VIROPHARMA INC
S-1/A, 1997-07-22
PHARMACEUTICAL PREPARATIONS
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<PAGE>
 
      
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY 22, 1997     
 
                                                      REGISTRATION NO. 333-30005
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                                ---------------
                                 
                              AMENDMENT NO. 3     
                                       TO
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                                ---------------

                            VIROPHARMA INCORPORATED
               (EXACT NAME OF REGISTRANT AS SPECIFIED IN CHARTER)
 
        DELAWARE                     2834                    23-2789550
     (STATE OR OTHER           (PRIMARY STANDARD           (I.R.S.EMPLOYER
     JURISDICTION OF              INDUSTRIAL             IDENTIFICATION NO.)
    INCORPORATION OR          CLASSIFICATION CODE
      ORGANIZATION)                 NUMBER)
 
                            76 GREAT VALLEY PARKWAY
                               MALVERN, PA 19355
                                 (610) 651-0200
              (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
       INCLUDING AREA CODE, OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)
 
                                ---------------

                                 CLAUDE H. NASH
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                            VIROPHARMA INCORPORATED
                            76 GREAT VALLEY PARKWAY
                               MALVERN, PA 19355
                                 (610) 651-0200
      (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING
                        AREA CODE, OF AGENT FOR SERVICE)
 
                                   COPIES TO:
          DAVID R. KING, ESQ.                       ALAN DEAN, ESQ.
      MORGAN, LEWIS & BOCKIUS LLP                DAVIS POLK & WARDWELL
         2000 ONE LOGAN SQUARE                    450 LEXINGTON AVENUE
         PHILADELPHIA, PA 19103                    NEW YORK, NY 10017
             (215) 963-5000                          (212) 450-4000
 
  APPROXIMATE DATE OF COMMENCEMENT 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 pur-
suant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier effec-
tive 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. [_]
 
                                ---------------
  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 WHICH 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>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+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.                                                               +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                             Subject to Completion
                               
                            Dated July 22, 1997     
 
PROSPECTUS
 
2,000,000 Shares
 
[LOGO OF VIROPHARMA INCORPORATED APPEARS HERE]

Common Stock
(par value $.002 per share)
   
All of the 2,000,000 shares of Common Stock, par value $.002 per share (the
"Common Stock"), offered hereby (the "Offering") are being offered by
ViroPharma Incorporated ("ViroPharma" or the "Company"). The Company's Common
Stock is quoted on the Nasdaq National Market under the symbol "VPHM." On July
21, 1997, the last reported sale price of the Common Stock was $16.50 per
share. See "Price Range of Common Stock."     
 
SEE "RISK FACTORS" COMMENCING ON PAGE 6 FOR CERTAIN INFORMATION THAT SHOULD BE
CONSIDERED BY PROSPECTIVE INVESTORS.
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
AND EXCHANGE 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 (1)     COMPANY (2)(3)
- --------------------------------------------------------------------------------
<S>                        <C>                <C>                 <C>
Per Share                  $                  $                   $
- --------------------------------------------------------------------------------
Total (3)                  $                  $                   $
- --------------------------------------------------------------------------------
</TABLE>
 
(1) The Company has agreed to indemnify the Underwriters against certain lia-
bilities, including liabilities under the Securities Act of 1933, as amended.
See "Underwriting."
 
(2) Before deducting expenses of the Offering payable by the Company, estimated
  to be $   .
 
(3) The Company has granted the Underwriters an option, exercisable within 30
days of the date hereof, to purchase an aggregate of up to 300,000 additional
shares, at the Price to Public less Underwriting Discounts and Commissions, to
cover over-allotments, if any. If all such additional shares are purchased, the
total Price to Public, Underwriting Discounts and Commissions and Proceeds to
Company will be $   , $    and $   , respectively. See "Underwriting."
 
The shares of Common Stock being offered by this Prospectus are offered by the
Underwriters, subject to prior sale, when, as and if delivered to and accepted
by the Underwriters, subject to approval of certain legal matters by Davis Polk
& Wardwell, counsel for the Underwriters. It is expected that delivery of the
shares of Common Stock will be made against payment therefor on or about    ,
1997 at the offices of J.P. Morgan Securities Inc., 60 Wall Street, New York,
New York.
 
J.P. MORGAN & CO.                                                COWEN & COMPANY
 
     , 1997
<PAGE>
 
CERTAIN PERSONS PARTICIPATING IN THIS OFFERING MAY ENGAGE IN TRANSACTIONS THAT
STABILIZE, MAINTAIN OR OTHERWISE AFFECT THE PRICE OF THE COMMON STOCK. SPECIFI-
CALLY, THE UNDERWRITERS MAY OVERALLOT IN CONNECTION WITH THE OFFERING, AND MAY
BID FOR, AND PURCHASE, SHARES OF THE COMMON STOCK IN THE OPEN MARKET. FOR A
DESCRIPTION OF THESE ACTIVITIES, SEE "UNDERWRITING".
 
IN CONNECTION WITH THIS OFFERING, CERTAIN UNDERWRITERS AND SELLING GROUP MEM-
BERS MAY ENGAGE IN PASSIVE MARKET MAKING TRANSACTIONS IN THE COMMON STOCK ON
NASDAQ IN ACCORDANCE WITH RULE 103 UNDER REGULATION M. SEE "UNDERWRITING."
 
No person has been authorized to give any information or to make any represen-
tation other than those contained in this Prospectus, and if given or made,
such information or representation must not be relied upon as having been
authorized by the Company or by any of the Underwriters. This Prospectus does
not constitute an offer to sell, or a solicitation of an offer to buy, the
Common Stock in any jurisdiction to any person to whom it is unlawful to make
such offer or solicitation. Neither the delivery of this Prospectus nor any
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.
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                               PAGE                                                           PAGE
<S>                                            <C>                  <C>                                       <C>    
Available Information........................     2                 Business.................................   23
Prospectus Summary...........................     3                 Management...............................   39
Risk Factors.................................     6                 Certain Transaction......................   47
Use of Proceeds..............................    15                 Principal Stockholders...................   49
Price Range of Common Stock..................    16                 Description of Capital Stock.............   52
Dividend Policy..............................    16                 Shares Eligible for Future Sale..........   54
Capitalization...............................    17                 Underwriting.............................   55
Dilution.....................................    18                 Legal Matters............................   56
Selected Financial Data......................    19                 Experts..................................   56
Management's Discussion and Analysis of                             Index to Financial Statements............  F-1 
  Financial Condition and Results of 
  Operations.................................    20
</TABLE>


"ViroPharma" and the Company's logo are trademarks and service marks of the
Company. The Company has filed applications to register these trademarks and
service marks in the United States and Canada. All other brand names or trade-
marks appearing in this Prospectus are the property of their respective owners.

 
                             AVAILABLE INFORMATION
 
The Company is subject to the informational requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance there-
with files reports, proxy, and other information with the Securities and
Exchange Commission (the "Commission"). Such reports, proxy statements, and
other information can be inspected and copied at the public reference facili-
ties maintained by the Commission at Judiciary Plaza, 450 Fifth Street, N.W.,
Washington, DC 20549, and at the following Regional Offices of the Commission:
500 West Madison Street, Suite 1400, Chicago, IL 60661 and 7 World Trade Cen-
ter, 13th Floor, New York, NY 10048. Copies of such material can also be
obtained from the Public Reference section of the Commission at Judiciary
Plaza, 450 Fifth Street, N.W., Washington, DC 20549, at prescribed rates. In
addition, registration statements and certain other filings made with the Com-
mission through its Electronic Data Gathering, Analysis and Retrieval ("EDGAR")
system are publicly available through the Commission's site on the Internet's
World Wide Web, located at http://www.sec.gov. The Registration Statement,
including all exhibits thereto and amendments thereof, has been filed with the
Commission through EDGAR.
 
                                       2
<PAGE>
 
                               PROSPECTUS SUMMARY
 
The following summary is qualified in its entirety by the more detailed infor-
mation and financial statements and notes thereto appearing elsewhere in this
Prospectus. Unless the context requires otherwise, the "Company" refers to
ViroPharma Incorporated, a Delaware corporation. This Prospectus contains for-
ward-looking statements which involve risks and uncertainties. The Company's
actual results may differ significantly from the results discussed in forward-
looking statements. Factors that might cause or contribute to such differences
include, but are not limited to, those discussed in "Risk Factors." Except as
otherwise noted, all information contained in this Prospectus assumes no exer-
cise of the Underwriters' over-allotment option.
 
                                  THE COMPANY
 
ViroPharma Incorporated ("ViroPharma" or the "Company") is a development stage
company engaged in the discovery and development of proprietary antiviral phar-
maceuticals for the treatment of diseases caused by RNA viruses. The Company
has focused its current drug development and discovery activities on a number
of RNA virus diseases, including viral meningitis, enterovirus respiratory dis-
ease ("summer flu"), hand-foot-and-mouth disease, the common cold, influenza,
hepatitis C and viral pneumonia. Each year, a major portion of the world's pop-
ulation is afflicted by at least one of these diseases, for which antiviral
therapies are currently either inadequate or unavailable.
 
ViroPharma's most advanced product candidate, pleconaril, is currently being
developed for the treatment of four RNA virus diseases. Initial preclinical
studies indicated that pleconaril is a potent, broad-spectrum, orally-active
inhibitor of several RNA viruses. In June 1996, ViroPharma completed a Phase
IIa challenge study in "summer flu" with pleconaril, in which all evaluated
disease measures were significantly reduced in treated subjects. In June 1997,
ViroPharma completed a Phase IIb clinical trial for viral meningitis which dem-
onstrated that pleconaril significantly reduced disease duration, the trial's
primary endpoint. No serious adverse events attributable to pleconaril have
been observed in the 139 participants in the clinical trials conducted by the
Company to date.
 
ViroPharma has commenced additional Phase II clinical trials for viral meningi-
tis, one in adolescents/adults and one in pediatric patients, and for "summer
flu". ViroPharma initiated a Phase II clinical trial of pleconaril for hand-
foot-and-mouth disease in March 1997 and anticipates initiating a Phase II
clinical trial for the common cold in asthmatics in late 1997. ViroPharma has
additional compounds in research and preclinical stages of development for the
treatment of influenza, hepatitis C, and viral pneumonia.
 
ViroPharma believes its drug discovery and development technologies and
expertise have potential applicability to a broad range of diseases caused by
RNA viruses. RNA viruses are responsible for the majority of human viral dis-
eases, causing illnesses ranging from acute and chronic ailments to fatal
infections. RNA viruses continue to emerge, spreading from rural and developing
regions of the world to urbanized centers. Despite efforts by the scientific
and medical communities to develop vaccines and pharmaceuticals to prevent and
treat certain of these diseases, medicines are currently inadequate or are not
available for the majority of RNA virus diseases. The Company believes the sig-
nificance and prevalence of RNA virus diseases, and the limited availability
and effectiveness of current antiviral pharmaceuticals, has created a compel-
ling need for new pharmaceuticals to treat these diseases.
 
ViroPharma, based on its experienced RNA virologists and its focus on RNA viral
diseases, believes it is a leader in RNA virology and RNA antiviral drug dis-
covery and development. The Company has focused its drug discovery and develop-
ment efforts on identifying and advancing inhibitors of the process of viral
RNA uncoating and replication. The Company believes that this process repre-
sents an attractive target for therapeutic intervention in disease caused by
RNA viruses. For RNA viruses to cause disease, they must replicate. Therefore,
inhibiting RNA virus replication can prevent, limit or stop disease. The viral
activities involved in this replication process are unique to RNA viruses, yet
universal among all RNA viruses. Therefore, technologies used for the develop-
ment of inhibitors of this process have potential applicability to a broad
range of diseases caused by RNA viruses. ViroPharma has discovered and charac-
terized RNA uncoating and replication activities, identified critical molecular
targets, developed novel high throughput screening assays and discovered and
optimized proprietary small molecule compounds identified by screening chemical
libraries, including the Company's specialized library. The Company believes
that it is the first company to utilize these technologies in combination to
develop antiviral pharmaceutical products.
 
                                       3
<PAGE>

 
 
The Company's objective is to become the leading discoverer, developer and mar-
keter of proprietary antiviral pharmaceuticals for RNA virus diseases through
the implementation of the following strategies: (1) focusing on RNA virus dis-
eases to capitalize on the significant market opportunity that they present,
(2) broadly applying its technological expertise in RNA virology to establish a
substantial product pipeline, (3) conducting parallel drug assessments to
accelerate, and enhance the efficiency of, drug discovery and development, (4)
pursuing disease indications which allow for rapid demonstration of efficacy to
expedite product development and (5) pursuing strategic relationships by
leveraging its leadership position in RNA virology to enhance its drug dis-
covery capabilities and licensing opportunities and to facilitate the commer-
cialization of its products. The Company has entered into an agreement with
respect to patents held by Sanofi S.A. ("Sanofi") to secure the exclusive
development and marketing rights for pleconaril in the United States and Canada
for use in a broad class of disease indications. Pleconaril was discovered at
Sanofi by scientists who are now with ViroPharma. The Company has also entered
into a collaborative drug discovery and development agreement with Boehringer
Ingelheim Pharmaceuticals, Inc. ("Boehringer Ingelheim") for one hepatitis C
target identified by ViroPharma. In addition, the Company is collaborating with
other pharmaceutical and technology companies, as well as academic institu-
tions, to access enabling technologies and compound libraries as they pertain
to the treatment of RNA virus diseases.
 
The Company is a development stage company which was incorporated in Delaware
on September 16, 1994 and commenced operations on December 5, 1994. The
Company's executive offices and research facility are located at 76 Great
Valley Parkway, Malvern, Pennsylvania 19355. Its telephone number is (610) 651-
0200 and the Internet e-mail address is [email protected]. ViroPharma also has
a home page on the World Wide Web.
 
                              RECENT DEVELOPMENTS
 
In June 1997, the Company completed a preliminary evaluation of data from its
Phase IIb clinical trial with the oral liquid formulation of pleconaril for the
treatment of viral meningitis. The Company's preliminary evaluation demon-
strated that pleconaril treatment resulted in a statistically significant
shortening of disease duration (58% reduction), the primary endpoint of the
study. This primary endpoint evaluates the time required for disease severity
(as measured by a multidimensional score, comprised of headache,
nausea/vomiting, photophobia, stiff neck, fever and myalgia) to be reduced to a
predetermined level indicating wellness. Statistical significance also was
observed in the secondary endpoints of time to complete absence of headache
(64% reduction), duration of analgesic use (54% reduction) and total analgesic
use (48% reduction). Clinically meaningful trends were observed in two addi-
tional secondary endpoints, while no adverse trends were observed in the three
remaining secondary endpoints. The trial results were based on a 39 patient,
multinational, double-blind, placebo-controlled study. In June 1997, the Com-
pany initiated two additional Phase II clinical trials with pleconaril in the
United States and Canada for viral meningitis, one in adolescents/adults and
one in pediatric patients.
 
                                  THE OFFERING
 
<TABLE>
 <S>                                            <C> 
 COMMON STOCK OFFERED.........................  2,000,000 shares

 COMMON STOCK OUTSTANDING AFTER THE OFFERING..  11,148,911 shares(1)

 USE OF PROCEEDS..............................  For the further development of
                                                pleconaril, including clinical
                                                trials and certain pre-
                                                marketing activities, ongoing
                                                research and development
                                                programs and general corporate
                                                purposes, which may include
                                                capital equipment expenditures.

 NASDAQ NATIONAL MARKET SYMBOL................  VPHM
</TABLE>
 
(1) Excludes 707,037 shares issuable upon exercise of options outstanding as of
July 1, 1997 at a weighted average exercise price of $4.07 per share and (ii)
shares issuable upon exercise of warrants to purchase 21,675 shares of Common
Stock at an exercise price of $2.94 per share. Includes 357,000 unvested shares
of Common Stock purchased by certain founders and a director of the Company and
71,795 shares issued in connection with the exercise of certain warrants. See
"Management--Executive Compensation," "Management--Stock Options," "Certain
Transactions--Transactions with Founders" and "--Right Grant and Exercise,"
"Description of Capital Stock--Warrants" and Note 11 of Notes to Financial
Statements.
 
                                       4
<PAGE>
 
                         SUMMARY FINANCIAL INFORMATION
 
<TABLE>
<CAPTION>
                          ----------------------------------------------------------------
                           PERIOD FROM
                           DECEMBER 5,
                                  1994
                           (INCEPTION)                              THREE MONTHS ENDED
                               THROUGH  YEAR ENDED DECEMBER 31,          MARCH 31,
                          DECEMBER 31,  ------------------------  ------------------------
                                  1994         1995         1996         1996         1997
                          ------------  -----------  -----------  -----------  -----------
                                                                        (UNAUDITED)
<S>                       <C>           <C>          <C>          <C>          <C>
STATEMENT OF OPERATIONS
 DATA
License fee.............  $        --   $       --   $ 1,000,000  $       --   $       --
Milestone revenue.......           --           --           --           --       750,000
Grant revenue...........           --        90,813      436,081          --           --
                          ------------  -----------  -----------  -----------  -----------
Total revenues..........           --        90,813    1,436,081          --       750,000
                          ------------  -----------  -----------  -----------  -----------
Operating expenses:
  Research and
   development..........        75,779    2,930,106    6,694,703    1,415,429    1,908,252
  General and
   administrative.......       243,318    1,091,299    1,421,524      220,173      764,569
                          ------------  -----------  -----------  -----------  -----------
Total operating
 expenses...............       319,097    4,021,405    8,116,227    1,635,602    2,672,821
                          ------------  -----------  -----------  -----------  -----------
Interest income, net....           --        75,730      285,142       55,824      191,407
                          ------------  -----------  -----------  -----------  -----------
Net loss................  $   (319,097) $(3,854,862) $(6,395,004) $(1,579,778) $(1,731,414)
                          ============  ===========  ===========  ===========  ===========
Pro forma net loss per
 share(1)...............                $     (0.98) $     (0.93) $     (0.32) $     (0.19)
Shares used in computing
 pro forma net loss
 per share(1)...........                  3,931,743    6,839,674    4,933,093    9,076,986
</TABLE>
 
<TABLE>   
<CAPTION>
                                                     --------------------------
                                                         AT MARCH 31, 1997
                                                          ACTUAL AS ADJUSTED(2)
                                                     ----------- --------------
                                                            (UNAUDITED)
<S>                                                  <C>         <C>
BALANCE SHEET DATA
Cash, cash equivalents and investments.............. $21,743,998    $52,463,998
Working capital.....................................  18,277,315     48,997,315
Total assets........................................  22,940,505     53,660,505
Loan Payable and Capital Leases--non-current........     583,312        583,312
Total stockholders' equity..........................  18,970,466     46,690,466
</TABLE>    
- -------
(1) See Note 2 of Notes to Financial Statements.
   
(2) Reflects the sale of 2,000,000 shares of Common Stock offered by the Com-
pany (at an assumed public offering price of $16.50 per share) and the applica-
tion of net proceeds therefrom. See "Use of Proceeds."     
 
                                       5
<PAGE>
 
                                  RISK FACTORS
 
An investment in the shares of Common Stock offered hereby involves a high
degree of risk. The following factors, in addition to the other information in
this Prospectus, should be considered carefully in evaluating the Company and
its business before purchasing shares of Common Stock offered hereby. This Pro-
spectus contains forward-looking statements which involve risks and uncertain-
ties. The Company's actual results may differ significantly from the results
discussed in forward-looking statements. Factors that might cause or contribute
to such a difference include, but are not limited to, those discussed in the
following risk factors.
 
EARLY STAGE OF DEVELOPMENT; CONTINUING OPERATING LOSSES; UNCERTAINTY OF FUTURE
PROFITABILITY
 
The Company is a development stage company which currently has no sources of
operating revenues and has incurred net operating losses since its inception in
1994. At March 31, 1997, the Company had an accumulated deficit of $12,300,377.
Such losses have resulted principally from costs incurred in research, develop-
ment, clinical trials and general and administrative costs associated with the
Company's operations. The Company expects that operating losses will continue
at increasing levels for at least the next several years as its research,
product development, clinical testing and marketing activities expand. Such
losses will continue unless and until such time as product approvals are
obtained and product sales generate sufficient revenue to offset expenses. The
Company's ability to achieve profitability will depend, in part, on its ability
to successfully develop, clinically test and obtain regulatory approvals for
its drug candidates, as well as its ability to manufacture and market any
approved products either by itself or in collaboration with others. There can
be no assurance that the Company will successfully complete its product devel-
opment efforts in a timely manner, if at all, that it will receive any regula-
tory approvals required for the clinical development, commercial manufacture or
marketing of its proposed products or that product sales based on such regula-
tory approvals will be profitable to the Company. Accordingly, the extent of
future losses and the time required to achieve profitability is highly uncer-
tain. See "Management's Discussion and Analysis of Financial Condition and
Results of Operations."
 
ABSENCE OF PRODUCTS; PRODUCT DEVELOPMENT RISKS
 
The Company has not completed the development of any products. Some of the
Company's drug candidates are currently undergoing clinical trials while others
are in research or preclinical development. The Company's drug candidates,
other than pleconaril, are not expected to be commercially available for at
least several years, if at all, and pleconaril is not expected to be commer-
cially available for at least three years, if at all. The Company has not begun
to market or generate revenues from the commercialization of any products. The
majority of the Company's drug candidates will require significant additional
research and development and laboratory testing prior to submission of any reg-
ulatory application, and all of its drug candidates will require significant
clinical testing and regulatory approval prior to commercialization. There can
be no assurance that the Company will be permitted by regulatory authorities to
conduct additional clinical testing of the Company's compounds or that, if per-
mitted, such additional clinical testing will prove that such drugs are safe
and efficacious to the extent necessary to permit the Company to obtain mar-
keting approvals for them from regulatory authorities. There can be no assur-
ance that the results of preclinical studies and completed clinical trials will
be indicative of results obtained in future clinical trials. Adverse or incon-
clusive clinical trial results concerning any of the Company's drug candidates
could result in increased costs and significantly delay the filing for mar-
keting approval for such drug candidates with the FDA or result in a filing for
a narrower indication. In such event, further studies would be required with
respect to other indications to support any filing of a supplemental applica-
tion covering such indications. There can be no assurance that the Company's
research and development, preclinical testing or clinical trials will be suc-
cessfully completed, that regulatory approvals will be obtained or will be as
broad as sought, that the Company's products will be capable of being produced
in commercial quantities at reasonable costs or that any products, if intro-
duced, will achieve market acceptance. Any problems or delays relating to
research and development, regulatory approval and manufacturing, and the
failure to address such problems or delays, could have a material adverse
effect on the Company. See "Business--Product Development and Research."
 
The Company's drug candidates and future product development efforts are sub-
ject to the risks of failure inherent in the development of pharmaceutical
products. These risks include the possibilities that any or all of the
Company's drug candidates will be found to be ineffective, unsafe, toxic or
otherwise fail to either meet applicable regulatory standards or receive neces-
sary regulatory approvals or clearances. There can be no assurance that unac-
ceptable toxicities or side effects will not occur at any dose level at any
time in the course of toxicological studies or human clinical trials of the
Company's drugs. The appearance of any such unacceptable toxicities or side
effects in toxicology studies or human clinical trials could cause the Company
or regulatory authorities to interrupt, limit, delay or abort the development
of any of the Company's drugs and could ultimately prevent their approval for
any of the targeted indications. Even after receiving approval, prod-
 
                                       6
<PAGE>
 
ucts may later exhibit adverse effects that prevent their widespread use and
necessitate their withdrawal from the market. There can be no assurance that
any products under development by the Company will be safe when administered
to patients. Furthermore, there is a risk that the Company's drug candidates,
even if safe and effective, will be difficult to develop into commercially
viable products, difficult to manufacture on a large scale or uneconomical to
market and that proprietary rights of third parties may preclude the Company
from marketing such drug candidates. Moreover, the Company's competitors may
succeed in developing technologies or products that are more effective or cost
effective than those of the Company. Rapid technological changes or develop-
ments by others may result in the Company's drug candidates becoming obsolete
or noncompetitive. See "--Competition," "--Rapid Technological Change and
Uncertainty."
 
DEPENDENCE ON MOST ADVANCED DRUG CANDIDATE
 
The Company's research and development resources are primarily dedicated to
its most advanced drug candidate, pleconaril. Significant delays in the
Company's clinical trials of pleconaril, unfavorable results in such trials,
failure to obtain regulatory approval for the commercialization of pleconaril
or any related product or failure to achieve market acceptance of pleconaril
or any related product could have a material adverse effect upon the Company.
There can be no assurance that pleconaril will be successfully developed.
Although the Company is currently seeking to develop other drug candidates and
expand the number of drug candidates it has under development, there can be no
assurance that it will be successful in such development or expansion. Fur-
thermore, the proceeds of this offering are not expected to be sufficient to
complete all clinical studies and other required testing for pleconaril or any
other of the Company's product development candidates. See "--Government Regu-
lation; No Assurance of Regulatory Approval" and "Business--Product Develop-
ment and Research."
 
UNCERTAINTY REGARDING CLINICAL TRIALS
 
The results of preclinical studies and initial clinical trials of the
Company's product candidates are not necessarily predictive of the results
from large-scale clinical trials. The Company must demonstrate through
preclinical studies and clinical trials that its product candidates are safe
and effective for use in each target indication before the Company can obtain
regulatory approvals for the commercial sale of those products. These studies
and trials may be very costly and time-consuming.
 
The rate of completion of clinical trials is dependent upon, among other fac-
tors, the rate of enrollment of patients. Enrollment may be impacted by the
acute nature and the seasonality of certain of the Company's disease targets
and the impossibility of anticipating the geographic locations of disease out-
breaks. Failure to accrue an adequate number of clinical patients during the
appropriate season could cause significant delays and increased costs. Such
delays and increased costs could have a material adverse effect on the
Company's drug development program. Furthermore, there can be no assurance
that if the Company's clinical trials are completed, the Company will be able
to submit a New Drug Application (an "NDA") as scheduled or that any such
application will be approved by the FDA in a timely manner, if at all.
 
The cost to the Company of conducting human clinical trials for any potential
product can vary dramatically based on a number of factors, including the
order and timing of clinical indications pursued and the extent of development
and financial support, if any, from corporate collaborators. The Company may
have difficulty obtaining sufficient patient populations, clinicians or sup-
port to conduct its clinical trials as planned and may have to expend substan-
tial additional funds to obtain access to such resources, or delay or modify
its plans significantly.
 
While the Company designs and manages its preclinical studies and clinical
trials, the Company engages contract research organizations to perform certain
aspects of such preclinical studies and clinical trials. As a result, the Com-
pany depends on such contract research organizations to assist in the comple-
tion of its studies and trials.
 
GOVERNMENT REGULATION; NO ASSURANCE OF REGULATORY APPROVAL
 
The production and marketing of products under development by the Company, as
well as its ongoing research and development activities, are and will be sub-
ject to regulation by governmental agencies, including the FDA in the United
States and similar regulatory authorities in other countries. Any potential
therapeutic product developed by the Company will be subject to rigorous
preclinical and clinical testing and approval pursuant to regulations adminis-
tered by the FDA, comparable agencies in other countries and, to a lesser
extent, by state regulatory authorities. The approval process for the
Company's drug candidates will involve significant time and expenditures.
There can be no assurance that the Company will be able to successfully com-
plete the clinical development of, and file its NDA for, pleconaril or any
other drug candidate. See "Business--Government Regulation."
 
                                       7
<PAGE>
 
Rigorous preclinical and clinical testing and the regulatory approval process
can take many years and require the expenditure of substantial resources. There
can be no assurance that the FDA or other regulatory authority approval for any
product candidates developed by the Company will be granted on a timely basis
or at all. Any delay in obtaining, or any failure to obtain, such approvals
would materially and adversely affect the marketing of the Company's drug can-
didates and the Company's business, financial position and results of opera-
tions. In addition, legislation may be enacted, or regulations promulgated in
the future which might adversely affect the Company's ability to develop, manu-
facture or market its drug candidates. If regulatory approval of a drug is
obtained, such approval may be conditioned upon certain limitations and
restrictions on the drug's use. Any FDA approvals that may be granted will be
subject to continual review, and later discovery of previously unknown problems
may result in withdrawal of products from marketing. Failure of the Company to
comply with applicable regulatory requirements can, among other things, result
in warning letters, fines, withdrawal of regulatory approvals, product recalls,
seizure of products, operating restrictions, injunctions or criminal prosecu-
tion. See "Business--Government Regulation."
 
UNCERTAIN ABILITY TO MEET CAPITAL NEEDS
 
The Company will require substantial additional funds for its research,
preclinical and clinical testing, operating expenses, regulatory applications,
manufacturing, marketing and sales programs. The Company has incurred losses
from its operations since inception. The Company expects to incur additional
operating losses over at least the next several years. The Company expects such
losses to increase over historical levels as the Company's research and devel-
opment expenses increase due to further clinical trials, manufacture of drug
substance and preclinical development of pleconaril, and further research and
development related to other product candidates. Moreover, the Company's cap-
ital requirements will depend on numerous factors, including the progress of
its research and development programs, the progress of preclinical and clinical
testing, the time and cost involved in obtaining regulatory approvals, the cost
of filing, prosecuting, defending and enforcing any patent claims and other
intellectual property rights, competing technological and market developments,
changes and developments in the Company's existing collaborative, licensing and
other relationships, the terms of any new collaborative, licensing and other
arrangements that the Company may establish and the development of commercial-
ization activities and arrangements. The Company's fixed commitments, including
salaries and fees for current employees and consultants, rent, payments under
license agreements and other contractual commitments, are substantial and are
likely to increase as additional agreements are entered into and additional
personnel are retained. The Company believes that the net proceeds of this
offering, together with proceeds from the collaborative drug discovery and
development agreement with Boehringer Ingelheim, available cash and interest
income, should be adequate to fund its current and anticipated levels of opera-
tions through the middle of 1999. The Company's cash requirements may vary
materially and could be significantly higher than those now planned because of
results of research and development and drug candidate testing, relationships
with strategic partners, changes in the focus and direction of the Company's
research and development programs, competitive and technological advances, the
FDA and foreign regulatory requirements and other factors. See "Use of Pro-
ceeds," "Management's Discussion and Analysis of Financial Condition and
Results of Operations--Liquidity and Capital Resources," "Business--Strategic
Relationships," "Business--Patents," "Management" and Notes to Financial State-
ments.
 
The Company will need to raise substantial additional capital to fund its
future operations. The proceeds of this offering, together with available cash,
are not expected to be sufficient to complete all clinical studies and other
development and required testing for pleconaril or any other of the Company's
product candidates. The Company will likely seek such additional funding
through public or private financing or collaborative, licensing and other
arrangements with corporate partners. If additional funds are raised by issuing
equity securities, further dilution to existing stockholders will result, and
future investors may be granted rights superior to those of existing stockhold-
ers. There can be no assurance, however, that additional financing will be
available when needed or, if available, will be available on acceptable terms.
Insufficient funds may prevent the Company from executing its business plan or
may require the Company to delay, scale back or eliminate certain of its
research and product development programs or license to third parties rights to
develop or commercialize products or technologies that the Company would other-
wise seek to develop or commercialize itself.
 
DEPENDENCE ON CORPORATE COLLABORATIONS; NEED FOR ADDITIONAL COLLABORATORS
 
The Company's strategy for the research, development and commercialization of
its drug candidates may require the Company to enter into various arrangements
with corporate and academic collaborators, licensors, licensees and others. The
Company may, therefore, be dependent upon the subsequent success of these third
parties in performing their responsibilities. The Company has obtained, and
intends to obtain in the future, licensed rights to certain proprietary tech-
nologies and compounds from other entities, individuals and research institu-
tions, to which it will be obligated to pay license fees and, if it develops
products based upon the licensed technology, to also make milestone payments
and pay royalties. There can be no assurance that the Company will be able to
enter into collaborative, license or other arrangements that the Company
 
                                       8
<PAGE>
 
deems necessary or appropriate to develop and commercialize its drug candi-
dates, or that any or all of the contemplated benefits from such collabora-
tive, license or other arrangements will be realized. Certain of the collabo-
rative, license or other arrangements that the Company may enter into in the
future may place responsibility on the Company's collaborative partners for
preclinical testing and human clinical trials and for the preparation and sub-
mission of applications for regulatory approval for potential pharmaceutical
or other products. Other collaborations may place responsibility on partners
for marketing, sales and distribution support for product commercialization.
Should any collaborative partner fail to develop or successfully commercialize
any drug candidate to which it has rights, the Company's business may be mate-
rially adversely affected. Moreover, these arrangements may require the Com-
pany to transfer certain material rights to such corporate partners, licensees
and others. In the event that the Company decides to license or sublicense
certain of its commercial rights, there can be no assurance that such arrange-
ments will not result in reduced product revenue to the Company. There can be
no assurance that any revenues or profits will be derived from the Company's
collaborative and other arrangements, that any of the Company's current stra-
tegic arrangements will continue or that the Company will enter into any
future collaborations. Furthermore, there can be no assurance that current or
future collaborators will not pursue alternative technologies or drug candi-
dates either on their own or in collaboration with others, including the
Company's competitors, as a means for developing treatments for the diseases
sought to be addressed by the Company's programs. See "Business--Strategic
Relationships."
 
UNCERTAIN ABILITY TO PROTECT PATENTS AND PROPRIETARY TECHNOLOGY AND
INFORMATION
   
Because of the substantial length of time and expense associated with bringing
new products through development and regulatory approval to the market place,
the pharmaceutical industry places considerable importance on obtaining patent
and trade secret protection for new technologies, products and processes. The
Company's ability to compete effectively depends, in part, on its ability to
protect its proprietary technology, both in the United States and abroad. The
Company intends to file applications as appropriate for patents covering the
composition of matter of its drug candidates, the proprietary processes for
producing such compositions, as well as the uses of its drug candidates. The
Company has one issued U.S. patent, one allowed U.S. patent application and
four patent applications pending with the U.S. Patent and Trademark Office
("PTO"). The Company has licensed from Sanofi S.A. the exclusive U.S. and
Canadian rights to antiviral agents for use in enterovirus and rhinovirus
indications, which are the subject of two issued U.S. patents and two related
Canadian patent applications owned by Sanofi S.A. The Company will be depen-
dent on Sanofi S.A. to prosecute such patent applications and may be dependent
on Sanofi S.A. to protect such patent rights. The Company also has filed four
patent applications in certain foreign jurisdictions on inventions developed
by the Company. There can be no assurance that the PTO or such foreign juris-
dictions will grant the Company's pending patent applications or that the Com-
pany will obtain any patents on its proprietary products for which it subse-
quently applies. No assurance can be given that any patents issued to, or
licensed by, the Company will not be challenged, invalidated or circumvented
by other parties, or that the rights granted thereunder will provide any com-
petitive advantage. Furthermore, there can be no assurance that others will
not independently develop similar products, duplicate any of the Company's
products or, if patents are issued to the Company, design around the patented
products developed by the Company.     
 
The Company also relies on trade secrets, know-how and continuing technolog-
ical advancements to support its competitive position. Although the Company
has entered into confidentiality and invention rights agreements with its
employees, consultants, advisors and collaborators, no assurance can be given
that such agreements will be honored or that the Company will be able to
effectively protect its rights to its unpatented trade secrets and know-how.
Moreover, there can be no assurance that others will not independently develop
substantially equivalent proprietary information and techniques or otherwise
gain access to the Company's trade secrets and know-how. In addition, many of
the Company's scientific and management personnel have been recruited from
other pharmaceutical companies where they were conducting research in areas
similar to those being pursued by the Company. As a result, the Company and
these individuals could be subject to allegations of trade secret violations
and similar claims.
 
In addition, to facilitate development of its proprietary technology base, the
Company may be required to obtain licenses to patents or other proprietary
rights from other parties, and such requirements could substantially delay the
Company's drug development or commercialization. There can be no assurance
that the patents of other parties will not have a material adverse effect on
the ability of the Company to do business or that any licenses required under
any patents or proprietary rights of other parties would be made available on
acceptable terms, if at all. If the Company does not obtain any such required
licenses, it could encounter delays in introducing products to market or may
be unable to develop, manufacture or sell products requiring such licenses.
The Company has not conducted any searches or made any independent investiga-
tions of the existence of any patents or proprietary rights of other parties.
 
The Company may, from time to time, collaborate with, and support research
conducted by, universities and governmental research organizations. There can
be no assurance that the Company will have, or be able to acquire, exclusive
rights to
 
                                       9
<PAGE>
 
the inventions or technical information derived from such collaborations or
that disputes will not arise as to rights in related research programs con-
ducted by the Company or such collaborators. See "Business--Strategic Relation-
ships."
 
In addition, the Company could incur substantial costs in defending any patent
infringement suits or in asserting any patent rights, including those licensed
to the Company by third parties, and in defending suits against it or its
employees relating to ownership of, or rights to, intellectual property, even
if the outcome is not adverse to the Company. Such disputes could substantially
delay the Company's drug development or commercialization. The PTO or a private
party could institute an interference proceeding involving the Company in con-
nection with one or more of the Company's patents or patent applications, and
such proceedings could result in an adverse decision as to priority of inven-
tion, in which case the Company would not be entitled to a patent on the inven-
tion at issue in the interference proceeding. The PTO or a private party could
also institute reexamination proceedings involving the Company in connection
with one or more of the Company's patents, and such proceedings could result in
an adverse decision as to the validity or scope of the patents. Opposition or
revocation proceedings could be instituted in the patent offices of foreign
jurisdictions, which proceedings, if decided adversely to the Company would
prevent the Company from establishing a patent position in such jurisdiction
based on the opposed or revoked patent. See "Business--Patents."
 
ABSENCE OF MARKETING AND SALES CAPABILITY
 
The Company is currently conducting market research on the multiple disease
indications for which pleconaril is being developed. The Company intends to
establish its marketing strategy based upon the results of this market research
coupled with information gained through its clinical trials. The Company may
elect to seek a marketing partner for certain disease indications, establish
its own sales force or pursue both alternatives. In order to develop its mar-
keting strategy, the Company has recently hired an Executive Director of Mar-
keting. The Company does not currently have a sales and marketing staff. Sig-
nificant additional expenditures, management resources and time will be
required to develop a marketing and sales capability, and there can be no
assurance that the Company will be successful either in developing a sales
force, entering into commercialization arrangements, penetrating the markets
for any proposed products it may develop or achieving market acceptance of its
products. The Company has entered, and in the future may enter, into marketing,
distribution, manufacturing, development or other third party arrangements,
which grant rights that may be exclusive to certain products to corporate part-
ners in return for royalties to be received on sales, if any. There can be no
assurance that the Company will be able to enter into any additional arrange-
ments, that any such arrangements will be successful or that the Company will
be able to obtain additional capital to conduct such activities directly. See
"Risk Factors--Dependence on Corporate Collaborations; Need for Additional Col-
laborators" and "Business--Marketing."
 
UNCERTAINTY OF PHARMACEUTICAL PRICING AND RELATED MATTERS; NEED FOR
REIMBURSEMENT
 
The future revenues and profitability of, and availability of capital for,
pharmaceutical companies such as the Company will be affected by the continuing
efforts of governmental and private third-party payors to contain or reduce the
costs of health care through various means. There have been, and the Company
expects there will continue to be, a number of federal, state and foreign pro-
posals to control the cost of drugs through governmental regulation. It is
uncertain what form any health care reform legislation may take or what actions
federal, state, foreign, and private payors may take in response to the pro-
posed reforms. The Company cannot predict when, if ever, any suggested reforms
will be implemented or the effect of any implemented reform on the Company's
business. Moreover, there can be no assurance that any implemented reform will
not have a material adverse effect on the Company's business, financial posi-
tion or results of operations.
 
The Company's ability to commercialize any products successfully will depend,
in part, on the extent to which reimbursement for the cost of such products and
related treatments will be available from government health administration
authorities, such as Medicare and Medicaid in the United States, private health
insurers and other organizations. Significant uncertainty exists as to the
reimbursement status of newly approved health care products, particularly for
indications for which there is no current effective treatment or for which med-
ical care typically is not sought, and there can be no assurance that adequate
third-party coverage will be available to enable the Company to maintain price
levels sufficient to realize an appropriate return on its investment in product
research and development. If adequate coverage and reimbursement levels are not
provided by government and third-party payors for use of the Company's prod-
ucts, the market acceptance of those products could be adversely affected.
 
COMPETITION
 
There are many entities, both public and private, including well-known, large
pharmaceutical companies, chemical companies, biotechnology companies and
research institutions, engaged in developing pharmaceuticals for human thera-
peutic
 
                                       10
<PAGE>
 
   
applications similar to the applications targeted by the Company. Many of these
companies have substantially greater financial, research and development, manu-
facturing, marketing and human resources than the Company. In addition, many of
the Company's competitors have significantly greater experience than the Com-
pany in conducting drug discovery, conducting preclinical testing and human
clinical trials of new pharmaceutical products, obtaining FDA and other regula-
tory approvals of products, manufacturing and marketing. Accordingly, certain
of the Company's competitors may succeed in obtaining regulatory approval for
products more rapidly or effectively than the Company. Such companies may suc-
ceed in developing products that are more effective or less costly than any
that may be developed by the Company and also may prove to be more successful
than the Company in the manufacture and marketing of any such products. See
"Business--Competition."     
 
RAPID TECHNOLOGICAL CHANGE AND UNCERTAINTY
 
The Company is engaged in the pharmaceutical business, which is characterized
by extensive research efforts and rapid technological progress. New develop-
ments in molecular biology, medicinal chemistry and other fields of biology and
chemistry are expected to continue at a rapid pace in both industry and acade-
mia. There can be no assurance that research and discoveries by others will not
render some or all of the Company's programs or drug candidates non-competitive
or obsolete.
 
The Company's proposed business strategy is based, in part, upon the applica-
tion of the Company's technology platform, which encompasses various elements
from the fields of biotechnology and chemistry, and the application of these
technologies to the discovery and development of pharmaceutical products for
the treatment of infectious human diseases. This strategy is subject to the
risks inherent in the development of new products using new and emerging tech-
nologies and approaches. There are no approved drugs on the market for the
treatment of certain of the disease indications being targeted by the Company,
and the Company believes that it is the first company to use these technologies
in combination to develop antiviral pharmaceutical products. There can be no
assurance that unforeseen problems will not develop with the Company's technol-
ogies or applications, that the Company will be able to successfully address
technological challenges it encounters in its research and development programs
or that commercially feasible products will ultimately be developed by the Com-
pany. See "--Competition" and "Business--Competition."
 
NO ASSURANCE OF MARKET ACCEPTANCE
 
There can be no assurance that the Company's drug candidates, if approved by
the FDA and other regulatory authorities, will achieve market acceptance. The
degree of market acceptance will depend upon a number of factors, including the
receipt and timing of regulatory approvals, the availability of third-party
reimbursement and the establishment and demonstration in the medical community
of the clinical safety, efficacy and cost-effectiveness of the Company's drug
candidates and their advantages over existing technologies and therapeutics.
There can be no assurance that the Company will be able to manufacture and suc-
cessfully market its drug candidates even if they perform successfully in clin-
ical applications. Furthermore, there can be no assurance that physicians or
the medical community in general will accept and utilize any therapeutic prod-
ucts that may be developed by the Company.
 
ABSENCE OF MANUFACTURING CAPABILITIES
 
The Company presently does not have the internal capability to manufacture
pharmaceutical products under the current Good Manufacturing Practices ("GMP")
prescribed by the FDA. The Company believes that it has sufficient quantities
of bulk drug substance to complete its clinical programs for viral meningitis,
"summer flu" and hand-foot-and-mouth disease. The Company will require addi-
tional quantities of pleconaril drug substance to complete its planned clinical
trials for the common cold. In February 1997, the Company amended its agreement
with Sanofi to permit the Company to engage a third party to manufacture bulk
drug substance. In April 1997, the Company entered into a Development Agreement
with SICOR S.A. and SELOC AG, related companies and subsidiaries of Schwarz
Pharma AG, for the manufacture of pleconaril bulk drug substance and the devel-
opment of a process for commercial-scale production of pleconaril. The Company
also is evaluating alternatives for the commercial manufacture of drug sub-
stance and drug product. FDA pre-approval inspection is required for all com-
mercial manufacturing sites.
 
Any contract manufacturers that the Company may use must adhere to GMP regula-
tions enforced by the FDA through its facilities inspection program. These
facilities must pass a plant inspection before the FDA will issue a pre-market
approval of the product. Moreover, while the Company does not currently intend
to manufacture any pharmaceutical products itself, it may choose to do so in
the future. The Company has no experience in the manufacture of pharmaceutical
products for clinical trials or commercial purposes. Should the Company decide
to manufacture products itself, the Company would be subject to the regulatory
requirements described above, would be subject to risks regarding delays or
difficulties encoun-
 
                                       11
<PAGE>
 
tered in manufacturing any such pharmaceutical products and would require sub-
stantial additional capital. In addition, there can be no assurance that the
Company will be able to manufacture any such products successfully and in a
cost-effective manner. See "Business--Manufacturing" and "Business--Government
Regulation."
 
If the Company should encounter delays or difficulties with contract manufac-
turers in producing, packaging or distributing its proposed products, market
introduction and subsequent sales of such products would be adversely affected
and the Company may have to seek alternative sources of supply. In the event
that the Company is required to seek alternative sources of supply, it may
incur additional costs or delays in product commercialization. If the Company
changes the source or location of supply or modifies the manufacturing proc-
ess, regulatory authorities will require the Company to demonstrate that the
product produced by the new source or from the modified process is equivalent
to the product used in any clinical trials conducted by the Company. Under the
terms of the Development Agreement, SICOR is obligated to deliver the first
batch of pleconaril bulk drug substance in the fourth quarter of 1997. If such
bulk drug substance is not shown to be equivalent, the Company's ability to
seek FDA or other regulatory approval could be delayed until additional clin-
ical trials are completed. Furthermore, there can be no assurance that the
Company will be able to enter into alternative supply arrangements at commer-
cially acceptable rates, if at all. No assurance can be given that the manu-
facturers utilized by the Company will be able to provide the Company with
sufficient quantities of its products or that the products supplied to the
Company will meet the Company's specifications or delivery, cost and other
requirements.
 
DEPENDENCE ON KEY PERSONNEL
 
Because of the specialized scientific nature of the Company's business, the
Company is highly dependent upon its ability to attract and retain qualified
scientific, technical and managerial personnel. There is intense competition
for qualified personnel in the pharmaceutical field, and there can be no
assurance that the Company will be able to continue to attract and retain
qualified personnel necessary for the development of its business. The loss of
the services of existing personnel, as well as the failure to recruit addi-
tional key scientific, technical and managerial personnel in a timely manner
would be detrimental to the Company's research and development programs and to
its business. Much of the know-how developed by the Company resides in its
scientific and technical personnel and is not readily transferable to other
personnel. The Company does not maintain "key man" life insurance on any of
its employees. Furthermore, the Company's anticipated growth and expansion
into areas and activities requiring additional expertise will require the
addition of new management personnel. The failure to attract and retain such
personnel could adversely affect the Company's business. See "Business--Human
Resources" and "Management."
 
ENVIRONMENTAL MATTERS AND HAZARDOUS MATERIALS
 
The Company's research and development processes involve the controlled use of
hazardous, infectious and radioactive materials. The Company is subject to
stringent federal, state and local laws, rules, regulations and policies gov-
erning the use, generation, manufacture, storage, air emission, effluent dis-
charge, handling and disposal of certain materials and wastes. There can be no
assurance that the Company will not be required to incur significant costs to
comply with environmental laws, rules, regulations and policies or that the
business, financial position or results of operations of the Company will not
be materially and adversely affected by current or future environmental laws,
rules, regulations and policies or by any releases or discharges of materials
which could be hazardous.
 
In its research activities, the Company utilizes radioactive and other mate-
rials that could be hazardous to human health, safety or the environment.
These materials and various wastes resulting from their use are stored at the
Company's facility pending ultimate use and disposal. Although the Company
believes that its safety procedures for handling and disposing of such mate-
rials comply with federal, state and local laws, rules, regulations and poli-
cies, the risk of accidental injury or contamination from these materials
cannot be entirely eliminated. In the event of such an accident, the Company
could be held liable for any resulting damages, and any such liability could
exceed the Company's resources. The Company does not maintain a separate
insurance policy for these types of risks.
 
PRODUCT LIABILITY; LIMITED INSURANCE COVERAGE
 
The Company's business exposes it to potential product liability risks which
are inherent in the testing, manufacturing and marketing of human therapeutic
products. The Company maintains claims made insurance against product lia-
bility and defense costs incurred in connection with clinical testing in the
amount of five million dollars per occurrence and five million dollars in the
aggregate. The Company does not currently have any insurance coverage with
regard to the commercial sale of products. There can be no assurance that
claims against the Company arising with respect to clinical testing or sale of
products will be successfully defended, that the insurance carried by the Com-
pany, if any, will be sufficient or that the Company will be able to obtain
additional, or maintain its current level of, product liability insurance on
acceptable
 
                                      12
<PAGE>
 
terms. In addition, there can be no assurance that any collaborators and
licensees of the Company will agree to indemnify the Company from, be ade-
quately insured against or have a sufficient net worth to protect the Company
from product liability claims. A successful claim against the Company in excess
of the Company's insurance coverage could have a material adverse effect on the
Company.
 
POSSIBLE VOLATILITY OF STOCK PRICE
 
The market price of the Common Stock is likely to be highly volatile as is fre-
quently the case with publicly traded emerging growth companies and biotech-
nology companies. Announcements by the Company or its competitors of technolog-
ical innovations or new products, existing and future collaborations, scien-
tific discoveries and results of clinical trials, as well as government regula-
tory action, developments or disputes concerning patent or proprietary rights,
market conditions and period-to-period fluctuations in financial results, could
have a significant impact on the Company's business and the market price of the
Common Stock. In addition, the stock market has experienced extreme price and
volume fluctuations. This volatility has significantly affected the market
prices of securities of many emerging growth and biotechnology companies. These
broad market fluctuations may adversely affect the market price of the
Company's Common Stock.
 
CONTROL BY EXISTING STOCKHOLDERS
 
Upon the closing of this offering, directors and officers of the Company and
related stockholders, who in the aggregate currently own beneficially 5,907,591
shares of Common Stock (excluding outstanding options and warrants to purchase
shares of Common Stock), will own beneficially in the aggregate shares of
Common Stock representing approximately 53.0% of the outstanding shares of
Common Stock. Accordingly, the Company's officers and directors and related
stockholders together will have the ability to elect a majority of the
Company's directors and thereby control the officers and management of the Com-
pany and will be able to control effectively all matters requiring stockholder
approval, including amendments to the Company's Second Amended and Restated
Certificate of Incorporation, mergers, share exchanges, the sale of all or sub-
stantially all of the Company's assets, going private transactions and other
fundamental transactions. Such concentration of ownership may have the effect
of delaying or preventing a change in control of the Company. See "Principal
Stockholders."
 
AVAILABILITY OF PREFERRED STOCK FOR ISSUANCE; ANTI-TAKEOVER PROVISIONS
 
In addition to its authorized shares of Common Stock, the Company's Second
Amended and Restated Certificate of Incorporation authorizes the issuance of up
to 5,000,000 shares of preferred stock, par value $.001 per share ("Preferred
Stock"). No shares of Preferred Stock of the Company currently are outstanding,
none will be outstanding upon the closing of this offering, and the Company has
no present intention to issue any shares of Preferred Stock. However, because
the rights and preferences of any series of Preferred Stock may be set by the
Board of Directors at its sole discretion, the rights and preferences of any
such Preferred Stock may be superior to those of the Common Stock and thus may
adversely affect the rights of the holders of Common Stock. See "Description of
Capital Stock--Preferred Stock."
 
The Company's Second Amended and Restated Certificate of Incorporation and By-
Laws and the Delaware General Corporation Law contain certain provisions that
could prevent or delay the acquisition of the Company by means of a tender
offer, proxy contest or otherwise, or could discourage a third party from
attempting to acquire control of the Company, even if such events would be ben-
eficial to the interests of the stockholders. These provisions, among other
things (i) divide the Board of Directors into three classes, each of which
serves for a staggered three-year term, (ii) prohibit the removal of directors
without cause by the stockholders and (iii) grant the Board of Directors the
authority, without action by the stockholders, to fix the rights and prefer-
ences of, and issue shares of, Preferred Stock. The Company is also subject to
Section 203 of the Delaware General Corporation Law which contains certain
anti-takeover provisions which prohibit a "business combination" between a cor-
poration and an "interested stockholder" within three years of the stockhold-
er's becoming an "interested stockholder" except in certain limited circum-
stances. The business combination provisions of Section 203 of the Delaware
General Corporation Law may have the effect of deterring merger proposals,
tender offers or other attempts to effect changes in control of the Company
that are not negotiated and approved by the Board of Directors. See "Descrip-
tion of Capital Stock."
 
SHARES ELIGIBLE FOR FUTURE SALE
 
Upon completion of this offering, the Company will have a total of 11,148,911
shares of Common Stock outstanding (11,448,911 shares if the Underwriters'
over-allotment option is exercised in full). Of these shares, 4,587,500 shares
(4,887,500 shares if the Underwriters' over-allotment option is exercised in
full) will be freely tradeable without restriction or registration under the
Securities Act of 1933, as amended (the "Securities Act"), by persons other
than "affiliates" of the
 
                                       13
<PAGE>
 
Company, as defined under the Securities Act. The remaining 6,561,411 shares
are "restricted securities" as that term is defined by Rule 144 as promulgated
under the Securities Act, and are eligible for immediate resale under Rule 144,
subject to the conditions and limitations of that rule. Of such "restricted
securities," 714,000 shares will be subject in varying degrees to the addi-
tional restrictions of stock purchase agreements. Holders of 5,851,277 of these
shares have agreed not to directly or indirectly sell or dispose of their
shares without the prior written consent of J.P. Morgan Securities Inc. for a
period of 90 days from the date of this Prospectus. See "Shares Eligible for
Future Sale" and "Underwriting."
 
The Company also has outstanding options to purchase 707,037 shares of Common
Stock and outstanding warrants to purchase 21,675 shares of Common Stock. The
shares of Common Stock underlying these options and warrants may also be sold
in the public market pursuant to Rule 144.
 
Stockholders of the Company are entitled to certain piggyback and demand regis-
tration rights with regard to 5,659,979 shares of Common Stock. In addition,
the founders of the Company are entitled to certain piggyback registration
rights with regard to 879,750 shares of Common Stock. By exercising such regis-
tration rights, subject to certain limitations, such holders could cause a sig-
nificant number of shares to be registered and sold in the public market. Such
sales may have an adverse effect on the market price for the Common Stock and
could impair the Company's ability to raise capital through an offering of its
equity securities. All such rights in connection with this offering have been
waived.
 
No predictions can be made of the effect, if any, that the sale or availability
for sale of additional shares of Common Stock under Rule 144, pursuant to reg-
istration rights or otherwise, will have on the trading price of the Common
Stock. Nevertheless, sales of substantial amounts of such shares in the public
market (and distributions by the Company's principal venture capital investors
and sales by such distributees who may qualify for resales under Rule 144(k)
without any volume limitation), or the perception that such sales could occur,
could adversely affect the trading price of the Common Stock and could impair
the Company's future ability to raise capital through an offering of its equity
securities.
 
NO DIVIDENDS
 
The Company has not declared or paid dividends on its Common Stock since its
inception and does not intend to declare or pay any dividends to its stock-
holders in the foreseeable future. See "Dividend Policy" and "Management's Dis-
cussion and Analysis of Financial Condition and Results of Operations."
 
DILUTION
   
Upon completion of this offering, purchasers of Common Stock in this offering
will incur immediate dilution of $12.01 in the per share net tangible book
value of their Common Stock from the assumed public offering price. See "Dilu-
tion."     
 
                                       14
<PAGE>
 
                                USE OF PROCEEDS
   
The net proceeds to the Company from the sale of the shares of Common Stock
offered hereby are estimated to be approximately $30.7 million ($35.4 million
if the Underwriter's over-allotment option is exercised in full), at an
assumed public offering price of $16.50 per share and after deducting the
Underwriters' fees and estimated offering expenses payable by the Company.
       
The Company intends to use the net proceeds of this offering as follows: (i)
approximately $20.0 million to fund further development of pleconaril,
including ongoing clinical trials and certain related pre-marketing activi-
ties, (ii) approximately $5.0 million for other ongoing research and develop-
ment programs and (iii) the balance for general corporate purposes and capital
equipment expenditures, including approximately $800,000 in initial construc-
tion costs related to new laboratory and office space, pursuant to a lease
which the Company entered into on July 21, 1997.     
 
The amounts actually expended for any single purpose will vary significantly
depending upon numerous factors, including the progress of the Company's
research and development programs, the results of preclinical and clinical
studies, the timing of regulatory approvals, technological advances, determi-
nations as to commercial potential of product candidates and the status of
competitive products. In addition, expenditures will be dependent upon the
establishment of collaborative arrangements with other companies, the avail-
ability of financing and other factors. See "Business--Product Development and
Research."
 
The Company believes that the net proceeds of this offering, together with the
proceeds from the collaborative drug discovery and development agreement with
Boehringer Ingelheim, available cash and expected interest income, will be
adequate to fund its current and anticipated levels of operations through the
middle of 1999. This estimate is based on assumptions about numerous factors,
including the factors described above. The Company also expects from time to
time to evaluate the possible licensing or acquisition of products, businesses
and technologies which complement the Company's business. The Company does not
currently have any understandings, commitments or agreements with respect to
any such possible licensing or acquisition. In addition, future unanticipated
events may make shifts in the allocation of funds necessary or desirable. The
proceeds of this offering are not expected to be sufficient to complete all
clinical studies for pleconaril and other development and required testing for
any other of the Company's product candidates. Moreover, additional funding
will be required before the Company is able to generate positive cash flows
from commercial activities. Pursuant to its agreement with Boehringer
Ingelheim, the Company has the right to obtain a loan in the amount of $1.0
million from Boehringer Ingelheim, creditable against future milestone pay-
ments that may be payable to the Company under the Agreement, at any time
during 1997. The Company does not have any other commitments to obtain any
additional funds, and there can be no assurance that required funds will be
available to the Company. See "Risk Factors--Uncertain Ability to Meet Capital
Needs."
 
Pending the application of the proceeds of this offering, the Company intends
to invest such proceeds in short-term interest-bearing United States govern-
ment securities and in short-term, interest-bearing investment grade securi-
ties. The Company intends to invest and use the net proceeds so as not to be
considered an investment company under the Investment Company Act of 1940.
 
                                      15
<PAGE>
 
                          PRICE RANGE OF COMMON STOCK
 
The Company's Common Stock is traded on the Nasdaq National Market under the
symbol "VPHM." The Company commenced trading on the Nasdaq National Market on
November 19, 1996. The following table sets forth the high and low closing sale
price per share of the Common Stock, as quoted on the Nasdaq National Market,
since the Company's initial public offering in November 1996.
 
