SCHEDULE 14A INFORMATION
                                 (Rule 14a-101)

           Proxy Statement Pursuant to Section 14(a) of the Securities
                              Exchange Act of 1934

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|X| Preliminary Proxy Statement               |_| Confidential, for Use of the
|_| Definitive Proxy Statement                    Commission Only (as
|_| Definitive Additional Materials               permitted by Rule 14a-6(e)(2))
|_| Soliciting Material Pursuant to
    Rule 14a-12

                              REPLIGEN CORPORATION
                (Name of Registrant as Specified in Its Charter)

    ------------------------------------------------------------------------
    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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                                 NOT APPLICABLE

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          pursuant to Exchange Act Rule 0-11 (Set forth the amount on which
          the filing fee is calculated and state how it was determined):

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                                                     PRELIMINARY PROXY MATERIALS

                              Repligen Corporation
                           41 Seyon Street, Building 1
                                Waltham, MA 02453
                                 (781-250-0111)

                                   ----------

                    NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

                                   ----------

To the Stockholders:

      The Annual Meeting of Stockholders of Repligen Corporation, a Delaware
Corporation ("Repligen") will be held on Thursday, September 12, 2002, 10:00
a.m. local time, at the offices of Repligen, 41 Seyon Street, Building 1,
Waltham, Massachusetts for the following purposes:

1.    To elect five members to the Board of Directors to serve for staggered
      terms or, if Proposal 2 is not adopted by the stockholders, to elect five
      members to the Board of Directors to serve for a term of one year, and
      until their successors are elected and qualified, or until their earlier
      death, resignation or removal;

2.    To consider and vote upon a proposal to approve an amended and restated
      certificate of incorporation and amended and restated by-laws that
      together (a) establish a classified board of directors having three
      classes with staggered three-year terms, (b) eliminate stockholder actions
      by written consent, (c) eliminate the right of stockholders to call
      special stockholder meetings and restrict the right of stockholders to
      bring nominations and other business before regular stockholder meetings,
      (d) establish that directors may be removed by the stockholders only for
      cause upon a vote of 75% of the shares of the Company's capital stock
      entitled to vote at the election of directors, (e) provide that, with
      certain limited exceptions, the provisions of the amended and restated
      certificate of incorporation may be amended only upon a vote of 75% of the
      voting power of all outstanding shares of the Company's capital stock
      entitled to vote generally in the election of directors, voting together
      as a single class, (f) provide that the amended and restated by-laws may
      be amended by majority vote of the directors present at any meeting of the
      Board of Directors at which a quorum is present or upon the vote of 75% of
      the voting power of all outstanding shares of the Company's capital stock
      entitled to vote generally in the election of directors, voting together
      as a single class and (g) delineate certain factors that the Board of
      Directors may consider when evaluating an offer of another party to make a
      tender or exchange offer or to effect a business combination.

3.    To ratify the selection of Ernst & Young LLP as the independent auditors
      of Repligen for the fiscal year ending March 31, 2003;

4.    To transact such other business as may properly come before the Annual
      Meeting and any adjournments thereof.

      Stockholders entitled to notice of and to vote at the Annual Meeting shall
be determined as of the close of business on July 15, 2002, the record date
fixed by the Board of Directors for such purpose.

                                        By Order of the Board of Directors


                                        Daniel P. Witt, Secretary

Waltham, Massachusetts
July ___, 2002



--------------------------------------------------------------------------------
IT IS IMPORTANT THAT YOUR SHARES BE REPRESENTED AT THE MEETING. WHETHER OR NOT
YOU PLAN TO ATTEND THE MEETING IN PERSON, YOU ARE REQUESTED TO COMPLETE, SIGN,
DATE AND MAIL PROMPTLY THE ENCLOSED PROXY WHICH IS BEING SOLICITED ON BEHALF OF
THE BOARD OF DIRECTORS. A RETURN ENVELOPE WHICH REQUIRES NO POSTAGE IF MAILED IN
THE UNITED STATES IS ENCLOSED FOR THAT PURPOSE. YOU MAY ALSO VOTE BY TELEPHONE
OR VIA THE INTERNET IN ACCORDANCE WITH THE INSTRUCTIONS LISTED ON THE PROXY
CARD.
--------------------------------------------------------------------------------



                              REPLIGEN CORPORATION
                           41 SEYON STREET, BUILDING 1
                                WALTHAM, MA 02453

                  ---------------------------------------------
                                 PROXY STATEMENT
                     FOR THE ANNUAL MEETING OF STOCKHOLDERS
                        TO BE HELD ON SEPTEMBER 12, 2002
                  ---------------------------------------------
                                 July ___, 2002

      Proxies in the form included with this proxy statement are solicited by
the Board of Directors (the "Board") of Repligen Corporation, a Delaware
corporation ("Repligen" or "Company"), for use at the Annual Meeting of
Stockholders of Repligen to be held, pursuant to the accompanying Notice of
Annual Meeting, on Thursday, September 12, 2002, 10:00 a.m. local time, or at
any adjournments thereof (the "Annual Meeting" or the "Meeting"), at Repligen's
principal executive offices at 41 Seyon Street, Building 1, Waltham,
Massachusetts 02453. Only stockholders of record as of July 15, 2002 (the
"Record Date") will be entitled to notice of and to vote at the Meeting and any
adjournments thereof. As of the Record Date, __________ shares of Common Stock,
$.01 par value (the "Common Stock"), of Repligen were issued and outstanding.

      Repligen's Annual Report to Stockholders, containing financial statements
for the fiscal year ended March 31, 2002, is being provided together with this
proxy statement to all stockholders entitled to vote. It is anticipated that
this proxy statement and the accompanying proxy will be first provided to
stockholders on or about August 8, 2002.

      The holders of Common Stock are entitled to one vote per share on any
proposal presented at the Annual Meeting. Stockholders may vote in person or by
proxy. Stockholders may vote by proxy by completing, signing, dating and
returning the accompanying proxy card or by voting by telephone or via the
internet in accordance with the instructions listed on the proxy card. Execution
of a proxy will not in any way affect a stockholder's right to attend the Annual
Meeting and vote in person. Any proxy given pursuant to this solicitation may be
revoked by the person giving it any time before it is voted. Proxies may be
revoked by: (1) filing with the Secretary of Repligen, or by telephone or
internet, in accordance with the instructions listed on the proxy card, before
the taking of the vote at the Annual Meeting, a written notice of revocation
bearing a later date than the proxy; (2) duly executing a later-dated proxy
relating to the same shares and delivering it to the Secretary of Repligen
before the taking of the vote at the Annual Meeting; or (3) attending the Annual
Meeting and voting in person (although attendance at the Annual Meeting will not
in and of itself constitute a revocation of a proxy). For those stockholders who
submit a proxy by telephone or via the internet, the date on which the proxy is
submitted in accordance with the instructions listed on the proxy card is the
date of the proxy. Any written notice of revocation or subsequent proxy should
be sent so as to be delivered to Repligen Corporation, 41 Seyon Street, Building
1, Waltham, Massachusetts 02453, Attention: Secretary, at or before the taking
of the vote at the Annual Meeting.

      Each of the persons named as attorneys in the proxies is a director and/or
officer of Repligen. All properly executed proxies returned in time to be
counted at the Annual Meeting will be voted as stated below under the heading
"Voting Procedures." Any stockholder submitting a proxy has the right to
withhold authority to vote for any individual nominee to the Board by writing
that nominee's name on the space provided on the proxy, checking the box next to
the name of such individual if voting by proxy via the internet or, if using the
telephone to vote by proxy, by following the verbal instructions for entering
the two digit number appearing on the proxy card immediately before the name of
such individual. In addition to the election of Directors, the stockholders will
consider and vote upon a proposal to ratify the selection of auditors and will
consider and vote upon a proposal to amend and restate Repligen's existing
certificate of incorporation and by-laws, as further described in this proxy
statement. Where a choice has been specified on the proxy with respect to a
matter, the shares represented by the proxy will be voted in accordance with the
specifications and will be voted FOR if no specification is indicated.

      The Board knows of no other matters to be presented at the Annual Meeting.
If any other matter should be presented at the Annual Meeting upon which a vote
properly may be taken, shares represented by all proxies received by the Board
will be voted with respect thereto in accordance with the judgment of the
persons named as attorneys in the proxies.


                                       2


                                VOTING PROCEDURES

      The representation, in person or by proxy, of at least a majority of the
outstanding shares of Common Stock entitled to vote at the Annual Meeting is
necessary to constitute a quorum for the transaction of business. Shares
represented by proxies pursuant to which votes have been withheld from any
nominee for director, or which contain one or more abstentions or broker
"non-votes," are counted as present or represented for purposes of determining
the presence or absence of a quorum for the Annual Meeting. A "non-vote" occurs
when a broker or other nominee holding shares for a beneficial owner votes on
one proposal, but does not vote on another proposal because the broker does not
have discretionary voting power and has not received instructions from the
beneficial owner.

      Election of Directors. Directors are elected by plurality of the votes
cast, in person or by proxy, at the Annual Meeting. The five nominees who
receive the highest number of affirmative votes of the shares present or
represented and voting on the election of directors at the Annual Meeting will
be elected to the Board of Directors. Shares present or represented and not so
marked as to withhold authority to vote for a particular nominee will be voted
in favor of a particular nominee and will be counted toward such nominee's
achievement of a plurality. Shares present at the meeting or represented by
proxy where the stockholder properly withholds authority to vote by marking the
"WITHHOLD" box on the proxy for such nominee will not be counted toward such
nominee's achievement of plurality.

      Amendment and Restatement of Repligen's Certificate of Incorporation and
By-laws. Approval of the proposal to amend and restate Repligen's existing
certificate of incorporation and by-laws will require the affirmative vote of a
majority of the outstanding shares of Common Stock of Repligen entitled to vote
on the proposal. Shares voted to abstain and shares subject to broker
"non-votes" are not considered to have voted for the proposal and have the
practical effect of a vote against the proposal.

      Other Matters. For all other matters being submitted to stockholders at
the Annual Meeting, the affirmative vote of the majority of shares present, in
person or represented by proxy, and voting on that matter is required for
approval. Shares voted to abstain are included in the number of shares present
or represented and voting on each matter. Shares subject to broker "non-votes"
are not considered to have been voted for the particular matter and have the
practical effect of reducing the number of affirmative votes required to achieve
a majority for such matter by reducing the total number of shares from which the
majority is calculated.

      EquiServe will serve as the Inspector of Elections and will count all
votes and ballots.


                                       3


                     PRINCIPAL HOLDERS OF VOTING SECURITIES

      The following table sets forth, as of June 30, 2002, the name of each
person who, to Repligen's knowledge, beneficially owned more than 5% of the
shares of Common Stock of Repligen outstanding at that date, the number of
shares beneficially owned by each of these persons, and the percentage of the
outstanding shares of the Company beneficially owned by each of these persons.



Name and Address of                                Amount and Nature of     Percent of
  Beneficial Owner                               Beneficial Ownership (1)    Class (2)
-------------------                              ------------------------   ----------
                                                                        
Lindsay A. Rosenwald, M.D. (3) ................         1,786,900              6.7%
c/o Paramount Capital Asset Management, Inc.
787 Seventh Avenue
New York, NY 10019

BVF Partners L.P. (4) .........................         3,370,400             12.7%
333 West Wacker Drive
Chicago, IL 60606


----------
(1)   Beneficial ownership, as such terms is used herein, is determined in
      accordance with Rule 13d-3(d)(1) promulgated under the Securities Exchange
      Act of 1934 and includes voting and/or investment power with respect to
      shares of Common Stock of Repligen. Unless otherwise indicated, the named
      person possesses sole voting and investment power with respect to the
      shares. The shares shown include shares issuable pursuant to options or
      warrants held by the named person that may be exercised within 60 days of
      the dates indicated below.

(2)   Percentages of ownership are based upon the number of shares of Common
      Stock issued and outstanding as of the dates indicated in the respective
      footnotes. Shares of Common Stock that may be acquired pursuant to options
      or warrants that are exercisable within 60 days of such date are deemed
      outstanding for computing the percentage ownership of the person holding
      such options or warrants, but are not deemed outstanding for the
      percentage ownership of any other person.

(3)   Paramount Capital Asset Management, Inc. ("PCAM") is the general partner
      of the Aries Domestic Fund II, L.P. ("Aries II"), a Delaware limited
      partnership, and also serves as the investment manager of the Aries Master
      Fund II, a Cayman Island exempted company (the "Master Fund"). Dr. Lindsay
      Rosenwald is the chairman and sole stockholder of PCAM. As a result, Dr.
      Rosenwald and PCAM may be deemed to have voting and investment control
      over the securities of Repligen held by Aries II and the Master Fund. Dr.
      Rosenwald and PCAM disclaim beneficial ownership of the securities held by
      Aries II and the Master Fund, except to the extent of their pecuniary
      interest therein, if any.

      Securities beneficially owned by Dr. Rosenwald are presented on an as
      converted basis and consist of the following as of May 31, 2002:

            a)    1,449,909 shares of Common Stock owned by the Master Fund,

            b)    304,241 shares of Common Stock owned by Aries II, and

            c)    32,750 shares of Common Stock which may be acquired upon the
                  exercise of presently exercisable warrants owned directly by
                  Dr. Rosenwald.

(4)   According to a Form 4 filed on June 10, 2002, Biotechnology Value Fund,
      L.P. ("BVF") shares voting and dispositive power over the shares of the
      Common Stock it beneficially owns with BVF Partners L.P. ("Partners").
      Biotechnology Value Fund II, L.P. ("BVF2") also shares voting and
      dispositive power over the shares of the Common Stock it beneficially owns
      with Partners. BVF Investments, L.L.C. ("Investments") also shares voting
      and dispositive power over the shares of the Common Stock it beneficially
      owns with Partners. Partners and BVF Inc. share voting and dispositive
      power over the shares of the Common Stock they beneficially own with, in
      addition to BVF, BVF2 and Investments, certain managed accounts on whose
      behalf Partners, as investment manager, purchased such shares. None of the
      managed accounts individually owns more than 5% of the Common Stock of
      Repligen. As of May 31, 2002, securities beneficially owned by BVF Inc.
      consist of the following:

            a)    1,108,000 shares of Common Stock owned by BVF,

            b)    697,179 shares of Common Stock owned by BVF2, and

            c)    1,565,221 shares of Common Stock owned by Investments.

                                   PROPOSAL 1
                              ELECTION OF DIRECTORS

      The number of directors is currently fixed at five. There are five
nominees for director. The five nominees are Walter C. Herlihy, Ph.D., Robert J.
Hennessey, G. William Miller, Alexander Rich, M.D. and Paul Schimmel, Ph.D. All
five nominees are currently directors of Repligen.


                                       4


      If Proposal 2 is approved by the stockholders, the Board will be divided
into three classes, with Class I Directors to serve on the Board until the
annual meeting in 2003, Class II Directors to serve on the Board until the
annual meeting in 2004, and Class III Directors to serve on the Board until the
annual meeting in 2005 and, in each case, until their successors have been duly
elected and qualified, or until such director's earlier death, resignation or
removal. The following table sets forth the nominees to be elected at the Annual
Meeting, the year each such nominee was first elected a director, the position
or positions with Repligen currently held by each nominee, and if Proposal 2 is
approved by the stockholders, the class of director of each nominee and the year
in which such nominee's term will expire:



                                                                             (If Proposal 2 Approved)
                                                                         -------------------------------
       Nominee's Name and
       Year Nominee First                                                                     Year Term
        Became A Director              Position(s) with the Company      Class of Director   Will Expire
    ------------------------       ----------------------------------    -----------------   -----------
                                                                                        
    Walter C. Herlihy, Ph.D.       President, Chief Executive Officer            I               2003
    1996                           and Director

    Robert J. Hennessey            Director                                     II               2004
    1998

    G. William Miller              Director                                     II               2004
    1982

    Alexander Rich, M.D.           Director                                     III              2005
    1981

    Paul Schimmel, Ph.D.           Director                                     III              2005
    1981


Alternatively, if Proposal 2 is not approved by the stockholders, the directors
of the Company will be elected to hold office until the next annual meeting of
stockholders and until their successors have been duly elected and qualified, or
until their earlier death, resignation or removal.

      Shares represented by all proxies received by the Board and not marked or
voted so as to withhold authority to vote for any individual director or for any
group of directors will be voted (unless one or more nominees are unable or
unwilling to serve) for the election of the nominees named above. The Board
knows of no reason why any nominee should be unable or unwilling to serve, but
if any nominee should be unable or unwilling to serve, proxies will be voted or
withheld in accordance with the judgment of the persons named as attorneys in
the proxies with respect to the directorship for which that nominee was unable
or unwilling to serve.

      The Board unanimously recommends a vote FOR each of the nominees for
election as directors.

