF PROPOSED TRANSFERS.  The holder of each certificate
representing Restricted Securities by acceptance thereof agrees to comply in all
respects with the provisions of this Section 2.3.  Prior to any proposed
transfer of any Restricted Securities, unless there is in effect a registration
statement under the Securities Act covering the proposed transfer, the holder
thereof shall give written notice to the Company of such holder's intention to
effect such transfer.  Each such notice shall describe the manner and
circumstances of the proposed transfer in sufficient detail, and shall be
accompanied (except in the following cases, with respect to which the
requirements set forth in the balance of this sentence need not be complied
with:  transactions in compliance with Rule 144 or Rule 144A so long as the
Company is furnished with evidence of compliance with such Rule; transactions
involving the distribution of Restricted Securities by any Investor which is a
general or limited partnership to any of its partners, or retired partners, or
to the estate of any of its partners or retired partners; transactions involving
the transfer of Restricted Securities by any holder who is an individual to his
family members or to a trust for the benefit of such shareholder or his family
members; or transfers not involving a change in beneficial ownership) by (i) a
written opinion of legal counsel who shall be reasonably satisfactory to the
Company addressed to the Company and reasonably satisfactory in form and
substance to the Company's counsel, to the effect that the proposed transfer of
the Restricted Securities may be effected without registration under the
Securities Act, (ii) a "no action" letter from the Commission to the effect that
the distribution of such securities without registration will not result in a 
recommendation by the staff of the Commission that action be taken with respect
thereto, or


                                          4.

<PAGE>

(iii) such other showing that may be reasonably satisfactory to legal counsel to
the Company, whereupon the holder of such Restricted Securities shall be
entitled to transfer such Restricted Securities in accordance with the terms of
the notice delivered by the holder to the Company.  Each certificate evidencing
the Restricted Securities transferred as above provided shall bear the
appropriate restrictive legend set forth in Section 2.2 above, except that such
certificate shall not bear such restrictive legend if in the opinion of counsel
for the Company such legend is not required in order to establish compliance
with any provisions of the Securities Act.  All Restricted Securities
transferred as above that continue to bear the restrictive legend set forth in
Section 2.2 shall continue to be subject to the provisions of this Section 2.3
in the same manner as before such transfer.

                               III. REGISTRATION RIGHTS

    3.1  REQUESTED REGISTRATION.  Prior to such time as the Company has
effected two registrations pursuant to this Section 3.1 and such registrations
have been declared or ordered effective, if the Company shall receive from
Initiating Holders a written request that the Company effect any registration
(other than a registration on Form S-3 or any comparable form of registration
statement) with respect to Registrable Securities having an anticipated
aggregate offering price to the public of at least $7,500,000 (before deduction
of underwriter commissions and expenses), the Company will:

         (a)  promptly give written notice of the proposed registration to all
other Holders; and

         (b)  as soon as practicable, use its diligent best efforts to effect
such registration (including, without limitation, the execution of an
undertaking to file post-effective amendments, appropriate qualification under
applicable blue sky or other state securities laws and appropriate compliance
with applicable regulations issued under the Securities Act) as may be so
requested and as would permit or facilitate the sale and distribution of all or
such portion of such Registrable Securities as are specified in such request,
together with all or such portion of the Registrable Securities of any Holder or
Holders joining in such request as are specified in a written request given
within 15 days after receipt of such written notice from the Company; provided
that the Company shall not be obligated to take any action to effect any such
registration, qualification or compliance pursuant to this Section 3.1:

              (i)  In any particular jurisdiction in which the Company would be
required to execute a general consent to service of process in effecting such
registration, qualification or compliance unless the Company is already subject
to service in such jurisdiction and except as may be required by the Securities
Act;
 
              (ii) Prior to the earlier to occur of (x) six months following
the effective date of the registration statement pertaining to the first
underwritten public offering of securities of the Company for its own account
and (y) August 31, 1997; or


                                          5.

<PAGE>

              (iii)     If at the time of the request to register Registrable
Securities the Company gives notice within 30 days of such request that it is
engaged or has fixed plans to engage within 90 days of the time of the request
in an initial firmly underwritten registered public offering as to which the
Holders may include Registrable Securities pursuant to Sections 3.1 or 3.2.

    Subject to the foregoing clauses (i) through (iii) and to Section 3.1(d),
the Company shall file a registration statement covering the Registrable
Securities so requested to be registered as soon as practicable after receipt of
the request of the Initiating Holders.

         (c)  UNDERWRITING.  If the Initiating Holders intend to distribute the
Registrable Securities covered by their request by means of an underwriting,
they shall so advise the Company as a part of their request made pursuant to
Section 3.1 and the Company shall include such information in the written notice
referred to in Section 3.1(a).  The right of any Holder to registration pursuant
to Section 3.1 shall be conditioned upon such Holder's participation in such
underwriting and the inclusion of such Holder's Registrable Securities in the
underwriting to the extent requested (unless otherwise mutually agreed by a
majority in interest of the Holders and such Holder) to the extent provided
herein.

    The Company shall (together with all Holders proposing to distribute their
securities through such underwriting) enter into an underwriting agreement in
customary form with the underwriter or underwriters selected for such
underwriting by a majority in interest of the Initiating Holders with the
approval of the Company, which approval shall not be unreasonably withheld.
Notwithstanding any other provision of this Section 3.1, if the underwriter
determines that marketing factors require a limitation of the number of shares
to be underwritten and so advises the Initiating Holders in writing, then the
Initiating Holders shall so advise all Holders (except those Holders who have
indicated to the Company their decision not to distribute any of their
Registrable Securities through such underwriting) and the number of shares of
Registrable Securities that may be included in the registration and underwriting
shall be allocated among all such Holders in proportion, as nearly as
practicable, to the respective amounts of Registrable Securities owned by such
Holders at the time of filing the registration statement. No Registrable
Securities excluded from the underwriting by reason of the underwriter's
marketing limitation shall be included in such registration.

    If any Holder disapproves of the terms of the underwriting, such person may
elect to withdraw therefrom by written notice to the Company, the underwriter
and the Initiating Holders.  The Registrable Securities and/or other securities
so withdrawn from such underwriting shall also be withdrawn from such
registration; provided, however, that, if by the withdrawal of such Registrable
Securities a greater number of Registrable Securities held by other Holders may
be included in such registration (up to the maximum of any limitation imposed by
the underwriters), then the Company shall offer to all Holders who have included
Registrable Securities in the registration the right to include additional
Registrable Securities in the same proportion used above in determining the
underwriter limitation; and, provided further that in the event that the
withdrawal of a Holder, and the subsequent inclusion of additional Registrable
Securities by other


                                          6.

<PAGE>

Holders, results in an anticipated aggregate offering price to the public of
less than $1,000,000 the Company shall no longer be required to effect such
registration pursuant to this Section 3.1.

    If the underwriter has not limited the number of Registrable Securities to
be underwritten, the Company may include securities for its own account or the
account of others in such registration if the underwriter so agrees and if the
number of Registrable Securities which would otherwise have been included in
such registration and underwriting will not thereby be limited.

         (d)  DELAY OF REGISTRATION.  If the Company shall furnish to the
Initiating Holders a certificate signed by the Chief Executive Officer of the
Company stating that, in the good faith judgment of the Board of Directors of
the Company, it would be seriously detrimental to the Company and its
shareholders for such registration statement to be filed on or before the date
filing would be required and it is therefore essential to defer the filing of
such registration statement, then the Company may direct that such request for
registration be delayed for two periods not in excess of 90 days each in any
one-year period.

    3.2  COMPANY REGISTRATION.

         (a)  If at any time or from time to time, the Company shall determine
to register any of its Common Stock, for its own account or for the account of
others (other than the Holders), other than a registration relating solely to
employee benefit plans or a registration relating solely to a Commission Rule
145 transaction or a registration on any registration form which does not
include substantially the same information as would be required to be included
in a registration statement covering the sale of Registrable Securities, the
Company will:

              (i)  promptly give to each Holder written notice thereof (which
shall include a list of the jurisdictions in which the Company intends to
attempt to qualify such securities under the applicable blue sky or other state
securities laws); and
 
              (ii) include in such registration (and any related qualification
under blue sky laws or other compliance), and in any underwriting involved
therein, all the Registrable Securities specified in a written request or
requests, made within 20 days after receipt of such written notice from the
Company, by any Holder or Holders.

         (b)  UNDERWRITING.  If the registration of which the Company gives
notice is for a registered public offering involving an underwriting, the
Company shall so advise the Holders as a part of the written notice given
pursuant to Section 3.2(a)(i).  In such event the right of any Holder to
registration pursuant to Section 3.2 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting to the extent provided herein.  All
Holders proposing to distribute their securities through such underwriting shall
(together with the Company and the other holders distributing their securities
through such underwriting) enter into an underwriting agreement in customary
form with the underwriter or underwriters selected for such underwriting by the
Company with the approval of the Board of Directors. Notwithstanding any other
provision of this Section 3.2, if the underwriter determines that marketing
factors require a limitation of the number of shares


                                          7.

<PAGE>

to be underwritten, the underwriter may limit the number of Registrable
Securities and shares of Common Stock to be included in the registration and
underwriting.  The Company shall so advise all Holders (except those Holders who
have indicated to the Company their decision not to distribute any of their
Registrable Securities or Common Stock through such underwriting), and the
number of shares of Registrable Securities that may be included in the
registration and underwriting shall be allocated among all Holders in
proportion, as nearly as practicable, to the respective amounts of Registrable
Securities owned by the Holders at the time of filing the registration
statement.

    No Registrable Securities excluded from the underwriting by reason of the
underwriter's marketing limitation shall be included in such registration.  If
any Holder disapproves of the terms of any such underwriting, such person may
elect to withdraw therefrom by written notice to the Company and the
underwriter.  The securities so withdrawn from such underwriting shall also be
withdrawn from such registration; provided, however, that, if by the withdrawal
of such securities a greater number of Registrable Securities held by other
Holders may be included in such registration (up to the maximum of any
limitation imposed by the underwriters), then the Company shall offer to all
Holders who have included Registrable Securities in the registration the right
to include additional Registrable Securities in the same proportion used above
in determining the underwriter limitation.

    3.3  EXPENSES OF REGISTRATION.  All Registration Expenses incurred in
connection with any registration, qualification or compliance pursuant to
Section 3.1, Section 3.2 or Section 3.9 herein shall be borne by the  Company. 
All Selling Expenses incurred in connection with any registrations hereunder
shall be borne by the holders of the securities so registered pro rata on the
basis of the number of shares so registered.  The Company shall not, however, be
required to pay for expenses of any registration proceeding begun pursuant to
Section 3.1, the request of which has been subsequently withdrawn by the
Initiating Holders (unless the withdrawal is based upon material information
concerning the Company of which the Initiating Holders were not aware at the
time of such request or unless the Holders of a majority of Registrable
Securities agree to forfeit their right to one requested registration pursuant
to Section 3.1 in which event such right shall be forfeited by all Holders), in
which case such expenses shall be borne by the holders of securities (including
Registrable Securities) requesting such registration in proportion to the number
of shares for which registration was requested. 

    3.4  REGISTRATION PROCEDURES.  In the case of each registration,
qualification or compliance effected by the Company pursuant to this Section 3,
the Company will keep each participating Holder advised in writing as to the
qualification and compliance and as to the completion thereof.  At its expense
the Company will:

         (a)  Keep such registration, qualification or compliance effective for
a period of 90 days or until the Holder or Holders have completed the
distribution described in the registration statement relating thereto, whichever
first occurs;

         (b)  Furnish such number of prospectuses and other documents incident
thereto in conformity with the requirements of the Act;


                                          8.

<PAGE>

         (c)  Prepare and file with the SEC such amendments and supplements to
such registration statement and the prospectus used in connection with such
registration statement as may be necessary to comply with the provisions of the
Act with respect to the disposition of all securities covered by such
registration statement;

         (d)  Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holders;
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions, unless the Company is
already subject to service in such jurisdiction and except as may be required by
the Act;

         (e)  In the event of any underwritten public offering, enter into and
perform its obligations under an underwriting agreement, in usual and customary
form, with the managing underwriter of such offering.  Each Holder participating
in such underwriting shall also enter into and perform its obligations under
such an agreement;

         (f)  Notify each Holder of Registrable Securities covered by such
registration statement at any time when a prospectus relating thereto is
required to be delivered under the Act or the happening of any event as a result
of which the prospectus included in such registration statement, as then in
effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing;

         (g)  Cause all such Registrable Securities registered pursuant
hereunder to be listed on each securities exchange on which similar securities
issued by the Company are then listed;

         (h)  Provide a transfer agent and registrar for all Registrable
Securities registered pursuant hereunder and a CUSIP number for all such
Registrable Securities, in each case not later than the effective date of such
registration; and

              (i)  Use its best efforts to furnish, at the request of any
Holder requesting registration of Registrable Securities pursuant to this
Section, on the date that such Registrable Securities are delivered to the
underwriters for sale in connection with a registration pursuant to this Section
if such securities are being sold through underwriters or, if such securities
are not being sold through underwriters, on the date that the registration
statement with respect to such securities becomes effective, (i) an opinion,
dated such date, of the counsel representing the Company for the purposes of
such registration, in form and substance as is customarily given to underwriters
in an underwritten public offering, addressed to the underwriters, if any, and
to the Holders requesting registration of Registrable Securities and (ii) a
letter dated such date, from the independent certified public accountants of the
Company, in form and substance as is customarily given by independent certified
public accountants to underwriters in an underwritten public offering, addressed
to the underwriters, if any, and to the Holders requesting registration  of
Registrable Securities.


                                          9.

<PAGE>

    3.5  INDEMNIFICATION.

         (a)  The Company will indemnify each Holder, each of its officers,
directors, partners and legal counsel, and each person controlling such Holder,
with respect to which registration, qualification or compliance has been
effected pursuant to this Section 3, against all claims, losses, damages and
liabilities (or actions in respect thereof) arising out of or based on (i) any
untrue statement (or alleged untrue statement) of a material fact contained in
any prospectus, offering circular or other similar document (including any
related registration statement, notification or the like) incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading in the light of the
circumstances under which they were made, or (ii) any violation by the Company
of any federal, state or common law rule or regulation applicable to the Company
in connection with any such registration, qualification or compliance, and will
reimburse each such Holder, each of its officers, directors, partners and legal
counsel, and each person  controlling such Holder, for any legal and any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, liability or action, as such expenses are incurred,
provided that the Company will not be liable in any such case to the extent that
any such claim, loss, damage, liability or expense arises out of or is based on
any untrue statement or omission based upon written information furnished to the
Company by an instrument duly executed by such Holder and stated to be
specifically for use therein or furnished by the Holder to the Company in
response to a request by the Company stating specifically that such information
will be used by the Company therein.

         (b)  Each Holder will, if Registrable Securities held by such Holder
are included in the securities as to which such registration, qualification or
compliance is being effected, indemnify the Company, each of its directors and
officers, each legal counsel and independent accountant of the Company, each
person who controls the Company within the meaning of the Securities Act, and
each other such Holder, each of its officers, directors, and partners and each
person controlling such Holder, against all claims, losses, damages and
liabilities (or actions in respect thereof) arising out of or based on any
untrue statement (or alleged untrue statement) of a material fact contained in
any such registration statement, prospectus, offering circular or other similar
document, or any omission (or alleged omission) to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading in the light of the circumstances under which they were made, and
will reimburse the Company, such Holders, such directors, officers, persons, or
control persons for any legal or any other expenses reasonably incurred in
connection with investigating or defending any such claim, loss, damage,
liability or action, as incurred, in each case to the extent, but only to the
extent, that such untrue statement (or alleged untrue statement) or omission (or
alleged omission) is made in such registration statement, prospectus, offering
circular or other document in reliance upon and in conformity with written
information furnished to the Company by an instrument duly executed by such
Holder and stated to be specifically for use therein; provided, however, that
the obligations of such Holders hereunder shall be limited to an amount equal to
the proceeds to each such Holder of Registrable Securities sold as contemplated
herein.


                                         10.

<PAGE>

         (c)  Each party entitled to indemnification under this Section 3.5
(the "Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has received written notice of any claim as to which indemnity may be sought,
and shall permit the Indemnifying Party to assume the defense of any such claim
or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose  approval shall not
unreasonably be withheld).  The Indemnified Party may participate in such
defense at such party's expense; provided, however, that the Indemnifying Party
shall bear the expense of such defense of the Indemnified Party if in the
opinion of counsel to the Indemnified Party representation of both parties by
the same counsel would be inappropriate due to actual or potential conflicts of
interest. The failure of any Indemnified Party to give notice as provided herein
shall relieve the Indemnifying Party of its obligations under this Section 3.5
only to the extent that such failure to give notice shall materially adversely
prejudice the Indemnifying Party in the defense of any such claim or any such
litigation.  No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the consent of each Indemnified Party, consent to
entry of any judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation.

    3.6  INFORMATION BY HOLDER.  Each Holder including securities of the
Company in any registration shall furnish to the Company such information
regarding such Holder and the distribution proposed by such Holder as the
Company may request in writing and as shall be required in connection with any
registration, qualification or compliance referred to in this Section 3.

    3.7  RULE 144 REPORTING.  With a view to making available the benefits of
certain rules and regulations of the Commission which may at any time permit the
sale of the Restricted Securities to the public without registration, after such
time as a public market exists for the Common Stock of the Company, the Company
agrees to:

         (a)  Use its best efforts to facilitate the sale of the Restricted
Securities to the public, without registration under the Securities Act,
pursuant to Rule 144 under the Securities Act, provided that this shall not
require the Company to file reports under the Securities Act and the Exchange
Act at anytime prior to the Company's being otherwise required to file such
reports.

         (b)  Make and keep public information available, as those terms are
understood and defined in Rule 144 under the Securities Act at all times after
90 days after the effective date of the first registration under the Securities
Act filed by the Company for an offering of its securities to the general
public;

         (c)  Use its best efforts to then file with the Commission in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Securities Exchange Act of 1934, as amended  (the
"Exchange Act") (at any time after it has become subject to such reporting
requirements);


                                         11.

<PAGE>

         (d)  So long as a Holder owns any Restricted Securities to furnish to
the Holder forthwith upon request a written statement by the Company as to its
compliance with the reporting requirements of said Rule 144 (at any time after
90 days after the effective date of the first registration statement filed by
the Company for an offering of its securities to the general public), and of the
Securities Act and the Exchange Act (at any time after it has become subject to
such reporting requirements), a copy of the most recent annual or quarterly
report of the Company, and such other reports and documents so filed by the
Company as such Holder may reasonably request in availing itself of any rule or
regulation of the Commission allowing a Holder to sell any such securities
without registration.

    3.8  "MARKET STAND-OFF" AGREEMENT.  Each Holder agrees not to sell or
otherwise transfer or dispose of any Common Stock (or other securities) of the
Company held by it for a period not to exceed 120 days following the effective
date of a registration statement of the Company filed under the Securities Act
if so requested by the Company and the underwriter of Common Stock (or other
securities of the Company), provided that:

         (a)  such agreement shall apply only to the first underwritten
registered public offering of the Company; and

         (b)  all officers and directors of the Company enter into similar
agreements and the Company uses its best efforts to cause all other holders of
at least 1% of the Company's voting securities enter into similar agreements. 
The Company may impose stop-transfer instructions with respect to the shares (or
securities) subject to the foregoing restriction until the end of such period.

    3.9  FORM S-3.  The Company shall use its best efforts to qualify for
registration on Form S-3 and to that end the Company shall register (whether or
not required by law to do so) its Common Stock under the Exchange Act within 12
months following the effective date of the first registration of any securities
of the Company on Form S-1.  After the Company has qualified for the use of Form
S-3, in addition to the rights contained in the foregoing provisions of this
Section 3, the Holders of Registrable Securities shall have the right to request
registrations on Form S-3 thereafter under this Section 3.9 (such requests shall
be in writing and shall state the number of shares of Registrable Securities to
be disposed of and the intended method of disposition of such shares by such
Holder or Holders), provided that the Company shall not be required to effect a
registration pursuant to this Section 3.9 unless the Holder or Holders
requesting registration propose to dispose of shares of Registrable Securities
which they reasonably anticipate will have an aggregate disposition price
(before deduction of underwriting discounts and expenses of sale) of at least
$1,000,000, and provided further that the Company shall not be required to
effect more than two registrations pursuant to this Section 3.9 in any 12 month
period.

    The Company shall give notice to all Holders of Registrable  Securities of
the receipt of a request for registration pursuant to this Section 3.9 and shall
provide a reasonable opportunity for other Holders to participate in the
registration.  Subject to the foregoing, the Company will use its best efforts
to effect promptly the registration of all shares of Registrable Securities on


                                         12.

<PAGE>

Form S-3, as the case may be, to the extent requested by the Holder or Holders
thereof for purposes of disposition.

    3.10 TRANSFER OF REGISTRATION RIGHTS. 

         (a)  Except as otherwise provided herein, the rights contained in this
Section 3 may be assigned or otherwise conveyed to a transferee or assignee of
Registrable Securities held by the Investors, which transferee or assignee shall
be considered a "Holder" for purposes of this Section 3, provided that (i) such
transfer is effected in accordance with applicable federal and state securities
laws, (ii) such transferee or assignee becomes a party to this Agreement or
agrees in writing to be subject to the terms hereof to the same extent as if he
were an original purchaser hereunder and (iii) such transferee or assignee (A)
is a wholly owned subsidiary or constituent partner (including limited partners
and retired partners) or affiliate of the transferring Holder if such Holder is
a partnership, or (B) acquires a number of shares of Registrable Securities
originally held by the transferring Holder equal to at least 1% of the then-
outstanding capital stock of the Company, and, provided further, that the
Company is given written notice by such Holder at the time of or within a
reasonable time after said transfer, stating the name and address of said
transferee or assignee and identifying the securities with respect to which such
registration rights are being assigned. 

         (b)  Except as otherwise provided herein, the rights contained in
Section 3, except for the rights contained in Section 3.1, may be assigned or
otherwise conveyed to a transferee or assignee of Registrable Securities held by
the Series A Warrant Holders, which transferee or assignee shall be considered a
"Holder" for purposes of this Section 3, provided that (i) such transfer is
effected in accordance with applicable federal and state securities laws, (ii)
such transferee or assignee becomes a party to this Agreement or agrees in
writing to be subject to the terms hereof to the same extent as if he were an
original purchaser hereunder and, provided further, that the Company is given
written notice by such Holder at the time of or within a reasonable time after
said transfer, stating the name and address of said transferee or assignee and
identifying the securities with respect to which such registration rights are
being assigned. 

    3.11 CERTAIN LIMITATIONS IN CONNECTION WITH FUTURE GRANTS OF REGISTRATION
RIGHTS.  From and after the date of this Agreement, the Company shall not,
without the prior written consent of the Holders of at least a majority of the
outstanding Registrable Securities enter into any agreement with any person or
persons providing for the granting to such holder of registration rights
superior to those granted to Holders pursuant to this Section 3.

    3.12 TERMINATION OF REGISTRATION RIGHTS.  All rights and duties provided
for with respect to any Holder in this Section 3 shall terminate on the later of
(a) the date five (5) years from the date of a Qualified IPO (as defined below
in Section 4.1 (d)), and (b) on which such Holder owns less than 1% of the then-
outstanding capital stock of the Company, except where such amount is held by a
Series A Warrant Holder.


                   IV. RIGHT OF FIRST REFUSAL ON COMPANY ISSUANCES


                                         13.

<PAGE>

    4.1  RIGHT OF FIRST REFUSAL.  The Company hereby grants to each Investor
(and its affiliates) who holds not less than 1,000,000 shares of Preferred Stock
(or Common Stock issued or issuable upon conversion of the Preferred Stock) the
right of first refusal to purchase, pro rata, all (or any part) of New
Securities (as defined in this Section 4.1) that the Company may, from time to
time propose to sell and issue.  In the case where the price per share at which
the New Securities are being offered is indeterminable or is equal to or less
than $1 (as adjusted for stock splits, reclassification or otherwise), such
Investor's (and its affiliates') pro rata share, for purposes of this right of
first refusal with respect to an offering at such a price, is the ratio, the
numerator of which is the number of shares of Common Stock then owned by such
Investor (and its affiliates) as a result of the conversion of any Preferred
Stock of the Company and issuable upon conversion of the Preferred Stock of the
Company then owned by such Investor (and its affiliates), and the denominator of
which is the total number of shares of Common Stock then outstanding as a result
of the conversion of any Preferred Stock of the Company or issuable upon
conversion of the Preferred Stock of the Company then outstanding.  In the case
where the price per share at which the New Securities are being offered is
greater than $1 (as adjusted for stock splits, reclassifications or otherwise),
such Investor's (and its affiliates') pro rata share, for purposes of this right
of first refusal with respect to an offering at such a price, is the ratio, the
numerator of which is the number of shares of Common Stock then owned by such
Investor (and its affiliates) as a result of the conversion of any Preferred
Stock of the Company and issuable upon conversion of the Preferred Stock of the
Company then owned by such Investor (and its affiliates), and the denominator of
which is the total number of shares of Common Stock outstanding immediately
prior to the issuance of the New Securities, assuming full conversion of all
outstanding shares of Preferred Stock of the Company.  This right of first
refusal shall be subject to the following provisions:

         (a)  "New Securities" shall mean any capital stock of the Company,
whether now authorized or not, and rights, options, or warrants to purchase said
capital stock, and securities of any type whatsoever that are, or may become,
convertible into said capital stock; provided, however, that "New Securities"
does not include (i) securities issued in any additional Closings (as defined in
the Series B Agreement); (ii) securities issuable upon conversion of or with
respect to Series A Preferred Stock or Series B Preferred Stock; (iii)
securities issued pursuant to an acquisition by the Company by merger, purchase
of substantially all of the assets, or other reorganization whereby the Company
owns more than 50% of the voting power of such entity; (iv) shares of the
Company's Common Stock (or related options) issued to employees, directors or
consultants of the Company pursuant to any employee stock offering, plan, or
arrangement approved by the Board of Directors; (v) shares of the Company's
Common Stock or Preferred Stock issued in connection with any stock split, stock
dividend, or similar recapitalization by the Company; (vi) securities issued
pursuant to equipment or debt financing or leases which are approved by the
Company's Board of Directors; (vii) securities issued pursuant to any corporate
partnering, strategic alliance, joint venture or licensing arrangement between
the Company and a third party; or (viii) securities issued by the Company other
than for cash or cash equivalents.

         (b)  In the event that the Company proposes to undertake an issuance
of New Securities, it shall give each Investor who together with its affiliates
holds not less than 1,000,000 shares of Common Stock of the Company issued or
issuable upon conversion of Preferred Stock,


                                         14.

<PAGE>

written notice of its intention, describing the type of New Securities, the
price, and the general terms upon which the Company proposes to issue the same. 
Each Investor who together with its affiliates holds not less than 1,000,000
shares of Common Stock of the Company, issued or issuable upon conversion of
Preferred Stock, shall have 20 days from the date of mailing of any such notice
to agree to purchase up to its full pro rata share of such New Securities for
the price and upon the general terms specified in the notice by giving written
notice to the Company and stating therein the quantity of New Securities to be
purchased.  Each Investor who together with its affiliates holds not less than
1,000,000 shares of Common Stock of the Company, issued or issuable upon
conversion of Preferred Stock, shall have a right of over allotment such that if
any Investor fails to exercise its right hereunder to purchase its full pro rata
portion of New Securities, the Company shall so notify the other Investors and
such Investors (and their affiliates) who have agreed to purchase all or any
part of their pro rata share of New Securities may purchase the nonpurchasing
Investors' portions on a pro rata basis, within ten days from the date of such
notice. 

         (c)  In the event that Investors (and their affiliates) fail to
exercise in full the right of first refusal within said 20 day period (plus the
ten day overallotment period, if applicable) the Company shall have 60 days
thereafter to sell or enter into an agreement providing for the closing of the
sale of the New Securities respecting which the Investors' (and their
affiliates') rights were not exercised within 30 days of such agreement at a
price and upon general terms no more favorable to the purchasers thereon than
specified in the Company's notice. In the event the Company has not sold the New
Securities within such 60 day period, the Company shall not thereafter issue or
sell any New Securities, without first offering such securities to the Investors
(and its affiliates) in the manner provided above. 

         (d)  The right of first refusal granted under this Agreement shall not
apply to and shall expire upon the first closing of the first firmly
underwritten public offering of Common Stock of the Company that is pursuant to
a registration statement filed with, and declared effective by, the Commission
under the Securities Act, covering the offer and sale of Common Stock to the
public at a per share price (prior to underwriter commissions and expenses) of
at least $2.50 (as adjusted for stock splits, dividends and similar events) and
at an aggregate offering price (before deduction for underwriter commissions and
expenses) of not less than $10,000,000 (a "Qualified IPO").

         (e)  This right of first refusal is assignable only to an affiliate of
a Holder or in connection with a sale or transfer of a number of shares of
Registrable Securities originally held by the assigning Holder equal to at least
1% of the then-outstanding capital stock of the Company.


                                         15.

<PAGE>

                                V. INFORMATION RIGHTS

    5.1  FINANCIAL INFORMATION.

         (a)  The Company will furnish the following information to each
Investor who holds together with its affiliates not less than 1,000,000 of
Common Stock issued or issuable upon conversion of Preferred Stock:

              (i)  As soon as practicable after the end of each fiscal year of
the Company, and in any event within 120 days thereafter, a consolidated balance
sheet of the Company and its subsidiaries, if any, as at the end of such fiscal
year, and consolidated statements of income and consolidated statements of cash
flows of the Company and its subsidiaries, if any, for such year, prepared in
accordance with generally accepted accounting principles consistently applied
and setting forth in each case in comparative form and figures for the previous
fiscal year, all in reasonable detail and certified by independent public
accountants of national standing selected by the Company.

              (ii) As soon as practicable after the end of each of the first
three quarterly accounting periods in each fiscal year, and in any event within
45 days thereafter, a consolidated balance sheet of the Company and its
subsidiaries, if any, as at the end of such quarter, and consolidated statements
of income and consolidated statements of cash flows of the Company and its
subsidiaries, if any, for each quarter and for the current fiscal year of the
Company to date, prepared in accordance with generally accepted accounting
principles consistently applied, except that such financial statements will not
contain the notes normally required by generally accepted accounting principles.

              (iii)     As soon as practicable after the adoption thereof, and
in any event no later than 15 days prior to the commencement of its fiscal year,
an annual operating plan for the forthcoming fiscal year, prepared on a
consolidated basis, including projected statements of profit and loss, cash flow
and balance sheets for each calendar quarter of such year, and, promptly after
preparation thereof, any revisions to such annual operating plan and any other
budgets.

         (b)  The covenants provided in Sections 5.1 and 5.2 shall terminate
upon the closing of a Qualified IPO.

    5.2  INSPECTION RIGHTS.  The Company shall permit each Investor who with
its affiliates holds at least 1,000,000 shares of Preferred Stock of the
Company, its attorney, or its other representative to visit and inspect the
Company's properties, to examine the Company's books of account and other
records, to make copies or extracts therefrom and to discuss the Company's
affairs, finances and accounts with its officers, management employees and
independent accountants, all at such reasonable times and as often as such
Investor may reasonably request.

    5.3  ASSIGNMENT OF RIGHTS TO INFORMATION.  The rights granted pursuant to
Sections 5.1 and 5.2 may not be assigned or otherwise conveyed by any Investor
or by any subsequent transferee of any such rights without the written consent
of the Company, which consent shall not


                                         16.

<PAGE>

be unreasonably withheld; provided that the Company may refuse such written
consent if the proposed transferee is a competitor of the Company as determined
by the Company's Board of Directors; and provided further, that no such written
consent shall be required if the transfer is made to a party who is not a
competitor of the Company and who is a parent, subsidiary, affiliate, partner or
group member of any Investor. 

    5.4  CONFIDENTIALITY.  Each Investor agrees that it will keep confidential
and will not disclose or divulge any confidential, proprietary or secret
information which such Investor may obtain from the Company, and which the
Company has prominently marked "confidential", "proprietary" or "secret" or has
otherwise identified as being such, pursuant to financial statements, reports
and other materials submitted by the Company as required hereunder, or pursuant
to visitation or inspection rights granted hereunder unless such information is
or becomes known to the Investor from a source other than the Company or is or
becomes publicly known, or unless the Company gives its written consent to the
Investor's release of such information, except that no such written consent
shall be required (and the Investor shall be free to release such information to
such recipient) if such information is to be provided to an Investor's counsel
or accountant, or to an officer, director or partner of an Investor, provided
that the Investor shall inform the recipient of the confidential nature of such
information, and shall instruct the recipient to treat the information as
confidential.

                                  VI. MISCELLANEOUS

    6.1  GOVERNING LAW.  This Agreement shall be governed by and construed in
accordance with the laws of the State of California applicable to contracts
between California residents entered into and to be performed entirely within
the State of California.

    6.2  SUCCESSORS AND ASSIGNS.  Except as otherwise provided herein, the
provisions hereof shall inure to the benefit of, and be binding upon, the
successors, assigns, heirs, executors and administrators of the parties hereto. 

    6.3  ENTIRE AGREEMENT.  This Agreement, the Series A Agreement and the
Series B Agreement constitute the full and entire understanding and agreement
among the parties with regard to the subjects hereof and thereof.

    6.4  NOTICES, ETC.  All notices and other communications required or
permitted hereunder shall be in writing and shall be effective five (5) days
after deposited by first-class mail, postage prepaid, with the United States
mail or delivery by hand or by messenger, if addressed (a) to an Investor, at
such Investor's address set forth on the attached Exhibit A, or at such other
address as such Investor shall have furnished to the Company in writing, or (b)
to any other holder of Registrable Securities, at such address as such holder
shall have furnished the Company in writing, or, until any such holder so
furnishes an address to the Company, then to and at the address of the last
holder of such Registrable Securities who has so furnished an address to the
Company, or (c) to the Company, at the address set forth below the Company's
name on the signature page to this Agreement or such other address as the
Company shall have furnished to each Investor and each such other holder in
writing.  Notwithstanding the above, any notice or


                                         17.

<PAGE>

communication to an address outside the United States shall be sent by telecopy
and confirmed in writing sent by courier guaranteeing delivery in no more than
two (2) business days.

    6.5  DELAYS OR OMISSIONS.  No delay or omission to exercise any right,
power or remedy accruing to any party, upon any breach or default of any other
party under this Agreement, shall impair any such right, power or remedy of such
party nor shall it be construed to be a waiver of any such breach or default, or
an acquiescence therein, or of or in any similar breach or default thereunder
occurring; nor shall any waiver of any single breach or default be deemed a
waiver of any other breach or default theretofore or thereafter occurring.  Any
waiver, permit, consent or approval of any kind or character on the part of any
party of any breach or default under this Agreement, or any waiver on the part
of any party of any provisions or conditions of this Agreement, must be in
writing and shall be effective only to the extent specifically set forth in such
writing.  All remedies, either under this Agreement, or by law or otherwise
afforded to any holder, shall be cumulative and not alternative.

    6.6  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which may be executed by less than all of the Investors,
each of which shall be enforceable against the parties actually executing such
counterparts, and all of which together shall constitute one instrument.
 
    6.7  SEVERABILITY.  In the case any provision of this Agreement shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

    6.8  AMENDMENTS.  The provisions of this Agreement may be amended at any
time and from time to time, and particular provisions of this Agreement may be
waived, with and only with an agreement or consent in writing signed by the
Company and by the holders of not less than a majority of the number of shares
of Registrable Securities outstanding as of the date of such amendment or
waiver.  Each Investor, Series A Warrant Holder, and Series B Warrant Holder
acknowledges that by the operation of this Section 6.8 the holders of a majority
of the outstanding Registrable Securities may have the right and power to
diminish or eliminate all rights of such Investor, Series A Warrant Holder, or
Series B Warrant Holder under this Agreement.  Notwithstanding anything herein
to the contrary, the parties agree that the Company may amend this Agreement at
any time after the date hereof, without obtaining the consent of any Holder, to
add as parties to this Agreement any purchasers of the Company's Series C
Preferred Stock pursuant to the Private Placement.  Any persons added to this
Agreement pursuant to this subparagraph shall become "Investors" under this
Agreement, and shares of Common Stock issuable upon conversion of the Series C
Preferred Stock held by such persons shall be "Registrable Securities" under
this Agreement.


                                         18.

<PAGE>

    The foregoing Investors Rights Agreement is hereby executed as of the date
first above written.

COMPANY
              
AVIRON   
              

By:
   ----
    J. Leighton Read, M.D.        
    Chief Executive Officer       
        1450 Rollins Road         
        Burlingame, CA 94010      
                   


INVESTORS:


Name of Investor:
                 ----------------------------

Authorized Signature:
                     ------------------------
                          Name and Title


                                         19.

<PAGE>

                                       INSTITUTIONAL VENTURE
                                       PARTNERS V
                                       by its General Partner
                                       Institutional Venture Management V


                                       By:
                                          -----------------------------------
                                            Reid W. Dennis
                                                 General Partner
                                                 3000 Sand Hill Road
                                                 Building 2, Suite 290
                                                 Menlo Park, CA  94025

                                       INSTITUTIONAL VENTURE
                                            MANAGEMENT V


                                       By:
                                          -----------------------------------

                                            Reid W. Dennis
                                            General Partner
                                                 3000 Sand Hill Road
                                                 Building 2, Suite 290
                                                 Menlo Park, CA  94025


                                       --------------------------------------
                                       J. Leighton Read, M.D.
                                            c/o Aviron
                                            1450 Rollins Road
                                            Burlingame, California 94010


                                       --------------------------------------
                                       Bernard Roizman
                                            5555 S. Everett, Apt. 11A
                                            Chicago, Illinois 60637


                                       --------------------------------------
                                       Betty Roizman
                                            5555 S. Everett, Apt. 11A


                                         20.

<PAGE>

                                            Chicago, Illinois 60637


                                         21.

<PAGE>

                                       ARCH VENTURE FUND LIMITED
                                       PARTNERSHIP
                                       a Delaware Limited Partnership

                                       By:  ARCH Development Corporation


                                       By:
                                          -----------------------------------
                                            Steven Lazarus, President

                                            135 South LaSalle Street
                                            Suite 3702
                                            Chicago, Illinois 60603


                                       --------------------------------------
                                       Albert L. Zesiger   

                                            75 Bluff Avenue
                                            Rowayton, Connecticut 06853


                                       --------------------------------------
                                       Peter Palese, Ph.D.
                                            414 Highwood Avenue
                                            Leonia, New Jersey 07605


                                       --------------------------------------
                                       John P. Curran
                                            237 Park Avenue
                                            Suite 900
                                            New York, New York 10017


                                         22.

<PAGE>



                                       --------------------------------------
                                       Steven R. Frank
                                            c/o Bear Sterns & Co.
                                            245 Park Avenue, 3rd Floor
                                            New York, NY  10169


                                       --------------------------------------
                                       David B. Musket     

                                            One Boston Place, 35th Floor
                                            Boston, Massachusetts 02108


                                       GC&H INVESTMENTS    


                                       By:
                                          -----------------------------------

                                       
                                       Name:
                                            ---------------------------------
                                                 Executive Partner

                                                 c/o Jeanne Meyer
                                                 Cooley Godward Castro 
                                                 Huddleson & Tatum
                                                 One Maritime Plaza, 20th Floor
                                                 San Francisco, California 94111


                                       --------------------------------------
                                       Julian N. Stern     

                                            84 Selby Lane
                                            Atherton, California 94027


                                       --------------------------------------
                                       Richard Whitley     
                                            216 Shades Crest Circle
                                            Birmingham, Alabama 35216


                                         23.

<PAGE>



                                       --------------------------------------
                                       Sally B. Whitley
                                            216 Shades Crest Circle
                                            Birmingham, Alabama 35216


                                       --------------------------------------
                                       Bruce A. Hironaka
                                            26 Lenox Road
                                            Kensington, California 94707  



                                       --------------------------------------
                                       Valerie Hironaka
                                            26 Lenox Road
                                            Kensington, California 94707


                                       THE MOUNT SINAI SCHOOL
                                       OF MEDICINE


                                       By:
                                          -----------------------------------
                                            Frank R. Landsberger, Ph.D
                                                 One Gustave L. Levy Plaza
                                                 New York, NY 10029-6574


                                       ACCEL IV L.P.
                                       
                                       By:  Accel IV Associates L.P.
                                            Its: General Partner


                                       By:
                                          -----------------------------------
                                            General Partner
                                                 1 Embarcadero Center
                                                 Suite 3820     
                                                 San Francisco, CA  94111


                                         24.

<PAGE>

                                       ACCEL JAPAN L.P.

                                       By:  Accel Japan Associates L.P.
                                            Its: General Partner


                                       By:
                                          -----------------------------------
                                            General Partner
                                                 1 Embarcadero Center
                                                 Suite 3820     
                                                 San Francisco, CA  94111



                                       ABINGWORTH BIOVENTURES


                                       By:
                                          -----------------------------------
                                            Daniel P. Finkelman
                                            Attorney-in-Fact
                                                 c/o Sanne & Cie
                                                 Boite Postale 566
                                                 L-2015 Luxembourg

                                       with a copy to:

                                            Dr. Stephen W. Bunting
                                                 Abingworth Management Limited
                                                 26 St. James Street
                                                 London SW1A 1HA
                                                 England


                                       FERRIS F. HAMILTON
                                       FAMILY TRUST


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         25.

<PAGE>


                                       MARY ANN HAMILTON
                                       TRUST FOR SELF


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       TAB PRODUCTS CO. PENSION PLAN


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------

                                       THE JENIFER ALTMAN 
                                       FOUNDATION


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       AMERICAN MEDICAL INT'L.
                                       PENSION PLAN


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         26.

<PAGE>

                                       TEMPLE-INLAND MASTER TRUST


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       ARTHUR D. LITTLE
                                       EMPLOYEE INVES. PLAN


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       THE DEAN WITTER FOUNDATION


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       ANDREW HEISKELL

                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         27.

<PAGE>



                                       ALFRED E. HELLER

                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       ELIZABETH HELLER MANDELL
                                       TRUST


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       DOMENIC MIZIO


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       THE RAISER MARITAL TRUST


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         28.

<PAGE>

                                       MARY VAN SCHUYLER RAISER


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       BARRIE RAMSAY ZESIGER


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       BEA ASSOCIATES
                                       PROFIT SHARING TRUST


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------

                                       BRINSON PARTNERS, INC.


                                       By:
                                          -----------------------------------
                                            Robert D. Blank
                                                 Partner
                                                 Brinson Partners, Inc.
                                                 209 South LaSalle Street
                                                 Suite 114
                                                 Chicago, IL 60604-1295


                                         29.

<PAGE>

                                       INTERHEALTH LIMITED, a California
                                       Limited Partnership


                                            ---------------------------------
                                            Dr. Alejandro Zaffaroni
                                            4005 Miranda Avenue, Suite 180
                                            Palo Alto, CA  94304

                                       ARCH VENTURE FUND II, L.P.
                                       a Delaware limited partnership

                                       By:  ARCH Management Partners II, L.P.
                                            its general partner

                                            By:  ARCH Venture Partners, L.P.
                                                 its general partner

                                                 By:  Lifework, Inc.
                                                      its general partner

                                                      By:
                                                         --------------------
                                                      Name:
                                                           ------------------
                                                      Title: Managing Director

                                  -------------------------------------------
                                  Eugene Garfield
                                  3501 Market Street
                                  Philadelphia, PA  19104


                                  -------------------------------------------
                                  Dr. H. R. Shepherd
                                  Opportunities Unlimited
                                  c/o Armstrong Pharmaceuticals
                                  71 Elm Street
                                  New Caanan, CT  06840


                                         30.

<PAGE>

                                  BRINSON VENTURE CAPITAL FUND III, L.P.


                                  By:  Brinson Partners, Inc.
                                       its General Partner


                                       By:
                                          -----------------------------------
                                            Robert D. Blank, Partner



                                  BRINSON TRUST COMPANY AS TRUSTEE
                                  OF THE BRINSON MAP VENTURE 
                                  CAPITAL FUND III



                                  By:
                                       --------------------------------------
                                       Robert D. Blank, Partner


                                         31.

<PAGE>

                                  WELLS FAMILY TRUST 
                                  S/P JOEL W. SCHRECK


                                  By:
                                     ------------------------------------
                                  Name:
                                       ----------------------------------
                                  Title:
                                        ---------------------------------



                                  A. CAREY ZESIGER REVOCABLE TRUST


                                  By:
                                     ------------------------------------
                                  Name:
                                       ----------------------------------
                                  Title:
                                        ---------------------------------


                                  NICOLA L. ZESIGER


                                  By:
                                     ------------------------------------
                                  Name:
                                       ----------------------------------
                                  Title:
                                        ---------------------------------


                                       ALEXA L. ZESIGER


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         32.

<PAGE>

                                       ALZA CORPORATION RETIREMENT PLAN


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                       SHEANA BUTLER


                                       By:
                                          -----------------------------------

                                            Name:
                                                 ----------------------------
                                            Title:
                                                  ---------------------------


                                         33.

<PAGE>

                                       ROVENT LIMITED PARTNERSHIP

                                       By:  Advent International Limited
                                            Partnership, General Partner

                                       By:  Advent International Corporation,
                                            General Partner


                                       By:
                                          -----------------------------------
                                            Charles Hsu, Vice President



                                       ADVENTACT LIMITED PARTNERSHIP

                                       By:  Advent International Limited
                                            Partnership, General Partner

                                       By:  Advent International Corporation,
                                            General Partner


                                       By:
                                          -----------------------------------
                                            Charles Hsu, Vice President


                                       GOLDEN GATE DEVELOPMENT AND INVESTMENT
                                       LIMITED PARTNERSHIP

                                       By:  Advent International Limited
                                            Partnership, General Partner

                                       By:  Advent International Corporation,
                                            General Partner


                                       By:
                                          -----------------------------------
                                            Charles Hsu, Vice President


                                         34.

<PAGE>

                                       ADVENT INTERNATIONAL INVESTORS II
                                       LIMITED PARTNERSHIP

                                       By:  Advent International Corporation,
                                            General Partner


                                       By:
                                          -----------------------------------
                                            Charles Hsu, Vice President



                                       --------------------------------------
                                       George Rupp
                                            202 Low Library
                                            Columbia University
                                            60 Morningside Drive
                                            New York, New York  10027


                                         35.

<PAGE>

                                      EXHIBIT A

                                SCHEDULE OF INVESTORS
                                 AS OF JULY 18, 1995


Name and Address                                                         Shares
- --------------------------------------------------------------------------------

SERIES A PREFERRED STOCK:

Institutional Venture Partners V . . . . . . . . . . . . . . . . .   2,955,000
Institutional Venture Management V . . . . . . . . . . . . . . . .      45,000
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


J. Leighton Read, M.D. . . . . . . . . . . . . . . . . . . . . . .     500,000
c/o Aviron
1450 Rollins Road
Burlingame, California 94010


Bernard Roizman, Sc.D. and Betty Roizman.. . . . . . . . . . . . .     100,000
5555 S. Everett, Apt. 11A
Chicago, Illinois 60637


Albert L. Zesiger. . . . . . . . . . . . . . . . . . . . . . . . .     300,000
75 Bluff Avenue
Rowayton, Connecticut 06853


Peter Palese, Ph.D.  . . . . . . . . . . . . . . . . . . . . . . .     100,000
Professor and Chairman
Department of Microbiology
Mount Sinai Medical Center
New York, New York 10029


John P. Curran . . . . . . . . . . . . . . . . . . . . . . . . . .      80,000
237 Park Avenue
Suite 900
New York, New York 10017


                                          1.

<PAGE>

Name and Address                                                         Shares
- --------------------------------------------------------------------------------

Steven R. Frank. . . . . . . . . . . . . . . . . . . . . . . . . .      50,000
c/o Bear Sterns & Co.
245 Park Avenue, 3rd Floor
New York, NY  10169


David B. Musket. . . . . . . . . . . . . . . . . . . . . . . . . .      50,000
One Boston Place, 35th Floor
Boston, Massachusetts 02108


GC&H Investments.. . . . . . . . . . . . . . . . . . . . . . . . .      50,000
c/o Jeanne Meyer
Cooley Godward Castro Huddleson & Tatum
One Maritime Plaza, 20th Floor
San Francisco, California 94111


Julian N. Stern. . . . . . . . . . . . . . . . . . . . . . . . . .      50,000
84 Selby Lane
Atherton, California 94025


Richard Whitley. . . . . . . . . . . . . . . . . . . . . . . . . .      10,000
Sally B. Whitley
216 Shades Crest Circle
Birmingham, Alabama 35216


Bruce A. Hironaka. . . . . . . . . . . . . . . . . . . . . . . . .      10,000
Valerie Hironaka
26 Lenox Road
Kensington, California 94707


ARCH VENTURE FUND  . . . . . . . . . . . . . . . . . . . . . . . .     700,000
Limited Partnership
135 South LaSalle Street
Suite 3702
Chicago, Illinois 60603


                                          2.

<PAGE>

Name and Address                                                         Shares
- --------------------------------------------------------------------------------

SERIES B PREFERRED STOCK:

Accel IV L.P.  . . . . . . . . . . . . . . . . . . . . . . . . . .   2,811,111
Accel Japan L.P. . . . . . . . . . . . . . . . . . . . . . . . . .     244,444
One Embarcadero Center
Suite 3820
San Francisco, CA  94111


Abingworth Bioventures . . . . . . . . . . . . . . . . . . . . . .   2,777,778
c/o Sanne & Cie
Boite Postale 566
L-2015 Luxembourg
Attn:  Karl U. Sanne
Telecopier: (352) 43 54 10

With a copy to:

    Dr. Stephen W. Bunting
    Abingworth Management Limited
    26 St. James's Street
    London SW1A 1HA
    England
    Telecopier:  (44) (71) 930-1891

and to:

    Daniel P. Finkelman, Esq.
    Testa, Hurwitz & Thibeault
    53 State Street, Exchange Place
    Boston, Massachusetts  02109
    Telecopier:  (617) 248-7100


Brinson Venture Capital Fund III, L.P. . . . . . . . . . . . . . .   1,910,624
Brinson Trust Company as Trustee of the. . . . . . . . . . . . . .     311,598
  Brinson MAP Venture Capital Fund III
c/o Brinson Partners, Inc.
209 South LaSalle Street
Suite 114
Chicago, IL 60604-1295


                                          3.

<PAGE>

Name and Address                                                         Shares
- --------------------------------------------------------------------------------

Institutional Venture Partners V. . . . . . . . . . . . . . . . .    2,695,500
Institutional Venture Management V. . . . . . . . . . . . . . . .       61,100
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


ARCH VENTURE FUND II, L. P.. . . . . . . . . . . . . . . . . . . .     277,778
135 South LaSalle Street
Suite 3702
Chicago, Illinois 60603

Ferris F. Hamilton Family Trust. . . . . . . . . . . . . . . . . .      49,500
Mary Ann Hamilton Trust for Self . . . . . . . . . . . . . . . . .      76,500
The Jenifer Altman Foundation. . . . . . . . . . . . . . . . . . .      49,500
American Medical Int'l. Pension Plan . . . . . . . . . . . . . . .     450,000
Temple-Inland Master Trust . . . . . . . . . . . . . . . . . . . .     495,000
Arthur D. Little Employee Inves. Plan. . . . . . . . . . . . . . .     405,000
The Dean Witter Foundation . . . . . . . . . . . . . . . . . . . .      72,000
Andrew Heiskell. . . . . . . . . . . . . . . . . . . . . . . . . .      76,500
Alfred E. Heller . . . . . . . . . . . . . . . . . . . . . . . . .      49,500
Elizabeth Heller Mandell Trust . . . . . . . . . . . . . . . . . .      49,500
Domenic Mizio. . . . . . . . . . . . . . . . . . . . . . . . . . .      76,500
The Raiser Marital Trust . . . . . . . . . . . . . . . . . . . . .      99,000
Mary Van Schuyler Raiser . . . . . . . . . . . . . . . . . . . . .      27,000
Barrie Ramsay Zesiger. . . . . . . . . . . . . . . . . . . . . . .      99,000
BEA Associates Profit Sharing Trust. . . . . . . . . . . . . . . .      99,000
Wells Family Trust S/P Joel W. Schreck . . . . . . . . . . . . . .      99,000
A. Carey Zesiger Revocable Trust . . . . . . . . . . . . . . . . .      36,000
Nicola L. Zesiger. . . . . . . . . . . . . . . . . . . . . . . . .      36,000
Alexa L. Zesiger . . . . . . . . . . . . . . . . . . . . . . . . .      31,500
Alza Corporation Retirement Plan . . . . . . . . . . . . . . . . .      49,500
Sheana Butler. . . . . . . . . . . . . . . . . . . . . . . . . . .      27,000
    c/o BEA Associates
    153 E. 53rd Street, 58th Floor
    New York, NY  10022

Dr. H.R. Shepherd. . . . . . . . . . . . . . . . . . . . . . . . .     166,667
Opportunities Unlimited
c/o Armstrong Pharmaceuticals
71 Elm Street
New Caanan, CT  06840


                                          4.

<PAGE>

Name and Address                                                         Shares
- --------------------------------------------------------------------------------

Dr. Alejandro Zaffaroni. . . . . . . . . . . . . . . . . . . . . .     277,778
Attention:  Gonzalo Silviera
c/o Interhealth Limited
4005 Miranda Avenue, Suite 180
Palo Alto, CA  94304

Eugene Garfield. . . . . . . . . . . . . . . . . . . . . . . . . .     277,778
3501 Market Street
Philadelphia, PA  19104

Peter Palese, Ph.D.  . . . . . . . . . . . . . . . . . . . . . . .      55,556
414 Highwood Avenue
Leonia, New Jersey 07605

GC&H Investments.. . . . . . . . . . . . . . . . . . . . . . . . .      40,000
c/o Jeanne Meyer
Cooley Godward Castro Huddleson & Tatum
One Maritime Plaza, 20th Floor
San Francisco, California 94111


COMMON STOCK:

Peter Palese, Ph.D.  . . . . . . . . . . . . . . . . . . . . . . .     750,000
414 Highwood Avenue
Leonia, New Jersey 07605


J. Leighton Read, M.D. . . . . . . . . . . . . . . . . . . . . . .     750,000
c/o Aviron
1450 Rollins Road
Burlingame, CA  94010


Bernard Roizman, Sc.D. . . . . . . . . . . . . . . . . . . . . . .     750,000
5555 S. Everett, Apt. 11A
Chicago, IL  60637


Richard J. Whitley . . . . . . . . . . . . . . . . . . . . . . . .     750,000
216 Shades Crest Circle
Birmingham, AL  35216


                                          5.

<PAGE>

                                      EXHIBIT B

                         SCHEDULE OF SERIES A WARRANT HOLDERS


Name and Address                                       No. of Shares Purchasable
- --------------------------------------------------------------------------------

Mount Sinai Medical Center . . . . . . . . . . . . . . . . . . . .     225,000
One Gustave L. Levy Plaza
New York, New York 10029-6574

<PAGE>

                                      EXHIBIT C

                         SCHEDULE OF SERIES B WARRANT HOLDERS



Name and Address                                       No. of Shares Purchasable
- --------------------------------------------------------------------------------


Lease Management Services, Inc.. . . . . . . . . . . . . . . . . .     194,445
2500 Sand Hill Road
Suite 101
Menlo Park, CA  94025

<PAGE>

                                  TABLE OF CONTENTS

                                                                            PAGE

I.  General.................................................................  2.
       1.1   Prior Agreement Superseded.....................................  2.

II.  Transferability........................................................  3.
       2.1   Restrictions on Transferability................................  3.
       2.2   Restrictive Legend.............................................  4.
       2.3   Notice of Proposed Transfers...................................  4.

III.  Registration Rights...................................................  5.
       3.1   Requested Registration.........................................  5.
       3.2   Company Registration...........................................  7.
       3.3   Expenses of Registration.......................................  8.
       3.4   Registration Procedures........................................  8.
       3.5   Indemnification................................................  9.
       3.6   Information by Holder.......................................... 11.
       3.7   Rule 144 Reporting............................................. 11.
       3.8   "Market Stand-off" Agreement................................... 12.
       3.9   Form S-3....................................................... 12.
       3.10  Transfer of Registration Rights................................ 12.
       3.11  Certain Limitations in Connection with Future Grants of
             Registration Rights............................................ 13.
       3.12  Termination of Registration Rights............................. 13.

IV.  RIGHT OF FIRST REFUSAL ON COMPANY ISSUANCES............................ 13.
       4.1   Right of First Refusal......................................... 13.

V.  Information Rights...................................................... 15.
       5.1   Financial Information.......................................... 15.
       5.2   Inspection Rights.............................................. 16.
       5.3   Assignment of Rights to Information............................ 16.
       5.4   Confidentiality................................................ 16.

VI.  Miscellaneous.......................................................... 17.
       6.1   Governing Law.................................................. 17.
       6.2   Successors and Assigns......................................... 17.
       6.3   Entire Agreement............................................... 17.
       6.4   Notices, etc................................................... 17.
       6.5   Delays or Omissions............................................ 17.
       6.6   Counterparts................................................... 18.
       6.7   Severability................................................... 18.
       6.8   Amendments..................................................... 18.


                                          i

<PAGE>

                                  TABLE OF CONTENTS
                                     (CONTINUED)

                                                                            PAGE


                                          ii


<PAGE>

                                                                   Exhibit 5.1

                               [Letterhead]

                              COOLEY GODWARD
                    COOLEY GODWARD CASTRO HUDDLESON & TATUM
                           Five Palo Alto Square
                            3000 El Camino Real
                          Palo Alto, CA 94306-2155
                            MAIN 415 843-5000
                            FAX 415 857-0663

June 3, 1996

Aviron
297 North Bernardo Avenue
Mountain View, CA 94043


RE:  OPINION


Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection 
with the filing on June 4, 1996 by Aviron (the "Company") of a Registration 
Statement on Form S-1 (the "Registration Statement") with the Securities and 
Exchange Commission (the "Commission"), including a prospectus (which may be 
filed with the Commission pursuant to Rule 424(b) of Regulation C promulgated 
under the Securities Act of 1933, as amended) (the "Prospectus"), and the 
underwritten public offering of up to 3,450,000 shares of the Company's 
common stock (the "Common Stock") (including 450,000 shares of Common Stock 
for which the underwriters have been granted an over allotment option).

In connection with this opinion, we have (i) examined and relied upon the 
Registration Statement and related Prospectus, the Company's Articles of 
Incorporation and Bylaws, as amended, and the originals or copies certified 
to our satisfaction of such records, documents, certificates, memoranda and 
other instruments as in our judgment are necessary or appropriate to enable 
to render the opinion expressed below and (ii) assumed that the shares of the 
Common Stock will be sold by the underwriters at a price established by the 
Pricing Committee of the Board of Directors of the Company.

On the basis of the foregoing, and in reliance thereon, we are of the opinion 
that the Common Stock, when sold and issued in accordance with the 
Registration Statement and related Prospectus, will be validly issued, fully 
paid and nonassessable.



<PAGE>

Aviron
June 3, 1996
Page 2


We consent to the reference to our firm under the caption "Legal Matters" in 
the Prospectus included in the Registration Statement and to the filing of 
this opinion as an exhibit to the Registration Statement.

Very truly yours,

COOLEY GODWARD CASTRO
HUDDLESON & TATUM




Robert J. Brigham


cc:  J. Leighton Read, M.D.




<PAGE>

                                                                    EXHIBIT 10.1

<PAGE>

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT HAS BEEN DELETED, AS
MARKED BY BRACKETS, AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.



                                  LICENSE AGREEMENT

    License Agreement dated as of July 1, 1992, between ARCH DEVELOPMENT
CORPORATION, an Illinois not-for-profit corporation ("ARCH"), and VECTOR
PHARMACEUTICALS, INC., a California corporation ("Licensee").


                                PRELIMINARY STATEMENT

    ARCH holds rights to the Licensed Patent Rights described below.

    Licensee wishes to obtain the right to exploit the Licensed Patent Rights
in commercial settings.

    Therefore, in consideration of the mutual obligations set forth herein and
of other valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, ARCH and Licensee agree as follows.

                                      ARTICLE I
                                     DEFINITIONS

    The following capitalized terms are used in this Agreement with the
following meanings:

    "AFFILIATE" means, as to any person or entity, any other person or entity
which is directly or indirectly controlled by, or is under common control with,
such person or entity.  For purposes of the preceding definition, "control"
means the right to control, or actual control of, the management of such other
entity, whether by ownership of voting securities, by agreement, or otherwise.

    "COMBINATION PRODUCT" means any product that is comprised in part of a
Licensed Product and in part of one or more other biologically active
diagnostic, preventive or therapeutic agents which are not themselves Licensed
Products (the "Other Agents").  "Other Agents" excludes diluents and vehicles of
Licensed Products.

    "COMMERCIAL SALE" means any transfer to another person or entity, for
value, after which transfer the seller has no right or power to determine the
transferee's resale price, if any.  A transfer by Licensee to an Affiliate or
sublicensee shall not constitute a Commercial Sale.  "Commercial Sale" does not
include distribution of free promotional samples of any Licensed Product or
Combination Product by Licensee or any of its Affiliates or sublicensees in
amounts determined to be commercially reasonable by Vector.

<PAGE>

    "IMPROVEMENTS" means all modifications, revisions or improvements to the
Inventions within the Scope hereafter owned by or subject to the rights of ARCH
which improve the performance, marketability, manufacture or quality of the
Inventions or any Licensed Product, but only to the extent such modifications,
revisions or improvements are not subject to the rights of any third party
funding source.

    "INVENTIONS" means the devices, machines, methods, processes,
manufactures, compositions of matter and uses (in each case whether patentable
or unpatentable) disclosed in or by the patents and patent applications listed
on Schedule I attached hereto.

    "LATER DEVELOPMENTS" means all discoveries, inventions, or other
proprietary matters within the Scope (other than Improvements) now or hereafter
owned by or subject to the rights of ARCH, but only to the extent such
discoveries, inventions or other proprietary matters are not subject to the
rights of any third party funding source.

    "LICENSED FIELD" means the prediction, monitoring,
diagnosis, prevention and treatment of disease in humans, animals and plants.

    "LICENSED PATENT RIGHTS" means (a) the patents and patent applications in
which are disclosed any and all Inventions, and (b) all patents and patent
applications which are divisions, continuations, continuations-in-part,
reissues, renewals, reexaminations, foreign counterparts, substitutions, or
extensions of or to any patent applications or patents described in clause (a)
of this sentence.

    "LICENSED PRODUCT" means any product within the scope of any claim of any
patent or patent application within the Licensed Patent Rights and any product
made by any art, method or process within the scope of any claim of any patent
or patent application within the Licensed Patent Rights.

    "NET SALES" means:

         (a)  with respect to Licensed Products, the gross sales price actually
    charged by Licensee or an Affiliate or sublicensee of Licensee in the
    Commercial Sale of such Licensed Product, less:

              (i)  trade, prompt payment, quantity or cash discounts, rebates,
         and non-affiliated brokers' or agents' commissions, each as actually
         and customarily allowed and taken;


                                         -2-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED



              (ii)  amounts actually repaid or credited to customers on account
         of rejections or returns of specified products on which Royalties have
         been paid hereunder or on account of retroactive price reductions
         affecting such products;

              (iii) customary freight and other transportation costs, including
         insurance charges, and duties, tariffs, sales, use and excise taxes
         and other governmental charges based directly on sales, turnover or
         delivery of the specified products and actually paid or allowed by
         Licensee, an Affiliate of Licensee or a sublicensee; and

              (iv)  commercially reasonable allowances for bad debts incurred
         with respect to the initial Licensed Product during the first full
         year of Commercial Sales of such Licensed Product, PROVIDED that such
         bad debt reserve shall be deemed extinguished within 180 days of the
         end of such first full year, and any amount of such reserve not
         actually debited in accordance with commercially reasonable practices
         during that period shall be deemed to be receipts of Net Sales for all
         purposes of this Agreement; and

         (b)  with respect to Combination Products, the gross sales price
    actually charged by Licensee or an Affiliate or sublicensee of Licensee in
    the Commercial Sale of such Combination Product, less the deductions set
    forth in subsections (a)(i) - (iv) above, multiplied by a fraction having
    (i) a numerator of [             ] and (ii) a denominator of the [        ]

    The "fair market value" for any Licensed Product or Other Agent shall be
    determined for [

         ] When no fair market value is available, the fraction set forth 
    above shall be changed to a fraction having (x) a numerator of [         ] 
    and (y) a denominator

    of [

              ] PROVIDED that in no event shall the fraction be less than [
                        ] if only one Other Agent is included with a Licensed
    Product(s) in such


                                         -3-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


    Combination Product, (B) [     ], if two Other Agents are included with a
    Licensed Product(s) in such Combination Product, and (C) [   ], if three or
    more Other Agents are included with a Licensed Product(s) in such
    Combination Product.  "Cost" as used above means [                      ]

    "PATENT COSTS" means a person's out-of-pocket expenses incurred in
connection with the preparation, filing, prosecution and maintenance of the
patents under the Licensed Patent Rights, including, among other items, the fees
and expenses of attorneys and patent agents, filing fees and maintenance fees,
but excluding costs involved in any patent infringement claims.

    "ROYALTIES" means all amounts payable under clauses (b) and
(c) of Section 3.1 of this Agreement.

    "SCOPE" means and shall be limited to (i) [          ] adapted for use in 
[    ] that are subject to an obligation of assignment to the University and 
in which ARCH has obtained property rights, and which have been developed (a) 
by [                                ] in the course of a collaborative 
research effort with one or more scientists from entities other than the 
University, or (b) by [    ]in the course of a research effort conducted 
principally in the laboratory [    ] and not in the course of a collaborative 
effort with one or more senior scientists at the University, and (ii) the 
[          ] described in [  ]of Schedule I attached hereto.  "Scope" does 
not include [               ]

    "SUBLICENSE" means any grant by Licensee of any rights to a sublicensee
under the terms of Section 2.1 of this Agreement.

    "TECHNICAL INFORMATION" means the technical information, know-how, 
processes, reagents, protocols, and samples of assay components, media and/or 
cell lines and procedures and formulations for producing same, if any, in 
ARCH's or [    ] possession, claimed or described in the Licensed Patent 
Rights, and which contribute in whole or in part to the practice of the 
Inventions.

    "TERRITORY" means worldwide.

    "UNIVERSITY" means the University of Chicago.


                                         -4-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


                                      ARTICLE II

                                   GRANT OF LICENSE

    2.1. GRANT.  ARCH hereby grants and agrees to grant to Licensee and its
Affiliates:

    (a)  an exclusive (except as otherwise specified in Sections
2.2 and 2.3) license to practice the Inventions and make, have made, use and
sell Licensed Products (whether singly or as part of a Combination Product, and
including the provision of services in connection therewith) under the Licensed
Patent Rights within the Licensed Field and within the Territory; and

    (b)  the exclusive right and authority to grant Sublicenses of the rights
granted in clause (a) above, subject to the provisions of this Agreement.

    2.2. RESERVATIONS.  ARCH reserves for itself and the University the 
irrevocable, non-transferable right to make and use (but not sell) Licensed 
Products and to use the Licensed Patent Rights, all for educational and 
research purposes only. In addition, the Inventions may have been conceived 
with the use of United States government funds.  Therefore, there is reserved 
from the rights granted hereunder the right of the United States government 
to practice the Inventions for its own purposes in such manner as it sees 
fit.  Licensee further acknowledges that third parties may have ownership 
interests in Improvements or Later Developments which may preclude the grant 
of an exclusive license to Licensee in such Improvements or Later 
Developments.  Neither ARCH nor the University shall have any obligation to 
pay Licensee a royalty or any other fee for the rights reserved in this 
Section.

    2.3. OTHER RIGHTS.  Licensee acknowledges and understands that pursuant 
to that certain Research Agreement by and between the University and 
[           ] dated [        ] as amended, the patents and patent 
applications identified as [    ] have been issued and filed [               ]
 ARCH agrees that it will use its good faith efforts to cause the University 
to obtain, and thereafter assign to ARCH, the patents and patent applications 
described above pursuant to the proposed Assignment Agreement between the 
University [    ] attached hereto as Exhibit A under substantially the same 
terms as are set forth in the [                ] so as to effectuate fully 
the intention of the parties to license to Licensee all of the patents and 
patent applications set forth on Schedule I attached hereto.  ARCH agrees 
that it will keep Licensee fully informed of the status of its efforts to 
obtain

                                         -5-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


[               ] agreement to the [                   ] as currently exists 
or as negotiated by ARCH in good faith.  Vector acknowledges that (i) 
notwithstanding ARCH's good faith efforts to enter into the [            ] 
with [                ] the agreement which ARCH may eventually enter into 
with [   ] may differ substantially from the [          ] and (ii) in the 
event the [        ] (or some other assignment instrument) is entered into 
between the University and [                  ] the rights granted in Section 
2.1 above are subject to all of the terms and conditions of such 
[             ] (or alternative assignment instrument).  ARCH shall not have 
any obligation to pay Licensee a royalty or any other fee for the rights 
granted to [  ] pursuant to the [              ] (or alternative assignment 
instrument).

    2.4. SUBLICENSES.  Licensee may enter into Sublicenses for the Licensed 
Patent Rights as Licensee shall determine in its reasonable discretion, 
PROVIDED that (i) Licensee shall give ARCH written notice of the execution of 
any Sublicense immediately upon such an event, (ii) Licensee shall promptly 
provide ARCH with a copy of each such Sublicense and any amendments and 
modifications thereto, (iii) Licensee may not assign any of its obligations 
hereunder to any sublicensee, (iv) each Sublicense shall provide that ARCH 
shall not be responsible for the performance by Licensee of any of Licensee's 
obligations under such Sublicense, and (v) the terms of any such Sublicense 
shall be consistent with the terms of this Agreement.  Upon the termination 
of this Agreement for any reason prior to the expiration of the 
last-to-expire patent under the Licensed Patent Rights, Licensee's rights 
(but not obligations) under each Sublicense shall automatically be deemed 
transferred to ARCH without the necessity of any notice or other 
communication from ARCH to the sublicensee, and each Sublicense shall 
continue thereafter in full force and effect in accordance with its terms.  
Licensee agrees to provide for such an event in each Sublicense in a manner 
reasonably acceptable to ARCH.

    2.5. IMPROVEMENTS. (a) ARCH hereby grants to Licensee an option, [    ] 
to include any Improvements within the licenses granted pursuant to Section 
2.1 on the terms otherwise set forth in this Agreement.  Licensee shall have 
the right, [    ] to request from [                     ] either 
telephonically or in writing, information regarding the existence or nature 
of any Improvements PROVIDED Licensee acknowledges and agrees that any 
failure of [ ] to provide such information will not constitute a breach of 
this Agreement by ARCH.  ARCH agrees to notify Licensee in writing of any 
Improvement [         ]of ARCH acquiring title to such Improvement, which 
notice shall describe the Improvement in general terms and shall be 
accompanied by a confidentiality agreement in reasonable form to be executed 
by Licensee.  Upon the execution of such

                                         -6-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


confidentiality agreement ARCH shall provide Licensee with sufficient details
regarding the subject Improvement to allow Licensee to evaluate its commercial
potential.

    (b)  Licensee shall have an exclusive period of [    ] after receipt of 
detailed information concerning an Improvement in which to notify ARCH in 
writing of its desire to exercise its option with respect to such 
Improvement.  If Licensee fails to deliver such notice within the applicable 
time, or notifies ARCH that it does not wish to exercise such option, 
Licensee shall have no further rights with respect to such Improvement of any 
kind or nature whatsoever.

    (c)  If Licensee exercises its option with respect to an Improvement, the
Improvement shall thereafter be deemed an "Invention" for all purposes of this
Agreement, and ARCH's and Licensee's rights and obligations with respect thereto
shall be as set forth in this Agreement.  Licensee agrees that it shall pay, or
at ARCH's option reimburse ARCH for, the Patent Costs incurred with respect to
the Licensed Patent Rights arising as a consequence of any such Invention
(including any Patent Costs for which ARCH is obligated to reimburse any
governmental agency), whether incurred before or after the date on which
Licensee exercises its option therefor.

    2.6. TECHNICAL INFORMATION.  ARCH agrees to provide Licensee with Technical
Information which comes within ARCH's possession from time to time during the
term of this Agreement.  Licensee shall be entitled to use (and shall be
entitled to allow its Affiliates and sublicensees to use) such Technical
Information internally in support of development, discovery, manufacturing and
marketing efforts for sales of Licensed Products, PROVIDED that any such use by
Licensee or its Affiliates or sublicensees shall be subject to the restrictions
set forth in Section 5.4 below.  ARCH further agrees to use its good faith
efforts to cause [                  ] to promptly deliver the reagents contained
in the Technical Information and the patent applications contained within the
Licensed Patent Rights in his possession to Licensee, at Licensee's expense.

    2.7. OWNERSHIP OF DISCOVERIES.  Each party acknowledges and agrees that any
and all discoveries, know-how, inventions, methods, ideas and the like
("Discoveries") made or discovered solely by its employees, consultants or
agents acting within the scope of their respective engagements shall be owned
solely by it and that any and all Discoveries made jointly by employees,
consultants or agents of each shall be jointly owned, all as determined in
accordance with U.S. laws of inventorship.  Nothing in the foregoing sentence
shall, however, be deemed to constitute the grant of any rights by one party to
the other in and to any Discoveries, or any other discoveries or inventions
owned by such party, which are not subject to this Agreement.


                                         -7-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED



                                     ARTICLE III

                                       PAYMENTS

    3.1. ROYALTIES.  For the licenses granted in Section 2.1 of this Agreement,
Licensee shall pay ARCH the amounts determined pursuant to subsections (a), (b)
and (c) below.

    (a)  Licensee shall provide ARCH written notice within fifteen (15) days 
of achievement of each of the milestone events set forth below in respect of 
any Licensed Products and Combination Products developed by Licensee, its 
Affiliates or sublicensees, [                                            ] 
events.  Within thirty (30) days after delivering each such notice, Licensee 
shall make the milestone payments to ARCH set forth below:

    (i)  Licensee, any of its Affiliates or any of its
    sublicensees [         ] for any such Licensed Product or Combination
    Product: [           ]

    (ii) [         ] with respect to any such Licensed Product or Combination 
    Product: [        ] and

    (iii)Licensee, any of its Affiliates or any of its sublicensees [    ] any
    such Licensed Product or Combination Product: [                    ]
    up to an aggregate maximum amount of [    .]  Such milestone payments shall
    be credited against any and all Royalties due to ARCH hereunder in amounts
    not to exceed [             ] of the Royalties due in any calendar quarter,
    if any, until Licensee shall have received credit for all such milestone 
    payments actually made.  If no U.S. patent issues to ARCH, or an issued 
    patent is invalidated, which patent or patent application contains 
    significant protection for the Inventions incorporated in a Licensed 
    Product for which milestone payments have been made, such milestone 
    payments shall instead be credited against any and all Royalties due to 
    ARCH hereunder in amounts not to exceed [               ] of the Royalties
    due in any calendar quarter.

    (b) A running royalty equal to [                ] of Net Sales of Licensed
Products and Combination Products sold by Licensee or any of its Affiliates; and

    (c) A running royalty determined with respect to each Sublicense entered
into by Licensee or any of its Affiliates as follows:


                                         -8-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


         (i) Where either (a) prior to execution of a Sublicense, Licensee or
         an Affiliate of Licensee has failed to [


                          ] or (b) Licensee has failed to provide evidence
         reasonably satisfactory to ARCH that [




                                                                          ] then

         all Licensee shall pay to ARCH [           ] of all amounts actually
         paid to Licensee or an Affiliate of Licensee by a sublicensee with
         respect to the Licensed Patent Rights so sublicensed (regardless of
         whether such payments are denominated as fees, royalties or otherwise,
         and whether paid at the time of or subsequent to the grant of such
         Sublicense), except that Licensee or an Affiliate of Licensee shall
         have the right to retain amounts received from such sublicensee
         specifically related to research and development funding activity,
         equity investments in Licensee or an Affiliate of Licensee by such
         sublicensee, loans by such sublicensee to Licensee or an Affiliate of
         Licensee, or other similar financing activities provided by such
         sublicensee for the benefit of Licensee or an Affiliate of Licensee;
         or

        (ii) in all other such cases, [   ] of Net Sales of Licensed Products
        and Combination Products sold by the subject sublicensee.

All payments made to ARCH pursuant to this Section 3.1 shall be non-refundable
under any and all circumstances.

    3.2. CALCULATION OF ROYALTIES. (a) Royalties shall be calculated on a
calendar quarter basis.  Payment of Royalties with respect to each calendar
quarter shall be due within sixty (60) days after the end of each quarter,
beginning with the calendar quarter in which the first commercial sale of
Licensed Products occurs.

    (b)  At the same time that it makes payment of Royalties due with respect
to a calendar quarter, Licensee shall deliver to ARCH a true and complete
accounting of Commercial Sales of Licensed Products and receipts from those
Commercial Sales by Licensee, its Affiliates and its sublicensees during the
quarter,


                                         -9-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


with separate accountings of (i) sales and receipts by country and by Licensed
Product and Combination Product, and (ii) a calculation of the Royalty due ARCH
for such calendar quarter showing the basis on which the Royalty for a
particular Licensed Product or Combination Product was determined.  If no
Commercial Sales of Licensed Products or Sublicense payments were made in such
quarter then Licensee's statement shall be a statement to such effect.

    (c)  Licensee hereby covenants and agrees that it shall promptly notify
ARCH of the occurrence of the events giving rise to Licensee's obligations to
make payments pursuant to 3.1(b) and (c) above.

    3.3. RECORDS. Licensee shall keep, and shall cause its Affiliates and
sublicensees to keep, accurate records in sufficient detail to permit the
Royalties payable under this Agreement to be determined.  During the term of
this Agreement and for a period of three (3) years following termination of this
Agreement, Licensee shall permit (and shall cause each of its Affiliates and
sublicensees to permit), upon written request by ARCH and reasonable notice to
Licensee, its books and records regarding the sale of Licensed Products and
Combination Products to be examined and copied from time to time (but in no
event more than twice in any calendar year), at the request of ARCH during
normal business hours by ARCH or any representative of ARCH, and shall require
each of its Affiliates and sublicensees to do the same.  Such examination shall
be made at ARCH's expense, except that if such examination discloses a
discrepancy of 5% or more in the amount of Royalties due ARCH, then Licensee
shall reimburse ARCH for the reasonable cost of such examination, including any
professional fees incurred by ARCH.  In connection with any examination or
copying of books or records in accordance with the preceding sentence, ARCH or
such representative of ARCH shall examine only such information as is required
to verify the Licensee's compliance under this Agreement.

    3.4. FOREIGN PAYMENTS.  In the event of transactions giving rise to an
obligation to make a payment hereunder with respect to which Licensee, any of
its Affiliates or any sublicensee receives payment in a currency other than
currency which is legal tender in the United States of America, all payments
required to be made by Licensee under Section 3.1 hereof shall be converted,
prior to payment, into United States dollars at the applicable rate of exchange
of Citibank, N.A., in New York, New York, on the last day of the quarter in
which such transaction occurred.

    3.5. OVERDUE PAYMENTS.  Payments due to ARCH under this Agreement shall, 
if not paid when due, bear simple interest at the lower of [    ] or the 
highest rate permitted by law, calculated on the basis of a 360 day year for 
the number of days actually elapsed, beginning on the due date and ending on 
the day prior to

                                         -10-

<PAGE>



the day on which payment is made in full.  Interest accruing under this Section
shall be due to ARCH on demand.  The accrual or receipt by ARCH of interest
under this Section shall not constitute a waiver by ARCH of any right it may
otherwise have to declare a default under this Agreement or to terminate this
Agreement.

    3.6. TERMINATION REPORT AND PAYMENT.  Within sixty (60) days after the date
of termination of this Agreement, Licensee shall make a written report to ARCH
which report shall state the number, description, and amount of Licensed
Products sold by Licensee, its Affiliates or any sublicensee upon which
Royalties are payable hereunder but which were not previously reported to ARCH,
a calculation of the Net Sales of such Licensed Products, and a calculation of
the Royalty payment due ARCH for such Licensed Products.  Concurrent with the
making of such report, Licensee shall make the Royalty payment due ARCH for such
period.

    3.7. PROGRESS REPORT.  Licensee shall provide ARCH with an annual written
report (the "Annual Report") delivered on or before February 28 of each year
during the term of this Agreement.  The Annual Reports shall be in reasonable
detail and shall include, with respect to the year just completed, reports
concerning (a) the status of Licensed Products targeted for commencement of
development efforts, (b) the status of Licensed Products under active
development, and (c) the status of developed Licensed Products.

                                      ARTICLE IV

                            NO WARRANTIES; INDEMNIFICATION

    4.1. WARRANTIES.  ARCH warrants that it has the right to enter into and
perform all of its obligations under this Agreement, and that to ARCH's
knowledge there exists no impediment to ARCH's right to enter into this
Agreement or perform its obligations hereunder.

    4.2. DISCLAIMER OF WARRANTIES.  Except as otherwise specifically set 
forth in Section 4.1 above, ARCH HEREBY EXPRESSLY DISCLAIMS ANY AND ALL 
WARRANTIES OF ANY KIND OR NATURE, WHETHER EXPRESS OR IMPLIED, RELATING TO THE 
INVENTIONS, THE TECHNICAL INFORMATION, THE LICENSED PRODUCTS, THE COMBINATION 
PRODUCTS OR LICENSED PATENT RIGHTS.  ARCH FURTHER HEREBY EXPRESSLY DISCLAIMS 
ANY EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A 
PARTICULAR PURPOSE, OR THAT THE PRACTICE OF THE LICENSED PATENT RIGHTS, OR 
THE MAKING, USING OR SELLING OF LICENSED PRODUCTS OR COMBINATION PRODUCTS, 
WILL NOT INFRINGE ANY PATENT, COPYRIGHT, TRADEMARK, OR OTHER RIGHTS OF THIRD 
PARTIES.  Without limiting the generality of the foregoing, ARCH expressly 
does not warrant (i) the patentability of any of

                                         -11-

<PAGE>



the Inventions, (ii) the accuracy of the Technical Information, or other 
information contained in the patents and patent applications listed on 
Schedule I attached hereto, or (iii) the accuracy, safety, or usefulness for 
any purpose, of the Technical Information, Licensed Patent Rights, 
Inventions, Licensed Products or Combination Products.  Nothing contained in 
this Agreement shall be construed as either a warranty or representation by 
ARCH as to the validity or scope of any of any Licensed Patent Rights.  ARCH 
assumes no liability in respect of any infringement of any patent or other 
right of third parties due to the activities of Licensee, any of its 
Affiliates or any sublicensee under this Agreement.

    4.3. INDEMNIFICATION. (a) None of ARCH, the University, any Affiliate of
any of the foregoing, or any trustee, director, officer, employee, agent or
representative of any of the foregoing (each an "Indemnified Person") shall have
any liability whatsoever to Licensee, any of its Affiliates, any sublicensee or
any other person for or on account of (and Licensee agrees and covenants, and
agrees to cause each of its Affiliates and sublicensees to agree and covenant,
not to sue any Indemnified Person in connection with) any injury, loss, or
damage, of any kind or nature, sustained by, or any damage assessed or asserted
against, or any other liability incurred by or imposed upon, Licensee, any of
its Affiliates or any sublicensee or any other person, arising out of or in
connection with or resulting from (i) the production, use or sale of the
Licensed Products and Combination Products by Licensee, any of its Affiliates or
its sublicensees, (ii) the use of any Technical Information or Invention by
Licensee, any of its Affiliates or its sublicensees, or (iii) any advertising or
other promotional activities with respect to either of the foregoing.  Licensee
shall indemnify and hold ARCH harmless against all claims, demands, losses,
damages or penalties (including but not limited to reasonable attorney's fees at
the pretrial, trial or appellate level) made against any Indemnified Person with
respect to items (i), (ii) and (iii) above (excluding claims made by any third
party alleging the invalidity or challenging the scope of any patent included in
the Licensed Patent Rights), whether or not such claims are groundless or
without merit or basis.  This Section 4.3(a) shall not apply to claims by any
third party brought against any Indemnified Person claiming an ownership
interest in the Inventions, Licensed Products, Combination Products, the
Licensed Patent Rights or the Technical Information.

    (b)  This Agreement is entered into by ARCH independently from the
University, and ARCH is acting independently from the University and in its own
private capacity and is not acting on behalf of the University, nor as its
contractor nor its agent.  Correspondingly, it is understood and agreed that the
University is not a party to this Agreement and in no manner shall be liable for
nor assume any responsibility or obligation for any claim,


                                         -12-

<PAGE>



cost or damages arising out of or resulting from this Agreement, the subject
matter licensed, or any action or lack thereof by ARCH, the University, Licensee
or any of Licensee's Affiliates or sublicensees with respect thereto.

    (c)  Licensee agrees to list ARCH, at Licensee's expense, as an additional
insured under each liability insurance policy covering products that Licensee
and each of its Affiliates and sublicensees obtains that includes any coverage
of claims relating to any of the Inventions, Licensed Patent Rights, Licensed
Products or Combination Products.  At ARCH's request, Licensee will supply ARCH
from time to time with copies of each such policy, and will notify ARCH in
writing of any termination of or reduction in coverage under any such policies.

    (d)  Licensee's obligations under this Section 4.3 shall survive the
expiration or earlier termination of all or any part of this Agreement.


                                      ARTICLE V

                PROSECUTION AND MAINTENANCE OF LICENSED PATENT RIGHTS

    5.1. PROSECUTION AND MAINTENANCE.  During the term of this Agreement, and
subject to the exceptions and provisions of Section 5.3 below, Licensee shall be
solely responsible for prosecuting and maintaining the patents under the
Licensed Patent Rights.  Except as otherwise specified in this Agreement,
Licensee shall pay when due all Patent Costs hereafter incurred with respect to
the Licensed Patent Rights.  Licensee shall provide ARCH with copies of all
official actions and other communications received by Licensee or its patent
counsel with respect to patents under the Licensed Patent Rights.  Licensee
shall further provide ARCH with copies of any and all draft filings with
governmental agencies with respect to the Licensed Patent Rights prior to the
submission to the recipients, and shall not submit any such filings without the
prior approval of ARCH (not unreasonably withheld or delayed).  Licensee and
ARCH shall mutually agree on the patent counsel to be employed by licensee in
connection with the performance of Licensee's obligations under this Article V.

    Section 5.2. COOPERATION.  ARCH agrees to cooperate with Licensee in the
preparation, filing, prosecution and maintenance of patents under the Licensed
Patent Rights, by disclosing such information as may be necessary and by
promptly executing such documents as Licensee may reasonably request to effect
such efforts.  Licensee shall reimburse ARCH for reasonable out-of-pocket costs
and expenses incurred by ARCH in connection with its cooperation with Licensee
under this Section 5.2. All patents


                                         -13-

<PAGE>



under the Licensed Patent Rights shall be filed, prosecuted and maintained in
ARCH's name or as ARCH shall designate.

    5.3. ARCH APPLICATIONS. (a) In the event that ARCH wishes to file a patent
application with respect to any of the Inventions in any jurisdiction in which
an application has not already been filed, ARCH shall identify the jurisdiction
and the Invention in writing to Licensee, and Licensee shall have ninety (90)
days after it receives such written notice in which to file such a patent
application.  If Licensee declines or fails to file such a patent application
within the earlier of (i) ninety (90) days after receiving the written notice,
or (ii) thirty (30) days prior to the filing deadline with respect to such
proposed patent application in such proposed jurisdiction, Licensee shall
immediately notify ARCH, and ARCH may, in ARCH's discretion but in ARCH's name,
file and prosecute such patent application.

    (b)  If Licensee determines to abandon a patent application previously
filed with respect to any of the Inventions, it will give ARCH at least ninety
(90) days prior written notice of its intention to abandon such application.
ARCH may, by written notice to Licensee, elect to continue the prosecution of
the application at ARCH's sole expense and in ARCH's name.  If ARCH determines
to abandon a patent application previously filed by Licensee with respect to any
of the Inventions, it will give Licensee at least ninety (90) days prior written
notice of its intention to abandon such application (but in no event shall such
period be less than thirty (30) days prior to any filing deadline with respect
to such application).  Licensee may thereafter elect to continue the prosecution
of the application at Licensee's sole expense but in ARCH's name.

    (c)  The abandonment of any patent application by Licensee in accordance
with the terms of this Agreement shall not in any way affect the obligations of
Licensee for the payment of any amounts owing hereunder with respect to
Royalties or otherwise, nor shall it affect Licensee's license in and to the
Licensed Patent Rights or otherwise cause the termination of this Agreement
(unless the abandoned patent application is the last-to-expire of the Licensed
Patent Rights).

    5.4. CONFIDENTIALITY. (a) Both Licensee and ARCH agree to treat (and, in
the case of Licensee, to cause its Affiliates and sublicensees to treat) as
confidential (i) all proprietary information with respect to the Inventions or
the Licensed Patent Rights (including the Technical Information) made available
by ARCH to Licensee or by Licensee to ARCH, and (ii) the terms and provisions
of this Agreement (PROVIDED that ARCH may provide all of the foregoing
information to the University).  ARCH acknowledges that Licensee may find it
beneficial to disclose such information provided by ARCH during the conduct of
Licensee's business.  Under such circumstances, Licensee may make


                                         -14-

<PAGE>



such information available to third parties (including shareholders of
Licensee), PROVIDED that Licensee shall first obtain from the recipients a
fully-executed confidentiality agreement which is at least as restrictive as the
confidentiality agreement Licensee employs to protect its own most valuable
trade secrets.

    (b)  Neither Licensee nor ARCH shall be bound by the provisions of Section
5.4 with respect to information which (i) was previously known to the recipient
at the time of disclosure; or (ii) is in the public domain at the time of
disclosure; or (iii) becomes a part of the public domain after the time of
disclosure, other than through disclosure by the recipient or some other third
party who is under an agreement of confidentiality with respect to the subject
information; or (iv) is required to be disclosed by law.

    (c)  Notwithstanding the provisions of Section 5.4(a), each of ARCH and the
University shall be entitled to make and permit to be made disclosures of
information included in the Technical Information and the Inventions in
scholarly journals and publications, subject to this Section 5(c).  ARCH agrees
that it shall use its good faith efforts to provide Licensee with a copy of any
manuscript proposed to be published at least 60 days prior to the scheduled
publication date.  Licensee will review the text or any other material provided
to determine if patentable subject matter is disclosed in such text and other
material, and will notify ARCH within 20 days of the receipt of the proposed
manuscript if it reasonably feels that patentable subject matter is disclosed
and that corresponding patent applications should be filed by Licensee in
accordance with Section 5.1 above.  If it is then determined by ARCH, in the
exercise of its reasonable judgement, that patent applications should be filed,
ARCH will use its good faith efforts to assist Licensee in the filing by
Licensee of patent applications with respect to the patentable subject matter
pursuant to Section 5.1 prior to the proposed publication date.

    (d)  Licensee and ARCH shall each take such actions as the other party may
reasonably request from time to time to safeguard the confidentiality of any
information subject to the terms of this Section 5.4.

    (e)  The obligations of Licensee and ARCH under this Section
5.4 shall survive the expiration or earlier termination of all or any other
part of this Agreement for three (3) years after such event.

    (f)  Licensee and ARCH acknowledge that ARCH has previously provided
Licensee with information described in Section 5.4(a) above, and that all such
information shall be deemed subject to


                                         -15-

<PAGE>



the provisions of this Section 5.(4) as if delivered immediately following the
execution of this Agreement.

                                      ARTICLE VI

                                     INFRINGEMENT

    6.1. NOTIFICATION.  In the event that either ARCH or Licensee becomes aware
of the infringement of any patent under the Licensed Patent Rights within the
Licensed Field, each shall promptly inform the other in writing of all details
available.

    6.2. LICENSEES RIGHT TO PROSECUTE. (a) In the event of infringement by a
third party of any patent under the Licensed Patent Rights within the Licensed
Field, Licensee may enforce the Licensed Patent Rights against the infringers by
appropriate legal proceedings or otherwise, provided that Licensee shall employ
counsel reasonably satisfactory to ARCH and shall inform ARCH of all
developments in such proceedings.  Licensee shall be responsible for all costs
and expenses of any enforcement activities, including legal proceedings, against
infringers which licensee initiates.  ARCH agrees to cooperate with and join in
any enforcement proceedings at the request of Licensee, and at Licensee's
expense.  ARCH may be represented by ARCH's counsel in any such legal
proceedings, at ARCH's own expense (subject to reimbursement under
Section 6.2(c)), acting in an advisory but not controlling capacity.

    (b)  The prosecution, settlement, or abandonment of any proceeding under
Section 6.2(a) shall be at Licensee's reasonable discretion, provided that
Licensee shall not have any right to surrender any of ARCH's rights to the
Licensed Patent Rights or to grant any infringer any rights to the Licensed
Patent Rights other than a sublicense subject to the conditions which would
apply to the grant of any other sublicense.

    (c)  All recoveries by way of royalties, damages and claims with respect to
infringement actions instituted, and claims made (including penalties and
interest), during the term of this Agreement, excluding any prosecuted by ARCH
under Section 6.3, shall belong to Licensee.  To the extent that Licensee's
recoveries with respect to an infringement action or claim exceed Licensee's
reasonable expenses with respect to such action or claim, Licensee shall
reimburse ARCH for ARCH's reasonable expenses for separate representation as
provided in Section 6.2(a) with respect to such action or claim.  The gross
amount of any such recoveries by Licensee, less any amounts already reimbursed
to ARCH for its expenses as provided in the immediately preceding sentence,
shall be considered Net Sales under this Agreement, giving rise to Royalty
obligations under Section 3.1(b), without any deductions of any kind.


                                         -16-

<PAGE>



    6.3. ARCH'S RIGHT TO PROSECUTE - WITHIN LICENSED FIELD.  In the event of
infringement by a third party of any Licensed Patent Rights within the Licensed
Field which ARCH wishes to prosecute, ARCH shall first make a written request
that Licensee proceed.  In the event that Licensee fails or declines to proceed
within ninety (90) days after receipt of a written request by ARCH to do so,
then, in ARCH's sole discretion, (i) ARCH may prosecute the infringer in the
name of ARCH or Licensee and (ii) the grant of license to Licensee may become
non-exclusive.  Any actions by ARCH pursuant to this clause shall be ARCH's own
expense, and ARCH may collect and retain for ARCH's own use any and all
recoveries in any proceeding by ARCH under this Section 6.3. Recoveries
collected and retained by ARCH under this Section 6.3 shall not be considered
Net Sales or give rise to royalty obligations under Article III.  Licensee will
cooperate with ARCH and execute any documents necessary for ARCH to exercise
ARCH's rights under this clause.  To the extent that ARCH's recoveries with
respect to an infringement action or claim exceed ARCH's reasonable expenses
with respect to such action or claim, ARCH shall reimburse Licensee for
Licensee's reasonable costs in connection with cooperating with ARCH in the
prosecution of such action or claim.

