IGEN INTERNATIONAL INC /DE
SC 13D/A, 1997-12-29
PATENT OWNERS & LESSORS
Previous: PROTECTION ONE INC, 11-K, 1997-12-29
Next: GLENGATE APPAREL INC, 10KSB, 1997-12-29



                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 1)*

                            IGEN INTERNATIONAL, INC.



                                (Name of Issuer)

                         Common Stock, $0.001 par Value



                         (Title of Class of Securities)

                                    449536101
                                 (CUSIP Number)

                              Stephen M. Vine, Esq.
                    Akin, Gump, Strauss, Hauer & Feld, L.L.P.
                               590 Madison Avenue
                            New York, New York 10022
                                 (212) 872-1000



                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                December 19, 1997
                      (Date of Event which Requires Filing
                               of this Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  which is the subject of this  Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [_].

Note: Six copies of this statement, including all exhibits, should be filed with
the  Commission.  See Rule 13d- 1(a) for other  parties to whom copies are to be
sent.

*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter disclosure
provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).

                         Continued on following page(s)
                               Page 1 of 50 Pages
                             Exhibit Index: Page 13




<PAGE>


                                                              Page 2 of 50 Pages


                                  SCHEDULE 13D

CUSIP No. 449536101

1        Name of Reporting Person
         I.R.S. Identification No. of Above Persons (ENTITIES ONLY)

                  White Rock Capital, Inc.

2        Check the Appropriate Box If a Member of a Group*
                                                     a.  [_]
                                                     b.  [x]
3        SEC Use Only

4        Source of Funds*

                  AF

5        Check Box If Disclosure of Legal  Proceedings  Is Required  Pursuant to
         Items 2(d) or 2(e) [_]

6        Citizenship or Place of Organization

                  Texas

                           7        Sole Voting Power
 Number of                                  0
   Shares
Beneficially               8        Shared Voting Power
  Owned By                                  794,500
    Each
  Reporting                9        Sole Dispositive Power
   Person                                   0
    With
                           10       Shared Dispositive Power
                                            794,500

11       Aggregate Amount Beneficially Owned by Each Reporting Person

                                            794,500

12       Check Box If the Aggregate Amount in Row (11) Excludes Certain
         Shares*                                              [x]

13       Percent of Class Represented By Amount in Row (11)

                                    5.24%

14       Type of Reporting Person*

                  CO; IA

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>


                                                              Page 3 of 50 Pages


                                  SCHEDULE 13D

CUSIP No. 449536101

1        Name of Reporting Person
         I.R.S. Identification No. of Above Persons (ENTITIES ONLY)

                  White Rock Capital Management, L.P.

2        Check the Appropriate Box If a Member of a Group*
                                                     a.  [_]
                                                     b.  [x]
3        SEC Use Only

4        Source of Funds*

                  AF

5        Check Box If Disclosure of Legal  Proceedings  Is Required  Pursuant to
         Items 2(d) or 2(e) [_]

6        Citizenship or Place of Organization

                  Texas

                           7        Sole Voting Power
 Number of                                  0
   Shares
Beneficially               8        Shared Voting Power
  Owned By                                  794,500
    Each
  Reporting                9        Sole Dispositive Power
   Person                                   0
    With
                           10       Shared Dispositive Power
                                            794,500

11       Aggregate Amount Beneficially Owned by Each Reporting Person

                                            794,500

12       Check Box If the Aggregate Amount in Row (11) Excludes Certain
         Shares*                                              [x]

13       Percent of Class Represented By Amount in Row (11)

                                    5.24%

14       Type of Reporting Person*

                  PN; IA

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>


                                                              Page 4 of 50 Pages


                                  SCHEDULE 13D

CUSIP No. 449536101

1        Name of Reporting Person
         I.R.S. Identification No. of Above Persons (ENTITIES ONLY)

                  White Rock Capital Partners, L.P.

2        Check the Appropriate Box If a Member of a Group*
                                                     a.  [_]
                                                     b.  [x]

3        SEC Use Only

4        Source of Funds*

                  WC

5        Check Box If Disclosure of Legal  Proceedings  Is Required  Pursuant to
         Items 2(d) or 2(e) [_]

6        Citizenship or Place of Organization

                  Texas

                           7        Sole Voting Power
 Number of                                  90,500
   Shares
Beneficially               8        Shared Voting Power
  Owned By                                  0
    Each
  Reporting                9        Sole Dispositive Power
   Person                                   90,500
    With
                           10       Shared Dispositive Power
                                            0

11       Aggregate Amount Beneficially Owned by Each Reporting Person

                                            90,500

12       Check Box If the Aggregate Amount in Row (11) Excludes Certain
         Shares*                                              [x]

13       Percent of Class Represented By Amount in Row (11)

                                    .60%

14       Type of Reporting Person*

                  PN; IV

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>


                                                              Page 5 of 50 Pages


                                  SCHEDULE 13D

CUSIP No. 449536101

1        Name of Reporting Person
         I.R.S. Identification No. of Above Persons (ENTITIES ONLY)

                  Thomas U. Barton

2        Check the Appropriate Box If a Member of a Group*
                                                     a.  [_]
                                                     b.  [x]
3        SEC Use Only

4        Source of Funds*

                  AF

5        Check Box If Disclosure of Legal  Proceedings  Is Required  Pursuant to
         Items 2(d) or 2(e) [_]

6        Citizenship or Place of Organization

                  United States

                           7        Sole Voting Power
 Number of                                  0
   Shares
Beneficially               8        Shared Voting Power
  Owned By                                  794,500
    Each
  Reporting                9        Sole Dispositive Power
   Person                                   0
    With
                           10       Shared Dispositive Power
                                            794,500

11       Aggregate Amount Beneficially Owned by Each Reporting Person

                                            794,500

12       Check Box If the Aggregate Amount in Row (11) Excludes Certain
         Shares*                                              [x]

13       Percent of Class Represented By Amount in Row (11)

                                            5.24%

14       Type of Reporting Person*

                  IN; IA

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>


                                                              Page 6 of 50 Pages


                                  SCHEDULE 13D

CUSIP No. 449536101

1        Name of Reporting Person
         I.R.S. Identification No. of Above Persons (ENTITIES ONLY)

                  Joseph U. Barton

2        Check the Appropriate Box If a Member of a Group*
                                                     a.  [_]
                                                     b.  [x]

3        SEC Use Only

4        Source of Funds*

                  AF

5        Check Box If Disclosure of Legal  Proceedings  Is Required  Pursuant to
         Items 2(d) or 2(e) [ ]

6        Citizenship or Place of Organization

                  United States

                           7        Sole Voting Power
 Number of                                  5,000
   Shares
Beneficially               8        Shared Voting Power
  Owned By                                  794,500
    Each
  Reporting                9        Sole Dispositive Power
   Person                                   5,000
    With
                           10       Shared Dispositive Power
                                            794,500

11       Aggregate Amount Beneficially Owned by Each Reporting Person

                                            799,500

12       Check Box If the Aggregate Amount in Row (11) Excludes Certain
         Shares*                                              [_]

13       Percent of Class Represented By Amount in Row (11)

                                    5.28%

14       Type of Reporting Person*

                  IN; IA

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>


                                                              Page 7 of 50 Pages


               This  Amendment No. 1 to Schedule 13D relates to shares of Common
Stock, $0.001 par value per share (the "Shares"),  of IGEN  International,  Inc.
(the "Issuer"). This Amendment No. 1 supplementally amends the initial statement
on Schedule  13D dated  December  11,  1997,  filed by certain of the  Reporting
Persons (as defined herein) (the "Initial  Statement").  This Amendment No. 1 is
being filed by the  Reporting  Persons to report that  certain of the  Reporting
Persons  have  purchased  Series B Stock (as  defined  herein)  from the Issuer.
Capitalized  terms used herein but not defined  herein  shall have the  meanings
ascribed  to  them  in  the  Initial   Statement.   The  Initial   Statement  is
supplementally amended as follows.


Item 2.        Identity and Background.

               This Statement is filed on behalf of White Rock Capital,  Inc., a
Texas corporation ("White Rock, Inc."),  White Rock Capital Management,  L.P., a
Texas  limited  partnership  ("White  Rock  Management"),   White  Rock  Capital
Partners,  L.P., a Texas limited partnership ("White Rock Partners"),  Thomas U.
Barton and Joseph U. Barton (collectively, the "Reporting Persons").

               This  Statement on Schedule 13D relates to  securities  that were
acquired by White Rock  Management  on behalf of certain  institutional  clients
(the "White Rock  Clients").  This Statement also relates to securities held for
the accounts of White Rock Partners and Joseph U. Barton.

               The general  partner of White Rock Partners is White Rock Capital
Management,  the general partner of which is White Rock, Inc. Each of White Rock
(as defined herein), White Rock Partners,  White Rock Management and White Rock,
Inc. is engaged in the investment and investment management business.  Thomas U.
Barton and Joseph U. Barton,  both of whom are United States  citizens,  are the
shareholders of White Rock,  Inc. The principal  occupation of each of Thomas U.
Barton and Joseph U. Barton is their  position as the general  partners of White
Rock Capital,  L.P., a Texas limited  partnership ("White Rock") at White Rock's
principal  office.  The principal  business address of each of White Rock, White
Rock Partners,  White Rock Management,  White Rock,  Inc.,  Thomas U. Barton and
Joseph U. Barton is 3131 Turtle Creek Boulevard, Suite 800, Dallas, Texas 75219.

               During the past five years, none of the Reporting  Persons,  and,
to the best of the Reporting Persons' knowledge,  any other person identified in
response to this Item 2 has been (a) convicted in a criminal proceeding,  or (b)
a party to any civil  proceeding  as a result of which he has been  subject to a
judgment,  decree or final order enjoining future  violations of, or prohibiting
or mandating activities subject to, federal or state securities laws, or finding
any violation with respect to such laws.

Item 3.        Source and Amount of Funds or Other Consideration.

               On December  16, 1997 certain of the White Rock Clients and White
Rock Partners  entered into a Purchase  Agreement with the Issuer (the "Purchase
Agreement"),  a form of which is attached  hereto as Exhibit B and  incorporated
herein by  reference.  Pursuant  to the  terms of the  Purchase  Agreement:  (i)
approximately  $3,500,000  of the working  capital of the White Rock Clients was
expended to purchase 3,500 shares of the Issuer's Series B Convertible Preferred
Stock (the "Series B Stock"),  which are the only  securities of the Issuer that
have been  purchased for the accounts of the White Rock Clients  since  December
11, 1997 (the date of filing of the last  statement  on  Schedule  13D) and (ii)
White Rock Partners expended approximately  $1,000,000 of its working capital to
purchase  1,000 shares of Series B Stock,  which are the only  securities of the



<PAGE>


                                                              Page 8 of 50 Pages

Issuer that have been  purchased  for its account  since  December 11, 1997 (the
date of filing of the last statement on Schedule 13D).

               The  Certificate  of  Designation  of the  Series  B  Stock  (the
"Certificate of Designation") provides that the holders of Series B Stock shall,
subject to  certain  restrictions,  have the right to convert  such stock at any
time and from time to time on or after  March [16] or [19],  1998 (the  "Initial
Conversion  Date")  into  fully  paid  non-assessable  Shares  (the  "Conversion
Shares").  The Certificate of Designation provides that the number of Conversion
Shares to be delivered by the Issuer shall equal: the stated value of the Series
B Stock being converted  ($1,000  multiplied by the number of shares of Series B
Stock  being  converted)  divided  by the  Conversion  Price (as  defined in the
Certificate  of  Designation)  in effect on the date the  holder of the Series B
Stock wishes to convert  such stock.  The  Certificate  of  Designation  further
provides for  optional  and  mandatory  redemption  by the Issuer under  certain
circumstances.

               Thomas U.  Barton  expended  approximately  $348 of his  personal
funds to purchase  options which have been acquired since December 11, 1997 (the
date of filing of the last  statement  on  Schedule  13D),  and which have since
expired.  White Rock Management  expended  approximately  $59,063 of the working
capital of the White Rock  Clients to  purchase  the Shares  reported  herein as
being acquired since December 11, 1997 (the date of filing of the last statement
on Schedule 13D).

               The  Shares  (and  securities  derivative  thereof)  held for the
accounts of the White Rock Clients, White Rock Partners and Joseph U. Barton may
be held through margin  accounts  maintained  with brokers,  which extend margin
credit as and when required to open or carry positions in their margin accounts,
subject to applicable federal margin regulations,  stock exchange rules and such
firm's credit policies.  The Shares which may be held in the margin accounts are
pledged as  collateral  security  for the  repayment  of debit  balances  in the
respective accounts.

Item 5.        Interest in Securities of the Issuer.

               (a)  (i) Each of White Rock  Management,  White  Rock,  Inc.  and
Thomas  U.  Barton  may  be  deemed  the  beneficial  owner  of  794,500  Shares
(approximately  5.24% of the total  number of Shares  outstanding).  This number
consists of (1) 704,000  Shares held for the  accounts of the White Rock Clients
and (2) 90,500 Shares held for the account of White Rock Partners.

                    (ii) Joseph U. Barton may be deemed the beneficial  owner of
799,500 Shares  (approximately 5.28% of the total number of Shares outstanding).
This number  consists  of (1)  704,000  Shares held for the account of the White
Rock Clients,  (2) 90,500 Shares held for the account of White Rock Partners and
(3) 5,000 Shares held for his account.

                    (iii)White Rock Partners may be deemed the beneficial  owner
of the  90,500  Shares  held for its  account  (approximately  .60% of the total
number of Shares outstanding).

               (b)  (i) Each of White  Rock  Management  (pursuant  to the White
Rock  Contract),  White  Rock,  Inc.  (as the  general  partner  of  White  Rock
Management),  Thomas U. Barton (as a shareholder of White Rock, Inc.) and Joseph
U. Barton (as a shareholder of White Rock, Inc.) is currently vested with shared
power to direct the voting and  disposition  of the 704,000  Shares held for the
accounts of the White Rock Clients.



<PAGE>


                                                              Page 9 of 50 Pages


                    (ii) Each of White Rock  Management (as the general  partner
of White Rock Partners),  White Rock, Inc. (as the general partner of White Rock
Management),  Thomas U. Barton (as a shareholder of White Rock, Inc.) and Joseph
U. Barton (as a  shareholder  of White Rock,  Inc.) may be deemed to have shared
power to direct the voting and  disposition  of the 90,500  Shares  held for the
account of White Rock Partners.

                    (iii)Joseph  U.  Barton  has the sole  power to  direct  the
voting and disposition of the 5,000 Shares held for his account.

                    (iv) White  Rock  Partners  has the sole power to direct the
voting and disposition of the 90,500 Shares held for its account.

               (c)       Except as disclosed in Item 6 and for the  transactions
disclosed on Annex A hereto, all of which were effected in the  over-the-counter
market in routine brokerage  transactions,  there have been no transactions with
respect to the Shares  since  December  11, 1997 (the date of filing of the last
statement  on Schedule  13D) by any of the  Reporting  Persons or the White Rock
Clients.

               (d)  (i) The  shareholders  or partners of each of the White Rock
Clients  have the right to  participate  in the receipt of  dividends  from,  or
proceeds from the sale of, the Shares,  held by the respective White Rock Client
in accordance  with their  partnership or ownership  interests in the respective
White Rock Client.

                    (ii) Joseph U. Barton has the sole right to  participate  in
the receipt of dividends from, or proceeds from the sale of, the Shares held for
his account.

                    (iii)The partners of White Rock  Partners  have the right to
participate in the receipt of dividends  from, or proceeds from the sale of, the
Shares  held by  White  Rock  Partners  in  accordance  with  their  partnership
interests in White Rock Partners.

               (e)       Not applicable.



<PAGE>


                                                             Page 10 of 50 Pages


Item 6.        Contracts,  Arrangements,  Understandings  in  Relationship  with
               Respect to Securities of the Issuer.

               The  Purchase   Agreement  and  Certificate  of  Designation  are
described  in Item 3 hereto  and  such  disclosure  is  incorporated  herein  by
reference; however, such disclosure is qualified in its entirety by reference to
the specific  provisions of such  agreements,  which provisions are incorporated
herein by reference.

               The Registration Rights Agreement entered into in connection with
the acquisition of the Series B Stock (the "Registration  Rights Agreement"),  a
form of which is  attached  hereto  as  Exhibit  C and  incorporated  herein  by
reference,  obligates the Issuer to have the Shares  underlying  such securities
registered  within a certain period of time. The  Registration  Rights Agreement
provides  that the  Issuer  shall,  on or  before  the  forty-fifth  (45th)  day
following Closing (as defined in the Purchase Agreement),  prepare and file with
the Securities and Exchange Commission a Registration Statement on Form S-3 as a
"shelf"  registration  statement  under Rule 415 covering the resale of at least
200% of the  number of shares  of  Registrable  Securities  (as  defined  in the
Registration  Rights  Agreement)  then  issuable  upon  conversion of all of the
Series B Shares issued at the Closing.

               The Registration  Rights Agreement grants to the holder of Series
B Stock  certain  "piggy-back"  registration  rights,  and  contains  provisions
relating to registration  procedures,  indemnification  and other  miscellaneous
matters, all of which are incorporated herein by reference.