<TABLE>   
<CAPTION>
                                                                 --------------
                                                                    HIGH    LOW
                                                                 ------- ------
<S>                                                              <C>     <C>
Year ended 1996
Fourth Quarter (Nov. 19 through Dec. 31)........................ $ 8.750 $7.000
Year ending 1997
First Quarter................................................... $13.750 $9.375
Second Quarter.................................................. $17.875 $9.688
Third Quarter (through July 21)................................. $17.875 $16.50
</TABLE>    
   
On July 21, 1997, the last reported closing price of the Common Stock on the
Nasdaq National Market was $16.50 per share. As of July 21, 1997, there were 41
holders of record of the Company's Common Stock.     
 
                                DIVIDEND POLICY
 
The Company has never declared or paid dividends on its capital stock and does
not anticipate paying cash dividends in the foreseeable future. The Company
currently intends to retain any future earnings for use in the operations,
development and growth of its business.
 
                                       16
<PAGE>
 
                                 CAPITALIZATION
   
The following table sets forth the capitalization of the Company as of March
31, 1997 (i) on an actual basis and (ii) as adjusted to give effect to the sale
by the Company of the 2,000,000 shares of Common Stock offered hereby at an
assumed public offering price of $16.50 per share (after deducting the Under-
writers' fees and estimated offering expenses payable by the Company). This
table 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.     
 
<TABLE>   
<CAPTION>
                                                 -----------------------------
                                                      AT MARCH 31, 1997
                                                       ACTUAL  AS ADJUSTED (1)
                                                 ------------  ---------------
                                                         (UNAUDITED)
<S>                                              <C>           <C>
Loan payable and capital leases--non-current.... $    583,312     $    583,312
Stockholders' equity:
  Preferred Stock, par value $.001 per share,
   5,000,000 shares authorized, none issued and
   outstanding, actual and as adjusted..........          --             --
  Common Stock, par value $.002 per share,
   27,000,000 shares authorized; 9,077,116
   shares issued and outstanding, actual; and
   11,077,116 shares issued and outstanding, as
   adjusted(1)..................................       18,154           22,154
  Additional paid-in capital....................   31,763,030       62,479,030
  Deferred compensation.........................     (608,598)        (608,598)
  Unrealized gain on available for sale
   securities...................................       98,257           98,257
  Deficit accumulated during the development
   stage........................................  (12,300,377)     (12,300,377)
                                                 ------------     ------------
Total stockholders' equity......................   18,970,466       49,690,466
Total capitalization............................ $ 19,553,778     $ 50,273,778
                                                 ============     ============
</TABLE>    
- -------
   
(1) Excludes (i) 684,578 shares issuable upon exercise of options outstanding
as of March 31, 1997 at a weighted average exercise price of $3.87 per share
and (ii) 103,272 shares issuable upon exercise of warrants outstanding as of
March 31, 1997 at a weighted average exercise price of $2.17 per share. As of
July 1, 1997, there were (i) 707,037 shares issuable upon exercise of options
outstanding at a weighted average exercise price of $4.07 per share and (ii)
21,675 shares issuable upon exercise of warrants at an exercise price of $2.94
per share. See "Management--Executive Compensation," "Management--Stock
Options," "Certain Transactions--Transactions with Founders," "Description of
Capital Stock" and Note 11 of Notes to Financial Statements.     
 
                                       17
<PAGE>
 
                                    DILUTION
   
Purchasers of the Common Stock offered hereby will experience an immediate
dilution in the net tangible book value of their Common Stock from the assumed
public offering price. The net tangible book value of the Company's Common
Stock as of March 31, 1997 was $18,970,466 or $2.09 per share. "Net tangible
book value" per share is equal to the Company's net tangible assets (tangible
assets less total liabilities) divided by the 9,077,116 shares of Common Stock.
"Dilution per share" represents the difference between the assumed public
offering price per share of the Common Stock and the pro forma net tangible
book value per share of the Company after giving effect to this offering. After
reflecting the sale of 2,000,000 shares of Common Stock offered by the Company
hereby at the assumed public offering price of $16.50 per share (after
deducting Underwriters' fees and estimated offering expenses) and the initial
application of the net proceeds therefrom, the pro forma net tangible book
value of the Company as of March 31, 1997 would have been $49,690,466 or $4.49
per share. The change represents an immediate increase in net tangible book
value of $2.40 per share to existing stockholders and an immediate dilution of
$12.01 per share to new investors purchasing the shares of Common Stock in this
offering. The following table illustrates this per share dilution:     
 
<TABLE>   
<S>                                                                 <C>   <C>
Assumed public offering price......................................       $16.50
  Net tangible book value per share before the offering............ $2.09
  Increase per share attributable to new investors in the
   offering........................................................  2.40
Pro forma net tangible book value per share after this offering....         4.49
                                                                          ------
Dilution per share to new investors................................       $12.01
                                                                          ======
</TABLE>    
 
The above information excludes (i) 684,578 shares issuable upon exercise of
options outstanding as of March 31, 1997 at a weighted average exercise price
of $3.87 per share and (ii) 103,272 shares issuable upon exercise of warrants
outstanding as of March 31, 1997 at a weighted average exercise price of $2.17
per share. As of July 1, 1997, there were (i) 707,037 shares issuable upon
exercise of options outstanding at a weighted average exercise price of $4.07
per share and (ii) 21,675 shares issuable upon exercise of warrants at an exer-
cise price of $2.94 per share. See "Management--Executive Compensation," "Man-
agement--Stock Options," "Description of Capital Stock" and Note 11 of Notes to
Financial Statements.
 
                                       18
<PAGE>
 
                            SELECTED FINANCIAL DATA
 
The selected financial data presented below under the caption "Balance Sheet
Data" as of December 31, 1995 and 1996, and under the caption "Statement of
Operations Data" for the period from December 5, 1994 (inception) through
December 31, 1994 and the years ended December 31, 1995 and December 31, 1996
are derived from and are qualified by reference to the financial statements of
the Company and the related notes thereto, which have been audited by KPMG Peat
Marwick LLP, independent certified public accountants and which are included
elsewhere in this Prospectus. The "Balance Sheet Data" as of December 31, 1994
are derived from audited financial statements not included in this Prospectus.
The selected financial data as of March 31, 1997 and for the three-month
periods ended March 31, 1996 and 1997 are derived from unaudited financial
statements. Such unaudited financial statements include all adjustments (con-
sisting only of normal recurring adjustments) necessary to present fairly the
information set forth herein. Operating results for the three months ended
March 31, 1997 are not necessarily indicative of the results to be expected for
the year ending December 31, 1997. The data set forth below should be read in
conjunction with Management's Discussion and Analysis of Financial Condition
and Results of Operations, the Financial Statements and the Notes thereto and
the other financial information included elsewhere in this Report. The Company
is considered a "development stage company" as described in Note 1 of the
Company's Financial Statements.
 
<TABLE>
<CAPTION>

                          ----------------------------------------------------------------
                           PERIOD FROM
                           DECEMBER 5,
                                  1994                                 THREE MONTHS      
                           (INCEPTION)  YEAR ENDED DECEMBER 31,       ENDED MARCH 31,    
                               THROUGH  ------------------------  ------------------------
                          DECEMBER 31,                                                  
                                  1994         1995         1996         1996         1997
                          ------------  -----------  -----------  -----------  -----------
                                                                        (UNAUDITED)
<S>                       <C>           <C>          <C>          <C>          <C>
STATEMENT OF OPERATIONS
 DATA:
License fee.............  $        --   $       --   $ 1,000,000  $       --   $       --
Milestone revenue.......           --           --           --           --       750,000
Grant revenue...........           --        90,813      436,081          --           --
                          ------------  -----------  -----------  -----------  -----------
Total revenues..........           --        90,813    1,436,081          --       750,000
                          ------------  -----------  -----------  -----------  -----------
Operating expenses:
Research and
 development............        75,779    2,930,106    6,694,703    1,415,429    1,908,252
General and                           
 administrative.........       243,318    1,091,299    1,421,524      220,173      764,569
                          ------------  -----------  -----------  -----------  -----------
Total operating
 expenses...............       319,097    4,021,405    8,116,227    1,635,602    2,672,821
Interest income, net....           --        75,730      285,142       55,824      191,407
                          ------------  -----------  -----------  -----------  -----------
Net loss................  $   (319,097) $(3,854,862) $(6,395,004) $(1,579,778) $(1,731,414)
                          ============  ===========  ===========  ===========  ===========
Pro forma net loss per
 share(1)...............                $     (0.98) $     (0.93) $     (0.32) $     (0.19)
Shares used in computing
 pro forma net loss per
 share(1)...............                  3,931,743    6,839,674    4,933,093    9,076,986
</TABLE>

<TABLE>
<CAPTION>
                              ------------------------------------------------
                                       AT DECEMBER 31,
                              ----------------------------------- AT MARCH 31,
                                   1994         1995         1996         1997
                              ---------  -----------  ----------- ------------
                                                                  (UNAUDITED)
<S>                           <C>        <C>          <C>         <C>
BALANCE SHEET DATA:
Cash, cash equivalents and
 investments................. $  22,870  $ 4,713,426  $22,547,679  $21,743,998
Working capital (deficit)....  (243,172)   3,270,375   20,001,703   18,277,315
Total assets.................    24,870    4,873,845   23,452,879   22,940,505
Loan payable and capital
 leases non-current..........       --           --       104,571      583,312
Mandatorily redeemable
 convertible preferred
 stock.......................    60,000    7,416,604          --           --
Total stockholders' equity
 (deficit)...................  (303,172)  (4,089,758)  20,605,161   18,970,466
</TABLE>
- -------
(1) See Note 2 of Notes to Financial Statements.
 
                                       19
<PAGE>
 
  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF
                                  OPERATIONS
 
This Prospectus contains forward-looking statements that involve risk and
uncertainties. The Company's actual results may differ significantly from the
results discussed in the forward-looking statements. Factors that might cause
or contribute to such differences include, but are not limited to, those dis-
cussed in "Risk Factors."
 
OVERVIEW
 
Since inception, the Company has devoted substantially all of its resources to
its research and product development programs. ViroPharma has generated no
revenues from product sales and has been dependent upon funding primarily from
equity financing. The Company does not expect any revenues from product sales
for at least the next three year period. The Company has not been profitable
since inception and has incurred a cumulative net loss of $12,300,377 through
March 31, 1997. Losses have resulted principally from costs incurred in
research and development activities and general and administrative expenses.
The Company expects to incur additional operating losses over at least the
next several years. The Company expects such losses to increase over histor-
ical levels as the Company's research and development expenses increase due to
further clinical trials, manufacture of drug substance and preclinical devel-
opment of pleconaril, and further research and development related to other
product candidates. The Company's ability to achieve profitability is depen-
dent on developing and obtaining regulatory approvals for its product candi-
dates, successfully commercializing such product candidates, which may include
entering into collaborative agreements for product development and commercial-
ization, and securing contract manufacturing services.
 
RESULTS OF OPERATIONS
 
Three months ended March 31, 1997 and 1996
The Company earned and received a milestone payment of $750,000 from Boehr-
inger Ingelheim during the three month period ended March 31, 1997. The Com-
pany earned no revenues during the three months ended March 31, 1996. Net
interest income increased to $191,407 for the three months ended March 31,
1997 from $55,824 for the three months ended March 31, 1996, principally due
to larger invested balances provided by the proceeds of the Company's initial
public offering completed in November 1996.
 
Research and development expenses increased to $1,908,252 for the three months
ended March 31, 1997 from $1,415,429 for the three months ended March 31,
1996. The increase was principally due to the cost of clinical trials related
to pleconaril and the advancement of drug candidates in the Company's influ-
enza, hepatitis C and viral pneumonia programs.
 
General and administrative expenses increased to $764,569 for the three months
ended March 31, 1997 from $220,173 for the three months ended March 31, 1996.
The increase was principally due to increased personnel expenses and public
company costs, as well as to increased costs associated with the pursuit of
corporate collaborations.
 
The net loss increased to $1,731,414 for the three months ended March 31, 1997
from $1,579,778 for the three months ended March 31, 1996.
 
Years ended December 31, 1996 and 1995
The Company received a non-refundable technology access fee of $1,000,000 from
Boehringer Ingelheim and earned $436,081 of grant revenue for the year ended
December 31, 1996. The Company earned $90,813 in grant revenues during the
year ended December 31, 1995. Net interest income increased to $285,142 for
the year ended December 31, 1996 from $75,730 for the year ended December 31,
1995, principally due to larger invested balances provided by the proceeds of
the Company's initial public offering.
 
Research and development expenses increased to $6,694,703 for the year ended
December 31, 1996 from $2,930,106 for the year ended December 31, 1995. The
increase was principally due to clinical trials related to pleconaril, a mile-
stone payable to Sanofi and the advancement of drug candidates in the
Company's influenza, hepatitis C and viral pneumonia programs.
 
General and administrative expenses increased to $1,421,524 for the year ended
December 31, 1996 from $1,091,299 for the year ended December 31, 1995. The
increase was principally due to increased salary expenses and facilities
costs, as well as to increased costs associated with the pursuit of corporate
collaborations.
 
                                      20
<PAGE>
 
The net loss increased to $6,395,004 for the year ended December 31, 1996 from
$3,854,862 for the year ended December 31, 1995.
 
Year ended December 31, 1995 and period ended December 31, 1994
The Company commenced operations on December 5, 1994. Therefore, the period
ended December 31, 1994 was 26 days long. Comparisons between such period and
the complete year 1995 may not be meaningful.
 
Grant revenue for the year ended December 31, 1995 was $90,813. The Company
earned no revenues for the period ended December 31, 1994. Interest income
aggregated $75,730 in 1995. There was no interest income in 1994. Research and
development expenses increased to $2,930,106 for the year ended December 31,
1995 from $75,779 for the period ended December 31, 1994. The increase was due
to 12 months of expenses being reflected in 1995, as well as expenses related
to the commencement of clinical development of pleconaril and increased
spending related to the Company's drug discovery efforts.
 
General and administrative expenses increased to $1,091,299 for the year ended
December 31, 1995 from $243,318 for the period ended December 31, 1994. The
increase was due to 12 months of expenses being reflected in 1995, as well as
to increased facilities costs and costs associated with the pursuit of corpo-
rate collaborations.
 
Net loss for the year ended December 31, 1995 was $3,854,862. Net loss for the
period ended December 31, 1994 was $319,097.
 
LIQUIDITY AND CAPITAL RESOURCES
 
The Company commenced operations in December 1994. The Company is a development
stage company and to date has not generated revenues from product sales. The
cash used in operations is for research and development activities and sup-
porting general and administrative expenses. Through March 31, 1997, the Com-
pany has used approximately $8.9 million in operating activities. The Company
invests its cash in short-term investments. Through March 31, 1997, the Company
has used approximately $15.0 million in investing activities, including approx-
imately $14.0 million in short-term investments and $1.0 million in equipment
purchases. Through March 31, 1997, the Company has financed its operations pri-
marily through an initial public offering of Common Stock and private place-
ments of redeemable preferred stock and Common Stock totaling approximately
$32.7 million. At March 31, 1997, the Company had cash and cash equivalents and
investments aggregating approximately $21.7 million.
   
The Company leases its corporate and research and development facilities under
an operating lease expiring in 1998. On July 21, 1997, the Company entered into
an operating lease for laboratory and office space commencing after the current
operating lease expires. The term of the new lease is ten years with two five-
year renewal options. Under the lease terms, the Company is required to con-
tribute approximately $800,000 in 1997 to the cost of the laboratory construc-
tion. The Company also has the right, under certain circumstances, to purchase
the new facility at a purchase price based on a pre-determined formula. The
Company has financed substantially all of its equipment under two master lease
agreements and one bank term loan. The bank term loan, in the principal amount
of $600,000, was entered into in February 1997, is payable in equal install-
ments over 72 months and bears interest at approximately 9% per annum. The Com-
pany is required to repay amounts outstanding under the two leases within
periods ranging from 32 to 48 months. As of May 31, 1997, outstanding
borrowings under these arrangements totaled approximately $1.3 million. The
Company is required to make a milestone payment to Sanofi, S.A. of up to $2
million upon the earlier of a future milestone event as defined in the agree-
ment with Sanofi or December 1998. In addition, the Company would also be
required to make certain significant additional payments, including royalties,
as defined, should agreed-upon future milestones be attained.     
 
The Company believes that the net proceeds of this offering, future proceeds
from the collaborative drug discovery and development agreement with Boehringer
Ingelheim (including a right to obtain a loan in the amount of $1 million at
the Company's option at any time in 1997, which will be creditable against a
future milestone payment), available cash and expected interest income, will be
adequate to fund its current and anticipated levels of operations through the
middle of 1999. The Company has incurred losses from its operations since
inception. The Company expects to incur additional operating losses over at
least the next several years. The Company expects such losses to increase over
historical levels as the Company's research and development expenses increase
due to the cost of further clinical trials, manufacture of drug substance and
preclinical development of pleconaril, and further research and development
related to other product candidates. The Company will require additional
financing for operations and expansion of its facilities prior to achieving
positive cash flows from its commercial activities. The Company expects that it
will need additional financing to complete all clinical studies for pleconaril
and other development and required testing for the Company's other product can-
didates.
 
                                       21
<PAGE>
 
To obtain this financing, the Company may seek to access the public or private
equity markets or enter into additional arrangements with corporate collabora-
tors. To the extent the Company raises additional capital by issuing equity
securities, ownership dilution to existing stockholders may result. There can
be no assurance, however, that additional financing will be available on
acceptable terms from any source.
 
In February 1997, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards No. 128 "Earnings Per Share" ("Statement 128").
The provisions of Statement 128 specify the computation, presentation and dis-
closure requirements for earnings (loss) per share effective for the year ended
December 31, 1997. Statement 128 will have no effect on earnings (loss) per
share calculations due to the antidilutive nature of the common stock equiva-
lents issued to date by the Company.
 
                                       22
<PAGE>
 
                                    BUSINESS
 
This Prospectus contains forward-looking statements which involve risks and
uncertainties. The Company's actual results may differ significantly from the
results discussed in forward-looking statements. Factors that might cause or
contribute to such differences include, but are not limited to, those discussed
in "Risk Factors."
 
OVERVIEW
 
ViroPharma Incorporated ("ViroPharma" or the "Company") is a development stage
company engaged in the discovery and development of proprietary antiviral phar-
maceuticals for the treatment of diseases caused by RNA viruses. The Company
has focused its current drug development and discovery activities on a number
of RNA virus diseases, including viral meningitis, enterovirus respiratory dis-
ease ("summer flu"), hand-foot-and-mouth disease, the common cold, influenza,
hepatitis C and viral pneumonia. Each year, a major portion of the world's pop-
ulation is afflicted by at least one of these diseases, for which antiviral
therapies are currently either inadequate or unavailable.
 
ViroPharma's most advanced product candidate, pleconaril, is currently being
developed for the treatment of four RNA virus diseases. Initial preclinical
studies indicated that pleconaril is a potent, broad-spectrum, orally-active
inhibitor of several RNA viruses. In June 1996, ViroPharma completed a Phase
IIa challenge study in "summer flu" with pleconaril, in which all evaluated
disease measures were significantly reduced in treated subjects. In June 1997,
ViroPharma completed a Phase IIb clinical trial for viral meningitis which dem-
onstrated that pleconaril significantly reduced disease duration, the trial's
primary endpoint. No serious adverse events attributable to pleconaril have
been observed in the 139 participants in the clinical trials conducted by the
Company to date.
 
ViroPharma has commenced additional Phase II clinical trials for viral meningi-
tis, one in adolescents/adults and one in pediatric patients, and for "summer
flu". ViroPharma initiated a Phase II clinical trial of pleconaril for hand-
foot-and-mouth disease in March 1997 and anticipates initiating a Phase II
clinical trial for the common cold in asthmatics in late 1997. ViroPharma has
additional compounds in research and preclinical stages of development for the
treatment of influenza, hepatitis C, and viral pneumonia.
 
ViroPharma believes its drug discovery and development technologies and
expertise have potential applicability to a broad range of diseases caused by
RNA viruses. RNA viruses are responsible for the majority of human viral dis-
eases, causing illnesses ranging from acute and chronic ailments to fatal
infections. RNA viruses continue to emerge, spreading from rural and developing
regions of the world to urbanized centers. Despite efforts by the scientific
and medical communities to develop vaccines and pharmaceuticals to prevent and
treat certain of these diseases, medicines are currently inadequate or are not
available for the majority of RNA virus diseases. The Company believes the sig-
nificance and prevalence of RNA virus diseases, and the limited availability
and effectiveness of current antiviral pharmaceuticals, has created a compel-
ling need for new pharmaceuticals to treat these diseases.
 
DISEASES CAUSED BY RNA VIRUSES
 
Viruses are intracellular parasites that require a living host cell within
which to reproduce. They are composed of genetic material enclosed in a protec-
tive protein coat. The genetic material of a virus, which may be in the form of
either deoxyribonucleic acid ("DNA") or ribonucleic acid ("RNA"), is unique and
characteristic of that virus and provides the blueprint for virus reproduction.
 
There are three fundamental classes of viruses: DNA viruses, retroviruses and
RNA viruses. DNA viruses store their genetic material as DNA and replicate
their DNA in a manner similar to human cells. Retroviruses and RNA viruses
store their genetic material as RNA. Retroviruses reproduce by first converting
their RNA into DNA in infected cells, then converting this DNA back into RNA.
RNA viruses, on the other hand, have the unique ability to directly reproduce
their RNA to create new RNA virus offspring through a process known as RNA rep-
lication. This ability to directly replicate RNA distinguishes RNA viruses from
DNA viruses, retroviruses and human cells.
 
Infection by viruses, and their ensuing replication, can lead to disease. Viral
epidemics, pandemics, acute outbreaks and chronic diseases continue to cause an
enormous amount of human suffering and death. DNA viruses cause diseases such
as herpes, hepatitis B and papillomas (warts). The retrovirus HIV (human immu-
nodeficiency virus) causes AIDS. RNA viruses, however, are responsible for the
majority of human viral diseases, causing a multitude of illnesses ranging from
acute and chronic ailments to fatal infections.
 
                                       23
<PAGE>

 
The following is a list of selected diseases caused by RNA viruses:
<TABLE> 
<CAPTION>  
- ---------------------------------------------------------------------------------------------------------------
                                           RNA VIRUS DISEASES/1/
 <S>                                             <C>                                <C> 
 Bronchiolitis                                   Enterovirus meningitis             Myocarditis
 Dengue fever                                    Hantavirus pulmonary syndrome      Pneumonia
 Diarrhea diseases                               Hemorrhagic conjunctivitis         Rabies
 Ebola fever                                     Hemorrhagic fevers                 Rhinovirus common cold
 Encephalitis                                    Hepatitis C, A, D and E            Rubella
 Enterovirus respiratory disease "summer flu"    Influenza                          Tick fevers
 Enterovirus hand-foot-and-mouth                 Measles                            Yellow fever
                                                 
- ------------
 /1/ The Company has focused its current drug development and discovery activities on the italicized diseases.
- ---------------------------------------------------------------------------------------------------------------
</TABLE> 
The medical community has attempted to address several of these diseases with
vaccines, which are prophylactic in nature and intended to prevent disease, and
antiviral pharmaceuticals, which are therapeutic in nature and intended to
treat disease. For most RNA virus diseases, however, medicines are either inad-
equate or simply not available.
 
Vaccines are designed to prevent disease by eliciting a protective antiviral
immune response in vaccinated individuals. This response involves the produc-
tion by the body of specific antibodies and white blood cells, both of which
attempt to destroy the virus and virus-infected cells. Vaccines do not exist
for most RNA virus diseases. Of those that are available, most are unable to
effectively control disease for one or more reasons. Many viruses constantly
and rapidly change their outer surface, thereby rendering existing vaccines
obsolete. Moreover, many individuals at greatest risk for serious disease,
including the young, the elderly and the immunocompromised, respond poorly to
vaccines. Finally, existing vaccines are not readily available to certain sus-
ceptible populations and, even when available, are often not widely used.
 
Antiviral pharmaceuticals to treat RNA virus diseases are limited. While there
are, in some cases, medicines available to reduce disease symptoms, there are
few drugs to effectively treat the underlying disease. Of these, amantadine and
the related drug rimantadine are used for influenza, ribavirin has been used
for viral pneumonia due to respiratory syncytial virus ("RS virus"), and inter-
feron alfa ("IFN") is currently used to treat hepatitis due to hepatitis C
virus ("HCV"). Additionally, immunoglobulin products are occasionally used for
treatment of some RNA virus diseases.
 
Based on the significance and prevalence of disease associated with RNA virus
infections and the limited means to prevent or treat these diseases, the Com-
pany believes that there is a significant market opportunity for the develop-
ment of effective therapeutics for RNA virus diseases. Moreover, the continued
emergence of RNA virus diseases and the recent spread of RNA viruses from rural
and developing regions of the world to urbanized centers underscores the com-
pelling need for new antiviral pharmaceuticals.
 
TREATING RNA VIRUS DISEASES
 
The RNA Virus Replication Process
Essential to the discovery and development of antiviral pharmaceuticals is the
ability to analyze the virus in a laboratory setting and to dissect the molec-
ular and biochemical events critical to virus replication. The manipulation of
RNA viruses and, in particular, the virus's RNA genome, requires special tech-
niques and skills. Historically, technical limitations have hampered investiga-
tion of RNA virus replication. Consequently, the scientific community's under-
standing of the molecular events of RNA virus replication is incomplete. How-
ever, significant recent advancements in biological and molecular technologies
related to the manipulation of RNA and RNA viruses have enabled the Company to
pursue the discovery and development of effective treatments for RNA virus dis-
eases.
 
                                       24
<PAGE>
 
The Company believes that the process of viral RNA uncoating and replication
represents an attractive target for the therapeutic intervention in disease
caused by RNA viruses. For RNA viruses to cause disease, they must replicate.
This process of RNA replication is depicted in the following diagram.
 
 
                             RNA VIRUS REPLICATION
 
                 [CHART OF RNA VIRUS REPLICATION APPEARS HERE]
 
  When an RNA virus enters a cell (1), its RNA is released from the
  virus's coat (2), allowing the unique multi-step process of RNA
  replication to proceed (3-4), after which new RNA virus offspring are
  created (5) and subsequently released from the infected cell (6). Each
  RNA virus offspring that infects a new cell repeats this replication
  process.
 
Inhibiting RNA virus replication can prevent, limit or stop disease. In addi-
tion to thwarting disease, the direct inhibition of viral RNA uncoating and
replication will reduce the possibility for generation of drug-resistant virus
offspring and decrease virus transmission from infected individuals to healthy
persons. RNA replication is a complicated process involving several viral pro-
teins that must act together in a coordinated fashion. Due to the nature of
this process, changes or mutations in these proteins are not readily tolerated.
Consequently, viral proteins required for RNA replication are not only specific
to the virus, they are among the least variable proteins of the virus. This is
in contrast to the highly variable viral surface proteins generally involved in
immune responses to virus infections. This invariability of the viral proteins
responsible for viral RNA replication represents an important attribute in
their selection as molecular targets for antiviral drug discovery and develop-
ment.
 
The ViroPharma Approach
ViroPharma, based on its experienced RNA virologists and its focus on RNA viral
diseases, believes that it is a leader in RNA virology and RNA antiviral drug
discovery and development. As a result of its focus on, and expertise in, RNA
virus replication, unique molecular target selection and assay development
technologies, and its development and possession of proprietary chemical inhib-
itors and its specialized chemical library, the Company believes that it is
well-positioned to develop effective antiviral pharmaceuticals for RNA virus
diseases.
 
While the RNA replication process is common among all RNA viruses, the detailed
molecular and biochemical mechanisms of RNA replication are currently not fully
understood. However, the Company has used its experience in RNA virology, RNA
virus uncoating and RNA replication, along with recent advances in biological,
molecular and informatics technologies, to gain an understanding of several
aspects of the RNA virus uncoating and replication process. Company scientists
have elucidated fundamental processes involved in virus uncoating and used this
knowledge to design compounds to inhibit these processes. They have also suc-
ceeded in discovering new virus enzyme activities that are essential to RNA
replication, which are the subject of a U.S. patent application filed by the
Company. Company scientists have further characterized several RNA virus repli-
cation activities and used the resulting information to develop novel drug
screening assays. The Company's assays are optimized for high sensitivity and
specificity and are validated for reproducibility. These assays are automated
using state-of-the-art robotics technologies to facilitate the high throughput
screening of large chemical libraries. Using its novel assays, the Company has
discovered proprietary small molecule compounds that inhibit the targeted
virus-specific activities.
 
Once active compounds are identified, the Company advances such compounds to
clinical drug candidates through a process of chemical optimization. This
process involves the rapid generation of an expanded chemical analog series
based
 
                                       25
<PAGE>
 
on the initial active compounds and utilizes an array of technologies including
computer-assisted pharmacophore modeling and drug design techniques, two-dimen-
sional and three-dimensional structure and substructure chemical database
searches and conventional medicinal chemistry, combinatorial chemistry and
automated high capacity chemical synthetic methods. The Company then evaluates
analog series in various biochemical and biological assays that assess compound
selectivity, potency, safety and bioavailability. Importantly, the Company
chemically optimizes active compounds for these four key parameters in paral-
lel, not sequentially. The Company believes that its combination of chemical
and biological technologies and parallel compound optimization process allows
it to accelerate drug discovery and development. The generation of large num-
bers of specific chemical analogs by the Company also enables it to rapidly
expand its valuable chemical library that is biased toward inhibitors of
enzymes and activities essential to RNA replication. The Company believes that
this library provides a significant advantage in its efforts to discover inhib-
itors for additional RNA virus diseases. The Company believes that its combined
technologies have never been applied to develop an approved pharmaceutical
product.
 
STRATEGY
 
The Company's objective is to become the leading discoverer, developer and mar-
keter of proprietary antiviral pharmaceuticals for RNA virus diseases. The Com-
pany seeks to achieve this objective through the implementation of the fol-
lowing strategies:
 
Focus on RNA Virus Diseases
RNA viruses cause the majority of human viral diseases, yet few effective
antiviral drugs are available to address these diseases. Based on the signifi-
cance and prevalence of disease associated with RNA viruses and the limited
means to effectively prevent or treat these diseases, the Company believes
there is a significant market opportunity for the development of effective
therapeutics for RNA virus diseases. The Company has focused a major portion of
its resources on this market opportunity.
 
Broadly Apply Technological Expertise in RNA Virology
The Company has leading expertise in RNA antiviral drug discovery, focusing on
RNA replication and involving the selection of specific molecular targets and
the development of novel drug screening assays, proprietary chemical inhibitors
and a specialized chemical library. Since RNA replication is unique to RNA
viruses, yet common to all RNA viruses, this process provides a broadly appli-
cable platform for drug discovery. The Company intends to continue to expand
and apply its expertise in RNA virology, RNA replication, chemical synthesis
methodologies and antiviral drug design to address the medical needs of dis-
eases caused by RNA viruses.
 
Conduct Parallel Drug Discovery Assessments
The key parameters in the drug discovery process are selectivity, potency,
safety and bioavailability. The Company accelerates and enhances the efficiency
of its drug discovery programs by simultaneously optimizing chemical compounds
for each of these parameters during the drug discovery process.
 
Pursue Indications for Rapid Demonstration of Efficacy
In order to expedite drug development, the Company initially targets disease
indications based upon the likelihood for rapid demonstration of efficacy in
clinical trials. The Company then pursues follow-on clinical development for
expanded disease indications.
 
Pursue Strategic Relationships by Leveraging RNA Virology Expertise
The Company leverages its leadership position in RNA virus antiviral drug dis-
covery and its broad antiviral clinical development capabilities through stra-
tegic relationships with pharmaceutical companies, specialized technology com-
panies and academic institutions. With these relationships, the Company
enhances its drug discovery capabilities and licensing opportunities and facil-
itates the commercialization of its potential products.
 
                                       26
<PAGE>

PRODUCT DEVELOPMENT AND RESEARCH
 
The Company has focused its current drug discovery and development activities
on a number of RNA virus diseases including viral meningitis, "summer flu,"
hand-foot-and-mouth disease, the common cold, influenza, hepatitis C and viral
pneumonia. The Company has drug candidates in various stages of research and
development for each of these RNA virus diseases. The following chart sets
forth the target disease indications and the status of the Company's lead
product candidates:
 
<TABLE>
<CAPTION>
DISEASE INDICATION  PRODUCT CANDIDATE       DEVELOPMENT STATUS (1)
- ------------------  ----------------------  -------------------------------------------
<S>                 <C>                     <C>
Viral               Pleconaril (oral)       Phase IIb clinical trial completed June
Meningitis                                  1997; additional trials in
                                            adolescents/adults and pediatric patients
                                            commenced in June 1997
"Summer Flu"        Pleconaril (oral)       Phase IIa challenge study completed April
                                            1996; Phase II clinical trial in natural
                                            infections commenced June 1997
Hand-Foot-          Pleconaril (oral)       Phase II clinical trial commenced March
and-Mouth                                   1997
Disease
Common Cold         Pleconaril (oral)       Phase II clinical trial in asthmatics
                                            anticipated in late 1997
                    Pleconaril (intranasal) Preclinical; IND anticipated late 1997
Influenza           VP 14221 series         Preclinical safety and pharmacokinetics
                                            studies
Hepatitis C         VP 31593 series         Chemical optimization
Viral               VP 36676 series         Chemical optimization
Pneumonia
</TABLE>
- -------
(1) For a discussion of preclinical testing and the phases of human clinical
trials, see "--Government Regulation."
 
The Company's most advanced product candidate, pleconaril, based on preclinical
studies, is a potent, broad spectrum, orally active inhibitor of enteroviruses
and rhinoviruses. Enteroviruses and rhinoviruses are closely related members of
a large, very prevalent group of RNA viruses that are responsible for wide-
spread human disease. According to the Center for Disease Control (the "CDC"),
there are 10 to 15 million enterovirus infections every year in the United
States. Enteroviruses cause viral meningitis, "summer flu," hand-foot-and-mouth
disease, myocarditis, pericarditis, encephalitis, herpangina, otitis media and
perinatal enteroviral disease. Rhinoviruses are responsible for up to 50% of
all acute respiratory illnesses and are the leading cause of the common cold.
 
The Company is currently developing pleconaril for four indications: viral men-
ingitis, "summer flu," hand-foot-and-mouth disease and the common cold. While
antibiotics are commonly prescribed by physicians to patients with these dis-
eases, they are ineffective at treating these virus infections. Prescription
and over-the-counter cough and cold remedies, analgesics and antipyretics are
also used to reduce symptoms of hand-foot-and-mouth disease, "summer flu" and
the common cold, but do not treat the underlying diseases. Currently, there are
no antiviral therapies available for any of the diseases caused by
enteroviruses or rhinoviruses. Pleconaril is not expected to be commercially
available for at least three years, if at all.
 
ViroPharma scientists have demonstrated that pleconaril inhibits enterovirus
and rhinovirus replication by a novel, virus- specific mode of action. The com-
pound binds to a specific site inside the coat protein of the virus, thereby
preventing the release of the viral RNA inside the cell and blocking the initi-
ation of the RNA replication process. In preclinical studies conducted by the
Company, pleconaril was shown to effectively inhibit the cell culture replica-
tion of 96% of the rhinoviruses and enteroviruses isolated from 332 human
patients. The patient population from which these viruses were isolated exhib-
ited the complete range of diseases caused by these viruses, including a number
of fatal infections. Moreover, orally administered pleconaril protected mice
from lethal infection by enteroviruses in three distinct animal model systems
and was effective even when therapy was initiated after infection in these mod-
els. Based on these results, the Company believes that pleconaril will be
effective against a broad spectrum of rhinoviruses and enteroviruses. There can
be no assurance that pleconaril will be clinically efficacious against diseases
caused by these viruses. See "Risk Factors--Uncertainty Regarding Clinical Tri-
als."
 
                                       27
<PAGE>
 
In Phase I single ascending dose studies with a capsule formulation of
pleconaril, plasma concentrations of drug increased proportionally to the oral
dose administered up to the highest dose tested (1000 mg). Maximum drug plasma
levels 20 times that required to inhibit the replication of the majority of the
clinical virus isolates referred to above were achieved with a single 200 mg
dose. In Phase I multidose studies conducted by the Company, doses up to 400 mg
administered three times per day for seven consecutive days were well-tolerated
by all subjects in the study. No serious adverse events attributable to the
drug were observed in the 50 subjects who received pleconaril during the course
of these Phase I studies. There can be no assurance that unacceptable
toxicities or side effects will not occur during development or that any
product will be effective or safe when administered to patients.
 
The Company has developed an oral liquid formulation of pleconaril, which the
Company has demonstrated is bioequivalent to the capsule formulation used in
Phase I studies. The liquid formulation is self-preserving, stable and contains
only GRAS (Generally Regarded As Safe) ingredients. This formulation provides
considerable flexibility in dosing and is being used in clinical trials for the
viral meningitis, "summer flu" and hand-foot-and-mouth disease indications and
will be used in clinical trials for the common cold indication. The Company is
also developing an intranasal formulation of pleconaril for use in the common
cold indication.
 
The Company has initiated a compassionate use, open-label protocol to provide
pleconaril to patients with chronic enterovirus meningoencephalitis and acute
enterovirus myocarditis. Patients with chronic meningoencephalitis are unable
to develop an antibody response to enterovirus central nervous system infec-
tions and suffer progressive neurological deterioration which can lead to sei-
zures, paralysis and death. Acute enteroviral myocarditis is an infection of
the heart muscle which may lead to congestive heart failure. The Company
believes that there are less than 500 patients afflicted with these diseases
worldwide.
 
The Company has entered into an agreement with Sanofi S.A. under which it has
received exclusive rights to develop and market all products relating to
pleconaril and related compounds for use in enterovirus and rhinovirus disease
indications in the United States and Canada, as well as a right of first
refusal in respect of any other indications in the United States and Canada.
Pleconaril was discovered at Sanofi by scientists now with ViroPharma. See "--
Strategic Relationships--Sanofi S.A." and "--Patents." Pleconaril has been
approved as a generic name for the Company's compound VP 63843 by the United
States Names Council (USAN) and is awaiting final approval from the World
Health Organization ("WHO").
 
Viral Meningitis
Infection of the central nervous system by enteroviruses can cause meningitis,
which is characterized by a severe headache, stiffness of the neck or back,
fever, nausea and malaise. The disease is typically severe and requires emer-
gency medical care. The disease occasionally progresses to serious neurologic
sequelae, particularly among infants infected before age one year. There is
currently no antiviral pharmaceutical for viral meningitis.
 
In order to establish the incidence and clinical course of enteroviral menin-
gitis and assess potential clinical endpoints for future drug efficacy studies,
the Company conducted an Adult Viral Meningitis Observational Study at three
medical centers (the University of Colorado, the University of Pennsylvania and
the University of Virginia) during the 1995 summer enterovirus season. The
results of this study demonstrated the severity and duration of the illness.
Adults presenting at emergency rooms complaining of severe headaches were con-
firmed to be enterovirus-infected by detection of viral RNA in their cerebro-
spinal fluid. Approximately 80% of these enterovirus-infected patients required
hospitalization, with an average stay of four days. Patients were unable to
resume full normal activities for an average of 16 days. All subjects received
some form of analgesic (70% received a narcotic) for an average of seven days
to manage their severe headache pain. From this study, the Company estimates
that 500,000 Americans contract enteroviral meningitis annually.
 
In June 1997, the Company completed a preliminary evaluation of data resulting
from a 39 patient, international multi- center, double blind, placebo con-
trolled Phase IIb trial with the oral liquid formulation of pleconaril for the
treatment of viral meningitis. The Company initiated this study at sites in the
United States in June 1996 and in Australia and South Africa in November 1996.
The results of the preliminary evaluation of the data for the endpoints in
which statistical significance was demonstrated are depicted in the graph below
for both the placebo-treated (light bars) and pleconaril-treated (dark bars)
groups. The data indicate that pleconaril treatment resulted in a statistically
significant shortening of disease duration (58% reduction), the primary end-
point of the study. This primary endpoint evaluates the time required for dis-
ease severity (as measured by a multidimensional score, comprised of headache,
nausea/vomiting, photophobia, stiff neck, fever and myalgia) to be reduced to a
predetermined level indicating wellness. Statistical significance also was
observed in the secondary endpoints of the time to complete absence of headache
(64% reduction), duration of analgesic use (54% reduction), and total analgesic
use (48% reduction). Clinically meaningful trends were observed in two addi-
tional
 
                                       28
<PAGE>
 
secondary endpoints, while no adverse trends were observed in the three
remaining secondary endpoints. In June 1997, the Company initiated two addi-
tional Phase II clinical trials with pleconaril in the United States and Canada
for viral meningitis, one in adolescents/adults and one in pediatric patients.
There can be no assurance that these trials will be successfully completed or
completed in a timely manner. See "Risk Factors--Absence of Products; Product
Development Risks," "Risk Factors--Dependence on Most Advanced Drug Candidate"
and "Risk Factors--Uncertainty Regarding Clinical Trials."
 
 
                      Phase IIB Study - Viral Meningitis
             Statistically Significant Disease Measure Reductions

                           [BAR GRAPH APPEARS HERE]

- -------
 /1/ This primary endpoint evaluates the time required for disease severity
     (as measured by a multidimensional score, comprised of headache,
     nausea/vomiting, photophobia, stiff neck, fever and myalgia) to be
     reduced to a predetermined level indicating wellness.
 
"Summer flu" (Enterovirus respiratory disease)
"Summer flu," or enterovirus respiratory disease, is an upper respiratory ill-
ness caused by enteroviruses and characterized initially by a sore throat and
cough, followed by a general influenza-like syndrome. While this disease occurs
throughout the year, it is most prevalent in the summer. The clinical illness
can persist for several weeks and typically results in a physician visit.
According to the CDC, there are an estimated 10 to 15 million cases of
enterovirus infection each year in the United States, many of which result in
"summer flu." There is currently no antiviral pharmaceutical for the treatment
of "summer flu."
 
During the spring of 1996, the Company conducted a Phase IIa challenge study
with pleconaril for "summer flu." In this double-blind, placebo-controlled
"summer flu" challenge study, the oral capsule formulation of pleconaril demon-
strated that all disease measures evaluated in the study were significantly
reduced in volunteers treated with pleconaril. Eight hours after the randomized
administration of either placebo or pleconaril, 33 volunteers were infected
with the enterovirus coxsackievirus A21. Subjects were then administered either
placebo or a 200 mg dose of pleconaril twice daily for seven days. Placebo-
treated subjects developed notable "summer flu" symptoms, while volunteers
treated with pleconaril showed pronounced and clinically significant reductions
in disease measures, including symptoms and virus load. Assessment of clinical
disease by five measures (subject and physician rating of disease symptoms,
nasal mucus production, fever and virus load in nasal secretions) showed, in
all cases, a significant reduction in the pleconaril-treated group. Depicted in
the graph below are the results of these disease measures for both the placebo-
treated (light bars) and pleconaril-treated (dark bars) subjects.
 
                                       29
<PAGE>
 
The Company initiated a Phase IIb multicenter, placebo-controlled, dose-ranging
clinical efficacy trial for the "summer flu" indication in June 1997. There can
be no assurance that this trial will be successfully completed or completed in
a timely manner. See "Risk Factors--Absence of Products; Product Development
Risks," "Risk Factors--Dependence on Most Advanced Drug Candidate" and "Risk
Factors--Uncertainty Regarding Clinical Trials."
 
 
       PHASE IIA STUDY - ENTEROVIRUS RESPIRATORY DISEASE ("SUMMER FLU")
                          DISEASE MEASURE REDUCTIONS


                          [BAR GRAPH APPEARS HERE] 


 
Hand-Foot-and-Mouth Disease
Hand-foot-and-mouth disease is a highly communicable enterovirus syndrome
afflicting all age groups, but predominantly affecting children and adoles-
cents. Following initial symptoms of fever, malaise and respiratory or abdom-
inal complaints, painful ulcerative lesions develop in the mouth and on the
palms and soles of the hands and feet. Affected individuals may have substan-
tial difficulty drinking and eating, which may necessitate hospitalization. The
Company initiated a placebo-controlled exploratory safety and efficacy trial in
children with hand-foot-and-mouth disease in March 1997. There can be no assur-
ance that this trial will be successfully completed or completed in a timely
manner. See "Risk Factors--Absence of Products; Product Development Risks,"
"Risk Factors--Dependence on Most Advanced Drug Candidate" and "Risk Factors--
Uncertainty Regarding Clinical Trials."
 
Common Cold
Rhinoviruses are the leading cause of the common cold. Many people experience
two or three colds per year with the accompanying symptoms of sneezing, nasal
obstruction, nasal discharge, headache and general malaise. The median duration
of illness is seven days, with symptoms persisting for two weeks in approxi-
mately 25% of persons. Complications associated with rhinovirus infections
include otitis media, pneumonia and asthmatic exacerbations resulting in
serious respiratory distress. Although there are cold remedies, analgesics and
antipyretics that may reduce cold symptoms, there is no antiviral pharmaceu-
tical to treat the common cold.
 
The Company's clinical development plan for the oral and intranasal formula-
tions of pleconaril contemplates initially treating patients with asthma and
upper respiratory tract rhinovirus infections. These individuals often develop
a concurrent lower respiratory tract rhinovirus infection, which can lead to
pronounced lower airway dysfunction lasting for weeks to months. Treatment of
this patient population provides an opportunity for both prophylactic and ther-
apeutic dosing. The Company anticipates initiating a clinical trial of the oral
liquid formulation of pleconaril in the treatment of rhinovirus infections in
moderate to severe asthmatics in late 1997. Should the product be approved for
use in this patient population, the Company would expect to expand clinical
development to include the general population.
 
The Company, in collaboration with Minnesota Manufacturing and Mining Company,
is developing an additional formulation of pleconaril for use in an intranasal
aerosol delivery system. The Company anticipates filing an IND application for
the intranasal formulation of pleconaril for the common cold indication in late
1997. There can be no assurance that these activities will be initiated, suc-
cessfully completed or completed in a timely manner. See "Risk Factors--Absence
of Products; Product Development Risks," "Risk Factors--Dependence on Most
Advanced Drug Candidate" and "Risk Factors--Uncertainty Regarding Clinical Tri-
als."
 
                                       30
<PAGE>
 
Influenza
Influenza virus is a major cause of human illness. In the United States,
approximately 10% to 20% of the population is infected with the influenza
virus each year. This disease is characterized by the sudden onset of head-
ache, chills and a dry cough, which is rapidly followed by fever, significant
myalgias and malaise. Fever and upper respiratory tract symptoms generally
last for three to five days, while the cough and weakness persist for an addi-
tional one to two weeks. Influenza can also be fatal. According to the WHO,
approximately 10,000 to 40,000 deaths occur each year in the United States as
a result of influenza. The very young, elderly and immunocompromised, and
those with medical conditions such as cardiovascular disease, pulmonary dis-
ease and pregnancy, are at greatest risk for serious or fatal complications
associated with influenza virus infections. The National Science and Tech-
nology Council currently estimates that the direct medical costs due to influ-
enza in the United States are $5 billion per year.
 
Immunization for influenza has demonstrated only limited success in control-
ling the disease. Due to the highly variable nature of the influenza virus
surface proteins, vaccines used one year are ineffective and obsolete the
next. New vaccines with components predicted to be important in the next
year's influenza season must be developed, manufactured and administered each
year. Even when forecasts result in vaccines with components closely matching
that year's actual circulating influenza virus strain, the immunity induced by
these vaccines is incomplete and short-lived. Reinfection with the same virus
strain or a variant strain can occur and result in disease in previously immu-
nized individuals. Finally, compliance with national immunization campaigns
has generally been insufficient to prevent epidemics.
 
The Company's principal molecular target in its influenza virus program is the
viral RNA transcriptase complex, which is required by the virus for RNA repli-
cation. The Company has developed a quantitative high throughput drug
screening assay that simultaneously measures several essential virus-encoded
replication activities. Using this assay, ViroPharma scientists have discov-
ered several specific inhibitors of influenza virus replication. The Company
has applied its chemical optimization process to establish structure-activity
relationships for these inhibitors with respect to potency and selectivity.
The Company's preclinical acute safety studies conducted to date indicate that
several of its lead compounds, currently designated the VP 14221 Series, are
well tolerated and are orally bioavailable. In addition, ViroPharma has filed
two patent applications with the PTO and one application in certain foreign
jurisdictions related to its active influenza virus compounds, has received a
Notice of Allowance from the PTO in respect of one of these applications, and
is preparing additional patent applications for influenza virus compounds.
There can be no assurance that clinical trials for this compound series will
be initiated or, if initiated, will lead to a determination that the compound
is safe and efficacious. No assurance can be given that such patents will
issue. See "Risk Factors--Absence of Products; Product Development Risks,"
"Risk Factors--Uncertainty Regarding Clinical Trials," "Risk Factors--Uncer-
tain Ability to Protect Patents and Proprietary Technology and Information"
and "--Patents."
 
Hepatitis C
HCV, first identified in 1989, is recognized as a major cause of chronic hepa-
titis worldwide. According to the CDC, there are currently approximately 4
million HCV infected individuals in the United States, with 150,000 new cases
identified each year. The WHO estimates that an additional 10 million individ-
uals are infected with HCV in Europe and a total of 170 million people are
infected worldwide. Populations in some geographic areas, such as Japan,
Spain, Hungary, Saudi Arabia, Southern Italy and Egypt, have particularly high
rates of infection. Approximately 85% of HCV infected persons will develop
chronic hepatitis, of which 20% will progress to liver cirrhosis. Chronic HCV
infection can also lead to the development of hepatocellular carcinoma and
liver failure.
 
There is currently no vaccine for HCV, an immunologically diverse virus, with
many naturally occurring variants in circulation. Such diversity, in combina-
tion with HCV's ability to change its surface proteins, may represent the
mechanism by which the virus escapes attack by the immune system and estab-
lishes persistent infections.
 
IFN is currently the only approved drug in the United States for treatment of
hepatitis due to HCV. While IFN treatment has been reported to improve serum
liver enzyme response in 20% to 40% of patients, the remainder do not respond
to IFN treatment. For patients who do respond, a sustained improvement of
liver function reportedly is seen in only 10% to 20% of patients; the majority
of patients relapse upon cessation of IFN treatment. Thus, while IFN repre-
sents the first treatment for chronic hepatitis C, its effectiveness is lim-
ited and its cure rate is low. Nevertheless, the Company estimates the current
market for IFN use in the treatment of hepatitis C to be over $1 billion
worldwide.
 
The Company focuses on key enzyme targets involved in the HCV RNA replication
process. Company scientists have discovered several key enzyme activities
associated with particular HCV proteins. These activities have been character-
ized and used to establish validated high throughput assays. The HCV RNA
helicase activity represents one such target. As a result of screening com-
pounds in the HCV RNA helicase assay, the Company has identified several
active and selective
 
                                      31
<PAGE>
 
compounds, currently designated the VP 31593 Series, and has begun chemical
optimization on such compounds. Based on its RNA helicase-related technology,
the Company has established a collaborative drug discovery and development
agreement with Boehringer Ingelheim. The Company is also developing assays for
additional HCV molecular targets. The Company has filed two patent applications
with the PTO, and two patent applications in certain foreign jurisdictions,
related to the HCV inhibitor compound series. The PTO has granted a patent on
one of these applications. The Company anticipates that it will file additional
patent applications within the next year. No assurance can be given that such
patents will issue. See "Risk Factors--Dependence on Corporate Collaborations;
Need for Additional Collaborators," "Risk Factors--Uncertain Ability to Protect
Patents and Proprietary Technology and Information," "--Strategic Relation-
ships--Boehringer Ingelheim Pharmaceuticals, Inc." and "--Patents."
 
Viral Pneumonia
RS virus is the major pediatric viral respiratory tract pathogen, causing pneu-
monia and bronchiolitis in infants and young children. During seasonal epidem-
ics, approximately 250,000 infants contract RS virus pneumonia, and up to 35%
are hospitalized. Of those hospitalized, mortality rates of up to 5% have been
reported. Children with underlying conditions such as prematurity, congenital
heart disease, bronchopulmonary dysplasia and various congenital or acquired
immunodeficiency syndromes are at greatest risk of serious RS virus morbidity
and mortality. RS virus is also implicated as a significant cause of mortality
in the elderly.
 
Vaccines are not currently available for prevention of RS virus disease.
Recently, the prophylactic use of an intravenous hyperimmune globulin infusion
was approved for RS virus disease in certain high risk infants. Ribavirin,
administered by aerosol to minimize the drug's adverse effects, is generally
reserved for only the most serious cases of RS virus pneumonia and bronchio-
litis. In both cases, drug administration can be difficult and inconvenient in
young patients.
 
The Company has developed a high throughput drug screening assay for RS virus
replication. Company scientists have discovered several inhibitory compounds,
currently designated the VP 36676 Series, with high potency and selectivity in
initial profiling evaluations. The Company has initiated chemical optimization
of these compounds. There can be no assurance that such chemical optimization
will be successfully completed or completed in a timely manner. See "Risk Fac-
tors--Absence of Products; Product Development Risks," "Risk Factors--Depen-
dence on Most Advanced Drug Candidate" and "Risk Factors--Uncertainty Regarding
Clinical Trials."
 
Other Potential RNA Virus Disease Targets
The Company believes that its drug discovery technologies and development
expertise are potentially applicable to a broad range of RNA virus diseases.
The Company also believes that certain RNA virus diseases represent immediate
extensions of the Company's current research and development programs. In addi-
tion to viral meningitis, "summer-flu," hand-foot-and-mouth disease, chronic
meningoencephalitis and myocarditis, enteroviruses cause additional diseases
for which the Company's most advanced drug candidate, pleconaril, may be effec-
tive. Of these, the Company is currently considering exploratory clinical
trials for pleconaril for enterovirus neonatal disease. There can be no assur-
ance that the Company will pursue this indication or, if the Company does
pursue this indication, that the Company will be able to successfully demon-
strate clinical efficacy. See "Risk Factors--Absence of Products; Product
Development Risks" and "Risk Factors--Uncertainty Regarding Clinical Trials."
 
Similarly, the Company's lead anti-influenza compound series acts by a virus-
specific mechanism that may make it potentially applicable to a large family of
viruses called bunyaviruses. Bunyaviruses cause widespread disease globally
including encephalitis, hemorrhagic fevers and the recently identified
hantavirus pulmonary syndrome. In the midwestern United States alone, there are
approximately 300,000 infections of La Crosse encephalitis virus annually
resulting in approximately 900 deaths. In Asia and Eastern Europe, a bunyavirus
called hantavirus is responsible for Korean hemorrhagic fever, a serious influ-
enza-like illness in which approximately 33% of the affected individuals
develop hemorrhagic disease and 5% to 10% die. In 1993, in the southwest United
States, a new hantavirus emerged that causes hantavirus pulmonary syndrome, a
serious respiratory disease that is fatal in approximately 50% of cases. This
new virus has now been detected in 27 states in the United States and has
recently appeared in Argentina, Brazil and Canada.
 
Assays and inhibitor compounds derived from the Company's HCV program may
accelerate antiviral drug discovery for the related virus group called
flaviviruses. There are 38 flaviviruses associated with human disease,
including the dengue fever viruses, yellow fever virus and Japanese encepha-
litis virus. Importantly, the epidemiology of these diseases is changing. For
example, with global urbanization, the incidence of dengue fever has increased
dramatically. Dengue fever viruses typically cause a severe influenza-like ill-
ness and, in a more serious form, can cause a fatal hemorrhagic disease. Prior
to 1970, only nine countries reported outbreaks of fatal dengue hemorrhagic
fever. As of 1995, at least 41 countries have
 
                                       32
<PAGE>
 
reported incidences of this serious form of dengue fever virus disease. The WHO
estimates that there are 50 million cases of dengue fever each year, and
500,000 cases of dengue hemorrhagic fever requiring hospitalization, of which
5% result in death.
 
There are currently no approved antiviral pharmaceuticals for any of the dis-
eases mentioned above.
 
STRATEGIC RELATIONSHIPS
 
ViroPharma pursues strategic relationships by leveraging its RNA virology
expertise, while seeking to maintain independence and flexibility in the devel-
opment and commercialization of its products. The Company has entered into sev-
eral development and licensing agreements and research collaborations and con-
tinues to seek opportunities to enhance its ability to discover, develop and
commercialize RNA antiviral drugs. There can be no assurance that the Company
will be able to enter into additional beneficial relationships or maintain its
current relationships.
 
Currently, the Company is a party to a licensing and co-marketing agreement
with one multinational pharmaceutical company, a drug discovery and development
agreement with another multinational pharmaceutical company, a development
agreement with an international pharmaceutical manufacturing company and sev-
eral licensing and collaborative agreements with various pharmaceutical and
technology companies and academic institutions for certain biological and chem-
ical technologies. From time to time, the Company engages in discussions
regarding additional strategic relationships. Currently, the Company does not
have any understandings, agreements or commitments to enter into any additional
strategic relationships.
 
Sanofi S.A.
In December 1995, the Company entered into an agreement with Sanofi under which
it received exclusive rights to develop and market all products relating to
pleconaril and related compounds for use in enterovirus and rhinovirus disease
indications in the United States and Canada, as well as a right of first
refusal in respect of any other indications in the United States and Canada.
The Company's rights include rights to use all of Sanofi's patents, know-how
and trademarks relating to pleconaril. The Company paid Sanofi a licensing fee
of $1,000,000 in February 1996 and is obligated to make a milestone payment of
up to $2,000,000 upon the earlier of enrollment of the first patient in a Phase
III trial or December 22, 1998. In addition, the Company is required to make
milestone payments upon the achievement of certain other development milestones
and, until the expiration of the last patent on pleconaril or any related drug,
royalty payments on any sales of products developed under the agreement in the
United States and Canada. Sanofi is required to pay the Company royalties on
sales in all other territories of the world during the term of the agreement
(as described below) and must reimburse certain of the milestone fees previ-
ously paid by the Company upon submission of pleconaril for regulatory approval
in Japan. The Company believes that the royalty rates payable by both the Com-
pany and Sanofi are comparable to the rates generally payable by other compa-
nies under similar arrangements. See "--Patents."
 
Upon the completion of data analysis from the Company's Phase II trials, Sanofi
has the option to co-develop the drug in the European Union. If Sanofi chooses
to co-develop, Sanofi has agreed to share all development costs and to make
royalty payments to the Company based on sales in the European Union. If Sanofi
does not choose to co-develop, it must make royalty payments to the Company
based on such sales at a higher royalty rate and will be required to reimburse
a percentage of all previously paid milestone fees and reduce future milestone
fees by the same percentage. In addition, if Sanofi does not choose to co-
develop and foreign regulatory authorities require significant additional
studies of pleconaril for use in the European Union, the Company will be
required to conduct such studies at its own expense.
 