                 Occupations Of Directors And Executive Officers

      Repligen's executive officers are appointed by, and serve at the
discretion of, the Board. Each executive officer is a full-time employee of
Repligen. The directors and executive officers of Repligen are as follows:



        Name                        Age                    Positions
        ----                        ---                    ---------
                                    
Walter C. Herlihy, Ph.D. (3).....    50   President, Chief Executive Officer and Director

James R. Rusche, Ph.D............    48   Senior Vice President, Research and Development

Daniel P. Witt, Ph.D.............    55   Vice President, Business Development

Robert J. Hennessey (2)(4).......    60   Director

G. William Miller (1)(2)(3)(4)...    77   Director

Alexander Rich, M.D (2)..........    77   Director

Paul Schimmel, Ph.D. (1)(3)......    61   Director


----------
(1)   Member of the Compensation Committee

(2)   Member of the Audit Committee

(3)   Member of the Executive Committee

(4)   Member of the Nominating Committee

                            Biographical Information

Walter C. Herlihy, Ph.D. joined Repligen in March 1996 as President, Chief
Executive Officer and Director in connection with Repligen's merger with Glycan
Pharmaceuticals, Inc. From July 1993 to March 1996, Dr. Herlihy was the
President and CEO of Glycan Pharmaceuticals, Inc. From October 1981 to June
1993, he held numerous research positions at Repligen, most recently as Senior
Vice President, Research and Development. Dr. Herlihy holds an A.B. degree in
chemistry from Cornell University and a Ph.D. in chemistry from MIT.


                                       5


James R. Rusche, Ph.D. joined Repligen in March 1996 as Vice President, Research
and Development in connection with Repligen's merger with Glycan
Pharmaceuticals, Inc. In January 2002, Dr. Rusche became Senior Vice President,
Research and Development. From July 1994 to March 1996, Dr. Rusche was Vice
President, Research and Development of Glycan Pharmaceuticals, Inc. From
February 1985 to June 1994, he held numerous research positions at Repligen,
most recently as Vice President, Discovery Research. Dr. Rusche holds a B.S.
degree in microbiology from the University of Wisconsin, LaCrosse and a Ph.D. in
immunology from the University of Florida.

Daniel P. Witt, Ph.D. joined Repligen in March 1996 as Vice President, Business
Development in connection with Repligen's merger with Glycan Pharmaceuticals,
Inc. From October 1993 to March 1996, Dr. Witt was Vice President, Business
Development of Glycan Pharmaceuticals, Inc. From April 1983 to September 1993,
he held numerous research positions at Repligen, most recently as Vice
President, Technology Acquisition. Dr. Witt holds a B.A. degree in chemistry
from Gettysberg College and a Ph.D. in biochemistry from the University of
Vermont.

Robert J. Hennessey has served as a director of Repligen since July 1998. Mr.
Hennessey is currently the Chairman of the Board of Genome Therapeutics Corp., a
biotechnology company. From 1993 to 2000, Mr. Hennessey also served as Chief
Executive Officer. From 1990 to 1993, Mr. Hennessey served as the President of
Hennessey & Associates Ltd., a strategic consulting firm to biotechnology and
healthcare companies. Prior to 1990, Mr. Hennessey held a variety of management
positions at Merck, SmithKline, Abbott and Sterling Drug. Mr. Hennessey is also
a director of PenWest Pharmaceuticals.

G. William Miller has served as a Director of Repligen since January 1982. Mr.
Miller is the Chairman of the Board of G. William Miller & Co., Inc., a private
merchant-banking firm. He has served in that capacity for over five years. From
January 1990 until February 1992, Mr. Miller was Chairman and Chief Executive
Officer of Federated Stores, Inc., an owner and operator of retail department
stores, supermarkets and real estate interests. Mr. Miller is a former Chairman
of the Board of Governors of the Federal Reserve System and served as Secretary
of the Treasury under President Carter. Mr. Miller is a director of the Simon
Property Group, Inc., a real estate investment trust, and GS Industries, Inc., a
producer of steel and related products. Mr. Miller is the Chairman of The H.
John Heinz Center for Science, Economics and the Environment, and Trustee of the
Marine Biological Laboratory.

Alexander Rich, M.D., Co-Founder and Co-Chairman of the Board of Directors of
Repligen, has been on the faculty of MIT since 1958 and is the Sedgwick
Professor of Biophysics. Internationally recognized for his contributions to the
molecular biology of nucleic acids, he has determined their three-dimensional
structure and has investigated their activity in biological systems. He is
widely known for his work in elucidating the three-dimensional structure of
transfer RNA, which is a component of the protein synthesizing mechanism and for
his discovery of a novel, left-handed form of DNA. He is a member of the
National Academy of Sciences, the American Philosophical Society, the Pontifical
Academy of Sciences, Rome and a foreign member of the French Academy of
Sciences, Paris. Dr. Rich has been a Director of Repligen since March 1981. Dr.
Rich is a director of Alkermes, Inc.

Paul Schimmel, Ph.D., Co-Founder and Co-Chairman of the Board of Directors of
Repligen, has been on the faculty of the Skaggs Institute of Chemical Biology at
Scripps Research Institute since 1997. He is well known for his work in
biophysical chemistry and molecular biology. His field of specialty is the
mechanism of action of proteins and the manner in which they act upon the
nucleic acids in the cell. This work involves broad applications of recombinant
DNA technology. He is a member of the National Academy of Sciences, received the
1978 ACS/Pfizer award for excellence in enzyme research, and is co-author of a
widely read textbook on biophysical chemistry. He also previously served as the
Chairman, Director of Biological Chemistry, American Chemical Society. Dr.
Schimmel has been a Director of Repligen since March 1981. Dr. Schimmel is a
director of Alkermes, Inc.

                 CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

      On March 9, 2000, Repligen sold an aggregate of 2,598,927 shares of Common
Stock to investors at $8.625 per share for an aggregate consideration of $22.4
million in a private placement pursuant to a stock purchase agreement by and
among the investors and Repligen. Paramount Capital, Inc. ("Paramount") acted as
the placement agent for the transaction and Repligen paid Paramount
approximately $1.57 million for its services plus Paramount's related
transactional expenses, and issued to Paramount a warrant to purchase up to
129,946 shares of our Common Stock at $9.49 per share. Repligen engaged
Paramount to act as placement agent for the private placement transaction
pursuant to a finder's agreement and Repligen terminated the financial advisory
agreement (described in the paragraph immediately below) with Paramount for an
additional payment by Repligen to Paramount of $200,000 in cash. Repligen
registered the 129,946 shares of Common Stock issuable upon exercise of the
warrant and the Securities and Exchange Commission declared such resale
registration statement effective on May 4, 2000.


                                       6


      Pursuant to a Financial Advisory Agreement dated as of July 15, 1999 by
and between Repligen and Paramount, Repligen engaged Paramount as a
non-exclusive financial adviser for an initial period of twelve months from the
date thereof. In exchange and as consideration for Paramount's financial
services, Repligen paid to Paramount $100,000 in cash and issued to Paramount
(and its designees) warrants to purchase an aggregate of 100,000 shares of
Common Stock of Repligen (the "Warrants"). Each Warrant is exercisable at $2.75
per share at any time prior to July 15, 2004. Pursuant to such Financial
Advisory Agreement, Repligen issued the Warrants to such designees in a private
placement transaction exempt from the registration requirements of the
Securities Act of 1933 pursuant to Regulation D, Rule 506 of the Securities Act
of 1933. There were no underwriters involved in such private placement
transaction. Repligen registered the shares underlying these Warrants and the
Securities and Exchange Commission declared such resale registration statement
effective on March 10, 2000.

      No family relationship exists among the officers and directors of
Repligen.

         INFORMATION REGARDING THE BOARD OF DIRECTORS AND ITS COMMITTEES

      The Board met four times during the fiscal year ended March 31, 2002.
During the fiscal year ended March 31, 2002, no director attended fewer than 75%
of the aggregate of (i) the total number of meetings of the Board and (ii) the
total number of meetings held by all committees of the Board on which such
director served.

      The Board has a standing Audit Committee, Compensation Committee,
Executive Committee and Nominating Committee. The Audit Committee, currently
consisting of Mr. Miller, Mr. Hennessey and Dr. Rich, is responsible for
determining the adequacy of Repligen's internal accounting and financial
controls. The Audit Committee met once with management and Repligen's
independent public accountants to review matters pertaining to the 2002 fiscal
year audit. No member of the Audit Committee is a member of Repligen's
management. The Compensation Committee, currently consisting of Dr. Schimmel and
Mr. Miller, is responsible for reviewing matters pertaining to the compensation
of Repligen's officers and the granting of stock options (other than stock
options which are automatically granted to certain members of the Board pursuant
to Repligen's stock option plan) and contributions to Repligen's Employee Stock
Ownership Plan. See "Compensation of Directors" and "Compensation Committee
Report to Shareholders." The Compensation Committee met once during the fiscal
year ended March 31, 2002. No member of the Compensation Committee is a member
of Repligen's management. The Executive Committee, currently consisting of Mr.
Miller, Dr. Schimmel and Dr. Herlihy (an employee of Repligen), is authorized to
exercise certain powers of the Board not specifically reserved to the Board by
Repligen's By-Laws or the General Corporation Law of the State of Delaware. The
Nominating Committee, currently consisting of Mr. Miller and Mr. Hennessey, is
responsible for identifying, reviewing and evaluating candidates to serve as
directors of Repligen and to recommend such candidates to the Board. The
Nominating Committee was formed in June 2002 and thus did not meet during the
fiscal year ended March 31, 2002. The Nominating Committee may, in its
discretion, consider potential candidates for membership on the Board that have
been recommended by stockholders. Any stockholder wishing to recommend a
potential candidate should submit a recommendation in writing to Repligen's
Secretary indicating the nominee's name, qualifications and other relevant
biographical information and providing confirmation of the nominee's consent to
serve as a director if nominated and elected. No member of the Nominating
Committee is a member of Repligen's management.


                                       7


               STOCK OWNERSHIP OF DIRECTORS AND EXECUTIVE OFFICERS

      The following table sets forth certain information as of June 30, 2002
with respect to beneficial ownership of shares of Repligen's Common Stock by all
directors and executive officers named in the Summary Compensation Table set
forth below under "Summary of Executive Compensation" individually, and by all
directors and executive officers of Repligen as a group.



                                                                     Amount and Nature of
Beneficial Owner                                                   Beneficial Ownership (1)   Percent of Class (2)
----------------                                                   ------------------------   --------------------
                                                                                                
Paul Schimmel, Ph.D. (3) ........................................          664,682                    2.5%
Alexander Rich, M.D. (4) ........................................          460,700                    1.7%
G. William Miller (5) ...........................................          129,000                      *
Robert J. Hennessey (6) .........................................           44,000                      *
Walter C. Herlihy (7) ...........................................          735,668                    2.7%
James R. Rusche (8) .............................................          246,668                      *
Daniel P. Witt (9) ..............................................          198,668                      *
All directors and executive officers as group (7 persons) (10) ..        2,482,386                    9.0%


----------
*     Less than one percent

(1)   Unless otherwise indicated, the named person possesses sole voting and
      investment power with respect to the shares. The shares shown include
      shares issuable pursuant to options held by the named person that may be
      exercised within 60 days of June 30, 2002.

(2)   Percentages of ownership are based upon 26,642,750 shares of Common Stock
      issued and outstanding as of June 30, 2002. Shares of Common Stock that
      may be acquired pursuant to options that are exercisable within 60 days of
      June 30, 2002 are deemed outstanding for computing the percentage
      ownership of the person holding such options, but are not deemed
      outstanding for the percentage ownership of any other person.

(3)   Includes 19,000 shares held by a trust for the benefit of Dr. Schimmel's
      sister, of which Dr. Schimmel is the trustee. Includes 30,000 shares
      issuable pursuant to stock options which are exercisable within 60 days of
      June 30, 2002.

(4)   Includes 60,000 shares held by Dr. Rich's spouse. Includes 30,000 shares
      issuable pursuant to stock options which are exercisable within 60 days of
      June 30, 2002.

(5)   Includes 59,000 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.

(6)   Includes 44,000 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.

(7)   Includes 580,000 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.

(8)   Includes 140,000 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.

(9)   Includes 109,500 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.

(10)  Includes 992,000 shares issuable pursuant to stock options which are
      exercisable within 60 days of June 30, 2002.


                                       8


                        SUMMARY OF EXECUTIVE COMPENSATION

                           Summary Compensation Table

      The table below shows compensation information with respect to services
rendered to Repligen in all capacities during the fiscal years ended March 31,
2002, 2001 and 2000 for the Chief Executive Officer and each of Repligen's other
most highly compensated executive or other officers who earned more than
$100,000 in salary and bonus in fiscal 2002 and were serving as executive
officers or such other officers as of March 31, 2002 (collectively, the "Named
Executive Officers").



                                                                                              Long-Term
                                                                                            Compensation(2)
                                                                                            ---------------
                                                            Annual Compensation (1)             Shares
                                         Fiscal      -------------------------------------    Underlying
Name and Principal Position               Year        Salary         Bonus        Other(3)    Options (#)
---------------------------              ------      --------       -------       --------    -----------
                                                                                 
Walter C. Herlihy, Ph.D. ..............   2002       $242,000       $50,000            --       50,000
President and Chief Executive             2001        220,000        40,000            --       50,000
Officer                                   2000        190,000        50,000            --           --

James R. Rusche, Ph.D. ................   2002       $172,000       $25,000            --       25,000
Senior Vice President, Research and       2001        150,000        25,000            --       25,000
Development                               2000        136,000        20,000            --       25,000

Daniel P. Witt, Ph.D. .................   2002       $152,000       $20,000            --       20,000
Vice President, Business                  2001        142,000        10,000            --           --
Development                               2000        136,000        10,000            --       25,000

Patrice Rioux, MD, Ph.D. ..............   2002        185,000       $ 7,000            --           --
Vice President, Medical Affairs           2001         48,384        10,000            --       75,000
                                          2000             --            --            --           --

Richard Boismenu, Ph.D. ...............   2002        115,000         1,500       $18,113        3,000
Senior Director, Immunology and           2001         18,615            --        13,747       20,000
Cell Biology                              2000             --            --            --           --


----------
(1)   In accordance with the rules of the Securities and Exchange Commission,
      other compensation in the form of perquisites and other personal benefits
      has been omitted in those instances where the aggregate amount of such
      perquisites and other personal benefits was less than the lower of $50,000
      or 10% of the total annual salary and bonus for the Named Executive
      Officer for such year.

(2)   Represents stock options granted during the fiscal years ended March 31,
      2002, 2001 or 2000. Repligen did not grant any restricted stock awards or
      stock appreciation rights or make any long-term incentive plan payouts
      during the fiscal years ended March 31, 2002, 2001 or 2000.

(3)   Represents relocation costs associated with Dr. Boismenu's employment.

Option Grants in Last Fiscal Year

The following table shows information regarding stock options granted to the
Named Executive Officers during the fiscal year ending March 31, 2002.

                       OPTIONS GRANTED IN LAST FISCAL YEAR



                                 Number of       Percent of                                       Potential
                                Securities     Total Options                             Realizable Value at Assumed
                                Underlying       Granted to     Exercise                 Annual Rates of Stock Price
                                  Options       Employees in     Price      Expiration        Appreciation For
Name                            Granted (#)     Fiscal Year    ($/Share)       Date            Option Term (1)
----                            -----------     -----------    ---------       ----            ---------------
                                                                                               5%            10%
                                                                                            -------       --------
                                                                                        
Walter Herlihy, Ph.D ......       50,000            18%          $2.66       4/3/2011       $83,643       $211,968
James R. Rusche, Ph.D .....       25,000             9%          $2.66       4/3/2011       $41,821       $105,984
Daniel P. Witt, Ph.D ......       20,000             7%          $2.66       4/3/2011       $33,457       $ 84,787
Patrice Rioux, MD, Ph.D ...           --            --              --             --            --             --
Richard Boismenu, Ph.D ....       20,000             7%          $2.66       4/3/2011       $33,457       $ 84,787


----------
(1)   These amounts represent hypothetical gains that could be achieved from the
      exercise of respective options and the subsequent sale of the Common Stock
      underlying such options if the options were exercised immediately prior to
      the end of the option term. These gains are based on assumed rates of
      stock price appreciation of 5% and 10% compounded annually from the date
      the respective options were granted to their expiration dates. The gains
      shown are net of the option exercise price, but do not include deductions
      for taxes or other expenses associated with the exercise of the options or
      sale of the underlying shares. The actual gains, if any, on the stock
      option exercises will depend on the future performance of the Common
      Stock, the optionholder's continued employment through the option period,
      the date on which the options are exercised, and the date on which the
      underlying shares of Common Stock are sold. These rates of appreciation
      are mandated by the rules of the Securities and Exchange Commission and do
      not represent Repligen's estimate or projection of the future Common Stock
      price.


                                       9


Option Exercises and Fiscal Year-End Values

The following table provides information regarding stock option exercises by the
Named Executive Officers and the number and value of the Named Executive
Officers' unexercised options at March 31, 2002.

Aggregated Option Exercises In Last Fiscal Year And Fiscal Year-End Option
Values



                         Shares                        Number of Securities
                        Acquired                      Underlying Unexercised         Value of Unexercised In-the-
                      on Exercise      Value        Options at Fiscal Year-End               Money Options
Name                      (1)       Realized ($)                (2)                      at Fiscal Year-End (3)
----                      ---       ------------                ---                      ----------------------

                                                   Exercisable    Unexercisable      Exercisable     Unexercisable
                                                   -----------    -------------      -----------     -------------
                                                                                        
Walter C. Herlihy ..       --            --            460,000          190,000       $1,065,700          $288,900
James R. Rusche ....       --            --            117,500           67,500          257,740            59,830
Daniel P. Witt .....       --            --             97,500           37,500          222,580            42,660
Patrice Rioux ......       --            --             15,000           60,000               --                --
Richard Boismenu ...       --            --                 --           20,000               --             4,300


(1)   None of the Named Executive Officers exercised any stock options during
      the fiscal year ended March 31, 2002.