               From time to time, each of the Reporting Persons and/or the White
Rock Clients may lend portfolio securities to brokers,  banks or other financial
institutions.  These  loans  typically  obligate  the  borrower  to  return  the
securities,  or an equal amount of securities  of the same class,  to the lender
and  typically  provide that the borrower is entitled to exercise  voting rights
and to retain  dividends  during the term of the loan.  From time to time to the
extent permitted by applicable laws, each of such persons or entities may borrow
the  Shares  for  the  purpose  of  effecting,   and  may  effect,   short  sale
transactions,  and may purchase  securities for the purpose of closing out short
positions in such securities.

               Except as set forth  herein,  the  Reporting  Persons  and/or the
White Rock Clients do not have any contracts,  arrangements,  understandings  or
relationships with respect to any securities of the Issuer.


Item 7.        Material to be Filed as Exhibits.

          A.   Joint Filing Agreement dated December 11, 1997 by and among White
               Rock Partners, White Rock Management, White Rock, Inc., Thomas U.
               Barton and Joseph U.  Barton  (filed as Exhibit A to the  Initial
               Statement and incorporated herein by reference).

          B.   Form of Purchase Agreement dated as of December 16, 1997.

          C.   Form of  Registration  Rights  Agreement dated as of December 16,
               1997.



<PAGE>


                                                             Page 11 of 50 Pages


                                   SIGNATURES

          After  reasonable  inquiry and to the best of my knowledge and belief,
the  undersigned  certifies that the  information set forth in this statement is
true, complete and correct.

Date:  December __, 1997           WHITE ROCK CAPITAL PARTNERS, L.P.

                                   By:  White Rock Capital Management, L.P.
                                        Its General Partner

                                        By:  White Rock Capital, Inc.
                                             Its General Partner

                                             By:  /S/ THOMAS U. BARTON
                                                  -----------------------------
                                                  Thomas U. Barton
                                                  President


                                   WHITE ROCK CAPITAL MANAGEMENT. L.P.

                                   By:  White Rock Capital Inc.
                                        Its General Partner

                                        By:  /S/ THOMAS U. BARTON
                                             ----------------------------------
                                             Thomas U. Barton
                                             President


                                   WHITE ROCK CAPITAL, INC.

                                   By:  /S/ THOMAS U. BARTON
                                        ---------------------------------------
                                        Thomas U. Barton
                                        President


                                   /S/ THOMAS U. BARTON
                                   --------------------------------------------
                                   Thomas U. Barton



                                   /S/ JOSEPH U. BARTON
                                   --------------------------------------------
                                   Joseph U. Barton


<PAGE>
<TABLE>
<CAPTION>


                                                                                                     Page 12 of 50 Pages


                                                         ANNEX A

                                       RECENT TRANSACTIONS IN THE COMMON STOCK OF
                                                IGEN INTERNATIONAL, INC.

                                                                                  Number of
                                                                                   Shares/
                                       Date of              Nature of              Option               Price Per
For the Account of                   Transaction           Transaction            Contracts            Share/Option
- ------------------                   -----------           -----------            ---------            ------------
<S>                                 <C>                   <C>                    <C>                  <C>
White Rock Clients/1/                 12/15/97                 BUY                  4,500                 13.125

Tom Barton                            12/20/97                 BUY                   10                   34.75
                                                                                                      (call options)

































/1/      Transactions effected at the direction of White Rock Management.

</TABLE>
<PAGE>


                                                             Page 13 of 50 Pages



                                  EXHIBIT INDEX

                                                                        Page No.
                                                                        --------

B.        Form of Purchase  Agreement  dated as of  December  16,
          1997....................................................        14

C.        Form  of  Registration  Rights  Agreement  dated  as of
          December 16, 1997.......................................        41





                                                             Page 14 of 50 Pages


                                    EXHIBIT B

                               PURCHASE AGREEMENT



PURCHASE  AGREEMENT  (this  "Agreement"),  dated as of December 16, 1997, by and
                             --------- 
among IGEN International,  Inc., a Delaware corporation (the "Company"), and the
                                                              -------
entities  whose names appear on the signature  pages  hereof.  Such entities are
each referred to herein as a "Purchaser" and, collectively, as the "Purchasers".
                              ---------                             ----------  


          The Company wishes to sell and each Purchaser  wishes to buy,  subject
to the terms and conditions set forth in this Agreement,  shares (the "Preferred
                                                                       ---------
Shares") of the Company's  Series B Convertible  Preferred Stock (the "Preferred
- ------                                                                 ---------
Stock"), in reliance on the exemption from securities  registration  afforded by
- -----
the provisions of Regulation D under the Securities Act of 1933, as amended (the
"Securities Act").
 --------------

          The  Preferred  Shares  are  convertible  pursuant  to the  terms of a
Certificate of Designation relating to the Preferred Stock, the form of which is
attached hereto as Exhibit A (the  "Certificate"),  into shares of the Company's
                   ---------        ----------- 
Common Stock,  $.001 par value (the "Common  Stock").  The term (i)  "Conversion
                                     -------------                    ----------
Shares" shall mean,  at any time,  the shares of Common Stock that are issued or
- ------
issuable upon conversion of the Preferred Shares, (ii) "Dividend Payment Shares"
                                                        -----------------------
shall  mean the  shares of Common  Stock  issued by the  Company  in  payment of
dividends  on  the  Preferred  Shares  in  accordance  with  the  terms  of  the
Certificate  and  (iii)  "Securities"  shall  mean  the  Preferred  Shares,  the
                          ----------    
Conversion Shares and the Dividend Payment Shares.

          The parties hereto agree as follows:

1.        PURCHASE AND SALE OF PREFERRED STOCK.
          ------------------------------------

          1.1       Agreement to Purchase  and Sell.  Upon the terms and subject
                    -------------------------------
to the  conditions  set forth herein,  the Company agrees to sell at the Closing
(as  defined  below),  and each  Purchaser  agrees to  purchase,  the  number of
Preferred  Shares  set  forth on the  signature  page  hereof  executed  by such
Purchaser,  at a purchase price equal to one thousand dollars ($1,000) times the
number of Preferred Shares purchased by such Purchaser (the "Purchase Price").
                                                             --------------    
                                     
          1.2       Closing.  Subject to the  satisfaction of the conditions set
                    -------
forth herein,  the closing of the purchase and sale of the Preferred Shares (the
"Closing")  will  be  deemed  to  occur  when  this  Agreement,  and  the  other
 -------
Transaction  Documents (as defined  below),  have been executed and delivered by
the Company and each  Purchaser,  and full payment of the amount of the Purchase
Price payable by each Purchaser has been made by such Purchaser by wire transfer
of same day funds to an account  designated by the Company  against  delivery by
the Company of duly executed  certificates  representing  the  Preferred  Shares
purchased by such Purchaser  hereunder.  The date on which the Closing is deemed
to occur is referred to herein as the "Closing Date".
                                       ------------ 

          1.3       Certain  Definitions.  When used herein,  (A) "business day"
                    --------------------
shall mean any day on which the New York Stock Exchange and commercial  banks in
the city of New York are open for  business  and (B) an  "affiliate"  of a party
shall  mean any  person or entity  controlling,  controlled  by or under  common
control with that party.



<PAGE>


                                                             Page 15 of 50 Pages


2.        REPRESENTATIONS AND WARRANTIES OF THE PURCHASER.
          -----------------------------------------------

          Each Purchaser,  solely with respect to it, hereby makes the following
representations  and  warranties  to the Company  (which shall be true as of the
date hereof and as of the Closing Date) and agrees with the Company that:

          2.1       Authorization;   Enforceability.   Such  Purchaser  is  duly
                    -------------------------------
organized,  validly  existing  and  in  good  standing  under  the  laws  of the
jurisdiction of its  organization  with full power and authority to purchase the
Preferred  Shares and to execute and deliver this Agreement.  Such Purchaser has
taken all  action  necessary  for the  authorization,  execution,  delivery  and
performance of this Agreement and the other Transaction Documents to which it is
a party, and its obligations  hereunder and thereunder,  and, upon execution and
delivery  thereof  by the  Company,  this  Agreement  and the other  Transaction
Documents to which it is a party constitute such  Purchaser's  valid and legally
binding  obligations,  enforceable in accordance  with their  respective  terms,
except  as  such  enforcement  may  be  limited  by (i)  applicable  bankruptcy,
insolvency,  reorganization or other laws of general application  relating to or
affecting  the  enforcement  of  creditors'  rights  generally  and (ii) general
principles of equity.

          2.2       Accredited Investor; Investment Intent. Such Purchaser is an
                    --------------------------------------
accredited investor, as defined in Rule 501 of Regulation D under the Securities
Act. Such Purchaser is acquiring the Preferred Shares solely for its own account
for investment  purposes as a principal and not with a view to the public resale
or  distribution  of all or any part thereof;  provided,  however that in making
such  representation,  such  Purchaser does not agree to hold the Securities for
any  minimum  or  specific  term and  reserves  the right to sell,  transfer  or
otherwise  dispose  of the  Securities  at  any  time  in  accordance  with  the
provisions  of this  Agreement  and  with  Federal  and  state  securities  laws
applicable to such sale, transfer or disposition.

          2.3       Information.  The Company has provided such  Purchaser  with
                    -----------
certain  written  information  regarding  the  Company  and has  granted to such
Purchaser  the  opportunity  to  ask  questions  of  and  receive  answers  from
representatives of the Company,  its officers,  directors,  employees and agents
concerning  the terms and  conditions  of the purchase and sale of the Preferred
Shares hereunder, and the Company and its business and prospects.

          2.4       Limitations on Disposition. Such Purchaser acknowledges that
                    --------------------------
the Preferred  Shares are "restricted  securities"  under the Securities Act and
that under the Securities Act and applicable  rules and regulations  neither the
Preferred  Shares nor any  interest  therein  may be offered  for sale or resold
absent  registration under the Securities Act or unless pursuant to an exemption
therefrom.

         2.5        Legend. Such Purchaser understands that the Preferred Shares
                    ------
shall bear at issuance the following legend:

          "The security  represented by this certificate has not been registered
          under the Securities Act of 1933, as amended (the  "Securities  Act"),
                                                              ---------------   
          or the  securities  laws of any state,  and may not be offered or sold
          unless  a  registration   statement   under  the  Securities  Act  and
          applicable  state  securities  laws shall have become  effective  with
          regard thereto, or an exemption from registration under the Securities
          Act and applicable  state  securities  laws is available in connection
          with  such  offer or sale.  Such  security  is issued  subject  to the
          provisions of (i) a Purchase Agreement, dated December __,1997, by and


                                       -2

<PAGE>


                                                             Page 16 of 50 Pages


          among IGEN  International,  Inc. (the  "Company")  and the  purchasers
          named  therein,  and  (ii)  a  Registration  Rights  Agreement,  dated
          December __, 1997, by and among the Company and such purchasers."

          Notwithstanding  the foregoing,  it is agreed that, as long as (A) the
resale or transfer  (including  without  limitation a pledge) of any Security is
registered  pursuant  to an  effective  registration  statement,  (B) the holder
thereof provides the Company with an opinion of counsel, in form,  substance and
scope customary for opinions of counsel in comparable  transactions (the cost of
which  shall be borne by such  holder) to the effect that such  Security  can be
sold publicly without  registration  under the Securities Act, (C) such Security
can be sold  pursuant to Rule 144 under the  Securities  Act ("Rule  144") and a
                                                               ---------  
registered  broker dealer provides to the Company a customary  broker's Rule 144
letter  and  such  holder   delivers   to  the  Company  a  customary   seller's
representation  letter,  or (D) such  Security is eligible for resale under Rule
144(k),  such Security shall be issued  without any legend or other  restrictive
language  and,  with respect to any Security  upon which such legend is stamped,
the  Company  shall  issue new  certificates  without  such legend to the holder
thereof upon request.

          2.6       Fees.   Such   Purchaser   is  not   obligated  to  pay  any
                    ----
compensation  or other fee,  cost or  related  expenditure  to any  underwriter,
broker,  agent or  other  representative  in  connection  with the  transactions
contemplated hereby.

3.        REPRESENTATIONS AND WARRANTIES OF THE COMPANY.
          ---------------------------------------------

          The Company hereby makes the following  representations and warranties
to each  Purchaser  (which  shall  be true as of the date  hereof  and as of the
Closing Date) and agrees with such Purchaser that:

          3.1       Organization,  Good Standing and Qualification.  Each of the
                    ----------------------------------------------
Company and its subsidiaries is a corporation  duly organized,  validly existing
and in good standing under the laws of the jurisdiction of its incorporation and
has all requisite  corporate power and authority to carry on its business as now
conducted.  Each of the  Company  and its  subsidiaries  is  duly  qualified  to
transact  business  and is in good  standing in each  jurisdiction  in which the
failure so to qualify would have a material  adverse effect on the  consolidated
business or financial  condition of the Company and its subsidiaries  taken as a
whole. The term  "subsidiaries"  means  corporations in which the Company has an
                  ------------   
equity interest of greater than 50%.

          3.2       Authorization;  Consents.  The  Company  has  the  requisite
                    ------------------------
corporate  power and authority to enter into and perform its  obligations  under
(i) this Agreement,  (ii) the Registration  Rights Agreement and (iii) all other
agreements,  documents,  certificates  or  other  instruments  delivered  by the
Company at the Closing (the  instruments  described in (i), (ii) and (iii) being
collectively referred to herein as the "Transaction Documents"),  to execute and
                                        ---------------------
perform its obligations  under the Certificate,  to issue and sell the Preferred
Shares to such  Purchaser in accordance  with the terms of the  Certificate,  to
issue  the  Conversion  Shares  upon  conversion  of  the  Preferred  Shares  in
accordance  with the terms thereof and to issue the Dividend  Payment  Shares in
accordance with the terms of the  Certificate.  All corporate action on the part
of the Company by its officers, directors and stockholders necessary for (A) the
authorization,  execution and delivery of, and the performance by the Company of
its  obligations  under,  the Transaction  Documents and (B) the  authorization,
execution and filing of, and performance by the Company of its obligations under
the Certificate has been taken,  and no further consent or  authorization of the
Company, its Board of Directors, its stockholders, or any governmental agency or


                                       -3-

<PAGE>


                                                             Page 17 of 50 Pages


organization or any other person or entity is required  (pursuant to any rule of
the National Association of Securities Dealers, Inc. or otherwise).

          3.3       Enforcement.  The Transaction  Documents and the Certificate
                    -----------
constitute valid and legally binding obligations of the Company,  enforceable in
accordance  with  their  respective  terms,  except as such  enforcement  may be
limited by (i) applicable bankruptcy,  insolvency,  reorganization or other laws
of general  application  relating to or affecting the  enforcement of creditors'
rights generally and (ii) general principles of equity.

          3.4       Disclosure    Documents;    Material    Agreements;    Other
                    ------------------------------------------------------------
Information. The Company has filed with the Commission: (i) the Company's Annual
- -----------
Report on Form 10-K for the year ended March 31, 1997, (ii) Quarterly Reports on
Form 10-Q for the quarters ended June 30, 1997 and September 30, 1997, (iii) all
Current Reports on Form 8-K required to be filed with the Commission since March
31, 1997 and (iv) the Company's definitive Proxy Statement for its 199[7] Annual
Meeting of Stockholders (collectively,  the "Disclosure Documents"). The Company
                                             --------------------
is not aware of any event that would  require the filing of, or with  respect to
which the Company intends to file, a Form 8-K after the Closing. Each Disclosure
Document, as of the date of the filing thereof with the Commission, conformed in
all material  respects to the  requirements  of the  Securities  Exchange Act of
1934, as amended (the "Exchange Act"), and the rules and regulations thereunder,
                       ------------
and, as of the date of such filing,  such Disclosure Document did not contain an
untrue  statement of material  fact or omit to state a material fact required to
be stated therein or necessary to make the statements  therein,  in light of the
circumstances  under  which  they  were  made,  not  misleading.   All  material
agreements  required to be filed as exhibits to the  Disclosure  Documents  have
been filed as  required.  To the best of the  Company's  knowledge,  neither the
Company nor any of its subsidiaries is in breach of any agreement to which it is
a party or by which it is bound where such breach is reasonably likely to have a
material adverse effect on the consolidated  business or financial  condition of
the Company and its subsidiaries  taken as a whole. To the best of the Company's
knowledge,  except as set forth in the  Disclosure  Documents or any schedule or
exhibit  attached  hereto,  the  Company  has  no  liabilities,   contingent  or
otherwise,  other than  liabilities  incurred in the ordinary course of business
which, under generally accepted accounting principles, which are not required to
be reflected in the Company's financial statements and which, individually or in
the  aggregate,  are not  material to the  consolidated  business  or  financial
condition of the Company and its  subsidiaries  taken as a whole.  The financial
statements  of the Company  included in the  Disclosure  Documents,  as of their
respective  dates  (A)  complied  as to  form  in  all  material  respects  with
applicable  accounting  requirements  and the published rules and regulations of
the  Commission  with respect  thereto and (B) have been  prepared in accordance
with generally accepted accounting principles  consistently applied at the times
and during the periods  involved  (except (i) as may be  otherwise  indicated in
such financial statements or the notes thereto, or (ii) in the case of unaudited
interim statements, to the extent they may exclude footnotes or may be condensed
or summary statements) and fairly present in all material respects the financial
position  of  the  Company  as of the  dates  thereof  and  the  results  of its
operations  and cash flows for the periods then ended  (subject,  in the case of
unaudited statements,  to normal year-end adjustments).  The written information
provided to the  Purchaser as described in paragraph  2.3 above does not contain
an untrue  statement of material  fact or omit to state a material fact required
to be stated therein or necessary to make the statements therein,in light of the
circumstances  under which they were made,  not  misleading and does not include
any material, non-public information.