The Sanofi agreement terminates on the later of the expiration of the last
patent on pleconaril or any related drug in the United States or Canada or ten
years following the commencement of the Company's sale of the drug in the
United States or Canada, or earlier under certain circumstances. In addition,
Sanofi has the right to terminate the agreement in the event that there is a
change of control that would materially and adversely affect the development,
manufacturing and marketing of the products under the agreement. The term auto-
matically renews for successive five year terms unless six months' prior
written notice of termination is given by either party. The Company and Sanofi
amended their agreement as of February 21, 1997 to permit the Company to seek
third party suppliers of pleconaril bulk drug supply. The Company also has the
right to manufacture, or contract with third parties to manufacture, any drug
product derived from the pleconaril drug substance. See "--Manufacturing."
 
Boehringer Ingelheim Pharmaceuticals, Inc.
In August 1996, the Company entered into a collaborative drug discovery and
development agreement with Boehringer Ingelheim for one hepatitis C target
identified by ViroPharma. Under this agreement, the Company granted to Boehr-
inger Ingelheim the exclusive worldwide rights to develop and commercialize
compounds discovered under the agreement. In
 
                                       33
<PAGE>
 
return, Boehringer Ingelheim paid a technology access fee of $1,000,000 to the
Company and is required to make research and milestone payments to the Company
in connection with the Company's transfer of HCV screening and assay technology
and at various stages in the development of compounds under this agreement. In
February 1997, ViroPharma achieved its first scientific milestone under this
agreement, for which it received a $750,000 milestone payment from Boehringer
Ingelheim. In addition, Boehringer Ingelheim is required to make royalty pay-
ments to the Company on sales of products developed and marketed under this
agreement beginning on the date a given product is first sold in a given
country and ending on the date that the last patent covering such product in
such country expires (or 12 years from the first sales in such country if a
patent is never issued for such product in such country). The amounts of
required royalty payments vary depending on which party originated the compound
for the product. The Company believes that the royalty rates payable under this
agreement are comparable to royalty rates generally payable by other companies
under similar agreements. Pursuant to the agreement with Boehringer Ingelheim,
the Company has the right to obtain a loan in the amount of $1,000,000 from
Boehringer Ingelheim, at any time during 1997, creditable against future mile-
stone payments that may be payable to the Company under the agreement. The term
of the agreement is two years.
 
Collaborative Agreements
The Company is a party to collaborative drug discovery agreements with various
pharmaceutical and technology companies, including 3-Dimensional Pharmaceuti-
cals, Inc. and NPS Pharmaceuticals, Inc. Generally, under these agreements, the
collaborators make available enabling technologies and compounds from their
chemical libraries, and ViroPharma applies such technology and compounds to RNA
virus diseases using the Company's proprietary RNA replication assays. If a
successful drug is discovered, these agreements typically provide for good
faith negotiations to establish the terms and conditions of a mutually accept-
able collaboration agreement. Generally, any such resulting collaborative
agreement will base the economic benefits to the parties upon the relative con-
tribution by each party to a drug's discovery and development.
 
The Company, in collaboration with Minnesota Manufacturing and Mining Company,
is developing an additional formulation of pleconaril for use in an intranasal
aerosal delivery system.
 
The Company has established material transfer and licensing agreements and
research collaborations with academic institutions and their affiliates,
including the Academy of Sciences of the Czech Republic, Northwestern Univer-
sity, Pennsylvania State University, Renssalear Polytechnic Institute, the Uni-
versity of Florida and Washington University. Generally, these agreements pro-
vide for the licensing to the Company of materials for either (i) an initial
fee and certain other fees payable by the Company, with, in most cases, no
future commercial rights for the institution or (ii) an initial fee payable by
the Company and certain rights to negotiate collaborative agreements for drug
development and commercialization.
 
PATENTS
 
ViroPharma believes that patent protection and trade secret protection are
important to its business and that the Company's future will depend, in part,
on its ability to maintain its technology licenses, maintain trade secret pro-
tection, obtain patents and operate without infringing the proprietary rights
of others both in the United States and abroad. The Company currently has
received one issued U.S. patent covering compounds active against HCV and one
Notice of Allowance for compounds active against influenza. The Company cur-
rently has four pending patent applications covering technology for identifying
inhibitors of RNA viruses, compounds active against influenza viruses, com-
pounds active against HCV, and compounds active against related RNA virus dis-
eases. The Company also has filed a patent application for technology for iden-
tifying inhibitors of RNA viruses, two patent applications covering compounds
active against HCV and a patent application covering compounds active against
influenza viruses in certain foreign jurisdictions. The Company has also
obtained a license from Sanofi, which grants the Company exclusive rights for
use in enterovirus and rhinovirus applications under two issued United States
patents and two related Canadian patent applications to develop, manufacture
and market antiviral compounds in the United States and Canada. Pleconaril,
which is currently in clinical trials, is covered by one of the licensed United
States patents, which expires in 2012, and one of the licensed Canadian patent
applications. The Company will be dependent on Sanofi to prosecute such patent
applications and may be dependent on Sanofi to protect such patent rights. As
patent applications in the United States are maintained in secrecy until pat-
ents issue and as publication of discoveries in the scientific or patent liter-
ature often lag behind the 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. Furthermore, the patent positions of biotechnology and pharma-
ceutical companies are 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 patents will issue from any of the Company's patent appli-
cations or, should patents issue, that the Company will be provided with ade-
quate protection against potentially competitive products. Furthermore, there
can be no assurance that
 
                                       34
<PAGE>
 
should patents issue, they will be of commercial value to the Company, or that
private parties, including competitors, will not successfully challenge the
Company's patents or circumvent the Company's patent position in the United
States or abroad. In the absence of adequate patent protection, the Company's
business may be adversely affected by competitors who develop comparable tech-
nology or products. Moreover, pursuant to the terms of the Uruguay Round Agree-
ments Act, patents filed on or after June 8, 1995 have a term of twenty years
from the date of such filing, irrespective of the period of time it may take
for such patent to ultimately issue. This may shorten the period of patent pro-
tection afforded to the Company's products as patent applications in the
biopharmaceutical sector often take considerable time to issue. Under the Drug
Price Competition and Patent Term Restoration Act of 1984, a patent which
claims a product, use or method of manufacture covering drugs and certain other
products may be extended for up to five years to compensate the patent holder
for a portion of the time required for FDA review of the product. This law also
establishes a period of time, following NDA approval, during which the FDA may
not accept or approve applications for certain similar or identical drugs from
other sponsors unless those sponsors provide their own safety and effectiveness
data. There can be no assurance that the Company will be able to take advantage
of either the patent term extension or marketing exclusivity provisions of this
law.
 
In order to protect the confidentiality of the Company's technology, including
trade secrets and know-how and other proprietary technical and business infor-
mation, the Company requires all of its employees, consultants, advisors and
collaborators to enter into confidentiality agreements that prohibit the use or
disclosure of information that is deemed confidential. The agreements also
oblige the Company's employees, consultants, advisors and collaborators to
assign to the Company ideas, developments, discoveries and inventions made by
such persons in connection with their work with the Company. There can be no
assurance that confidentiality will be maintained or disclosure prevented by
these agreements or that the Company's proprietary information or intellectual
property will be protected thereby or that others will not independently
develop substantially equivalent proprietary information or intellectual prop-
erty.
 
The pharmaceutical industry is highly competitive and patents have been applied
for by, and issued to, other parties relating to products competitive with
those being developed by the Company. Therefore, the Company's drug candidates
may give rise to claims that they infringe the patents or proprietary rights of
other parties existing now and in the future. Furthermore, to the extent that
ViroPharma or its consultants or research collaborators use intellectual prop-
erty owned by others in work performed for the Company, disputes may also arise
as to the rights in such intellectual property or in related or resulting know-
how and inventions. An adverse claim could subject the Company to significant
liabilities to such other parties and/or require disputed rights to be licensed
from such other parties. There can be no assurance that any license required
under any such patents or proprietary rights would be made available on terms
acceptable to the Company, if at all. If the Company does not obtain such
licenses, it may encounter delays in product market introductions, or may find
that the development, manufacture or sale of products requiring such licenses
may be precluded. In addition, the Company could incur substantial costs in
defending itself in legal proceedings instituted before the PTO or in a suit
brought against it by a private party based on such patents or proprietary
rights, or in suits by the Company asserting its patent or proprietary rights
against another party, even if the outcome is not adverse to the Company. The
Company has not conducted any searches or made any independent investigations
of the existence of any patents or proprietary rights of other parties. See
"Risk Factors--Uncertain Ability to Protect Patents and Proprietary Technology
and Information."
 
MANUFACTURING
 
The Company does not currently have manufacturing capabilities, nor does the
Company intend to develop such capabilities for any products in the near
future. The Company believes that internal manufacturing capabilities will not
be necessary to successfully commercialize its products. Pleconaril drug sub-
stance is prepared from readily available materials using well-established syn-
thetic processes. Technology involved in the production of pleconaril is pro-
prietary and covered by a patent licensed to the Company by Sanofi. In April
1997, the Company entered into a Development Agreement with SICOR S.A. and
SELOC AG, related companies and subsidiaries of Schwarz Pharma AG, for the man-
ufacture of pleconaril bulk drug substance and the development of a process for
commercial-scale production of pleconaril. The Company anticipates that its
current supply of pleconaril drug substance will be sufficient to complete its
ongoing clinical trials for viral meningitis, "summer flu" and hand-foot-and-
mouth disease. The Company believes that it will be able to obtain additional
drug substance from SICOR and, if necessary, other manufacturers for the pro-
duction of pleconaril drug product on terms acceptable to the Company. In the
event that SICOR is unable to satisfy the Company's requirements and the Com-
pany is required to find an additional or alternative source of supply, there
may be additional cost and delay in product development or commercialization.
The Company is currently negotiating with several contractors for the commer-
cial manufacture of the liquid formulation of pleconaril drug product. The Com-
pany has established quality control guidelines, which require that third party
manufacturers under contract produce the drug product in accordance with the
FDA's GMP requirements.
 
                                       35
<PAGE>
 
The Company maintains confidentiality agreements with potential and existing
manufacturers in order to protect its proprietary rights related to pleconaril.
For the preparation of other compounds, the Company intends to contract with
third-party manufacturers for preclinical research, manufacture of drug sub-
stances for clinical development and manufacture of drug products for commer-
cial sale. See "Risk Factors--Absence of Manufacturing Capabilities."
 
MARKETING
 
Under its agreement with Sanofi, the Company has the exclusive right to market
and sell pleconaril for all enterovirus and rhinovirus indications in the
United States and Canada. The Company is currently conducting market research
on the multiple disease indications for which pleconaril is being developed.
The Company intends to establish its marketing strategy based upon the results
of this market research coupled with information gained through its clinical
trials. The Company may elect to seek a marketing partner for certain disease
indications, establish its own sales force or pursue both alternatives. In
order to develop its marketing strategy, the Company has recently hired an
Executive Director of Marketing. The Company does not currently have a sales
and marketing staff. The success and commercialization of the Company's other
potential products will be dependent, in part, upon the ability of the Company
to maintain its existing arrangement with Boehringer Ingelheim, which governs
marketing of the Company's proposed product for hepatitis C, and to enter into
additional collaborative agreements for other potential products. There can be
no assurance that the Company will be successful in developing a sales force,
entering into collaborative arrangements, penetrating the markets for any pro-
posed products or achieving market acceptance of its products. There can be no
assurance that any such marketing arrangements will be available on terms
acceptable to the Company, if at all, that such third parties would perform
adequately their obligations as expected, or that any revenue would be derived
from such arrangements. See "Risk Factors--Absence of Marketing and Sales Capa-
bility," "Risk Factors--No Assurance of Market Acceptance" and "--Strategic
Relationships."
 
GOVERNMENT REGULATION
 
Regulation by governmental authorities in the United States and foreign coun-
tries is a significant factor in the Company's ongoing research and product
development activities and in the manufacturing and marketing of the Company's
drug candidates. All of the Company's products will require regulatory approval
by governmental agencies, principally the FDA, prior to commercialization. In
particular, therapeutic products for human use are subject to rigorous
preclinical and clinical testing and other approval requirements by the FDA and
similar health authorities in foreign countries. Various federal statutes and
regulations also govern or influence the manufacturing, safety, labeling, stor-
age, recordkeeping and marketing of such products. The process of obtaining
these approvals and the subsequent compliance with appropriate statutes and
regulations require the expenditure of substantial resources. Any failure by
the Company or its collaborators, licensors or licensees to obtain, or any
delay in obtaining, regulatory approval could adversely affect the marketing of
products then being developed by the Company and its ability to receive product
or royalty revenues.
 
The steps required before a new drug may be commercially distributed in the
United States include (i) conducting appropriate preclinical laboratory and
animal tests, (ii) submitting to the FDA an IND application which must be
approved before clinical trials may commence, (iii) conducting controlled human
clinical trials that establish the safety and efficacy of the drug product,
(iv) filing an NDA with the FDA and (v) obtaining FDA approval of the NDA prior
to any commercial sale or shipment of the drug. This process can take a number
of years and involve the expenditure of substantial resources. The results of
preclinical studies and initial clinical trials are not necessarily predictive
of the results from large-scale clinical trials, and clinical trials may
require substantial additional funds, delays or modifications due to, among
other factors, difficulty in obtaining sufficient patient populations, clini-
cians or support. In addition to obtaining FDA approval for each indication to
be treated with each product, each domestic drug manufacturing establishment
must register with the FDA, list its drug products with the FDA, comply with
GMP requirements and be subject to inspection by the FDA. Moreover, the submis-
sion of applications for approval may require additional time to complete manu-
facturing stability studies. Foreign manufacturing establishments distributing
drugs in the United States also must comply with GMP requirements and list
their products with the FDA. They are subject to periodic inspection by the FDA
or by local authorities under agreement with the FDA. See "Risk Factors--Gov-
ernment Regulation; No Assurance of Regulatory Approval."
 
Upon approval in the United States, a drug may only be marketed for the
approved indications in the approved dosage forms and dosages. The FDA also may
require post-marketing testing and surveillance to monitor safety and efficacy
history of the approved product and continued compliance with regulatory
requirements. Adverse experiences with the product must be reported to the FDA.
Product approvals may be withdrawn if compliance with regulatory requirements
is not maintained or if problems concerning safety or efficacy of the product
occur following approval.
 
                                       36
<PAGE>
 
The FDA also mandates that drugs be manufactured in conformity with GMP regu-
lations. In complying with the GMP regulations, manufacturers must continue to
expend time, money and effort in production, recordkeeping and quality control
to ensure that the product meets applicable specifications and other require-
ments. The FDA periodically inspects drug manufacturing facilities to ensure
compliance with applicable GMP requirements. Failure to comply subjects the
manufacturer to possible FDA action, such as warning letters, suspension of
manufacturing, seizure of the product, voluntary recall of a product or
injunctive action. The Company currently relies on, and intends to continue to
rely on, third parties to manufacture compounds and products. Such third par-
ties will be required to comply with GMP requirements.
 
Even after FDA approval has been obtained, and often as a condition to expe-
dited approval, further studies, including post-marketing studies, may be
required. Results of post-marketing studies may limit or expand the further
marketing of the products. Further, if there are any modifications to the
drug, including changes in indication, manufacturing process, manufacturing
facility or labeling, an NDA supplement may be required to be submitted to the
FDA.
 
Products marketed outside the United States which are manufactured in the
United States may be subject to certain FDA regulations, as well as regulation
by the country in which the products are to be sold. If products are marketed
abroad, the Company will also be subject to foreign regulatory requirements
governing clinical trials and pharmaceutical sales, which may vary from
country to country. In connection with certain of its strategic relationships,
the Company's collaborators may be responsible for the foreign regulatory
approval process of the Company's drugs, although the Company may be legally
liable for noncompliance.
 
The Company is also subject to various federal, state and local laws, rules,
regulations and policies relating to safe working conditions, laboratory and
manufacturing practices, the experimental use of animals and the use and dis-
posal of hazardous or potentially hazardous substances, including radioactive
compounds and infectious disease agents, used in connection with the Company's
research work. The extent of government regulation which might result from
future legislation or administrative action cannot be accurately predicted.
Moreover, although the Company believes that its safety procedures for han-
dling and disposing of such materials comply with current federal, state and
local laws, rules, regulations and policies, the risk of accidental injury or
contamination from these materials cannot be entirely eliminated.
 
Moreover, the Company anticipates that Congress, state legislatures and the
private sector will continue to review and assess controls on health care
spending. Any such proposed or actual changes could cause the Company or its
collaborators to limit or eliminate spending on development projects and may
otherwise impact the Company. Additionally, in both domestic and foreign mar-
kets, sales of the Company's proposed products 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. Significant uncertainty often exists as to
the reimbursement status of newly approved health care products. In addition,
third-party payors are increasingly challenging the price and cost effective-
ness of medical products and services. 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 the Company to maintain
price levels sufficient to realize an appropriate return on its investment in
product research and development. See "Risk Factors--Uncertainty of Pharmaceu-
tical Pricing and Related Matters; Need for Reimbursement."
 
COMPETITION
 
The pharmaceutical and biopharmaceutical industries are intensely competitive
and are characterized by rapid technological progress. Certain pharmaceutical
and biopharmaceutical companies and academic and research organizations cur-
rently engage in, or have engaged in, efforts related to the discovery and
development of new antiviral medicines. Significant levels of research in
chemistry and biotechnology occur in universities and other nonprofit research
institutions. These entities have become increasingly active in seeking patent
protection and licensing revenues for their research results. They also com-
pete with the Company in recruiting skilled scientific talent. There are cur-
rently available antiviral therapeutics which address certain of the disease
indications for which the Company is developing therapeutics. In addition,
many companies are developing therapies to treat viral diseases and, in this
regard, are in competition with the Company. The Company believes that its
ability to compete successfully will be based on its ability to create and
maintain scientifically advanced technology, develop proprietary products,
attract and retain scientific personnel, obtain patent or other protection for
its products, obtain required regulatory approvals and manufacture and suc-
cessfully market its products either alone or through outside parties. Some of
the Company's competitors have substantially greater financial, research and
development, manufacturing, marketing and human resources and greater experi-
ence in drug discovery, development, clinical trial management, FDA regulatory
review, manufacturing and marketing than ViroPharma. Moreover, the Company
believes that the technologies used by the Company have never been applied to
develop an approved pharmaceutical product. See "Risk Factors--Competition"
and "Risk Factors--Rapid Technological Change and Uncertainty."
 
                                      37
<PAGE>
 
HUMAN RESOURCES
   
As of July 1, 1997, ViroPharma had 44 full-time employees, including 12 persons
with Ph.D. or M.D. degrees. Thirty-four of ViroPharma's employees are engaged
in research and development activities at the Company's laboratory facility in
Malvern, Pennsylvania. A significant number of the Company's management and
professional employees have had prior experience with pharmaceutical, biotech-
nology or medical products companies. None of the Company's employees is cov-
ered by collective bargaining agreements. The Company believes that its rela-
tions with its employees are good. There can be no assurance that the Company
will be able to continue to attract and retain qualified personnel, and the
Company does not maintain "key man" life insurance on any of its employees. See
"Risk Factors--Dependence on Key Personnel."     
 
FACILITIES
   
The Company's principal facility consists of approximately 17,000 square feet
of leased laboratory and office space in Malvern, Pennsylvania. The lease
expires in 1998. On July 21, 1997, the Company entered into an operating lease
for approximately 48,400 square feet of laboratory and office space commencing
after the current operating lease expires. The term of the new lease is ten
years with two five-year renewal options. Under the lease terms, the Company is
required to contribute approximately $800,000 in 1997 to the cost of the labo-
ratory construction. The Company also has the right, under certain circum-
stances, to purchase the new facility at a purchase price based on a pre-deter-
mined formula.     
 
LEGAL PROCEEDINGS
 
The Company has no pending legal proceedings. There can be no assurance that
any future claims against the Company will be successfully defended, that the
insurance carried by the Company will be sufficient or that collaborators and
licensees will fully protect the Company from product liability or other
claims.
 
                                       38
<PAGE>
 
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
   
As of July 21, 1997, the executive officers and directors of the Company are as
follows:     
 
<TABLE>
<CAPTION>
NAME                          AGE   POSITION
<S>                           <C>   <C>
Claude H. Nash, Ph.D.         54    Chief Executive Officer, President and Chairman of the Board of Directors
Mark A. McKinlay, Ph.D.       46    Vice President, Research & Development
Marc S. Collett, Ph.D.        46    Vice President, Discovery Research
Johanna A. Griffin, Ph.D.     53    Vice President, Business Development
Guy D. Diana, Ph.D.           61    Vice President, Chemistry Research
Jon M. Rogers, M.D.           45    Vice President, Clinical Research
Vincent J. Milano             33    Vice President, Finance & Administration and Treasurer
Thomas F. Doyle               36    Executive Director, Counsel and Secretary
Michael Kelly                 32    Executive Director, Marketing
Frank Baldino, Jr., Ph.D.(1)  44    Director
Steve Dow (2)                 42    Director
Jon N. Gilbert                34    Director
Ann H. Lamont (2)             40    Director
Christopher Moller, Ph.D.(1)  43    Director
</TABLE>
- -------
(1) Member of Audit Committee.
(2) Member of Compensation Committee.
   
CLAUDE H. NASH, PH.D., a co-founder of the Company, has served as Chairman of
the Board of Directors since February 1997, and as Chief Executive Officer,
President and director since the Company's commencement of operations in
December 1994. From 1983 until 1994, Dr. Nash served as Vice President, Infec-
tious Disease and Tumor Biology at Schering-Plough Corporation, a pharmaceu-
tical company. Dr. Nash received his Ph.D. from Colorado State University.     
   
MARK A. MCKINLAY, PH.D., a co-founder of the Company, has served as Vice Presi-
dent, Research & Development since the Company's commencement of operations in
December 1994, and served as Secretary from December 1994 until February 1997.
From 1989 through 1994, Dr. McKinlay served in several positions, including
Senior Director, at Sterling Winthrop Pharmaceuticals Research Division, a
division of Sterling Winthrop Incorporated, a pharmaceutical company. Dr.
McKinlay received his Ph.D. from Renssalear Polytechnic Institute.     
   
MARC S. COLLETT, PH.D., a co-founder of the Company, has served as Vice Presi-
dent, Discovery Research of the Company since the Company's commencement of
operations in December 1994. From 1993 until he co-founded the Company, he
served as Senior Director, Viral Therapeutics at PathoGenesis Corporation, a
biotechnology company. Prior to joining PathoGenesis Corporation, Dr. Collett
served as Director, Virology & Antibody Engineering and Director, Biochemical
Virology at MedImmune, Inc., a biotechnology company, where he was employed
from 1988 to 1993. Dr. Collett received his Ph.D. from the University of Michi-
gan.     
   
JOHANNA A. GRIFFIN, PH.D., a co-founder of the Company, has served as Vice
President, Business Development since June 1995 and, from the Company's com-
mencement of operations in December 1994 until June 1995, served as Executive
Director, Business Development. From 1990 until she joined the Company, Dr.
Griffin served as Director of Molecular Biology at Boehringer Ingelheim Pharma-
ceuticals, Inc., a pharmaceutical company. Dr. Griffin received her Ph.D. from
the University of Alabama at Birmingham.     
   
GUY D. DIANA, PH.D., a co-founder of the Company, has served as Vice President,
Chemistry Research since June 1995 and, from the Company's commencement of
operations in December 1994 until June 1995, as Executive Director, Chemistry
Research. Prior to joining ViroPharma, he worked at Sterling Winthrop
Incorporated, a pharmaceutical company, for 33 years, most recently as a Senior
Fellow in Medicinal Chemistry, where he led the team that discovered
pleconaril. Dr. Diana received his Ph.D. from Rice University.     
   
JON M. ROGERS, M.D., has served as Vice President, Clinical Research since
joining ViroPharma in June 1996. From February 1995 until he joined the Com-
pany, Dr. Rogers was Vice President of Medical and Scientific Affairs for the
pharmaceuticals and diagnostics divisions of Boehringer Mannheim Corporation, a
pharmaceutical company. From August     
 
                                       39
<PAGE>
 
   
1989 through February 1995, Dr. Rogers served in various positions at Sterling
Winthrop Incorporated, a pharmaceutical company, the latest being Senior
Director of Clinical Research. Dr. Rogers received his M.D. from the University
of Cincinnati College of Medicine.     
   
VINCENT J. MILANO has served as Vice President, Finance & Administration of the
Company since February 1997, as Treasurer since July 1996, and as Executive
Director, Finance & Administration from April 1996 until February 1997. From
1985 until he joined the Company, Mr. Milano was with KPMG Peat Marwick LLP,
independent certified public accountants, where he was Senior Manager since
1991. Mr. Milano is a Certified Public Accountant. Mr. Milano received his B.S.
in accounting from Rider College.     
   
THOMAS F. DOYLE has served as Secretary since February 1997 and as Executive
Director, Counsel since joining the Company in November 1996. From 1990 until
he joined the Company, Mr. Doyle was a corporate attorney with the law firm of
Pepper, Hamilton & Scheetz. Mr. Doyle received his J.D. from Temple University
School of Law. Prior to attending Temple University, Mr. Doyle was a Certified
Public Accountant. Mr. Doyle received his B.S. in accounting from Mt. St.
Mary's College.     
   
MICHAEL KELLY has served as Executive Director, Marketing since joining the
Company in April 1997. From 1991 until he joined the Company, Mr. Kelly held
various positions at TAP Pharmaceuticals, a pharmaceutical company, the latest
being Manager of Hospital Account Executives within the Mid-Atlantic Region.
Mr. Kelly received his B.S. in Marketing from the Trenton State College and his
M.B.A. from Rider College.     
 
FRANK BALDINO, JR., PH.D., has served as a director of the Company since June
1995. Since 1987, Dr. Baldino has served as President, CEO and director of
Cephalon, Inc., an integrated specialty biopharmaceutical company that discov-
ers, develops, and markets products to treat neurological disorders. Dr.
Baldino is also a director of Integrated Systems Consulting Group, Inc. and
Pharmacopeia, Inc. He received his Ph.D. from Temple University.
 
STEVE DOW has served as a director of the Company since June 1995. Since 1983,
he has been a general partner of Sevin Rosen Funds, a venture capital firm
whose affiliates are principal stockholders in the Company. Mr. Dow also serves
on the Board of Directors of Citrix Systems and Arqule, Inc.
 
JON N. GILBERT has served as a director of the Company since September 1996.
Mr. Gilbert is a general partner of Frazier & Company L.P., a private equity
firm specializing in health care which he joined at its inception in 1991 and
whose affiliate is a principal stockholder in the Company. Mr. Gilbert received
his M.B.A. from Dartmouth College.
 
ANN H. LAMONT, a co-founder of the Company, has served as director of the Com-
pany since June 1995. Since 1986, Ms. Lamont has served as general partner and
managing member of certain limited partnerships affiliated with Oak Investment
Partners, a venture capital organization whose affiliates are principal stock-
holders in the Company.
 
CHRISTOPHER MOLLER, PH.D., has served as a director of the Company since June
1995. Since January 1990, Dr. Moller has served as managing director of Tech-
nology Leaders II Management L.P. and its predecessors, venture capital limited
partnerships whose affiliates are principal stockholders in the Company. Dr.
Moller received his Ph.D. from the University of Pennsylvania School of Medi-
cine.
 
All of the members of the Board of Directors were elected to the Board of
Directors pursuant to an Amended and Restated Shareholders' Voting Agreement,
dated as of May 31, 1996, by and among the Company and certain of its stock-
holders and executive officers (the "Voting Agreement"). Dr. Moller was re-
elected to the Board of Directors at the Company's annual meeting on May 28,
1997.
 
The Voting Agreement, which terminated upon completion of the Company's initial
public offering, provided for the designation of one director each by Oak
Investment Partners VI, Limited Partnership, Sevin Rosen Fund IV, L.P., TL Ven-
tures and Frazier & Company, Inc., the designation of two directors by the
holders of all outstanding shares of the Redeemable Preferred Stock and Common
Stock, voting together as a single class, and the designation of one director
by the holders of all of the outstanding shares of Common Stock, which director
was required to be the Chief Executive Officer of the Company. Ms. Lamont was
designated to be a director by Oak Investment Partners VI, Limited Partnership,
Mr. Dow was designated to be a director by Sevin Rosen Fund IV, L.P., Dr.
Moller was designated to be a director by TL Ventures and Mr. Gilbert was des-
ignated to be a director by Frazier & Company, Inc. In addition, Dr. Baldino
was designated to be a director by the holders of all outstanding shares of
Redeemable Preferred Stock and Common Stock voting as a single class, and Dr.
Nash was designated to be a director by the holders of Common Stock.
 
                                       40
<PAGE>
 
Each director is elected to hold office until the next annual meeting of stock-
holders and until his or her respective successor is elected and qualified.
Upon the closing of the Company's initial public offering in November 1996, the
Board of Directors was divided into three classes. Each class of directors
serves (after a transitional period in which the first class served until their
successors have been elected and qualified at the 1997 annual meeting of stock-
holders, the second class will serve until their successors have been elected
and qualified at the 1998 annual meeting of stockholders and the third class
will serve until their successors have been elected and qualified at the 1999
annual meeting of stockholders) for a term of three years and until their suc-
cessors have been elected and qualified. Officers serve at the discretion of
the Board of Directors. The terms of Mr. Dow and Ms. Lamont will expire at the
1998 annual meeting, the terms of Dr. Baldino, Mr. Gilbert and Dr. Nash will
expire at the 1999 annual meeting, and the term of Dr. Moller will expire at
the 2000 annual meeting.
 
SCIENTIFIC ADVISORY BOARD
 
The Company has assembled a Scientific Advisory Board consisting of individuals
with demonstrated expertise in particular fields who periodically advise the
Company on matters relating to long-term scientific planning, research and
development activities and technological matters. Several of the advisors have
had previous scientific working relationships with members of the Company's
management team.
 
Most of the members of the Scientific Advisory Board are employed by or have
consulting agreements with entities other than the Company, some of which enti-
ties may in the future compete with the Company, and are expected to devote
only a small portion of their time to the Company. They are not expected to
participate actively in the Company's affairs or in the development of the
Company's technology. Certain of the institutions with which such members of
the Scientific Advisory Board are affiliated may adopt new regulations or poli-
cies that limit the ability of the members to consult with the Company. The
loss of the services of certain of the members could adversely affect the Com-
pany, to the extent that the Company is pursuing research or development in
areas of a member's expertise. In addition, since the Company has not entered
into non-competition agreements with all members of the Scientific Advisory
Board, if any member of the Scientific Advisory Board were to consult with or
become employed by any competitor of the Company, the Company could be materi-
ally adversely affected.
 
Pursuant to several of the scientific advisory/consulting agreements entered
into with some of such members of the Scientific Advisory Board, any inventions
or other intellectual property discovered by the members may not become the
property of the Company but may remain the property of such persons or of such
persons' employers. In addition, the institutions with which such members are
affiliated may make available the research services of their personnel,
including the members of the Scientific Advisory Board, to competitors of the
Company pursuant to sponsored research agreements. Competitors of the Company
may gain access to trade secrets and other proprietary information developed by
the Company and disclosed to the members of the Scientific Advisory Board.
Thus, assistance provided by the various members is generally limited to advice
and consultation unless the Company has entered into separate collaborative
arrangements with the entities with which the members are affiliated. See "Risk
Factors--Uncertain Ability to Protect Patents and Proprietary Technology and
Information," "Business--Patents" and "Business--Strategic Relationships."
 
The members of the Company's Scientific Advisory Board are as follows:
 
HUGH E. BLACK, D.V.M., PH.D. is President of Hugh E. Black & Associates, Inc.
In 1994, Dr. Black retired from Schering-Plough Research Institute where he
served as Vice President, Drug Safety and Metabolism. Dr. Black received his
D.V.M. degree from the University of Toronto and his Ph.D. degree in veterinary
pathology from Ohio State University.
 
GARY L. DAVIS, M.D., is Professor of Medicine and the Director of the
Hepatobiliary Diseases Section of the Gastroenterology, Hepatology, and Nutri-
tion Division at the University of Florida College of Medicine in Gainesville.
Dr. Davis received his M.D. degree from the University of Minnesota.
 
JAMES B. FLANEGAN, PH.D., is Professor of Molecular Genetics and Microbiology
at the University of Florida College of Medicine in Gainesville. Dr. Flanegan
received his Ph.D. degree in biochemistry from the University of Michigan.
 
FREDERICK G. HAYDEN, M.D., is the S. Stuart Richardson Professor of Clinical
Virology in Internal Medicine and Professor of Internal Medicine and Pathology
at the University of Virginia School of Medicine in Charlottesville. Dr. Hayden
received his M.D. degree from Stanford University School of Medicine.
 
MICHAEL D. HAYRE, D.V.M., is Director of the Laboratory Animal Research Center,
The Rockefeller University in New York. Dr. Hayre received his D.V.M. degree
from Tuskegee University.
 
                                       41
<PAGE>
 
ROBERT A. LAMB, PH.D., SC.D., is the John Evans Professor of Molecular and Cell
Biology at Northwestern University and a Howard Hughes Medical Institute Inves-
tigator. Dr. Lamb received his Ph.D. in virology and Sc.D. degree from the Uni-
versity of Cambridge, England.
 
CHARLES M. RICE, PH.D., is Professor in the Department of Molecular
Microbiology at Washington University School of Medicine in St. Louis, Mis-
souri. Dr. Rice received his Ph.D. degree in biochemistry from the California
Institute of Technology.
 
MICHAEL G. ROSSMANN, PH.D., is the Hanley Professor of Biological Sciences at
Purdue University in West Lafayette, Indiana. Dr. Rossmann received his Ph.D.
degree in chemical crystallography from the University of Glasgow.
 
HARLEY A. ROTBART, M.D. is Professor in the Departments of Pediatrics and
Microbiology at the University of Colorado Health Science Center in Denver. Dr.
Rotbart received his M.D. degree from Cornell University Medical College.
 
RICHARD WHITLEY, M.D., is the Loeb Eminent Scholar and Professor of Pediatrics,
Microbiology and Medicine at University of Alabama at Birmingham. Dr. Whitley
received his M.D. degree from George Washington University School of Medicine.
 
Members of the Scientific Advisory Board receive consulting fees for their
services. In addition, to date, the Company has granted an aggregate of 66,300
options to members of the Scientific Advisory Board, of which 2,550 have been
exercised.
 
DIRECTOR COMPENSATION AND BOARD COMMITTEES
 
Non-employee directors who are not affiliated with investors in the Company
receive $10,000 annually, plus travel costs for each meeting of the Board of
Directors they attend.
 
In connection with the founding of the Company, Dr. Nash purchased 331,500
shares of Common Stock in December 1994. Dr. Nash paid $0.002 per share for the
Common Stock, then valued at $0.10 per share. Dr. Nash's shares vest in four
equal annual installments commencing on the first anniversary of the date of
issuance. The Company has the option to repurchase all unvested shares for
$0.10 per share. In addition, pursuant to a right granted in December 1994, Dr.
Baldino purchased 51,000 shares of Common Stock in January 1996 at $0.10 per
share. The shares vest in four equal annual installments commencing on the date
of issuance. The restrictions on Dr. Baldino's shares are identical to the
restrictions on Dr. Nash's shares. See "Certain Transactions--Transactions with
Founders" and "Certain Transactions--Right Grant and Exercise."
 
The Board of Directors has a Compensation Committee, which makes recommenda-
tions concerning salaries and incentive compensation for employees of and con-
sultants to the Company, and an Audit Committee, which reviews the results and
scope of the audit and other services provided by the Company's independent
auditors.
 
Dr. Baldino, Mr. Dow, Mr. Gilbert, Ms. Lamont and Dr. Moller are parties to
indemnification agreements with the Company. Pursuant to the agreements, the
directors are to be indemnified against liabilities and expenses incurred in
connection with their services to the Company to the fullest extent permitted
by Delaware law. Such indemnification is subject to the director's meeting the
applicable standard of care and to a determination to indemnify by a majority
of disinterested directors (as defined in the agreements) or by independent
counsel (also as defined in the agreements).
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
There are no compensation committee interlocks with other entities or insider
participation on the Compensation Committee. See "--Director Compensation and
Board Committees" for a description of Mr. Dow's and Ms. Lamont's indemnifica-
tion agreements with the Company, "Certain Transactions--Transactions with
Founders" for a description of Ms. Lamont's participation in the founding of
the Company and "Certain Transactions--Financings" for a description of partic-
ipation by Oak and Sevin Rosen, of which Ms. Lamont and Mr. Dow are principals,
in the Company's financings.
 
                                       42
<PAGE>
 
EXECUTIVE COMPENSATION
 
The following table sets forth certain information with respect to compensation
paid or earned during the fiscal years ended December 31, 1995 and December 31,
1996 to the Company's chief executive officer and the four other most highly
compensated executive officers of the Company (collectively, the "Named Execu-
tive Officers").
 
Summary Compensation
 
<TABLE>
<CAPTION>
                                 --------------------------------------------
                                            ANNUAL COMPENSATION
                                                                        OTHER
                                                                       ANNUAL
                                 YEAR SALARY($)    BONUS($) COMPENSATION $(1)
NAME AND POSITION                ---- ---------    -------- -----------------
<S>                              <C>  <C>          <C>      <C>
Claude H. Nash.................. 1996  $180,000     $18,000         $20,000(2)
 Chief Executive Officer and
 President                       1995   180,000(3)      --                --
Mark McKinlay................... 1996   165,000      16,500               --
 Vice President, Research &
 Development                     1995   165,000(3)      --                --
Marc S. Collett................. 1996   145,000      14,500               --
 Vice President, Discovery
 Research                        1995   145,000(3)      --                --
Johanna A. Griffin.............. 1996   125,000      12,500               --
 Vice President, Business
 Development                     1995   125,000(3)      --                --
Guy D. Diana.................... 1996   125,000      12,500               --
 Vice President, Chemistry
 Research                        1995   125,000(3)      --                --
</TABLE>
- -------
(1)  Excludes perquisites and other personal benefits, securities or property
which are, in the aggregate, less than 10% of the total annual salary and
bonus.
(2) Represents premiums paid by the Company for life insurance of which the
Company is not the beneficiary.
(3) In 1995, each Named Executive Officer also received cash payments for
deferred compensation for services performed in December 1994. Drs. Nash,
McKinlay, Collett, Griffin and Diana received payments of $6,923, $6,346,
$5,576, $4,807 and $4,807, respectively.
 
The following table provides information on stock options granted by the Com-
pany in the last fiscal year to the Named Executive Officers.
 
Option Grants in Last Fiscal Year
 
<TABLE>
<CAPTION>
                         ----------------------------------------------------------------
                                     INDIVIDUAL GRANTS
                         ------------------------------------------
                                                                    POTENTIAL REALIZABLE
                                                                            VALUE
                                                                      AT ASSUMED ANNUAL
                          NUMBER OF PERCENTAGE                            RATES OF
                         SECURITIES         OF                           STOCK PRICE
                         UNDERLYING      TOTAL                        APPRECIATION FOR
                            OPTIONS    OPTIONS  EXERCISE EXPIRATION    OPTION TERM(3)
                         GRANTED(1) GRANTED(2)     PRICE       DATE         5%        10%
NAME                     ---------- ----------  -------- ---------- ---------- ----------
<S>                      <C>        <C>         <C>      <C>        <C>        <C>
Claude H. Nash..........     17,850        6.1%    $2.16     7/1/06 $   24,248 $   61,448
Mark McKinlay...........     51,000       17.3      0.20     1/1/06      6,415     16,256
                              9,180        3.1      2.16     7/1/06     12,470     31,602
Marc S. Collett.........     38,250       13.0      0.20     1/1/06      4,811     12,192
                              9,180        3.1      2.16     7/1/06     12,470     31,602
Johanna A. Griffin......     19,763        6.7      2.16     7/1/06     26,846     68,034
Guy D. Diana............      8,288        2.8      2.16     7/1/06     11,259     28,531
</TABLE>
- -------
(1) These options are exercisable in four annual installments commencing on the
first anniversary of the date of grant.
(2) Based on an aggregate of 294,104 options granted to employees in 1996,
including options granted to the Named Executive Officers.
(3) Represents the hypothetical gains or "option spreads" that would exist for
the options at the end of their ten year term. These gains are based on assumed
rates of annual compound stock price appreciation of 5% and 10% from the date
the option was granted to the end of the option term and are calculated based
on the exercise price per share on the date of grant. Such 5% and 10% assumed
annual compound rates of stock price appreciation are mandated by the rules of
the Securities and Exchange Commission and do not represent the Company's esti-
mate or projection of the future Common Stock price.
 
                                       43
<PAGE>
 
The following table sets forth certain information concerning the number and
value of unexercised options held by each of the Named Executive Officers on
December 31, 1996.
 
Fiscal Year-End Option Values
 
<TABLE>
<CAPTION>
                          ------------------------------------------------------
                            NUMBER OF SECURITIES
                           UNDERLYING UNEXERCISED       VALUE OF UNEXERCISED
                                 OPTIONS(#)           IN-THE-MONEY OPTIONS($)
                          ------------------------- ----------------------------
                          EXERCISABLE UNEXERCISABLE EXERCISABLE UNEXERCISABLE(1)
NAME                      ----------- ------------- ----------- ----------------
<S>                       <C>         <C>           <C>         <C>
Claude H. Nash...........         --         17,850         --          $117,632
Mark McKinlay............         --         60,180         --           496,546
Marc S. Collett..........         --         47,430         --           387,534
Johanna A. Griffin.......         --         19,763         --           130,238
Guy D. Diana.............         --          8,288         --            54,618
</TABLE>
- -------
 
(1) Based on the difference between $8.75, which was the closing price per
share on December 31, 1996, and the exercise price of the option.
 
STOCK OPTIONS
 
The Company adopted the 1995 Stock Option Plan on September 20, 1995 (the
"Plan"). The Plan provides for grants of stock options ("Options") to employees
of the Company or its subsidiaries and consultants and advisors who perform
valuable services to the Company or its subsidiaries. The purposes of the Plan
are (i) to further the growth and success of the Company and its subsidiaries
by enabling selected employees of, and consultants and advisors to, the Company
and any subsidiaries to acquire shares of Common Stock, thereby increasing
their personal interest in the Company's growth and success and (ii) to provide
a means of rewarding outstanding performance by such persons to the Company
and/or its subsidiaries.
 
General
Subject to adjustment in certain circumstances as discussed below, the Plan
authorizes up to 1,200,000 shares of Common Stock for issuance pursuant to the
terms of the Plan. If and to the extent Options granted under the Plan expire
or are terminated or cancelled without having been fully exercised, the shares
of Common Stock subject to such unexercised portion of such Options again will
be available for grant under the Plan. Options to purchase an aggregate of
163,099 shares of Common Stock were granted prior to adoption of the Plan pur-
suant to non-qualified stock option agreements.
 
Administration of the Plan
The Plan is administered and interpreted by a committee (the "Committee") of
the Board of Directors of the Company. The Committee has the full power and
authority to take all actions and to make all determinations required or pro-
vided for under the Plan, any Option or any Option agreement ("Option Agree-
ment") entered into under the Plan and all such other actions and determina-
tions not inconsistent with the specific terms and provisions of the Plan
deemed by the Committee to be necessary or appropriate to the administration of
the Plan, any Option or any Option Agreement entered into under the Plan. The
Committee has plenary authority, in its discretion, to determine (i) the per-
sons to whom Options will be granted, (ii) the time or times at which Options
will be granted, (iii) the number of shares subject to each Option, (iv) the
Option price, (v) the time or times when each Option will become exercisable
and the duration of the exercise period and (vi) any restrictions on sale and
repurchase rights which will be placed upon the shares of Common Stock pur-
chased upon exercise of an Option. In addition, the Committee has the authority
to provide for acceleration of the exercisability of Options at any time prior
to termination of such Options. The members of the Compensation Committee cur-
rently serve as this Committee. See "--Director Compensation and Committees."
 
Grants
Options granted under the Plan may consist of (i) options intended to qualify
as incentive stock options ("ISOs") within the meaning of section 422 of the
Internal Revenue Code of 1986 (the "Code") or (ii) so-called "nonqualified
stock options" that are not intended to so qualify ("NQSOs").
 
Eligibility for Participation
Options may be granted to officers and employees of, or consultants or advisors
to, the Company or its subsidiaries. As of July 1, 1997, 44 employees were
eligible for grants under the Plan. Officers and employees are eligible to
receive ISOs or NQSOs, and consultants and advisors are eligible to receive
NQSOs only. As of July 1, 1997, 707,037 options were
 
                                       44
<PAGE>
 
outstanding and held by all participants as a group, at an average exercise
price of $4.07 per share. As of July 1, 1997, 149,940 options issued pursuant
to non-qualified stock option agreements prior to the adoption of the Plan
were outstanding.
 
Options
The option exercise price of any ISO granted under the Plan will not be less
than the fair market value of the underlying shares of Common Stock on the
date of grant, except that the option exercise price of an ISO granted to an
employee who owns more than 10% of the total combined voting power of all
classes of the stock of the Company or its subsidiaries may not be less than
110% of the fair market value of the underlying shares of Common Stock on the
date of grant. The option exercise price of an NQSO may be greater than, equal
to or less than the fair market value of the underlying shares of Common Stock
on the date of grant, but in any case not less than the minimum price under
applicable state law. The Committee will determine the term of each Option;
provided, however, that the exercise period for ISOs may not exceed ten years
from the date of grant and the exercise period of an ISO granted to a person
who owns more than 10% of the voting stock of the Company may not exceed five
years from the date of grant. Unless otherwise provided by the Committee,
Options granted under the Plan vest at a rate of 25% per year over a four-year
period. All options granted to date vest at a rate of 25% per year over a
four-year period, except that 8,288 options granted to Mr. Milano vested imme-
diately upon the completion of the Company's initial public offering, the
options granted to Mr. Doyle and Mr. Kelly vest over a three year period and
5,100 options in the aggregate granted to two consultants to the Company vest
upon the achievement of certain agreed-upon milestones. The option exercise
price must be paid in full at the time the notice of exercise of the Option is
delivered to the Company and must be tendered in the form specified by the
Committee which may be (i) in cash by bank certified, cashier's or personal
check, (ii) by delivery of shares of Common Stock owned by the participant and
having a fair market value on the date of exercise equal to the Option price
or (iii) any combination of (i) and (ii). Options are nontransferable except
by will or the laws of descent and distribution. An optionee whose relation-
ship with the Company or any subsidiary ceases for any reason (other than ter-
mination for cause, death or total disability, as such terms are defined in
the Plan) may exercise Options in the three-month period following such cessa-
tion (unless such Options terminate or expire sooner by their terms), or in
such longer period determined by the Committee in the case of NQSOs. In the
event an optionee's relationship terminates on account of disability or death,
such optionee (or his or her executors or legal representatives) may exercise
such Option during the 12-month period following such disability or death.
 
Amendment and Termination of the Plan
The Board of Directors may at any time modify and amend the Plan; provided,
however, that stockholder approval is required for any amendment which (i)
changes the class of persons eligible for the grant of Options, (ii) increases
(other than pursuant to the adjustment provisions discussed below) the maximum
number of shares subject to Options granted under the Plan, or (iii) materi-
ally increases benefits accruing to participants under the Plan, within the
meaning of Rule 16b-3 under the Exchange Act. The Board of Directors may ter-
minate the Plan at any time. The Plan will terminate on September 20, 2005,
unless terminated earlier by the Board of Directors or extended, although any
termination will not affect Options outstanding at such date.
 
Adjustment Provisions
Subject to the change of control provisions below, in the event of certain
transactions identified in the Plan, the Company may appropriately adjust (i)
the number and kind of shares for the acquisition of which Options may be
granted under the Plan and (ii) the number and kind of shares for which
Options are outstanding. Any such adjustment in outstanding Options will not
change the aggregate option exercise price payable with respect to shares sub-
ject to the unexercised portion of the outstanding Options but will include a
corresponding adjustment in the option exercise price per share.
 
Change of Control of the Company
Upon the dissolution or liquidation of the Company, a merger, consolidation,
or reorganization of the Company with one or more other corporations in which
the Company is not the surviving corporation, a sale or other transfer of sub-
stantially all of the assets of the Company to another corporation or any
transaction (including, without limitation, a merger or reorganization in
which the Company is the surviving corporation) approved by the Board of
Directors that results in any person or entity (other than persons and affili-
ates who meet certain requirements) owning 80 percent or more of the combined
voting power, or 80 percent or more of the total value, of all classes of
stock of the Company, the Plan and all Options outstanding thereunder shall
terminate, except to the extent provision is made in writing in connection
with such transaction for the continuation of the Plan and/or the assumption
of such Options theretofore granted, or for the substitution for such Options
of new options covering the stock of a successor corporation, or a parent or
subsidiary thereof, with appropriate adjustment as to the number and kinds of
shares and exercise prices, in which event the Plan and Options theretofore
granted will continue in the manner and under the terms so provided. In the
event of any such termination of the Plan, each individual
 
                                      45
<PAGE>
 
holding an Option will have the right (subject to the Plan's general limita-
tions on exercise), immediately before the occurrence of such termination and
during such period occurring before such termination as the Committee, in its
sole discretion, determines and designates, to exercise such Option in whole or
in part, subject to the limitations on the exercisability of an Option (in-
cluding the acceleration of such exercisability). The Committee shall send
written notice of an event that will result in such a termination to all indi-
viduals who hold Options not later than the time at which the Company gives
notice thereof to its stockholders.
 
Section 162(m)
Under Section 162(m) of the Code, the Company may be precluded from claiming a
federal income tax deduction for total remuneration in excess of $1,000,000
paid to the chief executive officer or to any of the other four most highly
compensated officers in any one year. Total remuneration would include amounts
received upon the exercise of stock options granted under the Plan. An excep-
tion does exist, however, for "performance-based compensation," including
amounts received upon the exercise of stock options pursuant to a plan approved
by stockholders that meets certain requirements. The Plan is intended to meet
the requirements of Treasury Regulation section 1.162-27(f), and the Options
granted under the Plan are intended to meet the requirements of "performance-
based compensation."
 
401(K) PROFIT SHARING PLAN & TRUST
 
Effective July 1, 1995, the Company adopted the ViroPharma 401(k) Employee Sav-
ings Plan (the "401(k) Plan"), a tax-qualified plan covering all of its
employees who have completed three months of service with the Company. Each
employee may elect to reduce his or her current compensation by up to 15%, sub-
ject to the statutory limit (a maximum of $9,500 in 1996) and have the amount
of the reduction contributed to the 401(k) Plan. The 401(k) Plan provides that
the Company may, as determined from time to time by the Board of Directors,
provide a discretionary contribution, which will be allocated based on the pro-
portion of the employee's compensation for the plan year to the aggregate com-
pensation for the plan year for all eligible employees. All employee contribu-
tions to the 401(k) Plan are fully vested at all times. The 401(k) Plan permits
distributions upon hardship, termination of employment, death, disability or
retirement. The 401(k) Plan does not permit loans. As of December 31, 1996, the
Company had made no contributions to the 401(k) Plan.
 
CONFIDENTIALITY AND INVENTIONS AGREEMENTS
 
The Company has entered into confidentiality and inventions agreements with
each of its employees. The agreements provide that, among other things, all
inventions, discoveries and ideas made or conceived by an employee during
employment which are useful to the Company or related to the business of the
Company or which were made or conceived with the use of the Company's time,
material, facilities or trade secret information, belong exclusively to the
Company, without additional compensation to the employee. The agreements also
have confidentiality provisions in favor of the Company and a noncompetition
provision in favor of the Company during employment.
 
                                       46
<PAGE>
 
                              CERTAIN TRANSACTIONS
 
TRANSACTIONS WITH FOUNDERS
 
Drs. Nash, Collett, McKinlay, Griffin and Diana and Ms. Lamont founded the Com-
pany in December 1994. In connection with the founding of the Company, Drs.
Nash, Collett, McKinlay, Griffin and Diana purchased 331,500, 102,000, 102,000,
63,750 and 63,750 shares of Common Stock, respectively, in December 1994 pur-
suant to restricted stock purchase agreements. Each paid $.002 per share for
the Common Stock, then valued at $0.10 per share. The shares vest in four equal
annual installments commencing on the first anniversary of the date of the
issuance. If the valuation of the Company is greater than $50,000,000 in con-
nection with certain fundamental transactions, such as a merger in which the
Company is not the surviving entity, a merger in which the Company survives,
but fifty percent or more of the voting stock outstanding prior to the merger
is transferred to new holders, or a sale of all or substantially all of the
assets of the Company, all such shares vest immediately. Prior to vesting, the
stockholders have full voting and dividend rights, but unvested shares may not
be transferred, with certain exceptions for, among others, transfers to family
members and to trusts for family members. The Company has the option to repur-
chase all unvested shares owned by a particular founder for $0.10 per share
upon termination of that founder's service to the Company as an employee, non-
employee director or non-employee consultant. However, the Company has cove-
nanted with certain investors not to make repurchases that would limit such
investors' qualification under Section 1202 of the Code. To make such a repur-
chase, the Company would need to obtain a waiver from such investors. In addi-
tion, for two years following the initial public offering, the holders of
shares of such stock, whether vested or unvested, are required to agree not to
transfer their shares for up to 180 days after the effective date of a regis-
tration statement filed pursuant to the Securities Act of 1933.
 
See "Management--Executive Compensation" for a description of option grants in
1996 to certain of the founders, "Management--Director Compensation and Commit-
tees" for a description of the Company's indemnification agreements with cer-
tain directors, including Ms. Lamont, and "Executive Compensation--Agreements
with Employees" for a description of the Company's confidentiality and inven-
tions agreements with all employees, including Drs. Nash, Collett, McKinlay,
Griffin and Diana. See "--Financings" for a description of the founders' par-
ticipation in the Company's equity financings.
 
FINANCINGS
 
Since December 1994, various officers, directors and greater than 5% stock-
holders have participated in the Company's equity financings. For information
regarding beneficial ownership of the Company's securities by officers, direc-
tors and greater than 5% stockholders of the Company, see "Principal Stockhold-
ers." These financings have included the following:
 
Between December 1994 and January 1995, the Company sold 675,000 shares of its
Series A Preferred Stock at $0.50 per share to a limited number of accredited
investors in a private placement. In connection with this offering, Drs. Nash,
Collett, McKinlay, Griffin and Diana purchased 140,000, 120,000, 20,000, 50,000
and 20,000 shares of Series A Preferred Stock, respectively. See "--Transac-
tions with Founders" for a description of the acquisition by these individuals
of Common Stock of the Company pursuant to restricted stock purchase agreements
and the acquisition of Series A Preferred Stock by Oak Investment Partners VI,
Limited Partnership and Oak VI Affiliates Fund, Limited Partnership. All shares
of Series A Preferred Stock converted into an aggregate of 344,250 shares of
Common Stock upon the closing of the Company's initial public offering.
 
Between June 1995 and October 1995, the Company sold 7,060,000 shares of Series
B Preferred Stock at $1.00 per share to a limited number of accredited
investors in a private placement. In connection with this financing, Oak
Investment Partners VI, Limited Partnership, Sevin Rosen Fund IV L.P. and Tech-
nology Leaders, L.P. each purchased two 9.5% Convertible Demand Promissory
Notes from the Company in the principal amounts of $100,000 and $50,000, and
Dr. Nash purchased a 9.5% Convertible Demand Promissory Note in the principal
amount of $30,000. All the notes were cancelled on the first closing date of
the sale of Series B Preferred Stock in partial or full payment for the shares
purchased at such closing by each party. In connection with their purchases of
notes, the Company issued to each of Oak Investment Partners VI, Limited Part-
nership, Sevin Rosen Fund IV L.P. and Technology Leaders, L.P. warrants to pur-
chase 49,998 shares of Series B Preferred Stock and to Dr. Nash a warrant to
purchase 10,000 shares of Series B Preferred Stock, all with exercise prices of
$1.00 per share. Oak Investment Partners VI, Limited Partnership subsequently
transferred rights to purchase 760 shares under the first warrant and 380
shares under the second warrant to its affiliate, Oak VI Affiliates Fund Lim-
ited Partnership. Technology Leaders L.P. later transferred its warrants to its
successor fund and an affiliate as follows: Technology Leaders II, L.P.
received warrants to purchase 18,577 and 9,287 shares, respectively, and Tech-
nology Leaders II Offshore C.V. received warrants to purchase 14,756 and 7,378
shares, respectively. Upon the closing of the Company's initial public offer-
ing, the warrants became exercisable for an aggregate of 81,597 shares of
Common Stock at $1.96 per share. In June 1997, the Company issued 71,795 shares
of Common Stock pursuant to a cashless exercise of warrants that were otherwise
exercisable on a cash basis for 81,597 shares of Common Stock.
 
                                       47
<PAGE>
 
Also in connection with the Series B financing, Oak Investment Partners VI,
Limited Partnership and Oak VI Affiliates Fund Limited Partnership purchased
1,954,400 and 45,600 shares of Series B Preferred Stock, respectively, Sevin
Rosen Fund IV L.P. and Sevin Rosen Bayless Management Company purchased
2,000,000 and 10,000 shares of Series B Preferred Stock, respectively, Tech-
nology Leaders II L.P. and Technology Leaders II Offshore C.V. purchased
1,114,600 and 885,400 shares of Series B Preferred Stock, respectively, and New
York Life Insurance Company purchased 1,000,000 shares of Series B Preferred
Stock. In addition, Dr. Nash purchased 30,000 shares of Series B Preferred
Stock. All outstanding shares of Series B Preferred Stock converted into an
aggregate of 3,600,600 shares of Common Stock upon the closing of the Company's
initial public offering.
 
In May 1996, the Company sold 3,222,222 shares of Series C Preferred Stock at
$2.25 per share to a limited number of accredited investors in a private place-
ment. In connection with the financing, Oak Investment Partners VI, Limited
Partnership and Oak VI Affiliates Fund, Limited Partnership purchased 497,830
and 11,615 shares of Series C Preferred Stock, respectively, Sevin Rosen Fund
IV L.P. and Sevin Rosen Bayless Management Company purchased 424,099 and 2,222
shares of Series C Preferred Stock, respectively, Technology Leaders II L.P.
and Technology Leaders II Offshore C.V. purchased 245,062 and 194,669 shares of
Series C Preferred Stock, respectively and Frazier Healthcare II L.P. and New
York Life Insurance Company purchased 1,500,000 and 214,503 shares of Series C
Preferred Stock, respectively. In addition, Drs. Nash, Collett, Griffin and
Diana purchased 28,889, 31,112, 11,111 and 11,111 shares of Series C Preferred
Stock, respectively. All outstanding shares of Series C Preferred Stock con-
verted into an aggregate of 1,643,333 shares of Common Stock upon closing of
the Company's initial public offering.
 
Oak Investment Partners VI, Limited Partnership and Oak VI Affiliates Fund,
Limited Partnership purchased 102,606 shares of Common Stock and 2,394 shares
of Common Stock, respectively, in connection with the Company's initial public
offering in November 1996. The Dow Family Trust purchased 14,000 shares of
Common Stock in connection with the Company's initial public offering. Mr. Dow
and his spouse are trustees of The Dow Family Trust, and he and members of his
immediate family are the beneficiaries.
 
RIGHT GRANT AND EXERCISE
 
Pursuant to a right granted in December 1994, Dr. Baldino purchased 51,000
shares of Common Stock under a January 1996 restricted stock purchase agreement
at $0.10 per share. The shares vest in four equal annual installments com-
mencing on the date of issuance. The restrictions on the shares are identical
to the restrictions on the shares of Common Stock issued to founders. See "--
Transactions with Founders."
 
See "Executive Compensation--Option Grants and Year-End Values" for a descrip-
tion of option grants to executive officers.
 
PROMISSORY NOTE
 
On June 12, 1997, the Company loaned $104,107 to Jon M. Rogers, M.D., Vice
President-Clinical Research of the Company, in connection with the relocation
of his residence required by his employment with the Company. The loan is evi-
denced by a promissory note (the "Rogers Note"), which bears interest at an
annual rate of 6.8% and comes due in full on the date of Dr. Rogers' resigna-
tion from the Company or in monthly installments beginning on the date of ter-
mination of Dr. Rogers' employment with the Company (other than by resigna-
tion), and extending over a period of between 48 months and 192 months thereaf-
ter, depending upon when the termination of employment occurs. The Rogers Note
provides that on each of the first four anniversaries of the date of the Rogers
Note, 25% of the original principal amount of the loan will be forgiven by the
Company so long as Dr. Rogers is in the Company's employ.
 
                                       48
<PAGE>
 
                             PRINCIPAL STOCKHOLDERS
   
The following table sets forth certain information regarding the beneficial
ownership of the Common Stock as of July 21, 1997, except as otherwise indi-
cated in the relevant footnote, as adjusted for the sale by the Company of the
Common Stock offered hereby, by (i) each person or group who is known by the
Company to own beneficially more than 5% of the Common Stock, (ii) each of the
Company's directors, (iii) each of the Named Executive Officers and (iv) all
current executive officers and directors as a group.     
 
                                                    ---------------------------
<TABLE>   
<CAPTION>
                                                          PERCENTAGE OF
                                                        OUTSTANDING SHARES
                                               NUMBER BENEFICIALLY OWNED (1)
                                            OF SHARES -----------------------
                                         BENEFICIALLY BEFORE THE    AFTER THE
                                             OWNED(1)   OFFERING  OFFERING(2)
                                         ------------ ----------  -----------
<S>                                      <C>          <C>         <C>
5% STOCKHOLDERS
Oak Investment Partners VI, Limited         1,573,003       17.2%        14.1%
Partnership(3)..........................
One Gorham Island
Westport, Connecticut 06880
Technology Leaders II L.P.(4)...........    1,266,700       13.9         11.4
800 The Safeguard Building
435 Devon Park Drive
Wayne, Pennsylvania 19087
Sevin Rosen Fund IV L.P.(5).............    1,264,962       13.8         11.4
550 Lytton Avenue, Suite 200
Palo Alto, CA 94301
Frazier Healthcare II L.P.(6)...........      765,000        8.4          6.9
Two Union Square
601 Union Street, Suite 2110
Seattle, Washington 98101
New York Life Insurance Company(7)......      619,397        6.8          5.6
51 Madison Avenue
New York, New York 10016
 
Wellington Management Company, LLP(8)...      503,000        5.5          4.5
75 State Street
Boston, MA 02109
NAMED EXECUTIVE OFFICERS AND DIRECTORS
Ann H. Lamont(3)........................    1,573,003       17.2         14.1
Steve Dow(5)(9).........................    1,278,962       14.0         11.5
Christopher Moller(4)...................    1,266,700       13.9         11.4
Jon N. Gilbert(6).......................      765,000        8.4          6.9
Claude H. Nash(10)......................      447,483        4.9          4.0
Marc S. Collett(11).....................      195,209        2.1          1.8
Mark A. McKinlay(12)....................      127,245        1.4          1.1
Johanna A. Griffin(13)..................       99,857        1.1            *
Guy D. Diana(14)........................       83,546          *            *
Frank Baldino, Jr.(15)..................       51,000          *            *
Vincent J. Milano(16)...................        9,836          *            *
Jon M. Rogers(17).......................        9,036          *            *
Thomas F. Doyle.........................          714          *            *
Michael Kelly...........................          --         --           --
All directors and executive officers as     5,907,591       64.6         53.0
a group (14 persons)(18)................
</TABLE>    
 * Less than one percent.
 
                                       49
<PAGE>
 
   
 (1) Applicable percentage of ownership is based on 9,148,911 shares of Common
Stock outstanding as of July 21, 1997 and 11,148,911 shares of Common Stock to
be outstanding upon consummation of this offering. In accordance with the rules
of the Securities and Exchange Commission, shares underlying options or war-
rants to purchase Common Stock that are exercisable as of the date of this Pro-
spectus or exercisable within 60 days thereafter are deemed outstanding and to
be beneficially owned by the person holding such option or warrant for purposes
of computing such person's percentage ownership, but are not treated as out-
standing for the purpose of computing the percentage ownership of any other
person.     
 (2) Assumes no exercise of Underwriters' over-allotment option.
 (3) Includes 1,537,139 shares of Common Stock owned by Oak Investment Partners
VI, Limited Partnership and 35,864 shares of Common Stock owned by Oak VI
Affiliates Fund, Limited Partnership. Ms. Lamont is a managing member of Oak
Associates VI, LLC and Oak VI Affiliates, LLC, the general partners of Oak
Investment Partners VI, Limited Partnership and Oak VI Affiliates Fund, Limited
Partnership, respectively. Ms. Lamont shares voting and investment power with
respect to the limited partnerships with the other managing members of Oak
Associates VI, LLC and Oak VI Affiliates, LLC, respectively. Ms. Lamont dis-
claims beneficial ownership of shares in which she has no pecuniary interest.
See "Description of Capital Stock--Warrants."
 (4) Includes 705,931 shares of Common Stock owned by Technology Leaders II
L.P. and 560,769 shares of Common Stock owned by Technology Leaders II Offshore
C.V. Dr. Moller is Managing Director of Technology Leaders II Management L.P.,
which is the general partner of Technology Leaders II L.P. and of Technology
Leaders II Offshore C.V. Dr. Moller shares voting and investment power with the
other managing directors of the general partner of the stockholders and dis-
claims beneficial ownership of shares in which he has no pecuniary interest.
See "Description of Capital Stock--Warrants."
 (5) Includes 1,258,728 shares of Common Stock owned by Sevin Rosen Fund IV
L.P. and 6,234 shares of Common Stock owned by Sevin Rosen Bayless Management
Company. Mr. Dow is general partner of SRB Associates IV L.P., general partner
of Sevin Rosen IV L.P., and an officer of Sevin Rosen Bayless Management Com-
pany. He shares voting and investment power with the other general partners and
officers, as applicable, and disclaims beneficial ownership of shares in which
he has no pecuniary interest. See "Description of Capital Stock--Warrants."
 (6) Mr. Gilbert is a member of Frazier Management, L.L.C., which is the man-
aging member of FHMII, LLC, which, in turn, is the general partner of Frazier
Healthcare II, L.P. Mr. Gilbert shares voting and investment power with the
other members of Frazier Management, L.L.C. and disclaims beneficial ownership
of shares in which he has no pecuniary interest.
   
 (7) As reflected in a Schedule 13G dated January 22, 1997.     
       
       
          
 (8) According to Wellington Management Company, LLP ("WMC"), it (i) is a reg-
istered investment advisor under the Investment Advisors Act of 1940, and (ii)
has shared power to dispose or direct the disposition of and to vote all of
such shares.     
   
 (9) Includes 14,000 shares of Common Stock owned by The Dow Family Trust, of
which Mr. Dow and his spouse are trustees and he and members of his family are
beneficiaries.     
   
(10) Includes 165,750 issued but unvested shares of Common Stock purchased by
Dr. Nash upon the founding of the Company in December 1994. Also includes 4,462
shares of Common Stock issuable upon exercise of currently exercisable options
and 200 shares of Common Stock held by Dr. Nash as custodian for two minor
children. See "Certain Transactions--Transactions with Founders" and "Descrip-
tion of Capital Stock--Warrants."     
   
(11) Includes 51,000 issued but unvested shares of Common Stock purchased by
Dr. Collett upon the founding of the Company in December 1994. Also includes
11,857 shares of Common Stock issuable upon exercise of currently exercisable
options. See "Certain Transactions--Transactions with Founders."     
   
(12) Includes 51,000 issued but unvested shares of Common Stock purchased by
Dr. McKinlay upon the founding of the Company in December 1994. Also includes
15,045 shares of Common Stock issuable upon exercise of currently exercisable
options. See "Certain Transactions--Transactions with Founders."     
   
(13) Includes 31,875 issued but unvested shares of Common Stock purchased by
Dr. Griffin upon the founding of the Company in December 1994. Also includes
4,940 shares of Common Stock issuable upon exercise of currently exercisable
options. See "Certain Transactions--Transactions with Founders."     
   
(14) Includes 31,875 issued but unvested shares of Common Stock purchased by
Dr. Diana upon the founding of the Company in December 1994. Also includes
2,072 shares of Common Stock issuable upon exercise of currently exercisable
options See "Certain Transactions--Transactions with Founders."     
   
(15) Includes 25,500 issued but unvested shares of Common Stock purchased by
Dr. Baldino in January 1996.     
 
                                       50
<PAGE>
 
   
(16) Represents 1,134 shares of Common Stock and currently exercisable options
to purchase 8,702 shares of Common Stock.     
   
(17) Represents 9,036 shares of Common Stock issuable upon exercise of exercis-
able options.     
   
(18) Includes 357,000 issued but unvested shares of Common Stock purchased by
the founders and a director of the Company. Includes options to purchase 56,114
shares of Common Stock, which either are exercisable as of July 21, 1997 or
will be exercisable within 60 days of the date of this Prospectus.     
 
                                       51
<PAGE>
 
                          DESCRIPTION OF CAPITAL STOCK
 
GENERAL
 
See the Second Amended and Restated Certificate of Incorporation, as amended
(the "Certificate"), and By-Laws of the Company, copies of which are filed as
exhibits to the Registration Statement of which this Prospectus is a part, for
additional information relating to the description of capital stock below.
 
The authorized capital stock of the Company consists of 32,000,000 shares,
including 27,000,000 shares of Common Stock, par value $0.002 per share, and
5,000,000 shares of Preferred Stock, par value $0.001 per share. At July 1,
1997 there were 9,148,911 shares of Common Stock outstanding held of record by
41 stockholders and no shares of Preferred Stock outstanding.
 
COMMON STOCK
 
Holders of Common Stock are entitled to one vote for each share held of record
on all matters submitted to a vote of stockholders and do not have cumulative
voting rights. Elections of directors are determined by a plurality of the
votes cast and the Board of Directors is divided into three classes, as nearly
equal in number as possible. The Certificate may be amended as permitted by
law. Except as otherwise required by law, all other matters are determined by a
majority of the votes cast. Holders of Common Stock are entitled to receive
ratably such dividends, if any, as may be declared by the Board of Directors
out of funds legally available therefor, subject to any preferential dividend
rights of outstanding Preferred Stock (none of which will be outstanding upon
the closing of this offering). Upon the liquidation, dissolution or winding up
of the Company, subject to any preferential liquidation rights of outstanding
Preferred Stock, the holders of Common Stock are entitled to receive ratably
the net assets of the Company available after the payment of all debts and
other liabilities. Holders of the Common Stock have no preemptive, subscrip-
tion, redemption or conversion rights. The outstanding shares of Common Stock
are fully paid and nonassessable. The rights, preferences and privileges of
holders of Common Stock are subject to, and may be adversely affected by, the
rights of the holders of shares of any series of Preferred Stock which the Com-
pany may designate and issue in the future. See "Risk Factors--Availability of
Preferred Stock for Issuance; Anti-Takeover Provisions," "--Preferred Stock"
and "--Anti-Takeover Provisions."
 
PREFERRED STOCK
 
The Company has authorized 5,000,000 shares of Preferred Stock, which the Board
of Directors has discretion to issue in such series and with such preferences
and rights as it may designate without the approval of the holders of Common
Stock. Such preferences and rights may be superior to those of the holders of
Common Stock. For example, the holders of Preferred Stock may be given a pref-
erence in payment upon liquidation of the Company, or for the payment or accu-
mulation of dividends before any distributions are made to the holders of
Common Stock. No shares of Preferred Stock are currently outstanding, none will
be outstanding upon the closing of this offering, and the Company has no plans,
agreements or understandings for the issuance of any shares of any series of
Preferred Stock. For a description of the possible anti-takeover effects of the
Preferred Stock, see "Risk Factors--Availability of Preferred Stock for Issu-
ance; Anti-Takeover Provisions" and "--Anti-Takeover Provisions."
 
WARRANTS
 
Pursuant to a Warrant Agreement dated as of September 13, 1995 (the "Warrant
Agreement"), the Company issued a warrant to purchase 42,500 shares of Series B
Preferred Stock to Comdisco, Inc. ("Comdisco"), an equipment supplier in con-
nection with a Master Lease Agreement between the Company and the equipment
supplier (the "Equipment Warrant"). Upon the closing of the Company's initial
public offering, the Equipment Warrant automatically became exercisable for
21,675 shares of Common Stock. The Equipment Warrant is exercisable at a price
of $2.94 per share and expires in November 2001. At Comdisco's discretion, the
purchase price may be paid in cash or by surrender of shares purchasable on
exercise pursuant to a formula in the agreement. The number of shares of Common
Stock purchasable under the warrant and the exercise price of the warrant are
subject to adjustment in the event of certain recapitalizations, reorganiza-
tions, stock splits and combinations and in the event of certain dilutive issu-
ances of capital stock by the Company. In addition, if the total cost of equip-
ment leased under the Master Lease Agreement exceeds $750,000, Comdisco will be
entitled to purchase additional shares under the warrant, as determined by a
formula in the Warrant Agreement.
 
INDEMNIFICATION AND LIMITATION OF LIABILITY
 
The Company's Certificate provides that a director of the Company shall not be
personally liable to the Company or its stockholders for monetary damages for a
breach of fiduciary duty as a director, except for liability (i) for any breach
of such
 
                                       52
<PAGE>
 
person's duty of loyalty, (ii) for acts or omissions not in good faith or
involving intentional misconduct or a knowing violation of law, (iii) for the
payment of unlawful dividends and certain other actions prohibited by Delaware
corporate law, and (iv) for any transaction resulting in receipt by such person
of an improper personal benefit.
 
The Company has obtained a directors' and officers' liability insurance policy
which provides directors and officers with insurance coverage for losses
arising from claims based on breaches of duty, negligence, error and other
wrongful acts. At present, there is no pending litigation or proceeding, and
the Company is not aware of any threatened litigation or proceeding, involving
any director, officer, employee or agent where indemnification will be required
or permitted under the Certificate or By-Laws. For a description of the
Company's indemnification agreements with certain of its directors, see "Cer-
tain Transactions--Transactions with Founders."
 
ANTI-TAKEOVER PROVISIONS
 
Classified Board and Other Matters
Upon the closing of the Company's initial public offering, the Company's Board
of Directors was divided into three classes, as nearly equal in number as pos-
sible. Each class of directors will serve (after a transitional period in which
the first class will serve until their successors have been elected and quali-
fied at the 1997 annual meeting of stockholders, the second class will serve
until their successors have been elected and qualified at the 1998 annual
meeting of stockholders and the third class will serve until their successors
have been elected and qualified at the 1999 annual meeting of stockholders),
for a term of three years and until their successors have been elected and
qualified. Accordingly, the Company's officers and directors, and related
stockholders who hold a majority of the shares of Common Stock entitled to vote
in any election of directors may elect all of the directors standing for elec-
tion and may exert considerable influence over the management and policies of
the Company and all matters requiring stockholder approval, including funda-
mental transactions. Moreover, under the Delaware General Corporation Law and
the Certificate, stockholders may remove a director only for cause. The classi-
fication of the Board of Directors, the voting control of the officers and
directors and the limitation on the removal of directors could have the effect
of making it more difficult for a third party to acquire, or discouraging a
third party from acquiring, control of the Company.
 
In addition, the ability of the Board of Directors to establish the rights of,
and to issue, substantial amounts of Preferred Stock without the need for
stockholder approval, which Preferred Stock may be used to create voting
impediments with respect to changes in control of the Company or dilute the
stock ownership of holders of Common Stock seeking to obtain control of the
Company, may have the effect of discouraging, delaying or preventing a change
in control of the Company. See "Risk Factors--Availability of Preferred Stock
for Issuance; Anti-Takeover Provisions," "--Common Stock" and "--Preferred
Stock."
 
Section 203 of Delaware General Corporation Law
Upon the consummation of the offering made hereby, the Company will be subject
to the provisions of Section 203 of the Delaware General Corporation Law, an
anti-takeover law ("Delaware 203"). In certain circumstances, Delaware 203 pre-
vents certain Delaware corporations, including those whose securities are
listed on the Nasdaq National Market, from engaging in a "business combination"
(which includes a merger or sale of more than 10% of the corporation's assets)
with any "Interested Stockholder" (generally, a stockholder who owns 15% or
more of the corporation's outstanding voting stock) for three years following
the date on which such stockholder became an "Interested Stockholder," unless
(i) the business combination or transaction which resulted in the Interested
Stockholder's becoming an Interested Stockholder is approved by the corpora-
tion's board of directors prior to the date the Interested Stockholder becomes
an Interested Stockholder or (ii) the transaction is approved by the board of
directors and the holders of at least 66 2/3% of the outstanding voting stock
of the corporation (excluding shares held by the Interested Stockholder). The
statutory ban does not apply if, upon consummation of the transaction in which
any person becomes an Interested Stockholder, the Interested Stockholder owns
at least 85% of the outstanding voting stock of the corporation (excluding
shares held by persons who are both directors and officers or by certain
employee stock plans). A Delaware corporation may "opt out" of Delaware 203
with an express provision either in its original certificate of incorporation
or in its certificate of incorporation or by-laws resulting from a stockhold-
ers' amendment approved by at least a majority of the outstanding voting
shares. The Company is subject to Delaware 203 and has not "opted out" of its
provisions. The business combination provisions of Section 203 of the Delaware
General Corporation law may have the effect of deterring merger proposals,
tender offers or other attempts to effect changes in control of the Company
that are not negotiated and approved by the Board of Directors.
 
TRANSFER AGENT AND REGISTRAR
 
The transfer agent and registrar for the shares of Common Stock is StockTrans,
Inc.
 
                                       53
<PAGE>
 
                        SHARES ELIGIBLE FOR FUTURE SALE
 
Upon completion of this offering, the Company will have a total of 11,148,911
shares of Common Stock outstanding (11,448,911 shares if the underwriter's
over-allotment is exercised in full). Of these shares, 4,587,500 shares of
Common Stock (4,887,500 shares if the underwriter's over-allotment is exercised
in full) will be freely tradeable without restriction or registration under the
Securities Act by persons other than "affiliates" of the Company, as defined
under the Securities Act. The remaining 6,561,411 shares of Common Stock out-
standing are "restricted securities" as that term is defined by Rule 144 as
promulgated under the Securities Act and may not be resold except pursuant to
an effective registration statement or an applicable exemption from registra-
tion, including Rule 144.
 
In general, under Rule 144 as currently in effect, any person (or persons whose
shares are aggregated) who has beneficially owned restricted securities for at
least one year (including the holding period of any prior owner except an
affiliate), is entitled to sell, within any three-month period, a number of
shares that does not exceed the greater of 1% of the then outstanding shares of
Common Stock (approximately 111,489 shares after the sale of Common Stock
offered hereby) or the average weekly trading volume of the Common Stock during
the four calendar weeks preceding such sale, provided that certain public
information about the Company as required by the rule is then available and the
seller complies with certain other requirements. In addition, under Rule 144(k)
a person who is not an affiliate, has not been an affiliate within three months
prior to sale and has beneficially owned the shares proposed to be sold for at
least two years (including the holding period of any prior owner except an
affiliate), is entitled to sell such shares under Rule 144 without regard to
any of the limitations described above. Of the 6,561,411 shares of Common Stock
that are considered to be "restricted securities," (i) all of such shares are
eligible for immediate resale under Rule 144 subject to the conditions and lim-
itations of that rule, and (ii) 714,000 shares will be subject in varying
degrees to the additional restrictions of a stock purchase agreement. Holders
of 5,851,277 of these 6,561,411 shares have agreed not to directly or indi-
rectly sell or dispose of their shares without the prior written consent of
J.P. Morgan Securities Inc. for a period of 90 days following the date of this
Prospectus. See "Certain Transactions--Transactions with Founders."
 
As of July 1, 1997, options to purchase a total of 707,037 shares of Common
Stock were outstanding with a weighted average exercise price of $4.07 per
share, of which options to purchase 62,794 shares of Common Stock were exercis-
able. An additional 471,288 shares of Common Stock were available for future
option grants under the Company's stock option plan as of July 1, 1997. The
Company has also granted warrants to purchase Common Stock. Upon the closing of
this offering, the Company will have outstanding warrants exercisable for
21,675 shares of Common Stock at $2.94 per share. All shares subject to options
and warrants are subject to lock-up agreements. See "Management--Stock
Options," and "Description of Capital Stock--Warrants."
 
Rule 701 under the Securities Act provides an exemption from the registration
requirements of the Act of offers and sales of securities issued pursuant to
certain compensatory benefit plans or written contracts of a company not sub-
ject to the reporting requirements of Sections 13 or 15(d) of the Securities
Exchange Act of 1934, as amended. The rule also provides that shares of Common
Stock acquired on the exercise of outstanding options may be resold by persons
other than affiliates subject only to the manner of sale provisions of Rule
144, and by affiliates subject to all provisions of Rule 144 except its one-
year minimum holding period. The Company also intends to file one or more reg-
istration statements on Form S-8 under the Securities Act to register shares of
Common Stock subject to stock options, which would also permit the resale of
the shares acquired upon the exercise of such options.
 
As of the date hereof, stockholders of the Company are entitled to certain pig-
gyback and demand registration rights with regard to 5,659,979 shares of Common
Stock upon the closing of this offering. In addition, the founders of the Com-
pany are entitled to certain piggyback registration rights with regard to
879,750 outstanding shares of Common Stock. By exercising such registration
rights, subject to certain limitations, such holders could cause a significant
number of shares to be registered and sold in the public market. Such sales may
have an adverse effect on the market price for the Common Stock and could
impair the Company's ability to raise capital through an offering of its equity
securities. All such rights in connection with this offering have been waived.
 
In addition, Rule 144A permits unlimited resales of restricted shares under
certain circumstances involving Qualified Institutional Buyers, which are gen-
erally defined as institutions with over $100 million invested in securities.
Such resales can be made without regard to any volume or other restrictions.
 
No predictions can be made of the effect, if any, that the sale or availability
for sale of additional shares of Common Stock, under Rule 144, pursuant to reg-
istration rights or otherwise, will have on the trading price of the Common
Stock. Nevertheless, sales of substantial amounts of such shares in the public
market (and distributions by the Company's principal venture capital investors
and sales by such distributees who may qualify for resales under Rule 144(k)
without any volume limitation), or the perception that such sales could occur,
could adversely affect the trading price of the Common Stock and could impair
the Company's future ability to raise capital through an offering of its equity
securities.
 
                                       54
<PAGE>
 
                                  UNDERWRITING
 
Under the terms and subject to the conditions contained in an Underwriting
Agreement dated the date of this Prospectus (the "Underwriting Agreement"), the
Underwriters named below, for whom J.P. Morgan Securities Inc. and Cowen & Com-
pany are acting as representatives (the "Representatives"), have severally
agreed to purchase, and the Company has agreed to sell them, the respective
numbers of shares of Common Stock set forth opposite their names below. Under
the terms and conditions of the Underwriting Agreement, the Underwriters are
obligated to take and pay for all such shares of Common Stock, if any are
taken. Under certain circumstances, the commitments of nondefaulting Under-
writers may be increased as set forth in the Underwriting Agreement.
 
                                                                         ------
<TABLE>
<CAPTION>
                                                                       NUMBER OF
                                                                          SHARES
   UNDERWRITERS                                                        ---------
   <S>                                                                 <C>
   J.P. Morgan Securities Inc. .......................................
   Cowen & Company ...................................................
                                                                       ---------
     Total............................................................ 2,000,000
                                                                       ---------
</TABLE>
 
The Underwriters propose initially to offer the Common Stock directly to the
public at the price set forth on the cover page of this Prospectus and to cer-
tain dealers at such price less a concession not in excess of $     per share.
The Underwriters may allow, and such dealers may reallow, a concession not in
excess of $     per share to certain other dealers. After the initial public
offering of the Common Stock, the public offering price and such concession may
be changed.
 
The Company has granted to the Underwriters an option, expiring at the close of
business on the 30th day after the date of this Prospectus, to purchase up to
300,000 additional shares of Common Stock at the public offering price, less
the underwriting discount. The Underwriters may exercise such option solely for
the purpose of covering over-allotments, if any. To the extent the Underwriters
exercise the option, each Underwriter will have a firm commitment, subject to
certain conditions, to purchase approximately the same percentage of such addi-
tional shares as the number set forth next to such Underwriter's name in the
preceding table bears to the total number of shares of Common Stock offered
hereby.
 
The Company has agreed to indemnify the Underwriters against certain liabili-
ties, including liabilities under the Securities Act.
   
The Company, its officers and directors and certain stockholders related to the
directors, have agreed, subject to certain exceptions, not to, directly or
indirectly, (i) sell, grant any option to purchase or otherwise transfer or
dispose of any shares of Common Stock or securities convertible into or
exchangeable or exercisable for shares of Common Stock or file a registration
statement under the Securities Act with respect to the foregoing or (ii) enter
into any swap or other agreement or transaction that transfers, in whole or in
part, the economic consequence of ownership of the Common Stock, without the
prior written consent of J.P. Morgan Securities Inc., for a period of 90 days
after the date of this Prospectus. The foregoing does not prohibit the
Company's sale of shares of Common Stock pursuant to the Underwriting Agree-
ment, the grant of options under the Company's 1995 Stock Option Plan, the
issuance of shares of Common Stock upon the exercise of options granted under
the 1995 Stock Option Plan or the issuance of shares of Common Stock upon the
exercise of outstanding warrants issued to Comdisco, Inc. J.P. Morgan Securi-
ties Inc. may, in its sole discretion at any time or from time to time, without
notice, release all or any portion of the shares subject to the lock-up
agreements.     
 
In connection with the offering, the Underwriters may engage in transactions
that stabilize, maintain or otherwise affect the price of the Common Stock.
Specifically, the Underwriters may overallot the offering, creating a syndicate
short position. In addition, the Underwriters may bid for, and purchase, shares
of Common Stock in the open market to cover syndicate shorts or to stabilize
the price of the Common Stock. Finally, the underwriting syndicate may reclaim
selling concessions allowed for distributing the Common Stock in the offering,
if the syndicate repurchases previously distributed Common Stock in syndicate
covering transactions, in stabilization transactions or otherwise. Any of these
activities may stabilize or maintain the market price of the Common Stock above
independent market levels. The Underwriters are not required to engage in these
activities, and may end any of these activities at any time.
 
                                       55
<PAGE>
 
The Underwriters and dealers may also engage in passive market making transac-
tions in the Common Stock in accordance with Rule 103 of Regulation M promul-
gated by the Securities and Exchange Commission. In general, a passive market
maker may not bid for, or purchase, the Common Stock at a price that exceeds
the highest independent bid. In addition, the net daily purchases made by any
passive market maker generally may not exceed 30% of its average daily trading
volume in the Common Stock during a specified two month prior period, or 200
shares, whichever is greater. A passive market maker must identify passive
market making bids as such on the Nasdaq electronic inter-dealer reporting sys-
tem. Passive market making may stabilize or maintain the market price of the
Common Stock above independent market levels. Underwriters and dealers are not
required to engage in passive market making and may end passive market making
activities at any time.
 
From time to time in the ordinary course of their respective businesses, the
Representatives and their respective affiliates have provided, and may in the
future provide, investment banking and other financial services to the Company
and its affiliates.
 
                                 LEGAL MATTERS
 
The validity of the securities offered hereby will be passed upon for the Com-
pany by Morgan, Lewis & Bockius LLP, Philadelphia, Pennsylvania, and for the
Underwriters by Davis Polk & Wardwell, New York, New York.
 
                                    EXPERTS
 
The financial statements of the Company as of December 31, 1995 and 1996 and
for the period from December 5, 1994 (inception) to December 31, 1994 and for
the years ended December 31, 1995 and 1996 have been included herein and in the
registration statement in reliance upon the report of KPMG Peat Marwick LLP,
independent certified public accountants, appearing elsewhere herein, and upon
the authority of said firm as experts in accounting and auditing.
 
                                       56
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                           Page
<S>                                                                        <C>
Independent Auditors' Report.............................................. F-2
Balance Sheets at December 31, 1995 and 1996 and March 31, 1997
(unaudited)............................................................... F-3
Statements of Operations for the period December 5, 1994 (inception) to
December 31, 1994, the years ended December 31, 1995 and 1996, the three
months ended March 31, 1996 and 1997 (unaudited) and the period December
5, 1994 (inception) to March 31, 1997 (unaudited)......................... F-4
Statements of Stockholders' Equity (Deficit) for the period December 5,
1994 (inception) to December 31, 1994, the years ended December 31, 1995
and 1996, and the three months ended March 31, 1997 (unaudited)........... F-5
Statements of Cash Flows for the period December 5, 1994 (inception) to
December 31, 1994, the years ended December 31, 1995 and 1996, the three
months ended March 31, 1996 and 1997 (unaudited) and the period December
5, 1994 (inception) to March 31, 1997 (unaudited)......................... F-6
Notes to Financial Statements............................................. F-7
</TABLE>
 
                                      F-1
<PAGE>
 
                          INDEPENDENT AUDITORS' REPORT
 
The Stockholders and Board of Directors
ViroPharma Incorporated:
 
We have audited the accompanying balance sheets of ViroPharma Incorporated (A
Development Stage Company) as of December 31, 1995 and 1996, and the related
statements of operations, stockholders' equity (deficit) and cash flows for the
period from December 5, 1994 (inception) to December 31, 1994 and for the years
ended December 31, 1995 and 1996 . These financial statements are the responsi-
bility 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 stan-
dards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of mate-
rial misstatement. An audit includes examining, on a test basis, evidence sup-
porting 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 pre-
sentation. We believe that our audits provide a reasonable basis for our opin-
ion.
 
In our opinion, the financial statements referred to above present fairly, in
all material respects, the financial position of ViroPharma Incorporated (A
Development Stage Company) as of December 31, 1995 and 1996, and the results of
its operations and its cash flows for the period from December 5, 1994 (incep-
tion) to December 31, 1994 and for the years ended December 31, 1995 and 1996,
in conformity with generally accepted accounting principles.
 
                                                     KPMG Peat Marwick LLP
 
Philadelphia, Pennsylvania
February 28, 1997
 
                                      F-2
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                                 BALANCE SHEETS
 
                         DECEMBER 31, 1995 AND 1996 AND
                           MARCH 31, 1997 (UNAUDITED)
 
<TABLE>
<CAPTION>
                                         -------------------------------------
                                              DECEMBER 31,
                                         ------------------------    MARCH 31,
                                                1995         1996         1997
                                         -----------  -----------  -----------
                                                                   (UNAUDITED)
<S>                                      <C>          <C>          <C>
ASSETS
Current assets:
  Cash and cash equivalents............. $   337,044  $10,810,310  $ 7,709,854
  Short term investments................   4,376,382   11,737,369   13,734,144
  Other current assets..................     103,948      197,171      220,044
                                         -----------  -----------  -----------
    Total current assets................   4,817,374   22,744,850   21,664,042
Equipment and leasehold improvements,
 net....................................         --       672,029      906,063
Restricted investment...................         --           --       300,000
Other assets............................      56,471       36,000       70,400
                                         -----------  -----------  -----------
    Total assets........................ $ 4,873,845  $23,452,879  $22,940,505
                                         ===========  ===========  ===========
LIABILITIES AND STOCKHOLDERS' EQUITY
 (DEFICIT)
Current liabilities:
  Accounts payable...................... $   310,560  $   356,171  $   274,753
  Notes payable.........................      37,500          --           --
  Loan payable--current.................         --           --       100,000
  Obligation under capital lease--
   current..............................         --        52,950       56,250
  Accrued expenses and other current
   liabilities..........................   1,198,939    2,334,026    2,955,724
                                         -----------  -----------  -----------
    Total current liabilities...........   1,546,999    2,743,147    3,386,727
Loan payable--noncurrent................         --           --       483,333
Obligation under capital lease--
 noncurrent.............................         --       104,571       99,979
                                         -----------  -----------  -----------
                                           1,546,999    2,847,718    3,970,039
                                         -----------  -----------  -----------
Mandatorily redeemable convertible
 preferred stock, par value $.001 per
 share (at redemption value which
 includes accretion of $19,104 at
 December 31, 1995); issuable in Series
 A, B and C. Authorized 10,315,000
 shares in 1995 and none in 1996 and
 1997; issued and outstanding 7,735,000
 shares in 1995 and none in 1996 and
 1997; converted into 5,588,191 common
 shares upon consummation of initial
 public offering in 1996................   7,416,604          --           --
                                         -----------  -----------  -----------
Stockholders' equity (deficit):
  Preferred stock, par value $.001 per
   share. Authorized 5,000,000 shares at
   December 31, 1996 and March 31, 1997;
   none outstanding.....................         --           --           --
  Common stock, par value $.002 per
   share. Authorized 12,790,000 shares
   at December 31, 1995 and 27,000,000
   shares at December 31, 1996 and March
   31, 1997; issued and outstanding
   828,750 shares at December 31, 1995,
   9,076,861 at December 31, 1996, and
   9,077,116 at March 31, 1997..........       1,657       18,154       18,154
  Additional paid-in capital............     103,577   31,758,996   31,763,030
  Deferred compensation.................     (47,775)    (661,337)    (608,598)
  Unrealized gains on available for sale
   securities...........................      26,742       58,311       98,257
  Deficit accumulated during the
   development stage....................  (4,173,959) (10,568,963) (12,300,377)
                                         -----------  -----------  -----------
      Total stockholders' equity
       (deficit)........................  (4,089,758)  20,605,161   18,970,466
Commitments:
                                         -----------  -----------  -----------
    Total liabilities and stockholders'
     equity (deficit)................... $ 4,873,845  $23,452,879  $22,940,505
                                         ===========  ===========  ===========
</TABLE>
- -------
See accompanying notes to financial statements.
 
                                      F-3
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF OPERATIONS
 
           PERIOD DECEMBER 5, 1994 (INCEPTION) TO DECEMBER 31, 1994,
                  THE YEARS ENDED DECEMBER 31, 1995 AND 1996,
           THE THREE MONTHS ENDED MARCH 31, 1996 AND 1997 (UNAUDITED)
   AND THE PERIOD DECEMBER 5, 1994 (INCEPTION) TO MARCH 31, 1997 (UNAUDITED)
 
<TABLE>
<CAPTION>
                          --------------------------------------------------------------------------------
                           DECEMBER 5,                                                              PERIOD
                                  1994                                                         DECEMBER 5,
                           (INCEPTION)        YEAR ENDED               THREE MONTHS                   1994
                                    TO       DECEMBER 31,             ENDED MARCH 31,       (INCEPTION) TO
                          DECEMBER 31,  ------------------------  ------------------------       MARCH 31,
                                  1994         1995         1996         1996         1997            1997
                          ------------  -----------  -----------  -----------  -----------  --------------
                                                                        (UNAUDITED)            (UNAUDITED)
<S>                       <C>           <C>          <C>          <C>          <C>          <C>
Revenues:
  License fee...........     $     --   $       --   $ 1,000,000  $       --   $       --     $  1,000,000
  Milestone revenue.....           --           --           --           --       750,000         750,000
  Grant revenue.........           --        90,813      436,081          --           --          526,894
                             ---------  -----------  -----------  -----------  -----------    ------------
    Total revenues......           --        90,813    1,436,081          --       750,000       2,276,894
                             ---------  -----------  -----------  -----------  -----------    ------------
Operating expenses
 incurred in the
 development stage:
  Research and
   development..........        75,779    2,930,106    6,694,703    1,415,429    1,908,252      11,608,840
  General and
   administrative.......       243,318    1,091,299    1,421,524      220,173      764,569       3,520,710
                             ---------  -----------  -----------  -----------  -----------    ------------
    Total operating
     expenses...........       319,097    4,021,405    8,116,227    1,635,602    2,672,821      15,129,550
                             ---------  -----------  -----------  -----------  -----------    ------------
    Loss from
     operations.........      (319,097)  (3,930,592)  (6,680,146)  (1,635,602)  (1,922,821)    (12,852,656)
Interest income, net....           --        75,730      285,142       55,824      191,407         552,279
                             ---------  -----------  -----------  -----------  -----------    ------------
    Net loss............     $(319,097) $(3,854,862) $(6,395,004) $(1,579,778) $(1,731,414)   $(12,300,377)
                             =========  ===========  ===========  ===========  ===========    ============
Accretion of redemption
 value attributable to
 mandatorily redeemable
 convertible preferred
 stock..................           --        19,104    1,597,341      116,415          --        1,616,445
                             ---------  -----------  -----------  -----------  -----------    ------------
Net loss allocable to
 common shareholders....     $(319,097) $(3,873,966) $(7,992,345) $(1,696,193) $(1,731,414)   $(13,916,822)
                             =========  ===========  ===========  ===========  ===========    ============
Pro forma net loss per
 share..................                $      (.98) $      (.93) $      (.32) $      (.19)
                                        ===========  ===========  ===========  ===========
Shares used in computing
 pro forma net loss per
 share..................                  3,931,743    6,839,674    4,933,093    9,076,986
                                        ===========  ===========  ===========  ===========
</TABLE>
- -------
See accompanying notes to financial statements.
 
                                      F-4
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                  STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT)
 
           PERIOD DECEMBER 5, 1994 (INCEPTION) TO DECEMBER 31, 1994,
                   THE YEARS ENDED DECEMBER 31, 1995 AND 1996
             AND THE THREE MONTHS ENDED MARCH 31, 1997 (UNAUDITED)
 
<TABLE>
<CAPTION>
                         -----------------------------------------------------------------------------------------------
                                                                                  UNREALIZED      DEFICIT
                                                             NOTES                  GAINS ON  ACCUMULATED          TOTAL
                           COMMON STOCK     ADDITIONAL  RECEIVABLE                 AVAILABLE   DURING THE  STOCKHOLDERS'
                         -----------------     PAID-IN   ON COMMON      DEFERRED    FOR SALE  DEVELOPMENT         EQUITY
                            SHARES  AMOUNT     CAPITAL       STOCK  COMPENSATION  SECURITIES        STAGE      (DEFICIT)
                         --------- ------- -----------  ----------  ------------  ---------- ------------  -------------
<S>                      <C>       <C>     <C>          <C>         <C>           <C>        <C>           <C>
Balance, December 5,
 1994 (Inception).......       --  $   --  $       --       $  --        $   --        $ --  $        --     $       --
 Issuance of common
  stock to founders.....   828,750   1,657      79,593      (1,625)      (79,625)        --           --             --
 Amortization of
  deferred
  compensation..........       --      --          --          --         15,925         --           --          15,925
 Net loss for period....       --      --          --          --            --          --      (319,097)      (319,097)
                         --------- ------- -----------  ----------  ------------   --------- ------------    -----------
Balance, December 31,
 1994...................   828,750   1,657      79,593      (1,625)      (63,700)        --      (319,097)      (303,172)
 Proceeds from notes
  receivable............       --      --          --        1,625           --          --           --           1,625
 Issuance costs of
  Series A and B
  preferred stock.......       --      --      (46,912)        --            --          --           --         (46,912)
 Unrealized gains on
  available for sale
  securities............       --      --          --          --            --       26,742          --          26,742
 Amortization of
  deferred
  compensation..........       --      --          --          --         15,925         --           --          15,925
 Accretion of redemption
  value attributable to
  mandatorily redeemable
  convertible preferred
  stock.................       --      --      (19,104)        --            --          --           --         (19,104)
 Value attributed to
  issuance of warrants..       --      --       90,000         --            --          --           --          90,000
 Net loss...............       --      --          --          --            --          --    (3,854,862)    (3,854,862)
                         --------- ------- -----------  ----------  ------------   --------- ------------    -----------
Balance, December 31,
 1995...................   828,750   1,657     103,577         --        (47,775)     26,742   (4,173,959)    (4,089,758)
 Deferred compensation
  resulting from grant
  of options............       --      --      753,461         --       (753,461)        --           --             --
 Amortization of
  deferred
  compensation..........       --      --          --          --        139,899         --           --         139,899
 Unrealized gains on
  available for sale
  securities............       --      --          --          --            --       31,569          --          31,569
 Issuance costs of
  Series C preferred
  stock.................       --      --      (27,100)        --            --          --           --         (27,100)
 Exercise of common
  stock options.........    72,420     145       6,955         --            --          --           --           7,100
 Value attributed to
  issuance of warrants..       --      --       19,920         --            --          --           --          19,920
 Accretion of redemption
  value attributable to
  mandatorily redeemable
  convertible preferred
  stock.................       --      --   (1,597,341)        --            --          --           --      (1,597,341)
 Conversion of preferred
  stock to common
  stock................. 5,588,191  11,177  16,253,022         --            --          --           --      16,264,199
 Issuance of common
  stock, net of issuance
  costs................. 2,587,500   5,175  16,246,502         --            --          --           --      16,251,677
 Net loss...............       --      --          --          --            --          --    (6,395,004)    (6,395,004)
                         --------- ------- -----------  ----------  ------------   --------- ------------    -----------
Balance, December 31,
 1996................... 9,076,861  18,154  31,758,996         --       (661,337)     58,311  (10,568,963)    20,605,161
 Exercise of common
  stock options
  (unaudited)...........       255     --           50         --            --          --           --              50
 Warrant expense
  (unaudited)...........       --      --        3,984         --            --          --           --           3,984
 Unrealized gain on
  available for sale
  securities
  (unaudited)...........       --      --          --          --            --       39,946          --          39,946
 Amortization of
  deferred compensation
  (unaudited)...........       --      --          --          --         52,739         --           --          52,739
 Net loss (unaudited)...       --      --          --          --            --          --    (1,731,414)    (1,731,414)
                         --------- ------- -----------  ----------  ------------   --------- ------------    -----------
Balance, March 31, 1997
 (unaudited)............ 9,077,116 $18,154 $31,763,030         --   $   (608,598)    $98,257 $(12,300,377)   $18,970,466
                         ========= ======= ===========  ==========  ============   ========= ============    ===========
</TABLE>
 
See accompanying notes to financial statements.
 
                                      F-5
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF CASH FLOWS
 
           PERIOD DECEMBER 5, 1994 (INCEPTION) TO DECEMBER 31, 1994,
                  THE YEARS ENDED DECEMBER 31, 1995 AND 1996,
           THE THREE MONTHS ENDED MARCH 31, 1996 AND 1997 (UNAUDITED)
   AND THE PERIOD DECEMBER 5, 1994 (INCEPTION) TO MARCH 31, 1997 (UNAUDITED)
 
<TABLE>
<CAPTION>
                         --------------------------------------------------------------------------------
                          DECEMBER 5,                                                              PERIOD
                                 1994                                                         DECEMBER 5,
                          (INCEPTION)        YEAR ENDED               THREE MONTHS                   1994
                                   TO       DECEMBER 31,             ENDED MARCH 31,       (INCEPTION) TO
                         DECEMBER 31,  ------------------------  ------------------------       MARCH 31,
                                 1994         1995         1996         1996         1997            1997
                         ------------  -----------  -----------  -----------  -----------  --------------
                                                                       (UNAUDITED)            (UNAUDITED)
<S>                      <C>           <C>          <C>          <C>          <C>          <C>
Cash flows from
 operating activities:
 Net loss..............  $   (319,097) $(3,854,862) $(6,395,004) $(1,579,778) $(1,731,414)   $(12,300,377)
 Adjustments to
  reconcile net loss to
  net cash used in
  operating activities:
 Non-cash compensation
  expense..............        15,925       15,925      139,899          --        52,739         224,488
 Non-cash warrant
  value................           --        90,000       19,920          --         3,984         113,904
 Depreciation and
  amortization
  expense..............           --           --        58,022          --        50,741         108,765
 Changes in assets and
  liabilities:
  Other current
   assets..............        (2,000)    (101,948)     (93,223)     (46,236)     (22,873)       (220,044)
  Other assets.........           --       (56,471)      20,471       20,324      (34,400)        (70,400)
  Accounts payable.....         2,207      308,353       45,611      310,145      (81,418)        274,753
  Accrued expenses and
   other current
   liabilities.........       103,335    1,095,604    1,135,087     (744,659)     621,698       2,955,724
                         ------------  -----------  -----------  -----------  -----------    ------------
   Net cash used in
    operating
    activities.........      (199,630)  (2,503,399)  (5,069,217)  (2,040,203)  (1,140,943)     (8,913,187)
                         ------------  -----------  -----------  -----------  -----------    ------------
Cash flows from
 investing activities:
 Purchase of
  equipment............           --           --      (730,052)         --      (284,775)     (1,014,828)
 Purchase of short-term
  investments..........           --   (11,018,731) (15,335,938)  (1,272,131)  (4,877,179)    (31,231,848)
 Sales of short-term
  investments..........           --     4,363,754          --           --           --        4,363,754
 Maturities of short-
  term investments.....           --     2,305,337    8,006,520    4,771,518    2,620,350      12,932,206
                         ------------  -----------  -----------  -----------  -----------    ------------
   Net cash provided by
    (used in) investing
    activities.........           --    (4,349,640)  (8,059,470)   3,499,387   (2,541,604)    (14,950,716)
                         ------------  -----------  -----------  -----------  -----------    ------------
Cash flows from
 financing activities:
 Net proceeds from
  issuance of preferred
  stock................        60,000    6,648,088    7,223,155          --           --       13,931,243
 Net proceeds from
  issuance of common
  stock................           --           --    16,258,777        5,000           50      16,258,827
 Proceeds from loan
  payable..............           --           --           --           --       600,000         600,000
 Proceeds received on
  notes receivable.....           --         1,625          --           --           --            1,625
 Proceeds from notes
  payable..............       162,500      517,500       12,500       12,500          --          692,500
 Payment of notes
  payable..............           --           --       (50,000)         --       (16,667)        (66,667)
 Obligation under
  capital lease........           --           --       157,521          --        (1,292)        156,229
                         ------------  -----------  -----------  -----------  -----------    ------------
   Net cash provided by
    financing
    activities.........       222,500    7,167,213   23,601,953       17,500      582,091      31,573,757
                         ------------  -----------  -----------  -----------  -----------    ------------
Net increase in cash
 and cash equivalents..        22,870      314,174   10,473,266    1,476,683   (3,100,456)      7,709,854
Cash and cash
 equivalents at
 beginning of period...           --        22,870      337,044      337,044   10,810,310             --
                         ------------  -----------  -----------  -----------  -----------    ------------
Cash and cash
 equivalents at end of
 period................  $     22,870  $   337,044  $10,810,310  $ 1,813,727  $ 7,709,854    $  7,709,854
                         ============  ===========  ===========  ===========  ===========    ============
Supplemental disclosure
 of noncash
 transactions:
 Conversion of Note
  Payable to Series A
  and Series B
  Preferred Stock......           --   $   642,500          --           --           --     $    642,500
 Conversion of
  mandatorily
  redeemable
  convertible preferred
  stock to common
  shares...............           --           --   $16,264,199          --           --     $ 16,264,199
 Notes issued for
  828,750 common
  shares...............  $      1,625          --           --           --           --     $      1,625
 Deferred
  compensation.........  $     79,625          --   $   753,461          --           --     $    833,086
 Accretion of
  redemption value
  attributable to
  mandatorily
  redeemable
  convertible preferred
  stock................           --   $    19,104  $ 1,597,341  $   116,415          --     $  1,616,445
 Unrealized gains on
  available for sale
  securities...........           --   $    26,742  $    31,569  $    26,742  $    39,946    $     98,257
</TABLE>
 
See accompanying notes to financial statements.
 
                                      F-6
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                         NOTES TO FINANCIAL STATEMENTS
 
                          DECEMBER 31, 1995 AND 1996
             (INFORMATION AS OF MARCH 31, 1997 AND WITH RESPECT TO
         THE THREE MONTHS ENDED MARCH 31, 1996 AND 1997 IS UNAUDITED)
 
1. ORGANIZATION AND BUSINESS ACTIVITIES
 
ViroPharma Incorporated (a development stage Company) (the "Company") was
incorporated in Delaware on December 5, 1994. The Company is a development
stage biopharmaceutical company committed to the discovery, development, and
commercialization of novel small molecule drugs to treat infections caused by
RNA viruses. The accompanying financial statements include the results of
operations of the Company from December 5, 1994 (inception) to March 31, 1997.
   
The Company is devoting substantially all of its efforts towards conducting
drug discovery and development, raising capital, conducting clinical trials
and pursuing regulatory approval for products under development, and
recruiting personnel and building infrastructure. In the course of such activ-
ities, the Company has sustained operating losses and expects such losses to
continue for the foreseeable future. The Company has not generated any signif-
icant revenues or product sales and has not achieved profitable operations or
positive cash flow from operations. The Company's deficit accumulated during
the development stage aggregated $12,300,377 through March 31, 1997. There is
no assurance that profitable operations, if ever achieved, could be sustained
on a continuing basis.     
 
The Company plans to continue to finance its operations with a combination of
stock issuances, private placements and follow-on public offerings, license
payments, payments from strategic research and development arrangements and,
in the longer term, revenues from product sales. There are no assurances, how-
ever, that the Company will be successful in obtaining an adequate level of
financing needed for the long-term development and commercialization of its
planned products.
 
2. BASIS OF ACCOUNTING AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
Cash and cash equivalents
The Company considers all highly liquid investments with an original maturity
of three months or less when purchased to be cash equivalents. All cash and
cash equivalents are held in United States (U.S.) financial institutions,
including commercial paper of U.S. companies, with a cost and fair value of
$248,659 at December 31, 1995, a cost and fair value of $11,047,013 and
$11,074,310, respectively, at December 31, 1996, and a cost and fair value of
$7,698,375 and $7,719,990, respectively, at March 31, 1997.
 
Short-term investments
Short-term investments consist primarily of debt securities backed by the U.S.
government. The Company's entire short-term investment portfolio is currently
classified as available for sale and is stated at fair value as determined by
quoted market values. Changes in the net unrealized holding gains and losses
are included as a separate component of stockholders' equity (deficit). For
purposes of determining gross realized gains and losses, the cost of short-
term investments sold is based upon specific identification. The Company has
not experienced any significant realized gains or losses on its investments
through March 31, 1997.
 
Concentration of credit risk
The Company invests its excess cash and short-term investments in accordance
with a policy objective that seeks to ensure both liquidity and safety of
principal. The policy limits investments to certain types of instruments
issued by the U.S. government and institutions with strong investment grade
credit ratings and places restrictions in their terms and concentrations by
type and issuer.
 
Equipment and leasehold improvements
Equipment and leasehold improvements are recorded at cost. Depreciation and
amortization is computed on a straight-line basis over the useful lives of the
assets or the lease term, whichever is shorter, ranging from two to seven
years.
 
The Company leases certain of its equipment and facilities under operating
leases. Operating lease payments are charged to operations over the related
period that such leased equipment is utilized in service.
 
 
                                      F-7
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
2. BASIS OF ACCOUNTING AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES--
(CONTINUED)
 
Assets and liabilities related to capital leases are recorded at the present
value of the future minimum rental payments using interest rates appropriate at
the inception of the lease. Capital lease amortization is included with depre-
ciation and amortization expense.
 
Expenditures for repairs and maintenance are expensed as incurred.
 
Patent costs
Patent application and maintenance costs are expensed as incurred.
 
Research and development
Research and product development costs are expensed as incurred.
 
Licensed technology
Costs incurred in obtaining the license rights to technology in the research
and development stage are expensed as incurred and in accordance with the spe-
cific contractual terms of such license agreements.
 
Accounting for income taxes
Deferred income tax assets and liabilities are determined based on differences
between the financial statement reporting and tax bases of assets and liabili-
ties and are measured using the enacted tax rates and laws that will be in
effect when the differences are expected to reverse. The measurement of
deferred income tax assets is reduced, if necessary, by a valuation allowance
for any tax benefits which are not expected to be realized. The effect on
deferred income tax assets and liabilities of a change in tax rates is recog-
nized in the period that such tax rate changes are enacted.
 
Revenue recognition--collaborative research, contract and license agreements
Collaborative research revenue from cost-reimbursement and grant agreements are
recorded as the related expenses are incurred, up to the contractual limits.
Contract and licensing revenue is recognized when milestones are met and the
Company's specific performance obligations have been satisfied in accordance
with the terms of the respective agreements. Cash received that is related to
future performance under such contracts is deferred and recognized as revenue
when earned.
 
Use of estimates
The preparation of 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.
 
Reverse stock split
On November 5, 1996, the Company effected a reverse stock split of its common
stock on a .51-for-1 basis. All common share and pro forma per share amounts in
the accompanying financial statements have been retroactively adjusted to
reflect the reverse stock split for all periods presented. Preferred stock
amounts have not been retroactively adjusted to reflect the reverse stock
split.
 
Stock-based compensation
The Company accounts for its stock option plan in accordance with the provi-
sions of Accounting Principles Board ("APB") Opinion No. 25, "Accounting for
Stock Issued to Employees", and related interpretations. As such, compensation
cost is measured on the date of grant as the excess of the current market price
of the underlying stock over the exercise price. Such compensation amounts are
amortized over the respective vesting periods of the option grant. On January
1, 1996, the Company adopted the disclosure provisions of SFAS No. 123, "Ac-
counting for Stock-Based Compensation," which permits entities to provide pro
forma net income (loss) and pro forma earnings (loss) per share disclosures for
employee stock option grants made in 1995 and in future years as if the fair-
value based method defined in SFAS No. 123 had been applied. The Company has
elected to continue to apply the accounting provisions of APB Opinion No 25 and
provide the pro forma disclosure requirements of SFAS No. 123.
 
 
                                      F-8
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
2. BASIS OF ACCOUNTING AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES--
(CONTINUED)
 
Pro forma net loss per share
For periods subsequent to the Company's Initial Public Offering (IPO), net loss
per share is calculated by dividing the net loss by the weighted average number
of common shares outstanding for the respective periods adjusted for the
dilutive effect, if any, of common stock equivalents which consist of stock
options and warrants using the treasury stock method. Common stock equivalents
that are anti-dilutive are excluded from net loss per share calculations subse-
quent to the IPO.
 
For periods prior to the Company's IPO, all common and common equivalent shares
from stock options and warrants and convertible preferred stock issued during
the twelve-month period prior to the IPO at prices below the IPO price are pre-
sumed to have been issued in contemplation of the IPO and have been included in
the calculation of pro-forma net loss per share as if they were outstanding for
all periods presented (using the treasury stock method and an IPO price of
$7.00 per share). The calculation of shares used in computing pro-forma net
loss per share prior to the Company's IPO also included all series of
mandatorily redeemable convertible preferred stock, assuming conversion into
shares of common stock (using the if-converted method) from their respective
original dates of issuance. In the computation of pro forma net loss per share,
accretion of the redemption value attributable to mandatorily redeemable con-
vertible preferred stock is not included as an increase to net loss.
 
The following table sets forth the calculation of total number of shares used
in the computation of pro forma net loss per share:
 
<TABLE>
<CAPTION>
                                        ---------------------------------------
                                            YEAR ENDED      THREE MONTHS ENDED
                                           DECEMBER 31,          MARCH 31,
                                        ------------------- -------------------
                                             1995      1996      1996      1997
                                        --------- --------- --------- ---------
<S>                                     <C>       <C>       <C>       <C>
Weighted average common shares
 outstanding...........................   828,750 2,053,114   891,480 9,076,986
Incremental shares assumed to be
 outstanding related to common stock,
 stock options and warrants granted and
 convertible preferred stock based on
 the treasury stock method.............   853,620   486,123    96,763       --
Convertible preferred stock (if
 converted method)..................... 2,249,373 4,300,437 3,944,850       --
                                        --------- --------- --------- ---------
Weighted average common and common
 equivalent shares used in computation
 of pro forma net loss per share....... 3,931,743 6,839,674 4,933,093 9,076,986
                                        ========= ========= ========= =========
</TABLE>
 
Interim financial statements (unaudited):
The balance sheet at March 31, 1997, the statements of operations and state-
ments of cash flows for the three months ended March 31, 1996 and 1997 and the
period from December 5, 1994 (inception) to March 31, 1997 and the statement of
stockholders' equity (deficit) for the three months ended March 31, 1997 are
unaudited. In the opinion of management of the Company, such unaudited finan-
cial statements include all adjustments (consisting of normal recurring
accruals) necessary for a fair presentation of financial results for the
interim periods. The results of operations for the three months ended March 31,
1997 are not necessarily indicative of results to be expected for the entire
year.
 
3. SHORT-TERM INVESTMENTS
 
Short-term investments consist of fixed income securities with original maturi-
ties of greater than three months but less than one year including U.S. trea-
sury instruments of agencies of the U.S. Government and high-grade commercial
paper. At December 31, 1995 and 1996 and March 31, 1997, all of the short-term
investments were deemed as "available for sale" investments.
 
 
                                      F-9
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
3. SHORT-TERM INVESTMENTS--(CONTINUED)
 
The following summarizes the "available for sale" investments at December 31,
1995 and 1996, and March 31, 1997:
 
<TABLE>
<CAPTION>
                                 ---------------------------------------------
                                                  GROSS      GROSS
                                             UNREALIZED UNREALIZED
                                        COST      GAINS     LOSSES  FAIR VALUE
                                 ----------- ---------- ---------- -----------
<S>                              <C>         <C>        <C>        <C>
Obligations of the U.S.
 Government and agencies of the
 U.S.:
  December 31, 1995............. $ 4,349,640    $26,742    $   --  $ 4,376,382
                                 ===========    =======    ======= ===========
Obligations of the U.S.
 Government and agencies of the
 U.S............................   5,383,095      7,877      6,160   5,384,812
Commercial paper................   6,295,963     56,594        --    6,352,557
                                 -----------    -------    ------- -----------
  December 31, 1996............. $11,679,058    $64,471    $ 6,160 $11,737,369
                                 ===========    =======    ======= ===========
Obligations of the U.S.
 Government and agencies of the
 U.S............................   7,045,448     11,032     17,020   7,039,460
Commercial paper................   6,612,054     82,630        --    6,694,684
                                 -----------    -------    ------- -----------
  March 31, 1997................ $13,657,502    $93,662    $17,020 $13,734,144
                                 ===========    =======    ======= ===========
</TABLE>
 
4. EQUIPMENT AND LEASEHOLD IMPROVEMENTS
 
Equipment and leasehold improvements consist of the following at December 31,
1996 and March 31, 1997:
 
<TABLE>
<CAPTION>
                                                             ------------------
                                                                 1996      1997
                                                             -------- ---------
     <S>                                                     <C>      <C>
     Computer and equipment................................. $603,265 $ 873,282
     Leasehold improvements.................................  126,786   141,546
                                                             -------- ---------
                                                              730,051 1,014,828
     Less accumulated depreciation and amortization.........   58,022   108,765
                                                             -------- ---------
                                                             $672,029 $ 906,063
                                                             ======== =========
</TABLE>
 
Included in equipment and leasehold improvements at December 31, 1996 and March
31, 1997 is approximately $215,000 of assets held under capital lease.
 
5. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES
 
Accrued expenses and other current liabilities consist of the following at
December 31, 1995 and 1996 and March 31, 1997:
 
<TABLE>
<CAPTION>
                                               --------------------------------
                                                   DECEMBER 31,
                                               ---------------------  MARCH 31,
                                                     1995       1996       1997
                                               ---------- ---------- ----------
     <S>                                       <C>        <C>        <C>
     License fee payable...................... $1,036,000 $1,333,332 $1,666,665
     Clinical development and research........        --     827,175  1,053,098
     Payroll and payroll taxes payable........     72,986     30,329     78,577
     Other current liabilities................     89,953    143,190    157,384
                                               ---------- ---------- ----------
                                               $1,198,939 $2,334,026 $2,955,724
                                               ========== ========== ==========
</TABLE>
 
 
                                      F-10
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
6. LICENSE AND RESEARCH AGREEMENTS
 
In December 1995, the Company entered into a license agreement with Sanofi S.A.
(Sanofi) for its most advanced drug candidate. Under the Sanofi agreement, the
Company was required to pay a license fee of $1,000,000. This amount was
charged to operations in 1995 and paid in February 1996. In addition, the Com-
pany is required to make a milestone payment of up to $2,000,000 upon the ear-
lier of the occurrence of a future milestone event, as defined, or three years
from the date of the agreement. The $2,000,000 milestone payment is being
charged to operations on a pro-rata monthly basis commencing in December 1995
over eighteen months, the expected time frame in which the milestone is antici-
pated to be achieved.
 
In connection with the Sanofi agreement, the Company is also required to make
certain significant additional payments, including royalties, as defined,
should agreed-upon future milestones be attained. At the present time, there
can be no assurance that such milestones will be attained.
 
The Company has entered into various licensing, research and other agreements.
Under these agreements, the Company is working in collaboration with various
other parties. Should any discoveries be made under such arrangements, the Com-
pany would be required to negotiate the licensing of the technology for the
development of the respective discoveries. There are no significant funding
commitments under any other agreement other than Sanofi.
 
In July 1996, the Company entered into a collaborative drug discovery and
development agreement with Boehringer Ingelheim Pharmaceuticals Inc. (BI) for
one hepatitis C target identified by the Company. Under this agreement, the
Company granted to BI the exclusive worldwide rights to develop and commer-
cialize compounds discovered under the agreement. In return, BI paid a non-
refundable technology access fee of $1,000,000 to the Company and is required
to make certain research and milestone payments, as defined, to the Company in
connection with the Company's transfer of HCV screening and assay technology
and at various stages in the development of compounds under the agreement. In
addition, BI is required to make royalty payments to the Company on sales of
products developed and marketed under this agreement.
 
In February 1997, the Company received a $750,000 milestone payment related to
the BI agreement. Such amount was recognized as revenue in the quarter ended
March 31, 1997 pursuant to the specific terms of the agreement.
 
In 1996, the Company recognized approximately $340,000 of grant revenue from a
not-for-profit entity for which a director of the Company serves as an officer.
 
7. COMMON STOCK AND COMMON STOCK OPTIONS
 
On November 22, 1996, the Company completed its Initial Public Offering (IPO)
of common stock. The Company sold 2,587,500 shares (including 337,500 shares
excised by the underwriters for the overallotment). Net proceeds approximated
$16,250,000.
 
Upon inception of the Company in December 1994, certain members of management
and a co-founder/director purchased 828,750 shares of common stock. Management
purchased 663,000 of these shares which vest annually over a four-year period.
The Company has the right to repurchase any unvested shares at the original
price paid for such shares should the employee leave the Company before such
shares are fully vested. A co-founder/director purchased 165,750 shares. The
difference between the deemed fair value and the price paid ($.002) per share,
for the aforementioned common stock at inception in December 1994 was $79,625,
which amount was recorded as deferred compensation. Compensation expense
related to these shares of common stock aggregated $15,925 in each of 1994,
1995 and 1996, and $3,982 in 1997. Pursuant to a right granted in December
1994, a director purchased in January 1996, 51,000 shares of common stock at
$.10 per share, pursuant to a restricted stock purchase agreement.
 
 
                                      F-11
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
7. COMMON STOCK AND COMMON STOCK OPTIONS--(CONTINUED)
 
The Company has adopted the 1995 Stock Option Plan (the "Plan") to provide eli-
gible individuals with an opportunity to acquire or increase an equity interest
in the Company and to encourage such individuals to continue in the employment
of the Company. Prior to the adoption of the Plan, stock options granted in
1994 and 1995 were non-qualified stock options. Stock options are granted at
the deemed fair market value of the stock on the day immediately preceding the
date of grant. Stock options are exercisable for a period not to exceed ten
years from the date of grant. Vesting of the stock options occurs, generally
25% per year, over four years. There are 1,200,000 shares reserved under the
Plan.
 
Stock option activity from December 5, 1994 (inception) to March 31, 1997 is as
follows:
 
<TABLE>
<CAPTION>
                                    ------------------------------------------
                                                           WEIGHTED- WEIGHTED-
                                                             AVERAGE   AVERAGE
                                      EXERCISE             REMAINING  EXERCISE
                                     PRICE PER   SHARE   CONTRACTUAL     PRICE
                                         SHARE OPTIONS  LIFE (YEARS) PER SHARE
                                    ---------- -------  ------------ ---------
<S>                                 <C>        <C>      <C>          <C>
Balance, December 5, 1994 (date of
 inception)........................ $      --      --                   $  --
  Granted..........................        .10 150,349                     .10
  Exercised........................        --      --                      --
  Canceled.........................        --      --                      --
                                               -------
Balance, December 31, 1994.........        .10 150,349          10.0       .10
  Granted..........................        .20  12,750                     .20
  Exercised........................        --      --                      --
  Canceled.........................        --      --                      --
                                               -------
Balance, December 31, 1995.........    .10-.20 163,099           8.7       .11
  Granted..........................    .20-.45 174,775                     .25
                                          2.16  95,869                    2.16
                                          5.25  23,460                    5.25
  Exercised........................        .10 (21,420)                    --
  Canceled.........................        --      --                      --
                                               -------
Balance, December 31, 1996.........   .10-5.25 435,783          8.75       .90
  Granted (unaudited)..............       8.75 229,800                    8.75
                                         12.00     250                   12.00
                                         13.00  17,000                   13.00
                                         13.25   2,000                   13.25
  Exercised (unaudited)............        .20    (255)                    --
  Canceled (unaudited).............        --      --                      --
                                               -------
Balance, March 31, 1997
 (unaudited).......................  .10-13.25 684,578          9.03      3.87
                                               =======
Shares exercisable at March 31,
 1997 (unaudited).................. $  .10-.20  52,428                  $  .13
                                               -------
</TABLE>
 
At December 31, 1996, there were 742,797 shares available for grant under the
Plan. In the quarter ended March 31, 1997, the Company granted 249,050 options
to its employees. Such options were granted at exercise prices equal to the
fair market value at the grant date.
 
During 1996, various executive officers and certain employees of the Company
were granted options to acquire 270,644 shares of common stock at exercise
prices ranging from $.20 to $2.16 per share. The exercise price of the options
was equal to the fair market value of the Common Stock on the date of grant, as
determined by the Board of Directors. However, for financial statement pur-
poses, the difference between a deemed value in the range of $2.35 to $5.25 per
share and the respective exercise prices at the grant dates has been recorded
as deferred compensation ($753,461) and is being amortized over the four-year
vesting period. Compensation expense for the aforementioned options aggregated
$123,974 for the year ended December 31, 1996, and $48,757 for the quarter
ended March 31, 1997.
 
 
                                      F-12
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                  NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
7. COMMON STOCK AND COMMON STOCK OPTIONS--(CONTINUED)
 
The per share weighted-average fair value of stock options granted during 1995
and 1996 ranged from $.14 to $4.45 per share, respectively, on the date of
grant. Such fair values were determined using the Black-Scholes option-pricing
model and are based on the following weighted-average assumptions: an expected
dividend yield of 0%, a risk-free interest rate of 7.5%, volatility of 50% and
an expected option life of ten years.
 
The Company applies APB Opinion No. 25 in accounting for its stock option
plan. Had the Company determined compensation cost for options granted during
1995 and 1996 based on the fair value at the grant date under SFAS No. 123,
the Company's net loss and pro forma net loss per share would have been
increased to the pro forma amounts under SFAS No. 123 indicated below:
 
<TABLE>
<CAPTION>
                                                      ------------------------
                                                           DECEMBER 31,
                                                             1995         1996
                                                      -----------  -----------
     <S>                                              <C>          <C>
     Net loss:
       As reported................................... $(3,854,862) $(6,395,004)
       Pro forma under SFAS No 123................... $(3,855,318) $(6,524,213)
                                                      ===========  ===========
     Pro forma net loss per share:
       As reported................................... $      (.98) $      (.93)
       Pro forma under SFAS No. 123.................. $      (.98) $      (.95)
                                                      ===========  ===========
</TABLE>
 
Pro forma net loss reflects only options granted in 1995 and 1996. Therefore,
the full impact of calculating compensation cost for stock options under SFAS
No. 123 is not reflected in the pro forma net loss amounts presented above
because compensation cost is incurred under SFAS 123 over the respective
vesting period of such options, and options granted by the Company prior to
January 1, 1995 are not reflected in the pro forma net loss figures above.
 
8. MANDATORILY REDEEMABLE CONVERTIBLE PREFERRED STOCK
 
The Company completed the sale of its Series A (675,000 shares) and Series B
(7,060,000 shares) mandatorily redeemable convertible preferred stock (the
Preferred Stock) at per share prices of $.50 and $1.00, respectively. Aggre-
gate net proceeds from these transactions totaled approximately $7,350,000,
which included a $162,500 promissory note with an investor was converted into
Series A Preferred Stock in June 1995.
 
On May 31, 1996, the Company sold 3,222,222 shares of Series C mandatorily
redeemable convertible preferred stock at a per share price of $2.25 for
aggregate net proceeds of approximately $7,223,000.
 
On November 22, 1996, all mandatorily redeemable convertible preferred stock
was converted into 5,588,191 shares of common stock on a .51 for 1 basis in
connection with completion of the Company's Initial Public Offering.
 
The Company also secured $480,000 in bridge financing loans in March and May
1995, which amounts were converted to Series B preferred stock in June 1995.
 
In 1995, in connection with the bridge financing, the Company issued 159,994
warrants to Series B investors to purchase Series B preferred stock at the
fair value of the Series B preferred stock at the date of issuance ($1.00 per
share). The deemed fair value of such warrants at their issuance date aggre-
gated $90,000, which amount was charged to operations in 1995.
 
The difference between the deemed fair market value of the Preferred Stock and
the liquidation amount was accreted on a pro-rata basis in the accompanying
financial statements through the consummation of the Company's IPO in November
1996, at which point all shares of Preferred Stock were converted into
5,588,191 common shares. All rights with respect to the Preferred Stock ceased
upon consummation of the IPO.
 
 
                                     F-13
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
9. INCOME TAXES
 
At December 31, 1996, the Company had available for Federal and state income
tax purposes net operating loss carryforwards of approximately $1,731,000. Such
carryforwards, which expire between 2011 and 1999, respectively, are available
to reduce future Federal and state taxable income, if any.
 
Based on "change in ownership" provisions of the Tax Reform Act of 1986, net
operating loss and research and development credit carryforwards may be subject
to annual limitations that could reduce the Company's ability to utilize these
carryforwards in the future.
 
Significant components of the Company's deferred tax assets and liabilities as
of December 31, 1995 and 1996 are shown below. At December 31, 1996, a valua-
tion allowance of $4,152,890 has been recognized to offset the deferred tax
assets as realization of such assets is uncertain. The change in the valuation
allowance for 1995 and 1996 was an increase of $1,480,287 and $2,545,044
respectively.
 
<TABLE>
<CAPTION>
                                                      ------------------------
                                                           DECEMBER 31,
                                                             1995         1996
                                                      -----------  -----------
     <S>                                              <C>          <C>
     Deferred tax assets:
       Net operating loss carryforwards.............. $   549,171  $   758,592
       Capitalized research and development costs....   1,033,238    2,848,527
       Expenses not currently deductible.............         --       533,333
       Capitalized start up costs....................      50,917       37,918
                                                      -----------  -----------
         Total gross deferred tax assets.............   1,633,326    4,178,370
     Deferred tax liability:
       Employee compensation.........................      25,480       25,480
                                                      -----------  -----------
         Net deferred tax assets.....................   1,607,846    4,152,890
     Valuation allowance.............................  (1,607,846)  (4,152,890)
                                                      -----------  -----------
         Total deferred tax assets...................         --           --
                                                      ===========  ===========
</TABLE>
 
10. 401(K) PROFIT SHARING PLAN
 
In 1995, the Company adopted a 401(k) Profit Sharing Plan (the "401(k) Plan")
available to all employees meeting certain eligibility criteria. The 401(k)
Plan permits participants to contribute up to 15% of their compensation not to
exceed the limits established by the Internal Revenue Code. All contributions
made by participants vest immediately in the participant's account. The Company
did not contribute to the 401(k) Plan in 1995, 1996, or 1997.
 
11. COMMITMENTS
 
In September 1995, the Company entered into a lease arrangement for the
financing of certain lab equipment, leasehold improvements, computers and
office equipment. The terms range from three to four years.
 
The lease line expired in September 1996. In connection with this arrangement,
63,750 warrants to purchase Series B preferred stock were originally granted to
the lessor at the original Series B issuance price of $1.00 per share. The
deemed fair value of such warrants at their issuance date aggregated $63,750,
which amount is being amortized to operations over the term of the lease
arrangement. The number of warrants and the related exercise price were
adjusted based on a formula to reflect the increase in per share price of the
Series C Preferred Stock over Series B Preferred Stock and the .51 for 1
reverse stock split to 21,675 warrants to purchase common stock at an exercise
price of $2.94 per share.
 
In October 1995, the Company entered into an operating lease agreement for its
present corporate facilities. The lease term is for two years with a one year
renewal option, subject to lessor consent. The option was exercised in February
1997 extending the term of the lease to October 1998.
 
 
                                      F-14
<PAGE>
 
                            VIROPHARMA INCORPORATED
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS--(CONTINUED)
 
11. COMMITMENTS--(CONTINUED)
 
In December 1995, the Company entered into a capital lease arrangement for the
financing of certain equipment. The terms of this arrangement are for four
years from the date of funding. The maximum amount that can be financed under
this arrangement is $620,000, which includes $120,000 of used equipment which
the Company is obligated to purchase at the end of the lease term for $24,000.
 
The Company's future minimum lease payments under the aforementioned leases for
years subsequent to December 31, 1996 are as follows:
 
<TABLE>
<CAPTION>
                                                            ------------------
     YEAR ENDING                                            OPERATING  CAPITAL
     DECEMBER 31,                                              LEASES   LEASES
     ------------                                           --------- --------
     <S>                                                    <C>       <C>
      1997.................................................  $378,337 $ 69,545
      1998.................................................   330,121   69,545
      1999.................................................   152,827   51,302
      2000.................................................    45,747    2,373
      2001 and thereafter..................................       --       --
                                                             -------- --------
         Total minimum lease payments......................  $907,032 $192,765
                                                             ======== ========
     Amounts representing interest.........................           $(35,244)
                                                                      --------
     Present value of net minimum lease payments...........           $157,521
     Current portion.......................................           $ 52,950
                                                                      --------
     Long term portion.....................................           $104,571
                                                                      ========
</TABLE>
 
Rent expense for the period from December 5, 1994 (date of inception) to
December 31, 1994, the years ended December 31, 1995 and 1996, and the three
month period ended March 31, 1997 aggregated $20,000, $271,000, $335,000, and
$106,450 respectively.
 
12. SUBSEQUENT EVENTS (UNAUDITED)
 
In February 1997, the Company entered into a $600,000 loan agreement with a
bank of which $583,333 is outstanding at March 31, 1997. The term of the loan
is six years, with principal and interest due monthly. The interest rate is
approximately 9% and is secured by certain equipment and a $300,000 certificate
of deposit.
 
In April 1997, the Company entered into a development agreement with SELOC AG
(SELOC) and SICOR S.A. (SICOR), subsidiaries of Schwarz Pharma AG, for the man-
ufacture of clinical supplies of pleconaril, the Company's most advanced drug
candidate. Under the terms of the agreement, SELOC and SICOR will manufacture
pleconaril for use in clinical trials and further develop the synthetic process
for production of commercial quantities of pleconaril.
   
On July 21, 1997, the Company entered into a lease for laboratory and office
space commencing after the current lease expires in 1998. The term of the new
lease is ten years with two five-year renewal options. Under the lease terms,
the Company is required to contribute approximately $800,000 in 1997 to the
cost of the laboratory construction. The Company also has the right, under cer-
tain circumstances, to purchase the new facility at a purchase price based on a
pre-determined formula.     
 
                                      F-15
<PAGE>
 
 
 
                [LOGO OF VIROPHARMA INCORPORATED APPEARS HERE]
                          
<PAGE>
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION
 
The following table sets forth an estimate of the expenses to be incurred by
the Company in connection with the sale of Common Stock being registered. All
amounts are estimates except the Securities and Exchange Commission registra-
tion fee, the National Association of Securities Dealers filing fee and the
Nasdaq National Market filing fee:
 
<TABLE>
<CAPTION>
                                                                       --------
       <S>                                                             <C>
       Securities and Exchange Commission registration fee............ $ 11,152
       National Association of Securities Dealers, Inc. Filing Fee....    4,180
       The Nasdaq Stock Market Listing Fee............................   17,500
       Transfer Agent and Registrar Fees..............................    5,000
       Printing and engraving expenses................................  100,000
       Legal fees and expenses........................................  100,000
       Accounting fees and expenses...................................   45,000
       Blue Sky fees and expenses (including legal fees)..............   15,000
       Miscellaneous..................................................    2,168
                                                                       --------
         Total........................................................ $300,000
                                                                       ========
</TABLE>
ITEM 14. INDEMNIFICATION OF DIRECTORS AND OFFICERS
 
The Delaware General Corporation Law and the Company's By-Laws provide for
indemnification of the Company's directors and officers for liabilities and
expenses that they may incur in such capacities. In general, directors and
officers are indemnified with respect to actions taken in good faith in a
manner reasonably believed to be in, or not opposed to, the best interests of
the Company, and with respect to any criminal action or proceeding, actions
that the indemnitee had no reasonable cause to believe were unlawful. Reference
is made to the Company's By-Laws filed as Exhibit 3.2 hereto.
 
In addition, certain directors of the Company are parties to indemnification
agreements with the Company. Pursuant to the agreements, such directors are to
be indemnified against liabilities and expenses incurred in connection with
their services to the Company to the fullest extent permitted by Delaware law.
Such indemnification is subject to the director's meeting the applicable stan-
dard of care and to a determination to indemnify by a majority of disinterested
directors (as defined in the agreements) or by independent counsel (also as
defined in the agreements).
 
The Underwriting Agreement provides that the Underwriter is obligated, under
certain circumstances, to indemnify directors, officers and controlling persons
of the Company against certain liabilities, including liabilities under the
Securities Act of 1933, as amended (the "Act"). Reference is made to the form
of Underwriting Agreement filed as Exhibit 1 hereto.
 
ITEM 15. RECENT SALES OF UNREGISTERED SECURITIES
 
 
Since December 1994, the registrant has issued and sold the following unregis-
tered securities:
 
  1. Upon the founding of the Company in December 1994, certain founders of
  the Company purchased an aggregate of 675,750 shares of Common Stock pur-
  suant to restricted stock purchase agreements. Each purchaser paid $0.002
  per share of Common Stock, then valued at $0.10 per share. In addition, an
  affiliate of a founder purchased 165,750 shares of Common Stock. The affil-
  iate paid $0.002 per share.
 
  2. From December 1994 to January 1995, the Company sold 350,000 shares of
  Series A Preferred Stock for an aggregate price of $175,000, or $0.50 per
  share, to certain of the founders of the Company. All of such outstanding
  shares of Series A Preferred Stock converted into an aggregate of 178,500
  shares of Common Stock upon completion of the Company's initial public
  offering.
 
  3. In December 1994, the Company sold an 8.5% Convertible Demand Promissory
  Note in the principal amount of $162,500 to an affiliate of a founder of
  the Company. In December 1994, the founder assigned the note to two affili-
  ates of another founder, who converted their notes into a total of 325,000
  shares of Series A Preferred Stock at $0.50 per share in June 1995. All of
  such outstanding shares of Series A Preferred Stock converted into an
  aggregate of 165,750 shares of Common Stock upon completion of the
  Company's initial public offering.
 
                                      II-1
<PAGE>
 
  4. Pursuant to a right granted in December 1994, a director purchased
  51,000 shares of Common Stock under a January 1996 restricted stock pur-
  chase agreement at $0.10 per share.
 
  5. In March and May 1995, the Company sold two 9.5% Convertible Demand
  Promissory Notes in the principal amounts of $100,000 and $50,000 to each
  of three private investors and one 9.5% Convertible Promissory Note in the
  principal amount of $30,000 to an executive officer. All the notes were
  cancelled in connection with such investors' and executive officer's pur-
  chase of Series B Preferred Stock described in paragraph 7 below, in par-
  tial or full payment for the shares.
 
  6. In connection with the purchase of the 9.5% Convertible Demand Promis-
  sory Notes, the Company issued warrants to purchase 49,998 shares of Series
  B Preferred Stock, respectively, to each of the three private investors and
  10,000 shares to the executive officer. Two of the private investors subse-
  quently transferred all or portions of the warrants to successors or affil-
  iates. Upon the closing of the Company's initial public offering, the war-
  rants automatically became exercisable for 25,499 shares of Common Stock
  for each of the private investors and 5,100 shares for the chief executive
  officer.
 
  7. Between June 1995 and October 1995, the Company sold 7,060,000 shares of
  Series B Preferred Stock for an aggregate of $7,060,000, or $1.00 per
  share, to private investors and an executive officer of the Company. All of
  such outstanding shares of Series B Preferred Stock converted into an
  aggregate of 3,600,600 shares of Common Stock upon the closing of the
  Company's initial public offering.
 
  8. In September 1995, the Company issued a warrant to purchase 42,500
  shares of Series B Preferred Stock at $1.50 per share to an equipment sup-
  plier in connection with a Master Lease Agreement between the Company and
  the equipment supplier. Upon the closing of the Company's initial public
  offering, the warrant automatically became exercisable for 21,675 shares of
  Common Stock at $2.94 per share.
 
  9. In May 1996, the Company sold 3,222,222 shares of Series C Preferred
  Stock for an aggregate of $7,249,999.50, or $2.25 per share, to private
  investors and the executive officers of the Company. All of such out-
  standing shares of Series C Preferred Stock converted into an aggregate of
  1,643,333 shares of Common Stock upon the closing of the Company's initial
  public offering.
 
  10. From 1994 to the present, the Company has granted options to acquire an
  aggregate of 728,712 shares of Common Stock, at exercise prices ranging
  from $0.10 to $13.25, to various directors, officers, employees and non-
  employees. To date, options to purchase 21,675 shares of Common Stock have
  been exercised.
 
  11. In June 1997, the Company issued 71,795 shares of Common Stock pursuant
  to a cashless exercise of warrants that were otherwise exercisable on a
  cash basis for 81,597 shares of Common Stock.
 
The Company believes that the transactions described above were exempt from
registration under Sections 3(a)(9), 3(b) or 4(2) of the Securities Act because
the subject securities were, respectively, either (i) exchanged by the issuer
with its existing security holders exclusively, with no commission or other
remuneration being paid or given directly or indirectly for soliciting such
exchange, (ii) issued pursuant to a compensatory benefit plan pursuant to Rule
701 under the Securities Act or (iii) sold to a limited group of persons, each
of whom was believed to have been a sophisticated investor or had a pre-
existing business or personal relationship with the Company or its management
and was purchasing for investment without a view to further distribution.
Restrictive legends were placed on stock certificates evidencing the shares
and/or agreements relating to the right to purchase such shares described
above.
 
Specifically, the Company believes that the transactions described in paragraph
1 and certain transactions described in paragraphs 2, 3, 5, 6, 7, 8, 9 and 11
were exempt from registration under Section 4(2) of the Securities Act. The
Company believes that the transactions relating to the conversion of the pre-
ferred stock and the notes described in paragraphs 2, 3, 5, 6, 7 and 9 were or
will be exempt from registration under Section 3(a)(9) of the Securities Act.
In respect of the right described in paragraph 4 and the options described in
paragraph 10, the Company is relying upon the fact that such grants were not
sales or, if such grants were sales, they and the exercises described were
exempt from registration under Sections 4(2) and 3(b) of the Securities Act.
The Company intends to file registration statements on Form S-8 under the Secu-
rities Act to register all of the shares of Common Stock underlying the
Company's outstanding options.
 
                                      II-2
<PAGE>
 
ITEM 16. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES
 
<TABLE>   
<CAPTION>
 (A)EXHIBIT DESCRIPTION
 ---------- -----------
 <C>        <S>
  1.1**     Form of Underwriting Agreement.
  3.1       Second Amended and Restated Certificate of Incorporation of the
            Company.(1) (Exhibit 3.1)
  3.2++     By-Laws of the Company, as amended.(1) (Exhibit 3.2)
  5**       Opinion of Morgan, Lewis & Bockius LLP regarding legality of the
            shares of Common Stock being offered.
 10.1++     1995 Stock Option Plan.(1) (Exhibit 10.1)
 10.2       ViroPharma 401(k) Employee Savings Plan, effective July 1, 1995.(1)
            (Exhibit 10.2)
 10.3       Lease dated September 19, 1995 between the Company and Centocor
            Property Management Corp.(1)
            (Exhibit 10.3)
 10.4       Master Lease Agreement dated September 13, 1995 between the Company
            and Comdisco, Inc.(1) (Exhibit 10.4)
 10.5       Master Equipment Lease No. 053-0005 dated December 1, 1995 between
            the Company and Phoenix Leasing Incorporated.(1) (Exhibit 10.5)
 10.6(a)+   Agreement dated December 22, 1995 between the Company and
            Sanofi.(1) (Exhibit 10.6)
 10.7+      Collaborative Research Agreement dated as of August 15, 1996
            between the Company and Boehringer Ingelheim Pharmaceuticals,
            Inc.(1) (Exhibit 10.7)
 10.8       Form of Employment Agreement.(1) (Exhibit 10.8)
 10.9       Form of Indemnification Agreement.(1) (Exhibit 10.9)
 10.10      Form of Employee Stock Purchase Agreement.(1) (Exhibit 10.10)
 10.11      Restricted Stock Purchase Agreement dated as of January 17, 1996,
            by and between the Company and Frank Baldino, Jr.(1) (Exhibit 10.11)
 10.12      Series B Convertible Preferred Stock Purchase Agreement dated as of
            June 16, 1995 among the Company and each of the entities on the
            "Schedule of Purchasers" attached thereto as Schedule A.(1)
            (Exhibit 10.12)
 10.13      Series C Convertible Preferred Stock Purchase Agreement dated as of
            May 30, 1996 among the Company and each of the individuals and
            entities on the "Schedule of Purchasers" attached thereto as
            Schedule A.(1)
            (Exhibit 10.13)
 10.14      Form of Warrants to Purchase Series B Preferred Stock dated March
            3, 1995 and May 12, 1995.(1)
            (Exhibit 10.14)
 10.15      Warrant Agreement dated as of September 13, 1995 between the
            Company and Comdisco, Inc.(1)
            (Exhibit 10.15)
 10.16      Amended and Restated Investors' Rights Agreement, dated as of May
            30, 1996, by and among the Company and the persons identified on
            Schedule A, Schedule B and the Schedule of Founders thereto.(1)
            (Exhibit 10.16)
 10.17      Form of Amendment to Employee Stock Purchase Agreement.(1) (Exhibit
            10.17)
 10.18      Amendment to Restricted Stock Purchase Agreement dated as of
            January 17, 1996, among the Company and Frank Baldino, Jr., dated
            as of January 17, 1996.(1) (Exhibit 10.18)
 10.19**    Development Agreement dated as of April 16, 1997, by and among
            SELOC AG, SICOR, S.A. and the Company.
 10.20**    First Amendment to Agreement dated as of February 21, 1997 by and
            between Sanofi and the Company.
 10.21**    Promissory Note of Jon M. Rogers and Traci J. Rogers, dated as of
            June 12, 1997.
 10.22**    Letter Agreement dated May 6, 1997, by and between the Company and
            Centocor, Inc.
 10.23*     Lease, dated July 21, 1997, between the Company and The Hankin
            Group.
 10.24*     Purchase Option Agreement, dated July 21, 1997, between the Company
            and The Hankin Group.
 10.25*     Escrow Agreement, dated July 21, 1997, among the Company, The
            Hankin Group and Manito Abstract Company, Inc.
 10.26*     Work Letter to Lease between the Company and The Hankin Group.
 23.1*      Consent of KPMG Peat Marwick LLP.
 23.2**     Consent of Morgan, Lewis & Bockius LLP (included in Exhibit 5).
 24**       Power of Attorney (included on signature page).
 27**       Financial Data Schedule.
</TABLE>    
 
(b) No Financial Statement Schedules filed.
- -------
* Filed herewith.
** Previously filed.
+ Portions of this exhibit were omitted and filed separately with the Secretary
of the Commission pursuant to an application for confidential treatment filed
with the Commission pursuant to Rule 406 under the Securities Act of 1933, as
amended.
++ Compensation plans and arrangements for executives and others.
(1) Filed as an Exhibit to Registration Statement on Form S-1 (File No. 333-
12407), as amended, initially filed on September 20, 1996.
 
                                      II-3
<PAGE>
 
ITEM 17. UNDERTAKINGS
 
A. The undersigned Registrant hereby undertakes to provide to the Underwriters
at the closing specified in the Underwriting Agreement certificates in such
denominations and registered in such names as required by the Underwriter to
permit prompt delivery to each purchaser.
 
A. Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the Regis-
trant pursuant to the foregoing provisions, or otherwise, the Registrant has
been informed that in the opinion of the Commission such indemnification is
against public policy as expressed in the Securities Act of 1933 and is, there-
fore, 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 suc-
cessful defense of any action, suit or proceeding) is asserted by such direc-
tor, officer or controlling person in connection with the securities being reg-
istered, 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 be governed by the final
adjudication of such issue.
 
B. The undersigned Registrant hereby 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 this Reg-
  istration Statement in reliance upon Rule 430A and contained in a 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 this Regis-
  tration Statement as of the time it was declared effective.
 
  (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
   
PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THE REGISTRANT HAS
DULY CAUSED THIS AMENDMENT TO THE REGISTRATION STATEMENT TO BE SIGNED ON ITS
BEHALF BY THE UNDERSIGNED, THEREUNTO DULY AUTHORIZED IN MALVERN, PENNSYLVANIA
ON JULY 22, 1997.     
 
                                        Viropharma Incorporated
 
                                              
                                        By:   /s/ Claude H. Nash, Ph.D.
                                            -----------------------------------
                                                  CLAUDE H. NASH, PH.D.
                                           PRESIDENT, CHIEF EXECUTIVE OFFICER
 
PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS REGISTRATION
STATEMENT HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN THE CAPACITIES AND ON THE
DATES INDICATED.

<TABLE>     
<CAPTION> 

<S>                                     <C>                     <C>  
/s/ Claude H. Nash, Ph.D.               President, Chief        July 22, 1997
- ---------------------------------------  Executive Officer      
CLAUDE H. NASH, PH.D.                    and Chairman of the    
                                         Board (Principal
                                         Executive Officer)
 
/s/ Vincent J. Milano                   Vice President,         July 22, 1997
- ---------------------------------------  Finance and            
VINCENT J. MILANO                        Administration         
                                         (Principal
                                         Financial and
                                         Accounting Officer)
 
                   *                    Director                July 22, 1997
- ---------------------------------------                         
FRANK BALDINO, JR., PH.D.                                      
 
                   *                    Director                July 22, 1997
- ---------------------------------------                         
STEVE DOW                                                       
 
                   *                    Director                July 22, 1997
- ---------------------------------------                         
JON N. GILBERT                                                 
 
                   *                    Director                July 22, 1997
- ---------------------------------------                         
ANN H. LAMONT                                                   
 
                   *                    Director                July 22, 1997
- ---------------------------------------                         
CHRISTOPHER MOLLER, PH.D.                                       July 22, 1997
                                                                
     
*By: /s/ Claude H. Nash, Ph.D.
    -------------------------------
    CLAUDE H. NASH, PH.D. AS
    ATTORNEY-IN-FACT
</TABLE>      

 
                                      II-5
<PAGE>
 
                                 EXHIBIT INDEX
 
<TABLE>   
<CAPTION>
 EXHIBIT  DESCRIPTION
 -------  -----------
 <C>      <S>
  1.1**   Form of Underwriting Agreement.
  3.1     Second Amended and Restated Certificate of Incorporation of the
          Company.(1) (Exhibit 3.1)
  3.2++   By-Laws of the Company, as amended.(1) (Exhibit 3.2)
  5**     Opinion of Morgan, Lewis & Bockius LLP regarding legality of shares
          of Common Stock being registered.
 10.1++   1995 Stock Option Plan.(1) (Exhibit 10.1)
 10.2     ViroPharma 401(k) Employee Savings Plan, effective July 1, 1995.(1)
          (Exhibit 10.2)
 10.3     Lease dated September 19, 1995 between the Company and Centocor
          Property Management Corp.(1)
          (Exhibit 10.3)
 10.4     Master Lease Agreement dated September 13, 1995 between the Company
          and Comdisco, Inc.(1) (Exhibit 10.4)
 10.5     Master Equipment Lease No. 053-0005 dated December 1, 1995 between
          the Company and Phoenix Leasing Incorporated.(1) (Exhibit 10.5)
 10.6(a)+ Agreement dated December 22, 1995 between the Company and Sanofi.(1)
          (Exhibit 10.6)
 10.7+    Collaborative Research Agreement dated as of August 15, 1996 between
          the Company and Boehringer Ingelheim Pharmaceuticals, Inc.(1)
          (Exhibit 10.7)
 10.8     Form of Employment Agreement.(1) (Exhibit 10.8)
 10.9     Form of Indemnification Agreement.(1) (Exhibit 10.9)
 10.10    Form of Employee Stock Purchase Agreement.(1) (Exhibit 10.10)
 10.11    Restricted Stock Purchase Agreement dated as of January 17, 1996, by
          and between the Company and Frank Baldino, Jr.(1) (Exhibit 10.11)
 10.12    Series B Convertible Preferred Stock Purchase Agreement dated as of
          June 16, 1995 among the Company and each of the entities on the
          "Schedule of Purchasers" attached thereto as Schedule A.(1) (Exhibit
          10.12)
 10.13    Series C Convertible Preferred Stock Purchase Agreement dated as of
          May 30, 1996 among the Company and each of the individuals and
          entities on the "Schedule of Purchasers" attached thereto as Schedule
          A.(1)
          (Exhibit 10.13)
 10.14    Form of Warrants to Purchase Series B Preferred Stock dated March 3,
          1995 and May 12, 1995.(1)
          (Exhibit 10.14)
 10.15    Warrant Agreement dated as of September 13, 1995 between the Company
          and Comdisco, Inc.(1)
          (Exhibit 10.15)
 10.16    Amended and Restated Investors' Rights Agreement, dated as of May 30,
          1996, by and among the Company and the persons identified on Schedule
          A, Schedule B and the Schedule of Founders thereto.(1) (Exhibit 10.16)
 10.17    Form of Amendment to Employee Stock Purchase Agreement.(1) (Exhibit
          10.17)
 10.18    Amendment to Restricted Stock Purchase Agreement dated as of January
          17, 1996, among the Company and Frank Baldino, Jr., dated as of
          January 17, 1996.(1) (Exhibit 10.18)
 10.19**  Development Agreement dated as of April 16, 1997, by and among SELOC
          AG, SICOR, S.A. and the Company.
 10.20**  First Amendment to Agreement dated as of February 21, 1997 by and
          between Sanofi and the Company.
 10.21**  Promissory Note of Jon M. Rogers and Traci J. Rogers, dated as of
          June 12, 1997.
 10.22**  Letter Agreement dated May 6, 1997, by and between the Company and
          Centocor, Inc.
 10.23*   Lease, dated July 21, 1997, between the Company and The Hankin Group.
 10.24*   Purchase Option Agreement, dated July 21, 1997, between the Company
          and The Hankin Group.
 10.25*   Escrow Agreement, dated July 21, 1997, among the Company, The Hankin
          Group and Manito Abstract Company, Inc.
 10.26*   Work Letter to Lease between the Company and The Hankin Group.
 23.1*    Consent of KPMG Peat Marwick LLP.
 23.2**   Consent of Morgan, Lewis & Bockius LLP (included in Exhibit 5).
 24**     Power of Attorney (included on signature page).
 27**     Financial Data Schedule.
</TABLE>    
- -------
* Filed herewith.
** Previously filed.
+ Portions of this exhibit were omitted and filed separately with the Secretary
of the Commission pursuant to an application for confidential treatment filed
with the Commission pursuant to Rule 406 under the Securities Act of 1933, as
amended.
++ Compensation plans and arrangements for executives and others.
(1) Filed as an Exhibit to Registration Statement on Form S-1 (File No. 333-
12407), as amended, initially filed on September 20, 1996.

<PAGE>
 
                                                                   EXHIBIT 10.23

                             LEASE FOR COMBINATION 

                            OFFICE/WAREHOUSE SPACE 

                                      AT 

                          EAGLEVIEW CORPORATE CENTER

                                 BUILDING NO. 

                          LANDLORD: THE HANKIN GROUP 

                        TENANT: VIROPHARMA INCORPORATED
<PAGE>
 
                               TABLE OF CONTENTS
                               -----------------
<TABLE>
<CAPTION>
 
 
                                                                   Page
<S>  <C>                                                           <C>
 
1.   LEASED SPACE AND PURPOSE.........................................1
2.   TERM.............................................................1
3.   RENT.............................................................3
5.   NEGATIVE COVENANTS OF TENANT; HAZARDOUS SUBSTANCES...............7
6.   LATE PAYMENT.....................................................9
7.   CONSTRUCTION OF LEASED SPACE....................................10
8.   TENANT'S ALTERATIONS............................................11
9.   MECHANIC'S LIENS................................................12
10.  CONDITION OF LEASED SPACE.......................................13
11.  COMMON AREA MAINTENANCE.........................................13
12.  ASSIGNMENT AND SUBLETTING.......................................14
13.  ACCESS TO LEASED SPACE..........................................15
14.  REPAIRS.........................................................15
15.  TERMINATION AND EXTENSION.......................................17
16.  SURRENDER OF LEASED SPACE.......................................17
17.  INDEMNIFICATION AND INSURANCE...................................18
18.  FIRE OR OTHER CASUALTY..........................................19
19.  CONDEMNATION....................................................21
20.  ESTOPPEL CERTIFICATES...........................................21
21.  DEFAULT.........................................................22
22.  REMEDIES........................................................22
23.  CONFESSION OF JUDGMENT FOR POSSESSION IN LIMITED
     CIRCUMSTANCE....................................................24
24.  WAIVER..........................................................25
25.  QUIET ENJOYMENT.................................................25
26.  FORCE MAJEURE...................................................25
27.  SUCCESSORS......................................................26
28.  LANDLORD'S LIABILITY............................................26
29.  SUBORDINATION...................................................26
30.  RULES AND REGULATIONS...........................................27
31.  GOVERNING LAW...................................................27
32.  SEVERABILITY....................................................27
33.  NOTICES.........................................................27
34.  BROKERS.........................................................28
35.  SIGNS...........................................................28
36.  SECURITY DEPOSIT; SECURITY
     INTEREST........................................................28
37.  USE OF INFORMATION IN
     ADVERTISING.....................................................30
38.  CAPTIONS........................................................30
40.  ACCESS TO THE LEASED SPACE AND COMMON AREAS.....................30
</TABLE> 

                                      -i-
<PAGE>
 
<TABLE> 
<CAPTION> 
                                                                   Page
                                                                   ----

<S>  <C>                                                           <C> 
41.  ATTORNEY FEES...................................................30
42.  SELF-HELP.......................................................31
43.  MEMORANDUM OF LEASE.............................................31
44.  LANDLORD REPRESENTATIONS AND WARRANTIES.........................32
45.  RENEWAL OPTION..................................................34
46.  SPACE RESERVATION AND EXPANSION OPTION..........................36
47.  RIGHT OF  FIRST REFUSAL.........................................38
48.  RESTRICTION ON LEASING TO COMPETITORS...........................39
49.  CREDIT AGAINST LAND PURCHASE....................................39
50.  CHANGE TO CPI INDEX.............................................39
51.  CERTAIN COVENANTS REGARDING THE DECLARATION.....................39
52.  ADDITIONAL PERMITTED TITLE EXCEPTIONS...........................40
53.  SEWER CAPACITY ALLOCATION.......................................41
54.  CALCULATION AND REIMBURSEMENT OF UNAMORTIZED VALUE OF
     DIRECT PAYMENT PORTION..........................................41
</TABLE>

Exhibits
- --------

A - Description of Leased Space
B - Work Letter
C - Rider to Lease or Agreement of Sale Regarding Industrial Waste Discharge
Within Eagleview Corporate Center
D - Rules and Regulations
E - Permitted Title Exceptions
F - Building Standard Specifications

                                     -ii-
<PAGE>
 
                                     LEASE
                                     -----

          LEASE is made this 21st day of July, 1997 between THE HANKIN GROUP, a
Pennsylvania general partnership ("Landlord"), with its office at Eagleview
Corporate Center, 717 Constitution Drive, P.O. Box 562, Exton, Pennsylvania
19341, and VIROPHARMA INCORPORATED, a Pennsylvania corporation ("Tenant"), with
its office at 76 Great Valley Parkway, Malvern, Pennsylvania 19355.

 1.  LEASED SPACE AND PURPOSE.
     ------------------------ 

     (a) Landlord hereby rents to Tenant 48,400 rentable square feet of space
("Leased Space") within the building to be constructed by Landlord at 405
Eagleview Boulevard ("Building"), also known as Lot 10 within the center
("Center" or "Eagleview Corporate Center") known as Eagleview Corporate Center,
Route 100, Lionville, Uwchlan Township, Chester County, Pennsylvania.  The
location of the Leased Space within the Building is shown and outlined in red in
the plan attached hereto as Exhibit "A".  The Leased Space include all fixtures,
                            -----------                                         
improvements, additions and other property installed therein at the Commencement
Date (hereafter defined), or at any time during the term of this Lease (other
than Tenant's movable personal property and trade fixtures), together with the
right to use, in common with others, the parking lot and all other public
portions of the Building and of the Center.

     (b) The Leased Space shall be used and occupied as a mixed-use facility
consisting of general office space, warehouse space and laboratory space in
connection with Tenant's Business (hereafter defined) and for no other purpose.
For purposes hereof, Tenant's Business shall be deemed to be the development and
commercialization of pharmaceutical products and research activities in
connection therewith.

 2.  TERM.
     ---- 

     (a) The term of this Lease and Tenant's obligation to pay rent hereunder
shall commence upon a date ("Commencement Date") which is the earlier of:

         (i)  the date when the Leased Space is "ready for occupancy"; or

         (ii) the date when Tenant shall take possession of the Leased Space
other than to complete installation of Tenant's Work (as defined in the Work
Letter),

     (b) The Leased Space shall be deemed "ready for occupancy" when Landlord
has "Substantially Completed" the Landlord's Work described in the Work Letter
attached hereto as Exhibit "B" ("Work Letter").   "Substantial Completion" or
                   -----------                                               
"Substantially Completed" shall mean such completion as shall enable Tenant to
reasonably and conveniently use and occupy the Leased Space for the conduct of
Tenant's Business.  Substantial Completion shall be deemed to have been achieved
even though minor or insubstantial details of construction, mechanical
adjustment or decoration remain to be performed, the non-completion of which
does not materially interfere with Tenant's use of the Leased Space,
installation of finishing work or the conduct of Tenant's Business therein.  In
no event, however, shall Substantial Completion be
<PAGE>
 
deemed to have occurred prior to (A) the issuance of a permanent certificate of
occupancy for the Leased Space by the municipality, and (B) the issuance of a
certificate of substantial completion by Landlord's general contractor which is
verified by Tenant's Consultant (as defined in the Work Letter); provided that
any disagreement as to whether Substantial Completion has occurred shall be
settled in the manner provided in the Work Letter.  If the Commencement Date
does not occur on or before the Target Date (hereafter defined), Tenant shall
have the following rights:

          (i)   Landlord shall be entitled to a fifteen (15) day grace period,
such that if the Commencement Date occurs within fifteen (15) days after the
Target Date, Tenant shall have no rights under subsections (ii) through (iv)
below;

          (ii)  If the Commencement Date occurs more than fifteen (15), but
within forty-five (45) days after the Target Date, Tenant shall receive one (1)
free day of Rent for each two (2) days within such period until the earlier of
the end of such period or the Commencement Date;

          (iii) If the Commencement Date occurs more than forty-five (45) days,
but within seventy-five (75) days after the Target Date, Tenant, in addition to
the rent credit provided above in subsection (ii), shall receive one (1) free
date of Rent for each day within such period until the earlier of the end of
such period or the Commencement Date; and

          (iv)  If the Commencement Date occurs more than seventy-five (75) days
after the Target Date, (A) Tenant, in addition to the rent credit provided above
in subsections (ii) and (iii), shall receive two (2) free days of Rent for each
day from the beginning of such seventy-five (75) day period to the Commencement
Date or (B) Tenant may elect to terminate this Lease, in which event neither
party shall have any further rights or obligations hereunder except that the
Security Deposit (hereafter defined) and Direct Payment Portion (as defined in
the Work Letter) paid by Tenant shall be returned by Landlord to Tenant within
thirty (30) days of such termination, and if not so paid, such unpaid amounts
shall accrue interest at the Default Rate (hereafter defined) from the date of
termination until paid in full.  (The limitations set forth in Section 28 hereof
shall not apply Landlord's liability for payment of the foregoing amounts.)

For purposes hereof, the Target Date shall be March 1, 1998 as such date may be
extended by reason of  "Tenant Delay" or "Change Orders" (as such terms are
defined in the Work Letter) or "Force Majeure" (as defined in Section 26 below).
 
     (c)  Tenant shall execute and deliver to Landlord a declaration of the
Commencement Date upon presentation by Landlord prior to taking occupancy.  The
term ("Term") of this Lease shall end ten (10) years after the Commencement Date
unless sooner terminated or renewed in accordance with this Lease; provided,
however, that if the Commencement Date is not the first day of a calendar month,
the Term shall extend to the last day of the calendar month which is ten (10)
years after the Commencement Date occurs.  The first ten (10) year period is
sometimes referred to herein as "Initial Term."

                                      -2-
<PAGE>
 
 3.  RENT.
     ---- 

     (a)  Definitions.

          (i)   Tenant and Landlord acknowledge and agree that the initial
rentable area of the Building will be 48,400 square feet and that, subject to
the terms and conditions of this Lease, Landlord may expand the rentable area of
the Building to a maximum of 86,500 square feet.  Until the expansion of the
Building, the rentable area of the Building leased to Tenant will be 48,400
square feet and "Tenant's Proportionate Share" shall be 100%.  Once expansion of
the Building shall be undertaken, Tenant's Proportionate Share shall be adjusted
in accordance with the ratio of Tenant's rentable area of the Building to the
total amount of rentable area available in the Building, whether occupied or
not.

          (ii)  "Real Estate Taxes" shall mean all taxes and assessments levied,
assessed or imposed at any time by any governmental authority upon or against
the Building and the land upon which the Building is situate, and also any tax
or assessment levied, assessed or imposed at any time by any governmental
authority in connection with the receipt of income or rents from said Building
or land to the extent that the same shall be in lieu of (and/or in lieu of an
increase in) all or a portion of any of the aforesaid taxes or assessments upon
or against the said Building and/or land.  If, however, any assessment included
within Real Estate Taxes is payable in installments extending beyond the term of
this Lease, Tenant shall only be obligated to pay those installments coming due
during the term of this Lease.  "Real Estate Taxes" shall not include any
penalty or interest as a result of Landlord's late payment.  Landlord further
agrees to make payment of Real Estate Taxes in a timely manner so as to take
advantage of any applicable discount and to provide to Tenant copies of receipts
for paid Real Estate Taxes not later than thirty (30) days after the Real Estate
Taxes are due.  Failure of Landlord to provide such receipts to Tenant shall
permit Tenant to suspend payment of Tenant's Proportionate Share of Real Estate
Taxes until such receipts are furnished to Tenant.

                At any time and from time to time during the term of this Lease,
Tenant, at its expense, shall have the right to institute proceedings
challenging the amount of Real Estate Taxes.  Landlord agrees to reasonably
cooperate with Tenant in connection therewith.  Any refund awarded shall be
reimbursed first to each party in proportion to the expenses incurred by such
party in prosecuting such appeal, with any balance thereof next being refunded
to Tenant in an amount equal to Tenant's Proportionate Share of  (A) the balance
of such award remaining after the foregoing cost reimbursements (B) multiplied
by a fraction (1) the numerator of which shall be the number of days during the
tax year for which the refund is awarded for which Tenant has paid Real Estate
Taxes pursuant to this Lease and (2) the denominator of which is 365.

          (iii) "Operating Expenses" shall mean that part of any and all
expenses reasonably and actually incurred by Landlord in connection with its
ownership, maintenance and operation of the Building, the land upon which the
Building is situate, excluding Real Estate Taxes and interest or amortization
payments on any mortgage, but including, without limitation, electricity (other
than as billed directly to tenants based on usage); insurance maintained on the

                                      -3-
<PAGE>
 
Building in accordance herewith; all direct and indirect labor costs; a
management fee for Landlord's management of the relationships with contractors
(other than the Association) providing yard and landscape maintenance, snow
clearance and insurance required to be maintained hereunder if Landlord, upon
request of Tenant, is able to place such insurance at more favorable premium
rates than Tenant is able to obtain, which management fee shall not exceed four
percent (4%) of the annual amount actually paid under such contracts
("Management Fee"); legal expenses; service contracts and supplies used in
connection with the cleaning, operating, labor and maintenance of the common
areas of the Building; all repairs required to be performed by Landlord as
provided for in this Lease (other than "Landlord's Work" as defined herein);
common area decoration, repairs and maintenance; snow removal; building
supplies; all charges for the common areas of the Building for electricity and
water, removal of trash, rubbish, garbage and refuse; the cost of operating an
identification sign or signs for the Building; replacing of paving, curbs,
walkways, directions or other signs; drainage; maintenance and monitoring of
fire sprinkling systems (if any); the Building's proportionate share of common
expenses owed to the Eagleview Corporate Center Association or its successor or
any other similar entity which owns and maintains the common areas of the Center
(collectively, "Association"); and such other expenses as Landlord may deem
necessary and proper in connection with the operation and maintenance of the
common areas of the Building, excluding any costs which under generally accepted
accounting principles ("GAAP") are capital expenditures; provided, however, that
Operating Expenses shall also include the annual amortization (over the
anticipated useful life established in accordance with GAAP) of a capital
improvement falling within any of the following categories: (i)   a labor saving
device or improvement which is intended to reduce or eliminate any other
component of Operating Expenses; (ii) an installation or improvement required by
reason of any law, ordinance or regulation, which requirement did not exist on
the date of this Lease and is generally applicable to similar buildings; (iii)
an installation or improvement which directly enhances safety of tenants in the
Building or Center generally.  Landlord shall have the right to bill Tenant
directly for any items of Operating Expenses which can be attributed directly to
Tenant's use only.

          Notwithstanding any provision to the contrary, Operating Expenses
shall not include:

               (A) any payments (such as salaries or fees) to the Landlord's
executive personnel or in-house site managers except for the Management Fee;
               (B) depreciation or interest, except to the extent permitted
above in connection with capital improvements;
               (C) mortgage or ground lease payments;
               (D) taxes on the Landlord's business (such as income, excess
profits, franchise, capital stock, estate, inheritance) except to the extent
same are in lieu of Real Estate Taxes or increases in Real Estate Taxes;
               (E) leasing commissions, broker's fees or legal fees incurred in
connection with leases of space in the Building;

                                      -4-
<PAGE>
 
               (F) legal fees that do not directly benefit Tenant or the
Building (provided that legal fees incurred in connection with leases of space
in the Building or in enforcing tenant obligations shall not be deemed to
benefit the Building);

               (G) costs to correct original construction defects or defective
repairs or replacements hereinafter provided by or at the direction of Landlord;
               (H) costs of repairs covered by valid warranties;
               (I) expenses paid directly by a tenant for any reason (such as
excessive utility use, direct utility consumption, damage for which such tenant
is responsible);
               (J) costs for improving any tenant's space;
               (K) any repair or other work necessitated by condemnation, fire
or other insured casualty;
               (L) any costs, fines and the like due to Landlord's violation of
any law, governmental rule or authority;
               (M) refinancing costs;
               (N) costs for any conversion of the heating system to gas heat
except to the extent such conversion is undertaken in an effort to reduce
Operating Expenses and the cost thereof is treated in the same manner as a
capital improvement;
               (O) costs paid to Landlord or its affiliates other than the
Management Fee which exceed those reasonably charged in arms length transactions
with third parties in the general area of the Building; and
               (P) services, benefits or both provided to some tenants but not
to Tenant.

     (b)  Tenant shall pay Landlord the minimum annual rent ("Minimum Annual
Rent") during the Initial Term in the amounts set forth below, which annual
amount shall be paid in equal monthly installments as set forth below on the
first day of each calendar month in advance. The first monthly installment of
Minimum Annual Rent shall be due on the Commencement Date.  If the Commencement
Date is not the first day of a calendar month, rent from the Commencement Date
to the first day of the following month apportioned at the Minimum Annual Rent
rate (based on a 365-day year) shall be paid.  All rent shall be payable, in
advance, and without prior notice or demand, at the address of Landlord set
forth in the heading of this Lease or at such other place, or to such other
person, as Landlord may from time to time direct in written notice to Tenant.
During the Initial Term, Minimum Annual Rent for each lease year (being 12
months from the Commencement Date or anniversary thereof) shall be as follows:

<TABLE>
<CAPTION>
              Rate per Rentable
 Lease Year      Square Foot     Annual Rent  Monthly Installment
 ----------      -----------     -----------  -------------------
<S>           <C>                <C>          <C>
     1             $11.38        $550,792.00       $45,899.33

     2             $11.88        $574,992.00       $47,916.00

     3             $12.38        $599,192.00       $49,932.67

    4-10           $13.38        $647,592.00       $53,966.00
</TABLE>

                                      -5-
<PAGE>
 
In addition to the foregoing, Tenant shall pay all amounts when and as required
in the Work Letter.

     (c) In addition, Tenant shall pay to Landlord as Additional Rent in
equal monthly installments one twelfth (1/12) of Tenant's Proportionate Share of
annual Real Estate Taxes and Operating Expenses, at the time of payment of each
monthly installment of Minimum Annual Rent, based upon the most recent costs of
Operating Expenses and Real Estate Taxes available. For the period from the
Commencement Date until the issuance of a statement pursuant to subparagraph
3(d) below, such monthly installment shall be equal to $9,000.

     (d) Within ninety (90) days of the expiration of each calendar year
Landlord shall furnish Tenant with a written statement of the actual Operating
Expenses and Real Estate Taxes incurred for such year itemizing the expenses
claimed by Landlord in reasonable detail.  Within ten (10) days of the rendition
of such statement, Tenant shall pay any amounts in excess of those collected
pursuant to the payments on account of Real Estate Taxes and Operating Expenses
pursuant to paragraph 3(c) hereof, and any overpayments shall be credited
against the next installment(s) of rent due under this Lease or, at Tenant's
option, refunded to Tenant.  In the event the first and/or last years of the
Term of this Lease shall not be full calendar years, then Tenant's obligation
for Operating Expenses and Real Estate Taxes attributable to such years shall be
pro rated.  Tenant may, at its own cost and expense, after full payment of all
sums due and owing, audit Landlord's books and records not more than once each
year within sixty (60) days after Landlord's delivery of its annual statement of
Operating Expenses, which books and records shall be maintained in accordance
with GAAP.  Notwithstanding the foregoing, if any said review of Landlord's
books and records reveals that any item(s) were incorrectly included in
Operating Expenses, Tenant shall have the right to inspect Landlord's books and
records with respect to such items for each prior lease year and an adjustment,
if any, shall be made in accordance herewith.  If Tenant's audit determines that
Landlord's total charges for Operating Expenses or Real Estate Taxes for a given
lease year exceed by more than 5% the total amount properly chargeable to Tenant
under this Lease for such year, Landlord, in addition to reimbursing Tenant such
excess amount, shall pay Tenant an amount equal to the cost of the audit.

4.   ADDITIONAL RENT.
     --------------- 

Tenant shall pay to Landlord as "Additional Rent" (in addition to sums payable
pursuant to paragraphs 3 (c) and 3(d)) the following:

     (a) Expenses Incurred by Landlord as a Result of Tenant's Default.
         -------------------------------------------------------------  
All sums which may become due by reason of Tenant's failure to comply with any
of the terms, conditions and covenants of this Lease to be kept and observed by
Tenant, and any and all damages, costs and expenses (including without
limitation thereto reasonable attorney's fees) which Landlord may suffer or
incur by reason of any default of Tenant and any damage to the Building or the
real estate of which the Building is a part caused by any negligence or wilful
misconduct of Tenant or violation of Tenant's covenants in Section 5(a) below,
together with interest to the date of

                                      -6-
<PAGE>
 
payment (whether before or after entry of judgment and issuance of execution
thereon) at a rate equal to five percent (5%) above the prime interest rate (or
similar rate if the prime interest rate is no longer published) of First Union
Bank or its successor, in effect on the date during the period said payment is
due ("Default Rate"), which shall continue to accrue interest at the Default
Rate after entry of judgment and issuance of execution thereon until paid in
full.

     (b) Use and Occupancy Taxes. All use and occupancy taxes imposed by
         -----------------------                                        
any governmental body allocable to the Leased Space.

     (c) Utilities.  All charges for heat, gas, water, electric, trash and
         ---------                                                        
sewage disposal for the Leased Space, whether billed directly by the providers
of the same to Tenant or by Landlord as the owner of the Building, which charges
shall not exceed the charges actually incurred by Landlord therefor.

For purposes of this Lease, the term "Rent" or "rent" shall be deemed to refer
to Minimum Annual Rent and Additional Rent.