(2)   Represents the aggregate number of stock options held as of March 31, 2002
      which can and cannot be exercised pursuant to the terms and provisions of
      the applicable stock option agreements and the 2002 Repligen Corporation
      Stock Option Plan (the "Plan").

(3)   The dollar values have been calculated by determining the difference
      between the fair market value of the securities underlying the options and
      the exercise price of the options. The fair market value of in-the-money
      options was calculated on the basis of the closing price per share for
      Common Stock on the Nasdaq National Market of $3.75 on March 29, 2002. Of
      the 1,065,000 options outstanding, 915,000 of these options were in the
      money as of March 31, 2002.

                            Compensation of Directors

      Drs. Schimmel and Rich, the Co-Chairmen of the Board of Directors, are
compensated pursuant to consulting agreements described below and receive no
separate compensation for attendance at meetings or otherwise as directors.

      Under the terms of the Plan, each non-employee director, beginning on
September 14, 2000, is granted an option to purchase 10,000 shares of Common
Stock at an option price equal to the fair market value of the Common Stock on
the date of grant, determined in accordance with the terms of the Plan (the
"Board Options"). These options vest in full on the first anniversary of the
date of the grant, provided such person is still a director on such anniversary.
Additionally, each newly-elected, non-employee director who joins the Board is
entitled to receive a Board Option to purchase 24,000 shares of Common Stock on
the date he or she joins the Board. These initial Board Options vest equally
over a three-year period from the date of grant. Board Options have a term of
ten years, subject to early termination in the event of death, removal or
resignation from the Board. No director is entitled to receive Board Options
covering more than an aggregate of 100,000 shares.

      Beginning in August 1999, Mr. Hennessey and Mr. Miller receive $1,000 plus
expenses for each board meeting attended.

      Repligen paid Drs. Schimmel and Rich $49,200 and $43,200, respectively,
during the fiscal year ended March 31, 2002 pursuant to consulting agreements,
which have similar terms. These agreements are automatically extended for
successive one-year terms unless terminated by either party at least 90 days
prior to the next anniversary date. Dr. Schimmel's agreement continues until
September 30, 2002 and Dr. Rich's agreement continues until October 31, 2002.
Drs. Schimmel and Rich have advised Repligen that they have no present intention
of terminating their agreements.


                                       10


Executive Employment Agreements

      On March 14, 1996, Repligen entered into a letter of agreement with Drs.
Herlihy, Rusche, and Witt in connection with Repligen's acquisition and merger
with Glycan Pharmaceuticals, Inc. (the "Herlihy Agreement," the "Rusche
Agreement," and the "Witt Agreement," respectively). Under the terms of the
Herlihy Agreement, Dr. Herlihy is entitled to a minimum salary of $160,000 per
annum, subject to periodic increases at the discretion of the Board of
Directors. Additionally, Dr. Herlihy is eligible for participation in all of
Repligen's welfare, profit sharing, retirement and savings plans on the same
basis as other employees of Repligen. Dr. Herlihy received a stock option to
purchase 100,000 shares of the Common Stock at $1.25 per share, vesting at 20%
per annum over five years pursuant to the Herlihy Agreement. Dr. Herlihy's
employment may be terminated, with or without cause, by either party upon 30
days prior written notice. In such event, Dr. Herlihy would be entitled to
continue receiving his salary for a period of eight months or until he finds
other employment, whichever occurs first.

      Under the terms of the Rusche Agreement, Dr. Rusche is entitled to a
minimum salary of $115,000 per annum, subject to periodic increases at the
discretion of the Board of Directors. Additionally, Dr. Rusche is eligible for
participation in all of Repligen's welfare, profit sharing, retirement and
savings plans on the same basis as other employees of Repligen. Dr. Rusche
received a stock option to purchase 60,000 shares of the Common Stock at $1.25
per share, vesting at 20% per annum over five years pursuant to the Rusche
Agreement. Dr. Rusche's employment may be terminated, with or without cause, by
either party upon 30 days prior written notice. In such event, Dr. Rusche would
be entitled to continue receiving his salary for a period of six months or until
he finds other employment, whichever occurs first.

      Under the terms of the Witt Agreement, Dr. Witt is entitled to a minimum
salary of $115,000 per annum, subject to periodic increases at the discretion of
the Board of Directors. Additionally, Dr. Witt is eligible for participation in
all of Repligen's welfare, profit sharing, retirement and savings plans on the
same basis as other employees of Repligen. Dr. Witt received a stock option to
purchase 60,000 shares of the Common Stock at $1.25 per share, vesting at 20%
per annum over five years pursuant to the Witt Agreement. Dr. Witt's employment
may be terminated, with or without cause, by either party upon 30 days prior
written notice. In such event, Dr. Witt would be entitled to continue receiving
his salary for a period of six months or until he finds other employment,
whichever occurs first.

Compensation Committee Interlocks and Insider Participation

      The Compensation Committee currently consists of Dr. Schimmel and Mr.
Miller. No member of the Compensation Committee is a current or former employee
of Repligen. There are no Compensation Committee interlocks between Repligen and
any other entities involving any of the executive officers or directors of such
entities.


                                       11


                          STOCK PRICE PERFORMANCE GRAPH

      The following graph compares the yearly percentage change in the
cumulative total stockholder return (change in stock price plus reinvested
dividends) on Repligen's Common Stock with the cumulative total return for the
Nasdaq Stock Market Index (U.S.) (the "Nasdaq Composite Index") and the Nasdaq
Pharmaceutical Stock Index (the "Nasdaq Pharmaceutical Index"). The comparisons
in the graph are required by the Securities and Exchange Commission and are not
intended to forecast or be indicative of possible future performance of
Repligen's Common Stock.

                                                NASDAQ
                        NASDAQ Stock        Pharmaceutical          RGEN Closing
        YEAR            Market Index         Stock Index            Stock Price
                           (U.S.)
        1997                100                  100                    100
        1998                152                  119                     81
        1999                205                  151                    209
        2000                381                  319                    655
        2001                152                  240                    196
        2002                153                  247                    255

                              [LINE GRAPH OMITTED]

Assumes $100 invested on March 31, 1997 in each of Repligen Corporation's Common
Stock, the securities comprising the Nasdaq Composite Index and the securities
comprising the Nasdaq Pharmaceutical Index.

                  COMPENSATION COMMITTEE REPORT TO STOCKHOLDERS

      The Compensation Committee, which meets on a periodic basis, is comprised
of two non-employee members of the Board of Directors. The Compensation
Committee formulates and administers Repligen's compensation policies for the
President and Chief Executive Officer and all vice presidents of Repligen. The
Compensation Committee is also responsible for determining to whom and under
what terms stock options should be granted (other than options which are
automatically granted to members of the Board of Directors) under the Plan.

Compensation Philosophy

      In designing its compensation programs, Repligen takes into account a
number of considerations, some relevant to companies in general and some
relevant primarily to biotechnology and other research and development intensive
companies. The ultimate goal of Repligen's compensation program is to motivate
each employee to enhance stockholder value, to provide a fair reward for this
effort, and to stimulate each employee's professional and personal growth. In
addition, Repligen's compensation program attempts to achieve the following:

      o Provide compensation which is consistent with Repligen's annual and
long-term objectives and achievements;

      o Promotion and reward of individual initiative, effort and
accomplishment; and

      o Establishment of a competitive total compensation package that enables
Repligen to attract and retain qualified and motivated personnel.


                                       12


Performance Criteria

      Since Repligen is still in the process of developing its proprietary
products and because of the highly volatile nature of biotechnology stocks in
general, it is not appropriate to use the traditional performance standards,
such as profit levels and stock performance, to measure the success of Repligen
and an individual's contribution to that success.

      Accordingly, the compensation of executive officers is based, for the most
part, on the achievement of certain goals by Repligen as a whole and the
individual (and his or her business unit) concerned. The Compensation Committee
therefore examines three specific areas in formulating the compensation packages
of its three most senior executives. Criteria and specific goals within each
category are as follows:

      Company Performance:

      o The extent to which key research, clinical, product manufacturing,
product sales and financial objectives of Repligen have been met during the
preceding fiscal year;

      o The development, acquisition and licensing of key technology; and

      o The achievement by Repligen of certain milestones, whether specified in
agreements with third party collaborators or determined internally.

      Executive Performance:

      o An executive's involvement in and responsibility for the development and
implementation of strategic planning and the attainment of strategic objectives
of Repligen;

      o The participation by an executive in the relationship between Repligen
and the investment community;

      o The involvement of an executive in personnel recruitment, retention and
morale; and

      o The responsibility of the executive in working within budgets,
controlling costs and other aspects of expense management.

      Other Factors:

      o The necessity of being competitive with companies in the pharmaceutical
and biotechnology industries, taking into account relative company size, stage
of development, performance and geographic location as well as individual
responsibilities and performance.

      Mix of Compensation

      Repligen's executive compensation has four principal components:

      o     base salary;

      o     annual cash bonuses;

      o     incentive and/or non-qualified stock options; and

      o     miscellaneous benefits.

      In each case, the Committee regularly compares the individual elements
comprising Repligen's executives' mix of compensation to that of a similar group
of other biotechnology companies.

      The comparison group is based on a multi-tiered classification of
representative companies within the biotechnology industry according to numerous
characteristics, including but not limited to company size, the number of
proprietary products, stage of development of Repligen's products and total
revenues. The tiered classification of biotechnology companies is reviewed
annually and, if appropriate, revised as members of such tiers change from year
to year.

      After completing a review of the comparison group's compensation policies,
the Committee determines competitive compensation levels for each executive
position.

      Levels of base salary are reviewed on an annual basis by the Committee.
Base salary may be altered in line with changes in compensation amongst the
companies included in the Committee's


                                       13


comparison group and further adjusted if the committee determines that an
executive's contribution to Repligen has increased or decreased.

      Annual cash bonuses are voted in April and calculated as a percentage of
an executive's base salary as determined by both the bonus schedule that is
established at the beginning of each fiscal year and by the various criteria set
forth above. Stock options are also awarded from time to time based upon the
same criteria and are intended both to retain and reward the executive and to
provide further incentive for him or her to continue contributing to the
long-term success of Repligen.

Respectfully submitted by the Compensation Committee,


G. William Miller
Paul Schimmel, Ph.D.

      The report of the Compensation Committee shall not be deemed incorporated
by reference by any general statement incorporating by reference this proxy
statement into any filing under the Securities Act of 1933 or under the
Securities Exchange Act of 1934, except to the extent that Repligen specifically
incorporates this information by reference, and shall not otherwise be deemed
filed under such Acts.

REPORT OF THE AUDIT COMMITTEE

      The Audit Committee for the last fiscal year consisted of Dr. Rich,
Committee Chairman, Mr. Hennessey and Mr. Miller. Each of the current members of
the Audit Committee is independent (as defined in the NASDAQ's listing
standards). That is, the Board has determined that none of the members of the
Audit Committee has a relationship to Repligen that may interfere with his
independence from Repligen and its management.

      The primary function of the Audit Committee is to assist the Board of
Directors in fulfilling its oversight responsibilities by reviewing financial
reports and other financial information provided by the Company to any
governmental body or the public, the Company's systems of internal controls
regarding finance, accounting, legal compliance and ethics that management and
the Board have established, and the Company's auditing, accounting and financial
processes generally. The Audit Committee annually recommends to the Board of
Directors the appointment of a firm of independent auditors to audit the
financial statements of the Company and meets with such personnel of the Company
to review the scope and the results of the annual audit, the amount of audit
fees, the Company's internal accounting controls, the Company's financial
statements contained in the Company's Annual Report to Stockholders and other
related matters. The Audit Committee's Charter contains a more detailed
description of the functions of the Audit Committee.

      The Audit Committee has reviewed and discussed with management the
financial statements for fiscal year 2002 audited by Arthur Andersen LLP, the
Company's independent auditors. The Audit Committee has discussed with Arthur
Andersen LLP various matters related to the financial statements, including
those matters required to be discussed by SAS 61 (Codification of Statements on
Auditing Standards, AU 380). The Audit Committee has also received the written
disclosures and the letter from Arthur Andersen LLP required by Independence
Standards Board Standard No. 1 (Independence Standards Board Standard No. 1,
Independence Discussions with Audit Committees), and has discussed with Arthur
Andersen LLP its independence. Based upon such review and discussions, the Audit
Committee recommended to the Board of Directors that the audited financial
statements be included in the Company's Annual Report on Form 10-K for the
fiscal year ending March 31, 2002 for filing with the Securities and Exchange
Commission.

AUDIT COMMITTEE

Dr. Alex Rich, Chairman
Robert Hennessey
G. William Miller

      The report of the Audit Committee shall not be deemed incorporated by
reference by any general statement incorporating by reference this proxy
statement into any filing under the Securities Act of 1933 or under the
Securities Exchange Act of 1934, except to the extent that Repligen specifically
incorporates this information by reference, and shall not otherwise be deemed
filed under such Acts.


                                       14


Audit Fees

The aggregate fees billed by Arthur Andersen LLP for professional services
rendered for the audit of Repligen's annual financial statements for the fiscal
year ended March 31, 2002 and for the review of the financial statements
included in Repligen's Forms 10-Q for the fiscal year ended March 31, 2002 were
$46,000.

Financial Information Systems Design and Implementation Fees

No fees were billed by Arthur Andersen LLP for financial information systems
design and implementation professional services for the fiscal year ended March
31, 2002.

All Other Fees

The aggregate fees billed by Arthur Andersen LLP for services other than those
described above for the fiscal year ended March 31, 2002 were $12,000.

Repligen's Audit Committee has determined that the provision of the services
provided by Arthur Andersen as set forth herein are compatible with maintaining
Arthur Andersen's independence.

                                   PROPOSAL 2
                        APPROVAL OF AMENDED AND RESTATED
                    CERTIFICATE OF INCORPORATION AND BY-LAWS

      In June 2002, the Board unanimously adopted, subject to stockholder
approval, an Amended and Restated Certificate of Incorporation as set forth in
Appendix A and Amended and Restated By-Laws as set forth in Appendix B. The
proposed Amended and Restated Certificate of Incorporation and Amended and
Restated By-Laws implement the classification of the Board into three classes of
directors with staggered terms of office and implement additional changes to the
Company's existing certificate of incorporation and by-laws designed to deter
hostile takeover attempts. The Board is not aware that any person or entity is
seeking to accumulate Repligen stock or otherwise obtain control of Repligen
through a tender offer, exchange offer or other means. The Board believes that
the proposed changes should be adopted in any event, so that Repligen, its
management and its stockholders may have greater assurance that Repligen will
not be subject to the disruptions and costs often associated with hostile
takeover efforts and that, in the event that a takeover proposal is received,
the Board will be in a better position to fully study the proposal and, if
appropriate, negotiate the most favorable transaction terms. The Board presently
does not intend to propose other anti-takeover measures in future proxy
solicitations.

Summary of Proposed Changes to the Certificate of Incorporation and By-Laws

      The following is a summary of the principal changes that the proposed
Amended and Restated Certificate of Incorporation and Amended and Restated
By-Laws together make to the Company's existing certificate of incorporation and
by-laws.

      Classified Board of Directors. The Company's existing by-laws provide that
all directors are to be elected annually for terms of one year. As a result, a
change in control of the Board can be completed by stockholders holding a
majority of the votes cast at a single annual meeting. The proposed amendments
to the Company's certificate of incorporation and by-laws provide that directors
will be classified into three classes, with no one class having more than one
director more than any other class. Class I Directors would hold office
initially for a term expiring at the 2003 annual meeting; Class II Directors
would hold office initially for a term expiring at the 2004 annual meeting; and
Class III Directors would hold office initially for a term expiring at the 2005
annual meeting. At each annual meeting following this initial classification and
election, the successors to the class of directors whose term expire at that
meeting would be elected for a term of office to expire at the third annual
meeting following the annual meeting at which the director was elected. See
Proposal 1, Election of Directors, on page [__] of this proxy statement for a
description of the initial member composition of each class of directors if this
Proposal 2 is adopted. If this Proposal 2 is approved, the classification of the
Board will become effective immediately and will be applicable to every
subsequent election of directors. The implementation of a classified board of
directors will have the practical effect of requiring at least two annual
meetings for a stockholder or group of stockholders to effect a change in
control of the


                                       15


Board (absent resignations), because only a minority of the directors will be
elected at each meeting.

      Stockholder Action By Written Consent. Delaware law allows that, unless
otherwise provided in the certificate of incorporation, the stockholders of a
corporation may take action by written consent in lieu of a meeting. Repligen's
current certificate of incorporation does not restrict the stockholders' ability
to take action by written consent and Repligen's current by-laws expressly
authorize stockholder action by written consent. The existing certificate of
incorporation and by-laws accordingly present the possibility that stockholder
action could be taken without prior notice to or the involvement of the Board.
The proposed Amended and Restated Certificate of Incorporation and Amended and
Restated By-Laws prohibit stockholders from taking action by written consent in
lieu of a meeting. If this Proposal 2 is approved, all stockholder actions will
be required to be taken at an annual or special meeting of the stockholders, and
the Board will have prior notice of and an opportunity to evaluate all such
actions.