          3.5       Capitalization.  The capitalization of the Company as of the
                    --------------
date hereof, including its authorized capital stock, the number of shares issued


                                       -4-

<PAGE>


                                                             Page 18 of 50 Pages


and  outstanding,  the  number of shares  issuable  and  reserved  for  issuance
pursuant to the Company's stock option plans,  the number of shares issuable and
reserved for issuance  pursuant to securities  (other than the Preferred Shares)
exercisable  for, or convertible  into or exchangeable  for any shares of Common
Stock and the  number of shares  initially  to be  reserved  for  issuance  upon
conversion of the Preferred  Shares is set forth on Schedule 3.5 hereto.  All of
                                                    ------------   
such  outstanding  shares of capital  stock have been, or upon issuance will be,
validly issued, fully paid and non-assessable. No shares of the capital stock of
the Company are subject to preemptive  rights or any other similar rights of the
stockholders of the Company or any liens or  encumbrances  created by or through
the Company.  Except as disclosed on Schedule 3.5, or as contemplated herein, as
                                     ------------   
of the date of this  Agreement and as of the Closing,  there are no  outstanding
options,  warrants,  scrip,  rights to subscribe to, calls or commitments of any
character  whatsoever  relating to, or securities or rights  convertible into or
exercisable or  exchangeable  for, any shares of capital stock of the Company or
any of its  subsidiaries,  or  arrangements  by which the  Company or any of its
subsidiaries is or may become bound to issue additional  shares of capital stock
of the Company or any of its subsidiaries.

          3.6       Valid  Issuance.  The Preferred  Shares are duly  authorized
                    ---------------
and, when issued,  sold and delivered in accordance  with the terms hereof,  (i)
will be duly and validly issued, fully paid and nonassessable, free and clear of
any taxes, liens,  claims,  preemptive or similar rights or encumbrances imposed
by or through the Company,  (ii) based in part upon the  representations of such
Purchaser in this  Agreement,  will be issued,  sold and delivered in compliance
with all applicable Federal and state securities laws and (iii) will be entitled
to all of the rights,  preferences and privileges set forth in the  Certificate.
The  Conversion  Shares are duly  authorized and reserved for issuance and, when
issued upon  conversion  of the Preferred  Shares in  accordance  with the terms
thereof, will be duly and validly issued, fully paid and nonassessable, free and
clear of any taxes, liens, claims,  preemptive or similar rights or encumbrances
imposed  by or  through  the  Company.  The  Dividend  Payment  Shares  are duly
authorized  and, upon the issuance  thereof in accordance  with the terms of the
Certificate, will be duly and validly issued, fully paid and nonassessable, free
and  clear  of any  taxes,  liens,  claims,  preemptive  or  similar  rights  or
encumbrances imposed by or through the Company.

          3.7       No Conflict with Other  Instruments.  Except as set forth on
                    -----------------------------------
Schedule 3.7, neither the Company nor any of its subsidiaries is in violation of
- ------------
any  provisions  of its  Certificate  of  Incorporation,  Bylaws  or  any  other
governing  document as amended and in effect on and as of the date hereof or, to
the best of the  Company's  knowledge,  in  default  (and no event has  occurred
which,  with notice or lapse of time or both,  would constitute a default) under
any  provision of any  instrument or contract to which it is a party or by which
it is bound, or of any provision of any Federal or state judgment, writ, decree,
order, statute, rule or governmental regulation applicable to the Company, which
would have a material adverse effect on the  consolidated  business or financial
condition of the Company and its  subsidiaries  taken as a whole. The execution,
delivery and performance of the Transaction Documents,  the execution and filing
of the Certificate, and the consummation of the transactions contemplated hereby
and thereby (including without limitation,  the issuance of the Preferred Shares
and the reservation  for issuance and issuance of the Conversion  Shares and the
Dividend Payment Shares) will not result in any such violation or be in conflict
with or  constitute,  with or without  the passage of time and giving of notice,
either a default  under any such  provision,  instrument or contract or an event
which results in the creation of any lien, charge or encumbrance upon any assets
of the Company or of any of its subsidiaries or the triggering of any preemptive
or anti-dilution rights or rights of first refusal or first offer on the part of
holders of the Company's securities.


                                       -5-

<PAGE>


                                                             Page 19 of 50 Pages


          3.8       Financial Condition; Taxes; Litigation.
                    --------------------------------------

               3.8.1     The Company's  financial  condition is, in all material
respects,  as described in the Disclosure  Documents,  except for changes in the
ordinary course of business and normal year-end adjustments that are not, in the
aggregate, materially adverse to consolidated business or financial condition of
the Company or its subsidiaries taken as a whole.  Except as otherwise described
in the Disclosure Documents,  there have been no material adverse changes to the
Company's business,  operations,  properties,  financial condition, prospects or
results  of  operations  since the date of the  Company's  most  recent  audited
financial statements contained in the Disclosure Documents.

               3.8.2     The Company  has filed all tax  returns  required to be
filed by it or obtained extensions of the due date for such returns and paid all
taxes  which are due,  except for taxes  which it  reasonably  disputes or which
could not  reasonably  be  expected  to have a  material  adverse  effect on the
consolidated business or financial condition of the Company and its subsidiaries
taken as a whole.

               3.8.3     Except  as set  forth in  Schedule  3.8.3,  each of the
                                                   ---------------
Company  and its  subsidiaries  is not the  subject  of any  pending  or, to the
Company's  knowledge,  threatened  inquiry,  investigation or  administrative or
legal proceeding by the Internal Revenue Service,  the taxing authorities of any
state or local jurisdiction,  the Commission or any state securities  commission
or other governmental or regulatory entity which could reasonably be expected to
have a  material  adverse  effect  on the  consolidated  business  or  financial
condition of the Company and its subsidiaries taken as a whole.

               3.8.4     Except  as set  forth in  Schedule  3.8.4,  there is no
                                                   ---------------    
material claim, litigation or administrative  proceeding or inquiry pending, or,
to the best of the Company's knowledge,  threatened,  against the Company or any
of its subsidiaries, or against any officer, director or employee of the Company
or any such  subsidiary in connection with such person's  employment  therewith.
Neither the Company nor any of its  subsidiaries is a party to or subject to the
provisions of, any order, writ,  injunction,  judgment or decree of any court or
government agency or instrumentality  which could reasonably be expected to have
a material adverse effect on the consolidated business or financial condition of
the Company and its subsidiaries.

          3.9  Reporting  Company;  Form S-3.  The  Company  is  subject  to the
               -----------------------------
reporting requirements of the Exchange Act, has a class of securities registered
under  Section  12 of the  Exchange  Act,  and has  filed all  reports  required
thereby.  The  Company is eligible to  register  the  Conversion  Shares and the
Dividend Payment Shares for resale on a registration statement on Form S-3 under
the Securities Act.

          3.10 Acknowledgement  of Dilution.  The Company  acknowledges that the
               ----------------------------
issuance of (i) the Conversion Shares upon conversion of the Preferred Shares in
accordance  with the  terms of the  Certificate  and (ii) the  Dividend  Payment
Shares in accordance with the terms of the Certificate may result in dilution of
the outstanding  shares of Common Stock, which dilution may be substantial under
certain market conditions.  The Company further acknowledges that its obligation
(x) to issue  Conversion  Shares upon conversion of the Preferred Shares and (y)
to issue Dividend Payment Shares in accordance with the terms of the Certificate
is unconditional and absolute regardless of the effect of any such dilution. The
Board of Directors of the Company has reviewed the  Transaction  Documents,  and
has  determined  that  the  transactions  contemplated  thereby  are in the best
interests of the Company and its stockholders.


                                       -6-

<PAGE>


                                                             Page 20 of 50 Pages


          3.11 Intellectual  Property.  The Company owns or  possesses  adequate
               ----------------------     
rights to inventions,  know-how, patents,  copyrights,  confidential information
and other  intellectual  property  rights  necessary to conduct the business now
operated by them,  or  presently  employed by them,  and have not  received  any
notice of  infringement  of or  conflict  with  asserted  rights of others  with
respect to any such rights that, if  determined  adversely to the Company or any
of its  subsidiaries,  would  individually  or in the aggregate  have a material
adverse  effect on the  consolidated  business  or  financial  condition  of the
Company and its subsidiaries taken as a whole.

          3.12 Registration Rights; Rights of Participation. Except as described
              ---------------------------------------------     
on Schedule  3.12 hereto,  (A) the Company has not granted or agreed to grant to
   --------------   
any person or entity any rights (including "piggy-back"  registration rights) to
have any securities of the Company  registered  with the Commission or any other
governmental authority and (B) no person or entity,  including,  but not limited
to, current or former stockholders of the Company, underwriters, brokers, agents
or other third parties, has any right of first refusal,  preemptive right, right
of  participation,  or any  similar  right to  participate  in the  transactions
contemplated  by  the  Certificate,  this  Agreement  or any  other  Transaction
Document which has not been waived.

          3.13 Trading on Nasdaq.  The Common Stock is authorized  for quotation
               -----------------
on the Nasdaq National Market system,  and trading in the Common Stock on Nasdaq
has not been  suspended.  The  Company  is (or will be at the  Closing)  in full
compliance with the designation criteria of the Nasdaq National Market, and does
not reasonably  anticipate  that the Common Stock will lose its designation as a
Nasdaq  National  Market  security,   whether  by  reason  of  the  transactions
contemplated by this Agreement or the other Transaction  Documents or otherwise.
Stockholder  approval for the issuance of the  Preferred  Shares is not required
under NASD Rule 4460.

          3.14 Solicitation.  Neither the Company nor any of its subsidiaries or
               ------------
affiliates, nor any person acting on its or their behalf, (i) has engaged in any
form of general  solicitation  or general  advertising  (within  the  meaning of
Regulation D under the Securities  Act) in connection  with the offer or sale of
the Preferred  Shares or (ii) has,  directly or  indirectly,  made any offers or
sales of any security or  solicited  any offers to buy any  security,  under any
circumstances that would require  registration of the Preferred Shares under the
Securities Act.

          3.15 Fees. Except as described on Schedule 3.15 hereto, the Company is
               ----                         -------------
not obligated to pay any compensation or other fee, cost or related  expenditure
to any underwriter, broker, agent or other representative in connection with the
transactions contemplated hereby.

          3.16 Foreign  Corrupt  Practices.  To the  knowledge  of the  Company,
               ---------------------------
neither the Company,  nor any of its  subsidiaries  nor any  director,  officer,
agent,  employee  or  other  person  acting  on  behalf  of the  Company  or any
subsidiary,  has (i) used any  corporate  funds for any  unlawful  contribution,
gift,  entertainment or other unlawful expenses relating to political  activity,
(ii) made any direct or  indirect  unlawful  payment to any  foreign or domestic
government official or employee,  or (iii) violated any provision of the Foreign
Corrupt Practices Act of 1977, as amended,  or made any bribe,  rebate,  payoff,
influence payment, kickback or other unlawful payment to any foreign or domestic
government official or employee.

          3.17 Other  Issuances of  Securities.  The Company has not issued (and
               -------------------------------
will not issue) any shares of Common  Stock or shares of any series of preferred
stock  (other than the  Preferred  Shares) or other  securities  or  instruments
convertible into,  exchangeable for or otherwise entitling the holder thereof to



                                       -7-

<PAGE>


                                                             Page 21 of 50 Pages


acquire  shares of Common Stock which would be  integrated  with the sale of the
Preferred  Shares,  or the  issuance of the  Conversion  Shares upon  conversion
thereof,  for purposes of determining whether  stockholder  approval is required
under the designation criteria of the Nasdaq National Market.

4.        COVENANTS OF THE COMPANY.

          4.1       Corporate  Existence.  The  Company  shall,  so  long as any
                    --------------------
Purchaser or any affiliate of such Purchaser  beneficially  owns any Securities,
maintain its  corporate  existence in good standing and shall pay all taxes when
due except for taxes  which the Company  reasonably  disputes or which could not
reasonably be expected to have a materially  adverse change on the  consolidated
business or financial condition of the Company and its subsidiaries.

          4.2       Provision of  Information.  The Company  shall  provide each
                    -------------------------
Purchaser with copies of its annual reports on Form 10-K,  quarterly  reports on
Form 10-Q,  current reports on Form 8-K and proxy statements and other materials
sent to  stockholders,  in each such case promptly after filing thereof with the
Commission,  until the  conversion or redemption of all of the Preferred  Shares
held by such Purchaser.

          4.3       Form D; Blue-Sky Qualification. The Company agrees to file a
                    ------------------------------
Form D with  respect to the  Securities  as required  under  Regulation D and to
provide a copy  thereof to each  Purchaser  promptly  upon  filing.  The Company
shall, on or before the Closing, take such action as is necessary to qualify the
Securities  for sale  under  applicable  state or  "blue-sky"  laws or obtain an
exemption  therefrom,  and shall  provide  evidence  of any such  action to such
Purchaser.

          4.4       Reporting Status. As long as such Purchaser or any affiliate
                    ----------------
of such Purchaser beneficially owns any Securities,  and until the date on which
any of the foregoing  may be sold to the public  pursuant to Rule 144(k) (or any
successor  rule or  regulation),  (i) the  Company  shall  timely  file with the
Commission all reports  required to be so filed pursuant to the Exchange Act and
(ii) the Company  shall not  terminate  its status as an issuer  required by the
Exchange Act to file reports thereunder even if the Exchange Act or the rules or
regulations thereunder would permit such termination.

          4.5       Use of Proceeds. The Company shall use the proceeds from the
                    ---------------
sale of the Preferred Shares for general corporate purposes.

          4.6       Listing. The Company shall, as soon as practicable following
                    -------
the Closing,  secure the designation and quotation of the Conversion  Shares and
Dividend  Payment  Shares on the Nasdaq  National  Market and shall use its best
efforts to maintain the  designation of the Common Stock on the Nasdaq  National
Market, the New York Stock Exchange or the American Stock Exchange.

          4.7       Reservation of Common Stock.  The Company shall at all times
                    ---------------------------
have  authorized  and reserved for issuance,  free from any  preemptive  rights,
solely  for  the  purpose  of  effecting  conversions  of the  Preferred  Shares
hereunder,  such number of shares of Common  Stock as shall from time to time be
sufficient  to  effect  the  conversion  of  all of the  Preferred  Shares  then
outstanding (the "Reserved Amount"). As of the Closing Date, the Reserved Amount
                  ---------------  
shall be equal to no less  than 175% of the  number  of  shares of Common  Stock
issuable  upon  conversion  of all  of the  Preferred  Shares  purchased  by the
Purchasers at the Closing  (assuming for such purpose that the Preferred  Shares
are  convertible  in full at such time).  If at any time the Reserved  Amount is
less than 125% of the number of Conversion  Shares  issuable upon  conversion of


                                       -8-

<PAGE>


                                                             Page 22 of 50 Pages

all of the Preferred Shares then  outstanding,  the Company shall take immediate
action (including  seeking  stockholder  authorization) to increase the Reserved
Amount to no less than 175% of the number of  Conversion  Shares into which such
outstanding Preferred Shares are then convertible. No Purchaser shall be issued,
upon conversion of a Preferred  Shares of Common Stock in an amount greater than
the product of (A) the Reserved  Amount in effect on the date on which notice of
such conversion or exercise is delivered to the Company pursuant to the terms of
the  Certificate  times (B) a fraction,  the numerator of which is the number of
Preferred  Shares  purchased by such Purchaser  hereunder and the denominator of
which is the number of Preferred Shares  purchased by the Purchasers  hereunder.
The  Company  shall  not  reduce  the  number of shares  reserved  for  issuance
hereunder without the written consent of the holders of at least 66% of the then
outstanding number of Preferred Shares.

          4.8       Use of Purchaser  Name. The Company shall not use,  directly
                    ----------------------
or indirectly,  any Purchaser's name in any advertisement,  announcement,  press
release or other similar  communication unless it has received the prior written
consent of such Purchaser for the specific use contemplated;  provided, however,
that the  Company  may  respond  to  inquiries  regarding  the  identity  of the
Purchasers from securities analysts or the media.

          4.9       Company's Instructions to Transfer Agent. On or prior to the
                    ----------------------------------------
Closing,  the Company shall execute and deliver irrevocable  instructions to its
transfer agent (the  "Transfer  Agent") (i) to issue  certificates  representing
Conversion  Shares upon  conversion of Preferred  Shares in accordance  with the
terms  thereof and receipt of (x) a valid  Conversion  Notice (as defined in the
Certificate) from a Purchaser, and (y) instructions from the Company pursuant to
the Certificate  regarding the number of Conversion  Shares and Dividend Payment
Shares (if any) to be issued in the name of such Purchaser or its nominee,  (ii)
to issue certificates representing the Dividend Payment Shares upon the issuance
thereof  in  accordance   with  the   Certificate  and  (iii)  to  deliver  such
certificates  to such Purchaser no later than the close of business on the third
(3rd) business day following the related Conversion Date or the Dividend Payment
Date (each as defined in the Certificate).  The Company represents to and agrees
with each Purchaser that it will not give any  instruction to the Transfer Agent
that will  conflict with the foregoing  instruction  or otherwise  restrict such
Purchaser's  right to convert the Preferred  Shares held by such Purchaser or to
receive  Conversion  Shares or Dividend  Payment  Shares in accordance  with the
terms of the Certificate.  In the event that the Company's relationship with the
Transfer  Agent should be terminated  for any reason,  the Transfer  Agent shall
continue  acting as transfer  agent pursuant to the terms hereof until such time
that a successor  transfer  agent is  appointed  by the Company and agrees to be
bound by the terms hereof.