 5.  NEGATIVE COVENANTS OF TENANT; HAZARDOUS SUBSTANCES.
     -------------------------------------------------- 

     (a)  Tenant will not:

          (i)    damage the Leased Space or any other part of the Building;

          (ii)   bring into or permit to be kept in the Leased Space any
dangerous, explosive or obnoxious substances except as may be used in Tenant's
Business which use Tenant shall undertake in compliance with all applicable laws
regulating same;

          (iii)  conduct itself or permit its agents, servants, employees or
invitees to conduct themselves in a manner that in Landlord's judgment
reasonably exercised is improper or unsafe except that the operation of, or
activities related to, Tenant's Business shall not be deemed to violate this
provision, provided same are undertaken in compliance with all applicable laws;

          (iv)   manufacture any commodity other than in the course of Tenant's
Business or prepare or dispense any food or beverages in the Leased Space,
except for consumption in the Leased Space by Tenant, its employees or invitees;

          (v)    remove, attempt to remove or manifest any intention to remove
Tenant's goods or property from the Leased Space other than in the ordinary
course of business;

          (vi)   do or suffer to be done, any act, matter or thing objectionable
to Landlord's fire insurance companies or Board of Underwriters whereby the fire
insurance or any other insurance now in force or hereafter to be placed by
Landlord on the Leased Space or the Building or Center shall become void or
suspended, or whereby the same shall be rated as a more hazardous risk than at
the Commencement Date.  Tenant agrees to pay to Landlord as Additional

                                      -7-
<PAGE>
 
Rent, any and all increases in premiums for insurance carried by Landlord on the
Leased Space, or on the Building, caused in any way by the occupancy of Tenant.

     (b)  Tenant's Responsibility Regarding Hazardous Substances.
          ------------------------------------------------------ 
 
          (i)   The following definitions shall apply herein:

                (A) Hazardous Substances. The term "Hazardous Substances," as
                    --------------------
used in this Lease, shall include, without limitation, flammables, explosives,
radioactive materials, asbestos, polychlorinated biphenyls (PCB's), chemicals
known to cause cancer or reproductive toxicity, pollutants, contaminants,
hazardous wastes, toxic substances or related materials, petroleum and petroleum
products, and substances declared to be hazardous or toxic under any law or
regulation now or hereafter enacted or promulgated by any governmental
authority.

                (B) Tenant Responsible Parties. The term "Tenant Responsible
                    --------------------------  
Parties" as used in this Lease shall mean Tenant, its employees, agents,
contractors and/or invitees.

          (ii)  Tenant's Restrictions. Tenant shall not cause or permit to
occur:

                (A) Any violation of any federal, state, or local law,
ordinance, or regulation now or hereafter enacted, related to environmental
conditions on, under, or about the Leased Space or Center, arising from the use
or occupancy of the Leased Space by any Tenant Responsible Party, including, but
not limited to, soil and ground water conditions; or

                (B) The use, generation, release, manufacture, refining,
production, processing, storage, or disposal of any Hazardous Substance on,
under, or about the Leased Space or Center except as may be used in Tenant's
Business which use Tenant shall undertake in compliance with all applicable Laws
(defined below).

          (iii) Environmental Clean-Up.

                (A) Tenant shall, at Tenant's own expense, comply with all laws
regulating the use, generation, storage, transportation, or disposal of
Hazardous Substances ("Laws") by Tenant Responsible Parties.

                (B) Tenant shall, at Tenant's own expense, make all submissions
to, provide all information required by, and comply with all requirements of all
governmental authorities ("Authorities") under the Laws as are applicable to use
of Hazardous Substances by Tenant Responsible Parties.

                (C) Should any Authority or any third party demand that a clean-
up plan be prepared and that a clean-up be undertaken because of any deposit,
spill, discharge, or other release of Hazardous Substances that occurs during
the Term of this Lease at or from the

                                      -8-
<PAGE>
 
Leased Space and which arises at any time from the use of Hazardous Substances
by Tenant Responsible Parties, then Tenant shall, at Tenant's own expense,
prepare and submit the required plans and all related bonds and other financial
assurances, and Tenant shall carry out all such clean-up plans.

                (D) Tenant shall promptly provide all information regarding the
use, generation, storage, transportation, or disposal of Hazardous Substances by
Tenant Responsible Parties that is requested by Landlord. If Tenant fails to
fulfill any duty imposed under this subparagraph (iii) within a reasonable time,
Landlord may do so; and in such case, Tenant shall cooperate with Landlord in
order to prepare all documents Landlord deems necessary or appropriate to
determine the applicability of the Laws to the Leased Space and use of Hazardous
Substances by Tenant Responsible Parties, and for compliance therewith, and
Tenant shall execute all documents promptly upon Landlord's request. No such
action by Landlord and no attempt made by Landlord to mitigate damages under any
Law shall constitute a waiver of any of Tenant's obligations under this
Subparagraph (iii).

                (E) Tenant's obligations and liabilities under this Subparagraph
(iii) shall survive the expiration of this Lease.

          (iv)  Tenant's Indemnity.

                (A) Tenant shall indemnify, defend, and hold harmless Landlord,
the manager of the Center, and their respective officers, directors,
beneficiaries, shareholders, partners, agents and employees, from all fines,
suits, procedures, claims, and actions of every kind, and all costs associated
therewith (including reasonable attorneys' and consultants' fees) arising out of
or in any way connected with any deposit, spill, discharge, or other release of
Hazardous Substances that occurs during the Term of this Lease at or from the
Leased Space and which arises at any time from use of Hazardous Substances by
Tenant Responsible Parties, or from failure by Tenant Responsible Parties to
provide all information, make all submissions, and take all steps required by
all Authorities under the Laws with respect thereto.

                (B) Tenant's obligations and liabilities under this Subparagraph
(iv) shall survive the expiration of this Lease.

                (C) Attached to this Lease as Exhibit "C" and made part hereof
                                              -----------
is a Rider regarding Industrial Waste Discharge within Eagleview Corporate
Center.

 6.  LATE PAYMENT
     ------------

If any payment required by Tenant under any of the terms hereof shall not be
paid within five (5) days after written notice from Landlord that such payment
is overdue, Tenant shall, upon demand, pay a late charge to Landlord equal to
the greater of (a) Fifty ($50.00) Dollars or (b) $.05 for each dollar so due,
and such late charge shall be deemed Additional Rent for purposes of this Lease;
provided, however, that such late charge shall be due immediately without notice

                                      -9-
<PAGE>
 
upon any failure to pay when due during any twelve (12) month period in which
Landlord shall have given such written notice on two (2) prior occasions.

 7.  CONSTRUCTION OF LEASED SPACE.
     ---------------------------- 

     (a) Landlord shall, without cost to Tenant except as provided in the
Work Letter, complete "Landlord's Work" as defined in the Work Letter attached
hereto. Tenant shall, without cost to Landlord, furnish the drawings and
specifications as Landlord may require to complete the Tenant Improvements and,
in addition, shall complete the construction and other items of work in the
Leased Space which are not within the scope of Landlord's Work.  If, at Tenant's
request, Landlord performs any items of work or furnishes any materials which
Landlord is not required to perform or furnish hereunder, Tenant shall pay
Landlord for such additional work and materials, at such reasonable rates as
Landlord may charge.  If the TI Plans as defined in the Work Letter, or a
description thereof which is reasonable to identify same, have not been attached
hereto upon execution hereof, the TI Plans when completed in accordance with the
Work Letter shall be initialed for identification by Landlord and Tenant and
become part of this Lease when so initialed.

     (b) Within thirty (30) days after the Commencement Date, Tenant shall
give Landlord a written list ("Final Punch List") of all contended defects, if
any, in Landlord's construction work and of all contended variances in
Landlord's Work from the requirements hereof.  Except for defects or
deficiencies which are not then discoverable by Tenant, or which are covered by
third-party warranties or Landlord's warranty set forth in the Work Letter
(collectively, "Defects"), any and all variances not set forth in the Final
Punch List shall be deemed to be waived by Tenant. Landlord shall correct all
items on the Final Punch List that constitute valid defects or variances within
sixty (60) days after Landlord's receipt of the Final Punch List, unless the
nature of the defect or variance is such that a longer period of time is
required to repair or correct the same, in which case Landlord shall exercise
due diligence in correcting such defect or variance at the earliest possible
date and with a minimum of interference with the operation of Tenant.  If
Landlord does not complete such work within the time specified above, Tenant
shall have the right to complete such work at Landlord's expense.  Any
disagreement that may arise between Landlord and Tenant with respect to whether
an item on the Final Punch List constitutes a valid defect or variance shall be
conclusively resolved in the manner contemplated by the Work Letter.

     (c) By occupying the Leased Space as Tenant, Tenant shall be deemed to
have accepted the Leased Space and to have acknowledged that the Leased Space is
in the condition required by this Lease, except as to any defects or variances
set forth on the Final Punch List or Defects.

                                      -10-
<PAGE>
 
8.   TENANT'S ALTERATIONS.
     -------------------- 

     (a)  Except as hereafter provided, Tenant shall make no alterations,
additions or improvements ("Tenant Alterations") to the Leased Space without the
consent of Landlord, which consent shall not be unreasonably withheld, delayed
or conditioned.  At the time of Landlord's consent, Landlord shall designate
whether Tenant shall be required to remove the proposed Tenant Alteration upon
termination of this Lease, and the absence of such designation in Landlord's
written consent shall be deemed Landlord's agreement that Tenant shall not be
obligated to remove Tenant Alterations upon the termination of this Lease.
Landlord also may impose such reasonable conditions as part of its consent as
Landlord deems appropriate, taking into consideration the nature of the proposed
Tenant Alteration, including, without limitation, requiring Tenant to furnish
Landlord with security for the payment of all costs to be incurred in connection
with such work, insurance, and copies of the plans, specification and permits
necessary for such work. Nothing herein, however, shall be construed to obligate
Tenant to construct any Tenant Alteration for which Landlord has given its
consent.

     (b)  Landlord's consent shall not be required for Tenant Alterations which
(i) do not adversely impact the structural integrity of the Building or the
systems serving the Building or their operation, (ii) are not visible from the
Building exterior and (iii) qualify under the following:

          (A)  The Tenant Alteration is to be made to portions of the Leased
Premises other than the laboratory areas and the cost thereof is $10,000 or less
with respect to any Tenant Alteration project (or $20,000 or less in the
aggregate with respect to Tenant Alteration projects undertaken over any twelve
(12) consecutive month period); or

          (B)  The Tenant Alteration is to be made to the laboratory areas of
the Leased Premises and the cost thereof is $50,000 or less with respect to any
Tenant Alteration project (or $100,000 or less in the aggregate with respect to
Tenant Alteration projects undertaken over any twelve (12) consecutive month
period).

Tenant Alterations described in this subsection (b) for which Landlord's consent
is not required hereinafter are called "Permitted Tenant Alterations."
Notwithstanding the foregoing, painting or carpeting of the interior of the
Leased Space and like cosmetic improvements shall not be deemed Tenant
Alterations regardless of the cost thereof.  Tenant shall not be obligated to
remove Permitted Tenant Alterations upon the termination of this Lease unless an
Event of Default has not occurred which is then continuing and Landlord so
requires such removal.

     (c)  All Tenant Alterations shall be done at Tenant's expense by
contractors approved by Landlord, which consent shall not be unreasonably
withheld, delayed or conditioned and shall be deemed given unless Landlord
notifies Tenant of its objections within ten (10) business days after delivery
of Tenant's request for consent. With respect to Tenant Alterations other than
the Permitted Tenant Alterations, no work shall be performed until the plans
therefore have been approved by Landlord, which approval shall not be
unreasonably withheld, delayed or

                                      -11-
<PAGE>
 
conditioned and shall be deemed approved unless Landlord notifies Tenant of
objections to the proposed plans within ten (10) business days after delivery to
Landlord of a complete set of the plans therefor.  In connection with the review
of plans submitted by Tenant, Landlord shall be reimbursed by Tenant for
Landlord's cost in reviewing such plans at the rate of $60 per hour; subject to
reasonable increase to reflect the then current hourly charge imposed for such
review by Landlord for its tenants in the Center generally, and prior to
undertaking any such review, Landlord shall provide a statement of the maximum
review hours to be dedicated to such review. With respect to Permitted Tenant
Alterations, Tenant shall provide Landlord with a copy of Tenant's application
for a building permit therefor, if applicable, (together with all attachments
thereto), and no review fee shall be charged to Tenant by Landlord in connection
therewith nor shall Landlord's approval of such application be required. Tenant
shall provide copies of as-built plans and specifications for all Tenant
Alterations to Landlord within a reasonable time of completion of the Tenant
Alteration.   All Tenant Alterations shall be done in a first class, workmanlike
manner and shall comply with all insurance requirements then made available to
Tenant and all applicable laws, ordinances, rules and regulations of
governmental authorities having jurisdiction thereover, and, where applicable,
with all reasonable requirements of Landlord imposed as a condition of such
consent.

     (d)  If, as a condition of Landlord's consent, removal of a Tenant
Alteration is required at termination of this Lease, Tenant shall promptly
remove such Tenant Alterations and repair any damage occasioned by such removal.
In default thereof, Landlord may effect said removal and repairs at Tenant's
expense.  With respect to any Tenant Alterations which Tenant is not obligated
to remove hereunder (including without limitation Permitted Tenant Alterations),
such Tenant Alterations, if not removed by Tenant upon the termination of this
Lease, shall be deemed abandoned by Tenant, and deemed a part of Landlord's
property, notwithstanding any provision of Section 16 to the contrary.

9.   MECHANIC'S LIENS.
     ---------------- 

Prior to Tenant's performing or ordering (other than through Landlord or
Landlord's contractors) any construction or other work on or about the Leased
Space for which a lien could be filed against the Leased Space or the Building,
Tenant shall enter into a written waiver of liens agreement with the contractor
who is to perform such work, and such written agreement shall be filed, in
accordance with the Mechanics' Lien Law of the state where the Building is
located prior to the commencement of such work.  Tenant's failure to enter into
or record such waiver of liens shall not be deemed a default hereunder.
Notwithstanding the foregoing, if any mechanics' or other lien shall be filed
against the Leased Space or the Building purporting to be for labor or material
furnished or to be furnished at the request of the Tenant other than through
Landlord or Landlord's contractors, then Tenant shall at its expense cause such
lien to be discharged of record by payment, bond or otherwise, within fifteen
(15) days after Tenant receives notice of the filing thereof.  If Tenant shall
fail to cause such lien to be discharged by payment, bond or otherwise within
such period, Landlord may cause such lien to be discharged by payment, bond or
otherwise, without investigation as to the validity thereof or as to any offsets
or defenses thereto, and Tenant shall, upon demand, reimburse Landlord for all
amounts paid and costs incurred,

                                      -12-
<PAGE>
 
including attorneys' fees, in having such lien discharged of record.  If,
however, Tenant notifies Landlord during such fifteen (15) day period that it
disputes the validity of such lien and provides security reasonably acceptable
to Landlord in an amount which is sufficient to discharge such lien in full,
Landlord shall refrain from satisfying such lien for a period not to exceed one
hundred twenty (120) days.

10.  CONDITION OF LEASED SPACE.
     ------------------------- 

Tenant acknowledges and agrees that, except as expressly set forth in this
Lease, there have been no representations or warranties made by or on behalf of
Landlord with respect to the Leased Space or the Building or with respect to the
suitability of either for the conduct of Tenant's Business.

11.  COMMON AREA MAINTENANCE.
     ----------------------- 

     (a)  Landlord shall provide all maintenance, repairs and replacements to
the common areas of the Building if the Building is a multi-tenant Building, and
to all common areas external to the Building. The cost of same shall be included
in the Operating Expenses to the extent provided in Section 3(a)(iii) unless the
necessity for the foregoing arises (a) from the gross negligence or willful and
wanton misconduct of Landlord or its employees or, subject to Section
3(a)(iii)(i) , by any other tenant of the Building or such tenant's agents,
employees, licensees, or invitees, in which case such cost shall not be included
as part of the Operating Expenses but shall be paid by Landlord (without
prejudice to Landlord's right to recover same from the responsible party), or
(b) from the negligence or willful and wanton misconduct of Tenant, its agents,
employees, licensees or invitees, in which case such cost shall be paid by
Tenant. Any such maintenance, replacements or repairs and any labor performed or
materials furnished by or upon the direction of Landlord shall be performed in a
good and workmanlike manner, using only materials of at least the same quality
and integrity as that being repaired or replaced, and performed and furnished in
compliance with all applicable laws, regulations, ordinances and requirements of
all duly constituted authorities or governmental bodies having jurisdiction over
the Building, and the requirements of any board of underwriters having
jurisdiction thereof. It is understood that this is a "triple net" lease, with
rent paid to Landlord intended to be net of taxes, repairs not covered by this
Section or Section 14, insurance and Operating Expenses.

     (b)  Unless otherwise agreed with Tenant in writing, Landlord agrees that
all maintenance to the common areas external to the Building which the
Association offers to perform or is obligated to perform for the benefit of lots
in the Center shall be performed by the Association. Landlord shall use diligent
efforts to enforce any such obligation of the Association. Except during such
period of time as Landlord or its affiliates control the Association, Landlord
shall not be liable in damages or otherwise for temporary delay or failure in
furnishing any service or facility to be provided by the Association.

     (c)  In the absence of a judgment to the contrary, in no event shall any
delay or failure to provide the services or obligations under subsections (a) or
(b) above, regardless of cause, be

                                      -13-
<PAGE>
 
deemed to be an eviction or disturbance of Tenant's use and possession of the
Leased Space, render Landlord liable to Tenant, authorize abatement of rent,
relieve Tenant from performance of its obligations under this Lease, or result
in a termination of this Lease.  The foregoing, however, shall not be deemed to
prevent Tenant's exercise of its rights under Section 42 hereof.

12.  ASSIGNMENT AND SUBLETTING.
     ------------------------- 

     (a)  Tenant shall not, without the prior written consent of Landlord,
assign or mortgage (except as permitted under Section 36(b) hereof) this Lease
or any interest therein or sublet the Leased Space or any part thereof. For the
purposes of this paragraph, the sale or assignment of a controlling interest in
the Tenant corporation or a majority interest in the Tenant partnership as the
case may be shall be deemed an assignment, but the assignment to a parent,
wholly-owned subsidiary of the Tenant or successor corporation shall be
permitted, provided that such assignee assumes the obligations of Tenant and
that such assignment shall not relieve Tenant of its obligations hereunder.  For
purposes herein, (A) a successor corporation is one into which Tenant is merged
or consolidated, or which acquired those of Tenant's assets or business located
in the Leased Space as of the date of the assignment, and (B) a controlling
interest shall mean the ownership of fifty percent or more of the beneficial
interest in the person or entity in question, unless the corporation is publicly
traded in which case such transfers of stock (whether or not a controlling
interest) shall not be deemed to be an assignment.  As to any other assignment,
Landlord agrees that it shall not unreasonably withhold its consent, provided
the business of Tenant's assignee or subtenant is no more hazardous than that of
Tenant, it being understood that it shall not be unreasonable for Landlord to
require, as a condition of such consent:

     (b)  That 50% of any money or other economic consideration received by
Tenant as a result of such subletting or assignment and which is not properly
allocable to any lease of Tenant's personal property in the Leased Space or sale
of Tenant's assets from the business operated at the Leased Space or sale of
Tenant's stock or other arms-length transaction, which exceeds, in the
aggregate, the total sums which Tenant is obligated to pay Landlord under this
Lease (pro rated to reflect obligations allocable to that portion of the Leased
Space subject to the sublease or assignment) shall be payable to Landlord as
Additional Rent under this Lease without affecting or reducing any other
obligation of Tenant hereunder; and

     (c)  Unless otherwise agreed in Landlord's consent, no subletting or
assignment shall release Tenant of Tenant's obligation or alter the primary
liability of Tenant to pay the rental and to perform all other obligations to be
performed by Tenant hereunder.  The acceptance of rental by Landlord from any
other person shall not be deemed to be a waiver by Landlord of any provision
hereof.  Consent to one assignment or subletting shall not be deemed consent to
any subsequent assignment or subletting.  In the event of default by any
assignee of Tenant or any successor of Tenant in the performance of any of the
terms hereof, Landlord may proceed directly against Tenant without the necessity
of exhausting remedies against such assignee or successor. Landlord may consent
to subsequent assignment or subletting of this Lease or amendments or
modifications to this Lease with assignees of Tenant, without notifying Tenant,
or any successor

                                      -14-
<PAGE>
 
of Tenant, and without obtaining its or their consent thereto and such action
shall not relieve Tenant of liability under this Lease.

13.  ACCESS TO LEASED SPACE.
     ---------------------- 

Landlord, its employees and agents, shall have the right to enter the Leased
Space at all reasonable times for the purpose of examining or inspecting the
same, showing the same to prospective purchasers or tenants of the Building, or
mortgagees, and making such alterations, repairs, improvements or additions to
the Leased Space or to the Building as Landlord may deem necessary or desirable
provided such alterations, repairs, improvements or additions do not adversely
affect Tenant's Business or use of the Leased Space or, except with Tenant's
consent, alter the Tenant Improvements performed in accordance with the Work
Letter.  Except in case of emergency in Landlord's reasonable judgment, any such
entry shall be after reasonable notice to Tenant and in compliance with Tenant's
practices from time to time established with respect to testing areas or other
areas where confidential information is located.  If a representative of Tenant
shall not be present to open and permit entry into the Leased Space at any time
when such entry by Landlord is necessary in an emergency, Landlord may enter by
means of a master key (or forcibly) without liability to Tenant and without such
entry constituting an eviction of Tenant or termination of this Lease.  All keys
must be returned to Landlord at the expiration or termination of the Lease.

14.  REPAIRS.
     ------- 

     (a)  Landlord shall perform all maintenance, replacements and repairs
necessary to maintain the roof, load bearing walls (other than paint and wall
coverings), floors (other than carpeting, tile and similar floor coverings),
foundations and other structural elements of the Building, and all plumbing and
electrical fixtures and equipment and HVAC system components serving portions of
the Building in addition to the Leased Space; provided, however, that Landlord
shall not be obligated for any of such repairs until the expiration of a
reasonable period of time after written notice that such repair is needed.  The
cost of same shall be included in the Operating Expenses to the extent provided
in Section 3(a)(iii) unless the necessity for any of the foregoing arises (a)
from the gross negligence or wilful and wanton misconduct of Landlord or its
employees or, subject to Section 3(a)(iii)(i)   hereof, by any other tenant of
the Building or such tenant's agents, employees, licensees, or invitees, in
which case such cost shall not be included as part of the Operating Expenses but
shall be paid by Landlord (without prejudice to Landlord's right to recover same
from the responsible party), or (b) negligence or wilful and wanton misconduct
of Tenant, its agents, employees, licensees or invitees, in which case such cost
shall be paid by Tenant.  Any such maintenance, replacements or repairs and any
labor performed or materials furnished by or upon the direction of Landlord
shall be performed in a good and workmanlike manner, using only materials of at
least the same quality and integrity as that being repaired or replaced, and
performed and furnished in compliance with all applicable laws, regulations,
ordinances and requirements of all duly constituted authorities or governmental
bodies having jurisdiction over the Building, and the requirements of any board
of underwriters having jurisdiction thereof.

                                      -15-
<PAGE>
 
     (b)  Except as the Landlord is obligated for repairs as provided above or
in Section 11, Tenant shall make, at its sole cost and expense, all repairs
necessary to maintain the Leased Space, including without limitation, all
plumbing, heating, ventilation, air conditioning and electrical lines, pipes,
fixtures and equipment not expressly to be maintained by Landlord pursuant to
subparagraph (a) and shall keep the Leased Space and the fixtures therein in
neat and orderly condition. Without limiting the generality of the foregoing,
Tenant at its expense is specifically required to make promptly all repairs (i)
to that portion of any pipes, lines, ducts, wires or conduits contained within
the Leased Space which exclusively serve the Leased Space; (ii) to the glass
windows, plate glass doors, and any fixtures or appurtenances composed of glass
and which are located within the Leased Space; (iii) to Tenant's sign(s); and
(iv) to any heating or air conditioning equipment installed in and exclusively
servicing the Leased Space. During the Term, Tenant at its own expense shall
keep in place a maintenance contract with a reputable heating and air
conditioning service company reasonably acceptable to Landlord, and provide
Landlord with a copy of the same. If the Tenant refuses or neglects to make such
repairs or fails to diligently prosecute the same to completion after written
notice from Landlord of the need therefore and a reasonable time for cure,
Landlord may make such repairs at the expense of Tenant and such expense shall
be collectible as Additional Rent. Any such repairs and any labor performed or
materials furnished in, on or about the Leased Space shall be performed and
furnished by Tenant in compliance with all applicable laws, regulations,
ordinances and requirements of all duly constituted authorities or central
bodies having jurisdiction over the Building, the requirements of any board of
underwriters having jurisdiction thereof, as well as any reasonable regulations
imposed by Landlord pertaining thereto. Without limitation of the foregoing,
Landlord shall have the right to approve any and all contractors and suppliers
to furnish materials and labor for such repairs, which consent shall not be
unreasonably withheld, delayed or conditioned.

     (c)  If required solely as a result of Tenant's particular activities at
the Leased Space (as opposed to general occupancy thereof by any tenant), Tenant
also shall comply with, and make any repairs and installations required by any
applicable law.

     (d)  Provided that Landlord shall exercise reasonable efforts to effectuate
its repairs in a manner which will keep at a minimum Landlord's interference
with Tenant's use and occupancy of the Leased Space, Landlord shall not be
liable by reason of any injury to or interference with Tenant's business arising
from the making of any repairs, alterations, additions or improvements in or to
the Leased Space, or the Building or Center or to any appurtenances or equipment
therein.

                                      -16-
<PAGE>
 
15.  TERMINATION AND EXTENSION.
     ------------------------- 

     (a)  It is hereby mutually agreed that either party hereto may terminate
this Lease at the end of the Term if a renewal right has not been exercised or,
if exercised, upon the end of any renewal term, by giving to the other party
written notice at least ninety (90) days prior thereto. In default of such
notice, this Lease shall continue upon the same terms and conditions in force
immediately prior to the expiration of the term hereof (except that the monthly
installment of Minimum Annual Rent shall be increased by the CPI Adjustment
(defined in Section 46) for a further period of one (1) month and so on from
month to month unless and until terminated by either party hereto giving the
other thirty (30) days' written notice for removal previous to the expiration of
the then current term; provided, however, that if Landlord shall have given
written notice prior to the expiration of the Term if a renewal right has not
been exercised or, if exercised, prior to the expiration of such renewal term,
of its intention to make changes to the terms and conditions of this Lease and
Tenant shall not within ten business (10) days from such notice notify Landlord
in writing of Tenant's intention to vacate the Leased Space at the end of the
then current term, Tenant shall be considered as Tenant under the terms and
conditions mentioned in such notice for a further term as above provided, or for
such further term as may be stated in such notice. In the event that Tenant
shall have given notice as stipulated in this Lease of intention to vacate the
Leased Space at the end of the Term or any renewal or extension thereof and
shall fail or refuse so to vacate same on the date designated by such notice,
then it is expressly agreed that Landlord shall have the option, either

          (i)   to disregard the notice so given as having no effect, in which
case the terms and conditions of this Section shall apply; or

          (ii)  Landlord may, at any time, give Tenant ten (10) days' written
notice of its intention to terminate this Lease; whereupon Tenant expressly
agrees to vacate the Leased Space at the expiration of the said period of ten
(10) days specified in said notice.

     (b)  If Tenant shall hold over after the expiration of the Term hereof (as
may be extended pursuant subsection (a) above), and Landlord shall not give
consent to such hold over by Tenant, such tenancy may be terminated as permitted
by applicable state law, and until Tenant has vacated the Leased Space, it
agrees to pay to Landlord rent at a monthly rental double the rate payable by
Tenant at the expiration of the Term of this Lease.

16.  SURRENDER OF LEASED SPACE.
     ------------------------- 

At the end of the Term of this Lease, Tenant shall surrender the Leased Space to
Landlord, in broom clean condition and in good order and repair except for
ordinary wear and tear and damage for which Tenant is not obligated to make
repairs under this Lease.  Subject to Sections 8 and 9 hereof and if Event of
Default has not occurred which is then continuing, Tenant shall have the right
at the end of the Term hereof to remove any Tenant Alterations and any
equipment, furniture, trade fixtures or other personal property placed in the
Leased Space by Tenant, provided that Tenant promptly repairs any damage to the
Leased Space caused by such removal.

                                      -17-
<PAGE>
 
Tenant shall repair all damage to the Leased Space caused by such removal and
restore the Leased Space to the condition in which they were prior to the
installation of the items so removed, reasonable wear and tear and damage by
casualty not caused by Tenant excepted. Tenant shall surrender the Leased Space
to Landlord at the end of the term hereof, without notice of any kind (except to
the extent required by Section 15 above), and Tenant waives all right to any
such notice as may be provided under any laws now or hereafter in effect in
Pennsylvania.  If Tenant shall fail to remove any Tenant Alterations which it
was required to remove pursuant to Section 8 of this Lease or any of its
equipment, furniture, trade fixtures or other personal property, Landlord may
remove and store the same at the expense of Tenant or sell the same on behalf of
Tenant at public or private sale in such manner as is commercially reasonable,
with any proceeds thereof to be first applied to the costs and expenses,
including attorney's fees, of the storage and sale and the payment of any
amounts owed hereunder by Tenant.

17.  INDEMNIFICATION AND INSURANCE.
     ----------------------------- 

     (a)  Tenant covenants and agrees that it shall, without notice or demand
and at its own cost and expense, indemnify and save harmless Landlord against
and from, and Landlord shall not be liable to Tenant for, any and all claims by
or on behalf of any person arising in any manner whatsoever from, out of, or in
connection with any accident, death, injury, or damage, loss or theft of
property in or about the Leased Space (whether involving property belonging to
Tenant or any other person) resulting from the negligence or wilful misconduct
of Tenant, its agents, employees, licensees or invitees, and from and against
all costs, reasonable attorney fees, expenses and liabilities incurred in or as
a result of any such claim or action or proceeding brought against Landlord by
reason of any such claim. Tenant, upon notice from Landlord, covenants to resist
or defend such action or proceeding by legal counsel reasonably satisfactory to
Landlord.

     (b)  Tenant shall keep in force public liability insurance with respect to
the Leased Space, including contractual insurance with respect to the covenants
and agreements above, with companies and in form reasonably acceptable to
Landlord to afford protection of not less than One Million ($1,000,000.00)
Dollars with respect to personal injury or death and property damage, and naming
Landlord as an additional insured and providing not less than thirty (30) days'
notice of cancellation. Copies of such policies or a certificate of insurance
evidencing same shall be delivered to Landlord.

     (c)  Landlord covenants and agrees that it shall, without notice or demand
and at its own cost and expense, indemnify and save harmless Tenant against and
from, and Tenant shall not be liable to Landlord for, any and all claims by or
on behalf of any person arising in any manner whatsoever from, out of, or in
connection with any accident, death, injury, or damage, loss or theft of
property in or about the Leased Space (whether involving property belonging to
Landlord or any other person) resulting from the gross negligence or wanton and
wilful misconduct of Landlord, its agents or employees, and from and against all
costs, reasonable attorney fees, expenses and liabilities incurred in or as a
result of any such claim or action or proceeding brought against Tenant by
reason of any such claim. Landlord, upon notice from

                                      -18-
<PAGE>
 
Tenant covenants to resist or defend such action or proceeding by legal counsel
reasonably satisfactory to Tenant.

     (d)  Landlord shall keep in force public liability insurance with respect
to the Building, including contractual insurance with respect to the covenants
and agreements above, with companies and in form reasonably acceptable to Tenant
to afford protection of not less than One Million ($1,000,000.00) Dollars with
respect to personal injury or death and property damage, and naming Tenant as an
additional insured and providing not less than thirty (30) days' notice of
cancellation. Copies of such policies or a certificate of insurance evidencing
same shall be delivered to Tenant.

     (e)  All insurance policies also shall contain a clause or endorsement
denying the insurer any rights of subrogation against Landlord, in the case of
Tenant's insurer, and Tenant, in the case of Landlord's insurer.  As to any loss
or damage covered by insurance containing a waiver of subrogation clause or
similar endorsement, each party hereby releases the other, to the extent of such
damaged party's insurance indemnities, from any and all liability for such loss
or damage even if such loss or damage shall be brought about by the fault or
negligence of such other party, or the agents, employees, invitees or licensees
of such other party; provided however, that this release shall be effective only
with respect to loss or damage occurring during such time as the applicable
policies of insurance shall contain a clause to the effect that this release
shall not affect said policies or the right of the insured to recover
thereunder.  If any policy does not contain such, the insured party shall, at
the written request of the other party to this release, have such a clause added
to said policy if an endorsement so providing is obtainable.  This subsection
(e) shall supersede any provisions to the contrary in subsection (a) and (c)
above.

18.  FIRE OR OTHER CASUALTY.
     ---------------------- 

     (a)  At all times during the effectiveness of this Lease, Landlord shall
maintain in full force and effect a policy of fire and extended coverage
insurance for the full replacement value of the Building, subject to a
commercially reasonable deductible. The premium for such insurance shall be
included as an Operating Expense. Such coverage shall be issued by any reputable
insurance company licensed in Pennsylvania, with at least a Best's rating of "A"
or better. Landlord agrees to deliver a certificate evidencing such insurance
coverage upon Tenant's request from time to time.

     (b)  If the Leased Space or the Building is partially damaged by fire or
other casualty such that Tenant is able to conduct its business therein at a
reduced but economically feasible level on a temporary basis, and insurance
proceeds are available to Landlord, the damages shall be repaired by and at the
expense of Landlord and the rent, until such repairs shall be made, shall be
apportioned from the date of such fire or other casualty according to the part
of the Leased Space which is usable by Tenant. Landlord agrees to repair such
damage within a reasonable period of time after receipt from Tenant of written
notice of such damage, except that Tenant agrees to repair and replace its own
furniture, furnishings and equipment which were not provided as part of the
Tenant Improvements. If Landlord is unable to complete reconstruction

                                      -19-
<PAGE>
 
of the damaged premises within two hundred ten (210) days from the date of the
casualty, Tenant shall have the right to terminate this Lease.

     (c)  If the Leased Space or Building is totally damaged or is rendered
wholly untenantable by fire or other casualty, each party shall have the right
to terminate the Lease by written notice to the other on or before thirty (30)
days after such casualty occurred.  If, however, Landlord consents in writing
within thirty (30) days following such casualty to reconstruct the damaged
premises to the condition which existed prior to such casualty and a reputable
contractor acceptable to Landlord and Tenant determines that such reconstruction
can be substantially completed within two hundred ten (210) days from the date
of such casualty, neither party shall have the right to terminate this Lease and
Landlord shall undertake reconstruction of the damaged premises.  If, however,
Landlord is unable to complete reconstruction of the damaged premises within two
hundred ten (210) days from the date of the casualty, Tenant shall have the
right to terminate this Lease.

     (d)  Whenever Landlord shall be obligated hereunder to reconstruct damaged
premises, Landlord agrees to undertake such reconstruction with reasonable
diligence and, if Tenant shall remain in possession of any portion of the Leased
Space, in such manner so as to minimize interference or disruption of Tenant's
use of the Leased Space. Reconstruction shall be performed in a good and
workmanlike manner, in accordance with standard construction practices and
safety procedures, using only materials of at least equal quality and integrity
as the materials damaged by the casualty, undertaken in such manner so as to
restore the damaged premises to substantially the condition which existed prior
to such casualty, and performed and furnished in compliance with all applicable
laws, regulations, ordinances and requirements of all duly constituted
authorities or governmental bodies having jurisdiction over the Building, and
the requirements of any board of underwriters having jurisdiction thereof. For
purposes of implementing the foregoing, the parties agree to substantially
adhere to the practices established by the Work Letter attached hereto.

     (e)  Upon the termination of this Lease under the conditions hereinbefore
provided, Tenant's liability for rent shall cease as of the day of the casualty.
Tenant shall promptly vacate and surrender the Leased Space to Landlord in its
"as is" condition, whereupon neither party shall have any further rights or
obligations hereunder except that Landlord shall reimburse to Tenant (i) any
portion of the Security Deposit not otherwise applied by Landlord in accordance
with this Lease, (ii) prepaid Rent paid by Tenant, and (iii) an amount equal to
the unamortized value of Tenant's Direct Payment Portion which would have
amortized over the remaining portion of the Initial Term. Such reimbursement
shall be made in full to Tenant not later than thirty (30) days following
termination of this Lease, and if not so paid, such unpaid amounts shall accrue
interest at the Default Rate specified in this Lease from the date of
termination until paid in full. The limitations set forth in Section 28 hereof
shall not apply Landlord's liability for payment of the foregoing amounts.

                                      -20-
<PAGE>
 
19.  CONDEMNATION.
     ------------ 

If the Leased Space or the Building or any material part of either shall be
condemned or otherwise subject to an eminent domain proceeding, then and in that
event, upon the transfer of title to the authority exercising such power, this
Lease shall terminate, and all rent paid in advance shall be apportioned as of
the date of such termination.  Notwithstanding the foregoing, if only a part of
the Leased Space shall be so taken and the part not so taken shall be sufficient
in Tenant's reasonable judgment for the economic and feasible operation of
Tenant's business, Tenant, at its election, may retain the part not so taken and
there shall be a proportional reduction in the rent.  All compensation awarded
or paid upon such a total or partial taking of the Leased Space shall belong to
and be the property of the Landlord and Tenant shall have the right to
compensation only to the extent the Tenant Improvements are impacted by such
condemnation and then only to the extent of Tenant's Direct Payment Portion (as
defined in Section 3 of the Work Letter). The foregoing shall not, however, be
construed to preclude the Tenant from prosecuting any claim directly against the
condemning authority in such condemnation proceedings for loss of business, or
depreciation to, damage to, or cost of removal of, or for the value of stock,
trade fixtures, furniture, and other personal property belonging to the Tenant,
provided, however, that no such award or claim shall diminish or otherwise
adversely affect the Landlord's award (subject to Tenant's interest therein as
aforesaid).

20.  ESTOPPEL CERTIFICATES.
     --------------------- 

At any time, and from time to time, upon the written request of Landlord or any
"Mortgagee" (as defined in section 29 hereof), Tenant, within ten (10) business
days of the date of such written request, agrees to execute and deliver to
Landlord and/or such Mortgagee, a written statement: (a) ratifying this Lease;
(b) confirming the commencement and expiration dates of the terms of this Lease;
(c) certifying that Tenant is in occupancy of the Leased Space, and that the
Lease is in full force and effect and has not been modified, assigned,
supplemented or amended except by such writings as shall be stated; (d)
certifying that all conditions and agreements under this Lease to be satisfied
or performed by Landlord have been satisfied and performed except as shall be
stated; (e) certifying that Landlord is not in default under the Lease and there
are no defenses or offsets against the enforcement of this Lease by Landlord, or
stating the defaults and/or defenses claimed by Tenant; (f) reciting the amount
of advance rent, if any, paid by Tenant and the date to which such rent has been
paid; (g) reciting the amount of security deposited with Landlord, if any; and
(h) any other information which Landlord or the Mortgagee reasonably may
require. The failure of Tenant to execute, acknowledge and deliver to Landlord
and/or any Mortgagee a statement in accordance with the provisions herein within
the period set forth herein shall constitute an acknowledgment by Tenant which
may be relied upon by any person holding or intending to acquire any interest
whatsoever in the Leased Space or the Building that this Lease has not been
assigned, amended, changed or modified, is in full force and effect and that the
Minimum Annual Rent, and Additional Rent have been duly and fully paid not
beyond the respective due dates immediately preceding the date of the request
for such statement and shall constitute as to any persons entitled to rely on
such statements (other than Landlord) a waiver of

                                      -21-
<PAGE>
 
any defaults by Landlord or defenses or offsets against the enforcement of this
Lease by Landlord which may exist prior to the date of the written request.

21.  DEFAULT.
     ------- 

The occurrence of any of the following shall constitute an "Event of Default" of
this Lease by Tenant:

     (a)  A failure by Tenant to pay, when due, any installment of rent
hereunder or any such other sum herein required to be paid by Tenant where such
failure continues for ten (10) days after written notice thereof from Landlord;
provided however said written notice shall not be required to be given by
Landlord more than twice in any twelve (12) month period.

     (b)  A failure by Tenant to observe and perform any other terms or
conditions of this Lease to be observed or performed by Tenant, where such
failure continues for thirty (30) days after written notice thereof from
Landlord to Tenant; provided that, if such default is of a nature that cannot be
reasonably cured within such thirty (30) day period, no default shall exist so
long as Tenant has commenced cure within such thirty (30) day period and
diligently pursues same to completion within ninety (90) days.

     (c)  The making by Tenant of any assignment for the benefit of creditors,
an adjudication that Tenant is bankrupt, insolvent, or unable to pay its debts;
the filing by or against Tenant of a petition in bankruptcy or of a petition for
reorganization or arrangement under any law relating to bankruptcy (unless, in
the case of a petition filed against Tenant, the same is dismissed within sixty
(60) days after the filing thereof); the appointment of a trustee or receiver to
take possession of substantially all of Tenant's assets located in the Leased
Space or of Tenant's interest in this Lease (unless possession is restored to
Tenant within thirty (30) days after such appointment); or the attachment,
execution or levy against, or other judicial seizure of, substantially all of
Tenant's assets located in the Leased Space or of Tenant's interest in this
Lease (unless the same is discharged within thirty (30) days after issuance
thereof).

22.  REMEDIES.
     -------- 

Upon the occurrence of any Event of Default by Tenant:

     (a)  Landlord may perform for the account of Tenant any such act, the
omission of which constituted an Event of Default by Tenant and immediately
recover as Additional Rent any expenditures made and the amount of any
obligations incurred in connection therewith, plus interest at the Default Rate
from the date the obligations are incurred by Landlord until payment therefor to
Landlord, whether before or after entry of judgment and issuance of execution
thereon.

     (b)  Landlord may accelerate all Minimum Annual Rent and Additional Rent
due for the balance of the Term of this Lease and declare the same to be
immediately due and payable.

                                      -22-
<PAGE>
 
In determining the amount of any future payments due Landlord relating to
Operating Expenses and/or Real Estate Taxes, Landlord shall make such
determination based upon the most recent estimates of Operating Expenses and/or
Real Estate Taxes available.

     (c)  Landlord, at its option, may serve notice upon Tenant that this Lease
and the then unexpired term thereof shall cease and expire and become absolutely
void on the date specified in such notice, to be not less than five (5) days
after the date of such notice without any right on the part of the Tenant to
save the forfeiture by payment of any sum due or by the performance of any term
or condition broken; and, thereupon and at the expiration of the time limit in
such notice, this Lease and the Term hereof, as well as the right, title and
interest of the Tenant hereunder, shall wholly cease and expire and become void
in the same manner and with the same force and effect (except as to Tenant's
liability) as if the date fixed in such notice were the date herein granted for
expiration of the Term of this Lease. Thereupon, Tenant shall immediately quit
and surrender to Landlord the Leased Space, and Landlord may enter into and
repossess the Leased Space by summary proceedings, detainer, ejectment or
otherwise and remove all occupants thereof and, at Landlord's option, any
property thereon, without being liable to indictment, prosecution or damages
therefor. No such expiration or termination of this Lease shall relieve Tenant
of its liability and obligations under this Lease, whether or not the Leased
Space shall be relet.

     (d)  Landlord may, at any time after the occurrence of any Event of
Default, re-enter and repossess the Leased Space and any part thereof and
attempt in its own name, as agent for Tenant if this Lease not be terminated, or
on its own behalf if this Lease be terminated, to relet all or any part of the
Leased Space for and upon such terms and to such persons and for such period or
periods as Landlord, in its sole discretion, shall determine, including a term
beyond the termination of this Lease; and Landlord shall not be required to
accept any tenant offered by Tenant or observe any instruction given by Tenant
about such reletting. For the purpose of such reletting, Landlord may decorate
or make repairs, changes, alterations or additions in or to the Leased Space to
the extent deemed by Landlord desirable or convenient; and the cost of such
decoration, repairs, changes, alterations or additions shall be charged to and
be payable by Tenant as Additional Rent hereunder, as well as any reasonable
brokerage and attorneys fees incurred by Landlord; and any sums collected by
Landlord from any new tenant obtained shall be credited against the balance of
the rent due hereunder as aforesaid. Tenant shall pay to Landlord monthly, on
the days when the rent would have been payable under this Lease, the amount due
hereunder less the amount obtained by Landlord from such new tenant.

     (e)  Landlord shall have the right of injunction, in the event of a breach
or threatened breach by Tenant of any of the terms and conditions hereof, to
restrain the same and the right to invoke any remedy allowed by law or in
equity, whether or not other remedies, indemnities or reimbursements are herein
provided. The rights and remedies given to Landlord in this Lease are distinct,
separate and cumulative remedies; and no one of them, whether or not exercised
by Landlord, shall be deemed to be in exclusion of any of the others.

                                      -23-
<PAGE>
 
     (f)  In the event of the occurrence of an Event of Default hereunder,
Landlord shall have the right to change the locks on the Leased Space and
exclude Tenant therefrom, and to discontinue all or part of the services and
facilities provided to Tenant under this Lease or otherwise, which action shall
not be deemed an eviction. Such action may be taken, however, only upon five (5
)days prior notice to Tenant, and Tenant hereby releases Landlord from any
liability for any damages sustained by Tenant or its property as a result of the
same.

     (g)  If Tenant has paid accelerated rent to Landlord and Landlord
thereafter re-lets any portion of the Leased Space, any sums collected by
Landlord from any new tenant obtained in excess of the cost of decoration,
repairs, changes, alterations or additions, and any reasonable brokerage and
attorneys fees incurred by Landlord in connection with such re-letting, to the
extent the same exceed all other damages incurred by Landlord as a result of
Tenant's default, shall be paid to Tenant if, as and when received by Landlord
from the replacement tenant, but in no event shall the amount to be paid to
Tenant by Landlord exceed the amount of accelerated rent and other damages paid
by Tenant to Landlord.

     (h)  Following an Event of Default, Landlord agrees not to unreasonably
withhold, delay or condition (including, for example, the requirement of any
back-rent payments by Tenant) its consent to any subtenants or assignees which
Tenant may propose for all or any portion of the Leased Space provided that
Landlord's acceptance of any such subtenant or assignee shall not be deemed to
cure Tenant's default nor otherwise relieve Tenant of its obligations hereunder,
unless Landlord otherwise agrees in writing. Any rent paid as a result of any
such assignment or sublease shall be applied in accordance with subsection (g)
above.

23.  CONFESSION OF JUDGMENT FOR POSSESSION IN LIMITED CIRCUMSTANCE.
     ------------------------------------------------------------- 

If Tenant fails to vacate the Leased Premises upon termination of this Lease or
an Event of Default under Section 21(a) shall have occurred, Landlord shall have
the further remedy of confession of judgment for possession:

ANY PROTHONOTARY OR ATTORNEY OF ANY COURT OF RECORD MAY APPEAR FOR TENANT TO
FILE AN AGREEMENT FOR ENTERING IN ANY COMPETENT COURT AN AMICABLE ACTION FOR
JUDGMENT EJECTMENT AGAINST TENANT AND ALL PERSONS CLAIMING UNDER TENANT, AND A
JUDGMENT FOR THE RECOVERY BY LANDLORD OF POSSESSION MAY ISSUE FORTHWITH WITHOUT
ANY PRIOR WRIT OR PROCEEDINGS WHATSOEVER.  IF FOR ANY REASON AFTER SUCH ACTION
SHALL HAVE BEEN COMMENCED, IT SHALL  BE CANCELED OR SUSPENDED AND POSSESSION OF
THE LEASED SPACE REMAINS IN OR IS RESTORED TO TENANT, LANDLORD SHALL HAVE THE
RIGHT UPON ANY SUBSEQUENT DEFAULT OR TERMINATION OF THIS LEASE OR ANY RENEWAL OR
EXTENSION HEREOF, TO BRING ONE OR MORE AMICABLE ACTIONS IN EJECTMENT AS
HEREINBEFORE SET FORTH TO RECOVER POSSESSION OF THE LEASED SPACE.  IF IN ANY
AMICABLE ACTION IN EJECTMENT, OR IN ASSUMPSIT FOR RENT OR CHARGES, LANDLORD
SHALL CAUSE TO BE FILED IN SUCH ACTION

                                      -24-
<PAGE>
 
AN AFFIDAVIT SETTING FORTH THE FACTS NECESSARY TO AUTHORIZE THE ENTRY OF
JUDGMENT AND IF A TRUE COPY OF THIS LEASE (AND THE TRUTH OF THE COPY STATED IN
SUCH AFFIDAVIT SHALL BE SUFFICIENT PROOF) BE FILED IN SUCH ACTION, IT SHALL NOT
BE NECESSARY TO FILE THE ORIGINAL AS A WARRANT OF ATTORNEY, ANY LAW, RULE OF
COURT, CUSTOM OR PRACTICE TO THE CONTRARY NOTWITHSTANDING.  TENANT EXPRESSLY
RELEASES TO LANDLORD, AND TO ANY AND ALL ATTORNEYS WHO MAY APPEAR FOR TENANT,
ALL ERRORS IN THE SAID PROCEEDINGS, AND ALL LIABILITY THEREFOR.

24.  WAIVER.
     ------ 

The failure or delay on the part of either party to enforce or exercise at any
time any of the terms and conditions of this Lease shall in no way be construed
to be a waiver thereof, nor in any way to affect the validity of this Lease or
any part hereof, or the right of such party to thereafter enforce each and every
such term or condition.  No waiver by either party of any breach of this Lease
shall be held to be a waiver of any other or subsequent breach.  The receipt by
Landlord of rent or the payment by Tenant of rent at a time when a default
exists under this Lease shall not be construed as a waiver of such default.  The
receipt by Landlord of a lesser amount than the rent due shall not be construed
to be other than a payment on account of the rent then due, nor shall any
statement on Tenant's check or any letter accompanying Tenant's check be deemed
an accord and satisfaction, and Landlord may accept such payment without
prejudice to Landlord's right to recover the balance of the rent due or to
pursue any other remedies provided in this Lease.  No act or thing done by this
Lease shall be deemed an acceptance or a surrender of the Leased Space, and no
agreement to accept such a surrender shall be valid unless in writing and signed
by the party against whom enforcement is sought.

25.  QUIET ENJOYMENT.
     --------------- 

If and so long as Tenant pays the rent reserved hereunder and observes and
performs all the terms and conditions on Tenant's part to be observed and
performed hereunder, Tenant shall and may peaceably and quietly have, hold and
enjoy the Leased Space for the entire Term hereof, subject to all of the
provisions of this Lease.

26.  FORCE MAJEURE.
     ------------- 

Time periods for performance of each party's obligations (including without
limitation construction obligations) under any of the terms of this Lease shall
be extended for periods of time during which performance is prevented due to
circumstances beyond the performing party's control, including without
limitation, embargoes, governmental regulations, act of God, war or other
strife, shortages or unavailability of materials or equipment which are "special
order items" described in the TI Plans or Change Orders, strikes, lockouts,
adverse weather conditions, bankruptcy or breach of contract by a subcontractor
(collectively, "Force Majeure).  Force Majeure shall not apply, however, to any
monetary obligation hereunder.  Notwithstanding the

                                      -25-
<PAGE>
 
foregoing, Tenant Delays which arise from Force Majeure shall extend the Target
Date without triggering any advance of the date rental obligations commence
hereunder.

27.  SUCCESSORS.
     ---------- 

The respective rights and obligations provided in this Lease shall bind and
shall inure to the parties hereto, and their successors and permitted assigns.

28.  LANDLORD'S LIABILITY.
     -------------------- 

Landlord's responsibility under this Lease shall be limited to its interest in
the Leased Space and in the Building, and no members of Landlord's partnership
shall be personally liable hereunder. Tenant agrees to look solely to Landlord's
interest in the Leased Space and in the Building for the collection of any
judgment, and, in entering any such judgment, the person entering the same shall
request the prothonotary to mark the judgment index accordingly.
Notwithstanding the foregoing, at all times during the term of this Lease,
Landlord shall maintain a minimum equity in the Building equal to the total
Direct Payment Portion (as defined in the Work Letter) paid by Tenant.  If the
Leased Space or the Building is transferred or conveyed, Landlord shall be
relieved of all covenants and obligations under this Lease thereafter accruing,
provided that notice of said transfer or conveyance is given to Tenant by
Landlord.

29.  SUBORDINATION.
     ------------- 

Landlord represents that no Mortgages (hereafter defined) currently encumber the
Building, any part thereof, or the land on which it is situate.  Upon delivery
of a nondisturbance and attornment agreement which is reasonably satisfactory to
Tenant, this Lease is, and all of Tenant's rights hereunder are and shall always
be, subject and subordinate to any such mortgage, leases of Landlord's property
(in sale-leaseback) pursuant to which Landlord has or shall retain the right of
possession of the Leased Space (and/or the Building) or security instruments
(collectively called "Mortgage") that now exist, or may hereafter be placed upon
the Leased Space or the Building, or any part thereof and all advances made or
to be made thereunder and extensions thereof, and if the holder of any such
interest forecloses or extinguishes Landlord's rights in the Building or Leased
Space, Tenant shall attorn to and recognize any such holder as the successor
Landlord under this Lease.  The aforesaid provision shall be self-operative and
no further instrument or document shall be necessary unless required by any such
Mortgagee or purchaser. Notwithstanding anything to the contrary set forth
above, any Mortgagee may at any time subordinate its Mortgage to this Lease,
without Tenant's consent, by execution of a written document subordinating such
Mortgage to this Lease to the extent set forth therein, thereupon this Lease
shall be deemed prior to such Mortgage.  Should Landlord or any Mortgagee or
purchaser desire confirmation of either such subordination or such attornment,
as the case may be, Tenant upon written request, and from time to time, will
execute and deliver without charge and in form reasonably satisfactory to
Tenant, Landlord, to the Mortgagee or the purchaser all instruments and/or
documents that may be required to acknowledge such subordination and/or

                                      -26-
<PAGE>
 
agreement to attorn, in recordable form within ten (10) business days following
a request therefor from Landlord.

30.  RULES AND REGULATIONS.
     --------------------- 

Tenant agrees to comply with the rules and regulations established by Landlord
from time to time, which Landlord agrees will be applied uniformly to all
tenants; provided, however, that none of such rules and regulation materially
and adversely affect Tenant's rights hereunder or operation of Tenant's Business
from the Leased Space, and Tenant is afforded a reasonable time from notice
thereof to achieve compliance therewith.  The existing rules and regulations are
attached hereto as Exhibit "D."
                   ------------

31.  GOVERNING LAW.
     ------------- 

This Lease shall be governed by and construed in accordance with the laws of the
state in which the Building is located.

32.  SEVERABILITY.
     ------------ 

If any provisions of this Lease shall prove to be invalid, void or illegal, it
shall in no way affect any other provision hereof and the remaining provisions
shall nevertheless remain in full force and effect.

33.  NOTICES.
     ------- 

All notices and statements required or permitted under this Lease shall be in
writing and delivered by either (a) United States Registered or Certified Mail,
return receipt requested, postage prepaid, (b) Federal Express or other
nationally recognized overnight courier service, fee prepaid, or (c) hand
delivery against written receipt therefor, in each case addressed as follows:

As to Tenant prior to Commencement Date:     ViroPharma Incorporated
                                             76 Great Valley Parkway
                                             Malvern, PA 19355
                                             Attention:  General Counsel

As to Tenant as of the Commencement Date:    ViroPharma Incorporated
                                             Eagleview Corporate Center
                                             405 Eagleview Boulevard
                                             Exton, PA 19341
                                             Attention:  General Counsel

As to Landlord:                              The Hankin Group
                                             P.O. Box 562
                                             717 Constitution Drive

                                      -27-
<PAGE>
 
                                             Eagleview Corporate Center
                                             Exton, PA  19341

Either party may at any time, in the manner set forth for giving notices to the
other, designate a different address to which notices to it shall be sent.
Notice given in accordance with this Section shall be deemed given and received
as of the earlier of (i) actual receipt or (ii) first attempted delivery which
is refused (as opposed to being returned for insufficient postage/fee, improper
address or like cause).

34.  BROKERS.
     ------- 

Tenant represents and warrants to Landlord that Tenant has not dealt with any
broker, firm, company or person in connection with the negotiation for or the
obtaining of this Lease, and each party shall indemnify, defend and hold
harmless the other from and against any claim by any person claiming a
commission or other form of compensation by virtue of having dealt with such
party with regard to this Lease, and any attorneys fees or other expenses
incurred by the other party in connection therewith.

35.  SIGNS.
     ----- 

Tenant shall not, without the prior written consent of Landlord, paint, place or
erect any sign on the exterior doors or walls of the Leased Space or of the
Building or Center.  Subject to applicable zoning requirements and Landlord and
Tenant's mutual agreement on sign graphics not to be unreasonably withheld,
Tenant shall have the right to maintain two signs on the Real Estate (hereafter
defined in Section 44(a)(i)) as follows:  (a) one sign shall be located at a
mutually agreeable site fronting on Eagleview Boulevard and have dimensions not
in excess of five (5) feet high by fifteen (15) feet wide, and (b) the other
sign shall be at a mutually agreeable site visible (as to sign structure not
necessarily sign graphics) from Route 100 and the Pennsylvania Turnpike and,
unless otherwise agreed by Landlord and Tenant, shall have maximum dimensions of
five (5) feet high by fifteen (15) feet wide.  Landlord shall be responsible to
obtain approval from the Association with respect to such signage and, as
declarant under the Covenants, hereby (i) approves the size of the signs
described herein, and (ii) agrees not to unreasonably withhold its consent to
the sign graphics on either sign as long as same is reasonably compatible with
other business signage located within the Center.

36.  SECURITY DEPOSIT; SECURITY INTEREST.
     ----------------------------------- 

     (a)  Security Deposit:
          ---------------- 

          (i)  Upon the execution of this Lease, Tenant agrees to deposit with
Landlord, the sum of $45,899.33 to be held by Landlord as security for the
faithful performance of all the terms and conditions of this Lease ("Security
Deposit").  The Security Deposit initially shall be paid by Tenant to Escrow
Agent (as defined in the Work Letter) who shall hold the Security Deposit in a
segregated account from the other Escrow Funds (also as defined in the Work

                                      -28-
<PAGE>
 
Letter) until the Commencement Date, at which time the Security Deposit shall be
paid directly to Landlord.  Should the Tenant breach any of the terms and
conditions of this Lease which continues beyond any applicable cure period and
required notice, Landlord shall have the right, at any time, to apply the
Security Deposit or any part thereof, for the purpose of curing any such default
or for the purpose of reimbursing Landlord for any damage or costs occasioned by
such default, but the right of Landlord to apply the Security Deposit shall not
affect any other remedies available to Landlord under this Lease or under
applicable law.  If the Security Deposit, or any part thereof, is so applied by
Landlord, Tenant shall, within ten (10) days after demand, deposit additional
funds with Landlord to restore the Security Deposit, and failure to do so shall
constitute an event of default under this Lease.