      Special Meetings of the Stockholders. The Company's by-laws presently
permit one or more stockholders holding at least a majority of the outstanding
shares of stock to request that a special meeting of stockholders be called. The
proposed Amended and Restated By-Laws provide that a special meeting may be
called only by the Chairman of the Board, a majority of the Board or the
President. The practical effect of this change, if approved, is that
stockholders desiring to bring business before a stockholder meeting may be
required to await the next annual meeting of stockholders and comply with the
advance written notice requirements described below.

      Business at Meetings of Stockholders. The Company's existing by-laws do
not require that a stockholder give advance written notice of business that it
wishes to introduce at a meeting of stockholders. Under the proposed Amended and
Restated By-Laws, a stockholder seeking to bring business before an annual
meeting of stockholders, or to nominate candidates for election as directors at
an annual meeting of stockholders, must provide timely notice of this intention
in writing. To be timely, a stockholder's notice must be delivered to our
Secretary at our principal executive offices not less than 120 days prior to the
first anniversary of the date of our notice of annual meeting provided with
respect to the previous year's annual meeting of stockholders, except that
different notice requirements apply if the date of the annual meeting is more
than 30 days before or more than 60 days after the first anniversary date of the
preceding year's annual meeting or if no proxy statement was delivered to
stockholders in connection with the preceding year's annual meeting. The
proposed Amended and Restated By-Laws include a similar notice requirement for
making nominations at special meetings and specify requirements as to the form
and content of a stockholder's notice. These provisions, if approved, may
preclude stockholders from bringing matters before an annual meeting of
stockholders or from making nominations for directors at an annual or special
meeting of stockholders.

      Removal of Directors. The Company's by-laws presently permit directors to
be removed, with or without cause, by vote of a majority of the stockholders
entitled to vote at an election of directors. The proposed Amended and Restated
Certificate of Incorporation and Amended and Restated By-Laws provide that a
director may be removed only for cause upon the vote of at least 75% of the
shares entitled to vote at an election of directors.

      Required Vote to Amend the Certificate of Incorporation and By-Laws. The
Company's existing certificate of incorporation and by-laws may be amended by a
majority vote of the stockholders. Most provisions of the proposed Amended and
Restated Certificate of Incorporation may be amended only by vote of at least
75% of the voting power of all outstanding shares of capital stock entitled to
vote generally in the election of directors, voting together as a single class,
except that the number of authorized shares of capital stock may be increased by
majority vote. The proposed Amended and Restated By-Laws may be amended by a
majority of the directors present at any regular or special meeting of the Board
of Directors at which a quorum is present, or upon the vote of at least 75% of
the voting power of all outstanding shares of capital stock entitled to vote
generally in the election of directors, voting together as a single class.

      Factors That The Board May Consider When Evaluating A Tender or Exchange
Offer or Potential Business Combination. The Company's existing certificate of
incorporation and by-laws do not delineate the factors that the Board may
consider when evaluating another party's offer to make a tender or exchange
offer or to effect a business combination. The proposed Amended and Restated
Certificate of Incorporation provides that in such circumstances, the Board, in
connection with the exercise of its judgment in determining what is in the best
interests of the Company as a whole, shall be authorized to give due
consideration to any such factors that it determines to be relevant, including,
without limitation: (i) the interests of the Company's stockholders, including
the possibility that these interests might be best served by the Company's
continued independence; (ii) whether the proposed transaction might violate
federal or state laws; (iii) not only the consideration being offered in the
proposed transaction, in relation to


                                       16


the then current market price for the Company's outstanding capital stock, but
also to the market price for the Company's capital stock over a period of years,
the estimated price that might be achieved in a negotiated sale of the Company
as a whole or in part or through orderly liquidation, the premiums over market
price for the securities of other corporations in similar transactions, current
political, economic and other factors bearing on securities prices and the
Company's financial condition and future prospects; and (iv) the social, legal
and economic effects upon employees, suppliers, customers, creditors and others
having similar relationships with the Company, upon the communities in which the
Company conducts its business and upon the economy of the state, region and
nation.

Existing Takeover Defenses

      Repligen has certain limited anti-takeover defenses in place at the
present time. These defenses would be unaffected by the proposed changes to the
certificate of incorporation and by-laws. These following is a summary of these
existing takeover defenses.

      Blank Check Preferred Stock. The Company's existing certificate of
incorporation authorizes the Board to issue up to 5,000,000 shares of "blank
check" preferred stock with voting and rights, preferences and privileges to be
designated solely by the Board. The Board may issue such shares to any third
party without seeking stockholder approval for the issuance. Although it
currently has no intention to do so, the Board could issue shares of preferred
stock with voting and conversion rights that could adversely affect the voting
power and other rights of the holders of common stock, including the loss of
voting control, and that could have economic rights senior to the common stock.
As a consequence, the issuance of shares of preferred stock of the Company could
have the effect of delaying or preventing a change in control of the Company,
and could have a material adverse effect on the market value of the common
stock.

      No Cumulative Voting. The Company's certificate of incorporation does not
provide for cumulative voting rights. Cumulative voting provides that each share
of stock normally having one vote is entitled to a number of votes equal to the
number of directors to be elected. A stockholder may then cast all such votes
for a single nominee or may allocate such votes among as many nominees as the
stockholder may choose. In the absence of cumulative voting, the holders of the
majority of the shares present or represented at a meeting in which directors
are to be elected have the power to elect all the directors to be elected at
such meeting, and no nominee can be elected without the support of holders of
the majority of shares present or represented by proxy at such meeting. The
absence of cumulative voting makes it difficult for a minority stockholder
adverse to a majority of the stockholders to obtain representation on the board
of directors.

      Delaware anti-takeover law. Subject to certain exceptions, Section 203 of
the Delaware General Corporation Law prohibits a publicly-held Delaware
corporation from engaging in a "business combination" with an "interested
stockholder" for a period of three years after the date of the transaction in
which the person became an interested stockholder, unless the interested
stockholder attained such status with the approval of our board of directors or
unless the business combination is approved in a prescribed manner. A "business
combination" is defined as a merger, asset sale or other transaction resulting
in a financial benefit to the interested stockholder. Subject to various
exceptions, an "interested stockholder" is a person who, together with
affiliates and associates, owns, or within the past three years did own, 15% or
more of a corporation's voting stock. Section 203 could prohibit or delay the
accomplishment of takeover attempts and, accordingly, may discourage such
takeover attempts. Although a Delaware corporation to which Section 203 applies
may elect not to be covered by Section 203, Repligen has made no such election
and is subject to Section 203.

Advantages and Disadvantages of the Proposed Changes to the Certificate of
Incorporation and By-Laws

      The Board is recommending the proposed changes to the Company's
certificate of incorporation and by-laws described in this Proposal 2 because
these changes, taken together, tend to discourage hostile bids for control of
the Company and, in the event that a third-party seeks to acquire the Company,
will enable the Board to exercise greater influence over the sale process and
thereby more effectively seek the most favorable acquisition terms.

      The Board believes that a hostile takeover attempt may be disadvantageous
to the Company and its stockholders. Hostile bids often are timed to take
advantage of a temporarily depressed stock price and designed to thwart the
possibility that more favorable bids or alternative transactions might be sought
or considered. Hostile takeover attempts consequently present the risk that the
Company might be sold on terms that are less favorable to the stockholders than
would be available in a negotiated, board-approved transaction, which can be
carefully planned and pursued at an opportune time in order to obtain maximum
value for the Company and its stockholders.


                                       17


      In addition, the proposed changes to the Company's certificate of
amendment and by-laws, particularly the implementation of a classified board of
directors, will assure continuity and stability of the Board. Although the
Company has not experienced problems with continuity and stability in the past,
the Board wishes to ensure that continuity and stability will be retained into
the future. The Board believes that continuity and stability of the Board
enables the Company to more effectively conceive, implement and benefit from
long-term strategic plans aimed at producing long-term value for the Company's
stockholders.

      The proposed changes to the Company's certificate of incorporation and
by-laws present certain potential disadvantages to the Company's stockholders.
The proposed changes could discourage a possible future takeover attempt that a
majority of the stockholders would have favored or that would have paid a
significant premium to stockholders. These changes also may enable the Board to
resist change and otherwise thwart the desires of a majority of the
stockholders. In addition, the proposed changes, particularly the implementation
of a classified board of directors, may be disadvantageous to stockholders
because they may limit their flexibility to determine the composition of the
Board or to make other changes even in circumstances where a majority of the
stockholders may be dissatisfied with the performance of the incumbent directors
or otherwise desire to make changes. Nevertheless, the Board has carefully
weighed the advantages and disadvantages of the proposed changes to the
stockholders of the Company, and has determined that the advantages outweigh the
disadvantages. In addition, the Board is mindful that the board of directors of
a Delaware corporation has a fiduciary duty to act in the best interests of the
stockholders. The Board believes that that this duty mitigates to a great extent
the potential disadvantages to stockholders of the changes proposed to the
certificate of incorporation and by-laws under this Proposal 2.

                                      *****

      The Board recommends a vote FOR the proposal to approve the Amended and
Restated Certificate of Incorporation as set forth in Appendix A and the Amended
and Restated By-Laws as set forth in Appendix B.

                                   PROPOSAL 3
                RATIFICATION OF SELECTION OF INDEPENDENT AUDITORS

      The Audit Committee of the Board of Directors of Repligen Corporation
annually considers and recommends to the Board the selection of Repligen's
independent public accountants. Effective June 12, 2002, as recommended by the
Audit Committee, the Board of Directors of Repligen dismissed Arthur Andersen
LLP as its independent certifying accountants and engaged Ernst & Young LLP to
serve as its independent certifying accountants for the fiscal year ending March
31, 2003, which engagement is being submitted to the stockholders for
ratification at the Annual Meeting.

      Arthur Andersen's audit reports on Repligen's financial statements for
each of the two most recent fiscal years ended Mach 31, 2002 and 2001 did not
contain an adverse opinion or disclaimer of opinion nor were they qualified or
modified as to any uncertainty, audit scope or accounting principles.

      In connection with the audits for the periods ending March 31, 2002 and
2001 and the subsequent interim period through the dismissal of Arthur Andersen
LLP, there were no disagreements with Arthur Andersen LLP on any matter of
accounting principles or practices, financial statement disclosure or auditing
scope or procedure, which, if not resolved to the satisfaction of Arthur
Andersen LLP, would have caused them to refer to such disagreement in connection
with their report.

      Within the two most recent fiscal years of Repligen ended March 31, 2002
and 2001 and the subsequent interim period through the dismissal of Arthur
Andersen LLP, none of the reportable events as defined in Item 304(a)(1)(v) of
Regulation S-K occurred, and Repligen did not consult Ernst & Young LLP with
respect to the application of accounting principles to a specified transaction,
either completed or proposed, or type of audit opinion that might be rendered on
Repligen's financial statements. Representatives of Ernst & Young LLP are
expected to be present at the Annual Meeting, with the opportunity to make a
statement if they desire to do so, and to be available to respond to appropriate
questions. Representatives of Arthur Andersen LLP are not expected to be present
at the Annual Meeting, have the opportunity to make a statement or be available
to respond to questions. The appointment of the independent auditors will be
ratified if it receives the affirmative vote of the holders of a majority of
shares of the Common Stock of Repligen present at the Annual Meeting, in person
or by proxy. Submission of the appointment of the auditors to the stockholders
for ratification will not limit the authority of the Board


                                       18


to appoint another accounting firm to serve as independent auditors if the
present auditors resign or their engagement is otherwise terminated.

      The Board recommends a vote FOR the ratification of Ernst & Young LLP as
independent auditors.

              SECTION 16 BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

      Section 16(a) of the Securities Exchange Act of 1934 requires Repligen's
directors, executive officers, and holders of more than ten percent of
Repligen's Common Stock (collectively, "Reporting Persons"), to file with the
Securities and Exchange Commission ("SEC") initial reports of ownership and
reports of changes in ownership of Common Stock of Repligen. Such Reporting
Persons are required by SEC regulation to furnish Repligen with copies of all
Section 16(a) reports they file. Based on its review of the copies of such
filings received by it with respect to the fiscal year ended March 31, 2002, all
required persons complied with all Section 16(a) filing requirements, except
that Dr. Schimmel filed a late Form 4 that reported two open market purchases of
the Company's Common Stock in February 2002 and Dr. Schimmel's appointment as
trustee of the Alfred Schimmel Trust in 1997, which at the time of such
appointment held shares of the Company's Common Stock.

                             STOCKHOLDERS' PROPOSALS

      Repligen must receive any proposal by a stockholder of Repligen intended
to be presented at the 2003 Annual Meeting of Stockholders at its principal
executive office not later than February 1, 2003 for inclusion in Repligen's
proxy statement and form of proxy relating to that meeting. Any such proposal
must comply with the requirements of the proxy solicitation rules of the SEC.

                                 OTHER BUSINESS

      Management does not know of any other matters to be brought before the
Meeting except those set forth in the notice thereof. If other business is
properly presented for consideration at the Meeting, it is intended that the
Proxies will be voted by the persons named therein in accordance with their
judgment on such matters.

      Even if you plan to attend the Meeting in person, please sign, date and
return the enclosed Proxy promptly. A postage-paid return-addressed envelope is
enclosed for your convenience. Your cooperation in giving this matter your
immediate attention and in returning your proxies will be appreciated.

                                    EXPENSES

      The cost of solicitation will be borne by Repligen, and in addition to
directly soliciting stockholders by mail, Repligen may request banks and brokers
to solicit their customers who have stock of Repligen registered in the name of
the nominee and, if so, will reimburse such banks and brokers for their
reasonable out-of-pocket costs. Solicitation by officers and employees of
Repligen may also be made of some stockholders in person or by mail or telephone
following the original solicitation. Repligen may, if appropriate, retain an
independent proxy solicitation firm to assist Repligen in soliciting proxies. If
Repligen does retain a proxy solicitation firm, Repligen would pay such firm's
customary fees and expenses which such fees would be expected to be
approximately $10,000, plus expenses.


                                       19


                                   APPENDIX A
                AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

                                       OF

                              REPLIGEN CORPORATION

                           (Incorporated May 29, 1981)

                                   * * * * * *

      I, Walter C. Herlihy, President and Chief Executive Officer of Repligen
Corporation (the "Corporation"), a corporation organized and existing under and
by virtue of the General Corporation Law of the State of Delaware, do hereby
certify that the Certificate of Incorporation of Repligen Corporation, as
amended, has been further amended, and restated as amended, in accordance with
provisions of Sections 242 and 245 of the General Corporation Law of the State
of Delaware, and, as amended and restated, is set forth in its entirety as
follows:

      FIRST. The name of the Corporation is Repligen Corporation.

      SECOND. The address of the registered office of the Corporation in the
State of Delaware is 2711 Centerville Road, Suite 400, Wilmington, New Castle
County, Delaware 19808. The name of its registered agent at such address is
Corporate Service Corporation.

      THIRD. The nature of the business or purposes to be conducted or promoted
is to engage in any lawful act or activity for which corporations may be
organized under the General Corporation Law of the State of Delaware.

      FOURTH. The total number of shares of all classes of capital stock which
the Corporation shall have authority to issue is 45,000,000 shares, consisting
of 40,000,000 shares of Common Stock with a par value of $.01 per share (the
"Common Stock") and 5,000,000 shares of Preferred Stock with a par value of $.01
per share (the "Preferred Stock").

      A description of the respective classes of stock and a statement of the
designations, powers, preferences and rights, and the qualifications,
limitations and restrictions of the Preferred Stock and Common Stock are as
follows:

      A. COMMON STOCK

      1. General. All shares of Common Stock will be identical and will entitle
the holders thereof to the same rights, powers and privileges. The rights,
powers and privileges of the holders of the Common Stock are subject to and
qualified by the rights of holders of the Preferred Stock.

      2. Dividends. Dividends may be declared and paid on the Common Stock from
funds lawfully available therefor as and when determined by the Board of
Directors and subject to any preferential dividend rights of any then
outstanding Preferred Stock.

      3. Dissolution, Liquidation or Winding Up. In the event of any
dissolution, liquidation or winding up of the affairs of the Corporation,
whether voluntary or involuntary, each issued and outstanding share of Common
Stock shall entitle the holder thereof to receive an equal portion of the net
assets of the Corporation available for distribution to the holders of Common
Stock, subject to any preferential rights of any then outstanding Preferred
Stock.

      4. Voting Rights. Except as otherwise required by law or this Amended and
Restated Certificate of Incorporation, each holder of Common Stock shall have
one vote in respect of each share of stock held of record by such holder on the
books of the Corporation for the election of directors and on all matters
submitted to a vote of stockholders of the Corporation. Except as otherwise
required by law or provided herein, holders of Common Stock shall vote together
with holders of the Preferred Stock as a single class, subject to any special or
preferential voting rights of any then outstanding Preferred Stock. There shall
be no cumulative voting.


                                       20


      B. PREFERRED STOCK

      The Preferred Stock may be issued in one or more series at such time or
times and for such consideration or considerations as the Board of Directors of
the Corporation may determine. Each series shall be so designated as to
distinguish the shares thereof from the shares of all other series and classes.
Except as otherwise provided in this Amended and Restated Certificate of
Incorporation, different series of Preferred Stock shall not be construed to
constitute different classes of shares for the purpose of voting by classes.