5.        CONDITIONS TO CLOSING.
          ---------------------

          5.1       Conditions  to  Purchaser's  Obligations  at  Closing.  Each
                    -----------------------------------------------------
Purchaser's  obligations  at  the  Closing,  including  without  limitation  its
obligation to purchase the Preferred Shares to be purchased by it hereunder, are
conditioned upon the fulfillment of each of the following events:

               (a)  the  representations and warranties of the Company set forth
                    in this Agreement  shall be true and correct in all material
                    respects as of the Closing Date of as if made on such date;

               (b)  the Company shall have complied with or performed all of the
                    agreements,  obligations  and  conditions  set forth in this
                    Agreement that are required to be complied with or performed
                    by the Company on or before the Closing;

                                       -9-

<PAGE>


                                                             Page 23 of 50 Pages



               (c)  the  Company  shall  have  delivered  to  such  Purchaser  a
                    certificate, signed by an officer of the Company, certifying
                    that the  conditions  specified  in  paragraphs  (a) and (b)
                    above have been fulfilled;

               (d)  the  Company  shall  have  delivered  to such  Purchaser  an
                    opinion of counsel for the Company,  dated as of the date of
                    the   Closing,   in  the  form   attached  as  Exhibit  5.1;
                                                                   ------------

               (e)  The  Company  shall  have  filed  the  Certificate  with the
                    Secretary  of State of the State of Delaware  and  furnished
                    such Purchaser with a file-stamped copy thereof;

               (f)  the  Company   shall  have   executed  and   delivered   the
                    Registration Rights Agreement;

               (g)  there  shall have been no  material  adverse  changes in the
                    Company's consolidated business or financial condition since
                    the date of the Company's most recent  financial  statements
                    contained in the Disclosure Documents;

               (h)  the Common  Stock  shall be  designated  for  quotation  and
                    actively traded on the Nasdaq National Market; and

               (j)  the Company shall have  authorized and reserved for issuance
                    upon  conversion of the Preferred  Shares 175% of the number
                    of shares of Common Stock  issuable upon  conversion  all of
                    the Preferred Shares issuable at the Closing.

          5.2  Conditions  to Company's  Obligations  at Closing.  The Company's
               -------------------------------------------------     
obligation  at the  Closing to issue and sell  Preferred  Shares to a  Purchaser
hereunder is subject to the satisfaction, at or before the Closing Date, of each
of the  following  conditions.  The  obligation of the Company to issue and sell
Preferred  Shares to any  Purchaser  hereunder is distinct and separate from its
obligation to issue and sell Preferred  Shares to any other Purchaser  hereunder
and the failure by one or more  Purchasers to fulfill the  conditions  set forth
herein or to  consummate  the purchase of Preferred  Shares  hereunder  will not
relieve the Company of its obligations with respect to any other Purchaser.

               (a)  the   representations   and  warranties  of  the  applicable
                    Purchaser shall be true and correct in all material respects
                    as of the Closing Date as if made on such date; and

               (b)  the  applicable   Purchaser  shall  have  complied  with  or
                    performed all of the agreements,  obligations and conditions
                    set forth in this Agreement that are required to be complied
                    with  or  performed  by  such  Purchaser  on or  before  the
                    Closing.

6.        INDEMNIFICATION.
          ---------------

          The Company  agrees to indemnify and hold harmless each  Purchaser and
its officers, directors,  employees and agents, and each person who controls the
Purchaser  within the meaning of the Securities Act or the Exchange Act (each, a
"Purchaser Indemnified Party") against any losses, claims, damages,  liabilities
 ---------------------------
or  reasonable   out-of-pocket  expenses  (including  the  reasonable  fees  and
disbursements  of counsel) as incurred,  joint or several,  to which it, they or
any of them, may become subject and not otherwise reimbursed,  arising out of or
in  connection  with the breach by the  Company  of any of its  representations,
warranties or covenants made herein;  provided,  that the Company shall not have
                                      --------  


                                      -11-

<PAGE>


                                                             Page 24 of 50 Pages


any obligation to any Purchaser  Indemnified Party with respect to any liability
to the  extent  such  liability  arises  from the gross  negligence  or  willful
misconduct on the part of such  Purchaser  Indemnified  Party as determined by a
court of competent jurisdiction.

          Each  Purchaser  agrees to indemnify and hold harmless the Company and
its officers, directors,  employees and agents, and each person who controls the
Company  within the meaning of the  Securities  Act or the Exchange Act (each, a
"Company  Indemnified  Party")  (a  Purchaser  Indemnified  Party  and a Company
 ---------------------------
Indemnified  Party are each hereinafter  referred to as an "Indemnified  Party")
                                                            ------------------
against any losses, claims, damages, liabilities or expenses (including the fees
and disbursements of counsel) as incurred,  joint or several,  to which it, they
or any of them, may become subject and not otherwise reimbursed,  arising out of
or  in   connection   with  the  breach  by  such   Purchaser   of  any  of  its
representations,  warranties  or  covenants  made  herein;  provided,  that such
                                                            --------
Purchaser  shall not have any obligation to any Company  Indemnified  Party with
respect to any  liability  to the extent  such  liability  arises from the gross
negligence or willful  misconduct on the part of such Company  Indemnified Party
as determined by a court of competent jurisdiction.

          Promptly  after  receipt  by an  Indemnified  Party of  notice  of the
commencement  of any  action  pursuant  to which  indemnification  may be sought
hereunder,  such Indemnified  Party will, if a claim in respect thereof is to be
made  against  the  other  party  (the  "Indemnifying  Party"),  deliver  to the
Indemnifying  Party  a  written  notice  of the  commencement  thereof  and  the
Indemnifying  Party  shall  have the right to  participate  in and to assume the
defense  thereof with counsel  reasonably  selected by the  Indemnifying  Party,
provided,  however, that an Indemnified Party shall have the right to retain its
own counsel,  with the reasonably  incurred fees and expenses of such counsel to
be paid by the Indemnifying  Party, if  representation of such Indemnified Party
by the counsel retained by the Indemnifying  Party would be inappropriate due to
actual  or  potential  conflicts  of  interest  under  applicable  standards  of
professional  conduct  between  such  Indemnified  Party  and  any  other  party
represented by such counsel in such  proceeding.  The failure to deliver written
notice to the Indemnifying Party within a reasonable time of the commencement of
any  such  action  will  not  relieve  the  Indemnifying  Party  of  any  of its
obligations  hereunder  with  respect to such  action  except to the extent such
failure is prejudicial to the  Indemnifying  Party's  ability to defend any such
action.

          No Indemnifying Party shall,  without the prior written consent of the
Indemnified  Party,  effect any  settlement of pending or  threatened  action in
respect  of  which  an  Indemnified  Party is or  could  have  been a party  and
indemnity could have been sought hereunder by such Indemnified Party unless such
settlement includes an unconditional  release of such Indemnified Party from all
liability  on any  claims  that  are  the  subject  matter  of such  action.  An
Indemnifying  Party will not be liable for any settlement of any action or claim
effected without its written consent.

7.        MISCELLANEOUS.
          -------------

          7.1       Survival;  Severability.  The  representations,  warranties,
                    -----------------------
covenants and  indemnities  made by the parties herein shall survive the Closing
notwithstanding  any due  diligence  investigation  made by or on  behalf of the
party seeking to rely thereon. In the event that any provision of this Agreement
becomes or is  declared  by a court of  competent  jurisdiction  to be  illegal,
unenforceable  or void,  this Agreement  shall continue in full force and effect
without said  provision;  provided that in such case the parties shall negotiate
in good  faith to  replace  such  provision  with a new  provision  which is not
illegal,  unenforceable  or  void,  as long  as  such  new  provision  does  not
materially change the economic benefits of this Agreement to the parties.


                                      -11-

<PAGE>


                                                             Page 25 of 50 Pages


          7.2       Successors  and Assigns.  The terms and  conditions  of this
                    -----------------------
Agreement  shall  inure to the  benefit  of and be binding  upon the  respective
successors  and assigns of the parties.  Nothing in this  Agreement,  express or
implied,  is intended to confer upon any party other than the parties  hereto or
their  respective  successors and assigns any rights,  remedies,  obligations or
liabilities under or by reason of this Agreement,  except as expressly  provided
in this Agreement. Each Purchaser may assign its rights hereunder, in connection
with any  private  sale or  transfer  of  Preferred  Shares,  as long  as,  as a
condition precedent to such transfer,  the transferee executes an acknowledgment
agreeing to be bound by the applicable  provisions of this  Agreement,  in which
case the term "Purchaser"  shall be deemed to refer to such transferee as though
such transferee were an original signatory hereto.

          7.3       Independent  Nature of Purchasers'  Obligations  and Rights.
                    -----------------------------------------------------------
The  obligations of each Purchaser  hereunder are several and not joint with the
obligations  of the  other  Purchasers  hereunder,  and no  Purchaser  shall  be
responsible  in any way for the  performance  of the  obligations  of any  other
Purchaser  hereunder.  Nothing  contained  herein or in any other  agreement  or
document delivered at the Closing, and no action taken by any Purchaser pursuant
hereto  or  thereto,   shall  be  deemed  to  constitute  the  Purchasers  as  a
partnership,  an  association,  a joint venture or any other kind of entity,  or
create a presumption  that the  Purchasers are in any way acting in concert with
respect to such obligations or the transactions  contemplated by this Agreement.
Each  Purchaser  shall be entitled to protect and enforce its rights,  including
without limitation the rights arising out of the Certificate,  this Agreement or
out of the other  Transaction  Documents,  and it shall not be necessary for any
other  Purchaser to be joined as an additional  party in any proceeding for such
purpose.

          7.4       No Reliance.  Each party  acknowledges  that (i) it has such
                    -----------
knowledge in business and financial matters as to be fully capable of evaluating
the  Certificate,  this  Agreement,  the  other  Transaction  Documents  and the
transactions  contemplated  hereby and  thereby,  (ii) it is not  relying on any
advice or  representation  of any other  party  (other than those  contained  or
described in this  Agreement or the other  Transaction  Documents) in connection
with  entering  into this  Agreement,  the other  Transaction  Documents or such
transactions,  (iii) it has not  received  from any such party any  assurance or
guarantee  as to the  merits  (whether  legal,  regulatory,  tax,  financial  or
otherwise) of entering into this Agreement or the other Transaction Documents or
the  performance of its obligations  hereunder and  thereunder,  and (iv) it has
consulted with its own legal, regulatory, tax, business,  investment,  financial
and  accounting  advisors  to the extent that it has deemed  necessary,  and has
entered into this Agreement and the other Transaction Documents based on its own
independent  judgment  and  on  the  advice  of its  advisors  as it has  deemed
necessary,  and not on any view (whether  written or oral) expressed by any such
party.

          7.5       Remedies.  The  remedies  provided  to a  Purchaser  in this
                    --------
Agreement shall be cumulative and in addition to all other remedies available to
such Holder  hereunder,  at law or in equity  (including  without  limitation  a
decree of  specific  performance  and/or  other  injunctive  relief),  no remedy
contained  herein  shall be deemed a waiver of  compliance  with the  provisions
giving  rise to such  remedy  and  nothing  contained  herein  shall  limit such
Purchaser's  right to pursue  actual  damages  for any failure by the Company to
comply with the terms of this Agreement.

          7.6       Governing  Law.  This  Agreement  shall be  governed  by and
                    --------------
construed under the laws of the State of New York without regard to the conflict
of laws  provisions  thereof.  Each  party  hereby  irrevocably  submits  to the
non-exclusive  jurisdiction  of the state and federal courts sitting in the City
of New York, borough of Manhattan, for the adjudication of any dispute hereunder
or in  connection  herewith  or with  any  transaction  contemplated  hereby  or


                                      -12-

<PAGE>


                                                             Page 26 of 50 Pages

discussed herein, and hereby irrevocably waives, and agrees not to assert in any
suit, action or proceeding,  any claim that it is not personally  subject to the
jurisdiction of any such court,  that such suit, action or proceeding is brought
in an inconvenient forum or that the venue of such suit, action or proceeding is
improper.  Each party hereby  irrevocably waives personal service of process and
consents  to process  being  served in any such suit,  action or  proceeding  by
mailing a copy  thereof to such party at the address in effect for notices to it
under this  Agreement  and agrees that such service  shall  constitute  good and
sufficient service of process and notice thereof. Nothing contained herein shall
be deemed to limit in any way any right to serve process in any manner permitted
by law.

          7.7       Counterparts.  This  Agreement may be executed in any number
                    ------------
of  counterparts,  each of which shall be deemed an  original,  and all of which
together shall constitute one and the same instrument.

          7.8       Headings.  The headings used in this  Agreement are used for
                    --------
convenience only and are not to be considered in construing or interpreting this
Agreement.

          7.9       Notices. Any notice, demand or request required or permitted
                    -------
to be  given  by the  Company  or a  Purchaser  pursuant  to the  terms  of this
Agreement  shall be in  writing  and  shall be deemed  given (i) when  delivered
personally or by verifiable facsimile  transmission (with a hard copy to follow)
on or before 5:00 p.m., eastern time, on a business day or, if such day is not a
business day, on the next succeeding business day, (ii) on the next business day
after timely  delivery to an overnight  courier and (iii) on the third  business
day after deposit in the U.S. mail (certified or registered mail, return receipt
requested, postage prepaid), addressed to the parties as follows:

          If to the Company:

          IGEN International, Inc.
          16020 Industrial Drive
          Gaithersburg, MD 20817
          Attn:     Messrs. Samuel J. Wohlstadter
                    George V. Migausky
                    Dr. Richard J. Massey
          Fax:
          with a copy to:

          Wilmer, Cutler & Pickering
          2445 M Street, N.W.
          Washington, DC  20037
          Attn:     Stephen P. Doyle, Esq.
          Fax:      202-663-6363

and if to any  Purchaser,  to such address for such Purchaser as shall appear on
the signature page hereof executed by such Purchaser,  or as shall be designated
by such Purchaser in writing to the Company.

          7.10      Expenses.  Except as otherwise provided herein,  each of the
                    --------
Company and the  Purchasers  shall pay all costs and expenses  that it incurs in
connection  with the  negotiation,  execution,  delivery and performance of this
Agreement.

                                      -13-

<PAGE>


                                                             Page 27 of 50 Pages



          7.11      Entire Agreement;  Amendments.  This Agreement and the other
                    -----------------------------
Transaction  Documents  (together  with the  Certificate)  constitute the entire
agreement  between the parties  with  regard to the  subject  matter  hereof and
thereof, superseding all prior agreements or understandings,  whether written or
oral,  between the parties.  Except as expressly  provided herein,  neither this
Agreement  nor any term  hereof  may be  amended  except  pursuant  to a written
instrument  executed  by the  Company  and the  holders  of at least  2/3 of the
Preferred Shares then  outstanding,  and no provision hereof may be waived other
than by a written instrument signed by the party against whom enforcement of any
such waiver is sought.

                  [Remainder of Page Intentionally Left Blank]



















                                      -14-

<PAGE>


                                                             Page 28 of 50 Pages


IN WITNESS WHEREOF,  the undersigned have executed this Agreement as of the date
first-above written.

IGEN INTERNATIONAL, INC.

By: __________________________
    Name:
    Title:


PURCHASER NAME:  ______________________________


By: _________________________
    Name:
    Title:


ADDRESS:

         _______________________________

         _______________________________

         Tel: __________________________

         Fax: __________________________


WITH COPIES OF NOTICES SENT TO:

         _______________________________

         _______________________________

         Tel: ___________________________

         Fax: ___________________________


NUMBER OF PREFERRED SHARES
TO BE PURCHASED: _________________

[_]Check  here if Purchaser  does not intend to be bound by the 4.9%  limitation
contained in subparagraph II.G.2 of the Certificate.