          (ii)   If the Tenant shall have complied with all material terms and
conditions of this Lease at the expiration of this Lease, the Security Deposit
(without interest and amounts properly withdrawn by Landlord and not refunded by
Tenant) shall be refunded to Tenant within thirty (30) days after the expiration
or sooner termination of this Lease (including without limitation permitted
terminations hereunder and terminations due to Landlord's default which
continues beyond applicable grace and cure periods following notice where
applicable); provided, however, that Tenant first shall have vacated the Leased
Space and surrendered possession thereof to the Landlord by delivery of keys, in
accordance with the Lease provisions and shall have returned the Leased Space to
Landlord in the condition required hereunder.

          (iii)  Nothing herein contained shall require Landlord to hold the
sums so deposited as a trust fund, nor establish any relationship other than
that of debtor and creditor with respect to said funds so deposited.

          (iv)   If Landlord shall assign or otherwise transfer its interest in
this Lease, Landlord shall transfer the Security Deposit to the assignee or
other transferee of such interest (with like obligation to transfer to any
subsequent assignee or other transferee), and upon such transfer, Landlord shall
be released and relieved from all liability and/or responsibility with respect
to this Security Deposit and/or the return or application thereof.

     (b)  As security for Tenant's performance of its obligations under this
Lease, and subject to the provision hereof, Tenant hereby grants to Landlord a
security interest under the Uniform Commercial Code in all fume hoods and
casework on or about the Leased Space which have been acquired or provided as
part of the Tenant Improvements (valued at approximately $240,000) and purchased
with Tenant's Direct Payment Portion, excluding, however, the Tenant's Lab
Equipment ("Landlord Priority Property").  Such security interest shall continue
only for the Initial Term and the Landlord Priority Property shall be deemed
released from such interest upon the expiration of the Initial Term provided no
Event of Default has occurred hereunder which is then continuing.  Although the
foregoing termination and release provision is intended to be self executing, if
requested by Tenant, Landlord shall execute a separate release agreement to
confirm the foregoing.  Tenant's acquiescence to Landlord's access to the Leased
Space and the property located therein during the term of this Lease is intended
to effectuate Landlord's possession thereof for the purpose of perfecting such
security interest.

                                      -29-
<PAGE>
 
Notwithstanding such possessory rights of Landlord, so long as Tenant has not
suffered an Event of Default under this Lease, Landlord shall permit Tenant to
use, consume or sell such property in the ordinary course of business.  Tenant,
upon request by Landlord, shall execute such financing statements and other
instruments as Landlord may require in order to perfect the lien of such
security interest, and Tenant hereby appoints Landlord (and any assignee of
Landlord's rights under this Lease) as Tenant's attorney-in-fact to execute on
behalf of Tenant, such financing statements and other instruments so requested
by Landlord, it being intended that such power of attorney be coupled with an
interest and irrevocable.

37.  USE OF INFORMATION IN ADVERTISING.
     --------------------------------- 

Landlord and any agent employed by Landlord shall be permitted to utilize the
name of Tenant and any occupant or user of the Leased Space, and other general
information about the Tenant and such occupant or user, and the terms of this
Lease, in advertising and promotional material utilized by them.

38.  CAPTIONS.
     -------- 

The title to paragraphs of this Lease are for convenience of reference only, and
are not to be construed as defining, limiting or modifying the scope or intent
of any of the terms and conditions of this Lease.

39.  ENTIRE AGREEMENT.
     ---------------- 

This Lease contains all covenants and agreements between Landlord and Tenant
relating in any manner to the rental, use and occupancy of the Leased Space and
Tenant's use of the Building and other matters set forth in this Lease.  No
prior agreement or understanding pertaining to the same shall be valid or of any
force or effect and the terms, covenants and conditions of this Lease shall not
be altered, modified or added to except in writing signed by Landlord and
Tenant.

40.  ACCESS TO THE LEASED SPACE AND COMMON AREAS.
     ------------------------------------------- 

Tenant shall have access to the Leased Space and common areas of the Building 24
hours a day, 365 days per year.

41.  ATTORNEY FEES.
     ------------- 

The prevailing party in any litigation or arbitration to enforce any obligation
under this Lease shall be entitled to have reimbursed by the other party all
reasonable costs of collection and fees for legal counsel incurred as a result
of enforcing or protecting any rights under this Lease.

                                      -30-
<PAGE>
 
42.  SELF-HELP.
     ----------

     (a)   If Landlord fails to fulfill its obligations under this Lease, Tenant
shall notify Landlord of such nonperformance. Except in the case where immediate
response is required to avoid physical damage to the Leased Space or persons or
Tenant's property therein, Landlord shall have thirty (30) days to cure such
nonperformance. If Landlord fails to complete cure within such thirty (30) days
after receipt of such notice from Tenant, Tenant shall have the right, but not
the obligation, to carry out such activities on behalf of Landlord so as to cure
such nonperformance. Landlord shall reimburse Tenant for all reasonable costs,
fees and expenses incurred by Tenant in connection with performing such cure.
Such reimbursement shall be made within fifteen (15) days after written demand
by Tenant, which demand shall be accompanied by appropriate invoices or other
materials to substantiate the amount for the requested reimbursement. If
Landlord fails to pay Tenant the amount requested within said fifteen (15) day
period, such unpaid amounts shall accrue interest at the Default Rate which
shall continue to accrue on any judgment obtained by Tenant against Landlord for
recovery of such unreimbursed amounts. Notwithstanding the foregoing rights,
Tenant shall not be entitled to set-off such amounts against Rent due hereunder,
and Tenant hereby expressly waives such right, unless and until Tenant shall
have obtained a final judgment against Landlord with respect to Landlord's
obligation under the Lease which Tenant alleges that Landlord failed to perform,
and such right of set-off shall be applicable only to the amount of the judgment
not paid within thirty (30) days and may be asserted by Tenant against
installments of Rent thereafter coming due.

     (b)   Following any termination of this Lease as a result of Landlord's
default which continues beyond applicable grace or cure periods following notice
where applicable, Tenant shall be entitled to recover from Landlord the
unamortized value of the Tenant Improvements paid for with Tenant's Direct
Payment Portion remaining to be amortized over the Initial Term of the Lease.
Such amount, if not paid within ten (10) business days of Tenant's demand
therefore, shall accrue interest at the Default Rate from the expiration of such
ten (10) day period until paid in full.

     (c)   Amounts due from Landlord to which the Default Rate has been applied
shall continue to accrue interest at the Default Rate after entry of judgment
and issuance of execution thereon until paid in full.

43.  MEMORANDUM OF LEASE.
     ------------------- 

Tenant, at its expense, shall be entitled to record a memorandum of lease which
Landlord shall execute and acknowledge.   Concurrently with the execution of
this Lease, Tenant and Landlord agree to execute such memorandum of lease along
with a termination thereof, both of which shall be in form and substance
sufficient to permit the recording of such instrument and otherwise reasonably
acceptable to Landlord and Tenant.  The termination of such memorandum of lease
shall be held in escrow by Riley, Riper, Hollin & Colagreco, as escrow agent,
until termination of this Lease, pursuant to a separate escrow agreement with
respect to which the parties agree to negotiate in good faith promptly upon or
following execution hereof.  In the absence of such

                                      -31-
<PAGE>
 
escrow agreement, the party designated as escrow agent shall hold such
termination until the earlier of (a) receipt of a court order directing release
of said termination or (b) written instructions from Landlord and Tenant
directing the release of said termination.

44.  LANDLORD REPRESENTATIONS AND WARRANTIES.
     --------------------------------------- 

     (a)   Landlord, to induce Tenant to enter into this Lease, represents,
warrants and agrees, as of the date first set forth above and the Commencement
Date, as follows, which representations and warranties shall survive until one
(1) year after the Building and Leased Space are Substantially Completed:

           (i)    Title to the Property.  To Landlord's Knowledge, Landlord owns
                  --------------------- 
the land upon which the Building is to be constructed ("Real Estate") and has
good and marketable title of record thereto, free of any liens or encumbrance
except for the Permitted Title Exceptions described on Exhibit "E" hereto.
                                                      ----------- 
Landlord's ownership of the Real Estate has never been challenged. No parties
other than Landlord are required to execute or consent to this Lease.

           (ii)   No Third Party Rights.  There are no options, licenses, 
                  ---------------------
leases, rights of first refusal, contracts for the sale of the Real Estate
(including conditional sales agreements) or similar arrangements respecting the
Real Estate other than as are to be entered with Tenant.

           (iii)  Condemnation.  Landlord has not received any notice or other
                  ------------                                                
communication from any governmental unit or other body having the power of
eminent domain indicating that any part of the Real Estate or other portion of
Eagleview Corporate Center has been, will or may be condemned.

           (iv)   Proceedings.  No action, suit, or proceeding currently is 
                  -----------   
pending against the Real Estate or, to Landlord's Knowledge, any other portion
of Eagleview Corporate Center in any court or before any board, commission
agency or other governmental instrumentality. Landlord has not received written
notice of any such threatened action, suit, or proceeding.

           (v)    Assessments; Public Improvements.  No assessments or notice of
                  --------------------------------                              
assessments for public improvements have been made against the Real Estate prior
to the date of this Lease which have not been paid, other than impact fees which
will be paid by Landlord, and no work has been commenced on new public
improvements authorized by ordinances enacted prior to the date hereof which
will result in an assessment against the Real Estate.

           (vi)   Zoning and Approvals.  The Real Estate is zoned planned
                  --------------------                                   
commercial/industrial.  All subdivision and land development approvals necessary
for the creation of the Real Estate as a separate lot with direct access to a
public road and for the construction of the Building on the Real Estate
(collectively "Approvals") have been obtained and are in full force and effect
as of this date.  Landlord is in full compliance with all Approvals and, to
Landlord's Knowledge, no condition or state of facts now exists which, with the
giving of

                                      -32-
<PAGE>
 
notice or expiration of applicable time period, could cause the invalidation,
termination or revocation of any of the Approvals.

           (vii)  Soil.  To Landlord's Knowledge, the soil and subsurface of the
                  ----                                                          
Real Estate is suitable in all respects for the development of the Building.

           (viii) Flood Plain.  To Landlord's Knowledge, no portion of the Real
                  -----------                                                  
Estate is located within a special flood hazard area as documented in the
"Department of Housing and Urban Development, Federal Insurance Administration
Special Flood Hazard Area Maps."

           (ix)   Wetlands.  To Landlord's Knowledge: (a) no portion of the Real
                  --------                                                      
Estate is comprised of "wetlands" as defined under any Federal, state or local
law, ordinance, regulation or ruling, and (b) no remediation or wetlands
reconstruction is required on the Real Estate on account of the fill or
relocation of any wetlands.

           (x)    Environmental.
                  ------------- 

                  (A)   Environmental Reports.  Landlord has delivered to Tenant
                        ---------------------
a true, correct and complete copy of the environmental report titled "Report of
Findings Phase I Environmental Assessment of the Eagleview Development" which
was prepared by SMC Environmental Services Group and bears the reference number
9939-91000 and date of June, 1992 ("Environmental Report"). The Environmental
Report covers the Real Estate, and, to Landlord's Knowledge, no facts or
circumstances have changed at the Real Estate which would make any potion of the
Environmental Report incorrect or misleading.

                  (B)   Compliance; Permits.  To Landlord's Knowledge, as of the
                        -------------------
date of this Lease, the Real Estate is in compliance with all applicable
Federal, state and local laws, regulations, ordinances, rulings , and directives
relating to protection or regulation of the environment ("Environmental Laws")
and with any permit or governmental authorization which relate to the
Environmental Laws.

                  (C)   Underground Storage Tanks.  To Landlord's Knowledge, no
                        -------------------------                              
underground storage tanks are located on the Real Estate nor have any
underground storage tanks been removed from the Real Estate.

           (xi)   Utilities.  The following utilities currently service the Real
                  ---------
Estate (or are available to service the Real Estate with appropriate
connections):  water, sewer, gas, telephone, electricity and conduits for fiber
optics and cable.  All approvals required for any necessary connections have
been obtained and remain in full force and effect.  All such utilities are
available currently at the boundary of the Real Estate and are available without
any limitation or allocation imposed by the utility provider or applicable
governmental authorities.

           (xii)  Covenants.   The Amended and Restated Declaration of Easements
                  ---------                                                     
and Protective Covenants recorded in Deed Book 2074 at Page 240 as amended by a
Supplement and

                                      -33-
<PAGE>
 
Clarification recorded in Deed Book 2363, page 499, a First Amendment recorded
in Deed Book 2596, page 550, a Second Amendment recorded in Deed Book 3590, page
1986, a Third Amendment recorded in Deed Book 3672, page 579 and a Fourth
Amendment recorded on Deed Book 4177, page 2306 (collectively, "Declaration")
and the Rider to Lease or Agreement of Sale Regarding Industrial Waste Discharge
Within Eagleview Corporate Center (which is referred to herein with the
Declaration as the "Covenants"), constitute all of the protective covenants or
similar agreements which effect Eagleview Corporate Center.  Landlord represents
and covenants that no private agreements exist which materially and adversely
affect Tenant's rights under this Lease or an owner's rights under the
Covenants, including the ability to seek enforcement thereof, nor will Landlord
hereafter enter into any such agreement.

           (xiii) Discovery of Facts.  If, prior to the Commencement Date,
                  ------------------                                      
Landlord acquires actual knowledge of any fact which would be required to be
disclosed by Landlord to render its representations and warranties true, correct
and complete, in all material respects, Landlord promptly shall disclose such
fact to Tenant.

     (b)   For purposes of this Section 44, the term (and similar terms) "to
Landlord's Knowledge" shall mean to the best knowledge of Landlord's President,
Executive Vice President and Director of Commercial Marketing  (including
without limitation knowledge deemed to be charged to Landlord by virtue of items
and facts disclosed in the reports of consultants in Landlord's possession
wherever located) such statement or fact is true and correct and such persons
possess no information which make such statement or fact incomplete or
misleading.

45.  RENEWAL OPTION.
     -------------- 

     (a)   Tenant shall have the right and option to extend the term of this
Lease for two (2) consecutive renewal terms, each of five (5) years duration.
The first renewal term, if exercised, shall commence on the day immediately
following the expiration of the Initial Term hereof, and the second renewal
term, if exercised, shall commence on the date immediately following the
expiration of the first renewal term.  The option to extend, as well as the
commencement of each renewal term, shall be conditioned on no uncured events of
default by Tenant then existing.

     (b)   Tenant shall exercise each renewal option only by delivering written
notice of same to Landlord not later than one (1) year prior to the expiration
of the then current term. Tenant's failure to timely exercise an option shall be
deemed a waiver of all rights under this Section, in which event this Lease
shall terminate upon expiration or earlier termination of the then current term.

     (c)   Each renewal term, if exercised, shall be upon all of the terms and
conditions of this Lease, except for provisions which, by their nature, are
limited to the Initial Term and for the change in Minimum Annual Rent which (i)
for the first renewal term, if exercised, shall be the greater of $15.00 per
rentable square foot or 90% of the FMRV determined in accordance with Subsection
(d) below and (ii) for the second renewal term, if exercised, shall be the
greater of $17.50 per rentable square foot or 90% of the FMRV determined in
accordance with Subsection

                                      -34-
<PAGE>
 
(d) below.  If, however, adjustment is made to the Minimum Annual Rent payable
during the Initial Term as required by the Work Letter, the base rent per
rentable square foot, being the $15.00 and $17.50 figures, shall be increased or
decreased proportionately.

     (d)   Fair Rental Value Calculation.  The FMRV shall mean the fair market 
           -----------------------------                               
rental rate per square foot of rentable area per year, calculated at the time of
the determination of the FMRV and based on leases within Chester County for
comparable space under comparable terms within comparable buildings at the time
in question. Subject to the foregoing, the FMRV shall be determined as follows:

           (i)    Not later than three (3) months nor sooner than six (6) months
prior to the commencement of a renewal term, Landlord shall notify Tenant in
writing of Landlord's estimate of the FMRV.  Within ten (10) days following
Landlord's notice of the FMRV, Tenant, by written notice to Landlord, either
will accept Landlord's statement of the FMRV or notify Landlord of Tenant's
estimate of the FMRV, if different from that set forth in Landlord's notice. In
the absence of such timely notice by Tenant to Landlord, Tenant will be deemed
to have accepted Landlord's statement of FMRV.  If Tenant shall furnish a
counter-estimate of the FMRV, Landlord, by written notice to Tenant within ten
(10) days after Landlord's receipt of Tenant's estimate, either may accept
Tenant's estimate in writing or, without prejudice to any position, suggest
alternative figures for the FMRV which are greater than Tenant's estimate
thereof and less than Landlord's initial statement.  In the absence of such
timely notice by Landlord to Tenant, Landlord will be deemed to have accepted
Tenant's statement of FMRV.  If Landlord and Tenant shall not have an agreement
as to the FMRV within thirty-five (35) days following Tenant's written notice to
Landlord exercising a renewal right, FMRV shall be determined by appraisal as
set forth in subsection (ii) below.

           (ii)   If FMRV is to be determined by appraisal, such determination
shall be by an appraiser who is a member of the American Institute of Real
Estate Appraisers or its successor organization (M.A.I.), and who is agreed upon
by Landlord and Tenant.  If Landlord and Tenant are unable to agree upon an
appraiser within the time period specified in subsection (i)   above, then,
within five (5) days thereafter, each shall appoint a M.A.I. appraiser and the
FMRV shall be the FMRV determined by such appraisers or the average thereof if
their respective appraisals differ by ten percent (10%) or less.  If either
party shall fail to appoint an appraiser within the time provided, the FMRV
determined by the appraiser timely appointed shall be the FMRV.  If the
appraisals delivered by the appraisers appointed by Landlord and Tenant differ
by more than ten percent (10%), the appraisers so appointed shall appoint a
third M.A.I. appraiser and the FMRV shall be the average of the appraisal
delivered by the third appraiser and whichever of the appraisals previously
delivered by the appraisers appointed by Landlord and Tenant is closer to the
appraisal of the third appraiser.  If the two appraisers are unable to agree
upon a third appraiser within ten (10) days from the date the later of their two
appraisals is delivered, such appointment, on application by either Landlord or
Tenant, will be made by the then President of the Real Estate Board for Chester
County or, if such person is unwilling or unable to make such appointment, by
the American Arbitration Association or its successor organization acting
through its office in Philadelphia or by its office located closest to
Philadelphia.  Landlord and

                                      -35-
<PAGE>
 
Tenant each shall pay the fees and expenses of the respective appraiser
appointed by each of them and shall pay in equal shares the fees and expenses of
the appraiser mutually agreed upon by Landlord and Tenant, or as may be
appointed by the first two appraisers, the then President of the Real Estate
Board for Chester County or the American Arbitration Association or its
successor, as applicable.

           (iii)  The determination of FMRV in accordance with this Section
shall be conclusive and binding on Landlord and Tenant.

46.  SPACE RESERVATION AND EXPANSION OPTION.
     -------------------------------------- 

     (a)   Tenant acknowledges that the Real Estate of which the Leased Space
is a part has been approved for a Building of not more than 86,500 rentable
square feet ("Total Building Area") and that, in accordance with this Lease,
Landlord initially will construct only 48,400 rentable square feet of the Total
Building Area.  Landlord hereby agrees not to construct the balance of the Total
Building Area for a period of five (5) years from the date of this Lease
("Reservation Period"), subject however to the following terms and conditions:

           (i)    Landlord's agreement not to construct the balance of the Total
Building Area not leased to Tenant hereby, consisting of 38,100 rentable square
feet ("Expansion Space"), shall be conditioned upon Tenant's payment to
Landlord, on an annual basis, of the following fee ("Reservation Fee"):

                  (A)   On the Commencement Date of this Lease, the sum of
$48,560; and

                  (B)   On or before each anniversary of the Commencement Date,
the amount of $48,560 increased by the percentage change, if any, in the CPI-U
(Philadelphia SMSA) ("CPI Index") from the monthly index which is published
immediately prior to the month in which the Commencement Date occurs to the
monthly index which is published immediately prior to the month in which the
anniversary of the Commencement Date occurs ("CPI Adjustment").

           (ii)   Tenant shall have the option to release from the Expansion
Space 19,050 square feet thereof (being one-half of the Expansion Space) which
is contiguous to the Building ("Released Area") at any time during the
Reservation Period by written notice to Landlord. If Tenant so notifies
Landlord, the Reservation Fee for the balance of the Reservation Period to be
paid by Tenant shall be reduced by one-half and the portion of the Reservation
Fee paid by Tenant for such year shall be refunded to Tenant, pro-rated for the
balance of such lease year remaining after the effective date of such release.
Upon such release, Landlord, at any time thereafter, may expand the Building by
the amount of the Released Area, but Landlord shall not be obligated to do so.

                                      -36-
<PAGE>
 
           (iii)  Upon the earlier of (A) Tenant's failure to timely pay a
Reservation Fee, (B) Tenant's written notice to Landlord that it has released
all of its rights under this Section 46, or (C) the fifth (5th) anniversary of
the Commencement Date, Tenant's rights under this Section shall be null and
void, and Landlord, at any time thereafter, may complete the full construction
of the Total Building Area, but Landlord shall not be obligated to do so.

           (iv)   Any expansion of the Building shall be undertaken by Landlord
in accordance with all applicable laws, regulations, codes, ordinances and
requirements of Landlord's insurance underwriters, and in such manner so as to
cause the exterior configuration and appearance thereof to be architecturally
and aesthetically consistent with the Building as initially constructed. Such
construction shall be performed in a good and workmanlike manner, using only new
materials of at least equal quality and integrity as those included in the
original Building. Such construction shall be undertaken in accordance with
standard construction and safety practices and, during the course thereof,
Landlord shall use reasonable efforts to minimize interference with Tenant's use
and enjoyment of the Leased Space. At all times during the course of
construction, Landlord guarantees that Tenant will have unimpeded access to the
Leased Space and 193 parking spaces.

     (b)   During the Reservation Period, Tenant shall have the right, as to
any portion of the Expansion Space not released by Tenant, to expand the Leased
Space to include such portion of the Expansion Space; provided that if Tenant
has not released any portion of the Expansion Space, Tenant agrees to lease at
least 50% of the Expansion Space and if Tenant has released a portion of the
Expansion Space, Tenant agrees to lease the balance of the Expansion Space. Such
right shall be exercised by written notice delivered to Landlord, and upon
receipt of such notice, the Leased Space shall be deemed to include the portion
of the Expansion Space as to which Tenant has exercised such right, and Tenant's
rights thereto shall be subject to all terms and conditions of this Lease except
that:  (i)   Tenant shall have no obligations with respect to the portion of the
Expansion Space so leased by Tenant (including without limitation Rent and
Additional Rent), until such portion of the Expansion Space has been
Substantially Completed as defined in this Lease,  (ii) the Minimum Annual Rent
payable with respect to the portion of the Expansion Space so leased by Tenant
shall be calculated during the initial Term of this Lease at a rate of $11.50
per rentable square foot increased by the change in the CPI Index from the month
in which the Commencement Date occurs to the month in which Substantial
Completion of the Expansion Space occurs (or the month closest to each of such
months if the CPI Index is not published for such month), and (iii) upon
Substantial Completion, Tenant's Proportionate Share set forth in Section 3(a)
of this Lease shall be adjusted to increase the rentable area of the Leased
Space by the rentable area of the portion of the Expansion Space leased by
Tenant.  Landlord at no additional cost to Tenant agrees to deliver such
Expansion Space to Tenant fit-out as 50% private office space and 50% open
office space in accordance with Landlord's building - standard materials as
defined in the Standard Specifications for Flex Buildings at Eagleview attached
hereto as Exhibit "F" and based upon such space configuration as Landlord and
          -----------                                                        
Tenant agree, such approval not to be unreasonably withheld, delayed or
conditional.

                                      -37-
<PAGE>
 
     (c)   Condition to Exercise of Rights.  A condition to Tenant's exercise
           -------------------------------                                   
of its rights under this Section 46 shall be that no uncured notice of default
exists under this Lease at the time of each exercise.  A further condition to
Tenant's exercise of its rights under Section 46(b) shall be that Tenant
demonstrates to Landlord's reasonable satisfaction a financial condition which
supports Tenant's obligations under this Lease for the total space which then
will be leased by Tenant.

47.  RIGHT OF FIRST REFUSAL.
     ---------------------- 
 
     (a)   Rights Available to Tenant.  Upon expiration of the Reservation 
           --------------------------                                     
Period, if Tenant has not exercised its right to lease any portion of the
Expansion Space prior to the expiration of the Reservation Period ("Available
Space"), Landlord shall have the right to lease any portion of the Available
Space completed or proposed to be built by Landlord, which leases may include
within the terms thereof tenant renewal rights.  Upon the expiration on each
initial lease of the Available Space to a tenant other than Tenant ("Other
Building Tenants"), Landlord agrees that Landlord will not enter into any
renewal lease (unless expressly permitted by the terms of such lease) or new
lease for any portion of the Available Space which becomes vacant, unless
Landlord shall have complied with the following:

           (i)    If Landlord desires to market or lease the Available Space,
Landlord shall notify Tenant of such decision in writing ("Offer Notice") and
shall offer to Tenant the opportunity to lease the space described in such Offer
Notice ("RFR Parcel") on the same terms and conditions set forth in the Offer
Notice.  The Offer Notice shall be accompanied by a written lease proposal from
Landlord and shall otherwise include all relevant information as to the terms of
such offer.  Tenant shall have fifteen (15) business days after receipt of the
Offer Notice to notify Landlord in writing that it will lease the RFR Parcel
from Landlord.

           (ii)   If (A)Tenant rejects or fails to respond to the Offer Notice
within the applicable period specified in subsection (i)   above, or (B)
Landlord and Tenant, despite reasonable, good faith efforts, do not execute a
lease for the RFR Parcel within forty-five (45) days after Tenant's exercise of
its rights hereunder, Landlord shall be entitled to lease the RFR Parcel
pursuant to the applicable Offer Notice, upon substantially the same terms and
conditions set forth in the Offer Notice; provided, however, that no such lease
shall be made on other terms materially less favorable to Landlord than the
terms set forth in the Offer Notice.  If Landlord has not so leased the RFR
Parcel on the terms specified in the Offer Notice (or on terms materially more
favorable to Landlord) within one (1) year from delivery of the Offer Notice,
Landlord shall not thereafter offer to lease or lease the RFR Parcel to any
party  (including the offeror named in the Offer Notice) without again complying
with the provisions of this Section 47.  All terms of this Section 47 shall
apply to such revised Offer Notice, including Tenant's opportunity to respond to
the revised Offer Notice within the applicable period specified above.  If
Landlord executes the lease contemplated by the Offer Notice within the
parameters permitted by this subsection, Tenant's rights hereunder shall be null
and void as to the RFR Parcel so leased, but shall continue to apply to the
balance of the Available Space which does not constitute part of the

                                      -38-
<PAGE>
 
RFR Parcel.  Otherwise, Tenant's rights hereunder shall expire with the
termination of this Lease, as renewed.

     (b)   Condition to Exercise of Rights.  A condition to Tenant's exercise of
           -------------------------------                                   
its rights under this Section shall be that no outstanding notice of default
exists under this Lease at each time of exercise.  The failure of such condition
with respect to any one exercise of Tenant's rights shall not preclude Tenant's
further exercise of its rights.

48.  RESTRICTION ON LEASING TO COMPETITORS.
     ------------------------------------- 

Landlord agrees that, for so long as this Lease is effective, Landlord will not
lease any portion of the Expansion Space (a) to a tenant whose primary business
or business to be operated from the Expansion Space is the research, development
and commercialization of pharmaceutical products which treat viral diseases, or
(b) pursuant to a lease which permits such tenant to use Hazardous Substances in
the Building without covenants with respect to Hazardous Substances which are at
least as onerous as the covenants set forth in Section 5 hereof.

49.  CREDIT AGAINST LAND PURCHASE.
     ---------------------------- 

If Tenant or its affiliate shall purchase from Landlord or its affiliate any
land which is now or hereafter a part of the Center other than the Real Estate,
and such purchase shall close at a time when Tenant has leased the Total
Building Area, the purchase price determined for such land shall be reduced by
an amount equal to two percent (2%) of the Minimum Annual Rent to be paid by
Tenant under the Lease for the Term (including exercised Renewals) following the
date of closing on such land up to a maximum reduction equal to ten percent
(10%) of the agreed upon purchase price prior to such reduction.

50.  CHANGE TO CPI INDEX.
     ------------------- 

If the CPI Index should be discontinued at any time during the Term of this
Lease, Landlord shall select a substitute index which most closely approximates
the CPI Index and which is reasonably acceptable to Tenant.  Upon agreement as
to such substitute index, all references to CPI Index shall be deemed to refer
thereto.  If the CPI Index shall not be published for the month required for
comparison hereunder, the CPI Index published for the month closest and prior
thereto shall be used.

51.  CERTAIN COVENANTS REGARDING THE DECLARATION
     -------------------------------------------

     (a)   Unless an uncured event of default shall exist hereunder, Tenant
shall be entitled to exercise all votes in the Association associated with the
Real Estate as Landlord's agent or proxy.  Landlord shall promptly provide
copies to Tenant of all notifications received by Landlord from the Association.

                                      -39-
<PAGE>
 
     (b)   Landlord and Tenant hereby agree that the approximately 7,700 square
feet of the Leased Space reserved for future laboratory expansion space shall be
characterized as additional warehouse space until actually used by Tenant for
laboratory purposes.

52.  ADDITIONAL PERMITTED TITLE EXCEPTIONS
     -------------------------------------

     (a)   Landlord and Tenant agree that utility easements may hereafter be
granted as an encumbrance on the Real Estate without Tenant's prior consent
thereto provided (i)   that the terms and scope thereof are reasonable given the
nature of the easement and (ii) such utility easement is located underground and
does not materially and adversely affect Tenant's use of, or current access to,
the Leased Space, or signage locations, or reduce available parking from that
required by municipal code.  Except for such easements and amendments to the
Covenants (adopted in accordance with the procedures applicable thereto), no
encumbrances other than the Permitted Title Exceptions shall be granted during
the Term hereof.

     (b)   Landlord also shall have the right to grant a first mortgage
encumbering the Real Estate and all improvements therein not owned by Tenant
which mortgage secure loans made to Landlord in connection with the development
and construction of improvements now or hereafter a part of the Real Estate, and
refinancing of such loans, subject, however, at all times to Section 28 hereof.
Landlord further covenants to Tenant to use commercially reasonable effort to
have such mortgage holder agree that insurance proceeds or casualty awards shall
be applied to restoration of the Real Estate and Building (including Tenant
Improvements).

     (c)   Tenant acknowledges and agrees that the Leased Space and Expansion
Space  (or portions thereof) may be made a part of a condominium intended to be
created by Landlord for the entire Building, which condominium shall be
exclusively limited to non-residential uses. Tenant shall reasonably cooperate
with Landlord in its efforts to create such condominium, including without
limitation, Tenant's execution of such documents and instruments as Landlord
reasonably may require in order to effectuate the creation of such condominium,
so long as Tenant incurs no cost or expense in connection therewith, and such
documentation does not in any material way adversely affect Tenant's rights and
obligations under this Lease or increase the amount of Tenant's Proportionate
Share.  It is intended that the Leased Space and each designated portion of the
Expansion Space shall be a separate condominium unit, or a unit and limited
common elements appurtenant to such unit.   Landlord shall have the right to
grant mortgages as encumbrances on each unit of said condominium (whether as a
single mortgage or as individual mortgages) and all improvements therein not
owned by Tenant which mortgages secure loans made to Landlord in connection with
the development and construction of improvements now or hereafter a part of the
Real Estate, and refinancing of such loans, subject, however, at all times to
Section 28 hereof.  Landlord further covenants to Tenant to use commercially
reasonable effort to have each such mortgage holder agree that insurance
proceeds or casualty awards shall be applied to restoration of the Real Estate
and Building (including Tenant Improvements).

                                      -40-
<PAGE>
 
53.  SEWER CAPACITY ALLOCATION
     -------------------------

For so long as the Term of this Lease is effective, Landlord hereby reserves to
the Real Estate a sewage capacity of 7,500 gpd and agrees not to allocate sewage
capacity currently available to the Center pursuant to the Treatment Plant
Expansion Agreement among Landlord, Uwchlan Township and the Uwchlan Township
Municipal Authority dated ____, 1993 (undated but notarized January 10, 1994)
("Sewer Agreement") in any manner which would deprive the Real Estate of a
sewage capacity of 7,500 gpd.  Tenant covenants and agrees that during the Term
of this Lease, it will not consume more that 4,000 gpd with respect to the
Leased Space and not more than an aggregate of 7,500 gpd for the Leased Space
and the Expansion Space if leased by Tenant.

54.  CALCULATION AND REIMBURSEMENT OF UNAMORTIZED VALUE OF DIRECT PAYMENT
     --------------------------------------------------------------------
     PORTION.
     ------- 

     (a)   Whenever in this Lease reference shall be made to the unamortized
value of Tenant's Direct Payment Portion, the same shall be calculated using a
straight-line method of amortization over a ten (10) year term measured as of
the Commencement Date.

     (b)   Landlord shall have the right to pay a portion of amounts to be
reimbursed by Landlord pursuant to Sections 2(b)(iv) and 18(c) by providing to
Tenant, at a location designated by Tenant, the Tenant's Lab Equipment and the
Landlord Priority Property, provided same are in the condition as existed on the
date of installation, reasonable wear and tear and damage caused by Tenant
excepted.  If Landlord exercises such right and delivers such items in the
condition aforesaid, a credit shall be deemed applied against amounts owed from
Landlord in an amount equal to the unamortized value of such items, determined
on a straight-line basis over a useful life of ten (10) years, measured as of
the Commencement Date.  The initial value of such items shall be as provided in
the Work Letter and Section 36(b), as applicable.

     IN WITNESS WHEREOF, the parties have caused this Lease to be duly executed
the day and year first above written, intending to be legally bound hereby.

                                 LANDLORD:

                                 THE HANKIN GROUP

                                 By: /s/ Robert S. Hankin 
                                     ---------------------------------
                                     Robert S. Hankin, General Partner

                                 TENANT:

                                 VIROPHARMA INCORPORATED

                                 By: /s/ Thomas F. Doyle
                                     ---------------------------------
                                     Thomas F. Doyle, Executive 
                                     Director, Counsel and Secretary

                                      -41-

<PAGE>
 
                                                                   EXHIBIT 10.24

                           Purchase Option Agreement
                           -------------------------


          This Purchase Option Agreement ("Agreement") is made this 21st day of
July, 1997 by and among The Hankin Group ("Owner"), and ViroPharma Incorporated
("Option-Holder").

                                   Background
                                   ----------

          Owner is the fee title holder of the real property described on
Exhibit A hereto, which property also is known as 405 Eagleview Boulevard (Lot
- ---------                                                                     
#10, Eagleview Corporate Center), Uwchlan Township, Pennsylvania ("Real
Property").  Pursuant to a certain Lease dated the date hereof ("Lease"), Owner
leased to Option-Holder a building initially consisting of 48,400 rentable
square feet ("Building") which Owner will construct on the Real Property and
which will be improved with certain tenant  improvements ("Tenant Improvements")
required by Option-Holder, the cost of which will partially be funded by Option-
Holder.  Owner, subject to Option Holder's rights under the Lease, may expand
the Building to 86,500 rentable square feet.

          As a material inducement for Option-Holder to enter into the Lease,
Owner has agreed to grant to Option-Holder a right to purchase the Real Property
and the Building, as expanded, together with all improvements now or hereafter
constructed thereon (collectively, "Option Property").  The parties are entering
into this Agreement to memorialize the terms and conditions upon which Option-
Holder may exercise its purchase option.

          NOW, THEREFORE, for and in consideration of $10.00, the receipt and
sufficiency of which hereby is acknowledged, and in consideration of the mutual
undertakings herein set forth, and intending to be legally bound hereby, Owner
and Option-Holder agree as follows:

                                   Agreement
                                   ---------
                                        
          1.   Defined Terms.  Capitalized terms not otherwise defined herein 
               -------------                        
shall have the meaning set forth in the Lease.

          2.   Purchase Option.
               --------------- 

               a.   Owner hereby grants to Option-Holder an option ("Purchase
Option") to purchase the Option Property which, subject to the requirements of
Section 2(c) below, may be exercised by Option-Holder during (1) the fifth (5th)
lease year of the Initial Term of the Lease, and (2) the ten (10th) lease year
of the Initial Term of the Lease (each, "Scheduled Exercise Period").

               b.   Option-Holder also shall have the right to exercise its
Purchase Option, subject to the requirements of Section 2(c) below, (1) at any
time during the Initial Term
<PAGE>
 
of the Lease following Owner's default thereunder which continues beyond
applicable grace or cure periods following notice where applicable, or (2) upon
a casualty or condemnation of the Option Property which permits the termination
of the Lease ("Lease Termination Event" which is referred to herein together
with each Scheduled Exercise Period as "Option Exercise Event").

               c.   Option-Holder may exercise its option only by delivering
written notice ("Exercise Notice") to Owner of its exercise of the Purchase
Option (the date of such Exercise Notice being referred to herein as the
"Exercise Date"), which notice shall be delivered not later than six (6) months
prior to the expiration of a Scheduled Exercise Period and not later than thirty
(30) days following a Lease Termination Event, which notice shall restate
Owner's duties pursuant to Sections 6(b), 7(c) and 8 below.

               d.   Each Exercise Notice shall include Option-Holder's check in
the amount of the Deposit (hereafter defined), which shall be payable to Title
Company (hereafter defined) as escrow agent and held in an interest bearing
escrow account until Closing. Interest earned on the Deposit shall be paid to
the party entitled hereunder to receive the Deposit, and if paid to Owner at
Closing, the full amount thereof shall be credited against the Purchase Price.

          3.   Option Price.
               ------------ 

               a.   The purchase price to be paid for the Option Property
("Option Price") shall be the sum of (1) the Base Amount (as hereafter defined)
increased by (2) the CPI Adjustment (hereafter defined).

               b.   The Option Price shall be calculated in accordance with the
following, with the valuation date being (a) the expiration date of the
Scheduled Exercise Period, if the Purchase Option is exercised pursuant to
Section 2(a) hereof, or (b) the termination date of the Lease if the Purchase
Option is exercised pursuant to Section 2(b) hereof:

                    (1)  The "Base Amount" initially shall be $6,800,000.00
("Initial Base Amount") which is based on an average Minimum Annual Rent over
the Initial Term of the Lease of $625,812 divided by a capitalization rate of
9.203%. The Initial Base Amount shall be adjusted in direct proportion to any
increase or decrease in the Minimum Annual Rent pursuant to Section 3(b)(2) of
the Work Letter attached to the Lease.

                    (2)  The Initial Base Amount shall be increased by the
following:

                         (a)  With respect to any portion of the Expansion Space
leased by Option-Holder pursuant to the Lease or otherwise subject to an
executed lease agreement, the average Minimum Annual Rent or average base rent
payable thereunder over the term of the subject lease, excluding unexercised
renewals, divided by a capitalization rate of 9.203%; and

                                      -2-
<PAGE>
 
                         (b)  With respect to any unleased portion of the
Expansion Space, the following shall apply:

                              i)   If any portion of the Expansion Space is
leased by a party other than Tenant, (A) the base rent payable for office space
over the term of such lease shall be averaged (and, if more than one such lease
shall exist, the average base rent for office space under each lease shall be
averaged); (B) the averaged base rent determined in accordance with provision
(A) shall then be divided by the square footage of the premises so leased; (C)
the averaged based rent per square foot determined in accordance with provision
(B) shall then be multiplied by the square footage of the vacant portion of the
Expansion Space, and (D) the amount determined in accordance with provision (C)
shall then be divided by a capitalization rate of 9.203%; and

                              ii)  If the Expansion Space consists only of
vacant shell space or space not then completed as shell space, Owner's "Cost of
Construction" (defined below) with respect to such portion of the Expansion
Space, subject, however, to the foregoing:

                                   a)   Owner demonstrates with evidence
commercially reasonably satisfactory to Option-Holder the Costs of Construction
thereof; and

                                   b)   "Cost of Construction" shall mean the
actual cost billed to Owner by its general contractor of supplying all labor and
materials involved to date in the construction of such space, including all
items as are included within the definition of "Cost of the Work" pursuant to
Article 8 of the "American Institute for Architects AIA Document A111 Standard
Form of Agreement Between Owner and Contractor where the basis of payment is the
Cost of the Work Plus a Fee," plus the fee charged to Owner by its general
contractor which shall not exceed ten percent (10%) of the Cost of Construction

                    (3)  The "CPI Adjustment" shall be the percentage change, if
any, in the CPI-U (Philadelphia SMSA) ("CPI Index") as of the month in which the
Exercise Date occurs over the comparable CPI Index in effect, (a) with respect
the Leased Space which is the subject of the Lease on the Commencement Date
hereof, during the month in which the Commencement Date occurs, (b) with respect
to the Expansion Space described above in subsection 2(a), during the month in
which commencement of the lease of the applicable Expansion Space occurs, and
(c) with respect to the Expansion Space described above in subsection 2(b),
during the month in which a certificate of occupancy has been issued for such
Expansion Space. The applicable CPI Adjustment shall be applied to each lease of
the Leased Space and Expansion Space, any vacant portion of the Expansion Space,
the Minimum Annual Rent, base rent or construction cost which are utilized in
calculating the Base Amount in accordance with clause (1) above.

                                      -3-
<PAGE>
 
                    (4)  If the CPI Index should be discontinued at any time
during the effectiveness of this Agreement, Owner shall select a substitute
index which most closely approximates the CPI Index and which is reasonably
acceptable to Option-Holder. Upon agreement as to such substitute index, all
references to CPI Index shall be deemed to refer thereto. If the CPI Index shall
not be published for the month required for comparison hereunder, the CPI Index
published for the month closest and prior thereto shall be used.

               c.   If the Purchase Option has been exercised pursuant to
Section 2(b)(1) above, any fee due to a mortgage holder in connection with
prepayment of any loan secured by mortgage on the Option Property ("Prepayment
Fee") shall be Owner's sole liability. If, however, the Purchase Option has been
exercised pursuant to Section 2(b)(2) above, the Option Price shall include the
Prepayment Fee due in connection with any mortgage encumbering the Option
Property. Owner, however, hereby agrees to use commercially reasonably efforts
to have each mortgage which encumbers the Option Property permit prepayment upon
a casualty or condemnation without the payment of any Prepayment Fee.

          4.   Payment of the Option Price.  The Option Price shall be paid to
               ---------------------------             
Option-Holder to Owner as follows:

               a.   Fifty Thousand Dollars ($50,000) ("Deposit") shall be paid
to Title Company as escrow agent, who shall deliver the Deposit to Seller at
Closing (which amount is separate from and in addition to the Security Deposit
paid by Option-Holder under the Lease);

               b.   The Security Deposit paid under the Lease not otherwise
utilized by Landlord pursuant to the Lease shall be retained by Seller and
credited against the Option Price; and

               c.   An amount equal to the Option Price less amounts paid
pursuant to subsections (a) and (b) above shall be paid to Seller on the Closing
Date by wire transfer of immediately available funds, certified check, title
company check or cashier's check.

          5.   Closing.
               ------- 

               a.   Within ninety (90) days from the Commencement Date of the
Lease, Owner shall notify Option-Holder in writing of the permitted date or
dates of Closing (hereafter defined) if Option-Holder exercises its Purchase
Option pursuant to Section 2(a)(1) hereof, the latest of which permitted dates
shall not be later than five (5) years plus ninety (90) days from the
Commencement Date ("First Scheduled Closing Date"). If Owner has provided such
notification and Option-Holder exercises its Option pursuant to Section 2(a)(1)
above, settlement on the sale of the Option Property from Owner to Option-Holder
("Closing") shall be held on the First Scheduled Closing Date. If Owner shall
have failed to provide notice as required by this section, the date for Closing
shall be determined in accordance with Subsection (c) below.

                                      -4-
<PAGE>
 
               b.   If Option-Holder has not exercised its Purchase Option
during the period contemplated by Section 2(a)(1) above, then, within ninety
(90) days from the fifth (5th) anniversary of the Commencement Date of the
Lease, Owner shall notify Option-Holder in writing of the permitted date or
dates of Closing if Option-Holder exercises its Purchase Option pursuant to
Section 2(a)(2) hereof, the latest of which permitted dates shall not be later
than five (5) years plus ninety (90) days from the fifth (5th) anniversary of
the Commencement Date ("Second Scheduled Closing Date"). If Owner has provided
such notification and Option-Holder has exercised its Option pursuant to Section
2(a)(2) above, Closing shall be held on the Second Scheduled Closing Date and
the Lease shall be deemed to continue through the Second Scheduled Closing Date.
If Owner shall have failed to provide notice when required by this section, the
date for Closing shall be determined in accordance with Subsection (c) below.

               c.   If Owner shall have failed to provide the notice required by
Subsections (a) or (b) above and Option-Holder has exercised its Option pursuant
to Section 2(a) above (as applicable), or if Option-Holder has exercised its
Option pursuant to Section 2(b) above, Closing shall be the later of ninety (90)
days after (A) the Exercise Date or (B) the expiration of the Scheduled Exercise
Period, as applicable.

               d.   Closing shall be held on the designated date at a time and
at such location as is mutually acceptable to Owner and Option-Holder. Except as
provided in Sections 3(c) hereof, Option-Holder shall have no liability for any
Prepayment Fees in connection with any Closing determined in accordance with
this Section.

          6.   Due Diligence Period.
               -------------------- 

               a.   Option-Holder shall have thirty (30) days from the Exercise
Date ("Due Diligence Period") to conduct due diligence on the Option Property,
including without limitation structural and systems inspections, environmental
inspections and, if tenants other than Option-Holder occupy any part of the
Option Property, review of Owner's books and records relating to the Option
Property. Owner shall afford Option-Holder and its consultants free access to
the Option Property to perform any and all studies and test in connection with
its due diligence, including without limitation boring and samples as part of
environmental investigation. If Option-Holder is dissatisfied with its due
diligence for any reason whatsoever other than a condition caused by Option-
Holder's occupancy of the Option-Property or otherwise the responsibility of
Option-Holder under the Lease, Option-Holder, by written notice ("Withdraw
Notice") to Owner delivered on or prior to the expiration of the Due Diligence
Period, may withdraw its exercise of the Purchase Option without liability, in
which case the Deposit shall be returned to Option-Holder. Option-Holder's
withdrawal of its exercised Option shall be subject to Option-Holder's rights
under Section 15 hereof if Option-Holder so designates in the Withdraw Notice
and identifies therein the basis for Option-Holder's withdrawal of its Exercise
Notice. If Option-Holder withdraws the Exercise Notice, Option-Holder, at 
Option-Holder's expense, promptly shall restore any disturbance or damage to the

                                      -5-
<PAGE>
 
Option Property caused by Option-Holder or its agents in the undertaking of
Option-Holder's rights hereunder.

               b.   Within five (5) business days of the Exercise Date, Owner
agrees to deliver to Option-Holder copies of contracts or commitments for
construction, labor or services entered by or at the direction of Owner with
respect to the Option Property ("Service Contracts") and copies of all leases
entered by Owner with respect to the Option Property other than the leases
entered with Option-Holder ("Other Leases"), and such rent rolls and operating
statements with respect to the Option Property as are reasonably available to
Owner. Option-Holder agrees to keep all such information confidential and
promptly return same to Owner if this Agreement is terminated for any reason.
Such obligation shall survive the termination of this Agreement, notwithstanding
any provision hereof to the contrary. Owner hereby covenants that during the
effectiveness of this Agreement no Service Contract shall be entered which is
not terminable on the Closing Date without expense to Option-Holder. Option-
Holder shall identify to Owner in writing on or prior to the expiration of the
Due Diligence period which of the Service Contracts Option-Holder desires to
assume, and Owner shall cause all other Service Contracts to be terminated as of
the Closing Date at no expense to Option-Holder.

               c.   Option-Holder assumes all risk and liability for injury to
persons and property in connection with the exercise of Option-Holder's rights
under this Section and agrees to indemnify, defend and hold harmless Owner from
any such claims or liability. Option-Holder's obligations under this Section
shall survive the termination of this Agreement, notwithstanding any provision
hereof to the contrary.

          7.   Title and Survey.
               ---------------- 

               a.   Title at Closing.  Owner shall convey to Option-Holder good
                    ----------------   
and marketable title of record to the Option Property, which is insurable as
such at regular rates by Option-Holder's designated title company ("Title
Company") which shall be Lawyers Title Insurance Corporation or such other
reputable title insurance company selected by Option-Holder as is authorized to
do business in the Commonwealth of Pennsylvania. Title shall be subject only to
the Permitted Title Exceptions which shall include, for purposes of this
Agreement (1) all matters identified on Exhibit B attached hereto, (2) all
                                        ---------            
easements and amendments to Covenants (as defined in the Lease) granted in
accordance with Section 52(a) of the Lease, and (3) all matters determined in
accordance with subsections (b), (c) and (d) below.

               b.   Title Report.  On or before thirty (30) days after the
                    ------------
Exercise Date ("Title Examination Period"), Option-Holder shall furnish to Owner
a title report ("Title Report") issued by Option-Holder's designated title
company, giving the then current condition of title to the Option Property and
any objections of Option-Holder to matters in the Title Report other than the
Permitted Title Exceptions determined under subsections (a)(1) and (a)(2) above.
Matters identified by the Title Report and not objected to by Option-Holder on
or before the end of the Title Examination Period shall be deemed to be
"Permitted Title Exceptions."

                                      -6-
<PAGE>
 
               c.   Survey.  On or before five (5) days after Exercise Date,
                    ------
Owner, at Owner's expense, shall provide Option-Holder with copies of any and
all surveys of the Option Property which Owner has in its possession. Option-
Holder, at Option-Holder's expense, shall have the right to obtain an on-the-
ground staked survey of the Option Property which (1) has been prepared in
accordance with the American Land Title Associations Specifications, (2) has
been prepared by a land surveyor duly licensed in the Commonwealth of
Pennsylvania selected by Option-Holder, and (3) is sufficient to cause Option-
Holder's title company to (A) delete the pre-printed survey exceptions from
Option-Holder's title policy and (B) not take exception for items which are not
Permitted Title Exceptions. Prior to the expiration of the Title Examination
Period, Option-Holder shall notify Owner in writing of any objections to matters
revealed by such survey other than the Permitted Title Exceptions determined
under subsections (a)(1) and (a)(2) above. Matters identified by such survey and
not objected to by Option-Holder on or before the end of the Option Examination
Period shall be deemed to be "Permitted Title Exceptions."

               d.   Objections.  Owner will notify Option-Holder in writing
                    ----------
whether Owner is unable or unwilling to cure to Option-Holder's satisfaction any
title or survey objections (other than the Permitted Title Exceptions) raised by
Option-Holder ("Title Problems"), which notice shall restate the effect set
forth in this Section of Owner's failure to respond in accordance with this
Section. Owner shall be obligated to remove and discharge of record or otherwise
cure to Option-Holder's satisfaction all Title Problems (other than matters
which existed of record prior to the commitment date of Option-Holder's title
commitment issued by Lawyers Title Insurance Corporation under commitment number
LIT-97-14739 excluding monetary liens and judgments for which Owner is
responsible) which have timely been raised by Option-Holder and which are liens
in a fixed or ascertainable amount or result from Owner's actions. Owner's
failure to deliver such notice to Option-Holder within ten (10) business days
after delivery of Option-Holder's notice of Title Problems shall be deemed
Owner's refusal to cure all of the Title Problems by the Closing Date,
excluding, however, those Title Problems which Owner is obligated hereunder to
cure. If Owner has not agreed to cure all Title Problems other than those which
Owner is obligated hereunder to cure, Option-Holder shall have ten (10) business
days from receipt of Owner's notice (or, if Owner has failed to give notice,
fifteen (15) days from delivery of Option-Holder's notice of Title Problems)
either (1) to withdraw, without liability, its exercise of the Purchase Option
by notice in writing to Owner delivered prior to the expiration of such fifteen
(15) day period, or (2) to accept such title as Owner can deliver without
reduction or abatement of the Option Price except to the extent of Title
Problems which Owner is obligated hereunder to cure. Option-Holder's failure to
timely deliver notice of termination shall be deemed Option-Holder's agreement
to accept such title as Owner can deliver without reduction or abatement of the
Option Price except to the extent of Title Problems which Owner is obligated
hereunder to cure.

               e.   Failure of Owner to Cure Title Problems.  If, on of before
                    ---------------------------------------
the Closing Date, Owner shall fail to cure those of the Title Problems which
Owner has agreed to

                                      -7-
<PAGE>
 
cure or is obligated hereunder to cure, Option-Holder, as its sole and exclusive
remedy, shall have the right:  (1) to withdraw, without liability, its exercise
of the Purchase Option by notice in writing to Owner, subject, however, to
Option-Holder's rights under Section 15 hereof, and, notwithstanding any
provision of the Lease to the contrary, recover from Owner personally all of
Option-Holder's reasonable actual third party costs arising from its exercise of
the Purchase Option, based upon third party invoices delivered by Option-Holder
to Owner not later than thirty (30) days after the failure of Owner to cure,
(2) to accept such title as Owner can deliver without reduction or abatement of
the Option Price except to the extent of Title Problems which Owner is obligated
hereunder to cure, or (3) to enforce the specific performance of Owner's
agreement to cure the Title Problems.

          8.   Representations and Warranties.  Within ten (10) business days
               ------------------------------                                
after the Exercise Date, Owner shall confirm to Option-Holder in writing that
the representations and warranties set forth in Section 46 of the Lease remain
true, complete and correct or set forth in reasonable detail any circumstances
which make such representations and warranties untrue, incomplete or incorrect.
If any such qualification to the representations and warranties shall, in
Option-Holder's sole discretion, materially and adversely affect the subject
Option Property or Option-Holder's intended use thereof or if Owner shall fail
to provide such written confirmation, Option-Holder shall have the right to
withdraw, without liability, its exercise of the Purchase Option, subject,
however, to Option-Holder's rights under Section 15 hereof.

          9.   Condition of the Option Property.  The Option Property shall be
               --------------------------------                               
delivered to Option-Holder on the Closing Date in the same condition which
existed on the Exercise Date, except for (1) reasonable wear and tear, (2)
consequences of condemnation or casualty to the extent repair, restoration or
cure is not required under the Lease,  (3) damage caused by Option-Holder, its
agents or employees.  Subject to the foregoing, Owner shall be responsible to
deliver the Option Property in compliance with all environmental legal
requirements relating to conditions which are (1) existing at the Option
Property on the Exercise Date and which are not Option-Holder's responsibility
under the Lease or (2) caused thereafter, but prior to the Closing Date by acts
or omissions of Owner, its affiliates or their respective employees, agents,
contractors, licensees or invitees.  Any remediation required by governmental
agencies to meet the requirements of the preceding sentence shall be performed
by Owner in accordance with all applicable laws prior to the Closing Date.

          10.   Damage or Destruction of Option Property by Casualty or
                -------------------------------------------------------
Condemnation. Owner and Option-Holder agree that, except as hereafter modified,
- ------------                                                                   
the Lease provisions for the portions of the Option Property which are leased by
Option-Holder shall govern their respective obligations if, after Option-
Holder's exercise of the Purchase Option, any portion of the Option Property is
damaged or destroyed by fire or other casualty or subjected to eminent domain
proceedings (together, "Casualty").  If the Lease shall be terminated as a
result of a Casualty, Option-Holder shall have the option either (a)  to
purchase the Option Property in its "as is" condition, in which case no
adjustment shall be made to the Option Price other than a credit to Option-
Holder for the amount of Owner's insurance deductible and all insurance proceeds
or

                                      -8-
<PAGE>
 
condemnation award ("Casualty Compensation"), as applicable, received by Owner
prior to such Closing Date and Owner shall assign to Option-Holder all of
Owner's rights to such insurance Casualty Compensation, or (2) to terminate its
exercise of the Purchase Option in which case this Agreement shall be null and
void and neither party shall have any further rights or obligations hereunder.
If, however, any mortgagee of the Option Property requires that Casualty
Compensation be applied against outstanding indebtedness secured by its
mortgage, Option-Holder shall be entitled to a credit against the Purchase Price
in the amount of the Casualty Compensation not received by Option-Holder.

          11.   Closing Obligations.  On the Closing Date,
                -------------------

                a.  Owner's Closing Deliveries:  Owner shall:
                    --------------------------

                    (1)   Deed.  Execute, acknowledge, and deliver to Option-
                          ----                
Holder a special warranty deed for the Option Property ("Deed") in proper form
for recording, conveying title to the Option Property as required by this
Agreement;

                    (2)   Assignment of Leases and Service Contracts. Execute
                          ------------------------------------------
and deliver to Option-Holder an assignment and assumption agreement ("Assignment
of Leases and Contracts") with respect to all of the Other Leases (including
security deposits paid by tenants under such leases) and all Service Contracts
which Option-Holder has agreed to assume, the form of which agreement shall be
reasonably acceptable to Option-Holder and Owner and which shall provide that
(A) Option-Holder assumes performance of all obligations so assigned which arise
after Closing and agrees to indemnify, defend and hold harmless Owner from
liability with respect thereto and (B) Owner agrees to indemnify, defend and
hold harmless Option-Holder from liability with respect to such assigned
obligations which relates to all periods prior to Closing;

                    (3)   Certified Rent Roll and Option-Holder Estoppel
                          ----------------------------------------------
Certificates. Deliver to Option-Holder a rent roll which identifies all of the
- ------------
Other Leases then in effect, the commencement and termination dates of each
lease, the security deposit paid by each tenant thereunder, and the current rent
due from each tenant thereunder, and (B) estoppel certificates from each tenant
under the Other Leases which shall be in form and substance reasonably
acceptable to Option-Holder and its lender;

                    (4)   Termination of the Lease.  Execute and deliver to
                          ------------------------
Option-Holder a Termination of Lease Agreement which confirms that the Lease
between Owner and Option-Holder has terminated (other than the indemnification
provisions thereunder which shall survive such termination with respect to acts
and omissions during the term of the Lease) and provide a mutual release by
Owner and Option-Holder with respect thereto, or which identifies outstanding
claims which either party may have against the other, the form of which shall be
reasonably acceptable to Option-Holder and Owner;

                                      -9-
<PAGE>
 
                    (5)   Evidence of Authority. Deliver to Option-Holder and
                          ---------------------
the Title Company evidence reasonably satisfactory to Option-Holder and the
title company that (A) Owner has the authority to execute and deliver the Deed
and all other documents to be executed and delivered by Owner at the Closing;
(B) the persons executing the Deed and such other documents on behalf of Owner
have full right, power and authority to do so; and (C) that all necessary action
on the part of Owner has been taken with respect to the valid execution and
delivery of this Agreement, and the consummation of the transactions
contemplated hereby;

                    (6)   Keys.  Deliver to Option-Holder all keys and alarm
                          ----
combinations to the Option Property;

                    (7)   Plans and Building Approvals.  Deliver to Option-
                          ----------------------------
Holder all plans, approvals and permits in its possession in connection with
construction of the Building;

                    (8)   Title Affidavits. Deliver to title company any normal
                          ----------------
and customary, reasonable certificates, affidavits, or other documents as may be
required by the title company to issue an owner's title policy;

                    (9)   FIRPTA Affidavit. Deliver to Option-Holder the
                          ----------------
certifications required by Section 1445 of the Internal Revenue Code;

                    (10)  Municipal Certificates.  Deliver to Option-Holder any
                          ----------------------
municipal certifications which are required as a condition to the transfer of
title to the Option Property; and

                    (11)  Miscellaneous.  Deliver such other assignments,
                          -------------
affidavits and documents as may be required pursuant to the provisions hereof or
mutually agreed by counsel for Owner and Option-Holder to be necessary to fully
consummate the transaction contemplated hereby.

               b.   Option-Holder's Deliveries.  At Closing, Option-Holder
                    --------------------------
shall:

                    (1)   Evidence of Authority.  Deliver to Owner evidence that
                          ---------------------            
(A) Option-Holder has the authority to execute and deliver all documents to be
executed and delivered by Option-Holder at the Closing, (B) the persons
executing the documents on behalf of Option-Holder have the full right, power
and authority to do so; and (C) all necessary action on the part of Option-
Holder has been taken with respect to the valid execution and delivery of this
Agreement, and the consummation of the transactions contemplated hereby;

                    (2)   Assignment of Leases.  Execute and deliver to Owner
                          --------------------
the Assignment of Leases and Contracts, thereby assuming all obligations of
Owner with respect to the agreements so assigned and security deposits under the
assigned leases;

                                      -10-
<PAGE>
 
                    (3)   Purchase Price.  Deliver the Option Price required
                          --------------
hereunder, either by certified check or wire transfer of immediately available
funds, as Owner may direct; and

                    (4)   Miscellaneous.  Deliver such other assignments,
                          -------------
affidavits and documents as may be required pursuant to the provisions hereof or
mutually agreed by counsel for Owner and Option-Holder to be necessary to fully
consummate the transaction contemplated hereby.

               c.   Amounts Claimed as Off-Set under the Lease.  If on the
                    ------------------------------------------
Closing Date, Option-Holder alleges that amounts are due from Owner for
nonperformance of Owner's obligations as lessor under the Lease and Option-
Holder shall have theretofore given Owner notice of such default to the extent
required under the Lease, Option-Holder shall pay the portion of the Purchase
Price equal to the amounts claimed due into an escrow account maintained by
Title Company or such other party who is acceptable to Owner and Option-Holder
to serve as escrow agent; provided, however, that the amounts claimed due are
supported by reasonable evidence of the costs incurred by Option-Holder with
respect Owner's alleged nonperformance. The party performing the duties of
escrow agent shall hold such amounts in an interest bearing escrow account (with
interest to follow the escrowed funds) until (1) receipt of a final order by a
court of competent jurisdiction which directs application of such escrow funds,
or (2) receipt of written instructions signed by Owner and Option-Holder which
direct application of such escrow funds, and, upon receipt of either of the
foregoing, the party performing the duties of escrow agent shall release the
escrowed funds in accordance with such instructions.

          12.  Transfer Taxes; Closing Costs; Allocation.
               -----------------------------------------

               a.   Owner's Costs. Owner shall pay the costs of (1) one-half of
                    -------------     
all transfer taxes, and (2) one-half of the fee of the title company to conduct
closing, not in excess of a total fee of $250.

               b.   Option-Holder's Costs.  Option-Holder shall pay the costs of
                    ---------------------
(1) the Title Report and Survey, if any, (2) the premium for an owner's title
policy, if obtained by Option-Holder, (3) one-half of all transfer taxes, (4)
recording the Deed, and any other conveyance documents that Option-Holder may
choose to record, and (5) one-half of the fee of the title company to conduct
closing, not in excess of a total fee of $250.

               c.   Other Costs.  All other expenses incurred by Option-Holder
                    -----------
or Owner with respect to the closing, including, but not limited to, attorneys
fees, shall be borne and paid exclusively by the party incurring same.

               d.   Proration and Expenses.  The following items shall be
                    ----------------------
adjusted or prorated between Option-Holder and Owner at closing and, for
purposes hereof, Option-Holder shall be deemed the owner of the Option Property
as of the Closing Date:

                                      -11-
<PAGE>
 
                    (1)   Real Estate Taxes.  Real estate and similar taxes for
                          -----------------
the then current tax year relating to the Option Property shall be prorated. If
the Closing Date shall occur before the tax rate is fixed for the then current
tax year, the apportionment of taxes shall be made on the basis of the tax rate
for the preceding tax year applied to the latest assessed valuation of the
Option Property, and when the tax rate is fixed for the tax year in which the
Closing Date occurs, Owner and Option-Holder to adjust the proration of taxes
and, if necessary, to refund or pay such sums to the other party as shall be
necessary to effect such adjustment. This obligation shall survive closing of
title.

                    (2)   Assessments.  All unpaid installments of assessments
                          -----------             
for municipal improvements, if any, which are due and payable before the
closing, shall be paid by Owner at the closing. From and after the Closing Date,
Option-Holder shall be solely responsible for payment of any such assessments.

                    (3)   Prepaid Rent.  All rent (including each tenant's
                          ------------
payment of operating expenses) paid by tenants under the Other Leases and by
Option-Holder under the Lease, shall be prorated and Owner shall credit to
Option-Holder all rent allocated to the Closing Date and periods thereafter
which has been collected from tenants and Option-Holder.
 
                    (4)   Utilities and Service Contracts. Any operating
                          -------------------------------
expenses for or pertaining to the public utility charges and service contracts
shall be prorated between Option-Holder and Owner at the closing.

          13.   Assignment of Purchase Option.  Option-Holder shall have the
                ------------------------------                              
right to transfer or assign ("Transfer") any or all of its rights under this
Agreement in connection with an assignment of the Lease which is permitted by
the Lease.

          14.   Default.
                ------- 

                a.  Default.  Either party shall be in default hereunder if such
                    -------
party fails to fulfill in a timely manner any covenant, agreement, or obligation
on such party's part in the manner required in this Agreement or breaches any
representations or warranties made by such party hereunder.

                b.  Notice Upon Default.  With the exception of a default by
                    -------------------
either party in concluding Closing, before either party shall be entitled to
declare this Agreement in default, the party who alleges a default by the other
party first shall have notified the party alleged to be in default in writing as
to the nature of the claimed default, and the party alleged to be in default
shall have fifteen (15) days after receipt of such notice in which to cure the
default.

                c.  Owner's Remedies.  If after the exercise by Option-Holder,
                    ----------------        
all of the conditions to Option-Holder's obligations have been satisfied or
properly waived by Option-

                                      -12-
<PAGE>
 
Holder, Option-Holder shall be in default hereunder beyond the period provided
in subsection (b) above, Owner's sole and exclusive remedies shall be (1) to
terminate this Agreement, and (2) to retain from the Deposit (and not to exceed
the Deposit) the amounts hereafter provided, with the balance of the Deposit, if
any, being returned to Option-Holder, whereupon neither party shall have any
further rights or liabilities hereunder, and (3) to exercise its rights pursuant
to Section 16(l) hereof. Amounts which Owner shall be permitted to deduct from
the Deposit are (i) all reasonable, actual third-party costs arising from
Owner's performance of this Agreement, based upon invoices of third parties
submitted by Owner to Option-Holder not later than ninety (90) days after the
termination of this Agreement and (ii) any late fee, extension fee and/or the
present values of any differential in the interest rate applicable to Owner's
refinancing of loans secured by a mortgage on the Option Property on the date of
Option-Holder's default and which would have been satisfied at Closing and which
Owner replaces at an interest rate in excess of the interest rate prevailing for
five (5) year loans on the date at which the Closing would have occurred had
Option-Holder not defaulted.

                d.  Option-Holder's Remedies.  If all of the conditions to
                    ------------------------
Owner's obligations have been satisfied or properly waived by Owner, Owner is in
default in the performance of its obligations hereunder beyond the period
provided in subsection (b) above, Option-Holder's sole and exclusive remedy
hereunder (except as may be permitted under Section 7(e) hereof) shall be
either: (i) to seek specific performance of this Agreement; or (ii) to terminate
this Agreement by notice in writing to Owner, in which case the Deposit shall be
returned to Option-Holder and Owner shall reimburse Option-Holder for all
reasonable, actual third-party costs arising from Option-Holder's performance of
this Agreement, based upon invoices of third parties submitted by Option-Holder
to Owner not later than ninety (90) days after the termination of this
Agreement, whereupon neither party shall have any further rights or liabilities
hereunder.

                e.  Attorney's Fees.  In any action or proceeding arising out of
                    ---------------
this Agreement, the prevailing party shall be entitled to reasonable attorney
fees and costs.

          15.   Resurrection of Withdrawn Rights.  If Option-Holder withdraws an
                --------------------------------                                
Exercise Notice for reasons set forth under Sections 7(e) or 8 hereof, or for
reasons under Section 6 hereof by a Withdraw Notice which specifies the reasons
for such withdraw, and Owner thereafter during the effectiveness of the Lease,
corrects the condition which triggered Option-Holder's withdraw of an Exercise
Notice, Owner shall notify Option-Holder that the condition has been corrected
which notice shall be provided not later than ten (10) business days after the
correction of such condition and include a reasonable statement of the
corrective action taken by Owner.  Option-Holder shall have thirty (30) days
from receipt of Owner's notice to re-exercise its Purchase Option.  If Option-
Holder fails to re-exercise the Purchase Option within such thirty (30) day
period, Option-Holder's rights hereunder shall be terminated and deemed null and
void, whereupon Owner shall be entitled to record the termination of the
memorandum of this Agreement.  If Option-Holder timely re-exercises its Purchase
Option, the Closing Date shall be determined in accordance with Section 5(c)
above, and unless the condition which prompted

                                      -13-
<PAGE>
 
Option-Holder's withdrawal of its Exercise Notice arose from the gross
negligence or wanton and wilful misconduct of Owner, or Owner's employees or
agents, Option-Holder shall pay as part of the Purchase Price any Prepayment Fee
due with respect to a first mortgage encumbering the Option Property.

          16.   Miscellaneous.
                ------------- 

                a.  Time of the Essence.  Time is of the essence for performance
                    -------------------
of all obligations hereunder.

                b.  Broker's Commission.  Each party represents and warrants to
                    -------------------
the others that it has incurred no liability to any real estate broker or agent
with respect to the payment of any commission regarding the consummation of the
sale of the Option Property. If any claims for commissions or fees are ever made
in connection with sales of the Option Property, all such claims shall be
handled and paid by the party whose actions or alleged commitments form the
basis of such claim, and such party shall indemnify, defend and hold harmless
the other from and against any and all such claims or demands.

                c.  Further Assurances.  The parties shall execute and deliver
                    ------------------
such additional documents and shall take such additional action or cause such
additional action to be taken, or to refrain from taking any action as may be
reasonably required to effect or implement all of the terms and conditions of
this Agreement and the transactions contemplated hereby.

                d.  Notices.  Any notice or other communication under this
                    -------
Agreement shall be in writing and addressed to Owner or Option-Holder at their
respective addresses set forth below (or to such other address as either may
designate by notice to the other):

As to Option-Holder prior to
Commencement Date of the Lease:     ViroPharma Incorporated
                                    76 Great Valley Parkway
                                    Malvern, PA 19355
                                    Attention:  General Counsel

As to Option-Holder as of the
Commencement Date of the Lease:     ViroPharma Incorporated
                                    Eagleview Corporate Center
                                    405 Eagleview Boulevard
                                    Exton, PA 19341
                                    Attention:  General Counsel

                                      -14-
<PAGE>
 
As to Owner:                        The Hankin Group
                                    P.O. Box 562
                                    717 Constitution Drive
                                    Eagleview Corporate Center
                                    Exton, PA  19341

All notices and statements required or permitted under this Agreement shall be
in writing and delivered by either (a) United States Registered or Certified
Mail, return receipt requested, postage prepaid, (b) Federal Express or other
nationally recognized overnight courier service, fee prepaid, or (c) hand
delivery against written receipt therefor. Notice given in accordance with this
Section shall be deemed given and received as of the earlier of (i) actual
receipt or (ii) first attempted delivery (including delivery which is refused).
The giving of notice under this Section by attorneys of Owner or Option-Holder
shall be deemed to be the acts of Owner or Option-Holder, as applicable,
however, the foregoing provisions governing the date on which a notice is deemed
to have been received shall mean and refer to the date on which a party to this
Agreement, and not its counsel or other recipient to which a copy of the notice
may be sent, is deemed to have received the notice.

                e.  Binding Effect.  This Agreement shall be binding upon and
                    --------------
shall inure to the benefit of the parties hereto and their respective successors
and permitted assigns.

                f.  Recording.  A short form memorandum of this Agreement shall
                    ---------
be recorded at Option-Holder's expense. Concurrently with the execution of this
Agreement, Option-Holder and Owner agree to execute such memorandum of this
Agreement along with a termination thereof, both of which shall be form and
substance sufficient to permit such instrument to be recorded and otherwise
reasonably acceptable to Option-Holder and Owner. The termination of such
memorandum of this Agreement shall be provided to Owner who hereby represents,
warrants and covenants not to record such termination unless and until this
Agreement shall have terminated.

                g.  Severability.  Any provision of this Agreement which is
                    ------------
determined by a court of competent jurisdiction to be invalid or unenforceable
shall be ineffective only to the extent of such invalidity or unenforceability
and shall not invalidate or render unenforceable the remaining provisions of
this Agreement, and this Agreement shall be construed to the fullest extent
permitted by law in such manner as to carry out the intent of this Agreement and
of the provision so deemed invalid or unenforceable.

                h.  Applicable Law.  This Agreement shall be construed under and
                    --------------
in accordance with the laws of the Commonwealth of Pennsylvania. 

                                      -15-
<PAGE>
 
                i.  Counterparts.  This Agreement may be executed in any number
                    ------------
of counterparts, each of which shall be deemed an original and all of which,
when taken together, shall constitute one fully binding Agreement even though
all original signatures do not appear on the same document.

                j.  Merger at Closing.  All representations and warranties set
                    -----------------
forth in this Agreement shall terminate at Closing and be merged into the Deed
except for obligations under Sections 6, 12 and 16(b) hereof which shall survive
Closing. Option-Holder acknowledges that it will have exercised the Purchase
Option, and purchase the Option Property, if at all, only after having had the
opportunity to inspect and examine the Option Property pursuant to Section 6
above. Accordingly, Option-Holder acknowledges and agrees that its decision to
purchase the Option Property is as a result of its own independent investigation
and inspection, and not as a result of or in reliance upon any representation or
warranty made or alleged to have been made by Owner, or any of Owner's agents
and representatives, except for such express warranties as may be contained in
the Lease or this Agreement.

                k.  Notice Restatements of Owner's Obligations.  Option-Holder's
                    ------------------------------------------
failure to include a restatement of Owner's obligations in its notices to Owner
as contemplated by Sections 2(c) and 7(d) hereof shall not be deemed a default
by Option-Holder nor a failure of Owner's obligations with respect to the
subject obligations.  If, however, Option-Holder shall fail to include such
restatement of Owner's obligations and Owner shall not perform within the time
periods set forth in this Agreement, the consequences set forth in Sections 2
and 7, as applicable, as a result of Owner's failure to respond shall not be
binding on Owner unless and until Option-Holder shall have sent written notice
to Owner that Owner's response is due and Owner shall not have responded
thereafter within the times for performance required under Sections 2 and 7, as
applicable.

                l.  Lease for Expansion Space. If Option-Holder has exercised
                    -------------------------
its Purchase Option and Option-Holder's rights under Section 46 of the Lease
have terminated in



                  [Remainder of page intentionally is blank.]

                                      -16-
<PAGE>
 
their entirety or only as to the Released Area, Owner shall not enter into any
leases for all or any portion of the vacant Expansion Space or Released Area (as
the case may be) until the expiration of the Due Diligence Period and thereafter
only with Option-Holder's prior written consent thereto.  If Option-Holder
denies its consent to any lease proposed by Owner, the terms of which are
evidenced by a letter of intent signed by Owner and the proposed lessee which
sets forth in reasonable detail the terms of such lease ("Proposed Lease"), the
following shall apply:

                    (1)   If Option-Holder thereafter defaults with respect to
its Purchase Option, Option-Holder shall be obligated to lease from Owner the
space contemplated by the Proposed Lease on the same terms and conditions as
were presented to Option-Holder for its consent; and

                    (2)   If Option-Holder thereafter withdraws an Exercise
Notice or terminates its exercise of the Purchase Option and the reason such
Exercise Notice is withdrawn or the Purchase Option is terminated is due to a
condition other than one which results from Owner's action, Option-Holder shall
be obligated to lease from Owner the space contemplated by the Proposed Lease on
the same terms and conditions as were presented to Option-Holder for its consent
except that (A) the term of such lease shall not exceed one (1) year, and (B)
Owner shall be obligated to use commercially reasonably efforts to find a
replacement tenant or tenants for the space so leased by Option-Holder.

Unless otherwise agreed by Owner and Option-Holder such lease shall be effective
as of the date of Option-Holder's default or withdrawal.

               m.   Complete Agreement; Modifications. This Agreement is the
                    ---------------------------------
complete Agreement of the parties hereto. Neither this Agreement nor any
provision hereof may be waived, modified, discharged, or terminated except by an
instrument in writing signed by the party against which the enforcement of such
waiver, modification, discharge, or termination is sought, and then only to the
extent set forth in such instrument

          IN WITNESS WHEREOF, Owner and Option-Holder have caused this Agreement
to be duly executed under seal as of the date set forth above.

                                 THE HANKIN GROUP

                                 By:   /s/ Robert S. Hankin
                                    -------------------------------------
                                       Robert S. Hankin, General Partner

                                 VIROPHARMA INCORPORATED

                                 By:   /s/ Thomas F. Doyle
                                    -------------------------------------
                                       Thomas F. Doyle, Executive Director,
                                       Counsel and Secretary

                                      -17-

<PAGE>
 
                                                                EXHIBIT 10.25

                               ESCROW AGREEMENT
                               ----------------

          This Escrow Agreement ("Agreement") is made this 21st day of July
1997 by and between THE HANKIN GROUP, a Pennsylvania partnership ("Landlord"),
VIROPHARMA, INC. ("Tenant"), and MANITO ABSTRACT COMPANY, INC. ("Escrow Agent").

                              B A C K G R O U N D

          By lease dated July ___, 1997 (the "Lease"), Landlord  leased to
Tenant certain space in a building to be constructed by Landlord on premises
known as Lot 10 Eagleview Corporate Center, Uwchlan Township, Chester County,
Pennsylvania. Exhibit B, entitled "Work Letter to Lease", of the Lease sets
forth Landlord's and Tenant's respective rights and obligations with respect to
construction of the "Leased Space" which is the subject of the Lease. Exhibit B,
Paragraph 3b, of the Lease entitled "Cost of Tenant Improvements" more
particularly provides for the mechanism for the payment by Tenant of its share
of the cost of construction of the Leased Space, from funds to be deposited in
escrow by Tenant with Escrow Agent. The escrow obligations as set forth in
Exhibit B, Paragraph 3b, of the Lease , as more fully described herein, are
hereinafter collectively called the "Escrow Arrangements."

          In accordance with Article 36 entitled "Security Deposit:  Security
Interest", of the Lease, Tenant agrees to deposit funds in escrow as security
for Tenant's performance of all the terms and conditions of the Lease ("Security
Deposit").  The escrow obligations concerning the Security Deposit also are set
forth herein.

     NOW, THEREFORE, the parties hereto, each intending to be legally bound
hereby, agree as follows:

          1.  Terms not otherwise defined herein shall have the meaning provided
in the Lease.

          2.  Escrow Agent hereby agrees to serve as escrow agent and to perform
the duties of "Escrow Agent" set forth herein.  Escrow Agent agrees that no fee
shall be due for the performance of its services hereunder, nor shall any
reimbursement be claimed for costs incurred by Escrow Agent in the performance
of its duties hereunder.

          3.  Upon receipt by Escrow Agent from time to time of the Escrow Funds
received from Tenant, Escrow Agent shall deposit the same in an interest bearing
account with CoreStates Bank, Wilmington Trust Company, or a commercial bank
whose deposits are insured by the US government, up to $100,000.00 and which is
approved by Landlord and Tenant (such approval not to be unreasonably withheld).
Such Escrow Funds shall be held and disbursed by Escrow Agent in accordance with
the provisions of the "Escrow Arrangements" which are attached hereto as Exhibit
"A" and made a part hereof and incorporated herein by reference.  Upon receipt
and deposit of the Escrow Funds, Escrow Agent shall send written 

                                      -1-
<PAGE>
 
notice to Landlord and Tenant identifying the bank and account number where the
same has been deposited.

          4.  Escrow Agent shall hold the Security Deposit in an account
segregated from the Escrow Funds until the Commencement Date, as defined in
Article 2 of the Lease, at which time the Security Deposit shall be paid
directly to Landlord.

          5.  By signing this Agreement, Escrow Agent acknowledges receipt from
Tenant of $45,899.33 which is the Security Deposit and $155,000 which is
Tenant's First payment of the Escrow Funds.  Escrow Agent agrees to promptly
deposit such funds in the escrow accounts to be maintained in accordance with
this Agreement and notify Landlord and Tenant as to the bank location and
account number.

          6.   Escrow Agent shall not be liable for any act or omissions arising
out of its performance of its duties as Escrow Agent under this Agreement,
except such as may constitute gross negligence or willful misconduct, and
Landlord and Tenant shall otherwise indemnify, defend and save harmless Escrow
Agent for any claim, cost or expense arising out of Escrow Agent's agreement to
act as escrow agent hereunder.  In the event of any dispute as to the
disposition of the Security Deposit funds or the Escrow Funds, Escrow Agent may
continue to hold the same until resolution of the dispute, or pay or deliver the
Security Deposit Funds or the Escrow Funds into Court whereupon Escrow Agent be
relieved of any further obligation as escrow agent.

          7.  Any notices required or given pursuant to this Agreement shall be
sent by certified mail, return receipt requested, or Federal Express or other,
nationally recognized overnight courier service, or by hand delivery against
receipt, addressed as follows:

As to Tenant: prior to   VIROPHARMA, INC.
Commencement Date:       76 Great Valley Parkway
                         Malvern, PA 19355
                         Attention:  General Counsel

As to Tenant as of the   VIROPHARMA, INC.
Commencement Date:       Eagleview Corporate Center
                         405 Eagleview Boulevard
                         Exton, PA  19341
                         Attention:  General Counsel

                                      -2-
<PAGE>
 
As to Landlord:        THE HANKIN GROUP
                       P.O. Box 562
                       717 Constitution Drive
                       Eagleview Corporate Center
                       Exton, PA  19341
                       Attention: Robert S. Hankin, Partner
                   
With a copy to:        EDWARD J. HOLLIN, ESQUIRE
                       Riley, Riper, Hollin & Colagreco
                       P.O. Box 568
                       240 Daylesford Plaza
                       Paoli, PA  19301

As to Escrow Agent:    MANITO ABSTRACT COMPANY, INC.
                       P.O. Box 841
                       Church and Market Streets
                       West Chester, PA  19380-0841
                       Attention: Bruce West, President

 
     8.   This Agreement and the Lease provisions incorporated herein by
reference constitute the entire agreement of the parties hereto and shall be
binding upon the parties hereto, their respective successor and assigns.
Notwithstanding the foregoing, Escrow Agent shall not assign its duties
hereunder without the prior written consent of Landlord and Tenant.

     9.   No modifications or supplements to this Agreement shall be effective
unless in writing signed by all parties hereto.

     10.  This Agreement may be executed in any number of identical
counterparts.  If so executed, each of such counterparts is to be deemed an
original for all purposes, and all such counterparts shall collectively
constitute one agreement, but in making proof of this Agreement it shall not be
necessary to produce or account for more than one such counterpart.

                                      -3-
<PAGE>
 
          IN WITNESS WHEREOF, the parties hereto have executed this Escrow
Agreement as of the day and year first above written.

                              LANDLORD

                              THE HANKIN GROUP


                              BY: /s/ [SIGNATURE APPEARS HERE]
                                 ------------------------------


                              TENANT:

                              VIROPHARMA, INC.


                              BY: /s/ [SIGNATURE APPEARS HERE]
                                 ------------------------------


                              MANITO ABSTRACT COMPANY, INC.



                              BY:
                                 ------------------------------

                                      -4-
<PAGE>
 
                                   EXHIBIT A






           (5)    Tenant's initial contribution of $834,760.00 toward the Direct
Payment Portion ("Escrow Funds") shall be paid by Tenant into an escrow account 
("Escrow Account") as follows:  $155,000 shall be paid by Tenant at the time of 
the execution of the Lease; $200,000 shall be paid on or before August 1, 1997; 
and the balance of $479,760 shall be paid on or before August 31, 1997.  The 
Escrow Funds shall maintained by Manito Abstract Company ("Escrow Agent"), as a 
segregated, interest bearing account which, unless otherwise agreed by Tenant, 
is fully insured up to $100,000 by the United States Government, and otherwise 
in accordance with an escrow agreement to be entered which shall be 
substantially in the form attached hereto as Schedule 5. All interest earned on 
                                             ----------
the Escrow Funds shall remain the property of Tenant, but shall constitute a 
portion of the Escrow Funds subject to disbursement in accordance herewith.  If,
however, Manito Abstract Company now or hereafter requires a fee for the 
performance of its duties as Escrow Agent, Tenant and Landlord, upon the request
of either party, shall designate another party to serve as Escrow Agent which is
reasonably acceptable to Landlord and Tenant and does not require the payment of
any fee for performance of the duties as Escrow Agent.

           (6)    As Tenant Improvements progress, Landlord shall submit to 
Tenant's Consultant invoices for payment of such portion of the Tenant 
Improvements which has been Substantially Completed or for materials for the 
Tenant Improvements delivered to the site.  Such invoice shall be submitted on 
an AIA form 702/703 or other form reasonably acceptable to Tenant's Consultant 
and shall include such requisitions for payment, bills, charges and other 
supporting documentation as Tenant's Consultant shall reasonably request.  
Tenant,



                                      -5-


<PAGE>
 
either directly or acting through Tenant's Consultant, shall approve or reject 
such invoices within five (5) business days of receipt, or the same shall be 
deemed approved.  Any rejection of an invoice shall state the reasons therefor
with particularity, and Tenant shall state which sums reflected in the invoice 
Tenant objects to, and the portion which is not objected to by Tenant shall be 
disbursed in accordance with the provisions below.  If Landlord and Tenant 
cannot agree on whether the Landlord's Work reflected in an invoice has been 
Substantially Completed in accordance with the TI Plans and the other 
requirements of the Lease, such dispute shall be decided in accordance with 
Section 9 hereto.

           (7)    Upon approval of an invoice, Tenant, either directly or acting
through Tenant's Consultant, shall, in writing, authorize the Escrow Agent to 
pay over to Landlord from the Escrow Account, one-half of the TI Cost reflected 
by such invoice and the balance shall be earmarked as funds reserved for payment
of such invoice which shall be paid over to Landlord upon the earlier of (A) 
Substantial Completion of the Tenant Improvements or (B) at such time as the 
total of all invoices for the Tenant Improvements equals or exceeds $3,117,810. 
At such time as the total of all invoices for the Tenant Improvements equals or 
exceeds $3,117,810, the entire TI Cost reflected in an invoice shall be paid to 
Landlord.  Any portion of the Escrow Funds remaining in the Escrow Account after
all payments due Landlord have been paid shall be paid over to Tenant.

<PAGE>
 
                                                                   EXHIBIT 10.26


                                   EXHIBIT B

                             WORK LETTER TO LEASE

          Subject to and in consideration of the provisions of the Lease
("Lease") to which this Exhibit is attached, Landlord shall cause its general
contractor, Eagleview Commercial Construction Company, Inc. ("General
Contractor"), to construct the Building and certain tenant improvements in the
Leased Space as set forth in this Exhibit.  The provisions of this Exhibit shall
have the same force and effect as if this Exhibit were a numbered Section of the
Lease.

          In order to induce Landlord and Tenant to enter into the Lease (which
is hereby incorporated by reference), and in consideration of the mutual
covenants hereinafter contained, Landlord and Tenant mutually agree as follows:

          1.  Terms.  The capitalized terms herein shall have the same meanings
              -----                                                            
as ascribed thereto in the Lease unless otherwise expressly provided herein to
the contrary.  The provisions of this Work Letter are intended to supplement the
Lease which, together, are the complete agreement of the parties with respect to
construction of the Landlord's Work (hereafter defined).  In the event of any
conflict between the provisions of the Lease and the provisions of this Work
Letter, the provisions of the this Work Letter shall control.

          2.  Construction Obligations.
              ------------------------

              a.  Landlord will construct and install, at Landlord's expense,
the base building improvements ("Base Building Improvements") in accordance with
the base building plans and the specifications set forth on Schedule 1 attached
                                                            ----------         
hereto ("Base Building Plans"). Landlord shall have all responsibility for
seeing that the Base Building Plans comply with all applicable laws, codes,
rules or regulations of any governmental authority having jurisdiction over same
("Construction Requirements").

              b.  In addition to the Base Building Improvements, Landlord shall
fit-out the Leased Space as generally described on Schedule 2 attached hereto
                                                   ----------
("Tenant Space Plans") and shall construct, furnish and install certain
improvements within the Leased Space required to implement the Tenant Space
Plans ("Tenant Improvements") in accordance with the plans and specification for
the Tenant Improvements set forth on Schedule 3 attached hereto ("TI Plans"),
                                     ----------                              
which TI Plans have been prepared by Tenant's consultant OMNI Technologies, Inc.
("Tenant's Consultant") and approved by Landlord.  Any review and approval by
Landlord of TI Plans in accordance with this Work Letter shall not imply
approval by Landlord as to compliance of the TI Plans with Construction
Requirements or of the compatibility of the TI Plans with the Base Building
Improvements.  The foregoing shall be Tenant's sole obligation hereunder.
<PAGE>
 
              c.  If the TI Plans have not been finalized at the time this Work
Letter is executed, the following shall apply:

                  (1)   Tenant and Tenant's Consultant shall develop proposed TI
Plans and submit them to Landlord for approval within fourteen (14) business
days from the date hereof.

                  (2)   Landlord shall review the TI Plans and respond to Tenant
with comments and/or approval within ten (10) business days after Landlord
receives Tenant's proposed TI Plans. Landlord agrees not to unreasonably delay,
withhold or condition its approval of Tenant's proposed TI Plans.

                  (3)   Tenant shall incorporate any changes to the proposed TI
Plans reasonably requested by Landlord within ten (10) business days after
Landlord has commented upon the proposed TI Plans, and the proposed TI Plans, as
revised, shall be submitted to Landlord for final approval, which Landlord shall
not unreasonably withhold, delay or condition.

                  (4)   Within ten (10) business days after Landlord's receipt
of such revised TI Plans, Landlord shall deliver to Tenant and Tenant's
Consultant any further reasonable revisions which Landlord requires or
recommends, along with an estimate prepared by General Contractor, substantially
on a line-item basis, of the total TI Cost (hereafter defined) to complete the
Tenant Improvements based on the current TI Plans and any further revisions last
proposed by Landlord.

                  (5)   Within five (5) business days of final approval of the
TI Plans by Landlord and Tenant, Tenant shall submit the TI Plans to the
appropriate governmental bodies of the Commonwealth of Pennsylvania for any
approvals which are a precondition to the issuance of a building permit for the
Tenant Improvements from Uwchlan Township. Tenant shall promptly provide such
approval to Landlord, and within five (5) business days of Landlord's receipt
thereof, Landlord shall submit the TI Plans to Uwchlan Township for the issuance
of a building permit and any other municipal approvals necessary for the
construction of the Tenant Improvements in accordance with the TI Plans. Each
party shall cooperate with any reasonable request of the other in connection
with such applications for approvals, and Tenant and Landlord shall cooperate to
cause to be made to the TI Plans such changes as are necessary to obtain any
such approval and building permit. If all necessary permits and approvals from
Uwchlan Township for construction of the Tenant Improvements based on such TI
Plans are not received within sixty (60) days from Landlord's application for
such approvals and necessary permits, Tenant shall have the right to terminate
this Lease, in which event neither party shall have any further rights or
obligations hereunder or under the Lease except that the Security Deposit and
Direct Payment Portion then paid by Tenant shall be returned by Landlord to
Tenant within thirty (30) days of such termination and if not so paid, such
unpaid amounts shall accrue interest at the Default Rate specified in the Lease
from the date of termination until paid in full.

                                      -2-
<PAGE>
 
                  (6)   After final approval of the TI Plans by applicable
governmental authorities and the issuance of a building permit, the TI Plans
shall serve as the plans for completing the Tenant Improvements, and no further
changes shall be made thereto without the consent of the other party.

              d.  Landlord shall provide to Tenant copies of all approvals,
permits, inspection reports, and other governmental consents required for
construction of the Base Building Improvements and the Tenant Improvements
(together, "Landlord's Work") which are not Tenant's responsibility hereunder.
Tenant shall provide to Landlord copies of all approvals and permits required
for construction of the Tenant Improvements which are not Landlord's
responsibility hereunder.

              e.  Landlord shall cause the Landlord's Work to be performed in a
good and workmanlike manner using only new materials (unless otherwise specified
by Tenant in writing or in the TI Plans) of the quality and type set forth in
the Base Building Plans and TI Plans and shall cause construction of the
Landlord's Work to be undertaken in compliance with all Construction
Requirements.

          3.  Competitive Bidding and Work Costs.
              ---------------------------------- 

              a.  Competitive Bidding.

                  (1)   Within two (2) business days from the date the TI Plans
have been approved by Landlord and Tenant, Landlord shall cause General
Contractor to submit bids to not less than three (3) subcontractors for all
portions of the Tenant Improvements which cost in excess of $3,000 and which are
to be performed by a subcontractor. General Contractor shall include any
subcontractor suggested by Tenant as a party to bid on a particular subcontract.
Landlord agrees to accept such bids as are acceptable to Tenant (and which may
not be the lowest bidder), such approval not to be unreasonably withheld.

                  (2)   Within five (5) business days of the receipt of all bids
required pursuant to subsection (1) above, Landlord shall deliver to Tenant and
Tenant's Consultant an update to the estimate of the total TI Cost. Tenant shall
have the right to make one (1) substantial revision to the proposed TI Plans
following receipt from Landlord of such estimate as Tenant deems necessary to
reduce the estimated total TI Cost. If Tenant exercises such right, Tenant shall
so notify Landlord in writing within five (5) business days after receipt of
such TI Cost estimate from Landlord, whereupon the procedures outlined in
Section 2(c) shall be repeated as necessary.

              b.  Cost of Tenant Improvements.

                  (1)   "TI Cost" shall mean the actual cost billed to Landlord
by General Contractor of supplying all labor and materials to perform the Tenant
Improvements and alterations to the Base Building as is necessary for the Tenant
Improvements, including all items

                                      -3-
<PAGE>
 
as are included within the definition of "Cost of the Work" pursuant to Article
8 of the "American Institute for Architects AIA Document A111 Standard Form of
Agreement Between Owner and Contractor where the basis of payment is the Cost of
the Work Plus a Fee," plus the fee charged to Landlord by General Contractor
which shall not exceed ten percent (10%) of the TI Cost, plus an amount equal to
$39,550.00 representing the agreed-upon value of Tenant's laboratory equipment
listed on Schedule 4 hereto being contributed by Tenant ("Tenant's Lab
          ----------                                                  
Equipment").

                  (2)   The budgeted TI Cost is $2,763,610 ("TI Budget"), of
which Tenant shall pay $834,760.00 in cash and contribute Tenant's Lab Equipment
having an agreed value of $39,550.00. The excess, if any, of the TI Cost over
the TI Budget which is not due to delays caused by Landlord or General
Contractor, or their respective employees or subcontractors, including without
limitation errors in construction of Landlord's Work, hereinafter is called the
"TI Overrun." If the TI Overrun is not more than $354,200.00, Tenant shall pay
one-half the TI Overrun in cash, and Minimum Annual Rent during the Initial Term
shall increase by a sum equal to the remaining one-half of the TI Overrun
multiplied by .152. If the TI Overrun is more than $354,200.00, Tenant shall pay
in cash the balance of the TI Overrun over $177,100.00, and Minimum Annual Rent
during the Initial Term shall increase by $26,919.20. The total cash payments
required to be paid by Tenant toward the TI Cost, including that portion of TI
Overrun to be paid in cash by Tenant, hereinafter are collectively called the
"Direct Payment Portion." If, however, the TI Cost shall be less than the TI
Budget ("TI Surplus"), one-half of the TI Surplus shall be returned by the
Escrow Agent (defined in subsection (4) below) to Tenant in cash from the Escrow
Funds (defined in subsection (5) below) and the Minimum Annual Rent during the
Initial Term shall decrease by a sum equal to the remaining one-half of the TI
Surplus multiplied by .152.

                  (3)   Landlord acknowledges that the TI Budget has been priced
to include any modifications to the Base Building based on proposed TI Plans
upon which Landlord estimated the TI Budget and which have been superseded by
the TI Plans attached hereto. Tenant acknowledges that Landlord has not had an
opportunity to price the cost of construction of the Tenant Improvements as
described on the approved TI Plans attached hereto, and Landlord shall advise
Tenant of the estimated TI Cost for Tenant Improvements excluding finished
laboratory space within ten (10) days of the date hereof, and for finished
laboratory space within thirty (30) days of the date hereof. Upon receipt of
such estimate for total TI Cost, Tenant shall have the right to revise the TI
Plans to reduce the estimated cost thereof without such event being deemed a
Tenant Delay or requiring adjustment to the Target Date as long as (i)
Landlord's estimate for the total TI Cost exceeds the TI Budget, (ii) Tenant
delivers the revised TI Plans to Landlord within ten (10) business days of the
date Tenant receives Landlord's estimate for total TI Cost, (iii) no material
modifications to the Base Building are required to accommodate such revisions,
and (iv) no delay is occasioned by the need to order materials or equipment
which can not be delivered or is not available within Landlord's required time
schedule in order to achieve Substantial Completion by March 1, 1998 (and if a
delay arises due to the foregoing subsection (iv), the Tenant Delay will be
measured only to the extent of the actual delay in the delivery of such items).
If material modifications are required to the Base

                                      -4-
<PAGE>
 
Building as a result of such revisions, the Target Date shall be extended by the
number of days necessary to adapt the Base Building to accommodate the Tenant
Improvements in accordance with the revised TI Plans. Any TI Overrun which
results form Landlord's pricing of the approved TI Plans (as revised) or which
is otherwise determined in accordance with this Section shall be paid by Tenant
to Escrow Agent within ten (10) business days and thereafter disbursed as part
of the Escrow Funds.

                  (4)   Throughout the course of construction, Landlord shall
lead value engineering efforts to assist Tenant in avoiding TI Overrun. At such
time as Landlord determines a TI Overrun will occur or has occurred, Landlord
will immediately notify Tenant and Tenant's Consultant as to the projected
amount of the TI Overrun and reasons therefor. Thereupon, Landlord, General
Contractor and Tenant's Consultant shall examine the cause of such TI Overrun
and undertake such reasonable modifications to the TI Plans, given the stage of
the work in process, as Tenant's Consultant deems advisable to reduce the amount
of the projected TI Overruns. The amount of the TI Overrun projected after such
adjustments shall be paid by Tenant to Escrow Agent, added to the Escrow Funds
and disbursed in accordance with the procedures outlined in subsection (5)
below. Upon request of Tenant or Tenant's Consultant from time to time during
appropriate stages of the Landlord's Work, Landlord shall provide an updated
estimate of the TI Cost which includes a comparison of actual costs against
projected costs and an estimate of the TI Cost to complete the remaining
portions of the Tenant Improvements.

                  (5)   Tenant's initial contribution of $834,760.00 toward the
Direct Payment Portion ("Escrow Funds") shall be paid by Tenant into an escrow
account ("Escrow Account") as follows: $155,000 shall be paid by Tenant at the
time of the execution of the Lease; $200,000 shall be paid on or before August
1, 1997; and the balance of $ 479,760 shall be paid on or before August 31,
1997. The Escrow Funds shall maintained by Manito Abstract Company ("Escrow
Agent"), as a segregated, interest bearing account which, unless otherwise
agreed by Tenant, is fully insured up to $100,000 by the United States
Government, and otherwise in accordance with an escrow agreement to be entered
which shall be substantially in the form attached hereto as Schedule 5. All
                                                            ----------
interest earned on the Escrow Funds shall remain the property of Tenant, but
shall constitute a portion of the Escrow Funds subject to disbursement in
accordance herewith. If, however, Manito Abstract Company now or hereafter
requires a fee for the performance of its duties as Escrow Agent, Tenant and
Landlord, upon the request of either party, shall designate another party to
serve as Escrow Agent which is reasonably acceptable to Landlord and Tenant and
does not require the payment of any fee for performance of the duties as Escrow
Agent.

                  (6)   As Tenant Improvements progress, Landlord shall submit
to Tenant's Consultant invoices for payment of such portion of the Tenant
Improvements which has been Substantially Completed or for materials for the
Tenant Improvements delivered to the site. Such invoice shall be submitted on an
AIA form 702/703 or other form reasonably acceptable to Tenant's Consultant and
shall include such requisitions for payment, bills, charges and other supporting
documentation as Tenant's Consultant shall reasonably request. Tenant,

                                      -5-
<PAGE>
 
either directly or acting through Tenant's Consultant, shall approve or reject
such invoices within five (5) business days of receipt, or the same shall be
deemed approved. Any rejection of an invoice shall state the reasons therefor
with particularity, and Tenant shall state which sums reflected in the invoice
Tenant objects to, and the portion which is not objected to by Tenant shall be
disbursed in accordance with the provisions below. If Landlord and Tenant cannot
agree on whether the Landlord's Work reflected in an invoice has been
Substantially Completed in accordance with the TI Plans and the other
requirements of the Lease, such dispute shall be decided in accordance with
Section 9 hereto.

                  (7)   Upon approval of an invoice, Tenant, either directly or
acting through Tenant's Consultant, shall, in writing, authorize the Escrow
Agent to pay over to Landlord from the Escrow Account, one-half of the TI Cost
reflected by such invoice and the balance shall be earmarked as funds reserved
for payment of such invoice which shall be paid over to Landlord upon the
earlier of (A) Substantial Completion of the Tenant Improvements or (B) at such
time as the total of all invoices for the Tenant Improvements equals or exceeds
$3,117,810. At such time as the total of all invoices for the Tenant
Improvements equals or exceeds $3,117,810, the entire TI Cost reflected in an
invoice shall be paid to Landlord. Any portion of the Escrow Funds remaining in
the Escrow Account after all payments due Landlord have been paid shall be paid
over to Tenant.

          4.  Construction.
              ------------ 

              a.  Attached hereto as Schedule 6 is a tentative construction 
                                     ----------
schedule ("Construction Schedule") which sets forth milestone dates for
completion of the Landlord's Work. Landlord shall supervise the completion of
the Landlord's Work and diligently cause the General Contractor to pursue
Substantial Completion thereof with reasonable diligence by the Target Date and
otherwise in accordance with the performance dates specified on the Construction
Schedule. Landlord agrees to achieve Substantial Completion by the Target Date,
subject to the terms and conditions set forth in Section 2 of the Lease.

              b.  After a building permit for the Base Building Improvements has
been issued, Landlord shall cause the General Contractor to begin construction
of the Base Building Improvements in accordance with the Base Building Plans.

              c.  After a building permit for the Tenant Improvements has been
issued, Landlord shall cause the General Contractor to begin construction of the
Tenant Improvements in accordance with the TI Plans.

              d.  Status meetings shall be held once every two weeks between
Landlord, General Contractor, Tenant and Tenant's Consultant concerning the
status of the Landlord's Work. Landlord shall cause telefaxed summaries to be
sent to Tenant and Tenant's Consultant of the progress of the Landlord's Work on
a daily basis beginning twenty (20) days prior to the date the General
Contractor estimates that Substantial Completion will occur and

                                      -6-
<PAGE>
 
shall thereafter keep Tenant or Tenant's Consultant informed as to any change of
the dates on which Substantial Completion will occur.

              e.  Tenant, from time to time, may submit to the Landlord any
changes or additions ("Change Order(s)") to the TI Plans desired by Tenant,
which changes or additions shall be subject to Landlord's approval, which shall
not be unreasonably withheld, conditioned or delayed. Landlord's approval shall
include written notice to Tenant of: (i) changes, if any, to the TI Cost
resulting from any additional cost of constructing the Tenant Improvements and
indication of whether such change would result in a TI Overrun, (ii) any
increase in the cost of the Base Building Improvements resulting from Change
Orders, and (iii) anticipated delays, if any, to the Target Date and the
completion of the Base Building Improvements and the Tenant Improvements, as the
case may be. Tenant, within twenty-four (24) hours of receipt of Landlord's
statement (or the first business day after receipt of Landlord's notice if the
expiration of such twenty-four (24) hours does not fall on a business day),
notify Landlord whether or not to proceed with the Change Order. If Tenant fails
to give such notice, Tenant shall be deemed to have elected not to proceed with
the Change Order. Tenant's notice to proceed with the Change Order shall be
deemed Tenant's acceptance of any revised TI Cost and the specified delay, and
Tenant's Consultant shall promptly revise the TI Plans to incorporate such
changes or additions. Adjustments to the TI Cost as a result of approved Change
Orders shall be allocated to the parties in the same manner provided in Section
3(b)(2) hereof, provided, however, that if the effect of any Change Order shall
be to increase the cost of the Tenant Improvements above the TI Budget, Tenant,
upon acceptance of the Change Order, shall pay one-half of the increased cost
due to such approved Change Order directly to Landlord and the other one-half to
Escrow Agent, which amount shall be added to the Escrow Funds but disbursed to
Landlord when the improvements contemplated by the Change Order have been
Substantially Completed.
 
          5.  Inspections and Scheduling
              --------------------------

              a.  Tenant and Tenant's Consultant shall have the right, from time
to time, to observe the progress of the Base Building Improvements and the
Tenant Improvements, to inspect installation of the Tenant Improvements, to
check all products and labor comprising the Tenant Improvements, and to reject
any work or product which is not in substantial conformance with the Base
Building Plans and the TI Plans. In the event of a dispute concerning
conformance with the Base Building Plans and the TI Plans, the dispute shall be
submitted to dispute resolution in accordance with this Work Letter. No such
observation or inspection shall be deemed to waive any rights of Tenant under
Section 7 of the Lease, so long as Tenant shall promptly notify Landlord if, in
the course of such inspection, Tenant, either directly or through Tenant's
Consultant, observes conditions which Tenant believes are not in accordance with
the TI Plans. Landlord shall be available, and cause the General Contractor to
be available, to Tenant or Tenant's Consultant from time to time upon reasonable
prior notice when necessary or desirable for the purpose of reviewing the Base
Building Improvements or the Tenant Improvements. Landlord shall use its best
efforts to keep Tenant informed as to all material governmental inspections and
shall permit Tenant or Tenant's Consultant to be present thereat,

                                      -7-
<PAGE>
 
giving reasonable prior notice of same. Landlord shall promptly deliver to
Tenant all revisions of the Construction Schedule.

              b.  Landlord shall cause to be kept such full and detailed
accounts as may be necessary for proper financial management under this Work
Letter with respect to the Tenant Improvements. Tenant and Tenant's Consultant
shall be afforded access to all records, books, correspondence, instructions,
drawings, receipts, vouchers, memoranda and similar data relating to the Tenant
Improvements maintained by Landlord and General Contractor. Landlord agrees to
cause such records to be preserved for a period of three years, or for such time
as required by law after final payment, for Tenant's audit at any time, at
Tenant's expense.

          6.  Landlord's Warranty.
              ------------------- 

              a.  Landlord shall deliver the Landlord's Work at the Commencement
Date free and clear of all liens other than the Permitted Title Exceptions.
Landlord also shall deliver the Landlord's Work in broom clean condition with
all construction debris removed from the Real Estate as a condition to
Substantial Completion of the Leased Space.

              b.  In addition to (and not in lieu of) Landlord's obligation
under the Lease with respect to repairs, Landlord warrants to Tenant that the
Base Building Improvements and the Tenant Improvements will be free from
material defects in workmanship and materials for a period of one (1) year from
the date of Substantial Completion. Therefore, if prior to the expiration of
such warranty period, it is determined that any of the workmanship or material
used in the Tenant Improvements is defective (and such defect was not caused by
the act or omission of Tenant, Tenant's Consultant or their respective
employees), and Tenant shall, prior to the expiration of such warranty period,
so notify Landlord in writing that such workmanship or material is defective,
Landlord shall cause such defective workmanship or material to be appropriately
corrected, repaired or replaced without cost or expense to Tenant. Such
correction, repair or replacement shall be performed as promptly as practical
and in such manner so as to minimize interference with Tenant's operation in or
about the Leased Space. If a dispute arises concerning Landlord's obligations
under this Section, such dispute shall be submitted to dispute resolution
applicable under this Work Letter. Landlord and Tenant acknowledge that Tenant's
sole and exclusive remedy hereunder shall be limited to the correction of the
defect in accordance with the approved Base Building Plans and TI Plans (as
modified by approved Change Orders), and that, upon Landlord's failure to
correct any such defect, Tenant shall have the right to specific performance or
Tenant may elect to correct the defect, subject to Tenant's rights and
limitations under Section 42 of the Lease; provided, however, that Landlord's
liability with respect thereto shall not be limited as provided in Section 28 of
the Lease. Landlord makes no express or implied warranties to Tenant with
respect to the construction of the Landlord's Work, other than as expressly
stated in the Lease and this Work Letter.

                                      -8-
<PAGE>
 
          7.  Tenant Installations.
              -------------------- 

              a.  As set forth in Section 3 above, Landlord, at its expense,
shall cause the Tenant's Lab Equipment to be installed in the Leased Premises
and shall use reasonable efforts to cause the Tenant's Lab Equipment to be among
the last components of the Tenant Improvements to be completed at the Leased
Premises. Tenant, at its expense, shall be responsible for the removal of the
Tenant's Lab Equipment from its present location and the delivery of same to
Landlord at the Leased Premises. Landlord shall provide Tenant with at least
fourteen (14) days written notice prior to the anticipated date that the
Tenant's Lab Equipment must be available to Landlord at the Leased Premises.
Notwithstanding any provision hereof to the contrary, title to the Tenant's Lab
Equipment shall remain in Tenant during the term of the Lease and the Tenant's
Lab Equipment shall be considered as part of Tenant's trade fixtures, except
that Tenant shall have no obligation to remove the Tenant's Lab Equipment (or
any other component of the Tenant Improvements) upon termination of the Lease.

              b.  Trade fixtures, furniture installation, telephone
installation, data transmission equipment installation and security systems
wiring and installation which are not installed as part of the Tenant
Improvements ("Tenant Work"), if any, not initially or thereafter included in
the Tenant Improvements, shall be performed by Tenant, at Tenant's expense,
through contractors selected by Tenant and approved by Landlord, such approval
not to be unreasonably withheld, conditioned or delayed. Landlord shall allow
Tenant reasonable access to the Leased Space for the purpose of performing
Tenant Work, and Landlord and Tenant shall each cause their contractors and/or
subcontractors for the Tenant Improvements and the Tenant Work to cooperate with
each other in facilitating the mutual access to the Leased Space; and in
coordinating the timing of the stages of the construction of the Tenant
Improvements and the Tenant Work so as to facilitate the completion of both on a
timely basis.

              c.  Tenant's contractors shall not delay the construction of the
Tenant Improvements. During the Tenant Work, Tenant and its contractors shall be
responsible for providing adequate protection for Tenant's trade fixtures,
equipment and other property in the Premises from the Landlord's Work, inclement
weather and the elements in general.

              d.  If otherwise available, taking into consideration the stage of
construction, Landlord shall cause General Contractor to furnish Tenant with
adequate water, electricity and HVAC to the Leased Space during the performance
of any Tenant Work upon request of Tenant and at a cost to Tenant equal to the
actual cost therefor, without markup.

          8.  Tenant Delay.
              ------------ 

              a.  If a delay shall occur in achieving Substantial Completion as
the result of (i) any direction by Tenant or Tenant's Consultant that the
General Contractor delay proceeding with the Tenant Improvements or any segment
of the Tenant Improvements in anticipation of a possible revision to the TI
Plans desired by Tenant or for any reason other than a dispute about proper
compliance with the Base Building Plans or TI Plans, (ii) any revision to the

                                      -9-
<PAGE>
 
final TI Plans (except as otherwise provided by Section 3(b)(2) hereof)
authorized by Tenant or Tenant's Consultant, (iii) any interference in the
construction of the Base Building Improvements or the Tenant Improvements caused
by Tenant, Tenant's Consultant or their respective employees, agents or
subcontractors; or (iv) any other act or omission of Tenant, Tenant's
Consultant, or their respective employees, agents or subcontractors (any of such
events being a "Tenant Delay"), then Tenant shall be obligated to commence
payment of rent on the date that the Commencement Date would otherwise have
occurred if there had not been a Tenant Delay (even though the Tenant
Improvements have not been Substantially Completed). Notwithstanding the
foregoing, (i) a Tenant Delay will not be deemed to have occurred unless
Landlord has notified Tenant of the nature thereof within ten (10) days of the
occurrence thereof, and (ii) the commencement of Tenant's rent obligations
required pursuant to the preceding sentence shall been deemed to have occurred
if the aggregate number of days of Tenant Delay is fifteen (15) days or less. A
Tenant Delay shall not be deemed to include any period of delay as the result of
Force Majeure in accordance with Section 26 of the Lease or the act or omission
of Landlord or the General Contractor, or their agents, employees, contractors
or subcontractors; except that an event which otherwise would be a Tenant Delay
if not caused by Force Majeure shall, notwithstanding anything above to the
contrary, extend the Target Date as provided by Section 2 of the Lease. Landlord
and Tenant shall take all commercially reasonable actions required to mitigate
the length of any Tenant Delay.

              b.  The extent of any Tenant Delay shall be determined in the
following manner:  Landlord shall notify Tenant in writing that a Tenant Delay
is pending or has occurred and the estimated length of the Tenant Delay involved
as soon as practicable after the information necessary to estimate such Tenant
Delay is available (which notice shall include the basis for the Landlord's
estimate) and, as Landlord obtains the information to calculate the actual
Tenant Delay, Landlord shall so notify Tenant, providing it with the basis used
in calculating such Tenant Delay.  In the event of a dispute concerning the
length of any Tenant Delay, the dispute shall be submitted to dispute resolution
applicable under this Work Letter.

          9.  Dispute Resolution Procedure.   Any dispute which arises in
              ----------------------------                               
connection with the performance of the Landlord's Work, and which is not
resolved between Landlord and Tenant within five (5) business days from the date
Landlord and Tenant recognize that a dispute exists, shall be determined by an
independent mediator ("Mediator") who is selected by Tenant's Consultant and the
architect hired by Landlord to design the Base Building Improvements. If such
Mediator is not selected within two (2) business days of the expiration of the
foregoing five (5) day period, then either Landlord or Tenant may apply to the
local chapter of the American Institute of Architects (or the Philadelphia
chapter if no local chapter is considered to encompass Uwchlan Township) for
appointment of the Mediator by such agency. Any party selected or appointed to
serve as Mediator shall have at least ten (10) years of construction or design
experience and the decision of such Mediator shall be final and binding on
Landlord and Tenant and enforced by any court of competent jurisdiction.
Landlord and Tenant shall each pay one-half of the fee of the Mediator.
Notwithstanding the foregoing, the determination of the Mediator shall not be
final and binding on the issue of which party is responsible to pay any costs in
connection with alleged non-performance of Landlord's Work or its conformity to
the TI Plans;

                                     -10-
<PAGE>
 
except as permitted below, Landlord and Tenant shall comply with any directives
of the Mediator in connection with any work to be performed or correction to any
work determined by the Mediator to be defective, but the foregoing shall be
without prejudice to either party's right to recover from the other, the cost of
such additional work which is adjudicated to have not been within the scope of
Landlord's Work. If, however, Tenant disagrees with Mediator's determination and
agrees to pay the additional costs to have the Landlord's Work performed in
accordance with Tenant's directions, then, upon Tenant payment of such
additional amounts in the same manner as a Change Order, Landlord shall cause
Landlord's Work to be performed in accordance with Tenant's directions, but the
foregoing shall be without prejudice to Tenant's right to recover from Landlord
the cost of such additional work if so adjudicated by a court of competent
jurisdiction.

          10. Builder's Risk Insurance.  At all times during the construction
              ------------------------                                       
of the Landlord's Work, Landlord agrees to maintain, either directly or through
its General Contractor, builder's risk insurance coverage for the full
replacement cost of the Landlord's Work, and otherwise in accordance with the
requirements identified on the Certificate of Insurance attached hereto as
Schedule 7, and workers compensation insurance as required by applicable laws.
- ----------                                                                    
Upon request from Tenant or Tenant's Consultant, from time to time, Landlord
shall deliver evidence satisfactory to Tenant that such insurance coverage is in
place.

          11. Notices.  All notices or communications hereunder shall be given
              -------                                                         
in accordance with Section 33 of the Lease.  Initial addresses for notice to
Tenant's Consultant and General Contractor are as follows:

              Tenant's Consultant:    OMNI Technologies, Inc.
                                      P.O. Box 871
                                      Lansdale, PA 19446
                                      Attn:  Vito Fabiano

              General Contractor:     Eagleview Commercial Construction 
                                      Company, Inc.
                                      P.O. Box 562
                                      717 Constitution Drive
                                      Eagleview Corporate Center
                                      Exton, PA  19341

          12. Schedules.  The following Schedules attached to this Work Letter
              ---------                                                       
are incorporated by reference and made a part hereof:

          Schedule 1 -  Description of Building Plans and Specifications
          Schedule 2 -  Description of Tenant Space
          Schedule 3 -  Description of TI Plans
          Schedule 4 -  Description of Tenant's Lab Equipment
          Schedule 5 -  Escrow Agreement

                                     -11-
<PAGE>
 
          Schedule 6 -  Construction Schedule
          Schedule 7 -  Certificate of Insurance evidencing Builder's Risk 
                        Coverage

     IN WITNESS WHEREOF, the parties execute this Work Letter, intending to be
legally bound hereby.

                                       LANDLORD:

                                       THE HANKIN GROUP


                                       By: /s/ Robert S. Hankin
                                          ----------------------------------
                                          Robert S. Hankin, General Partner
 
                                       TENANT:

                                       VIROPHARMA INCORPORATED


                                       By: /s/ Thomas F. Doyle
                                          ----------------------------------
                                          Thomas F. Doyle, Executive Director,
                                          Counsel and Secretary


                                     -12-

<PAGE>
 
                        Consent of Independent Auditors
                        -------------------------------

                                                                    Exhibit 23.1

The Board of Directors
ViroPharma Incorporated:


        We consent to the use of our report included herein and to the
references to our firm under the headings "Selected Financial Data" and
"Experts" in the prospectus.




Philadelphia, PA                       /s/ KPMG Peat Marwick LLP
July 22, 1997



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