      The Board of Directors is expressly authorized to provide for the issuance
of all or any shares of the undesignated Preferred Stock in one or more series,
each with such designations, preferences, voting powers (or special,
preferential or no voting powers), relative, participating, optional or other
special rights and privileges and such qualifications, limitations or
restrictions thereof as shall be stated in the resolution or resolutions adopted
by the Board of Directors to create such series, and a certificate of said
resolution or resolutions (a "Certificate of Designation") shall be filed in
accordance with the General Corporation Law of the State of Delaware. The
authority of the Board of Directors with respect to each such series shall
include, without limitation of the foregoing, the right to provide that the
shares of each such series may be: (i) subject to redemption at such time or
times and at such price or prices; (ii) entitled to receive dividends (which may
be cumulative or non-cumulative) at such rates, on such conditions, and at such
times, and payable in preference to, or in such relation to, the dividends
payable on any other class or classes or any other series; (iii) entitled to
such rights upon the dissolution of, or upon any distribution of the assets of,
the Corporation; (iv) convertible into, or exchangeable for, shares of any other
class or classes of stock, or of any other series of the same or any other class
or classes of stock of the Corporation at such price or prices or at such rates
of exchange and with such adjustments, if any; (v) entitled to the benefit of
such limitations, if any, on the issuance of additional shares of such series or
shares of any other series of Preferred Stock; or (vi) entitled to such other
preferences, powers, qualifications, rights and privileges, all as the Board of
Directors may deem advisable and as are not inconsistent with law and the
provisions of this Amended and Restated Certificate of Incorporation.

      FIFTH. The Corporation is to have perpetual existence.

      SIXTH. The following provisions are included for the management of the
business and the conduct of the affairs of the Corporation, and for further
definition, limitation and regulation of the powers of the Corporation and of
its Board of Directors and stockholders:

            1. The business and affairs of the Corporation shall be managed by
or under the direction of the Board of Directors of the Corporation.

            2. The Board of Directors of the Corporation is expressly authorized
to adopt, amend or repeal the By-laws of the Corporation, subject to any
limitation thereof contained in the By-laws. The stockholders shall also have
the power to adopt, amend or repeal the By-laws of the Corporation; provided,
however, that, in addition to any vote of the holders of any class or series of
stock of the Corporation required by law or by this Amended and Restated
Certificate of Incorporation, the affirmative vote of the holders of at least
seventy-five percent (75%) of the voting power of all of the then outstanding
shares of the capital stock of the Corporation entitled to vote generally in the
election of directors, voting together as a single class, shall be required to
adopt, amend or repeal any provision of the By-laws of the Corporation.

            3. Stockholders of the Corporation may not take any action by
written consent in lieu of a meeting.

            4. Special meetings of stockholders may be called at any time only
by the President, the Chairman of the Board of Directors (if any) or a majority
of the Board of Directors. Business transacted at any special meeting of
stockholders shall be limited to matters relating to the purpose or purposes
stated in the notice of meeting.

            5. The books of the Corporation may be kept at such place within or
without the State of Delaware as the By-laws of the Corporation may provide or
as may be designated from time to time by the Board of Directors of the
Corporation.

      SEVENTH.

      1. Number of Directors. The number of directors which shall constitute the
whole Board of Directors shall be determined by resolution of a majority of the
Board of Directors, but in no event shall the number of directors be less than
three. The number of directors may be decreased at any time and from time to
time by a majority of the directors then in office, but only to eliminate
vacancies existing by reason of the death, resignation, removal or expiration of
the term of one or more directors. The directors shall be


                                       21


elected at the annual meeting of stockholders (or, if so determined by the Board
of Directors, at a special meeting of stockholders), by such stockholders as
have the right to vote on such election. Directors need not be stockholders of
the Corporation.

      2. Classes of Directors. The Board of Directors shall be and is divided
into three classes: Class I, Class II and Class III. No one class shall have
more than one director more than any other class.

      3. Election of Directors. Elections of directors need not be by written
ballot except as and to the extent provided in the By-laws of the Corporation.

      4. Terms of Office. Each director shall serve for a term ending on the
date of the third annual meeting following the annual meeting at which such
director was elected; provided, however, that each initial director in Class I
shall serve for a term ending on the date of the annual meeting next following
the end of the Corporation's fiscal year ending March 31, 2003; each initial
director in Class II shall serve for a term ending on the date of the annual
meeting next following the end of the Corporation's fiscal year ending March 31,
2004; and each initial director in Class III shall serve for a term ending on
the date of the annual meeting next following the end of the Corporation's
fiscal year ending March 31, 2005.

      5. Allocation of Directors Among Classes in the Event of Increases or
Decreases in the Number of Directors. In the event of any increase or decrease
in the authorized number of directors, (i) each director then serving as such
shall nevertheless continue as director of the class of which he or she is a
member until the expiration of such director's current term or his or her prior
death, removal or resignation and (ii) the newly created or eliminated
directorships resulting from such increase or decrease shall be apportioned by
the Board of Directors among the three classes of directors so as to ensure that
no one class has more than one director more than any other class. To the extent
possible, consistent with the foregoing rule, any newly created directorships
shall be added to those classes whose terms of office are to expire at the
earliest dates following such allocation, unless otherwise provided for from
time to time by resolution adopted by a majority of the directors then in
office, though less than a quorum. No decrease in the number of directors
constituting the whole Board of Directors shall shorten the term of an incumbent
Director.

      6. Tenure. Notwithstanding any provisions to the contrary contained
herein, each director shall hold office until his or her successor is elected
and qualified, or until his or her earlier death, resignation or removal.

      7. Vacancies. Unless and until filled by the stockholders, any vacancy in
the Board of Directors, however occurring, including a vacancy resulting from an
enlargement of the Board of Directors, may be filled only by vote of a majority
of the directors then in office, even if less than a quorum, or by a sole
remaining director. A director elected to fill a vacancy shall be elected for
the unexpired term of his or her predecessor in office, if applicable, and a
director chosen to fill a position resulting from an increase in the number of
directors shall hold office until the next election of the class for which such
director shall have been chosen and until his or her successor is elected and
qualified, or until his or her earlier death, resignation or removal.

      8. Quorum. A majority of the total number of the whole Board of Directors
shall constitute a quorum at all meetings of the Board of Directors. In the
event one or more of the directors shall be disqualified to vote at any meeting,
then the required quorum shall be reduced by one for each such director so
disqualified; provided, however, that in no case shall less than one-third (1/3)
of the total number of the whole Board of Directors constitute a quorum. In the
absence of a quorum at any such meeting, a majority of the directors present may
adjourn the meeting from time to time without further notice other than
announcement at the meeting, until a quorum shall be present.

      9. Action at Meeting. At any meeting of the Board of Directors at which a
quorum is present, the vote of a majority of those present shall be sufficient
to take any action, unless a different vote is specified by law or the
Corporation's By-laws.

      10. Removal. Any one or more or all of the directors may be removed, only
for cause, by the holders of at least seventy-five percent (75%) of the shares
then entitled to vote at an election of directors.

      11. Stockholder Nominations and Introduction of Business, Etc. Advance
notice of stockholder nominations for election of directors and other business
to be brought by stockholders before a meeting of stockholders shall be given in
the manner provided in the By-laws of the Corporation.


                                       22


      12. Rights of Preferred Stock. The provisions of this Article are subject
to the rights of the holders of any series of Preferred Stock from time to time
outstanding.

      EIGHTH. No director (including any advisory director) of the Corporation
shall be personally liable to the Corporation or its stockholders for monetary
damages for breach of fiduciary duty as a director notwithstanding any provision
of law imposing such liability; provided, however, that, to the extent provided
by applicable law, this provision shall not eliminate the liability of a
director (i) for any breach of the director's duty of loyalty to the Corporation
or its stockholders, (ii) for acts or omissions not in good faith or which
involve intentional misconduct or a knowing violation of law, (iii) under
Section 174 of the General Corporation Law of the State of Delaware, or (iv) for
any transaction from which the director derived an improper personal benefit. No
amendment to or repeal of this provision shall apply to or have any effect on
the liability or alleged liability of any director for or with respect to any
acts or omissions of such director occurring prior to such amendment or repeal.

      NINTH. The Board of Directors of the Corporation, when evaluating any
offer of another party (a) to make a tender or exchange offer for any equity
security of the Corporation or (b) to effect a business combination, shall, in
connection with the exercise of its judgment in determining what is in the best
interests of the Corporation as whole, be authorized to give due consideration
to any such factors as the Board of Directors determines to be relevant,
including, without limitation:

            (i) the interests of the Corporation's stockholders, including the
      possibility that these interests might be best served by the continued
      independence of the Corporation;

            (ii) whether the proposed transaction might violate federal or state
      laws;

            (iii) not only the consideration being offered in the proposed
      transaction, in relation to the then current market price for the
      outstanding capital stock of the Corporation, but also to the market price
      for the capital stock of the Corporation over a period of years, the
      estimated price that might be achieved in a negotiated sale of the
      Corporation as a whole or in part or through orderly liquidation, the
      premiums over market price for the securities of other corporations in
      similar transactions, current political, economic and other factors
      bearing on securities prices and the Corporation's financial condition and
      future prospects; and

            (iv) the social, legal and economic effects upon employees,
      suppliers, customers, creditors and others having similar relationships
      with the Corporation, upon the communities in which the Corporation
      conducts its business and upon the economy of the state, region and
      nation.

In connection with any such evaluation, the Board of Directors is authorized to
conduct such investigations and engage in such legal proceedings as the Board of
Directors may determine.

      TENTH.

      1. Actions, Suits and Proceedings Other than by or in the Right of the
Corporation. The Corporation shall indemnify each person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the Corporation), by
reason of the fact that he or she is or was, or has agreed to become, a director
or officer of the Corporation, or is or was serving, or has agreed to serve, at
the request of the Corporation, as a director, officer or trustee of, or in a
similar capacity with, another corporation, partnership, joint venture, trust or
other enterprise (including any employee benefit plan) (all such persons being
referred to hereafter as an "Indemnitee"), or by reason of any action alleged to
have been taken or omitted in such capacity, against all expenses (including
attorneys' fees), judgments, fines and amounts paid in settlement actually and
reasonably incurred by him or her or on his or her behalf in connection with
such action, suit or proceeding and any appeal therefrom, if he or she acted in
good faith and in a manner he or she reasonably believed to be in, or not
opposed to, the best interests of the Corporation, and, with respect to any
criminal action or proceeding, had no reasonable cause to believe his or her
conduct was unlawful. The termination of any action, suit or proceeding by
judgment, order, settlement, conviction or upon a plea of nolo contendere or its
equivalent, shall not, of itself, create a presumption that the person did not
act in good faith and in a manner which he or she reasonably believed to be in,
or not opposed to, the best interests of the Corporation, and, with respect to
any criminal action or proceeding, had reasonable cause to believe that his or
her conduct was unlawful. Notwithstanding anything to the contrary in this
Article, except as set forth in Section 6 below, the Corporation shall not
indemnify an Indemnitee seeking indemnification in connection with a proceeding
(or part thereof) initiated by the Indemnitee unless the initiation thereof was
approved by the Board of Directors of the Corporation.


                                       23


      2. Actions or Suits by or in the Right of the Corporation. The Corporation
shall indemnify any Indemnitee who was or is a party or is threatened to be made
a party to any threatened, pending or completed action or suit by or in the
right of the Corporation to procure a judgment in its favor by reason of the
fact that he or she is or was, or has agreed to become, a director or officer of
the Corporation, or is or was serving, or has agreed to serve, at the request of
the Corporation, as a director, officer or trustee of, or in a similar capacity
with, another corporation, partnership, joint venture, trust or other enterprise
(including any employee benefit plan), or by reason of any action alleged to
have been taken or omitted in such capacity, against all expenses (including
attorneys' fees) and amounts paid in settlement actually and reasonably incurred
by him or her or on his or her behalf in connection with such action, suit or
proceeding and any appeal therefrom, if he or she acted in good faith and in a
manner he or she reasonably believed to be in, or not opposed to, the best
interests of the Corporation, except that no indemnification shall be made in
respect of any claim, issue or matter as to which such person shall have been
adjudged to be liable to the Corporation unless and only to the extent that the
Court of Chancery of Delaware or the court in which such action or suit was
brought shall determine upon application that, despite the adjudication of such
liability but in view of all the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses (including
attorneys' fees) which the Court of Chancery of Delaware or such other court
shall deem proper.

      3. Indemnification for Expenses of Successful Party. Notwithstanding the
other provisions of this Article, to the extent that an Indemnitee has been
successful, on the merits or otherwise, in defense of any action, suit or
proceeding referred to in Sections 1 and 2 of this Article, or in defense of any
claim, issue or matter therein, or on appeal from any such action, suit or
proceeding, he or she shall be indemnified against all expenses (including
attorneys' fees) actually and reasonably incurred by him or her or on his or her
behalf in connection therewith. Without limiting the foregoing, if any action,
suit or proceeding is disposed of, on the merits or otherwise (including a
disposition without prejudice), without (i) the disposition being adverse to the
Indemnitee, (ii) an adjudication that the Indemnitee was liable to the
Corporation, (iii) a plea of guilty or nolo contendere by the Indemnitee, (iv)
an adjudication that the Indemnitee did not act in good faith and in a manner he
or she reasonably believed to be in or not opposed to the best interests of the
Corporation, and (v) with respect to any criminal proceeding, an adjudication
that the Indemnitee had reasonable cause to believe his or her conduct was
unlawful, the Indemnitee shall be considered for the purpose hereof to have been
wholly successful with respect thereto.

      4. Notification and Defense of Claim. As a condition precedent to his or
her right to be indemnified, the Indemnitee must notify the Corporation in
writing as soon as practicable of any action, suit, proceeding or investigation
involving him or her for which indemnity will or could be sought. With respect
to any action, suit, proceeding or investigation of which the Corporation is so
notified, the Corporation will be entitled to participate therein at its own
expense and/or to assume the defense thereof at its own expense, with legal
counsel reasonably acceptable to the Indemnitee. After notice from the
Corporation to the Indemnitee of its election so to assume such defense, the
Corporation shall not be liable to the Indemnitee for any legal or other
expenses subsequently incurred by the Indemnitee in connection with such claim,
other than as provided below in this Section 4. The Indemnitee shall have the
right to employ his or her own counsel in connection with such claim, but the
fees and expenses of such counsel incurred after notice from the Corporation of
its assumption of the defense thereof shall be at the expense of the Indemnitee
unless (i) the employment of counsel by the Indemnitee has been authorized by
the Corporation, (ii) counsel to the Indemnitee shall have reasonably concluded
that there may be a conflict of interest or position on any significant issue
between the Corporation and the Indemnitee in the conduct of the defense of such
action or (iii) the Corporation shall not in fact have employed counsel to
assume the defense of such action, in each of which cases the fees and expenses
of counsel for the Indemnitee shall be at the expense of the Corporation, except
as otherwise expressly provided by this Article. The Corporation shall not be
entitled, without the consent of the Indemnitee, to assume the defense of any
claim brought by or in the right of the Corporation or as to which counsel for
the Indemnitee shall have reasonably made the conclusion provided for in clause
(ii) above.

      5. Advance of Expenses. Subject to the provisions of Section 6 below, in
the event that the Corporation does not assume the defense pursuant to Section 4
of this Article of any action, suit, proceeding or investigation of which the
Corporation receives notice under this Article, any expenses (including
attorneys' fees) incurred by an Indemnitee in defending a civil or criminal
action, suit, proceeding or investigation or any appeal therefrom shall be paid
by the Corporation in advance of the final disposition of such matter, provided,
however, that the payment of such expenses incurred by an Indemnitee in advance
of the final disposition of such matter shall be made only upon receipt of an
undertaking by or on behalf of the Indemnitee to repay all amounts so advanced
in the event that it shall ultimately be determined that the indemnitee is not
entitled to be indemnified by the Corporation as authorized in this Article.
Such undertaking may be accepted without reference to the financial ability of
such person to make such repayment.


                                       24


      6. Procedure for Indemnification. In order to obtain indemnification or
advancement of expenses pursuant to Section 1, 2, 3 or 5 of this Article, the
Indemnitee shall submit to the Corporation a written request, including in such
request such documentation and information as is reasonably available to the
Indemnitee and is reasonably necessary to determine whether and to what extent
the Indemnitee is entitled to indemnification or advancement of expenses. Any
such indemnification or advancement of expenses shall be made promptly, and in
any event within 60 days after receipt by the Corporation of the written request
of the Indemnitee, unless with respect to requests under Section 1, 2 or 5 the
Corporation determines, by clear and convincing evidence, within such 60-day
period that the Indemnitee did not meet the applicable standard of conduct set
forth in Section 1 or 2, as the case may be. Such determination shall be made in
each instance by (a) a majority vote of the directors of the Corporation who are
not at that time parties to the action, suit or proceeding in question
("disinterested directors"), even though less than a quorum, (b) if there are no
such disinterested directors, or if such disinterested directors so direct, by
independent legal counsel (who may be regular legal counsel to the corporation)
in a written opinion, (c) a majority vote of a quorum of the outstanding shares
of stock of all classes entitled to vote for directors, voting as a single
class, which quorum shall consist of stockholders who are not at that time
parties to the action, suit or proceeding in question, or (d) a court of
competent jurisdiction.