                                      -15-


                                                             Page 29 of 50 Pages

                                                                    Exhibit A to
                                                              Purchase Agreement


                      SERIES B CONVERTIBLE PREFERRED STOCK

          The  designation,  powers,  preferences  and  rights  of the  Series B
Convertible  Preferred Stock of IGEN International,  Inc. (the "Company") are as
follows:


I.        DESIGNATION AND AMOUNT.
          ----------------------

          The designation of this series, which consists of twenty-five thousand
(25,000) shares of preferred stock, par value $.001 (the "Preferred Shares"), is
                                                          ----------------  
the Series B Convertible  Preferred  Stock (the "Series B Preferred  Stock") and
                                                 ------------------------- 
the face amount  shall be One Thousand  Dollars  ($1,000) per share (the "Stated
                                                                          ------
Value").
- -----

II.       CONVERSION.
          ----------

          A.        Right to Convert.  Subject to the  limitations  contained in
                    ----------------
paragraph G below,  a holder of  Preferred  Shares (a  "Holder")  shall have the
                                                        ------
right to convert such  Preferred  Shares at any time and from time to time on or
after the  Initial  Conversion  Date (as  defined  below)  into  fully  paid and
non-assessable  shares (the "Conversion  Shares") of the Company's Common Stock,
                             ------------------ 
$.001 par value (the "Common  Stock"),  in  accordance  with the terms hereof (a
                      -------------   
"Conversion").  As used herein,  "Initial  Conversion  Date" means the ninetieth
 ----------                       -------------------------     
(90th) day following the Issue Date and "Issue Date" means the date on which the
                                         ----------
Preferred Shares are issued pursuant to the Purchase  Agreement by and among the
Company and the  purchasers  (the  "Purchasers")  named  therein (the  "Purchase
                                    ----------                          --------
Agreement").
- ---------

          B.        Conversion Notice. In order to convert Preferred Shares, the
                    -----------------
Holder thereof shall send by facsimile transmission,  at any time prior to 11:59
p.m.,  eastern  time,  on the date on which the  Holder  wishes  to effect  such
Conversion  (the  "Conversion  Date"),  to the  Company  and  to its  designated
                   ---------------- 
transfer  agent for the Common  Stock  (the  "Transfer  Agent")  (i) a notice of
                                              ---------------    
conversion stating the number of Preferred Shares to be converted (a "Conversion
                                                                      ----------
Notice") and (ii) a copy of the  certificate or  certificates  representing  the
- ------     
Preferred Shares being converted.  The Holder shall thereafter send the original
of the Conversion Notice and of such certificate or certificates to the Company.
The Company shall issue a new certificate for Preferred Shares in the event that
less than all of the Preferred Shares represented by a certificate  delivered to
the Company in connection  with a Conversion  are  converted.  Upon receipt of a
Conversion  Notice,  the Company shall  calculate the amount of dividends  which
have accrued on such Preferred Shares as provided herein up to and including the
Conversion Date, the applicable Conversion Price and a calculation of the number
of shares of Common Stock  issuable  upon such  Conversion,  and shall  promptly
submit such  information to the Transfer  Agent.  In the case of a dispute as to
the  calculation  of the  Conversion  Price or the number of  Conversion  Shares
issuable upon a Conversion,  the Company shall  promptly issue to the Holder the
number of Conversion  Shares that are not disputed and shall submit the disputed
calculations  to its  independent  accountants  within two (2) business  days of
receipt  of such  Holder's  Conversion  Notice.  The  Company  shall  cause such
accountant to calculate the  Conversion  Price as provided  herein and to notify
the  Company  and the  Holder of the  results  in  writing no later than two (2)
business days following the day on which it received the disputed  calculations.
Such accountant's  calculation shall be deemed conclusive absent manifest error.



<PAGE>


                                                             Page 30 of 50 Pages

The fees of any such accountant  shall be borne by the party whose  calculations
are most at variance with those of such accountant.

          C.        Number of Conversion Shares; Conversion Price. The number of
                    ---------------------------------------------
Conversion  Shares to be delivered by the Company pursuant to a Conversion shall
be  equal  to (A) the  aggregate  Stated  Value of the  Preferred  Shares  being
converted divided by (B) the Conversion Price. Subject to adjustment as provided
          ----------
in Section III below, the "Conversion Price" shall be equal to $13.96.
                           ----------------   

          D.        Delivery of Common Stock Upon Conversion.  Upon receipt of a
                    ----------------------------------------
Conversion  Notice  pursuant to paragraph B above,  the Company shall,  no later
than the close of  business  on the  third  (3rd)  business  day  following  the
Conversion Date set forth in such Conversion Notice (the "Delivery Date"), issue
                                                          -------------  
and deliver or cause to be delivered to the Holder certificates representing the
number of  Conversion  Shares as shall be  determined as provided in paragraph C
above.  If any  Conversion  would create a  fractional  Conversion  Share,  such
fractional  Conversion  Share shall be disregarded  and the number of Conversion
Shares issuable upon such Conversion,  in the aggregate,  shall be rounded up or
down to the  nearest  whole  number  of  Conversion  Shares.  Conversion  Shares
delivered to the Holder shall not contain any restrictive  legend as long as the
sale of such  Conversion  Shares by the  Holder  is  covered  by a  registration
statement which has been filed and declared  effective  pursuant to the terms of
the  Registration  Rights  Agreement by and among the Company and the Purchasers
(the  "Registration  Rights  Agreement")  or may be made pursuant to Rule 144(k)
       -------------------------------   
under the Securities Act or any successor rule or provision.

          E.        Failure to Deliver  Conversion Shares. In the event that the
                    -------------------------------------
Company  fails for any reason to  deliver  to a Holder the number of  Conversion
Shares  issuable  upon  conversion  of the  Preferred  Shares  specified  in the
applicable  Conversion  Notice  on or  before  the  Delivery  Date  therefor  (a
"Conversion  Default"),  and such Conversion  Default  continues for longer than
 -------------------
five (5)  business  days,  the  Company  shall pay to the Holder  cash  payments
("Conversion  Default Payments") in the amount of (i) (N/365) multiplied by (ii)
  ----------------------------                                -------------   
the Stated Value of the Preferred  Shares  represented by the Conversion  Shares
which  remain the subject of such  Conversion  Default  multiplied  by (iii) the
                                                        --------------
lower of twenty-four  percent (24%) and the maximum rate permitted by applicable
law, where "N" equals the number of days elapsed  between the original  Delivery
Date of such Conversion Shares and the earlier to occur of (A) the date on which
all of such  Conversion  Shares are issued and  delivered to such Holder and (B)
the date on which such  Preferred  Shares  are  redeemed  pursuant  to the terms
hereof.  Cash  amounts  payable  hereunder  shall be paid on or before the fifth
(5th) business day of the calendar  month  following the calendar month in which
such amount has accrued.  Nothing  herein shall limit a Holder's right to pursue
actual damages for the Company's failure to issue and deliver  Conversion Shares
on the applicable Delivery Date (including, without limitation, damages relating
to any purchase of shares of Common  Stock by such Holder to make  delivery on a
sale effected in anticipation of receiving  Conversion  Shares upon Conversion),
and such Holder shall have the right to pursue all  remedies  available to it at
law  or  in  equity  (including,   without  limitation,  a  decree  of  specific
performance and/or injunctive relief).

          F.        Mandatory  Conversion.  On the date  which is five (5) years
                    ---------------------
following  the Issue Date (the  "Maturity  Date"),  so long as the Common  Stock
                                 --------------  
shall be designated for quotation on the Nasdaq National Market system or listed
on the New York Stock Exchange or American Stock  Exchange,  and actively traded
thereon, all Preferred Shares then outstanding shall be automatically  converted
into the  number of shares of Common  Stock  equal to the  Stated  Value of such
shares   divided  by  the   Conversion   Price  then  in  effect  (a  "Mandatory
         -----------                                                   ---------


                                       -2-

<PAGE>


                                                             Page 31 of 50 Pages

Conversion"),  and the Maturity  Date shall be deemed the  Conversion  Date with
- ----------
respect to such Mandatory  Conversion.  If a Mandatory  Conversion  occurs,  the
Company and the Holder shall follow the  procedures  for Conversion set forth in
this  Section II;  provided,  however,  that the Holder shall not be required to
send the Conversion Notice contemplated by paragraph B above.

          G.   Limitations on Right to Convert.
               -------------------------------

               1.        In no event shall a Holder be  permitted to convert any
Preferred  Shares in excess of that number of such shares upon the Conversion of
which the number of Conversion  Shares to be issued pursuant to such Conversion,
when added to the number of shares of Common Stock issued  pursuant to all prior
Conversions of Preferred Shares and issuances of Dividend Payment Shares,  would
exceed 19.99% of the number of  outstanding  shares of Common Stock on the Issue
Date  (subject  to  equitable  adjustments  from  time  to time  for the  events
described in Section III below) (the "Cap Amount"),  except that such limitation
                                      ----------  
shall  not apply in the event  that the  Company  obtains  the  approval  of its
stockholders  as  required  by NASD  Rule  4460 (or any  other  similar  rule or
regulation)  for  issuances of Common Stock in excess of such amount;  provided,
                                                                       --------
however that it is  understood  and agreed that any Holder  which has  converted
- -------
Preferred Shares into a number of Conversion  Shares that equals or exceeds such
Holder's  Allocation  Amount (as defined  below) shall have the right to require
the  Company,  upon  written  notice to such  effect,  to seek such  stockholder
approval  as soon as  practicable  (but in no event later than  forty-five  (45)
days)  following  the Company's  receipt of such notice.  Until such approval is
obtained,  no Purchaser (as defined in the Purchase  Agreement) shall be issued,
upon Conversion of Preferred Shares, Conversion Shares in an amount greater than
the product of (A) the Cap Amount times (B) a fraction,  the  numerator of which
                                  ----- 
is the number of Preferred  Shares  purchased by such Purchaser  pursuant to the
Purchase  Agreement  and the  denominator  of which is the  aggregate  number of
Preferred  Shares  purchased by all of the  Purchasers  pursuant to the Purchase
Agreement (the "Allocation  Amount"). In the event that any Purchaser shall sell
                ------------------    
or otherwise  transfer all or any of its Preferred Shares,  the transferee shall
be allocated a pro rata portion of such Purchaser's  Allocation Amount and shall
be  similarly  bound.  In the event that any  Holder  shall  convert  all of the
Preferred  Shares held by it into a number of Conversion  Shares  which,  in the
aggregate,  is less than such Holder's  Allocation  Amount,  then the difference
between such  Holder's  Allocation  Amount and the number of  Conversion  Shares
actually  issued to such Holder shall be allocated to the respective  Allocation
Amounts  of the  remaining  Holders of  Preferred  Shares on a pro rata basis in
proportion  to the  number of  Preferred  Shares  then held by each such  Holder
relative to the aggregate number of Preferred Shares then outstanding.

               2.        Except with respect to a Holder which indicates that it
elects not to be bound by the provisions of this subparagraph 2 on the signature
page of the Purchase  Agreement  executed by such Holder,  in no event shall any
Holder be permitted to convert Preferred Shares in excess of that number of such
shares  upon the  Conversion  of which (x) the number of shares of Common  Stock
beneficially  owned by such Holder  (other than shares of Common Stock which may
be deemed  beneficially  owned  except  for being  subject  to a  limitation  on
conversion  or  exercise   analogous  to  the   limitation   contained  in  this
subparagraph  2) plus (y) the number of shares of Common Stock issuable upon the
                 ----   
Conversion  of such  Preferred  Shares is equal to or  exceeds  (z) 4.99% of the
                                          --------------------   
number of shares of Common Stock then issued and outstanding.  Nothing contained
herein  shall be deemed to restrict the right of a Holder to convert such excess
number of Preferred  Shares at such time as such Conversion will not violate the
provisions of this subparagraph (2). To the extent that the limitation contained


                                       -3-

<PAGE>

                                                             Page 32 of 50 Pages


in this  subparagraph 2 applies,  the  determination of whether Preferred Shares
are  convertible  shall  be in the  sole  discretion  of  the  Holder,  and  the
submission  of  a  Conversion  Notice  shall  be  deemed  to  be  such  Holder's
determination  that the  Preferred  Shares  described  therein  are  convertible
hereunder.

          H.             "Trading  Day"  shall  mean any day on which the Common
                          ------------
Stock is traded for any period on the Nasdaq National Market or on the principal
securities exchange or market on which the Common Stock is then traded.

III.      ADJUSTMENTS TO CONVERSION PRICE.

          A.        Adjustment  to  Conversion  Price Due to Stock Split,  Stock
                    ------------------------------------------------------------
Dividend,  Etc. If prior to the Conversion of all of the Preferred  Shares,  (i)
- --------------
the number of outstanding  shares of Common Stock is increased by a stock split,
stock dividend, reclassification, the distribution to holders of Common Stock of
rights or warrants  entitling them to subscribe for or purchase  Common Stock at
less than the then  Current  Market  Price (as defined  below)  thereof or other
similar event, the Conversion Price shall be  proportionately  reduced,  or (ii)
the number of outstanding shares of Common Stock is decreased by a reverse stock
split,  combination or  reclassification  of shares or other similar event,  the
Conversion Price shall be proportionately  increased. In such event, the Company
shall notify the Transfer  Agent of such change on or before the effective  date
thereof.  The "Current Market Price" per share of Common Stock on any date shall
               --------------------
be the  average of the closing  sale prices for the Common  Stock as reported by
Nasdaq, or by the principal  securities market on which the Common Stock is then
traded,  on the five (5)  consecutive  Trading Days  selected by the Company not
later than the earlier of the date in question  and the Trading Day  immediately
prior to the "ex" date,  if any,  with respect to the  issuance or  distribution
requiring such computation.  The term "'ex' date", when used with respect to any
issuance or distribution,  means the first Trading Day on which the Common Stock
trades  regular way in the market from which such average  closing price is then
to be determined without the right to receive such issuance or distribution.  In
the absence of one or more such  quotations,  the Company  shall  determine  the
current  market  price  on  the  basis  of  such   quotations  as  it  considers
appropriate.

          B.        Adjustment Due to Merger,  Consolidation,  Etc. If, prior to
                    ----------------------------------------------
the  Conversion  of all of the  Preferred  Shares,  there  shall be any  merger,
consolidation, exchange of shares, recapitalization,  reorganization, redemption
or other  similar  event,  as a result of which  shares of Common Stock shall be
changed  into the same or a  different  number of shares of the same or  another
class or  classes of stock or  securities  of the  Company or another  entity or
there is a sale of all or substantially all the Company's assets, then each such
Holder  shall  thereafter  have the  right to  receive  upon  Conversion  of the
Preferred  Shares  held  by it and  in  lieu  of  the  shares  of  Common  Stock
immediately theretofore issuable upon conversion,  such stock, securities and/or
other assets (the "Change of Control Consideration"),  if any, which such Holder
                   ------------------------------- 
would  have been  entitled  to receive in such  transaction  had such  Preferred
Shares been converted  immediately  prior to such  transaction,  and in any such
case  appropriate  provisions  shall be made  with  respect  to the  rights  and
interests  of such  Holder  to the end that the  provisions  hereof  (including,
without limitation, provisions for the adjustment of the Conversion Price and of
the number of shares issuable upon a Conversion)  shall thereafter be applicable
as  nearly  as may be  practicable  in  relation  to any  securities  thereafter
deliverable  upon  the  exercise  hereof.  The  Company  shall  not  effect  any
transaction  described  in this  paragraph  B unless  (i) it first  gives to the
Holder no less than  twenty  (20) days'  prior  written  notice of such  merger,
consolidation, exchange of shares, recapitalization,  reorganization, redemption


                                       -4-

<PAGE>


                                                             Page 33 of 50 Pages


or other similar  event,  and makes a public  announcement  of such event at the
same  time  that it  gives  such  notice  and (ii) the  resulting  successor  or
acquiring  entity  (if  not the  Company)  assumes  by  written  instrument  the
obligations of the Company under this  Certificate,  including the terms of this
paragraph B.  Notwithstanding  the provisions of paragraph  II.A.  above, in the
event that the Company delivers a notice of a merger, consolidation, exchange of
shares, recapitalization,  reorganization,  redemption or other similar event to
each Holder which  specifies an effective  date  therefor  which is prior to the
Initial Conversion Date, each Holder shall have the right to convert,  from time
to time following the delivery of such notice to such Holder,  any or all of the
Preferred  Shares held by it, so that such  Holder  shall be entitled to receive
the Change of Control  Consideration with respect to any Conversion Shares which
it received pursuant to a Conversion occurring prior to such effective date.

          C.        Distribution  of Assets.  If, prior to the Conversion of all
                    -----------------------
of the  Preferred  Shares,  the Company  shall  declare or pay any  dividends to
holders of Common Stock,  or declare or make any  distribution of its assets (or
rights  to  acquire  its  assets)  to  holders  of  Common  Stock  as a  partial
liquidating  dividend,  by way of return of capital or otherwise,  including any
dividend or  distribution  in cash or shares of capital stock of a subsidiary of
the Company  (collectively,  a  "Distribution"),  then, upon a Conversion by the
                                 ------------  
Holder occurring after the record date for determining  shareholders entitled to
such  Distribution  but prior to the effective date of such  Distribution,  each
Holder  shall be entitled to receive the amount of such assets  which would have
been  payable to such  Holder had such  Holder been the holder of such shares of
Common Stock on the record date for the  determination of shareholders  entitled
to  such  Distribution.   The  Company  shall  deliver  written  notice  of  any
Distribution  to each Holder no less than twenty (20) business days prior to the
effective date thereof. Notwithstanding the provisions of paragraph II.A. above,
in the event that the Company delivers a notice of a Distribution to the Holders
which  specifies  an  effective  date  therefor  which is  prior to the  Initial
Conversion Date, each Holder shall have the right to convert,  from time to time
following  the  delivery  of  such  notice  to  such  Holder,  any or all of the
Preferred  Shares held by it, so that such  Holder  shall be entitled to receive
such  Distribution  with  respect to any  Conversion  Shares  which it  received
pursuant to a Conversion occurring prior to such effective date.

          D.        No Fractional  Shares.  If any adjustment under this Section
                    ---------------------
III would  create a  fractional  share of Common  Stock or a right to  acquire a
fractional share of Common Stock, such fractional share shall be disregarded and
the number of shares of Common Stock issuable upon  Conversion  shall be rounded
up or down to the nearest whole number of shares.