    6.4  INFRINGEMENT OF RIGHTS OF THIRD PARTIES.  If a Licensed Product
becomes the subject of a claim for patent infringement anywhere in the world by
virtue of the incorporation of the Licensed Patent Rights or the Inventions, the
parties shall promptly give notice to the other and meet to consider the claim
and the appropriate course of action.  Licensee shall have the right to conduct
the defense of any such suit brought against Licensee and either or both of ARCH
and the University using counsel reasonably acceptable to ARCH, and shall have
the sole right and authority to settle any such suit, PROVIDED that (i) ARCH and
the University, as applicable, shall have the right (but not the obligation) to
participate in such suit at their own cost and expense, and (ii) Licensee shall
not have any right to surrender any of ARCH's or the University's rights to the
Licensed Patent Rights or to grant to any person or entity any rights to the
Licensed Patent Rights other than a sublicense subject to the conditions which
would apply to the grant of any other sublicense hereunder.  In those
circumstances where a third party asserts that its patent dominates the Licensed
Patent Rights and Licensee's right to practice such is at issue, Licensee shall
have the right to require ARCH's participation in any such suit, upon reasonable
prior written notice, but at Licensee's expense.


                                         -17-

<PAGE>



                                     ARTICLE VII

                                     TERMINATION

    7.1  ARCH RIGHT TO TERMINATE.  ARCH shall have the right (without prejudice
to any of its other rights conferred on it by this Agreement) to terminate this
Agreement if Licensee (or, with respect to subsection (d) below, any of its
Affiliates):

    (a)  is in default in (i) payments specified in Section 3.1 above, (ii)
payments of any reimbursement obligations provided for in this Agreement, or
(iii) the making or giving of any reports or notices required to be made or
given under this Agreement, and Licensee fails to remedy any such default within
thirty (30) days after written notice thereof by ARCH;

    (b)  is in material breach of Sections 2.4, 3.3, 3.7, 4.3(c), 5.1, 5.4,
10.2(b) or 10.7 hereof, or Articles VIII or XI, and Licensee fails to remedy any
such default within ninety (90) days after written notice thereof by ARCH;

    (c)  knowingly or wilfully makes any materially false report; or

    (d)  shall commence a voluntary case as a debtor under the Bankruptcy Code
of the United States or any successor statute (the "Bankruptcy Code"), or if an
involuntary case shall be commenced against Licensee under the Bankruptcy Code
and the petition in such case is not dismissed within 30 days of the
commencement of the case, or if an order for relief shall be entered in such
case, or if the same or any similar circumstance shall occur under the laws of
any foreign jurisdiction.

    7.2. LICENSEE RIGHT TO TERMINATE.  Licensee may terminate this Agreement at
any time by written notice to ARCH, given at least ninety (90) days prior to the
termination date specified in the notice.

    7.3. EFFECT OF TERMINATION.

    (a)  In the event of the termination of this Agreement for any reason,
whether by Licensee or ARCH, Licensee shall immediately cease and shall cause
each of its Affiliates to immediately cease (i) using, making and having made
the Inventions, the Technical Information and any Licensed Products or
Combination Products derived therefrom, and shall return to ARCH, or deliver as
ARCH directs, the Inventions and the Technical Information then in its
possession, and (ii) selling any Licensed Products or Combination Products out
of inventories accumulated by Licensee prior to the effective date of
termination within sixty (60) days of such date.


                                         -18-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


    (b)  Notwithstanding the termination of this Agreement, the following
provisions of this Agreement shall survive:

         (i)  Licensee's obligation to pay Royalties accrued or accruable;

         (ii) Licensee's obligations under Articles III, IV and XI, Sections 
         5.1, 5.2, 5.4 and, to the extent proceedings have been initiated, 
         Section 6.2, and this Section 7.3(b); and

         (iii) any cause of action or claim of Licensee or ARCH, accrued or to
         accrue, because of any breach or default by the other party.

    7.4. EXPIRATION OF PATENT RIGHTS.  This Agreement shall terminate upon the
expiration of the last-to-expire patents of the Licensed Patent Rights, provided
that ARCH's and Licensee's obligations under Sections 4.2 and 5.4 shall survive
and continue in effect as provided in such Sections.

                                     ARTICLE VIII

                                     ADVERTISING

    Each party agrees not to use (and Licensee agrees to prohibit its 
Affiliates and sublicensees from using) the name of the other party (and, in 
the case of Licensee, the names of the University and the inventors of the 
Inventions) in any commercial activity, marketing, advertising or sales 
brochures except with the prior written consent of the other party, which 
such consent may be granted or withheld in such party's sole and complete 
discretion, PROVIDED that, with the prior written consent of ARCH not 
unreasonably withheld or delayed, Licensee may disclose (i) the names of 
ARCH, the University and the inventors) of the Inventions to banks, 
commercial finance institutions or prospective investors from which Licensee 
may attempt to obtain debt or equity financing, (ii) the identities of ARCH, 
the University and the inventor(s) of the Inventions and their respective 
connections to, and ownership interests in, the Inventions and the Licensed 
Patent Rights, and (iii) the identity of [        ] in advertising and sales 
materials.

                                      ARTICLE IX

                                  LATER DEVELOPMENTS

    9.1. ARCH hereby grants Licensee the right to negotiate to obtain, on the
terms set forth in this Article IX, a license on any Later Developments, which
license shall be on mutually agreeable terms.


                                         -19-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


    9.2. ARCH shall notify Licensee of any Later Developments by a writing
referring to this provision within ninety (90) days of learning of such Later
Development, in sufficient detail to allow Licensee to evaluate the commercial
potential of such Later Development.  Licensee shall then have ninety (90) days
after receipt of such disclosure to submit to ARCH a written offer to license
the subject Later Developments on the terms set forth in Licensee's written
offer.  If Licensee shall fail to make such an offer within such period, its
rights to obtain such Later Development shall be void, and Licensee shall have
no interest in or right to such Later Development.

    9.3. If Licensee makes the offer described in Section 9.2 above, ARCH
shall, within a period of ninety (90) days of the receipt of such offer, notify
Licensee in writing of either (i) ARCH's acceptance of such offer, or (ii)
ARCH's acceptance of a competing offer which is, taking into consideration the
overall economic benefit to ARCH of Licensee's offer and the competing offer,
deemed by ARCH to be materially more favorable to ARCH.  If ARCH accepts
Licensee's offer to license the subject Later Development, the license shall be
on the terms set forth in the offer and otherwise on the terms and conditions
set forth in this Agreement to the extent not inconsistent with the offer.  If
ARCH does not accept Licensee's offer, ARCH shall disclose to Licensee in said
notice the basis for its decision, including the disclosure of the terms of the
competing offer which ARCH deemed materially more favorable to ARCH.

                                      ARTICLE X

                                    MISCELLANEOUS

    10.1. GOOD FAITH EFFORTS. [                          ]

    10.2. ASSIGNMENT. (a) This Agreement may, at any time and upon sixty (60) 
days prior notice to Licensee, be assigned by ARCH without such assignment 
operating to terminate, impair or in any way change the rights which ARCH 
would have had, or any of the obligations or rights which Licensee would have 
had, if such assignment had not occurred, PROVIDED, however, that in no event 
shall ARCH assign this Agreement to any entity deemed by Licensee in the 
exercise of its reasonable discretion to be (i) an operating or research and 
development competitor of Licensee, or (ii) a financial investor entity 
(excluding any Affiliate of ARCH or the University) which owns a controlling 
interest in any entity described in (i) above.  From and after the making of 
such assignment, the assignee shall be substituted for ARCH as a party 
hereto, and ARCH shall no longer be bound hereby, and shall have not further 
obligations hereunder.

    (b) This Agreement may be assigned by Licensee to an Affiliate of Licensee
    upon at least thirty (30) days prior


                                         -20-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


written notice to ARCH, PROVIDED, that in no event shall such assignment relieve
Licensee of its liability for the performance of Licensee's obligations
hereunder, nor shall it deprive ARCH of its rights to terminate this Agreement
or enforce its rights against Licensee or Licensee's assignee as specifically
provided herein.  This Agreement shall not be assigned by Licensee in any other
circumstances without the prior written consent of ARCH,
[                                                      ]

    10.3. ENTIRE AGREEMENT, AMENDMENT AND WAIVER.  This Agreement (including 
any schedules and exhibits attached) contains the entire understanding of the 
parties with respect to the subject matter hereof.  This Agreement may be 
amended, modified or altered only by an instrument in writing duly executed 
by the parties hereto.  The waiver of a breach hereunder may be effected only 
by a writing signed by the waiving party and shall not constitute a waiver of 
any other breach.

    10.4. NOTICES.  Any notice or report required or permitted to be given or 
made under this Agreement by one of the parties hereto to the other shall be 
in writing and shall be given by personal delivery or by United States 
registered or certified mail, return receipt requested, addressed as follows:

    If to ARCH:         ARCH Development Corporation
                        1115-25 East 58th Street
                        Chicago, Illinois 60637
                        Attention: President

                        with a copy to:

                        Thomas M. Fitzpatrick, Esq.
                        Fitzpatrick Law Offices
                        20 North Wacker Drive
                        Chicago, Illinois 60606

    If to Licensee:     Vector Pharmaceuticals, Inc.
                        4009 Miranda Avenue, Suite 275
                        Palo Alto, CA 94304
                        Attention: President

    with a copy to:     Alan Mendelson, Esq.
                        Cooley, Godward, Castro, Huddleson &
                             Tatum
                        Five Palo Alto Square, 4th Floor
                        Palo Alto, CA 94306

or to such other address of which the intended recipient shall have notified
the sender by a written notice given in accordance with the terms of this
Section.  Any notice under this Agreement shall be effective when received.


                                         -21-

<PAGE>



    10.5. SEVERABILITY.  In the event that any one or more of the provisions 
of this Agreement should for any reason be held by any court or authority 
having jurisdiction over this Agreement, or either of the parties hereto, to 
be invalid, illegal or unenforceable, such provision or provisions shall be 
reformed to approximate as nearly as possible the intent of the parties, and 
the validity of the remaining provisions shall not be affected.

    10.6. GOVERNING LAW.  The interpretation and performance of this 
Agreement shall be governed by the laws of the State of Illinois applicable 
to contracts made and to be performed in that state.

    10.7. MARKING.  Licensee shall place in a conspicuous location on any 
Licensed Product (or its packaging where appropriate) made or sold under this 
Agreement, a patent notice in accordance with the laws concerning the marking 
of patented articles.

    10.8. IMPLEMENTATION.  Each party shall, at the request of the other 
party, execute any document reasonably necessary to implement the provision 
of this Agreement.

    10.9. COUNTERPARTS.  This Agreement may be executed in multiple 
counterparts, each of which when taken together shall constitute one and the 
same instrument.

    10.10 CAPTIONS.  The captions used in this Agreement are for convenience 
only, and are not intended by the parties to be used in the construction or 
application of the terms hereof.

                                      ARTICLE XI

                                   EXPORT CONTROLS

    Neither Licensee nor ARCH shall (i) knowingly transfer, directly or 
indirectly, any controlled technical data obtained or to be obtained from the 
other party hereto to a destination outside the United States, or (ii) 
knowingly ship, directly or indirectly, any product produced using such 
controlled technical data to any destination outside the United States, in 
either case in violation of the U.S. Department of Commerce's Export 
Administration Regulations.

                                         -22-

<PAGE>



    IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective duly authorized officers or representatives on the
date first above written.


ARCH:                                  ARCH Development Corporation, an
                                       Illinois not-for-profit corporation


                                       By: /s/ S Tazauus
                                           ------------------------------------
                                            Its President
                                                -------------------------------

Licensee:                              Vector Pharmaceuticals, Inc., a
                                       California corporation

                                       By: /s/ L Reed
                                           ------------------------------------
                                            Its President
                                                -------------------------------


                                         -23-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


                                      Schedule I

                           PATENTS AND PATENT APPLICATIONS

1.  [                                                 ]

2.  [                                                                  ]

3.  [                                            ]

4.  [                                            ]

5.  [                                 ]

6.  [                               ]

7.  [                                                                    ]

8.  [                                                                 ]


                                         -24-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


                                     Schedule II

                  AGREEMENTS, ASSIGNMENTS, ENCUMBRANCES OR LICENSES



    Those agreements, assignments, encumbrances, licenses and rights granted 
to [                ] pursuant to an Assignment Agreement attached hereto as 
Exhibit 1 anticipated to be entered into between the University [ ]promptly 
following the execution of this Agreement.

                                         -25-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


                                    EXHIBIT 1 TO
                                 LICENSE AGREEMENT


                                 ASSIGNMENT AGREEMENT


    ASSIGNMENT AGREEMENT dated as of this 26th day of June, 1992 between the
UNIVERSITY OF CHICAGO, an Illinois not for profit corporation ("University") and
[    ] formerly known as [                ]

                                PRELIMINARY STATEMENT.

    The University and [     ] have previously entered into a Research 
Agreement dated [              ] as amended ("Research Agreement"), pursuant 
to which [     ] has funded certain University research.

    Several patent applications have been filed in the name of [     ] 
covering inventions resulting from the research conducted at the University 
pursuant to the Research Agreement.

    [    ] desires to assign the rights to such patent applications to the 
University, and the University desires to be assigned the rights to such 
patent applications.

    NOW THEREFORE, in consideration of the mutual promises and covenants 
contained herein and other good and valuable consideration, the receipt and 
sufficiency of which is hereby acknowledged, the University and [      ] 
agree as follows.

                                      AGREEMENT

    1.   DEFINITIONS.  For purposes of this Agreement, the following terms
shall have the following meanings:

    "PATENT RIGHTS" shall mean each and every (a) patent application listed in
    Exhibit A attached hereto, together with any patents which issue from any
    such patent application, and (b) patent applications which are divisions,
    continuations, continuations-in-part, foreign counterparts, reissues,
    renewals, re-examinations, substitutions, or extensions of or to any patent
    applications or patents described in clause (a) of this sentence, together
    with patents that issue from such patent applications.

    "PATENT COSTS" shall mean the out of pocket expenses incurred by [    ] in
    connection with the preparation, filing, prosecution and maintenance of the
    patents under the Patent Rights, as documented in Exhibit B attached
    hereto.

    "START-UP COMPANY" shall mean a corporation with fewer than one hundred
    employees or less than three years of operations.

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


    "ESTABLISHED CORPORATION" shall mean a corporation with one hundred or more
    employees and at least three years of operations.

    "VECTOR" shall mean the invention described as [         ] together with 
any patents which issue from such patent application,     and patent 
applications which are divisions, continuations, continuations-in-part, 
foreign counterparts, reissues, renewals, re-examinations, substitutions, 
or extensions of or to such patent application or patents, together with 
patents that issue from such patent applications.

    "[          ]" shall mean the invention described
    as [             ] and patent applications which are divisions,
    continuations, continuations-in-part,. foreign counterparts, reissues,
    renewals, re-examinations, substitutions, or extensions of or to such
    patent, together with patents that issue from such patent applications.

    2.   ASSIGNMENT AND TERMINATION. [             ] hereby assigns to the 
University all of [              ] right, title and interest in and to the 
Patent Rights, and disclaims and terminates all of right, title and interest 
in and to the Patent Rights.

    3.   CONTINGENCIES.

    (a)  If the University shall enter into a license agreement for any of 
the Patent Rights with a third party, the University shall notify [    ] of 
the name, address and contact name of the licensee under such license.

    (b)  If the University shall enter into a license agreement for any of 
the Patent Rights with a Start-Up Company, the University shall include in 
such license agreement the following conditions, one of which licensee shall 
select prior to the date of first commercial sale of Licensed Products (as 
that term shall be defined in the license agreement):

    (i) that the licensee negotiate in good faith either a marketing or a
    research collaboration agreement with [   ] with respect to such Licensed
    Products;

    (ii) that the licensee reimburse [        ] (through the University)
    for [        ] Patent Costs with respect to the specific Patent Rights
    covered by the license within ninety (90) days of licensee's first
    commercial sale of any such Licensed Products.

    (c)  If the University shall enter into a license agreement for any of the
Patent Rights with an Established Corporation, the


                                         -2-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


University shall include in such license agreement the condition that, upon
execution of the license agreement, licensee reimburse [          ] (through the
University) for [        ] Patent Costs with respect to the specific Patent
Rights covered by the license.

    (d)  If the University executes a license agreement for the Vector, the
University shall include in such agreement the requirement that upon the grant
by such licensee of a nonexclusive sublicense of the Vector (which sublicense
does not pertain to a research or development collaboration) , licensee shall
offer [       ] a sublicense on substantially the same terms.

    (e)  If the University shall enter into a license agreement with respect 
to [                             ] the University shall pay to [  ]of any 
fees or royalties that the University receives from the licensee under such 
license agreement.

    4.   BOOKS AND RECORDS.  The University shall keep accurate books and 
records of its income and receipts, and all expenses and disbursements, 
related to the Patent Rights.  [      ] shall have the right to inspect only 
the portions of such books and records which specifically relate to the 
contingencies listed in Section 3 above, at reasonable times and intervals 
and upon reasonable notice, at [        ] expense.

    5.   REPRESENTATIONS AND WARRANTIES.

    (a)  [     ] hereby represents and warrants to the University as follows:

    (i)  [     ] has the full power and right to execute this Agreement, and
         this Agreement has been duly executed and delivered by [       ] and
         constitutes the legal, valid and binding obligation of [       ]
         enforceable against it in accordance with its terms, except to the
         extent that such enforceability (A) may be limited by bankruptcy,
         insolvency or other laws affecting the enforcement of creditors'
         rights generally, and (B) as to equitable relief, is subject to the
         discretion of the court before which any proceeding may be brought.

    (ii) This Agreement assigns all of [        ] right, title and interest in
         the Patent Rights to the University, and terminates all of [      ]
         right to license the-Patent Rights, and, except for the interest of 
         [   ]created pursuant to this Agreement, [       ] has no other right,
         claim or interest in any of the Patent Rights.

    (iii) As of the date of this Agreement, none of the Patent Rights are
          subject to any agreements, assignments, encumbrances or restrictions;
          provided however, that


                                         -3-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


         [       ] makes no representations as to persons or entities that may
         have rights to or in the Patent Rights as inventors or arising through
         the University.

    (iv) [       ] makes no product or other warranty except as expressly
         provided in this Agreement to the University of any kind, express or
         implied, including any implied warranty of fitness for use or for a
         particular purpose or for merchantability.

    (b)  The University hereby represents and warrants to [        ] that the
University has the full power and right to execute this Agreement, and this
Agreement has been duly executed and delivered by the University and constitutes
the legal, valid and binding obligation of the University, enforceable against
it in accordance with its terms, except to the extent that such enforceability
(A) may be limited by bankruptcy, insolvency or other laws affecting the
enforcement of creditors' rights generally, and (B) as to equitable relief, is
subject to the discretion of the court before which any proceeding may be
brought.

    6.   FURTHER ASSURANCES. [       ] agrees that, up on the written request 
of the University at any time and from time"to time, [       ] shall execute 
and deliver such other documents and take such other acts as the University 
shall reasonably request in order to effectuate, clarify or otherwise 
implement the agreements set forth in this Agreement, including without 
limitation, such documents and instruments of assignment or transfer as the 
University may deem appropriate to effectuate the assignment contemplated by 
this Agreement.

    7.   LICENSING DECISIONS.  Without prejudice to Section 3 hereof, all
decisions as to the marketing and development of the Patent Rights, including
without limitation, decisions relating to the future licensing or assignment of
the Patent Rights, shall be made by the University in its sole and absolute
discretion.

    8.   ASSIGNMENT.  This Agreement shall be binding upon and shall inure to 
the benefit of the successors or assigns of the University and [        ] as 
the case may be.  [         ] acknowledges that the University shall have the 
right to assign all of the Patent Rights, and all of its rights and 
obligations under this Agreement, to ARCH Development Corporation ("ARCH"), 
an affiliate controlled by the University, in which event all such rights and 
obligations shall be rights and obligations of ARCH, and [               ] 
shall look to ARCH, and not the University, for the performance thereof.

    9.   TERM.  This Agreement shall be in effect until the last expiration
date of any of the Patent Rights provided that the University's obligations to
make the payments described in


                                         -4-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED


Section 3 hereof shall terminate as to any particular Patent Right(s) at such
time as such Patent Right(s) shall expire.

    10.  NONDISCLOSURE AND NON-USE.  [       ] agrees not to publish or 
disclose any information to any third persons about the Patent Rights, or any 
rights relating thereto, except to inform such third persons that all 
inquiries relating to such Patent Rights should be directed to ARCH. 
[        ] further agrees not to use the Patent Rights without the prior 
written consent of the University, provided that [        ] may use the 
Patent Rights for non-commercial research purposes, or pursuant to Sections 
3(b) - 3(d) of this Agreement.

    11.  GOVERNING LAW.  This Agreement shall be governed by, and interpreted 
in accordance with, the laws of the State of Illinois applicable to contracts 
entered into between Illinois residents to be performed solely in Illinois.

    12.  NOTICE.  Any payment, notice or other communication required or
desired to be made to either party hereunder shall be made or given to the
following address:

    If to [       ]        [



                                     ]

    If to University:        c/o ARCH Development Corporation
                             1115-25 East 58th Street
                             Chicago, Illinois 60637
                             Attention: President

    Either party may change its address for notice by notice to the other 
party in accordance with this Section 12.  All notices shall be deemed 
effective on the date received.

    IN WITNESS WHEREOF, [            ] and the University have caused this
Agreement to be executed as of the day and year first above written.

                             THE UNIVERSITY OF CHICAGO


                             By: /s/ Fred Clifford
                                 -------------------------------------
                                  Its: Director of Special Payouts
                                       -------------------------------

                           [

                                 ]

                             By: /s/
                                 -------------------------------------
                                  Its:
                                       -------------------------------


                                         -5-

<PAGE>

                       CONFIDENTIAL TREATMENT REQUESTED



                                      EXHIBIT A

[                                                                              ]


Foreign counterparts of the above applications are also included.

<PAGE>


                       CONFIDENTIAL TREATMENT REQUESTED


                                      EXHIBIT B

                       TOTAL U.S. & INTERNATIONAL PATENT COSTS

[                                                                              ]

<PAGE>

                                                                  EXHIBIT 10.2



<PAGE>


CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT HAS BEEN DELETED, AS
MARKED BY BRACKETS, AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.




                          TECHNOLOGY TRANSFER AGREEMENT

   This Technology Transfer Agreement (the "Agreement") is made and entered into
as of February 9, 1993, by and between MOUNT SINAI SCHOOL OF MEDICINE OF THE
CITY UNIVERSITY OF NEW YORK, a corporation organized and existing under the laws
of New York ("MOUNT SINAI"), and VECTOR PHARMACEUTICALS, INC., a corporation
organized and existing under the laws of California ("VECTOR").

                                    ARTICLE 1

                                   BACKGROUND

   1.1       VECTOR is in the business of developing preventative, therapeutic
and diagnostic products for humans, plants and animals.

   1.2       MOUNT SINAI is a School of Medicine which engages in research and
teaching in the biomedical sciences and which is the assignee of certain
Property (as hereinafter defined) developed in the conduct of those activities.

   1.3       MOUNT SINAI and VECTOR have entered into a Stock Issuance Agreement
on even date herewith, in the form attached hereto as Exhibit A, pursuant to
which MOUNT SINAI will be issued shares of VECTOR's common stock (the "Stock
Issuance Agreement").

   1.4       VECTOR is desirous of obtaining, and MOUNT SINAI is willing to
assign, sell, transfer and convey in

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


consideration for the VECTOR common stock to be issued pursuant to the Stock
Issuance Agreement, all right, title and interest, on a worldwide basis, in and
to the Property (as defined below).

                                    ARTICLE 2

                                   DEFINITIONS

   2.1       The term "AFFILIATE" shall mean, with respect to each party, any
entity which controls, is controlled by or is under common control with that
party.

   2.2 The term "INVENTORS" shall mean [






                                                                              ]



   2.3       The term "FDA" shall mean the United States Food and Drug
Administration.

   2.4       The term "RELATED TECHNOLOGY" shall mean (i) all patentable
information, discoveries, inventions, and the like other than those claimed in
the Patent Rights or MOUNT SINAI Improvements, and any and all patent rights
relating thereto, the use of which pertains to [



                                       -2-

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


                                                                     ]     and
which are not otherwise subject to the rights or any third party, but only to
the extent such discovery, invention and the like shall have occurred or been
reduced to practice during the period extending from [


                                             ]

   2.5  The term "PRODUCT" shall mean any substance, composition or article of
manufacture covered by a claim of one or more of the patents or patent
applications contained in the Patent Rights or the Mount Sinai Improvements, to
the extent acquired by VECTOR pursuant to Section 3.4.

   2.6  The term "PATENT RIGHTS" shall mean all information, inventions or
discoveries covered by the patents and patent applications listed on Exhibit B
hereto ("Inventions"), and any and all patents issuing therefrom, owned by MOUNT
SINAI or any MOUNT SINAI Affiliate.  "Patents" as used in this Agreement shall
include, without limitation, all substitutions, divisionals, reissues,
continuations, continuations-in-part that cover Inventions specifically
described in the

                                       -3-

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


patents and applications listed in Exhibit B, inventors' certificates and all
foreign counterparts of the aforementioned which MOUNT SINAI now owns or
hereafter acquires and which MOUNT SINAI has the lawful right to assign and
disclose.

   2.7  The term "MOUNT SINAI IMPROVEMENTS" shall mean all modifications,
revisions or improvements to the Inventions and any and all patent rights
relating thereto which are commercially necessary for the development,
manufacture, use or sale of the Inventions or Products, in which MOUNT SINAI in
the future acquires any interest and with regard to which MOUNT SINAI has the
lawful right to disclose and assign, but only to the extent such modification,
revision or improvement shall have occurred or been reduced to practice from the
date of filing of the patent applications listed, or the patent applications
underlying an issued patent listed, on Exhibit B hereto, up to and including the
one (1) year period following the effective date of this Agreement and only to
the extent such modification, revision or improvement was [                    ]

   2.8  The term "TECHNICAL INFORMATION" shall mean (i) all know-how, trade
secrets, data, processes, reagents, samples of assay components, media and/or
cell lines; and (ii) procedures and formulations for producing any such assay
components, models, procedures, devices,

                                       -4-

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


methods, formulas, protocols; and (iii) information: (a) necessary for the
practice and commercial exploitation of the Inventions contained within the
Patent Rights, or to the extent VECTOR exercises its option in accordance with
the provisions of Section 3.4, any MOUNT SINAI Improvements; and (b) which are [

                                                                   ] owned or
acquired by MOUNT SINAI and which MOUNT SINAI has the lawful right to assign and
disclose; and (c) which [

                                                                   ] Technical
Information shall include, without limitation, all medical, pharmacological,
toxicological and other scientific data relating to any Product.

   2.9  The term "PROPERTY" shall mean all Patent Rights and Technical
Information.

                                    ARTICLE 3

                              ASSIGNMENT OF RIGHTS

   3.1  ASSIGNMENT OF PROPERTY.  In consideration of the issuance by VECTOR of
shares of its Common Stock and the Warrants, as further set forth in Article 5,
MOUNT SINAI hereby assigns to VECTOR, effective upon receipt by MOUNT SINAI of
the shares of Common Stock and Warrants, as provided in Article 5, all of its
rights, title and interest in and to the Property, and upon such request by
VECTOR, MOUNT SINAI agrees to promptly execute

                                       -5-

<PAGE>


assignment and other documents, testify and take other acts, at VECTOR's expense
and as reasonably requested by VECTOR, in order to apply for and obtain, in
VECTOR's name and for its benefit, patents, trade secrets, and all other
technology and intellectual property rights throughout the world related to any
of the Property and, to the extent VECTOR exercises its option in accordance
with the provisions of Section 3.4, any MOUNT SINAI Improvements, and to
transfer, effect, confirm, perfect, record, preserve, protect and enforce all
rights, title and interest transferred hereunder.

   3.2  LIMITATIONS ON ASSIGNMENT.  The rights and interests assigned under
Section 3.1 are subject to the following limitations:

        (a)  GOVERNMENT RIGHTS.  VECTOR understands that the Property may have
been developed under a funding agreement with the Government of the United
States of America (the "Government") and, if so, that the Government may have
certain rights relative thereto, including, but not limited to those arising
under 35 U.S.C. Sections 200-212 and the regulations promulgated thereunder.
This Agreement is explicitly made subject to the Government's rights under any
such agreement and any applicable law or regulation.  To the extent that there
is a conflict between any such agreement, applicable law or regulation and this
Agreement, the terms of such

                                       -6-

<PAGE>

Government agreement, applicable law or regulation shall prevail.

   (b)  RIGHTS OF THIRD PARTY FUNDING SOURCES.  VECTOR understands that portions
of the Property may have been developed and/or discovered by the Inventors
pursuant to funds supplied pursuant to contractual relationships between one or
more of the Inventors and third party, non-Governmental funding entities
("Funding Entities"), and if so, that such Funding Entities may have or may
believe themselves to have, certain rights relative thereto with respect to the
Property and VECTOR further acknowledges that in that event it shall have no
rights against MOUNT SINAI regarding any such technology.

   (c)  RETAINED RIGHTS.  VECTOR hereby grants MOUNT SINAI a fully-paid,
royalty-free, irrevocable, non-exclusive license to make, have made and use the
Inventions contained within the Patent Rights, and the Technical Information,
for educational, research and other non-commercial purposes only, including the
right to publish the scientific findings from research related to the Property
in scholarly journals and publications and to make scientific presentations.

   3.3  MOUNT SINAI AND THE INVENTORS.  VECTOR understands that MOUNT SINAI's
ongoing obligations apply only to the extent that MOUNT SINAI has the lawful
right

                                       -7-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


to disclose and assign the Property.  VECTOR further understands and agrees that
some Inventors are not currently, have never been, or may not in the future be
employed by MOUNT SINAI and are not subject to the conditions of employment with
MOUNT SINAI, including MOUNT SINAI's faculty rules.  Further, VECTOR agrees that
MOUNT SINAI is not required to and has no obligation to VECTOR under this
Agreement or otherwise to make certain that the Inventors comply with the terms
of this Agreement or with the terms and conditions of MOUNT SINAI's policies or
its faculty rules.

   3.4  MOUNT SINAI IMPROVEMENTS.  MOUNT SINAI hereby grants to VECTOR an option
to acquire any MOUNT SINAI Improvements in accordance with the provisions of
this Section 3-4.  MOUNT SINAI agrees to notify VECTOR in writing of any MOUNT
SINAI Improvements within [            ] business days of the filing of an
invention disclosure statement with MOUNT SINAI's Dean's office or its Office of
Science and Technology Development concerning such MOUNT SINAI Improvement,
pursuant to MOUNT SINAI's policies, by one or more of the Inventors.  VECTOR
shall have a period of [            ] with a right to extend such period for an
additional [            ] with the prior written consent of MOUNT SINAI, not to
be withheld unreasonably, after receipt of such notice in which to notify MOUNT
SINAI in writing of its desire to exercise

                                       -8-

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


its option with respect to such MOUNT SINAI Improvement.  If VECTOR exercises
its option with respect to such MOUNT SINAI Improvement, such MOUNT SINAI
Improvement shall promptly thereafter be assigned as provided for in Section
3.1, and Exhibit B shall be amended accordingly.  In the event VECTOR fails to
deliver to MOUNT SINAI a notice of election to exercise such option, or notifies
MOUNT SINAI that it elects not to exercise such option, VECTOR shall have no
further rights with respect to such MOUNT SINAI Improvement, and in such event,
MOUNT SINAI shall be free to license, assign or otherwise develop or dispose of
such MOUNT SINAI Improvement.

   3.5  DELIVERY OF TANGIBLE PROPERTY.  As soon as practicable after the
effective date of this Agreement or the effective date of VECTOR's exercise of
its option pursuant to Section 3.4, as the case may be, but in no event later
than [               ] after such effective date (unless otherwise requested by
VECTOR), MOUNT SINAI shall cause to be delivered to VECTOR, at VECTOR's expense,
any and all tangible manifestations of the Property which are produced by the
Inventors and which are in MOUNT SINAI's possession and control, including,
without limitation, [



                                  ]in its control which are necessary for the

                                       -9-
<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


preparation or practice of the Inventions covered by the Patent Rights, or, to
the extent VECTOR has exercised its option in accordance with the provisions of
Section 3.4., MOUNT SINAI Improvements.  [                         ] MOUNT SINAI
each retain the right to refrain from producing the above materials if, in their
respective opinion, such release would be inappropriate after taking into
consideration [

                                                                               ]

   3.6  RELATED TECHNOLOGY.  MOUNT SINAI shall notify VECTOR of any Related
Technology by a writing referring to this provision [                 ] days of
learning of such Related Technology, in sufficient detail to the extent such
information is available to MOUNT SINAI [                     ]  Upon receipt of
such disclosure, VECTOR shall have the opportunity to negotiate exclusively with
MOUNT SINAI for the terms of a license or assignment to such Related Technology
provided VECTOR so notifies MOUNT SINAI in writing within [
      ] of receipt of such disclosure written notice of its intent to so
negotiate.  In the event VECTOR decides not to exercise its right of first
negotiation, the remainder of this provision shall be of no further force and
effect as to that Related Technology.  In the event VECTOR decides to exercise
its right of first negotiation, both parties will negotiate in good faith for a
period of 120

                                      -10-

<PAGE>

days to license or assign the technology.  If no agreement is reached after the
expiration of the 120 day period, MOUNT SINAI shall be free to license, assign
or otherwise develop or dispose of such Related Technology.  Notwithstanding the
foregoing sentence, MOUNT SINAI shall not license, assign or otherwise develop
or dispose of such Related Technology to a third party on terms substantially
less favorable to MOUNT SINAI than those last offered by VECTOR.


                                    ARTICLE 4

                         REPRESENTATIONS AND WARRANTIES

   4.1  OWNERSHIP OF THE PROPERTY.  MOUNT SINAI represents and warrants that (i)
it has received an assignment of the rights of the Inventors in and to the
Patent Rights and has recorded each such Assignment with the United States
Patent and Trademark Office, (ii) except as otherwise provided herein, MOUNT
SINAI has not granted any license or made any assignment of the Patent Rights
and knows of no obligation to grant any such license or to make any such
assignment, (iii) MOUNT SINAI knows of no liens, encumbrances, agreements or
understandings of any kind, either written, oral or implied which would have a
material adverse effect on VECTOR's rights hereunder, except as set forth in
Exhibit C hereto, which Exhibit C sets forth all

                                      -11-

<PAGE>

information known to MOUNT SINAI, and (iv) the execution, delivery and
performance of this Agreement does not conflict with, constitute a breach of, or
in any way violate any arrangement, understanding or agreement of which MOUNT
SINAI has knowledge.

   4.2  NO INFRINGEMENT BY MOUNT SINAI.  MOUNT SINAI represents and warrants
that it has no knowledge that any individual or entity has asserted that MOUNT
SINAI, or any employee, agent, representative or other person affiliated with
MOUNT SINAI is infringing or has infringed any foreign or domestic patent or has
misappropriated or improperly used or disclosed any trade secret, confidential
information or know-how which relates in any manner to the subject matter of
this Agreement.

   4.3  NO INFRINGEMENT.  MOUNT SINAI represents and warrants that it has no
knowledge that any person or individual is infringing or has infringed any
Patent Rights or has misappropriated or improperly used or disclosed any trade
secret, confidential information, or know-how which relates in any manner to the
subject matter of this Agreement.

   4.4 PATENT PROCEEDINGS.  MOUNT SINAI represents and warrants that it has no
knowledge that any patent application within the Patent Rights is the subject of
any pending interference, opposition,

                                      -12-

<PAGE>

cancellation or other protest proceeding, except as otherwise set forth in
Exhibit C.

   4.5  KNOWLEDGE OF THIRD PARTY PATENTS.  MOUNT SINAI represents and warrants
that it has no knowledge of any foreign or domestic patent or patent application
which is reasonably expected by MOUNT SINAI to restrict VECTOR from
manufacturing, using or selling any Product or any portion of the Technical
Information.

   4.6  WARRANTY DISCLAIMER.  Notwithstanding the foregoing, nothing in this
Agreement is or shall be construed as:

        (i)  a warranty or representation by MOUNT SINAI as to the validity or
scope of any patent or patent application within the Patent Rights;

        (ii) a warranty or representation that anything made, used, sold or
otherwise disposed of under any license granted in this Agreement is or will be
free from infringement of patents, copyrights and other rights of third parties;

        (iii)  a warranty or representation that the Inventors have not entered
into arrangements with third parties unbeknownst to MOUNT SINAI, other than
those set forth in Exhibit C hereto, which may be inconsistent with the
assignment of the entire rights of the Inventors in and to the Property.

   4.7  NO WARRANTY OF MERCHANTABILITY OR FITNESS

                                      -13-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


FOR PARTICULAR PURPOSE.  MOUNT SINAI MAKES NO REPRESENTATION AND EXTENDS NO
WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  MOUNT SINAI FURTHER
AFFIRMATIVELY STATES THAT IT HAS NO INFORMATION WHATSOEVER REGARDING VECTOR'S
INTENDED USE OR DEVELOPMENT OF THE PRODUCTS.

   4.8  MOUNT SINAI KNOWLEDGE.  For the purpose of this Agreement, information,
data, knowledge or material available or in the possession of an Inventor,
regardless of whether the Inventor is an employee of MOUNT SINAI, is [





                                                             ]


                                    ARTICLE 5

                          CONSIDERATION FOR ASSIGNMENT

   For the consideration as set forth herein, VECTOR will issue to MOUNT SINAI
no sooner than five days after execution of this Agreement:

   5.1 One hundred seventy-five thousand (175,000) shares of VECTOR's Common
Stock pursuant to the Stock Issuance Agreement.

   5.2  Three (3) warrants, in the forms and

                                      -14-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


pursuant to the terms attached hereto as Exhibits D-1, D-2 and D-3,
respectively, to purchase up to 225,000 shares of VECTOR'S Series A Preferred
Stock (individually, a "Warrant" and collectively, the "Warrants"), each
exercisable for a term of five (5) years, commencing upon the occurrence of the
following milestone events and with respect to the following amounts:

        (a)  the first Warrant to be exercisable with respect to [
       ] shares to be issued upon [


                                             ]

        (b)  the second Warrant to be exercisable with respect to [
            ] shares to be issued upon [


                                                    ]

        (c)  the third Warrant to be exercisable with respect to [
                       ] shares upon [

                                                            ]

   5.3  The Warrants shall be exercisable at such a price per share as set forth
in the Warrants under

                                      -15-

<PAGE>

Paragraph 3, "Purchase Price."


                                    ARTICLE 6

                          ASSUMPTION OF RISK, RELEASE,
                          INDEMNIFICATION AND INSURANCE

   6.1  VECTOR assumes all risk for loss or damage arising out of a Product.
MOUNT SINAI and its representatives assume no responsibility for and are hereby
released from any losses or damages which may arise out of a Product (including,
without limitation, losses related to personal injury and property damage and
all general, direct, special, incidental, exemplary, punitive and/or
consequential damages), whether due to MOUNT SINAI's or its representatives'
sole, joint or several negligence (whether active or passive) or otherwise.
VECTOR agrees to defend, indemnify and save harmless MOUNT SINAI and its
representatives from and against all claims, liabilities, damages, lawsuits,
losses and expenses (including attorney's fees) alleged to be caused by or have
arisen out of a Product, whether due to MOUNT SINAI's or its representatives'
sole, joint or several negligence (whether active or passive) or otherwise.

   6.2  INSURANCE.  VECTOR shall obtain a commercially prudent amount of
insurance covering any personal injury or property damage that may arise out of
VECTOR's or its Transferee's use, sale or distribution of

                                      -16-

<PAGE>

the Product and to add MOUNT SINAI as an additional insured on each such policy.
It is expressly agreed and understood that no insurance company, insurer or
bonding company or their successors or assigns shall have any rights of
subrogation or other rights against MOUNT SINAI or its representatives.


                                    ARTICLE 7

                            CONFIDENTIAL INFORMATION

   MOUNT SINAI and VECTOR each agree that all information contained in documents
marked "Confidential" ("Confidential Information") which are forwarded to one by
the other shall be received in strict confidence, used only for the purposes of
this Agreement, and not disclosed by the recipient party, its agents or
employees without the prior written consent of the other party, unless such
Confidential Information (i) was in the public domain at the time of disclosure,
(ii) later became part of the public domain through no act or omission of the
recipient party, its employees, agents, successors, or assigns, (iii) was
lawfully disclosed to the recipient party by a third party having the right to
disclose it, or (iv) was already known by the recipient at the time of
disclosure.  Each party's obligation of confidence hereunder shall be fulfilled
by using the same degree of care with the other party's Confidential

                                      -17-

<PAGE>

Information as it uses to protect its own Confidential Information.  MOUNT SINAI
and VECTOR each further agree to treat as Confidential Information the terms and
provisions of this Agreement, except with respect to clause (ix) below and
except that MOUNT SINAI may, at its sole option, disclose the terms and
provisions of this Agreement to the Inventors provided that each Inventor
executes a confidentiality agreement substantially in the form attached hereto
as Exhibit E. Nothing contained herein shall prevent MOUNT SINAI or VECTOR or
their respective Transferees from disclosing information, except for
Confidential Information, to the extent such information is required to be
disclosed (v) in connection with the securing of necessary governmental
authorization for VECTOR or its Transferees' manufacture, use or sale of a
Product, (vi) for the purpose of VECTOR or its Transferees' compliance with
governmental regulations, or (vii) for the purpose of licensing or distribution
and sale of any Product, (viii) in connection with the development, manufacture,
use or sale of any Product, or (ix) in connection with VECTOR's financing
efforts.

                                      -18-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


                                    ARTICLE 8

                                PATENTS AND COSTS

   VECTOR shall reimburse MOUNT SINAI for all out-of-pocket legal fees, costs
and expenses incurred in connection with the preparation, filing, prosecution
and maintenance of the patents and patent applications
reflected on Exhibit B (the "Patent Costs") incurred [
              ] In addition, VECTOR shall reimburse MOUNT SINAI for all Patent
Costs incurred [
                         ] under the following circumstances and according to
the following schedule: [           ] of the Patent Costs attributable to [
            ] shall be payable by VECTOR on [

                                                                 ] The remaining
[                                     ] of such Patent Costs shall be payable by
VECTOR [


                          ]


                                    ARTICLE 9

                              INTELLECTUAL PROPERTY

   9.1  DEFENSE OF THIRD PARTY INFRINGEMENT SUITS.

                                      -19-

<PAGE>


In the event any Product manufactured or sold by VECTOR or its Transferee
becomes the subject of a claim for patent, trade secret or other proprietary
right infringement anywhere in the world, VECTOR shall promptly notify MOUNT
SINAI.  MOUNT SINAI shall have the right, but not the obligation, at its sole
option and at its own expense, to participate in any suit which may be brought
by VECTOR.

   9.2  SUITS AGAINST INFRINGING THIRD PARTIES.  In the event either party
becomes aware of any actual or threatened infringement of the Property, that
party shall promptly notify the other.  VECTOR or its Transferee shall be
entitled to prosecute any and all infringements of any proprietary rights in the
Property, at its own expense.  All monetary compensation awarded in connection
with any infringement suit under this Section shall be paid to VECTOR or its
Transferee.

   9.3. COOPERATION.  MOUNT SINAI agrees to cooperate with and assist VECTOR, as
reasonably requested by VECTOR and at VECTOR's expense, in any claims or suits
undertaken by VECTOR pursuant to Sections 9.1 and 9.2, and VECTOR shall keep
MOUNT SINAI informed as to the status of the defense or prosecution of the same.


                                   ARTICLE 10
                                  MISCELLANEOUS

                                      -20-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


   10.1 PROMOTIONAL ADVERTISING.  VECTOR agrees not to identify MOUNT SINAI in
any promotional advertising or other promotional materials to be disseminated to
the public or any portion thereof, or to use the name of any MOUNT SINAI
employee, former employee, or trademark, service mark, trade name, or symbol of
MOUNT SINAI, or that is associated with them, without MOUNT SINAI's or such
employee's, prior written consent, except materials used in connection with
VECTOR's financing efforts, which representation must be accurate and
appropriate.  For example, VECTOR or its Transferees may not represent that
MOUNT SINAI endorses or approves any of its financing efforts.
Notwithstanding the foregoing, VECTOR may disclose the names of MOUNT SINAI and
the Inventors to prospective investors, lenders, or partners and may [

                                                                      ] (or any
subsequent title for purposes of identification) [
                                ] in any VECTOR materials.

   10.2 ENTIRE AGREEMENT.  This Agreement, the Stock Issuance Agreement and the
Warrants contain the entire agreement and understanding between the parties with
respect to the subject matter hereof, and merge all prior discussions,
representations and negotiations, either written or oral, between the parties
with respect

                                      -21-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


to the subject matter of this Agreement.  Nothing herein is intended to limit,
expand, or otherwise affect the terms of the Stock Issuance Agreement.

   10.3 ASSIGNMENT.  This Agreement shall not be assignable by either party
except that VECTOR may assign this agreement to an Affiliate or to a corporation
with which it merges or which owns all or substantially all of VECTOR's stock.
In the event that this Agreement is properly assigned it shall be binding upon
and inure to the benefit of MOUNT SINAI, VECTOR and their respective assigns and
successors in interest.  Any assignment which is not in accordance with this
Section 10.3 will be void.  Nothing contained in this Agreement shall be
construed as limiting in any way VECTOR's right and ability to sell, license,
lease or otherwise transfer the Property.

   10.4 HEADINGS.  The headings used in this Agreement are for convenience of
reference only and are not intended to be a part of or to affect the meaning or
interpretation of this Agreement.

   10.5 CONSULTING.  MOUNT SINAI hereby agrees to grant, upon execution of this
Agreement, an exemption [                                  ] from the rules
governing the conduct of faculty of MOUNT SINAI, so as to allow [          ] to
consult with and for VECTOR, to enter into a consulting agreement with VECTOR
and, in the course of such engagement as a consultant, [

                                      -22-

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED

                                    ]except that this will not include [




                                          ]

   10.6 AMENDMENT.  No amendment or modification hereof shall be valid or
binding upon the parties unless made in writing and signed by both parties.

   10.7 FORCE MAJEURE.  Any delays in performance by any party under this
Agreement shall not be considered a breach of this Agreement if and to the
extent caused by occurrences beyond the reasonable control of the party
effected, including but not limited to, acts of God, embargoes, governmental
restrictions, strikes or other concerted acts or workers, fire, flood,
explosion, riots, wars, civil disorder, rebellion or sabotage.  The party
suffering such occurrence shall immediately notify the other party and any time
for performance hereunder shall be extended by the actual time of delay caused
by the

                                      -23-

<PAGE>

occurrence.

   10.8 ADDRESSES.  The reports to be made hereunder to MOUNT SINAI shall be
made by mailing the reports to MOUNT SINAI's address.  Notices provided for
herein shall effectively be given by mailing the same by certified or registered
mail, properly addressed.  For the purposes of making payments and giving
notices, the addresses of the parties hereto are as follows:

If to MOUNT SINAI:     The Mount Sinai School of Medicine
                       One Gustave L. Levy Place
                       New York, NY  10029-6574

                       Attention:  Director, Office of
                                   Science and Technology
                                   Development

If to VECTOR:          Vector Pharmaceuticals, Inc.
                       1815 Old Country Road
                       Belmont, CA 94002
                       Attention: President

or to such subsequent addresses as either party may furnish the other by giving
notice thereof as provided in this Section 10-8.

   10.9 INDEPENDENT CONTRACTORS.  In making and performing this Agreement, MOUNT
SINAI and VECTOR act and shall act at all times as independent contractors and
nothing contained in this Agreement shall be construed or implied to create an
agency, partnership or employer and employee relationship between MOUNT SINAI
and VECTOR.  At no time shall one party make commitments or incur any charges or
expenses for or in the name of the other party except as specifically provided
herein.

                                      -24-

<PAGE>

   10.10     SEVERABILITY.  If any term, condition or provision of this
Agreement is held to be unenforceable for any reason, it shall, if possible, be
interpreted rather than voided, in order to achieve the intent of the parties to
this Agreement to the extent possible.  In any event, all other terms,
conditions and provisions of this Agreement shall be deemed valid and
enforceable to the full extent.

   10.11     WAIVER.  None of the terms, covenants, and conditions of this
Agreement can be waived except by the written consent of the party waiving
compliance.

   10.12     APPLICABLE LAW.  This Agreement shall be construed, interpreted,
and applied in accordance with the laws of the State of California as applied to
contracts entered into and performed entirely within California.

                                      -25-


<PAGE>

   IN WITNESS WHEREOF, the parties hereto have executed this Agreement by their
duly authorized officers or representatives.

                                      MOUNT SINAI SCHOOL OF MEDICINE

                                      By /s/ Nathan Kase
                                         -----------------------------
                                      Title   Dean
                                           ---------------------------

                                      VECTOR

                                      By /s/ L. Read
                                         -----------------------------
                                      Title  Chairman and CEO
                                           ---------------------------

                                      -26-

<PAGE>


                                    EXHIBIT A

                         COMMON STOCK ISSUANCE AGREEMENT

   This Agreement is made as of the____ day of _______________, 1993, by and
between Vector Pharmaceuticals, Inc., a California corporation (the
"Corporation"), and Mount Sinai School of Medicine ("Mount Sinai").

                                   WITNESSETH:

   WHEREAS, the Corporation desires to issue, and Mount Sinai desires to
purchase Common Stock of the Corporation as herein described, on the terms and
conditions hereinafter set forth; and

   WHEREAS, the issuance of Common Stock hereunder is in connection with and in
consideration of the assignment by Mount Sinai of certain technology to the
Corporation, as more fully set forth in that certain Technology Transfer
Agreement of even date herewith (the "Technology Agreement").

   NOW, THEREFORE, IT IS AGREED between the parties as follows:

   1. Mount Sinai hereby agrees to purchase from the Corporation and the
Corporation agrees to sell to Mount Sinai 175,000 shares of the Corporation's
Common Stock (the "Common Stock") at $.05 per share, for an aggregate purchase
price of Eight Thousand Seven Hundred and Fifty Dollars ($8,750.00). Payment of
the purchase price shall be made by the assignment to Mount Sinai of the
"Property," as defined in and pursuant to the Technology Agreement.  The parties
agree that the value of the Property is equal to or greater than the aggregate
purchase price of the Common Stock.

   2.   Mount Sinai acknowledges that it is aware that the Common Stock to be
issued to it by the Corporation pursuant to this Agreement has not been
registered under the Act, and that the Common Stock is deemed to constitute
"restricted securities" under Rule 144 promulgated under the Securities Act of
1933, as amended (the "Act").  In this connection, Mount Sinai warrants and
represents to the Corporation that Mount Sinai is purchasing the Common Stock
for Mount Sinai's own account and Mount Sinai has no present intention of
distributing or selling said stock except as permitted under the Act and Section
25102(f) of the California Corporations Code.  Mount Sinai further warrants and
represents that Mount Sinai has either (i) preexisting personal or business
relationships with the Corporation or any of its officers, directors or
controlling persons, or (ii) the capacity to protect its own interests in
connection with the purchase of the Common Stock by virtue of the business or
financial expertise of any professional advisors to Mount Sinai who are
unaffiliated with and who are not compensated by the Corporation or any of its
affiliates, directly or indirectly.  Mount Sinai further acknowledges that the
exemption from registration under Rule 144 will not be available for at least
three years from the date of sale of the Common Stock unless at least two years
from

                                       1.

<PAGE>

the date of sale (i) a public trading market then exists for the Common Stock of
the Corporation, (ii) adequate information concerning the Corporation is then
available to the public, and (iii) other terms and conditions of Rule 144 are
complied with; and that any sale of the Common Stock may be made only in limited
amounts in accordance with such terms and conditions.

   3.   All certificates representing any shares of Common Stock subject to the
provisions of this Agreement shall have endorsed thereon the following legends:

   (a)  THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR
INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY
STATE SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE
ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY
APPLICABLE STATE SECURITIES LAWS.

   (b)  THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A RIGHT OF
FIRST REFUSAL OPTION IN FAVOR OF THE CORPORATION AND/OR ITS ASSIGNEE(S), AS
PROVIDED IN THE BYLAWS OF THE CORPORATION.

   (c)  Any legend required to be placed thereon by appropriate Blue Sky
officials.

   4.   Without in any way limiting the foregoing, Mount Sinai further agrees
that it shall in no event make any disposition of all or any portion of the
Common Stock which it is purchasing unless and until:

        (i) There is then in effect a registration statement under the Act
covering such proposed disposition and such disposition is made in accordance
with said registration statement; or

        (ii)  (a) It shall have notified the Corporation of the proposed
disposition and shall have furnished the Corporation with a detailed statement
of the circumstances surrounding the proposed disposition, (b) it shall have
furnished the Corporation with an opinion of its own counsel to the effect that
such disposition will not require registration of such shares under the Act, and
(c) such opinion of its counsel shall have been concurred in by counsel for the
Corporation, such concurrence not to be unreasonably withheld, and the
Corporation shall have advised it of such concurrence.

   5.   Subject to the provisions of Sections 3 and 4, the shares of the
Corporation's Common Stock acquired hereunder are transferable, in whole or in
part, without charge to the holder hereof (except for transfer taxes), upon
surrender of the certificate representing such shares, properly endorsed;
PROVIDED, HOWEVER, that the Corporation's Bylaws provide for a right of first
refusal in favor of the Company with respect to all sales, assignments, pledges
or transfers of shares of stock of the Company or any interest therein.  The
Company agrees, however, that transfers of the Common Stock acquired hereunder
to any person or entity listed on Schedule 1 (the "Permitted Transferees")
hereto shall not be subject to such right of first

                                       2.

<PAGE>


refusal and hereby waives any such rights with respect thereto, provided that
any subsequent transfer by any of the Permitted Transferees shall nonetheless be
subject to such right of first refusal.

   6.   The Corporation shall not be required (i) to transfer on its books any
shares of Common Stock of the Corporation which shall have been sold or
transferred in violation of any of the provisions set forth in this Agreement or
(ii) to treat as owner of such shares or to accord the right to vote as such
owner or to pay dividends to any transferee to whom such shares shall have been
so transferred.

   7.   Mount Sinai hereby agrees that for a period of not less than 90 days and
up to a maximum of 180 days following the effective date of the first
registration statement of the Corporation covering Common Stock (or other
securities) to be sold on its behalf in an underwritten public offering, it
shall not, to the extent requested by the Corporation and any underwriter, sell
or otherwise transfer or dispose of (other than to donees who agree to be
similarly bound) any Common Stock of the Corporation held by it at any time
during such period except Common Stock included in such registration; provided,
however, that all officers and directors of the Corporation who hold securities
of the Corporation or options to acquire securities of the Corporation enter
into similar agreements.

   In order to enforce the foregoing covenant, the Corporation may impose stop-
transfer instructions with respect to the Common Stock held by Mount Sinai (and
the shares or securities of every other person subject to the foregoing
restriction) until the end of such period.

   8.   The parties agree to execute such further instruments and to take such
further action as may reasonably be necessary to carry out the intent of this
Agreement.

   9.   Any notice required or permitted hereunder shall be given in writing and
shall be deemed effectively given upon personal delivery or delivery by express
courier, or four days after deposit in the United States Post Office, by
registered or certified mail with postage and fees prepaid, addressed to the
other party hereto at its address hereinafter shown below its signature or at
such other address as such party may designate by ten days' advance written
notice to the other party hereto.

   10.  This Agreement shall be governed by the laws of the State of California
and interpreted and determined in accordance with the laws of the State of
California, as such laws are applied by California courts to contracts made and
to be performed entirely in California by residents of that state.

   11.  This Agreement shall inure to the benefit of the successors and assigns
of the Corporation and, subject to the restrictions on transfer herein set
forth, shall be binding upon Mount Sinai, its successors and assigns.


                                       3.

<PAGE>

   12.  This Agreement constitutes the entire agreement of the parties with
respect to the subject matter hereof.

   IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the
day and year first above written.

                                      VECTOR PHARMACEUTICALS, INC.

                                      By_______________________________
                                        J. Leighton Read

                                      Address:  1815 Old County Road
                                                Belmont, CA 94002


                                      MOUNT SINAI SCHOOL OF MEDICINE

                                      By_______________________________

                                      Address:_________________________
                                              _________________________


                                       4.

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE 1

                              PERMITTED TRANSFEREES

                       [


                                                            ]


<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


                                    EXHIBIT B


                         PATENTS AND PATENT APPLICATIONS

                             DESCRIPTION OF PROPERTY



1.  [




                                                                               ]

2.  [





                                                                               ]


<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


3.  [



                                                                               ]


4.  [


                                                                               ]

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


                                    EXHIBIT C


        1.  [



                                        ]

        2.  [


                                        ]


<PAGE>


             [For the current versions of Exhibits D-1, D-2, and D-3
        of the Mount Sinai Agreement, see Exhibits 4.3, 4.4, 4.5, and 4.6
          to the Registration Statement on Form S-1 filed with the SEC
                     on behalf of Aviron on June 5, 1996.]


<PAGE>


                                                                    EXHIBIT 10.3


<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


                MATERIALS TRANSFER AND INTELLECTUAL PROPERTY AGREEMENT


      This is an Agreement, effective as of the 24th day of February, 1995 (the
      "Effective Date"), between Aviron, a corporation incorporated in the
      State of California, with offices located at 1450 Rollins Road,
      Burlingame, California 94010 ("AVIRON"), and the Regents of the
      University of MICHIGAN, a constitutional corporation of the State of
      MICHIGAN, with offices located at Wolverine Tower, Room 2071, 3003 South
      State Street, Ann Arbor, Michigan 48109-1280, USA ("MICHIGAN").  AVIRON
      and MICHIGAN agree as follows:

1.    BACKGROUND.

1.1   MICHIGAN possesses intellectual property and technology relating to a
      cold-adapted influenza vaccine and MASTER STRAINS useful in the
      production of PRODUCTS for vaccination against influenza, and potentially
      for gene therapy and other uses.

1.2   AVIRON acknowledges that the MASTER STRAINS are the property of MICHIGAN,
      held in confidence by and to be held in confidence for MICHIGAN.

1.3   AVIRON desires to obtain, and MICHIGAN, consistent with its mission of
      education and research, desires to grant rights and make covenants to
      allow AVIRON to develop, manufacture, use, and sell PRODUCTS produced
      using the MASTER STRAINS and KNOW-HOW for a defined geographic TERRITORY.

2.    DEFINITIONS.

2.1   "AFFILIATE(S)", shall mean any individual, corporation, partnership,
      proprietorship or other entity controlled by,


                                          1

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                                              CONFIDENTIAL TREATMENT REQUESTED


      controlling, or under common control with AVIRON through equity
      ownership, ability to elect directors, or by virtue of a majority of
      overlapping directors, and shall include any individual, corporation,
      partnership, proprietorship or other entity directly or indirectly
      beneficially owning, owned by or under common ownership with AVIRON to
      the extent of [                         ] or more of the voting
      securities of or voting interest in the owned entity.

2.2   "FIRST COMMERCIAL SALE" shall mean the first sale of any PRODUCT by
      AVIRON or an AFFILIATE or SUBLICENSEE, other than for use in clinical
      trials being conducted to obtain governmental approvals to market
      PRODUCTS.

2.3   "IMPROVEMENTS" shall mean any patentable improvements or
      know-how relating to [                                                    
                                                             ] for PRODUCTS and
      [                                                        ] for the MASTER
      STRAINS developed by MICHIGAN's JAPAN CONTRACTEE, AVIRON, AFFILIATES, or
      SUBLICENSEES.

      The term "IMPROVEMENTS" is not intended to include [                      
                                                                                
                                                                                
                                                                                
                                                                      ]

2.4   "JAPAN CONTRACTEE" shall mean the entity contracting with MICHIGAN for
      the rights to make, use and sell PRODUCTS in Japan (including the current
      contracting entity and any replacement or successor entity that may so
      contract with MICHIGAN).

2.5   "KNOW-HOW" shall mean the production processes, information data, and
      knowledge developed as of the Effective Date by MICHIGAN's faculty member
      Dr. Maassab, or under his direction


                                          2

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      at MICHIGAN, and necessary or useful for [                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                            ]

2.6   "MASTER STRAINS" shall mean donor strains of influenza viruses [          
                                            ] developed by MICHIGAN's faculty
      member Dr. Maassab, and provided by MICHIGAN hereunder, having the
      characteristics of and significant homology to the following [            
                                                                                
                                                                                
                                                                                
                 ]

2.7   "NET SALES" shall mean the sum, over the term of this Agreement, of all
      amounts actually received and all other consideration actually received
      (or, when in a form other than cash or its equivalent, the fair market
      value thereof when received) by AVIRON and its AFFILIATES and
      SUBLICENSEES from persons or entities due to or by reason of the sale,
      distribution or use of PRODUCTS, less the following deductions and
      offsets, but only to the extent such sums are otherwise included in the
      computation of NET SALES, or are paid by AVIRON and its AFFILIATES and
      SUBLICENSEES and not otherwise reimbursed: refunds, rebates, replacements
      or credits actually allowed and taken by purchasers for return of
      PRODUCTS; government-mandated rebates or refunds given by AVIRON,
      AFFILIATES and SUBLICENSEES for purchases of PRODUCTS; customary trade,
      quantity and cash discounts actually allowed and taken; excise,
      value-added, transportation, use and sales taxes actually paid by AVIRON
      and its AFFILIATES and SUBLICENSEES for PRODUCTS; and


                                          3

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      shipping and handling charges actually paid by AVIRON and its AFFILIATES
      and SUBLICENSEES for PRODUCTS.  Sales of PRODUCTS intended for resale to
      third parties, made internally amongst AVIRON and its AFFILIATES and
      SUBLICENSEES, shall not be deemed sales for purposes of calculating "NET
      SALES" subject to royalty pursuant to Paragraph 5.3 of this Agreement
      (note that the resale by the recipient shall be included in the
      calculation of "NET SALES" and subject to royalty).  Whenever the term
      "PRODUCT" may apply to a property during various stages of manufacture,
      use or sale, "NET SALES," as otherwise defined, shall be derived from the
      sale, distribution or use of such PRODUCT by AVIRON or AFFILIATES or
      SUBLICENSEES at the stage of its highest invoiced value to unrelated
      third parties.

2.8   "PATENTS" means any patent applications or patents covering MASTER
      STRAINS and KNOW-HOW, and also covering IMPROVEMENTS other than those
      owned by AVIRON, AFFILIATES and SUBLICENSEES, under which and to the
      extent that MICHIGAN has the right to grant rights and for which MICHIGAN
      does not have to pay a royalty to a third party.  PATENTS owned by
      MICHIGAN shall be referred to herein as "MICHIGAN PATENTS."

2.9   "PARTIES", in singular or plural usage as required by the context, shall
      mean AVIRON and/or MICHIGAN.

2.10  "PRIOR CONTRACTEE" shall mean [                                           
                                                                ] MICHIGAN's
      former licensee in the TERRITORY to the MASTER STRAINS pursuant to a
      terminated agreement.

2.11  "PRODUCTS" shall mean (i) [                                               
                                                                                
                                                                                
                                                              ] as well as (ii) 
      [


                                          4

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


                                                                              ]

2.12  "ROYALTY QUARTERS" shall mean the three-month periods ending on the last
      day of March, June, September and December of each year.

2.13  "SUBLICENSEE(S)" shall mean any person or entity, except an AFFILIATE,
      sublicensed by AVIRON under this Agreement to make, have made, use,
      market or sell, PRODUCTS in the TERRITORY.

2.14  "TECHNOLOGICAL DATA" shall mean any technical data or information
      relating to the MASTER STRAINS and to PRODUCTS which may be necessary or
      useful to exercise the rights to MASTER STRAINS and KNOW-HOW granted
      under this Agreement and to obtain regulatory approval of PRODUCTS in the
      TERRITORY, and which are generated by AVIRON, its AFFILIATES and
      SUBLICENSEES, or by[                                                      
                                      ] or by MICHIGAN's JAPAN CONTRACTEE or
      PRIOR CONTRACTEE where such technical data or information is actually
      provided to MICHIGAN.  The term includes without limitation[              
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
            ]

2.15  "TERRITORY" means all countries of the world except Japan.


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<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED

2.16  "VALID CLAIMS" means any claim(s) in an unexpired patent or pending in a
      patent application included within MICHIGAN PATENTS which has not been
      held unenforceable, unpatentable, or invalid by a decision of a court or
      other governmental agency of competent jurisdiction, unappealable or
      unappealed within the time allowed for appeal, and which has not been
      admitted to be invalid or unenforceable through reissue or disclaimer. 
      If in any country there should be two or more such decisions conflicting
      with respect to the validity of the same claim, the decision of the
      higher or highest tribunal shall thereafter control; however, should the
      tribunals be of equal rank, then the decision or decisions upholding the
      claim shall prevail when the conflicting decisions are equal in number,
      and the majority of decisions shall prevail when the conflicting
      decisions are unequal in number.

3.    GRANT OF RIGHTS; COVENANTS OF MICHIGAN.

3.1   MICHIGAN hereby grants to AVIRON the exclusive right, under any of
      MICHIGAN's rights in the MASTER STRAINS, KNOW-HOW and TECHNOLOGICAL DATA,
      to use MASTER STRAINS and to practice and use KNOW-HOW and TECHNOLOGICAL
      DATA solely to make, have made, use, market and sell, PRODUCTS in the
      TERRITORY; with the right to grant sublicenses to AFFILIATES and
      SUBLICENSEES subject to the terms and provisions of Article 10 below.

3.2   MICHIGAN also hereby grants to AVIRON the exclusive license under
      PATENTS, to make, have made, use, market, import, offer for sale and sell
      PRODUCTS in the TERRITORY; with the right to grant sublicenses to
      AFFILIATES and SUBLICENSEES subject to the terms and provisions of
      Article 10 below.  MICHIGAN reserves the right to practice any PATENTS
      for internal research and education purposes within the TERRITORY, and to
      license and practice any PATENTS for any purpose outside of the
      TERRITORY.


                                          6

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


3.3   MICHIGAN further grants to AVIRON the exclusive option to extend the
      definition of the term "TERRITORY" under this Agreement to include Japan,
      should MICHIGAN's agreement with the current JAPAN CONTRACTEE expire or
      terminate for any reason.  MICHIGAN shall notify AVIRON of any such
      expiration or termination, and AVIRON shall thereafter have [             
                                                                                
                                                                 ] AVIRON may
      exercise this option without payment of additional consideration other
      than as provided under this Agreement.

3.4   During the term of this Agreement MICHIGAN covenants not to enter into
      any agreement allowing any other party to use MASTER STRAINS or practice
      KNOW-HOW, TECHNOLOGICAL DATA, or IMPROVEMENTS for the purpose of the
      commercial manufacture or sale of PRODUCTS in the TERRITORY.


3.5   MICHIGAN further reserves the right to grant to the U.S. Government a
      nonexclusive, irrevocable, royalty-free license or licenses, with the
      right to sublicense, to any patents and patent applications covered by
      this Agreement, to the extent that such grant of license(s) is or may be
      required by research funding agreements between the University and the
      U.S. Government.

4.    PROVISION AND USE OF MASTER STRAINS; USE OF PRODUCTS.

4.1   Within thirty (30) days after the payment of the Agreement issue fee by
      AVIRON as set forth in Paragraph 5.1 below, MICHIGAN shall provide to
      AVIRON [                                                                  
                                                                                
                                                                                
                                                                                
                                                                             ]


                                          7

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED


4.2   AVIRON, AFFILIATES and SUBLICENSEES shall use MASTER STRAINS
      only for the development, manufacture and sale of PRODUCTS.

4.3   AVIRON, AFFILIATES and SUBLICENSEES may make new passages of the MASTER 
      STRAINS, [                          ] All MASTER STRAIN samples, including
      all passages made by AVIRON and AFFILIATES and SUBLICENSEES, shall be the
      property of MICHIGAN.

4.4   AVIRON, AFFILIATES and SUBLICENSEES shall not provide MASTER STRAINS
      including passages thereof to any third party.

4.5   AVIRON, AFFILIATES and SUBLICENSEES shall return or destroy at MICHIGAN's
      option all [                                                              
                                                                                
                                                                                
                                                                                
                                                                                
                                                                     ] to
      MICHIGAN upon any termination of this Agreement.

4.6   It is acknowledged that the MASTER STRAINS are confidential materials of
      MICHIGAN, pursuant to Article 16 below, and that unauthorized disclosure
      or transfer to third parties may result in financial detriment to
      MICHIGAN.  AVIRON agrees to use its best efforts to limit use of all
      MASTER STRAINS for [                                                      
                                                             ]to treat the
      MASTER STRAINS as confidential pursuant to the terms of Article 16 below,
      and to limit access to the MASTER STRAINS to those of AVIRON's and its
      AFFILIATES' and SUBLICENSEES' employees reasonably requiring same for the
      purpose of manufacturing and commercialization of PRODUCTS, who further
      are obligated in writing to treat the MASTER STRAINS in a manner and to
      an equivalent extent as provided herein with regard to confidentiality,
      use and non-disclosure.


                                          8

<PAGE>

4.7   AVIRON, AFFILIATES and SUBLICENSEES shall use their best efforts to
      manufacture, analyze and store PRODUCTS and MASTER STRAINS in accordance
      with all applicable government laws and regulatory agency requirements. 
      AVIRON, AFFILIATES and SUBLICENSEES shall be responsible for maintaining
      the stability and viability of the MASTER STRAINS.

4.8   During the course of the Agreement, MICHIGAN shall have the right to
      request, at reasonable intervals and quantities, such batch samples of
      PRODUCTS from AVIRON, AFFILIATES and SUBLICENSEES as it may desire for
      non-human research purposes only.  PRODUCTS supplied to MICHIGAN prior to
      the FIRST COMMERCIAL SALE shall be maintained in confidence by MICHIGAN
      pursuant to the terms of Article 16 below and shall not be transferred to
      any third party unless required by law.

4.9   During the term of this Agreement, MICHIGAN shall not authorize the
      transfer of any MASTER STRAINS samples to any third party other than the
      JAPAN CONTRACTEE (subject to restrictions equivalent to those made under
      MICHIGAN's contract with the current JAPAN CONTRACTEE), except: (i)
      transfers required under any contractual obligations existing as of the
      Effective Date, and transfers required (and only to the extent required)
      under future research agreements between MICHIGAN and the Federal
      Government; (ii) transfers required by the Federal Government or by law;
      (iii) transfers, including publicly available deposits, of materials
      incorporating derivatives of MASTER STRAINS (such as reassortants), in
      support of academic publications and as consistent with generally
      accepted publication policies, made under arrangements restricting the
      use of such materials to uses for research purposes only; (iv) transfers
      for research purposes only, and only when made on terms reasonably
      acceptable to AVIRON; and (v) transfers as provided under Paragraph 11.2
      or otherwise agreed upon in advance by AVIRON.


                                          9

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      MICHIGAN acknowledges that this is a material obligation under this
      Agreement.

      Should MICHIGAN authorize a transfer in violation of this Paragraph 4.9
      to a third party which thereafter develops a vaccine product produced
      from a seed virus derived from the MASTER STRAINS so received, and that
      vaccine product is distributed in competition with PRODUCTS manufactured,
      marketed, distributed or sold by AVIRON, AFFILIATES or SUBLICENSEES,
      then[                                                                     
                                                                                
                                                                                
                                                                                
                                                                                
                                    ] This [                                    
                                                                                
                                                                                
                                                                                
             ] This remedy is not exclusive.

4.10  Should any transfer of MASTER STRAINS occur directly from MICHIGAN to a
      third party, excluding transfers from MICHIGAN permitted under Paragraph
      4.9 or occurring prior to the Effective Date, and that third party
      thereafter develops a vaccine product produced from a seed virus derived
      from the MASTER STRAINS so received, and that vaccine product is
      distributed in competition with PRODUCTS manufactured, marketed,
      distributed or sold by AVIRON, AFFILIATES or SUBLICENSEES, then [         
                                                                                
                                                                                
                   ]

4.11  MICHIGAN represents that, to its knowledge, all third parties which have
      received MASTER STRAINS directly from MICHIGAN prior to the Effective
      Date are listed on the List of Known


                                          10

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      Recipients of MASTER STRAINS which is attached hereto and incorporated
      herein as Exhibit B.

5.    CONSIDERATION.

5.1   AVIRON shall pay to MICHIGAN a non-creditable, non-refundable
      fee of [                                                ] upon execution
      of this Agreement.

5.2   AVIRON shall also pay to MICHIGAN a further non-creditable,
      non-refundable fee of [                                                ]
      within thirty (30) days of [                                              
                                                                                
                                                                                
                                                                                
                                                       ] (AVIRON shall notify
      MICHIGAN within thirty (30) days of [                                     
                       ] described in this Paragraph.)

5.3   AVIRON shall also pay MICHIGAN, with respect to each ROYALTY QUARTER, a
      royalty equal to:

      (i)    [                                          ] of NET SALES of
             AVIRON and AFFILIATES for all PRODUCTS defined under Subparagraph
             2.11(i) above; and

      (ii)   [                                               ] of NET SALES of
             AVIRON and AFFILIATES for all other PRODUCTS.

      Where NET SALES are generated for PRODUCTS that are vaccines which
      actually contain, in final form, more than one virus, then the royalty
      rate otherwise payable upon those NET SALES under Subparagraph 5.3(i) or
      (ii) above shall be multiplied by a fraction, the numerator of which
      shall be [                                                                
                                                                                
                                                       ] and the


                                          11

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


      denominator of which shall be [                                          
                   ]

5.5   AVIRON shall also transfer to MICHIGAN, upon execution of this Agreement,
      shares of AVIRON stock and warrants to shares of AVIRON stock according
      to the terms of the Stock Transfer Agreement which is attached hereto and
      incorporated herein as Exhibit A. (Note: AVIRON's obligations under the
      Stock Transfer Agreement are deemed by the Parties to be material
      obligations of this Agreement, and MICHIGAN has certain termination
      rights applicable to this Agreement pursuant to Section 1.2 of the Stock
      Transfer Agreement.)

5.6   AVIRON and MICHIGAN shall execute, simultaneously with this Agreement, a
      Research Agreement under which AVIRON shall support continued research
      relating to the MASTER STRAINS by MICHIGAN for at least [           ]
      with a support commitment by AVIRON of [                             ].

5.7   The PARTIES acknowledge that the consideration to be received by MICHIGAN
      herein is made by AVIRON in exchange for the rights granted hereunder
      especially to MASTER STRAINS, and also to KNOW-HOW, PATENTS (if any,
      including PATENTS covering IMPROVEMENTS), and TECHNOLOGICAL DATA.  AVIRON
      acknowledges that the provision of the physical MASTER STRAINS, KNOW-HOW
      and TECHNOLOGICAL DATA by MICHIGAN, and AVIRON's and its AFFILIATES and
      SUBLICENSEES access to MASTER STRAINS, KNOW-HOW and TECHNOLOGICAL DATA
      thereby gained, is sufficient to create the obligations for consideration
      agreed to herein.

6.    REPORTS.

6.1   Within [                          ] after the close of each ROYALTY
      QUARTER during the term of this Agreement (including the close of any
      ROYALTY QUARTER immediately following any termination of this Agreement),
      AVIRON shall report to


                                          12

<PAGE>

      MICHIGAN all royalties accruing to MICHIGAN during such ROYALTY QUARTER. 
      Such quarterly reports shall indicate for each ROYALTY QUARTER the gross
      sales and NET SALES of PRODUCTS by AVIRON, AFFILIATES and SUBLICENSEES;
      as well as the various calculations used to arrive at said amounts,
      including the quantity, description (nomenclature and type designation),
      country of manufacture and country of sale of PRODUCTS.  In case no
      payment is due for any such period, AVIRON shall so report.

6.2   AVIRON covenants that it will promptly establish and consistently employ
      a system of specific nomenclature and type designations for PRODUCTS so
      that various types can be identified and segregated in the reports owed
      under Paragraph 6.1, where necessary; AVIRON, AFFILIATES and SUBLICENSEES
      shall consistently employ such system when rendering invoices thereon and
      henceforth agree to inform MICHIGAN, or its auditors, when requested as
      to the details concerning such nomenclature system as well as to all
      additions thereto and changes therein.

6.3   AVIRON shall keep, and shall require its AFFILIATES and SUBLICENSEES to
      keep, true and accurate records and books of account containing data
      reasonably required for the computation and verification of payments to
      be made as provided by this Agreement, which records and books shall be
      open for inspection upon reasonable notice during business hours by
      either MICHIGAN auditor(s) or an independent certified accountant
      selected by MICHIGAN, for the purpose of verifying the amount of payments
      due and payable.  Without in any way foreshortening any applicable
      statute of limitations, said right of inspection will exist for four (4)
      years from the date of origination of any such record, and this
      requirement and right of inspection shall survive any termination of this
      Agreement.  MICHIGAN shall be responsible for all expenses of such
      inspection, except that if such


                                          13

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


      inspection reveals an underpayment of royalties to MICHIGAN in excess of
      ten percent (10%), then said inspection shall be at AVIRON's expense and
      such underpayment shall become immediately due and payable to MICHIGAN.

6.4   The reports provided for hereunder shall be certified by an authorized
      representative of AVIRON to be correct to the best of AVIRON's knowledge
      and information.

7.    TIMES ANID CURRENCIES OF PAYMENTS.

7.1   All payments accrued during each ROYALTY QUARTER shall be due and payable
      in Ann Arbor, Michigan on the date each quarterly report is due (as
      provided in Paragraph 6.1), shall be included with such report and shall
      be paid in United States dollars.  AVIRON agrees to make all payments due
      hereunder to MICHIGAN by check made payable to "The Regents of The
      University of Michigan" and sent according to the instructions for
      notices set forth in Article 23 herein.

7.2   On all amounts outstanding and payable to MICHIGAN, interest shall accrue
      from the date such amounts are due and payable at [                       
                                                                                
                                 ] or at such lower rate as may be required by
      law.

7.3   Where NET SALES are generated in foreign currency, such foreign currency
      shall be converted into its equivalent in United States dollars at the
      exchange rate of such currency as reported (or if erroneously reported,
      as subsequently corrected) in the Wall Street Journal on the last
      business day of the ROYALTY QUARTER during which such payments are
      received by AVIRON, AFFILIATES or SUBLICENSEES (or if not reported on
      that date, as quoted by the Chase Manhattan Bank, N.A., in New York City,
      New York).


                                          14

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



7.4   Except as provided in the definition of NET SALES, all royalty payments
      to MICHIGAN under this Agreement shall be without deduction for sales,
      use, excise, personal property or other similar taxes or other duties
      imposed on such payments by the government of any country or any
      political subdivision thereof; and any and all such taxes or duties shall
      be assumed by and paid by AVIRON.

8.    COMMERCIALIZATION.

8.1   As between MICHIGAN and AVIRON, it is understood that AVIRON has the
      responsibility for obtaining any governmental approvals to manufacture
      and/or sell PRODUCTS.

8.2   AVIRON agrees to [                        ] (i) to develop PRODUCTS,
      obtain any government approvals necessary, and manufacture and sell
      PRODUCTS at the earliest possible date; (ii) to effectively exploit,
      market and manufacture in sufficient quantities to meet anticipated
      customer demand; and (iii) to make the benefits of the PRODUCTS
      reasonably available to the public.

8.3   AVIRON shall [                                                            
                       ] to commercialize (or have commercialized) PRODUCTS
      designed and marketed for all commercially feasible fields of use.

8.4   Within thirty (30) days of the FIRST COMMERCIAL SALE, AVIRON shall resort
      by written letter to MICHIGAN the date and general terms of that sale.

8.5   [                                                                         
                                                                                
                                                                                
                                                                                


                                          15

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



                                ]

9.    TECHNOLOGICAL DATA: IMPROVEMENTS.

9.1   As soon as practical and not later than forty-five (45) days after the
      Effective Date, each PARTY shall disclose to the other TECHNOLOGICAL DATA
      in its possession (including TECHNOLOGICAL DATA received by MICHIGAN from
      its PRIOR CONTRACTEE), to the extent not previously made available to
      the other PARTY.

9.2   During the course of this Agreement, MICHIGAN shall provide AVIRON with
      any additional TECHNOLOGICAL DATA as said TECHNOLOGICAL DATA is developed 
      [                       ] or when said TECHNOLOGICAL DATA is received by
      MICHIGAN if generated by MICHIGAN's JAPAN CONTRACTEE.

9.3   At least once every six (6) months, AVIRON shall submit to MICHIGAN (i)
      copies of all reports relating to the TECHNOLOGICAL DATA which AVIRON,
      including its AFFILIATES and SUBLICENSEES, has generated since the last
      reporting period, and (ii) a report informing MICHIGAN of the status of
      the developmental work respecting PRODUCTS.

9.4   All TECHNOLOGICAL DATA and IMPROVEMENTS developed or acquired by AVIRON,
      AFFILIATES and SUBLICENSEES (other than TECHNOLOGICAL DATA acquired from
      MICHIGAN), whether or not patented, shall be disclosed to MICHIGAN and an
      irrevocable, royalty-free license, with the right to sublicense outside
      the TERRITORY to the JAPAN CONTRACTEE, to utilize such TECHNOLOGICAL DATA
      or IMPROVEMENTS only with regard to the manufacture, use, marketing or
      sale of PRODUCTS shall be granted to MICHIGAN.  Upon request by MICHIGAN,
      AVIRON shall


                                          16

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      file, prosecute and maintain patents on AVIRON's and its AFFILIATES' and
      SUBLICENSEES' IMPROVEMENTS outside the TERRITORY (I.E., in Japan) using
      patent counsel selected by AVIRON and MICHIGAN shall reimburse AVIRON for
      its costs associated with such patent filing, prosecution and maintenance
      outside the TERRITORY.  AVIRON shall be responsible for prosecuting and
      maintaining at its own expense all other patents and patent applications
      on its IMPROVEMENTS.

10.   SUBLICENSING.

10.1  AVIRON shall have the exclusive right to grant sublicenses to its rights
      under Article 3 above to AFFILIATES and SUBLICENSEES, to make, have made,
      use, market and sell, PRODUCTS in the TERRITORY.

10.2  AVIRON shall notify MICHIGAN of every sublicense agreement and each
      amendment thereto, within thirty (30) days after their execution, and
      indicate the name of the SUBLICENSEE or AFFILIATE, the territory of the
      sublicense, and the scope of the sublicense.

10.3  Any sublicense granted by AVIRON under this Article 10 shall provide for
      [








                                          17

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



                  ]

10.4  All sublicenses shall be consistent with the terms and conditions of this
      Agreement, and shall contain all terms as required by this Agreement,
      including acknowledgement of MICHIGAN's disclaimer of warranty and the
      limitation on MICHIGAN's liability, as described by Article 13; and also
      including the following obligations and duties at least to the extent
      described in the various noted sections herein, and to the extent
      required so as to allow AVIRON to fulfill its obligations under the
      various sections herein: obligations and restrictions relating to MASTER
      STRAINS, PRODUCTS, and their ownership and use (Article 4); duties of use
      of a nomenclature system (Paragraph 6.2); duties to keep records
      (Paragraph 6.4); obligations regarding the periodic reporting, disclosure
      and grant of rights to TECHNOLOGICAL DATA and IMPROVEMENTS (Article 9);
      duties to avoid improper representations or responsibilities (Paragraph
      13.4); obligations to defend, hold harmless, and indemnify MICHIGAN
      (Article 14); obligations to obtain insurance (Paragraph 14.3);
      obligations relating to the return and non-use of MASTER STRAINS and
      TECHNOLOGICAL DATA and prohibitions on the manufacture of PRODUCTS after
      termination of the Agreement (Paragraph 15.5); duties to provide rights
      to MICHIGAN to TECHNOLOGICAL DATA and IMPROVEMENTS upon termination of
      the Agreement (Paragraph 15.6); duties relating to Confidential
      Information (Article 16) and to pre-publication disclosure (Article 17);
      duties to control export (Article 20); and duties to restrict the use of
      MICHIGAN's name (Article 22).  With respect to SUBLICEENSEES sublicensed
      solely to manufacture PRODUCTS for sale to AVIRON and AFFILIATES, duties
      regarding use of a nomenclature system and recordkeeping may be
      inapplicable.


                                          18

<PAGE>

11.   PATENT APPLICATIONS AND MAINTENANCE.

11.1  MICHIGAN shall control, subject to AVIRON's participation as provided in
      Paragraph 11.2, all aspects of preparing, filing, prosecuting, and
      maintaining MICHIGAN PATENTS in the TERRITORY, including foreign filings
      and Patent Cooperation Treaty filings.  AVIRON shall, at its own expense,
      perform all actions and execute or cause to be executed all documents
      necessary to support such filing, prosecution, or maintenance.

11.2  MICHIGAN shall notify AVIRON of all information received by MICHIGAN
      relating to the preparation, filing, prosecution and maintenance of
      MICHIGAN PATENTS, including any lapse, revocation, surrender,
      invalidation or abandonment of any of the MICHIGAN PATENTS, in sufficient
      time to allow AVIRON to review and comment upon such information.  AVIRON
      shall have the right to use its own patent counsel in making its review
      and comment.  MICHIGAN shall deposit or otherwise make available MASTER
      STRAINS as part of the prosecution of any MICHIGAN PATENTS only after
      notification of AVIRON, and only provided AVIRON does not reasonably
      object.

11.3  MICHIGAN may in its sole discretion decide to refrain from or to cease
      prosecuting or maintaining any of the MICHIGAN PATENTS in the TERRITORY,
      including any foreign filing or any Patent Cooperation Treaty filing.  In
      the event that MICHIGAN makes such decision, MICHIGAN shall notify AVIRON
      promptly and in sufficient time to permit AVIRON at its sole discretion
      to continue such prosecution or maintenance at AVIRON's expense.  If
      AVIRON elects to continue such prosecution or maintenance, MICHIGAN shall
      execute such documents and perform such acts at AVIRON's expense as may
      be reasonably necessary for AVIRON to so continue such prosecution or
      maintenance; however, in no circumstance may MASTER STRAINS samples be
      provided to any entity for patent

                                          19

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      purposes (e.g., registration of samples with a materials repository
      agency for public access) without MICHIGAN's express consent.

11.4  AVIRON shall reimburse patent expenses paid by MICHIGAN as follows: 
      MICHIGAN shall provide notice to AVIRON of all reasonable and necessary
      expenses paid by MICHIGAN, with sufficiently detailed documentation to
      support such expenses in monitoring, drafting, filing, prosecuting and
      maintaining the MICHIGAN PATENTS in the TERRITORY, and in maintaining or
      asserting its inventorship or ownership interest in MICHIGAN PATENTS,
      including [                                                               
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                               ] The first such notice of expenses provided by
      MICHIGAN shall include [                                                  
                                                                                
                                                                      ] Within
      thirty (30) days of the receipt of each such notice, AVIRON shall
      reimburse MICHIGAN for all such reasonable and necessary expenses, except
      that AVIRON shall not be required to reimburse [                          
                                                                                
                                                                                
                      ] however, in any case where AVIRON fails to promptly
      reimburse MICHIGAN for any above-described expenses (whether or not
      related to filings requested by AVIRON), [                                
                                                                                
                                                                                
                                                  ]


                                          20

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



12.   INFRINGEMENT.

12.1  During the term of this Agreement, AVIRON shall have the first option to
      police MICHIGAN PATENTS against infringement by other parties in the
      TERRITORY.  This right to police includes defending any action for
      declaratory judgment of noninfringement or invalidity; and prosecuting,
      defending or settling all infringement and declaratory judgment actions
      at its expense and through counsel of its selection, except that any such
      settlement shall only be made with the advice and consent of MICHIGAN. 
      MICHIGAN shall provide reasonable assistance to AVIRON with respect to
      such actions, provided AVIRON shall reimburse MICHIGAN for out-of-pocket
      expenses incurred in connection with any such assistance rendered at
      AVIRON's request or reasonably required by MICHIGAN.  In the event AVIRON
      elects to institute any such action or suit, MICHIGAN agrees to be named
      as a nominal party therein.  MICHIGAN retains the right to participate,
      with counsel of its own choosing, in any action under this Paragraph
      12.1.

12.2  In the event that AVIRON shall institute an action for infringement of
      MICHIGAN PATENTS or defend a declaratory judgment or other action with
      respect to MICHIGAN PATENTS, any portion of any resulting settlement
      payments or damages awarded which is received by AVIRON, less [           
                                                                                
                                                                                
                                                    ] paid and unrecovered by
      AVIRON, shall be paid[    ] to AVIRON and [   ] to MICHIGAN.

12.3  In the event that AVIRON fails to take action to abate any alleged
      infringement of MICHIGAN PATENTS within[                                  
                   ] of a request by MICHIGAN to do so (or within such shorter
      period which might be required to preserve the legal rights of MICHIGAN
      under the laws of any relevant government or political subdivision
      thereof), then MICHIGAN shall have


                                          21

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


      the right to take such action (including prosecution of a suit) at its
      expense and AVIRON shall use reasonable efforts to cooperate in such
      action, at AVIRON's expense.  In the event MICHIGAN elects to institute
      any such action or suit, AVIRON agrees to be named as a nominal party
      therein.  MICHIGAN shall have full authority to settle on such terms as
      MICHIGAN shall determine, except that MICHIGAN shall not reach any
      settlement whereby it licenses a third party under any MICHIGAN PATENTS
      in the TERRITORY without the consent of AVIRON.  Any portion of any
      resulting settlement payments or damages awarded which is received by
      MICHIGAN, less [                                                          
                                                                                
                                                                                
                                                               ] paid and
      unrecovered by MICHIGAN, shall be paid [     ] to MICHIGAN and [     ]to
      AVIRON.

12.4  AVIRON shall promptly notify MICHIGAN in writing in detail of the
      discovery of any allegation by a third party of infringement resulting
      from the practice of PATENTS, and of the initiation of any legal action
      by AVIRON or by any third party with regard to any alleged infringement
      or noninfringement.  AVIRON shall in a timely manner keep MICHIGAN
      informed and provide copies to MICHIGAN of all documents regarding all
      such proceedings or actions instituted by AVIRON.

13.   NO WARRANTIES; LIMITATION ON MICHIGAN'S LIABILTTY.

13.1  MICHIGAN, including its fellows, officers, employees and agents, makes no
      representations or warranties that any PATENTS are or will be held valid,
      or that the manufacture, use, sale or other distribution of any PRODUCTS
      will not infringe upon any patent or other rights not vested in MICHIGAN.


                                          22

<PAGE>

13.2  MICHIGAN, INCLUDING ITS FELLOWS, OFFICERS, EMPLOYEES AND AGENTS, MAKES NO
      REPRESENTATIONS, EXTENDS NO WARRANTIES OF ANY KIND, EITHER EXPRESS OR
      IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF
      MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, AND ASSUMES NO
      RESPONSIBILITIES WHATEVER WITH RESPECT TO DESIGN, DEVELOPMENT,
      MANUFACTURE, USE, SALE OR OTHER DISPOSITION BY AVIRON, AFFILIATES OR
      SUBLICENSEES OF MASTER STRAINS OR PRODUCTS.

13.3  THE ENTIRE RISK AS TO PERFORMANCE OF PRODUCTS AND AS TO THE SAFE USE AND
      HANDLING OF MASTER STRAINS AND PRODUCTS IS ASSUMED BY AVIRON, AFFILIATES
      AND SUBLICENSEES.  In no event shall MICHIGAN, including its fellows,
      officers, employees and agents, be responsible or liable for any direct,
      indirect, special, incidental, or consequential damages or lost profits
      to AVIRON, AFFILIATES, SUBLICENSEES or any other individual or entity
      regardless of legal theory.  The above limitations on liability apply
      even though MICHIGAN, its fellows, officers, employees or agents may have
      been advised of the possibility of such damage.  Regardless of any
      testing which may have been done at MICHIGAN, MICHIGAN makes no
      representations regarding the efficacy or safety of PRODUCTS.

13.4  AVIRON shall not, and shall require that its AFFILIATES and SUBLICENSEES
      do not, make any statements, representations or warranties or accept any
      liabilities or responsibilities whatsoever to or with regard to any
      person or entity which are inconsistent with any disclaimer or limitation
      included in this Article 12.

14.   INDEMNITY; INSURANCE.

14.1  AVIRON shall defend, indemnify and hold harmless and shall require its
      AFFILIATES and SUBLICENSEES to defend, indemnify and hold harmless
      MICHIGAN, its fellows, officers, employees


                                          23

<PAGE>

      and agents, for and against any and all claims, demands, damages, losses,
      and expenses of any nature (including attorneys, fees and other
      litigation expenses), resulting from, but not limited to, death, personal
      injury, illness, property damage, economic loss or products liability
      arising from or in connection with, any of the following:

      (1)    Any manufacture, use, sale or other disposition by AVIRON,
             AFFILIATES, SUBLICENSEES or transferees of MASTER STRAINS or
             PRODUCTS;

      (2)    The direct or indirect use by any person of MASTER STRAINS or
             PRODUCTS made, used, sold or otherwise distributed by AVIRON,
             AFFILIATES or SUBLICENSEES;

      (3)    The use, handling, storage or disposal by AVIRON, AFFILIATES or
             SUBLICENSEES of PRODUCTS, MASTER STRAINS, or any type of
             derivative of MASTER STRAINS;

      (4)    The use by AVIRON, AFFILIATES or SUBLICENSEES of KNOW-HOW,
             IMPROVEMENTS or TECHNOLOGICAL DATA.

      No approval, review, inspection nor receipt by MICHIGAN of any
      TECHNOLOGICAL DATA, IMPROVEMENTS, samples or otherwise or representations
      made with respect thereto shall in any manner relieve AVIRON and its
      AFFILIATES and SUBLICENSEES of the responsibilities under this Paragraph
      14.1.

14.2  MICHIGAN shall be entitled to participate at its option and expense
      through counsel of its own selection, and may join in any legal actions
      related to any such claims, demands, damages, losses and expenses under
      Paragraph 12.1 above, provided MICHIGAN reasonably cooperates with
      AVIRON's handling of such action.


                                          24

<PAGE>


                                              CONFIDENTIAL TREATMENT REQUESTED



14.3  Prior to any clinical trials on humans, use in humans, or distribution of
      any PRODUCT commercially or for any human use by AVIRON or an AFFILIATE,
      AVIRON shall purchase and maintain in effect a policy of product
      liability insurance.  [                                                   
                                                                                
                                                                                
                                                   ] Each such insurance policy
      shall provide [                                                           
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                 ] AVIRON shall
      furnish certificate(s) of such insurance to MICHIGAN, upon request.