      7. Remedies. The right to indemnification or advances as granted by this
Article shall be enforceable by the Indemnitee in any court of competent
jurisdiction if the Corporation denies such request, in whole or in part, or if
no disposition thereof is made within the 60-day period referred to above in
Section 6. Unless otherwise provided by law, the burden of proving that the
Indemnitee is not entitled to indemnification or advancement of expenses under
this Article shall be on the Corporation. Neither the failure of the Corporation
to have made a determination prior to the commencement of such action that
indemnification is proper in the circumstances because the Indemnitee has met
the applicable standard of conduct, nor an actual determination by the
Corporation pursuant to Section 6 that the Indemnitee has not met such
applicable standard of conduct, shall be a defense to the action or create a
presumption that the Indemnitee has not met the applicable standard of conduct.
The Indemnitee's expenses (including attorneys' fees) incurred in connection
with successfully establishing his or her right to indemnification, in whole or
in part, in any such proceeding shall also be indemnified by the Corporation.

      8. Subsequent Amendment. No amendment, termination or repeal of this
Article or of the relevant provisions of the General Corporation Law of the
State of Delaware or any other applicable laws shall affect or diminish in any
way the rights of any Indemnitee to indemnification under the provisions hereof
with respect to any action, suit, proceeding or investigation arising out of or
relating to any actions, transactions or facts occurring prior to the final
adoption of such amendment, termination or repeal.

      9. Other Rights. The indemnification and advancement of expenses provided
by this Article shall not be deemed exclusive of any other rights to which an
Indemnitee seeking indemnification or advancement of expenses may be entitled
under any law (common or statutory), agreement or vote of stockholders or
disinterested directors or otherwise, both as to action in his or her official
capacity and as to action in any other capacity while holding office for the
Corporation, and shall continue as to an Indemnitee who has ceased to be a
director or officer, and shall inure to the benefit of the estate, heirs,
executors and administrators of the Indemnitee. Nothing contained in this
Article shall be deemed to prohibit, and the Corporation is specifically
authorized to enter into, agreements with officers and directors providing
indemnification rights and procedures different from those set forth in this
Article. In addition, the Corporation may, to the extent authorized from time to
time by its Board of Directors, grant indemnification rights to other employees
or agents of the Corporation or other persons serving the Corporation and such
rights may be equivalent to, or greater or less than, those set forth in this
Article.

      10. Partial Indemnification. If an Indemnitee is entitled under any
provision of this Article to indemnification by the Corporation for some or a
portion of the expenses (including attorneys' fees), judgments, fines or amounts
paid in settlement actually and reasonably incurred by him or her or on his or
her behalf in connection with any action, suit, proceeding or investigation and
any appeal therefrom but not, however, for the total amount thereof, the
Corporation shall nevertheless indemnify the Indemnitee for the portion of such
expenses (including attorneys' fees), judgments, fines or amounts paid in
settlement to which the Indemnitee is entitled.

      11. Insurance. The Corporation may purchase and maintain insurance, at its
expense, to protect itself and any director, officer, employee or agent of the
Corporation or another corporation, partnership, joint venture, trust or other
enterprise (including any employee benefit plan) against any expense, liability
or loss incurred by him or her in any such capacity, or arising out of his or
her status as such, whether or not the Corporation would have the power to
indemnify such person against such expense, liability or loss under the General
Corporation Law of the State of Delaware.


                                       25


      12. Merger or Consolidation. If the Corporation is merged into or
consolidated with another corporation and the Corporation is not the surviving
corporation, the surviving corporation shall assume the obligations of the
Corporation under this Article with respect to any action, suit, proceeding or
investigation arising out of or relating to any actions, transactions or facts
occurring prior to the date of such merger or consolidation.

      13. Savings Clause. If this Article or any portion hereof shall be
invalidated on any ground by any court of competent jurisdiction, then the
Corporation shall nevertheless indemnify each Indemnitee as to any expenses
(including attorneys' fees), judgments, fines and amounts paid in settlement in
connection with any action, suit, proceeding or investigation, whether civil,
criminal or administrative, including an action by or in the right of the
Corporation, to the fullest extent permitted by an applicable portion of this
Article that shall not have been invalidated and to the fullest extent permitted
by applicable law.

      14. Definitions. Terms used herein and defined in Section 145(h) and
Section 145(i) of the General Corporation Law of the State of Delaware shall
have the respective meanings assigned to such terms in such Section 145(h) and
Section 145(i).

      15. Subsequent Legislation. If the General Corporation Law of the State of
Delaware is amended after adoption of this Article to expand further the
indemnification permitted to Indemnitees, then the Corporation shall indemnify
such persons to the fullest extent permitted by the General Corporation Law of
the State of Delaware, as so amended.

      ELEVENTH. The Corporation reserves the right to amend or repeal any
provision contained in this Amended and Restated Certificate of Incorporation in
the manner prescribed by the laws of the State of Delaware and all rights
conferred upon stockholders are granted subject to this reservation, provided,
however, that in addition to any vote of the holders of any class or series of
stock of the Corporation required by law, this Amended and Restated Certificate
of Incorporation or a Certificate of Designation with respect to a series of
Preferred Stock, the affirmative vote of the holders of shares of voting stock
of the Corporation representing at least seventy-five percent (75%) of the
voting power of all of the then outstanding shares of the capital stock of the
Corporation entitled to vote generally in the election of directors, voting
together as a single class, shall be required to (i) reduce or eliminate the
number of authorized shares of Common Stock or the number of authorized shares
of Preferred Stock set forth in Article FOURTH or (ii) amend or repeal, or adopt
any provision inconsistent with, Parts A and B of Article FOURTH and Articles
FIFTH, SIXTH, SEVENTH, EIGHTH, NINTH, TENTH and this Article ELEVENTH of this
Amended and Restated Certificate of Incorporation.


                                       26


      IN WITNESS WHEREOF, the undersigned has hereunto signed his name and
affirms that the statements made in this Amended and Restated Certificate of
Incorporation are true under the penalties of perjury this ____ day of
_______________, 2002.


                                        _____________________________________
                                        Walter C. Herlihy
                                        President and Chief Executive Officer


                                       27


                              AMENDED AND RESTATED

                                     BY-LAWS

                                       OF

                              REPLIGEN CORPORATION



                                     BY-LAWS

                                TABLE OF CONTENTS

                                                                           Page
                                                                           ----

ARTICLE 1 - Stockholders .................................................   1
    1.1   Place of Meetings ..............................................   1
    1.2   Annual Meeting .................................................   1
    1.3   Special Meetings ...............................................   1
    1.4   Notice of Meetings .............................................   1
    1.5   Voting List ....................................................   1
    1.6   Quorum .........................................................   1
    1.7   Adjournments ...................................................   1
    1.8   Voting and Proxies .............................................   2
    1.9   Action at Meeting ..............................................   2
    1.10  Introduction of Business at Meetings ...........................   2
    1.11  Action without Meeting .........................................   3

ARTICLE 2 - Directors ....................................................   3
    2.1   General Powers .................................................   3
    2.2   Number; Election and Qualification .............................   4
    2.3   Classes of Directors ...........................................   4
    2.4   Terms in Office ................................................   4
    2.5   Allocation of Directors Among Classes in the Event
          of Increases or Decreases in the Number of Directors ...........   4
    2.6   Tenure .........................................................   4
    2.7   Vacancies ......................................................   4
    2.8   Resignation ....................................................   4
    2.9   Regular Meetings ...............................................   4
    2.10  Special Meetings ...............................................   4
    2.11  Notice of Special Meetings .....................................   4
    2.12  Meetings by Telephone Conference Calls .........................   4
    2.13  Quorum .........................................................   5
    2.14  Action at Meeting ..............................................   5
    2.15  Action by Written Consent ......................................   5
    2.16  Removal ........................................................   5
    2.17  Committees .....................................................   5
    2.18  Compensation of Directors ......................................   5
    2.19  Amendments to Article ..........................................   5

ARTICLE 3 - Officers .....................................................   5
    3.1   Enumeration ....................................................   5
    3.2   Election .......................................................   6
    3.3   Qualification ..................................................   6
    3.4   Tenure .........................................................   6
    3.5   Resignation and Removal ........................................   6
    3.6   Vacancies ......................................................   6
    3.7   Chairman of the Board and Vice-Chairman of the Board ...........   6
    3.8   President ......................................................   6
    3.9   Vice Presidents ................................................   6
    3.10  Secretary and Assistant Secretaries ............................   6
    3.11  Treasurer and Assistant Treasurers .............................   7
    3.12  Salaries .......................................................   7
    3.13  Action with Respect to Securities of Other Corporations ........   7


                                      -ii-


ARTICLE 4 - Capital Stock ................................................   7
    4.1   Issuance of Stock ..............................................   7
    4.2   Certificates of Stock ..........................................   7
    4.3   Transfers ......................................................   7
    4.4   Lost, Stolen or Destroyed Certificates .........................   7
    4.5   Record Date ....................................................   8

ARTICLE 5 - General Provisions ...........................................   8
    5.1   Fiscal Year ....................................................   8
    5.2   Corporate Seal .................................................   8
    5.3   Notices ........................................................   8
    5.4   Waiver of Notice ...............................................   8
    5.5   Evidence of Authority ..........................................   8
    5.6   Facsimile Signatures ...........................................   8
    5.7   Reliance upon Books, Reports and Records .......................   8
    5.8   Time Periods ...................................................   8
    5.9   Certificate of Incorporation ...................................   8
    5.10  Transactions with Interested Parties ...........................   8
    5.11  Severability ...................................................   9
    5.12  Pronouns .......................................................   9

ARTICLE 6 - Amendments ...................................................   9
    6.1   By the Board of Directors ......................................   9
    6.2   By the Stockholders ............................................   9



                              AMENDED AND RESTATED

                                     BY-LAWS

                                       OF

                    REPLIGEN CORPORATION (the "Corporation")

                            ARTICLE 1 - Stockholders

      1.1 Place of Meetings. All meetings of stockholders shall be held at such
place within or without the State of Delaware as may be designated from time to
time by the Chairman of the Board (if any), the board of directors of the
Corporation (the "Board of Directors") or the President or, if not so
designated, at the registered office of the Corporation.

      1.2 Annual Meeting. The annual meeting of stockholders for the election of
directors and for the transaction of such other business as may properly be
brought before the meeting shall be held on a date to be fixed by the Chairman
of the Board (if any), Board of Directors or the President (which date shall not
be a legal holiday in the place where the meeting is to be held) at the time and
place to be fixed by the Chairman of the Board, the Board of Directors or the
President and stated in the notice of the meeting.

      1.3 Special Meetings. Special meetings of stockholders may be called at
any time by the Chairman of the Board (if any), a majority of the Board of
Directors or the President and shall be held at such place, on such date and at
such time as shall be fixed by the Board of Directors or the person calling the
meeting. Business transacted at any special meeting of stockholders shall be
limited to matters relating to the purpose or purposes stated in the notice of
meeting.

      1.4 Notice of Meetings. Except as otherwise provided by law, written
notice of each meeting of stockholders, whether annual or special, shall be
given not less than 10 nor more than 60 days before the date of the meeting to
each stockholder entitled to vote at such meeting. The notices of all meetings
shall state the place, date and hour of the meeting. The notice of a special
meeting shall state, in addition, the purpose or purposes for which the meeting
is called. If mailed, notice is given when deposited in the United States mail,
postage prepaid, directed to the stockholder at his or her address as it appears
on the records of the Corporation.

      1.5 Voting List. The officer who has charge of the stock ledger of the
Corporation shall prepare, at least 10 days before every meeting of
stockholders, a complete list of the stockholders entitled to vote at the
meeting, arranged in alphabetical order, and showing the address of each
stockholder and the number of shares registered in the name of each stockholder.
Such list shall be open to the examination of any stockholder, for any purpose
germane to the meeting, during ordinary business hours, for a period of at least
10 days prior to the meeting, either at a place within the metropolitan area of
the city where the meeting is to be held, which place shall be specified in the
notice of the meeting, or if not so specified, at the place where the meeting is
to be held. The list shall also be produced and kept at the time and place of
the meeting during the whole time of the meeting, and may be inspected by any
stockholder who is present. This list shall presumptively determine the identity
of the stockholders entitled to vote at the meeting and the number of shares
held by each of them.

      1.6 Quorum. Except as otherwise provided by law, the Certificate of
Incorporation or these By-Laws, the holders of a majority of the shares of the
capital stock of the Corporation issued and outstanding and entitled to vote at
the meeting, present in person or represented by proxy, shall constitute a
quorum for the transaction of business. Shares held by brokers which such
brokers are prohibited from voting (pursuant to their discretionary authority on
behalf of beneficial owners of such shares who have not submitted a proxy with
respect to such shares) on some or all of the matters before the stockholders,
but which shares would otherwise be entitled to vote at the meeting ("Broker
Non-Votes") shall be counted, for the purpose of determining the presence or
absence of a quorum, both (a) toward the total voting power of the shares of
capital stock of the Corporation and (b) as being represented by proxy. If a
quorum has been established for the purpose of conducting the meeting, a quorum
shall be deemed to be present for the purpose of all votes to be conducted at
such meeting, provided that where a separate vote by a class or classes, or
series thereof, is required, a majority of the voting power of the shares of
such class or classes, or series, present in person or represented by proxy
shall constitute a quorum entitled to take action with respect to that vote on
that matter. If a quorum shall fail to attend any meeting, the chairman of the
meeting or the holders of a majority of the voting power of the shares of stock
entitled to vote who are present, in person or by proxy, may adjourn the meeting
to another place, date, or time.

      1.7 Adjournments. Any meeting of stockholders may be adjourned to any
other time and to any other place at which a meeting of stockholders may be held
under these By-Laws by the stockholders present or represented at the meeting
and entitled to vote, although less than a quorum, or, if no stockholder is
present, by any officer entitled to preside at or to act as Secretary of such
meeting. It shall not be necessary to notify any stockholder of any adjournment
of less than 30 days if the time and place of the adjourned meeting are
announced at the meeting at which adjournment is taken, unless after the



adjournment a new record date is fixed for the adjourned meeting. At the
adjourned meeting, the Corporation may transact any business which might have
been transacted at the original meeting.

      1.8 Voting and Proxies. At any meeting of the stockholders, each
stockholder shall have one vote for each share of stock entitled to vote at such
meeting held of record by such stockholder and a proportionate vote for each
fractional share so held, unless otherwise provided in the Certificate of
Incorporation. Each stockholder of record entitled to vote at a meeting of
stockholders, may vote or express such consent or dissent in person or may
authorize another person or persons to vote or act for such stockholder by
written proxy executed by such stockholder or his or her authorized agent or by
a transmission permitted by law and delivered to the Secretary of the
Corporation. No such proxy shall be voted or acted upon after three years from
the date of its execution, unless the proxy expressly provides for a longer
period. Any copy, facsimile telecommunication or other reliable reproduction of
the writing or transmission created pursuant to this Section 1.8 may be
substituted or used in lieu of the original writing or transmission for any and
all purposes for which the original writing or transmission could be used,
provided that such copy, facsimile telecommunication or reproduction shall be a
complete reproduction of the entire original writing or transmission.

      1.9 Action at Meeting. When a quorum is present at any meeting of
stockholders, the holders of a majority of the stock present or represented and
voting on a matter (or if there are two or more classes of stock entitled to
vote as separate classes, then in the case of each such class, the holders of a
majority of the stock of that class present or represented and voting on such
matter) shall decide any matter to be voted upon by the stockholders at such
meeting (other than the election of directors), except when a different vote is
required by express provision of law, the Certificate of Incorporation or these
By-Laws. Any election of directors by the stockholders shall be determined by a
plurality of the votes cast by the stockholders entitled to vote at such
election, except as otherwise provided by the Certificate of Incorporation. For
the purposes of this paragraph, Broker Non-Votes represented at the meeting but
not permitted to vote on a particular matter shall not be counted, with respect
to the vote on such matter, in the number of (a) votes cast, (b) votes cast
affirmatively, or (c) votes cast negatively.

      1.10 Introduction of Business at Meetings.

            A. Annual Meetings of Stockholders.

                  (1) Nominations of persons for election to the Board of
            Directors and the proposal of business to be considered by the
            stockholders may be made at an annual meeting of stockholders (a)
            pursuant to the Corporation's notice of meeting, (b) by or at the
            direction of the Board of Directors or (c) by any stockholder of the
            Corporation who was a stockholder of record at the time of giving of
            notice provided for in this Section 1.10, who is entitled to vote at
            the meeting and who complies with the notice procedures set forth in
            this Section 1.10.

                  (2) For nominations or other business to be properly brought
            before an annual meeting by a stockholder pursuant to clause (c) of
            paragraph (A)(1) of this Section 1.10, the stockholder must have
            given timely notice thereof in writing to the Secretary of the
            Corporation and such other business must otherwise be a proper
            matter for stockholder action. To be timely, a stockholder's notice
            shall be delivered to the Secretary at the principal executive
            offices of the Corporation not later than the close of business on
            the one hundred twentieth (120th) day nor earlier than the close of
            business on the one hundred fiftieth (150th) day prior to the first
            anniversary of the date of the proxy statement delivered to
            stockholders in connection with the preceding year's annual meeting;
            provided, however, that if either (i) the date of the annual meeting
            is more than thirty (30) days before or more than sixty (60) days
            after the first anniversary date of the preceding year's annual
            meeting or (ii) no proxy statement was delivered to stockholders in
            connection with the preceding year's annual meeting, notice by the
            stockholder to be timely must be so delivered not earlier than the
            close of business on the ninetieth (90th) day prior to such annual
            meeting and not later than the close of business on the later of the
            sixtieth (60th) day prior to such annual meeting or the close of
            business on the tenth (10th) day following the day on which public
            announcement of the date of such meeting is first made by the
            Corporation. Such stockholder's notice shall set forth (a) as to
            each person whom the stockholder proposes to nominate for election
            or reelection as a director, all information relating to such person
            that is required to be disclosed in solicitations of proxies for
            election of directors, or is otherwise required, in each case
            pursuant to Regulation 14A under the Securities Exchange Act of
            1934, as amended (the "Exchange Act") (including such person's
            written consent to being named in the proxy statement as a nominee
            and to serving as a director if elected); (b) as to any other
            business that the stockholder proposes to bring before the meeting,
            a brief description of the business desired to be brought before the
            meeting, the reasons for conducting such business at the meeting and
            any material interest in such business of such stockholder and the
            beneficial owner, if any, on whose behalf the proposal is made; and
            (c) as to the stockholder giving the notice and the beneficial
            owner, if any, on whose behalf the nomination or proposal is made
            (i) the name and address of such stockholder, as they appear on the
            Corporation's books, and of such beneficial owner and (ii) the class
            and number of shares of capital stock of the Corporation that are
            owned beneficially and held of record by such stockholder and such
            beneficial owner.


                                      -2-


                  (3) Notwithstanding anything in the second sentence of
            paragraph (A)(2) of this Section 1.10 to the contrary, in the event
            that the number of directors to be elected to the Board of Directors
            of the Corporation is increased and there is no public announcement
            by the Corporation naming all of the nominees for director or
            specifying the size of the increased Board of Directors at least
            seventy (70) days prior to the first anniversary of the preceding
            year's annual meeting (or, if the annual meeting is held more than
            thirty (30) days before or sixty (60) days after such anniversary
            date, at least seventy (70) days prior to such annual meeting), a
            stockholder's notice required by this Section 1.10 shall also be
            considered timely, but only with respect to nominees for any new
            positions created by such increase, if it shall be delivered to the
            Secretary at the principal executive office of the Corporation not
            later than the close of business on the tenth (10th) day following
            the day on which such public announcement is first made by the
            Corporation.

            B. Special Meetings of Stockholders. Only such business shall be
            conducted at a special meeting of stockholders as shall have been
            brought before the meeting pursuant to the Corporation's notice of
            meeting. Nominations of persons for election to the Board of
            Directors may be made at a special meeting of stockholders at which
            directors are to be elected pursuant to the Corporation's notice of
            meeting (a) by or at the direction of the Board of Directors or (b)
            provided that the Board of Directors has determined that directors
            shall be elected at such meeting, by any stockholder of the
            Corporation who is a stockholder of record at the time of giving of
            notice of the special meeting, who shall be entitled to vote at the
            meeting and who complies with the notice procedures set forth in
            this Section 1.10. If the Corporation calls a special meeting of
            stockholders for the purpose of electing one or more directors to
            the Board of Directors, any such stockholder may nominate a person
            or persons (as the case may be), for election to such position(s) as
            specified in the Corporation's notice of meeting, if the
            stockholder's notice required by paragraph (A)(2) of this Section
            1.10 shall be delivered to the Secretary at the principal executive
            offices of the Corporation not earlier than the ninetieth (90th) day
            prior to such special meeting nor later than the later of (x) the
            close of business on the sixtieth (60th) day prior to such special
            meeting or (y) the close of business on the tenth (10th) day
            following the day on which public announcement is first made of the
            date of such special meeting and of the nominees proposed by the
            Board of Directors to be elected at such meeting.

            C. General.

                  (1) Only such persons who are nominated in accordance with the
            procedures set forth in this Section 1.10 shall be eligible to serve
            as directors and only such business shall be conducted at a meeting
            of stockholders as shall have been brought before the meeting in
            accordance with the procedures set forth in this Section 1.10.
            Except as otherwise provided by law, the Certificate of
            Incorporation or these By-Laws, the chairman of the meeting shall
            have the power and duty to determine whether a nomination or any
            business proposed to be brought before the meeting was made or
            proposed, as the case may be, in accordance with the procedures set
            forth in this Section 1.10 and, if any proposed nomination or
            business is not in compliance herewith, to declare that such
            defective proposal or nomination shall be disregarded.

                  (2) For purposes of this Section 1.10, "public announcement"
            shall mean disclosure in a press release reported by the Dow Jones
            News Service, Associated Press, PR Newswire, Reuters or comparable
            national news service or in a document publicly filed by the
            Corporation with the Securities and Exchange Commission pursuant to
            Section 13, 14 or 15(d) of the Exchange Act.

                  (3) Notwithstanding the foregoing provisions of this Section
            1.10, a stockholder shall also comply with all applicable
            requirements of the Exchange Act and the rules and regulations
            thereunder with respect to the matters set forth herein. Nothing in
            this Section 1.10 shall be deemed to affect any rights of the
            holders of any series of Preferred Stock to elect directors under
            specified circumstances.

      1.11 Action without Meeting. Stockholders of the Corporation may not take
any action by written consent in lieu of a meeting. Notwithstanding any other
provision of law, the Certificate of Incorporation or these By-Laws, and
notwithstanding the fact that a lesser percentage may be specified by law, the
affirmative vote of the holders of at least seventy-five percent (75%) of the
votes which all the stockholders would be entitled to cast at any annual
election of directors or class of directors shall be required to amend or
repeal, or to adopt any provision inconsistent with, this Section 1.11.

                              ARTICLE 2 - Directors

      2.1 General Powers. The business and affairs of the Corporation shall be
managed by or under the direction of a Board of Directors, who may exercise all
of the powers of the Corporation except as otherwise provided by law or the
Certificate of Incorporation. In the event of a vacancy in the Board of
Directors, the remaining directors, except as otherwise provided by law or the
Certificate of Incorporation, may exercise the powers of the full Board of
Directors until the vacancy is filled.


                                      -3-


      2.2 Number; Election and Qualification. The number of directors which
shall constitute the whole Board of Directors shall be determined by resolution
of the Board of Directors, but in no event shall be less than three. The number
of directors may be decreased at any time and from time to time by a majority of
the directors then in office, but only to eliminate vacancies existing by reason
of the death, resignation, removal or expiration of the term of one or more
directors. The directors shall be elected at the annual meeting of stockholders
(or, if so determined by the Board of Directors pursuant to Section 1.10 hereof,
at a special meeting of stockholders), by such stockholders as have the right to
vote on such election. Directors need not be stockholders of the Corporation.

      2.3 Classes of Directors. The Board of Directors shall be and is divided
into three classes: Class I, Class II and Class III. No one class shall have
more than one director more than any other class.

      2.4 Terms in Office. Each director shall serve for a term ending on the
date of the third annual meeting following the annual meeting at which such
director was elected; provided, however, that each initial director in Class I
shall serve for a term ending on the date of the annual meeting next following
the end of the Corporation's fiscal year ending March 31, 2003; each initial
director in Class II shall serve for a term ending on the date of the annual
meeting next following the end of the Corporation's fiscal year ending March 31,
2004; and each initial director in Class III shall serve for a term ending on
the date of the annual meeting next following the end of the Corporation's
fiscal year ending March 31, 2005.

      2.5 Allocation of Directors Among Classes in the Event of Increases or
Decreases in the Number of Directors. In the event of any increase or decrease
in the authorized number of directors, (i) each director then serving as such
shall nevertheless continue as a director of the class of which he or she is a
member until the expiration of such director's current term or his or her prior
death, removal or resignation and (ii) the newly created or eliminated
directorships resulting from such increase or decrease shall be apportioned by
the Board of Directors among the three classes of directors, subject to the
second sentence of Section 2.3. To the extent possible, consistent with the
foregoing rule, any newly created directorships shall be added to those classes
whose terms of office are to expire at the earliest dates following such
allocation, unless otherwise provided for from time to time by resolution
adopted by a majority of the directors then in office, although less than a
quorum. No decrease in the number of directors constituting the whole Board of
Directors shall shorten the term of an incumbent Director.

      2.6 Tenure. Notwithstanding any provisions to the contrary contained
herein, each director shall hold office until his or her successor is elected
and qualified, or until his or her earlier death, resignation or removal.

      2.7 Vacancies. Unless and until filled by the stockholders, any vacancy in
the Board of Directors, however occurring, including a vacancy resulting from an
enlargement thereof, may be filled by vote of a majority of the directors then
in office, although less than a quorum, or by a sole remaining director. A
director elected to fill a vacancy shall be elected for the unexpired term of
his or her predecessor in office, if any, and a director chosen to fill a
position resulting from an increase in the number of directors shall hold office
until the next election of directors of the class for which such director was
chosen and until his or her successor is elected and qualified, or until his or
her earlier death, resignation or removal.

      2.8 Resignation. Any director may resign by delivering his or her written
resignation to the Corporation at its principal office or to the President or
Secretary. Such resignation shall be effective upon receipt unless it is
specified to be effective at some other time or upon the happening of some other
event.

      2.9 Regular Meetings. Regular meetings of the Board of Directors may be
held without notice at such time and place, either within or without the State
of Delaware, as shall be determined from time to time by the Board of Directors;
provided that any director who is absent when such a determination is made shall
be given notice of the determination. Regular meetings of the Board of Directors
shall be held at such place or places, on such date or dates, and at such time
or times as shall have been established by the Board of Directors and publicized
among all directors. A notice of each regular meeting shall not be required.

      2.10 Special Meetings. Special meetings of the Board of Directors may be
held at any time and place, within or without the State of Delaware, designated
in a call by the Chairman of the Board (if any), the President, two or more
directors, or by one director in the event that there is only a single director
in office.

      2.11 Notice of Special Meetings. Notice of any special meeting of
directors shall be given to each director by the Secretary or by the officer or
one of the directors calling the meeting. Notice shall be duly given to each
director (i) by giving notice to such director in person or by telephone at
least 48 hours in advance of the meeting, (ii) by sending a telegram or
delivering written notice by facsimile transmission or by hand, to his or her
last known business or home address at least 48 hours in advance of the meeting,
or (iii) by mailing written notice to his or her last known business or home
address at least 72 hours in advance of the meeting. A notice or waiver of
notice of a meeting of the Board of Directors need not specify the purposes of
the meeting.

      2.12 Meetings by Telephone Conference Calls. Directors or any members of
any committee designated by the Board of Directors may participate in a meeting
of the Board of Directors or such committee by means of conference


                                      -4-


telephone or similar communications equipment by means of which all persons
participating in the meeting can hear each other, and participation by such
means shall be deemed to constitute presence in person at such meeting.

      2.13 Quorum. A majority of the total number of the whole Board of
Directors shall constitute a quorum at all meetings of the Board of Directors.
In the event one or more of the directors shall be disqualified to vote at any
meeting, then the required quorum shall be reduced by one for each such director
so disqualified; provided, however, that in no case shall less than one-third
(1/3) of the total number of the whole Board of Directors constitute a quorum.
In the absence of a quorum at any such meeting, a majority of the directors
present may adjourn the meeting from time to time without further notice other
than announcement at the meeting, until a quorum shall be present.

      2.14 Action at Meeting. At any meeting of the Board of Directors at which
a quorum is present, the vote of a majority of those present shall be sufficient
to take any action, unless a different vote is specified by law, the Certificate
of Incorporation or these By-Laws.

      2.15 Action by Written Consent. Any action required or permitted to be
taken at any meeting of the Board of Directors or of any committee of the Board
of Directors may be taken without a meeting, if all members of the Board of
Directors or committee, as the case may be, consent to such action in writing,
and the written consent is filed with the minutes of proceedings of the Board of
Directors or committee.

      2.16 Removal. Unless otherwise provided in the Certificate of
Incorporation, any one or more or all of the directors may be removed, only for
cause, by the holders of at least seventy-five percent (75%) of the shares then
entitled to vote at an election of directors.

      2.17 Committees. The Board of Directors may, by resolution passed by a
majority of the whole Board, designate one or more committees, each committee to
consist of one or more of the directors of the Corporation. The Board of
Directors may designate one or more directors as alternate members of any
committee, who may replace any absent or disqualified member at any meeting of
such committee. In the absence or disqualification of a member of a committee,
the member or members of such committee present at any meeting and not
disqualified from voting, whether or not such member or members constitute a
quorum, may unanimously appoint another member of the Board of Directors to act
at such meeting in the place of any such absent or disqualified member. Any such
committee, to the extent provided in the resolution of the Board of Directors
and subject to the provisions of the General Corporation Law of the State of
Delaware, shall have and may exercise all the powers and authority of the Board
of Directors in the management of the business and affairs of the Corporation
and may authorize the seal of the Corporation to be affixed to all papers which
may require it. Each such committee shall keep minutes and make such reports as
the Board of Directors may from time to time request. Except as the Board of
Directors may otherwise determine or as provided herein, any committee may make
rules for the conduct of its business, but unless otherwise provided by the
directors or in such rules, its business shall be conducted as nearly as
possible in the same manner as is provided in these By-Laws for the Board of
Directors. Adequate provisions shall be made for notice to members of all
meeting of committees. One-third (1/3) of the members of any committee shall
constitute a quorum unless the committee shall consist of one (1) or two (2)
members, in which event one (1) member shall constitute a quorum; and all
matters shall be determined by a majority vote of the members present. Action
may be taken by any committee without a meeting if all members thereof consent
thereto in writing, and the consent is filed with the minutes of the proceedings
of such committee.

      2.18 Compensation of Directors. Directors may be paid such compensation
for their services and such reimbursement for expenses of attendance at meetings
as the Board of Directors may from time to time determine. No such payment shall
preclude any director from serving the Corporation or any of its parent or
subsidiary corporations in any other capacity and receiving compensation for
such service.

      2.19 Amendments to Article. Notwithstanding any other provisions of law,
the Certificate of Incorporation or these By-Laws, and notwithstanding the fact
that a lesser percentage may be specified by law, the affirmative vote of the
holders of a least seventy-five percent (75%) of the votes which all the
stockholders would be entitled to cast at any annual election of directors or
class of directors shall be required to amend or repeal, or to adopt any
provision inconsistent with, this Article 2.

                              ARTICLE 3 - Officers

      3.1 Enumeration. The officers of the Corporation shall consist of a
President, a Secretary, a Treasurer and such other officers with such other
titles as the Board of Directors shall determine, including, but not limited to,
a Chairman of the Board, a Vice-Chairman of the Board, and one or more Vice
Presidents, Assistant Treasurers and Assistant Secretaries. The Board of
Directors may appoint such other officers as it may deem appropriate.


                                      -5-


      3.2 Election. The President, Treasurer and Secretary shall be elected
annually by the Board of Directors at its first meeting following the annual
meeting of stockholders. Other officers may be appointed by the Board of
Directors at such meeting or at any other meeting.

      3.3 Qualification. No officer need be a stockholder. Any two or more
offices may be held by the same person.

      3.4 Tenure. Except as otherwise provided by law, by the Certificate of
Incorporation or by these By-Laws, each officer shall hold office until his or
her successor is elected and qualified, unless a different term is specified in
the vote choosing or appointing such officer, or until his or her earlier death,
resignation or removal.

      3.5 Resignation and Removal. Any officer may resign by delivering his or
her written resignation to the Chairman of the Board (if any), to the Board of
Directors at a meeting thereof, to the Corporation at its principal office or to
the President or Secretary. Such resignation shall be effective upon receipt
unless it is specified to be effective at some other time or upon the happening
of some other event.

      Any officer may be removed at any time, with or without cause, by vote of
a majority of the entire number of directors then in office.

      Except as the Board of Directors may otherwise determine, no officer who
resigns or is removed shall have any right to any compensation as an officer for
any period following his or her resignation or removal, or any right to damages
on account of such removal, whether his or her compensation be by the month or
by the year or otherwise, unless such compensation is expressly provided in a
duly authorized written agreement with the Corporation.

      3.6 Vacancies. The Board of Directors may fill any vacancy occurring in
any office for any reason and may, in its discretion, leave unfilled for such
period as it may determine any offices other than those of President, Treasurer
and Secretary. Each such successor shall hold office for the unexpired term of
his predecessor and until his or her successor is elected and qualified, or
until his or her earlier death, resignation or removal.

      3.7 Chairman of the Board and Vice-Chairman of the Board. The Chairman of
the Board, if any, shall preside at all meetings of the Board of Directors and
stockholders at which he or she is present and shall perform such duties and
possess such powers as are designated by the Board of Directors. If the Board of
Directors appoints a Vice-Chairman of the Board, he or she shall, in the absence
or disability of the Chairman of the Board, perform the duties and exercise the
powers of the Chairman of the Board and shall perform such other duties and
possess such other powers as may from time to time be designated by the Board of
Directors.

      3.8 President. The President shall, subject to the direction of the Board
of Directors, have general charge and supervision of the business of the
Corporation. Unless otherwise provided by the Board of Directors, and provided
that there is no Chairman of the Board or that the Chairman and Vice-Chairman,
if any, are not available, the President shall preside at all meetings of the
stockholders, and, if a director, at all meetings of the Board of Directors.
Unless the Board of Directors has designated another officer as the Chief
Executive Officer, the President shall be the Chief Executive Officer of the
Corporation. The President shall perform such other duties and shall have such
other powers as the Board of Directors may from time to time prescribe. The
President shall have the power to enter into contracts and otherwise bind the
Corporation in matters arising in the ordinary course of the Corporation's
business.

      3.9 Vice Presidents. Any Vice President shall perform such duties and
possess such powers as the Board of Directors or the President may from time to
time prescribe. In the event of the absence, inability or refusal to act of the
President, the Vice President (or if there shall be more than one, the Vice
Presidents in the order determined by the Board of Directors) shall perform the
duties of the President and, when so performing, shall have all the powers of
and be subject to all the restrictions upon the President. The Board of
Directors may assign to any Vice President the title of Executive Vice
President, Senior Vice President or any other title selected by the Board of
Directors. Unless otherwise determined by the Board of Directors, any Vice
President shall have the power to enter into contracts and otherwise bind the
Corporation in matters arising in the ordinary course of the Corporation's
business.

      3.10 Secretary and Assistant Secretaries. The Secretary shall perform such
duties and shall have such powers as the Board of Directors or the President may
from time to time prescribe. In addition, the Secretary shall perform such
duties and have such powers as are incident to the office of secretary,
including without limitation the duty and power to give notices of all meetings
of stockholders and special meetings of the Board of Directors, to attend all
meetings of stockholders and the Board of Directors and keep a record of the
proceedings, to maintain a stock ledger and prepare lists of stockholders and
their addresses as required, to be custodian of corporate records and the
corporate seal and to affix and attest to the same on documents.

      Any Assistant Secretary shall perform such duties and possess such powers
as the Board of Directors, the President or the Secretary may from time to time
prescribe. In the event of the absence, inability or refusal to act of the
Secretary, the


                                      -6-


Assistant Secretary (or if there shall be more than one, the Assistant
Secretaries in the order determined by the Board of Directors) shall perform the
duties and exercise the powers of the Secretary.

      In the absence of the Secretary or any Assistant Secretary at any meeting
of stockholders or directors, the person presiding at the meeting shall
designate a temporary secretary to keep a record of the meeting.

      3.11 Treasurer and Assistant Treasurers. The Treasurer shall perform such
duties and shall have such powers as the Board of Directors or the President may
from time to time prescribe. In addition, the Treasurer shall perform such
duties and have such powers as are incident to the office of treasurer,
including without limitation the duty and power to keep and be responsible for
all funds and securities of the Corporation, to deposit funds of the Corporation
in depositories selected in accordance with these By-Laws, to disburse such
funds as ordered by the Board of Directors, to make proper accounts for such
funds, and to render as required by the Board of Directors statements of all
such transactions and of the financial condition of the Corporation.

      The Assistant Treasurers shall perform such duties and possess such powers
as the Board of Directors, the President or the Treasurer may from time to time
prescribe. In the event of the absence, inability or refusal to act of the
Treasurer, the Assistant Treasurer (or if there shall be more than one, the
Assistant Treasurers in the order determined by the Board of Directors) shall
perform the duties and exercise the powers of the Treasurer.

      3.12 Salaries. Officers of the Corporation shall be entitled to such
salaries, compensation or reimbursement as shall be fixed or allowed from time
to time by the Board of Directors.

      3.13 Action with Respect to Securities of Other Corporations. Unless
otherwise directed by the Board of Directors, the President or any officer of
the Corporation authorized by the President shall have power to vote and
otherwise act on behalf of the Corporation, in person or by proxy, at any
meeting of stockholders of or with respect to any action of stockholders of any
other corporation in which the Corporation may hold securities and otherwise to
exercise any and all rights and powers which this Corporation may possess by
reason of its ownership of securities in such other corporation.

                            ARTICLE 4 - Capital Stock

      4.1 Issuance of Stock. Unless otherwise voted by the stockholders and
subject to the provisions of the Certificate of Incorporation, the whole or any
part of any unissued balance of the authorized capital stock of the Corporation
or the whole or any part of any issued, authorized capital stock of the
Corporation held in its treasury may be issued, sold, transferred or otherwise
disposed of by vote of the Board of Directors in such manner, for such
consideration and on such terms as the Board of Directors may determine.

      4.2 Certificates of Stock. Every holder of stock of the Corporation shall
be entitled to have a certificate, in such form as may be prescribed by law and
by the Board of Directors, certifying the number and class of shares owned by
such stockholder in the Corporation. Each such certificate shall be signed by,
or in the name of the Corporation by, the Chairman or Vice-Chairman, if any, of
the Board of Directors, or the President or a Vice President, and the Treasurer
or an Assistant Treasurer, or the Secretary or an Assistant Secretary of the
Corporation. Any or all of the signatures on such certificate may be a
facsimile.

      Each certificate for shares of stock which are subject to any restriction
on transfer pursuant to the Certificate of Incorporation, the By-Laws,
applicable securities laws or any agreement among any number of shareholders or
among such holders and the Corporation shall have conspicuously noted on the
face or back of such certificate either the full text of such restriction or a
statement of the existence of such restriction.

      4.3 Transfers. Except as otherwise established by rules and regulations
adopted by the Board of Directors, and subject to applicable law, shares of
stock may be transferred on the books of the Corporation by the surrender to the
Corporation or its transfer agent of the certificate representing such shares,
properly endorsed or accompanied by a written assignment or power of attorney
properly executed, and with such proof of authority or the authenticity of
signature as the Corporation or its transfer agent may reasonably require.
Except as may be otherwise required by law, by the Certificate of Incorporation
or by these By-Laws, the Corporation shall be entitled to treat the record
holder of stock as shown on its books as the owner of such stock for all
purposes, including the payment of dividends and the right to vote with respect
to such stock, regardless of any transfer, pledge or other disposition of such
stock, until the shares have been transferred on the books of the Corporation in
accordance with the requirements of these By-Laws.

      4.4 Lost, Stolen or Destroyed Certificates. The Corporation may issue a
new certificate of stock in place of any previously issued certificate alleged
to have been lost, stolen, or destroyed, upon such terms and conditions as the
President may prescribe, including the presentation of reasonable evidence of
such loss, theft or destruction and the giving of such indemnity as the
President may require for the protection of the Corporation or any transfer
agent or registrar.


                                      -7-


      4.5 Record Date. The Board of Directors may fix in advance a date as a
record date for the determination of the stockholders entitled to notice of or
to vote at any meeting of stockholders or entitled to receive payment of any
dividend or other distribution or allotment of any rights in respect of any
change, conversion or exchange of stock, or for the purpose of any other lawful
action. Such record date shall not be more than 60 nor less than 10 days before
the date of such meeting, nor more than 60 days prior to any other action to
which such record date relates.

      If no record date is fixed, the record date for determining stockholders
entitled to notice of or to vote at a meeting of stockholders shall be at the
close of business on the day before the day on which notice is given, or, if
notice is waived, at the close of business on the day before the day on which
the meeting is held. The record date for determining stockholders for any other
purpose shall be at the close of business on the day on which the Board of
Directors adopts the resolution relating to such purpose.

      A determination of stockholders of record entitled to notice of or to vote
at a meeting of stockholders shall apply to any adjournment of the meeting;
provided, however, that the Board of Directors may fix a new record date for the
adjourned meeting.

                         ARTICLE 5 - General Provisions

      5.1 Fiscal Year. Except as otherwise designated from time to time by the
Board of Directors, the fiscal year of the Corporation shall begin on the first
day of April and end on the last day of March.

      5.2 Corporate Seal. The corporate seal shall be in such form as shall be
approved by the Board of Directors.

      5.3 Notices. Except as otherwise specifically provided herein or required
by law or the Certificate of Incorporation, all notices required to be given to
any person pursuant to these by-laws shall be in writing and may in every
instance be effectively given by hand delivery to the recipient thereof, by
depositing such notice in the mails, postage paid, or by sending such notice by
prepaid telegram or facsimile transmission. Any such notice shall be addressed
to such person at his or her last known address as the same appears on the books
of the Corporation. The time when such notice is received shall be deemed to be
the time of the giving of the notice.

      5.4 Waiver of Notice. Whenever any notice whatsoever is required to be
given by law, by the Certificate of Incorporation or by these By-Laws, a waiver
of such notice either in writing signed by the person entitled to such notice or
such person's duly authorized attorney, or by telegraph, facsimile transmission
or any other available method, whether before, at or after the time stated in
such waiver, or the appearance of such person or persons at such meeting in
person or by proxy, shall be deemed equivalent to such notice.

      5.5 Evidence of Authority. A certificate by the Secretary, or an Assistant
Secretary, or a temporary Secretary, as to any action taken by the stockholders,
directors, a committee or any officer or representative of the Corporation
shall, as to all persons who rely on the certificate in good faith, be
conclusive evidence of such action.

      5.6 Facsimile Signatures. In addition to the provisions for use of
facsimile signatures elsewhere specifically authorized in these By-Laws,
facsimile signatures of any officer or officers of the Corporation may be used
whenever and as authorized by the Board of Directors or a committee thereof.

      5.7 Reliance upon Books, Reports and Records. Each director, each member
of any committee designated by the Board of Directors, and each officer of the
Corporation shall, in the performance of his or her duties, be fully protected
in relying in good faith upon the books of account or other records of the
Corporation and upon such information, opinions, reports or statements presented
to the Corporation by any of its officers or employees or committees of the
Board of Directors so designated, or by any other person as to matters which
such director or committee member reasonably believes are within such other
person's professional or expert competence and who has been selected with
reasonable care by or on behalf of the Corporation.

      5.8 Time Periods. In applying any provision of these By-Laws that requires
that an act be done or not be done a specified number of days prior to an event
or that an act be done during a period of a specified number of days prior to an
event, calendar days shall be used, the day of the doing of the act shall be
excluded, and the day of the event shall be included.

      5.9 Certificate of Incorporation. All references in these By-Laws to the
Certificate of Incorporation shall be deemed to refer to the Certificate of
Incorporation of the Corporation, as amended and in effect from time to time.

      5.10 Transactions with Interested Parties. No contract or transaction
between the Corporation and one or more of the directors or officers, or between
the Corporation and any other corporation, partnership, association, or other
organization in which one or more of the directors or officers are directors or
officers, or have a financial interest, shall be void or voidable solely for
this reason, or solely because such director or officer is present at or
participates in the meeting of


                                      -8-


the Board of Directors or a committee of the Board of Directors which authorizes
the contract or transaction or solely because his, her or their votes are
counted for such purpose, if:

            (1) The material facts as to his or her relationship or interest and
      as to the contract or transaction are disclosed or are known to the Board
      of Directors or the committee, and the Board or committee in good faith
      authorizes the contract or transaction by the affirmative vote of a
      majority of the disinterested directors, even though the disinterested
      directors be less than a quorum;

            (2) The material facts as to his or her relationship or interest and
      as to the contract or transaction are disclosed or are known to the
      stockholders entitled to vote thereon, and the contract or transaction is
      specifically approved in good faith by vote of the stockholders; or

            (3) The contract or transaction is fair as to the Corporation as of
      the time it is authorized, approved or ratified, by the Board of
      Directors, a committee of the Board of Directors, or the stockholders.

      Common or interested directors may be counted in determining the presence
of a quorum at a meeting of the Board of Directors or of a committee which
authorizes the contract or transaction.

      5.11 Severability. Any determination that any provision of these By-Laws
is for any reason inapplicable, illegal or ineffective shall not affect or
invalidate any other provision of these By-Laws.

      5.12 Pronouns. All pronouns used in these By-Laws shall be deemed to refer
to the masculine, feminine or neuter, singular or plural, as the identity of the
persons or persons so designated may require.

                             ARTICLE 6 - Amendments

      6.1 By the Board of Directors. Except as is otherwise set forth in these
By-Laws, these By-Laws may be altered, amended or repealed, or new by-laws may
be adopted, by the affirmative vote of a majority of the directors present at
any regular or special meeting of the Board of Directors at which a quorum is
present.

      6.2 By the Stockholders. Except as otherwise set forth in these By-Laws,
these By-Laws may be altered, amended or repealed or new by-laws may be adopted
by the affirmative vote of the holders of at least 75% of the voting power of
all of the then outstanding shares of the capital stock of the Corporation
entitled to vote generally in the election of directors, voting together as a
single class, provided notice of such alteration, amendment, repeal or adoption
of new by-laws shall have been stated in the notice of such special meeting.


                                      -9-


Dear Shareholder:

Please take note of the important information enclosed with this Proxy. There
are a number of issues related to the operation of the Company that require your
immediate attention.

Your vote counts, and you are strongly encouraged to exercise your right to vote
your shares.

Please mark the boxes on the proxy card to indicate how your shares will be
voted. Then sign the card, detach it and return your proxy in the enclosed
postage paid envelope.

Thank you in advance for your prompt consideration of these matters.

Sincerely,
Repligen Corporation

                                      PROXY

                              REPLIGEN CORPORATION

                           41 SEYON STREET, BUILDING 1
                                WALTHAM, MA 02453

                       SOLICITED BY THE BOARD OF DIRECTORS
                     FOR THE ANNUAL MEETING OF SHAREHOLDERS

      The undersigned hereby appoints Walter C. Herlihy and Daniel P. Witt, and
each of them alone, proxies with full power of substitution, to vote all shares
of common stock of the Corporation which the undersigned is entitled to vote at
the Annual Meeting of Shareholders of Repligen Corporation to be held on the
12th day, September, 2002 at 10:00 a.m., local time, at the offices of the
Corporation, 41 Seyon Street, Waltham, Massachusetts 02453, and any adjournments
thereof, upon matters set forth in the Notice of Annual Meeting of Shareholders
and Proxy Statement dated July 18, 2002, a copy of which has been received by
the undersigned. The proxies are further authorized to vote, in their
discretion, upon such other business as may be incidental to the meeting or any
adjournments thereof.


                                                                       
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   SEE REVERSE SIDE                CONTINUED AND TO BE SIGNED ON REVERSE SIDE              SEE REVERSE SIDE
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        VOTE BY TELEPHONE                                                            VOTE BY INTERNET
It's fast, convenient, and                                                   It's fast, convenient, and your
immediate!  Call Toll-Free on a                                              vote is immediately confirmed
Touch-Tone Phone 1-877-PRX-VOTE                                              and posted.
(1-877-779-8683).
----------------------------------                                           ----------------------------------

Follow these four easy steps:                                                Follow these four easy steps:
1. Read the accompanying Proxy                                               1. Read the accompanying Proxy
Statement/Prospectus and Proxy                                               Statement/Prospectus and Proxy
Card.                                                                        Card.

2. Call the toll-free number                                                 2. Go to the Website
1-877-PRX-VOTE (1-877-779-8683).                                             http://www.eproxyvote.com/rgen

3. Enter your 14-digit Voter                                                 3. Enter your 14-digit Voter
Control Number located on your                                               Control Number located on your
Proxy Card above your name.                                                  Proxy Card above your name.

4. Follow the recorded                                                       4. Follow the instructions
instructions.                                                                provided.
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YOUR VOTE IS IMPORTANT!                                                      YOUR VOTE IS IMPORTANT!
Call 877-PRX-VOTE anytime!                                                   Go to http://www.eproxyvote.com/
                                                                             rgen anytime!



DO NOT RETURN YOUR PROXY CARD IF YOU ARE VOTING BY TELEPHONE OR INTERNET

Please mark votes as in this example. /X/

THE SHARES REPRESENTED BY THIS PROXY WILL BE VOTED AS DIRECTED OR, IF NO
DIRECTION IS GIVEN, WILL BE VOTED FOR THE ELECTION OF DIRECTORS AND FOR THE
PROPOSALS IN ITEM 2 AND 3, AND AUTHORITY WILL BE DEEMED GRANTED UNDER ITEM 4 TO
HAVE THE PROXIES VOTED UPON SUCH ADJORNMENTS THEREOF.

1. To elect five persons to the Board of Directors to serve for staggered terms
or, if Proposal 2 is not adopted by the stockholders, to elect five persons to
the Board of Directors for the ensuing year.

Nominees: Robert J. Hennessey, Walter C. Herlihy, Ph.D., G. William Miller,
Alexander Rich, M.D., Paul Schimmel, Ph.D

For               Withheld          For all nominees except as noted below
/ /               / /               /  /__________________________________

2. To approve an amended and restated certificate of incorporation and amended
and restated by-laws.

For               Against           Abstain
/ /              / /               / /

3. To ratify the selection of Ernst & Young LLP as the independent auditors of
Repligen for the fiscal year ending March 31, 2003.

For               Against           Abstain
/ /              / /               / /

4.  In their discretion, the proxies are authorized to vote upon such other
    matters as may properly come before the meeting or any adjournment thereof.

/ / MARK HERE FOR ADDRESS CHANGE AND NOTE AT LEFT.

(If signing as attorney, executor, trustee, or guardian, please give your full
title as such. If stock is held jointly, each owner should sign.)

Signature:        Date:             Signature:       Date:
     --------         --------          --------          --------