IV.       DIVIDENDS.

          A.        Dividends;  Stock Payment  Option.  Each Holder of Preferred
                    ---------------------------------
Shares shall be entitled to receive,  to the extent permitted by applicable law,
subject to the prior,  full payment of any accumulated  and unpaid  dividends on
any class or series of Senior Securities (as defined below) and in preference to
the  payment of any  dividend  on any class or series of Junior  Securities  (as
defined below), cumulative dividends ("Dividends") on each Preferred Share in an
                                       --------- 
amount equal to, on an  annualized  basis,  the Stated  Value of such  Preferred
Share times 7.75%,  compounded annually.  Dividends shall accrue and be payable,
      -----    
whether or not earned or declared,  on each Preferred  Share from the Issue Date
through the earlier to occur of (A) the Maturity Date (as defined below) and (B)
the  redemption  or  conversion  thereof in  accordance  with the terms  hereof.
Accrued  Dividends on a Preferred Share shall be payable on each Conversion Date
(as defined below), on the Maturity Date (as defined below) and on any Mandatory


                                       -5-

<PAGE>


                                                             Page 34 of 50 Pages

Redemption  Date or  Optional  Redemption  Date  (as  defined  below)  (each,  a
"Dividend  Payment  Date").  If,  on any  date,  Dividends  on  any  outstanding
 -----------------------
Preferred  Shares have not been paid with respect to all Dividend  Payment Dates
preceding such date, the aggregate  amount of such Dividends shall be fully paid
before any  distribution,  whether by way of  dividend  or  otherwise,  shall be
declared,  paid or set apart with respect to any Junior  Securities  on or after
such  date.  Dividends  shall be paid  either in cash or,  at the  option of the
Company (the "Stock Payment  Option"),  and subject to the  satisfaction  of the
              --------------------- 
conditions set forth in paragraph B below (the "Stock Payment  Conditions"),  in
                                                -------------------------  
shares (the "Dividend Payment Shares") of the Common Stock. Cash Dividends shall
             -----------------------  
be paid to each Holder  within five (5) Business Days  following the  applicable
Dividend Payment Date by delivering  immediately  available funds to such Holder
in accordance  with such Holder's wiring  instructions.  Any amount of Dividends
payable  in  cash  which  is not  paid  within  five  (5)  Business  Days of the
applicable  Dividend Payment Date shall bear interest at an annual rate equal to
the lower of (x) the "prime" rate (as  published in the Wall Street  Journal) on
such  fifth  Business  Day plus  three  percent  (3%) and (y) the  highest  rate
permitted by  applicable  law, for the number of days elapsed from such Dividend
Payment Date until such amount is paid in full (the "Default Interest Rate").
                                                     ---------------------  

          B.        Conditions to Stock Payment Option. If the Company wishes to
                    ----------------------------------
exercise the Stock  Payment  Option,  it may do so only if each of the following
conditions has been satisfied as of the relevant Conversion Date:

                    1.   the  number  of  shares  of  Common  Stock  authorized,
unissued  and  unreserved  for all  other  purposes,  or  held in the  Company's
treasury,  is sufficient to pay 125% of the aggregate  number of (x)  Conversion
Shares issuable upon the conversion in full of the Preferred  Shares and (y) the
number of Dividend Payment Shares issuable pursuant to such option;

                    2.   the  Dividend   Payment   Shares  are   authorized  for
quotation on the Nasdaq National Market or for listing or quotation on any other
national securities exchange or market on which the Common Stock may be listed;

                    3.   the   Registration   Statement   (as   defined  in  the
Registration  Rights  Agreement)  is effective and available for the sale of the
Dividend  Payment  Shares by the Holder or such shares may be sold to the public
pursuant to Rule 144(k);

                    4.   a Mandatory  Redemption  Event (as defined  herein) has
not occurred or be continuing; and

                    5.   the Company has delivered to each Holder a certificate,
signed by an executive officer of the Company, setting forth:

                         *    the amount of the Dividend to which such Holder is
                              entitled and, if not the same,  the amount of such
                              payment to be made in Dividend Payment Shares;

                         *    the  number  of  Dividend  Payment  Shares  to  be
                              delivered  in payment of such  Dividends,  and the
                              calculation therefor; and

                         *    a  statement   to  the  effect  that  all  of  the
                              conditions set forth in  sub-paragraphs  1-4 above
                              have been satisfied.


                                       -6-

<PAGE>


                                                             Page 35 of 50 Pages


          C.        Delivery of Dividend  Payment  Shares.  Upon exercise of the
                    -------------------------------------
Stock Payment Option, the Company shall deliver to each Holder, on or before the
third (3rd)  Business Day following the  applicable  Dividend  Payment Date (the
"Dividend Payment Share Delivery Date"),  the aggregate number of whole Dividend
 ------------------------------------
Payment  Shares that is determined by dividing (x) the amount of the Dividend to
which such Holder is entitled as of such  Dividend  Payment Date with respect to
all of such Holder's Preferred Shares by (y) the applicable  Conversion Price on
such  Dividend  Payment Date. No  fractional  Dividend  Payment  Shares shall be
issued;  the Company shall,  in lieu thereof,  either issue a number of Dividend
Payment  Shares which  reflects a rounding up to the next whole number of shares
or pay such  amount in cash.  Dividend  Payment  Shares  shall be fully paid and
non-assessable,  free and  clear of any  liens,  claims,  preemptive  rights  or
encumbrances imposed by or through the Company.

          D.        Failure to Deliver  Dividend  Payment  Shares.  In the event
                    ---------------------------------------------
that the  Company  fails for any reason to  deliver to a Holder the  appropriate
number of  Dividend  Payment  Shares on or before the third (3rd)  Business  Day
following the  applicable  Dividend  Payment Share  Delivery  Date,  the Company
shall,  upon written  notice by such Holder,  immediately  pay the amount of the
Dividend in cash,  together with interest at an annual rate equal to the Default
Interest Rate on such unpaid amount accruing daily from the applicable  Dividend
Payment Date until the date on which such amount is paid. Each Holder shall have
the  right to pursue  actual  damages  for the  Company's  failure  to issue and
deliver  Dividend Payment Shares on the Dividend Payment Share Delivery Date for
a Dividend,  including, without limitation,  damages relating to any purchase of
shares of Common  Stock by such Holder to make  delivery  on a sale  effected in
anticipation  of receiving  Dividend  Payment  Shares,  such damages to be in an
amount equal to (A) the  aggregate  amount paid by such Holder for the shares of
Common Stock so purchased minus (B) (i) the aggregate amount of net proceeds, if
                          -----
any, received by such Holder from the sale of the Dividend Payment Shares issued
by the Company  with  respect to such  Dividend  and (ii) the amount of any cash
received in lieu of such Dividend  Payment  Shares  pursuant to the  immediately
preceding  sentence  (excluding any interest accrued  thereon),  and such Holder
shall have the right to pursue all remedies  available to it at law or in equity
(including,   without  limitation,  a  decree  of  specific  performance  and/or
injunctive  relief with  respect to the  Company's  failure to deliver  Dividend
Payment Shares).

          E.        Exercise of Stock Payment  Option.  In order for the Company
                    ---------------------------------
to exercise the Stock Payment Option,  it must deliver written notice thereof (a
"Stock  Payment  Exercise  Notice") to each Holder on or before the tenth (10th)
 --------------------------------
Business Day prior to the Initial  Conversion  Date (as defined below) and prior
to the first day of each  calendar  quarter  thereafter  specifying  whether the
Company intends to pay Dividends during such calendar quarter (or shorter period
in the case of the notice  delivered  prior to the Initial  Conversion  Date) in
Dividend Payment Shares or cash. Upon delivering a Stock Payment Exercise Notice
to a Holder,  the Company  thereafter shall be irrevocably bound by its election
made therein to deliver  Dividend  Payment  Shares or cash,  as the case may be,
during the period to which such notice relates.

V.        PAYMENT UPON DISSOLUTION.
          ------------------------

          (a)       Upon the  occurrence  of (x) any  insolvency  or  bankruptcy
proceedings, or any receivership,  liquidation,  reorganization or other similar
proceedings  in  connection  therewith,  commenced  by  the  Company  or by  its
creditors,  as such, or relating to its assets or (y) the  dissolution  or other
winding  up of the  Company  whether  total or  partial,  whether  voluntary  or
involuntary and whether or not involving  insolvency or bankruptcy  proceedings,


                                       -7-

<PAGE>


                                                             Page 36 of 50 Pages


or (z) any  assignment  for the benefit of creditors or any  marshalling  of the
material  assets or material  liabilities  of the Company  (each, a "Liquidation
                                                                     -----------
Event"),  no  distribution  shall be made to the holders of any shares of Junior
- -----
Securities  (as defined  below)  unless,  following the payment of  preferential
amounts on all Senior  Securities  (as defined  below),  each Holder  shall have
received  the  Liquidation  Preference  (as defined  below) with respect to each
Preferred Share then held by such Holder.  In the event that upon the occurrence
of a Liquidation Event, and following the payment of preferential amounts on all
Senior  Securities (as defined below),  the assets available for distribution to
the  Holders  and the holders of Pari Passu  Securities  (as defined  below) are
insufficient  to pay  the  Liquidation  Preference  with  respect  to all of the
outstanding  Preferred  Shares  and the  preferential  amounts  payable  to such
holders, the entire assets of the Company shall be distributed ratably among the
Preferred  Shares and the shares of Pari Passu  Securities  in proportion to the
ratio that the  preferential  amount  payable on each such share (which shall be
the  Liquidation  Preference  in the  case of a  Preferred  Share)  bears to the
aggregate  preferential amount payable on all such shares. If, after the payment
of all preferential amounts to the holders of Senior Securities, the Holders and
the holders of Pari Passu Securities, there are assets of the Company remaining,
the  holders  of  Junior  Securities  shall  share  in such  assets  ratably  in
accordance with the respective terms of such Junior Securities.

          (b)       The  "Liquidation  Preference"  with  respect to a Preferred
                          -----------------------                    
Share shall mean an amount  equal to the Stated  Value of such  Preferred  Share
plus any accrued and unpaid Dividends  thereon.  "Junior  Securities" shall mean
                                                  ------------------
the Common  Stock and all other  capital  stock of the Company that are not Pari
Passu Securities or do not have a preference over the Preferred Stock in respect
of dividends,  redemption or distribution upon liquidation.  "Senior Securities"
                                                              -----------------
shall mean any  securities of the Company which by their terms have a preference
over the  Preferred  Stock in respect of dividends,  redemption or  distribution
upon liquidation. "Pari Passu Securities" shall mean any securities ranking pari
                   ---------------------      
passu  with  the  Preferred  Stock  in  respect  of  dividends,  redemption  and
distribution upon liquidation.

VI.            OPTIONAL REDEMPTION BY THE COMPANY.
               ----------------------------------

          A.        Optional  Redemption.  The Company shall have the right,  at
                    --------------------
any time  commencing on the date which is thirty-six (36) months after the Issue
Date  (the  "Initial  Optional   Redemption  Date"),  to  redeem  (an  "Optional
             ------------------------------------                       --------
Redemption")  all of the  Preferred  Shares  then  outstanding  at the  Optional
- ----------                                                       
Redemption Price (as defined herein); provided, however, that in order to effect
an Optional  Redemption,  the Company  shall have provided to each Holder thirty
(30) Trading  Days' prior written  notice of the effective  date of the Optional
Redemption (the "Optional  Redemption  Date").  Nothing  contained  herein shall
                 --------------------------   
prevent a Holder from converting any or all of its Preferred  Shares at any time
or from time to time prior to the Optional Redemption Date.

          B.        Optional  Redemption Price. The "Optional  Redemption Price"
                    --------------------------       --------------------------
shall mean the Stated Value of the Preferred Shares being redeemed multiplied by
                                                                   -------------
(A) 103% if the  Optional  Redemption  Date occurs  during the twelve (12) month
period  beginning on the Initial  Optional  Redemption  Date and (B) 100% if the
Optional  Redemption  Date  occurs  after the last day of such twelve (12) month
period.

          C.        Payment of Optional  Redemption Price. The Company shall pay
                    -------------------------------------
the Optional  Redemption  Price to each Holder  within five (5) business days of
the  Optional  Redemption  Date.  If  the  Company  fails  to pay  the  Optional
Redemption  Price on or before such fifth  business  day,  interest at an annual
rate equal to the Default  Interest Rate  (calculated  as of such fifth business


                                       -8-

<PAGE>


                                                             Page 37 of 50 Pages

day) shall  accrue on such unpaid  amount on a daily basis  calculated  from the
Optional Redemption Date until the date on which such amount is paid in full.

VII.      MANDATORY REDEMPTION BY THE HOLDER.
          ----------------------------------

          A.        Mandatory Redemption. Subject to the provisions of paragraph
                    --------------------
F below,  in the event that a Mandatory  Redemption  Event (as  defined  herein)
occurs, each Holder shall have the right, upon written notice to the Company, to
have  all or any  portion  of the  Preferred  Shares  then  held by such  Holder
redeemed by the Company (a "Mandatory  Redemption") at the Mandatory  Redemption
                            ---------------------  
Price (as  defined  herein) in same day funds.  Such  notice  shall  specify the
effective date of such Mandatory  Redemption (the "Mandatory  Redemption  Date")
                                                   ---------------------------
and the number of Preferred Shares to be redeemed.  The Optional Redemption Date
and the Mandatory  Redemption  Date are  sometimes  each referred to herein as a
"Redemption Date".
 ---------------

          B.        Mandatory Redemption Price. The "Mandatory Redemption Price"
                    --------------------------       --------------------------
shall be equal  to the  Stated  Value of the  Preferred  Shares  being  redeemed
multiplied by (i) during the  twelve-month  period following the Issue Date (the
- -------------
"Initial Redemption  Period"),  one hundred and nine percent (109%), (ii) during
 --------------------------
the twelve-month  period following the end of the Initial Redemption Period, one
hundred  and six percent  (106%),  and (iii)  thereafter,  one hundred and three
percent (103%).

          C.        Payment of Mandatory  Redemption Price.The Company shall pay
                    --------------------------------------
the  Mandatory  Redemption  Price to each  Holder who has  requested a Mandatory
Redemption  within five (5) business days of the Mandatory  Redemption  Date. If
the Company fails to pay the Mandatory  Redemption Price to a Holder within five
(5)  business  days of the  Mandatory  Redemption  Date,  such  Holder  shall be
entitled  to  interest  at an annual  rate equal to the  Default  Interest  Rate
(calculated  as of such 5th business  day) from the  Mandatory  Redemption  Date
until the Mandatory Redemption Price has been paid in full.

          D.        Mandatory  Redemption  Event.  Each of the following  events
                    ----------------------------
shall be deemed a "Mandatory Redemption Event":
                   -------------------------- 

          1.        the  Company  fails  for  any  reason   (including   without
limitation (x) as a result of not having a sufficient number of shares of Common
Stock  authorized  and  reserved  for  issuance,  or  (y)  due  to  the  listing
requirements  of any  quotation  system or exchange on which the Common Stock is
quoted  or listed  with  which  the  Company  is unable to comply as a result of
voluntary  action  undertaken by the Company or a failure by the Company to take
action) to issue  shares of Common  Stock to a Holder and  deliver  certificates
representing  such shares to such Holder as and when required by the  provisions
hereof upon Conversion of any Preferred  Shares,  and such failure continues for
twenty (20) Business Days;

          2.        any material  representation or warranty made by the Company
in the Purchase  Agreement,  the  Registration  Rights  Agreement,  or any other
agreement,  document,  certificate or other  instrument  delivered in connection
with the transactions contemplated hereby or thereby is inaccurate or misleading
in any material respect as of the date such representation or warranty was made;

          3.        if  following  the  declaration  of   effectiveness  of  the
Registration  Statement (as defined in the  Registration  Rights  Agreement) and


                                       -9-

<PAGE>


                                                             Page 38 of 50 Pages


while  the  effectiveness  of  the  Registration  Statement  is  required  to be
maintained  pursuant  to the terms of the  Registration  Rights  Agreement,  the
effectiveness  of the Registration  Statement  lapses for any reason  (including
without  limitation,  the  issuance  of a stop order) or is  unavailable  to the
Holder for the sale of  Conversion  Shares in  accordance  with the terms of the
Registration Rights Agreement,  and such lapse or unavailability continues for a
period of ten (10)  Business  Days,  provided  that the  cause of such  lapse or
unavailability  results from voluntary  action  undertaken by the Company or its
failure to take action; and

          4.        the Common Stock is not quoted on the Nasdaq National Market
or listed on the New York Stock  Exchange or American  Stock Exchange due to any
voluntary action or the failure to take action on the part of the Company.

          Notwithstanding the foregoing, to the extent that the Company uses its
best  efforts  to take  action to avoid a  Mandatory  Redemption  Event and such
action is  unsuccessful,  such  failed  attempt,  in and of itself,  will not be
deemed to trigger a Mandatory Redemption Event.

          E.        Failure to Pay Redemption  Amounts.  If the Company fails to
                    ----------------------------------
pay the Mandatory  Redemption Price within ten (10) business days of the payable
date  therefor,  and has not exercised the Penalty  Option (as defined below) in
accordance  with paragraph F below,  then the Holder shall have the right at any
time, so long as the Company  remains in default,  to require the Company,  upon
written notice, to immediately issue, in lieu of the Mandatory Redemption Price,
the  number  of shares of Common  Stock of the  Company  equal to the  Mandatory
Redemption  Price divided by the Conversion  Price in effect on such  Conversion
                  ----------  
Date as is specified by the Holder in writing to the Company.