15.   TERM AND TERMINATION.

15.1  This Agreement will become effective on its Effective Date and, unless
      terminated under another, specific provision of this Agreement, will
      remain in effect until and terminate upon the latter of (i) the last to
      expire of MICHIGAN PATENTS, or (ii) the twentieth anniversary date of the
      date of the FIRST COMMERCIAL SALE; unless otherwise extended by written
      agreement of the PARTIES.  Upon expiration of this Agreement pursuant to
      this Paragraph 15.1 (i) or (ii), AVIRON shall have the right to require
      that MICHIGAN [                                                           
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                             ]


                                          25

<PAGE>

15.2  Upon any termination of this Agreement, and except as provided herein to
      the contrary, all rights and obligations of the PARTIES hereunder shall
      cease, except as follows:

      (1)    Obligations to pay royalties and other sums accruing hereunder up
             to the day of such termination;

      (2)    MICHIGAN's rights to inspect books and records as described in
             Article 6, and AVIRON's obligations to keep such records for the
             required time;

      (3)    Obligations to hold harmless, defend and indemnify MICHIGAN under
             Article 14;

      (4)    Any cause of action or claim of AVIRON or MICHIGAN accrued or to
             accrue because of any breach or default by the other PARTY
             hereunder;

      (5)    The general rights, obligations, and understandings of Articles 2,
             13, 20, 22, 30 and 31;

      (6)    Each PARTY's duty of confidentiality, to the extent set out in
             Article 16;

      (7)    MICHIGAN's licenses to any IMPROVEMENTS and TECHNOLOGICAL DATA of
             AVIRON, AFFILIATES and SUBLICENSEES, as provided in Paragraph 9.4
             above and Paragraph 15.6 below;

      (8)    Solely upon termination by expiration according to Paragraph
             15.1 (i) or (ii) , a non-exclusive right under MICHIGAN's rights
             for AVIRON to practice and use KNOW-HOW, TECHNOLOGICAL DATA and
             IMPROVEMENTS, as provided in Paragraph 3.1;

      (9)    The obligations of Paragraph 15.5 below; and


                                          26

<PAGE>

      (10)   All other terms, provisions, representations, rights and
             obligations contained in this Agreement that by their sense and
             context are intended to survive until performance thereof by
             either or both PARTIES.

15.3  If AVIRON shall at any time default in the payment of any royalty or the
      making of any report hereunder, or shall make any false report, or if
      either PARTY shall commit any material breach of any covenant or promise
      herein contained, and shall fail to remedy any such default, breach or
      report within thirty (30) days after written notice thereof by the other
      PARTY specifying such default, then that other PARTY may, at its option,
      terminate this Agreement and the rights granted herein by notice in
      writing to such effect.  Any such termination shall be without prejudice
      to either PARTY's other legal rights for breach of this Agreement.

15.4  Subject to AVIRON's right to terminate pursuant to Paragraph 15.3 above,
      AVIRON may terminate this Agreement by giving MICHIGAN a notice of
      termination, which shall include a statement of the reasons, whatever
      they may be, for such termination and the termination date established by
      AVIRON, which date shall not be sooner than twelve (12) months after the
      date of the notice.  Such notice shall be deemed by the PARTIES to be
      final and, immediately upon receipt of such notice of termination,
      MICHIGAN shall have the right to enter into agreements with third parties
      for the provision of MASTER STRAINS and KNOW-HOW for the manufacture,
      sale, and/or use of PRODUCTS and this Agreement shall immediately
      terminate upon execution by MICHIGAN of any such agreement with a third
      party.

15.5  Upon any termination of this Agreement, AVIRON shall, and shall require
      that its AFFILIATES and SUBLICENSEES shall:


                                          27

<PAGE>

      (1)    Promptly return to MICHIGAN or destroy at MICHIGAN's option the
             MASTER STRAINS and materials as required under Paragraph 4.5;

      (2)    Promptly return to MICHIGAN all TECHNOLOGICAL DATA disclosed to
             AVIRON by MICHIGAN, its JAPAN CONTRACTEE and its PRIOR CONTRACTEE,
             and except according to Subparagraph 15.2 (8), refrain from any
             further use of such TECHNOLOGICAL DATA;

      (3)    Promptly provide to MICHIGAN all TECHNOLOGICAL DATA developed or
             obtained by AVIRON, AFFILIATES and SUBLICENSEES not otherwise
             previously disclosed to MICHIGAN; and

      (4)    Except according to Subparagraph 15.2 (8), refrain from all
             further use of KNOW-HOW, PATENTS and TECHNOLOGICAL DATA made
             available by MICHIGAN, or its JAPAN CONTRACTEE or PRIOR
             CONTRACTEE, under this Agreement.

15.6  Upon any termination of this Agreement, MICHIGAN shall have an
      irrevocable, royalty-free right, with the right to sublicense that right,
      to use TECHNOLOGICAL DATA and IMPROVEMENTS of AVIRON, AFFILIATES and
      SUBLICENSEES, only with regard to the manufacture, use or sale of
      PRODUCTS.

16.   CONFIDENTIAL INFORMATION.

16.1  All MASTER STRAINS, KNOW-HOW, TECHNOLOGICAL DATA, and information
      comprising or relating to IMPROVEMENTS and PATENTS provided by one PARTY
      to the other PARTY pursuant to the terms of this Agreement shall be
      deemed "Confidential Information" if it is initially marked as
      confidential when provided to the recipient PARTY, or, if orally
      disclosed, if it is indicated as confidential at the time that it is
      disclosed and is reduced to a writing marked as confidential


                                          28

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



      and provided to the recipient PARTY within one (1) month thereafter. (All
      TECHNOLOGICAL DATA provided to AVIRON [by MICHIGAN or directly] from
      MICHIGAN's JAPAN CONTRACTEE or PRIOR CONTRACTEE shall automatically be
      deemed Confidential Information.)

16.2  For the duration of this Agreement, and for a period of [                 
                ] thereafter, such Confidential Information shall not be used
      by the recipient PARTY for purposes other than those stated in this
      Agreement and shall be protected from disclosure to third parties (except
      as allowed by this Agreement) with the same degree of care as the
      recipient PARTY would apply to its own confidential information (MICHIGAN
      may release all Confidential Information covering TECHNOLOGICAL DATA and
      IMPROVEMENTS to its JAPAN CONTRACTEE, and also pursuant to any sublicense
      as authorized by Paragraphs 9.4 and 15.6). AVIRON shall require that its
      AFFILIATES and SUBLICENSEES given access to Confidential Information are
      bound to this obligation to the same extent as AVIRON. (Note that use of
      MASTER STRAINS and PRODUCTS are also subject to the restrictions of
      Article 4 and Paragraph 15.5.)

16.3  The obligations regarding non-disclosure and non-use set forth in
      Paragraph 16.2 above shall not apply to any information or data which:

      (1)    Is or becomes published or otherwise publicly available other than
             by acts of the recipient PARTY in contravention of this Agreement;

      (2)    Can be shown by written records to have been disclosed to the
             recipient PARTY by a third party (not the JAPAN CONTRACTEE or
             PRIOR CONTRACTEE) who is not under an obligation of
             confidentiality to the other PARTY;


                                          29

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


      (3)    Can be shown by written records to have been known to the
             recipient PARTY at the time of disclosure by the other PARTY
             hereunder;

      (4)    Can be shown by written records to have been developed by the
             recipient PARTY independent of disclosures by the other PARTY;

      (5)    Is required to be disclosed by law or court order, including
             Michigan Freedom of Information Act requirements; or

      (6)    Is disclosed solely to the extent necessary to obtain governmental
             approvals of PRODUCTS.

17.   PUBLICATIQN.

      This Agreement shall not be construed as to constrain or prohibit [       
                   ] or [                                                    ]
      from presenting at symposia, national, or regional professional meetings,
      and from publishing in journals, theses or dissertations, or otherwise of
      his own choosing, presentations and publications relating to the MASTER
      STRAINS, KNOW-HOW and TECHNOLOGICAL DATA, provided, however, that AVIRON
      shall have been furnished copies of any such proposed publication or
      presentation at least thirty (30) days in advance of the submission of
      the proposed publication or presentation to a journal, editor, or other
      third party.  AVIRON shall have thirty (30) days after receipt of said
      copies, to object to the proposed publication or presentation, either
      because it contains Confidential Information of AVIRON (as defined in
      Article 16 above), or because it contains potentially patentable subject
      matter of AVIRON, or to identify potentially patentable subject matter of
      MICHIGAN, needing protection.  In the event that AVIRON makes such
      objection, then MICHIGAN shall refrain from making


                                          30

<PAGE>



      such publication or presentation until said Confidential Information of
      AVIRON is removed, or, for a maximum of six (6) months after the receipt
      of the objection, in order for AVIRON to file applications covering its
      patentable subject matter (delays of a publication or presentation in
      order to file applications covering patentable subject matter of MICHIGAN
      shall be at MICHIGAN's discretion).

18.   ASSIGNMENT.

      Due to the unique relationship between the PARTIES, this Agreement shall
      not be assignable by either PARTY without the prior written consent of
      the other PARTY.  Any attempt to assign this Agreement without such
      consent shall be void from the beginning.  MICHIGAN shall not withhold
      consent for AVIRON to assign this Agreement to a purchaser of all or
      substantially all of AVIRON's business.  No assignment shall be effective
      unless and until the intended assignee agrees in writing to accept all of
      the terms and conditions of this Agreement.  Further, AVIRON shall
      refrain from pledging any of the license rights granted in this Agreement
      as security for any creditor.

19.   REGISTRATION AND RECORDATION.

19.1  If the terms of this Agreement, or any assignment or license under this
      Agreement are or become such as to require that the Agreement or license
      or any part thereof be registered with or reported to a national or
      supranational agency of any area in which AVIRON, AFFILIATES or
      SUBLICENSEES would do business, AVIRON will, at its expense, undertake
      such registration or report.  Prompt notice and appropriate verification
      of the act of registration or report or any agency ruling resulting from
      it will be supplied by AVIRON to MICHIGAN.


                                          31

<PAGE>

19.2  Any formal recordation of this Agreement or any license herein granted
      which is required by the law of any country, as a prerequisite to
      enforceability of the Agreement or license in the courts of any such
      country or for other reasons, shall also be carried out by AVIRON at its
      expense, and appropriately verified proof of recordation shall be
      promptly furnished to MICHIGAN.

20.   LAWS AND REGULATIONS OF THE UNITED STATES; EXPORT.

20.1  This Agreement shall be subject to all United States laws and regulations
      now or hereafter applicable to the subject matter of this Agreement.

20.2  AVIRON shall comply, and shall require its AFFILIATES and SUBLICENSEES to
      comply, with all provisions of any applicable laws, regulations, rules
      and orders relating to the rights and license herein granted and to the
      testing, production, transportation, export, packaging, labeling, sale or
      use of PRODUCTS, or otherwise applicable to AVIRON's or its AFFILIATES'
      or SUBLICENSEES' activities hereunder.  AVIRON shall obtain, and shall
      require its AFFILIATES and SUBLICENSEES to obtain, such written
      assurances regarding export and re-export of technical data (including
      PRODUCTS made by use of technical data) as may be required by the Office
      of Export Administration Regulations, and AVIRON hereby gives such
      written assurances as may be required under those Regulations to
      MICHIGAN.

21.   BANKRUPTCY.

      If during the term of this Agreement, AVIRON shall make an assignment for
      the benefit of creditors, or if proceedings in voluntary or involuntary
      bankruptcy shall be instituted on behalf of or against AVIRON, or if a
      receiver or trustee shall be appointed for the property of AVIRON,
      MICHIGAN may,


                                          32

<PAGE>



      at its option, terminate this Agreement and revoke all rights herein
      granted by written notice to AVIRON, provided, however, that MICHIGAN may
      not terminate this Agreement pursuant to this Article 21 so long as
      AVIRON continues to perform its obligations under this Agreement.

22.   USE OF MICHIGAN'S NAME.

      AVIRON agrees to refrain from using and to require AFFILIATES and
      SUBLICENSEES to refrain from using the name of MICHIGAN in publicity or
      advertising without the prior written approval of MICHIGAN.  Reports in
      scientific literature and presentations of joint research and development
      work are not considered publicity.

23 .  NOTICES.

      Any notice, request, report or payment required or permitted to be given
      or made under this Agreement by either PARTY shall be given by sending
      such notice by certified or registered mail, return receipt requested, to
      the address set forth below or such other address as such PARTY shall
      have specified by written notice given in conformity herewith.  Any
      notice not so given shall not be valid unless and until actually
      received, and any notice given in accordance with the provisions of this
      Paragraph shall be effective when mailed.

      To MICHIGAN:                     The University of Michigan
                                       Technology Management Office
                                       Wolverine Tower, Room 2071
                                       3003 South State Street
                                       Ann Arbor, MI 48109-1280

                                       Attn:  File #257


                                          33

<PAGE>



     To AVIRON:                        Aviron
                                       1450 Rollins Road
                                       Burlingame, California 94010

                                       Attn:  CEO

           with a copy to:

                                       Cooley Godward
                                       Five Palo Alto Square
                                       4th Floor
                                       Palo Alto, CA 94306-2155

                                       Attn:  Barbara Kosacz

24.   INVALIDITY.

      In the event that any term, provision, or covenant of this Agreement
      shall be determined by a court of competent jurisdiction to be invalid,
      illegal or unenforceable, that term will be curtailed, limited or
      deleted, but only to the extent necessary to remove such invalidity,
      illegality or unenforceability, and the remaining terms, provisions and
      covenants shall not in any way be affected or impaired thereby.

25.   ENTIRE AGREEMENT AND AMENDMENTS.

      This Agreement contains the entire understanding of the PARTIES with
      respect to the matter contained herein.  The PARTIES may, from time to
      time during the continuance of this Agreement, modify, vary or alter any
      of the provisions of this Agreement, but only by an instrument duly
      executed by authorized officials of both PARTIES hereto.


                                          34

<PAGE>

26.   WAIVER.

      No waiver by either PARTY of any breach of this Agreement, no matter how
      long continuing or how often repeated, shall be deemed a waiver of any
      subsequent breach thereof, nor shall any delay or omission on the part of
      either PARTY to exercise any right, power, or privilege hereunder be
      deemed a waiver of such right, power or privilege.

27.   ARTICLE HEADINGS.

      The Article headings herein are for purposes of convenient reference only
      and shall not be used to construe or modify the terms written in the text
      of this Agreement.

28.   NO AGENCY RELATIONSHIP.

      The relationship between the PARTIES is that of independent contractor
      and contractee.  Neither PARTY shall be deemed to be an agent of the
      other in connection with the exercise of any rights hereunder, and
      neither shall have any right or authority to assume or create any
      obligation or responsibility on behalf of the other.

29.   FORCE MAJEURE.

      Neither PARTY hereto shall be deemed to be in default of any provision of
      this Agreement, or for any failure in performance, resulting from acts or
      events beyond the reasonable control of such PARTY, such as Acts of God,
      acts of civil or military authority, civil disturbance, war, strikes,
      fires, power failures, natural catastrophes or other "force majeure"
      events.


                                          35

<PAGE>

30.   GOVERNING LAW.

      This Agreement and the relationships between the PARTIES shall be
      governed in all respects by the law of the State of Michigan
      (notwithstanding any provisions governing conflict of laws under such
      Michigan law to the contrary), except that questions affecting the
      construction and effect of any patent shall be determined by the law of
      the country in which the patent has been granted.

31.   JURISDICTION AND FORUM.

      The PARTIES hereby consent to the jurisdiction of the courts of the State
      of Michigan over any dispute concerning this Agreement or the
      relationship between the PARTIES.  Should AVIRON bring any claim, demand
      or other action against MICHIGAN, its fellows, officers, employees or
      agents, arising out of this Agreement or the relationship between the
      PARTIES, AVIRON agrees to bring said action only in the Michigan Court of
      Claims.

      IN WITNESS WHEREOF, the PARTIES hereto have executed this Agreement in
      duplicate originals by their duly authorized officers or representatives.


      FOR AVIRON                       FOR THE REGENTS OF THE
                                       UNIVERSITY OF MICHIGAN


      By /s/ L. Read                   By /s/ Robert L. Robb
         --------------------------       ------------------------------------
        (authorized representative)      (authorized representative)

      Typed Name LEIGHTON READ         Typed Name Robert L. Robb
                 ------------------              ----------------------------
      Title CEO                        Title Director, Technology Management
            -----------------------          Office
                                             ---------------------------------
      Date March 9, 1995               Date 3-15-95
           ------------------------        ----------------------------------

                                       MASTER STRAINS AGREEMENT-
                                       AVIRON-03/07/95


                                          36

<PAGE>

EXHIBIT A TO MATERIALS TRANSFER AND INTELLECTUAL PROPERTY
AGREEMENT BETWEEN AVIRON AND THE REGENTS OF THE UNIVERSITY OF
MICHIGAN, EFFECTIVE AS OF FEBRUARY 24, 1995.

STOCK TRANSFER AGREEMENT


                                          37

<PAGE>

                               STOCK TRANSFER AGREEMENT


      THIS AGREEMENT is made as of February 24, 1995, by and among AVIRON, a
California corporation (the "Company") and THE REGENTS OF THE UNIVERSITY OF
MICHIGAN, a Michigan constitutional corporation ("MICHIGAN").

      WHEREAS, the Company and Michigan have entered into a Materials Transfer
and Intellectual Property Agreement (the "Technology Agreement") dated as of
February 24, 1995 (the "Execution Date").

      WHEREAS, in connection with the granting to Aviron by Michigan of certain
rights under the Technology Agreement, the Company has agreed to issue to
Michigan shares of its Series B Preferred Stock and, under certain
circumstances, a Warrant to purchase certain shares of the Company's capital
stock, as more fully described below;

      NOW, THEREFORE, in consideration of the mutual promises, covenants and
conditions hereinafter set forth, the parties hereto mutually agree as follows:


                                      SECTION 1

      ISSUANCE OF THE SHARES; AUTHORIZATION OF THE SHARES AND WARRANT

      1.1    ISSUANCE OF THE SHARES.  In reliance upon the representations and
agreements of Michigan contained herein, within thirty (30) days of the
Execution Date (the "Issue Date"), in partial consideration of the Technology
Agreement, the Company shall issue to Michigan 1,323,734 shares of its Series B
Preferred Stock (the "Shares"), having the rights, restrictions, privileges and
preferences set forth in the Amended and Restated Articles of Incorporation of
the Company, as amended by the Certificate of Amendment, both attached hereto as
Exhibit A (the "Articles").

      1.2    AUTHORIZATION OF SHARES AND WARRANT.  On or before the Issue Date,
the Company shall have (a) authorized the issuance of the Shares; (b) adopted
and filed the Articles with the Secretary of State of the State of California;
and (c) authorized, under the circumstances set forth in this Agreement, a
warrant to purchase shares of its common stock ("Common Stock") in the form
attached hereto as Exhibit B (the "Warrant").  Failure by the Company to meet
its obligations under this Section 1.2 by the Issue Date shall be a material
breach of this Agreement and the Technology Agreement.  In addition to all other
legal rights which Michigan may have by reason of such breach, Michigan shall
have the right upon such breach to immediately terminate this Agreement and the
Technology Agreement, and to require specific performance by the Company of its
obligations upon termination of the Technology Agreement, including those set
forth in Sections 4.5 and 15.5 thereof.  Upon the Issue Date the Company shall
deliver to Michigan copies of all requisite board and shareholder consents and a
file-


                                          1

<PAGE>

stamped copy of the Articles, accompanied by a certificate signed by an officer
of the Company certifying that the Company's obligations under this Section 1.2
have been fulfilled.


                                      SECTION 2

                    REPRESENTATIONS AND WARRANTIES OF THE COMPANY

          The Company hereby represents and warrants to Michigan as follows:

      2.1    ORGANIZATION AND STANDING.  The Company is a corporation duly
organized, validly existing, and in good standing under the laws of the State of
California.  The Company has all requisite corporate power to own and operate
its properties and assets, and to carry on its business as presently and as
proposed to be conducted.  The Company is qualified to do business as a foreign
corporation in each jurisdiction in which such qualification is required and
where the failure to be so qualified would have a material adverse effect on the
Company's business.  The Company has no subsidiaries.

      2.2    CORPORATE POWER.  The Company has all requisite legal and
corporate power to execute and deliver this Agreement and any other agreement
contemplated hereby, to transfer and issue the Shares and to issue the Warrant,
and to carry out and perform its obligations under the terms of this Aareement.

      2.3    ARTICLES.  Upon the Issue Date, the Articles, in the form attached
hereto as Exhibit A, will be the true, correct and complete Articles of
Incorporation of the Company.

      2.4    CAPITALIZATION.

      (a)    The authorized capital stock of the Company consists, or will
consist upon the Issue Date, of 35,000,000 shares of Common Stock, of which
3,484,270 shares are issued and outstanding, and 25,000,000 shares of Preferred
Stock; 5,225,000 shares of which have been designated Series A Preferred Stock,
of which 5,000,000 are issued and outstanding; 18,650,000 shares of which have
been designated Series B Preferred Stock, of which 16,666,667 are issued and
outstanding.  All such issued and outstanding shares have been duly authorized
and validly issued, and are fully paid and nonassessable.  The rights,
restrictions, privileges and preferences of the Series A Preferred Stock and
Series B Preferred Stock are as stated in the Articles.  As of the Execution
Date, and taking into account the Shares to be issued under this Agreement, the
Shares represent five percent (5%) of the issued and outstanding shares of
capital stock of the Company.

      (b)    Excepting that certain Amended and Restated Investors Rights
Agreement, dated as of September 3, 1993, among the Company and the other
parties named therein, as amended to date (the "Rights Agreement" a copy of
which is attached hereto as Exhibit C), and except as set forth herein or on the
schedule attached hereto as Exhibit D or in the Articles, as of the Execution
Date there are no outstanding rights of first refusal, preemptive rights or
other


                                          2.

<PAGE>

rights, options, warrants, conversion rights, or other agreements either
directly or indirectly for the purchase or acquisition from the Company of any
shares of its capital stock.

      2.5    Authorization.  All corporate action on the part of the Company,
its directors and shareholders necessary for the sale and issuance of the
Shares, and the Common Stock issuable upon conversion of the Shares (the
"Underlying Stock") and the performance of the Company's obligations hereunder
and under each of the other agreements contemplated hereby and the reservation
of the Underlying Stock has been taken or will be taken prior to the Issue Date.
The Shares (and the Underlying Stock), when issued in compliance with the
provisions of this Agreement, will be validly issued and will be fully paid and
nonassessable, and will be free of any liens or encumbrances; provided, however,
that the Shares (and the Underlying Stock) may be subject to restrictions on
transfer under state and/or federal securities laws as set forth herein.

      2.6    Litigation.  Neither the Company nor any of its property is
subject to any claim, action, suit, proceeding, arbitration or any investigation
before any court or other authority having jurisdiction and, to the best of the
Company's knowledge, none of the same is, or has been, threatened against the
Company or any of its property.  The Company is not a party or subject to the
provision of any order, writ, injunction, judgment or decree of any court or
governmental agency or instrumentality.  There is no action, suit or proceeding
by the Company currently pending or that the Company presently intends to
initiate.

      2.7    Other Agreements.  The execution and delivery of this Agreement by
the Company and the consummation of the transactions contemplated under the
Technology Agreement and this Agreement do not and will not, with either the
passage of time or the giving of notice, conflict with or result in the breach
of any condition or provision of, or constitute a default under, any contract,
mortgage, lien, lease, agreement, indenture or instrument to which the Company
is a party or any judgment to which it is subject.

      2.8    Governmental Consents.  All consents, approvals, orders or
authorizations of, or registrations, qualifications, designations, declarations
or filings with, any governmental authority required on the part of the Company
in connection with the valid execution and delivery of this Agreement, the
offer, transfer, sale or issuance of the Shares and the Underlying Stock, and
the consummation of all other transactions contemplated by this Agreement shall
have been obtained and will be effective on the Issue Date, except for notices
required or permitted to be filed with certain state and federal securities
commissions after such date, which notices the Company shall file on a timely
basis.

      2.9    Offering.  Assuming the accuracy of the representations and
warranties of the Purchaser contained in Section 3 hereof, the offer, issue and
sale of the Shares is exempt from registration under the Securities Act of 1933,
as amended ("Securities Act"), and under the Uniform Securities Act of Michigan.

      2.10   Absence of Material Adverse Liabilities.  The Company has no
liabilities, current or contingent, nor are its properties subject to any claim
or lien, that currently materially and adversely affect the ability of the
Company to conduct its business as presently conducted.


                                          3.

<PAGE>

      2.11   Operating Rights.  The Company has all material operating
authority, licenses, franchises, permits, certificates, consents, rights and
privileges as are necessary to the operation of its business as now conducted.


                                      Section 3

                      REPRESENTATIONS AND WARRANTIES OF MICHIGAN

      Michigan hereby represents and warrants only to the Company with respect
to the issuance of the Shares as follows:

      3.1    Authorization.  Michigan has all the requisite power and is duly
authorized to execute and deliver this Agreement and each other agreement
contemplated hereby and has taken all necessary action to consummate the
transactions contemplated hereby and thereby.  This Agreement, the Technology
Agreement, and each other agreement contemplated hereby have been duly executed
and delivered by Michigan and constitute valid and binding obligations of
Michigan, enforceable in accordance with their respective terms subject to laws
of general application relating to bankruptcy, insolvency and the relief of
debtors.

      3.2    Accredited Investor.  Michigan is an accredited investor within
the meaning of Regulation D, as promulgated under the Securities Act.

      3.3    Experience.  Michigan, alone or together with its advisors, is
experienced in evaluating and investing, in start-up biomedical research
companies such as the Company.

      3.4    Investment.  Michigan is acquiring the Shares for investment, for
its own account and not with a view to, or for resale in connection with, any
distribution thereof, and it has no present intention of selling or distributing
the Shares or the Underlying Stock.  Michigan understands that the Shares and
the Underlying Stock have not been registered under the Securities Act by reason
of a specific exemption from the registration provisions of the Securities Act
which depends upon, among other things, the bona fide nature of the investment
intent as expressed herein.

      3.5    Rule 144 and Rule 144A.  Michigan acknowledges that, because they
have not been registered under the Securities Act, the Shares and the Underlying
Stock must be held indefinitely unless subsequently registered under the
Securities Act or an exemption from such registration is available.  Michigan is
aware of the provisions of Rule 144 and Rule 144A promulgated under the
Securities Act, which rules permit limited resale of securities purchased in a
private placement subject to the satisfaction of certain conditions.

      3.6    No Public Market.  Michigan understands that no public market now
exists for any of the securities issued by the Company and that it is uncertain
whether a public market will ever exist for the Shares or the Underlying Stock.


                                          4.

<PAGE>

      3.7    Access to Data.  Michigan has received and reviewed such
information that it deemed necessary to make an informed decision concerning its
receipt of the Shares and has had an opportunity to discuss the Company's
business, management and financial affairs with its management.

      3.8    Restrictions on Transfer.  Michigan further agrees not to make any
disposition of all or any part of the Shares in any event unless and until:

             (a)     There is then in effect a registration statement under the
Securities Act covering such proposed disposition and such disposition is made
in accordance with said registration statement; or

             (b)     Michigan shall have (i) notified the Company of the
proposed disposition, (ii) furnished the Company with a detailed statement
of the circumstances surrounding the proposed disposition, and (iii) furnished
the Company with an opinion of counsel for Michigan to the effect that such
disposition will not require registration of such shares under the Act, and such
opinion of counsel for Michigan shall have been concurred in by the Company's
counsel and the Company shall have advised Michigan of such concurrence.

      3.9    Legends.  Michigan understands and agrees that all certificates
evidencing the Shares shall bear the following legend:

      "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
      UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED FOR
      SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE
      REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN OPINION
      OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY AND ITS COUNSEL THAT
      SUCH REGISTRATION IS NOT REQUIRED."


                                      Section 4

                                   INVESTOR RIGHTS

      4.1    Right of First Refusal on Company Issuances.  The Company hereby
grants to Michigan, for so long as it holds not less than 1,000,000 shares of
the Company's Series B Preferred Stock (or Common Stock issued or issuable upon
conversion of the Series B Preferred Stock) the right of first refusal to
purchase, pro rata, all (or any part) of New Securities (as defined in this
Section 4.1) that the Company may, from time to time propose to sell and issue. 
In the case where the price per share at which the New Securities are being
offered is indeterminable or is equal to or less than One Dollar ($1.00) (as
adjusted for stock splits, reclassification or otherwise), Michigan's pro rata
share, for purposes of this right of first refusal with respect to an offering
at such a price, is the ratio, the numerator of which is the number


                                          5.

<PAGE>

of shares of Common Stock then owned by Michigan as a result of the conversion
of any Series B Preferred Stock of the Company and issuable upon conversion of
the Series B Preferred Stock of the Company then owned by Michigan, and the
denominator of which is the total number of shares of Common Stock then
outstanding as a result of the conversion of any Series A and Series B Preferred
Stock of the Company or issuable upon conversion of the Series A and Series B
Preferred Stock of the Company then outstanding.  In the case where the price
per share at which the New Securities are being offered is greater than One
Dollar ($1.00) (as adjusted for stock splits, reclassifications or otherwise),
Michigan's pro rata share, for purposes of this right of first refusal with
respect to an offering at such a price, is the ratio, the numerator of which is
the number of shares of Common Stock then owned by Michigan as a result of the
conversion of any Series B Preferred Stock of the Company and issuable upon
conversion of the Series B Preferred Stock of the Company then owned by
Michigan, and the denominator of which is the total number of shares of Common
Stock outstanding immediately prior to the issuance of the New Securities,
assuming full conversion of all outstanding shares of Series A and Series B
Preferred Stock of the Company.  This right of first refusal shall be subject to
the following provisions:

             (a)     "New Securities" shall mean any capital stock of the
Company, whether now authorized or not, and rights, options, or warrants to
purchase said capital stock, and securities of any type whatsoever that are, or
may become, convertible into said capital stock; provided, however, that "New
Securities" does not include (i) securities issuable upon conversion of or with
respect to Series A Preferred Stock or Series B Preferred Stock; (ii) the
Warrant Shares (as defined in Section 5.2 hereof) issuable under Section 5 of
this Agreement; (iii) securities issued pursuant to an acquisition by the
Company by merger, purchase of substantially all of the assets, or other
reorganization whereby the Company owns more than fifty percent (50%) of the
voting power of such entity; (iv) shares of the Company's Common Stock (or
related options) issued to employees, directors or consultants of the Company
pursuant to any employee stock offering, plan, or arrangement approved by the
Board of Directors; (v) shares of the Company's Common Stock or Series A or
Series B Preferred Stock issued in connection with any stock split, stock
dividend, or similar recapitalization by the Company; (vi) securities issued
pursuant to equipment or debt financing or leases which are approved by the
Company's Board of Directors; (vii) securities issued pursuant to any corporate
partnering, strategic alliance, joint venture or licensing arrangement between
the Company and a third party; or (viii) securities issued by the Company other
than for cash or cash equivalents.  The Company agrees that it shall give
Michigan notice of the issuance of any of its securities under the circumstances
described in the foregoing clauses (vi), (vii) and (viii) not more than thirty
(30) days after the date of such issuance, which notice shall describe the
securities issued and the consideration received therefor.

             (b)     In the event that the Company proposes to undertake an
issuance of New Securities, it shall give Michigan, so long as it holds not less
than 1,000,000 shares of Common Stock of the Company issued or issuable upon
conversion of the Series B Preferred Stock, written notice of its intention,
describing the type of New Securities, the price, and the general terms upon
which the Company proposes to issue the same.  Michigan, as well as each
Investor (as defined under the Rights Agreement) who together with its
affiliates holds not less than


                                          6.

<PAGE>

1,000,000 shares of Common Stock of the Company issued or issuable upon
conversion of the Series A or Series B Preferred Stock, shall have twenty (20)
days from the date of mailing of any such notice to agree to purchase up to its
full pro rata share of such New Securities for the price and upon the general
terms specified in the notice by giving written notice to the Company and
stating therein the quantity of New Securities to be purchased.  Michigan, so
long as it holds not less than 1,000,000 shares of Common Stock of the Company
issued or issuable upon conversion of the Series B Preferred Stock, and each
Investor who together with its affiliates holds not less than 1,000,000 shares
of Common Stock of the Company issued or issuable upon conversion of the Series
A or Series B Preferred Stock, shall have a right of over allotment such that if
Michigan or any Investor fails to exercise its right to purchase its full pro
rata portion of New Securities, the Company shall so notify Michigan and the
other Investors and Michigan and such Investors (and their affiliates) who have
agreed to purchase all or any part of their pro rata share of New Securities may
purchase Michigan's or the nonpurchasing Investors' portions on a pro rata
basis, within ten days from the date of such notice.

             (c)     In the event that Michigan and the Investors (and their
affiliates) fail to exercise in full the right of first refusal within said
twenty (20) day period (plus the ten day overallotment period, if applicable)
the Company shall have sixty (60) days thereafter to sell or enter into an
agreement providing for the closing of the sale of the New Securities respecting
which Michigan's and the Investors' (and their affiliates') rights were not
exercised within thirty (30) days of such agreement at a price and upon general
terms no more favorable to the purchasers thereon than specified in the
Company's notice.  In the event the Company has not sold the New Securities
within such sixty (60) day period, the Company shall not thereafter issue or
sell any New Securities, without first offering such securities to the Investors
(and its affiliates) in the manner provided above.

             (d)     The right of first refusal granted under this Agreement
shall not apply to and shall expire upon the first closing of the first firmly
underwritten public offering of Common Stock of the Company that is pursuant to
a registration statement filed with, and declared effective by, the United
States Securities and Exchange Commission under the Securities Act.

             (e)     This right of first refusal is not assignable by Michigan.

      4.2    Information Rights.  The Company will furnish the following
information to Michigan, for so long as it holds not less than 1,000,000 shares
of Common Stock issued or issuable upon conversion of the Series B Preferred
Stock:

             (i)     As soon as practicable after the end of each fiscal year
of the Company, and in any event within one hundred and twenty (120) days
thereafter, a consolidated balance sheet of the Company and its subsidiaries, if
any, as at the end of such fiscal year, and consolidated statements of income
and consolidated statements of cash flows of the Company and its subsidiaries,
if any, for such year, prepared in accordance with generally accepted accounting
principles consistently applied and setting forth in each case in comparative
form and figures for the previous fiscal year, all in reasonable detail and
certified by independent public accountants of national stariding selected by
the Company.


                                          7.

<PAGE>

             (ii)    As soon as practicable after the end of each of the first
three quarterly accounting periods in each fiscal year, and in any event within
forty-five (45) days thereafter, a consolidated balance sheet of the Company and
its subsidiaries, if any, as at the end of such quarter, and consolidated
statements of income and consolidated statements of cash flows of the Company
and its subsidiaries, if any, for each quarter and for the current fiscal year
of the Company to date, prepared in accordance with generally accepted
accounting principles consistently applied, except that such financial
statements will not contain the notes normally required by generally accepted
accounting principles.

      The Company agrees and acknowledges that information furnished to it
under this Section 4.2 may be subject to disclosure by law, including the
Michigan Freedom of Information Act ("FOIA").  Subject to such disclosure
requirements, Michigan agrees to make reasonable efforts not to disclose such
information to any third party.  Michigan shall be under no obligation to seek
exemptions or exclusions of such information from the requirements of FOIA.

      4.3    Registration Rights.

      The Company hereby grants to Michigan the identical rights with respect
to the registration of the Shares, the Underlying Stock and the Warrant Shares
(as defined in Section 5.2 hereof) as are granted under Section 3.2 through 3.12
of the Rights Agreement to each Holder (as defined under the Rights Agreement),
as though (i) Michigan were a "Holder," (ii) the Shares and the Warrant Shares,
collectively, were "Shares," and (iii) the Warrant Shares were included within
the definition of "Registrable Securities," under the Rights Agreement. 
Michigan understands and agrees that its rights under this Section 4.3 shall be
on parity with, and not superior to, the rights granted to the parties to the
Rights Agreement under Sections 3.2 through 3.12 of the Rights Agreement, as
though Michigan were a party thereto.  In addition, Michigan agrees that it
shall be subject to any amendment or waiver of Sections 3.2 through 3.12 of the
Rights Agreement pursuant to the vote of a majority of the holders of the
outstanding Registrable Securities (as defined under the Rights Agreement) under
Section 6.8 of the Rights Agreement, provided such amendment or waiver applies
equally to both the holders of the majority and the holders of the minority of
such outstanding Registrable Securities.


                                      Section 5

                             OBLIGATION TO ISSUE WARRANT

      5.1    Conditions of Issuance.  In partial consideration of the
Technology Agreement and subject to the remaining provisions of this Section 5,
the Company shall be obligated, upon the First Commercial Sale of any Product
(as such capitalized terms are defined under Sections 2.2 and 2.11 of the
Technology Agreement) (the "Warrant Issue Date"), to issue to Michigan a
warrant, in the form attached hereto as Exhibit B (the "Warrant"), on the terms
set forth below.  The Company's obligations under this Section 5 shall terminate
immediately upon any termination of the Technology Aareement.


                                          8.

<PAGE>

      5.2    Shares Issuable upon Exercise of Warrant.  Subject to the
provisions of Section 5.4 below, the Warrant shall be exercisable for a number
of shares of the Company Common Stock (the "Warrant Shares") equal to one and
twenty-five one-hundredths percent (1.25%) of the total number of issued and
outstanding shares of the Company Common Stock on the Issue Date (including, on
an as-converted basis, outstanding shares of Preferred Stock of the Company);
provided, however, that for purposes of calculating this percentage, "issued and
outstanding shares of the Company Common Stock" shall not include shares of the
Company Common Stock, or securities convertible into the Company Common Stock:

             (i)     issued in connection with an acquisition by the Company of
another entity by merger, purchase of substantially all of its assets, or other
reorganization whereby the Company acquires, directly or indirectly, more than
50% of the voting power of such entity;

             (ii)    issued in connection with any corporate partnering,
strategic alliance, joint venture or licensing arrangement between the Company
and a third party not involving or relating to the Technology or a Product (as
such capitalized terms are defined under Sections 2.2. and 2.11 of the
Technology Agreement);

             (iii)   issued by the Company other than for cash or cash
equivalents in transactions not involving or relating to the Technology or a
Product (as such capitalized terms are defined under Sections 2.2 and 2.11 of
the Technology Agreement); or

             (iv)    issued to employees, directors or consultants which are
subject to a right to repurchase at cost (i.e. "unvested" shares).

      Notwithstanding the foregoing, if as of the Warrant Issue Date there
shall not have been an Initial Public Offering (as defined in 5.3 below), then
the Company may elect to make the Warrant exercisable for shares of the
Company's Preferred Stock convertible into the number of shares of the Company
Common Stock determined above, with rights and preferences substantially the
same as the rights and privileges of the most recent series of Preferred Stock
issued by the Company to outside investors (such Preferred Stock shall also
constitute "Warrant Shares," notwithstanding the definition of such term set
forth above).  The rights granted Michigan under Section 4.3 hereof shall apply
to the Warrant Shares regardless of whether they consist of Common Stock or
Preferred Stock of the Company.

      5.3    Warrant Exercise Price.  The initial per share exercise price for
the Warrant (the "Exercise Price") shall be equal to one hundred twenty-five
percent (125%) of the price at which shares of the Company Common Stock are
first sold to the public pursuant to a firm commitment underwritten public
offering registered under the Securities Act, other than a registration relating
solely to a transaction under Rule 145 of the Securities Act (or any successor
thereto) or to an employee benefit plan of the Company (the "Initial Public
Offering"); or, if as of the Warrant Issue Date, there shall not have been an
Initial Public Offering, the Exercise Price shall be equal to one hundred
twenty-five percent (125%) of the per share price of the securities issued to
outside investors in the Company's most recent equity financing transaction
prior to the Warrant Issue Date in which it raised at least $2 million.


                                          9.

<PAGE>

      5.4    Acquisition of the Company Prior to Warrant Issue Date.

             (a)     Notwithstanding anything to the contrary in this Section
5, in the event that prior to the Warrant Issue Date there is any consolidation
of the Company with, or merger of the Company into, any other corporation or
other entity or person, or any other corporate reorganization in which the
Company shall not be the continuing, or surviving entity of such consolidation,
merger or reorganization, or any transaction or series of transactions by the
Company (other than financing transactions in which equity securities are issued
to multiple purchasers solely for cash) in which in excess of fifty percent
(50%) of the Company's voting power is transferred, or any sale or conveyance of
all or substantially all of the assets of the Company (any of the foregoing
events being hereafter referred to as an "Acquisition") the Company may, at its
sole option, by giving written notice of such election to Michigan prior to the
effective date of the Acquisition (the "Acquisition Date"), elect to cancel its
obligation to issue the Warrant under this Section 5, in which event the
royalties payable by the Company under Paragraphs 5.3(i) and (ii) of the
Technology Agreement shall each be doubled, without any need to amend such
agreement; provided, however, that in the event such doubled royalty rate is or
becomes thereafter unduly economically burdensome to the Company, due to, for
example but without limitation, the markets in which the Company intends to
market Products or the obligations of the Company to pay to any third party
royalties for additional rights or technology necessary for the
commercialization of the Products, then Michigan agrees to consider, in good
faith, an alternative consideration in lieu of such doubled royalty rate under
this Agreement, upon request of the Company.

             (b)     If the Company does not elect to cancel the Warrant under
Section 5.4(a) above, then following the Acquisition, the Company or its
successor shall remain obligated under this Section 5 to issue the Warrant on
the Warrant Issue Date.  When and if issued after such an Acquisition, the
Warrant shall be exercisable for the amount and type of securities or other
consideration that would have been issuable in the Acquisition to a holder of
the number of shares of the Company's capital stock for which the Warrant would
have been exercisable under Section 5.2 above on the Acquisition Date, as if the
Acquisition Date were the same as the Warrant Issue Date.  The Exercise Price of
the Warrant if issued after such an Acquisition shall be equal to one hundred
twenty-five percent (125%) of the Acquisition Price.


                                      Section 6

                                    MISCELLANEOUS

      6.1    Governing Law.  This Agreement shall be governed by and 
construed in accordance with the laws of the State of California applicable 
to contracts between California residents entered into and to be performed 
entirely within the State of California.

      6.2    Successors and Assigns.  Except as otherwise provided herein, the
provisions hereof shall inure to the benefit of, and be binding upon, the
successors, assigns, heirs, executors and administrators of the parties hereto.


                                         10.

<PAGE>

      6.3    Entire Agreement; Amendment.  This Agreement and the other
documents delivered pursuant hereto constitute the final, complete and exclusive
understanding and agreement between the parties with regard to the subjects
hereof and thereof.  Any term of this Agreement may be amended and the
observance of any term of this Agreement may be waived, with the written consent
of Michigan and the Company.

      6.4    Notices.  All notices or other communications pursuant to this
Agreement shall be in writing and deemed given if delivered personally,
telecopied, sent by nationally-recognized, overnight courier or mailed by
registered or certified mail (return receipt requested) postage prepaid to the
parties at the following addresses (or at such other address for a party as
shall be specified by like notice) to the other party hereunder:

      To the Company:

             1450 Rollins Road
             Burlingame, CA  94010
             Attention:   J. Leighton Read, M.D.,
                          Chairman and Chief Executive Officer
             Telephone:   (415) 696-9116
             Fax:         (415) 347-6274

      with a copy to:

             Cooley Godward Castro Huddleson & Tatum
             Five Palo Alto Square
             Palo Alto, CA  94306
             Attention:   Robert J. Brigham, Esq.
             Telephone:   (415) 843-5000
             Fax:         (415) 857-0663

      To Michigan:

             University of Michigan
             Treasurer's Office
             5024 Fleming Administration Building
             Ann Arbor, MI  48109-1340
             Telephone:   (313) 763-1299
             Fax:         (313) 747-1483


                                          11

<PAGE>

      with a copy to:

             University of Michigan
             Technology Management Office
             3003 S. State Street
             Wolverine Tower, Room 2071
             Ann Arbor, MI 48109-1280
             Attention:   Robert L. Robb, Director
             Telephone:   (313) 763-0614
             Fax:         (313) 936-1330

      Notwithstanding the foregoing, any payment of funds required hereunder
may be made by wire transfer in accordance with written instructions given by
the receiver to the sender.

      6.5    California Corporate Securities Law.  THE SALE OF THE SECURITIES
WHICH ARE THE SUBJECT OF THIS AGREEMENT HAS NOT BEEN QUALIFIED WITH THE
COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA AND THE ISSUANCE OF SUCH
SECURITIES OR THE PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION THEREFOR
PRIOR TO SUCH QUALIFICATION IS UNLAWFUL UNLESS THE SALE OF SECURITIES IS EXEMPT
FROM THE QUALIFICATION BY SECTION 25100, 25102 OR 25105 OF THE CALIFORNIA
CORPORATIONS CODE.  THE RIGHTS OF ALL PARITES TO THIS AGREEMENT ARE EXPRESSLY
CONDITIONED UPON SUCH QUALIFICATION BEING OBTAINED, UNLESS THE SALE IS SO
EXEMPT.

      6.6    Counterparts.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, and all of which shall
constitute one and the same instrument.

      The foregoing Stock Transfer Agreement is hereby executed as of the date
      first above written.


      AVIRON                           THE REGENTS OF THE
                                       UNIVERSITY OF MICHIGAN

      By:   /s/ J. Leighton Read       By:   /s/ Robert L. Robb
          -------------------------       -----------------------------------
            J. Leighton Read, M.D.     Name: Robert L. Robb
                                             ---------------------------------
            Chief Executive Officer    Title: Director, Technology Management
                                              Office
          -------------------------           --------------------------------


                                         12.

<PAGE>

                               CERTIFICATE OF AMENDMENT
                                          OF
                              ARTICLES OF INCORPORATION
                                          OF
                                        AVIRON



J. Leighton Read and Alan C. Mendelson certify that:

1.    They are the Chief Executive Officer and the Secretary, respectively, of
      Aviron, a California corporation.

2.    Article III.B of the Articles of Incorporation of this corporation is 
      amended to read in full as follows:

             B.      Five million two hundred twenty-five thousand (5,225,000)
of the authorized shares of Preferred Stock are hereby designated "Series A
Preferred Stock." Eighteen million six hundred and fifty thousand (18,650,000)
of the authorized shares of Preferred Stock are hereby designated "Series B
Preferred Stock." The Series A Preferred Stock and Series B Preferred Stock are
collectively referred to as the "Preferred Stock."

3.    The foregoing amendment of Articles of Incorporation has been duly
      approved by the Board of Directors.

4.    The forgoing amendment has been duly approved by the required vote of the
      shareholders of the Corporation in accordance with Sections 902 and 903
      of the California Corporations Code.  The total number of outstanding
      shares of the Corporation is 3,484,270 shares of Common Stock, 5,000,000
      shares of Series A Preferred Stock, and 16,666,667 shares of Series B
      Preferred Stock.  The number of shares voting in favor of the amendment
      equated or exceeded the vote required.  The percentage vote required was
      more than 50% of the outstanding shares of the Series B Preferred Stock
      and more than 50% of the outstanding shares of the Common Stock and the
      Preferred Stock, voting together on an as-converted basis.


<PAGE>

      We further declare under penalty of perjury under the laws of the State of
California that the matters set forth in this certificate are true and correct
of our own knowledge.

Date:                 , 1995
      ----------------



                                       --------------------------------------
                                       J. Leighton Read, Chief Executive
                                                         Officer



                                        --------------------------------------
                                       Alan C. Mendelson, Secretary


                                          2.

<PAGE>

[Letterhead State of California Office of the Secretary of State]



             I, TONY MILLER, ACTING SECRETARY OF STATE OF THE STATE OF
      CALIFORNIA, HEREBY CERTIFY:

             THAT THE ANNEXED TRANSCRIPT HAS BEEN COMPARED WITH THE RECORD OF
      FILE IN THIS OFFICE, OF WHICH IT PURPORTS TO BE A COPY, AND THAT SAME IS
      FULL, TRUE AND CORRECT



[Seal]                                      IN WITNESS WHEREOF, I EXECUTE THIS
                                            CERTIFICATE AND AFFIX THE GREAT SEAL
                                            OF THE STATE OF CALIFORNIA
                                                        APR 18 1994


                                       /s/ Tony Miller
                                       ACTING SECRETARY OF STATE


<PAGE>

                                                    E N D O R S E D           
                                                       F I L E D              
                                        In the office of the Secretary of State
                                               of the State of California      
                                                      APR 15 1994             

                                                      TONY MILLER             
                                               Acting Secretary of State      


                               CERTIFICATE OF AMENDMENT
                       OF RESTATED ARTICLES OF INCORPORATION OF
                                        AVIRON
      
      J. Leighton Read and Alan C. Mendelson certify that:

      ONE:   They are the Chairman of the Board and the Secretary,
respectively, of Aviron, a California corporation (the "Corporation").

      TWO:   Article III, Section B of the Restated Articles of Incorporation
of the Corporation is amended in its entirety to read as follows:

             B.      Five million two hundred twenty-five thousand (5,225,000)
      of the authorized shares of Preferred Stock are hereby designated "Series
      A Preferred Stock." Seventeen million two hundred seventy-five thousand
      (17,275,000) of the authorized shares of Preferred Stock are hereby
      designated as "Series B Preferred Stock." The Series A Preferred Stock
      and Series B Preferred Stock are collectively referred to as the
      "Preferred Stock."

      THREE: The amendment herein set forth has been duly approved by the board
of directors.

      FOUR:  The foregoing amendment of the Corporation's Restated Articles of
Incorporation have been duly approved by the required vote of shareholders in
accordance with Sections 902 and 903 of the Corporations Code.  The total number
of outstanding shares of the Corporation is 3,427,750 shares of Common Stock,
5,000,000 shares of Series A Preferred Stock and 16,666,667 shares of Series B
Preferred Stock.  The number of shares voting in favor of the amendment equaled
or exceeded the vote required.  The percentage vote required was more than 50%
of the Common Stock and Preferred Stock voting together on an as-converted
basis, 50% of the Preferred Stock voting together on an as-converted basis and
50% of the Series B Preferred Stock.

      We further declare under penalty of perjury under the laws of the State
of California that the matters set forth in the foregoing Certificate of
Amendment are true and correct of our own knowledge.


<PAGE>

      IN WITNESS WHEREOF, the undersigned have executed this Certificate of
Amendment on April 15, 1994.


                                       /s/ J. Leighton Read
                                       ---------------------------------------
                                       J. Leighton Read, Chairman of the Board


                                       /s/ Alan C. Mendelson
                                       ---------------------------------------
                                       Alan C. Mendelson, Secretary


<PAGE>

                                      EXHIBIT A

                ARTICLES OF INCORPORATION AND CERTIFICATE OF AMENDMENT


<PAGE>

[Letterhead of Secretary of State of California


                                 CORPORATION DIVISION



      I, MARCH FONG EU, Secretary of State of the State of California, hereby
certify:

      That the annexed transcript has been compared with the corporate record
on file in this office, of which it purports to be a copy, and that same is
full, true and correct.


                                       IN WITNESS WHEREOF, I execute this    
                                       certificate and affix the Great Seal    
                                       of the State of California this

                                                    SEP - 3 1993



[Seal]



                                                /s/ March Fong Eu
                                                           SECRETARY OF STATE


<PAGE>

                                                     E N D O R S E D           
                                                        F I L E D              
                                         In the office of the Secretary of State
                                               of the State of California      
                                                       AUG 31 1993             

                                            MARCH FONG EU, Secretary of State   


                                 AMENDED AND RESTATED

                             ARTICLES OF INCORPORATION OF

                                        AVIRON


           J. Leighton Read and Alan C. Mendelson certify that:

           1.     They are the Chief Executive Officer and Secretary,
respectively, of Aviron, a California corporation (the "Corporation").

           2.     The Articles of Incorporation of this Corporation are amended
and restated as follows:


                                        "I.

           The name of this corporation is Aviron.

                                         II.

           The purpose of this corporation is to engage in any lawful act or
activity for which a corporation may be organized under the General Corporation
Law of California other than the banking business, the trust company business or
the practice of a profession permitted to be incorporated by the California
Corporations Code.

                                         III.

           A.     This corporation is authorized to issue two classes of stock
to be designated, respectively, "Common Stock" and "Preferred Stock."  The total
number of shares which the corporation is authorized to issue is Sixty Million
(60,000,000) shares.  Thirty-Five Million (35,000,000) shares shall be Common
Stock.  Twenty-Five Million (25,000,000) shares shall be Preferred Stock.

           The Preferred Stock may be issued from time to time in one or more
series.  Subject to the protective provisions set forth in Section 5 below, the
Board of Directors is hereby authorized, to fix or alter the dividend rights,
dividend rate, conversion rights, voting rights, rights and terms of redemption
(including sinking fund provisions), redemption price or prices, and the
liquidation preferences of any wholly unissued series of Preferred Stock, and
the number


                                          1.
<PAGE>

of shares constituting any such series and the designation thereof, or any of
them; and to increase or decrease the number of shares of any series subsequent
to the issuance of shares of that series, but not below the number of shares of
such series then outstanding.  In case the number of shares of any series shall
be so decreased, the shares constituting such decrease shall resume the status
that they had prior to the adoption of the resolution originally fixing the
number of shares of such series.

           B.     Five million two hundred twenty-five thousand (5,225,000) of
the authorized shares of Preferred Stock are hereby designated "Series A
Preferred Stock." Seventeen million sixty-six thousand six hundred sixty-seven
(17,066,667) of the authorized shares of Preferred Stock are hereby designated
"Series B Preferred Stock." The Series A Preferred Stock and Series B Preferred
Stock are collectively referred to as the "Preferred Stock."

           C.     The respective rights, preferences, privileges, restrictions
and other matters relating to the Series A Preferred Stock and Series B
Preferred Stock are as follows:

           1.     DIVIDENDS.  The holders of the Preferred Stock shall be
entitled to receive, payable in preference and priority to the holders of Common
Stock, when and as declared by the Board of Directors, out of any assets at the
time legally available therefor, dividends at the rate of:

                  (a)     with respect to the Series A Preferred Stock, $.05
per share per annum (as appropriately adjusted for any combination,
consolidation, stock distribution, stock dividend or similar event with respect
to such shares (a "Recapitalization")); and

                  (b)     with respect to the Series B Preferred Stock, $.09
per share per annum (as adjusted for any Recapitalization).

Such dividends shall not be cumulative and no right to such dividends shall
accrue to holders of Series A Preferred Stock or Series B Preferred Stock unless
declared by the Board of Directors.  No dividends shall be declared or paid with
respect to the Common Stock (other than a dividend payable solely in Common
Stock of the Corporation) unless a dividend of equal or greater amount per share
(on an as-if-converted to Common Stock basis) is first declared and paid with
respect to the Series A Preferred Stock and Series B Preferred Stock.  Each
share of Preferred Stock shall rank on parity with every other share of
Preferred Stock, irrespective of series, with regard to dividends, and no
dividends shall be paid, declared or set apart for payment on the shares of any
series of Preferred Stock unless at the same time a dividend for the same
Percentage of the respective dividend rates shall also be paid, declared or set
apart for payment, as the case may be, on the shares of Preferred Stock or each
other series then outstanding.


                                          2.

<PAGE>

So long as any shares of Preferred Stock shall be outstanding, no dividend,
whether in cash or property, shall be paid or declared, nor shall any other
distribution be made, on any Common Stock, nor shall any shares of any Common
Stock of the Corporation be purchased, redeemed, or otherwise acquired for value
by the Corporation (except for acquisitions of Common Stock by the Corporation
from the founders, directors, employees or consultants of the Corporation
pursuant to agreements which permit the Corporation to repurchase such shares
upon termination of employment or consulting relationship or in exercise of the
Corporation's right of first refusal upon a proposed transfer) until all accrued
but unpaid dividends on the Preferred Stock shall have been paid or declared and
set apart.  In the event dividends are paid on any share of Common Stock, an
additional dividend shall be paid with respect to all outstanding shares of
Preferred Stock in an amount for each such share of Preferred Stock equal to the
aggregate amount of such dividends for all shares of Common Stock into which
each such share of Preferred Stock could then be converted.  The provisions of
this Section 1(b) shall not, however, apply to (i) a dividend payable in Common
Stock, (ii) the acquisition of shares of any Common Stock in exchange for shares
of any other Common Stock, or (iii) any repurchase of any outstanding securities
of the Corporation that is approved by the Corporation's Board of Directors.

           2.     LIQUIDATION PREFERENCE.

                  (a)     In the event of any liquidation, dissolution or
winding up of the Corporation, either voluntary or involuntary, the holders of
the Series A Preferred Stock and Series B Preferred Stock shall be entitled to
receive, prior and in preference to any distribution of any of the assets or
surplus funds of the Corporation to the holders of Common Stock by reason of
their ownership thereof, the amount of $.50 and $.90 per share, respectively
(appropriately adjusted for an Recapitalization), plus all declared but unpaid
dividends on such share for each share of Series A Preferred Stock or Series B
Preferred Stock then held by them.  If upon the occurrence of such event, the
assets and funds thus distributed among the holders of the Series A Preferred
Stock and Series B Preferred Stock shall be insufficient to permit the payment
to such holders of the full aforesaid preferential amount, then the entire
assets and funds of the Corporation legally available for distribution shall be
distributed among the holders of the Series A Preferred Stock and Series B
Preferred Stock in proportion to the full amounts to which they would otherwise
be entitled and in proportion to the number of shares of Series A Preferred
Stock and Series B Preferred Stock then held by them.

                  (b)     After payment to the holders of the Series A
Preferred Stock and Series B Preferred Stock of the amount set forth in
subparagraph (a) above, the entire remaining assets and funds of the Corporation
legally available for distribution, if any, shall be distributed among the
holders of the Series A Preferred Stock, Series B Preferred Stock and Common
Stock pro rata based on the number of shares of Common Stock held by them
(assuming conversion of all Series A Preferred Stock and Series B Preferred
Stock).


                                          3.

<PAGE>

                  (c)     A consolidation or merger of the Corporation with or
into any other corporation or corporations, or a sale of all or substantially
all of the assets of the Corporation, other transaction or series of related
transactions resulting in a change of voting control shall be deemed a
liquidation, dissolution or winding up within the meaning of this Section 2 if
(a) more than 50% of the outstanding securities of each class of the surviving
entity, or (b) an interest in equity securities representing at least 50% of the
voting power or at least 50% of the equity interest in the surviving entity, is
not owned by persons who were holders of capital stock or securities convertible
into capital stock of the Corporation immediately prior to such merger,
consolidation or sale; provided, however, that the sale of Preferred Stock to
private investors pursuant to a Preferred Stock Purchase Agreement shall not
constitute a liquidation, dissolution or winding up within the meaning of this
section.

           3.     VOTING RIGHTS.  Except as otherwise expressly provided herein
or as required by law, the holder of each share of the Series A Preferred Stock
and Series B Preferred Stock shall be entitled to the number of votes equal to
the number of shares of Common Stock into which such share of Series A Preferred
Stock or Series B Preferred Stock could be converted on the record date for the
vote or the date of the solicitation of any written consent of shareholders and
shall have voting rights and powers equal to the voting rights and powers of the
Common Stock (except as otherwise expressly provided herein or as required by
law, voting together with the Common Stock as a single class) and shall be
entitled to notice of any stockholders' meeting in accordance with the Bylaws of
the Corporation.  Fractional votes shall not, however, be permitted and any
fractional voting rights resulting from the above formula (after aggregating
all shares into which shares of Series A Preferred Stock or Series B Preferred
Stock held by each holder could be converted) shall be rounded to the nearest
whole number (with one-half being rounded upward).

           4.     CONVERSION.  The holders of the Series A Preferred Stock and
Series B Preferred Stock shall have conversion rights as follows (the
"Conversion Rights"):

                  (a)     RIGHT TO CONVERT.  Each share of Series A Preferred
Stock and Series B Preferred Stock shall be convertible, at the option of the
holder thereof, at any time after the date of issuance of such share, at the
office of the Corporation or any transfer agent for such stock.  The number of
fully paid and nonassessable shares of Common Stock to which a holder of Series
A Preferred Stock shall be entitled upon conversion shall be the product
obtained by multiplying the "Series A Conversion Rate" then in effect
(determined as provided in Section 4(b)) by the number of shares of Series A
Preferred Stock being converted.  The number of fully paid and nonassessable
shares of Common Stock to which a holder of Series B Preferred Stock shall be
entitled upon conversion shall be the product obtained by multiplying the
"Series B Conversion Rate" then in effect (determined as provided in Section
4(c)) by the number of shares of Series B Preferred being converted.


                                          4.

<PAGE>

                  (b)     SERIES A CONVERSION RATE.  The conversion rate in
effect at any time for conversion of the Series A Preferred Stock (the "Series A
Conversion Rate") shall be the quotient obtained by dividing $.50 by the "Series
A Conversion Price," calculated as provided in Section 4(d).

                  (c)     SERIES B CONVERSION RATE.  The conversion rate in
effect at any time for conversion of the Series B Preferred Stock (the "Series B
Conversion Rate") shall be the quotient obtained by dividing $.90 by the "Series
B Conversion Price," calculated as provided in Section 4(d).

                  (d)     CONVERSION PRICE.  The conversion price for the
Series A Preferred Stock shall initially be $.50 (the "Series A Conversion
Price").  The conversion price of the Series B Preferred Stock shall initially
be $.90 (the "Series B Conversion Price").  Such initial Series A Conversion
Price and Series B Conversion Price (the "Conversion Prices") shall be adjusted
from time to time in accordance with this Section 4. All references to the
Conversion Prices herein shall mean the Conversion Prices as so adjusted.

                  (e)     AUTOMATIC CONVERSION.  Each share of Series A
Preferred Stock and Series B Preferred Stock shall automatically be converted
into shares of Common Stock at the then effective Conversion Price immediately
upon (i) the closing of the sale of the Corporation's Common Stock in a firm
commitment, underwritten public offering registered under the Securities Act of
1933, as amended (other than a registration relating solely to a transaction
under Rule 145 under such Act (or any successor thereto) or to an employee
benefit plan of the Company), at a public offering price equal to or exceeding
$2.50 per share of Common Stock (appropriately adjusted for any
Recapitalization) and the aggregate net proceeds to the Corporation (before
deduction for underwriter commissions and expenses relating to the issuance,
including without limitation fees of the Corporation's counsel) of which equal
or exceed $10,000,000 or (ii) upon receipt by the Corporation of the affirmative
vote at a duly noticed shareholders meeting or pursuant to a duly solicited
written consent of approval of the holders of at least a majority of the then
outstanding shares of the Series A Preferred Stock and Series B Preferred Stock
voting together as a single class in favor of the conversion of all of the
shares of Series A Preferred Stock and Series B Preferred Stock into Common
Stock.

                  (f)     MECHANICS OF CONVERSION.  Before any holder of Series
A Preferred Stock or Series B Preferred Stock shall be entitled to convert the
same into shares of Common Stock, he shall surrender the certificate or
certificates thereof, duly endorsed, at the office of the Corporation or of any
transfer agent for such stock, and shall give written notice to the Corporation
at such office that he elects to convert the same and shall state therein the
name or names in which he wishes the certificate or certificates for shares of
Common Stock to be issued.  The Corporation shall, as soon as practicable
thereafter, issue and deliver at such office to such holder of Series A
Preferred Stock or Series B Preferred Stock, a certificate or


                                          5.

<PAGE>

certificates for the number of shares of Common Stock to which he shall be
entitled as aforesaid.  Such conversion shall be deemed to have been made
immediately prior to the close of business on the date of surrender of the
shares of Series A Preferred Stock or Series B Preferred Stock to be converted,
except that in the case of an automatic conversion pursuant to Section 4(e)
hereof, such conversion shall be deemed to have been made (i) immediately prior
to the closing of the offering referred to in Section 4(e)(i) or (ii)
immediately upon the approval by vote or written consent referred to in Section
4(e)(ii) above, and the person or persons entitled to receive the shares of
Common Stock issuable upon such conversion shall be treated for all purposes as
the record holder or holders of such shares of Common Stock on such date.

                  (g)     ADJUSTMENTS TO CONVERSION PRICE.

                          (i)     SPECIAL DEFINITIONS.  For purposes of this
Section 4(g) "ORIGINAL ISSUE DATE" shall mean the date on which a share of
Series B Preferred Stock was first issued.

                          (ii)    ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS
OF COMMON STOCK.  In the event the Corporation at any time or from time to time
after the Original Issue Date shall declare or pay any dividend on the Common
Stock payable in Common Stock or in any right to acquire Common Stock, or shall
effect a subdivision of the outstanding shares of Common Stock into a greater
number of shares of Common Stock (by stock split, reclassification or
otherwise), or in the event the outstanding shares of Common Stock shall be
combined or consolidated, by reclassification or otherwise, into a lesser number
of shares of Common Stock, then the respective Conversion Prices of the Series A
Preferred Stock and Series B Preferred Stock in effect immediately prior to such
event shall, concurrently with the effectiveness of such event, be
proportionately decreased or increased, as appropriate.

                  (h)     OTHER DISTRIBUTIONS.  In the event the Corporation
shall at any time or from time to time make or issue, or fix a record date for
the determination of holders of Common Stock entitled to receive, a dividend or
other distribution payable in securities of the Corporation or any of its
subsidiaries, then in each such event provision shall be made so that the
holders of Series A Preferred Stock and Series B Preferred Stock shall receive,
upon the conversion thereof, the securities of the Corporation or any of its
subsidiaries which they would have received had their stock been converted into
Common Stock on the date of such event.

                  (i)     NO IMPAIRMENT.  The Corporation will not, by
amendment of its Articles of Incorporation or through any reorganization,
transfer of assets, consolidation, merger, dissolution, issue or sale of
securities or any other voluntary action, avoid or seek to avoid the observance
or performance of any of the terms to be observed or performed hereunder by the
Corporation, but will at all times in good faith assist in the carrying out of
all the provisions of this Section 4 and in the taking of all such action as may
be necessary or


                                          6.

<PAGE>

appropriate in order to protect the Conversion Rights of the holders of the
Series A Preferred Stock and Series B Preferred Stock against impairment.

                  (j)     CERTIFICATES AS TO ADJUSTMENTS.  Upon the occurrence
of each adjustment or readjustment of the Conversion Price pursuant to this
Section 4, the Corporation at its expense shall promptly compute such adjustment
or readjustment in accordance with the terms hereof and cause independent public
accountants selected by the Corporation to verify such computation and prepare
and furnish to each holder of Series A Preferred Stock and Series B Preferred
Stock a certificate setting forth such adjustment or readjustment and showing in
detail the facts upon which such adjustment or readjustment is based.  The
Corporation shall, upon the written request at any time of any holder of Series
A Preferred Stock or Series B Preferred Stock, furnish or cause to be furnished
to such holder a like certificate setting forth (i) such adjustments and
readjustments, (ii) the Conversion Price at the time in effect, and (iii) the
number of shares of Common Stock and the amount, if any, of other property which
at the time would be received upon the conversion of Series A Preferred Stock or
Series B Preferred Stock.

                  (k)     NOTICES OF RECORD DATE.  In the event of any taking
by the Corporation of a record of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend (other than a cash dividend) or other distribution, any security or
right convertible into or entitling the holder thereof to receive shares of
Common Stock, or any right to subscribe for, purchase or otherwise acquire any
shares of stock of any class or any other securities or property, or to receive
any other right, the Corporation shall mail to each holder of Series A Preferred
Stock and Series B Preferred Stock at least 20 days prior to the date specified
therein, a notice specifying the date on which any such record is to be taken
for the purpose of such dividend, distribution, security or right, and the
amount and character of such dividend, distribution, security or right.

                  (1)     ISSUE TAXES.  The Corporation shall pay any and all
issue and other taxes, excluding federal, state or local income taxes, that may
be payable in respect of any issue or delivery of shares of Common Stock on
conversion of shares of Series A Preferred Stock or Series B Preferred Stock
pursuant hereto; provided, however, that the Corporation shall not be obligated
to pay any transfer taxes resulting from any transfer requested by any holder
in connection with any such conversion.

                  (m)     RESERVATION OF STOCK ISSUABLE UPON CONVERSION.  The
Corporation shall at all times reserve and keep available out of its authorized
but unissued shares of Common Stock, solely for the purpose of effecting the
conversion of the shares of the Series A Preferred Stock and Series B Preferred
Stock, such number of its shares of Common Stock as shall from time to time be
sufficient to effect the conversion of all outstanding shares of the Series A
Preferred Stock and Series B Preferred Stock; and if at any time the number of
authorized but unissued shares of Common Stock shall not be sufficient to effect
the conversion of all then


                                          7.

<PAGE>

outstanding shares of the Series A Preferred Stock and Series B Preferred Stock,
the Corporation will take such corporate action as may, in the opinion of its
counsel, be necessary to increase its authorized but unissued shares of Common
Stock to such number of shares as shall be sufficient for such purpose,
including, without limitation, engaging in best efforts to obtain the requisite
shareholder approval of any necessary amendment to this Articles of
Incorporation.

                  (n)     CONSENT TO CERTAIN DISTRIBUTIONS.  Each holder of
Series A Preferred Stock and Series B Preferred Stock shall be deemed to have
consented for purposes of Sections 502, 503 and 506 of the General Corporation
Law to distributions and payments made by the Corporation and approved by the
Board of Directors of the Corporation in connection with the repurchases of
shares of Common Stock issued or to held by directors, board advisors and
employees of, or consultants to, the Corporation upon termination of their
employment or services.

                  (o)     FRACTIONAL SHARES.  No fractional share shall be
issued upon the conversion of any share or shares of Series A Preferred Stock or
Series B Preferred Stock.  All shares of Common Stock (including fractions
thereof) issuable upon conversion of more than one share of Series A Preferred
Stock or Series B Preferred Stock by a holder thereof shall be aggregated for
purposes of determining whether the conversion would result in the issuance of
any fractional share.  If, after the aforementioned aggregation, the conversion
would result in the issuance of a fraction of a share of Common Stock, the
Corporation shall, in lieu of issuing any fractional share, pay the holder
otherwise entitled to such fraction a sum in cash equal to the fair market value
of such fraction on the date of conversion (as determined in good faith by the
Board of Directors of the Corporation).

                  (p)     NOTICES.  Any notice required by the provisions of
this Section 4 to be given to the holders of shares of Series A Preferred Stock
and Series B Preferred Stock shall be deemed given if deposited in the United
States mail, postage prepaid, and addressed to each holder of record at its
address appearing on the books of the Corporation.  Nothwithstanding the above,
any notice or communication to an address outside the United States shall be
sent by telecopy and confirmed in writing sent by courier guaranteeing delivery
in no more than two (2) business days.

                  (q)     ADJUSTMENTS.  In case of any reorganization or any
reclassification of the capital stock of the Corporation, any consolidation or
merger of the Corporation with or into another corporation or corporations, or
the conveyance of all or substantially all of the assets of the Corporation to
another corporation, each share of Series A Preferred Stock and Series B
Preferred Stock shall thereafter be convertible into the number of shares of
stock or other securities or property (including cash) to which a holder of the
number of shares of Common Stock deliverable upon conversion of such share of
Series A Preferred Stock or Series B


                                          8.

<PAGE>

Preferred Stock would have been entitled upon the record date of (or date of, if
no record date is fixed) such reorganization, reclassification, consolidation,
merger or conveyance; and, in any case, appropriate adjustment (as determined by
the Board of Directors) shall be made in the application of the provisions
herein set forth with respect to the rights and interests thereafter of the
holders of such Series A Preferred Stock or Series B Preferred Stock, to the end
that the provisions set forth herein shall thereafter be applicable, as nearly
as equivalent as is practicable, in relation to any shares of stock or the
securities or property (including cash) thereafter deliverable upon the
conversion of the shares of such Series A Preferred Stock or Series B Preferred
Stock.

           5.     RESTRICTIONS AND LIMITATIONS.  So long as at least 5,000,000
of the authorized shares of Preferred Stock remain outstanding, the Corporation
shall not, without the vote or written consent by the holders of majority of the
then outstanding shares of Series A Preferred Stock and Series B Preferred
Stock, voting together as a single class on an as converted basis:

                  (a)     Amend, repeal or waive any provision of, or add any
provision to, the Corporation's Articles of Incorporation if such action would
alter or change in an adverse manner the preferences, rights, privileges or
powers of, or the restrictions provided for the benefit of, the Preferred Stock;

                  (b)     Increase the total number of authorized shares of
Common Stock or Preferred Stock of the Corporation or the number of shares
designated as any series of Preferred Stock;

                  (c)     Authorize or issue, or obligate itself to issue, any
other equity security senior to the Series A Preferred Stock or Series B
Preferred Stock as to dividend or redemption rights, liquidation preferences,
conversion rights, voting rights or otherwise, or create any obligation or
security convertible into or exchangeable for, or having any option rights to
purchase, any such equity security which is senior to the Series A Preferred
Stock or Series B Preferred Stock; provided, however, that an equity security
issued subsequent to the issuance of the Series A Preferred Stock or Series B
Preferred Stock for a share price and corresponding liquidation price higher
than that of the Series A Preferred Stock or Series B Preferred Stock shall not
be deemed senior to the Series A Preferred Stock or Series B Preferred Stock
solely by reason of such share price and liquidation price;

                  (d)     Do any act or thing which would result in taxation of
the holders of shares of the Series A Preferred Stock or Series B Preferred
Stock under Section 305 of the Internal Revenue Code of 1968, as amended (the
"Code") (or any comparable provision of the Code as hereafter from time to time
amended);


                                          9.

<PAGE>

                  (e)     Effect any sale or other conveyance of all or
substantially all of the assets of the Corporation or any of its subsidiaries,
or any consolidation or merger involving the Corporation or any of its
subsidiaries with or into any other corporation, if more than 50% of the
surviving entity is not owned by persons who were holders of capital stock or
securities convertible into capital stock of the Corporation immediately prior
to such merger, consolidation or sale; or

                  (f)     Set aside any amounts for or purchase, or declare or
pay any dividend or make any other distribution on, any shares of capital stock
other than the Series A Preferred Stock or Series B Preferred Stock except for
repurchases required by current agreements with directors, consultants or
employees.

           6.     NO REISSUANCE OF PREFERRED STOCK.  No share or shares of
Series A Preferred Stock or Series B Preferred Stock acquired by the Corporation
by reason of redemption, purchase, conversion or otherwise shall be reissued,
and all such shares shall be returned to the status of undesignated shares of
Preferred Stock.

                                         IV.

           A.     The liability of the directors of this corporation for
monetary damages shall be eliminated to the fullest extent permissible under
California law.

           B.     This corporation is authorized to provide indemnification of
agents (as defined in Section 317 of the California Corporations Code) for
breach of duty to the corporation and its shareholders through bylaw provisions
or through agreements with the agents, or through shareholder resolutions, or
otherwise, to the fullest extent permitted by California law.

           C.     Any repeal or modification of this Article shall only be
prospective and shall not affect the rights under this Article in effect at the
time of the alleged occurrence of any act or omission to act giving rise to
liability or indemnification.

           3.     The foregoing Amended and Restated Articles of Incorporation
has been duly approved by the board of directors.

           4.     The foregoing Amended and Restated Articles of Incorporation
has been duly approved by the required vote of shareholders in accordance with
Sections 902 and 903 of the Corporations Code.  The total number of Outstanding
shares of the corporation is 3,419,000 shares of Common Stock and 5,000,000
shares of Series A Preferred Stock.  The number of shares voting in favor of the
amendment equaled or exceeded the vote required.  The percentage vote required
was more than 50% of the Common Stock and 66 2/3% of the Series A Preferred
Stock voting as a separate class.


                                       10.

<PAGE>

We further declare under penalty of perjury under the laws of the State of
California that the matters set forth in this certificate are true and correct
of our own knowledge

DATE: 8/30/93

                                       /s/ J. Leighton Road
                                       ---------------------------------------
                                       J. Leighton Read, Chief Executive
                                                         Officer


                                       /s/ Alan C. Mendelson
                                       ---------------------------------------
                                       Alan C. Mendelson, Secretary


                                         11.

<PAGE>

                                      EXHIBIT B

                                   FORM OF WARRANT


<PAGE>

EXHIBIT B TO STOCK TRANSFER AGREEMENT

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY NOT BE OFFERED FOR SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED
WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144
OR AN OPINION OF COUNSEL, REASONABLY SATISFACTORY TO THE COMPANY AND ITS
COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.


                              WARRANT TO PURCHASE SHARES
                                          OF

                                    --------------

Company:                  AVIRON, a California corporation (the "Company"), and
                          any corporation that shall succeed to the obligations
                          of the Company under this Warrant.

Number of Shares:         _______________
Class of Stock:           _______________
Initial Exercise Price:   _______________
Date of Grant:            _______________

      THIS CERTIFIES THAT, for value received, The Regents of the University of
Michigan ("Michigan") or any permitted transferee of its rights hereunder is
entitled to purchase the above number (as adjusted pursuant to Section 5 hereof)
of fully paid and nonassessable shares of the above Class of Stock of the
Company at the Initial Exercise Price above (as adjusted pursuant to Section 5
hereof), subject to the provisions and upon the terms and conditions set forth
herein.  The Expiration Date of this Warrant shall be five years from the Date
of Grant.

I.    Definitions.

      In addition to the terms defined above, the following capitalized terms
shall have the following meanings, unless the context otherwise requires:

      (a)     "Act" shall mean the Securities Act of 1933, as amended, or any
similar federal statute, and the rules and regulations thereunder, as shall be
in effect at the time.

      (b)     "Common Stock" shall mean shares of the authorized common stock
of the Company and any stock into which such common stock may hereafter be
exchanged.

      (c)     "Warrantholder" shall mean any person who shall at the time be
the holder of this Warrant.


                                          1.

<PAGE>



      (d)     "Shares" shall mean the shares of the Class of Stock that the
Warrantholder is entitled to purchase upon exercise of this Warrant, as adjusted
pursuant to Section 5 hereof.

      (e)     "Warrant Price" shall mean the Initial Exercise Price at which
this Warrant may be exercised, as adjusted pursuant to Section 5 hereof.

2.    Term.

      The purchase right represented by this Warrant is exercisable, in whole
or in part, at any time on or before the Expiration Date.

3.    Method of Exercise; Payment; Issuance of New Warrant.

      Subject to Section 2 hereof, the purchase right represented by this
Warrant may be exercised by the Warrantholder, in whole or in part, by the
surrender of this Warrant (with the notice of exercise form attached hereto as
Appendix A duly executed) at the principal office of the Company and by the
payment to the Company, by check made payable to the Company drawn on a United
States bank and for United States funds of an amount equal to the then
applicable Warrant Price per share multiplied by the number of Shares then being
purchased.  In the event of any exercise of the purchase right represented by
this Section 3, certificates for the Shares so purchased shall be delivered to
the Warrantholder within thirty (30) days of receipt of such payment and, unless
this Warrant has been fully exercised or expired, a new Warrant representing the
portion of the Shares, if any, with respect to which this Warrant shall not then
have been exercised shall also be issued to the Warrantholder within such thirty
(30) day period.

4.    Exercise Price.

      The Warrant Price at which this Warrant may be exercised shall be the
Initial Exercise Price, as adjusted from time to time pursuant to Section 5
hereof.

5.    Adjustment of Number and Kind of Shares and Adjustment of Warrant Price.

      5.1     Certain Definitions.  As used in this Section 5 the following
terms shall have the following respective meanings:

              (a)     "Options" shall mean rights, options or warrants to
subscribe for, purchase or otherwise acquire either shares of Common Stock or
Convertible Securities;


                                          2.

<PAGE>

              (b)     "Convertible Securities" shall mean any evidences of
indebtedness, shares of stock or other securities directly or indirectly
convertible into or exchangeable for Common Stock.

      5.2     Adjustments.  The number and kind of securities purchasable upon
the exercise of this Warrant and the Warrant Price shall be subject to
adjustment from time to time upon the occurrence of certain events, as follows:

              (a)     Reclassification, Reorganization, Consolidation or
Merger.  In the case of any reclassification of the Class of Stock that the
Warrantholder is entitled to purchase upon exercise of this Warrant, or any
reorganization, consolidation or merger of the Company with or into another
corporation (other than a merger or reorganization with respect to which the
Company is the surviving corporation and which does not result in any
reclassification of such Class of Stock), the Company, or such successor
corporation, as the case may be, shall execute a new warrant, providing that the
Warrantholder shall have the right to exercise such new warrant and upon such
exercise to receive, in lieu of each share of the Class of Stock theretofore
issuable upon exercise of this Warrant, the kind of securities receivable upon
such reclassification, reorganization, consolidation or merger by a holder of
shares of the same Class of Stock of the Company.  The Warrant Price and the
number of shares of such new securities to be received by the Warrancholder upon
exercise of the Warrant shall be adjusted so that the Warrantholder shall
receive upon exercise of the Warrant and payment of the same aggregate
consideration the number of shares of new securities which the Warrantholder
would have owned immediately following such reclassification, reorganization,
consolidation or merger if the Warrantholder had exercised the Warrant
immediately prior to such reclassifications, reorganization, consolidation or
merger.  The provisions of this subsection (a) shall similarly apply to
successive reclassification, reorgranizations, consolidations or mergers.

              (b)     Split, Subdivision or Combination of Shares.  If the
Company at any time while this Warrant remains outstanding and unexpired shall
split, subdivide or combine the Class of Stock for which this Warrant is then
exercisable, the Warrant Price shall be proportionately decreased in the case of
a split or subdivision or proportionately increased in the case of a
combination.  Any adjustment under this subsection (b) shall become effective
when the split, subdivision or combination becomes effective.

              (c)     Stock Dividends.  If the Company at any time while this 
Warrant remains outstanding and unexpired shall pay a dividend with respect 
to the Class of Stock for which this Warrant is then exercisable, payable in 
shares of that Class of Stock, Options or Convertible Securities, the Warrant 
Price shall be adjusted, from and after the date of determination of the 
stockholders entitled to receive such dividend or distributions, to that 
price determined by multiplying the Warrant Price in effect immediately prior 
to such date of determination by a fraction (i) the numerator of which shall 
be the total number of shares of that Class of Stock outstanding immediately 
prior to such dividend or distribution, and (ii) the denominator of which 
shall be the total number of shares of the same Class of Stock outstanding 
immediately after such dividend or distribution (including shares of that 
Class of Stock issuable upon exercise, conversion or exchange of any Options 
or Convertible Securities issued as such dividend or

                                          3.

<PAGE>

distribution).  If the Options or Convertible Securities issued as such dividend
or distribution by their terms provide, with the passage of time or otherwise,
for any decrease in the consideration payable to the Company, or any increase in
the number of shares issuable upon exercise, conversion or exchange thereof (by
change of rate or otherwise), the Warrant Price shall, upon any such decrease or
increase becoming effective, be reduced to reflect such decrease or increase as
if such decrease or increase became effective immediately prior to the issuance
of the Options or Convertible Securities as the dividend or distribution.  Any
adjustment under this subsection (c) shall become effective on the record date
set for such dividend or distribution.

              (d)     Adjustment Of Number of Shares.  Upon each adjustment in
the Warrant Price pursuant to Section 5(b) or 5(c) above, the number of Shares
issuable upon exercise of this Warrant shall be adjusted to the product obtained
by multiplying the number of Shares issuable immediately prior to such
adjustment in the Warrant Price by a fraction (i) the numerator of which shall
be the Warrant Price immediately prior to such adjustment, and (ii) the
denominator of which shall be the Warrant Price immediately after such
adjustment.

6.    Notice of Adjustments.

      So long as this Warrant remains outstanding and unexpired, whenever the
Warrant Price shall be adjusted pursuant to Section 5 hereof, the Company shall
issue a certificate signed by its chief financial officer setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated and the Warrant
Price after giving effect to such adjustment, and shall cause a copy of such
certificate to be mailed (by first class mail, postage prepaid) to the
Warrantholder.

7.    Right to Convert Warrant Into Stock.

      7.1     Right to Convert.  In addition to the rights granted under
Section 3 of this Warrant, the Warrantholder shall have the right to require the
Company to convert this Warrant (the "Conversion Right") into shares of the
Class of Stock for which the Warrant is then exercisable, as provided in this
Section 7. Upon exercise of the Conversion Right, the Company shall deliver to
the Warrantholder (without payment by the Warrantholder of any Warrant Price)
that number of shares of stock equal to the quotient obtained by dividing (x)
the value of this Warrant at the time the Conversion Right is exercised
(determined by subtracting the aggregate Warrant Price immediately prior to the
exercise of the Conversion Right from the aggregate fair market value of the
Shares issuable upon exercise of this Warrant immediately prior to the exercise
of the Conversion Right, as determined pursuant to Section 7.3 below) by (y) the
fair market value (as determined pursuant to Section 7.3 below) of one share of
that Class of Stock immediately prior to the exercise of the Conversion Right.

      7.2     Method of Exercise.  So long as the Warrant remains outstanding
and unexpired, the Conversion Right may be exercised at any time by the
Warrantholder by the surrender of this Warrant at the principal office of the
Company together with a written statement specifying that the Warrantholder
thereby intends to exercise the Conversion Right.  Certificates of the shares of
stock issuable upon exercise of the Conversion Right shall be delivered to the


                                          4.

<PAGE>

Warrantholder within thirty (30) days following the Company's receipt of this
Warrant together with the aforesaid written statement.

      7.3     Valuation of Stock.  For purposes of this Section 7, the fair
market value of one share of the Class of Stock issuable upon exercise of this
Warrant shall, mean:

              (a)     The product of (i) the average of the closing price or,
if no closing price is reported, the closing bid and asked prices of the Common
Stock, quoted in the Over-The-Counter Market Summary or the closing price quoted
on any exchange on which the Common Stock is listed, whichever is applicable, as
published in the Western Edition of The Wall Street Journal for the ten (10)
trading days prior to the date of determination of fair market value, and (ii)
the number of shares of Common Stock into which each share of the Class of Stock
is then convertible, if applicable;

              (b)     If the Common Stock is not traded Over-The-Counter or on
an exchange, the fair market value of the Class of Stock per share shall be as
determined in good faith by the Company's Board of Directors; provided, however,
that if the Warrantholder disputes in writing the fair market value determined
by the Board of Directors within thirty (30) days of being informed of such fair
market value, the fair market value shall be determined by an independent
appraiser, appointed in good faith by the Company's Board of Directors.

8.    Compliance With Act; Transferability of Warrant; Disposition of Shares.

      8.1     Legends.  This Warrant and the Shares issued upon exercise
thereof shall be imprinted with a legend in substantially the following form:

      "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
      UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED FOR
      SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE
      REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN OPINION
      OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY AND ITS COUNSEL THAT
      SUCH REGISTRATION IS NOT REQUIRED."

      8.2     Transferability of Warrant and Shares.  This Warrant and the
Shares issued upon exercise thereof shall not be sold, transferred or assigned
in whole or in part without compliance with applicable federal and state
securities laws by the transferor and the transferee (including, without
limitation, the delivery of investment representation letters and legal opinions
reasonably satisfactory to the Company, if reasonably requested by the Company).
Subject to the provisions of this Section 8.2, title to this Warrant may be
transferred in the same manner as a negotiable instrument transferable by
endorsement and delivery.

9.    Rights of the Holder.


                                          5.

<PAGE>

      The Warrantholder shall not, by virtue hereof, be entitled to any rights
of a shareholder in the Company, either at law or equity, and the rights of the
Warrantholder are limited to those expressed in this Warrant.  Nothing contained
in this Warrant shall be construed as conferring upon the Warrantholder hereof
the right to vote or to consent or to receive notice as a shareholder of the
Company on any matters or with respect to any rights whatsoever as a shareholder
of the Company.  No dividends or interest shall be payable or accrued in respect
of this Warrant or the interest represented hereby or the Shares purchasable
hereunder until, and only to the extent that, this Warrant shall have been
exercised in accordance with its terms.

10.   Miscellaneous.

      No fractional shares shall be issued in connection with any exercise
hereunder, but in lieu of such fractional shares the Company shall make a cash
payment therefor upon the basis of the Warrant Price then in effect.  The terms
and provisions of this Warrant shall inure to the benefit of, and be binding
upon, the Company and the Warrantholder and their respective successors and
assigns.  This Warrant shall be governed by and construed under the laws of the
State of California as applied to contracts entered into between residents of
the State of California to be wholly performed in the State of California.  The
titles of the sections and subsections of this Warrant are for convenience only
and are not to be considered in construing this Warrant.  All pronouns used in
the Warrant shall be deemed to include masculine, feminine and neuter forms.

                                            AVIRON, a California corporation


                                            By:
                                               -------------------------------
                                            Name:
                                                 -----------------------------
                                            Title:
                                                  ----------------------------


                                          6.

<PAGE>

                                      APPENDIX A
                                  NOTICE OF EXERCISE
TO:   AVIRON


              1.   The undersigned hereby elects to purchase shares of the
stock of Aviron, a California corporation, pursuant to terms of the attached
Warrant, and tenders herewith payment of the purchase price of such shares in
full, together with all applicable transfer taxes, if any.

              2.   Please issue a certificate or certificates representing said
shares of the stock in the name of the undersigned or in such other name as is
specified below.

              3.   The undersigned represents it is acquiring the shares of
stock solely for its own account for investment and not as a nominee for any
other party and not with a view toward the resale or distribution thereof within
the meaning of the Securities Act of 1933, as amended.



                        --------------------------------------
                                        (Name)


                        --------------------------------------
                                      (Address)


                        --------------------------------------
                           (Taxpayer Identification Number)



- ----------------------------------------
     (print name of Warrantholder)


By:
   -------------------------------------
Title:
      ----------------------------------
Date:
     -----------------------------------


                                          7.

<PAGE>

                                      EXHIBIT C
                   AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT


<PAGE>

                                        AVIRON
                   Amended and Restated Investors Rights Agreement
                                  September 3, 1993


                                          1.

<PAGE>

                                  TABLE OF CONTENTS

                                                                            Page
                                                                            ----
1.  Certain Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . 2.

2.  Transferability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.
    2.1    Restrictions on Transferability . . . . . . . . . . . . . . . . . 3.
    2.2    Restrictive Legend. . . . . . . . . . . . . . . . . . . . . . . . 3.
    2.3    Notice of Proposed Transfers. . . . . . . . . . . . . . . . . . . 3.

3.  Registration Rights. . . . . . . . . . . . . . . . . . . . . . . . . . . 4.
    3.1    Requested Registration. . . . . . . . . . . . . . . . . . . . . . 4.
    3.2    Company Registration. . . . . . . . . . . . . . . . . . . . . . . 6.
    3.3    Expenses of Registration. . . . . . . . . . . . . . . . . . . . . 7.
    3.4    Registration Procedures . . . . . . . . . . . . . . . . . . . . . 8.
    3.5    Indemnification . . . . . . . . . . . . . . . . . . . . . . . . . 9.
    3.6    Information by Holder . . . . . . . . . . . . . . . . . . . . . .10.
    3.7    Rule 144 Reporting. . . . . . . . . . . . . . . . . . . . . . . .10.
    3.8    "Market Stand-off" Agreement. . . . . . . . . . . . . . . . . . .11.
    3.9    Form S-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.
    3.10   Transfer of Registration Rights . . . . . . . . . . . . . . . . .12.
    3.11   Certain Limitations in Connection with Future Grants of
           Registration Rights . . . . . . . . . . . . . . . . . . . . . . .12.
    3.12   Termination of Registration Rights. . . . . . . . . . . . . . . .13.

4.  Right of First Refusal on Company Issuances. . . . . . . . . . . . . . .13.
    4.1      Right of First Refusal. . . . . . . . . . . . . . . . . . . . .13.

5.  Information Rights . . . . . . . . . . . . . . . . . . . . . . . . . . .15.
    5.1    Financial Information . . . . . . . . . . . . . . . . . . . . . .15.
    5.2    Inspection Rights . . . . . . . . . . . . . . . . . . . . . . . .15.
    5.3    Assignment of Rights to Information . . . . . . . . . . . . . . .15.
    5.4    Confidentiality . . . . . . . . . . . . . . . . . . . . . . . . .16.

6.  Miscellaneous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16.
    6.1    Governing Law . . . . . . . . . . . . . . . . . . . . . . . . . .16.
    6.2    Successors and Assigns. . . . . . . . . . . . . . . . . . . . . .16.
    6.3    Entire Agreement. . . . . . . . . . . . . . . . . . . . . . . . .16.
    6.4    Notices, etc. . . . . . . . . . . . . . . . . . . . . . . . . . .16.
    6.5    Delays or Omissions . . . . . . . . . . . . . . . . . . . . . . .17.
    6.6    Counterparts. . . . . . . . . . . . . . . . . . . . . . . . . . .17.
    6.7    Severability. . . . . . . . . . . . . . . . . . . . . . . . . . .17.
    6.8    Amendments. . . . . . . . . . . . . . . . . . . . . . . . . . . .17.


                                          i.

<PAGE>

                                  TABLE OF CONTENTS
                                     (continued)

EXHIBITS

    A.     Schedule of Investors
    B.     Schedule of Series A Warrant Holders
    C.     Schedule of Series B Warrant Holders


                                         ii.

<PAGE>

                                        Aviron


                   AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT

      This Amended and Restated Investors Rights Agreement (the "Agreement") is
entered into as of September 3, 1993, by and among Aviron, a California
corporation (the "Company"), the parties listed on Exhibit A hereto (the
"Investors"), the parties listed on Exhibit B hereto (the "Series A Warrant
Holders") and the parties listed on Exhibit C hereto (the "Series B Warrant
Holders").

                                       RECITALS

      A.     The Investors are the purchasers of the Company's Series A
Preferred Stock pursuant to that certain Series A Preferred Stock Purchase
Agreement, dated as of June 19, 1992, by and among the Company and the
purchasers named therein (the "Series A Agreement") and the purchasers of the
Company's Series B Preferred Stock pursuant to that certain Series B Preferred
Stock Purchase Agreement, dated as of the date hereof, by and among the Company
and the Purchasers named therein (the "Series B Agreement").

      B.     The Series A Warrant Holders are the holders of either Series A
Preferred Stock or Warrants to purchase Series A Preferred Stock of the Company,
the Series B Warrant Holders are the holders of either Series B Preferred Stock
or Warrants to purchase Series B Preferred Stock of the Company, and the
Founders are Peter Palese, J. Leighton Read, Bernard Roizman and Richard J.
Whitley, in connection with which the Company desires to extend certain rights
herein, subject to the obligations provided for herein, in accordance with the
terms of this Agreement.

      C.     It is anticipated that future sales of securities of a similar
nature may occur.

      D.     In order to facilitate the grant by the Company of additional
rights, the Company, the Investors, the Series A Warrant Holders and the Series
B Warrant Holders desire to terminate the Investor Rights Agreement, dated as of
June 19, 1992 as amended January 8, 1993, among the Company and the parties
named therein (the "Original Investor Rights Agreement"), and set forth in a
single agreement the registration and information rights and right of first
refusal granted to the Investors, the Series A Warrant Holders, the Series B
Warrant Holders and the Founders.

                                      AGREEMENT

      NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants, and conditions set forth in this Agreement and in the
agreements pursuant to which the Investors acquired their securities in the
Company, the parties mutually aggree as follows:


                                          1.

<PAGE>

      1.     CERTAIN DEFINITIONS.  As used in this Agreement, the following
terms shall have the following respective meanings:

      "Commission" shall mean the Securities and Exchange Commission or any
other federal agency at the time administering the Securities Act.

      "Securities Act" shall mean the Securities Act of 1933, as amended, or
any similar federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

      "Restricted Securities" shall mean the securities of the Company required
to bear the legend set forth in Section 2.2 hereof.

      "Shares" shall mean the securities of the Company held by the Investors
and Founders as described on Exhibit A, the securities issuable upon exercise of
the Warrants to purchase Series A Preferred Stock held by the Series A Warrant
Holders as described on Exhibit B and the securities issuable upon exercise of
the Warrants to purchase Series B Preferred Stock held by the Series B Warrant
Holders as described on Exhibit C.

      "Registrable Securities" means (i) shares of Common Stock issued or
issuable pursuant to the conversion or exercise of the Shares and (ii) shares of
Common Stock issued as a dividend or other distribution with respect to, or in
exchange or in replacement of, the Shares, excluding in all cases, however
(including exclusion from the calculation of the number of outstanding
Registrable Securities), any Registrable Securities sold by a person, (x) in a
transaction pursuant to Rule 144, or (y) pursuant to a registration statement
under this Agreement or (z) in a transaction in which his rights under this
Agreement are not transferred, including a transaction pursuant to a
registration statement under this Agreement.

      The terms "register," "registered" and "registration" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act, and the declaration or ordering of the
effectiveness of such registration statement by the Commission.

      "Registration Expenses" shall mean all expenses incurred by the Company
in complying with Sections 3.1, 3.2 and 3.9 hereof, including, without
limitation, all registration and filing fees, printing expenses, fees and
disbursements of counsel for the Company, fees and disbursements of a single
special counsel for the Holders not to exceed $10,000, blue sky fees and
expenses, and the expense of any special audits incident to or required by any
such registration (but excluding the compensation of regular employees of the
Company which shall be paid in any event by the Company).

      "Selling Expenses" shall mean all underwriting discounts and selling
commissions applicable to the sale.

      "Holder" shall mean any holder of outstanding Registrable Securities.


                                          2.

<PAGE>

      "Initiating Holders" shall mean any Holder or Holders of not less than
40% of the then outstanding Registrable Securities.

      "Common Stock" shall mean shares of the Company's Common Stock, no par
value.

      "Preferred Stock" shall mean shares of the Company's Series A Preferred
Stock and Series B Preferred Stock, no par value.

      2.     TRANSFERABILITY.

      2.1    RESTRICTIONS ON TRANSFERABILITY.  The Shares and any Preferred
Stock or Common Stock into which the Shares may be convertible or exercisable,
shall not be transferable except upon the conditions specified in this
Agreement, which conditions are intended to insure compliance with the
provisions of the Securities Act, or, in the case of Section 3.8 hereof, to
assist in an orderly distribution.  Each Investor will cause any proposed
transferee of the Shares (or of the Preferred Stock or Common Stock into which
the Shares may be convertible or exercisable) held by an Investor to agree to
take and hold such securities subject to the provisions and upon the conditions
specified in this Agreement.

      2.2    RESTRICTIVE LEGEND.  Each certificate representing (i) the Shares,
or (ii) shares of the Company's Common Stock or Preferred Stock issued upon
conversion or exercise of the Shares and (iii) any securities issued in respect
of the Shares or such Common Stock or Preferred Stock, shall (unless otherwise
permitted by the provisions of Section 2.3 below) be stamped or otherwise
imprinted with a legend in substantially the following form (in addition to any
legend required under applicable state securities laws):

      THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR
      INVESTMENT UNDER AN EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE
      SECURITIES ACT OF 1933.  SUCH SHARES MAY NOT BE OFFERED, SOLD OR
      TRANSFERRED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT UNDER
      SAID ACT OR AN EXEMPTION THEREFROM OR IN CONTRAVENTION OF THE AGREEMENT
      COVERING THE PURCHASE OF THESE SHARES AND RESTRICTING THEIR TRANSFER. 
      COPIES OF THE AGREEMENT MAY BE OBTAINED AT NO COST BY WRITTEN REQUEST
      MADE BY THE HOLDER OF RECORD OF THIS CERTIFICATE TO THE SECRETARY OF THE
      CORPORATION AT ITS PRINCIPAL OFFICE.

      2.3    NOTICE OF PROPOSED TRANSFERS.  The holder of each certificate
representing Restricted Securities by acceptance thereof agrees to comply in all
respects with the provisions of this Section 2.3. Prior to any proposed transfer
of any Restricted Securities, unless there is in effect a registration statement
under the Securities Act covering the proposed transfer, the holder thereof
shall give written notice to the Company of such holder's intention to effect
such transfer.  Each such notice shall describe the manner and circumstances of
the proposed transfer in sufficient detail, and shall be accompanied (except in
the following cases, with respect to


                                          3.

<PAGE>

which the requirements set forth in the balance of this sentence need not be
complied with: transactions in compliance with Rule 144 or Rule 144A so long as
the Company is furnished with evidence of compliance with such Rule;
transactions involving the distribution of Restricted Securities by any Investor
which is a general or limited partnership to any of its partners, or retired
partners, or to the estate of any of its partners or retired partners;
transactions involving the transfer of Restricted Securities by any holder who
is an individual to his family members or to a trust for the benefit of such
shareholder or his family members; or transfers not involving a change in
beneficial ownership) by (i) a written opinion of legal counsel who shall be
reasonably satisfactory to the Company addressed to the Company and reasonably
satisfactory in form and substance to the Company's counsel, to the effect that
the proposed transfer of the Restricted Securities may be effected without
registration under the Securities Act, (ii) a "no action" letter from the
Commission to the effect that the distribution of such securities without
registration will not result in a recommendation by the staff of the Commission
that action be taken with respect thereto, or (iii) such other showing that may
be reasonably satisfactory to legal counsel to the Company, whereupon the holder
of such Restricted Securities shall be entitled to transfer such Restricted
Securities in accordance with the terms of the notice delivered by the holder to
the Company.  Each certificate evidencing the Restricted Securities transferred
as above provided shall bear the appropriate restrictive legend set forth in
Section 2.2 above, except that such certificate shall not bear such restrictive
legend if in the opinion of counsel for the Company such legend is not required
in order to establish compliance with any provisions of the Securities Act.  All
Restricted Securities transferred as above that continue to bear the restrictive
legend set forth in Section 2.2 shall continue to be subject to the provisions
of this Section 2.3 in the same manner as before such transfer.

      3.     REGISTRATION RIGHTS.

      3.1    REQUESTED REGISTRATION.  Prior to such time as the Company has 
effected two registrations pursuant to this Section 3.1 and such 
registrations have been declared or ordered effective, if the Company shall 
receive from Initiating Holders a written request that the Company effect any 
registration (other than a registration on Form S-3 or any comparable form of 
registration statement) with respect to Registrable Securities having an 
anticipated aggregate offering price to the public of at least $7,500,000 
(before deduction of underwriter commissions and expenses), the Company will:

             (a)    promptly give written notice of the proposed registration
to all other Holders; and

             (b)    as soon as practicable, use its diligent best efforts to
effect such registration (including, without limitation, the execution of an
undertaking to file post-effective amendments, appropriate qualification under
applicable blue sky or other state securities laws and appropriate compliance
with applicable regulations issued under the Securities Act) as may be so
requested and as would permit or facilitate the sale and distribution of all or
such portion of such Registrable Securities as are specified in such request,
together with all or such portion of the Registrable Securities of any Holder or
Holders joining in such request as are specified in a written request given
within 15 days after receipt of such written notice from the Company;


                                          4.

<PAGE>

provided that the Company shall not be obligated to take any action to effect
any such registration, qualification or compliance pursuant to this Section 3.1:

                    (i)    In any particular jurisdiction in which the Company
would be required to execute a general consent to service of process in
effecting such registration, qualification or compliance unless the Company is
already subject to service in such jurisdiction and except as may be required by
the Securities Act;

                    (ii)   Prior to the earlier to occur of (x) six months
following the effective date of the registration statement pertaining to the
first underwritten public offering of securities of the Company for its own
account and (y) August 31, 1997; or

                    (iii)  If at the time of the request to register
Registrable Securities the Company gives notice within 30 days of such request
that it is engaged or has fixed plans to engage within 90 days of the time of
the request in an initial firmly underwritten registered public offering as to
which the Holders may include Registrable Securities pursuant to Sections 3.1 or
3.2.


     Subject to the foregoing clauses (i) through (iii) and to Section 
3.1(d), the Company shall file a registration statement covering the 
Registrable Securities so requested to be registered as soon as practicable 
after receipt of the request of the Initiatin Holders.

             (c)    UNDERWRITING.  If the Initiating Holders intend to
distribute the Registrable Securities covered by their request by means of an
underwriting, they shall so advise the Company as a part of their request made
pursuant to Section 3.1 and the Company shall include such information in the
written notice referred to in Section 3.l(a).  The right of any Holder to
registration pursuant to Section 3.1 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting to the extent requested (unless
otherwise mutually agreed by a majority in interest of the Holders and such
Holder) to the extent provided herein.

      The Company shall (together with all Holders proposing to distribute
their securities through such underwriting) enter into an underwriting agreement
in customary form with the underwriter or underwriters selected for such
underwriting by a majority in interest of the Initiating Holders with the
approval of the Company, which approval shall not be unreasonably withheld. 
Notwithstanding any other provision of this Section 3.1, if the underwriter
determines that marketing factors require a limitation of the number of shares
to be underwritten and so advises the Initiating Holders in writing, then the
Initiating Holders shall so advise all Holders (except those Holders who have
indicated to the Company their decision not to distribute any of their
Registrable Securities through such underwriting) and the number of shares of
Registrable Securities that may be included in the registration and underwriting
shall be allocated among all such Holders in proportion, as nearly as
practicable, to the respective amounts of Registrable Securities owned by such
Holders at the time of filing the registration statement.  No Registrable
Securities excluded from the underwriting by reason of the underwriter's
marketing limitation shall be included in such registration.


                                          5.

<PAGE>

      If any Holder disapproves of the terms of the underwriting, such person
may elect to withdraw therefrom by written notice to the Company, the
underwriter and the Initiating Holders.  The Registrable Securities and/or other
securities so withdrawn from such underwriting shall also be withdrawn from such
registration; provided, however, that, if by the withdrawal of such Registrable
Securities a greater number of Registrable Securities held by other Holders may
be included in such registration (up to the maximum of any limitation imposed by
the underwriters), then the Company shall offer to all Holders who have included
Registrable Securities in the registration the right to include additional
Registrable Securities in the same proportion used above in determining the
underwriter limitation; and, provided further that in the event that the
withdrawal of a Holder, and the subsequent inclusion of additional Registrable
Securities by other Holders, results in an anticipated aggregate offering price
to the public of less than $1,000,000 the Company shall no longer be required to
effect such registration pursuant to this Section 3.1.

      If the underwriter has not limited the number of Registrable Securities
to be underwritten, the Company may include securities for its own account or
the account of others in such registration if the underwriter so agrees and if
the number of Registrable Securities which would otherwise have been included in
such registration and underwriting will not thereby be limited.

             (d)    DELAY OF REGISTRATION.  If the Company shall furnish to the
Initiating Holders a certificate signed by the Chief Executive Officer of the
Company stating that, in the good faith judgment of the Board of Directors of
the Company, it would be seriously detrimental to the Company and its
shareholders for such registration statement to be filed on or before the date
filing would be required and it is therefore essential to defer the filing of
such registration statement, then the Company may direct that such request for
registration be delayed for two periods not in excess of 90 days each in any
one-year period.

      3.2    COMPANY REGISTRATION.

             (a)    If at any time or from time to time, the Company shall
determine to register any of its Common Stock, for its own account or for the
account of others (other than the Holders), other than a registration relating
solely to employee benefit plans or a registration relating solely to a
Commission Rule 145 transaction or a registration on any registration form which
does not include substantially the same information as would be required to be
included in a registration statement covering the sale of Registrable
Securities, the Company will:

                    (i)    promptly give to each Holder written notice thereof
(which shall include a list of the jurisdictions in which the Company intends to
attempt to qualify such securities under the applicable blue sky or other state
securities laws); and

                    (ii) include in such registration (and any related
qualification under blue sky laws or other compliance), and in any underwriting
involved therein, all the Registrable Securities specified in a written request
or requests, made within 20 days after receipt of such written notice from the
Company, by any Holder or Holders.



                                          6.

<PAGE>

             (b)    UNDERWRITING.  If the registration of which the Company
gives notice is for a registered public offering involving an underwriting, the
Company shall so advise the Holders as a part of the written notice given
pursuant to Section 3.2(a)(i). In such event the right of any Holder to
registration pursuant to Section 3.2 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting to the extent provided herein.  All
Holders proposing to distribute their securities through such underwriting shall
(together with the Company and the other holders distributing their securities
through such underwriting) enter into an underwriting agreement in customary
form with the underwriter or underwriters selected for such underwriting by the
Company with the approval of the Board of Directors.  Notwithstanding any other
provision of this Section 3.2, if the underwriter determines that marketing
factors require a limitation of the number of shares to be underwritten, the
underwriter may limit the number of Registrable Securities and shares of Common
Stock to be included in the registration and underwriting.  The Company shall so
advise all Holders (except those Holders who have indicated to the Company their
decision not to distribute any of their Registrable Securities or Common Stock
through such underwriting), and the number of shares of Registrable Securities
that may be included in the registration and underwriting, shall be allocated
among all Holders in proportion, as nearly as practicable, to the respective
amounts of Registrable Securities owned by the Holders at the time of filing the
registration statement.

      No Registrable Securities excluded from the underwriting by reason of the
underwriter's marketing limitation shall be included in such registration.  If
any Holder disapproves of the terms of any such underwriting, such person may
elect to withdraw therefrom by written notice to the Company and the
underwriter.  The securities so withdrawn from such underwriting shall also be
withdrawn from such registration; provided, however, that, if by the withdrawal
of such securities a greater number of Registrable Securities held by other
Holders may be included in such registration (up to the maximum of any
limitation imposed by the underwriters), then the Company shall offer to all
Holders who have included Registrable Securities in the registration the right
to include additional Registrable Securities in the same proportion used above
in determining the underwriter limitation.

      3.3    EXPENSES OF REGISTRATION.  All Registration Expenses incurred in
connection with any registration, qualification or compliance pursuant to
Section 3.1, Section 3.2 or Section 3.9 herein shall be borne by the Company. 
All Selling Expenses incurred in connection with any registrations hereunder
shall be borne by the holders of the securities so registered pro rata on the
basis of the number of shares so registered.  The Company shall not, however, be
required to pay for expenses of any registration proceeding, begun pursuant to
Section 3.1, the request of which has been subsequently withdrawn by the
Initiating Holders (unless the withdrawal is based upon material information
concerning the Company of which the Initiating Holders were not aware at the
time of such request or unless the Holders of a majority of Registrable
Securities agrees to forfeit their right to one requested registration pursuant
to Section 3.1 in which event such right shall be forfeited by all Holders), in
which case such expenses shall be borne by the holders of securities (including
Registrable Securities) requesting such registration in proportion to the number
of shares for which registration was requested.


                                          7.

<PAGE>

      3.4    REGISTRATION PROCEDURES.  In the case of each registration,
qualification or compliance effected by the Company pursuant to this Section 3,
the Company will keep each participating Holder advised in writing as to the
qualification and compliance and as to the completion thereof.  At its expense
the Company will:

             (a)    Keep such registration, qualification or compliance
effective for a period of 90 days or until the Holder or Holders have completed
the distribution described in the registration statement relating thereto,
whichever first occurs;

             (b)    Furnish such number of prospectuses and other documents
incident thereto in conformity with the requirements of the Act;

             (c)    Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with such registration statement as may be necessary to comply with the
provisions of the Act with respect to the disposition of all securities covered
by such registration statement;

             (d)    Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holders;
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions, unless the Company is
already subject to service in such jurisdiction and except as may be required by
the Act;

             (e)    In the event of any underwritten public offering, enter
into and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of such offering.  Each Holder
participating, in such underwriting, shall also enter into and perform its
obligations under such an agreement;

             (f)    Notify each Holder of Registrable Securities covered by
such registration statement at any time when a prospectus relating thereto is
required to be delivered under the Act or the happening of any event as a result
of which the prospectus included in such registration statement, as then in
effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing;

             (g)    Cause all such Registrable Securities registered pursuant
hereunder to be listed on each securities exchange on which similar securities
issued by the Company are then listed;

             (h)    Provide a transfer agent and registrar for all Registrable
Securities registered pursuant hereunder and a CUSIP number for all such
Registrable Securities, in each case not later than the effective date of such
registration; and

             (i)    Use its best efforts to furnish, at the request of any
Holder requesting registration of Registrable Securities pursuant to this
Section, on the date that such Registrable


                                          8.

<PAGE>

Securities are delivered to the underwriters for sale in connection with a
registration pursuant to this Section if such securities are being sold through
underwriters or, if such securities are not being sold through underwriters, on
the date that the registration statement with respect to such securities becomes
effective, (i) an opinion, dated such date, of the counsel representing the
Company for the purposes of such registration, in form and substance as is
customarily given to underwriters in an underwritten public offering, addressed
to the underwriters, if any, and to the Holders requesting, registration of
Registrable Securities and (ii) a letter dated such date, from the independent
certified public accountants of the Company, in form and substance as is
customarily given by independent certified public accountants to underwriters in
an underwritten public offering, addressed to the underwriters, if any, and to
the Holders requesting registration of Registrable Securities.

      3.5    INDEMNIFICATION.

             (a)    The Company will indemnify each Holder, each of its
officers, directors, partners and legal counsel, and each person controlling
such Holder, with respect to which registration, qualification or compliance has
been effected pursuant to this Section 3, against all claims, losses, damages
and liabilities (or actions in respect thereof) arising out of or based on (i)
any untrue statement (or alleged untrue statement) of a material fact contained
in any prospectus, offering circular or other similar document (including any
related registration statement, notification or the like) incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, in the light of the
circumstances under which they were made, or (ii) any violation by the Company
of any federal, state or common law rule or regulation applicable to the Company
in connection with any such registration, qualification or compliance, and will
reimburse each such Holder, each of its officers, directors, partners and legal
counsel, and each person controlling such Holder, for any legal and any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, liability or action, as such expenses are incurred,
provided that the Company will not be liable in any such case to the extent that
any such claim, loss, damage, liability or expense arises out of or is based on
any untrue statement or omission based upon written information furnished to the
Company by an instrument duly executed by such Holder and stated to be
specifically for use therein or furnished by the Holder to the Company in
response to a request by the Company stating specifically that such information
will be used by the Company therein.

             (b)    Each Holder will, if Registrable Securities held by such
Holder are included in the securities as to which such registration,
qualification or compliance is being effected, indemnify the Company, each of
its directors and officers, each legal counsel and independent accountant of the
Company, each person who controls the Company within the meaning of the
Securities Act, and each other such Holder, each of its officers, directors, and
partners and each person controlling such Holder, against all claims, losses,
damages and liabilities (or actions in respect thereof) arising out of or based
on any untrue statement (or alleged untrue statement) of a material fact
contained in any such registration statement, prospectus, offering circular or
other similar document, or any omission (or alleged omission) to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the


                                          9.

<PAGE>

circumstances under which they were made, and will reimburse the Company, such
Holders, such directors, officers, persons, or control persons for any legal or
any other expenses reasonably incurred in connection with investigating or
defending any such claim, loss, damage, liability or action, as incurred, in
each case to the extent, but only to the extent, that such untrue statement (or
alleged untrue statement) or omission (or alleged omission) is made in such
registration statement, prospectus, offering circular or other document in
reliance upon and in conformity with written information furnished to the
Company by an instrument duly executed by such Holder and stated to be
specifically for use therein; provided, however, that the obligations of such
Holders hereunder shall be limited to an amount equal to the proceeds to each
such Holder of Registrable Securities sold as contemplated herein.

             (c)    Each party entitled to indemnification under this Section
3.5 (the "Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has received written notice of any claim as to which indemnity may be sought,
and shall permit the Indemnifying Party to assume the defense of any such claim
or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld).  The Indemnified Party may participate in such
defense at such party's expense; provided, however, that the Indemnifying Party
shall bear the expense of such defense of the Indemnified Party if in the
opinion of counsel to the Indemnified Party representation of both parties by
the same counsel would be inappropriate due to actual or potential conflicts of
interest.  The failure of any Indemnified Party to give notice as provided
herein shall relieve the Indemnifying Party of its obligations under this
Section 3.5 only to the extent that such failure to give notice shall materially
adversely prejudice the Indemnifying Party in the defense of any such claim or
any such litigation.  No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the consent of each Indemnified Party, consent to
entry of any judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation.

      3.6    INFORMATION BY HOLDER.  Each Holder including securities of the
Company in any registration shall furnish to the Company such information
regarding such Holder and the distribution proposed by such Holder as the
Company may request in writing and as shall be required in connection with any
registration, qualification or compliance referred to in this Section 3.

      3.7    Rule 144 REPORTING.  With a view to making available the benefits
of certain rules and regulations of the Commission which may at any time permit
the sale of the Restricted Securities to the public without registration, after
such time as a public market exists for the Common Stock of the Company, the
Company agrees to:

             (a)    Use its best efforts to facilitate the sale of the
Restricted Securities to the public, without registration under the Securities
Act, pursuant to Rule 144 under the Securities Act, provided that this shall not
require the Company to file reports under the Securities Act and



                                         10.

<PAGE>

the Exchange Act at anytime prior to the Company's being otherwise required to
file such reports.

             (b)    Make and keep public information available, as those terms
are understood and defined in Rule 144 under the Securities Act at all times
after 90 days after the effective date of the first registration under the
Securities Act filed by the Company for an offering of its securities to the
general public;

             (c)    Use its best efforts to then file with the Commission in a
timely manner all reports and other documents required of the Company under the
Securities Act and the Securities Exchange Act of 1934, as amended (the
"Exchange Act") (at any time after it has become subject to such reporting
requirements);

             (d)    So long as a Holder owns any Restricted Securities to
furnish to the Holder forthwith upon request a written statement by the Company
as to its compliance with the reporting requirements of said Rule 144 (at any
time after 90 days after the effective date of the first registration statement
filed by the Company for an offering of its securities to the general public),
and of the Securities Act and the Exchange Act (at any time after it has become
subject to such reporting requirements), a copy of the most recent annual or
quarterly report of the Company, and such other reports and documents so filed
by the Company as such Holder may reasonably request in availing itself of any
rule or regulation of the Commission allowing a Holder to sell any such
securities without registration.

      3.8    "MARKET STAND-OFF" AGREEMENT.  Each Holder agrees not to sell or
otherwise transfer or dispose of any Common Stock (or other securities) of the
Company held by it for a period not to exceed 120 days following the effective
date of a registration statement of the Company filed under the Securities Act
if so requested by the Company and the underwriter of Common Stock (or other
securities of the Company), provided that:

             (a)    such agreement shall apply only to the first underwritten
registered public offering of the Company; and

             (b)    all officers and directors of the Company enter into
similar agreements and the Company uses its best efforts to cause all other
holders of at least 1% of the Company's voting securities enter into similar
agreements.  The Company may impose stop-transfer instructions with respect to
the shares (or securities) subject to the foregoing restriction until the end of
such period.

      3.9    Form S-3.  The Company shall use its best efforts to qualify for
registration on Form S-3 and to that end the Company shall register (whether or
not required by law to do so) its Common Stock under the Exchange Act within 12
months following the effective date of the first registration of any securities
of the Company on Form S-1.  After the Company has qualified for the use of Form
S-3, in addition to the rights contained in the foregoing provisions of this
Section 3, the Holders of Registrable Securities shall have the right to request
registrations on Form S-3 thereafter under this Section 3.9 (such requests shall
be in writing and shall state the number of shares of Registrable Securities to
be disposed of and the intended


                                         11.

<PAGE>

method of disposition of such shares by such Holder or Holders), provided that
the Company shall not be required to effect a registration pursuant to this
Section 3.9 unless the Holder or Holders requesting registration propose to
dispose of shares of Registrable Securities which they reasonably anticipate
will have an aggregate disposition price (before deduction of underwriting
discounts and expenses of sale) of at least $1,000,000, and provided further
that the Company shall not be required to effect more than two registrations
pursuant to this Section 3.9 in any 12 month period.

      The Company shall give notice to all Holders of Registrable Securities of
the receipt of a request for registration pursuant to this Section 3.9 and shall
provide a reasonable opportunity for other Holders to participate in the
registration.  Subject to the foregoing, the Company will use its best efforts
to effect promptly the registration of all shares of Registrable Securities on
Form S-3, as the case may be, to the extent requested by the Holder or Holders
thereof for purposes of disposition.

      3.10   TRANSFER OF REGISTRATION RIGHTS

             (a)    Except as otherwise provided herein, the rights contained
in this Section 3 may be assigned or otherwise conveyed to a transferee or
assignee of Registrable Securities held by the Investors, which transferee or
assignee shall be considered a "Holder" for purposes of this Section 3, provided
that (i) such transfer is effected in accordance with applicable federal and
state securities laws, (ii) such transferee or assignee becomes a party to this
Agreement or agrees in writing to be subject to the terms hereof to the same
extent as if he were an original purchaser hereunder and (iii) such transferee
or assignee (A) is a wholly owned subsidiary or constituent partner (including
limited partners and retired partners) or affiliate of the transferring Holder
if such Holder is a partnership, or (B) acquires a number of shares of
Registrable Securities originally held by the transferring Holder equal to at
least 1% of the then-outstanding capital stock of the Company, and, provided
further, that the Company is given written notice by such Holder at the time of
or within a reasonable time after said transfer, stating the name and address of
said transferee or assignee and identifying the securities with respect to which
such registration rights are being assigned.

             (b)    Except as otherwise provided herein, the rights contained
in Section 3, except for the rights contained in Section 3.1, may be assigned
or otherwise conveyed to a transferee or assignee of Registrable Securities held
by the Series A Warrant Holders, which transferee or assignee shall be
considered a "Holder" for purposes of this Section 3, provided that (i) such
transfer is effected in accordance with applicable federal and state securities
laws, (ii) such transferee or assignee becomes a party to this Agreement or
agrees in writing to be subject to the terms hereof to the same extent as if he
were an original purchaser hereunder and, provided further, that the Company is
given written notice by such Holder at the time of or within a reasonable time
after said transfer, stating the name and address of said transferee or assignee
and identifying the securities with respect to which such registration rights
are being assigned.

      3.11   CERTAIN LIMITATIONS IN CONNECTION WITH FUTURE GRANTS OF
             REGISTRATION RIGHTS.

From and after the date of this Agreement, the Company shall not, without the
prior written consent of the Holders of at least a majority of the outstanding
Registrable Securities, enter into


                                         12.

<PAGE>

any agreement with any person or persons providing for the granting to such
holder of registration rights superior to those granted to Holders pursuant to
this Section 3.

      3.12   TERMINATION OF REGISTRATION RIGHTS.  All rights and duties
provided for with respect to any Holder in this Section 3 shall terminate on the
later of (a) the date five (5) years from the date of a Qualified IPO (as
defined below in Section 4.1(d)), and (b) on which such Holder owns less than 1%
of the then-outstanding capital stock of the Company, except where such amount
is held by a Series A Warrant Holder.

      4.     RIGHT OF FIRST REFUSAL ON COMPANY ISSUANCES.

      4.1    RIGHT OF FIRST REFUSAL.  The Company hereby grants to each
Investor (and its affiliates) who holds not less than 1,000,000 shares of
Preferred Stock (or Common Stock issued or issuable upon conversion of the
Preferred Stock) the right of first refusal to purchase, pro rata, all (or any
part) of New Securities (as defined in this Section 4.1) that the Company may,
from time to time propose to sell and issue.  In the case where the price per
share at which the New Securities are being offered is indeterminable or is
equal to or less than $1 (as adjusted for stock splits, reclassification or
otherwise), such Investor's (and its affiliates') pro rata share, for purposes
of this right of first refusal with respect to an offering at such a price, is
the ratio, the numerator of which is the number of shares of Common Stock then
owned by such Investor (and its affiliates) as a result of the conversion of any
Preferred Stock of the Company and issuable upon conversion of the Preferred
Stock of the Company then owned by such Investor (and its affiliates), and the
denominator of which is the total number of shares of Common Stock then
outstanding as a result of the conversion of any Preferred Stock of the Company
or issuable upon conversion of the Preferred Stock of the Company then
outstanding.  In the case where the price per share at which the New Securities
are being offered is greater than $1 (as adjusted for stock splits,
reclassifications or otherwise), such Investor's (and its affiliates') pro rata
share, for purposes of this right of first refusal with respect to an offering
at such a price, is the ratio, the numerator of which is the number of shares of
Common Stock then owned by such Investor (and its affiliates) as a result of the
conversion of any Preferred Stock of the Company and issuable upon conversion of
the Preferred Stock of the Company then owned by such Investor (and its
affiliates), and the denominator of which is the total number of shares of
Common Stock outstanding immediately prior to the issuance of the New
Securities, assuming full conversion of all outstanding shares of Preferred
Stock of the Company.  This right of first refusal shall be subject to the
following provisions:

             (a)    "New Securities" shall mean any capital stock of the
Company, whether now authorized or not, and rights, options, or warrants to
purchase said capital stock, and securities of any type whatsoever that are, or
may become, convertible into said capital stock; provided, however, that "New
Securities" does not include (i) securities issued in any additional Closings
(as defined in the Series B Agreement); (ii) securities issuable upon conversion
of or with respect to Series A Preferred Stock or Series B Preferred Stock;
(iii) securities issued pursuant to an acquisition by the Company by merger,
purchase of substantially all of the assets, or other reorganization whereby the
Company owns more than 50% of the voting power of such entity; (iv) shares of
the Company's Common Stock (or related options) issued to employees, directors
or consultants of the Company pursuant to any employee stock offering, plan, or
arrangement


                                         13.

<PAGE>

approved by the Board of Directors; (v) shares of the Company's Common Stock or
Preferred Stock issued in connection with any stock split, stock dividend, or
similar recapitalization by the Company; (vi) securities issued pursuant to
equipment or debt financing or leases which are approved by the Company's Board
of Directors; (vii) securities issued pursuant to any corporate partnering,
strategic alliance, joint venture or licensing arrangement between the Company
and a third party; or (viii) securities issued by the Company other than for
cash or cash equivalents.

             (b)    In the event that the Company proposes to undertake an
issuance of New Securities, it shall give each Investor who together with its
affiliates holds not less than 1,000,000 shares of Common Stock of the Company
issued or issuable upon conversion of Preferred Stock, written notice of its
intention, describing the type of New Securities, the price, and the general
terms upon which the Company proposes to issue the same.  Each Investor who
together with its affiliates holds not less than 1,000,000 shares of Common
Stock of the Company, issued or issuable upon conversion of Preferred Stock,
shall have 20 days from the date of mailing of any such notice to agree to
purchase up to its full pro rata share of such New Securities for the price and
upon the general terms specified in the notice by giving written notice to the
Company and stating therein the quantity of New Securities to be purchased. 
Each Investor who together with its affiliates holds not less than 1,000,000
shares of Common Stock of the Company, issued or issuable upon conversion of
Preferred Stock, shall have a right of over allotment such that if any Investor
fails to exercise its right hereunder to purchase its full pro rata portion of
New Securities, the Company shall so notify the other Investors and such
Investors (and their affiliates) who have agreed to purchase all or any part of
their pro rata share of New Securities may purchase the nonpurchasing
Investors' portions on a pro rata basis, within ten days from the date of such
notice.

             (c)    In the event that Investors (and their affiliates) fail to
exercise in full the right of first refusal within said 20 day period (plus the
ten day overallotment period, if applicable) the Company shall have 60 days
thereafter to sell or enter into an agreement providing for the closing of the
sale of the New Securities respecting which the Investors' (and their
affiliates') rights were not exercised within 30 days of such agreement at a
price and upon general terms no more favorable to the purchasers thereon than
specified in the Company's notice.  In the event the Company has not sold the
New Securities within such 60 day period, the Company shall not thereafter
issue or sell any New Securities, without first offering such securities to the
Investors (and its affiliates) in the manner provided above.

             (d)    The right of first refusal granted under this Agreement
shall not apply to and shall expire upon the first closing of the first firmly
underwritten public offering of Common Stock of the Company that is pursuant to
a registration statement filed with, and declared effective by, the Commission
under the Securities Act, covering the offer and sale of Common Stock to the
public at a per share price (prior to underwriter commissions and expenses) of
at least $2.50 (as adjusted for stock splits, dividends and similar events) and
at an aggregate offering price (before deduction for underwriter commissions and
expenses) of not less than $10,000,000 (a "Qualified IPO").

             (e)    This right of first refusal is assignable only to an
affiliate of a Holder or in connection with a sale or transfer of a number of
shares of Registrable Securities originally held


                                         14.

<PAGE>

by the assigning Holder equal to at least 1% of the then-outstanding capital
stock of the Company.

      5.     INFORMATION RIGHTS.

      5.1    FINANCIAL INFORMATION. (a) The Company will furnish the following
information to each Investor who holds together with its affiliates holds not
less than 1,000,000 of Common Stock issued or issuable upon conversion of
Preferred Stock:

             (i)    As soon as practicable after the end of each fiscal year of
the Company, and in any event within 120 days thereafter, a consolidated balance
sheet of the Company and its subsidiaries, if any, as at the end of such fiscal
year, and consolidated statements of income and consolidated statements of cash
flows of the Company and its subsidiaries, if any, for such year, prepared in
accordance with generally accepted accounting principles consistently applied
and setting forth in each case in comparative form and figures for the previous
fiscal year, all in reasonable detail and certified by independent public
accountants of national standing selected by the Company.

             (ii)   As soon as practicable after the end of each of the first
three quarterly accounting periods in each fiscal year, and in any event within
45 days thereafter, a consolidated balance sheet of the Company and its
subsidiaries, if any, as at the end of such quarter, and consolidated statements
of income and consolidated statements of cash flows of the Company and its
subsidiaries, if any, for each quarter and for the current fiscal year of the
Company to date, prepared in accordance with generally accepted accounting
principles consistently applied, except that such financial statements will not
contain the notes normally required by generally accepted accounting principles.

             (iii)  As soon as practicable after the adoption thereof, and in
any event no later than 15 days prior to the commencement of its fiscal year, an
annual operating plan for the forthcoming fiscal year, prepared on a
consolidated basis, including projected statements of profit and loss, cash
flow and balance sheets for each calendar quarter of such year, and, promptly
after preparation thereof, any revisions to such annual operating plan and any
other budgets.

             (b)    The covenants provided in Sections 5.1 and 5.2 shall
terminate upon the closing of a Qualified IPO.

      5.2    INSPECTION RIGHTS.  The Company shall permit each Investor who
with its affiliates holds at least 1,000,000 shares of Preferred Stock of the
Company, its attorney, or its other representative to visit and inspect the
Company's properties, to examine the Company's books of account and other
records, to make copies or extracts therefrom and to discuss the Company's
affairs, finances and accounts with its officers, management employees and
independent accountants, all at such reasonable times and as often as such
Investor may reasonably request.

      5.3    ASSIGNMENT OF RIGHTS TO INFORMATION.  The rights granted pursuant
to Sections 5.1 and 5.2 may not be assigned or otherwise conveyed by an investor
or by any subsequent


                                         15.

<PAGE>

transferee of any such rights without the written consent of the Company, which
consent shall not be unreasonably withheld; provided that the Company may refuse
such written consent if the proposed transferee is a competitor of the Company
as determined by the Company's Board of Directors; and provided further, that no
such written consent shall be required if the transfer is made to a party who is
not a competitor of the Company and who is a parent, subsidiary, affiliate,
partner or group member of any Investor.

      5.4    CONFIDENTIAL. Each Investor agrees that it will keep confidential
and will not disclose or divulge any confidential, proprietary or secret
information which such Investor may obtain from the Company, and which the
Company has prominently marked "confidential", "proprietary" or "secret" or has
otherwise identified as being such, pursuant to financial statements, reports
and other materials submitted by the Company as required hereunder, or pursuant
to visitation or inspection rights granted hereunder unless such information is
or becomes known to the Investor from a source other than the Company or is or
becomes publicly known, or unless the Company gives its written consent to the
Investor's release of such information, except that no such written consent
shall be required (and the Investor shall be free to release such information to
such recipient) if such information is to be provided to an Investor's counsel
or accountant, or to an officer, director or partner of an Investor, provided
that the Investor shall inform the recipient of the confidential nature of such
information, and shall instruct the recipient to treat the information as
confidential.

      6.     MISCELLANEOUS.

      6.1    GOVERNING LAW.  This Agreement shall be governed by and construed
in accordance with the laws of the State of California applicable to contracts
between California residents entered into and to be performed entirely within
the State of California.

      6.2    SUCCESSORS AND ASSIGNS.  Except as otherwise provided herein, the
provisions hereof shall inure to the benefit of, and be binding upon, the
successors, assigns, heirs, executors and administrators of the parties hereto.

      6.3    ENTIRE AGREEMENT.  This Agreement, the Series A Agreement and the
Series B Agreement constitute the full and entire understanding and agreement
among the parties with regard to the subjects hereof and thereof.  This
Agreement supersedes the Original Investors Rights Agreement which is hereby
terminated, effective upon the initial Closing under the Series B Agreement.

      6.4    NOTICES, ETC.  All notices and other communications required or
permitted hereunder shall be in writing and shall be effective five (5) days
after deposited by first-class mail, postage prepaid, with the United States
mail or delivery by hand or by messenger, if addressed (a) to an Investor, at
such Investor's address set forth on the attached Exhibit A, or at such other
address as such Investor shall have furnished to the Company in writing, or (b)
to any other holder of Registrable Securities, at such address as such holder
shall have furnished the Company in writing, or, until any such holder so
furnishes an address to the Company, then to and at the address of the last
holder of such Registrable Securities who has so furnished an address to the
Company, or (c) to the Company, at the address set forth below the Company's


                                         16.

<PAGE>

name on the signature page to this Agreement or such other address as the
Company shall have furnished to each Investor and each such other holder in
writing.  Notwithstanding the above, any notice or communication to an address
outside the United States shall be sent by telecopy and confirmed in writing
sent by courier guaranteeing delivery in no more than two (2) business days.

      6.5    DELAYS OR OMISSIONS.  No delay or omission to exercise any right,
power or remedy accruing to any party, upon any breach or default of any other
party under this Agreement, shall impair any such right, power or remedy of such
party nor shall it be construed to be a waiver of any such breach or default, or
an acquiescence therein, or of or in any similar breach or default thereunder
occurring; nor shall any waiver of any single breach or default be deemed a
waiver of any other breach or default theretofore or thereafter occurring.  Any
waiver, permit, consent or approval of any kind or character on the part of any
party of any breach or default under this Agreement, or any waiver on the part
of any party of any provisions or conditions of this Agreement, must be in
writing and shall be effective only to the extent specifically set forth in such
writing.  All remedies, either under this Agreement, or by law or otherwise
afforded to any holder, shall be cumulative and not alternative.

      6.6    COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which may be executed by less than all of the Investors,
each of which shall be enforceable against the parties actually executing such
counterparts, and all of which together shall constitute one instrument.

      6.7    SEVERABILITY.  In the case any provision of this Agreement shall
be invalid, illegal or unenforceable, the validity, legality and enforceability
of the remaining provisions shall not in any way be affected or impaired
thereby.

      6.8    AMENDMENTS.  The provisions of this Agreement may be amended at
any time and from time to time, and particular provisions of this Agreement may
be waived, with and only with an agreement or consent in writing signed by the
Company and by the holders of not less than a majority of the number of shares
of Registrable Securities outstanding as of the date of such amendment or
waiver.  Each Investor and Series A Warrant Holder and Series B Warrant Holder
acknowledges that by the operation of this Section 6.8 the holders of a majority
of the outstanding Registrable Securities may have the right and power to
diminish or eliminate all rights of such investor, Series A Warrant Holder or
Series B Warrant Holder under this Agreement.  Notwithstanding anything herein
to the contrary, the parties agree that the Company may amend this Agreement at
any time after the date hereof, without obtaining the consent of any Holder, to
add as parties to this Agreement any purchasers of the Company's Series B
Preferred Stock pursuant to Section 2 of that certain Series B Preferred Stock
Purchase Agreement between the Company and certain persons dated on or about the
date of this Agreement.  Any persons added to this Agreement pursuant to this
subparagraph shall become "Holders" and "Investors" under this Agreement, and
shares of Common Stock issuable upon conversion of the Series B Preferred Stock
held by such persons shall be "Registrable Securities" under this Agreement.


                                         17.

<PAGE>

      The foregoing Investors Rights Agreement is hereby executed as of the
date first above written.


COMPANY                                INSTITUTIONAL VENTURE
                                           PARTNERS V
AVIRON                                     by its General Partner
                                       Institutional Venture Management V


By: /s/ L. Read                        By: /s/ Reid W. Dennis
   --------------------------------       -----------------------------------
    J. Leighton Read, M.D.                 Reid W. Dennis
    Chief Executive Officer                    General Partner
        1450 Rollins Road                      3000 Sand Hill Road
        Burlingame, CA 94010                   Building 2, Suite 290
                                               Menlo Park, CA 94025


                                       INSTITUTIONAL VENTURE
                                           MANAGEMENT V


                                       By: /s/ Reid W. Dennis
                                          -----------------------------------
                                           Reid W. Dennis
                                               General Partner
                                               3000 Sand Hill Road
                                               Building 2, Suite 290
                                               Menlo Park, CA 94025


                                       /s/ L. Read
                                       --------------------------------------
                                       J. Leighton Read, M.D.
                                           c/o Aviron
                                           1450 Rollins Road
                                           Burlingame, California 94010


                                       /s/ Bernard Roizman
                                       --------------------------------------
                                       Bernard Roizman
                                           5555 S. Everett, Apt. 11A
                                           Chicago, Illinois 60637


                                       /s/ Betty Roizman
                                       --------------------------------------
                                       Betty Roizman
                                           5555 S. Everett, Apt. 11A
                                           Chicago, Illinois 60637


                                         18.

<PAGE>

                                       ARCH Venture Fund Limited Partnership a
                                       Delaware Limited Partnership

                                       By:  ARCH Development Corporation


                                       By: /s/ S. Lazarus
                                          -----------------------------------
                                           Steven Lazarus, President

                                            c/o ARCH Development Corporation
                                            The University of Chicago
                                            1101 East 58th Street
                                            Walker 213
                                            Chicago, Illinois 60637


                                       /s/ Albert L. Zesiger
                                       --------------------------------------
                                       Albert L. Zesiger
                                           75 Bluff Avenue
                                           Rowayton, Connecticut 06853


                                       /s/ Peter Palese
                                       --------------------------------------
                                       Peter Palese, Ph.D.
                                           414 Highwood Avenue
                                           Leonia, New Jersey 07605



                                       --------------------------------------
                                       John P. Curran
                                           230 Park Avenue
                                           Suite 1245
                                           New York, New York 10169



                                       --------------------------------------
                                       Steven R. Frank
                                           c/o Bear Stearns & Co.
                                           245 Park Avenue, 3rd Floor
                                           New York, NY 10169



                                       --------------------------------------
                                       David B. Musket
                                           One Boston Place, 35th Floor
                                           Boston, Massachusetts 02108


                                         19.

<PAGE>

                                       GC&H Investments


                                       By: /s/ John L. Cardoza
                                            ---------------------------------

                                       Name: John L. Cardoza
                                            ---------------------------------
                                             Executive Partner

                                             c/o Jeanne Meyer
                                             Cooley Godward Castro
                                             Huddleson & Tatum
                                             One Maritime Plaza, 20th Floor
                                             San Francisco, California 94111


                                       /s/ Julian N. Stern
                                       --------------------------------------
                                       Julian N. Stern
                                           84 Selby Lane
                                           Atherton, California 94025



                                       /s/ Richard Whitley
                                       --------------------------------------
                                       Richard Whitley
                                           216 Shades Crest Circle
                                           Birmingham, Alabama 35216



                                       --------------------------------------
                                       Sally B. Whitley
                                           216 Shades Crest Circle
                                           Birmingham, Alabama 35216


                                       /s/ Bruce A. Hironaka
                                       --------------------------------------
                                       Bruce A. Hironaka
                                           26 Lenox Road
                                           Kensington, California 94707


                                       /s/ Valerie L. Hironaka
                                       --------------------------------------
                                       Valerie Hironaka
                                           26 Lenox Road
                                           Kensington, California 94707


                                         20.

<PAGE>

                                       THE MOUNT SINAI SCHOOL
                                       OF MEDICINE


                                       By:
                                          -----------------------------------
                                           Frank R. Landsberger, Ph. D
                                           One Gustave L. Levy Plaza
                                           New York, NY 10029-6574


                                       ACCEL IV L.P.

                                       By: Accel IV Associates L.P.
                                           Its: General Partner


                                       By: /s/ Illegible
                                          -----------------------------------
                                           General Partner
                                                1 Embarcadero Center
                                                Suite 3820
                                                San Francisco, CA 94111


                                       ACCEL JAPAN L.P.

                                       By: Accel Japan Associates L.P.
                                           Its: General Partner


                                       By: /s/ Illegible
                                          -----------------------------------
                                           General Partner
                                                1 Embarcadero Center
                                                Suite 3820
                                                San Francisco, CA 94111


                                       ABINGWORTH BIOVENTURES

                                       By: /s/ Allen Latta
                                          -----------------------------------
                                           Allen J. Latta
                                           Attorney-in-Fact
                                                c/o Sanne & Cie
                                                Boite Postale 566
                                                L-2015 Luxembourg


                                         21.

<PAGE>

                                       with a copy to:

                                           Dr. Stephen W. Bunting
                                               Abingworth Management
                                               Limited
                                               26 St. James Street
                                               London SW1A 1HA
                                               England


                                       FERRIS F. HAMILTON
                                       FAMILY TRUST


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       MARY ANN HAMILTON
                                       TRUST FOR SELF


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       TAB PRODUCTS CO.  PENSION PLAN


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------




                                         22.

<PAGE>

                                       THE JENIFER ALTMAN
                                       FOUNDATION


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       AMERICAN MEDICAL INT'L.
                                       PENSION PLAN


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------

                                       TEMPLE-INLAND MASTER TRUST


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       ARTHUR D. LITTLE
                                       EMPLOYEE INVES. PLAN


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                         23.

<PAGE>

                                       THE DEAN WITTER FOUNDATION


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       ANDREW HEISKELL


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------

                                       ALFRED E. HELLER


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                       ELIZABETH HELLER MANDELL
                                       TRUST


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                         24.

<PAGE>

                                       DOMENIC MIZIO


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                               --------------------------------


                                       THE RAISER MARITAL TRUST


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                               --------------------------------


                                       MARY VAN SCHUYLER RAISER


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                               --------------------------------



                                       BARRIE RAMSAY ZESIGER


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                               --------------------------------


                                         25.

<PAGE>

                                       BEA ASSOCIATES
                                       PROFIT SHARING TRUST


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                               --------------------------------


                                       BRINSON PARTNERS, INC.


                                       By:
                                          -----------------------------------
                                           Robert D. Blank
                                            Partner
                                            Brinson Partners, Inc.
                                            209 South LaSalle Street
                                            Suite 114
                                            Chicago, IL 60604-1295


                                       /s/ Alejandro Zaffaroni
                                       --------------------------------------
                                       Dr. Alejandro Zaffaroni, Ph.D.
                                           c/o Interhealth Limited
                                           4005 Miranda Avenue, Suite 180
                                           Palo Alto, CA 94304


                                       ARCH VENTURE FUND II, L.P.
                                       a Delaware limited partnership

                                       By:  ARCH Management Partners II, L.P.
                                               its general partner

                                           By:  ARCH Venture Partners, L.P.
                                              its general partner

                                               By:  Lifework, Inc.
                                                  its general partner

                                                    By: /s/ Robert Nelsen
                                                       ----------------------
                                                        Robert Nelsen
                                                      -----------------------,
                                                      Managing Director


                                         26.

<PAGE>

                                       /s/ Eugene Garfield
                                       --------------------------------------
                                       Eugene Garfield
                                           Institute of Scientific Information
                                           3501 Market Street
                                           Philadelphia, PA 19104


                                       /s/ H. R. Sheperd
                                       --------------------------------------
                                       Dr. H. R. Shepherd
                                            Opportunities Unlimited
                                            c/o Armstrong Pharmaceuticals
                                            71 Elm Street
                                            New Caanan, CT 06840


                                         27.

<PAGE>

                                 BRINSON VENTURE CAPITAL FUND III, L.P.


                                       By: Brinson Partners, Inc.
                                           its General Partner


                                       By: /s/ Robert D. Blank
                                          -----------------------------------
                                           Robert D. Blank, Partner


                                       BRINSON TRUST COMPANY AS TRUSTEE
                                       OF THE BRINSON MAP VENTURE
                                       CAPITAL FUND III


                                       By: /s/ Robert D. Blank
                                          -----------------------------------
                                            Robert D. Blank,
                                            Assistant Trust Officer


                                         28.

<PAGE>

                                       WELLS FAMMY TRUST
                                       S/P JOEL W. SCHRECK


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                              ---------------------------------


                                       A. CAREY ZESIGER REVOCABLE TRUST


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                              ---------------------------------


                                       NICOLA L. ZESIGER


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: Albert L. Zesiger
                                              ---------------------------------

                                         Title: Managing Director
                                              ---------------------------------


                                       ALEXA L. ZESIGER


                                           BEA ASSOCIATES
                                           ATTORNEY-IN-FACT

                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                         Name: ALBERT L. ZESIGER
                                              ---------------------------------

                                         Title: MANAGING DIRECTOR
                                              ---------------------------------


                                         29.

<PAGE>

                                       ALZA CORPORATION RETIREMENT PLAN


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------



                                       SHEANA BUTLER


                                           Bea Associates
                                           Attorney-in-Fact
                                       By: /s/ Albert L. Zesiger
                                          -----------------------------------

                                       Name: Albert L. Zesiger
                                            ---------------------------------

                                       Title: Managing Director
                                             --------------------------------


                                         30.

<PAGE>
                                       ROVENT Limited Partnership

                                       By: Advent International Limited 
                                           Partnership, General Partner

                                       By: Advent International Corporation,
                                           General Partner


                                       By: /s/ Charles Hsu
                                          -----------------------------------
                                                Charles Hsu, Vice President


                                       ADVENTACT Limited Partnership


                                       By: Advent International Limited 
                                           Partnership, General Partner

                                       By: Advent International Corporation,
                                           General Partner


                                       By: /s/ Charles Hsu
                                          -----------------------------------
                                                Charles Hsu, Vice President


                                       Golden Gate Development and Investment
                                       Limited Partnership


                                       By: Advent International Limited 
                                           Partnership, General Partner

                                       By: Advent International Corporation,
                                           General Partner


                                       By: /s/ Charles Hsu
                                          -----------------------------------
                                                Charles Hsu, Vice President


                                         31.

<PAGE>

                                       Advent International Investors II 
                                       Limited Partnership

                                       By: Advent International Corporation,
                                           General Partner


                                       By: /s/ Charles Hsu
                                          -----------------------------------
                                                Charles Hsu, Vice President


                                         32.

<PAGE>

                                       /s/ George Rupp
                                       --------------------------------------
                                       George Rupp
                                           202 Low Library
                                           Columbia University
                                           60 Morningside Drive
                                           New York, New York 10027


                                         33.

<PAGE>

                                      EXHIBIT A

                                SCHEDULE OF INVESTORS
                               AS OF SEPTEMBER 3, 1993

Name and Address                                                    Shares
- --------------------------------------------------------------------------------

Series A Preferred Stock:

Institutional Venture Partners V . . . . . . . . . . . . . . . .      2,955,000
Institutional Venture Management V . . . . . . . . . . . . . . .         45,000
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


J. Leighton Read, M.D. . . . . . . . . . . . . . . . . . . . . .        500,000
c/o Interhealth
4009 Miranda Avenue, Suite 275
Palo Alto, California 94304


Bernard Roizman, Sc.D. and Betty Roizman . . . . . . . . . . . .        100,000
5555 S. Everett, Apt. 11A
Chicago, Illinois 60637


Albert L. Zesiger. . . . . . . . . . . . . . . . . . . . . . . .        300,000
75 Bluff Avenue
Rowayton, Connecticut 06853


Peter Palese, Ph.D.  . . . . . . . . . . . . . . . . . . . . . .        100,000
Professor and Chairman
Department of Microbiology
Mount Sinai Medical Center
New York, New York 10029


John P. Curran . . . . . . . . . . . . . . . . . . . . . . . . .         80,000
230 Park Avenue
Suite 1245
New York, New York 10169


                                          1.

<PAGE>

Name and Address                                                    Shares
- --------------------------------------------------------------------------------

Steven R. Frank. . . . . . . . . . . . . . . . . . . . . . . . .         50,000
c/o Bear Stearns & Co.
245 Park Avenue, 3rd Floor
New York, NY 10169


David B. Musket. . . . . . . . . . . . . . . . . . . . . . . . .         50,000
One Boston Place, 35th Floor
Boston, Massachusetts 02108


GC&H Investments . . . . . . . . . . . . . . . . . . . . . . . .         50,000
c/o Jeanne Meyer
Cooley Godward Castro Huddleson & Tatum
One Maritime Plaza, 20th Floor
San Francisco, California 94111


Julian N. Stem . . . . . . . . . . . . . . . . . . . . . . . . .         50,000
84 Selby Lane
Atherton, California 94025


Richard Whitley. . . . . . . . . . . . . . . . . . . . . . . . .         10,000
Sally B. Whitley
216 Shades Crest Circle
Birmingham, Alabama 35216


Bruce A. Hironaka. . . . . . . . . . . . . . . . . . . . . . . .         10,000
Valerie Hironaka
26 Lenox Road
Kensington, California 94707


ARCH VENTURE FUND. . . . . . . . . . . . . . . . . . . . . . . .        700,000
Limited Partnership
c/o ARCH Development Corporation
The University of Chicago
1101 East 58th Street
Walker 213
Chicago Illinois 60637


                                          2.

<PAGE>

Name and Address                                                    Shares
- --------------------------------------------------------------------------------

SERIES B PREFERRED STOCK:

Accel IV L.P.. . . . . . . . . . . . . . . . . . . . . . . . . .      2,811,111
Accel Japan L.P. . . . . . . . . . . . . . . . . . . . . . . . .        244,444
One Embarcadero Center
Suite 3820
San Francisco, CA 94111


Abingworth Bioventures . . . . . . . . . . . . . . . . . . . . .      2,777,778
c/o Sanne & Cie
Boite Postale 566
L-2015 Luxembourg,
Attn: Karl U. Sanne
Telecopier: (352) 43 54 10

With a copy to:

    Dr. Stephen W. Bunting
    Abingworth Management Limited
    26 St. James's Street
    London SW1A 1HA
    England
    Telecopier:  (44)(71) 930-1891

and to:

    Allen J. Latta, Esq.
    Buchalter, Nerner, Fields & Younger
    601 S. Figueroa Street, 25th Floor
    Los Angeles, CA 90017
    Telecopier:  (213) 896-0400


Brinson Venture Capital Fund III, L.P. . . . . . . . . . . . . .      1,910,624
Brinson Trust Company as Trustee of the. . . . . . . . . . . . .        311,598
:Brinson MAP Venture Capital Fund III
c/o Brinson Partners, Inc.
209 South LaSalle Street
Suite 114
Chicago IL 60604-1295


                                          3.

<PAGE>

Name and Address                                                    Shares
- --------------------------------------------------------------------------------

Institutional Venture Partners V . . . . . . . . . . . . . . . .      2,695,500
Institutional Venture Management V . . . . . . . . . . . . . . .         61,100
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


ARCH VENTURE FUND II, L.P. . . . . . . . . . . . . . . . . . . .        277,778
c/o ARCH Development Corporation
The University of Chicago
1101 East 58th Street
Walker 213
Chicago, Illinois 60637


Ferris F. Hamilton Family Trust. . . . . . . . . . . . . . . . .         49,500
Mary Ann Hamilton Trust for Self . . . . . . . . . . . . . . . .         76,500
The Jenifer Altman Foundation. . . . . . . . . . . . . . . . . .         49,500
American Medical Int'l. Pension Plan . . . . . . . . . . . . . .        450,000
Temple-Inland Master Trust . . . . . . . . . . . . . . . . . . .        495,000
Arthur D. Little Employee Inves. Plan. . . . . . . . . . . . . .        405,000
The Dean Witter Foundation . . . . . . . . . . . . . . . . . . .         72,000
Andrew Heiskell. . . . . . . . . . . . . . . . . . . . . . . . .         76,500
Alfred E. Heller . . . . . . . . . . . . . . . . . . . . . . . .         49,500
Elizabeth Heller Mandell Trust . . . . . . . . . . . . . . . . .         49,500
Domenic Mizio. . . . . . . . . . . . . . . . . . . . . . . . . .         76,500
The Raiser Marital Trust . . . . . . . . . . . . . . . . . . . .         99,000
Mary Van Schuyler Raiser . . . . . . . . . . . . . . . . . . . .         27,000
Barrie Ramsay Zesiger. . . . . . . . . . . . . . . . . . . . . .         99,000
BEA Associates Profit Sharing Trust. . . . . . . . . . . . . . .         99,000
Wells Family Trust S/P Joel W. Schreck . . . . . . . . . . . . .         99,000
A. Carey Zesiger Revocable Trust . . . . . . . . . . . . . . . .         36,000
Nicola L. Zesiger. . . . . . . . . . . . . . . . . . . . . . . .         36,000
Alexa L. Zesiger . . . . . . . . . . . . . . . . . . . . . . . .         31,500
Alza Corporation Retirement Plan . . . . . . . . . . . . . . . .         49,500
Sheana Butler: . . . . . . . . . . . . . . . . . . . . . . . . .         27,000
    c/o BEA Associates
    153 E. 53rd Street, 58th Floor
    New York, NY 10022


Dr. H.R. Shepherd. . . . . . . . . . . . . . . . . . . . . . . .        166,667
Opportunities Unlimited
c/o Armstrong Pharmaceuticals
71 Elm Street
New Caanan, CT 06840


                                          4.

<PAGE>

Name and Address                                                    Shares
- --------------------------------------------------------------------------------

Dr. Alejandro Zaffaroni. . . . . . . . . . . . . . . . . . . . .        277,778
Attention: Gonzalo Silviera
c/o Interhealth Limited
4005 Miranda Avenue, Suite 180
Palo Alto, CA 94304


Eugene Garfield. . . . . . . . . . . . . . . . . . . . . . . . .        277,778
Institute of Scientific Information
3501 Market Street
Philadelphia, PA 19104


Peter Palese, Ph.D . . . . . . . . . . . . . . . . . . . . . . .         55,556
414 Highwood Avenue
Leonia, New Jersey 07605


GC&H Investments . . . . . . . . . . . . . . . . . . . . . . . .         40,000
c/o Jeanne Meyer
Cooley Godward Castro Huddleson & Tatum
One Maritime Plaza, 20th Floor
San Francisco, California 94111


Common Stock:


Peter Palese, Ph.D . . . . . . . . . . . . . . . . . . . . . . .        750,000
414 Highwood Avenue
Leonia, New Jersey 07605


J. Leighton Read, M.D. . . . . . . . . . . . . . . . . . . . . .        750,000
c/o Aviron
1450 Rollins Road
Burlingame, CA 94010


Bernard Roizman, Sc.D. . . . . . . . . . . . . . . . . . . . . .        750,000
5555 S. Everett, Apt. 11A
Chicago IL 60637


Richard J. Whitley . . . . . . . . . . . . . . . . . . . . . . .        750,000
216 Shades Crest Circle
Vestavia, AL 35216


                                          5.

<PAGE>

                                      EXHIBIT B
                         SCHEDULE OF SERIES A WARRANT HOLDERS

Name and Address                                      No. of Shares Purchasable
- --------------------------------------------------------------------------------

Mount Sinai Medical Center . . . . . . . . . . . . .       225,000
One Gustave L. Levy Plaza
New York, New York 10029-6574


                                          6.

<PAGE>

                                     EXHIBIT C

                         SCHEDULE OF SERIES B WARRANT HOLDERS


Name and Address                                      No. of Shares Purchasable
- --------------------------------------------------------------------------------


Institutional Venture Management V . . . . . . . . .         8,000
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


Institutional Venture Partners V . . . . . . . . . .       392,000
Building 2, Suite 290
3000 Sand Hill Road
Menlo Park, California 94025


                                          7.

<PAGE>

                                      EXHIBIT D

                               CAPITALIZATION SCHEDULE


Pursuant to the 1992 Stock Option Plan (the "Option Plan"), the Company has
reserved 3,860,000 shares of Common Stock for issuance upon exercise of options
granted under the Option Plan.  As of September 3, 1993, options to purchase
1,912,034 shares (net of cancellations) have been granted to employees and
consultants of which 69,270 shares have been exercised.

On February 9, 1993, the Company entered into a Technology Transfer Agreement
with The Mount Sinai School of Medicine ("Mount Sinai") pursuant to which the
Company acquired certain technologies.  In exchange, Aviron issued 175,000
shares of Common Stock and Warrants to purchase, in the aggregate, 225,000
shares of Series A Preferred Stock (the "Series A Warrants").  The Series A
Warrants become exercisable at various times upon the occurrence of certain
milestones.

On June 1, 1993, the Company entered into agreements with Institutional Venture
Partners ("IVP") and Institutional Venture Management ("IVM") to provide a
bridge loan to the Company.  In consideration for the loan, IVP and IVM received
warrants to purchase a total of 400,000 shares of Series B Preferred Stock (the
"Series B Warrants").  The Series B Warrants expire at the earlier of (i) the
closing of an initial public offering of Common Stock pursuant to a registration
statement under the Securities Act of 1933, as amended or (ii) June 1, 1995.

On March 30, 1994, the Company issued to Lease Management Services, Inc. a
warrant to purchase 116,667 shares of Series B Preferred Stock in connection
with an equipment lease.


<PAGE>

EXHIBIT B TO MATERIALS TRANSFER AND INTELLECTUAL PROPERTY AGREEMENT BETWEEN
AVIRON AND THE REGENTS OF THE UNIVERSITY OF MICHIGAN, EFFECTIVE AS OF
February 24, 1995

LIST OF KNOWN RECIPIENTS OF MASTER STRAINS


                                          38

<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



LIST OF KNOWN RECIPIENTS OF MASTER STRAINS


[                                                                               
                                                                                
                                                                                
                                                                                
                                                        ]

Transfers to recipients noted on the following memo and the following letter:


<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED


[The University of Michigan School of Public Health Letterhead]



                                   November 7, 1994



J. Leighton Reed, M.D.
Chairman and C.E.O.
Aviron
1450 Rollins Road
Burlingame, California 94010

Dear Dr. Reed:

    As requested, I am furnishing you with the names of the organizations that
furnished the two "Master" strains [                                            
                       ]

1.  [                                                                           
                  ]

2.  [                                                                           
                                   ]

3.  [                                                                           
                      ]

4.  [                                                                           
                                    ]

5.  [                                                                           
                                                ]

                                      Sincerely,
                                   [              ]


[           ]


<PAGE>

                                              CONFIDENTIAL TREATMENT REQUESTED



[The University of Michigan School of Public Health Letterhead]


                                                                2/14/95


    To:            Mike Kope-J.D.-Attorney-TMO


    From:          [                                                   ]


    Re:            Distribution of the Master-Strain


    [                                                                           
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                       ]

<PAGE>


                               STOCK TRANSFER AGREEMENT


    THIS AGREEMENT is made as of February 24, 1995, by and among AVIRON, a
California corporation (the "Company") and THE REGENTS OF THE UNIVERSITY OF
MICHIGAN, a Michigan constitutional corporation ("Michigan").

    WHEREAS, the Company and Michigan have entered into a Materials Transfer
and Intellectual Property Agreement (the "Technology Agreement") dated as of
February 24, 1995 (the "Execution Date").

    WHEREAS, in connection with the granting to Aviron by Michigan of certain
rights under the Technology Agreement, the Company has agreed to issue to
Michigan shares of its Series B Preferred Stock and, under certain
circumstances, a Warrant to purchase certain shares of the Company's capital
stock, as more fully described below;

    NOW, THEREFORE, in consideration of the mutual promises, covenants and
conditions hereinafter set forth, the parties hereto mutually agree as follows:


                                      SECTION 1

           ISSUANCE OF THE SHARES; AUTHORIZATION OF THE SHARES AND WARRANT

    1.1  ISSUANCE OF THE SHARES.  In reliance upon the representations and
agreements of Michigan contained herein, within thirty (30) days of the
Execution Date (the "Issue Date"), in partial consideration of the Technology
Agreement, the Company shall issue to Michigan 1,323,734 shares of its Series B
Preferred Stock (the "Shares"), having the rights, restrictions, privileges and
preferences set forth in the Amended and Restated Articles of Incorporation of
the Company, as amended by the Certificate of Amendment, both attached hereto as
Exhibit A (the "Articles").

    1.2  AUTHORIZATION OF SHARES AND WARRANT.  On or before the Issue Date, the
Company shall have (a) authorized the issuance of the Shares; (b) adopted and
filed the Articles with the Secretary of State of the State of California; and
(c) authorized, under the circumstances set forth in this Agreement, a warrant
to purchase shares of its common stock ("Common Stock") in the form attached
hereto as Exhibit B (the "Warrant").  Failure by the Company to meet its
obligations under this Section 1.2 by the Issue Date shall be a material breach
of this Agreement and the Technology Agreement.  In addition to all other legal
rights which Michigan may have by reason of such breach, Michigan shall have the
right upon such breach to immediately terminate this Agreement and the
Technology Agreement, and to require specific performance by the Company of its
obligations upon termination of the Technology Agreement, including those set
forth in Sections 4.5 and 15.5 thereof.  Upon the Issue Date the Company shall
deliver to Michigan copies of all requisite board and shareholder consents and a
file-stamped copy of the


                                          1.

<PAGE>

Articles, accompanied by a certificate signed by an officer of the Company
certifying that the Company's obligations under this Section 1.2 have been
fulfilled.


                                      SECTION 2

                    REPRESENTATIONS AND WARRANTIES OF THE COMPANY

    The Company hereby represents and warrants to Michigan as follows:

    2.1  ORGANIZATION AND STANDING.  The Company is a corporation duly
organized, validly existing, and in good standing under the laws of the State of
California.  The Company has all requisite corporate power to own and operate
its properties and assets, and to carry on its business as presently and as
proposed to be conducted.  The Company is qualified to do business as a foreign
corporation in each jurisdiction in which such qualification is required and
where the failure to be so qualified would have a material adverse effect on the
Company's business.  The Company has no subsidiaries.

    2.2  CORPORATE POWER.  The Company has all requisite legal and corporate
power to execute and deliver this Agreement and any other agreement contemplated
hereby, to transfer and issue the Shares and to issue the Warrant, and to carry
out and perform its obligations under the terms of this Agreement.

    2.3  ARTICLES. Upon the Issue Date, the Articles, in the form attached
hereto as Exhibit A, will be the true, correct and complete Articles of
Incorporation of the Company.

    2.4  CAPITALIZATION.

         (a)  The authorized capital stock of the Company consists, or will
consist upon the Issue Date, of 35,000,000 shares of Common Stock, of which
3,484,270 shares are issued and outstanding, and 25,000,000 shares of Preferred
Stock; 5,225,000 shares of which have been designated Series A Preferred Stock,
of which 5,000,000 are issued and outstanding; 18,650,000 shares of which have
been designated Series B Preferred Stock, of which 16,666,667 are issued and
outstanding.  All such issued and outstanding shares have been duly authorized
and validly issued, and are fully paid and nonassessable.  The rights,
restrictions, privileges and preferences of the Series A Preferred Stock and
Series B Preferred Stock are as stated in the Articles.  As of the Execution
Date, and taking into account the Shares to be issued under this Agreement, the
Shares represent five percent (5%) of the issued and outstanding shares of
capital stock of the Company.

         (b)  Excepting that certain Amended and Restated Investors Rights
Agreement, dated as of September 3, 1993, among the Company and the other
parties named therein, as amended to date (the "Rights Agreement" a copy of
which is attached hereto as Exhibit C), and except as set forth herein or on the
schedule attached hereto as Exhibit D or in the Articles, as of


                                          2.

<PAGE>

the Execution Date there are no outstanding rights of first refusal, preemptive
rights or other rights, options, warrants, conversion rights, or other
agreements either directly or indirectly for the purchase or acquisition from
the Company of any shares of its capital stock.

    2.5  AUTHORIZATION.  All corporate action on the part of the Company, its
directors and shareholders necessary for the sale and issuance of the Shares,
and the Common Stock issuable upon conversion of the Shares (the "Underlying
Stock") and the performance of the Company's obligations hereunder and under
each of the other agreements contemplated hereby and the reservation of the
Underlying Stock has been taken or will be taken prior to the Issue Date.  The
Shares (and the Underlying Stock), when issued in compliance with the provisions
of this Agreement, will be validly issued and will be fully paid and
nonassessable, and will be free of any liens or encumbrances; provided, however,
that the Shares (and the Underlying Stock) may be subject to restrictions on
transfer under state and/or federal securities laws as set forth herein.

    2.6  LITIGATION.  Neither the Company nor any of its property is subject to
any claim, action, suit, proceeding, arbitration or any investigation before any
court or other authority having jurisdiction and, to the best of the Company's
knowledge, none of the same is, or has been, threatened against the Company or
any of its property.  The Company is not a party or subject to the provision of
any order, writ, injunction, judgment or decree of any court or governmental
agency or instrumentality.  There is no action, suit or proceeding by the
Company currently pending or that the Company presently intends to initiate.

    2.7  OTHER AGREEMENTS.  The execution and delivery of this Agreement by the
Company and the consummation of the transactions contemplated under the
Technology Agreement and this Agreement do not and will not, with either the
passage of time or the giving of notice, conflict with or result in the breach
of any condition or provision of, or constitute a default under, any contract,
mortgage, lien, lease, agreement, indenture or instrument to which the Company
is a party or any judgment to which it is subject.

    2.8  GOVERNMENTAL CONSENTS.  All consents, approvals, orders or
authorizations of, or registrations, qualifications, designations, declarations
or filings with, any governmental authority required on the part of the Company
in connection with the valid execution and delivery of this Agreement, the
offer, transfer, sale or issuance of the Shares and the Underlying Stock, and
the consummation of all other transactions contemplated by this Agreement shall
have been obtained and will be effective on the Issue Date, except for notices
required or permitted to be filed with certain state and federal securities
commissions after such date, which notices the Company shall file on a timely
basis.

    2.9  OFFERING.  Assuming the accuracy of the representations and warranties
of the Purchaser contained in Section 3 hereof, the offer, issue and sale of the
Shares is exempt from registration under the Securities Act of 1933, as amended
("Securities Act"), and under the Uniform Securities Act of Michigan.


                                          3.

<PAGE>

    2.10 ABSENCE OF MATERIAL ADVERSE LIABILITIES.  The Company has no
liabilities, current or contingent, nor are its properties subject to any claim
or lien, that currently materially and adversely affect the ability of the
Company to conduct its business as presently conducted.

    2.11 OPERATING RIGHTS.  The Company has all material operating authority,
licenses, franchises, permits, certificates, consents, rights and privileges as
are necessary to the operation of its business as now conducted.


                                      SECTION 3

                      REPRESENTATIONS AND WARRANTIES OF MICHIGAN

    Michigan hereby represents and warrants only to the Company with respect to
the issuance of the Shares as follows:

    3.1  AUTHORIZATION.  Michigan has all the requisite power and is duly
authorized to execute and deliver this Agreement and each other agreement
contemplated hereby and has taken all necessary action to consummate the
transactions contemplated hereby and thereby.  This Agreement, the Technology
Agreement, and each other agreement contemplated hereby have been duly executed
and delivered by Michigan and constitute valid and binding obligations of
Michigan, enforceable in accordance with their respective terms subject to laws
of general application relating to bankruptcy, insolvency and the relief of
debtors.

    3.2  ACCREDITED INVESTOR.  Michigan is an accredited investor within the
meaning of Regulation D, as promulgated under the Securities Act.

    3.3  EXPERIENCE.  Michigan, alone or together with its advisors, is
experienced in evaluating and investing in start-up biomedical research
companies such as the Company.

    3.4  INVESTMENT.  Michigan is acquiring the Shares for investment, for its
own account and not with a view to, or for resale in connection with, any
distribution thereof, and it has no present intention of selling or distributing
the Shares or the Underlying Stock.  Michigan understands that the Shares and
the Underlying Stock have not been registered under the Securities Act by reason
of a specific exemption from the registration provisions of the Securities Act
which depends upon, among other things, the bona fide nature of the investment
intent as expressed herein.

    3.5  RULE 144 AND RULE 144A.  Michigan acknowledges that, because they have
not been registered under the Securities Act, the Shares and the Underlying
Stock must be held indefinitely unless subsequently registered under the
Securities Act or an exemption from such registration is available.  Michigan is
aware of the provisions of Rule 144 and Rule 144A promulgated under the
Securities Act, which rules permit limited resale of securities purchased in a
private placement subject to the satisfaction of certain conditions.


                                          4.

<PAGE>

    3.6  NO PUBLIC MARKET.  Michigan understands that no public market now
exists for any of the securities issued by the Company and that it is uncertain
whether a public market will ever exist for the Shares or the Underlying Stock.

    3.7  ACCESS TO DATA.  Michigan has received and reviewed such information
that it deemed necessary to make an informed decision concerning its receipt of
the Shares and has had an opportunity to discuss the Company's business,
management and financial affairs with its management.

    3.8  RESTRICTIONS ON TRANSFER.  Michigan further agrees not to make any
disposition of all or any part of the Shares in any event unless and until:

         (a)  There is then in effect a registration statement under the
Securities Act covering such proposed disposition and such disposition is made
in accordance with said registration statement; or

         (b)  Michigan shall have (i) notified the Company of the proposed
disposition, (ii) furnished the Company with a detailed statement of the
circumstances surrounding the proposed disposition, and (iii) furnished the
Company with an opinion of counsel for Michigan to the effect that such
disposition will not require registration of such shares under the Act, and such
opinion of counsel for Michigan shall have been concurred in by the Company's
counsel and the Company shall have advised Michigan of such concurrence.

    3.9  LEGENDS.  Michigan understands and agrees that all certificates
evidencing the Shares shall bear the following legend:

    "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
    REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT
    BE OFFERED FOR SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN
    EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144
    OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY AND
    ITS COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED."


                                      SECTION 4

                                   INVESTOR RIGHTS

    4.1  RIGHT OF FIRST REFUSAL ON COMPANY ISSUANCES.   The Company hereby
grants to Michigan, for so long as it holds not less than 1,000,000 shares of
the Company's Series B Preferred Stock (or Common Stock issued or issuable upon
conversion of the Series B Preferred Stock) the right of first refusal to
purchase, pro rata, all (or any part) of New Securities (as


                                          5.

<PAGE>

defined in this Section 4.1) that the Company may, from time to time propose to
sell and issue.  In the case where the price per share at which the New
Securities are being offered is indeterminable or is equal to or less than One
Dollar ($1.00) (as adjusted for stock splits, reclassification or otherwise),
Michigan's pro rata share, for purposes of this right of first refusal with
respect to an offering at such a price, is the ratio, the numerator of which is
the number of shares of Common Stock then owned by Michigan as a result of the
conversion of any Series B Preferred Stock of the Company and issuable upon
conversion of the Series B Preferred Stock of the Company then owned by
Michigan, and the denominator of which is the total number of shares of Common
Stock then outstanding as a result of the conversion of any Series A and Series
B Preferred Stock of the Company or issuable upon conversion of the Series A and
Series B Preferred Stock of the Company then outstanding.  In the case where the
price per share at which the New Securities are being offered is greater than
One Dollar ($1.00) (as adjusted for stock splits, reclassifications or
otherwise), Michigan's pro rata share, for purposes of this right of first
refusal with respect to an offering at such a price, is the ratio, the numerator
of which is the number of shares of Common Stock then owned by Michigan as a
result of the conversion of any Series B Preferred Stock of the Company and
issuable upon conversion of the Series B Preferred Stock of the Company then
owned by Michigan, and the denominator of which is the total number of shares of
Common Stock outstanding immediately prior to the issuance of the New
Securities, assuming full conversion of all outstanding shares of Series A and
Series B Preferred Stock of the Company.  This right of first refusal shall be
subject to the following provisions:

         (a)  "New Securities" shall mean any capital stock of the Company,
whether now authorized or not, and rights, options, or warrants to purchase said
capital stock, and securities of any type whatsoever that are, or may become,
convertible into said capital stock; provided, however, that "New Securities"
does not include (i) securities issuable upon conversion of or with respect to
Series A Preferred Stock or Series B Preferred Stock; (ii) the Warrant Shares
(as defined in Section 5.2 hereof) issuable under Section 5 of this Agreement;
(iii) securities issued pursuant to an acquisition by the Company by merger,
purchase of substantially all of the assets, or other reorganization whereby the
Company owns more than fifty percent (50%) of the voting power of such entity;
(iv) shares of the Company's Common Stock (or related options) issued to
employees, directors or consultants of the Company pursuant to any employee
stock offering, plan, or arrangement approved by the Board of Directors; (v)
shares of the Company's Common Stock or Series A or Series B Preferred Stock
issued in connection with any stock split, stock dividend, or similar
recapitalization by the Company; (vi) securities issued pursuant to equipment or
debt financing or leases which are approved by the Company's Board of Directors;
(vii) securities issued pursuant to any corporate partnering, strategic
alliance, joint venture or licensing arrangement between the Company and a third
party; or (viii) securities issued by the Company other than for cash or cash
equivalents.  The Company agrees that it shall give Michigan notice of the
issuance of any of its securities under the circumstances described in the
foregoing clauses (vi), (vii) and (viii) not more than thirty (30) days after
the date of such issuance, which notice shall describe the securities issued and
the consideration received therefor.

         (b)  In the event that the Company proposes to undertake an issuance
of New Securities, it shall give Michigan, so long as it holds not less than
1,000,000 shares of Common


                                          6.

<PAGE>

Stock of the Company issued or issuable upon conversion of the Series B
Preferred Stock, written notice of its intention, describing the type of New
Securities, the price, and the general terms upon which the Company proposes to
issue the same.  Michigan, as well as each Investor (as defined under the Rights
Agreement) who together with its affiliates holds not less than 1,000,000 shares
of Common Stock of the Company issued or issuable upon conversion of the Series
A or Series B Preferred Stock, shall have twenty (20) days from the date of
mailing of any such notice to agree to purchase up to its full pro rata share of
such New Securities for the price and upon the general terms specified in the
notice by giving written notice to the Company and stating therein the quantity
of New Securities to be purchased.  Michigan, so long as it holds not less than
1,000,000 shares of Common Stock of the Company issued or issuable upon
conversion of the Series B Preferred Stock, and each Investor who together with
its affiliates holds not less than 1,000,000 shares of Common Stock of the
Company issued or issuable upon conversion of the Series A or Series B Preferred
Stock, shall have a right of over allotment such that if Michigan or any
Investor fails to exercise its right to purchase its full pro rata portion of
New Securities, the Company shall so notify Michigan and the other Investors and
Michigan and such Investors (and their affiliates) who have agreed to purchase
all or any part of their pro rata share of New Securities may purchase
Michigan's or the nonpurchasing Investors' portions on a pro rata basis, within
ten days from the date of such notice.

         (c)  In the event that Michigan and the Investors (and their
affiliates) fail to exercise in full the right of first refusal within said
twenty (20) day period (plus the ten day overallotment period, if applicable)
the Company shall have sixty (60) days thereafter to sell or enter into an
agreement providing for the closing of the sale of the New Securities respecting
which Michigan's and the Investors' (and their affiliates') rights were not
exercised within thirty (30) days of such agreement at a price and upon general
terms no more favorable to the purchasers thereon than specified in the
Company's notice.  In the event the Company has not sold the New Securities
within such sixty (60) day period, the Company shall not thereafter issue or
sell any New Securities, without first offering such securities to the Investors
(and its affiliates) in the manner provided above.

         (d)  The right of first refusal granted under this Agreement shall not
apply to and shall expire upon the first closing of the first firmly
underwritten public offering of Common Stock of the Company that is pursuant to
a registration statement filed with, and declared effective by, the United
States Securities and Exchange Commission under the Securities Act.

         (e)  This right of first refusal is not assignable by Michigan.

    4.2  INFORMATION RIGHTS.  The Company will furnish the following
information to Michigan, for so long as it holds not less than 1,000,000 shares
of Common Stock issued or issuable upon conversion of the Series B Preferred
Stock:

         (i)  As soon as practicable after the end of each fiscal year of the
Company, and in any event within one hundred and twenty (120) days thereafter, a
consolidated balance sheet of the Company and its subsidiaries, if any, as at
the end of such fiscal year, and consolidated


                                          7.

<PAGE>

statements of income and consolidated statements of cash flows of the Company
and its subsidiaries, if any, for such year, prepared in accordance with
generally accepted accounting principles consistently applied and setting forth
in each case in comparative form and figures for the previous fiscal year, all
in reasonable detail and certified by independent public accountants of national
standing selected by the Company.

         (ii) As soon as practicable after the end of each of the first three
quarterly accounting periods in each fiscal year, and in any event within forty-
five (45) days thereafter, a consolidated balance sheet of the Company and its
subsidiaries, if any, as at the end of such quarter, and consolidated statements
of income and consolidated statements of cash flows of the Company and its
subsidiaries, if any, for each quarter and for the current fiscal year of the
Company to date, prepared in accordance with generally accepted accounting
principles consistently applied, except that such financial statements will not
contain the notes normally required by generally accepted accounting principles.

    The Company agrees and acknowledges that information furnished to it under
this Section 4.2 may be subject to disclosure by law, including the Michigan
Freedom of Information Act ("FOIA").  Subject to such disclosure requirements,
Michigan agrees to make reasonable efforts not to disclose such information to
any third party.  Michigan shall be under no obligation to seek exemptions or
exclusions of such information from the requirements of FOIA.

    4.3  REGISTRATION RIGHTS.

    The Company hereby grants to Michigan the identical rights with respect to
the registration of the Shares, the Underlying Stock and the Warrant Shares (as
defined in Section 5.2 hereof) as are granted under Section 3.2 through 3.12 of
the Rights Agreement to each Holder (as defined under the Rights Agreement), as
though (i) Michigan were a "Holder," (ii) the Shares and the Warrant Shares,
collectively, were "Shares," and (iii) the Warrant Shares were included within
the definition of "Registrable Securities," under the Rights Agreement.
Michigan understands and agrees that its rights under this Section 4.3 shall be
on parity with, and not superior to, the rights granted to the parties to the
Rights Agreement under Sections 3.2 through 3.12 of the Rights Agreement, as
though Michigan were a party thereto.  In addition, Michigan agrees that it
shall be subject to any amendment or waiver of Sections 3.2 through 3.12 of the
Rights Agreement pursuant to the vote of a majority of the holders of the
outstanding Registrable Securities (as defined under the Rights Agreement) under
Section 6.8 of the Rights Agreement, provided such amendment or waiver applies
equally to both the holders of the majority and the holders of the minority of
such outstanding Registrable Securities.


                                          8.

<PAGE>

                                      SECTION 5

                             OBLIGATION TO ISSUE WARRANT

    5.1  CONDITIONS OF ISSUANCE.  In partial consideration of the Technology
Agreement and subject to the remaining provisions of this Section 5, the Company
shall be obligated, upon the First Commercial Sale of any Product (as such
capitalized terms are defined under Sections 2.2 and 2.11 of the Technology
Agreement) (the "Warrant Issue Date"), to issue to Michigan a warrant, in the
form attached hereto as Exhibit B (the "Warrant"), on the terms set forth below.
The Company's obligations under this Section 5 shall terminate immediately upon
any termination of the Technology Agreement.

    5.2  SHARES ISSUABLE UPON EXERCISE OF WARRANT.  Subject to the provisions
of Section 5.4 below, the Warrant shall be exercisable for a number of shares of
the Company Common Stock (the "Warrant Shares") equal to one and twenty-five
one-hundredths percent (1.25%) of the total number of issued and outstanding
shares of the Company Common Stock on the Issue Date (including, on an
as-converted basis, outstanding shares of Preferred Stock of the Company);
PROVIDED, HOWEVER, that for purposes of calculating this percentage, "issued and
outstanding shares of the Company Common Stock" shall NOT include shares of the
Company Common Stock, or securities convertible into the Company Common Stock:

              (i)   issued in connection with an acquisition by the Company of
another entity by merger, purchase of substantially all of its assets, or other
reorganization whereby the Company acquires, directly or indirectly, more than
50% of the voting power of such entity;

              (ii)  issued in connection with any corporate partnering,
strategic alliance, joint venture or licensing arrangement between the Company
and a third party not involving or relating to the Technology or a Product (as
such capitalized terms are defined under Sections 2.2. and 2.11 of the
Technology Agreement);

              (iii) issued by the Company other than for cash or cash
equivalents in transactions not involving or relating to the Technology or a
Product (as such capitalized terms are defined under Sections 2.2 and 2.11 of
the Technology Agreement); or

              (iv) issued to employees, directors or consultants which are
subject to a right to repurchase at cost (i.e. "unvested" shares).

    Notwithstanding the foregoing, if as of the Warrant Issue Date there shall
not have been an Initial Public Offering (as defined in 5.3 below), then the
Company may elect to make the Warrant exercisable for shares of the Company's
Preferred Stock convertible into the number of shares of the Company Common
Stock determined above, with rights and preferences substantially the same as
the rights and privileges of the most recent series of Preferred Stock issued by
the Company to outside investors  (such Preferred Stock shall also constitute
"Warrant Shares," notwithstanding the definition of such term set forth above).
The rights granted


                                          9.

<PAGE>

Michigan under Section 4.3 hereof shall apply to the Warrant Shares regardless
of whether they consist of Common Stock or Preferred Stock of the Company.

    5.3  WARRANT EXERCISE PRICE.  The initial per share exercise price for the
Warrant (the "Exercise Price") shall be equal to one hundred twenty-five percent
(125%) of the price at which shares of the Company Common Stock are first sold
to the public pursuant to a firm commitment underwritten public offering
registered under the Securities Act, other than a registration relating solely
to a transaction under Rule 145 of the Securities Act (or any successor thereto)
or to an employee benefit plan of the Company (the "Initial Public Offering");
or, if as of the Warrant Issue Date, there shall not have been an Initial Public
Offering, the Exercise Price shall be equal to one hundred twenty-five percent
(125%) of the per share price of the securities issued to outside investors in
the Company's most recent equity financing transaction prior to the Warrant
Issue Date in which it raised at least $2 million.

    5.4  ACQUISITION OF THE COMPANY PRIOR TO WARRANT ISSUE DATE.

         (a)   Notwithstanding anything to the contrary in this Section 5, in
the event that prior to the Warrant Issue Date there is any consolidation of the
Company with, or merger of the Company into, any other corporation or other
entity or person, or any other corporate reorganization in which the Company
shall not be the continuing or surviving entity of such consolidation, merger or
reorganization, or any transaction or series of transactions by the Company
(other than financing transactions in which equity securities are issued to
multiple purchasers solely for cash) in which in excess of fifty percent (50%)
of the Company's voting power is transferred, or any sale or conveyance of all
or substantially all of the assets of the Company (any of the foregoing events
being hereafter referred to as an "Acquisition") the Company may, at its sole
option, by giving written notice of such election to Michigan prior to the
effective date of the Acquisition (the "Acquisition Date"), elect to cancel its
obligation to issue the Warrant under this Section 5, in which event the
royalties payable by the Company under Paragraphs 5.3(i) and (ii) of the
Technology Agreement shall each be doubled, without any need to amend such
agreement; PROVIDED, HOWEVER, that in the event such doubled royalty rate is or
becomes thereafter unduly economically burdensome to the Company, due to, for
example but without limitation, the markets in which the Company intends to
market Products or the obligations of the Company to pay to any third party
royalties for additional rights or technology necessary for the
commercialization of the Products, then Michigan agrees to consider, in good
faith, an alternative consideration in lieu of such doubled royalty rate under
this Agreement, upon request of the Company.

         (b) If the Company does not elect to cancel the Warrant under Section
5.4(a) above, then following the Acquisition, the Company or its successor shall
remain obligated under this Section 5 to issue the Warrant on the Warrant Issue
Date.  When and if issued after such an Acquisition, the Warrant shall be
exercisable for the amount and type of securities or other consideration that
would have been issuable in the Acquisition to a holder of the number of shares
of the Company's capital stock for which the Warrant would have been exercisable
under Section 5.2 above on the Acquisition Date, as if the Acquisition Date were
the same as the Warrant Issue


                                         10.

<PAGE>

Date.  The Exercise Price of the Warrant if issued after such an Acquisition
shall be equal to one hundred twenty-five percent (125%) of the Acquisition
Price.


                                      SECTION 6

                                    MISCELLANEOUS

    6.1  GOVERNING LAW.  This Agreement shall be governed by and construed in
accordance with the laws of the State of California applicable to contracts
between California residents entered into and to be performed entirely within
the State of California.

    6.2  SUCCESSORS AND ASSIGNS.  Except as otherwise provided herein, the
provisions hereof shall inure to the benefit of, and be binding upon, the
successors, assigns, heirs, executors and administrators of the parties hereto.

    6.3  ENTIRE AGREEMENT; AMENDMENT.  This Agreement and the other documents
delivered pursuant hereto constitute the final, complete and exclusive
understanding and agreement between the parties with regard to the subjects
hereof and thereof. Any term of this Agreement may be amended and the observance
of any term of this Agreement may be waived, with the written consent of
Michigan and the Company.

    6.4  NOTICES.  All notices or other communications pursuant to this
Agreement shall be in writing and deemed given if delivered personally,
telecopied, sent by nationally-recognized, overnight courier or mailed by
registered or certified mail (return receipt requested) postage prepaid to the
parties at the following addresses (or at such other address for a party as
shall be specified by like notice) to the other party hereunder:

    To the Company:

         1450 Rollins Road
         Burlingame, CA  94010
         Attention:     J. Leighton Read, M.D.,
                        Chairman and Chief Executive Officer
         Telephone:     (415) 696-9116
         Fax:           (415) 347-6274


                                         11.

<PAGE>

    with a copy to:

         Cooley Godward Castro Huddleson & Tatum
         Five Palo Alto Square
         Palo Alto, CA 94306
         Attention:     Robert J. Brigham, Esq.
         Telephone:  (415) 843-5000
         Fax:  (415) 857-0663

    To Michigan:

         University of Michigan
         Treasurer's Office
         5024 Fleming Administration Building
         Ann Arbor, MI  48109-1340
         Telephone:     (313) 763-1299
         Fax:           (313) 747-1483

    with a copy to:

         University of Michigan
         Technology Management Office
         3003 S. State Street
         Wolverine Tower, Room 2071
         Ann Arbor, MI 48109-1280
         Attention:     Robert L. Robb, Director
         Telephone:     (313) 763-0614
         Fax:           (313) 936-1330

    Notwithstanding the foregoing, any payment of funds required hereunder may
be made by wire transfer in accordance with written instructions given by the
receiver to the sender.

    6.5  CALIFORNIA CORPORATE SECURITIES LAW.  THE SALE OF THE SECURITIES WHICH
ARE THE SUBJECT OF THIS AGREEMENT HAS NOT BEEN QUALIFIED WITH THE COMMISSIONER
OF CORPORATIONS OF THE STATE OF CALIFORNIA AND THE ISSUANCE OF SUCH SECURITIES
OR THE PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION THEREFOR PRIOR TO
SUCH QUALIFICATION IS UNLAWFUL UNLESS THE SALE OF SECURITIES IS EXEMPT FROM THE
QUALIFICATION BY SECTION 25100, 25102 OR 25105 OF THE CALIFORNIA CORPORATIONS
CODE.  THE RIGHTS OF ALL PARTIES TO THIS AGREEMENT ARE EXPRESSLY CONDITIONED
UPON SUCH QUALIFICATION BEING OBTAINED, UNLESS THE SALE IS SO EXEMPT.


                                         12.

<PAGE>

    6.6  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, and all of which shall
constitute one and the same instrument.

    The foregoing Stock Transfer Agreement is hereby executed as of the date
first above written.


AVIRON                                 THE REGENTS OF THE
                                       UNIVERSITY OF MICHIGAN


By:                                    By:
   ----------------------------           ---------------------------------
    J. Leighton Read, M.D.             Name:
                                            -------------------------------
    Chief Executive Officer            Title:
                                             ------------------------------


                                         13.

<PAGE>

                                      EXHIBIT A

                ARTICLES OF INCORPORATION AND CERTIFICATE OF AMENDMENT

<PAGE>

                                      EXHIBIT B

                                   FORM OF WARRANT

<PAGE>

EXHIBIT B TO STOCK TRANSFER AGREEMENT

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY NOT BE OFFERED FOR SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED
WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144
OR AN OPINION OF COUNSEL, REASONABLY SATISFACTORY TO THE COMPANY AND ITS
COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.


                           WARRANT TO PURCHASE SHARES
                                       OF
                                 ---------------

COMPANY:                 AVIRON, a California corporation (the "Company"), and
                         any corporation that shall succeed to the obligations
                         of the Company under this Warrant.

NUMBER OF SHARES:        
                         ----------
CLASS OF STOCK:          
                         ----------
INITIAL EXERCISE PRICE:  
                         ----------
DATE OF GRANT:           
                         ----------

     THIS CERTIFIES THAT, for value received, The Regents of the University of
Michigan ("Michigan") or any permitted transferee of its rights hereunder is
entitled to purchase the above number (as adjusted pursuant to Section 5 hereof)
of fully paid and nonassessable shares of the above Class of Stock of the
Company at the Initial Exercise Price above (as adjusted pursuant to Section 5
hereof), subject to the provisions and upon the terms and conditions set forth
herein.  The Expiration Date of this Warrant shall be five years from the Date
of Grant.

1.   DEFINITIONS.

     In addition to the terms defined above, the following capitalized terms
shall have the following meanings, unless the context otherwise requires:

     (a)  "Act" shall mean the Securities Act of 1933, as amended, or any
similar federal statute, and the rules and regulations thereunder, as shall be
in effect at the time.

     (b)  "Common Stock" shall mean shares of the authorized common stock of the
Company and any stock into which such common stock may hereafter be exchanged.

     (c)  "Warrantholder" shall mean any person who shall at the time be the
holder of this Warrant.


                                       1.

<PAGE>

     (d)  "Shares" shall mean the shares of the Class of Stock that the
Warrantholder is entitled to purchase upon exercise of this Warrant, as adjusted
pursuant to Section 5 hereof.

     (e)  "Warrant Price" shall mean the Initial Exercise Price at which this
Warrant may be exercised, as adjusted pursuant to Section 5 hereof.

2.   TERM.

     The purchase right represented by this Warrant is exercisable, in whole or
in part, at any time on or before the Expiration Date.

3.   METHOD OF EXERCISE; PAYMENT; ISSUANCE OF NEW WARRANT.

     Subject to Section 2 hereof, the purchase right represented by this Warrant
may be exercised by the Warrantholder, in whole or in part, by the surrender of
this Warrant (with the notice of exercise form attached hereto as Appendix A
duly executed) at the principal office of the Company and by the payment to the
Company, by check made payable to the Company drawn on a United States bank and
for United States funds of an amount equal to the then applicable Warrant Price
per share multiplied by the number of Shares then being purchased. In the event
of any exercise of the purchase right represented by this Section 3,
certificates for the Shares so purchased shall be delivered to the Warrantholder
within thirty (30) days of receipt of such payment and, unless this Warrant has
been fully exercised or expired, a new Warrant representing the portion of the
Shares, if any, with respect to which this Warrant shall not then have been
exercised shall also be issued to the Warrantholder within such thirty (30) day
period.

4.   EXERCISE PRICE.

     The Warrant Price at which this Warrant may be exercised shall be the
Initial Exercise Price, as adjusted from time to time pursuant to Section 5
hereof.

5.   ADJUSTMENT OF NUMBER AND KIND OF SHARES AND ADJUSTMENT OF WARRANT PRICE.

     5.1  CERTAIN DEFINITIONS.  As used in this Section 5 the following terms
shall have the following respective meanings:

          (a)  "Options" shall mean rights, options or warrants to subscribe
for, purchase or otherwise acquire either shares of Common Stock or Convertible
Securities;


                                       2.

<PAGE>

          (b)  "Convertible Securities" shall mean any evidences of
indebtedness, shares of stock or other securities directly or indirectly
convertible into or exchangeable for Common Stock.

     5.2  ADJUSTMENTS.  The number and kind of securities purchasable upon the
exercise of this Warrant and the Warrant Price shall be subject to adjustment
from time to time upon the occurrence of certain events, as follows:

          (a)  Reclassification, Reorganization, Consolidation or Merger.  In
the case of any reclassification of the Class of Stock that the Warrantholder is
entitled to purchase upon exercise of this Warrant, or any reorganization,
consolidation or merger of the Company with or into another corporation (other
than a merger or reorganization with respect to which the Company is the
surviving corporation and which does not result in any reclassification of such
Class of Stock), the Company, or such successor corporation, as the case may be,
shall execute a new warrant, providing that the Warrantholder shall have the
right to exercise such new warrant and upon such exercise to receive, in lieu of
each share of the Class of Stock theretofore issuable upon exercise of this
Warrant, the kind of securities receivable upon such reclassification,
reorganization, consolidation or merger by a holder of shares of the same Class
of Stock of the Company.  The Warrant Price and the number of shares of such new
securities to be received by the Warrantholder upon exercise of the Warrant
shall be adjusted so that the Warrantholder shall receive upon exercise of the
Warrant and payment of the same aggregate consideration the number of shares of
new securities which the Warrantholder would have owned immediately following
such reclassification, reorganization, consolidation or merger if the
Warrantholder had exercised the Warrant immediately prior to such
reclassifications, reorganization, consolidation or merger.  The provisions of
this subsection (a) shall similarly apply to successive reclassification,
reorganizations, consolidations or mergers.

          (b)  Split, Subdivision or Combination of Shares.  If the Company at
any time while this Warrant remains outstanding and unexpired shall split,
subdivide or combine the Class of Stock for which this Warrant is then
exercisable, the Warrant Price shall be proportionately decreased in the case of
a split or subdivision or proportionately increased in the case of a
combination.  Any adjustment under this subsection (b) shall become effective
when the split, subdivision or combination becomes effective.

          (c)  Stock  Dividends.  If the Company at any time while this Warrant
remains outstanding and unexpired shall pay a dividend with respect to the Class
of Stock for which this Warrant is then exercisable, payable in shares of that
Class of Stock, Options or Convertible Securities, the Warrant Price shall be
adjusted, from and after the date of determination of the stockholders entitled
to receive such dividend or distributions, to that price determined by
multiplying the Warrant Price in effect immediately prior to such date of
determination by a fraction (i) the numerator of which shall be the total number
of shares of that Class of Stock outstanding immediately prior to such dividend
or distribution, and (ii) the denominator of which shall be the total number of
shares of the same Class of Stock outstanding immediately after such dividend or
distribution (including shares of that Class of Stock issuable upon exercise,
conversion or exchange of any Options or Convertible Securities issued as such
dividend or


                                       3.

<PAGE>

distribution).  If the Options or Convertible Securities issued as such dividend
or distribution by their terms provide, with the passage of time or otherwise,
for any decrease in the consideration payable to the Company, or any increase in
the number of shares issuable upon exercise, conversion or exchange thereof (by
change of rate or otherwise), the Warrant Price shall, upon any such decrease or
increase becoming effective, be reduced to reflect such decrease or increase as
if such decrease or increase became effective immediately prior to the issuance
of the Options or Convertible Securities as the dividend or distribution.  Any
adjustment under this subsection (c) shall become effective on the record date
set for such dividend or distribution.

          (d)  Adjustment Of Number of Shares.  Upon each adjustment in the
Warrant Price pursuant to Section 5(b) or 5(c) above, the number of Shares
issuable upon exercise of this Warrant shall be adjusted to the product obtained
by multiplying the number of Shares issuable immediately prior to such
adjustment in the Warrant Price by a fraction (i) the numerator of which shall
be the Warrant Price immediately prior to such adjustment, and (ii) the
denominator of which shall be the Warrant Price immediately after such
adjustment.

6.   NOTICE OF ADJUSTMENTS.

     So long as this Warrant remains outstanding and unexpired, whenever the
Warrant Price shall be adjusted pursuant to Section 5 hereof, the Company shall
issue a certificate signed by its chief financial officer setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated and the Warrant
Price after giving effect to such adjustment, and shall cause a copy of such
certificate to be mailed (by first class mail, postage prepaid) to the
Warrantholder.

7.   RIGHT TO CONVERT WARRANT INTO STOCK.

     7.1  RIGHT TO CONVERT.  In addition to the rights granted under Section 3
of this Warrant, the Warrantholder shall have the right to require the Company
to convert this Warrant (the "Conversion Right") into shares of the Class of
Stock for which the Warrant is then exercisable, as provided in this Section 7.
Upon exercise of the Conversion Right, the Company shall deliver to the
Warrantholder (without payment by the Warrantholder of any Warrant Price) that
number of shares of stock equal to the quotient obtained by dividing (x) the
value of this Warrant at the time the Conversion Right is exercised (determined
by subtracting the aggregate Warrant Price immediately prior to the exercise of
the Conversion Right from the aggregate fair market value of the Shares issuable
upon exercise of this Warrant immediately prior to the exercise of the
Conversion Right, as determined pursuant to Section 7.3 below) by (y) the fair
market value (as determined pursuant to Section 7.3 below) of one share of that
Class of Stock immediately prior to the exercise of the Conversion Right.

     7.2  METHOD OF EXERCISE.  So long as the Warrant remains outstanding and
unexpired, the Conversion Right may be exercised at any time by the
Warrantholder by the surrender of this Warrant at the principal office of the
Company together with a written statement specifying that the Warrantholder
thereby intends to exercise the Conversion Right. Certificates of the shares of
stock issuable upon exercise of the Conversion Right shall be delivered to the


                                       4.

<PAGE>

Warrantholder within thirty (30) days following the Company's receipt of this
Warrant together with the aforesaid written statement.

     7.3  VALUATION OF STOCK.  For purposes of this Section 7, the fair market
value of one share of the Class of Stock issuable upon exercise of this Warrant
shall mean:

          (a)  The product of (i) the average of the closing price or, if no
closing price is reported, the closing bid and asked prices of the Common Stock,
quoted in the Over-The-Counter Market Summary or the closing price quoted on any
exchange on which the Common Stock is listed, whichever is applicable, as
published in the Western Edition of The Wall Street Journal for the ten (10)
trading days prior to the date of determination of fair market value, and (ii)
the number of shares of Common Stock into which each share of the Class of Stock
is then convertible, if applicable;

          (b)  If the Common Stock is not traded Over-The-Counter or on an
exchange, the fair market value of the Class of Stock per share shall be as
determined in good faith by the Company's Board of Directors; provided, however,
that if the Warrantholder disputes in writing the fair market value determined
by the Board of Directors within thirty (30) days of being informed of such fair
market value, the fair market value shall be determined by an independent
appraiser, appointed in good faith by the Company's Board of Directors.

8.   COMPLIANCE WITH ACT; TRANSFERABILITY OF WARRANT; DISPOSITION OF SHARES.

     8.1  LEGENDS.  This Warrant and the Shares issued upon exercise thereof
shall be imprinted with a legend in substantially the following form:

     "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED FOR
     SALE, SOLD, PLEDGED  OR  OTHERWISE  TRANSFERRED  WITHOUT  AN EFFECTIVE
     REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN OPINION
     OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY AND ITS COUNSEL THAT SUCH
     REGISTRATION IS NOT REQUIRED."

     8.2  TRANSFERABILITY OF WARRANT AND SHARES.  This Warrant and the Shares
issued upon exercise thereof shall not be sold, transferred or assigned in whole
or in part without compliance with applicable federal and state securities laws
by the transferor and the transferee (including, without limitation, the
delivery of investment representation letters and legal opinions reasonably
satisfactory to the Company, if reasonably requested by the Company). Subject to
the provisions of this Section 8.2, title to this Warrant may be transferred in
the same manner as a negotiable instrument transferable by endorsement and
delivery.

9.   RIGHTS OF THE HOLDER.


                                       5.

<PAGE>

     The Warrantholder shall not, by virtue hereof, be entitled to any rights of
a shareholder in the Company, either at law or equity, and the rights of the
Warrantholder are limited to those expressed in this Warrant.  Nothing contained
in this Warrant shall be construed as conferring upon the Warrantholder hereof
the right to vote or to consent or to receive notice as a shareholder of the
Company on any matters or with respect to any rights whatsoever as a shareholder
of the Company.  No dividends or interest shall be payable or accrued in respect
of this Warrant or the interest represented hereby or the Shares purchasable
hereunder until, and only to the extent that, this Warrant shall have been
exercised in accordance with its terms.

10.  MISCELLANEOUS.

     No fractional shares shall be issued in connection with any exercise
hereunder, but in lieu of such fractional shares the Company shall make a cash
payment therefor upon the basis of the Warrant Price then in effect. The terms
and provisions of this Warrant shall inure to the benefit of, and be binding
upon, the Company and the Warrantholder and their respective successors and
assigns. This Warrant shall be governed by and construed under the laws of the
State of California as applied to contracts entered into between residents of
the State of California to be wholly performed in the State of California. The
titles of the sections and subsections of this Warrant are for convenience only
and are not to be considered in construing this Warrant. All pronouns used in
the Warrant shall be deemed to include masculine, feminine and neuter forms.

                                   AVIRON, A CALIFORNIA CORPORATION


                                   By:
                                      ------------------------------------------
                                   Name:
                                        ----------------------------------------
                                   Title:
                                         ---------------------------------------


                                       6.

<PAGE>

                                   APPENDIX A

                               NOTICE OF EXERCISE


TO:  AVIRON


          1.   The undersigned hereby elects to purchase shares of the stock of
Aviron, a California corporation, pursuant to terms of the attached Warrant, and
tenders herewith payment of the purchase price of such shares in full, together
with all applicable transfer taxes, if any.

          2.   Please issue a certificate or certificates representing said
shares of the stock in the name of the undersigned or in such other name as is
specified below.

          3.   The undersigned represents it is acquiring the shares of stock
solely for its own account for investment and not as a nominee for any other
party and not with a view toward the resale or distribution thereof within the
meaning of the Securities Act of 1933, as amended.


                    ----------------------------------------
                                     (Name)


                    ----------------------------------------
                                    (Address)


                    ----------------------------------------
                        (Taxpayer Identification Number)



- -----------------------------------
     (print name of Warrantholder)

By:
   --------------------------------
Title:
      -----------------------------
Date:
     ------------------------------


                                       7.

<PAGE>

                                      EXHIBIT C

                   AMENDED AND RESTATED INVESTORS RIGHTS AGREEMENT

<PAGE>

                                      EXHIBIT D

                               CAPITALIZATION SCHEDULE


Pursuant to the 1992 Stock Option Plan (the "Option Plan"), the Company has
reserved 3,860,000 shares of Common Stock for issuance upon exercise of options
granted under the Option Plan.  As of September 3, 1993, options to purchase
1,912,034 shares (net of cancellations) have been granted to employees and
consultants of which 69,270 shares have been exercised.

On February 9, 1993, the Company entered into a Technology Transfer Agreement
with The Mount Sinai School of Medicine ("Mount Sinai") pursuant to which the
Company acquired certain technologies.  In exchange, Aviron issued 175,000
shares of Common Stock and Warrants to purchase, in the aggregate, 225,000
shares of Series A Preferred Stock (the "Series A Warrants").  The Series A
Warrants become exercisable at various times upon the occurrence of certain
milestones.

On June 1, 1993, the Company entered into agreements with Institutional Venture
Partners ("IVP") and Institutional Venture Management ("IVM") to provide a
bridge loan to the Company.  In consideration for the loan, IVP and IVM received
warrants to purchase a total of 400,000 shares of Series B Preferred Stock (the
"Series B Warrants").  The Series B Warrants expire at the earlier of (i) the
closing of an initial public offering of Common Stock pursuant to a registration
statement under the Securities Act of 1933, as amended or (ii) June 1, 1995.

On March 30, 1994, the Company issued to Lease Management Services, Inc. a
warrant to purchase 116,667 shares of Series B Preferred Stock in connection
with an equipment lease.


<PAGE>


                                                                    EXHIBIT 10.5

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT HAS BEEN DELETED AS
MARKED BY BRACKETS, AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.

                          DEVELOPMENT AND LICENSE AGREEMENT


    THIS DEVELOPMENT AND LICENSE AGREEMENT (the "AGREEMENT") is made as of the
3rd day of May, 1995 by and between AVIRON, a California corporation with its
principal place of business at 1450 Rollins Road, Burlingame, California, 94010,
U.S.A. ("AVIRON"), and SANG-A PHARM. Co., LTD., a Korean corporation with its
principal place of business at 640-9 Dueng Chon Dong, Kangseo-Ku, Seoul, South
Korea ("SANG-A").


                                       RECITALS

    WHEREAS, Aviron is a biopharmaceutical company engaged in the business of
developing vaccines for the prevention of various diseases in humans; and

    WHEREAS, Sang-A is a Korean company interested in establishing vaccine
development and manufacturing capabilities; and

    WHEREAS, the parties desire to collaborate in the clinical development,
manufacture, distribution, marketing and sale of certain vaccine and other human
therapeutic products, on a product-by-product basis;

    NOW, THEREFORE, in consideration of the promises and covenants set forth
below, the parties hereby agree as follows:


                                      AGREEMENT

                                      ARTICLE I
                                     DEFINITIONS


    The capitalized terms used herein but not separately defined shall have the
meanings set forth in Exhibit A hereto.


                                      ARTICLE 2
                                 DEVELOPMENT PROGRAM


    2.1  COMMENCEMENT OF DEVELOPMENT PROGRAM. Following [
    ] for a particular Partner Product, such Product will be deemed available
for development in South and North Korea by Sang-A and Sang-A shall commence a
program of clinical development for such Partner Product, as further set forth
herein (the "DEVELOPMENT PROGRAM").


                                          1.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    2.2  DEVELOPMENT OBLIGATIONS OF SANG-A.

         2.2.1  SANG-A COMMITMENT.  Sang-A hereby agrees to conduct at its own
expense all clinical development work necessary to obtain all Government
Approvals for the commercialization of each Partner Product in South and North 
Korea.

         2.2.2  DEVELOPMENT EFFORT. [

                                                   ]     Sang-A shall work
diligently, consistent with accepted business practices and legal requirements, 
to develop each Partner Product, devoting the same degree of attention and 
diligence to such development efforts as similar companies devote to development
activities for products of comparable market potential. Sang-A agrees to provide
scientific, technical, clinical and regulatory personnel, equipment, time and 
resources to the development of each Partner Product sufficient to meet its 
obligations hereunder.

         2.2.3  DEVELOPMENT REPORTS; NOTICES.  Sang-A will deliver to Aviron,
in English, a summary of any annual development plan prepared by or on behalf of
Sang-A for any Partner Product in a Development Program, and any other reports
or information reasonably requested by Aviron to enable it to comply with any
obligations to its licensors, as described in Section 3.3. Aviron will provide
Sang-A with an annual development plan and quarterly progress reports, in
English, upon the request of Sang-A.

         2.2.4  VISIT OF FACILITIES.  Representatives of either party may, upon
reasonable request and prior notice and at mutually agreed upon times and
intervals, (i) visit such party's facilities where the development of Partner
Products is being conducted, and (ii) consult informally with personnel of such
party conducting the Development Program during such visits, by telephone,
facsimile transmission or other manner as the parties shall agree.  Aviron may
also visit any of Sang-A's sublicensees' facilities in which such development
activities are being conducted.

    2.3  DEVELOPMENT OBLIGATIONS OF AVIRON.

         2.3.1  ACCESS TO AVIRON DATA.  Subject to the terms of this Agreement,
Sang-A shall be entitled access to Aviron Data for each Partner Product, as such
Data become available, for use in the Development Program.  Sang-A shall be
permitted to use and reference all Aviron Data in any regulatory filings
necessary for Government Approval in South and North Korea.  Notwithstanding the
foregoing, Sang-A agrees that it shall treat all Aviron Data as Confidential
Information, subject to the terms of Article 10 hereof.

         2.3.2  ACCESS COSTS; POTENTIAL CORPORATE PARTNERS.  Provided Aviron
and/or its Affiliates [
       ] Sang-A's access to the Aviron Data shall be [

                       ] Sang-A expressly acknowledges and agrees, however, that
Aviron may enter into an arrangement with one or more corporate partners for the
development


                                          2.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

of certain or all Partner Products in countries outside South and North Korea, [
                                                          ] In the event Aviron
enters into such an agreement, and Aviron is unable, [
                                                                        ]Aviron
will pay an amount not to exceed [                        ] for such right on
behalf of Sang-A, and Sang-A shall be responsible for the balance of any amount
required from such partner for access to Aviron Data.

         2.3.3  SUPPLY OF CLINICAL MATERIALS.  Aviron shall use [            ]
    to supply, or cause to be supplied, such amounts of Clinical Materials
    necessary to obtain Government Approval for Partner Products and necessary
    for Sang-A's activities pursuant to the Development Program.  Sang-A agrees
    that it shall use such Clinical Materials only for purposes of pursuing IND
    allowance of the relevant Partner Product and conducting the Development
    Program, and that it shall not transfer any Clinical Materials to a third
    party without the prior written approval of Aviron.  As the need for a
    continuous supply of Clinical Materials arises the parties shall negotiate
    agreements, on a Product-by-Product basis, containing the terms upon which
    such Clinical Materials will be supplied (the "Clinical Supply
    Agreements").  With respect to the Cold Adapted Influenza Product, [





                                                               ]

         2.3.4  TECHNICAL ASSISTANCE.  Aviron shall provide technical
assistance to Sang-A, as provided in Article 6 hereof.

         2.3.5  AVIRON CLINICAL DEVELOPMENT. Notwithstanding the above, nothing
in this Agreement shall be construed to impose an obligation on Aviron to
conduct clinical or pre-clinical development for any given Partner Product.

    2.4  COORDINATION OF THE DEVELOPMENT PROGRAM, To facilitate and coordinate
the relationship of Aviron and Sang-A with regard to the Development Program for
each Partner Product, Sang-A and Aviron shall establish a plan covering the
mechanisms for the exchange of technical, business and regulatory information
under this Agreement, including the appointment by each party of a "Project
Coordinator." [

                                                                      ]


                                          3.

<PAGE>

    2.5  REGULATORY MATTERS.

         2.5.1  COMPLIANCE WITH REGULATIONS.  Sang-A shall conduct its efforts
hereunder in compliance with all applicable regulatory requirements, including
without limitation, any equivalents in South and North Korea to the U.S. FDA
Good Clinical Practice, Good Laboratory Practice and Good Manufacturing Practice
regulations.

         2.5.2  REGULATORY FILINGS.  Sang-A shall, at its own expense, prepare,
file and shall be the owner and party of record sponsoring all filings with the
regulatory authorities with respect to the Partner Products in South and North
Korea (the "REGULATORY FILINGS"), and Sang-A shall be responsible for causing
such applications to progress through the approval process.  Aviron shall have
rights of consultation with Sang-A personnel responsible for Regulatory Filings
with respect to the preparation and submission of such Regulatory Filings, and
Aviron shall cooperate with Sang-A in such manner as Sang-A may reasonably
request to assist in obtaining regulatory approval for such Partner Products or
Improvements.  Sang-A shall promptly deliver to Aviron summaries, in English, of
all such Regulatory Filings and correspondence, at Sang-A's expense.  Sang-A
shall deliver English language translations of all Regulatory Filings and
correspondence at Aviron's request.

         2.5.3  MAINTENANCE OF RECORDS.  Sang-A shall maintain records with
respect to activities conducted under the Development Program in sufficient
detail and in good scientific manner appropriate for Government Approval
purposes in South and North Korea and as will reflect all studies conducted,
results achieved and data obtained by Sang-A in the course of the Development
Program.

         2.5.4  ADVERSE EVENT REPORTING.  Each party agrees to report to the
other, immediately upon receipt of the information, any serious adverse event
which is reported to occur as a result of use of a Partner Product.  Such events
must be reported in as much detail as possible, whether or not there is proof of
a causal connection between the events and use of a Partner Product.  A serious
adverse event includes any experience relating to a Partner Product which is
reasonably regarded to be medically significant.  Each party also agrees to
provide to the other copies of all reports that are made to governmental health
authorities concerning material safety, efficacy or quality matters with respect
to any Partner Product.


                                      ARTICLE 3
                                   GRANT OF RIGHTS

    3.1  LICENSE.  Subject to the terms of this Agreement, Aviron hereby grants
to Sang-A, and Sang-A hereby accepts, an exclusive (even as to Aviron) right and
license and/or sublicense, as the case may be (i) to practice and use the Aviron
Technology in South and North Korea for the purpose of conducting clinical
development of, manufacturing and marketing Partner Products for use in the
Licensed Field, and (ii) to make, use, sell, offer for sale and distribute such
Partner Products in South and North Korea.


                                          4.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    3.2  SANG-A RIGHT TO SUBLICENSE.  Except for the right to manufacture
Partner Products, Sang-A shall have the right, in South and North Korea, to
sublicense the rights granted pursuant to Section 3.1 (but with no further right
to sublicense) to one or more third parties: PROVIDED, HOWEVER, [


                               ]

    3.3  LICENSE GRANT LIMITATIONS.  Sang-A acknowledges and understands that
certain aspects of the Aviron Technology as well as certain of the Clinical
Materials related to one or more of the Partner Products are or may be licensed
or assigned to Aviron pursuant to agreements with one or more third parties,
which such agreements existing as of the Effective Date are set forth on
Schedule 2 (the "Prior License Agreements").  Sang-A further acknowledges that
its rights granted hereunder are subject to the terms and conditions of such
Prior License Agreements including, without limitation, those terms and
conditions contained in the Cold Adapted Influenza Agreement as further
discussed in Section 3.4 below.  Sang-A further understands and agrees that in
no event shall the rights contained in this Agreement with respect to the Aviron
Technology be construed as conferring upon Sang-A any greater rights than are
conferred upon Aviron by such third party licensors under their respective
agreements with Aviron.  Sang-A further understands and agrees that in no way
shall ARCH Development Corporation, as Aviron's licensor, be responsible for
Aviron's performance under this Agreement.

    3.4  COLD ADAPTED INFLUENZA PRODUCT.

         3.4.1  Sang-A understands and acknowledges that, with respect to the
Cold Adapted Influenza Product, the license granted under Section 3.1 is a
sublicense of rights received by Aviron from the University of Michigan and the
National Institutes of Health ("NIH"), and is subject to the terms and
conditions of the Cold Adapted Influenza Agreement attached hereto as Exhibit B
and the Cooperative Research and Development Agreement referred to in Schedule
2. For convenience only, attached hereto as Exhibit C hereto is a list of the
major terms and conditions contained in the Cold Adapted Influenza Agreement
that affect Sang-A's rights and obligations hereunder as a sublicensee of
Aviron's rights to the Cold Adapted Influenza Product, including in particular,
restrictions regarding the handling and use of the Master Seeds.  Sang-A
explicitly acknowledges and understands that these terms and conditions, as more
fully reflected in the Cold Adapted Influenza Agreement itself, are incorporated
into this Agreement and have the same force and effect as if such terms were
included in the main text of this Agreement.

         3.4.2  Any material breach by Sang-A of the applicable terms of the
Cold Adapted Influenza Agreement shall be deemed a breach hereunder, and shall
subject Sang-A to possible termination of this Agreement with respect to the
Cold Adapted Influenza Product.


                                          5.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

         3.4.3  In the event the Cold Adapted Influenza Agreement is terminated
for any reason, [

                                                         ]



                                      ARTICLE 4
                        TECHNOLOGY ACCESS PAYMENTS; ROYALTIES

    4.1  TECHNOLOGY ACCESS PAYMENTS.  In consideration for access to the Aviron
Technology hereunder, Sang-A agrees that within forty-five (45) days after the
occurrence of the following milestone events for each Partner Product, Sang-A
shall pay to Aviron the nonrefundable milestone payments listed below in U.S.
dollars:

         4.1.1 [
                                          ]and

         4.1.2 [
                                          ]

    4.2  ROYALTIES.

         4.2.1  Except as provided in Section 4.2.2 below Sang-A shall pay to
Aviron, on a Product-by-Product basis, a royalty equal to [             ] of 
Net Sales for each Partner Product sold by Sang-A, its Affiliates or permitted
sublicensees.

         4.2.2  With respect to the Cold Adapted Influenza Product, Sang-A
shall pay to Aviron a royalty equal to [         ] of Net Sales for each such
Partner Product sold by Sang-A, its Affiliates or permitted sublicensees.

         4.2.3 Sang-A shall pay royalties under Sections 4.2.l and 4.2.2 for
each Partner Product for a term of [                             ] such Partner
Product in South or North Korea.


                                      ARTICLE 5
                         PAYMENT PROCEDURES; RECORDS; AUDITS

    5.1  PAYMENT PERIOD; REPORTS.  Sang-A shall pay to Aviron royalties as set
forth in Article 4 as follows: (i) within sixty (60) days after the end of each
calendar quarter if (a) Aviron has completed an initial public offering under
the Securities Act of 1933, (b) Aviron is a reporting company under the
Securities and Exchange Act of 1934, or (c) if Aviron has been acquired or
merged with a third party; or (ii) within one hundred and twenty (120) days
after each calendar year if none of the facts set forth in (a), (b) or (c) of
clause (i) apply.  Each respective payment period will be referred to in this
Agreement as a "PAYMENT PERIOD".  Such


                                          6.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

payment shall be accompanied by a report identifying Net Sales of each Partner
Product, and the computation of the royalties payable to Aviron, and any other
additional information regarding the marketing and sales of Partner Products as
is necessary to allow Aviron to comply with its obligations under the Prior
License Agreements.

    5.2  CURRENCY.  Payments shall be in United States Dollars, remitted to
Aviron at its address specified herein.  Any conversion from Korean currency
shall be made at the exchange rate utilized by the Exchange Bank of Korea
prevailing at the close of the last business day of that Payment Period.

    5.3  RECORDS.  During the term of this Agreement, Sang-A shall keep full
and accurate books and records setting forth, for each Partner Product on which
royalties are due, gross sales, all deductions allowed in arriving at Net Sales
and any other information sufficient in detail to allow the calculation of
royalties to be paid by Sang-A.  During the term of this Agreement and for a
period of three (3) years thereafter, Sang-A shall permit Aviron, at Aviron's
expense, by independent certified public accountants employed by Aviron and
reasonably acceptable to Sang-A, to examine relevant books and records at any
reasonable time, within five (5) years of the payment of such royalties.  If it
is determined that there was an underpayment of royalties due Aviron of five
percent (5%) or more, without prejudice to any other rights Aviron may have,
Sang-A shall promptly pay to Aviron the balance of the royalties due.  Sang-A
shall also reimburse Aviron for the cost of such verification examination.
Where required, Sang-A shall also permit Aviron's licensors to examine its books
and records, at such licensors' expense, on terms consistent with Aviron's
rights to do the same.

    5.4  WITHHOLDINGS.  Payments to Aviron under Section 4.2 shall be made
without deduction other than such amount (if any) as Sang-A is required by law
to deduct or withhold in South or North Korea.  Sang-A shall obtain a receipt
from the relevant taxing authorities for all withholding taxes paid and forward
such receipts to Aviron to enable Aviron to claim any and all tax credits for
which it may be eligible.  Sang-A shall reasonably assist Aviron in claiming
exemption from such deductions or withholdings under any double taxation or
similar agreement or treaty from time to time in force.  All payments made to
Aviron under Section 4.1 shall be made [
                                              ]


                                      ARTICLE 6
                  DEVELOPMENT AND MANUFACTURING TECHNICAL ASSISTANCE

    Aviron agrees to provide Sang-A with technical assistance in the
establishment of Sang-A's vaccine clinical development and manufacturing
capabilities in South and North Korea so as to enable it to perform its
obligations under this Agreement.  Upon the reasonable request of Sang-A, Aviron
will do one or more of the following, as it deems appropriate under the
circumstances:


                                          7.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    (a)  Hire outside consultants, such as GMP consultants, contract research
organizations or clinical trial consultants, to work on Sang-A's behalf in South
and North Korea and/or in the U.S., all at Sang-A's expense;

    (b) [






                ]

    (c) [






                                                                            ]


                                      ARTICLE 7
                         PROMOTION AND MARKETING OBLIGATIONS

    7.1  MARKETING EFFORTS.  Sang-A agrees to use [                         ]
to promote the sale, marketing and distribution of the Partner Products in South
and North Korea [
                                                  ]

    7.2  COMMERCIAL MANUFACTURING.  Sang-A agrees that, at a minimum, it will
manufacture sufficient amounts of each Partner Product to satisfy demand for
such Partner Product in South and North Korea.  Sang-A shall manufacture all
such Product in accordance with all applicable laws in South and North Korea.

    7.3  SALES AND ADVERTISING ACTIVITIES.  Sang-A will be responsible for
packaging the Partner Products for sale under this Agreement, including, without
limitation, designing and producing all packaging materials and product inserts,
all in forms to be approved in writing by Aviron prior to first use by Sang-A,
such approval not to be unreasonably withheld and to be provided within [
     ] after submission of materials to Aviron.

    7.4  MARKETING PLANS.  Sang-A will provide Aviron with English summaries of
any marketing and/or strategic plans it develops for its internal use with
respect to any Partner Product.


                                          8.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    7.5  SALES REPORTS.  Throughout the Royalty Term and the Aviron Licensor
Payment Term for each Partner Product, Sang-A shall submit to Aviron quarterly
sales reports detailing Sang-A's sales of the Partner Product in the preceding
quarter, which reports shall be submitted to Aviron within sixty (60) days after
the end of each quarter. In addition, during the Royalty Term, Sang-A shall
furnish Aviron with copies of any market research reports relating to Partner
Product sales and Partner Product competition which Sang-A commissions or
otherwise obtains, which reports shall be submitted to Aviron promptly after
receipt thereof by Sang-A.

    7.6  EXPENSES.  All expenses incurred by Sang-A in connection with its
obligations hereunder will be borne solely by Sang-A.  Sang-A will be
responsible for appointing its own employees, agents and representatives, who
will be compensated by Sang-A.

    7.7  TRADEMARKS.  Sang-A agrees to consult with Aviron on the use of
trademarks for Partner Products and, where possible, to use trademarks now owned
by Aviron or acquired by Aviron during the term of this Agreement. Sang-A may
propose an alternate trademark for use in South and North Korea, which, if
approved by Aviron, shall be jointly owned by the parties.


                                      ARTICLE 8

                         [                                 ]

    During the term of this Agreement and upon Sang-A's written request, Aviron
will conduct, in collaboration with Sang-A, further research and development
with respect to Aviron's [                     ] on terms and conditions to be
agreed upon by the parties, for Sang-A's use in South and North Korea.


                                      ARTICLE 9
                               MANUFACTURING AGREEMENTS


    9.1  RIGHT OF FIRST REFUSAL.  Provided Sang-A satisfies the prerequisites
set forth in Section 9.2 below and subject to Sang-A's obligation in Section 9.3
below, Aviron grants a right of first refusal to supply up to [            ] of
Aviron's (and its Affiliates' and sublicensees') requirements for each Partner
Product, except the Epstein Barr Virus Vaccine, in each of the countries listed
in Schedule 3 hereto (the "MANUFACTURING TERRITORY").  Aviron shall promptly
notify Sang-A upon the allowance of the first IND for each Partner Product in
the Manufacturing Territory.  Sang-A shall have until the earlier of (a) [
                                                                           ] or
(b) [                                                                      ] to
deliver written notice to Aviron that it intends to exercise its right of first
refusal to commercially manufacture such Product.  At that time, Sang-A shall
specify which countries of the Manufacturing Territory, and the market
percentages of each such country (up to the maximum of [       ] it intends to
supply, and at what price.  The parties shall then proceed to negotiate, in-good
faith, a commercial supply agreement containing the terms upon which such


                                        9.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

Partner Product will be supplied by Sang-A to Aviron or Aviron's Affiliates or
sublicensees; PROVIDED, HOWEVER, that if Sang-A cannot manufacture the product
at a price and within a timeline that is competitive with other commercial
suppliers, Aviron shall be free to refuse to enter into a supply arrangement
with Sang-A.  The "competitive" price and timeline referred to in the foregoing
sentence shall be determined as follows: [






                                        ]

    9.2  PREREQUISITES.   Aviron may refuse to allow Sang-A to exercise its
right of first refusal with respect to the manufacture of any given Partner
Product in the event Sang-A cannot prove that it has satisfied, or will satisfy
within a timeframe acceptable to Aviron, the following prerequisites:

         9.2.1 [
                      ]

         9.2.2 [
                              ]

         9.2.3 [
                                              ] and

         9.2.4 [
         ]

    9.3  AVIRON CORPORATE PARTNERS. Sang-A acknowledges and understands that
Aviron intends to enter into transactions with one or more corporate partners in
which such corporate partners will acquire marketing rights to some or all of
the Partner Products in some or all of the countries in the Manufacturing
Territory.  In the event Sang-A has exercised its right of first refusal
pursuant to Section 9.1 above with respect to certain Partner Products in the
Manufacturing Territory, and any of Aviron's corporate partners so desires,
Sang-A agrees that, upon Aviron's request, [


                                         10.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                      ARTICLE 10
                                   CONFIDENTIALITY

    10.1 CONFIDENTIALITY.  During the term of this Agreement, and for [       ]
thereafter, each party hereto will maintain in confidence all Confidential
Information disclosed by the other party hereto, including without limitation
Confidential Information disclosed to Sang-A pursuant to Sang-A's information
rights under Article 15 of this Agreement.  Neither party will use, disclose,
transfer or grant use of such Confidential Information except as expressly
authorized by this Agreement.  To the extent that disclosure is authorized by
this Agreement, the disclosing party will obtain prior written agreement from
its employees, agents, consultants or clinical investigators to whom disclosure
is to be made to hold in confidence and not make use of such information for any
purpose other than those permitted by this Agreement.  Each party will use at
least the same standard of care as it uses to protect its own trade secrets,
proprietary information or materials to ensure that such employees, agents,
consultants and clinical investigators do not disclose or make any unauthorized
use of such Confidential Information.  Each party will promptly notify the other
upon discovery of any unauthorized use or disclosure of the Confidential
Information.

    10.2  EXCEPTIONS.  Confidential Information shall not include any
information which:

         10.2.1  was already known to the receiving party, other than under an
obligation of confidentiality, at the time of disclosure by the other party as
evidenced by written records;

         10.2.2  was generally available to the public or otherwise part of the
public domain at the time of its disclosure to the other party;

         10.2.3  became generally available to the public or otherwise part of
the public domain after its disclosure and other than through any act or
omission of the receiving party in breach of this Agreement;

         10.2.4  was disclosed to the receiving party, other than under an
obligation of confidentiality, by a Third Party who had no obligation to the
other party not to disclose such information to others as evidenced by written
records;

         10.2.5  is required to be disclosed in a judicial or administrative
proceeding after all reasonable legal remedies for maintaining such information
in confidence have been exhausted; or


                                         11.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

         10.2.6  is subsequently and independently developed by employees,
consultants or agents of the disclosing party without reference to any
Confidential Information, as evidenced by written record.

    10.3  AUTHORIZED DISCLOSURE.  Each party may disclose the Confidential
Information to the extent such disclosure is reasonably necessary in filing or
prosecuting patent applications, prosecuting or defending litigation or
complying with applicable governmental regulations, provided that if such party
is required to make any such disclosure of the Confidential Information it will
to the extent practicable give reasonable advance notice to the other party of
such disclosure requirement and, except to the extent inappropriate in the case
of patent applications, will use its best efforts to secure confidential
treatment of such information required to be disclosed.  Sang-A may disclose
(subject to the confidentiality restrictions contained herein) Confidential
Information to third party contractors, investigators and regulatory
authorities, to the extent necessary to perform its obligations under this
Agreement, provided such third parties execute confidentiality agreements
containing terms no less strict than those contained herein.

    10.4  AGREEMENT CONFIDENTIAL.  The parties agree that the contents of this
Agreement shall constitute Confidential Information, and as such, will not be
disclosed by either party without the written consent of the other, except as
required by law or prior contractual obligation.

    10.5  NON-USE OF AVIRON'S LICENSORS' NAMES.  Sang-A agrees to refrain from
using the names of Mount Sinai School of Medicine, the University of Michigan or
ARCH Development Corporation in any publicity or advertising without the written
consent of Aviron and such entity.


                                      ARTICLE 11
                        INTELLECTUAL PROPERTY; PATENT EXPENSES

    11.1  OWNERSHIP OF INTELLECTUAL PROPERTY.  Aviron shall retain all of its
rights, title and interest in and to all Aviron Technology, Aviron Data,
Clinical Materials, copyrights, trade name, and all other industrial and
intellectual property embodied in or covering the Partner Products.  Except as
otherwise expressly provided in this Agreement, Sang-A has no right, title or
interest in any industrial or intellectual property relating to the Aviron
Technology, the Clinical Materials or the Aviron Data.

    11.2  PROSECUTION AND MAINTENANCE OF LICENSED PATENTS.

          11.2.1 PROSECUTION AND MAINTENANCE.  [


                                               ]  In the event Sang-A elects not
to pursue prosecution of any National Application under this Section 11.2,


                                         12.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

Sang-A shall give Aviron not less than two (2) months' notice before any
relevant deadline and Aviron shall pursue, at its expense, prosecution of such
patent application.  In such event Sang-A's license under Section 3.1 to
practice the inventions claimed in such application or patent will terminate.
Sang-A will have the option to reactivate such license within six (6) months
following such termination, in the event Aviron pursues such patent application
at its own expense, by delivery to Aviron of the following: (i) reimbursement
for all patent costs incurred by Aviron in the Prosecution of such patent
application, (ii) payment of interest on such patent costs at a rate of [
     ] per annum and (iii) a late fee of [
                        ]

         11.2.2  CREDITS.  Sang-A shall have the right to credit against any
royalties owed pursuant to Section 4.2 [                                     ]
provided, that in no event shall Aviron be paid less than [       ] of such owed
royalties in any given Payment Period.

    11.3  INVENTIONS.  Each party acknowledges and agrees that any and all
Inventions that are made or discovered pursuant to this Agreement solely by its
employees or agents shall be owned solely by it (the "AVIRON INVENTIONS" or the
"SANG-A INVENTIONS" as the case may be), and that all Inventions made jointly by
employees or agents of each pursuant to this Agreement shall be jointly owned
("JOINT INVENTIONS"), all as determined in accordance with U.S. laws of
inventorship.  Sang-A shall have the exclusive right to practice and use Joint
Inventions within South and North Korea pursuant to Section 3.1, and shall have
the right to file and control any patent applications on Joint Inventions in
South and North Korea.  Aviron shall have the exclusive right, and Sang-A hereby
grants to Aviron such right, to practice and use all Joint Inventions outside
South and North Korea, and shall have the right to file and control any patent
applications on such Joint Inventions outside South and North Korea.  With the
exception of Aviron Inventions that constitute Licensed Patents subject to
Section 11.2 above, each party shall bear the costs of prosecuting and
maintaining any patents on its own Inventions.

    11.4  LICENSE TO SANG-A INVENTIONS.  Sang-A agrees promptly to disclose to
Aviron in writing all Sang-A Inventions in sufficient detail to allow Aviron to
evaluate such Invention.  Subject to the terms of this Agreement, Sang-A hereby
grants to Aviron a non-exclusive, royalty-free, perpetual license to practice
and use the Sang-A Inventions outside South and North Korea, with the right to
sublicense to Aviron's corporate partners (but with no further right to
sublicense) and to the University of Michigan, pursuant to the Cold Adapted
Influenza Agreement.  In addition, Sang-A hereby grants to Aviron a first right
of negotiation for an exclusive, royalty-bearing license to commercially use any
Sang-A Inventions outside South and North Korea exercisable for a period of [
            ] from the date Sang-A discloses such Invention in writing to
Aviron.  Any inventions made by Sang-A that are unrelated to either (i) Aviron
Technology or (ii) processes, methods, techniques and the like useful for the
manufacture of Partner Products shall not be covered by the license and option
granted in this Section 11.4.


                                         13.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    11.5 THIRD PARTY PATENT INFRINGEMENT.  In the event either Aviron or Sang-A
learns of any third party patents which may cover the manufacture, use or sale
of any Partner Product in South or North Korea, such party will notify the
other.  The parties agree to confer in good faith regarding such potential
infringement risk and to explore reasonable alternatives for avoiding such risk.
If the parties cannot agree on the existence or extent of the risk, or on a
course of action for avoiding the agreed upon risk, and Sang-A continues to
believe in good faith that sale of the Partner Product would create an
unjustified risk of infringement liability, Sang-A may negotiate and enter into
a license for such third party patent, in which event Sang-A shall [
                                  ] and Sang-A may offset [              ] of
the cost of such royalties against royalties owed to Aviron under Section 4.2
for such Partner Product(s): PROVIDED, HOWEVER, that [
                                                                             ]

    11.6  INFRINGEMENT OF AVIRON TECHNOLOGY.  In the event Sang-A or Aviron
becomes aware of any actual or threatened infringement of any Aviron Technology
in South or North Korea, that party shall promptly notify the other.  Aviron
shall have the first right to bring, at its own expense, any infringement action
against any person or entity infringing the Aviron Technology directly or
contributorily.  Sang-A shall cooperate with Aviron as reasonably requested, at
Aviron's expense.  If Sang-A so desires, it may join such infringement action at
its own expense.  Any and all amounts recovered with respect to such an
infringement action shall be applied first to reimburse the parties for their
out-of-pocket expenses (including reasonable attorneys' fees) in prosecuting
such infringement.  The remainder shall be shared [                 ] Aviron and
[                  ] Sang-A.  In the event Aviron is unable or unwilling to
commence an action against the alleged infringer within one-hundred twenty (120)
days of the date of Aviron's becoming aware of such infringement, Sang-A may,
but shall not be required to, prosecute the alleged infringement or threatened
infringement.  In such event Sang-A shall act in its own name and at its own
expense.  Aviron shall cooperate with Sang-A as reasonably requested, at Sang-
A's expense.  If Aviron so desires, it may join such action at a later date, at
its own expense.  Any amounts recovered with respect to such an action shall be
applied first to reimburse the parties for their out-of-pocket expenses
(including reasonable attorneys' fees) in prosecution of such infringement. [
                        ]


                                      ARTICLE 12
                                 TERM AND TERMINATION

    12.1  TERM.  Except as otherwise provided herein, the term of this
Agreement shall commence on the Effective Date and shall extend, on a Partner
Product-by-Partner Product basis, until ten (10) years from the date of First
Commercial Sale of such Partner Product.

    12.2  EXTENSION TO TERM.  Aviron hereby grants Sang-A an option to extend
this Agreement, and the licenses granted to Sang-A under Article 3, on a Partner
Product-by-Partner Product basis, for the longer of (i) an additional ten (10)
year period or (ii) the expiration of the Licensed Patent covering such Partner
Product on the same terms and conditions as are set forth


                                         14.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

in this Agreement; EXCEPT THAT, with respect to the [

                                                      ] the royalties owed with
respect to such Partner Products will be[
                                                ] and with respect to all other
Partner Products, no royalties shall be owed.  Sang-A shall exercise its option
granted under this Section 12.2 by notifying Aviron in writing of such exercise
at least six (6) months prior to the expiration of the term of this Agreement.

    12.3  MATERIAL BREACH BY SANG-A.

         12.3.1  BREACH OF DEVELOPMENT EFFORTS.  Sang-A shall be deemed in
breach of Section 2.2.2 with respect to a specific Partner Product under the
following circumstances:

         (a)  If, within [      ] following the date a Partner Product receives
[
                                                                ] or

          (b)  If, within [      ] following the date Aviron, its Affiliate
and/or sublicensee [


       ]

         12.3.2  BREACH OF MARKETING EFFORTS.  If, within [
                                                                               ]
of a Partner Product in South or North Korea, [
                                                        ]

         12.3.3  PRODUCT-BY-PRODUCT TERMINATION.  Following a material breach
by Sang-A of any provision of this Agreement with respect to any Partner
Product, including without limitation, Section 3.4.2 (Cold Adapted Influenza
Agreement), Section 4.1 (milestone payments), Section 4.2 or 4.3 (royalty
payments), Section 12.3.1 (development diligence) or Section 12.3.2 (marketing
diligence), Aviron shall have the right to terminate all rights and licenses
granted to Sang-A under this Agreement relating to such Partner Product if Sang-
A fails to cure such breach within thirty (30) days written notice thereof.  For
purposes of a breach of Section 12.3.1 or Section 12.3.2, Sang-A may cure such
breach by either remedying the breach within the thirty (30) day period or by
delivering to Aviron a comprehensive plan to cure such breach, which plan is
reasonably acceptable to Aviron.  Both parties acknowledge and agree that any
failure by Sang-A to comply with the terms of future commercial supply
agreements for any Partner Product shall in no way constitute a breach
hereunder, but shall be governed solely by such other agreements.


                                         15.

<PAGE>

         12.3.4    TERMINATION IN ENTIRETY.  Notwithstanding any of the above,
in the event Sang-A breaches any provision of Article 10 (Confidentiality), its
obligations with respect to the use of Clinical Materials in Section 2.3.3, or
its obligations under Section 15.3.4 (purchase obligation) Aviron shall have the
right to terminate this Agreement in its entirety immediately upon written
notice.

    12.4  EFFECT OF TERMINATION.

         (a)  Upon partial termination of this Agreement pursuant to Section
12.3.3:

              (i)   all rights and licenses granted to Sang-A with respect to
such Partner Product, and all sublicenses granted by Sang-A pursuant to Section
3.2 with respect to such Partner Product, shall terminate; and

              (ii)  Sang-A shall promptly (a) assign to Aviron all right, title
and interest in and to any Regulatory Filings in South and North Korea
pertaining to such Partner Product and (b) return to Aviron, or at Aviron's
request destroy, all Aviron Data, Clinical Materials and Confidential
Information relating to such Partner Product.

         (b)  Upon termination of this Agreement in its entirety pursuant to
Sections 12.3.4:

              (i)  all rights and licenses granted to Sang-A with respect to
all Partner Products, and all sublicenses granted by Sang-A pursuant to Section
3.2 with respect to all Partner Products, shall terminate; and

              (ii) Sang-A shall promptly (a) assign to Aviron all right, title
and interest in and to all Regulatory Filings in South and North Korea
pertaining to all Partner Products and (b) return to Aviron, or at Aviron's
request destroy, all Aviron Data, Clinical Materials and Confidential
Information relating to any Partner Products.

         (c)  Notwithstanding any early termination or expiration of this
Agreement, the rights and obligations of the parties under Articles 10, 11 and
14 and Sang-A's surviving obligations under any of the Prior License Agreements
will survive such termination or expiration.


                                      ARTICLE 13
                            REPRESENTATIONS AND WARRANTIES

    13.1  MUTUAL REPRESENTATIONS AND WARRANTIES.  Each party hereby represents
and warrants:


                                         16.

<PAGE>

         13.1.1  CORPORATE POWER.  Such party is duly organized and validly
existing under the laws of the state or country of its incorporation and has
full corporate power and authority to enter into this Agreement and to carry out
the provisions hereof.

         13.1.2  DUE AUTHORIZATION.  Such party is duly authorized to execute
and deliver this Agreement and to perform its obligations hereunder.

         13.1.3  BINDING AGREEMENT.  This Agreement is a legal and valid
obligation binding upon it and enforceable in accordance with its terms.  The
execution, delivery and performance of this Agreement by such party does not
conflict with any agreement, instrument or understanding, oral or written, to
which it is a party or by which it may be bound, nor violate any law or
regulation of any court, governmental body or administrative or other agency
having jurisdiction over it.


                                      ARTICLE 14
                                   INDEMNIFICATION

    14.1  INDEMNIFICATION BY SANG-A.  Sang-A expressly and unequivocally agrees
to and hereby does indemnify, defend and hold Aviron harmless from and against
all claims, damages, losses, costs and expenses, including attorneys' fees,
arising in favor of any person, firm or corporation resulting from or arising
out of liability in any way relating to the Partner Products ("Claims"),
including without limitation, the development, manufacture, packaging, use, sale
or other distribution of Partner Products by Sang-A, the use by Sang-A of any
Aviron Data or the Aviron Technology, or any representation made or warranty
given by Sang-A with respect to any Partner Product, provided that Aviron (i)
gives Sang-A notice of such Claim, (ii) cooperates with Sang-A, at Sang-A's
expense, in the defense of such Claim, and (iii) gives Sang-A the right to
control the defense and settlement of any such Claim, except that Sang-A shall
not enter into any settlement that affects Aviron's rights or interest without
Aviron's prior written approval; PROVIDED, HOWEVER, that Sang-A shall not so
indemnify and hold Aviron harmless for any Claims arising from defects in any
Partner Product raw materials supplied by Aviron which are present at the time
of acceptance of such materials by Sang-A.  Aviron shall have no authority to
settle any claim on behalf of Sang-A.


                                      ARTICLE 15
                    INVESTMENT OBLIGATIONS AND INFORMATION RIGHTS

    15.1  INVESTMENT LETTER.  Sang-A agrees to sign the form of Investment
Letter appended hereto as Exhibit D simultaneously upon execution of this
Agreement.

    15.2  INITIAL INVESTMENT.  Within thirty (30) days of the execution of this
Agreement, but in no event prior to the date Aviron's amended articles of
incorporation, in


                                         17.

<PAGE>

substantially the form attached as Exhibit E, have been approved by the State of
California, Sang-A hereby agrees to pay Aviron the amount of $3,971,515, in
exchange for 2,941,863 shares of Series C Preferred Stock of the Company.  The
parties intend that the amended articles of incorporation will be filed within
two (2) weeks of the Effective Date.

    15.3  FUTURE INVESTMENT.  During the period set forth in Section 15.3.5,
Sang-A hereby agrees to purchase ten percent (10%) of any offering of New
Securities (as defined in this Section 15.3) that Aviron may, from time to time,
propose to sell and issue, at the offering price for such offering of New
Securities offered to all other offering participants.  This purchase obligation
shall be subject to the following provisions:

         15.3.1  "NEW SECURITIES" shall mean any capital stock of Aviron,
whether now authorized or not, and rights, options, or warrants to purchase said
capital stock, and securities of any type whatsoever that are, or may become,
convertible into said capital stock, whether publicly or privately offered;
PROVIDED, HOWEVER, THAT "NEW SECURITIES" DOES NOT INCLUDE (i) securities
issuable upon conversion of or with respect to Preferred Stock; (ii) the Warrant
Shares issuable under and defined in the Stock Transfer Agreement between Aviron
and the Regents of the University of Michigan dated February 24, 1995; (iii)
securities issued pursuant to an acquisition of an entity by Aviron by merger,
purchase of substantially all of the assets, or other reorganization whereby
Aviron owns more than fifty percent (50%) of the voting power of such entity;
(iii) shares of Aviron's Common Stock (or related options) issued to employees,
directors or consultants of Aviron pursuant to any employee stock offering,
plan, or arrangement approved by the Board of Directors; (iv) shares of Aviron's
Common Stock or Preferred Stock issued in connection with any stock split, stock
dividend, or similar recapitalization by Aviron; (v) securities issued pursuant
to equipment or debt financing or leases which are approved by Aviron's Board of
Directors; (vi) securities issued pursuant to any corporate partnering,
strategic alliance, joint venture or licensing arrangement between Aviron and a
third party; or (vii) securities issued by Aviron other than for cash or cash
equivalents.

         15.3.2  In the event that Aviron proposes to undertake an issuance of
New Securities, Aviron shall, at its option, give Sang-A written notice of its
intention, describing the type of New Securities to be issued, the price, and
the general terms upon which Aviron proposes to issue the New Securities.  If
Aviron does not provide Sang-A with such notice with respect to a particular
offering of New Securities, Sang-A will have no purchase obligation with regard
to such offering.

         15.3.3  Once Aviron has given notice to Sang-A pursuant to the
preceding Section 15.3.2, Sang-A shall deliver payment for such New Securities
on the closing date of such offering of New Securities, provided that the date
of receipt of Aviron's notice is more than thirty (30) days prior to such
closing date.  If Aviron fails to notify Sang-A within the periods specified in
this Section 15.3.3, Sang-A shall nonetheless be required to deliver such
payment, prior to lapse of such thirty (30) day period.


                                         18.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

         15.3.4  In the event that Sang-A fails to meet its purchase obligation
under this Section 15.3, Aviron shall have the right to terminate Sang-A's
rights under this Agreement pursuant to Section 12.2.4.

         15.3.5  Sang-A's purchase obligation shall expire on the earlier of
(a) [               ] following the payment date of Sang-A's initial investment,
pursuant to Section 15.2 of this Agreement, or (b) following the closing of the
first firmly underwritten public offering of Common Stock of Aviron pursuant to
a registration statement filed with, and declared effective by, the United
States Securities and Exchange Commission.

         15.3.6  Sang-A's investment obligations under this Section 15.3 are not
assignable by Sang-A.

    15.4  FINANCIAL INFORMATION.

         15.4.1  Aviron will furnish the following information to Sang-A so
long as Sang-A, together with its Affiliates, holds at least 1,000,000 shares of
Aviron Common Stock issued or issuable upon conversion of any Aviron Preferred
Stock held by Sang-A:

              (a)  As soon as practicable after the end of each fiscal year of
Aviron, and in any event within 120 days thereafter, a consolidated balance
sheet of Aviron and its subsidiaries, if any, as at the end of such fiscal year,
and consolidated statements of income and consolidated statements of cash flows
of Aviron and its subsidiaries, if any, for such year, prepared in accordance
with generally accepted accounting principles consistently applied and setting
forth in each case in comparative form and figures for the previous fiscal year,
all in reasonable detail and certified by independent public accountants of
national standing selected by the company.

              (b)  As soon as practicable after the end of each of the first
three quarterly accounting periods in each fiscal year, and in any event within
45 days thereafter, a consolidated balance sheet of Aviron and its subsidiaries,
if any, as at the end of such quarter, and consolidated statements of income and
consolidated statements of cash flows of Aviron and its subsidiaries, if any,
for each quarter and for the current fiscal year of Aviron to date, prepared in
accordance with generally accepted accounting principles consistently applied,
except that such financial statement will not contain the notes normally
required by generally accepted accounting principles.

              (c)  As soon as practicable after the adoption thereof, and in
any event no later than 15 days prior to the commencement of its fiscal year, an
annual operating plan for the forthcoming fiscal year, prepared on a
consolidated basis, including projected statements of profit and loss, cash flow
and balance sheets for each calendar quarter of such year, and, promptly after
preparation thereof, any revisions to such annual operating plan and any other
budgets.


                                         19.

<PAGE>

         15.4.2  The covenants provided in Sections 15.4.1(a) and (b) shall
terminate at the first firmly underwritten public offering of Common Stock of
Aviron pursuant to a registration statement filed with, and declared effective
by, the United States Securities and Exchange Commission.

    15.5  INSPECTION RIGHTS.  Aviron shall permit Sang-A, so long as Sang-A,
together with its affiliates, holds at least 1,000,000 shares of Preferred Stock
of Aviron, its attorney, or its other representative, to visit and inspect
Aviron's properties, to examine Aviron's books of account and other records, to
make copies or extracts therefrom and to discuss Aviron's affairs, finances and
accounts with its officers, management employees and independent accountants,
all at such reasonable times and as often as Sang-A may reasonably request.

    15.6  ASSIGNMENT OF RIGHTS TO INFORMATION.  The rights granted pursuant to
Sections 15.4 and 15.5 may not be assigned or otherwise conveyed by Sang-A or by
any subsequent transferee of Sang-A without the written consent of Aviron, which
consent shall not be unreasonably withheld, provided that Aviron may refuse such
written consent if the proposed transferee is a competitor of Aviron as
determined by Aviron's Board of Directors, and provided further that no such
written consent shall be required if the transfer is made to a party who is not
a competitor of Aviron and who is an affiliate of Sang-A.


                                      ARTICLE 16
                                    MISCELLANEOUS

    16.1  ENTIRE AGREEMENT; AMENDMENTS.  This Agreement sets forth the entire
agreement and understanding between the parties and supersedes all previous
agreements, promises, representations, understandings and negotiations, whether
written or oral, between the parties with respect to the subject matter hereof.
None of the terms of this Agreement shall be amended or modified except in
writing signed by the parties hereto.

    16.2  AGREEMENT REGISTRATION.  Sang-A shall pay all costs and legal fees in
connection with registration of this Agreement with the appropriate Korean
authorities, including without limitation all filings necessary to qualify this
agreement as a Technology Inducement Agreement under the Foreign Capital
Inducement Act (FCIA) of 1960.  Prior to the Effective Date, Sang-A shall also
take all necessary steps, as expeditiously as possible, to secure the approval
of this Agreement by the Korean government.

    16.3  ASSIGNMENT.  Neither party may assign any right or obligation
hereunder without the prior written consent of the other party, except if such
assignment arises under a transaction in which the assigning party is selling
its entire business or a line of business to which this Agreement relates or
that party is being acquired by or merging with a third party.  This Agreement
shall be binding upon and inure to the benefit of the parties' respective
successors and assigns.  Any attempted assignment in violation of this provision
shall be void and of no effect.


                                         20.

<PAGE>

    16.4  SEVERABILITY.  If, and solely to the extent that, any provision of
this Agreement shall be invalid or unenforceable, or shall render this entire
Agreement to be unenforceable or invalid, such offending provision shall be of
no effect and shall not affect the validity of the remainder of this Agreement
or any of its provisions; PROVIDED, HOWEVER, the parties shall use their
respective reasonable efforts to renegotiate the offending provisions to best
accomplish the original intentions of the parties.


    16.5  WAIVERS.  A waiver by either party of any term or condition of this
Agreement in any one instance shall not be deemed or construed to be a waiver of
such term or condition for any similar instance in the future or of any
subsequent breach hereof.  All rights, remedies, undertakings, obligations and
agreements contained in this Agreement shall be cumulative and none of them
shall be a limitation of any other remedy, right, undertaking, obligation or
agreement.

    16.6  FURTHER DOCUMENTS.  Each party hereto agrees to execute such further
documents and take such further steps as the other party reasonably determines
may be necessary or desirable to effectuate the purposes of this Agreement.

    16.7  COMPLIANCE WITH LAW.  Each party hereto shall comply with all
applicable laws, rules, ordinances, guidelines, consent decrees and regulations
of any federal, state or other governmental authority.

    16.8  FORCE MAJEURE.  No party shall be liable for failure to perform or
delay in performing obligations set forth in this Agreement, and no party shall
be deemed in breach or default of its obligations, if, to the extent and for so
long as, such failure, delay, breach or default is due to natural disasters or
any similar causes reasonably beyond the control of such party.  The parties
agree that blocked currency shall not qualify as a Force Majeure.  Any party
desiring to invoke the protection of Force Majeure shall promptly notify the
other party of such desire and shall use reasonable efforts to resume
performance of its obligations.  In the event a delay covered by this Section
exceeds one (1) year, this Agreement shall be terminable upon written notice by
the aggrieved party.

    16.9  DISPUTE RESOLUTION.  In the event a dispute arises between the
parties relating to the validity, construction, enforceability or performance of
this Agreement or any alleged breach or the grounds for the termination thereof
(a "DISPUTE"), the aggrieved party shall notify the other party in writing of
such Dispute, and the parties shall attempt to resolve such dispute in good
faith.  If, within thirty (30) days of such written notice, the parties have not
succeeded in resolving the Dispute, the matter shall be referred by the
aggrieved party for review and resolution by the Chief Executive Officers
("CEOS") of Aviron and Sang-A.  The CEOs shall attempt in good faith to resolve
the Dispute for a period of thirty (30) days.  If no successful resolution of
the Dispute has been mutually agreed to at the end of this period, either party
shall be free to seek legal or equitable relief under Section 16.10.

    16.10  GOVERNING LAW; JURISDICTION.  This Agreement is deemed to have been
entered into in the State of California, United States of America, and its
interpretation,


                                         21.

<PAGE>

construction, and the remedies for its enforcement or breach are to be applied
pursuant to and in accordance with the laws of the State of California.  In any
legal action relating to this Agreement, each party agrees (a) to the exercise
of jurisdiction over it by a state or federal court in California, and (b) that
if such party brings an action it shall be instituted in one of the courts
specified in clause (a) above.  Each party acknowledges and agrees that any
judgment rendered in any such legal action may be enforced against it through
the courts or other relevant authorities in any country or jurisdiction in which
it now or may in the future maintain a principal place of business, and each
party hereby irrevocably consents to all processes in connection with any such
enforcement.

    16.11  OFFICIAL LANGUAGE.  The official text of this Agreement and any
appendices, exhibits and schedules hereto, or any notice given or accounts or
statements required by this Agreement shall be in English.  In the event of any
dispute concerning the construction or meaning of this Agreement, reference
shall be made only to this Agreement as written in English and not to any other
translation into any other language.

    16.12  NOTICES.  Any notice, consent or approval permitted or required
under this Agreement shall be in writing sent by registered or certified
airmail, postage pre-paid, or by overnight courier or by facsimile (confirmed by
mail) and addressed as follows:

    If to Sang-A:             SANG-A PHARM. CO., LTD.
                              640-9 Deung Chon Dong
                              Kangseo-Ku
                              Seoul
                              South Korea
                              Attention:  Research and Development Department

    with a copy to:           HANBO GROUP
                              316, Daechi-Dong
                              Kangnam-Gu
                              C.P.O. Box 6226
                              Seoul
                              South Korea
                              Attention:  International Legal Department

    If to Aviron:             AVIRON
                              1450 Rollins Road
                              Burlingame, California 94010
                              Attention:  J. Leighton Read

    with a copy to:           COOLEY GODWARD CASTRO HUDDLESON & TATUM
                              Five Palo Alto Square, 4th Floor
                              Palo Alto, CA 94306
                              Attention:  Barbara A. Kosacz, Esq.


                                         22.

<PAGE>

All notices shall be deemed to be effective on the date of mailing.  In case any
party changes its address at which notices are to be received, written notice of
such change shall be given as soon as practicable to the other party.

    16.13  HEADINGS.  Headings in this Agreement are included for ease of
reference only and shall have no legal effect.

    16.14  RELATIONSHIP OF THE PARTIES.  Nothing hereunder shall be deemed to
authorize either party to act for, represent or bind the other except as
expressly provided in this Agreement.

    16.15  PUBLICITY.  Neither party shall issue any press release or other
publicity materials, or make any presentation with respect to the existence of
this Agreement or the terms and conditions hereof without the prior written
consent of the other party, which consent shall not be unreasonably withheld.
This restriction shall not apply to disclosures required by law or regulation,
including as may be required in connection with any filings made with the
Securities and Exchange Commission or by the disclosure policies of a major
Stock Exchange.

    IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the date first written above by their duly authorized officers.


AVIRON                                    SANG-A PHARM. CO., LTD.




By:     /s/ L. Read                       By:   /s/ W. K Chung
    --------------------------              --------------------------
       J. Leighton Read                        Won Keun Chung

Title:  Chairman of the Board             Title: Vice Chairman
        and Chief Executive Officer


                                          23

<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
STATE 0F CALIFORNIA                )              CAPACITY CLAIMED BY SIGNER

COUNTY OF SANTA CLARA              )              Though statute does not
                                                  require the Notary to fill in
                                                  the data below, doing so may
                                                  prove invaluable to persons
                                                  relying on the document.

On May 3, 1995 before me, C. Cassandrea Miller    / / Individual
personally appeared Won Keun Chung                /X/ Corporate Officer(s)
                                                      Vice Chairman

     / /  personally known to me                  / / Partner(s)   / / Limited
          -or-                                                    / /  General
     /X/  proved to me on the basis of            / / Attorney-in-Fact
               satisfactory evidence
               to be the person(s) whose name(s)  / / Trustee(s)
               is/are subscribed to the within    / /  Guardian/Conservator
               instrument and acknowledged to me  / /  Other:
               that he/she/they executed the                 -----------------
               same in his/her/their authorized        -----------------------
               capacity(ies), and that by his/
               her/their signature(s) on the
               instrument the person(s) or the
               entity upon behalf of which the
               person(s) acted, executed the
               instrument.

- --------------------------
     OFFICIAL SEAL                                SIGNER IS REPRESENTING:
  C. CASSANDREA MILLER                            Name of person(s) or
Notary Public - California                        entity(ies)
   SANTA CLARA COUNTY        Witness my hand and
My Commission Expires        official seal.       -----------------------
     July 10, 1995
- --------------------------                        -----------------------

                              /s/ C. Cassandrea Miller
                              ------------------------
                              Signature of the Notary
- --------------------------------------------------------------------------------

This certificate must be      Title or Type of Document: License Agreement
attached to the document      Number of Pages: 83   Data of Document: 5/3/95
described at right:


                              Signer(s) other than named above:
                                                               ---------------
*1993 National Notary Assocation.  Canoga Park, CA
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

<PAGE>

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
STATE 0F CALIFORNIA                )              CAPACITY CLAIMED BY SIGNER

COUNTY OF SANTA CLARA              )              Though statute does not
                                                  require the Notary to fill in
                                                  the data below, doing so may
                                                  prove invaluable to persons
                                                  relying on the document.

On May 3, 1995 before me, C. Cassandrea Miller    / / Individual
personally appeared J. Leighton Read              /X/ Corporate Officer(s)
                                                      Chairman & CEO

     / /  personally known to me                  / / Partner(s)   / / Limited
          -or-                                                    / /  General
     /X/  proved to me on the basis of            / / Attorney-in-Fact
               satisfactory evidence
               to be the person(s) whose name(s)  / / Trustee(s)
               is/are subscribed to the within    / /  Guardian/Conservator
               instrument and acknowledged to me  / /  Other:
               that he/she/they executed the                 -----------------
               same in his/her/their authorized        -----------------------
               capacity(ies), and that by his/
               her/their signature(s) on the
               instrument the person(s) or the
               entity upon behalf of which the
               person(s) acted, executed the
               instrument.

- --------------------------
     OFFICIAL SEAL                                SIGNER IS REPRESENTING:
  C. CASSANDREA MILLER                            Name of person(s) or
Notary Public - California                        entity(ies)
   SANTA CLARA COUNTY        Witness my hand and
My Commission Expires        official seal.       ----------------------- 
     July 10, 1995                                                        
- --------------------------                        ----------------------- 

                              /s/ C. Cassandrea Miller
                              ------------------------
                              Signature of the Notary
- --------------------------------------------------------------------------------

This certificate must be      Title or Type of Document: License Agreement
attached to the document      Number of Pages: 83   Data of Document: 5/3/95
described at right:


                              Signer(s) other than named above:
                                                               ---------------
*1993 National Notary Assocation.  Canoga Park, CA
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>

                                             CONFIDENTIAL TREATMENT REQUESTED

                                    Exhibit A

                                   DEFINITIONS

     "AFFILIATE" shall mean any entity that directly or indirectly Owns, is
Owned by or is under common Ownership with, a party to this Agreement, where
"Own" or "Ownership" means direct or indirect possession of at least
[           ] of the outstanding voting securities of a corporation or a
comparable equity interest in any other type of entity.

     "ARCH AGREEMENT" shall mean License Agreement between ARCH Development
Corporation (University of Chicago) and Aviron dated as of July 1, 1992

     "AVIRON DATA" shall mean all data arising out of all [




              ] all to the extent Aviron has the right to disclose and/or
license the use of such information to Sang-A.

     "AVIRON TECHNOLOGY" shall mean Licensed Patents and Technical Information.

     "CLINICAL MATERIALS" shall mean, with respect to each Partner Product, any
materials, including without limitation,  [

                   ]  In specific, with respect to the Cold Adapted Influenza
Product, Clinical Materials shall be comprised of  [                         ]

     "COLD ADAPTED INFLUENZA AGREEMENT"" shall mean that certain Materials
Transfer and Intellectual Property Agreement entered into by and between Aviron
and the University of Michigan, effective as of February 24, 1995, appended
hereto as Exhibit B.

     "COLD ADAPTED INFLUENZA PRODUCT" means any vaccine product which (i) is
covered by a valid claim of a Patent, as defined in Section 2.8 of the Cold
Adapted Influenza Agreement or (ii) incorporates, or the manufacture, use or
sale of which utilizes, Master Strains or Know-How, as defined in Sections 2.6
and 2.5, respectively, of the Cold Adapted Influenza Agreement.

     "CONFIDENTIAL INFORMATION" shall mean any confidential information, data,
and any other information relating to (i) any Aviron Technology, research
project, work in process, future development, scientific engineering,
manufacturing, marketing, business plan, financial or personnel matter relating
to either party, its present or future products, sales, suppliers, customers,
employees, investors or business, whether in oral, written, graphic or
electronic






                                       A-1

<PAGE>

                                             CONFIDENTIAL TREATMENT REQUESTED

form, or (ii) any of Aviron's licensors' technology, know-how, improvements,
patents or biological materials.  Confidential Information shall also include
any Clinical Materials transferred from Aviron to Sang-A during this Agreement
for use hereunder.

     "EFFECTIVE DATE" shall mean the date this Agreement is deemed approved by
the Korean government, if such approval is necessary.  Otherwise, the Effective
Date shall be the date this Agreement is signed.

     "FIRST COMMERCIAL SALE" shall mean the first sale for use or consumption by
the general public of a Partner Product in South or North Korea, as the case may
be, after all required Government Approvals have been granted.

     "GMP" shall mean the Good Manufacturing Practice regulations promulgated by
the U.S. Food and Drug Administration or its equivalent in another country.

     "GOVERNMENT APPROVAL" shall mean any approvals, licenses, registrations or
authorizations of any federal, state or local regulatory agency, ministry,
department, bureau or other government entity necessary for the development,
use, marketing, sale or distribution of any Partner Products.

     "IND" (OR, "INVESTIGATIONAL NEW DRUG APPLICATION") shall mean an
application to the U.S. Food and Drug Administration ("FDA") to commence human
clinical testing of a drug, or its equivalent in another country.

     "INVENTIONS" shall mean any and all ideas, inventions or discoveries
relating to (i) the Aviron Technology, including without limitation any new uses
thereof, or (ii) processes, techniques, methods, or the like useful for the
manufacture of any Partner Product, which are made, created, conceived or
reduced to practice by or on behalf of Sang-A or by Aviron or acquired by
Aviron, during the term of this Agreement, and any and all patents, patent
applications and patent rights, and any substitutions, divisionals,
provisionals, continuations, continuations-in-part, renewals, reissues,
confirmations or registrations, and extensions thereof which are appurtenant to
such inventions or discoveries.

     "LICENSED FIELD" means  [


            ]

     "LICENSED PATENTS" shall mean all patent applications (including
substitutions, continuations, continuations-in-part, divisionals and
provisionals) and patents (including renewals, reissues, confirmations or
registrations, and extensions thereof) in South and North Korea now owned or
licensed (with right to sublicense) or hereafter acquired or licensed during the
term of this Agreement (with right to sublicense), by or on behalf of Aviron or
any of its Affiliates, claiming inventions necessary or useful to the
development, manufacture, use or sale of a Partner Product.





                                       A-2

<PAGE>


                                             CONFIDENTIAL TREATMENT REQUESTED

     "MANUFACTURING APPROVALS" shall mean all necessary regulatory approvals
related to the manufacture of a Partner Product for use in a given country.

     "MASTER SEEDS" means  [
     ]

     "MASTER STRAIN" means [

                                        ]  licensed to Aviron pursuant to the
Cold Adapted Influenza Agreement.

     "NDA" (OR "NEW DRUG APPLICATION") shall mean an application to FDA to
commence commercial sale of a drug, or its equivalent in another country.

     "NET SALES" shall mean the actual gross invoice price of each Partner
Product sold by Sang-A, its Affiliates or sublicensees to third parties less, to
the extent included therein, the total of (i) ordinary and customary trade
discounts, (ii) sales and excise taxes, and other similar taxes, customs, duty
and compulsory payments to governmental authorities (other than income taxes)
actually paid or deducted and related to the sale, and (iii) credits given to
customers for rejects or returns of the Partner Product, all as determined in
accordance with generally accepted accounting principles ("GAAP"), consistently
applied.  For purposes of this definition, sales by Sang-A to an Affiliate do
not constitute third party sales and are not included in Net Sales.

     "PARTNER PRODUCTS" shall mean each of the products listed on Schedule 1, as
amended from time to time, and any improvements thereto, all as and to the
extent developed by or on behalf of Aviron outside South and North Korea [

     ]

     "TECHNICAL INFORMATION" shall mean all know-how, trade secrets, inventions,
data, technology and other information now owned or licensed (with right to
sublicense) by Aviron, or hereafter acquired or licensed (with right to
sublicense) by Aviron during the term of this Agreement which are necessary or
useful to the formulation, development, manufacture or sale of Partner Products
including, but not limited to,  [


                           ]





                                       A-3

<PAGE>


                                    EXHIBIT B



(See Exhibit 10.3 to the Registration Statement on Form S-1 filed
on behalf of Aviron with the SEC.)

<PAGE>


                                             CONFIDENTIAL TREATMENT REQUESTED

                                    EXHIBIT C

              PRIMARY RESTRICTIONS REGARDING COLD-ADAPTED INFLUENZA


All references to Section and Article numbers in this Exhibit are to the Cold
Adapted Influenza Agreement, appended to this Agreement as Exhibit B.

     a.   SECTION 4.3. All Master Seeds, including all derivatives made by Sang-
A, shall be the property of Michigan.

     b.   SECTIONS 4.4 AND 4.6. Sang-A shall not provide any Master Seeds or
derivatives thereof to any third party.  Sang-A shall limit access to such
materials to those employees reasonably requiring such access  [
                 ] which employees are further obligated in writing to treat
those materials in a confidential manner and not to provide same to any third
party.

     c.   SECTION 4.6, Article 16.  Sang-A must keep confidential, and not use
except as provided in the Cold Adapted Influenza Agreement, the Master Seeds,
and any know-how or technical data related thereto, for a period of  [
                     ]  after termination of the Cold Adapted Influenza
Agreement.  This undertaking is subject to the usual exceptions (publication,
disclosure by a third party, legally required to be disclosed, etc.).

     d.   SECTION 4.7. Sang-A will use its best efforts to manufacture and store
the Master Seeds and Cold Adapted Influenza Products in accordance with all
applicable government laws and regulations.

     e.   SECTION 4.8. Michigan shall have the right to request from Sang-A, at
reasonable intervals and quantities, such batch samples of vaccine products as
it may desire for non-human research purposes only.

     f.   SECTION 6.2-6.4. Sang-A shall consistently employ a system of specific
nomenclature and type designations for Cold Adapted Influenza Products so that
various types can be identified in reports owed to Aviron (and by Aviron to
Michigan) under Section 7.5 of this Agreement.

     g.   ARTICLE 9. At least once every (6) months Sang-A will report to Aviron
relating to any "Technological Data" (as defined in Section 2.14) and
"Improvements" (as defined in Section 2.3) generated by Sang-A during such
reporting period.  This report will be forwarded to Michigan.  Michigan retains
an irrevocable, royalty-free license to all Technological Data and Improvements
to use in the manufacture, use or sale of Cold Adapted Influenza Products.

     h.   ARTICLES 13 AND 14.  Michigan makes no representations or warranties
regarding the Master Strains.  In addition, Sang-A agrees not to make any
statements, representations or warranties inconsistent with such disclaimer.
Sang-A must defend, indemnify and hold harmless Michigan, its fellows, officers,
employees and agents for and against any and all claims,



                                       C-1

<PAGE>


                                             CONFIDENTIAL TREATMENT REQUESTED

damages, losses, and expenses of any nature resulting from, but not limited to,
death, personal injury, illness, property damage, economic loss or products
liability arising from or in connection with (i) any manufacture, use or other
disposition by Sang-A of the Master Seeds or vaccine products, (ii) the direct
or indirect use by any person of Master Seeds or vaccine products made or used
by Sang-A, (iii) the use, handling, storage or disposal of Master Seeds, any
derivatives or products by Sang-A, and (iv) the use bv Sang-A of anv know-how or
technical data sublicensed from Michigan.  Finally, [
                                                              ] in accordance
with Section 14.3.

     i.   ARTICLE 15. SECTION 4.5. The sublicense to Sang-A of the Cold Adapted
Influenza Product must terminate upon termination of the Cold Adapted Influenza
Agreement.  In such event, at Michigan's option, Sang-A must destroy or return
to Michigan (or to Aviron, for return to Michigan) [
     ]   Further, in such event Sang-A must also provide to Michigan any
technical data or information relating to the manufacture of the Cold Adapted
Influenza Product generated by Sang-A, which Michigan shall have an irrevocable,
royalty-free right to use in the manufacture, use or sale of such Products.

     j.   ARTICLE 20. Sang-A must comply with all applicable laws regarding the
testing, production, transportation, export, packaging, labeling, sale or use of
Cold Adapted Influenza Products.

     k.   ARTICLE 22.  Sang-A must refrain from using the name of Michigan in
publicity or advertising without the prior written consent of Michigan.








                                       C-2

<PAGE>


                                    EXHIBIT D

                               FORM OF INVESTMENT LETTER

May__, 1995


J. Leighton Read, M.D.
Chief Executive Officer
Aviron
1450 Rollins Road
Burlingame, CA 94010

Dear Dr. Read:

The undersigned ("Purchaser") hereby makes the following certifications and
representations with respect to the two million nine hundred forty-one thousand
eight hundred sixty-three (2,941,863) shares (the "Shares") of Series C
Preferred, Stock of Aviron, a California corporation (the "Company"), which are
being acquired by the undersigned for a cash consideration of $3,971,515.

     1.   AUTHORIZATION.  Purchaser has all the requisite power and is duly
authorized to execute and deliver the License and Development Agreement and each
other agreement contemplated thereby and has taken all necessary action to
consummate the transactions contemplated thereby.  The License and Development
Agreement and each other agreement contemplated thereby have been duly executed
and delivered by Purchaser and constitute valid and binding obligations of
Purchaser, enforceable in accordance with their respective terms subject to laws
of general application relating to bankruptcy, insolvency and the relief of
debtors.

     2.   ACCREDITED INVESTOR.  Purchaser is an accredited investor within the
meaning of Regulation D under the Securities Act of 1933, as amended (the
"Securities Act").

     3.   EXPERIENCE.  Purchaser, alone or together with its advisors, is
experienced in evaluating and investing in start-up biomedical research
companies such as the Company.

     4.   INVESTMENT.  Purchaser is acquiring the Shares for investment for its
own account and not with a view to, or for resale in connection with, any
distribution thereof, and it has no present intention of selling or distributing
the Shares or the Common Stock issuable upon conversion of the Shares (the
"Underlying Stock").  Purchaser understands that the Shares (and the Underlying
Stock) to be purchased by it have not been registered under the Securities Act
by reason of a specific exemption from the registration provisions of the
Securities Act which depends upon, among other things, the bona fide nature of
the investment intent as expressed herein.



                                       D-1

<PAGE>


     5.   RULE 144 AND RULE 144A.  Purchaser acknowledges that, because they
have not been registered under the Securities Act, the Shares (and the
Underlying Stock) it is purchasing must be held indefinitely unless subsequently
registered under the Securities Act or an exemption from such registration is
available.  Purchaser is aware of the provisions of Rule 144 and Rule 144A
promulgated under the Securities Act, which rules permit limited resale of
securities purchased in a private placement subject to the satisfaction of
certain conditions.

     6.   NO PUBLIC MARKET.  Purchaser understands that no public market now 
exists for any of the securities issued by the Company and that it is 
uncertain whether a public market will ever exist for the Shares or the 
Underlying Stock.

     7.   ACCESS TO DATA.  Purchaser has received and reviewed such information
that such Purchaser deemed necessary to make an informed decision concerning the
purchase of the Shares and has had an opportunity to discuss the Company's
business, management and financial affairs with its management.

The Purchaser further agrees not to make any disposition of all or any part of
the Shares in any event unless and until:

     a. The Company shall have received a letter secured by the Purchaser from
the Securities and Exchange Commission stating that no action will be
recommended to the Commission with respect to the proposed disposition; or

     b. There is then in effect a registration statement under the Securities 
Act covering such proposed disposition and such disposition is made in 
accordance with said registration statement; or

     c.   (i) The Purchaser shall have notified the Company of the proposed
disposition and shall have furnished the Company with a detailed statement of
the circumstances surrounding the proposed disposition, (ii) the Purchaser shall
have furnished the Company with an opinion of counsel for the Purchaser to the
effect that such disposition will not require registration of such shares under
the Act, and (iii) such opinion of counsel for the Purchaser shall have been
concurred in by the Company's counsel and the Company shall have advised the
Purchaser of such concurrence.








                                       D-2

<PAGE>


The Purchaser understands and agrees that all certificates evidencing the shares
to be issued to the Purchaser may bear the following legend:

     "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED FOR
     SALE, SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE
     REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN OPINION
     OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY AND ITS COUNSEL THAT SUCH
     REGISTRATION IS NOT REQUIRED."



SANG-A PHARM.  CO., LTD.


By
   ---------------------------------
     Won Keun Chung
     Vice Chairman








                                       D-3


<PAGE>

                                    EXHIBIT E

                              AMENDED AND RESTATED

                          ARTICLES OF INCORPORATION OF

                                     AVIRON

     J.   Leighton Read and Alan C. Mendelson certify that:

     1.   They are the Chief Executive Officer and Secretary, respectively, of
Aviron, a California corporation (the "Corporation").

     2.   The Articles of Incorporation of this Corporation are amended and
restated as follows:

                                       "I.

     The name of this corporation is Aviron.

                                       II.

     The purpose of this corporation is to engage in any lawful act or activity
for which a corporation may be organized under the General Corporation Law of
California other than the banking business, the trust company business or the
practice of a profession permitted to be incorporated by the California
Corporations Code.

                                      III.

     A.   This corporation is authorized to issue two classes of stock to be
designated, respectively, "Common Stock" and "Preferred Stock." The total number
of shares which the corporation is authorized to issue is Ninety-Six Million
(96,000,000) shares.  Fifty-Three Million (53,000,000) shares shall be Common
Stock.  Forty-Three Million (43,000,000) shares shall be Preferred Stock.

     The Preferred Stock may be issued from time to time in one or more series.
Subject to the protective provisions set forth in Section 5 below, the Board of
Directors is hereby authorized to fix or alter the dividend rights, dividend
rate, conversion rights, voting rights, rights and terms of redemption
(including sinking fund provisions), redemption price or prices, and the
liquidation preferences of any wholly unissued series of Preferred Stock, and
the number





                                       E-1

<PAGE>

of shares constituting any such series and the designation thereof, or any of
them; and to increase or decrease the number of shares of any series subsequent
to the issuance of shares of that series, but not below the number of shares of
such series then outstanding.  In case the number of shares of any series shall
be so decreased, the shares constituting such decrease shall resume the status
that they had prior to the adoption of the resolution originally fixing the
number of shares of such series.

     B.   Five million two hundred twenty-five thousand (5,225,000) of the
authorized shares of Preferred Stock are hereby designated "Series A Preferred
Stock." Eighteen million six hundred fifty thousand (18,650,000) of the
authorized shares of Preferred Stock are hereby designated "Series B Preferred
Stock," and eighteen million (18,000,000) of the authorized shares of Preferred
Stock are hereby designated "Series C Preferred Stock." The Series A Preferred
Stock, Series B Preferred Stock and Series C Preferred Stock are collectively
referred to as the "Preferred Stock."

     C.   The respective rights, preferences, privileges, restrictions and other
matters relating to the Preferred Stock are as follows:

     1.   DIVIDENDS.  The holders of the Preferred Stock shall be entitled to
receive, payable in preference and priority to the holders of Common Stock, when
and as declared by the Board of Directors, out of any assets at the time legally
available therefor, dividends at the rate of:

          (a)  with respect to the Series A Preferred Stock, $.05 per share per
annum (as appropriately adjusted for any combination, consolidation, stock
distribution, stock dividend, stock split or similar event with respect to such
shares (a "Recapitalization"));

          (b)  with respect to the Series B Preferred Stock, $.09 per share per
annum (as adjusted for any Recapitalization); and

          (c)  with respect to the Series C Preferred Stock, $.135 per share
per annum (as adjusted for any Recapitalization).

Such dividends shall not be cumulative and no right to such dividends shall
accrue to holders of Preferred Stock unless declared by the Board of Directors.
No dividends shall be declared or paid with respect to the Common Stock (other
than a dividend payable solely in Common Stock of the Corporation) unless a
dividend of equal or greater amount per share (on an as-if-converted to Common
Stock basis) is first declared and paid with respect to the Preferred Stock.
Each share of Preferred Stock shall rank on parity with every other share of
Preferred Stock, irrespective of series, with regard to dividends, and no
dividends shall be paid, declared or set apart for payment on the shares of any
series of Preferred Stock unless at the same time a





                                       E-2



<PAGE>

dividend for the same percentage of the respective dividend rates shall also be
paid, declared or set apart for payment, as the case may be, on the shares of
Preferred Stock or each other series then outstanding.

So long as any shares of Preferred Stock shall be outstanding, no dividend,
whether in cash or property, shall be paid or declared, nor shall any other
distribution be made, on any Common Stock, nor shall any shares of the Common
Stock of the Corporation be purchased, redeemed, or otherwise acquired for value
by the Corporation (except for acquisitions of Common Stock by the Corporation
from the founders, directors, employees or consultants of the Corporation
pursuant to agreements which permit the Corporation to repurchase such shares
upon termination of an employment or consulting relationship or in exercise of
the Corporation's right of first refusal upon a proposed transfer) until all
accrued but unpaid dividends on the Preferred Stock shall have been paid or
declared and set apart.  In the event dividends are paid on any share of Common
Stock, an additional dividend shall be paid with respect to all outstanding
shares of Preferred Stock in an amount for each such share of Preferred Stock
equal to the aggregate amount of such dividends for all shares of Common Stock
into which each such share of Preferred Stock could then be converted.  The
provisions of this Section l(b) shall not, however, apply to (i) a dividend
payable in Common Stock, (ii) the acquisition of shares of any Common Stock in
exchange for shares of any other Common Stock, or (iii) any repurchase of any
outstanding securities of the Corporation that is approved by the Corporation's
Board of Directors.

     2.   LIQUIDATION PREFERENCE.

          (a)  In the event of any liquidation, dissolution or winding up of the
Corporation, either voluntary or involuntary, the holders of the Series A
Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock shall be
entitled to receive, prior and in preference to any distribution of any of the
assets or surplus funds of the Corporation to the holders of Common Stock by
reason of their ownership thereof, the amount of S.50, $.90, and $1.35 per
share, respectively (appropriately adjusted for any Recapitalization), plus all
declared but unpaid dividends on such share for each share of Series A Preferred
Stock, Series B Preferred Stock, or Series C Preferred Stock then held by them.
If upon the occurrence of such event, the assets and funds thus distributed
among the holders of the Preferred Stock shall be insufficient to permit the
payment to such holders of the full aforesaid preferential amount, then the
entire assets and funds of the Corporation legally available for distribution
shall be distributed among the holders of the Preferred Stock in proportion to
the full amounts to which they would otherwise be entitled and in proportion to
the number of shares of Preferred Stock then held by them.

          (b)  After payment to the holders of Preferred Stock of the amount set
forth in subparagraph (a) above, the entire remaining assets and funds of the
Corporation legally




                                       E-3

<PAGE>

available for distribution, if any, shall be distributed among the holders of
the Preferred Stock and Common Stock pro rata based on the number of shares of
Common Stock held by them (assuming conversion of all Preferred Stock).

          (c)  A consolidation or merger of the Corporation with or into any
other corporation or corporations, or a sale of all or substantially all of the
assets of the Corporation, other transaction or series of related transactions
resulting in a change of voting control shall be deemed a liquidation,
dissolution or winding up within the meaning of this Section 2 if (a) more than
50% of the outstanding securities of each class of the surviving entity, or (b)
an interest in equity securities representing at least 50% of the voting power
or at least 50% of the equity interest in the surviving entity, is not owned by
persons who were holders of capital stock or securities convertible into capital
stock of the Corporation immediately prior to such merger, consolidation or
sale; provided, however, that the sale of Preferred Stock to private investors
pursuant to a Preferred Stock Purchase Agreement shall not constitute a
liquidation, dissolution or winding up within the meaning of this section.

     3.   VOTING RIGHTS.  Except as otherwise expressly provided herein or as
required by law, the holder of each share of Preferred Stock shall be entitled
to the number of votes equal to the number of shares of Common Stock into which
such share of Preferred Stock could be converted on the record date for the vote
or the date of the solicitation of any written consent of shareholders and shall
have voting rights and powers equal to the voting rights and powers of the
Common Stock (except as otherwise expressly provided herein or as required by
law, voting together with the Common Stock as a single class) and shall be
entitled to notice of any stockholders' meeting in accordance with the Bylaws of
the Corporation.  Fractional votes shall not, however, be permitted and any
fractional voting rights resulting from the above formula (after aggregating all
shares into which shares of Preferred Stock held by each holder could be
converted) shall be rounded to the nearest whole number (with one-half being
rounded upward).

     4.   CONVERSION.  The holders of Preferred Stock shall have conversion
rights as follows (the "Conversion Rights"):

          (a)  RIGHT TO CONVERT.  Each share of Preferred Stock shall be
convertible, at the option of the holder thereof, at any time after the date of
issuance of such share, at the office of the Corporation or any transfer agent
for such stock.  The number of fully paid and nonassessable shares of Common
Stock to which a holder of Series A Preferred Stock shall be entitled upon
conversion shall be the product obtained by multiplying the "Series A Conversion
Rate" then in effect (determined as provided in Section 4(b)) by the number of
shares of Series A Preferred Stock being converted.  The number of fully paid
and nonassessable shares of Common Stock to which a holder of Series B Preferred
Stock shall be entitled upon conversion shall be the product obtained by
multiplying the "Series B Conversion Rate" then in effect (determined as
provided in Section 4(c)) by the number of shares of Series B Preferred




                                       E-4

<PAGE>

being converted.  The number of fully paid and nonassessable shares of Common
Stock to which a holder of Series C Preferred Stock shall be entitled upon
conversion shall be the product obtained by multiplying the "Series C Conversion
Rate" then in effect (determined as provided in Section 4(d)) by the number of
shares of Series C Preferred being converted.

          (b)  SERIES A CONVERSION RATE.  The conversion rate in effect at any
time for conversion of the Series A Preferred Stock (the "Series A Conversion
Rate") shall be the quotient obtained by dividing $.50 by the "Series A
Conversion Price," calculated as provided in Section 4(e).

          (c)  SERIES B CONVERSION RATE.  The conversion rate in effect at any
time for conversion of the Series B Preferred Stock (the "Series B Conversion
Rate") shall be the quotient obtained by dividing $.90 by the "Series B
Conversion Price," calculated as provided in Section 4(e).

          (d)  SERIES C CONVERSION RATE.  The conversion rate in effect at any
time for conversion of the Series C Preferred Stock (the "Series C Conversion
Rate") shall be the quotient obtained by dividing $1.35 by the "Series C
Conversion Price," calculated as provided in Section 4(e).

          (e)  CONVERSION PRICE.  The conversion price for the Series A
Preferred Stock shall initially be $.50 (the "Series A Conversion Price").  The
conversion price of the Series B Preferred Stock shall initially be S.90 (the
"Series B Conversion Price").  The conversion price of the Series C Preferred
Stock shall initially be $1.35 (the "Series C Conversion Price"). Such initial
Series A Conversion Price, Series B Conversion Price and Series C Conversion
Price (the "Conversion Prices") shall be adjusted from time to time in
accordance with this     Section 4. All references to the Conversion Prices
herein shall mean the Conversion Prices as so adjusted.

          (f)  AUTOMATIC CONVERSION.  Each share of Preferred Stock shall
automatically be converted into shares of Common Stock at the then effective
Conversion Price immediately upon (i) the closing of the sale of the
Corporation's Common Stock in a firm commitment, underwritten public offering
registered under the Securities Act of 1933, as amended (other than a
registration relating solely to a transaction under Rule 145 under such Act (or
any successor thereto) or to an employee benefit plan of the Company), at a
public offering price equal to or exceeding $2.50 per share of Common Stock
(appropriately adjusted for any Recapitalization) and the aggregate net proceeds
to the Corporation (before deduction for underwriter commissions and expenses
relating to the issuance, including without limitation fees of the Corporation's
counsel) of which equal or exceed $10,000,000 or (ii) upon receipt by the
Corporation of the affirmative vote at a duly noticed shareholders meeting or
pursuant to a duly





                                       E-5

<PAGE>

solicited written consent of approval of the holders of at least a majority of
the then outstanding shares of the Series A Preferred Stock, the Series B
Preferred Stock, and the Series C Preferred Stock, voting together as a single
class in favor of the conversion of all of the shares of Preferred Stock into
Common Stock.

          (g)  MECHANICS OF CONVERSION.  Before any holder of Preferred Stock
shall be entitled to convert the same into shares of Common Stock, the holder
shall surrender the certificate or certificates thereof, duly endorsed, at the
office of the Corporation or of any transfer agent for such stock, and shall
give written notice to the Corporation at such office that he elects to convert
the same and shall state therein the name or names in which he wishes the
certificate or certificates for shares of Common Stock to be issued.  The
Corporation shall, as soon as practicable thereafter, issue and deliver at such
office to such holder of Preferred Stock, a certificate or certificates for the
number of shares of Common Stock to which he shall be entitled as aforesaid.
Such conversion shall be deemed to have been made immediately prior to the close
of business on the date of surrender of the shares of Preferred Stock to be
converted, except that in the case of an automatic conversion pursuant to
Section 4(f) hereof, such conversion shall be deemed to have been made (i)
immediately prior to the closing of the offering referred to in Section 4(f)(i)
or (ii) immediately upon the approval by vote or written consent referred to in
Section 4(f)(ii) above, and the person or persons entitled to receive the shares
of Common Stock issuable upon such conversion shall be treated for all purposes
as the record holder or holders of such shares of Common Stock on such date.

          (h)  ADJUSTMENTS TO CONVERSION PRICE.

               (i)  SPECIAL DEFINITIONS.  For purposes of this Section 4(h)
"ORIGINAL Issue Date" shall mean the date on which a share of Preferred Stock
was first issued.

               (ii) ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF COMMON
STOCK.  In the event the Corporation at any time or from time to time after the
Original Issue Date shall declare or pay any dividend on the Common Stock
payable in Common Stock or in any right to acquire Common Stock, or shall effect
a subdivision of the outstanding shares of Common Stock into a greater number of
shares of Common Stock (by stock split, reclassification or otherwise), or in
the event the outstanding shares of Common Stock shall be combined or
consolidated, by reclassification or otherwise, into a lesser number of shares
of Common Stock, then the respective Conversion Prices of the Series A Preferred
Stock, Series B Preferred Stock and Series C Preferred Stock in effect
immediately prior to such event shall, concurrently with the effectiveness of
such event, be proportionately decreased or increased, as appropriate.

          (i)  OTHER DISTRIBUTIONS.  In the event the Corporation shall at any
time or from time to time make or issue, or fix a record date for the
determination of holders of Common Stock entitled to receive, a dividend or
other distribution payable in securities of the





                                       E-6

<PAGE>

Corporation or any of its subsidiaries, then in each such event provision shall
be made so that the holders of Preferred Stock shall receive, upon the
conversion thereof, the securities of the Corporation or any of its subsidiaries
which they would have received had their stock been converted into Common Stock
on the date of such event.

          (j)  NO IMPAIRMENT.  The Corporation will not, by amendment of its
Articles of Incorporation or through any reorganization, transfer of assets,
consolidation, merger, dissolution, issue or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed hereunder by the Corporation, but will at
all times in good faith assist in the carrying out of all the provisions of this
Section 4 and in the taking of all such action as may be necessary or
appropriate in order to protect the Conversion Rights of the holders of the
Preferred Stock against impairment.

          (k)  CERTIFICATES AS TO ADJUSTMENTS.  Upon the occurrence of each
adjustment or readjustment of the Conversion Price pursuant to this Section 4,
the Corporation at its expense shall promptly compute such adjustment or
readjustment in accordance with the terms hereof and cause independent public
accountants selected by the Corporation to verify such computation and prepare
and furnish to each holder of Preferred Stock a certificate setting forth such
adjustment or readjustment and showing in detail the facts upon which such
adjustment or readjustment is based.  The Corporation shall, upon the written
request at any time of any holder of Preferred Stock, furnish or cause to be
furnished to such holder a like certificate setting forth (i) such adjustments
and readjustments, (ii) the Conversion Price at the time in effect, and (iii)
the number of shares of Common Stock and the amount, if any, of other property
which at the time would be received upon the conversion of Preferred Stock.

          (l)  NOTICES OF RECORD DATE.  In the event of any taking by the
Corporation of a record of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend (other than a cash dividend) or other distribution, any security or
right convertible into or entitling the holder thereof to receive shares of
Common Stock, or any right to subscribe for, purchase or otherwise acquire any
shares of stock of any class or any other securities or property, or to receive
any other right, the Corporation shall mail to each holder of Preferred Stock at
least 20 days prior to the date specified therein, a notice specifying the date
on which any such record is to be taken for the purpose of such dividend,
distribution, security or right, and the amount and character of such dividend,
distribution, security or right.

          (m)  ISSUE TAXES.  The Corporation shall pay any and all issue and
other taxes, excluding federal, state or local income taxes, that may be payable
in respect of any issue or delivery of shares of Common Stock on conversion of
shares of Preferred Stock pursuant






                                       E-7

<PAGE>


hereto; provided, however, that the Corporation shall not be obligated to pay
any transfer taxes resulting from any transfer requested by any holder in
connection with any such conversion.

          (n)  RESERVATION OF STOCK ISSUABLE UPON CONVERSION.  The Corporation
shall at all times reserve and keep available out of its authorized but unissued
shares of Common Stock, solely for the purpose of effecting the conversion of
the shares of the Preferred Stock, such number of its shares of Common Stock as
shall from time to time be sufficient to effect the conversion of all
outstanding shares of the Preferred Stock; and if at any time the number of
authorized but unissued shares of Common Stock shall not be sufficient to effect
the conversion of all then outstanding shares of the Preferred Stock, the
Corporation will take such corporate action as may, in the opinion of its
counsel, be necessary to increase its authorized but unissued shares of Common
Stock to such number of shares as shall be sufficient for such purpose,
including, without limitation, engaging in best efforts to obtain the requisite
shareholder approval of any necessary amendment to this Articles of
Incorporation.

          (o)  CONSENT TO CERTAIN DISTRIBUTIONS.  Each holder of Preferred Stock
shall be deemed to have consented for purposes of Sections 502, 503 and 506 of
the General Corporation Law to distributions and payments made by the
Corporation and approved by the Board of Directors of the Corporation in
connection with the repurchases of shares of Common Stock issued or to held by
directors, board advisors and employees of, or consultants to, the Corporation
upon termination of their employment or services.

          (p)  FRACTIONAL SHARES.  No fractional share shall be issued upon the
conversion of any share or shares of Preferred Stock.  All shares of Common
Stock (including fractions thereof) issuable upon conversion of more than one
share of Preferred Stock by a holder thereof shall be aggregated for purposes of
determining whether the conversion would result in the issuance of any
fractional share.  If, after the aforementioned aggregation, the conversion
would result in the issuance of a fraction of a share of Common Stock, the
Corporation shall, in lieu of issuing any fractional share, pay the holder
otherwise entitled to such fraction a sum in cash equal to the fair market value
of such fraction on the date of conversion (as determined in good faith by the
Board of Directors of the Corporation).

          (q)  NOTICES.  Any notice required by the provisions of this Section 4
to be given to the holders of shares of Preferred Stock shall be deemed given if
deposited in the United States mail, postage prepaid, and addressed to each
holder of record at its address appearing on the books of the Corporation.
Notwithstanding the above, any notice or communication to an address outside the
United States shall be sent by telecopy and confirmed in writing sent by courier
guaranteeing delivery in no more than two (2) business days.


          (r)  ADJUSTMENTS.  In case of any reorganization or any
reclassification of the capital stock of the Corporation, any consolidation or
merger of the Corporation with or into





                                       E-8

<PAGE>

another corporation or corporations, or the conveyance of all or substantially
all of the assets of the Corporation to another corporation, each share of
Preferred Stock shall thereafter be convertible into the number of shares of
stock or other securities or property (including cash) to which a holder of the
number of shares of Common Stock deliverable upon conversion of such share of
Preferred Stock would have been entitled upon the record date of (or date of, if
no record date is fixed) such reorganization, reclassification, consolidation,
merger or conveyance; and, in any case, appropriate adjustment (as determined by
the Board of Directors) shall be made in the application of the provisions
herein set forth with respect to the rights and interests thereafter of the
holders of such Preferred Stock, to the end that the provisions set forth herein
shall thereafter be applicable, as nearly as equivalent as is practicable, in
relation to any shares of stock or the securities or property (including cash)
thereafter deliverable upon the conversion of the shares of such Preferred
Stock.

     5.   RESTRICTIONS AND LIMITATIONS.  So long as at least 5,000,000 of the
authorized shares of Preferred Stock remain outstanding, the Corporation shall
not, without the vote or written consent by the holders of majority of the then
outstanding shares of Series A Preferred Stock, Series B Preferred Stock, and
Series C Preferred Stock, voting together as a single class on an as-converted
basis:

          (a)  Amend, repeal or waive any provision of, or add any provision to,
the Corporation's Articles of Incorporation if such action would alter or change
in an adverse manner the preferences, rights, privileges or powers of, or the
restrictions provided for the benefit of, the Preferred Stock;

          (b)  Increase the total number of authorized shares of Common Stock or
Preferred Stock of the Corporation or the number of shares designated as any
series of Preferred Stock;

          (c)  Authorize or issue, or obligate itself to issue, any other equity
security senior to the Series A Preferred Stock Series B Preferred Stock or
Series C Preferred Stock as to dividend or redemption rights, liquidation
preferences, conversion rights, voting rights or otherwise, or create any
obligation or security convertible into or exchangeable for, or having any
option rights to purchase, any such equity security which is senior to the
Series A Preferred Stock, Series B Preferred Stock or Series C Preferred Stock;
provided, however, that an equity security issued subsequent to the issuance of
the Series A Preferred Stock, Series B Preferred Stock or Series C Preferred
Stock for a share price and corresponding liquidation price higher than that of
the Series A Preferred Stock, Series B Preferred Stock, or Series C Preferred
Stock shall not be deemed senior to the Series A Preferred Stock, Series B
Preferred Stock or Series C Preferred Stock solely by reason of such share price
and liquidation price;








                                       E-9

<PAGE>

          (d)  Do any act or thing which would result in taxation of the holders
of shares of the Preferred Stock under Section 305 of the Internal Revenue
Code of 1968, as amended (the "Code") (or any comparable provision of the Code 
as hereafter from time to time amended);

          (e)  Effect any sale or other conveyance of all or substantially 
all of the assets of the Corporation or any of its subsidiaries, or any 
consolidation or merger involving the Corporation or any of its subsidiaries 
with or into any other corporation, if more than 50% of the surviving entity 
is not owned by persons who were holders of capital stock or securities 
convertible into capital stock of the Corporation immediately prior to such 
merger, consolidation or sale; or

          (f)  Set aside any amounts for or purchase, or declare or pay any
dividend or make any other distribution on, any shares of capital stock other
than the Series A Preferred Stock, Series B Preferred Stock or Series C
Preferred Stock, except for repurchases required by current agreements with
directors, consultants or employees.

     6.   NO REISSUANCE OF PREFERRED STOCK.  No share or shares of Preferred
Stock acquired by the Corporation by reason of redemption, purchase, conversion
or otherwise shall be reissued, and all such shares shall be returned to the
status of undesignated shares of Preferred Stock.


                                       IV.

     A.   The liability of the directors of this corporation for monetary
damages shall be eliminated to the fullest extent permissible under California
law.

     B.   This corporation is authorized to provide indemnification of agents
(as defined in Section 317 of the California Corporations Code) for breach of
duty to the corporation and its shareholders through bylaw provisions or through
agreements with the agents, or through shareholder resolutions, or otherwise, to
the fullest extent permitted by California law.

     C.   Any repeal or modification of this Article shall only be prospective
and shall not affect the rights under this Article in effect at the time of the
alleged occurrence of any act or omission to act giving rise to liability or
indemnification."


     3.   The foregoing Amended and Restated Articles of Incorporation has been
duly approved by the board of directors.







                                      E-10

<PAGE>


     4.   The foregoing Amended and Restated Articles of Incorporation has been
duly approved by the required vote of shareholders in accordance with Sections
902 and 903 of the Corporations Code.  The total number of outstanding shares of
the corporation is 3,486,370 shares of Common Stock, 5,000,000 shares of Series
A Preferred Stock and 17,990,401 shares of Series B Preferred Stock.  The number
of shares voting in favor of the amendment equaled or exceeded the vote
required.  The percentage vote required was more than 50% of the Common Stock,
50% of the Series A Preferred Stock and Series B Preferred Stock voting together
as a separate class and more than 50% of the Common Stock and Preferred Stock
voting together on an as-converted basis.

We further declare under penalty of perjury under the laws of the State of
California that the matters set forth in this certificate are true and correct
of our own knowledge.

DATE:
     --------------

                                   ----------------------------------------
                                   J. Leighton Read, Chief Executive Officer



                                   ----------------------------------------
                                   Alan C. Mendelson, Secretary








                                      E-11

<PAGE>


                                             CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE 1

                                PARTNER PRODUCTS



1)   Cold adapted influenza vaccine

2)   Recombinant influenza vaccine

3)   Respiratory syncytial virus vaccine

4)   Herpes simplex virus vaccine

5)   [                                 ]

6)   Cytomegalovirus vaccine

7)   Epstein-Barr virus vaccine

8)   [                                                 ]

9)   [                                                                 ]



                                       1-1

<PAGE>



                                   SCHEDULE 2

                       PRIOR LICENSE AGREEMENTS OF AVIRON


License Agreement between ARCH Development Corporation (University of Chicago)
and Aviron dated as of July 1, 1992

Technology Transfer Agreement between Mount Sinai School of Medicine of the City
University of New York and Aviron dated as of February 9, 1993

Cold Adapted Influenza Agreement between Aviron and the University of Michigan
dated as of February 24, 1995

Public Health Service Cooperative Research and Development Agreement between the
National Institutes of Health and Aviron









                                       2-1

<PAGE>

                                             CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE 3

                             MANUFACTURING TERRITORY


1)   United States of America

2)   [     ]

3)   [     ]

4)   [     ]

5)   [     ]

6)   [     ]

7)   [     ]








                                       3-1


<PAGE>

                                                                    EXHIBIT 10.6

<PAGE>

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT HAS BEEN DELETED, AS
MARKED BY BRACKETS, AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND
EXCHANGE COMMISSION PURSUANT TO RULE 406 OF THE SECURITIES ACT OF 1933, AS
AMENDED.

                                PUBLIC HEALTH SERVICE

                    COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

    This Cooperative Research and Development Agreement, hereinafter referred
    to as the "CRADA," consists of this Cover Page, an attached Agreement, a
    Signature Page, and various Appendices referenced in the Agreement.  This
    Cover Page serves to identify the Parties to this CRADA:

    (1)  the following Bureau(s), Institute(s), or Division(s) of the National
    Institutes of Health: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS
    DISEASES, ("NIAID"), hereinafter singly or collectively referred to as the
    "NIH;" and

    (2)  AVIRON, which has offices at 1450 Rollins Road, Burlingame, CA 94010,
    hereinafter referred to as the "Collaborator."


    Our proposal, including its attachments, contain confidential commercial
    information.  Pursuant to 45 C. F. R. Section 5.65, we have designated
    those pages that include such confidential information with a stamp or in
    the page footer.  It is Aviron's position that such information is exempt
    from disclosure under the Freedom of Information Act and we understand that
    we will receive predisclosure notification of any request for information
    we have designated as confidential which the Institute determines it is
    required to disclose.

<PAGE>


NIH Patent Policy Board, April 24, 1989

                    COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

              Article 1. INTRODUCTION

    This Cooperative Research and Development Agreement (CRADA) between NIH and
the Collaborator will be effective when signed by all parties.  By signing this
CRADA, the Collaborator acknowledges that it has received and read a copy of the
Policy Statement on Cooperative Research and Development Agreements and
Intellectual Property Licensing which is attached as Appendix A.  The research
and development project(s) which will be undertaken by each of the Parties in
the course of this CRADA are detailed in the Research Plan (RP) which is
attached as Appendix B. The funding and staffing commitments of the Parties are
set forth in Appendix C. Any exceptions or changes to the CRADA are set forth in
Appendix D.

              Article 2. DEFINITIONS

    As used in this CRADA, the following terms shall have the indicated
    meanings:

2.1           "Cooperative Research and Development Agreement" or "CRADA" means
         this agreement, entered into by NIH pursuant to the Federal Technology
         Transfer Act of 1986 and Executive Order 12591 of October 10, 1987.

2.2           "Proprietary Information" means confidential scientific,
         business, or financial information provided that such information:

         2.2.1     is not publicly known or available from other sources who
                   are not under a confidentiality obligation to the source of
                   the information;

         2.2.2     has not been made available by its owners to others without
                   a confidentiality obligation;

         2.2.3     is not already known by or available to the receiving Party
                   without a confidentiality obligation; or

         2.2.4     does not relate to potential hazards or cautionary warnings
                   associated with the production, handling, or use of the
                   subject matter of the Research Plan of this CRADA.

2.3           "Subject Data" means all recorded information first produced in
         the performance of this CRADA.

2.4           "Research Results" means all tangible materials other than
         Subject Data first produced in the performance of this CRADA.


                                         2 -

<PAGE>

NIH Patent Policy Board, April 24, 1989

2.5           "Subject Invention" means any invention, conceived or reduced to
         practice in the performance of research under this CRADA, that may be
         patentable under 35 U.S.C. Section 101 or Section 161, protectable
         under 7 U.S.D. Section 2321, or otherwise protectable by other types
         of U.S. or foreign "Intellectual Property" ("IP") right.

2.6           "Government" means the U.S. Government and any of its agencies.

2.7           "Research Plan" or "RP" means the statement in Appendix B of the
         respective research and development commitments of the Parties to this
         CRADA.

2.8           "Principal Investigator" or "PI" means the persons designated
         respectively by the Parties to this CRADA who will be responsible for
         the scientific and technical conduct of the RP.

              Article 3. COOPERATIVE RESEARCH

3.1           RESEARCH TEAM.  The Parties agree to establish a joint research
         and development team (hereinafter referred to as the "Team")
         comprising at least the Principal Investigators designated pursuant to
         Article 3.3 to conduct and monitor the research in accordance with the
         RP. Although the members of the Team shall be considered as having
         been delegated to the Team, they shall continue to remain employed by
         their respective employers under their respective terms of employment.

3.2           REVIEW OF WORK. Periodic conferences shall be held by the Team to
         review work progress. It is understood that the nature of this
         cooperative research precludes a guarantee of its completion within
         the specified period of performance or limits of allocated financial
         or staffing support. Accordingly, research under this CRADA is to be
         performed on a best efforts basis.

3.3           PRINCIPAL INVESTIGATORS. NIH research work under this CRADA will
         be performed by the Laboratory identified in the RP, and the NIH
         Principal Investigator (PI) designated in the RP will be responsible
         for the scientific and technical conduct of this project on behalf of
         NIH. Also designated in the RP is the Collaborator PI, who will be
         responsible for the scientific and technical conduct of this project
         on behalf of the Collaborator.

3.4           RESEARCH PLAN CHANGE. The RP may be modified by mutual written
         consent of the Principal Investigators. Substantial changes in the
         scope of the RP will be treated as amendments under Article 14.6.


                                         3 -

<PAGE>

NIH Patent Policy Board, April 24, 1989

              Article 4. REPORTS

4.1           INTERIM REPORTS.  The Parties shall exchange formal written
         interim progress reports on a schedule agreed to by the PIs, but at
         least within six (6) months after this CRADA becomes effective and at
         least within every six (6) months thereafter.  Such reports shall set
         forth the technical progress made, identifying such problems as may
         have been encountered and establishing goals and objectives requiring
         further effort.

4.2           FINAL REPORTS.  The Parties shall exchange final reports of their
         results within four (4) months after completing the projects described
         in the RP or after the termination of this CRADA.

              Article 5. FINANCIAL AND STAFFING OBLIGATIONS

5.1           NIH AND COLLABORATOR CONTRIBUTIONS. The NIH contribution to the
         RP in the form of personnel, services, and property only is designated
         in Appendix C.  The Collaborator contribution to the RP in the form of
         personnel, services, property, support for staffing and/or funding is
         designated in Appendix C. Payment schedules, if applicable, are also
         indicated in Appendix C.

5.2           INSUFFICIENT AND EXCESS FUNDS. NIH shall not be obligated to
         perform any of the research specified herein or to take any other
         action required by this CRADA if the funding is not provided as set
         forth in Appendix C. NIH shall return excess funds to the Collaborator
         when it sends its final fiscal report pursuant to Article 5.3, except
         for staffing support pursuant to Article 11.3.

5.3           ACCOUNTING RECORDS.  NIH shall maintain separate and distinct
         current accounts, records, and other evidence supporting all its
         obligations under this CRADA, and shall provide the Collaborator an
         annual report reflecting the use of the Collaborator's funds and a
         final such fiscal report at the time that final reports are exchanged
         pursuant to Article 4.2.

              Article 6. TITLE TO PROPERTY

6.1           CAPITAL EQUIPMENT.  The purchase or use of capital equipment to
         carry out this CRADA does not affect the ownership rights that would
         otherwise apply.  Equipment purchased by NIH with funds provided by
         the Collaborator shall be the property of NIH.  All capital equipment
         provided under this CRADA by one party for the use of another Party
         remains the property of the providing Party unless other disposition
         is mutually agreed upon in writing by the PIs.  If title to this
         equipment remains with the providing Party, that Party is responsible
         for maintenance of the equipment and the costs of its transportation
         to and from the site where it will be used.


                                         4 -

<PAGE>

NIH Patent Policy Board, April 24, 1989

              Article 7. INTELLECTUAL PROPERTY RIGHTS AND APPLICATIONS

7.1           REPORTING.  The Parties shall promptly report to each other in
         writing each Subject Invention resulting from the research conducted
         under this CRADA that is reported to them by their respective
         employees.  Such reports shall be treated in confidence by the
         receiving Party until such time as a patent or other Intellectual
         Property (IP) application, as appropriate, claiming that Subject
         Invention has been filed.  Because of the royalty sharing provisions
         for Government inventors in the Federal Technology Transfer Act of
         1986, and in view of Article 8.3 of this CRADA which grants the
         Government only a research license on inventions made solely by the
         Collaborator, the Collaborator acknowledges a special duty to report
         all Subject Inventions to NIH so that NIH may determine whether or not
         inventorship properly includes NIH investigators.

7.2           COLLABORATOR EMPLOYEE INVENTIONS.  The Collaborator may elect to
         retain IP rights to any Subject Invention made solely by a
         Collaborator employee.  The Collaborator shall notify NIH promptly
         upon making this election.  If the Collaborator does not elect to
         retain its IP rights, the Collaborator shall offer to assign these IP
         rights to the Subject Invention to NIH pursuant to Article 7.5. If NIH
         declines such assignment, the Collaborator may release its IP rights
         to employee inventors pursuant to Article 7.6.

7.3           NIH EMPLOYEE INVENTIONS.  NIH, on behalf of the U.S. Government,
         may elect to retain IP rights to each Subject Invention made solely by
         NIH employees.  If NIH does not elect to retain IP rights, NIH shall
         offer to assign these IP rights to such Subject Invention to the
         Collaborator pursuant to Article 7.5. If the Collaborator declines
         such assignment, NIH may release IP rights in such Subject Invention
         to its employee inventors pursuant to Article 7.6.

7.4           JOINT INVENTIONS.  Each Subject Invention made jointly by NIH and
         Collaborator employees shall be jointly owned by NIH and the
         Collaborator.  The Collaborator may elect to file the joint patent or
         other IP application(s) thereon and shall notify NIH promptly upon
         making this election.  If the Collaborator decides to file such
         applications, it shall do so in a timely manner and at its own
         expense.  If the Collaborator does not elect to file such
         application(s), NIH, on behalf of the U.S. Government, shall have the
         right to file the joint applications in a timely manner and at its own
         expense.  If either Party decides not to retain its IP rights to a
         jointly owned Subject Invention, it shall offer to assign such rights
         to the other Party pursuant to Article 7.5. If the other Party
         declines such assignment, the offering Party may release its IP rights
         to employee inventors pursuant to Article 7.6.


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7.5           FILING OF PATENT APPLICATIONS.  With respect to Subject
         Inventions made by the Collaborator as described in Article 7.2 or by
         NIH as described in Article 7.3, a Party exercising its right to
         retain IP rights to a Subject Invention agrees to file patent or other
         IP applications in a timely manner and at its own expense.  The Party
         may elect not to file a patent or other IP application thereon in any
         particular country or countries, provided it so advises the other
         Party ninety (90) days prior to the expiration of any applicable
         filing deadline, priority period, or statutory bar date, and hereby
         agrees to assign its IP right, title, and interest in such country or
         countries to the Subject Invention to the other Party and to cooperate
         in the preparation and filing of a patent or other IP applications.
         In any countries in which title to patent or other IP rights is
         transferred to the Collaborator, the Collaborator agrees that NIH
         inventors will share in any royalty distribution that the Collaborator
         pays to its own inventors.

7.6           RELEASE TO INVENTORS.  In the event neither of the Parties to the
         CRADA elects to file a patent or other IP application on a Subject
         Invention, either or both (if a joint invention) may release their IP
         rights to their respective employee inventor(s) with a non-exclusive,
         non-transferrable, royalty-free license being retained by each Party.

7.7           PATENT EXPENSES.  The expenses attendant to the filing of patent
         or other IP applications generally shall be paid by the Party filing
         such application.  If an exclusive license to any Subject Invention is
         granted to the Collaborator, the Collaborator shall reimburse NIH for
         the reasonable past and Collaborator-approved ongoing funds expended
         worldwide for filing, prosecuting, and maintaining any applications
         claiming such exclusively-licensed inventions and any patents or other
         IP grants that may issue on such applications.  The Collaborator may
         waive its exclusive license rights on any application, patent, or
         other IP grant at any time, and incur no subsequent compensation
         obligation for that application, patent, or IP grant.

7.8           PROSECUTION OF INTELLECTUAL PROPERTY APPLICATIONS.  Each Party
         shall provide the other Party with copies of the applications it files
         on any Subject Invention along with the power to inspect and make
         copies of all documents retained in the patent or other IP application
         files by the applicable patent or other IP office.  The Parties agree
         to consult with each other with respect to the prosecution of NIH
         Subject Inventions described in Article 7.3 and joint Subject
         Inventions described in Article 7.4. If the Collaborator elects to
         file and prosecute IP applications on joint Subject Inventions
         pursuant to Article 7.4, NIH will be granted an associate power of
         attorney (or its equivalent) on such IP applications.


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                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

              Article 8. LICENSING

8.1           OPTION FOR EXCLUSIVE COMMERCIALIZATION LICENSE.  With respect to
         Government IP rights to any Subject Invention not made solely by the
         Collaborator's employees for which a patent or other IP application is
         filed, NIH hereby grants to the Collaborator[



                     ]The license will specify the licensed fields of use,
         breadth of exclusivity, and royalties.  Royalty rates will be based on
         product sales and the rates conventionally granted in the field
         identified in the RP for inventions with reasonably similar commercial
         potential.  Royalty rates generally will not exceed a rate within the
         range of 5 - 8% for exclusive commercialization licenses.  Contingent
         royalty schemes based on, e.g., patent issuance or non-issuance, and
         provisions treating the stacking of royalties or packaging of other
         licensed inventions developed under this CRADA may be provided.
         Exclusive licensees will be expected to reimburse NIH for IP expenses
         related to each licensed intellectual property, and may be permitted
         to offset such reimbursement against future product royalties.

8.2           EXERCISE OF LICENSE OPTION. The option of Article 8.1 must be
         exercised by written notice mailed within three (3) months after the
         patent or other IP application is filed to the NIH Office of
         Technology Transfer, 6011 Executive Boulevard, Suite 325, Rockville,
         MD 20852. Exercise of this option by the Collaborator initiates a
         negotiation period that expires nine (9) months after the patent or
         other IP application filing date. If the last proposal by the
         Collaborator has not been responded to in writing by the NIH within
         this nine (9) month period, the negotiation period shall be extended
         to expire one (1) month after NIH so responds, during which month the
         Collaborator may accept in writing the final license proposal of NIH.
         After that time, NIH will be free to license such IP rights to others.

8.3           GOVERNMENT INTELLECTUAL PROPERTY RIGHTS. For inventions developed
         wholly by NIH investigators or jointly with a Collaborator under this
         CRADA, NIH are required by the Federal Technology Transfer Act of 1986
         (15 U.S.C. at Section 3710a[b](2]) to retain at least a nonexclusive,
         irrevocable, paid-up license to practice the invention or to have the
         invention practiced throughout the world by or on behalf of the U.S.
         Government.  For inventions developed wholly by the Collaborator under
         this CRADA, the Collaborator agrees to grant a research license as
         described in Article 8.4 to the Government.

    8.4  RESEARCH LICENSES[


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NIH Patent Policy Board, April 24, 1989




                              ]

8.5           JOINT INVENTIONS NOT EXCLUSIVELY LICENSED.  In the event that the
         Collaborator does not acquire an exclusive commercialization license
         to IP rights in joint Subject Inventions described in Article 7.4,
         then each Party shall have the right to use the joint Subject
         Invention and to license its use to others.  The Parties may agree to
         a joint licensing approach for such IP rights.

              Article 9. PROPRIETARY RIGHTS AND PUBLICATION

9.1           RIGHT OF ACCESS.  NIH and the Collaborator agree to exchange all
         Subject Data and Research Results produced in the course of research
         under this CRADA, whether developed solely by NIH, jointly with the
         Collaborator, or solely by the Collaborator.  Tangible research
         products developed under a CRADA will be shared equally by the Parties
         to the CRADA unless other disposition is agreed to by the Principal
         Investigators.  All Parties to the CRADA will be free to utilize
         Subject Data and Research Results for their own purposes, consistent
         with their obligations under this CRADA.

9.2           OWNERSHIP OF SUBJECT DATA AND RESEARCH RESULTS.  Subject to the
         sharing requirements of Article 9.1, the producing Party will retain
         ownership of and title to all Subject Inventions, all Subject Data,
         and all Research Results produced solely by their investigators.
         Jointly developed Subject Inventions, Subject Data, and Research
         Results will be jointly owned; however, except as may be afforded
         through IP rights that require public disclosure of the protected
         subject matter (e.g., patents), NIH do not have statutory authority to
         license (or agree with the Collaborator to limit dissemination of)
         Subject Data or Research Results developed solely by NIH investigators
         or jointly with the Collaborator.  Accordingly, NIH will not agree to
         exclude others from utilizing or commercializing such Subject Data or
         Research Results.

9.3           PROPRIETARY AND CONFIDENTIAL INFORMATION.  Each Party agrees to
         limit its disclosure of Proprietary Information to the amount
         necessary to carry out the Research Plan of this CRADA, and shall
         place a confidentiality notice on all such information.  Research
         materials required for the RP may also be designated as Proprietary
         Information.  Each party receiving Proprietary Information agrees that
         any information so designated shall be used by it only for the
         purposes described in the attached Research Plan.  Any party may
         object to the designation of information as Proprietary Information by
         another Party and may decline to accept such


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                                               CONFIDENTIAL TREATMENT REQUESTED

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         information.  Data and research products developed solely by the
         Collaborator may be designated as Proprietary Information when they
         are wholly separable from the data and research products developed
         jointly with NIH investigators, and advance designation of such data
         and product categories is set forth in the RP.  The exchange of
         confidential information, e.g., patient data, should be similarly
         limited and treated.  Unless disclosure is otherwise mutually agreed
         upon, all Parties to this CRADA agree to keep CRADA Subject Data and
         Research Results confidential, to the extent permitted by law, until
         they are published or corresponding patent or other IP application(s)
         have been filed.

9.4           PROTECTION OF PROPRIETARY INFORMATION.  Proprietary information
         shall not be disclosed, copied, reproduced, or otherwise made
         available to any other person or entity without the consent of the
         owning Party except as required under court order or the Freedom of
         Information Act (5 U.S.C. Section 552).  Each Party agrees to use its
         best efforts to maintain the confidentiality of Proprietary
         Information.  Each Party agrees that another Party is not liable for
         the disclosure of Proprietary Information which, after notice to and
         consultation with the concerned Party, another Party in possession of
         the Proprietary Information determines may not lawfully be withheld,
         provided the concerned Party has been given an opportunity to obtain
         a court order to enjoin disclosure.

9.5           DURATION OF CONFIDENTIALITY OBLIGATION.  The obligation to
         maintain the confidentiality of Proprietary Information shall expire
         at the earlier of the date when the information is no longer
         Proprietary Information as defined in Article 2.2 or[
         ]after the expiration or termination date of this CRADA.  The
         Collaborator may request an extension to this term when necessary to
         protect Proprietary Information relating to products not yet
         commercialized.

9.6           PUBLICATION.  The Parties are encouraged to make publicly
         available the results of their research.  Before either Party submits
         a paper or abstract for publication or otherwise intends to publicly
         disclose information about a Subject Invention, Subject Data, or
         Research Results, the other Party shall be provided thirty (30) days
         to review the proposed publication or disclosure to assure that
         Proprietary Information is protected.  The publication or other
         disclosure shall be delayed for up to thirty (30) additional days upon
         written request by any Party as necessary to preserve U.S. or foreign
         patent or other IP rights.


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              Article 10.  REPRESENTATIONS AND WARRANTIES

10.1          REPRESENTATIONS AND WARRANTIES OF NIH.  NIH hereby represents and
         warrants to the Collaborator that the Official signing this CRADA has
         authority to do so.

10.2          REPRESENTATIONS AND WARRANTIES OF THE COLLABORATOR.  The
         Collaborator hereby represents and warrants to NIH that the
         Collaborator has the requisite power and authority to enter into this
         CRADA and to perform according to its terms, and that the
         Collaborator's Official signing this CRADA has authority to do so.
         The Collaborator further represents that it is financially able to
         satisfy any funding commitments made in Appendix C.

              Article 11.  TERMINATION

11.1          TERMINATION BY MUTUAL CONSENT.  NIH and the Collaborator may
         terminate this CRADA, or portions thereof, at any time by mutual
         written consent.  In such event, the Parties shall specify the
         disposition of all property, inventions, patent or other IP
         applications, and other results of work accomplished or in progress,
         arising from or performed under this CRADA.

11.2          UNILATERAL TERMINATION.  Either NIH or the Collaborator may
         unilaterally terminate this entire CRADA at any time by giving written
         notice at least thirty (30) days prior to the desired termination
         date, and any rights accrued in property, patents, or other IP shall
         be disposed of as in 11.1.

11.3          STAFFING.  If this CRADA is mutually or unilaterally terminated
         prior to its expiration, funds will nevertheless remain available to
         NIH for continuing any staffing commitment made by the Collaborator
         pursuant to Article 5.1 above and Appendix C, if applicable, for a
         period of six (6) months after such termination.  If there are
         insufficient funds to cover this expense, the Collaborator agrees to
         pay the difference.

11.4          NEW COMMITMENTS.  No Party shall make new commitments related to
         this CRADA after a mutual or unilateral termination and shall, to the
         extent feasible, cancel all outstanding commitments and contracts by
         the termination date.

11.5          TERMINATION COSTS.  Concurrently with the exchange of final
         reports pursuant to Articles 4.2 and 5.3, NIH shall submit to the
         Collaborator for payment a statement of all costs incurred prior to
         the date of termination and for all reasonable termination costs
         including the cost of returning Collaborator property or removal of
         abandoned property.


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NIH Patent Policy Board, April 24, 1989

              Article 12.  DISPUTES

12.1          SETTLEMENT.  Any dispute arising under this CRADA which is not
         disposed of by agreement of the Principal Investigators shall be
         submitted jointly to the signatories of this CRADA.  If the
         signatories are unable to jointly resolve the dispute within thirty
         (30) days after notification thereof, the Assistant Secretary of
         Health (or his/her designee) shall propose a resolution.  Nothing in
         this section shall prevent any Party from pursuing any and all
         administrative and/or judicial remedies which may be available.

12.2          CONTINUATION OF WORK.  Pending the resolution of any dispute or
         claim pursuant to this Article, the Parties agree that performance of
         all obligations shall be pursued diligently in accordance with the
         direction of the NIH signatory.

              Article 13.  LIABILITY

13.1          PROPERTY.  The U.S. Government shall not be responsible for
         damages to any property of the Collaborator provided to it or acquired
         by it pursuant to this CRADA.

13.2          NO WARRANTIES.  Except as specifically stated in Article 10, the
         Parties make no express or implied warranty as to any matter
         whatsoever, including the conditions of the research or any invention
         or product, whether tangible or intangible, made, or developed under
         this CRADA, or the ownership, merchantability, or fitness for a
         particular purpose of the research or any invention or product.

13.3          INDEMNIFICATION.  The Collaborator agrees to hold the U.S.
         Government harmless and to indemnify the Government for all
         liabilities, demands, damages, expenses, and losses arising out of the
         use by the Collaborator for any purpose of the Subject Data, Research
         Results, and/or Subject Inventions produced in whole or in part by NIH
         employees under this CRADA, unless due to the negligence of NIH, its
         employees or agents.  The Collaborator shall be liable for any claims
         or damages it incurs in connection with this CRADA.  NIH have no
         authority to indemnify the Collaborator.

13.4          FORCE MAJEURE.  Neither Party shall be liable for any
         unforeseeable event beyond its reasonable control not caused by the
         fault or negligence of such Party, which causes such Party to be
         unable to perform its obligations under this CRADA, and which it has
         been unable to overcome by the exercise of due diligence.  In the
         event of the occurrence of such a force majeure event, the Party
         unable to perform shall promptly notify the other Party.  It shall
         further use its best efforts to resume performance as quickly as
         possible and shall suspend performance only for such period of time as
         is necessary as a result of the force majeure event.


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              Article 14.  MISCELLANEOUS

14.1          GOVERNING LAW.  The construction, validity, performance, and
         effect of this CRADA shall be governed by Federal Law, as applied by
         the Federal Courts in the District of Columbia.  Federal law and
         regulations will preempt any conflicting or inconsistent provisions in
         this CRADA.

14.2          ENTIRE AGREEMENT.  This CRADA constitutes the entire agreement
         between the Parties concerning the subject matter of this CRADA and
         supersedes any prior understanding or written or oral agreement.

14.3          HEADINGS.  Titles and headings of the sections and subsections of
         this CRADA are for the convenience of reference only, do not form a
         part of this CRADA, and shall in no way affect its interpretation.

14.4          WAIVERS.  None of the provisions of this CRADA shall be
         considered waived by any Party hereto unless such waiver is given in
         writing to the other Party.  The failure of a Party to insist upon
         strict performance of any of the terms and conditions hereof, or
         failure or delay to exercise any rights provided herein or by law,
         shall not be deemed a waiver of any rights of any Party.

14.5          SEVERABILITY.  The illegality or invalidity of any provisions of
         this CRADA shall not impair, affect, or invalidate the other
         provisions of this CRADA.

14.6          AMENDMENTS.  If either Party desires a modification to this
         CRADA, the Parties shall, upon reasonable notice of the proposed
         modification or extension by the Party desiring the change, confer in
         good faith to determine the desirability of such modification or
         extension.  Such modification shall not be effective until a written
         amendment is signed by the signatories to this CRADA or by their
         representatives duly authorized to execute such amendment.

14.7          ASSIGNMENT.  Neither this CRADA nor any rights or obligations of
         any Party hereunder shall be assigned or otherwise transferred by
         either Party without the prior written consent of the other Party.

14.8          NOTICES.  All notices pertaining to or required by this CRADA
         shall be in writing and shall be signed by an authorized
         representative and shall be delivered by hand or sent by certified
         mail, return receipt requested, with postage prepaid, to the addresses
         indicated on the signature page for each Party.  Notices regarding the
         exercise of license options shall be made pursuant to Article 8.2. Any
         Party may change such address by notice given to the other Party in
         the manner set forth above.


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14.9          INDEPENDENT CONTRACTORS.  The relationship of the Parties to this
         CRADA is that of independent contractors and not as agents of each
         other or as joint venturers or partners.  Each party shall maintain
         sole and exclusive control over its personnel and operations.
         Collaborator employees who will be working at NIH facilities may be
         asked to sign a Guest Researcher or Special Volunteer Agreement
         appropriately modified in view of the terms of this CRADA.

14.10         USE OF NAME OR ENDORSEMENTS.  By entering into this CRADA, NIH
         does not directly or indirectly endorse any product or service
         provided, or to be provided, whether directly or indirectly related to
         either this CRADA or to any patent or other IP license or agreement
         which implements this CRADA by its successors, assignees, or
         licensees.  The Collaborator shall not in any way state or imply that
         this CRADA is an endorsement of any such product or service by the
         U.S. Government or any of its organizational units or employees.

14.11         EXCEPTIONS TO THIS CRADA.  Any exceptions or modifications to
         this CRADA that are agreed to by the Parties prior to their execution
         of this CRADA are set forth in Appendix D.

14.12         REASONABLE CONSENT.  Whenever a Party's consent or permission is
         required under this CRADA, such consent or permission shall not be
         unreasonably withheld.

              Article 15.  DURATION OF AGREEMENT

15.1          DURATION.  It is mutually recognized that the duration of this
         project cannot be rigidly defined in advance, and that the
         contemplated time periods for various phases of the RP are only good
         faith guidelines subject to adjustment by mutual agreement to fit
         circumstances as the RP proceeds.  In no case will the term of this
         CRADA extend beyond the term indicated in the RP unless it is revised
         in accordance with Article 14.6.

15.2          SURVIVABILITY.  The provisions of Articles 4.2, 5.2, 5.3, 6.1,
         Articles 7 - 9, 11.3, 11.5, 12.1, 13.3, and 14.10 shall survive the
         termination of this CRADA.


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                                      APPENDIX A


                               NIH POLICY STATEMENT ON

                   COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENTS

                         AND INTELLECTUAL PROPERTY LICENSING

<PAGE>

NIH Patent Policy Board, April 24, 1989


                            NATIONAL INSTITUTES OF HEALTH
                                 POLICY STATEMENT ON
                   COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENTS
                         AND INTELLECTUAL PROPERTY LICENSING


    This statement sets forth the policies of the National Institutes of Health
(NIH) on various aspects of cooperative research and intellectual property
licensing.  These policies apply to the negotiation of NIH Cooperative Research
and Development Agreements (CRADAs).  License agreements for intellectual
property rights to inventions developed under a CRADA or through the NIH
intramural research programs, whether negotiated by NIH or the National
Technical Information Service on their behalf, will also incorporate these
policies.  This statement may be revised from time to time as NIH consider
appropriate.*

    To implement the Federal Technology Transfer Act of 1986 (FTTA, 15 U.S.C.
at Section 3710), Executive Order 12591 of April 10, 1987, orders Federal
laboratories to assist universities and the private sector in broadening our
national technology base by moving new knowledge from the research laboratory
into the development of new procedures and processes.  While Federal patent law
(35 U.S.C. at Sections 200-212) authorizes the licensing of Government-owned 
patent rights, the FTTA seeks to facilitate technological collaboration at
an earlier stage.  Thus, the FTTA authorizes Federal laboratories to enter into
CRADAs and to agree to grant intellectual property rights in advance to
collaborators for inventions made in whole or part by Federal employees under
the CRADA.  Besides assisting in the transfer of commercially useful
technologies from Federal laboratories to the marketplace, CRADAs make outside
resources more accessible to Federal laboratories.

    NIH, an agency of the Public Health Service (PHS) within the Department of
Health and Human Services (DHHS), is among the world's preeminent biomedical
research organizations.  Their general mission is to conduct biomedical and
behavioral research that will lead to the better health of the American people.
For the NIH investigator, this agency mission prescribes the exploration of
ideas, the communication of ideas and information to colleagues, and a
responsibility for the prompt and accurate publication of findings.  Under the
FTTA (15 U.S.C. at Section 3710a[a][2]), technology transfer, consistent with
mission responsibilities, is also a responsibility of each laboratory science
and engineering professional.

- ---------------

Questions or comments about this Statement and requests for updated versions
should be directed to the NIH Office of Technology Transfer at (301) 496-0750.
This Statement is effective on an interim basis, and will be revised after
October 1, 1989.

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NIH Patent Policy Board March 27, 1989



To support their mission, NIH have developed an interdisciplinary and
synergistic research environment that promotes the free exchange of ideas and
information.  In order to safeguard the collegiality and integrity of, as well
as public confidence in, the NIH research programs, the following cooperative
research technology transfer policies have been adopted.

    1.   RESEARCH FREEDOM:

    NIH investigators generally are free to choose the subject matter of their
research, consistent with the mission of their Institute and the research
programs of their Laboratories.  No CRADAs or license agreement may contravene
this freedom.

    2.   RESEARCH POLICY:

    NIH research results generally are disseminated freely through publication
in the scientific literature and presentations at public fora.  Brief delays in
this dissemination of research results may be permitted under a CRADA as
necessary in order to file corresponding patent or other intellectual property
applications.  NIH consider the filing of such applications to be an important
component of their research efforts.

    3.   COOPERATIVE RESEARCH AND DEVELOPMENT UNDER A CRADA:

    As defined by the FTTA (15 U.S.C. at Section 3710a[d][1]), a CRADA means
any agreement, between one or more Federal Laboratories and one or more non-
Federal parties, under which the Government provides personnel, services,
facilities, equipment, or other resources (but not funds), and the non-Federal
parties provide funds, personnel, services, facilities, equipment, or other
resources toward the conduct of specified research or development efforts.
Cooperative research and development activities are intended to facilitate the
transfer of Federally-funded research and development for use by State and local
governments, universities, and the private sector, particularly small business.

    4.   NIH CRADAS:

    As adopted by NIH, a CRADA is a standardized agreement intended to provide
an appropriate legal framework for, and to expedite the approval of, cooperative
research and development projects.  The use of CRADAs is encouraged for
cooperative efforts because they permit NIH to accept, retain, and use funds,
personnel services, and property to collaborating parties.  NIH may permit their
investigators to enter into CRADAs with collaborators who will make a
significant intellectual contribution to the research project undertaken or who
will contribute essential research materials or technical resources not
otherwise reasonably available.  While NIH welcome contributions to their gift
funds for research purposes, they do not view CRADAs as a general funding source
or a mechanism for sponsored research.  This approach to


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NIH Patent Policy Board March 27, 1989

implementing the FTTA has been chosen in order to maintain the public's
confidence in NIH through maintaining an independence from reliance on industry
funding.

    5.   SELECTION OF COLLABORATORS UNDER A CRADA:

    Collaborators under a CRADA may be suggested by potential Collaborators or
by NIH investigators.  Generally, the decision to initiate the approval process
for a CRADA is made by the involved NIH investigator and laboratory chief based
on scientific considerations and the desire for the public to benefit from the
commercialization of particular NIH research.  For some cooperative projects,
where the development and commercialization potential is more immediate relative
to the basic research aspects, NIH may seek a collaborator(s) which has both
scientific expertise and commercialization capabilities.  In certain areas of
research, e.g., where the Government has the intellectual lead or where both
scientific and commercialization capabilities are deemed essential at the
outset, NIH may competitively seek a collaborator through Federal Register
notification.  The PHS has also developed policy guidelines for ensuring
fairness of access to PHS laboratories such as NIH in the process of initiating
and developing CRADAs.

    6.   PROPRIETARY OR CONFIDENTIAL INFORMATION AND MATERIALS:

    NIH recognize that an effective collaborative research program may require
the disclosure of proprietary information to NIH investigators.  Although
agreements to maintain confidentiality are permitted under a CRADA,
collaborators should limit their disclosure of proprietary information to the
amount necessary to carry out the research plan of the CRADA.  The mutual
exchange of confidential information, e.g., patient data, should be similarly
limited.  NIH also recognize that cooperative research may require the exchange
of proprietary research materials.  Such materials may be used only for the
purposes specified in the research plan set forth in the CRADA.  All parties to
the CRADA will agree to keep CRADA research results confidential to the extent
permitted by law until they are published in the scientific literature or
presented at a public forum.

    7.   TREATMENT OF DATA AND RESEARCH
         PRODUCTS PRODUCED UNDER A CRADA:

    The NIH investigator and the collaborator will agree to exchange all data
and research products developed in the course of the research under a CRADA
whether developed solely by NIH, jointly with the collaborator, or solely by the
collaborator.  In general, tangible research products developed under a CRADA
will be shared equally by the parties to the CRADA.  All parties to a CRADA will
be free to utilize such data and research products for their own purposes.  Data
and research products developed solely by the collaborator may be designated as
proprietary by the collaborator when they are wholly separable from the data and
research products developed jointly with NIH investigators; however, except as
may be afforded through intellectual property rights that require public
disclosure of the protected subject matter (e.g., patents), NIH will not agree
to exclude others from utilizing or commercializing the data or research
products developed


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NIH Patent Policy Board March 27, 1989

solely by NIH investigators or jointly with the collaborator under a CRADA.

    8.   OWNERSHIP AND LICENSING OF NIH INTELLECTUAL PROPERTY RIGHTS:

    Pursuant to the FTTA (15 U.S.C. at Section 3710a[b][2]), a Federal
laboratory is authorized to own and license patent rights to inventions made in
whole or part by its employees under a CRADA.  The term "invention" is defined
at Section 3703(9) to mean any invention or discovery which is or may be
patentable or otherwise protected under Title 35, or any novel variety of plant
which is or may be protectable under the Plant Variety Protection Act (7 U.S.C.
Section 2321 et seq.). The patent law (35 U.S.C. at Section 207), authorizes the
ownership and licensing of intramural inventions.  Executive Order 12591 at
Section l(b)(1)(B) further authorizes the transfer of Government intellectual
property rights.  Although the FTTA speaks broadly of the transfer of
"technology," NIH do not have statutory authority to license (or to agree to
limit dissemination of) technology developed in whole or in part by their
investigators under a CRADA unless a patent, PVPA certificate, or other
intellectual property application has been filed for that technology.  NIH will
retain the Government ownership interest in, but license rights to, all
intellectual property rights to inventions developed solely through intramural
research or developed in whole or in part by their investigators under a CRADA.

    9.   GENERAL LICENSING POLICY:

    NIH recognize that under the FTTA and the patent licensing law to which 
it refers, Congress and the President have chosen to utilize the patent 
system as the primary mechanism for transferring Government inventions to the 
private sector.  The importance of patents to commercialization in the 
biomedical field is further reflected by the Drug Price Competition and 
Patent Term Restoration Act of 1984 (Pub. L. 98-419).  A fundamental 
principle of the patent system is that the owner of a patent have 
time-limited "right to exclude others from making, using, or selling the 
[patented] invention." The reason for such a period of exclusivity is to 
encourage industry to invest the resources necessary to bring an invention 
from the discovery stage through subsequent development, clinical trials, 
regulatory approvals, and ultimately into commercial production.  NIH 
accordingly are willing to grant exclusive commercialization licenses under 
their patent or other intellectual property rights in cases where substantial 
additional risks, time, and costs must be undertaken by a licensee prior to 
commercialization.  Under a CRADA, NIH are also willing, to agree to grant 
exclusive commercialization licenses in advance to collaborators.  NIH will 
attempt, however, to license their intramural inventions nonexclusively in 
cases where an invention reflects a relatively more advanced stage in its 
commercial development, e.g., when an NIH investigator invents a patentable 
new therapeutic use for a known and FDA-approved compound.

    Federal laboratories are authorized to negotiate license agreements for
Government-owned patent rights in intramural inventions pursuant to 35 U.S.C.
Section 207.  Although Section 207 does


                                         5 -

<PAGE>


NIH Patent Policy Board March 27, 1989

not apply to intellectual property license agreements authorized by the FTTA for
inventions made under a CRADA, NIH have adopted the following approach of
Section 207 for all license agreements:

              Each Federal Agency [may] ... grant nonexclusive, exclusive or
              partially exclusive licenses under Federally owned patent
              applications, patents, or other forms of protection ... on such
              terms and conditions ... as determined appropriate in the public
              interest.

    NIH have determined it to be appropriate in the public interest to grant
nonexclusive research licenses and either exclusive or nonexclusive
commercialization licenses to DHHS-owned intellectual property.

    10.  GOVERNMENT INTELLECTUAL PROPERTY RIGHTS:

    For inventions developed wholly by NIH investigators or jointly with a
collaborator under a CRADA, NIH are required by the FTTA at 15 U.S.C. Section
3710a(b)(2) to retain at least a nonexclusive, irrevocable, paid-up license to
practice the invention or to have the invention practiced throughout the world
by or on behalf of the U.S. Government.  When granting exclusive or partially
exclusive licenses to NIH intramural inventions, 35 U.S.C. Section 208, as
implemented by 37 C.F.R. Section 404.7(2)(i), requires the reservation of
similar Government rights.  NIH will not assert an ownership right in inventions
made solely by a collaborator under a CRADA, but will require the grant of a
research license, as described below, to the Government for inventions made
wholly by a collaborator under a CRADA.

    11.  RESEARCH LICENSES:

    NIH will reserve the right under any CRADA and intellectual property
license to grant nonexclusive licenses to make and to use the invention for
purposes of research involving the invention itself, and not for purposes of
commercial manufacture of, or in lieu of purchase as a commercial product for
use in other research.  The purpose of the research license is to facilitate
basic academic research.  NIH intend to consult with any involved
commercialization licensee(s) before granting research licenses to commercial
entities.

    12.  COMMERCIALIZATION LICENSES:

    NIH are willing to consider requests for nonexclusive or exclusive
commercialization licenses to intellectual property rights to inventions
developed under a CRADA or in the course of intramural research, pursuant to
applicable statutes and regulations.  Under a CRADA, NIH generally will grant a
time-limited option to negotiate, in good faith, the terms of a license that
fairly reflects the relative contributions of the parties, the risks incurred by
the collaborator, and the costs of subsequent research and development needed to
bring the results of CRADA research to the marketplace.  NIH contemplate the
drafting of a model invention license to serve as the


                                         6 -

<PAGE>

NIH Patent Policy Board March 27, 1989

starting point for license negotiations.  It is contemplated further that such a
model will reduce negotiations essentially to matters of execution fees, royalty
rates, and minimum annual royalties.  Royalty rates will be based on product
sales and the rates conventionally granted in the field identified in the
CRADA's research plan for inventions with reasonably similar commercial
potential.  Royalty rates generally will not exceed a rate within the range of 5
- - 8 % for exclusive commercialization licenses.  Contingent royalty schemes
based on, e.g., patent issuance or nonissuance, and clauses treating the
stacking of royalties or packaging of other inventions developed under the CRADA
may be provided.  Exclusive licensees will be expected to reimburse NIH for
intellectual property-related expenses, and may be permitted to offset such
reimbursement against future product royalties.

    13.  NONEXCLUSIVE COMMERCIALIZATION LICENSES:

    Unless a request for exclusive commercialization license is made under a
CRADA or submitted for an intramural invention, NIH will attempt to license
their inventions nonexclusively.  Such nonexclusive licenses generally will
follow the guidelines of 37 C.F.R., Part 404.

    14.  EXCLUSIVE COMMERCIALIZATION LICENSES:

    All NIH exclusive commercialization licenses will require the submission by
a prospective licensee of an acceptable development and commercialization plan
as described by 35 U.S.C. Section 209(a) and subsequent, periodic reports on
utilization of the invention as described by Section 209(f)(1).  All such plans
and reports will be treated in confidence and as privileged from disclosure
under the Freedom of Information Act.  Modification provisions as described by
Section 209(f)(2) - (4) may apply.  In appropriate cases, NIH may also reserve
the right to grant separate exclusive commercialization licenses in various
fields of use.  The remaining provisions of 35 U.S.C. Sections 200 - 212 will
also apply to licenses to NIH intramural inventions.

    NIH also consider the following provisions for exclusive commercialization
licenses to be necessary and appropriate in the public interest:

    (i)  the exclusive licensee must pledge its reasonable best efforts to
    commercialize a licensed invention, and the development and
    commercialization plan mentioned above may serve as the measure of such
    efforts;

    (ii) NIH shall have the right, after notice and opportunity to cure, to
    terminate or render nonexclusive any license granted: (1) if the licensee
    is not reasonably engaged in research, development, clinical trials,
    manufacturing, marketing, sublicensing, or other activities reasonably
    necessary to the expeditious commercial dissemination of the licensed
    inventions; or (2) when the licensee cannot reasonably satisfy unmet health
    and safety needs;

    (iii) in order to maximize the commercialization of the licensed invention
    in other


                                         7 -

<PAGE>

NIH Patent Policy Board March 27, 1989

    fields of use not utilized by the exclusive licensee through ongoing
    development, manufacturing, or sublicensing, NIH reserve the right to
    require the licensee to grant sublicenses to responsible applicants, on
    reasonable terms, in such other fields of use, unless the licensee can
    reasonably demonstrate that such a sublicense would be contrary to sound
    and reasonable business practice and the granting of the sublicense would
    not materially increase the availability to the public of the licensed
    invention; and

    (iv) exclusive licenses to DHHS inventions, whether developed under a CRADA
    or through intramural research, must agree to not unreasonably deny
    requests for sublicense or cross license rights from future CRADA
    collaborators when the possibility of acquiring such derivative rights is
    necessary in order to permit a proposed cooperative research project with
    NIH to go forward, and the exclusive licensee has been given a reasonable
    opportunity to join as a party to the proposed CRADA.

    15.  COMPLIANCE UNDER A CRADA WITH OTHER POLICIES:

    For research conducted pursuant to a CRADA, collaborators must agree to
comply with PHS and NIH policies and guidelines concerning, e.g., human subjects
research, the use of research animals including non-wild chimpanzees,
recombinant DNA, and other policy statements as may be promulgated from time to
time.

    16.  WAIVERS:

    NIH will consider requests to modify any of the foregoing policies in
special cases where public health exigencies or commercial situations warrant
such a modification.  Modifications dealing with business terms such as
royalties are not decided by the NIH investigators and should be discussed with
the appropriate NIH technology management personnel.

    17.   SPECIAL CONSIDERATION AND PREFERENCE UNDER A CRADA:

    NIH will give special consideration to entering into CRADAs with small
business firms and consortia involving small business firms; and will give
preference to business units located in the United States which agree to
manufacture substantially in the United States products which embody inventions
developed in the course of research under CRADAs.


                                         8 -

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                      APPENDIX B


                                    RESEARCH PLAN



TITLE OF CRADA: Development of a Live, Attenuated Cold-Adapted Influenza Vaccine

NIH/ADAMHA PRINCIPAL INVESTIGATOR:               Carole A. Heilman, Ph.D.
                                             ------------------------

COLLABORATOR PRINCIPAL INVESTIGATOR:        J. Leighton Read, M.D.
                                             ------------------------

TERM OF CRADA: (5) years.
              -----------

CONFLICTS OF INTEREST INFORMATION: Describe any relevant past, present, or
contemplated relationships between the NIH/ADAMHA Principal Investigator and
his/her Laboratory and the Collaborator in sufficient detail to permit reviewers
of this CRADA to determine whether or not any conflicts of interest exist:
[




                  ]

The Research Plan which follows this page should be concise but of sufficient
detail to permit reviewers of this CRADA to evaluate the scientific merit of the
proposed collaboration.  The RP should explain the scientific importance of the
collaboration and the research goals of NIH/ADAMHA and the Collaborator.  The
respective contributions in terms of expertise and/or research materials of
NIH/ADAMHA and Collaborator should be summarized.  Initial and subsequent
projects contemplated under the RP, and the time periods estimated for their
completion, should be described, and pertinent methodological considerations
summarized.  Pertinent literature references may be cited and additional
relevant information included.  Include additional pages to identify the
Principal Investigators of all other Parties to this CRADA.

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED
    Cold Adapted Influenza Vaccine CRADA                             Appendix B

1.     GOAL OF THIS CRADA

This CRADA is being undertaken to advance the CA influenza vaccine system from 
its current status to an FDA approved vaccine for use [



         ] To accomplish this goal, the NIH and Aviron must show that the
vaccine can be consistently manufactured and remain safe after transfer to a new
producer, and that [                                ] envisioned here is 
efficacious in the target populations.

Clinical trials will be conducted to enable FDA approval for [
                ] These trials as well as other studies will also be designed to
assess the cost-effectiveness of the vaccine system in order to support the
widest possible recommendations from the CDC's Advisory Committee on
Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) and
other recommending bodies.

2.  DETAILED DESCRIPTION OF THE RESEARCH PLAN

This application describes a preliminary clinical program based on the review
of the data.  It will be modified based on discussions with the FDA, as well as
the clinical investigators who will be participating in these trials and
investigators having extensive previous experience with this vaccine.

The specific studies proposed are:

    1.  [

              ]

          [




                                ]

    2.   [


AVIRON CONFIDENTIAL                                                       PAGE 1
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    Cold Adapted Influenza Vaccine CRADA                             Appendix B

                         ]

    3.   [







                             ]

    4.   [





                                                 ]


    5.   [





                                               ]

[











                                                             ]

AVIRON CONFIDENTIAL                                                       PAGE 2
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    Cold Adapted Influenza Vaccine CRADA                             Appendix B

[











             ]


AVIRON CONFIDENTIAL                                                       PAGE 3
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    Cold Adapted Influenza Vaccine CRADA                             Appendix B


3.  RESPECTIVE CONTRIBUTIONS OF THE PARTIES

Contributions to the main elements of this program are listed below.  Aviron and
the NIH intend to work collaboratively and in consultation with each other in
this program via joint committees involving the Principal Investigators and
other key contributors.  As NIH scientists and their contractors have extensive
experience with the evaluation and manufacture of this vaccine, it is expected
that their reasonable assistance will be provided to transfer know-how to Aviron
as required in support of this project.

1.  Development of Clinical Trial Plan                     [     ]

2 . Development of Clinical Protocol Design                [     ]

3 . Enrollment of Subjects by DMID contractors             [     ]

4.  Enrollment of Subjects in non-NIH sponsored sites      [     ]

5.  Ops Manual, Investigators Brochure, Case Report Forms  [     ]

6.  IND preparation and filing                             [     ]

7.  Supply of vaccine and placebo for trials defined here  [     ]

8.  Supply of challenge virus or inactivated vaccine       [     ]

9.  Development of a Data Safety and Monitoring Function   [     ]
    and the preparation of the relevant information
    needed for safety evaluation in pediatric populations

10. Site Monitoring                                        [     ]

11. Monitoring of VTEU sites for compliance with DHHS      [     ]
    regulations

12. Central Laboratory Facility and sample transport       [     ]

13. Standardized Reagents                                  [     ]

14. Data processing and statistical analysis               [     ]

15. Data reports for regulatory filings                    [     ]

16. Publication of results                                 [     ]

17. Manufacturing and Commercial Sale                      [     ]

18. Aviron travel, supplies, and personnel                 [     ]

19. Extra NIH travel, admin. support as delineated         [     ]
    in App. C                                      

20. Supply of all vaccine for investigator proposed        [     ]
    trials

AVIRON CONFIDENTIAL                                                       PAGE 4
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    Cold Adapted Influenza Vaccine CRADA                             Appendix B

[




                       ]

21. Special requirements of investigator proposed trials   [     ]

22. Special Clinical Trials (i.e., in high risk            [     ]
    populations)

23. IND preparation and filing for product licensure in    [     ]
    high risk populations


AVIRON CONFIDENTIAL                                                       PAGE 5
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

    Cold Adapted Influenza Vaccine CRADA                             Appendix B


4.  ABSTRACT OF THE PLAN FOR PUBLIC RELEASE

Influenza is a major health problem in the United States and all other countries
because annual epidemics typically cause several days of severe illness in
approximately one fifth of the population and many deaths occur in high risk
individuals.  Existing vaccines are effective, but poorly utilized due to
misunderstanding about vaccine safety and efficacy, and the unpleasant route of
administration via injection.  The individual components of an intranasally-
delivered live attenuated cold adapted influenza vaccine have been shown to be
safe and effective in testing over many seasons of influenza epidemics.  This
CRADA is intended to provide the necessary data for FDA approval regarding
safety and efficacy of a [               ] this vaccine which could be used on 
an annual basis to provide influenza prophylaxis [                      ][


                                                                               ]
of the population will also be evaluated.

5.  RELATED CRADAS

Aviron does not have any other CRADAs with the NIH.

6. - 8. Items for NIH Principal Investigator

6.  RELATED MTAs

[


                       ]

7.  RELATED PATENT APPLICATIONS AND PATENTS

None

8.  AVOIDANCE OF CONFLICT OF INTERESTS AND ASSURANCE OF FAIR ACCESS


See attached.


AVIRON CONFIDENTIAL                                                       PAGE 6
MAY 19, 1995

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

[Logo]



                            - DRAFT CLINICAL TRIAL PLAN -
           [                                                         ]

    Study     Phase      Age            Group         Number        Year
     -----     -----      ---            -----         ------        ----

    (1)       [                                                          ]



    (2)       [                                                          ]



    (3)       [                                                          ]



    (4)       [                                                          ]



    (5)       [                                                          ]

AVIRON

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED


- - [


[Logo]










                                                                               ]
AVIRON

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                      APPENDIX C
                 FINANCIAL AND STAFFING CONTRIBUTIONS OF THE PARTIES

I.  ANNUAL INSTITUTE (DMID, NIAID) CONTRIBUTIONS (INTERNAL):

    A.   Supply funds:    [     ]

    B.   Equipment funds: [     ](photocopier and/or computer equipment)

    C.   Travel funds:    [   ]

    D.   Time requirements of NIAID personnel: [     ] FTE Professional
                                               [     ] FTE Administrative

    E.   Contract support:  approx: [          ]      VTEUs*         YEAR 1**
          [                                          [               [
                                               ]

    *VTEUs=Vaccine Treatment and Evaluation Units



                                                                   ]

                                                      NON-VTEUs
                                                  [                ]
                                                                     ] Total

    **exact amounts spent at any one VTEU site may vary but the total
    expenditure per year for all VTEUs is expected to remain constant at
    approx:  [               ]

II. TO BE PROVIDED TO NIAID BY AVIRON ANNUALLY:

    A.   Supply funds:     [     ]

    B.   Equipment funds:  [     ]

    C.   Travel funds:     [     ]

                         travel to VTEU sites
                         travel to scientific meetings

    D.   Personnel funds:  [     ]

- --------------------------------------------------------------------------------
                                    NIAID/CRADA:
                                      Appendix C

                                                                     Page 1 of 2

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                 [


                                                             ]

II. continued

    E.   Contract support:  [   ]

    F.   Overhead:  [                                    ]

    NIAID has the discretion to transfer funds between categories if it is
    appropriate to support objectives of the CRADA.

    NIAID has the authority to carry over funds from one year to the next
    throughout the CRADA as long as funding is used in direct support of the
    CRADA, as outlined in Appendix C.

III. ANNUAL COMPANY CONTRIBUTIONS (INTERNAL): All dollars in Thousands ($000)

                             Year 1    Year 2    Year 3    Year 4    Year 5
                              ------    ------    ------    ------    ------
    A.   Supply funds:       $  [                                          ]

    B.   Equipment funds:    $  [                                          ]
         (see note 1)

    C.   Travel funds:       $  [                                          ]

III. ANNUAL COMPANY CONTRIBUTIONS (INTERNAL) continued
    All Dollars in Thousands (5000)

                             Year 1    Year 2    Year 3    Year 4    Year 5
                              ------    ------    ------    ------    ------

    D.   Time requirements of  $  [                                          ]
         Company personnel

    E.   Contract support:     $  [                                          ]
         (See Note 2)


Notes:

(1) Equipment includes dedicated facility requirements.

(2) Contract support represents development and manufacturing to be performed
    by a third party for Aviron, and research support to University of Michigan
    and other clinical support.


- --------------------------------------------------------------------------------
                                    NIAID/ CRADA:
                                      Appendix C

                                                                     Page 2 of 2

<PAGE>

                                      APPENDIX D

                      EXCEPTIONS OR MODIFICATIONS TO THIS CRADA


- --------------------------------------------------------------------------------
                            NIAID/Aviron CRADA - #A1000062
                                      Appendix D

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED
NIH Patent Policy Board, April 24, 1989

                    COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

              Article 1. INTRODUCTION

    This Cooperative Research and Development Agreement (CRADA) between NIH and
the Collaborator will be effective when signed by all parties.  By signing this
CRADA, the Collaborator acknowledges that it has received and read a copy of the
Policy Statement on Cooperative Research and Development Agreements and
Intellectual Property Licensing which is attached as Appendix A.  The research
and development project(s) which will be undertaken by each of the Parties in
the course of this CRADA are detailed in the Research Plan (RP) which is
attached as Appendix B. The funding and staffing commitments of the Parties are
set forth in Appendix C. Any exceptions or changes to the CRADA are set forth in
Appendix D.

              Article 2. DEFINITIONS

    As used in this CRADA, the following terms shall have the indicated
meanings:

2.1             "Cooperative Research and Development Agreement" or "CRADA" 
      means this agreement, entered into by NIH pursuant to the Federal 
      Technology Transfer Act of 1986 and Executive Order 12591 of October 10, 
      1987.

2.2             "Confidential Information": shall mean all technical, 
      scientific, product, manufacturing, production, business, and 
      financial information, [               
                     ] and disclosed by either Party to the other under this
      CRADA, which are [
                                     ] provided that such information:

      2.2.1     is not publicly known or available from other sources who
                are not under a confidentiality obligation to the source of
                the information;

      2.2.2     has not been made available by the disclosing Party to
                others without a confidentiality obligation;

      2.2.3     is not already known by or available to the receiving Party
                without a confidentiality obligation; or

      2.2.4     cannot be demonstrated through adequate written
                documentation as being independently developed or acquired
                by the receiving Party without reference to or reliance upon
                such Confidential Information.

                [

                Heilman/Aviron CRADA (AI#000062) Appendix D page 2

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

                         ] All information to be deemed confidential under this
         Agreement [

              ] Notwithstanding the foregoing, the Parties may disclose any 
         information relating to potential hazards or cautionary warnings 
         associated with production, handling, or use of the subject matter 
         of the Research Plan of this CRADA to any governmental authority in 
         accordance with applicable laws and regulations.

2.3           "Subject Invention" means any invention, conceived or reduced to 
         practice in the performance of research under this CRADA, that may be 
         patentable under 35 U.S.C. Section 101 or Section 161, protectable 
         under 7 U.S.C. Section 2321, or otherwise protectable by other types 
         of U.S. or foreign "Intellectual Property" ("IP") right.

2.4           "Government" means the U.S. Government and any of its agencies.

2.5           "Research Plan" or "RP" means the statement in Appendix B of the
         respective research and development commitments of the Parties to this
         CRADA.

2.6           "Principal Investigator" or "PI" means the persons designated
         respectively by the Parties to this CRADA who will be responsible for
         the scientific and technical conduct of the RP.

2.7           "Clinical Data and Research Results" means all information, data,
         tangible materials, and results[




                     ]

2.8           "Raw Data" means the[



                                           ]

              Article 3. COOPERATIVE RESEARCH

3.1           RESEARCH TEAM.  The Parties agree to establish a joint research
         and development team (hereinafter referred to as the "Team")
         comprising at least the Principal Investigators designated pursuant to
         Article 3.3 to conduct and monitor the research in accordance with the
         RP.  Although the members of the Team shall be


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 3

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

         considered as having been delegated to the Team, they shall continue
         to remain employed by their respective employers under their
         respective terms of employment.

3.2           REVIEW OF WORK.  Periodic conferences shall be held by the Team
         to review work progress.  It is understood that the nature of this
         cooperative research precludes a guarantee of its completion within
         the specified period of performance or limits of allocated financial
         or staffing support.  Accordingly, research under this CRADA is to be
         performed on a best efforts basis.

3.3           PRINCIPAL INVESTIGATORS.  NIH research work under this CRADA will
         be performed by the Laboratory identified in the RP, and the NIH
         Principal Investigator (PI) designated in the RP will be responsible
         for the scientific and technical conduct of this project on behalf of
         NIH.  Also designated in the RP is the Collaborator PI, who will be
         responsible for the scientific and technical conduct of this project
         on behalf of the Collaborator.

3.4           RESEARCH PLAN CHANGE.  The RP may be modified by mutual written
         consent of the Principal Investigators.  Substantial changes in the
         scope of the RP will be treated as amendments under Article 14.6.

3.5           FILING OF INVESTIGATIONAL NEW DRUG APPLICATION (IND).  The
         Parties understand that Collaborator is to file and own any new IND
         for the technology which is the subject of this CRADA.  Collaborator
         will supply all manufacturing information required by the U.S. Food
         and Drug Administration ("FDA") in support of such IND.
         [



                           ] NIH grants Collaborator an exclusive right of
         reference to[                                           ] and any new[
                                            ]shall be confidential and made
         available exclusively to Collaborator for use in obtaining regulatory
         approval for the commercialization and marketing of[

                                ]NIH shall take appropriate precautions to
         ensure that Collaborator may review, cross reference or, as
         appropriate, otherwise use[                      ]in conducting
         critical trials within the scope of this CRADA, and in fulfilling all
         the requirements necessary for obtaining FDA approval to market
         products incorporating the technology which is the subject of this
         CRADA.

              Article 4. REPORTS

4.1           INTERIM REPORTS.  The Parties shall exchange formal written
         interim progress reports on a schedule agreed to by the PIs, but at
         least within six (6) months after this


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 4

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

         CRADA becomes effective and at least within every six (6) months
         thereafter.  Such reports shall set forth the technical progress made,
         identifying such problems as may have been encountered and
         establishing goals and objectives requiring further effort.

4.2           FINAL REPORTS.  The Parties shall exchange final reports of their
         results within four (4) months after completing the projects
         described in the RP or after the termination of this CRADA.

              Article 5. FINANCIAL AND STAFFING OBLIGATIONS

5.1           NIH AND COLLABORATOR CONTRIBUTIONS.  The NIH contribution to the
         RP in the form of[

                                                                    ]The
         Collaborator contribution to the RP in the form of[


                                                 ]

5.2           INSUFFICIENT AND EXCESS FUNDS.  NIH shall not be obligated to
         perform any of the research specified herein or to take any other
         action required by this CRADA if the funding is not provided as set
         forth in Appendix C. NIH shall return excess funds to the Collaborator
         when it sends its final fiscal report pursuant to Article 5.3, except
         for staffing support pursuant to Article 11.3.

5.3           ACCOUNTING RECORDS.  NIH shall maintain separate and distinct
         current accounts, records, and other evidence supporting all its
         obligations under this CRADA, and shall provide the Collaborator an
         annual report reflecting the use of the Collaborator's funds and a
         final such fiscal report at the time that final reports are
         exchanged pursuant to Article 4.2.

              Article 6. TITLE TO PROPERTY

6.1           CAPITAL EQUIPMENT. The purchase or use of capital equipment to
         carry out this CRADA does not affect the ownership rights that would
         otherwise apply. Equipment purchased by NIH with funds provided by the
         Collaborator shall be the property of NIH. All capital equipment
         provided under this CRADA by one party for the use of another Party
         remains the property of the providing Party unless other disposition
         is mutually agreed upon in writing by the PIs. If title to this
         equipment remains with the providing Party, that Party is responsible
         for maintenance of the equipment and the costs of its transportation
         to and from the site where it will be used.

              Article 7. INTELLECTUAL PROPERTY RIGHTS AND APPLICATIONS

7.1           REPORTING. The Parties shall promptly report to each other in
         writing each


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 5

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

         Subject Invention resulting from the research conducted under this
         CRADA that is reported to them by their respective employees.  Such
         reports shall be treated in confidence by the receiving Party until
         such time as a patent or other Intellectual Property (IP) application,
         as appropriate, claiming that Subject Invention has been filed.
         Because of the royalty sharing provisions for Government inventors in
         the Federal Technology Transfer Act of 1986, and in view of Article
         8.2 of this CRADA which grants the Government only a research license
         on inventions made solely by the Collaborator, the Collaborator
         acknowledges a special duty to report all Subject Inventions to NIH so
         that NIH may determine whether or not inventorship properly includes
         NIH investigators.

7.2           COLLABORATOR EMPLOYEE INVENTIONS. The Collaborator may elect to
         retain IP rights to any Subject Invention made solely by a
         Collaborator employee. The Collaborator shall notify NIH promptly upon
         making this election. If the Collaborator does not elect to retain its
         IP rights, the Collaborator shall offer to assign these IP rights to
         the Subject Invention to NIH pursuant to Article 7.5. If NIH declines
         such assignment, the Collaborator may release its IP rights to
         employee inventors pursuant to Article 7.6.

7.3           NIH EMPLOYEE INVENTIONS. NIH, on behalf of the U.S. Government,
         may elect to retain IP rights to each Subject Invention made solely by
         NIH employees. If NIH does not elect to retain IP rights, NIH shall
         offer to assign these IP rights to such Subject Invention to the
         Collaborator pursuant to Article 7.5. If the Collaborator declines
         such assignment, NIH may release IP rights in such Subject Invention
         to its employee inventors pursuant to Article 7.6.

7.4           JOINT INVENTIONS.  Each Subject Invention made jointly by NIH and
         Collaborator employees shall be jointly owned by NIH and the
         Collaborator. The Collaborator may elect to file the joint patent or
         other IP application(s) thereon and shall notify NIH promptly upon
         making this election. If the Collaborator decides to file such
         applications, it shall do so in a timely manner and at its own
         expense. If the Collaborator does not elect to file such
         application(s), NIH, on behalf of the U.S. Government, shall have the
         right to file the joint applications in a timely manner and at its own
         expense. If either Party decides not to retain its IP rights to a
         jointly owned Subject Invention, it shall offer to assign such rights
         to the other Party pursuant to Article 7.5. If the other Party
         declines such assignment, the offering Party may release its IP rights
         to employee inventors pursuant to Article 7.6.

7.5           FILING OF PATENT APPLICATIONS. With respect to Subject Inventions
         made by the Collaborator as described in Article 7.2 or by NIH as
         described in Article 7.3, a Party exercising its right to retain IP
         rights to a Subject Invention agrees to file patent or other IP
         applications in a timely manner and at its own expense. The Party may
         elect not to file a patent or other IP application thereon in any
         particular country or


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 6

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         countries, provided it so advises the other Party ninety (90) days
         prior to the expiration of any applicable filing deadline, priority
         period, or statutory bar date, and hereby agrees to assign its IP
         right, title, and interest in such country or countries to the Subject
         Invention to the other Party and to cooperate in the preparation and
         filing of a patent or other IP applications.  In any countries in
         which title to patent or other IP rights is transferred to the
         Collaborator, the Collaborator agrees that NIH inventors will share in
         any royalty distribution that the Collaborator pays to its own
         inventors.

7.6           RELEASE TO INVENTORS.  In the event neither of the Parties to the
         CRADA elects to file a patent or other IP application on a Subject
         Invention, either or both (if a joint invention) may release their IP
         rights to their respective employee inventor(s) with a non-exclusive,
         non-transferrable, royalty-free license being retained by each Party.

7.7           PATENT EXPENSES.  The expenses attendant to the filing of patent
         or other IP applications generally shall be paid by the Party filing
         such application.  If an exclusive license to any Subject Invention is
         granted to the Collaborator, the Collaborator shall reimburse NIH for
         the reasonable past and Collaborator-approved ongoing funds expended
         worldwide for filing, prosecuting, and maintaining any applications
         claiming such exclusively-licensed inventions and any patents or other 
         IP grants that may issue on such applications.  The Collaborator may
         waive its exclusive license rights on any application, patent, or
         other IP grant at any time, and incur no subsequent compensation
         obligation for that application, patent, or IP grant.

7.8           PROSECUTION OF INTELLECTUAL PROPERTY APPLICATIONS.  Each Party
         shall provide the other Party with copies of the applications it files
         on any Subject Invention along with the power to inspect and make
         copies of all documents retained in the patent or other IP application
         files by the applicable patent or other IP office.  The Parties agree
         to consult with each other with respect to the prosecution of NIH
         Subject Inventions described in Article 7.3 and joint Subject
         Inventions described in Article 7.4. If the Collaborator elects to
         file and prosecute IP applications on joint Subject Inventions
         pursuant to Article 7.4, NIH will be granted an associate power of
         attorney (or its equivalent) on such IP applications.

              Article 8. LICENSING

8.1           OPTION FOR EXCLUSIVE COMMERCIALIZATION LICENSE.  With respect to
         Government IP rights to any Subject Invention not made solely by the
         Collaborator's employees for which a patent or other IP application is
         filed.  NIH hereby grants to the Collaborator[




                                        ]The license will specify the licensed
         fields of use,


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 7

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

         breadth of exclusivity, and royalties.  Royalty rates will be based on
         product sales and the rates conventionally granted in the field
         identified in the RP for inventions with reasonably similar commercial
         potential.  Royalty rates generally will not exceed a rate within the
         range of[                                ] Contingent royalty schemes
         based on, e.g., patent issuance or non-issuance, and provisions 
         treating the stacking of royalties or packaging of other licensed 
         inventions developed under this CRADA may be provided.  Exclusive 
         licensees will be expected to reimburse NIH for IP expenses related to 
         each licensed intellectual property, and may be permitted to offset 
         such reimbursement against future product royalties.

8.2           EXERCISE OF LICENSE OPTION.  The option of Article 8.1 must be
         exercised by written notice mailed within three (3) months after the
         patent or other IP application is filed to the NIH Office of
         Technology Transfer, 6011 Executive Boulevard, Suite 325, Rockville,
         MD 20852.  NIH shall promptly advise Collaborator of the filing of
         any patent or other IP application. Exercise of this option by the
         Collaborator initiates a negotiation period that expires nine (9)
         months after the patent or other IP application filing date.  If the
         last proposal by the Collaborator has not been responded to in writing
         by the NIH within this nine (9) month period, the negotiation period
         shall be extended to expire three (3) months after NIH so responds,
         during which month the Collaborator may accept in writing the final
         license proposal of NIH.   After that time, NIH will be free to
         license such IP rights to others.  In the event that NIH and the
         Collaborator do not enter into a license during this negotiation
         period, NIH agrees not to make an offer on more favorable terms to a
         third Party without first offering the Collaborator those more
         favorable terms.

8.3           GOVERNMENT INTELLECTUAL PROPERTY RIGHTS.  For inventions developed
         wholly by NIH investigators or jointly with a Collaborator under this
         CRADA, NIH is required by the Federal Technology Transfer Act of 1986
         (15 U.S.C. Section 3710a[b](2)) to retain at least a nonexclusive,
         irrevocable, paid-up license to practice the invention or to have the
         invention practiced throughout the world by or on behalf of the U. S.
         Government.  For inventions developed wholly by the Collaborator under
         this CRADA, the Collaborator agrees to grant a research license as
         described in Article 8.4 to the Government.  In the event the
         Collaborator is granted one or more exclusive licenses to inventions
         under Article 8.1 of this CRADA, NIH shall not grant to any third
         Party any commercialization license with respect to any such invention
         for the same field of use as granted to Collaborator.  NIH shall be
         free to grant commercialization licenses for any fields of use not
         specified in an exclusive license to the Collaborator.

8.4           RESEARCH LICENSES.[


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 8

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989






                                                    ]

8.5           JOINT INVENTIONS NOT EXCLUSIVELY LICENSED.  In the event that the
         Collaborator does not acquire an exclusive commercialization license
         to IP rights in joint Subject Inventions described in Article 7.4,
         then each Party shall have the right to use the joint Subject
         Invention and to license its use to others.  The Parties may agree to
         a joint licensing approach for such IP rights.

              Article 9. PROPRIETARY RIGHTS AND PUBLICATION

9.1           RIGHT OF ACCESS.  NIH and the Collaborator agree to exchange all
         Clinical Data, Research Results and Raw Data produced in the course of
         research under this CRADA, whether developed solely by NIH, jointly
         with the Collaborator, or solely by the Collaborator.  Tangible
         research products developed under a CRADA will be shared equally by
         the Parties to the CRADA unless other disposition is agreed to by the
         Principal Investigators.  All Parties to the CRADA will be free to
         utilize Subject Data and Research Results for their own purposes,
         consistent with their obligations under this CRADA.

         [



                   Heilman/Aviron CRADA (AI#000062) Appendix D page 9

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

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                                                 ]

9.2           OWNERSHIP AND USE OF CLINICAL DATA AND RESEARCH RESULTS AND RAW
         DATA.  Subject to the sharing requirements of Article 9.1, all
         Clinical Data and Research Results and all Raw Data, whether produced
         solely by one party's investigators and other employees and personnel
         or jointly by both parties' investigators and other employees and
         personnel will be[








                        ]

9.3           CONFIDENTIAL INFORMATION.  Each Party agrees to limit its
         disclosure of Proprietary Information to the amount necessary to carry
         out the Research Plan of this CRADA, and shall place a confidentiality
         notice on all such information.  Materials required for the RP may
         also be designated as Confidential Information from the party
         receiving Confidential Information.  Each party receiving Confidential
         Information from the other Party agrees that any information so
         designated shall be used by it only for the purposes described in the
         attached Research Plan.  Any party may object to the designation of
         information as Confidential Information by another Party and may
         decline to accept such information.  In addition to all other
         information identified as Confidential Information as set forth in
         Section 2.2 above, data and research products developed solely by the
         Collaborator may be designated as Confidential Information when they
         are wholly separable from the data and research products developed
         jointly with NIH investigators, and advance designation of such data
         and product categories is set forth in the Research Plan.  The
         exchange of confidential information, e.g., patient data, should be
         similarly limited and treated.  Unless disclosure is otherwise
         mutually agreed upon, all Parties to this CRADA agree to keep CRADA
         Clinical Data, Research Results, and Raw Data confidential, to the
         extent permitted by law, until they are published or corresponding
         patent or other IP application(s) have been published.  The use of
         Confidential Information shall be governed by Sections 9.4 and 9.6
         below.  However, nothing contained herein shall be deemed to restrict
         publication of summary clinical data consistent with NIH policy.
         Information provided to one or more third parties pursuant to
         Confidential Disclosure Agreements in connection with their
         determination of the desirability of entering into a CRADA for cold
         adapted


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 10

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

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         influenza vaccine development shall be maintained as Confidential
         Information.

9.4           PROTECTION OF CONFIDENTIAL INFORMATION.  No Confidential
         information obtained or disclosed in the conduct of research or as a
         result of activities under this CRADA shall be disclosed, copied,
         reproduced, or otherwise made available to any other person or entity
         without the consent of the owning Party except as required under
         court order or the Freedom of Information Act (5 U.S.C. Section 552).
         Each Party agrees to use its best efforts to maintain the
         confidentiality of Proprietary Information.  Each Party agrees that
         the other Party is not liable for the disclosure of Confidential
         Information it determines may not lawfully be withheld, provided the
         concerned Party has been given an opportunity to obtain a court order
         to enjoin disclosure.

9.5           DURATION OF CONFIDENTIALITY OBLIGATION.  Except as provided in
         Section 9.6, the obligation to maintain the confidentiality of
         Confidential Information shall expire at the earlier of the date when
         the information is no longer Proprietary Information as defined in
         Article 2.2 or [        ] after the expiration or termination date of
         this CRADA; provided that upon the expiration of this [          ]
         period, the Collaborator may request a [          ] extension period
         to this term when necessary to protect Confidential Information
         relating to products not yet commercialized.  NIH may not unreasonably
         deny such request and shall, upon such notice, refrain from disclosing
         any such Confidential Information for said [          ] extension
         period.  If one or more third parties were provided access to certain
         proprietary information pursuant to Confidential Disclosure Agreements
         in connection with their determination of the desirability of entering
         into a CRADA for cold adapted Influenza vaccine development, NIH shall
         require such third party or parties to maintain the confidentiality of
         such information for the term of this CRADA plus any extension granted
         under this Article.

9.6           CONSISTENCY WITH POLICIES OF THE FOOD AND DRUG ADMINISTRATION
         (FDA).  Notwithstanding any other provisions of this Agreement, all
         information submitted to FDA under this Agreement by Collaborator or
         NIH shall be treated as Confidential Information by NIH; provided that
         if FDA determines that certain information submitted to it is not
         Confidential, NIH must treat such information as Confidential only if
         such information is "Confidential Information" as defined in Article
         2.2. If the information is submitted to FDA solely by Collaborator,
         NIH's confidentiality obligations will not begin until Collaborator
         has provided notice of the submission.

9.7           PUBLICATION.  The Parties are encouraged to make publicly
         available the results of their research.  Before either Party submits
         a paper or abstract for publication or


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 11

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

NIH Patent Policy Board, April 24, 1989

         otherwise intends to publicly disclose information about a Subject
         Invention, [                             ] the other Party shall be
         provided thirty (30) days to review the proposed publication or 
         disclosure. Such publication or other disclosure shall be delayed for 
         up to sixty (60) additional days upon written request by any Party as 
         necessary to preserve U.S. or foreign patent, trade secret, or other IP
         rights.

              Article 10.  REPRESENTATIONS AND WARRANTIES

10.1          REPRESENTATIONS AND WARRANTIES OF NIH.  NIH hereby represents and
         warrants to the Collaborator that the Official signing this CRADA has
         authority to do so.

10.2          REPRESENTATIONS AND WARRANTIES OF THE COLLABORATOR.  The
         Collaborator hereby represents and warrants to NIH that the
         Collaborator has the requisite power and authority to enter into this
         CRADA and to perform according to its terms, and that the
         Collaborator's Official signing this CRADA has authority to do so.
         The Collaborator further represents that it is financially able to
         satisfy any funding commitments made in Appendix C.

              Article 11. TERMINATION

11.1          TERMINATION BY MUTUAL CONSENT.  NIH and the Collaborator may
         terminate this CRADA, or portions thereof, at any time by mutual
         written consent.  In such event, the Parties shall specify the
         disposition of all property, inventions, patent or other IP
         applications, and other results of work accomplished or in progress,
         arising from or performed under this CRADA.

11.2          MATERIAL BREACH.  Either NIH or the Collaborator may propose
         termination of this CRADA by giving written notice of a material
         breach of the other party's obligations as specified herein.  Any such
         notice shall specify the obligation or obligations believed to be
         breached and actions that may be taken to cure such breach.  After
         receipt of such notice, the parties agree to negotiate in good faith in
         an effort to achieve resolution and avoid termination.  Termination
         may not become effective until at least ninety (90) days following
         receipt of such notice in order to provide the notified party
         opportunity to respond.  For purposes of this Article, material breach
         shall mean substantial failure by or inability of either party to
         fulfill obligations under the CRADA.

11.3          STAFFING.  If this CRADA is mutually or unilaterally terminated
         prior to its

                   Heilman/Aviron CRADA (AI#000062) Appendix D page 12

<PAGE>

NIH Patent Policy Board, April 24, 1989

         expiration, funds will nevertheless remain available to NIH for
         continuing any staffing  commitment made by the Collaborator pursuant
         to Article 5.1 above and Appendix C, if applicable, for a period of
         six (6) months after such termination. If there are insufficient funds
         to cover this expense, the Collaborator agrees to pay the difference.

11.4          NEW COMMITMENTS. No Party shall make new commitments related to
         this CRADA after a mutual or unilateral termination and shall, to the
         extent feasible, cancel all outstanding commitments and contracts by
         the termination date.

11.5          TERMINATION COSTS. Concurrently with the exchange of final
         reports pursuant to Articles 4.2 and 5.3, NIH shall submit to the
         Collaborator for payment a statement of all costs incurred prior to
         the date of termination which Collaborator has agreed to pay pursuant
         to Appendix C, if applicable, and for all reasonable termination costs
         including the cost of returning Collaborator property or removal of
         abandoned property.

              Article 12. DISPUTES

12.1          SETTLEMENT. Any dispute arising under this CRADA which is not
         disposed of by agreement of the Principal Investigators shall be
         submitted jointly to the signatories of this CRADA. If the signatories
         are unable to jointly resolve the dispute within thirty (30) days
         after notification thereof, the Assistant Secretary of Health (or
         his/her designee) shall propose a resolution. Nothing in this section
         shall prevent any Party from pursuing any and all administrative
         and/or judicial remedies which may be available.

12.2          CONTINUATION OF WORK. Pending the resolution of any dispute or
         claim pursuant to this Article, the Parties agree that performance of
         all obligations shall be pursued diligently in accordance with the
         direction of the NIH signatory.

              Article 13.  LIABILITY

13.1          PROPERTY.  The U.S. Government shall not be responsible for
         damages to any property of the Collaborator provided to it or acquired
         by it pursuant to this CRADA.

13.2          NO WARRANTIES.  Except as specifically stated in Article 10, the
         Parties make no express or implied warranty as to any matter
         whatsoever, including the conditions of the research or any invention
         or product, whether tangible or intangible, made, or developed under
         this CRADA, or the ownership, merchantability, or fitness for a
         particular purpose of the research or any invention or product.


                   Heilman/Aviron CRADA (AI#000062) Appendix D page 13

<PAGE>

NIH Patent Policy Board, April 24, 1989


13.3          INDEMNIFICATION.  The Collaborator agrees to hold the U.S.
         Government harmless and to indemnify the Government for all
         liabilities, demands, damages, expenses, and losses arising out of the
         use by the Collaborator for any purpose of the Subject Data, Research
         Results, and/or Subject Inventions produced in whole or in part by NIH
         employees under this CRADA, unless due to the negligence of NIH, its
         employees or agents. The Collaborator shall be liable for any claims
         or damages it incurs in connection with this CRADA. NIH has no
         authority to indemnify the Collaborator.

13.4          FORCE MAJEURE. Neither Party shall be liable for any
         unforeseeable event beyond its reasonable control not caused by the
         fault or negligence of such Party, which causes such Party to be
         unable to perform its obligations under this CRADA, and which it has
         been unable to overcome by the exercise of due diligence. In the event
         of the occurrence of such a force majeure event, the Party unable to
         perform shall promptly notify the other Party. It shall further use
         its best efforts to resume performance as quickly as possible and
         shall suspend performance only for such period of time as is necessary
         as a result of the force majeure event.

              Article 14. MISCELLANEOUS

14.1          GOVERNING LAW. The construction, validity, performance, and
         effect of this CRADA shall be governed by Federal Law, as applied by
         the Federal Courts in the District of Columbia. Federal law and
         regulations will preempt any conflicting or inconsistent provisions in
         this CRADA.

14.2          ENTIRE AGREEMENT. This CRADA constitutes the entire agreement
         between the Parties concerning the subject matter of this CRADA and
         supersedes any prior understanding or written or oral agreement.

14.3          HEADINGS. Titles and headings of the sections and subsections of
         this CRADA are for the convenience of reference only, do not form a
         part of this CRADA, and shall in no way affect its interpretation.

14.4          WAIVERS. None of the provisions of this CRADA shall be considered
         waived by any Party hereto unless such waiver is given in writing to
         the other Party. The failure of a Party to insist upon strict
         performance of any of the terms and conditions hereof, or failure or
         delay to exercise any rights provided herein or by law, shall not
         be deemed a waiver of any rights of any Party.

14.5          SEVERABILITY. The illegality or invalidity of any provisions of
         this CRADA shall not impair, affect, or invalidate the other
         provisions of this CRADA.


                   Heilman/Aviron CRADA (AI#000062) page 14

<PAGE>

NIH Patent Policy Board, April 24, 1989

14.6          AMENDMENTS.  If either Party desires a modification to this
         CRADA, the Parties shall, upon reasonable notice of the proposed
         modification or extension by the Party desiring the change, confer in
         good faith to determine the desirability of such modification or
         extension.  Such modification shall not be effective until a written
         amendment is signed by the signatories to this CRADA or by their
         representatives duly authorized to execute such amendment.

14.7          ASSIGNMENT.  Neither this CRADA nor any rights or obligations of
         any Party hereunder shall be assigned or otherwise transferred by
         either Party without the prior written consent of the other Party.

14.8          NOTICES.  All notices pertaining to or required by this CRADA
         shall be in writing and shall be signed by an authorized
         representative and shall be delivered by hand or sent by certified
         mail, return receipt requested, with postage prepaid, to the addresses
         indicated on the signature page for each Party.  Notices regarding the
         exercise of license options shall be made pursuant to Article 8.2. Any
         Party may change such address by notice given to the other Party in
         the manner set forth above.

14.9          INDEPENDENT CONTRACTORS.  The relationship of the Parties to this
         CRADA is that of independent contractors and not as agents of each
         other or as joint venturers or partners. Each party shall maintain
         sole and exclusive control over its personnel and operations.
         Collaborator employees who will be working at NIH facilities may be
         asked to sign a Guest Researcher or Special Volunteer Agreement
         appropriately modified in view of the terms of this CRADA.

14.10         USE OF NAME OR ENDORSEMENTS. By entering into this CRADA, NIH
         does not directly or indirectly endorse any product or service
         provided, or to be provided, whether directly or indirectly related to
         either this CRADA or to any patent or other IP license or agreement
         which implements this CRADA by its successors, assignees, or
         licensees. The Collaborator shall not in any way state or imply that
         this CRADA is an endorsement of any such product or service by the
         U.S. Government or any of its organizational units or employees.

14.11         EXCEPTIONS TO THIS CRADA. Any exceptions or modifications to this
         CRADA that are agreed to by the Parties prior to their execution of
         this CRADA are set forth in Appendix D.

14.12         REASONABLE CONSENT. Whenever a Party's consent or permission is
         required under this CRADA, such consent or permission shall not be
         unreasonably withheld.

              Article 15.  DURATION OF AGREEMENT


                   Heilman/Aviron CRADA (AI#000062) page 15

<PAGE>

NIH Patent Policy Board, April 24, 1989

15.1          DURATION.  It is mutually recognized that the duration of this
         project cannot be rigidly defined in advance, and that the
         contemplated time periods for various phases of the RP are only good
         faith guidelines subject to adjustment by mutual agreement to fit
         circumstances as the RP proceeds.  In no case will the term of this
         CRADA extend beyond the term indicated in the RP unless it is revised
         in accordance with Article 14.6.

15.2          SURVIVABILITY.  The provisions of Articles 4.2, 5.2, 5.3, 6.1,
         Articles 7 - 9, 11.3, 11.5, 12.1, 13.3, and 14.10 shall survive the
         termination of this CRADA.


                   Heilman/Aviron CRADA (AI#000062) page 16

<PAGE>

NIH Patent Policy Board, April 24, 1989

                                 CRADA SIGNATURE PAGE

FOR NIH:

/s/ Anthony S. Fauci         6/18/95
- -------------------------     ----------
Anthony S. Fauci, M.D.        Date
Director NIAID


Mailing Address for Notices:

Technology Transfer Branch
National Institute of Allergy & Infectious Diseases
9000 Rockville Pike
Bldg. 31, Rm. 7A32
Bethesda, MD 20892


FOR THE COLLABORATOR:   (The undersigned expressly certifies or affirms that
the contents of any statements made or reflected in this document are truthful
and accurate.


/s/ J. Leighton Read, M.D.         28 Feb., 1995
- ------------------------------     ---------------
J. Leighton Read, M.D.             Date
Chairman and CEO, Aviron

Mailing Address for Notices:

Aviron
- ------------------------------
1450 Rollins Road
- ------------------------------
Burlingame, CA  94010
- ------------------------------



[Include additional signature and address blocks as necessary for all Parties to
this CRADA]

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                                            TRADE SECRETS AND/OR
                                                         CONFIDENTIAL COMMERCIAL
                                                          /FINANCIAL INFORMATION
                                                                 EXEMPT FROM THE
                                                                 F0IA DISCLOSURE
                                                           [5 U.S.C. 552(b) (4)]

                                 ASSIGNMENT OF CRADA

    THIS ASSIGNMENT OF CRADA [

    ] is by Wyeth-Ayerst Laboratories (Wyeth-Ayerst), which has offices at 145
King of Prussia Road, Radnor, PA 19087 (hereinafter "Assignor"), a division of
American Home Products Corporation, a corporation of the State of Delaware,
U.S.A., having its principal place of business at Five Giralda Farms, Madison,
New Jersey 07940-0874, U.S.A.

    WHEREAS, Assignor and the National Institute of Allergy and Infectious
Diseases (NIAID) are parties to a Cooperative Research and Development
Agreement ("CRADA") [                          ] and

    WHEREAS, Assignor is desirous of assigning certain of its rights and
obligations under the CRADA to Aviron ("Assignee") having its principal place of
business at 1450 Rollins Road, Burlingame, California 94010, as provided for in
Article 14.7 of said CRADA, which Article requires prior written consent of the
parties; and

    WHEREAS, NIAID has given its written consent to this assignment by
Assignor, as provided for in Article 14.7 of said CRADA; and

    WHEREAS, in satisfaction of its sole remaining financial obligation to
NIAID under CRADA [                                                ] Assignor
shall pay said sum to NIAID subsequent to the consummation of the present
Assignment; and

    NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, Assignor does hereby bargain, sell, assign, transfer, convey
and deliver to Assignee and its successors and assigns all of Assignor's right,
title and interest in, to and under the CRADA.  However, the provisions of
paragraphs 6.1, 12.1, 13.2, 13.3 (but only to the extent that Collaborator under
CRADA is Wyeth-Ayerst), 14.10 and Article 9 shall remain in effect as between
NIAID and Assignor.

<PAGE>

    Assignor does hereby agree, from and after the date hereof upon request of
Assignee, to execute such other documents, to take such actions, and to make 
such filings, as Assignee may request in order to obtain the full benefit of 
this Assignment of CRADA and Assignor's rights and obligations hereunder.

    IN WITNESS WHEREOF, Assignor has caused this Assignment of CRADA to be
executed as of the day and year first above written.

                                       ASSIGNOR:

National Institute of Allergy               WYETH-AYERST LABORATORIES
and Infectious Diseases

By: /s/ Anthony S. Fauci                By: /s/ Robert Essner
   --------------------------------        ------------------------------------
Name:                                  Name:  Robert Essner
Title:                                 Title: President
Date: 6/8/95                           Date:  May 30, 1995
     ------------------------------          ----------------------------------

<PAGE>
                                                CONFIDENTIAL TREATMENT REQUESTED

                                                                    EXHIBIT 10.8

<PAGE>

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT HAS
BEEN DELETED, AS NOTED BY BRACKETS, AND HAS BEEN FILED SEPARATELY
WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 406
OF THE SECURITIES ACT OF 1933, AS AMENDED.


                               DATED 7th November 1995
                              ------------------------


                                EVANS MEDICAL LIMITED
                                         and
                                        AVIRON

                           ------------------------------
                                  MANUFACTURING AND
                                DEVELOPMENT AGREEMENT
                           ------------------------------



                                    Stringer Saul
                                     Marcol House
                                  293 Regent Street
                                    London W1R 7PD

<PAGE>

THIS AGREEMENT is made the 7th day of November 1995

BETWEEN

    EVANS MEDICAL LIMITED of Evans House, Regent Park,
    Kingston Road, Leatherhead, Surrey, KT22 7PQ, United
    Kingdom

    (hereinafter called "Evans")

    - and -

    AVIRON a corporation incorporated in the State of
    California, located at 1450 Rollins Road, Burlingame,
    California, 94010, United States of America

    (hereinafter called "Aviron")

WHEREAS

    A.   Aviron is the exclusive licensee of Michigan, the legal and beneficial
         owner, of all the commercial rights to the Master Strain and the
         rights to the technology associated with and required for the
         production of the Virus Seed from the Master Strain.

    B.   Evans has experience in the production of influenza vaccines.

    C.   The parties wish to enter arrangements with regard to the Development
         and thereafter the manufacture by Evans of the Vaccine.

IT IS AGREED as follows:

DEFINITIONS

In this Agreement the following words and phrases shall have the
following meanings:-

"Approved          named senior personnel of Aviron (who
Personnel"         individually shall previously have signed Evans' usual form
                   of confidentiality agreement covering such situations)
                   notified to Evans

"Change of         means in respect of either party if greater
Control"           than fifty per cent. (50%) of its assets or voting shares
                   become vested in or subject to the direction of a person,
                   firm, corporation or other instrument, other than the
                   parties in which presently vested such that there is


                                        - 1 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                   an effective change of control of that party

"Clinical          [
Trials"

                                     ] to be conducted in accordance with this
                   Agreement in respect of the Vaccine as may be necessary to
                   obtain Regulatory Approval

"Commencement      1 November 1994
Date"

"Commercial        production of the Vaccine for all purposes other
Production"        than the Trials Production, and whether or not as a
                   consequence of Aviron obtaining the Regulatory Approval.
                   Such Commercial Production, if conducted by Evans, will be
                   conducted in a facility licensed by the relevant regulatory
                   authority for such purpose

"Early Phase III   those clinical field trials conducted by or
Trials"            on behalf of Aviron using material manufactured by Evans[
                                           ][
                                                          ]

"Development"      the development of a manufacturing process for Production of
                   the Vaccine

"Evans'            those costs incurred by Evans[
Production
Costs"                               ]

"the Further       the rights to[
Rights"

                                                                        ]

"Late Phase III    those clinical trials conducted by or on
Trials"            behalf of Aviron using materials, if Evans is the
                   manufacturer, manufactured by Evans in a facility licensed
                   by the relevant regulatory authority for the manufacture of
                   the Vaccine for commercial sale.[
                                                                 ]

"the               Evans' Manufacturing Licence No[                     ]
Manufacturing      granted pursuant to the Medicines Act 1968 permitting
Licence"           Evans to manufacture and/or assemble the Vaccine, among
                   other things

"Manufacturing     the exclusive right to carry out the manufacture of
Rights"            [                          ] the Vaccine insofar as is
                   required for the Commercial Production for Aviron or any
                   other party to whom Aviron may grant,

                                        - 2 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                   license or allow rights in respect of the Working Seed or
                   the Vaccine

"Master Strain"    live attenuated influenza vaccine seeds as are further
                   defined in the Michigan Agreement

"Michigan"         the Regents of the University of Michigan, a constitutional
                   corporation of the State of Michigan with offices located at
                   Wolverine Tower, Room 2071, 3003 South State Street, Ann
                   Arbor, Michigan, 48109-1280, USA

"Michigan          a certain Materials Transfer and Intellectual Property
Agreement"         Agreement between Aviron and Michigan dated 24 February
                   1995, attached as Schedule 4

"Price"            that amount calculated in accordance with clause 9 herein

"Production"       the Trials Production and the Commercial Production or
                   either of them, as the context requires

"Regulatory        all such marketing authorisations and/or
Approval"          product licences and any other approvals from the relevant
                   regulatory authority responsible for such matters as are
                   necessary to enable Evans to manufacture, distribute and
                   sell the Vaccine

[        ]          [                                ]

"Restricted        all technical information relating to the Master Seeds,
Information"       the Virus Seeds and the manufacture of the Vaccine disclosed
                   in confidence to Evans by Aviron excluding any such
                   information which:

                   (a)  is or was already known to Evans at the time of
                        disclosure or communication by Aviron;

                   (b)  was at the time of such disclosure or communication by
                        Aviron or thereafter becomes or became published
                        accessible to the public or otherwise in the public
                        domain other than through any breach of this Agreement
                        by Evans;

                   (c)  must be disclosed to Government Inspectors in the
                        discharge of statutory obligations provided that before
                        disclosure Evans shall use


                                        - 3 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                        reasonable endeavors as it would in respect of its own
                        restricted information to obtain from such government
                        inspectors any assurances as regards confidentiality as
                        may be afforded to such information in the
                        circumstances;

                   (d)  is disclosed by Evans to the relevant regulatory
                        authority in there course of applying for, obtaining or
                        maintaining Regulatory Approval;

                   (e)  is hereafter disclosed to Evans without any obligations
                        of confidence by a third party who has not derived it
                        directly or indirectly from Aviron;

                   (f)  is required to be disclosed by law

"the               the requirements and specifications attached hereto as
Specification"     Schedule 1, whether formulated before or after the
                   Development, as the same, may be amended from time to time by
                   agreement between the parties

"the Test"         the testing protocol[



                                                       ]

"Trials            production of the Vaccine in sufficient quantities to
Production"        enable Aviron to conduct the Clinical Trials

"Vaccine"          cold-adapted influenza vaccine[

                                                              ]

"VAT"              United Kingdom value added tax or any other tax levied in
                   substitution therefor

"Virus Seed"       [

                                                   ]

"Working Seed"     [

                                                   ]


                                        - 4 -

<PAGE>


                                                CONFIDENTIAL TREATMENT REQUESTED

                                        PART I

1.       TRIALS PRODUCTION

1.1      Aviron requires the performance of the Trials Production to enable it
         to conduct the Clinical Trials.  Subject to Aviron providing
         sufficient Virus Seeds suitable for the purpose, Evans hereby agrees
         to perform the Development and thereafter the Trials Production of the
         Vaccine for Aviron at the Price and otherwise on the terms set out in
         Part II hereof.

1.2      Aviron shall notify Evans of the trial programme in accordance with
         which Aviron shall conduct the Clinical Trials.  Should the Clinical
         Trials or any of them involve any product produced or supplied by
         Evans (other than the Vaccine) Aviron shall promptly and fully notify
         Evans of the trial programme, the manner in which such Clinical Trials
         are to be conducted, and the results thereof.  [

                 ] Accordingly, in respect of the Trials Production of the
         Vaccine for any particular Influenza season[



                ]

1.3      Aviron shall keep Evans fully and regularly informed of the progress
         of the Clinical Trials.

1.4      Aviron shall inform Evans of the results of the Clinical Trials no
         later than or, where practicable, earlier than the said results are
         released or allowed to be released to any third party.

1.5      Promptly after the execution of this Agreement, and in no event later
         than 45 days thereafter, the parties will work together in good faith
         and agree upon the Specification, the Test and the required Product
         Recall Procedures.  Aviron agrees and acknowledges that Evans shall
         not be obliged to manufacture Vaccine under this Agreement in
         accordance with a specification to which it has not agreed.

2.       COMMERCIAL PRODUCTION

         It is the agreed intention of the parties that Evans shall carry out
         the Development associated with the Commercial Production.  Further,
         it is the agreed intention of the parties that Evans shall have the
         Manufacturing Rights for at least[              ] of Aviron's
         requirements of Commercial Production for Europe.  In accordance with
         that intention should Aviron intend to offer for exploitation the
         Manufacturing Rights


                                        - 5 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         it shall enter good faith negotiations with Evans with a view to Evans
         undertaking the Commercial Production in respect of at least the said
         [                     ] proportion of Aviron's requirements for such
         countries.  Should those negotiations not result within a reasonable
         time in agreement between the parties then Aviron may offer the
         Manufacturing Rights and the conduct of the Commercial Production to
         any third party[





                             ] For the avoidance of doubt it is acknowledged and
         agreed that the Manufacturing Rights are independent of the Further
         Rights.  Aviron shall[





                                                         ]

3.       MICHIGAN LICENCE

         Evans acknowledges the existence of Aviron's licence under the
         Michigan Agreement (attached hereto as Schedule 4) and acknowledges
         and accepts that Aviron may only grant to Evans such rights as Aviron
         is permitted to grant pursuant to the Michigan Agreement.  In that
         regard Evans accepts:

3.1      [

                                                         ]


3.2      Evans shall not provide any[
                                 ]Evans shall limit access to the[
                       ]supplied by Aviron to those employees reasonably
         requiring such access for the purpose of the Development and
         Production of the Vaccine, which employees are governed by Evans'
         customary confidentiality obligations.

3.3      Evans must keep confidential and must not use except as provided in
         this Agreement, the[          ]and any know-how or technical data
         related thereto for a period of ten years after termination of the
         Michigan Agreement.  The terms of this subclause 3.3 will in all
         events apply to the [        ] but shall not apply to any [
          ]know-how or technical data which:

         3.3.1     is or becomes public knowledge through no act or default of
                   Evans;


                                        - 6 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         3.3.2     was known to Evans prior to its supply or disclosure to it
                   by Aviron;

         3.3.3     is disclosed to Evans by a third party with no obligations
                   of confidentiality attached; or

         3.3.4     is required to be disclosed by law.

3.4      Aviron shall:

         3.4.1     use every reasonable effort to honour and observe its
                   obligations under the Michigan Agreement and shall not act
                   or fail to act in any way which might jeopardise or cause to
                   be terminated the Michigan Agreement; and,

         3.4.2     promptly notify Evans of any amendment to the Michigan
                   Agreement; and,

         3.4.3     make every reasonable effort to notify Evans in writing of
                   the expiry or termination of the Michigan Agreement at least
                   six weeks prior to either event.

3.5      Evans will[                                          ]to manufacture
         and store the Virus Seeds, the Working Seeds and Vaccine in accordance
         with all applicable government laws and regulations.

3.6      Aviron, on Michigan's behalf, may request from Evans at reasonable
         times and in reasonable quantities at a price equal to[

                        ]such batch samples of Vaccine as it may desire for
         non-human research purposes only, PROVIDED THAT Evans shall be under
         no obligation under this sub-clause or otherwise[



                                                       ]

3.7      Evans acknowledges Michigan's warranty disclaimer and limitation of
         liability contained in the Michigan Agreement but makes no assessment
         or admission of its validity or reasonableness.  Notwithstanding such,
         Evans will not make any statements, representations or warranties
         inconsistent with such warranty disclaimer or limitation of liability
         other than in pursuance or prosecution of its own rights and remedies.

3.8      Evans will indemnify Michigan, its fellows, officers, employees and
         agents for and against any and all claims, damages, losses and
         expenses of any nature resulting from, but not limited to, death,
         personal injury,


                                        - 7 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         illness, or property damage, arising from or in connection with:

         3.8.1     any manufacture, use or other disposition by Evans of the
                   Working Seeds or Vaccine;

         3.8.2     the direct or indirect use by any person of Working Seeds or
                   Vaccine made or used by Evans;

         3.8.3     the use, handling, storage or disposal of Working Seeds, any
                   derivatives or Vaccine by Evans; or

         3.8.4     the unauthorized and negligent use by Evans of any know-how,
                   technical data, sub-licensed to Aviron from Michigan, or
                   developed by Evans pursuant to the Development,

         where but only where such claims, damages, losses and expenses are a
         direct consequence of the negligence of Evans, its agents or
         employees.

3.9      Evans shall not use the name of Michigan in publicity or advertising
         concerning the Vaccine, the Working Seed or the Virus Seed without the
         prior written consent of Michigan, such consent not to be unreasonably
         or arbitrarily withheld nor delayed.  Reports in scientific literature
         and presentations of joint research and development work are not
         considered publicity for the purpose of this clause.

3.10     Aviron may request from Evans at reasonable times and in reasonable
         quantities, at a Price equal to[

                     ]such batch samples of Working Seed as Aviron may require
         PROVIDED THAT Evans shall be under no obligation under this sub-clause
         or otherwise to produce extra batches of Working Seed solely or
         substantially to meet such requirements.

4.       MANUFACTURING LICENCE

         Performance by Evans of Production shall at all times be conditional
         upon the maintenance of the whole, or appropriate section, of the
         Manufacturing Licence.  Evans will maintain the Manufacturing Licence
         in full force and effect throughout the term of this Agreement.
         Should for any reason other than the default or negligence of Aviron
         the Manufacturing Licence expire lapse or be revoked Evans shall
         forthwith notify Aviron of such occurrence and shall make every
         reasonable effort to restore, renew or replace the Manufacturing
         Licence.  Should within[                       ]the Manufacturing
         Licence not be restored, renewed or replaced, or if no authorisation
         to manufacture is granted to Evans in


                                        - 8 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         substitution therefor, Aviron may by written notice to Evans,
         terminate this Agreement.


5.       GRANT OF FURTHER RIGHTS

         Should Aviron intend to exploit the Further Rights, it shall keep
         Evans fully and promptly informed of its intentions in regard thereto
         and shall consider[   



                                                         ]

6.       PROCESS TECHNOLOGY

6.1      Evans acknowledges and agrees that process technology specific solely
         to the Vaccine and developed by Evans in the course of the Development
         shall be[



                                                                ]Aviron shall
         be responsible for the[


                              ] All other process technology developed by Evans
         pursuant to this Agreement shall be [





                                       ]

6.2      In respect of process technology developed by Evans pursuant to this
         Agreement which is the property of Evans,[




                                               ]

6.3      Evans shall notify Aviron should it be approached by any third party
         wishing to exploit any process technology developed by Evans pursuant
         to this Agreement which is the property of Evans in respect of[      ]
         and upon receipt of such notification, Aviron may request the parties
         enter negotiations for a licence in respect thereof prior to any
         rights being licensed exclusively to such a third party.


                                        - 9 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                                       PART II

7.      PRODUCTION, ASSEMBLY, STORAGE AND QUALITY CONTROL

7.1      Evans shall perform all Production of the Vaccine in accordance with
         the Specification.  For the avoidance of doubt the Specification may
         not be amended or modified by Aviron without Evans's prior written
         agreement which shall not be unreasonably withheld.

7.2      The method of supply, storage and handling of materials, components
         and the Vaccine; the specifications for the materials, components and
         the finished products; the methods of manufacture and/or assembly of
         the Vaccine; the Quality Control and Quality Assurance methods and
         procedures to be employed for the Vaccine; and the Health and Safety
         precautions that need to be observed in the handling, storage,
         processing or quality control of the materials, components and Vaccine
         shall be as specified or referred to in the Specification.

7.3      Evans shall not deviate from such mutually agreed methods and
         procedures without prior written approval from Aviron except insofar
         as is required by the relevant regulatory authority or applicable laws
         or as is required for the maintenance of the Manufacturing Licence.
         Evans shall promptly notify Aviron of such requirements and any
         deviation in accordance therewith.

7.4      Evans shall be entitled to purchase and instal all such new or
         replacement tooling or parts as may be required exclusively for the
         Production of the Vaccine [








                                                                         ]

7.5      Should Evans and Aviron agree that it is necessary or desirable for
         the effective and efficient undertaking of the Development and the
         Production, [

                                 ] and Aviron acknowledges and


                                        - 10 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         agrees that [

                                                              ] as described in
         clause 9 herein.

7.6      Any amount payable under sub-clauses 7.4 and 7.5 herein shall be made
         in accordance with clause 9 herein.

8.       SUPPLY OF VIRUS SEED

8.1      Pursuant to the Michigan Agreement, Aviron shall acquire from Michigan
         the Master Strain which Aviron shall [

                                       ] Aviron shall supply the Virus Seed to
         Evans [

                   ] Evans warrants and undertakes that it shall [





                        ] then in that event Evans shall indemnify Aviron
         against any and all claims, damages, losses and expenses of any nature
         (excluding economic loss or loss of profits or consequential loss of
         whatever nature) arising from or in connection with Evans' failure to
         [                                              ] other than in
         accordance with its required procedures.  For the avoidance of doubt,
         should Evans have [






                                             ]

8.2      Aviron shall supply to Evans at all times throughout the existence of
         this Agreement the Virus Seed in sufficient quantities and in good
         time to enable Evans to perform [


                                  ]

8.3      Aviron shall ensure that all of the Virus Seed supplied to Evans at
         any time shall comply with in all respects [
                           ] any Regulatory Approval and all applicable rules
         and regulations regarding the same.

8.4      Evans shall have no responsibility regarding testing of the Virus Seed
         upon receiving the same from Aviron [


                                        - 11 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


                              ]

8. 5     Evans shall be responsible for the importation of the Virus Seed into
         the United Kingdom and for export of the Vaccine from the United
         Kingdom to Aviron [


                                         ]

9.       THE PRICE AND OTHER PAYMENTS

9.1      The Price of the [

                     ] shall be in respect of the Trials Production either:

         9.1.1     where Evans undertakes both the Trials Production and the
                   Commercial Production an amount equal to [


                                                                        ];
                   or,

         9.1.2     where Evans undertakes the Trials Production only and [


                                  ] an amount equal to [


                                        ]; and,

         9.1.3     where Evans undertakes the Trials Production only and [     
                             ]Aviron either:

                   9.1.3.1 [

                                       ] or,

                   9.1.3.2 [




                                                 ]

                   then in addition to any amount paid or payable in accordance
                   with clause 9.1.2, an amount equal to [

                                          ] such amount payable in respect of
                   sub-clause 9.1.3.2 or sub-clause 9.1.3.2 upon [


                                        - 12 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                                               ]

9.2      Evans may [
                    ] the Price shall be subject to [

              ] variation with effect from the [                        ]
         of the Commencement Date and with effect from each anniversary
         thereof.  Any Price variation [

                                                                        ]
         Any variation in the Price shall reflect actual variations in [
                                            ]

9.3      Evans will invoice Aviron for Vaccine despatched and Aviron shall pay
         the invoice not later than thirty (30) days from the date of the
         invoice.  In respect of any invoice rendered for Trials Production in
         accordance with sub-clause 9.1.1, should it transpire that the Vaccine
         should have been invoiced in accordance with sub-clause 9.1.2 then any
         payment made shall be deemed to have been a part payment in respect of
         the amount due and Evans shall invoice Aviron for the balance which
         shall be payable in accordance with this clause. In respect of any
         invoice rendered for Trials Production in accordance with sub-clause
         9.1.1, should it transpire that the Vaccine should have been invoiced
         in accordance with sub-clause 9.1.3 then any payment made shall be
         deemed to have been a part payment in respect of the amount due and
         Evans shall invoice Aviron for the balance which shall be payable
         immediately.  Where settlement of any amount payable hereunder is not
         made by the due date Evans (without prejudice to its other rights) may
         charge interest at a rate of [                ] or part thereof on the
         amount outstanding.  In the event of non-payment of any invoice or
         part thereof by Aviron, Evans (without prejudice to its other rights
         and remedies) [



                                               ]

9.4      In respect of any amount payable pursuant to sub-clauses 7.4 and 7.5
         herein and for any[




                                                      ]

9.5      Upon termination of this Agreement, Aviron shall have the option
         either: (i) to purchase from Evans, at the Price, or (ii) to direct
         Evans to destroy, in which event Evans shall nonetheless be paid the
         Price, [


                                        - 13 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                                  ] are reasonable given Aviron's requirements
         for the Vaccine prior to termination together with all of Evans' [

                                      ]  Notwithstanding the foregoing, in the
         event of termination of this Agreement due to breach by Evans, Aviron
         shall not be obliged to pay Evans the Price, but shall instead pay [

                                        ]

9.6      Evans shall give Aviron such assistance as is reasonable to allow
         Aviron to conduct its affairs in the most advantageous manner in
         respect of VAT.  Any costs to Evans associated with such assistance
         shall be met by Aviron.

10.      SUPPLIES AND ORDERS

10.1     Evans shall use all reasonable efforts to supply the Vaccine whether
         pursuant to the Trials Production or the Commercial Production in
         accordance with the forecasts supplied by Aviron pursuant to this
         Clause.

10.2     Within [                          ] following the date of execution
         hereof the parties shall mutually agree upon a production schedule for
         the first year of the Trials Production [                 ] thereafter
         the parties shall mutually agree upon a production schedule for the
         second and third years of the Trials Production.  Thereafter, the
         parties shall mutually agree upon as necessary a production schedule
         for any remaining period prior to obtaining Regulatory Approval for
         the Vaccine.

10.3     All orders submitted by Aviron to Evans must be in writing and shall
         be accepted or rejected by Evans in a timely manner in writing, and no
         order shall be binding upon either party until such time as it has
         been accepted by Evans in accordance herewith.

10.4     Other than the Virus Seed or the syringes, which shall be supplied by
         Aviron, Evans shall provide all materials and/or components required
         for Trials Production of the Vaccine.

10.5     If the Virus Seed and/or purchase orders to be supplied by Aviron or
         on its behalf do not reach Evans by any agreed date, Evans and Aviron
         shall agree new delivery dates for the Vaccine which are commensurate
         with the actual dates of supply to Evans but subject to clause 10.7
         herein.


                                        - 14 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

10. 6    It is accepted that whilst Evans will [



                                         ]

10.7     Evans will at the request of Aviron deliver the Vaccine to Aviron at
         any address as Aviron may specify but all Prices are [


                                                                  ]
10.8     If Aviron fails to pay for any Vaccine in accordance with the
         provisions hereof within the stated periods for payment Evans, in
         addition to its rights under clause 9.3 herein, may:

         10.8.1    sell or otherwise dispose of to Michigan or its designee any
                   of the Vaccine the subject of any order made by Aviron and
                   accepted by Evans but not yet delivered; and

         10.8.2    suspend or cancel any further supplies or deliveries of the
                   Vaccine hereunder.

10.9      [
                                                                             ]
         property in and title to any batch of the Vaccine or any part thereof
         shall remain with Evans unless and until Aviron shall have paid the
         Price in full for that batch of the Vaccine.

10.10    All Vaccine will be supplied on the terms and conditions herein
         contained and in the event of any order for Vaccine being made by
         Aviron on its Standard Conditions of Purchase or being accepted by
         Evans on its Standard Conditions of Sale it is hereby agreed that any
         such Standard Conditions shall be of no effect and that the terms and
         conditions set forth in this Agreement shall prevail.

10.11    In the event that Evans is unable to deliver any Vaccine against the
         agreed delivery date for that Vaccine, Evans shall immediately advise
         Aviron to this effect, explain the reason for the delay, and agree a
         revised delivery date with Aviron.  Evans shall make every reasonable
         effort to ensure that Aviron is not unduly inconvenienced by delay in
         the delivery of the Vaccine.

10.12    Should Evans fail to deliver any Vaccine in accordance with an agreed
         order within [                 ] of an agreed delivery day then Aviron
         may give to Evans [             ] written notice requiring Evans to
         remedy its default and should Evans fail to remedy its default on or
         before the expiry of the said [                     ] period,


                                        - 15 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         Aviron may terminate this Agreement unless any failure to supply by
         Evans is due to:

         10.12.1   Aviron's failure to supply the Virus Seed;

         10.12.2 [
                                               ] or

         10.12.3 [


                                    ]

11.      INVENTORY

11.1     Evans shall submit to Aviron a statement on the status of all orders
         placed by Aviron which have not been fulfilled at that date.

11.2     At the end of a Production campaign Evans shall list and inform Aviron
         of all unused Virus Seed that has been supplied by Aviron.  By return
         Aviron may request Evans to destroy all such Virus Seed, or may
         request Evans to return them to Aviron at Aviron's expense.

12.      [                          ] TECHNOLOGY

         Upon Evans' request the parties shall enter into good faith
         negotiations with respect to Aviron granting to Evans an exclusive
         licence in respect of Aviron's [                          ] technology
         for use in Europe.  Such licence shall be on terms to be agreed but
         shall include payment by Evans of a royalty based upon [


                                    ]

13.      ACCESS BY AVIRON

         Subject to receiving reasonable prior notice from Aviron, Evans shall
         allow Approved Personnel access to that part of the Evans premises
         dedicated to the Production at any time during normal business hours
         to inspect and/or reconcile virus Seeds, Working Seeds, materials,
         components and Vaccine held at Evans premises on behalf of Aviron, and
         to audit any manufacturing and/or assembly processes (including the
         related Quality Assurance and Quality Control operations) being
         performed by Evans for Aviron under this Agreement. Evans shall
         inform Aviron of any findings of any regulatory inspection or audit
         insofar as those findings may affect the Production contemplated under
         this Agreement, together with any corrective action required and/or
         taken. Evans shall


                                        - 16 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         provide to Aviron copies of all correspondence between Evans and the
         relevant regulatory authorities with respect to such audit, subject to
         Evans' right to withhold or excise any information which Evans
         considers to be confidential or commercially sensitive.  Evans shall
         grant to Aviron access to those records in the possession of Evans
         regarding the manufacture of the Vaccine as may be necessary in
         compiling submissions to the US Food and Drug Administration ("FDA")
         or responding to any enquiries from the FDA.  [



                                                                 ]

14.      WARRANTY

14.1     Aviron shall, within a period of [
                                                           ] inform Evans of any
         failure of the Vaccine to meet the Specification.  Should Aviron fail
         to inform Evans within the said period of [
                  ] Aviron shall be deemed to have accepted the Vaccine.

14.2     Evans shall make no charge hereunder in respect of any batch where
         the failure to meet the Specification arises from any act or omission
         on its part.  Subject to the written agreement of Aviron, Evans shall
         at its expense either correct or cause to be corrected the deficiency
         in that batch of the Vaccine or if the defect cannot be corrected
         Evans shall indemnify Aviron against all reasonable costs and expenses
         of replacing the relevant batch and Evans shall destroy the batch or
         return it to Aviron (as may be agreed) for destruction.  Subject to
         either party's obligations at law to act other than in compliance with
         this provision each party shall give to the other reasonable
         assistance with any recall of the Vaccine (which shall be conducted in
         accordance with Evans' Product Recall Procedure which is attached
         hereto as Schedule 2) including provision of relevant information and
         the list of customers to whom the recall products have been supplied
         and the issue of notices, warnings and information as reasonably
         requested by the relevant party to enable that party to comply with
         its recall procedures.

14.3     If notwithstanding the above Vaccine is released for distribution and
         is subsequently found to be faulty or defective and is not in
         compliance with the Specification then Evans shall indemnify Aviron
         against all costs, claims and expenses arising directly or indirectly
         from the replacement of such vaccine and its recall for destruction
         unless the fault or defect arises from any act or omission on Aviron's
         part or was otherwise caused by the negligence of Aviron, its agents
         or [


                                        - 17 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

                   ] For the avoidance of doubt the aforesaid indemnity shall
         not be operative and Evans shall not be liable thereunder should the
         Vaccine be in accordance with the Specification.

14.4     Subject to clause 14.3 Aviron shall be solely responsible for the
         recall of Vaccine sold in Aviron's livery in accordance with the
         Regulatory Approval granted to Aviron.

15.      LIABILITY FOR LOSS AND CLAIMS

15.1     Liability for third party claims against either party or any loss or
         damage suffered resulting from the supply of any Vaccine manufactured
         and/or assembled under this Agreement will be subject to the following
         provisions:

         15.1.1    Evans shall be liable for and shall indemnify Aviron [



                                                                             ]

         15.1.2    Aviron shall be liable for and shall indemnify Evans [



                                                                             ]

         15.1.3    Without prejudice to the right to be indemnified pursuant to
                   15.1.1 and 15.1.2 neither party limits liability for death
                   or personal injury arising out of that party's negligence.

15.2     Evans shall be liable for any loss of or damage to Aviron materials,
         components or Vaccine arising from Evans's negligence whilst at Evans
         premises, [

                                          ]

15.3     Other than as specified in Clause 15.2, Evans shall not be liable for
         any loss of or damage to [


                      ] In respect of all such losses or damages Aviron hereby:


                                        - 18 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         15.3.1 [
                                         ] and;
         15.3.2 [




                                                         ]

16.      CONFIDENTIALITY

16.1     Evans acknowledges that much of the Restricted Information disclosed
         to it hereunder will be deemed to be confidential information under
         the Michigan Agreement and so subject to clause 3.3.  Accordingly,
         Evans undertakes that during the period of this Agreement and for a
         period of [                                                        ]
         it will treat as confidential all Restricted Information and shall
         not disclose such information to any third party except with the prior
         written agreement of Aviron.

16.2     Evans shall be entitled to use such Restricted Information and may
         disclose such Restricted Information to its own personnel, under
         obligations of secrecy, only to the extent necessary for Evans to
         perform its obligations to Aviron under this Agreement.

16.3     In the event of any inconsistency or conflict between the provisions
         of the Michigan Agreement in respect of Restricted Information and any
         provision of this Agreement, the provisions of the Michigan Agreement
         shall prevail, but only insofar as: (a) such provision is an
         obligation of Aviron which has been assumed by Evans under this
         Agreement and, (b) the performance of this Agreement would be rendered
         impossible by the application of both of the conflicting or
         inconsistent provisions.

16.4     On the expiry or termination of this Agreement, Evans will return to
         Aviron all Restricted Information in its possession and Evans shall
         not make any further use of that information.

16.5     In this Clause references to Evans or Aviron shall be deemed to
         include any Affiliate of that party.

16.6     Aviron undertakes to keep confidential all information received by it
         directly or indirectly from Evans or obtained by it pursuant to the
         performance of this Agreement which relates in any way to Evans's
         business including but not limited to Evans's technical know-how in
         relation to the Development and to the Production of the Vaccine
         provided however that this obligation of confidentiality shall not
         apply to such information:


                                        - 19 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED

         16.6.1    which is or was already known to Aviron at the time it was
                   received or obtained from Evans;

         16.6.2    which was at the time that it was received or obtained from
                   Evans by Aviron or thereafter becomes or became published,
                   accessible to the public or otherwise in the public domain
                   other than through any breach of this Agreement by Aviron;

         16.6.3    which must be disclosed to government inspectors in the
                   discharge of statutory obligations;

         16.6.4    which is hereafter disclosed to Aviron without any
                   obligations of confidence by a third party who has not
                   derived it directly or indirectly from Evans.

17.      ASSIGNMENT

17.1     [





                         ]

17.2     Notwithstanding clause 17.1 Evans may without Aviron's consent procure
         the performance of any of its obligations by any Affiliate of Evans
         but Evans shall not thereby be relieved of responsibility for the
         performance of such obligations, and the provisions of clause 17.1
         shall not apply.

17.3     [


                          ]

18.      FORCE MAJEURE

18.1     If the performance of any part of this Agreement by either party is
         prevented, hindered or delayed by any act, events, non-happenings,
         omissions or accidents beyond the control of that party (force
         majeure) then that party shall (subject to compliance with Clause
         18.2) be excused from such performance to the extent that such party
         is necessarily prevented, hindered or delayed thereby during the
         continuance of the matter constituting "force majeure" and this
         Agreement shall be deemed suspended so long as and to the extent that
         any such cause prevents, hinders or delays its performance.

18.2     The party affected by force majeure shall give notice to the other
         party as soon as practical after the matter


                                        - 20 -

<PAGE>

                                                CONFIDENTIAL TREATMENT REQEUSTED

         constituting force majeure has arisen or occurred giving the other
         party full particulars of the nature and extent of such matter.  The
         affected party shall additionally at its own cost and expense take all
         reasonable steps as may be necessary to overcome the force majeure and
         to minimize its effects.

18.3     If the duration of any force majeure occurrence exceeds two months the
         parties shall consult with a view to determining what steps they may
         agree to take, appropriate to the force majeure circumstances, in
         relation to this Agreement.

19.      TERM

         Performance of this Agreement shall commence from the Commencement
         Date and subject to termination in accordance with any other right of
         termination specified herein this Agreement shall continue in force
         until terminated by either party giving not less than six (6) months
         notice in writing to the other party which notice may be given at any
         time after 31 December 1996.

20.      TERMINATION

20.1     Either party may terminate this Agreement:

         20.1.1    forthwith if the other party has committed any breach of any
                   of the terms of this Agreement, and in the case of any such
                   breach which is capable of remedy has not remedied that
                   breach within [         ] of being required by written notice
                   from the other party so to do; or

         20.1.2    by [                        ] prior written notice if the
                   other party becomes bankrupt, goes into liquidation (either
                   voluntary or compulsory, unless as part of a bona fide
                   scheme of reconstruction, re-organization or amalgamation),
                   makes a general assignment for the benefit of its creditors
                   (whether voluntary or compulsory) or has a receiver
                   appointed for its property or imposes suffers or incurs any
                   process or occurrence having similar effect; or

         20.1.3    by[

                                 ]
                   but without prejudice to any right of either party to sue
                   for any antecedent breach of this Agreement.

20.2     This Agreement shall, unless expiring or terminating earlier in
         accordance with any other provision herein,


                                        - 21 -

<PAGE>

         terminate upon termination of the Michigan Agreement.  In such event,
         at Michigan's option as notified to Evans by Aviron, Evans shall, at
         Aviron's cost, [


                   ] Evans shall provide [





                                                      ]

20.3     Any termination of this Agreement (however occasioned) shall not
         affect any accrued rights or liabilities of either of the parties nor
         shall it affect the coming into force or the continuance in force of
         any provision hereof which is expressly intended to come into or
         continue in force on or after such termination, including (but not
         limited to) clauses 2, 3, 9, 12, 14, 15 and 16.

21.      NOTICE

         Any notice or other communication required or permitted to be given
         under this Agreement by either party shall be deemed to be
         sufficiently served if sent to the other party by pre paid airmail
         post or fax addressed to that party at the address set out in this
         Agreement or to any other address so designated in writing by that
         party.

         Any such notice shall in the case of a notice sent by post be deemed
         to have been served ten (10) days after the date on which it is
         mailed.

         In the case of a notice or communication by fax, the fax must be
         confirmed by sending a copy of the same by pre paid airmail post
         within seven (7) days, in which event the date of service shall be the
         date of transmission of the fax.

22.      MISCELLANEOUS

22.1     This Agreement shall be governed and construed in accordance with the
         laws of England.

22.2     No amendment or modification of this Agreement shall be valid or
         binding upon either party unless made in writing and signed by an
         authorized representative of that party.

22.3     Evans and Aviron represent to each other that the respective officer
         or officers of each company who have signed this Agreement are duly
         authorized to do so.

22.4     Any waiver by either party of a breach of any provision of this
         Agreement shall not be considered as a waiver of


                                        - 22 -

<PAGE>

    any continued or subsequent breach of the same or any other provision
    thereof.

22.5     Nothing in this Agreement shall create, or be deemed to create, a
         partnership or the relationship of principal and agent or employer and
         employee between the parties.

22.6     This Agreement contains the entire agreement between the parties with
         respect to the subject matter hereof, supersedes all previous
         agreements understandings or letters of intent between the parties
         with respect thereto.

22.7     If any provision of this Agreement is held by any court or other
         competent authority to be void or unenforceable in whole or part, this
         Agreement shall continue to be valid as to the other provisions
         thereof and the remainder of the affected provision.

22.8     The clause and paragraph headings in this Agreement are for ease of
         reference only and are not to be taken into account in the
         construction or interpretation of any covenant condition or proviso to
         which they refer.

22.9     Unless the context otherwise requires, references:

         22.9.1    to numbered clauses and Schedules are references to the
                   relevant clause in or Schedule to this Agreement; and

         22.9.2    in any Schedule to a numbered paragraph are references to
                   the relevant paragraph in that Schedule

22.10    Words in this Agreement importing the singular meaning, where the
         context so allows, include the plural meaning and vice versa.

IN WITNESS WHEREOF, the parties have executed this Agreement as of the day and
the year first above written.


                                        - 23 -

<PAGE>

For and on behalf of
EVANS MEDICAL LIMITED

         Full Name
         and Title:          M.J. HARVEY (UK OPERATIONS DIRECTOR)
                              . . . . . . . . . . . . . . . . . . . .
         Signature:          /s/ M. J. Harvey
                              . . . . . . . . . . . . . . . . . . . .

In the presence of:          S. R. PARISH
                              . . . . . . . . . . . . . . . . . . . .

         Witness's signature:/s/ S. R. Parish
                              . . . . . . . . . . . . . . . . . . . .

         Address:            EVANS MEDICAL
                              . . . . . . . . . . . . . . . . . . . .

                             CASICILL ROAD, LIVERPOOL
                              . . . . . . . . . . . . . . . . . . . .

         Occupation:         S. R. PARISH
                              . . . . . . . . . . . . . . . . . . . .



For and on behalf of
AVIRON

         Full Name
         and Title:          LEIGHTON READ (CEO)
                              . . . . . . . . . . . . . . . . . . . .

         Signature:          /s/ L. Read
                              . . . . . . . . . . . . . . . . . . . .

In the presence of:          Julie C. Neumann
                              . . . . . . . . . . . . . . . . . . . .

         Witness's signature:/s/ Julie C. Neumann
                              . . . . . . . . . . . . . . . . . . . .

         Address:            297 N. Bernardo Avenue
                              . . . . . . . . . . . . . . . . . . . .

                             Mountain View, CA  94043
                              . . . . . . . . . . . . . . . . . . . .

         Occupation:         Controller
                              . . . . . . . . . . . . . . . . . . . .


                                        - 24 -

<PAGE>

                                      SCHEDULE I
                                  THE SPECIFICATION


[Not Completed in Original Document]

<PAGE>

                                      SCHEDULE 2
                              PRODUCT RECALL PROCEDURES

<PAGE>

                                               CONFIDENTIAL TREATMENT REQUESTED

                                      SCHEDULE 2

                             ADVERSE EXPERIENCE REPORTING
                         AND PROVISION OF MEDICAL INFORMATION


1.   ADVERSE EXPERIENCE REPORTING
     [





                            ]

1.2  [










                                            ]

1.3  [



                      ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


2.   PROVISION OF MEDICAL INFORMATION

2.1  [





                    ]

2.2  [







                                  ]

2.3  [





                                                              ]

3.   PRODUCT COMPLAINTS

3.1  [


                    ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


     SPONTANEOUS ADVERSE EVENT (ADE) REPORTING PROCEDURE - INDIVIDUAL CASE
     REPORTS
    [
















                         ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


[                                                                              ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


[                                                                              ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


[                                                                              ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


                               PRODUCT RECALL PROCEDURE

                              INITIATING PRODUCT RECALL

[





                   ]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


                                      SCHEDULE 3
                                       THE TEST

[Not Completed in Original Document]

<PAGE>

                                                CONFIDENTIAL TREATMENT REQUESTED


                                      SCHEDULE 4
                                  MICHIGAN AGREEMENT



[See Exhibit 10.3 to the Registration Statement on Form S-1 filed
on behalf of Aviron with the SEC                  ]


<PAGE>


                                        AVIRON

                              1996 EQUITY INCENTIVE PLAN

                                ADOPTED MARCH 6, 1996

                       APPROVED BY STOCKHOLDERS ________, 1996


1.   PURPOSES.

     (a)   The purpose of the Plan is to provide a means by which selected
Employees of and Consultants to the Company and its Affiliates may be given an
opportunity to benefit from increases in value of the stock of the Company
through the granting of (i) Incentive Stock Options, (ii) Nonstatutory Stock
Options, (iii) stock bonuses, (iv) rights to purchase restricted stock, and (v)
stock appreciation rights, all as defined below.  The Plan is successor to, and
restatement of, the Company's 1992 Stock Option Plan.

     (b)   The Company, by means of the Plan, seeks to retain the services of
persons who are now Employees of or Consultants, to secure and retain the
services of new Employees and Consultants, and to provide incentives for such
persons to exert maximum efforts for the success of the Company and its
Affiliates.

     (c)   The Company intends that the Stock Awards issued under the Plan
shall, in the discretion of the Board or any Committee to which responsibility
for administration of the Plan has been delegated pursuant to subsection 3(c),
be either (i) Options granted pursuant to Section 6 hereof, including Incentive
Stock Options and Nonstatutory Stock Options, (ii) stock bonuses or rights to
purchase restricted stock granted pursuant to Section 7 hereof, or (iii) stock
appreciation rights granted pursuant to Section 8 hereof.  All Options shall be
separately designated Incentive Stock Options or Nonstatutory Stock Options at
the time of grant, and in such form as issued pursuant to Section 6, and a
separate certificate or certificates will be issued for shares purchased on
exercise of each type of Option.

2.   DEFINITIONS.

     (a)   "AFFILIATE" means any parent corporation or subsidiary corporation,
whether now or hereafter existing, as those terms are defined in Sections 424(e)
and (f) respectively, of the Code.

     (b)   "BOARD" means the Board of Directors of the Company.

     (c)   "CODE" means the Internal Revenue Code of 1986, as amended.


                                          1.

<PAGE>

     (d)   "COMMITTEE" means a Committee appointed by the Board in accordance
with subsection 3(c) of the Plan.

     (e)   "COMPANY" means Aviron, a Delaware corporation.

     (f)   "CONCURRENT STOCK APPRECIATION RIGHT" or "CONCURRENT RIGHT" means a
right granted pursuant to subsection 8(b)(2) of the Plan.

     (g)   "CONSULTANT" means any person, including an advisor, engaged by the
Company or an Affiliate to render consulting services and who is compensated for
such services, provided that the term "Consultant" shall not include Directors
who are paid only a director's fee by the Company or who are not compensated by
the Company for their services as Directors.

     (h)   "CONTINUOUS STATUS AS AN EMPLOYEE, DIRECTOR OR CONSULTANT" means the
employment or relationship as a Director or Consultant is not interrupted or
terminated.  The Board, in its sole discretion, may determine whether Continuous
Status as an Employee, Director or Consultant shall be considered interrupted in
the case of:  (i) any leave of absence approved by the Board, including sick
leave, military leave, or any other personal leave; or (ii) transfers between
locations of the Company or between the Company, Affiliates or their successors.

     (i)   "COVERED EMPLOYEE" means the chief executive officer and the four
(4) other highest compensated officers of the Company for whom total
compensation is required to be reported to shareholders under the Exchange Act,
as determined for purposes of Section 162(m) of the Code.

     (j)   "DIRECTOR" means a member of the Board.

     (k)   "DISINTERESTED PERSON" means a Director:  who either:  (i) was not
during the one year prior to service as an administrator of the Plan granted or
awarded equity securities pursuant to the Plan or any other plan of the Company
or any Affiliate entitling the participants therein to acquire equity securities
of the Company or any Affiliate except as permitted by Rule 16b-3(c)(2)(i); or
(ii) is otherwise considered to be a "disinterested person" in accordance with
Rule 16b-3(c)(2)(i), or any other applicable rules, regulations or
interpretations of the Securities and Exchange Commission.

     (l)   "EMPLOYEE" means any person, including Officers and Directors,
employed by the Company or any Affiliate of the Company.  Neither service as a
Director nor payment of a director's fee by the Company shall be sufficient to
constitute "employment" by the Company.

     (m)   "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.


                                          2.

<PAGE>

     (n)   "FAIR MARKET VALUE" means, as of any date, the value of the common
stock of the Company determined as follows:

           (1)     If the common stock is listed on any established stock
exchange or a national market system, including without limitation the National
Market of The Nasdaq Stock Market, the Fair Market Value of a share of common
stock shall be the closing sales price for such stock (or the closing bid, if no
sales were reported) as quoted on such system or exchange (or the exchange with
the greatest volume of trading in common stock) on the last market trading day
prior to the day of determination, as reported in the Wall Street Journal or
such other source as the Board deems reliable;

           (2)     If the common stock is quoted on The Nasdaq Stock Market
(but not on the National Market thereof) or is regularly quoted by a recognized
securities dealer but selling prices are not reported, the Fair Market Value of
a share of common stock shall be the mean between the bid and asked prices for
the common stock on the last market trading day prior to the day of
determination, as reported in the Wall Street Journal or such other source as
the Board deems reliable;

           (3)     In the absence of an established market for the common
stock, the Fair Market Value shall be determined in good faith by the Board.

     (o)   "INCENTIVE STOCK OPTION" means an Option intended to qualify as an
incentive stock option within the meaning of Section 422 of the Code and the
regulations promulgated thereunder.

     (p)   "INDEPENDENT STOCK APPRECIATION RIGHT" or "INDEPENDENT RIGHT" means
a right granted pursuant to subsection 8(b)(3) of the Plan.

     (q)   "NONSTATUTORY STOCK OPTION" means an Option not intended to qualify
as an Incentive Stock Option.

     (r)   "OFFICER" means a person who is an officer of the Company within the
meaning of Section 16 of the Exchange Act and the rules and regulations
promulgated thereunder.

     (s)   "OPTION" means a stock option granted pursuant to the Plan.

     (t)   "OPTION AGREEMENT" means a written agreement between the Company and
an Optionee evidencing the terms and conditions of an individual Option grant.
Each Option Agreement shall be subject to the terms and conditions of the Plan.

     (u)   "OPTIONEE" means an Employee or Consultant who holds an outstanding
Option.

     (v)   "OUTSIDE DIRECTOR" means a Director who either (i) is not a current
employee of the Company or an "affiliated corporation" (within the meaning of
Treasury regulations


                                          3.

<PAGE>

promulgated under Section 162(m) of the Code), is not a former employee of the
Company or an "affiliated corporation" receiving compensation for prior services
(other than benefits under a tax qualified pension plan), was not an officer of
the Company or an "affiliated corporation" at any time, and is not currently
receiving direct or indirect remuneration from the Company or an "affiliated
corporation" for services in any capacity other than as a Director, or (ii) is
otherwise considered an "outside director" for purposes of Section 162(m) of the
Code.

     (w)   "PLAN" means this Aviron 1996 Equity Incentive Plan.

     (x)   "RULE 16B-3" means Rule 16b-3 of the Exchange Act or any successor
to Rule 16b-3, as in effect when discretion is being exercised with respect to
the Plan.

     (y)   "STOCK APPRECIATION RIGHT" means any of the various types of rights
which may be granted under Section 8 of the Plan.

     (z)   "STOCK AWARD" means any right granted under the Plan, including any
Option, any stock bonus, any right to purchase restricted stock, and any Stock
Appreciation Right.

     (aa)  "STOCK AWARD AGREEMENT" means a written agreement between the
Company and a holder of a Stock Award evidencing the terms and conditions of an
individual Stock Award grant.  Each Stock Award Agreement shall be subject to
the terms and conditions of the Plan.

     (bb)  "TANDEM STOCK APPRECIATION RIGHT" or "TANDEM RIGHT" means a right
granted pursuant to subsection 8(b)(1) of the Plan.

3.   ADMINISTRATION.

     (a)   The Plan shall be administered by the Board unless and until the
Board delegates administration to a Committee, as provided in subsection 3(c).

     (b)   The Board shall have the power, subject to, and within the
limitations of, the express provisions of the Plan:

           (1)     To determine from time to time which of the persons eligible
under the Plan shall be granted Stock Awards; when and how each Stock Award
shall be granted; whether a Stock Award will be an Incentive Stock Option, a
Nonstatutory Stock Option, a stock bonus, a right to purchase restricted stock,
a Stock Appreciation Right, or a combination of the foregoing; the provisions of
each Stock Award granted (which need not be identical), including the time or
times when a person shall be permitted to receive stock pursuant to a Stock
Award; whether a person shall be permitted to receive stock upon exercise of an
Independent Stock Appreciation Right; and the number of shares with respect to
which a Stock Award shall be granted to each such person.


                                          4.

<PAGE>

           (2)     To construe and interpret the Plan and Stock Awards granted
under it, and to establish, amend and revoke rules and regulations for its
administration.  The Board, in the exercise of this power, may correct any
defect, omission or inconsistency in the Plan or in any Stock Award Agreement,
in a manner and to the extent it shall deem necessary or expedient to make the
Plan fully effective.

           (3)     To amend the Plan or a Stock Award as provided in Section
14.

           (4)     Generally, to exercise such powers and to perform such acts
as the Board deems necessary or expedient to promote the best interests of the
Company which are not in conflict with the provisions of the Plan.

     (c)   The Board may delegate administration of the Plan to a committee
composed of not fewer than two (2) members (the "Committee"), all of the members
of which Committee shall be Disinterested Persons and may also be, in the
discretion of the Board, Outside Directors.  If administration is delegated to a
Committee, the Committee shall have, in connection with the administration of
the Plan, the powers theretofore possessed by the Board (and references in this
Plan to the Board shall thereafter be to the Committee), subject, however, to
such resolutions, not inconsistent with the provisions of the Plan, as may be
adopted from time to time by the Board.  The Board may abolish the Committee at
any time and revest in the Board the administration of the Plan.
Notwithstanding anything in this Section 3 to the contrary, at any time the
Board or the Committee may delegate to a committee of one or more members of the
Board the authority to grant Stock Awards to eligible persons who (1) are not
then subject to Section 16 of the Exchange Act and/or (2) are either (i) not
then Covered Employees and are not expected to be Covered Employees at the time
of recognition of income resulting from such Stock Award, or (ii) not persons
with respect to whom the Company wishes to avoid the application of Section
162(m) of the Code.

     (d)   Any requirement that an administrator of the Plan be a Disinterested
Person shall not apply if the Board or the Committee expressly declares that
such requirement shall not apply.  Any Disinterested Person shall otherwise
comply with the requirements of Rule 16b-3.

4.   SHARES SUBJECT TO THE PLAN.

     (a)   Subject to the provisions of Section 13 relating to adjustments upon
changes in stock, the stock that may be issued pursuant to Stock Awards shall
not exceed in the aggregate one million seven hundred fifty thousand (1,750,000)
shares of the Company's common stock (after giving effect to the one-for-five
reverse split of the Company's Common Stock approved in March, 1996).  If any
Stock Award shall for any reason expire or otherwise terminate, in whole or in
part, without having been exercised in full, the stock not acquired under such
Stock Award shall revert to and again become available for issuance under the
Plan.  Shares subject to Stock Appreciation Rights exercised in accordance with
Section 8 of the Plan shall not be available for subsequent issuance under the
Plan.


                                          5.

<PAGE>

     (b)   The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

5.   ELIGIBILITY.

     (a)   Incentive Stock Options and Stock Appreciation Rights appurtenant
thereto may be granted only to Employees.  Stock Awards other than Incentive
Stock Options and Stock Appreciation Rights appurtenant thereto may be granted
only to Employees or Consultants.

     (b)   A Director shall in no event be eligible for the benefits of the
Plan unless at the time of grant the Director is also an Employee or Consultant.

     (c)   No person shall be eligible for the grant of an Incentive Stock
Option if, at the time of grant, such person owns (or is deemed to own pursuant
to Section 424(d) of the Code) stock possessing more than ten percent (10%) of
the total combined voting power of all classes of stock of the Company or of any
of its Affiliates unless the exercise price of such Option is at least one
hundred ten percent (110%) of the Fair Market Value of such stock at the date of
grant and the Option is not exercisable after the expiration of five (5) years
from the date of grant, or in the case of a restricted stock purchase award, the
purchase price is at least one hundred percent (100%) of the Fair Market Value
of such stock at the date of grant.

     (d)   Subject to the provisions of Section 13 relating to adjustments upon
changes in stock, no person shall be eligible to be granted Options and Stock
Appreciation Rights covering more than one hundred fifty thousand (150,000)
(after giving effect to the one-for-five reverse split of the Company's Common
Stock approved in March, 1996) shares of the Company's common stock in any
calendar year.

6.   OPTION PROVISIONS.

     Each Option shall be in such form and shall contain such terms and
conditions as the Board shall deem appropriate.  The provisions of separate
Options need not be identical, but each Option shall include (through
incorporation of provisions hereof by reference in the Option or otherwise) the
substance of each of the following provisions:

     (a)   TERM.  No Option shall be exercisable after the expiration of ten
(10) years from the date it was granted.

     (b)   PRICE.  The exercise price of each Incentive Stock Option shall be
not less than one hundred percent (100%) of the Fair Market Value of the stock
subject to the Option on the date the Option is granted; the exercise price of a
Nonstatutory Stock Option shall be not less than eighty-five percent (85%) of
the Fair Market Value of the stock subject to the Option on the date the Option
is granted.  Notwithstanding the foregoing, an Incentive Stock Option may be
granted with an exercise price lower than that set forth in the preceding
sentence if such Option is granted


                                          6.

<PAGE>

pursuant to an assumption or substitution for another option in a manner
satisfying the provisions of Section 424(a) of the Code.

     (c)   CONSIDERATION.  The purchase price of stock acquired pursuant to an
Option shall be paid, to the extent permitted by applicable statutes and
regulations, either (i) in cash at the time the Option is exercised, or (ii) at
the discretion of the Board or the Committee, at the time of the grant of the
Option, (A) by delivery to the Company of other common stock of the Company, (B)
according to a deferred payment or other arrangement (which may include, without
limiting the generality of the foregoing, the use of other common stock of the
Company) with the person to whom the Option is granted or to whom the Option is
transferred pursuant to subsection 6(d), or (C) in any other form of legal
consideration that may be acceptable to the Board.

     In the case of any deferred payment arrangement, interest shall be payable
at least annually and shall be charged at the minimum rate of interest necessary
to avoid the treatment as interest, under any applicable provisions of the Code,
of any amounts other than amounts stated to be interest under the deferred
payment arrangement.

     (d)   TRANSFERABILITY.  An Incentive Stock Option shall not be
transferable except by will or by the laws of descent and distribution, and
shall be exercisable during the lifetime of the person to whom the Incentive
Stock Option is granted only by such person.  A Nonstatutory Stock Option shall
not be transferable except by will, by the laws of descent and distribution or
pursuant to a qualified domestic relations order satisfying the requirements of
Rule 16b-3 and any administrative interpretations or pronouncements thereunder
(a "QDRO"), and shall be exercisable during the lifetime of the person to whom
the Option is granted only by such person or any transferee pursuant to a QDRO.
Notwithstanding the foregoing, the person to whom the Option is granted may, by
delivering written notice to the Company, in a form satisfactory to the Company,
designate a third party who, in the event of the death of the Optionee, shall
thereafter be entitled to exercise the Option.

     (e)   VESTING.  The total number of shares of stock subject to an Option
may, but need not, be allotted in periodic installments (which may, but need
not, be equal).  The Option Agreement may provide that from time to time during
each of such installment periods, the Option may become exercisable ("vest")
with respect to some or all of the shares allotted to that period, and may be
exercised with respect to some or all of the shares allotted to such period
and/or any prior period as to which the Option became vested but was not fully
exercised.  The Option may be subject to such other terms and conditions on the
time or times when it may be exercised (which may be based on performance or
other criteria) as the Board may deem appropriate.  The provisions of this
subsection 6(e) are subject to any Option provisions governing the minimum
number of shares as to which an Option may be exercised.

     (f)   TERMINATION OF EMPLOYMENT OR RELATIONSHIP AS A DIRECTOR OR
CONSULTANT.  In the event an Optionee's Continuous Status as an Employee,
Director or Consultant terminates (other than upon the Optionee's death or
disability), the Optionee may exercise his or her Option (to the extent that the
Optionee was entitled to exercise it at the date of termination) but only


                                          7.

<PAGE>

within such period of time ending on the earlier of (i) the date three (3)
months after the termination of the Optionee's Continuous Status as an Employee,
Director or Consultant (or such longer or shorter period specified in the Option
Agreement), or (ii) the expiration of the term of the Option as set forth in the
Option Agreement.  If, after termination, the Optionee does not exercise his or
her Option within the time specified in the Option Agreement, the Option shall
terminate, and the shares covered by such Option shall revert to and again
become available for issuance under the Plan.

     An Optionee's Option Agreement may also provide that if the exercise of
the Option following the termination of the Optionee's Continuous Status as an
Employee, Director, or Consultant (other than upon the Optionee's death or
disability) would result in liability under Section 16(b) of the Exchange Act,
then the Option shall terminate on the earlier of (i) the expiration of the term
of the Option set forth in the Option Agreement, or (ii) the tenth (10th) day
after the last date on which such exercise would result in such liability under
Section 16(b) of the Exchange Act.  Finally, an Optionee's Option Agreement may
also provide that if the exercise of the Option following the termination of the
Optionee's Continuous Status as an Employee, Director or Consultant (other than
upon the Optionee's death or disability) would be prohibited at any time solely
because the issuance of shares would violate the registration requirements under
the Act, then the Option shall terminate on the earlier of (i) the expiration of
the term of the Option set forth in the first paragraph of this subsection 6(f),
or (ii) the expiration of a period of three (3) months after the termination of
the Optionee's Continuous Status as an Employee, Director or Consultant during
which the exercise of the Option would not be in violation of such registration
requirements.

     (g)   DISABILITY OF OPTIONEE.  In the event an Optionee's Continuous
Status as an Employee, Director or Consultant terminates as a result of the
Optionee's disability, the Optionee may exercise his or her Option (to the
extent that the Optionee was entitled to exercise it at the date of
termination), but only within such period of time ending on the earlier of (i)
the date twelve (12) months following such termination (or such longer or
shorter period specified in the Option Agreement), or (ii) the expiration of the
term of the Option as set forth in the Option Agreement.  If, at the date of
termination, the Optionee is not entitled to exercise his or her entire Option,
the shares covered by the unexercisable portion of the Option shall revert to
and again become available for issuance under the Plan.  If, after termination,
the Optionee does not exercise his or her Option within the time specified
herein, the Option shall terminate, and the shares covered by such Option shall
revert to and again become available for issuance under the Plan.

     (h) DEATH OF OPTIONEE.  In the event of the death of an Optionee during,
or within a period specified in the Option after the termination of, the
Optionee's Continuous Status as an Employee, Director or Consultant, the Option
may be exercised (to the extent the Optionee was entitled to exercise the Option
at the date of death) by the Optionee's estate, by a person who acquired the
right to exercise the Option by bequest or inheritance or by a person designated
to exercise the option upon the Optionee's death pursuant to subsection 6(d),
but only within the period ending on the earlier of (i) the date twelve (12)
months following the date of death (or such


                                          8.

<PAGE>

longer or shorter period specified in the Option Agreement), or (ii) the
expiration of the term of such Option as set forth in the Option Agreement.  If,
at the time of death, the Optionee was not entitled to exercise his or her
entire Option, the shares covered by the unexercisable portion of the Option
shall revert to and again become available for issuance under the Plan.  If,
after death, the Option is not exercised within the time specified herein, the
Option shall terminate, and the shares covered by such Option shall revert to
and again become available for issuance under the Plan.

     (i)   EARLY EXERCISE.  The Option may, but need not, include a provision
whereby the Optionee may elect at any time while an Employee, Director or
Consultant to exercise the Option as to any part or all of the shares subject to
the Option prior to the full vesting of the Option.  Any unvested shares so
purchased may be subject to a repurchase right in favor of the Company or to any
other restriction the Board determines to be appropriate.

     (j)   RE-LOAD OPTIONS.  Without in any way limiting the authority of the
Board or Committee to make or not to make grants of Options hereunder, the Board
or Committee shall have the authority (but not an obligation) to include as part
of any Option Agreement a provision entitling the Optionee to a further Option
(a "Re-Load Option") in the event the Optionee exercises the Option evidenced by
the Option agreement, in whole or in part, by surrendering other shares of
Common Stock in accordance with this Plan and the terms and conditions of the
Option Agreement.  Any such Re-Load Option (i) shall be for a number of shares
equal to the number of shares surrendered as part or all of the exercise price
of such Option; (ii) shall have an expiration date which is the same as the
expiration date of the Option the exercise of which gave rise to such Re-Load
Option; and (iii) shall have an exercise price which is equal to one hundred
percent (100%) of the Fair Market Value of the Common Stock subject to the Re-
Load Option on the date of exercise of the original Option.  Notwithstanding the
foregoing, a Re-Load Option which is an Incentive Stock Option and which is
granted to a 10% stockholder (as described in subsection 5(c)), shall have an
exercise price which is equal to one hundred ten percent (110%) of the Fair
Market Value of the stock subject to the Re-Load Option on the date of exercise
of the original Option and shall have a term which is no longer than five (5)
years.

     Any such Re-Load Option may be an Incentive Stock Option or a Nonstatutory
Stock Option, as the Board or Committee may designate at the time of the grant
of the original Option; PROVIDED, HOWEVER, that the designation of any Re-Load
Option as an Incentive Stock Option shall be subject to the one hundred thousand
dollar ($100,000) annual limitation on exercisability of Incentive Stock Options
described in subsection 12(d) of the Plan and in Section 422(d) of the Code.
There shall be no Re-Load Options on a Re-Load Option.  Any such Re-Load Option
shall be subject to the availability of sufficient shares under subsection 4(a)
and shall be subject to such other terms and conditions as the Board or
Committee may determine which are not inconsistent with the express provisions
of the Plan regarding the terms of Options.

7.   TERMS OF STOCK BONUSES AND PURCHASES OF RESTRICTED STOCK.


                                          9.

<PAGE>

     Each stock bonus or restricted stock purchase agreement shall be in such
form and shall contain such terms and conditions as the Board or the Committee
shall deem appropriate.  The terms and conditions of stock bonus or restricted
stock purchase agreements may change from time to time, and the terms and
conditions of separate agreements need not be identical, but each stock bonus or
restricted stock purchase agreement shall include (through incorporation of
provisions hereof by reference in the agreement or otherwise) the substance of
each of the following provisions as appropriate:

     (a)   PURCHASE PRICE.  The purchase price under each restricted stock
purchase agreement shall be such amount as the Board or Committee shall
determine and designate in such agreement but in no event shall the purchase
price be less than eighty-five percent (85%) of the stock's Fair Market Value on
the date such award is made.  Notwithstanding the foregoing, the Board or the
Committee may determine that eligible participants in the Plan may be awarded
stock pursuant to a stock bonus agreement in consideration for past services
actually rendered to the Company for its benefit.

     (b)   TRANSFERABILITY.  No rights under a stock bonus or restricted stock
purchase agreement shall be transferable except by will or the laws of descent
and distribution or pursuant to a qualified domestic relations order satisfying
the requirements of Rule 16b-3 and any administrative interpretations or
pronouncements thereunder, so long as stock awarded under such agreement remains
subject to the terms of the agreement.

     (c)   CONSIDERATION.  The purchase price of stock acquired pursuant to a
stock purchase agreement shall be paid either:  (i) in cash at the time of
purchase; (ii) at the discretion of the Board or the Committee, according to a
deferred payment or other arrangement with the person to whom the stock is sold;
or (iii) in any other form of legal consideration that may be acceptable to the
Board or the Committee in its discretion.  Notwithstanding the foregoing, the
Board or the Committee to which administration of the Plan has been delegated
may award stock pursuant to a stock bonus agreement in consideration for past
services actually rendered to the Company or for its benefit.

     (d)   VESTING.  Shares of stock sold or awarded under the Plan may, but
need not, be subject to a repurchase option in favor of the Company in
accordance with a vesting schedule to be determined by the Board or the
Committee.

     (e)   TERMINATION OF EMPLOYMENT OR RELATIONSHIP AS A DIRECTOR OR
CONSULTANT.  In the event a Participant's Continuous Status as an Employee,
Director or Consultant terminates, the Company may repurchase or otherwise
reacquire any or all of the shares of stock held by that person which have not
vested as of the date of termination under the terms of the stock bonus or
restricted stock purchase agreement between the Company and such person.

8.   STOCK APPRECIATION RIGHTS.


                                         10.

<PAGE>

     (a)   The Board or Committee shall have full power and authority,
exercisable in its sole discretion, to grant Stock Appreciation Rights under the
Plan to Employees and Consultants.  To exercise any outstanding Stock
Appreciation Right, the holder must provide written notice of exercise to the
Company in compliance with the provisions of the Stock Award Agreement
evidencing such right.  If a Stock Appreciation Right is granted to an
individual who is at the time subject to Section 16(b) of the Exchange Act (a
"Section 16(b) Insider"), the Stock Award Agreement of grant shall incorporate
all the terms and conditions at the time necessary to assure that the subsequent
exercise of such right shall qualify for the safe-harbor exemption from
short-swing profit liability provided by Rule 16b-3 promulgated under the
Exchange Act (or any successor rule or regulation).  Except as provided in
subsection 5(d), no limitation shall exist on the aggregate amount of cash
payments the Company may make under the Plan in connection with the exercise of
a Stock Appreciation Rights.

     (b)   Three types of Stock Appreciation Rights shall be authorized for
issuance under the Plan:

           (1)     TANDEM STOCK APPRECIATION RIGHTS.  Tandem Stock Appreciation
Rights will be granted appurtenant to an Option, and shall, except as
specifically set forth in this Section 8, be subject to the same terms and
conditions applicable to the particular Option grant to which it pertains.
Tandem Stock Appreciation Rights will require the holder to elect between the
exercise of the underlying Option for shares of stock and the surrender, in
whole or in part, of such Option for an appreciation distribution.  The
appreciation distribution payable on the exercised Tandem Right shall be in cash
(or, if so provided, in an equivalent number of shares of stock based on Fair
Market Value on the date of the Option surrender) in an amount up to the excess
of (A) the Fair Market Value (on the date of the Option surrender) of the number
of shares of stock covered by that portion of the surrendered Option in which
the Optionee is vested over (B) the aggregate exercise price payable for such
vested shares.

           (2)     CONCURRENT STOCK APPRECIATION RIGHTS.  Concurrent Rights
will be granted appurtenant to an Option and may apply to all or any portion of
the shares of stock subject to the underlying Option and shall, except as
specifically set forth in this Section 8, be subject to the same terms and
conditions applicable to the particular Option grant to which it pertains.  A
Concurrent Right shall be exercised automatically at the same time the
underlying Option is exercised with respect to the particular shares of stock to
which the Concurrent Right pertains.  The appreciation distribution payable on
an exercised Concurrent Right shall be in cash (or, if so provided, in an
equivalent number of shares of stock based on Fair Market Value on the date of
the exercise of the Concurrent Right) in an amount equal to such portion as
shall be determined by the Board or the Committee at the time of the grant of
the excess of (A) the aggregate Fair Market Value (on the date of the exercise
of the Concurrent Right) of the vested shares of stock purchased under the
underlying Option which have Concurrent Rights appurtenant to them over (B) the
aggregate exercise price paid for such shares.

           (3)     INDEPENDENT STOCK APPRECIATION RIGHTS.  Independent Rights
will be granted independently of any Option and shall, except as specifically
set forth in this Section 8,


                                         11.

<PAGE>

be subject to the same terms and conditions applicable to Nonstatutory Stock
Options as set forth in Section 6.  They shall be denominated in share
equivalents.  The appreciation distribution payable on the exercised Independent
Right shall be not greater than an amount equal to the excess of (A) the
aggregate Fair Market Value (on the date of the exercise of the Independent
Right) of a number of shares of Company stock equal to the number of share
equivalents in which the holder is vested under such Independent Right, and with
respect to which the holder is exercising the Independent Right on such date,
over (B) the aggregate Fair Market Value (on the date of the grant of the
Independent Right) of such number of shares of Company stock.  The appreciation
distribution payable on the exercised Independent Right shall be in cash or, if
so provided, in an equivalent number of shares of stock based on Fair Market
Value on the date of the exercise of the Independent Right.

9.   CANCELLATION AND RE-GRANT OF OPTIONS.

     (a)   The Board or the Committee shall have the authority to effect, at
any time and from time to time,  (i) the repricing of any outstanding Options
and/or any Stock Appreciation Rights under the Plan and/or (ii) with the consent
of any adversely affected holders of Options and/or Stock Appreciation Rights,
the cancellation of any outstanding Options and/or any Stock Appreciation Rights
under the Plan and the grant in substitution therefor of new Options and/or
Stock Appreciation Rights under the Plan covering the same or different numbers
of shares of stock, but having an exercise price per share not less than:
eighty-five percent (85%) of the Fair Market Value for a Nonstatutory Stock
Option, one hundred percent (100%) of the Fair Market Value in the case of an
Incentive Stock Option or, in the case of an Incentive Stock Option held by a
10% stockholder (as described in subsection 5(c)), not less than one hundred ten
percent (110%) of the Fair Market Value per share of stock on the new grant
date.  Notwithstanding the foregoing, the Board or the Committee may grant an
Option and/or Stock Appreciation Right with an exercise price lower than that
set forth above if such Option and/or Stock Appreciation Right is granted as
part of a transaction to which section 424(a) of the Code applies.

     (b)   Shares subject to an Option or Stock Appreciation Right canceled
under this Section 9 shall continue to be counted against the maximum award of
Options and Stock Appreciation Rights permitted to be granted pursuant to
subsection 5(d) of the Plan.  The repricing of an Option and/or Stock
Appreciation Right under this Section 9, resulting in a reduction of the
exercise price, shall be deemed to be a cancellation of the original Option
and/or Stock Appreciation Right and the grant of a substitute Option and/or
Stock Appreciation Right; in the event of such repricing, both the original and
the substituted Options and Stock Appreciation Rights shall be counted against
the maximum awards of Options and Stock Appreciation Rights permitted to be
granted pursuant to subsection 5(d) of the Plan.  The provisions of this
subsection 9(b) shall be applicable only to the extent required by Section
162(m) of the Code.

10.  COVENANTS OF THE COMPANY.

     (a)   During the terms of the Stock Awards, the Company shall keep
available at all times the number of shares of stock required to satisfy such
Stock Awards.


                                         12.

<PAGE>

     (b)   The Company shall seek to obtain from each regulatory commission or
agency having jurisdiction over the Plan such authority as may be required to
issue and sell shares of stock upon exercise of the Stock Award; provided,
however, that this undertaking shall not require the Company to register under
the Securities Act of 1933, as amended (the "Securities Act") either the Plan,
any Stock Award or any stock issued or issuable pursuant to any such Stock
Award.  If, after reasonable efforts, the Company is unable to obtain from any
such regulatory commission or agency the authority which counsel for the Company
deems necessary for the lawful issuance and sale of stock under the Plan, the
Company shall be relieved from any liability for failure to issue and sell stock
upon exercise of such Stock Awards unless and until such authority is obtained.

11.  USE OF PROCEEDS FROM STOCK.

     Proceeds from the sale of stock pursuant to Stock Awards shall constitute
general funds of the Company.

12.  MISCELLANEOUS.

     (a)   The Board shall have the power to accelerate the time at which a
Stock Award may first be exercised or the time during which a Stock Award or any
part thereof will vest pursuant to subsection 6(e), 7(d) or 8(b),
notwithstanding the provisions in the Stock Award stating the time at which it
may first be exercised or the time during which it will vest.

     (b)   Neither an Employee, a Consultant nor any person to whom a Stock
Award is transferred in accordance with the Plan shall be deemed to be the
holder of, or to have any of the rights of a holder with respect to, any shares
subject to such Stock Award unless and until such person has satisfied all
requirements for exercise of the Stock Award pursuant to its terms.

     (c)   Nothing in the Plan or any instrument executed or Stock Award
granted pursuant thereto shall confer upon any Employee, Consultant or other
holder of Stock Awards any right to continue in the employ of the Company or any
Affiliate or to continue acting as a Consultant or shall affect the right of the
Company or any Affiliate to terminate the employment of any Employee with or
without notice and with or without cause, or the right to terminate the
relationship of any Consultant pursuant to the terms of such Consultant's
agreement with the Company or Affiliate.

     (d)   To the extent that the aggregate Fair Market Value (determined at
the time of grant) of stock with respect to which Incentive Stock Options are
exercisable for the first time by any Optionee during any calendar year under
all plans of the Company and its Affiliates exceeds one hundred thousand dollars
($100,000), the Options or portions thereof which exceed such limit (according
to the order in which they were granted) shall be treated as Nonstatutory Stock
Options.


                                         13.

<PAGE>

     (e)   The Company may require any person to whom a Stock Award is granted,
or any person to whom a Stock Award is transferred in accordance with the Plan,
as a condition of exercising or acquiring stock under any Stock Award, (1) to
give written assurances satisfactory to the Company as to such person's
knowledge and experience in financial and business matters and/or to employ a
purchaser representative reasonably satisfactory to the Company who is
knowledgeable and experienced in financial and business matters, and that he or
she is capable of evaluating, alone or together with the purchaser
representative, the merits and risks of exercising the Stock Award; and (2) to
give written assurances satisfactory to the Company stating that such person is
acquiring the stock subject to the Stock Award for such person's own account and
not with any present intention of selling or otherwise distributing the stock.
The foregoing requirements, and any assurances given pursuant to such
requirements, shall be inoperative if (i) the issuance of the shares upon the
exercise or acquisition of stock under the Stock Award has been registered under
a then currently effective registration statement under the Securities Act, or
(ii) as to any particular requirement, a determination is made by counsel for
the Company that such requirement need not be met in the circumstances under the
then applicable securities laws.  The Company may, upon advice of counsel to the
Company, place legends on stock certificates issued under the Plan as such
counsel deems necessary or appropriate in order to comply with applicable
securities laws, including, but not limited to, legends restricting the transfer
of the stock.

     (f)   To the extent provided by the terms of a Stock Award Agreement, the
person to whom a Stock Award is granted may satisfy any federal, state or local
tax withholding obligation relating to the exercise or acquisition of stock
under a Stock Award by any of the following means or by a combination of such
means:  (1) tendering a cash payment; (2) authorizing the Company to withhold
shares from the shares of the common stock otherwise issuable to the participant
as a result of the exercise or acquisition of stock under the Stock Award; or
(3) delivering to the Company owned and unencumbered shares of the common stock
of the Company.

13.  ADJUSTMENTS UPON CHANGES IN STOCK.

     (a)   If any change is made in the stock subject to the Plan, or subject
to any Stock Award, without the receipt of consideration by the Company (through
merger, consolidation, reorganization, recapitalization, reincorporation, stock
dividend, dividend in property other than cash, stock split, liquidating
dividend, combination of shares, exchange of shares, change in corporate
structure or other transaction not involving the receipt of consideration by the
Company), the Plan will be appropriately adjusted in the class(es) and maximum
number of shares subject to the Plan pursuant to subsection 4(a) and the maximum
number of shares subject to award to any person during any calendar year
pursuant to subsection 5(d), and the outstanding Stock Awards will be
appropriately adjusted in the class(es) and number of shares and price per share
of stock subject to such outstanding Stock Awards.  Such adjustments shall be
made by the Board or the Committee, the determination of which shall be final,
binding and conclusive.  (The conversion of any convertible securities of the
Company shall not be treated as a "transaction not involving the receipt of
consideration by the Company".)


                                         14.

<PAGE>

     (b)   In the event of:  (1) a dissolution, liquidation or sale of
substantially all of the assets of the Company; (2) a merger or consolidation in
which the Company is not the surviving corporation; or (3) a reverse merger in
which the Company is the surviving corporation but the shares of the Company's
common stock outstanding immediately preceding the merger are converted by
virtue of the merger into other property, whether in the form of securities,
cash or otherwise, then to the extent permitted by applicable law:  (i) any
surviving corporation or an Affiliate of such surviving corporation shall assume
any Stock Awards outstanding under the Plan or shall substitute similar Stock
Awards for those outstanding under the Plan, or (ii) such Stock Awards shall
continue in full force and effect.  In the event any surviving corporation and
its Affiliates refuse to assume or continue such Stock Awards, or to substitute
similar options for those outstanding under the Plan, then, with respect to
Stock Awards held by persons then performing services as Employees, Directors or
Consultants, the time during which such Stock Awards may be exercised shall be
accelerated and the Stock Awards terminated if not exercised prior to such
event.

14.  AMENDMENT OF THE PLAN AND STOCK AWARDS.

     (a)   The Board at any time, and from time to time, may amend the Plan.
However, except as provided in Section 13 relating to adjustments upon changes
in stock, no amendment shall be effective unless approved by the stockholders of
the Company within twelve (12) months before or after the adoption of the
amendment, where the amendment will modify the Plan in any way that would
require stockholder approval in order for the Plan to satisfy the requirements
of Section 422 of the Code or to comply with the requirements of Rule 16b-3
(e.g., increases in the number of shares available for awards or changes to
eligibility for Awards).

     (b)   The Board may in its sole discretion submit any other amendment to
the Plan for stockholder approval, including, but not limited to, amendments to
the Plan intended to satisfy the requirements of Section 162(m) of the Code and
the regulations promulgated thereunder regarding the exclusion of performance-
based compensation from the limit on corporate deductibility of compensation
paid to certain executive officers.

     (c)   It is expressly contemplated that the Board may amend the Plan in
any respect the Board deems necessary or advisable to provide eligible Employees
or Consultants with the maximum benefits provided or to be provided under the
provisions of the Code and the regulations promulgated thereunder relating to
Incentive Stock Options and/or to bring the Plan and/or Incentive Stock Options
granted under it into compliance therewith.

     (d)   Rights and obligations under any Stock Award granted before
amendment of the Plan shall not be impaired by any amendment of the Plan unless
(i) the Company requests the consent of the person to whom the Stock Award was
granted and (ii) such person consents in writing.

     (e)   The Board at any time, and from time to time, may amend the terms of
any one or more Stock Award; provided, however, that the rights and obligations
under any Stock Award


                                         15.

<PAGE>

shall not be impaired by any such amendment unless (i) the Company requests the
consent of the person to whom the Stock Award was granted and (ii) such person
consents in writing.

15.  TERMINATION OR SUSPENSION OF THE PLAN.

     (a)   The Board may suspend or terminate the Plan at any time.  Unless
sooner terminated, the Plan shall terminate ten (10) years from the date the
Plan is adopted by the Board or approved by the stockholders of the Company,
whichever is earlier.  No Stock Awards may be granted under the Plan while the
Plan is suspended or after it is terminated.

     (b)   Rights and obligations under any Stock Award granted while the Plan
is in effect shall not be impaired by suspension or termination of the Plan,
except with the consent of the person to whom the Stock Award was granted.

16.  EFFECTIVE DATE OF PLAN.

     The Plan shall become effective as determined by the Board, but no Stock
Awards granted under the Plan shall be exercised unless and until the Plan has
been approved by the stockholders of the Company, which approval shall be within
twelve (12) months before or after the date the Plan is adopted by the Board.


                                         16.


<PAGE>


                                        AVIRON

                    1996 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN 

                                ADOPTED MARCH 6, 1996

                    APPROVED BY STOCKHOLDERS ______________, 1996


1.  PURPOSE.

    (a)  The purpose of the Aviron 1995 Non-Employee Directors' Stock Option
Plan (the "Plan") is to provide a means by which each director of Aviron, a
Delaware corporation (the "Company") who is not otherwise an employee of the
Company or of any Affiliate of the Company (each such person being hereafter
referred to as a "Non-Employee Director") will be given an opportunity to
purchase stock of the Company.

    (b)  The word "Affiliate" as used in the Plan means any parent corporation
or subsidiary corporation of the Company as those terms are defined in Sections
424(e) and (f), respectively, of the Internal Revenue Code of 1986, as amended
from time to time (the "Code").

    (c)  The Company, by means of the Plan, seeks to retain the services of
persons now serving as Non-Employee Directors of the Company, to secure and
retain the services of persons capable of serving in such capacity, and to
provide incentives for such persons to exert maximum efforts for the success of
the Company.

2.  ADMINISTRATION.

    (a)  The Plan shall be administered by the Board of Directors of the
Company (the "Board") unless and until the Board delegates administration to a
committee, as provided in subparagraph 2(b).


                                          1.

<PAGE>

    (b)  The Board may delegate administration of the Plan to a committee
composed of not fewer than two (2) members of the Board (the "Committee").  If
administration is delegated to a Committee, the Committee shall have, in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject, however, to such resolutions, not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board.  The
Board may abolish the Committee at any time and revest in the Board the
administration of the Plan.

3.  SHARES SUBJECT TO THE PLAN.

    (a)  Subject to the provisions of paragraph 10 relating to adjustments upon
changes in stock, the stock that may be sold pursuant to options granted under
the Plan shall not exceed in the aggregate two hundred thousand (200,000) shares
of the Company's common stock (after giving effect to the one-for-five reverse
split of the Company's Common Stock approved in March, 1996).  If any option
granted under the Plan shall for any reason expire or otherwise terminate
without having been exercised in full, the stock not purchased under such option
shall again become available for the Plan.

    (b)  The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

4.  ELIGIBILITY.

    Options shall be granted only to Non-Employee Directors of the Company.  

5.  NON-DISCRETIONARY GRANTS.

    (a)  Each person who is, after the Effective Date, elected for the first
time to be a Non-Employee Director automatically shall, upon the date of initial
election to be a Non-Employee Director by the Board or stockholders of the
Company, be granted an option to purchase fifteen


                                          2.

<PAGE>

thousand (15,000) shares of common stock of the Company (after giving effect to
the one-for-five reverse split of the Company's Common Stock approved in March,
1996) on the terms and conditions set forth herein.

    (b)  On December 31st of each year, commencing with December 31, 1996, (i)
each person who is then a Non-Employee Director and continuously has been a
Non-Employee Director since December 31st of the immediately preceding year
automatically shall be granted an option to purchase three thousand (3,000)
shares of common stock of the Company (after giving effect to the one-for-five
reverse split of the Company's Common Stock approved in March, 1996) on the
terms and conditions set forth herein, and (ii) each other person who is then a
Non-Employee Director automatically shall be granted an option to purchase, on
the terms and conditions set forth herein, the number of shares of common stock
of the Company (rounded up to the nearest whole share) determined by multiplying
three thousand (3,000) shares (after giving effect to the one-for-five reverse
split of the Company's Common Stock approved in March, 1996) by a fraction, the
numerator of which is the number of days the person continuously has been a
Non-Employee Director as of the date of such grant and the denominator of which
is 365.

6.  OPTION PROVISIONS.

    Each option shall be subject to the following terms and conditions:

    (a)  The term of each option commences on the date it is granted and,
unless sooner terminated as set forth herein, expires on the date ("Expiration
Date") ten (10) years from the date of grant.  If the optionee's service as a
Non-Employee Director or employee of or consultant to the Company or any
Affiliate terminates for any reason or for no reason, the option shall terminate
on the earlier of the Expiration Date or the date twelve (12) months following
the date


                                          3.

<PAGE>

of termination of all such service; PROVIDED, HOWEVER, that if such termination
of service is due to the optionee's death, the option shall terminate on the
earlier of the Expiration Date or eighteen (18) months following the date of the
optionee's death.  In any and all circumstances, an option may be exercised
following termination of the optionee's service as a Non-Employee Director or
employee of or consultant to the Company or any Affiliate only as to that number
of shares as to which it was exercisable on the date of termination of such
service under the provisions of subparagraph 6(e).

    (b)  The exercise price of each option shall be one hundred percent (100%)
of the fair market value of the stock subject to such option on the date such
option is granted.  

    (c)  Payment of the exercise price of each option is due in full in cash
upon any exercise when the number of shares being purchased upon such exercise
is less than 1,000 shares.   However, when the number of shares being purchased
upon an exercise is 1,000 or more shares, the optionee may elect to make payment
of the exercise price under one of the following alternatives:

         (i)  Payment of the exercise price per share in cash or by check at
the time of exercise; or

         (ii) Provided that at the time of the exercise the Company's common
stock is publicly traded and quoted regularly in the Wall Street Journal,
payment by delivery of shares of common stock of the Company already owned by
the optionee, held for the period required to avoid a charge to the Company's
reported earnings, and owned free and clear of any liens, claims, encumbrances
or security interest, which common stock shall be valued at its fair market
value on the date preceding the date of exercise; or


                                          4.

<PAGE>

         (iii)     Payment by a combination of the methods of payment specified
in subparagraph 6(c)(i) and 6(c)(ii) above.

    Notwithstanding the foregoing, this option may be exercised pursuant to a
program developed under Regulation T as promulgated by the Federal Reserve Board
which results in the receipt of cash (or check) by the Company prior to the
issuance of shares of the Company's common stock.

    (d)  An option shall not be transferable except by will or by the laws of
descent and distribution, or pursuant to a qualified domestic relations order
satisfying the requirements of Rule 16b-3 under the Securities Exchange Act of
1934 ("Rule 16b-3") and shall be exercisable during the lifetime of the person
to whom the option is granted only by such person (or by his guardian or legal
representative) or transferee pursuant to such an order.  Notwithstanding the
foregoing, the optionee may, by delivering written notice to the Company in a
form satisfactory to the Company, designate a third party who, in the event of
the death of the optionee, shall thereafter be entitled to exercise the option.

    (e)  The option shall become exercisable in installments over a period of
three (3) years from the date of grant commencing on the date one (1) year after
the date of grant of the option, with thirty-three percent (33%) becoming
exercisable one (1) year after the date of the grant, thirty-four percent (34%)
becoming exercisable two (2) years after the date of grant and the remaining
thirty-three percent (33%) becoming exercisable three (3) years after the date
of grant; provided that the optionee has, during the entire period prior to such
vesting date, continuously served as a Non-Employee Director or employee of or
consultant to the Company or any Affiliate


                                          5.

<PAGE>

of the Company, whereupon such option shall become fully exercisable in
accordance with its terms with respect to that portion of the shares represented
by that installment.

    (f)  The Company may require any optionee, or any person to whom an option
is transferred under subparagraph 6(d), as a condition of exercising any such
option:  (i) to give written assurances satisfactory to the Company as to the
optionee's knowledge and experience in financial and business matters; and (ii)
to give written assurances satisfactory to the Company stating that such person
is acquiring the stock subject to the option for such person's own account and
not with any present intention of selling or otherwise distributing the stock. 
These requirements, and any assurances given pursuant to such requirements,
shall be inoperative if (i) the issuance of the shares upon the exercise of the
option has been registered under a then-currently-effective registration
statement under the Securities Act of 1933, as amended (the "Securities Act"),
or (ii), as to any particular requirement, a determination is made by counsel
for the Company that such requirement need not be met in the circumstances under
the then-applicable securities laws. 

    (g)  Notwithstanding anything to the contrary contained herein, an option
may not be exercised unless the shares issuable upon exercise of such option are
then registered under the Securities Act or, if such shares are not then so
registered, the Company has determined that such exercise and issuance would be
exempt from the registration requirements of the Securities Act.

    (h)  The Company (or a representative of the underwriters) may, in
connection with the first underwritten registration of the offering of any
securities of the Company under the Securities Act, require that any optionee
not sell or otherwise transfer or dispose of any shares of common stock or other
securities of the Company during such period (not to exceed one hundred eighty


                                          6.

<PAGE>

(180) days) following the effective date of the registration statement of the
Company filed under the Securities Act as may be requested by the Company or the
representative of the underwriters.

7.  COVENANTS OF THE COMPANY.

    (a)  During the terms of the options granted under the Plan, the Company
shall keep available at all times the number of shares of stock required to
satisfy such options.

    (b)  The Company shall seek to obtain from each regulatory commission or
agency having jurisdiction over the Plan such authority as may be required to
issue and sell shares of stock upon exercise of the options granted under the
Plan; PROVIDED, HOWEVER, that this undertaking shall not require the Company to
register under the Securities Act either the Plan, any option granted under the
Plan, or any stock issued or issuable pursuant to any such option.  If, after
reasonable efforts, the Company is unable to obtain from any such regulatory
commission or agency the authority which counsel for the Company deems necessary
for the lawful issuance and sale of stock under the Plan, the Company shall be
relieved from any liability for failure to issue and sell stock upon exercise of
such options.  

8.  USE OF PROCEEDS FROM STOCK.

    Proceeds from the sale of stock pursuant to options granted under the Plan
shall constitute general funds of the Company.

9.  MISCELLANEOUS.

    (a)  Neither an optionee nor any person to whom an option is transferred
under subparagraph 6(d) shall be deemed to be the holder of, or to have any of
the rights of a holder


                                          7.

<PAGE>

with respect to, any shares subject to such option unless and until such person
has satisfied all requirements for exercise of the option pursuant to its terms.

    (b)  Throughout the term of any option granted pursuant to the Plan, the
Company shall make available to the holder of such option, not later than one
hundred twenty (120) days after the close of each of the Company's fiscal years
during the option term, upon request, such financial and other information
regarding the Company as comprises the annual report to the stockholders of the
Company provided for in the Bylaws of the Company and such other information
regarding the Company as the holder of such option may reasonably request.

    (c)  Nothing in the Plan or in any instrument executed pursuant thereto
shall confer upon any Non-Employee Director any right to continue in the service
of the Company or any Affiliate or shall affect any right of the Company, its
Board or stockholders or any Affiliate to terminate the service of any
Non-Employee Director with or without cause.

    (d)  No Non-Employee Director, individually or as a member of a group, and
no beneficiary or other person claiming under or through him, shall have any
right, title or interest in or to any option reserved for the purposes of the
Plan except as to such shares of common stock, if any, as shall have been
reserved for him pursuant to an option granted to him.

    (e)  In connection with each option made pursuant to the Plan, it shall be
a condition precedent to the Company's obligation to issue or transfer shares to
a Non-Employee Director, or to evidence the removal of any restrictions on
transfer, that such Non-Employee Director make arrangements satisfactory to the
Company to insure that the amount of any federal or other


                                          8.

<PAGE>

withholding tax required to be withheld with respect to such sale or transfer,
or such removal or lapse, is made available to the Company for timely payment of
such tax.

    (f)  As used in this Plan, "fair market value" means, as of any date, the
value of the common stock of the Company determined as follows:

         (i)  If the common stock is listed on any established stock exchange
or a national market system, including without limitation the National Market of
The Nasdaq Stock Market , the Fair Market Value of a share of common stock shall
be the closing sales price for such stock (or the closing bid, if no sales were
reported) as quoted on such system or exchange (or the exchange with the
greatest volume of trading in common stock) on the last market trading day prior
to the day of determination, as reported in the Wall Street Journal or such
other source as the Board deems reliable;

         (ii) If the common stock is quoted on The Nasdaq Stock Market (but not
on the National Market thereof) or is regularly quoted by a recognized
securities dealer but selling prices are not reported, the Fair Market Value of
a share of common stock shall be the mean between the bid and asked prices for
the common stock on the last market trading day prior to the day of
determination, as reported in the Wall Street Journal or such other source as
the Board deems reliable;

         (iii)     In the absence of an established market for the common
stock, the Fair Market Value shall be determined in good faith by the Board.


                                          9.

<PAGE>

Notwithstanding the foregoing, the Fair Market Value of the common stock for an
option granted on the Effective Date shall be the price per share at which
shares of common stock are first sold to the public in the Company's initial
public offering.

10. ADJUSTMENTS UPON CHANGES IN STOCK.

    (a)  If any change is made in the stock subject to the Plan, or subject to
any option granted under the Plan (through merger, consolidation,
reorganization, recapitalization, reincorporation, stock dividend, dividend in
property other than cash, stock split, liquidating
dividend, combination of shares, exchange of shares, change in corporate
structure or otherwise), the Plan and outstanding options will be appropriately
adjusted in the class(es) and maximum number of shares subject to the Plan and
the class(es) and number of shares and price per share of stock subject to
outstanding options.

    (b)  In the event of:  (1) a dissolution, liquidation or sale of
substantially all of the assets of the Company; (2) a merger or consolidation in
which the Company is not the surviving corporation; (3) a reverse merger in
which the Company is the surviving corporation but the shares of the Company's
common stock outstanding immediately preceding the merger are converted by
virtue of the merger into other property, whether in the form of securities,
cash or otherwise; or (4) any other capital reorganization (including a sale of
stock of the Company to a single purchaser or single group of affiliated
purchasers) after which less than fifty percent (50%) of the outstanding voting
shares of the new or continuing corporation are owned by shareholders of the
Company immediately before such transaction, the time during which options
outstanding under the Plan may be exercised shall be accelerated to permit the
optionee to exercise all such


                                         10.

<PAGE>

options in full prior to such event, and the options shall terminate if not
exercised prior to such event.

11. AMENDMENT OF THE PLAN.

    (a)  The Board at any time, and from time to time, may amend the Plan,
PROVIDED, HOWEVER, that the Board shall not amend the plan more than once every
six (6) months, with respect to the provisions of the Plan which relate to the
amount, price and timing of grants, other than to comport with changes in the
Code, the Employee Retirement Income Security Act, or applicable regulations or
rulings thereunder.  Except as provided in paragraph 10 relating to adjustments
upon changes in stock, no amendment shall be effective unless approved by the
stockholders of the Company within twelve (12) months before or after the
adoption of the amendment, where the amendment will modify the Plan in any way
if such modification requires stockholder approval in order for the Plan to
comply with the requirements of Rule 16b-3 or Section 162(m) of the Internal
Revenue Code.

    (b)  Rights and obligations under any option granted before any amendment
of the Plan shall not be impaired by such amendment unless (i) the Company
requests the consent of the person to whom the option was granted and (ii) such
person consents in writing.

12. TERMINATION OR SUSPENSION OF THE PLAN.

    (a)  The Board may suspend or terminate the Plan at any time.  No options
may be granted under the Plan while the Plan is suspended or after it is
terminated.


                                         11.

<PAGE>

    (b)  Rights and obligations under any option granted while the Plan is in
effect shall not be impaired by suspension or termination of the Plan, except
with the consent of the person to whom the option was granted.

    (c)  The Plan shall terminate upon the occurrence of any of the events
described in Section 10(b) above.

13. EFFECTIVE DATE OF PLAN; CONDITIONS OF EXERCISE.

    (a)  The Plan shall become effective upon the Effective Date, subject to
the condition that the Plan is approved by the stockholders of the Company.

    (b)  No option granted under the Plan shall be exercised or exercisable
unless and until the condition of subparagraph 13(a) above has been met.


                                         12.


<PAGE>



                                        AVIRON

                          1996 EMPLOYEE STOCK PURCHASE PLAN

                                ADOPTED MARCH 6, 1996

                    APPROVED BY STOCKHOLDERS  _____________, 1996


1.   PURPOSE.

     (a)   The purpose of the 1996 Employee Stock Purchase Plan (the "Plan") is
to provide a means by which employees of Aviron, a Delaware corporation (the
"Company"), and its Affiliates, as defined in subparagraph 1(b), which are
designated as provided in subparagraph 2(b), may be given an opportunity to
purchase stock of the Company.

     (b)   The word "Affiliate" as used in the Plan means any parent
corporation or subsidiary corporation of the Company, as those terms are defined
in Sections 424(e) and (f), respectively, of the Internal Revenue Code of 1986,
as amended (the "Code").

     (c)   The Company, by means of the Plan, seeks to retain the services of
its employees, to secure and retain the services of new employees, and to
provide incentives for such persons to exert maximum efforts for the success of
the Company.

     (d)   The Company intends that the rights to purchase stock of the Company
granted under the Plan be considered options issued under an "employee stock
purchase plan" as that term is defined in Section 423(b) of the Code.

2.   ADMINISTRATION.

     (a)   The Plan shall be administered by the Board of Directors (the
"Board") of the Company unless and until the Board delegates administration to a
Committee, as provided in subparagraph 2(c).  Whether or not the Board has
delegated administration, the Board shall have the final power to determine all
questions of policy and expediency that may arise in the administration of the
Plan.

     (b)   The Board shall have the power, subject to, and within the
limitations of, the express provisions of the Plan:

           (i)     To determine when and how rights to purchase stock of the
Company shall be granted and the provisions of each offering of such rights
(which need not be identical).


                                          1.

<PAGE>

           (ii)    To designate from time to time which Affiliates of the
Company shall be eligible to participate in the Plan.

           (iii)    To construe and interpret the Plan and rights granted under
it, and to establish, amend and revoke rules and regulations for its
administration.  The Board, in the exercise of this power, may correct any
defect, omission or inconsistency in the Plan, in a manner and to the extent it
shall deem necessary or expedient to make the Plan fully effective.

           (iv)    To amend the Plan as provided in paragraph 13.

           (v)     Generally, to exercise such powers and to perform such acts
as the Board deems necessary or expedient to promote the best interests of the
Company and its Affiliates and to carry out the intent that the Plan be treated
as an "employee stock purchase plan" within the meaning of Section 423 of the
Code.

     (c)   The Board may delegate administration of the Plan to a Committee
composed of not fewer than two (2) members of the Board (the "Committee").  If
administration is delegated to a Committee, the Committee shall have, in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject, however, to such resolutions, not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board.  The
Board may abolish the Committee at any time and revest in the Board the
administration of the Plan.

3.   SHARES SUBJECT TO THE PLAN.

     (a)   Subject to the provisions of paragraph 12 relating to adjustments
upon changes in stock, the stock that may be sold pursuant to rights granted
under the Plan shall not exceed in the aggregate two hundred fifty thousand
(250,000) shares of the Company's common stock (the "Common Stock") (after
giving effect to the one-for-five reverse split of the Company's Common Stock
approved in March, 1996).  If any right granted under the Plan shall for any
reason terminate without having been exercised, the Common Stock not purchased
under such right shall again become available for the Plan.

     (b)   The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

4.   GRANT OF RIGHTS; OFFERING.

     The Board or the Committee may from time to time grant or provide for the
grant of rights to purchase Common Stock of the Company under the Plan to
eligible employees (an "Offering") on a date or dates (the "Offering Date(s)")
selected by the Board or the Committee.  Each Offering shall be in such form and
shall contain such terms and conditions as the Board or the Committee shall deem
appropriate, which shall comply with the requirements of Section 423(b)(5) of
the Code that all employees granted rights to purchase stock under the Plan
shall have the same


                                          2.

<PAGE>

rights and privileges.  The terms and conditions of an Offering shall be
incorporated by reference into the Plan and treated as part of the Plan.  The
provisions of separate Offerings need not be identical, but each Offering shall
include (through incorporation of the provisions of this Plan by reference in
the document comprising the Offering or otherwise) the period during which the
Offering shall be effective, which period shall not exceed twenty-seven (27)
months beginning with the Offering Date, and the substance of the provisions
contained in paragraphs 5 through 8, inclusive.

5.   ELIGIBILITY.

     (a)   Rights may be granted only to employees of the Company or, as the
Board or the Committee may designate as provided in subparagraph 2(b), to
employees of any Affiliate of the Company.  Except as provided in subparagraph
5(b), an employee of the Company or any Affiliate shall not be eligible to be
granted rights under the Plan, unless, on the Offering Date, such employee has
been in the employ of the Company or any Affiliate for such continuous period
preceding such grant as the Board or the Committee may require, but in no event
shall the required period of continuous employment be greater than two (2)
years.  In addition, unless otherwise determined by the Board or the Committee
and set forth in the terms of the applicable Offering, no employee of the
Company or any Affiliate shall be eligible to be granted rights under the Plan,
unless, on the Offering Date, such employee's customary employment with the
Company or such Affiliate is for at least twenty (20) hours per week and at
least five (5) months per calendar year.

     (b)   The Board or the Committee may provide that, each person who, during
the course of an Offering, first becomes an eligible employee of the Company or
designated Affiliate will, on a date or dates specified in the Offering which
coincides with the day on which such person becomes an eligible employee or
occurs thereafter, receive a right under that Offering, which right shall
thereafter be deemed to be a part of that Offering.  Such right shall have the
same characteristics as any rights originally granted under that Offering, as
described herein, except that:

           (i)     the date on which such right is granted shall be the
"Offering Date" of such right for all purposes, including determination of the
exercise price of such right;

           (ii)    the period of the Offering with respect to such right shall
begin on its Offering Date and end coincident with the end of such Offering; and

           (iii)    the Board or the Committee may provide that if such person
first becomes an eligible employee within a specified period of time before the
end of the Offering, he or she will not receive any right under that Offering.

     (c)   No employee shall be eligible for the grant of any rights under the
Plan if, immediately after any such rights are granted, such employee owns stock
possessing five percent


                                          3.

<PAGE>

(5%) or more of the total combined voting power or value of all classes of stock
of the Company or of any Affiliate.  For purposes of this subparagraph 5(c), the
rules of Section 424(d) of the Code shall apply in determining the stock
ownership of any employee, and stock which such employee may purchase under all
outstanding rights and options shall be treated as stock owned by such employee.

     (d)   An eligible employee may be granted rights under the Plan only if
such rights, together with any other rights granted under "employee stock
purchase plans" of the Company and any Affiliates, as specified by Section
423(b)(8) of the Code, do not permit such employee's rights to purchase stock of
the Company or any Affiliate to accrue at a rate which exceeds twenty five
thousand dollars ($25,000) of fair market value of such stock (determined at the
time such rights are granted) for each calendar year in which such rights are
outstanding at any time.

     (e)   Officers of the Company and any designated Affiliate shall be
eligible to participate in Offerings under the Plan, provided, however, that the
Board may provide in an Offering that certain employees who are highly
compensated employees within the meaning of Section 423(b)(4)(D) of the Code
shall not be eligible to participate.

6.   RIGHTS; PURCHASE PRICE.

     (a)   On each Offering Date, each eligible employee, pursuant to an
Offering made under the Plan, shall be granted the right to purchase up to the
number of shares of Common Stock of the Company purchasable with a percentage
designated by the Board or the Committee not exceeding fifteen percent (15%) of
such employee's Earnings (as defined in subparagraph 7(a)) during the period
which begins on the Offering Date (or such later date as the Board or the
Committee determines for a particular Offering) and ends on the date stated in
the Offering, which date shall be no later than the end of the Offering.  The
Board or the Committee shall establish one or more dates during an Offering (the
"Purchase Date(s)") on which rights granted under the Plan shall be exercised
and purchases of Common Stock carried out in accordance with such Offering.

     (b)   In connection with each Offering made under the Plan, the Board or
the Committee may specify a maximum number of shares that may be purchased by
any employee as well as a maximum aggregate number of shares that may be
purchased by all eligible employees pursuant to such Offering.  In addition, in
connection with each Offering that contains more than one Purchase Date, the
Board or the Committee may specify a maximum aggregate number of shares which
may be purchased by all eligible employees on any given Purchase Date under the
Offering.  If the aggregate purchase of shares upon exercise of rights granted
under the Offering would exceed any such maximum aggregate number, the Board or
the Committee shall make a pro rata allocation of the shares available in as
nearly a uniform manner as shall be practicable and as it shall deem to be
equitable.


                                          4.

<PAGE>

     (c)   The purchase price of stock acquired pursuant to rights granted
under the Plan shall be not less than the lesser of:

           (i)     an amount equal to eighty-five percent (85%) of the fair
market value of the stock on the Offering Date; or

           (ii)    an amount equal to eighty-five percent (85%) of the fair
market value of the stock on the Purchase Date.

7.   PARTICIPATION; WITHDRAWAL; TERMINATION.

     (a)   An eligible employee may become a participant in the Plan pursuant
to an Offering by delivering a participation agreement to the Company within the
time specified in the Offering, in such form as the Company provides.  Each such
agreement shall authorize payroll deductions of up to the maximum percentage
specified by the Board or the Committee of such employee's Earnings during the
Offering.  "Earnings" is defined as an employee's regular salary or wages
(including amounts thereof elected to be deferred by the employee, that would
otherwise have been paid, under any arrangement established by the Company that
is intended to comply with Section 125, Section 401(k), Section 402(h) or
Section 403(b) of the Code or that provides non-qualified deferred
compensation), which shall include overtime pay, but shall exclude bonuses,
commissions, incentive pay, profit sharing, other remuneration paid directly to
the employee, the cost of employee benefits paid for by the Company or an
Affiliate, education or tuition reimbursements, imputed income arising under any
group insurance or benefit program, traveling expenses, business and moving
expense reimbursements, income received in connection with stock options,
contributions made by the Company or an Affiliate under any employee benefit
plan, and similar items of compensation, or such other set of inclusions or
exclusions as may be determined by the Board or the Committee.  The payroll
deductions made for each participant shall be credited to an account for such
participant under the Plan and shall be deposited with the general funds of the
Company.  A participant may reduce (including to zero) or increase such payroll
deductions, and an eligible employee may begin such payroll deductions, after
the beginning of any Offering only as provided for in the Offering.  A
participant may make additional payments into his or her account only if
specifically provided for in the Offering and only if the participant has not
had the maximum amount withheld during the Offering.

     (b)   At any time during an Offering, a participant may terminate his or
her payroll deductions under the Plan and withdraw from the Offering by
delivering to the Company a notice of withdrawal in such form as the Company
provides.  Such withdrawal may be elected at any time prior to the end of the
Offering except as provided by the Board or the Committee in the Offering.  Upon
such withdrawal from the Offering by a participant, the Company shall distribute
to such participant all of his or her accumulated payroll deductions (reduced to
the extent, if any, such deductions have been used to acquire stock for the
participant) under the Offering, without interest, and such participant's
interest in that Offering shall be automatically terminated.  A participant's
withdrawal from an Offering will have no effect upon such participant's
eligibility


                                          5.

<PAGE>

to participate in any other Offerings under the Plan but such participant will
be required to deliver a new participation agreement in order to participate in
subsequent Offerings under the Plan.

     (c)   Rights granted pursuant to any Offering under the Plan shall
terminate immediately upon cessation of any participating employee's employment
with the Company and any designated Affiliate, for any reason, and the Company
shall distribute to such terminated employee all of his or her accumulated
payroll deductions (reduced to the extent, if any, such deductions have been
used to acquire stock for the terminated employee) under the Offering, without
interest.

     (d)   Rights granted under the Plan shall not be transferable by a
participant otherwise than by will or the laws of descent and distribution, or
by a beneficiary designation as provided in paragraph 14 and, otherwise during
his or her lifetime, shall be exercisable only by the person to whom such rights
are granted.

8.   EXERCISE.

     (a)   On each Purchase Date specified therefor in the relevant Offering,
each participant's accumulated payroll deductions and other additional payments
specifically provided for in the Offering (without any increase for interest)
will be applied to the purchase of whole shares of stock of the Company, up to
the maximum number of shares permitted pursuant to the terms of the Plan and the
applicable Offering, at the purchase price specified in the Offering.  No
fractional shares shall be issued upon the exercise of rights granted under the
Plan.  The amount, if any, of accumulated payroll deductions remaining in each
participant's account after the purchase of shares which is less than the amount
required to purchase one share of stock on the final Purchase Date of an
Offering shall be held in each such participant's account for the purchase of
shares under the next Offering under the Plan, unless such participant withdraws
from such next Offering, as provided in subparagraph 7(b), or is no longer
eligible to be granted rights under the Plan, as provided in paragraph 5, in
which case such amount shall be distributed to the participant after such final
Purchase Date, without interest.  The amount, if any, of accumulated payroll
deductions remaining in any participant's account after the purchase of shares
which is equal to the amount required to purchase whole shares of stock on the
final Purchase Date of an Offering shall be distributed in full to the
participant after such Purchase Date, without interest.

     (b)   No rights granted under the Plan may be exercised to any extent
unless the shares to be issued upon such exercise under the Plan (including
rights granted thereunder) are covered by an effective registration statement
pursuant to the Securities Act of 1933, as amended (the "Securities Act") and
the Plan is in material compliance with all applicable state, foreign and other
securities and other laws applicable to the Plan.  If on a Purchase Date in any
Offering hereunder the Plan is not so registered or in such compliance, no
rights granted under the Plan or any Offering shall be exercised on such
Purchase Date, and the Purchase Date shall be delayed until the Plan is subject
to such an effective registration statement and such compliance, except that the
Purchase Date shall not be delayed more than twelve (12) months and the Purchase
Date shall in no event be more than twenty-seven (27) months from the Offering
Date.  If on the Purchase Date


                                          6.

<PAGE>

of any Offering hereunder, as delayed to the maximum extent permissible, the
Plan is not registered and in such compliance, no rights granted under the Plan
or any Offering shall be exercised and all payroll deductions accumulated during
the Offering (reduced to the extent, if any, such deductions have been used to
acquire stock) shall be distributed to the participants, without interest.

9.   COVENANTS OF THE COMPANY.

     (a)   During the terms of the rights granted under the Plan, the Company
shall keep available at all times the number of shares of stock required to
satisfy such rights.

     (b)   The Company shall seek to obtain from each federal, state, foreign
or other regulatory commission or agency having jurisdiction over the Plan such
authority as may be required to issue and sell shares of stock upon exercise of
the rights granted under the Plan.  If, after reasonable efforts, the Company is
unable to obtain from any such regulatory commission or agency the authority
which counsel for the Company deems necessary for the lawful issuance and sale
of stock under the Plan, the Company shall be relieved from any liability for
failure to issue and sell stock upon exercise of such rights unless and until
such authority is obtained.

10.  USE OF PROCEEDS FROM STOCK.

     Proceeds from the sale of stock pursuant to rights granted under the Plan
shall constitute general funds of the Company.

11.  RIGHTS AS A STOCKHOLDER.

     A participant shall not be deemed to be the holder of, or to have any of
the rights of a holder with respect to, any shares subject to rights granted
under the Plan unless and until the participant's shareholdings acquired upon
exercise of rights under the Plan are recorded in the books of the Company.

12.  ADJUSTMENTS UPON CHANGES IN STOCK.

     (a)   If any change is made in the stock subject to the Plan, or subject
to any rights granted under the Plan (through merger, consolidation,
reorganization, recapitalization, reincorporation, stock dividend, dividend in
property other than cash, stock split, liquidating dividend, combination of
shares, exchange of shares, change in corporate structure or other transaction
not involving the receipt of consideration by the Company), the Plan and
outstanding rights will be appropriately adjusted in the class(es) and maximum
number of shares subject to the Plan and the class(es) and number of shares and
price per share of stock subject to outstanding rights.  Such adjustments shall
be made by the Board or the Committee, the determination of which shall be
final, binding and conclusive.  (The conversion of any convertible securities of
the Company shall not be treated as a "transaction not involving the receipt of
consideration by the


                                          7.

<PAGE>

Company.")

     (b)   In the event of:  (1) a dissolution or liquidation of the Company;
(2) a merger or consolidation in which the Company is not the surviving
corporation; (3) a reverse merger in which the Company is the surviving
corporation but the shares of the Company's Common Stock outstanding immediately
preceding the merger are converted by virtue of the merger into other property,
whether in the form of securities, cash or otherwise; or (4) the acquisition by
any person, entity or group within the meaning of Section 13(d) or 14(d) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act") or any
comparable successor provisions (excluding any employee benefit plan, or related
trust, sponsored or maintained by the Company or any Affiliate of the Company)
of the beneficial ownership (within the meaning of Rule 13d-3 promulgated under
the Exchange Act, or comparable successor rule) of securities of the Company
representing at least fifty percent (50%) of the combined voting power entitled
to vote in the election of directors, then, as determined by the Board in its
sole discretion (i) any surviving or acquiring corporation may assume
outstanding rights or substitute similar rights for those under the Plan, (ii)
such rights may continue in full force and effect, or (iii) participants'
accumulated payroll deductions may be used to purchase Common Stock immediately
prior to the transaction described above and the participants' rights under the
ongoing Offering terminated.

13.  AMENDMENT OF THE PLAN.

     (a)   The Board at any time, and from time to time, may amend the Plan.
However, except as provided in paragraph 12 relating to adjustments upon changes
in stock, no amendment shall be effective unless approved by the stockholders of
the Company within twelve (12) months before or after the adoption of the
amendment, where the amendment will:

           (i)     Increase the number of shares reserved for rights under the
     Plan;

           (ii)    Modify the provisions as to eligibility for participation in
     the Plan (to the extent such modification requires stockholder approval in
     order for the Plan to obtain employee stock purchase plan treatment under
     Section 423 of the Code or to comply with the requirements of Rule 16b-3
     promulgated under the Securities Exchange Act of 1934, as amended ("Rule
     16b-3")); or

           (iii)    Modify the Plan in any other way if such modification
     requires stockholder approval in order for the Plan to obtain employee
     stock purchase plan treatment under Section 423 of the Code or to comply
     with the requirements of Rule 16b-3.

It is expressly contemplated that the Board may amend the Plan in any respect
the Board deems necessary or advisable to provide eligible employees with the
maximum benefits provided or to be provided under the provisions of the Code and
the regulations promulgated thereunder relating to employee stock purchase plans
and/or to bring the Plan and/or rights granted under it into compliance
therewith.


                                          8.

<PAGE>

     (b)   Rights and obligations under any rights granted before amendment of
the Plan shall not be impaired by any amendment of the Plan, except with the
consent of the person to whom such rights were granted, or except as necessary
to comply with any laws or governmental regulations, or except as necessary to
ensure that the Plan and/or rights granted under the Plan comply with the
requirements of Section 423 of the Code.


14.  DESIGNATION OF BENEFICIARY.

     (a)   A participant may file a written designation of a beneficiary who is
to receive any shares and cash, if any, from the participant's account under the
Plan in the event of such participant's death subsequent to the end of an
Offering but prior to delivery to the participant of such shares and cash.  In
addition, a participant may file a written designation of a beneficiary who is
to receive any cash from the participant's account under the Plan in the event
of such participant's death during an Offering.

     (b)   Such designation of beneficiary may be changed by the participant at
any time by written notice.  In the event of the death of a participant and in
the absence of a beneficiary validly designated under the Plan who is living at
the time of such participant's death, the Company shall deliver such shares
and/or cash to the executor or administrator of the estate of the participant,
or if no such executor or administrator has been appointed (to the knowledge of
the Company), the Company, in its sole discretion, may deliver such shares
and/or cash to the spouse or to any one or more dependents or relatives of the
participant, or if no spouse, dependent or relative is known to the Company,
then to such other person as the Company may designate.

15.  TERMINATION OR SUSPENSION OF THE PLAN.

     (a)   The Board in its discretion, may suspend or terminate the Plan at
any time.  No rights may be granted under the Plan while the Plan is suspended
or after it is terminated.

     (b)   Rights and obligations under any rights granted while the Plan is in
effect shall not be impaired by suspension or termination of the Plan, except as
expressly provided in the Plan or with the consent of the person to whom such
rights were granted, or except as necessary to comply with any laws or
governmental regulation, or except as necessary to ensure that the Plan and/or
rights granted under the Plan comply with the requirements of Section 423 of the
Code.

16.  EFFECTIVE DATE OF PLAN.

     The Plan shall become effective on the same day that the Company's initial
public offering of shares of common stock becomes effective (the "Effective
Date"), but no rights granted under


                                          9.

<PAGE>

the Plan shall be exercised unless and until the Plan has been approved by the
stockholders of the Company within twelve (12) months before or after the date
the Plan is adopted by the Board or the Committee, which date may be prior to
the Effective Date.


                                         10.


<PAGE>

                                     AVIRON

                      VANNI BUSINESS PARK INDUSTRIAL LEASE

                                    ARTICLE I

                                     PARTIES

     THIS Lease, dated, for reference purposes only, August 29, 1995, is made by
and between the Vanni Business Park General) Partnership ("Lessor") and Aviron,
a California corporation. ("Lessee")

                                   ARTICLE II

                                    PREMISES

     Lessor hereby leases to Lessee and Lessee leases from Lessor for the term,
at the rental, and upon all of the conditions set forth herein, that certain
real property situated in the County of Santa Clara, State of California,
commonly known as 297 North Bernardo Avenue, Mountain View, California 94043,
and more particularly described in the site plan prepared by Dennis Kobza &
Associates, A.I.A., marked Exhibit "A" which is attached hereto and incorporated
herein.  Said real property, including the land and all improvements therein, is
called "the Premises".

                                   ARTICLE III

                                      TERM

     SECTION 3.01.  TERM.    The team of this lease shall be for ten (10) years,
commencing on November 1, 1995 ("Commencement Date").

     SECTION 3.02.  OPTION TO EXTEND.

     (a)  Lessee is given two (2) options to extend the Lease Term for five (5)
year periods each (the "Extended Terms), following expiration of the initial
Lease Term, which options may be exercised only by written notice (the "Option
Notice") from Lessee to Lessor given not less than one hundred eighty (180) days
prior to the end of the initial Lease Term, or not less than one hundred eighty
(180) days prior to the end of the then expiring Extended Term; provided,
however, if Lessee is in material default on the date of giving the Option
Notice, the Option Notice shall be totally ineffective, or if Lessee is in
material default on the date an Extended Term is to commence, such Extended Term
shall not commence and this Lease shall expire at the end of the initial Lease
Term or at the end of the then expiring Extended Term.  In the event of an
Extended Term, the Extended Term shall be subject to all the terms and
conditions of this Lease excepting rent which shall be at ninety-five percent
(95%) of the then fair market rental value of the Premises, as determined under
subparagraph (b) below, but in no event less than the monthly rent prevailing on
the last month of the then expiring initial Lease Term or Extended Term.

     (b)  The parties shall agree on the fair market rental value of the
Premises for each respective Extended Term, including fair market periodic
adjustments thereto, during the first thirty (30) days after the exercise by
Lessee of an option to extend the Lease Tenn.  The fair market rental
determination shall not take into account the improvements to the Premises
installed or constructed at Lessee's sole expense. If the parties are able to
agree on the fair market rental value for the Extended Term, (including periodic
Adjustments thereto), then such agreed value shall be the fair market rental
value for purposes of determining the rent for the Extended Term.

     In the event the parties are unable to agree on the fair market rental
value for the Premises (including periodic adjustments) within that time, then
at Lessee's written request, within ten (10) days of the expiration of that
thirty (30) day period, each party shall separately designate an appraiser to
make this determination.  Within five (5) business days of their appointment,
the two designated appraisers shall jointly designate a third appraiser.  The
failure of either party to appoint an appraiser within the time allowed shall be
deemed equivalent to appointing the appraiser appointed by the other party.  No
person shall be appointed or designated an appraiser unless he or she is then a
member


                                                                               1

<PAGE>

of MAI.  Appraisal shall be on the basis of the Premises "as is" except for
improvements and fixtures which were constructed at Lessee expense, or are the
sole property of Lessee. If, within ten (10) business days after the appointment
of all appraisers, a majority of the appraisers concur on the value of the then
current fair market rental value for the Premises, including fair market
periodic adjustments thereto, that appraisal shall be the accepted fair market
rental value.  If a majority of the appraisers do not concur within that period,
the determination of the appraiser whose appraisal is neither highest nor lowest
shall be the accepted fair market rental value.  The parties shall share the
appraisal expenses equally.

     SECTION 3.03.    DELAY IN ACCESS. The parties agree that if for any reason
Lessor cannot deliver access to the Premises to Lessee for the purpose of
commencing the Tenant Improvements on or before November 1, 1995, such failure
shall not constitute a breach of  this agreement by Lessor.  Lessee shall not be
obligated to pay rent, nor shall the Lease Term commence until access to the
Premises is tendered to Lessee.

     SECTION 3.04.    EARLY POSSESSION.  If Lessee occupies the Premises prior
to the Commencement Date, such occupancy shall be subject to all provisions
hereof, and Lessee shall pay rent for such period at the initial monthly rates
set forth below; provided, however, that Lessee may enter the Premises thirty
(30) days prior to the Commencement Date solely for the purpose of installing
fixtures or laboratory equipment or constructing tenant improvements without
being required to pay rent.

                                   ARTICLE IV


                             RENT: SPECIAL NET LEASE

     SECTION 4.01.    RENT.  The first month's rent shall be due and payable
upon execution of this Lease by Lessee.  From and after the Commencement Date,
Lessee shall pay to Lessor rent for Premises in advance, on the first day of
each month based on the following schedule of rents:

             Rent Per     Square                         Monthly
     Months Square Foot   Footage                        Base Rent
     ------ -----------   -------                        ---------
     01-12  1.35  "NNN"  42,800 sq. ft.                  $57,780.00
     13-24  1.35  "NNN"  52,800 sq. ft.                  $71,280.00
     25-48  1.45  "NNN"  52,800 sq. ft.                  $76,560.00
     49-72  1.50  "NNN"  52,800 sq. ft.                  $79,200.00
     73-96  1.60  "NNN"  52,800 sq. ft.                  $84,480.00
     97-120 1.65  "NNN"  52,800 sq. ft.                  $87,120.00

     Rent for any period during the term hereof which is for less than one month
shall be a pro rata portion of the monthly installment.  Rent shall be payable
in lawful money of the United States to Lessor at the address stated herein or
to such other persons or at such other places as Lessor may designate in
writing.

     SECTION 4.02.    SPECIAL NET LEASE.   This Lease is what is commonly called
a "Net, Net, Net Lease", it being understood that the Lessor shall receive the
rent set forth in Section 4.01 free and clear of any and all other impositions,
taxes, liens, charges or expenses of any nature except as otherwise provided in
this agreement.  In addition to the rent reserved by Section 4.01, Lessee shall
pay to the parties respectively entitled thereto all insurance premiums, taxes,
assessments, operating charges, management fees, maintenance charges, and any
other charges, costs and expenses which arise or may be contemplated under any
provisions of this Lease for the entire Premises during the term hereof.  All of
such charges, costs and expenses shall constitute additional rent, and upon the
failure of Lessee to pay any of such costs, charges or expenses, Lessor shall
have the same rights and remedies as otherwise provided in this Lease for the
failure of Lessee to pay rent. It is the intention of the parties hereto that
this Lease shall not be terminable for any reason by the Lessee, and that Lessee
shall in no event be entitled to any abatement of or reduction in rent payable
under this Lease, except as herein expressly provided.  Any present or future
law to the contrary shall not alter this agreement of the parties.

                                    ARTICLE V


                                                                               2
                                                                               -

<PAGE>

                                SECURITY DEPOSIT

Lessee shall deposit with Lessor, upon execution of this Lease, $87,120.00 as
security for Lessee's faithful performance of Lessee's obligations hereunder.
If Lessee fails to pay rent or other charges due hereunder, or otherwise
defaults with respect to any provision of this Lease, Lessor may, after the
expiration of any applicable period of curing such default as set forth herein,
without waiving or releasing Lessee from any obligation under this Lease, and
without waiving Lessor's right to treat such failure as a default hereof, use,
apply, or retain all or any portion of said deposit for the payment of any rent
or other charge in default or for the payment of any other sum to which Lessor
may become obligated by reason of Lessee's default, or to compensate Lessor for
any loss or damage which Lessor may suffer thereby.  If Lessor so uses or
applies all or any portion of said deposit, Lessee shall within ten (10) days
after written demand therefor deposit cash with Lessor in an amount sufficient
to restore said deposit to the full amount hereinabove stated and Lessee's
failure to do so shall be a material breach of this Lease.  If Lessee performs
all of Lessee's obligations hereunder, said deposit shall be returned to Lessee
(or, at Lessee's option, to the last assignee, if any, of Lessee's interest
hereunder) at the expiration of the term hereof, including extension, and after
Lessee has vacated the Premises.

     No trust relationship is created herein between Lessor and Lessee with
respect to said security deposit, and Lessor may commingle it, use it in
ordinary business, transfer or assign it, or use it in any combination of those
ways.  In the event of termination of Lessor's interest in this Lease, Lessor
shall transfer said deposit to Lessor's successor in interest, whereupon if such
successor acknowledges receipt thereof and assumes all of Lessor's obligations
under this Lease, Lessee agrees to release Lessor from all liability for the
return of such deposit or the accounting therefor.

                                   ARTICLE VI

                                       USE

     SECTION 6.01.  USE.  The Premises shall be used and occupied for offices,
warehouse, biomedical laboratory research and development, assembly, wholesale
sales, and any other legal use which is otherwise in compliance with the
reasonable rules and regulations that may be imposed by Lessor from time to time
on the business park.  Lessor represents, but does not warrant, that these
general uses are allowable, but that Lessee should consult and confirm with any
and all applicable governmental agencies that any specific use of the Premises
is allowable.  Lessee shall not use nor permit the use of the Premises in any
manner that will create waste or a nuisance or unreasonably disturb any other
tenants.  This Lease does not grant to Lessee any exclusive-use rights that
would prevent other tenants or lessees from conducting businesses or operations
within the business park similar to the business or operations of Lessee.

     SECTION 6.02.  COMPLIANCE WITH LAW.

     (a)  Lessor warrants to Lessee that the Premises, in its state existing on
the Commencement Date, does not violate any laws, or permits, licenses, or
covenants or restrictions of record, or any applicable building code, regulation
or ordinance in effect on such Commencement Date.

     (b)  Except as provided in paragraph 6.02(a) or elsewhere in this Lease,
Lessee shall, at Lessee's expense, comply promptly with all applicable statutes,
ordinances, rules, regulations, orders, covenants, and restrictions of record in
effect during the term or any part of the term hereof, regulating the use by
Lessee of the Premises.  Any Americans with Disabilities Act (ADA) requirements
resulting from the Lessee's use of the Premises shall be the responsibility of
Lessee.

     SECTION 6.03.  CONDITION OF PREMISES.

     (a)  Lessor shall deliver the Premises to Lessee, for the purpose of
constructing Lessee's tenant improvements, in an "as is" condition on the Lease
Commencement Date, except that the Premises shall be clean and free of debris
and toxic and radioactive materials.  Prior to the Commencement Date, Lessor
shall release to Lessee certain previously prepared reports, as requested by
Lessee, relating to the Premises, including a copy of the certified closure
report from


                                                                               3
                                                                               -

<PAGE>

the City of Mountain View Fire Department.  Such report shall include a
statement confirming that radioactive materials previously existing on the
premises, if any, have been removed to the extent that the Premises conforms, as
of the date of the report, to California state and City regulatory requirements
governing the allowable amounts of such materials on the Premises.

     All existing laboratory fixtures attached to the Premises, including cold
rooms, casework, vented fume hoods, and DI RO water system, shall remain in
place on the Premises, but shall not become the property of Lessee.  Lessor
further warrants to Lessee that, to the best of Lessor's knowledge, all HVAC,
electrical, roof, and plumbing systems are in good and working condition, and
that the Premises are free from any outstanding litigation, environmental
contamination, and code violations.  In the event that it is determined that any
of these warranties have been violated as of the Commencement Date, then it
shall be the obligation of Lessor, after receipt of written notice from Lessee
setting forth with specificity the nature of the violation, to promptly, at
Lessor's sole cost, rectify such violation.  Lessee's failure to give such
written notice to Lessor within ninety (90) days of the Lease Commencement Date,
shall cause the conclusive presumption that Lessor has complied with all of
Lessor's obligations hereunder.

     (b)  Except as otherwise provided in this Lease, Lessee hereby accepts the
Premises in their condition existing as of the Lease Commencement Date, subject
to all laws governing and regulating the use of the Premises, and accepts this
Lease subject thereto.  Lessee acknowledges that, except as expressly set forth
herein, neither Lessor nor Lessor's agent has made any representation or
warranty as to the present or future suitability of the Premises for the conduct
of Lessee's business.


                                   ARTICLE VII

                          HAZARDOUS OR TOXIC MATERIALS

     Lessee shall not emit, dump, dispose, or release on the Premises any Toxic
Materials, and Lessee shall not allow or permit any agent, vendor, or other
entity acting on Lessee's behalf to emit, dump, dispose, or release on the
Premises, any Toxic Materials.  Lessee shall not bring, use, or store on the
Premises, or emit, dump, dispose, or release from the Premises, any Toxic
Materials in violation of any laws, regulations, ordinances, or statutes which
are now in existence or which may be enacted in the future.  Lessee shall remain
in full and complete compliance with all laws, regulations, ordinances, and
statutes with respect to Toxic Materials, and Lessee shall install and keep in
good working order any monitoring devices that are necessary to insure Lessee's
full and complete compliance therewith.

     Lessee shall indemnify and hold Lessor harmless from any claims,
liabilities, costs, or expenses incurred or suffered by Lessor arising from
Lessee's bringing, using, emitting, dumping, disposing, or releasing upon the
Premises, or generating or creating at or emitting, dumping, disposing, or
releasing from the Premises, any Toxic Materials, or arising from the bringing,
using, emitting, dumping, disposing, or releasing upon the Premises, or
generating or creating at or emitting, dumping, disposing, or releasing from the
Premises, any Toxic Materials by any agent, vendor, or other entity acting on
Lessee's behalf.  Lessee's indemnification and hold harmless obligations as set
forth in this Article VII above include, without limitation, all of the
following: (i) claims, liabilities, costs or expenses resulting from or based
upon administrative, judicial (civil or criminal), or other action, legal or
equitable, brought by any private or public person under common law or any
Federal, State, County or Municipal law, ordinance or regulation, (ii) claims,
liabilities, costs, or expenses pertaining to the cleanup or containment of
Toxic Materials, the identification of the pollutants in the Toxic Materials,
the identification of the scope of any environmental contamination, the removal
of pollutants from soils, the provision of an alternative public drinking water
source, or the long term monitoring of ground water and surface waters, and
(iii) all costs of defending such claims.  Lessee shall comply, at its sole
cost, with all laws pertaining to such Toxic Materials.  Lessee's hold harmless
and indemnity obligations hereunder shall survive the expiration or termination
of this Lease.

     For the purposes of this Article VII, "Toxic Materials" includes, without
limitation, any toxic or hazardous gaseous, liquid, or solid materials or waste,


                                                                               4
                                                                               -

<PAGE>

or any material or substance having characteristics of ignitability,
corrosivity, reactivity, or extraction procedure toxicity or substances or
materials which are listed on any of the Environmental Protection Agency's lists
of hazardous wastes or which are identified in Sections 66680 through 66685 of
Title 22 of the California Code of Regulations as the same may be amended from
time to time.


     Except as may be disclosed in the hazardous materials report delivered to
Lessee by Lessor, to the best knowledge of Lessor, there are no Toxic Materials
present on or about the Premises and no action, proceeding, or claim is pending
or threatened concerning the Premises concerning any Toxic Material or pursuant
to any environmental law.

     Lessor shall indemnify Lessee and hold Lessee harmless from any claims,
liabilities, costs, or expenses incurred or suffered by Lessee arising from the
existence of Toxic Materials on the Premises prior to or on the Commencement
Date.

                                  ARTICLE VIII

                      MAINTENANCE, REPAIRS AND ALTERATIONS

     SECTION 8.01.  MAINTENANCE - PREMISES.  Throughout the term, Lessee agrees
to keep and maintain all improvements and appurtenances in or serving the
Premises, including all sewer connections, plumbing, heating and cooling
appliances, and wiring, in the same order, condition and repair as they are in
on the Commencement Date, or may be put in during the term, reasonable use and
wear excepted.  Lessee hereby expressly waives the provisions of any law
permitting repairs by a tenant at the expense of a landlord, including, without
limitation, all rights of Lessee under Sections 1941 and 1942 of the California
Civil Code.  Lessee agrees to keep the Premises clean and in sanitary condition
as required by the health, sanitary and police ordinances and regulations of any
political subdivision having jurisdiction.  Lessee further agrees to keep the
interior of the Premises, such as the windows, floors, walls, doors, showcases
and fixtures clean and neat in appearance and to remove all trash and debris
which may be found in or around the Premises.  If Lessee refuses or neglects to
commence such repairs and/or maintenance required under this agreement or does
not diligently prosecute same to completion within thirty (30) days of written
notice thereof, then Lessor may enter the Premises and cause such repairs and/or
maintenance to be made.  Lessee agrees that upon demand, it shall pay to Lessor
the cost of any such repairs, together with accrued interest from the date of
payment at the prime commercial lending rate then in effect at Bank of America.
Notwithstanding anything to the contrary above, if Lessee fails to maintain the
Premises according to the Lease terms, Lessor may elect to enter into a
maintenance contract with a third party for the provision of all or a part of
Lessee's maintenance obligations as set forth in this Paragraph.  Upon such
election, Lessee shall be relieved from its obligations to perform only those
maintenance obligations covered by the maintenance contract, and Lessee shall
bear its pro rata share, as set forth in Paragraph 8.02 below, of the costs of
such maintenance contract which shall be paid in advance on a monthly basis with
Lessee's rent payments.

     SECTION 8.02.  MAINTENANCE - COMMON AREAS.  Lessor shall be responsible for
maintaining in a safe, good, and clean condition, the common areas, structure
and roof of the Premises and the common areas of the business park as a whole.
Lessee shall have the obligation to notify Lessor, in writing, of any repairs or
maintenance to the common areas, structure, or roof which may be required, and
Lessor shall have a reasonable time to make such repairs, provided that Lessor
promptly commences such repairs and diligently prosecutes the same to
completion.

     Lessee shall pay to Lessor, as additional rent, in the manner and at the
time provided below, Lessee's proportionate share, as defined below, of all
costs and expenses incurred by Lessor in the operation and maintenance of the
common areas of the business park during the term of this Lease.  Such costs and
expenses shall include, without limiting the generality of the foregoing, all
maintenance, pest control, security, gardening, landscaping, cost of public
liability, property damage, vandalism and malicious mischief, earthquake, and
other insurance deemed necessary by the Landlord, real property taxes, property
management costs, including a management fee equal to three percent (3%) of the
monthly rent, painting, lighting, cleaning, trash removal, depreciation of


                                                                               5
                                                                               -

<PAGE>

equipment, fireprotection, and similar items.

     Lessee's proportionate share of such common area expenses shall be 21.7%
which is based upon the square footage of 52,800 square feet for the Premises
and the total square footage of the business park which is 243,364 square feet.

     Lessor shall bill Lessee monthly for Lessee's proportionate share of such
common area costs, which proportionate share shall be based upon the previous
month's actual costs and expenses.  Lessee shall pay such proportionate share
within 15 days of receipt of said billing statement from Lessor.  Lessor agrees
to make its books and records pertaining to the common area costs available for
Lessee's inspection upon request.

     If any of Lessee's repair obligations under section 8.01 or reimbursement
obligations under section 8.02 would require Lessee to pay all or any portion of
any charge which should be treated as a capital improvement under generally
accepted accounting principles, then Lessee shall pay that portion of the cost,
or if pursuant to this Section 8.02 then Lessee's proportionate share of that
portion of the cost, of such capital improvement determined by multiplying such
cost by a fraction, the numerator of which is the number of years and/or
fractions of years remaining in the lease term, including extensions, at the
time the capital improvement project commences, and the denominator of which is
the useful life of such capital improvement. If Lessee does not exercise its
option to extend the lease term under Section 3.02, then the numerator used to
determine Lessee's proportionate share shall be deemed changed retroactively to
reflect only the lease term without extensions and Lessor shall refund to Lessee
the amount called for by such adjustment.

     SECTION 8.03. ALTERATIONS AND ADDITIONS.  No alterations or additions shall
be made to the Premises by Lessee without the prior written consent of Lessor
which Lessor will not unreasonably withhold.  Lessee may make nonstructural
alterations not exceeding Twenty-Five Thousand Dollars ($25,000.00) without the
approval of Lessor if such alterations meet all applicable codes, laws, and
ordinances.

     As a condition to giving its consent, Lessor may require that Lessee agree
to remove any such alterations or improvements at the expiration of the term.
All structural changes, alterations, or additions to be made to the Premises
shall be under the supervision of a competent architect or competent licensed
structural engineer and made in accordance with plans and specifications which
have been furnished to and approved by Lessor prior to commencement of work,
which approval shall not be unreasonably withheld. If the written consent of
Lessor to any proposed alterations by Lessee shall have been obtained, Lessee
agrees to advise Lessor in writing of the date upon which such alterations will
commence in order to permit Lessor to post a notice of non-responsibility.  All
such alterations, changes and additions shall be constructed in good and
workmanlike manner in accordance with all ordinances and laws relating thereto.
Upon request, Lessor shall advise Lessee in writing whether Lessor reserves the
right to require Lessee to remove any alterations to the Premises upon
termination of the Lease.  Except for alterations that cannot be removed without
structural injury to the Premises, at any time Lessee may remove any alterations
or fixtures installed by Lessee from the Premises provided that Lessee repairs
all damages occasioned by such removal.

     SECTION 8.04.  NO TENANT IMPROVEMENT ALLOWANCE.

     Lessor shall not provide any tenant improvement allowance under this Lease.

     SECTION 8.05.  PLUMBING.  Lessee shall not use the plumbing facilities for
any purpose other than that for which they were constructed.  The expense of any
breakage, stoppage or other damage relating to the plumbing and resulting from
the introduction by Lessee, its agents, employees, or invitees of foreign
substances into the plumbing facilities shall be borne by Lessee.

                                   ARTICLE IX

                                    INSURANCE

     SECTION 9.01. PROPERTY/RENTAL INSURANCE-- PREMISES.  During the term,
Lessor shall keep the Premises insured against loss or damage by fire and those



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<PAGE>

risks normally included in the term "all risk" including (a) flood coverage, (b)
earthquake coverage at the election of Lessor, (c) coverage for loss of rents
(provided that notwithstanding anything set forth herein to the contrary rent
shall abate at least to the extent of any rent insurance received by Lessor) and
(d) boiler and machinery coverage if the Lessor reasonably deems such coverage
necessary.  Any deductibles shall be paid by Lessor if the deductible arises
from damage solely to the Premises.  The amount of such insurance shall be not
less than one hundred percent (100%) of the replacement value of the Premises.
Any recovery received from said insurance policy shall be paid to Lessor.

     Lessee, in addition to the rent and other charges provided herein, agrees
to pay to Lessor its pro rata share of the premiums for all such insurance,
which pro rata share is identical to that provided in Section 8.02, above.  The
insurance premiums shall be paid in accordance with Article IV, within thirty
(30) days of Lessee's receipt of a copy of Lessor's statement therefor.

     SECTION 9.02. PROPERTY INSURANCE--FIXTURES AND INVENTORY.  During the 
term, Lessee shall, at its sole expense, maintain insurance with "all risk" 
coverage on any fixtures, leasehold improvements, furnishings, merchandise, 
equipment, or personal property in or on the Premises, whether in place as of 
the date hereof or installed hereafter, for the full replacement value 
thereof, and Lessor shall not have any responsibility nor pay any costs for 
maintaining any types of such insurance.  Any deductibles shall be paid by 
Lessee.

     SECTION 9.03.  LESSOR'S LIABILITY INSURANCE.  During the term, Lessor may
maintain a policy or policies of comprehensive general liability insurance
insuring Lessor and Lessee (and such others as designated by Lessor) against
liability for bodily injury, death and property damage on or about the Premises
or the common area of the business park, with combined single limit coverage of
not less than Two Million Dollars ($2,000,000).

     Lessee, in addition to the rent and other charges provided herein, agrees
to pay to Lessor its pro rata share of the premiums for all such insurance,
which pro rata share is identical to that provided in Section 8.02, above.  The
insurance premiums shall be paid in accordance with Article IV, within thirty
(30) days of Lessee's receipt of a copy of Lessor's statement therefor.

     SECTION 9.04. LESSEE'S LIABILITY INSURANCE.  During the term, Lessee shall,
at its sole expense, maintain for the mutual benefit of Lessor and Lessee,
comprehensive general liability and property damage insurance against claims for
bodily injury, death or property damage occurring in or about the Premises or
arising out of the use or occupancy of the Premises, with combined single limit
coverage of not less than Two Million Dollars ($2,000,000).  The limits of such
insurance shall not limit the liability of Lessee.  Lessee shall furnish to
Lessor prior to the Commencement Date, and at least thirty (30) days prior to
the expiration date of any policy, certificates indicating that the liability
insurance required by Lessee above is in full force and effect; that Lessor has
been named as an additional insured; and that all such policies will not be
cancelled unless thirty (30) days' prior written notice of the proposed
cancellation has been given to Lessor.  The insurance shall be with insurers
approved by Lessor and with policies in form satisfactory to Lessor, provided
however, that such approval shall not be unreasonably withheld.  Said policies
shall provide that Lessor, although an additional insured, may recover for loss
covered by such insurance suffered by Lessor by reason of Lessee's negligence
and shall include a broad form liability endorsement.

     SECTION 9.05.  WAIVER OF SUBROGATION.  Lessor hereby releases Lessee, and
Lessee hereby releases Lessor, and their respective officers, agents, employees
and servants, from any and all claims or demands of damages, loss, expense, or
injury to the Premises, or to the furnishings and fixtures and equipment, or
inventory or other property of either Lessor or Lessee in, or about or upon the
Premises, or claims for bodily injury or death which is caused by or results
from perils, events or happenings which are the subject of insurance and carried
by the respective parties and in force or required to be in force pursuant to
this Article IX at the time of any such loss; provided, however, that such
waiver shall be effective only to the extent permitted by the insurance covering
such loss and to the extent such insurance is not prejudiced thereby.  Each
party shall cause each insurance policy obtained by it to provide that the
insurance company waives all right of recovery by way of subrogation against
either party in connection with any damage covered by any policy.


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<PAGE>

     SECTION 9.06.  INDEMNIFICATION.  Except in the case of Lessor's own acts or
omission, Lessee will indemnify Lessor and save it harmless from and against any
and all claims, actions, damages, liability and expense in connection with loss
of life, personal injury and/or damage to property arising from or out of any
occurrence in, upon or at the Premises (other than those arising from the
construction of the Premises or Building), or the occupancy or use by Lessee of
the Premises or any part hereof, or caused wholly or in part by acts or
omissions of Lessee, its agents, contractors, employees, servants, licensees, or
concessionaires or by anyone permitted to be on the Premises by Lessee.  In case
Lessor shall be made a party to any such litigation commenced by or against
Lessee, then Lessee shall protect and hold Lessor harmless from all claims,
liabilities, costs and expenses, and shall pay all costs, expenses and
reasonable legal fees incurred by Lessor in connection with such litigation.

     SECTION 9.07.  PLATE GLASS REPLACEMENT.  Lessee shall replace at its sole
expense, any and all plate glass and other glass in and about the Premises which
is damaged or broken by vandalism.  If any plate glass or other glass in and
about the Premises is damaged or broken by causes other than vandalism, then
Lessor shall replace the same and Lessee shall reimburse Lessor an amount equal
to Lessor's cost of replacement, provided that such amount shall not exceed the
deductible then in effect on Lessor's insurance policy, if any, covering the
damaged glass. Nothing herein shall be construed to require Lessor to carry
plate glass insurance.

     SECTION 9.08. WORKER'S COMPENSATION INSURANCE.  Lessee shall, at its sole
expense, maintain and keep in force during the term a policy or policies of
Worker's Compensation insurance or any other employee benefit insurance
sufficient to comply with all applicable laws, statutes, ordinances and
governmental rules, regulations or requirements.

                                    ARTICLE X

                              DAMAGE OR DESTRUCTION

     SECTION 10.01.  RIGHT TO TERMINATE ON DESTRUCTION OF PREMISES.  Lessor and
Lessee shall have the right to terminate this Lease if, during the term, the
Premises are damaged to an extent exceeding fifty percent (50%) of the then
reconstruction cost of the Premises as a whole.  Lessor and Lessee shall also
have the right to terminate this Lease if any portion of the Premises is damaged
by a peril not required to be insured hereunder.  In either case, Lessor and
Lessee may elect to terminate as provided above by written notice to Lessee or
Lessor delivered within thirty (30) days of the happening of such damage.

     SECTION 10.02. REPAIRS BY LESSOR.  If Lessor and Lessee shall not elect to
terminate this Lease pursuant to Section 10.01, Lessor shall, immediately upon
receipt of insurance proceeds paid in connection with such casualty, but in no
event later than one hundred twenty (120) days after such damage has occurred,
proceed to repair or rebuild the Premises, on the same plan and design as
existed immediately before such damage or destruction occurred and will proceed
expeditiously to complete such restoration, subject to such delays as may be
reasonably attributable to governmental restrictions or failure to obtain
materials or labor, or other causes beyond the control of Lessor.  Lessee shall
be liable for the repair and replacement of all fixtures, leasehold
improvements, furnishings, merchandise, equipment and personal property as
provided in Section 9.02.

     SECTION 10.03.  REDUCTION OF RENT DURING REPAIRS.  In the event Lessee is
able to continue to conduct its business during the making of repairs, the rent
then prevailing will be equitably reduced in the proportion that the square
footage of the unusable part of the Premises bears to the square footage of the
whole thereof for the period that repairs are being made.  No rent shall be
payable while the Premises are wholly unusable due to casualty damage.

     SECTION 10.04.  ARBITRATION.  Any controversy or claim arising out of or
relating to this Article shall be settled by arbitration in accordance with the
rules of the American Arbitration Association as then in effect, and judgment
upon the award rendered by the arbitration may be entered in any court having
jurisdiction.  The expenses of arbitration shall be borne by the parties as
allocated by the arbitrators.  The party desiring arbitration shall serve notice
upon the other party, together with designation of the first party's arbitrator.


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<PAGE>

     SECTION 10.05.  LESSOR'S OVERRIDING RIGHT TO TERMINATE.  Notwithstanding
anything to the contrary herein, during the last twelve (12) months of the Lease
Term and during the last 12 months of an Extended Term, if any, if the
discounted present value of the rent due hereunder for the balance of the term,
using as the discount rate the prime commercial lending rate in effect at the
Bank of America as of the date Lessor is to commence repairs pursuant to Section
10.02 hereof, is less than the cost of repairing the damage to the Premises,
Lessor may at its option terminate this lease upon thirty (30) days' written
notice.

                                   ARTICLE XI

                               REAL PROPERTY TAXES

     SECTION 11.01.  PAYMENT OF TAXES.  Lessee shall pay the real property tax,
as defined in Section 11.02, applicable to the Premises during the term of this
Lease.  All such payments shall be made at least ten (10) days prior to the
delinquency date of such payment.  If any such taxes paid by Lessee shall cover
any period of time prior to or after the expiration of the term hereof, Lessor
shall pay such taxes and Lessee shall reimburse Lessor therefor.  Lessee's share
of such taxes shall be equitably prorated to cover only the period of time
within the tax fiscal year during which this Lease shall be in effect, and
Lessor shall reimburse Lessee to the extent required.  If Lessee shall fail to
pay any such taxes, Lessor shall have the right to pay the same, in which case
Lessee shall repay such amount to Lessor with Lessee's next rent installment
together with interest at the prime commercial lending rate then in effect at
the Bank of America.

     SECTION 11.02. DEFINITION OF "REAL PROPERTY TAX".  As used herein, the term
"real property tax" shall include any form of real estate tax or assessment,
general, special, supplemental, ordinary or extraordinary, and any license fee,
commercial rental tax, improvement bond or bonds, levy or tax (other than
inheritance, personal income, corporate, franchise or estate taxes) imposed on
the Premises by any authority having the direct or indirect power to tax,
including any improvement district thereof, as against any legal or equitable
interest of Lessor in the Premises or in the real property of which the Premises
are a part, as against Lessor's right to rent or other income therefrom, and as
against Lessor's business of leasing the Premises.

     SECTION 11.03. JOINT ASSESSMENT.  If the Premises are not separately
assessed, Lessee's liability shall be an equitable proportion of the real
property taxes for all of the land and improvements included within the tax
parcel assessed, such proportion to be determined by Lessor in accordance with
Lessee's proportionate share of the total square footage of the business park.
Lessee shall reimburse Lessor said proportionate amount at least ten (10) days
prior to the delinquency date of the real property tax.

     SECTION 11.04.  PERSONAL PROPERTY TAXES.

     (a)  Lessee shall pay prior to delinquency all taxes assessed against and
levied upon trade fixtures, furnishings, equipment and all other personal
property of Lessee contained in the Premises or elsewhere.  When possible,
Lessee shall cause said trade fixtures, furnishings, equipment and all other
personal property to be assessed and billed separately from the real property of
Lessor.

     (b)  If any of Lessee's said personal property shall be assessed with
Lessor's real property, Lessee shall pay Lessor the taxes attributable to Lessee
within 10 days after receipt of a written statement setting forth the taxes
applicable to Lessee's property.

     (c)  If Lessee shall fail to pay any such taxes, Lessor shall have the
right to pay the same, in which case Lessee shall repay such amount to Lessor
with Lessee's next rent installment together with interest at the prime
commercial lending rate then charged by the Bank of America.

                                   ARTICLE XII

                            UTILITIES AND JANITORIAL

     Lessee shall pay prior to delinquency throughout the term the cost of
water, gas, heating, cooling, sewer, telephone, electricity, garbage, air


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<PAGE>

conditioning and ventilation, janitorial service, and all other materials and
utilities supplied to the Premises.  If any such services are not separately
metered to Lessee, Lessee shall pay its proportionate share of all charges which
are jointly metered, the determination to be made by Lessor in good faith, and
payment to be made by Lessee within fifteen (15) days of receipt of the
statement for such charges.

                                  ARTICLE XIII

                            ASSIGNMENT AND SUBLETTING

     SECTION 13.01.  LESSOR'S CONSENT REQUIRED.  Except as provided in Section
13.02, below, Lessee shall not voluntarily or by operation of law assign,
transfer, mortgage, sublet, or otherwise transfer or encumber all or any part of
Lessee's interest in this lease or in the Promises, without Lessor's prior
written consent which Lessor shall not unreasonably withhold.  Lessee must make
such request to Lessor in writing and by certified mail.  Lessor shall respond
to Lessee's request for consent hereunder within twenty (20) days after Lessee's
request and any attempted assignment, transfer, mortgage, encumbrance, or
subletting without such consent shall be void, and shall constitute a breach of
this lease.  If Lessor does not respond within such twenty (20) days, Lessee's
request shall be deemed approved.

     SECTION 13.02.  LESSEE AFFILIATE.  Lessee may assign or sublet the
Premises, or any portion thereof, to any corporation which controls, is
controlled by, or is under common control with Lessee, or to any corporation
resulting from the merger or consolidation with Lessee, or to any person or
entity which acquires all, or substantially all of the assets of Lessee as a
going concern of the business that is being conducted on the Premises, without
the consent of Lessor, provided that said assignee assumes, in full, the
obligations of Lessee under this Lease.  Any such assignment shall not, in any
way, affect or limit the liability of Lessee under the terms of this Lease.

     SECTION 13.03. NO RELEASE OF LESSEE.  Regardless of Lessor's consent, no
subletting or assignment shall release Lessee of Lessee's obligation or alter
the primary liability of Lessee to pay the rent and to perform all other
obligations to be performed by Lessee hereunder.  The acceptance of rent by
Lessor from any other person shall not be deemed consent to any subsequent
assignment or subletting.  In the event of default by any assignee of Lessee or
any successor of Lessee, in the performance of any of the terms hereof, Lessor
may proceed directly against Lessee without the necessity of exhausting remedies
against said assignee.

     SECTION 13.04. ATTORNEYS' FEES. In the event Lessee shall assign or sublet
the Premises or request the consent of Lessor to any assignment or subletting
or if Lessee shall request the consent of Lessor for any act Lessee proposes to
do then Lessee shall pay Lessor's reasonable attorneys' fees incurred in
connection therewith.

     SECTION 13.05. EXCESS RENT.  In the event Lessor shall consent to a
sublease or an assignment under the lease, Lessee shall pay to Lessor with its
regularly scheduled rent payments fifty percent (50%) of all sums collected by
Lessee from a sublessee or assignee which are in excess of (i) the rent then
owing pursuant to Article IV above for such space, (ii) the present market
rental premium, if any, for all tenant improvements for such space paid by
Lessee, and (iii) all leasing commissions, reasonable attorneys' fees and other
costs, reasonable expenses and liabilities incurred by Lessee in connection with
the sublet or assignment.  Lessor shall not share compensation received by
Lessee for the sale of its trade fixtures, goodwill, stock, or property other
than the Lease.

     SECTION 13.06. NO IMPAIRMENT OF SECURITY.  Lessee's written request to 
Lessor for consent to an assignment or subletting shall be accompanied by (a) 
the name and legal composition of the proposed sublessee; (b) the nature of 
the proposed sublessee's business to be carried on in the Premises; (c) the 
terms and provisions of the proposed sublease; and (d) such financial and 
other reasonable information as Lessor may request concerning the proposed 
sublessee. Lessor's consent shall not be deemed unreasonably withheld if 
consent is denied because the prospective sublessee or assignee will impair 
Lessor's security.

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<PAGE>

                                   ARTICLE XIV

                               DEFAULTS; REMEDIES

     SECTION 14.01.  DEFAULTS.  The occurrence of any one or more of the
following events shall constitute a material default and breach of this Lease by
Lessee:

     (a)  The abandonment of the Premises by Lessee;

     (b)  The failure by Lessee to make any payment of rent or any other payment
required to be made by Lessee hereunder, as and when due, where such failure
shall continue for a period of five (5) days after written notice hereof from
Lessor to Lessee.  In the event that Lessor serves Lessee with a Notice to Pay
Rent or Quit pursuant to applicable Unlawful Detainer statutes such Notice to
Pay Rent or Quit shall also constitute the notice required by this Section;

     (c)  The failure by Lessee to observe or perform any of the covenants,
conditions or provisions of this Lease to be observed or performed by Lessee,
other than described in paragraph (b) above, where such failure shall continue
for a period of 10 days after written notice hereof from Lessor to Lessee;
provided, however, that if the nature of Lessee's default is such that more than
10 days are reasonably required for its cure, then Lessee shall not be deemed to
be in default if Lessee commences such cure within said 10 day period and
thereafter diligently prosecutes such cure to completion;

     (d)  (i) The making by Lessee of any general arrangement or assignment for
the benefit of creditors; (ii) Lessee becomes a "debtor" as defined in 11 U.S.C.
Section 101 or any successor statute thereto; (iii) the taking or suffering of
any action by Lessee under any insolvency or bankruptcy act; (iv) the
appointment of a trustee or receiver to take possession of substantially all of
Lessee's assets located at the Premises or of Lessee's interest in this Lease,
or (v) the attachment, execution or other judicial seizure of substantially all
of Lessee's assets located at the Premises or of Lessee's interest in this
Lease.  Provided, however, in the event that any provisions of this Section
14.01(d) is contrary to any applicable law, such provision shall be of no force
or effect;

     (e)  The discovery by Lessor that any financial statement given to Lessor
by Lessee, any assignee of Lessee, any successor in interest of Lessee or any
guarantor of Lessee's obligation hereunder, and any of them, was materially
false.

     SECTION 14.02.  REMEDIES.  In the event of any such material default or
breach by Lessee, Lessor may at any time thereafter, with or without notice or
demand and without limiting Lessor in the exercise of any right or remedy which
Lessor may have by reason of such default or breach:

     (a)  Terminate Lessee's right to possession of the Premises by any lawful
means, in which case this Lease shall terminate and Lessee shall immediately
surrender possession of the Premises to Lessor.  In such event Lessor shall be
entitled to recover from Lessee all damages incurred by Lessor by reason of
Lessee's default including, but not limited to, the cost of recovering
possession of the Premises and reasonable attorney's fees related thereto; the
worth at the time of award determined by the court having jurisdiction thereof
of the amount by which the unpaid rent for the balance of the term after the
time of such award exceeds the amount of such rental loss for the same period
that Lessee proves could be reasonably avoided.

     (b)  Maintain Lessee's right to possession in which case this Lease shall
continue in effect whether or not Lessee shall have abandoned the Premises. In
such event Lessor shall be entitled to enforce all of Lessor's rights and
remedies under this Lease, including the right to recover the rent as it becomes
due hereunder.

     (c)  Pursue any other remedy now or hereafter available to Lessor under the
laws or judicial decisions of the State of California.  Unpaid installments of
rent and other unpaid monetary obligations of Lessee under the terms of this
Lease shall bear interest from the date due at the prime rate then charged by
Bank of America.


                                                                              11
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<PAGE>

     SECTION 14.03. DEFAULT BY LESSOR. Lessor shall not be in default unless
Lessor fails to perform obligations required of Lessor within a reasonable time,
but in no event later than thirty (30) days after written notice by Lessee to
Lessor and to the holder of any first mortgage or deed of trust covering the
Premises whose name and address shall have theretofore been furnished to Lessee
in writing, specifying wherein Lessor has failed to perform such obligation;
provided, however, that if the nature of Lessor's obligation is such that more
than thirty (30) days are required for performance then Lessor shall not be in
default if Lessor commences performance within such 30-day period and thereafter
diligently prosecutes the same to completion.  In the event Lessor does not
commence performance within the thirty (30) day period provided herein, or does
not diligently prosecute the same to completion, Lessee may perform such
obligation and will be reimbursed for its expenses by Lessor together with
interest thereon at the prime commercial lending rate then charged by the Bank
of America, provided, however, that if the parties are in dispute as to what
constitutes Lessor's obligations under this agreement, any such dispute shall be
resolved by arbitration in a manner identical to that provided in Section 10.04
above.

     Nothing herein shall be deemed applicable in the event of Lessor's delay in
delivery of the Premises.  In that situation, all rights and remedies shall be
determined under Section 3.03 above.

     SECTION 14.04.  LATE CHARGES.  Lessee hereby acknowledges that late payment
by Lessee to Lessor of rent and other sums due hereunder will cause Lessor to
incur costs not contemplated by this Lease, the exact amount of which will be
extremely difficult to ascertain, Such costs include, but are not limited to,
processing and accounting charges, and late charges which may be imposed on
Lessor by the terms of any mortgage or trust deed covering the Premises.
Accordingly, if any installment of rent or any other sum due from Lessee shall
not be received by Lessor or Lessor's designated agent within three (3) business
days after Lessee's receipt of written notice, by first class mail, that such
amount is due and owing, Lessee shall pay to Lessor a late charge equal to 10%
of such overdue amount.  The parties hereby agree that such late charge
represents a fair and reasonable estimate of the costs Lessor will incur by
reason of late payment by Lessee.  Acceptance of any such late charge by Lessor
shall in no event constitute a waiver of Lessee's default with respect to such
overdue amount, nor prevent Lessor from exercising any of the other rights and
remedies granted hereunder.  In the event that a late charge is payable
hereunder, whether or not collected, for three (3) consecutive installments of
rent, then rent shall automatically become due and payable quarterly in advance,
rather than monthly, notwithstanding section 4.01 or any other provision of this
Lease to the contrary.

     SECTION 14.05.  IMPOUNDS.  In the event that a late charge is payable
hereunder, whether or not collected, for three (3) installments of rent or any
other monetary obligation of Lessee under the terms of this Lease within a
twelve (12) month period, Lessee shall pay to Lessor, if Lessor shall so
request, in addition to any other payments required under this Lease, a monthly
advance installment, payable at the same time as the monthly rent, as estimated
by Lessor, for real property tax and insurance expenses on the Premises which
are payable by Lessee under the terms of this Lease.  Such fund shall be
established to insure payment when due, before delinquency, of any or all such
real property taxes and insurance premiums.  If the amounts paid to Lessor by
Lessee under the provisions of this paragraph are insufficient to discharge the
obligations of Lessee to pay such real property taxes and insurance premiums as
the same become due, Lessee shall pay to Lessor, within three (3) business days
after Lessor's demand, such additional sums necessary to pay such obligations.
All moneys paid to Lessor under this paragraph may be intermingled with other
moneys of Lessor and shall not bear interest.  In the event of a default in the
obligations of Lessee to perform under this Lease, then any balance remaining
from funds paid to Lessor under the provisions of this paragraph may, at the
option of Lessor, be applied to the payment of any monetary default of Lessee in
lieu of being applied to the payment of real property tax and insurance
premiums.

                                   ARTICLE XV

                            CONDEMNATION OF PREMISES.

     SECTION 15.01.  TOTAL CONDEMNATION.  If the entire Premises, whether by
exercise of governmental power or the sale or transfer by Lessor to any
condemnor


                                                                              12
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<PAGE>

under threat of condemnation or while proceedings for condemnation are pending,
at any time during the term, shall be taken by condemnation such that there does
not remain a portion suitable for occupation, this Lease shall then terminate as
of the date transfer of possession is required.  Upon such condemnation, all
rent shall be paid up to the date transfer of possession is required, and Lessee
shall have no claim against Lessor for the value of the unexpired term of this
Lease.

     SECTION 15.02.  PARTIAL CONDEMNATION.  If any portion of the Premises is
taken by condemnation during the term, whether by exercise of governmental power
or the sale or transfer by Lessor to a condemnor under threat of condemnation or
while proceedings for condemnation are pending, this Lease shall remain in full
force and effect except that in the event a partial taking leaves the Premises
unfit for normal and proper conduct of the business of Lessee, as reasonably
determined by Lessee, then Lessee shall have the right to terminate this Lease
effective upon the date transfer of possession is required.  Moreover, Lessor
and Lessee shall have the right to terminate this Lease effective on the date
transfer of possession in required if more than thirty-three percent (33%) of
the total square footage of the Premises is taken by condemnation.  Lessee and
Lessor may elect to exercise their respective rights to terminate this Lease
pursuant to this Section by serving written notice to the other within one
hundred twenty (120) days of their receipt of notice of condemnation.  All rent
shall be paid up to the date of termination, and Lessee shall have no claim
against Lessor for the Lease value of any unexpired term of this Lease.  If this
Lease shall not be cancelled, the rent after such partial taking shall be that
percentage of the adjusted base rent specified herein, equal to the percentage
which the square footage of the untaken part of the Premises, immediately after
the taking, bears to the square footage of the entire Premises immediately
before the taking.  Any sums owing hereunder which are calculated on the basis
of Lessee's pro rata share (as set forth in Section 8.02) shall also be adjusted
to reflect the decreased square footage of the Premises due to the condemnation.
During the last twelve (12) months of the Lease Term and during the last 12
months of the Extended Term, if any, if Lessee's continued use of the Premises
requires alterations and repair by reason of a partial taking, all such
alterations and repair shall be made by Lessee at Lessee's expense.

     SECTION 15.03.  AWARD TO LESSEE.  In the event of any condemnation, whether
total or partial, Lessee shall have the right to claim and recover from the
condemning authority such compensation as may be separately awarded or
recoverable by Lessee for loss of its business fixtures, or equipment belonging
to Lessee immediately prior to the condemnation or for the interruption of
Lessee's business, or its moving costs.  The balance of any condemnation award
shall belong to Lessor and Lessee shall have no further right to recover from
Lessor or the condemning authority for any additional claims arising out of such
taking.

                                   ARTICLE XVI

                                 ENTRY BY LESSOR

     Lessee shall permit Lessor and its agent to enter the Premises at all
reasonable times for any of the following purposes: to inspect the Premises; to
maintain the building in which the Premises are located; to make such repairs,
alterations, and additions to the Premises as Lessor is obligated to make or may
make as a result of normal maintenance and repair; to show the Premises and post
"To Lease" signs for the purposes of reletting during the last ninety (90) days
of the term; to show the Premises as part of a prospective sale by Lessor or to
post notices of non-responsibility.  Lessor shall give Lessee twenty-four hours
prior notice before entering the Premises, except in the case of an emergency,
where no notice is required.  Lessor shall have such right of entry without any
rebate of rent to Lessee for any loss of occupancy or quiet enjoyment of the
Premises thereby occasioned.

                                  ARTICLE XVII

                              ESTOPPEL CERTIFICATE

     (a)  Lessee shall at any time upon not less than fifteen (15) days' prior
written notice from Lessor execute, acknowledge and deliver to Lessor a
statement in writing (i) certifying that this Lease is unmodified and in full
force and effect (or, if modified, stating the nature of such modification and
certifying that this Lease, as so modified, is in full force and effect) and the
date to


                                                                              13
                                                                              --

<PAGE>

which the rent and other charges are paid in advance, if any, and (ii)
acknowledging that there are not, to Lessee's knowledge, any uncured defaults on
the part of Lessor hereunder, or specifying such defaults if any are claimed.
Any such statement may be conclusively relied upon by any prospective purchaser
or encumbrancer of the Premises.

     (b)  Lessee's failure to deliver such statement within such time shall be
conclusive upon Lessee (i) that this Lease is in full force and effect, without
modification except as may be represented by Lessor, (ii) that there are no
uncured defaults in Lessor's performance, and (iii) that not more than one
month's rent has been paid in advance; or such failure may be considered by
Lessor as a default by Lessee under this Lease.

                                  ARTICLE XVIII

                               LESSOR'S LIABILITY

     The term "Lessor" as used herein shall mean only the owner or owners at the
time in question of the fee title or a Lessee's interest in a ground lease of
the Premises.  In the event of any transfer of such title or interest, and
provided such successor assumes all obligations of Lessor hereunder, Lessor
herein named (and in case of any subsequent transfers then the grantor) shall be
relieved from and after the date of such transfer of all liability as respects
Lessor's obligations thereafter to be performed, provided that any funds in the
hands of Lessor or the then grantor at the time of such transfer, in which
Lessee has an interest, shall be delivered to the grantee.  The obligations
contained in this Lease to be performed by Lessor shall, subject as aforesaid,
be binding on Lessor's successors and assigns, only during their respective
periods of ownership. Notwithstanding any such transfer of ownership, the Lease
shall remain in full force and effect unless terminated as otherwise provided in
this Lease.

                                   ARTICLE XIX

                            EXPIRATION ON TERMINATION

     SECTION 19.01. SURRENDER OF  POSSESSION.  Lessee agrees to deliver up and
surrender to Lessor possession of the Premises and all improvements thereon, in
as good order and condition as when possession was taken by Lessee, excepting
only ordinary wear and tear or any permitted alterations.  Upon termination of
this Lease, Lessor may reenter the Premises and remove all persons and property
therefrom.  If Lessee shall fail to remove any effects which it is entitled to
remove from the Premises upon the termination of this Lease, for any cause
whatsoever, Lessor, at its option, may remove the same and store or dispose of
them, and Lessee agrees to pay to Lessor on demand any and all reasonable
expenses incurred in such removal and in making the Premises free from all dirt,
litter, and debris, including all storage and insurance charges.  If the
Premises are not surrendered at the end of the Term, Lessee shall indemnify
Lessor against loss or liability resulting from delay by Lessee in so
surrendering the Premises, including, without limitation, actual damages for
lost rents.

     SECTION 19.02.  HOLDING OVER.  If Lessee, with or without Lessor's consent,
remains in possession of the Premises after expiration of the term and if Lessor
and Lessee have not executed an express written agreement as to such holding
over, then such occupancy shall be a tenancy from month to month, at a monthly
rental equivalent to 200% of the monthly rental in effect immediately prior to
such expiration if the remainder in possession is without Lessor's consent, and
at a monthly rental equivalent to 125% of the monthly rental in effect
immediately prior to such expiration if the remainder in possession is with
Lessor's consent, such payments to be made as herein provided. In the event of
such holding over all of the terms of this Lease including the payment of all
charges owing hereunder other than rent shall remain in force and effect on said
month to month basis.

                                   ARTICLE  XX

                              RIGHT OF FIRST NOTICE

     While this Lease is in full force and effect with no default by the Lessee,


                                                                              14
                                                                              --

<PAGE>

and subject to any prior rights granted to any other party, Lessee shall have
the right to first notice of the availability of any space located in the
buildings at 319 and 329 North Bernardo Avenue, Mountain View, California, if
such space becomes vacant at any time or from time to time during the Lease
Term.  In the event that such space becomes available for lease, Lessor shall
notify Lessee of such availability.  If Lessee, within five (5) business days
after receipt of Lessor's notice, indicates in writing Lessee's agreement to
lease such space on the same terms and conditions as set forth in this Lease,
and Lessee agrees to timely commence rental payments for such space, then Lessor
shall lease such space to Lessee on the same terms stated in this Lease.  If
Lessee does not indicate its agreement in writing within five (5) business days
of receipt of the notice from Lessor, then Lessor shall have the right to lease
the space or any part thereof to any third party, and Lessee shall have no other
rights in or to said space.

                                   ARTICLE XXI

                             MISCELLANEOUS PROVISIONS

     SECTION 21.01. SEVERABILITY.  The invalidity of any provision of this Lease
as determined by a court of competent jurisdiction, shall in no way affect the
validity of any other provision hereof.

     SECTION 21.02. INTEREST ON PAST-DUE OBLIGATIONS.  Except as expressly
herein provided, any amount due to either Lessor or Lessee not paid when due
shall bear interest at the prime commercial lending rate then in effect at Bank
of America.  Payment of such interest shall not excuse or cure any default by
either Lessor or Lessee under this Lease.

     SECTION 21.03. TIME OF ESSENCE.  Time is of the essence in the performance
of all obligations under this Lease.

     SECTION 21.04. ADDITIONAL RENT.  Any monetary obligations of Lessee to
Lessor under the terms of this Lease shall be deemed to be rent.

     SECTION 21.05. INCORPORATION OF PRIOR AGREEMENTS: AMENDMENTS.  This Lease
contains all agreements of the parties with respect to any matter mentioned
herein.  No prior agreement or understanding pertaining to any such matter shall
be effective.  This Lease may be modified in writing only, signed by the parties
in interest at the time of the modification.  Except as otherwise stated in this
Lease, Lessee hereby acknowledges that neither the Lessor nor any employees or
agents of the Lessor has made any oral or written warranties or representations
to Lessee relative to the condition or use by Lessee of said Premises and Lessee
acknowledges that Lessee assumes all responsibility regarding the Occupational
Safety Health Act, the legal use and adaptability of the Premises and the
compliance thereof with all applicable laws and regulations in effect during the
term of this Lease except as otherwise specifically stated in this Lease.

     SECTION 21.06. NOTICES.  Any notice required or permitted to be given
hereunder shall be in writing and may be given by personal delivery or by
facsimile, Federal Express, or certified mail, and if given personally or by
mail, shall be deemed sufficiently given if addressed to Lessee or to Lessor at
the address noted below the signature of the respective parties, as the case
may be. Either party may by notice to the other specify a different address for
notice purposes.  A copy of all notices required or permitted to be given to
Lessor hereunder shall be concurrently transmitted to such party or parties at
such addresses as Lessor may from time to time hereafter designate by notice to
Lessee.  Notice shall be considered effective either 72 hours after mailing or
upon actual receipt, whichever is earlier.

     SECTION 21.07. WAIVERS.  No waiver by Lessor of any provision hereof shall
be deemed a waiver of any other provision hereof or of any subsequent breach by
Lessee of the same or any other provisions.  Lessor's consent to, or approval
of, any act shall not be deemed to render unnecessary the obtaining of Lessor's
consent to or approval of any subsequent act by Lessee.  The acceptance of rent
hereunder by Lessor shall not be a waiver of any preceding breach by Lessee of
any provision hereof, other than the failure of Lessee to pay the particular
rent so accepted, regardless of Lessor's knowledge of such preceding breach at
the time of acceptance of such rent.


                                                                              15
                                                                              --

<PAGE>

     SECTION 21.08. RECORDING.  Either Lessor or Lessee shall, upon request of
the other, execute, acknowledge and deliver to the other a "short form"
memorandum of this Lease for recording purposes.

     SECTION 21.09. CUMULATIVE REMEDIES.  No remedy or election hereunder shall
be deemed exclusive but shall, wherever possible, be cumulative with all other
remedies at law or in equity.

     SECTION 21.10. COVENANTS AND CONDITIONS.  Each provision of this Lease
performable by Lessee or Lessor shall be deemed both a covenant and a condition.

     SECTION 21.11. BINDING EFFECT, CHOICE OF LAW: VENUE.  Subject to any
provisions hereof restricting assignment or subletting by Lessee and subject to
the provisions of Article XVIII, this Lease shall bind the parties, their
personal representatives, successors and assigns.  This Lease shall be governed
by the laws of the State of California.  Venue for any action or proceeding
brought to enforce or defend this agreement, and for any other purpose
hereunder, shall be Santa Clara County.

     SECTION 21.12. SUBORDINATION OF LEASEHOLD.  Lessee agrees that this Lease
is and shall be, at all times, subject and subordinate to the lien of any
mortgage or other encumbrances which Lessor may create against the Premises
including all renewals, replacements and extensions thereof; provided, however,
that regardless of any default under any such mortgage or encumbrance or any
sale of the Premises under such mortgage, so long as Lessee performs all
covenants and conditions of this Lease and continues to make all payments
hereunder, this Lease and Lessee's possession and rights hereunder shall not be
disturbed by the mortgagee or anyone claiming under or through such mortgagee.
Any future subordination to which this Lease is subject shall be accompanied by
a nondisturbance agreement in favor of Lessee which recognizes the terms and
conditions of the Lease.  Lessor agrees to request from the current lender a
nondisturbance agreement in favor of Lessee.

     SECTION 21.13. ATTORNEYS' FEES. If either party herein brings an action to
enforce the terms hereof or declare rights hereunder, the prevailing party in
any such action, on trial or appeal, shall be entitled to reasonable attorneys'
fees to be paid by the losing party as fixed by the Court.

     SECTION 21.14. AUCTIONS.  Lessee shall not conduct, nor permit to be
conducted, either voluntarily or involuntarily, any auction upon the Premises
without first having obtained Lessor's prior written consent.  Notwithstanding
anything to the contrary in this Lease, Lessor shall not be obligated to
exercise any standard of reasonableness in determining whether to grant such
consent.

     SECTION 21.15. SIGNS.  Lessee shall not place any sign upon the Premises
without Lessor's prior written consent, which consent shall not be unreasonably
withheld.

     SECTION 21.16. VOLUNTARY SURRENDER OR MERGER.  The voluntary or other
surrender of this Lease by Lessee, or a mutual cancellation thereof, or a
termination by Lessor, shall not work a merger, and shall, at the option of
Lessor, terminate all or any existing subtenancies or may, at the option of
Lessor, operate as an assignment to Lessor of any or all of such subtenancies.

     SECTION 21.17. GUARANTOR.  In the event that there is a guarantor of this
Lease, said guarantor shall have the same obligations as Lessee under this
Lease.

     SECTION 21.18. QUIET POSSESSION.  Upon Lessee paying the rent for the
Premises and observing and performing all of the covenants, conditions and
provisions on Lessee's part to be observed and performed hereunder, Lessee shall
have quiet possession of the Premises for the entire term hereof subject to all
of the provisions of this Lease, The individuals executing this Lease on behalf
of Lessor represent and warrant to Lessee that they are fully authorized and
legally capable of executing this Lease on behalf of Lessor and that such
execution is binding upon all parties holding an ownership interest in the
Premises.

     SECTION 21.19. RULES AND REGULATIONS.  Lessee agrees that it will abide 
by, keep and observe all reasonable rules and regulations which Lessor may 
make from time to time for the management, safety, care and cleanliness of the

                                                                              16
                                                                              --

<PAGE>

building and grounds, the parking of vehicles and the preservation of good 
order therein as well as for the convenience of other occupants and tenants 
of the building.  Lessor shall give Lessee fifteen (15) days' notice to cure 
Lessee's violations of such rules and regulations of Lessor, and the 
continued violations of any such rules and regulations shall be deemed a 
material breach of this Lease.  Lessee, however, shall not be bound by any 
future rules or regulations, unless it shall approve same, which approval 
shall not be unreasonably withheld.

     SECTION 21.20. EASEMENTS. Lessor reserves to itself the right, from time 
to time, at Lessor's sole cost to grant such easements, rights and 
dedications that Lessor deems necessary or desirable, and to cause the 
recordation of Parcel Maps and restrictions, so long as such easements, 
rights, dedications, Maps and restrictions do not unreasonably interfere with 
the use of the Premises by Lessee nor increase Lessee's obligations hereunder 
nor decrease Lessee's rights hereunder.  Lessee shall sign any of the 
aforementioned documents upon fifteen (15) days written notice of Lessor and 
failure to do so shall constitute a material breach of this Lease.

     SECTION 21.21. CORPORATE AUTHORITY.  Each individual executing this Lease
on behalf of a corporation represents and warrants that he is duly authorized to
execute and deliver this Lease on behalf of the corporation in accordance with a
duly adopted resolution of the Board of Directors of the corporation, and that
this Lease is binding upon said corporation in accordance with its terms.

     SECTION 21.22. DELAYS FOR CAUSE.  In any case where either party hereto is
required to do any act, delays caused by or resulting from Acts of God, war,
civil commotion, fire, flood or other casualty, labor difficulties, shortages of
labor, materials or equipment, government regulations, unusually severe weather,
or other causes beyond such party's reasonable control shall not be counted in
determining the time during which work shall be completed, whether such time be
designated by a fixed date, a fixed time or "a reasonable time", and such time
shall be deemed to be extended by the period of such delay.

     SECTION 21.23. SQUARE FOOTAGE.  The parties agree that the leased 
Premise is approximately 52,800 square feet, said square footage being 
measured from the face of the outside (concrete) walls and includes the 
covered docks and entry ways.

LESSOR AND LESSEE HAVE CAREFULLY READ AND REVIEWED THIS LEASE AND EACH TERM AND
PROVISION CONTAINED HEREIN AND, BY EXECUTION OF THIS LEASE, SHOW THEIR INFORMED
AND VOLUNTARY CONSENT THERETO.  THE PARTIES HEREBY AGREE THAT, AT THE TIME THIS
LEASE IS EXECUTED THE TERMS OF THIS LEASE ARE COMMERCIALLY REASONABLE AND
EFFECTUATE THE INTENT AND PURPOSE OF LESSOR AND LESSEE WITH RESPECT TO THE
PREMISES.

The Parties hereto have executed this Lease at the place and on the date
specified below.

     Executed at Watsonville, California, on September 15, 1995.

     Lessor:                            Address:
     VANNI BUSINESS PARK GENERAL        c/o Jay Paul Company
     PARTNERSHIP                        1093 South Green Valley Road
                                        Watsonville, CA 95076

     By: /s/ Jay Paul
        ---------------------------
          Jay Paul, General Partner

     Lessee:

     AVIRON,                            1450 Rollins Road
     a California Corporation           ---------------------------
                                        Burlingame, CA 94010
                                        ---------------------------
     BY: /s/ Francis R. Cano
        ---------------------------
          Francis R. Cano, President



                                                                              17
                                                                              --


<PAGE>
                                                                    EXHIBIT 11.1
 
                 STATEMENT OF COMPUTATION OF NET LOSS PER SHARE
 
   
<TABLE>
<CAPTION>
                                                                                                THREE MONTHS ENDED
                                                          YEAR ENDED DECEMBER 31,                   MARCH 31,
                                                 -----------------------------------------  --------------------------
                                                     1993          1994          1995           1995          1996
                                                 ------------  ------------  -------------  ------------  ------------
<S>                                              <C>           <C>           <C>            <C>           <C>
Net loss.......................................  $ (3,772,000) $ (6,502,000) $ (11,403,000) $ (3,757,000) $ (3,736,000)
                                                 ------------  ------------  -------------  ------------  ------------
                                                 ------------  ------------  -------------  ------------  ------------
Weighted average shares of Common Stock
 outstanding:                                         673,007       687,474        697,288       696,645       697,520
Shares related to staff accounting bulletin
 topic 4D:
  Stock options and warrants...................       270,351       270,351        270,351       270,351       270,351
  Common Stock.................................       421,503       421,503        421,503       421,503       421,503
  Convertible Preferred Stock (Series C).......     3,235,579     3,235,579      3,235,579     3,235,579     3,235,579
                                                 ------------  ------------  -------------  ------------  ------------
Shares used in computing net loss per share....     4,600,440     4,614,907      4,624,721     4,624,078     4,624,953
                                                 ------------  ------------  -------------  ------------  ------------
                                                 ------------  ------------  -------------  ------------  ------------
Net loss per share.............................  $      (0.82) $      (1.41) $       (2.47) $      (0.81) $      (0.81)
                                                 ------------  ------------  -------------  ------------  ------------
                                                 ------------  ------------  -------------  ------------  ------------
Calculation of shares outstanding for computing
 pro forma net loss per share:
  Shares used in computing net loss
   per share...................................     4,600,440     4,614,907      4,624,721     4,624,078     4,624,953
  Adjusted to reflect the effect of the assumed
   conversion of Preferred Stock from the date
   of issuance (1).............................     2,096,014     4,333,333      4,557,921     4,437,447     4,598,080
                                                 ------------  ------------  -------------  ------------  ------------
Shares used in computing pro forma net loss per
 share.........................................     6,696,454     8,948,240      9,182,642     9,061,525     9,223,033
                                                 ------------  ------------  -------------  ------------  ------------
                                                 ------------  ------------  -------------  ------------  ------------
Pro forma net loss per share...................  $      (0.56) $      (0.73) $       (1.24) $      (0.41) $      (0.41)
                                                 ------------  ------------  -------------  ------------  ------------
                                                 ------------  ------------  -------------  ------------  ------------
</TABLE>
    
 
- ---------------------
(1) Series A and B shares

<PAGE>
                                                                    EXHIBIT 23.1
 
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
   
    We  consent  to  the reference  to  our  firm under  the  captions "Selected
Financial Data" and "Experts"  and to the  use of our  report dated January  26,
1996  (except as to the  first paragraph of Note  1 and Note 10  as to which the
date is May  30, 1996),  in the Registration  Statement (Form  S-1) and  related
Prospectus  of Aviron  for the  registration of  3,450,000 shares  of its Common
Stock.
    
 
   
                                          /s/ Ernst & Young LLP
    
 
                                              ERNST & YOUNG LLP
   
Palo Alto, California
June 4, 1996
    

<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   12-MOS                   3-MOS
<FISCAL-YEAR-END>                          DEC-31-1995             DEC-31-1996
<PERIOD-START>                             JAN-01-1995             JAN-01-1996
<PERIOD-END>                               DEC-31-1995             MAR-31-1996
<CASH>                                          11,532                  10,000
<SECURITIES>                                         0                       0
<RECEIVABLES>                                        0                       0
<ALLOWANCES>                                         0                       0
<INVENTORY>                                          0                       0
<CURRENT-ASSETS>                                18,498                  15,367
<PP&E>                                           1,987                   2,638
<DEPRECIATION>                                     712                     822
<TOTAL-ASSETS>                                  19,878                  17,275
<CURRENT-LIABILITIES>                            1,723                   2,563
<BONDS>                                              0                       0
                                0                       0
                                     39,844                  40,028
<COMMON>                                           317                   1,579
<OTHER-SE>                                    (22,624)                (27,440)
<TOTAL-LIABILITY-AND-EQUITY>                    19,878                  17,275
<SALES>                                              0                       0
<TOTAL-REVENUES>                                 1,707                     188
<CGS>                                                0                       0
<TOTAL-COSTS>                                        0                       0
<OTHER-EXPENSES>                                13,472                   4,107
<LOSS-PROVISION>                                     0                       0
<INTEREST-EXPENSE>                                 158                      37
<INCOME-PRETAX>                               (11,403)                 (3,736)
<INCOME-TAX>                                         0                       0
<INCOME-CONTINUING>                           (11,403)                 (3,736)
<DISCONTINUED>                                       0                       0
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                  (11,403)                 (3,736)
<EPS-PRIMARY>                                   (1.24)                  (0.41)
<EPS-DILUTED>                                   (1.24)                  (0.41)
        

</TABLE>


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