          F.        Penalty  Option.  In the event that a  Mandatory  Redemption
                    ---------------
Event  described in paragraph  D.3 or D.4 above  occurs and is  continuing,  the
Company may, in lieu of redeeming Preferred Shares as provided herein, elect (i)
to increase the rate at which Dividends will accrue on the Preferred  Shares and
be payable hereunder to fourteen percent (14)%, such increase to be effective as
of the related Mandatory  Redemption Date and (ii) to pay such Dividends in cash
within  five  business  days of the end of each  calendar  month in  which  such
increased Dividends have accrued (the "Penalty Option"). Upon the termination of
                                       -------------- 
the applicable  Mandatory  Redemption  Event,  such increased  Dividend rate and
payment  frequency  will revert back to the Dividend rate and payment  frequency
otherwise provided in this Certificate. The Company shall give written notice to
each Holder of its  intention  to exercise  the Penalty  Option  within five (5)
business days of receiving notice of a Mandatory Redemption from a Holder.

VIII.     MISCELLANEOUS.

          A.        Notices.  Except as otherwise  provided herein,  any notice,
                    -------
demand or request  required or  permitted to be given by the Company or a Holder
pursuant  to the  terms of this  Certificate  shall be in  writing  and shall be
deemed  given  (i)  when  delivered   personally  or  by  verifiable   facsimile
transmission  (with a hard copy to follow),  (ii) on the next business day after
timely  delivery to an  overnight  courier and (iii) on the third  business  day
after deposit in the U.S. mail  (certified or registered  mail,  return  receipt
requested, postage prepaid), addressed as follows:


                                      -10-

<PAGE>


                                                             Page 39 of 50 Pages


     If to the Company:

     IGEN International, Inc.
     16020 Industrial Drive
     Gaithersburg, MD 20817
     Attn:     Messrs. Samuel J. Wohlstadter
               George V. Migausky
               Dr. Richard J. Massey
     Fax:

     with a copy to:

     Wilmer, Cutler & Pickering
     2445 M Street, N.W.
     Washington, DC  20037
     Attn:     Stephen P. Doyle, Esq.
     Fax:      202-663-6363

and if to a Holder,  at such  address as such Holder  shall have  furnished  the
Company in writing.

          B.        Transfer of Preferred  Shares. A Holder may sell or transfer
                    -----------------------------
all or any  portion of the  Preferred  Shares to any person or entity as long as
such sale or  transfer  is the subject of an  effective  registration  statement
under the Securities Act or is exempt from registration thereunder and otherwise
is made in accordance with the terms of the Purchase  Agreement.  From and after
the date of such sale or transfer, the transferee hereof shall be deemed to be a
Holder.  Upon any such sale or transfer,  the Company shall,  promptly following
the return of the certificate or certificates  representing the Preferred Shares
that are the  subject  of such  sale or  transfer,  issue  and  deliver  to such
transferee a new certificate in the name of such transferee.

          C.        Lost or Stolen  Certificate.  Upon receipt by the Company of
                    ---------------------------
evidence  of  the  loss,  theft,  destruction  or  mutilation  of a  certificate
representing  Preferred Shares,  and (in the case of loss, theft or destruction)
of  indemnity  or security  reasonably  satisfactory  to the  Company,  and upon
surrender and cancellation of such  certificate if mutilated,  the Company shall
execute and deliver to the Holder a new certificate identical in all respects to
the original certificate.

          D.        No Voting  Rights.  Except as provided by applicable law and
                    -----------------
paragraph G below,  the  Holders of the  Preferred  Shares  shall have no voting
rights  with  respect to the  business,  management  or affairs of the  Company;
provided that the Company shall provide each Holder with prior  notification  of
each  meeting  of  stockholders  (and  copies  of  proxy  statements  and  other
information sent to such stockholders).

          E.        Remedies, Characterization,  Other Obligations, Breaches and
                    ------------------------------------------------------------
Injunctive  Relief.  The remedies provided to a Holder in this Certificate shall
- ------------------    
be  cumulative  and in addition to all other  remedies  available to such Holder
under this  Certificate,  at law or in equity  (including  without  limitation a
decree of  specific  performance  and/or  other  injunctive  relief),  no remedy
contained  herein  shall be deemed a waiver of  compliance  with the  provisions
giving  rise to such  remedy  and  nothing  contained  herein  shall  limit such
Holder's right to pursue actual damages for any failure by the Company to comply


                                      -11-

<PAGE>


                                                             Page 40 of 50 Pages


with the terms of this  Certificate.  The  Company  agrees with each Holder that
there shall be no  characterization  concerning  this  instrument  other than as
specifically  provided  herein.  Amounts set forth or  provided  for herein with
respect to payments, conversion and the like (and the computation thereof) shall
be the  amounts to be  received  by the Holder  hereof and shall not,  except as
expressly provided herein, be subject to any other obligation of the Company (or
the performance thereof).

          F.        Failure or Delay not Waiver. No failure or delay on the part
                    ---------------------------
of a Holder in the  exercise of any power,  right or privilege  hereunder  shall
operate as a waiver  thereof,  nor shall any single or partial  exercise  of any
such power,  right or privilege preclude other or further exercise thereof or of
any other right, power or privilege.

          G.        Protective   Provisions.
                    -----------------------

                    So long as  Preferred  Shares are  outstanding,  the Company
shall not,  without  first  obtaining  the  approval  of the Holders of at least
two-thirds (2/3) of the then outstanding Preferred Shares:

          1.        alter or change (x) the rights, preferences or privileges of
the Series B Preferred Stock or (y) any other capital stock of the Company so as
to affect adversely the Series B Preferred Stock;

          2.        create  any new class or series of  capital  stock  having a
preference  over or ranking  pari passu with the Series B Preferred  Stock as to
redemption,   the  payment  of  dividends  or  distribution  of  assets  upon  a
Liquidation  Event or any other  liquidation,  dissolution  or winding up of the
Company;

          3.        increase  the  authorized  number  of  shares  of  Series  B
Preferred Stock; or

          4.        re-issue  any shares of Series B Preferred  Stock which have
been converted in accordance with the terms hereof.

          In the event  that  Holders of at least  two-thirds  (2/3) of the then
outstanding  shares of Series B  Preferred  Stock  agree to allow the Company to
alter or change the rights,  preferences or privileges of the Series B Preferred
Stock,  pursuant to the terms  hereof,  then the Company will deliver  notice of
such  approved  change,  no later  than the  twentieth  (20th)  day prior to the
effective date of such approved change, to the holders of the Series B Preferred
Stock that did not agree to such alteration or change (the "Dissenting Holders")
and the  Dissenting  Holders  shall  have the right to convert  their  Preferred
Shares at any time and from time to time following  delivery of such notice.  No
such change shall be effective to the extent that,  by its terms,  it applies to
less than all of the Holders of Preferred Shares then outstanding.


                                      -12-


                                                             Page 41 of 50 Pages


                                    EXHIBIT C

                          REGISTRATION RIGHTS AGREEMENT


          REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of December
                                               ---------   
16, 1997, by and among IGEN  International,  Inc., a Delaware  corporation  (the
"Company"),  and each of the entities whose names appear on the signature  pages
 -------    
hereof.  Such  entities  are each  referred  to  herein  as a  "Purchaser"  and,
                                                                --------- 
collectively, as the "Purchasers".
                      ----------   

          The Company has agreed, on the terms and subject to the conditions set
forth  in  the  Purchase   Agreement  of  even  date  herewith  (the   "Purchase
                                                                        --------
Agreement"), to issue and sell to each Purchaser shares (the "Preferred Shares")
- ---------                                                     ----------------
of the Company's Series B Convertible  Preferred Stock (the "Preferred  Stock").
                                                             ----------------
The Preferred  Shares are convertible  pursuant to the Company's  Certificate of
Designation (the  "Certificate")  into shares (the  "Conversion  Shares") of the
                   -----------                       ------------------   
Company's Common Stock (the "Common  Stock").  In order to induce the Purchasers
                             ------------- 
to enter into the Purchase Agreement,  the Company has agreed to provide certain
registration   rights  under  the  Securities  Act  of  1933,  as  amended  (the
"Securities Act"), and under applicable state securities laws. Capitalized terms
 --------------
used herein and not  otherwise  defined shall have the  respective  meanings set
forth in the Purchase Agreement.

          In  consideration  of  each  Purchaser   entering  into  the  Purchase
Agreement,   and  other  good  and  valuable  consideration,   the  receipt  and
sufficiency of which are hereby acknowledged, the parties agree as follows:

          1.       DEFINITIONS.
                   -----------

          For purposes of this  Agreement,  the  following  terms shall have the
meanings specified:

          (a)  "Closing"  shall  have  the  meaning  specified  in the  Purchase
                -------    
          Agreement;


          (b)  "Registration  Deadline" means the ninetieth (90th) day following
                ----------------------
          Closing;

          (c)  "Holder"  means any person owning or having the right to acquire,
                ------
          through  conversion  of  Preferred  Shares or  otherwise,  Registrable
          Securities,  including  initially  each  Purchaser and  thereafter any
          permitted assignee thereof;

          (d)  "Register",   "registered"   and   "registration"   refer   to  a
                --------      ----------           ------------
          registration   effected  by  preparing  an  d  filing  a  registration
          statement or  statements  in compliance  with the  Securities  Act and
          pursuant  to Rule 415 under the  Securities  Act  ("Rule  415") or any
                                                              ---------   
          successor   rule  providing  for  the  offering  of  securities  on  a
          continuous basis  ("Registration  Statement"),  and the declaration or
                              -----------------------
          ordering  of  effectiveness  of  the  Registration  Statement  by  the
          Securities and Exch ange Commission (the "Commission"); and
                                                    ----------


          (e)  "Registrable  Securities"  means the  Conversion  Shares  and the
                -----------------------    
          Dividend  Payment  Shares ( as  defined in the  Certificate),  and any



          


<PAGE>


                                                             Page 42 of 50 Pages


          other  shares of Common  Stock  issuable  pursuant to the terms of the
          Certificate,  whether as payment of a redemption  price or  otherwise,
          and any shares of capital  stock issued or issuable  from time to time
          (with any adjustments) in replacement of, in exchange for or otherwise
          in respect of the Conversion Shares or the Dividend Payment Shares.

     2.   MANDATORY REGISTRATION.
          ----------------------

          (a)  On or before the forty-fifth  (45th) day following  Closing,  the
Company shall prepare and file with the Commission a  Registration  Statement on
Form S-3 as a "shelf" registration  statement under Rule 415 covering the resale
of at least 200% of the number of shares of Registrable Securities then issuable
on  conversion  of  all of the  Preferred  Shares  issued  at the  Closing.  The
Registration  Statement shall state,  to the extent  permitted by Rule 416 under
the Securities Act, that it also covers such  indeterminate  number of shares of
Common Stock as may be required to effect  conversion of the Preferred Shares to
prevent dilution resulting from stock splits, stock dividends or similar events,
or by reason of changes in the Conversion  Price in accordance with the terms of
the Certificate.

          (b)  The Company shall use its best efforts to cause the  Registration
Statement  to become  effective  as soon as  practicable  following  the  filing
thereof, but in no event later than the Registration  Deadline, and shall submit
to the  Commission,  within five (5) business days after the Company learns that
no  review  of the  Registration  Statement  will be made  by the  staff  of the
Commission or that the staff of the  Commission  has no further  comments on the
Registration  Statement,  as the case may be, a request for  acceleration of the
effectiveness  of the  Registration  Statement to a time and date not later than
forty-eight  (48) hours after the  submission of such request,  and maintain the
effectiveness  of the  Registration  Statement until the earlier to occur of (i)
the date on which all of the  Registrable  Securities have been sold pursuant to
the  Registration  Statement  and (ii) the  date on which  all of the  remaining
Registrable  Securities (in the reasonable  opinion of counsel to the Purchaser)
may be immediately sold to the public without registration and without regard to
the amount of Registrable  Securities which may be sold by a Holder thereof at a
given time (the "Registration Period").
                 -------------------   
          

          (c)  If (A) the  Registration  Statement is not declared  effective by
the  Commission  on  or  before  the  Registration   Deadline,   (B)  after  the
Registration  Statement has been declared effective by the Commission,  sales of
Registrable  Securities  cannot  be  made by a  Holder  under  the  Registration
Statement for any reason not within the exclusive  control of such Holder (other
than such  Registrable  Securities as are then freely saleable  pursuant to Rule
144(k)  under the  Securities  Act),  (C) the Common  Stock is not  included for
quotation on the Nasdaq Stock Market  ("Nasdaq") or listed on the New York Stock
                                        ------
Exchange  or  other  national   securities   exchange  at  any  time  after  the
Registration  Deadline,  the  Company  shall  pay to each  Holder  an  amount (a
"Registration  Default  Payment")equal to the lesser of (x) two percent (2%) per
 ------------------------------
month  and  (y)  the  highest  rate  permitted  by  applicable  law,  times  the
Liquidation  Preference (as defined in the  Certificate) of the Preferred Shares
held  by  such  Holder,   accruing  daily  and  compounded  monthly,   from  the
Registration Deadline or, where the Registration Statement has become effective,
from  the  date on which  the  Registration  Statement  lapses  or is  otherwise
unavailable,  or the from the date on which  Common Stock is no longer so quoted
or  listed,  until  the date on which the  Registration  Statement  is  declared
effective or becomes  available for sales of Registrable  Securities or the date
on which the Common  Stock is  included  for  quotation  on Nasdaq or such other
national securities exchange, as the case may be; provided, however, that if the
Registration  Statement is not declared effective by the Registration  Deadline,
and such delay is not due to a failure by the Company to use its best efforts to



                                       -2-

<PAGE>


                                                             Page 43 of 50 Pages


cause  the  Registration  Statement  to  become  effective,   including  without
limitation a failure to respond  promptly to comments by the  Commission  on the
Registration  Statement,  the  Registration  Deadline  shall be extended  for an
additional thirty (30) days; and provided,  further,  that in no event shall the
aggregate of all  Registration  Default  Payments made by the Company  hereunder
exceed three million dollars  ($3,000,000).  The  Registration  Default Payments
paid or payable  by the  Company  hereunder  shall be in  addition  to any other
remedies  available  to a Holder at law or in equity or pursuant to the terms of
the Certificate or any other Transaction Document. Registration Default Payments
shall be made  within five (5) days after the end of each period that gives rise
to such  obligation,  provided  that,  if any such period  extends for more than
thirty (30) days, payments shall be made at the end of each thirty-day period.

3.        PIGGYBACK REGISTRATION.
          ----------------------

          If at any time prior to the expiration of the Registration Period, (i)
the Company proposes to register shares of Common Stock under the Securities Act
in  connection  with the public  offering  of such shares for cash (other than a
registration  relating  solely to the sale of  securities to  participants  in a
Company stock plan or employee stock award or a  registration  on Form S-4 under
the Securities Act or any successor or similar form  registering  stock issuable
upon a  reclassification,  a  business  combination  involving  an  exchange  of
securities or an exchange offer for securities of the issuer or another  entity)
(a "Proposed  Registration") and (ii) a registration statement covering the sale
    ---------------------- 
of all of the  Registrable  Securities  is not then  effective and available for
sales thereof by the Holders,  the Company  shall,  at such time,  promptly give
each Holder written notice of such Proposed Registration. Each Holder shall have
thirty  (30) days from its  receipt of such  notice to deliver to the  Company a
written request specifying the amount of Registrable Securities that such Holder
intends to sell and such Holder's intended method of distribution.  Upon receipt
of such request, the Company shall use its best efforts to cause all Registrable
Securities  which the Company has been  requested  to register to be  registered
under the Securities  Act to the extent  necessary to permit their sale or other
disposition in accordance with the intended methods of distribution specified in
the request of such Holder;  provided,  however, that the Company shall have the
                             --------   ------- 
right to postpone or withdraw any registration effected pursuant to this Section
3 without  obligation  to the Holder.  If, in connection  with any  underwritten
public  offering  for the account of the Company,  the  managing  underwriter(s)
thereof  shall impose a limitation on the number of shares of Common Stock which
may be included in the Registration  Statement because, in such  underwriter(s)'
judgment,  marketing or other  factors  dictate such  limitation is necessary to
facilitate public distributions,  then the Company shall be obligated to include
in such  Registration  Statement  only such limited  portion of the  Registrable
Securities with respect to which each Holder has requested  inclusion  hereunder
as such  underwriter(s)  shall permit.  Any exclusion of Registrable  Securities
shall be made  pro  rata  among  the  Holders  seeking  to  include  Registrable
Securities  in the  Registration  Statement,  in  proportion  to the  number  of
Registrable Securities sought to be included by such Holders; provided, however,
that the Company shall not exclude any Registrable Securities unless the Company
has first  excluded  all  outstanding  securities,  the holders of which are not
entitled to inclusion of such securities in such  Registration  Statement or are
not  entitled  to pro  rata  inclusion  with  the  Registrable  Securities;  and
provided,  further,  however,  that,  after  giving  effect  to the  immediately
preceding  proviso,  any exclusion of Registrable  Securities  shall be made pro
rata  with  holders  of  other  securities  having  the  right to  include  such
securities in the Registration Statement.

                                       -3-

<PAGE>


                                                             Page 44 of 50 Pages



4.        OBLIGATIONS OF THE COMPANY.
          --------------------------     

          In addition to performing its obligations  hereunder,  including those
pursuant to paragraphs 2(a) and 2(b) above, the Company shall:

          (a)  prepare  and  file  with  the  Commission   such  amendments  and
supplements to the Registration  Statement and the prospectus used in connection
with  the  Registration  Statement  as may  be  necessary  to  comply  with  the
provisions  of  the  Securities  Act or to  maintain  the  effectiveness  of the
Registration  Statement during the Registration  Period, or as may be reasonably
requested by a Holder in order to incorporate information concerning such Holder
or such Holder's intended method of distribution;

          (b)  in the  event  that the  number  of  shares  available  under the
Registration Statement filed by the Company hereunder is insufficient during any
period  of  three  consecutive  trading  days to cover  150% of the  Registrable
Securities  then  issued or  issuable,  the  Company  shall  promptly  amend the
Registration  Statement, or file a new Registration Statement, or both, so as to
cover 200% of such Registrable Securities,  in any event as soon as practicable,
but not later than the tenth  business day  following the last day of such three
day period.  Any  Registration  Statement filed pursuant to this Section 4 shall
state that, to the extent  permitted by Rule 416 under the Securities  Act, such
Registration  Statement  also covers  such  indeterminate  number of  additional
shares of Common Stock as may become issuable upon conversion of the Debentures.
Unless and until such amendment or new Registration Statement becomes effective,
each Holder shall have the rights described in paragraph 2(c) above;

          (c)  secure  the   designation   and  quotation  of  the   Registrable
Securities  on the Nasdaq  Stock  Market or the listing  thereof on the New York
Stock Exchange or the American Stock Exchange;

          (d)  furnish to each Holder  such  number of copies of the  prospectus
included in such Registration Statement,  including a preliminary prospectus, in
conformity with the requirements of the Securities Act, and such other documents
as such Holder may reasonably  request in order to facilitate the disposition of
such Holder's Registrable Securities;

          (e)  use all  commercially  reasonable  efforts to register or qualify
the  Registrable  Securities  under the  securities  or "blue  sky" laws of such
jurisdictions  within the United  States as shall be reasonably  requested  from
time to time by a Holder,  and do any and all other acts or things  which may be
necessary or advisable  to enable such Holder to  consummate  the public sale or
other disposition of the Registrable Securities in such jurisdictions;  provided
that the Company shall not be required in connection therewith or as a condition
thereto  to qualify to do  business  or to file a general  consent to service of
process in any such jurisdiction;

          (f)  in  the  event  of  an   underwritten   public  offering  of  the
Registrable  Securities  pursuant  to  Sections  2 or 3 hereof,  enter  into and
perform its obligations under an underwriting  agreement, in usual and customary
form reasonably acceptable to the Company, with the managing underwriter of such
offering;

          (g)  notify each Holder  immediately  upon the occurrence of any event
as a result of which the prospectus included in such Registration  Statement, as



                                       -4-

<PAGE>


                                                             Page 45 of 50 Pages

then in effect,  contains an untrue statement of material fact or omits to state
a  material  fact  required  to be  stated  therein  or  necessary  to make  the
statements  therein not misleading in light of the circumstances  then existing,
and as  promptly  as  practicable,  prepare,  file and  furnish to each Holder a
reasonable  number of copies of a supplement or an amendment to such  prospectus
as may be necessary so that such prospectus does not contain an untrue statement
of material fact or omit to state a material fact required to be stated  therein
or  necessary  to make the  statements  therein not  misleading  in light of the
circumstances then existing;

          (h) use all commercially reasonable efforts to prevent the issuance of
any stop order or other order suspending the  effectiveness of such Registration
Statement and, if such an order is issued,  to obtain the withdrawal  thereof at
the  earliest  possible  time and to notify each Holder of the  issuance of such
order and the resolution thereof;

          (i)  furnish  to each  Holder,  on the  date  that  such  Registration
Statement becomes effective, (x) an opinion, dated such date, of outside counsel
representing the Company (and reasonably acceptable to such Holder) addressed to
such Holder,  regarding the effectiveness of the Registration  Statement and the
absence of any stop order,  and (y) in the case of an  underwriting  pursuant to
Sections  2 or 3 hereof,  (A) an  opinion,  dated  such  date,  of such  outside
counsel,  in form and substance as is customarily  given to  underwriters  in an
underwritten  public  offering,  and (B) a letter,  dated  such  date,  from the
Company's independent certified public accountants,  in form and substance as is
customarily given by independent certified public accountants to underwriters in
an underwritten public offering,  addressed to the underwriters,  if any, and to
each Holder;

          (j) provide each Holder and its  representatives  the  opportunity  to
conduct a reasonable inquiry of the Company's financial and other records during
normal  business hours and make available its officers,  directors and employees
for questions regarding  information which such Holder may reasonably request in
order to fulfill any due diligence obligation on its part; and

          (k) permit  counsel  for each  Holder (at such  Holder's  expense)  to
review such Registration  Statement and all amendments and supplements thereto a
reasonable period of time prior to the filing thereof with the Commission.

     5.   OBLIGATIONS OF EACH HOLDER.
          --------------------------

         In  connection  with the  registration  of the  Registrable  Securities
pursuant to the Registration Statement, each Holder shall:

               (a) furnish to the Company in writing such information  regarding
itself and the intended  method of disposition of Registrable  Securities as the
Company shall reasonably request in order to effect the registration thereof;

               (b) upon receipt of any notice from the Company of the  happening
of any  event of the  kind  described  in  paragraph  4(g) or 4(h),  immediately
discontinue  disposition of Registrable  Securities pursuant to the Registration
Statement  until the  filing  of the  supplement  or  amendment  referred  to in
paragraph  4(g) or withdrawal of the stop order  referred to in paragraph  4(h);
and


                                       -5-

<PAGE>


                                                             Page 46 of 50 Pages


               (c) in the event of an  underwritten  offering of the Registrable
Securities  pursuant  to  Sections  2 or 3 hereof,  enter into a  customary  and
reasonable  underwriting  agreement  and  execute  such other  documents  as the
managing underwriter for such offering may reasonably request.

     6.   INDEMNIFICATION.
          ---------------

          In the  event  that  any  Registrable  Securities  are  included  in a
Registration Statement under this Agreement:

          (a)  To the extent  permitted by law, the Company shall  indemnify and
hold  harmless  each Holder,  the  officers,  directors,  employees,  agents and
representatives  of such  Holder,  and each person,  if any,  who controls  such
Holder within the meaning of the Securities  Act or the Securities  Exchange Act
of 1934,  as amended  (the "1934  Act"),  against any losses,  claims,  damages,
liabilities  or reasonable  out-of-pocket  expenses  (whether  joint or several)
(collectively,   including  legal  or  other  expenses  reasonably  incurred  in
connection with investigating or defending same, "Losses"),  insofar as any such
Losses arise out of or are based upon (i) any untrue statement or alleged untrue
statement of a material fact contained in such Registration Statement, including
any  preliminary  prospectus  or  final  prospectus  contained  therein  or  any
amendments or supplements  thereto,  or (ii) the omission or alleged omission to
state  therein a material fact  required to be stated  therein,  or necessary to
make the statements therein, in light of the circumstances under which they were
made, not  misleading.  The Company will  reimburse  such Holder,  and each such
officer, director, employee, agent, representative or controlling person for any
legal or other  expenses as reasonably  incurred by any such entity or person in
connection with investigating or defending any Loss; provided, however, that the
foregoing indemnity shall not apply to amounts paid in settlement of any Loss if
such  settlement is effected  without the consent of the Company  (which consent
shall not be  unreasonably  withheld),  nor shall the  Company be  obligated  to
indemnify  any person for any Loss to the extent that such Loss arises out of or
is based upon and in  conformity  with  written  information  furnished  by such
person expressly for use in such Registration Statement; and provided,  further,
that the Company  shall not be required  to  indemnify  any person to the extent
that any Loss results from such person selling  Registrable  Securities (i) to a
person  to whom  there  was not  sent  or  given,  at or  prior  to the  written
confirmation  of the  sale of such  shares,  a copy of the  prospectus,  as most
recently  amended or  supplemented,  if the Company has previously  furnished or
made available copies thereof or (ii) during any period following written notice
by the Company to such Holder of an event described in Section 4(g) or 4(h).

          (b)  To the extent permitted by law, each Holder, acting severally and
not jointly,  shall  indemnify  and hold  harmless the  Company,  the  officers,
directors,  employees,  agents  and  representatives  of the  Company,  and each
person,  if any, who controls the Company  within the meaning of the  Securities
Act or the 1934 Act,  against  any Losses to the extent (and only to the extent)
that any such  Losses  arise out of or are  based  upon and in  conformity  with
written  information  furnished  by  such  Holder  expressly  for  use  in  such
Registration  Statement;  and such  Holder  will  reimburse  any  legal or other
expenses as reasonably  incurred by the Company and any such officer,  director,
employee,  agent,  representative,  or controlling  person,  in connection  with
investigating or defending any such Loss; provided,  however, that the foregoing
indemnity shall not apply to amounts paid in settlement of any such Loss if such
settlement is effected  without the consent of such Holder,  which consent shall
not be unreasonably  withheld;  provided,  that, in no event shall any indemnity
under this  subsection  6(b) exceed the net purchase price of securities sold by
such Holder under the Registration Statement.

                                       -6-

<PAGE>


                                                             Page 47 of 50 Pages



          (c)  Promptly after receipt by an indemnified party under this Section
6 of  notice of the  commencement  of any  action  (including  any  governmental
action),  such  indemnified  party will, if a claim in respect  thereof is to be
made  against  any  indemnifying  party  under this  Section  6,  deliver to the
indemnifying  party  a  written  notice  of the  commencement  thereof  and  the
indemnifying  party  shall  have the right to  participate  in and to assume the
defense thereof with counsel  mutually  satisfactory  to the parties;  provided,
however,  that an  indemnified  party  shall  have the right to  retain  its own
counsel,  with the reasonably  incurred fees and expenses of one such counsel to
be paid by the indemnifying  party, if  representation of such indemnified party
by the counsel retained by the indemnifying  party would be inappropriate  under
applicable  standards  of  professional  conduct  due  to  actual  or  potential
conflicting  interests  between  such  indemnified  party  and any  other  party
represented by such counsel in such  proceeding.  The failure to deliver written
notice to the indemnifying party within a reasonable time of the commencement of
any such action, to the extent prejudicial to its ability to defend such action,
shall relieve such indemnifying  party of any liability to the indemnified party
under this Section 6 with respect to such action, but the omission so to deliver
written  notice to the  indemnifying  party will not relieve it of any liability
that it may have to any indemnified party otherwise than under this Section 6 or
with respect to any other action.

          (d)  In the event that the indemnity  provided in paragraph (a) or (b)
of this Section 6 is unavailable or insufficient to hold harmless an indemnified
party for any  reason,  the Company and each  Holder  agree,  severally  and not
jointly,  to  contribute  to the  aggregate  Losses to which the Company or such
Holder  may be subject  in such  proportion  as is  appropriate  to reflect  the
relative fault of the Company and such Holder in connection  with the statements
or omissions which resulted in such Losses;  provided,  however, that in no case
shall such Holder be  responsible  for any amount in excess of the net  purchase
price of securities sold by it under the Registration Statement.  Relative fault
shall be  determined  by  reference to whether any alleged  untrue  statement or
omission relates to information  provided by the Company or by such Holder.  The
Company  and each  Holder  agree  that it would  not be just  and  equitable  if
contribution  were  determined  by pro rata  allocation  or any other  method of
allocation which does not take account of the equitable  considerations referred
to above. Notwithstanding the provisions of this paragraph (d), no person guilty
of  fraudulent  misrepresentation  (within the  meaning of Section  11(f) of the
Securities  Act) shall be  entitled to  contribution  from any person who is not
guilty of such  fraudulent  misrepresentation.  For  purposes of this Section 6,
each person who  controls a Holder  within the meaning of either the  Securities
Act or  the  Exchange  Act  and  each  officer,  director,  employee,  agent  or
representative of such Holder shall have the same rights to contribution as such
Holder,  and each person who controls  the Company  within the meaning of either
the  Securities  Act or the Exchange Act and each officer,  director,  employee,
agent  or   representative  of  the  Company  shall  have  the  same  rights  to
contribution  as the Company,  subject in each case to the applicable  terms and
conditions of this paragraph (d).

          (e)  The obligations of the Company and each Holder under this Section
6 shall survive the conversion or redemption,  if any, of the Preferred  Shares,
the  completion  of  any  offering  of  Registrable  Securities  pursuant  to  a
Registration Statement under this Agreement, or otherwise.


                                       -7-

<PAGE>


                                                             Page 48 of 50 Pages


     7.   REPORTS.
          -------

          With a view to making  available  to each Holder the  benefits of Rule
144  under the  Securities  Act  ("Rule  144")  and any  other  similar  rule or
regulation  of the  Commission  that may at any time  permit such Holder to sell
securities of the Company to the public without registration, the Company agrees
to:

          (a)  make and keep public  information  available,  as those terms are
understood and defined in Rule 144;

          (b)  file with the Commission in a timely manner all reports and other
documents required of the Company under the Securities Act and the 1934 Act; and

          (c)  furnish  to  such  Holder,  so  long  as  such  Holder  owns  any
Registrable  Securities,  forthwith upon request (i) a written  statement by the
Company,  if true, that it has complied with the reporting  requirements of Rule
144, the  Securities Act and the 1934 Act, (ii) a copy of the most recent annual
or quarterly report of the Company and such other reports and documents so filed
by the Company,  and (iii) such other information as may be reasonably requested
in  availing  such  Holder of any rule or  regulation  of the  Commission  which
permits the selling of any such securities without registration.

     8.   MISCELLANEOUS.
          -------------

          (a)  Expenses of Registration.  All expenses,  other than underwriting
               ------------------------
discounts  and  commissions  and fees and  expenses  of counsel to each  Holder,
incurred  in  connection  with  the  registrations,  filings  or  qualifications
described herein,  including (without  limitation) all registration,  filing and
qualification fees, printers' and accounting fees, the fees and disbursements of
counsel for the Company,  and the fees and disbursements  incurred in connection
with the opinion and letter  described in paragraph 4(i) hereof,  shall be borne
by the Company.

          (b)  Amendment; Waiver. Any provision of this Agreement may be amended
               -----------------
               only pursuant to a written instrument executed by the Company and
               Holders  of  two-thirds  (2/3)  of  the  outstanding  Registrable
               Securities. Any waiver of the provisions of this Agreement may be
               made only pursuant to a written instrument  executed by the party
               against  whom  enforcement  is sought.  Any  amendment  or waiver
               effected in accordance  with this paragraph shall be binding upon
               each Holder, each future Holder, and the Company.  The failure of
               any party to exercise any right or remedy under this Agreement or
               otherwise,  or the delay by any party in exercising such right or
               remedy, shall not operate as a waiver thereof.

          (c)  Notices.  Any notice,  demand or request required or permitted to
               -------
               be given by any party to any other party pursuant to the terms of
               this Agreement  shall be in writing and shall be deemed given (i)
               when delivered personally or by verifiable facsimile transmission
               (with an  original  to  follow) on or before  5:00 p.m.,  eastern
               time, on a business day or, if such day is not a business day, on
               the next  succeeding  business day, (ii) on the next business day
               after  timely  delivery  to  a  nationally-recognized   overnight
               courier and (iii) on the third  business day after deposit in the
               U.S.  mail   (certified  or  registered   mail,   return  receipt
               requested, postage prepaid), addressed to the parties as follows:


                                       -8-

<PAGE>


                                                             Page 49 of 50 Pages


     If to the Company:

     IGEN International, Inc.
     16020 Industrial Drive
     Gaithersburg, MD 20817
     Attn:     Messrs. Samuel J. Wohlstadter
               George V. Migausky
               Dr. Richard J. Massey
     Fax:

     with a copy to:

     Wilmer, Cutler & Pickering
     2445 M Street, N.W.
     Washington, DC  20037
     Attn:     Stephen P. Doyle, Esq.
     Fax:      202-663-6363

and if to any Holder,  to such address as shall be  designated by such Holder in
writing to the Company.

          (d)  Termination.  This  Agreement  shall  terminate on the earlier to
               -----------
occur of (a) the end of the Registration Period and (b) the date on which all of
the  Registrable  Securities  have  been  publicly  distributed;  but  any  such
termination   shall  be  without  prejudice  to  (i)  the  parties'  rights  and
obligations  arising from  breaches of this  Agreement  occurring  prior to such
termination and (ii) the indemnification and contribution obligations under this
Agreement.

          (e)  Assignment.  The rights of a Holder  hereunder  shall be assigned
               ----------
automatically   to  any  transferee  of  the  Preferred  Shares  or  Registrable
Securities  from such Holder as long as: (i) the Company is, within a reasonable
period of time  following  such  transfer,  furnished with written notice of the
name and address of such transferee,  (ii) the transferee agrees in writing with
the Company to be bound by all of the provisions  hereof and (iii) such transfer
is made in accordance with the applicable requirements of the Purchase Agreement
and the Certificate.

          (f)  Counterparts.  This  Agreement  may be  executed  in two or  more
               ------------
counterparts,  each of  which  shall be  deemed  an  original,  and all of which
together  shall be deemed  one and the same  instrument.  This  Agreement,  once
executed by a party,  may be  delivered  to any other party  hereto by facsimile
transmission.

          (g)  Governing Law. This Agreement  shall be governed by and construed
               -------------
in  accordance  with the laws of the  State of New York  without  regard  to the
conflict of laws provisions thereof.

                                       -9-

<PAGE>


                                                             Page 50 of 50 Pages



          IN WITNESS WHEREOF, the undersigned have executed this Agreement as of
the date first-above written.

IGEN INTERNATIONAL, INC.


By: __________________________
     Name:
     Title:


PURCHASER NAME:  ______________________________


By: _________________________
     Name:
     Title:






                                      -10-



© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission