SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                    FORM 10-K

[X]  ANNUAL REPORT  PURSUANT TO SECTION 13 OR 15(d) OF THE  SECURITIES  EXCHANGE
     ACT OF 1934
                    For the fiscal year ended March 31, 2001

                                       OR

[ ]  TRANSITION  REPORT  PURSUANT  TO  SECTION  13 OR  15(d)  OF THE  SECURITIES
     EXCHANGE  ACT OF 1934

          For the transition period from ____________ to _____________

                         Commission file number: 0-14656

                              REPLIGEN CORPORATION
             (Exact name of Registrant as specified in its charter)

          Delaware                                          04-2729386
   (State or other jurisdiction of                       (I.R.S. Employer
   incorporation or organization)                        Identification No.)

117 Fourth Avenue, Needham, Massachusetts                02494
(Address of principal executive offices)                 (Zip Code)

       Registrant's telephone number, including area code: (781) 449-9560

        Securities registered pursuant to Section 12(b) of the Act: None


          Securities registered pursuant to Section 12(g) of the Act:

                          Common Stock, $0.01 Par Value
                                (Title of Class)

Indicate by checkmark  whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  Registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days. Yes __X__ No_____.

Indicate by check mark if disclosure of delinquent  filers  pursuant to Item 405
of Regulation  S-K is not contained  herein,  and will not be contained,  to the
best of Registrant's  knowledge,  in definitive proxy or information  statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K |_|

State  the  aggregate   market  value  of  the  voting  common  equity  held  by
non-affiliates  of the  Registrant.  The  aggregate  market  value,  computed by
reference  to the closing  sale price of such stock quoted on NASDAQ on June 15,
2001 was approximately $49,785,492.

Indicate the number of shares outstanding of each of the registrant's classes of
common stock as of June 15, 2001: 26,633,950.

                       DOCUMENTS INCORPORATED BY REFERENCE

The Company intends to file a definitive Proxy Statement  pursuant to Regulation
14A within 120 days of the end of the fiscal year ended March 31, 2001. Portions
of such Proxy  Statement are  incorporated by reference in Part III of this Form
10-K.



Item 1.   BUSINESS

     Any  statements  which are not  historical  facts  contained in this Annual
Report on Form 10-K, including,  without, limitation,  projections or statements
concerning  use and  success of  technology,  progress  of product  development,
programs or clinical  trials,  completion,  timing and  benefits of  development
programs, liquidity, suitability of products for specific applications,  product
performance,  advantages or significance of technology,  benefits and results of
acquisitions, collaborations and strategic and other alliances, and improvements
to operating and other  results,  are  forward-looking  statements  that involve
risks and uncertainties,  including but not limited to those relating to product
demand,  pricing,   market  acceptance,   the  effect  of  economic  conditions,
intellectual  property  rights  and  litigation,  the  results  of  governmental
proceedings,  competitive  products,  risks in timing and  success  of  clinical
trials and product development, the results of financing efforts, the ability to
exploit  technologies,  the  ability to complete  transactions,  and other risks
identified  under the caption  "Certain  Factors That May Affect Future Results"
and  elsewhere in this Annual  Report,  as well as in our other  Securities  and
Exchange  Commission filings.  Our actual results may differ  significantly from
the results discussed in the forward-looking statements.

The Company

     Repligen  Corporation  ("Repligen")  develops new drugs for autism,  immune
system diseases and  mitochondrial  disease.  Our lead therapeutic  products are
secretin  for autism,  CTLA4-Ig  for stem cell  transplantation  and uridine for
mitochondrial  disease. We also manufacture and market products based on Protein
A for the  purification  of  antibodies,  and we own  commercial  rights  to two
products  based on synthetic  forms of secretin for the  diagnosis of pancreatic
function.  Repligen was  incorporated in March 1981, under the laws of the State
of Delaware. Our principal executive officers are at 117 Fourth Avenue, Needham,
Massachusetts 02494 and our telephone number is (781) 449-9560.

Secretin for Autism

     Autism is a developmental  disorder  characterized  by poor  communication,
impaired social interaction and repetitive  behavior.  Many autistic individuals
also have  gastrointestinal  dysfunction.  Secretin is a hormone produced in the
small  intestine  which  regulates  the  function of the pancreas as part of the
process of  digestion.  A form of secretin  derived from pigs is approved by the
United  States  Food  and  Drug  Administration  ("FDA")  for use in  diagnosing
problems with pancreatic function.  Anecdotal reports indicate that secretin may
have beneficial effects in some autistic children, including improvements in the
social deficit which is the defining feature of autism.

     We have  completed  an  FDA-approved  Phase 2  clinical  trial  on a human,
synthetic  form of secretin in order to evaluate its  potential  benefits on the
gastrointestinal,  social, communicative and behavioral symptoms of autism. This
trial was a randomized,  double-blind,  placebo-controlled  study which enrolled
126 autistic children aged 3 to 6 at multiple sites in the United States. All of
the children had  gastrointestinal  symptoms and moderate to severe  symptoms of
autism.  Each  patient  received  3 doses of  secretin  or a  placebo  at 3 week
intervals.  Patients were assessed before the first dose and two weeks after the
third dose with  multiple  standardized  tests  including  clinical and parental
evaluations,  a daily diary of gastrointestinal  and autistic symptoms and video
taping of structured play sessions.

     Results from the trial indicated that parents of secretin-treated  children
rated their child's symptoms to be improved  compared to children who received a
placebo,  a result that was


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statistically  significant.  We also identified two biological  parameters which
defined a group of patients whose symptoms were highly  variable over time. When
these patients were removed from the analysis, the beneficial effect of secretin
was  also  observed  in two  types  of  evaluations  carried  out  by a  trained
psychologist.  This trial also  evaluated  the safety of secretin.  There was no
statistically significant increase in the side-effects (adverse events) observed
in secretin-treated patients versus patients who received a placebo.

     We have also initiated a research  effort to better  understand the biology
of  secretin  and its  mechanism  of action in autistic  patients.  We intend to
analyze multiple  biological  parameters in the multiple blood,  urine and stool
samples  that were  collected  from  these  patients  to search  for  additional
biological markers which may be correlated with the response to secretin. We are
also  investigating the neurobiology of secretin in animals to better understand
its mechanism of action.

     According  to the  American  Society  for Autism,  there are  approximately
500,000 individuals affected by autism in the United States. There are currently
no FDA-approved  drugs for the treatment of autism and no drug therapy which has
been reported to improve the social or communicative deficits of autism.

     In February  2000, we were issued a U.S.  patent for the use of secretin in
the treatment of autism which will expire in 2018. We are currently  prosecuting
additional patent applications in the United States, Europe and Japan.

CTLA4-Ig for Transplantation and Immune Disorders

     We are also  developing  a  product  named  "CTLA4-Ig,"  based on a natural
regulator  of the immune  system.  CTLA4-Ig  has been shown in animal  models to
selectively block unwanted immune responses in organ transplantation and several
autoimmune diseases.  We are conducting our initial clinical testing of CTLA4-Ig
in patients receiving a stem cell (bone marrow) transplant, which is a potential
cure for several cancers of the immune system,  including leukemia,  myeloma and
lymphoma.  A stem cell  transplant  is also a  potential  treatment  for certain
metabolic diseases, autoimmune diseases and sickle cell anemia.

     Despite the  clinical  potential of stem cell  transplantation,  its use is
limited by a severe and potentially life-threatening complication - graft versus
host disease ("GVHD"), in which the newly transplanted immune system attacks the
tissues  of the  recipient.  To  minimize  this  complication,  most  stem  cell
transplants  require a search  for a  genetically  "matched"  donor  which  only
partially  eliminates  GVHD and which can delay  treatment  for  months and cost
$25,000 or more.

     In June 1999,  the results of a Phase 1 clinical  trial of our  CTLA4-Ig in
stem cell transplantation were published in the New England Journal of Medicine.
The trial involved eleven patients who received a graft from a family member who
was  only  partially   genetically   matched  with  the  patient.   The  results
demonstrated  that  pre-treatment of stem cells (bone marrow) from a genetically
"mismatched" family member with CTLA4-Ig prior to transplantation  resulted in a
lower  incidence of GVHD than expected based on prior  experience.  We intend to
further evaluate CTLA4-Ig for stem cell  transplantations in which the donor and
recipient  are  genetically  "mismatched"  in an  FDA-approved  Phase 2 clinical
trial.

     In the last five years,  a new technique  has been  developed to reduce the
morbidity and mortality of stem cell transplantation.  In this "mini-transplant"
procedure,  the patient receives substantially less radiation treatment prior to
the  transplant.  While  this can  reduce  side  effects  and the time  spent in
intensive  care,  the problem of GVHD remains.  We intend to evaluate the


                                        3


use of  CTLA4-Ig  to prevent the  development  of GVHD in  patients  receiving a
"mini-transplant" in a second Phase 2 clinical trial.  Reduction of the severity
of GVHD in this setting may enable stem cell  transplantation to be applied to a
broader  range of cancer  patients  and to other  diseases for which the current
morbidity associated with the transplant is unacceptable.

     Repligen  has  obtained an  exclusive  license to the patent  rights of the
University  of Michigan  which  pertain to CTLA4-Ig and is  prosecuting  patents
filed by the University  related to compositions of matter and methods of use of
CTLA4-Ig.  We also  believe  that the  University  of Michigan  and Repligen are
entitled to rights to certain  U.S.  patents on  compositions  and uses of CTLA4
which have been issued to Bristol-Myers Squibb Company. (For more information on
our intellectual property rights to CTLA4-Ig, please see "Legal Proceedings.")

Uridine for Mitochondrial Disorders

     Mitochondria  are small  structures  present in every  cell which  serve to
produce  energy  for  cellular  processes.  Defects  in the genes  which  encode
mitochondrial  proteins are responsible for mitochondrial  disease which affects
multiple organs, particularly the nervous system, heart, liver and lungs. Inborn
forms of mitochondrial  disease affect approximately 20,000 people in the United
States and result in  symptoms,  including  seizures,  skeletal and heart muscle
weakness and neurological and cognitive defects.

     It has recently been  recognized  that a second function of mitochondria is
to produce uridine,  an essential  precursor for the synthesis of RNA and DNA as
well as other cellular functions. This insight led researchers at The University
of California, San Diego ("UCSD") to evaluate synthetic uridine as a therapy for
mitochondrial disease.

     In Phase 1 clinical trials carried out by UCSD,  daily oral  administration
of uridine or an analog of uridine  was  evaluated  in 14  patients.  This study
indicated  that the therapy is well  tolerated  in patients  with  mitochondrial
disease  including a few who have  received it for more than two years.  Several
patients also had marked  improvements in their symptoms,  including a reduction
in the number of seizures,  improved muscle strength and  improvements in kidney
function.  Repligen is  currently  preparing  for a  placebo-controlled  Phase 2
clinical trial to extend these observations.

     In  December  2000,  Repligen  exclusively  licensed  the  rights to patent
applications  from UCSD for the treatment of mitochondrial  disease with uridine
or analogs of uridine.

Protein A Products for Antibody Manufacturing

     Protein A is a naturally  occurring  protein  used in the  purification  of
antibodies.  Virtually all therapeutic monoclonal antibodies are manufactured by
a process in which an impure mixture  containing the desired antibody product is
passed  over a solid  support to which  Protein A has been  chemically  attached
(immobilized).  The immobilized Protein A binds the antibody product while other
impurities are washed away. The antibody is then recovered from the support in a
substantially purified form.

     We  manufacture  and market  several  forms of  recombinant  Protein A. Our
primary  customers  incorporate  our  product  into their  proprietary  antibody
purification   systems  which  they  sell  directly  to  the  biotechnology  and
pharmaceutical  industry.  We also manufacture an immobilized  Protein A product
which is  marketed  by  Amersham  Pharmacia  Biotech.  Substantially  all of our
product sales for the last three years have been sales of Protein A.


                                        4


     In the past four years,  the sales of  therapeutic  antibody  products have
increased from $300 million in 1997 to  approximately  $2 billion in 2000.  This
growth is based on the growth of new therapeutic  antibody  products,  including
Rituxin(R) for lymphoma,  Herceptin(TM)  for breast cancer,  Synagis(TM) for RSV
infection,  Remicade(TM)  for Crohn's  disease and arthritis and  Enbrel(TM) for
arthritis.  There are more than 100 additional  monoclonal antibodies in various
stages of clinical  testing which may lead to additional  growth of the antibody
market and in the demand for Protein A.

     We own a patent in the U.S. covering the protein A gene and the manufacture
of recombinant Protein A which expires in 2009. Similar patents have been issued
to us in certain European countries and Japan which expire in 2002.

Secretin Diagnostic Products

     In October  1999,  we  acquired  the  commercial  rights to two  diagnostic
products based on synthetic  forms of porcine  (pig-derived)  and human secretin
from  ChiRhoClin,  Inc., a private  company.  Both of these  products  have been
evaluated  in  clinical  trials for their  safety  and  efficacy  in  diagnosing
pancreatic function and gastrinoma.  A New Drug Application for each product has
been filed with the FDA. In March 2000,  the FDA issued an  "approvable  letter"
for the  use of  synthetic  porcine  secretin  in the  diagnosis  of  pancreatic
function.  The FDA issued a second  "approvable  letter" issued in November 2000
which contained questions  concerning the manufacture and quality control of the
synthetic  porcine  substance.  Final approval to market this synthetic  porcine
product  will be based on a  satisfactory  response by  ChiRhoClin  to questions
raised by the FDA.

     We   intend   to   market   these   diagnostic    products    directly   to
gastroenterologists  in the U.S. The FDA has granted both  products  Orphan Drug
Status  which means that they will each have a seven year period of  exclusivity
following final approval of the NDA.

Repligen's Business Strategy

     Our primary  objective  is to develop  drugs  based on  naturally-occurring
peptides,  proteins and nucleotides.  By harnessing the natural actions of these
compounds,  it may be possible to modify a disease process in a specific way and
with a minimum of toxicity.  We intend to maintain the commercial  rights to our
lead product  candidates  through  "proof of efficacy"  clinical  trials.  After
demonstration  of a product  candidate's  therapeutic  potential,  we may seek a
biotechnology  or  pharmaceutical  partner for further  clinical  development or
commercialization of our product candidates.

     We seek to control our operating losses by out-sourcing  certain aspects of
clinical product development and manufacturing.  In addition,  we seek to offset
some of the expenses  associated with product  development with profits from the
sales of Protein A products  and,  pending  FDA  approval,  secretin  diagnostic
products. We intend to seek additional current product opportunities to increase
our current product revenues as we increase expenditures on clinical development
of our therapeutic products.

Sales and Marketing

     We sell our rProtein A(TM) products primarily through value-added resellers
including Amersham Pharmacia Biotech, AB ("APBiotech"),  PE Biosystems, Inc. and
Millipore  Corporation,  and through  distributors in certain  foreign  markets.
Pending  approval  by the FDA,


                                        5


we   intend  to  market   our   secretin   diagnostic   products   directly   to
gastroenterologists in the United States.

Customers

     Customers  for our  Protein A products  include  chromatography  companies,
diagnostics companies,  biopharmaceutical  companies and laboratory researchers.
During  fiscal 2001,  customers  that  accounted  for more than 10% of our total
revenues were APBiotech and PE Biosystems Inc.

Employees

     As of June 15, 2001,  we had 40  employees.  Of the 40  employees,  26 were
engaged in research,  development and manufacturing and 14 in administrative and
marketing functions.  Doctorates or other advanced degrees are held by 15 of our
employees.  Each of our employees has signed a  confidentiality  agreement.  Our
employees are not covered by a collective bargaining agreement.

Patents, Licenses and Proprietary Rights

     Our policy is to seek patent  protection  for our  significant  proprietary
products.   We  pursue   patent   protection  in  the  United  States  and  file
corresponding patent applications in relevant foreign jurisdictions.  We believe
that patents are an important  element in the protection of our  competitive and
proprietary position, but other elements,  including trade secrets,  orphan drug
status and know-how, are also important. We own or have exclusive rights to more
than 15 U.S. patents and corresponding foreign equivalents. In addition, we have
rights to more than 20 U.S. pending patent applications. The invalidation of key
patents  owned or  licensed  by us or the failure of patents to issue on pending
patent applications could create increased  competition,  with potential adverse
effects on our business prospects.

     In March  1999,  we  acquired  the  rights to certain  patent  applications
claiming the  therapeutic  use of secretin to treat  autism and other  pervasive
developmental  disorders.  In February 2000, we received a U.S.  patent covering
the use of secretin in the  treatment  of autism or the symptoms of autism which
will expire in 2018.  Additional related patent applications are currently being
prosecuted in the United States and key foreign markets.

     As part of our  program  to  develop  drugs  directed  to the  immune  cell
receptors known as CD28, B7 and CTLA4 (costimulatory  factors),  we licensed the
rights to certain patent  applications  from the University of Michigan in 1992.
In September 1995, we assigned these patent rights to Genetics  Institute,  Inc.
In January 1996, Genetics Institute, Inc. returned the rights to CTLA4-Ig to us.
In November  1999,  we executed an agreement  with  Genetics  Institute  and the
University of Michigan which  confirmed the prior  transfer of certain  CTLA4-Ig
related  rights from  Genetics  Institute to the  University of Michigan and the
exclusive  license  of those  rights  to us.  We have an  unrestricted  right to
sub-license  our CTLA4-Ig  rights.  (For more  information  on our  intellectual
property rights to CTLA4-Ig, please see "Legal Proceedings.")

     We have licensed two patent applications from the University of California,
San Diego (UCSD)  covering  novel  methods for the  treatment  of  mitochondrial
disease and for the treatment of autism in patients  with  abnormal  metabolism.
Under the terms of the license agreement, Repligen receives exclusive commercial
rights  to  both  inventions  and  will  pay  UCSD  an  up-front  fee,  clinical
development  milestones  and  royalties  on product  sales.  Repligen  will also
support two research projects at UCSD. One patent  application covers the use of
analogs of uridine,  a naturally


                                        6


occurring component of RNA and DNA, for the treatment of diseases  characterized
by defects in the function of mitochondria.  A second patent  application covers
the use of uridine and a form of uridine,  triacetyl  uridine  ("TAU"),  for the
correction of defects in purine  metabolism which produce the symptoms of autism
or pervasive developmental disorder.

     We own U.S.  and  European  patents  covering  recombinant  Protein A which
expire in 2009 and 2002  respectively.  We also own rights to modified  forms of
Protein A which were  licensed to  APBiotech  in December  1998 as part of a ten
year agreement covering the supply of recombinant Protein A to APBiotech.

     We  also  rely  upon  trade  secret  protection  for our  confidential  and
proprietary  information.  Our  policy  is to  require  each  of our  employees,
consultants and significant scientific  collaborators to execute confidentiality
agreements  upon the  commencement  of an employment or consulting  relationship
with us. These agreements  generally  provide that all confidential  information
developed or made known to the individual  during the course of the individual's
relationship  with us is to be kept  confidential  and not  disclosed  to  third
parties  except  in  specific  circumstances.  In  the  case  of  employees  and
consultants,  the agreements  generally provide that all inventions conceived by
the  individual  in the course of  rendering  services to Repligen  shall be our
exclusive property.

Competition

     Our Protein A products compete on the basis of quality,  performance,  cost
effectiveness,   and   application   suitability   with   numerous   established
technologies   for  protein   purification.   Additional   products   using  new
technologies  which may be competitive with our products may also be introduced.
Many of the companies selling or developing competitive products have financial,
manufacturing and distribution resources significantly greater than ours.

     The field of drug  development in which we are involved is characterized by
rapid technological change. New developments are expected to continue at a rapid
pace in both industry and academia.  There are many  companies,  both public and
private,  including  large  pharmaceutical  companies,  chemical  companies  and
specialized biotechnology companies,  engaged in developing products competitive
with  products  that we have under  development.  Many of these  companies  have
greater capital,  human resources,  research and development,  manufacturing and
marketing  experience  than we do. They may succeed in developing  products that
are  more  effective  or  less  costly  than  any  that  we may  develop.  These
competitors  may also prove to be more  successful than we are in production and
marketing.  In addition,  academic,  government and  industry-based  research is
intense,  resulting in considerable  competition in obtaining qualified research
personnel,  submitting  patent filings for protection of  intellectual  property
rights and establishing  corporate  strategic  alliances.  We can not be certain
that research, discoveries and commercial developments by others will not render
any of our programs or potential products noncompetitive.

Manufacturing

     We manufacture Protein A products from recombinant strains of bacteria.  We
manufacture  a modified form of Protein A for AP Biotech under a ten year supply
agreement  which was  initiated  in  December  1998.  Certain  fermentation  and
recovery  operations  are  carried  out  by  third  parties.  The  purification,
immobilization, packaging and quality control testing of Protein A are conducted
at our facilities in Needham,  Massachusetts.  (For more  information  about our
manufacturing facilities,  please see "Description of Property.") We maintain an
active quality


                                       7


assurance  effort to support the regulatory  requirements of our customers.  Our
secretin diagnostic product is purchased from ChiRhoClin,  Inc. who manufactures
it through third party contractors.

Government Regulation

     The development of drug candidates,  such as secretin or CTLA4-Ig, by us or
our collaborative partners are subject to regulation in the United States by the
FDA and abroad by foreign  equivalents.  Product development and approval within
the FDA  regulatory  framework  usually  takes a  significant  number  of years,
involves the  expenditure  of  substantial  capital  resources and timelines for
development are uncertain.

     Before  clinical  testing in the United  States of any drug  candidate  may
begin, FDA  requirements for preclinical  efficacy and safety must be completed.
Required  toxicity  testing  typically  involves  characterization  of the  drug
candidate in several animal  species.  Safety and efficacy data are submitted to
the FDA as part of an  Investigational  New  Drug  Application  ("IND")  and are
reviewed by the FDA prior to the commencement of human clinical trials.

     Clinical trials involve the  administration of the drug to human volunteers
or  patients  under  the  supervision  of a  qualified  investigator,  usually a
physician,  with an FDA-approved  protocol.  Human clinical trials are typically
conducted in three sequential phases:

o    Phase  1  clinical  trials  represent  the  initial  administration  of the
     investigational  drug to a small group of human subjects to test for safety
     (adverse effects), dose tolerance, absorption, biodistribution, metabolism,
     excretion  and  clinical  pharmacology  and,  if  possible,  to gain  early
     evidence regarding efficacy.

o    Phase 2  clinical  trials  typically  involve a small  sample of the actual
     intended patient population and seek to assess the efficacy of the drug for
     specific targeted indications,  to determine dose tolerance and the optimal
     dose range,  and to gather  additional  information  relating to safety and
     potential adverse effects.

o    Once  an  investigational  drug  is  found  to have  some  efficacy  and an
     acceptable  safety  profile in the  targeted  patient  population,  Phase 3
     clinical  trials are  initiated to establish  further  clinical  safety and
     efficacy  of the  investigational  drug in a broader  sample of the general
     patient  population  at  multiple  study  sites in order to  determine  the
     overall risk-benefit ratio of the drug and to provide an adequate basis for
     product  approval.  The Phase 3 clinical  development  program  consists of
     expanded,  large-scale  studies  of  patients  with the  target  disease or
     disorder,  to obtain  definitive  statistical  evidence of the efficacy and
     safety of the proposed product.

     All data obtained from a comprehensive development program are submitted in
a New Drug Application (NDA) to the FDA and the corresponding  agencies in other
countries for review and approval.  The NDA includes  information  pertaining to
clinical  studies and the  manufacture of the new drug.  Review of an NDA by the
FDA can be a  time-consuming  process  and the FDA may  request  that we  submit
additional data or carry out additional studies.

Certain Factors That May Affect Future Results

     Additional  risks  and  uncertainties  that  we are  unaware  of or that we
currently  deem  immaterial  also  may  become  important  factors  that  affect
Repligen.


                                       8


WE MAY BE DEPENDENT ON OUR COLLABORATIVE  PARTNERS TO DEVELOP,  CONDUCT CLINICAL
TRIALS FOR, AND MANUFACTURE, MARKET AND SELL OUR PRINCIPAL PRODUCTS.

     We conduct some of our development activities,  and may conduct most of our
commercialization  activities,  through  collaborations.  Our collaborations are
heavily dependent on the efforts and activities of our  collaborative  partners.
Our  existing  and  any  future  collaborations  may  not be  scientifically  or
commercially successful.

     For  example,  if any of our  collaborative  partners  were  to  breach  or
terminate an agreement  with us, reduce its funding or otherwise fail to conduct
the  collaboration  successfully,  we may  need to  devote  additional  internal
resources to the program that is the subject of the collaboration, scale back or
terminate the program or seek an alternative partner.

THE MARKET MAY NOT BE RECEPTIVE TO OUR PRODUCTS UPON THEIR INTRODUCTION.

     The commercial success of our products that are approved for marketing will
depend upon their acceptance by the medical  community and third party payors as
being  clinically  useful,  cost effective and safe. All of the products that we
are developing are based upon new technologies or therapeutic  approaches.  As a
result, it is hard to predict market acceptance of our products.

     Other factors that we believe will materially  affect market  acceptance of
our products and services include:

     o    the timing of receipt of  marketing  approvals  and the  countries  in
          which such approvals are obtained;

     o    the safety, efficacy and ease of administration of our products;

     o    the success of physician education programs; and

     o    the availability of government and third party payor  reimbursement of
          our products.

WE COMPETE  WITH LARGER,  BETTER  FINANCED  AND MORE MATURE  PHARMACEUTICAL  AND
BIOTECHNOLOGY  COMPANIES WHO ARE CAPABLE OF DEVELOPING NEW APPROACHES THAT COULD
MAKE OUR PRODUCTS AND TECHNOLOGY OBSOLETE.

     The  market  for  therapeutic  and  bioprocessing   products  is  intensely
competitive,  rapidly  evolving  and  subject  to  rapid  technological  change.
Pharmaceutical and mature  biotechnology  companies have  substantially  greater
financial, manufacturing,  marketing, research and development resources than we
have.  New  approaches  to the  treatment  of our  targeted  diseases  by  these
competitors may make our products and technologies obsolete or noncompetitive.

WE HAVE INCURRED  SUBSTANTIAL  LOSSES, WE EXPECT TO CONTINUE TO INCUR LOSSES AND
WE WILL NOT BE SUCCESSFUL UNTIL WE REVERSE THIS TREND.

     We have incurred  losses in each year since our founding in 1981. We expect
to continue to incur operating losses for the foreseeable future.

     While  we  generate  revenue  from  product  sales,  this  revenue  is  not
sufficient  to cover  the  costs of our  clinical  trials  and drug  development
programs.  We expect to increase  our spending  significantly  as we continue to
expand our research and development programs and  commercialization  activities.
As a result, we will need to generate  significant  revenues in order to achieve
profitability.  We cannot be certain  whether or when this will occur because of
the significant uncertainties that affect our business.


                                       9


IF WE DO NOT OBTAIN  ADDITIONAL  CAPITAL FOR OUR DRUG DEVELOPMENT  PROGRAMS,  WE
WILL BE UNABLE TO DEVELOP OR DISCOVER NEW DRUGS.

     We need  additional  long-term  financing  to develop our drug  development
programs  through  the  clinical  trial  process as  required by the FDA and our
bioprocessing  products business. We also need additional long-term financing to
support  future  operations  and  capital  expenditures,  including  capital for
additional  personnel  and  facilities.  If we spend more  money than  currently
expected  for our  drug  development  programs  and our  bioprocessing  products
business,  we will need to raise  additional  capital by selling  debt or equity
securities,   by  entering  into  strategic   relationships   or  through  other
arrangements.  We may be unable to raise any  additional  amounts on  reasonable
terms  when they are  needed  due to the  volatile  nature of the  biotechnology
marketplace.  If we are unable to raise this additional  capital, we may have to
delay or  postpone  critical  clinical  studies  or  abandon  other  development
programs.

IF OUR CLINICAL  TRIALS ARE NOT  SUCCESSFUL,  WE WILL NOT BE ABLE TO DEVELOP AND
COMMERCIALIZE ANY RELATED PRODUCTS.

     In order to obtain  regulatory  approvals  for the  commercial  sale of our
future products, we and our collaborative  partners will be required to complete
extensive  clinical  trials in humans to demonstrate  the safety and efficacy of
the products. We have limited experience in conducting clinical trials.

     The  submission of an IND may not result in FDA  authorization  to commence
clinical trials. If clinical trials begin, we or our collaborative  partners may
not complete testing  successfully  within any specific time period,  if at all,
with  respect  to  any of  our  products.  Furthermore,  we,  our  collaborative
partners,  or the FDA,  may  suspend  clinical  trials  at any  time on  various
grounds,  including a finding that the subjects or patients are being exposed to
unacceptable  health risks.  Clinical  trials,  if  completed,  may not show any
potential  product to be safe or effective.  Thus, the FDA and other  regulatory
authorities may not approve any of our potential products for any indication.

     The rate of  completion  of clinical  trials is  dependent in part upon the
rate of  enrollment  of  patients.  Patient  enrollment  is a  function  of many
factors, including the size of the patient population, the proximity of patients
to clinical sites, the eligibility  criteria for the study, and the existence of
competitive clinical trials.  Delays in planned patient enrollment may result in
increased costs and program delays.

WE MAY NOT  OBTAIN  REGULATORY  APPROVALS;  THE  APPROVAL  PROCESS IS COSTLY AND
LENGTHY.

     We must obtain regulatory approval for our ongoing  development  activities
and before marketing or selling any of our future  products.  We may not receive
regulatory   approvals  to  conduct  clinical  trials  of  our  products  or  to
manufacture  or market our products.  In addition,  regulatory  agencies may not
grant  such  approvals  on a  timely  basis  or may  revoke  previously  granted
approvals.

     The process of obtaining  FDA and other  required  regulatory  approvals is
lengthy  and  expensive.  The time  required  for FDA and  other  clearances  or
approvals is uncertain and typically  takes a number of years,  depending on the
complexity  and  novelty of the  product.  Our  analysis of data  obtained  from
preclinical   and   clinical   activities   is  subject  to   confirmation   and
interpretation by regulatory  authorities,  which could delay,  limit or prevent
regulatory  approval.  Any delay in  obtaining  or  failure  to obtain  required
clearance or approvals could materially adversely affect our


                                       10


ability to generate  revenues  from the affected  product.  We have only limited
experience in filing and prosecuting  applications  necessary to gain regulatory
approvals.

     We also are subject to numerous foreign regulatory  requirements  governing
the  design  and  conduct  of the  clinical  trials  and the  manufacturing  and
marketing of our future products. The approval procedure varies among countries.
The time required to obtain foreign  approvals  often differs from that required
to obtain FDA approvals.  Moreover, approval by the FDA does not ensure approval
by regulatory authorities in other countries.

     All of the foregoing  regulatory  risks also are applicable to development,
manufacturing and marketing  undertaken by our  collaborative  partners or other
third parties.

EVEN IF WE OBTAIN  MARKETING  APPROVAL,  OUR PRODUCTS WILL BE SUBJECT TO ONGOING
REGULATORY  REVIEW  WHICH  WILL BE  EXPENSIVE  AND MAY  EFFECT  OUR  ABILITY  TO
SUCCESSFULLY COMMERCIALIZE OUR PRODUCTS.

     Even if we receive regulatory  approval of a product,  such approval may be
subject  to  limitations  on the  indicated  uses for which the  product  may be
marketed,  which may limit the size of the  market  for the  product  or contain
requirements for costly  post-marketing  follow-up studies.  The manufacturer of
our products for which we have  obtained  marketing  approval will be subject to
continued  review  and  periodic  inspections  by the FDA and  other  regulatory
authorities.  The subsequent  discovery of previously  unknown problems with the
product,  clinical  trial  subjects,  or with the  manufacturer  or facility may
result in restrictions on the product or manufacturer,  including  withdrawal of
the product from the market.

     If we fail to comply with  applicable  regulatory  requirements,  we may be
subject to fines,  suspension or withdrawal  of  regulatory  approvals,  product
recalls, seizure of products, operating restrictions, and criminal prosecution.

IF WE ARE UNABLE TO OBTAIN AND MAINTAIN PATENTS FOR OUR PRODUCTS, WE WILL NOT BE
ABLE TO SUCCEED COMMERCIALLY.

     We must obtain and  maintain  patent and trade  secret  protection  for our
products and  processes in order to protect  them from  unauthorized  use and to
produce a financial  return  consistent  with the  significant  time and expense
required to bring our products to market.  Our success will depend,  in part, on
our ability to:

     o    obtain  and   maintain   patent   protection   for  our  products  and
          manufacturing processes;

     o    preserve our trade secrets; and

     o    operate without infringing the proprietary rights of third parties.

     We can not be sure that any patent  applications  relating to our  products
that we will file in the future or that any currently pending  applications will
issue on a timely basis, if ever. Since patent applications in the United States
are  maintained  in  secrecy  until  patents  issue  and  since  publication  of
discoveries  in the  scientific  or patent  literature  often lag behind  actual
discoveries,  we cannot be certain that we were the first to make the inventions
covered by each of our pending patent  applications or that we were the first to
file patent  applications for such inventions.  Even if patents are issued,  the
degree of protection afforded by such patents will depend upon the:

     o    scope of the patent claims;

     o    validity and  enforceability  of the claims  obtained in such patents;
          and


                                       11


     o    our willingness and financial ability to enforce and/or defend them.

     The patent  position of  biotechnology  and  pharmaceutical  firms is often
highly uncertain and usually  involves  complex legal and scientific  questions.
Moreover,  no  consistent  policy has  emerged in the United  States and in many
other  countries  regarding  the  breadth  of claims  allowed  in  biotechnology
patents.  Patents which may be granted to us in certain foreign countries may be
subject to opposition proceedings brought by third parties or result in suits by
us which may be costly and result in adverse consequences for us.

     If our  competitors  prepare  and file  patent  applications  in the United
States  that  claim  technology  also  claimed  by us,  we may  be  required  to
participate  in  interference  proceedings  declared  by  the  U.S.  Patent  and
Trademark  Office to  determine  priority of  invention,  which would  result in
substantial costs to us.

     In addition, patents blocking our manufacture,  use or sale of our products
could be issued to third parties in the United States or foreign countries.  The
issuance  of  blocking  patents or an  adverse  outcome  in an  interference  or
opposition  proceeding,  could subject us to  significant  liabilities  to third
parties  and  require  us to  license  disputed  rights  from  third  parties on
unfavorable terms, if at all, or cease using the technology.

WE MAY BECOME  INVOLVED IN EXPENSIVE  PATENT  LITIGATION  OR OTHER  INTELLECTUAL
PROPERTY  PROCEEDINGS  WHICH COULD RESULT IN  LIABILITY  FOR DAMAGES OR STOP OUR
DEVELOPMENT AND COMMERCIALIZATION EFFORTS.

     There has been substantial  litigation and other proceedings  regarding the
complex patent and other intellectual  property rights in the pharmaceutical and
biotechnology  industries.  We may become a party to patent  litigation or other
proceedings regarding intellectual property rights.

     Other  types of  situations  in  which we may  become  involved  in  patent
litigation or other intellectual property proceedings include:

     o    We may initiate  litigation or other proceedings against third parties
          to enforce our patent rights.

     o    We may initiate  litigation or other proceedings against third parties
          to seek to  invalidate  the patents  held by such third  parties or to
          obtain a judgment  that our products or services do not infringe  such
          third parties' patents.

     o    If our competitors file patent applications that claim technology also
          claimed  by us,  we may  participate  in  interference  or  opposition
          proceedings to determine the priority of invention.

     o    If third parties  initiate  litigation  claiming that our processes or
          products infringe their patent or other intellectual  property rights,
          we will need to defend against such claims.

     The  cost to us of any  patent  litigation  or  other  proceeding,  even if
resolved in our favor, could be substantial. Some of our competitors may be able
to sustain the cost of such litigation or proceedings  more  effectively than we
can because of their  substantially  greater  financial  resources.  If a patent
litigation or other intellectual  property proceeding is resolved unfavorably to
us, we or our  collaborative  partners  may be enjoined  from  manufacturing  or
selling our products and


                                       12


services  without  a  license  from  the  other  party  and be held  liable  for
significant  damages.  We may not be able to  obtain  any  required  license  on
commercially acceptable terms or at all.

     Uncertainties  resulting  from the initiation  and  continuation  of patent
litigation  or other  proceedings  could have a material  adverse  effect on our
ability to compete in the marketplace.  Patent  litigation and other proceedings
may also absorb significant management time.

WE HAVE LIMITED SALES AND MARKETING EXPERIENCE AND CAPABILITIES.

     We  have  limited  sales,   marketing  and   distribution   experience  and
capabilities.  We may, in some instances, rely significantly on sales, marketing
and distribution  arrangements with our  collaborative  partners and other third
parties.  In these instances,  our future revenues will be materially  dependent
upon the success of the efforts of these third parties.

     If in the future we determine to perform sales,  marketing and distribution
functions ourselves, we would face a number of additional risks, including:

     o    we may not be able to attract and build a significant  marketing staff
          or sales force;

     o    the cost of  establishing a marketing  staff or sales force may not be
          justifiable in light of any product revenues; and

     o    our direct sales and marketing efforts may not be successful.

WE HAVE LIMITED MANUFACTURING  CAPABILITIES AND WILL BE DEPENDENT ON THIRD PARTY
MANUFACTURERS.

     We have limited  manufacturing  experience and no commercial or pilot scale
manufacturing  facilities  for the  production of  pharmaceuticals.  In order to
continue to develop pharmaceutical products, apply for regulatory approvals and,
ultimately,  commercialize any products, we will need to develop,  contract for,
or otherwise arrange for the necessary manufacturing capabilities.

     We currently  rely upon third parties to produce  material for  preclinical
and clinical testing purposes and expect to continue to do so in the future.  We
also expect to rely upon third parties, including our collaborative partners, to
produce  materials  required  for the  commercial  production  of certain of our
products if we succeed in obtaining necessary regulatory  approvals.  We believe
that there is no  proprietary  aspect to the  manufacture  of our  products.  We
believe our products could be manufactured at other facilities;  however,  there
are a limited number of manufacturers  that operate under the FDA's  regulations
for good  manufacturing  practices  which are capable of  manufacturing  for us.
Timing for the  initiation of new  manufacturers  is  uncertain,  and, if we are
unable to arrange for third party manufacturing of our products,  or to do so on
commercially reasonable terms, we may not be able to complete development of our
products or market them.

     To the extent  that we enter  into  manufacturing  arrangements  with third
parties,  we are dependent upon these third parties to perform their obligations
in a  timely  manner.  If such  third  party  suppliers  fail to  perform  their
obligations, we may be adversely affected in a number of ways, including:

     o    we may not be able to meet commercial demands for our products;


                                       13


     o    we may not be able to initiate or continue clinical trials of products
          that are under development; and

     o    we may be delayed in submitting  applications for regulatory approvals
          for our products.

     The  manufacture  of  products  by us and our  collaborative  partners  and
suppliers is subject to regulation by the FDA and comparable agencies in foreign
countries.  Delay in  complying  or  failure to comply  with such  manufacturing
requirements could materially adversely affect the marketing of our products.

IF WE ARE UNABLE TO CONTINUE TO HIRE AND RETAIN SKILLED TECHNICAL AND SCIENTIFIC
PERSONNEL, THEN WE WILL HAVE TROUBLE DEVELOPING PRODUCTS.

     Our success  depends  largely upon the continued  service of our management
and  scientific  staff and our ability to attract,  retain and  motivate  highly
skilled scientific, management and marketing personnel. Potential employees with
an expertise in the field of  biochemistry,  regulatory  affairs and/or clinical
development of new drug and  biopharmaceutical  manufacturing  are not generally
available in the market and are  difficult  to attract and retain.  We also face
significant  competition for such personnel from other  companies,  research and
academic  institutions,  government  and other  organizations  who have superior
funding and  resources  to be able to attract  such  personnel.  The loss of key
personnel or our inability to hire and retain  personnel who have  technical and
scientific backgrounds could materially adversely affect our product development
efforts and our business.

OUR STOCK PRICE COULD BE VOLATILE,  WHICH COULD CAUSE YOU TO LOSE PART OR ALL OF
YOUR INVESTMENT.

     The market price of our common stock, like that of the common stock of many
other  development stage  biotechnology  companies,  may be highly volatile.  In
addition,   the  stock  market  has   experienced   extreme   price  and  volume
fluctuations.  This volatility has  significantly  affected the market prices of
securities  of many  biotechnology  and  pharmaceutical  companies  for  reasons
frequently unrelated to or disproportionate to the operating  performance of the
specific  companies.  These broad market  fluctuations  may adversely affect the
market price of our common stock.

Item 2.  DESCRIPTION OF PROPERTY

     Our executive office, research and manufacturing  facilities are located at
117 Fourth  Avenue in Needham,  Massachusetts.  We occupy  approximately  15,000
square  feet under a six-year  sublease,  which  expires on April 30,  2002.  We
believe  that  suitable  additional  or  alternate  space will be  available  at
commercially reasonable terms when our lease expires.

Item 3.  LEGAL PROCEEDINGS

     Repligen and the University of Michigan (the "University") believe that the
University  is  entitled to rights to certain  United  States  patents  owned by
Bristol-Myers Squibb Company ("BMS"), which patents cover claims for composition
and methods of use for CTLA4.  On August 31, 2000,  Repligen and the  University
filed a  complaint  against  BMS at the  United  States  District  Court for the
District of Michigan in Detroit,  Michigan seeking correction of inventorship on
these patents. A correction of inventorship would result in the University being
designated as a co-assignee  on any  corrected BMS patent.  Repligen  would then
have rights to such  technology


                                       14


pursuant  to a  2000  License  Agreement  with  the  University,  a  1995  Asset
Acquisition  Agreement  with Genetics  Institute  and other related  agreements.
Repligen's  failure to obtain  shared  ownership  rights in the BMS  patents may
restrict  Repligen's  ability  to  commercialize  CTLA4-Ig.   Repligen  and  the
University have also filed patents related to compositions of matter and methods
of use of CTLA4-Ig.

Item 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

     No matters were submitted to a vote of our security  holders of the Company
through  solicitation  of proxies or  otherwise,  during the last quarter of the
fiscal year ended March 31, 2001.

                                     PART II

Item 5.  MARKET FOR REGISTRANT'S COMMON STOCK AND RELATED STOCKHOLDER MATTERS

Market Information

     Our common stock is traded  over-the-counter  on the Nasdaq National Market
under the  symbol  "RGEN."  The  following  table  sets  forth  for the  periods
indicated  the high and low bid  quotations  for the common stock as reported by
Nasdaq.  These quotations reflect  inter-dealer  prices,  without retail markup,
markdown or commission and may not necessarily reflect actual transactions.

         Fiscal Year 2001              High                   Low
         ----------------              ----                   ---
         Fourth Quarter              $5.875                $2.031
         Third Quarter                8.688                 3.000
         Second Quarter               8.875                 5.313
         First Quarter                9.688                 4.000

         Fiscal Year 2000
         ----------------
         Fourth Quarter             $18.000                $2.875
         Third Quarter                4.875                 2.688
         Second Quarter               3.188                 2.375
         First Quarter                3.469                 2.563

Stockholders and Dividends

     As of June 15, 2001 there were  approximately 929 stockholders of record of
our common stock.  We have not paid any dividends since our inception and do not
intend to pay any dividends on our common stock in the foreseeable future.

ITEM 6.   SELECTED CONSOLIDATED FINANCIAL DATA

     The following  selected  financial data are derived from, and are qualified
in their  entirety by reference  to, the  consolidated  financial  statements of
Repligen as of and for the years ended March 31, 2001, 2000, 1999, 1998 and 1997
which have been audited by Arthur Andersen LLP,  independent public accountants.
The selected  financial data set forth below should be read in conjunction  with
the consolidated  financial statements of Repligen and the related notes thereto
and "Management's  Discussion and Analysis of Financial Condition and Results of
Operations"  included  elsewhere  in this report and our report on Form 10-K for
the years ended March 31, 2000, 1999, 1998 and 1997.


                                       15




                                                          Years Ended March 31,
                                        --------------------------------------------------------
                                         2001         2000        1999        1998        1997
                                        --------    --------    --------    --------    --------
                                                  (In thousands, except per share amounts)
                                                                         
Operating Statement Data:
Revenues:
   Product                              $  2,083    $  2,041    $  1,010    $  1,114    $  1,554
   Research and development                  172         863       1,268         917       1,180
   Other                                      91          74         100         129         799
                                        --------    --------    --------    --------    --------
       Total revenues                   $  2,346    $  2,978    $  2,378    $  2,160    $  3,533
                                        --------    --------    --------    --------    --------

 Costs and expenses:
    Research and development               5,786       3,754       2,882       1,420       1,927
    Selling, general & administrative      2,493       2,480       1,563       1,281       1,940
    Cost of product sales                  1,400       1,107         689         480         537
    Restructuring (credit) charge             --          --          --          --        (111)
                                        --------    --------    --------    --------    --------

       Total costs and expenses            9,679       7,341       5,134       3,181       4,293
                                        --------    --------    --------    --------    --------

  Loss from operations                    (7,333)     (4,363)     (2,756)     (1,021)       (760)
                                        --------    --------    --------    --------    --------

  Investment income                        2,054         547         212         225         269

  Net loss                              $ (5,279)   $ (3,816)   $ (2,544)   $   (796)   $   (491)
                                        ========    ========    ========    ========    ========

 Net loss per common share              $  (0.20)   $  (0.18)   $  (0.14)   $  (0.05)   $  (0.03)
                                        ========    ========    ========    ========    ========
 Weighted average common shares
outstanding                               26,548      21,538      18,018      16,502      15,678
                                        ========    ========    ========    ========    ========


                                                           (In thousands)
                                                           As of March 31,
                                         2001         2000        1999        1998        1997
                                        --------    --------    --------    --------    --------
                                                                         
Balance Sheet Data:
  Cash and investments                  $ 29,930    $ 34,033    $  3,251    $  4,726    $  3,538
 Working capital                          24,398      34,473       3,860       5,377       3,990
  Total assets                            32,148      36,287       5,224       6,513       5,621
  Accumulated deficit                   (135,959)   (130,680)   (126,864)   (124,320)   (123,533)
  Stockholders' equity                    30,891      35,090       4,592       6,124       4,919


Item 7. MANAGEMENT'S  DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

Overview

     The following  Management's  Discussion and Analysis of Financial Condition
and Results of Operations contains forward-looking statements that involve risks
and uncertainties.  When used in this report, the words "intend,"  "anticipate,"
"believe,"  "estimate,"  "plan" and  "expect"  and similar  expressions  as they
relate to us are  included to identify  forward-looking  statements.  Repligen's
actual  results  could  differ   materially  from  those  anticipated  in  these
forward-looking  statements and are a result of certain factors, including those
set forth under "Certain  Factors that May Affect Future  Results" and elsewhere
in this report.


                                       16


Results of Operations

Fiscal Year Ended March 31, 2001 Compared with Fiscal Year Ended March 31, 2000

     Revenues

     Total revenues for fiscal 2001 were  $2,346,000,  compared to $2,978,000 in
fiscal 2000, a decrease of $632,000 or 21%. This decrease in revenue is a result
of the  discontinuance  of  research  collaborations  and grants  programs  that
occurred during fiscal 2000 as we focus our efforts on our own proprietary  drug
programs.

     Product revenues for fiscal 2001 were $2,083,000,  compared to $2,041,  000
in fiscal  2000,  an increase of $42,000 or 2%.  Product  sales under our supply
agreement with AP Biotech  increased  during fiscal 2001  partially  offset by a
decrease  in sales of our  Protein A product  as a result of the timing of large
production scale orders.

     Research and development revenues for fiscal 2001 were $172,000 compared to
$863,000 in fiscal 2000, a decrease of $691,000 or 80%.  During  fiscal 2000, we
received non-recurring  licensing payments and completed our SBIR grants for NIH
and NSF.

     Cost and Expenses

     Total  costs and  expenses  for fiscal  2001 were  $9,679,000  compared  to
$7,341,000 in fiscal 2001, an increase of $2,338,000 or 32%.

     Research and development  expenses for fiscal 2001 were $5,786,000 compared
to $3,754,000 in fiscal 2000, an increase of $2,032,000 or 54%. This increase is
largely due to increased clinical and manufacturing costs related to development
activities for secretin, CTLA4-Ig and uridine.

     Selling,   general  and  administrative   expenses  for  fiscal  2001  were
$2,493,000 compared to $2,480,000 in fiscal 2000, an increase of $13,000 or .5%.
This  increase was  attributable  to increases in payroll and related  expenses,
non-cash charges related to the issuance of warrants,  and increased shareholder
communication  expenses  as a result  of an  expanded  shareholder  base.  These
increases were partially  offset by a decrease in financial  advisory costs that
were incurred during fiscal 2000.

     Cost  of  products  sold  for  fiscal  2001  was  $1,400,000,  compared  to
$1,107,000 in fiscal 2000, an increase of $293,000 or 26%. Cost of product sales
in fiscal 2001 was 67% of product  revenues  versus 54% of product  revenues for
fiscal  2000.  These  increases  are a result of increased  personnel  costs and
production costs.

     Investment income

     Investment  income for fiscal 2001 was $2,054,000,  compared to $547,000 in
fiscal 2000,  an increase of  $1,507,000  or 276%.  The  increase in  investment
income is due to higher average cash, cash equivalent and marketable  securities
balances as result of the common stock  financings  that took place during March
2000.

Fiscal Year Ended March 31, 2000 Compared with Fiscal Year Ended March 31, 1999

     Revenues

     Total  revenues for fiscal 2000 were  $2,978,000  compared to $2,378,000 in
fiscal  1999,  an  increase  of  $601,000  or 25%.  This  increase  was  largely
attributable  to  increased  product  sales of  recombinant  Protein A offset by
decreased research and development revenue.


                                       17


     Product revenues for fiscal 2000 were $2,041,000  compared to $1,010,000 in
fiscal  1999,  an increase of  $1,031,000  or 102%.  The increase in the product
sales volume is attributed to the  initiation of product  shipments to APBiotech
under a supply agreement  executed in May 1999 and strong demand from monoclonal
antibody producers for Protein A products.

     Research and development revenues for fiscal 2000 were $863,000 compared to
$1,268,000  in fiscal  1999,  a decrease  of $405,000  or 32%.  The  decrease in
research and development  revenues of $405,000 or 32% from fiscal 1999 levels is
primarily attributable to the discontinuance of certain research  collaborations
and grant programs.

     Costs and Expenses

     Total expenses for fiscal 2000 were  $7,341,000,  compared to $5,134,000 in
fiscal 1999, an increase of $2,207,000 or 43%.

     Research and development expenses for fiscal 2000 were $3,754,000, compared
to  $2,882,000  in fiscal 1999,  an increase of $872,000,  or 30%.  Research and
development  costs for fiscal 2000  include a $1,000,000  payment to  ChiRhoClin
pursuant  to  our  license   agreement  with  them.  Fiscal  1999  research  and
development costs include $1,035,000 in costs associated with the acquisition of
rights to  certain  patent  applications  covering  the use of  secretin  in the
treatment  of autism.  In addition,  the  increase in research  and  development
expenses in 2000 reflects  increased costs  associated with our drug development
programs for secretin and CTLA4-Ig.

     Selling,   general  and  administrative   expenses  for  fiscal  2000  were
$2,480,000,  compared to  $1,563,000  in fiscal 1999, an increase of $917,000 or
59%. Included in selling,  general and  administrative  expenses for fiscal 2000
were one time  charges  associated  with a  financial  advisory  agreement  with
Paramount  Capital  of  $493,000,   including  a  non-cash  charge  of  $188,000
associated with the issuance of warrants to purchase common stock.

     Cost of product  sales for fiscal  2000  totaled  $1,107,000,  compared  to
$689,000 in fiscal 1999,  which  represents  an increase of $418,000 or 61% over
the prior fiscal year. Costs of product sales in fiscal 2000 were 54% of product
revenues  versus 68% of product  revenues for fiscal 1999. The increase in costs
of product  sales and decrease in cost of revenues as a  percentage  of sales is
due primarily to increased  Protein A product sales. In addition,  during fiscal
2000,  we  incurred  additional  expenses  associated  with the  start-up of the
manufacture of Protein A for AP Biotech and the write off of inventory resulting
from the  introduction  of a new Protein A product that took place during fiscal
1999.

     Investment income

     Investment  income for fiscal 2000 was  $547,000,  compared to $212,000 for
fiscal 1999, an increase of $335,000 or 158%. The increase in investment  income
is due to  higher  average  cash,  cash  equivalent  and  marketable  securities
balances as a result of the private placement that took place in May 1999.

Liquidity and Capital Resources

     We  have  financed  our  operations   primarily  through  sales  of  equity
securities  and  revenues  derived from product  sales,  collaborative  research
agreements, government grants, and payments on licensing and royalty agreements.
At March 31, 2001 we had cash, cash  equivalents,  and marketable  securities of
$29,930,000, compared to $34,033,000 at March 31, 2000.


                                       18


     Repligen's   operating  activities  in  2001  used  cash  of  approximately
$4,620,000, consisting of the net loss from operations for the year, an increase
in inventory and a decrease in accrued expenses.  These cash uses were offset by
noncash  charges  for  depreciation  and  amortization  and  stock  and  warrant
issuances and an increase in accounts payable.  During fiscal 2001, we purchased
$185,000 of capital equipment, consisting of laboratory and office equipment. We
received  cash of  $677,000  from the  proceeds  of  stock  option  and  warrant
exercises.

     We expect to incur significantly higher costs in fiscal 2002 as a result of
expanded  research  and  development  costs  associated  with the  expansion  of
activities  associated with clinical trials of our proprietary  drug candidates.
In addition,  under terms of our secretin diagnostic  agreement with ChiRhoClin,
if the FDA  approves  an  NDA,  we will be  required  to pay  ChiRhoClin  future
milestones in cash and through issuance of our common stock as well as royalties
on sales.  We believe that we have  sufficient  resources to satisfy our working
capital and capital  expenditure  requirements for the next twenty-four  months.
Should we need to  secure  additional  financing  to meet our  future  liquidity
requirements,  we may not be able to  secure  such  financing,  or  obtain  such
financing on favorable terms because of the volatile nature of the biotechnology
marketplace.

     We do not  currently use  derivative  financial  instruments.  We generally
place our marketable security investments in high quality credit instruments, as
specified in our investment policy guidelines. Our investment policy also limits
the amount of credit exposure to any one issue,  issuer, and type of investment.
We do not expect any material loss from our marketable securities.

New Accounting Standards

     In June 1998,  the FASB  issued  SFAS No. 133,  Accounting  for  Derivative
Instruments  and Hedging  Activities.  As amended in June 1999, the statement is
effective for all fiscal  quarters of all fiscal years  beginning after June 15,
2000. In June 2000,  the FASB issued  statement No. 138,  which is a significant
amendment to SFAS NO. 133. SFAS No. 133 and its amendments  establish accounting
and reporting standards for derivative instruments, including certain derivative
instruments   embedded  in  other   contracts   (collectively   referred  to  as
derivatives) and for hedging  activities.  The Emerging Issues Task Force (EITF)
has also issued a number of derivative-related  tentative and final consensuses.
We do not expect the adoption of these  statements to have a material  impact on
our consolidated financial position or results of operations.

     In March  2000,  the FASB  issued  Interpretation  No. 44,  Accounting  for
Certain  Transactions  Involving Stock  Compensation--An  Interpretation  of APB
Opinion No. 25. The  Interpretation  clarifies  the  application  of  Accounting
Principles  Board  Opinion  (APB)  No. 25 in  certain  situations,  as  defined.
Interpretation  No. 44 is effective  July 1, 2000;  however,  it covers  certain
events  occurring  during  the period  after  December  15,  1998 but before the
effective  date,  the effects of applying  this  Interpretation  No. 44 would be
recognized on a prospective  basis from the effective  date.  Accordingly,  upon
initial application of the final  Interpretation No. 44, no adjustments would be
made to the financial  statements  for periods  before the effective date and no
expense would be recognized for any additional  compensation  cost measured that
is  attributable  to periods  before the  effective  date.  The adoption of this
statement had no material impact on our financial statements.

     In  September  2000,  the EITF  issued  00-19,  Accounting  for  Derivative
Financial  Instruments  Indexed to and  Potentially  Settled in a Company's  Own
Stock, which requires freestanding contracts that are settled in a company's own
stock,   including  common  stock  warrants,  to  be  designated  as  an  equity
instrument, asset or a liability. Under the provisions of EITF 00-19, a contract
designated  as an asset or a liability  must be carried at fair value,  with any


                                       19


changes  in fair  value  recorded  in the  results  of  operations.  A  contract
designated as an equity  instrument  must be included  within equity and no fair
value adjustments are required.  We do not expect the adoption of this statement
to have a material impact on our consolidated  financial  position or results of
operations.

Item 8.  FINANCIAL STATEMENTS

     All  financial  statements  required to be filed  hereunder are filed as an
exhibit hereto, are listed under item 14 (a) (1) and are incorporated  herein by
reference.

Item 9.  CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND
         FINANCIAL DISCLOSURE

         Not applicable.

                                    PART III

Item 10. DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

     Information  regarding our  directors  and  executive  officers will be set
forth under the captions "Election of Directors,"  "Occupations of Directors and
Executive  Officers,"  "Biographical  Information,"  "Information  Regarding the
Board of Directors and its Committees" and "Section 16 (a) Beneficial  Ownership
Reporting  Compliance" in our definitive  proxy statement for our annual meeting
of  stockholders  to be held on September  13, 2001 which will be filed with the
SEC within 120 days of March 31, 2001 and is incorporated herein by reference.

Item 11. EXECUTIVE COMPENSATION

     Information  required  by this Item will be set  forth  under the  captions
"Summary of Executive  Compensation"  and  "Compensation  of  Directors"  in our
definitive  proxy statement for our annual meeting of stockholders to be held on
September 13, 2001 which will be filed with the SEC within 120 days of March 31,
2001 and is incorporated herein by reference.

Item 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

     Information  required  by this Item will be set  forth  under the  captions
"Principal  Holders of Voting  Securities"  and "Stock  Ownership  of  Executive
Officers and Directors" in our definitive proxy statement for our annual meeting
of  stockholders  to be held on September  13, 2001 which will be filed with the
SEC within 120 days of March 31, 2001 and is incorporated herein by reference.

Item 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

     Information  required  by this  Item will be set  forth  under the  caption
"Certain  Relationships  and  Related  Transactions"  in  our  definitive  proxy
statement  for our annual  meeting of  stockholders  to be held on September 13,
2001 which  will be filed with the SEC within 120 days of March 31,  2001 and is
incorporated herein by reference.


                                       20


                                     PART IV

Item 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K

The following documents are filed as part of this Annual Report on Form 10-K:


(a) (1)   Financial Statements:

The consolidated  financial  statements required by this item are submitted in a
separate section beginning on page F-2 of this Report, as follows:

                                                                            Page
                                                                            ----
Report of Independent Public Accountants..................................  F-2
Consolidated Balance Sheets as of March 31, 2001 and 2000.................  F-3
Consolidated Statements of Operations for the Years Ended
March 31, 2001, 2000, and 1999............................................  F-4
Consolidated Statements of Stockholders' Equity for the Years
Ended March 31, 2001, 2000, and 1999......................................  F-5
Consolidated Statements of Cash Flows for the Years Ended March 31,
2001, 2000, and 1999 .....................................................  F-6
Notes to Consolidated Financial Statements................................  F-7

(a) (2)   Financial Statement Schedules:
           None

(a) (3)   Exhibits:

The  Exhibits  which  are  filed as part of this  Annual  Report  or  which  are
incorporated by reference are set forth in the Exhibit Index hereto.

(b)  Reports on Form 8-K:

No current  reports on Form 8-K were filed during the last quarter of our fiscal
year ended March 31, 2001.


                                       21


                                  EXHIBIT INDEX
                                  -------------
Exhibit
Number                     Document Description
- ------                     --------------------

3.1      Restated Certificate of Incorporation,  dated June 30, 1992 and amended
         September  30, 1999  (filed as Exhibit  4.1 to  Repligen  Corporation's
         Quarterly  Report on Form 10-Q for the quarter ended September 30, 1999
         and incorporated herein by reference).

3.2      By-laws  (filed  as  Exhibit  3.4 to  Repligen  Corporation's  Form S-1
         Registration   Statement  No.  33-3959  and   incorporated   herein  by
         reference).

4.1      Specimen   Stock   Certificate   (filed  as  Exhibit  4.2  to  Repligen
         Corporation's   Form  S-1   Registration   Statement  No.  33-3959  and
         incorporated herein by reference).

4.2      Form  of  Warrant   Agreement   (filed  as  Exhibit   4.1  to  Repligen
         Corporation's  Form 10-Q for the quarter  ended  September 30, 1999 and
         incorporated herein by reference).

4.3      Form of Common Stock Purchase Warrant (filed as Exhibit 4.3 to Repligen
         Corporation's  Form  S-3  Registration   Statement  No.  333-36280  and
         incorporated herein by reference).

4.4      Stock  Purchase  Agreement  dated  as of March 7,  2000,  by and  among
         Repligen  Corporation  and the  investors  listed on Schedule I thereto
         (filed as Exhibit  4.1 to Repligen  Corporation's  Form 8-K filed March
         21, 2000 and incorporated herein by reference).

4.5      Common Stock Purchase Warrant dated July 24, 2000 (filed as Exhibit 4.1
         to Repligen Corporation's Form 10-Q for the quarter ended September 30,
         2000 and incorporated herein by reference).

4.6      The Amended 1992  Repligen  Corporation  Stock Option Plan,  as amended
         (filed  as  Exhibit  4.2 to  Repligen  Corporation's  Form 10-Q for the
         quarter ended September 30, 2000 and incorporated herein by reference).

10.1*    Consulting Agreement,  dated October 1, 1981, between Dr. Paul Schimmel
         and  Repligen   Corporation   (filed  as  Exhibit   10.14  to  Repligen
         Corporation's   Form  S-1   Registration   Statement  No.  33-3959  and
         incorporated herein by reference).

10.2*    Consulting  Agreement,  dated November 1, 1981,  between Dr.  Alexander
         Rich and  Repligen  Corporation  (filed as  Exhibit  10.15 to  Repligen
         Corporation's   Form  S-1   Registration   Statement  No.  33-3959  and
         incorporated herein by reference).

10.3*    Employment   Agreement,   dated  March  14,  1996,   between   Repligen
         Corporation  and Walter C. Herlihy  (filed as Exhibit 10.43 to Repligen
         Corporation's  Annual  Report on Form 10-K for the year ended March 31,
         1996 and incorporated herein by reference).

10.4*    Employment   Agreement,   dated  March  14,  1996,   between   Repligen
         Corporation  and James R.  Rusche  (filed as Exhibit  10.44 to Repligen
         Corporation's  Annual  Report on Form 10-K for the year ended March 31,
         1996 and incorporated herein by reference).


                                       22


10.5*    Employment   Agreement,   dated  March  14,  1996,   between   Repligen
         Corporation  and  Daniel P. Witt  (filed as Exhibit  10.45 to  Repligen
         Corporation's  Annual  Report on Form 10-K for the year ended March 31,
         1996 and incorporated herein by reference).

10.6     Sublease  Agreement  dated as of May 1, 1996  between T Cell  Sciences,
         Inc.  and  Repligen  Corporation  (filed as Exhibit  10.46 to  Repligen
         Corporation's  Annual  Report on Form 10-K for the year ended March 31,
         1996 and incorporated herein by reference).

#10.7    Patent  Purchase  Agreement dated as of March 9, 1999 among the Company
         and Autism  Research  Institute and Victoria Beck (filed as Exhibit 2.1
         to  Repligen   Corporation's   Form  8-K/A  filed  June  15,  1999  and
         incorporated herein by reference).

#10.8    Manufacturing  Transfer  Agreement  dated as of December 31, 1998 among
         the Company and Amersham Pharmacia Biotech AB (filed as Exhibit 10.1 to
         Repligen  Corporation's  Quarterly  Report on Form 10-Q for the quarter
         ended December 31, 1998 and incorporated herein by reference).

#10.9    Supply  Agreement  dated  as of May 26,  1999 by and  between  Repligen
         Corporation and Amersham Pharmacia Biotech AB (filed as Exhibit 10.1 to
         Repligen  Corporation's  Quarterly  Report on Form 10-Q for the quarter
         ended June 30, 1999 and incorporated herein by reference).

10.11    Licensing  Agreement  by and  between  ChiRhoClin,  Inc.  and  Repligen
         Corporation (filed as Exhibit 10.1 to Repligen Corporation's  Quarterly
         Report  on Form  10-Q  for the  quarter  ended  December  31,  1999 and
         incorporated herein by reference).

10.12    Finders  Agreement by and between  Repligen  Corporation  and Paramount
         Capital,  Inc.  dated as of March 2,  2000  (filed  as  Exhibit  4.2 to
         Repligen  Corporation's  Form 8-K filed March 21, 2000 and incorporated
         herein by reference).

10.13    Patent  Purchase  Agreement  dated  as of May 9,  2000  by and  between
         Tolerance  Therapeutics LLC and Repligen  Corporation (filed as Exhibit
         10.1 to Repligen  Corporation's  Quarterly  Report on Form 10-Q for the
         quarter ended June 30, 2000 and incorporated herein by reference).

10.14    License Agreement with University of Michigan (filed as Exhibit 10.1 to
         Repligen  Corporation's  Quarterly  Report on Form 10-Q for the quarter
         ended September 30, 2000 and incorporated herein by reference).

21+      Subsidiaries of the Registrant.

23+      Consent of Arthur Andersen LLP.

- -----------
#  Confidential treatment obtained as to certain portions.

*  Management contract or compensatory plan or arrangement

+  Filed herewith.

The exhibits  listed above are not contained in the copy of the annual report on
Form 10-K  distributed  to  stockholders.  Upon the  request of any  stockholder
entitled to vote at the 2001 annual  meeting,  the Registrant  will furnish that
person without charge a copy of any exhibits  listed above.  Requests  should be
addressed to Repligen Corporation, 117 Fourth Avenue, Needham, MA 02494.


                                       23


                                   SIGNATURES

     Pursuant  to the  requirements  of  Section  13 or 15(d) of the  Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.

                                           REPLIGEN CORPORATION

                                           By: /s/ Walter C. Herlihy
                                              --------------------------------
                                               Walter C. Herlihy
                                               President and Chief
                                               Executive Officer
                                               (Principal executive, financial
                                               and accounting officer)
                                               Date: June 29, 2001

                                POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS,  that each person whose  signature  appears
below hereby makes,  constitutes  and appoints Walter C. Herlihy with full power
to act without the other, his true and lawful  attorney-in-fact  and agent, with
full power of substitution  and  resubstitution,  for him and in his name, place
and stead,  in any and all capacities to sign any or all amendments to this Form
10-K,  and to file the same with all exhibits  thereto,  and other  documents in
connection therewith, with the Securities and Exchange Commission, granting unto
said  attorney-in-fact and agents, and each of them, full power and authority to
do and perform each and every act and thing  requisite  and necessary to be done
in  connection  therewith,  as fully to all intents and  purposes as he might or
could  do  in  person,   hereby   ratifying   and   confirming   all  that  said
attorney-in-fact  and agents of any of them, or any  substitute or  substitutes,
lawfully do or cause to be done by virtue hereof.

     Pursuant to the  requirements of the Securities  Exchange Act of 1934, this
report  has  been  signed  below  by the  following  persons  on  behalf  of the
Registrant and in the capacities and on the dates indicated.

       Signature                       Title                            Date
       ---------                       -----                            ----


/s/ Alexander Rich             Co-Chairman of the Board of         June 29, 2001
- --------------------------     Directors
 Alexander Rich, M.D.

/s/ Paul Schimmel              Co-Chairman of the Board of         June 29, 2001
- --------------------------     Directors
 Paul Schimmel, Ph.D.

/s/ Walter C. Herlihy          President, Chief Executive Officer  June 29, 2001
- --------------------------     and  Director (Principal executive,
     Walter C. Herlihy         financial and accounting officer)


/s/ Robert J. Hennessey        Director                            June 29, 2001
- --------------------------
     Robert J. Hennessey

/s/ G. William Miller          Director                            June 29, 2001
- --------------------------
     G. William Miller


                                       24



                          INDEX TO FINANCIAL STATEMENTS



                                                                         Page
                                                                         ----

Report of Independent Public Accountants                                 F-2

Balance Sheets as of March 31, 2001 and 2000                             F-3

Statements of Operations for the Years
 Ended March 31, 2001, 2000 and 1999                                     F-4

Statement of Stockholders' Equity for the Years
 Ended March 31, 2001, 2000 and 1999                                     F-5

Statements of Cash Flows for the Years
 Ended March 31, 2001, 2000 and 1999                                     F-6

Notes to Financial Statements                                            F-7




                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS


To Repligen Corporation:

     We have audited the accompanying  balance sheets of Repligen Corporation (a
Delaware  corporation) as of March 31, 2001 and 2000 and the related  statements
of operations,  stockholders'  equity and cash flows for each of the three years
in the  period  ended  March  31,  2001.  These  financial  statements  are  the
responsibility of the Company's management.  Our responsibility is to express an
opinion on these financial statements based on our audits.

     We conducted our audits in accordance  with  auditing  standards  generally
accepted in the United States.  Those standards require that we plan and perform
the audit to obtain reasonable  assurance about whether the financial statements
are free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements.  An
audit also includes  assessing the accounting  principles  used and  significant
estimates  made by  management,  as well as  evaluating  the  overall  financial
statement  presentation.  We believe that our audits provide a reasonable  basis
for our opinion.

     In our opinion,  the financial statements referred to above present fairly,
in all material respects,  the financial position of Repligen  Corporation as of
March 31, 2001 and 2000 and the results of its operations and its cash flows for
each of the three years in the period ended March 31, 2001, in  conformity  with
accounting principles generally accepted in the United States.

                                              ARTHUR ANDERSEN LLP

Boston, Massachusetts
May 21, 2001


                                      F-2


                              REPLIGEN CORPORATION
                                 BALANCE SHEETS




                                     ASSETS
                                                                               As of March 31,
                                                                             2001              2000
                                                                        -------------------------------
                                                                                    
Current assets:
  Cash and cash equivalents                                             $  16,163,625     $  25,226,546
  Marketable securities                                                     7,773,427         8,806,367
  Accounts receivable, less reserves of $25,000                               812,481           847,838
  Inventories                                                                 634,723           547,448
  Prepaid expenses and other current assets                                   270,252           241,654
                                                                        -------------     -------------
    Total current assets                                                   25,654,508        35,669,853
                                                                        -------------     -------------

Property, plant and equipment, at cost:
  Equipment                                                                 1,103,527         1,092,831
  Leasehold improvements                                                      331,501           473,289
  Furniture and fixtures                                                      473,288           157,475
                                                                        -------------     -------------
                                                                            1,908,316         1,723,595
    Less -- accumulated depreciation and amortization                       1,464,195         1,187,343
                                                                        -------------     -------------
                                                                              444,121           536,252
                                                                        -------------     -------------

Long-term marketable securities                                             5,992,478                --
Other assets, net                                                              56,882            81,382
                                                                        -------------     -------------

                                                                        $  32,147,989     $  36,287,487
                                                                        =============     =============

                      LIABILITIES AND STOCKHOLDERS' EQUITY

Current liabilities:
  Accounts payable                                                      $     529,914     $     425,565
  Accrued expenses                                                            726,910           771,520
                                                                        -------------     -------------
    Total current liabilities                                               1,256,824         1,197,085
                                                                        -------------     -------------

Commitments and Contingencies (Note 4 & 5)

Stockholders' equity:
Preferred stock, $0.01 par value, authorized,
  5,000,000 shares, issued and outstanding, none                                   --                --
Common stock, $0.01 par value, authorized,
   40,000,000 shares, issued and outstanding, 26,628,950
   shares and 26,315,979 shares
   at March 31, 2001 and 2000, respectively                                   266,289           263,159
Additional paid-in capital                                                166,583,684       165,507,184
Accumulated deficit                                                      (135,958,808)     (130,679,941)
                                                                        -------------     -------------
  Total stockholders' equity                                               30,891,165        35,090,402
                                                                        -------------     -------------

                                                                        $  32,147,989     $  36,287,487
                                                                        =============     =============


   The accompanying notes are an integral part of these financial statements.


                                      F-3


                              REPLIGEN CORPORATION
                            STATEMENTS OF OPERATIONS



                                                                       Years Ended March 31,
                                                             2001               2000               1999
                                                        --------------------------------------------------
                                                                                     
Revenues:
    Product                                             $  2,083,529       $  2,040,828       $  1,009,655
    Research and development                                 171,615            863,035          1,268,036
    Other                                                     91,554             73,969             99,711
                                                        ------------       ------------       ------------
    Total revenues                                         2,346,698          2,977,832          2,377,402
                                                        ------------       ------------       ------------

Costs and expenses:
    Research and development                               5,786,392          3,753,908          2,882,124
    Selling, general and administrative                    2,493,014          2,480,398          1,562,750
    Cost of product sales                                  1,399,849          1,106,642            688,618
                                                        ------------       ------------       ------------
    Total costs and expenses                               9,679,255          7,340,948          5,133,492
                                                        ------------       ------------       ------------

    Loss from operations                                  (7,332,557)        (4,363,116)        (2,756,090)
                                                        ------------       ------------       ------------

Investment income                                          2,053,690            546,733            212,157
                                                        ------------       ------------       ------------

Net loss                                                $ (5,278,867)      $ (3,816,383)      $ (2,543,933)
                                                        ============       ============       ============

Basic and diluted net loss per share                    $      (0.20)      $      (0.18)      $      (0.14)
                                                        ============       ============       ============

Basic and diluted weighted average
  shares outstanding                                      26,547,238         21,537,584         18,017,650
                                                        ============       ============       ============


   The accompanying notes are an integral part of these financial statements.


                                      F-4


                              REPLIGEN CORPORATION
                       STATEMENTS OF STOCKHOLDERS' EQUITY



                                                     Number of          Common                                             Total
                                                      Common          Stock $.01    Additional        Accumulated      Stockholders'
                                                      Shares          Par Value   Paid-in Capital       Deficit            Equity
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         
Balance, March 31, 1998                             18,001,785         $180,017     $130,264,048    ($124,319,625)       $6,124,440
- ------------------------------------------------------------------------------------------------------------------------------------
Issuance of common stock and warrants                  262,500            2,625        1,008,559               --         1,011,184
Net loss                                                    --               --               --       (2,543,933)       (2,543,933)
- ------------------------------------------------------------------------------------------------------------------------------------
Balance, March 31, 1999                             18,264,285          182,642      131,272,607     (126,863,558)        4,591,691
- ------------------------------------------------------------------------------------------------------------------------------------
Issuance of common stock and warrants                6,198,927           61,989       29,772,917               --        29,834,906
Issuance of warrants                                        --               --          188,265               --           188,265
Exercise of stock options                               64,458              645          147,293               --           147,938
Exercise of warrants                                 1,788,309           17,883        4,126,102               --         4,143,985
Net loss                                                    --               --               --       (3,816,383)       (3,816,383)
- ------------------------------------------------------------------------------------------------------------------------------------
Balance, March 31, 2000                             26,315,979          263,159      165,507,184     (130,679,941)       35,090,402
- ------------------------------------------------------------------------------------------------------------------------------------
Issuance of common stock for patent
   acquisition                                          30,000              300          183,450               --           183,750
Issuance of warrants                                        --               --          218,735               --           218,735
Exercise of stock options                               34,200              342           24,354               --            24,696
Exercise of warrants                                   248,771            2,488          649,961               --           652,449
Net loss                                                    --               --               --       (5,278,867)       (5,278,867)
- ------------------------------------------------------------------------------------------------------------------------------------
Balance, March 31, 2001                             26,628,950         $266,289     $166,583,684    ($135,958,808)      $30,891,165
- ------------------------------------------------------------------------------------------------------------------------------------


   The accompanying notes are an integral part of these financial statements.


                                      F-5


                              REPLIGEN CORPORATION
                            STATEMENTS OF CASH FLOWS




                                                                                                Years Ended March 31,
                                                                                     2001               2000               1999
                                                                                 ---------------------------------------------------
                                                                                                              
Cash flows from operating activities:
   Net loss                                                                      $ (5,278,867)      $ (3,816,383)      $ (2,543,933)
   Adjustments to reconcile net loss to net cash
   used in operating activities --
      Depreciation and amortization                                                   276,852            324,409            268,217
      Issuance of stock options and warrants for services                             218,735            188,265            126,270
      Non cash expense related to common stock issued for patent
      acquisition                                                                     183,750                 --            884,914
   Changes in assets and liabilities
      Accounts receivable                                                              35,357           (418,118)          (216,863)
      Inventories                                                                     (87,276)            82,882             40,488
      Prepaid expenses and other current assets                                       (28,598)           (60,037)           (25,389)
      Accounts payable                                                                104,350            156,857            167,989
      Accrued expenses and other                                                      (44,610)           457,594             59,614
      Unearned income                                                                      --            (49,969)            16,637
                                                                                 ------------       ------------       ------------

         Net cash used in operating activities                                     (4,620,307)        (3,134,500)        (1,222,056)
                                                                                 ------------       ------------       ------------

   Cash flows from investing activities:
      Purchases of marketable securities                                          (49,959,538)        (8,806,367)                --
      Redemptions of marketable securities                                         45,000,000                 --                 --
      Purchases of property, plant and equipment                                     (184,721)          (217,256)          (252,737)
      Decrease in other assets                                                         24,500              7,090                 --
                                                                                 ------------       ------------       ------------

         Net cash used in investing activities                                     (5,119,759)        (9,016,533)          (252,737)
                                                                                 ------------       ------------       ------------

   Cash flows from financing activities:
      Exercise of warrants                                                            652,449          4,143,984                 --
      Exercise of stock options                                                        24,696            147,938                 --
      Issuance of common stock and warrants                                                --         29,834,906                 --
                                                                                 ------------       ------------       ------------

         Net cash provided by financing activities                                    677,145         34,126,828                 --
                                                                                 ------------       ------------       ------------

   Net (decrease) increase in cash and cash equivalents                            (9,062,921)        21,975,795         (1,474,793)

   Cash and cash equivalents, beginning of year                                    25,226,546          3,250,751          4,725,544
                                                                                 ------------       ------------       ------------

   Cash and cash equivalents, end of year                                        $ 16,163,625       $ 25,226,546       $  3,250,751
                                                                                 ============       ============       ============


   The accompanying notes are an integral part of these financial statements.


                                      F-6


                              REPLIGEN CORPORATION

                          NOTES TO FINANCIAL STATEMENTS

1.   Summary of Significant Accounting Policies

     Repligen  Corporation  ("Repligen"  or the "Company")  develops  innovative
therapeutic  products for  debilitating  pediatric  diseases  including  autism,
leukemia,  metabolic and immune  system  diseases  based on  naturally-occurring
peptides  and  proteins.  Lead  therapeutic  products  are  secretin for autism,
CTLA4-Ig for stem cell  transplantation  and uridine for mitochondrial  disease.
Repligen   manufactures  and  markets  products  based  on  Protein  A  for  the
purification of antibodies,  and owns commercial rights to two products based on
synthetic  forms of  secretin  for the  diagnosis  of  pancreatic  function.  In
addition,  the  Company  has  licensed  to third  parties  certain  intellectual
property pertaining to its former programs on biological products.

     The accompanying  financial  statements  reflect the application of certain
accounting  policies  described in this note and  elsewhere in the  accompanying
notes to the financial statements.

Use of Estimates

     The  preparation  of financial  statements  in  conformity  with  generally
accepted  accounting  principles  requires  management  to  make  estimates  and
assumptions  that  affect the  reported  amounts of assets and  liabilities  and
disclosure of  contingent  assets and  liabilities  at the date of the financial
statements  and the  reported  amounts  of  revenues  and  expenses  during  the
reporting period. Actual results could differ from those estimates.

Reclassifications

     The Company has reclassified  certain prior-year  information to conform to
the current year's presentation.

Revenue Recognition

     The Company  recognizes  revenue  related to product sales upon shipment of
the product.

     Research and development revenue derived from collaborative arrangements is
recognized as earned under cost plus fixed-fee contracts,  or on a straight-line
basis over development contracts,  which approximates when work is performed and
costs are  incurred.  Research  and  development  expenses  in the  accompanying
statements  of operations  include  funded and unfunded  expenses.  In addition,
under  certain  contracts,  the  Company  recognizes  research  and  development
revenues as milestones are achieved.  Licensing and royalties from the Company's
licensed  technologies  are  recognized as earned.  Unearned  income  represents
amounts received prior to recognition of revenue.

     The Company  applies  Staff  Accounting  Bulletin  (SAB) No.  101,  Revenue
Recognition.  SAB No.  101  requires  companies  to  recognize  certain  upfront
nonrefundable  fees and milestone payments over the life of the related alliance
when such fees are received in  conjunction  with  alliances  that have multiple
elements. The adoption of SAB No. 101 had no significant impact on the Company's
financial statements.


                                      F-7


Comprehensive Income

     The Company applies Statement of Financial  Accounting Standards (SFAS) No.
130, Reporting  Comprehensive  Income.  SFAS No. 130 requires  disclosure of all
components of comprehensive income on an annual and interim basis. Comprehensive
income is  defined as the  change in equity of a  business  enterprise  during a
period  from  transactions  and other  events and  circumstances  from  nonowner
sources. The Company's  comprehensive loss is equal to reported net loss for all
periods presented.

Cash, Cash Equivalents & Investments

     The Company  applies SFAS No. 115,  Accounting  for Certain  Instruments in
Debt and Equity  Securities.  At March 31, 2001, the Company's cash  equivalents
and marketable securities are classified as held-to-maturity  investments as the
Company  has  the  positive  intent  and  ability  to  hold  to  maturity.  Cash
equivalents are short-term,  highly liquid investments with original  maturities
of less than three months.  Marketable  securities are investments with original
maturities of greater than three months.  Long-term  marketable  securities  are
investment grade securities with maturities of greater than one year.

     Cash  and  cash  equivalents  and  marketable  securities  consist  of  the
following at March 31, 2001 and 2000 were as follows:

                                                              March 31,
                                                         2001            2000
                                                     ---------------------------
Cash and cash equivalents
     Cash                                            $   222,766     $    50,946
     Commercial paper and corporate bonds                489,719      17,031,292
     U.S. Government and agency securities                    --       7,342,874
     Money market accounts                            15,451,140         801,434
                                                     -----------     -----------
     Total cash and cash equivalents                 $16,163,625     $25,226,546
                                                     ===========     ===========

Marketable securities
     U.S. Government and agency securities           $        --     $ 2,951,823
     Corporate and other debt securities               7,773,427       5,854,544
                                                     -----------     -----------
     (Average maturity of 7.2 months)                $ 7,773,427     $ 8,806,367
                                                     ===========     ===========

Long -term marketable securities
     Corporate and other debt securities             $ 5,992,478     $        --
                                                     ===========     ===========
     (Average maturity of 16 months)

Inventories

     Inventories  are  stated  at the  lower of cost  (first-in,  first-out)  or
market.  Work-in-process  and finished  goods  inventories  consist of material,
labor, outside processing costs and manufacturing overhead. Inventories at March
31, 2001 and 2000 consist of the following:

                                                      Year Ended March 31,
                                                       2001          2000
                                                     ----------------------
     Raw materials and work-in-process ........      $459,288      $371,405
     Finished goods ...........................       175,435       176,043
                                                     --------      --------
        Total .................................      $634,723      $547,448
                                                     ========      ========

                                      F-8


Depreciation and Amortization

     The  Company  provides  for  depreciation  and  amortization  by charges to
operations in amounts  estimated to allocate the cost of fixed assets over their
estimated useful lives, on a straight-line basis, as follows:

     Description                       Estimated Useful Life
     -----------                       ---------------------

     Equipment                  3-5 years
     Leasehold improvements     Shorter of term of the lease or estimated useful
                                life
     Furniture and fixtures     5-7 years

Earnings Per Share

     The  Company  applies  SFAS No.  128,  Earnings  per  Share.  SFAS No.  128
establishes standards for computing and presenting earnings per share. Basic net
loss per share  represents  net loss divided by the weighted  average  number of
common shares  outstanding  during the period.  The dilutive effect of potential
common  shares,  consisting  of  outstanding  stock  options  and  warrants,  is
determined  using the  treasury  stock method in  accordance  with SFAS No. 128.
Diluted weighted average shares  outstanding for 2001, 2000 and 1999 exclude the
potential  common shares from warrants and stock options  because to do so would
have been antidilutive for the years presented.  Accordingly,  basic and diluted
net loss per share is the same.  The number of potential  common shares prior to
application  of the treasury  stock method at March 31, 2001,  2000 and 1999 was
1,904,387, 2,484,953 and 4,498,249 shares, respectively.

Fair Value of Financial Instruments

     In accordance with SFAS No. 107,  Disclosure  About Fair Value of Financial
Instruments,  the carrying  amounts of the Company's cash and cash  equivalents,
marketable securities, accounts receivable and accounts payable approximate fair
value due to the short-term nature of these instruments.

Concentrations of Credit Risk and Significant Customers

     Financial   instruments   that   subject   the   Company   to   significant
concentrations  of credit risk consist  primarily of cash and cash  equivalents,
marketable  securities and accounts  receivable.  The Company's cash equivalents
and marketable securities are invested in financial instruments with high credit
ratings.  Concentration  of credit risk with respect to accounts  receivable  is
limited to customers to whom the Company makes  significant  sales.  The Company
does not believe  significant  risk exists at March 31, 2001. To control  credit
risk,  the  Company  performs  regular  credit  evaluations  of  its  customers'
financial conditions and maintains allowances for potential credit losses.

     Revenues from significant customers as a percentage of the Company's total
revenues are as follows:

                                            Year Ended March 31,
                                         2001       2000      1999
                                       ----------------------------
                  Customer A              42%        14%       12%
                  Customer B              19%        16%        1%
                  Customer C               5%        16%       --%
                  Customer D              --%         9%       16%
                  Customer E              --%         3%        3%
                  Customer F               5%         3%       13%


                                      F-9



     Significant  accounts  receivable balances as a percentage of the Company's
total trade accounts receivable balances are as follows:

                                        Year Ended March 31,
                                          2001        2000
                                        --------------------
                        Customer A         53%         --%
                        Customer B         26%         32%
                        Customer C         10%         --%

Segment Reporting

     The  Company  applies  SFAS  No.  131,  Disclosures  about  Segments  of an
Enterprise  and Related  Information.  SFAS No. 131  establishes  standards  for
reporting   information   regarding   operating  segments  in  annual  financial
statements and requires selected  information for those segments to be presented
in  interim  financial  reports  issued  to  stockholders.  SFAS  No.  131  also
establishes  standards for related  disclosures  about products and services and
geographic areas. The chief operating decision maker, or decision-making  group,
in making decisions how to allocate resources and assess performance, identifies
operating  segments as components of an enterprise about which separate discrete
financial  information  is available for  evaluation.  To date,  the Company has
viewed its  operations  and manages its business as  principally  one  operating
segment. As a result, the financial  information disclosed herein represents all
of  the  material  financial  information  related  to the  Company's  principal
operating segment.

The following table represents the Company's revenue by geographic area:

                            Year Ended March 31,
                       2001          2000          1999
                     ------------------------------------
United States           58%           53%           68%
Europe                  40%           44%           28%
Other                    2%            3%            4%
                       ----          ----          ----
Total                  100%          100%          100%
                       ====          ====          ====

New Accounting Standards

     In June 1998, the Financial  Accounting  Standards Board (FASB) issued SFAS
No. 133,  Accounting  for  Derivative  Instruments  and Hedging  Activities.  As
amended in June 1999, the statement is effective for all fiscal  quarters of all
fiscal years  beginning  after June 15, 2000. In June 2000, the FASB issued SFAS
No. 138, which is a significant  amendment to SFAS No. 133. SFAS No. 133 and its
amendments   establish   accounting  and  reporting   standards  for  derivative
instruments,   including  certain  derivative   instruments  embedded  in  other
contracts  (collectively referred to as derivatives) and for hedging activities.
The   Emerging   Issues   Task  Force   (EITF)  has  also  issued  a  number  of
derivative-related  tentative  and  final  consensuses.  We do  not  expect  the
adoption  of these  statements  to have a  material  impact on our  consolidated
financial position or results of operations.

     In March  2000,  the FASB  issued  Interpretation  No. 44,  Accounting  for
Certain  Transactions  Involving Stock  Compensation--An  Interpretation  of APB
Opinion No. 25. The  Interpretation  clarifies  the  application  of  Accounting
Principles  Board  Opinion  (APB)  No. 25 in  certain  situations,  as  defined.
Interpretation  No. 44 is effective  July 1, 2000;  however,  it covers  certain
events  occurring  during  the period  after  December  15,  1998 but before the
effective  date,  the effects of applying  this  Interpretation  No. 44 would be
recognized on a prospective  basis from the effective  date.  Accordingly,  upon
initial application of the final Interpretation No. 44,


                                      F-10



     no adjustments would be made to the financial statements for periods before
the  effective  date and no  expense  would  be  recognized  for any  additional
compensation  cost measured that is attributable to periods before the effective
date.  The adoption of this  statement  had no material  impact on our financial
statements.

     In  September  2000,  the EITF  issued  00-19,  Accounting  for  Derivative
Financial  Instruments  Indexed to and  Potentially  Settled in a Company's  Own
Stock, which requires freestanding contracts that are settled in a company's own
stock,   including  common  stock  warrants,  to  be  designated  as  an  equity
instrument, asset or a liability. Under the provisions of EITF 00-19, a contract
designated  as an asset or a liability  must be carried at fair value,  with any
changes  in fair  value  recorded  in the  results  of  operations.  A  contract
designated as an equity  instrument  must be included  within equity and no fair
value  adjustments are required.  The adoption of this statement had no material
impact on our financial statements.

2.   Income Taxes

     The Company  accounts for income taxes under SFAS No. 109,  Accounting  for
Income  Taxes.   At  March  31,  2001,   the  Company  had  net  operating  loss
carryforwards for income tax purposes of approximately $105,654,000. The Company
also had available tax credit carryforwards of approximately $4,476,000 at March
31, 2001 to reduce  future  federal  income taxes,  if any. Net  operating  loss
carryforwards  and  available  tax credits  are  subject to review and  possible
adjustment  by the Internal  Revenue  Service and may be limited in the event of
certain changes in the ownership interest of significant stockholders.

     The net operating loss carryforwards and tax credit carryforwards are
approximately as follows:

                                     Net Operating Loss        Tax Credit
     Expiration Date                    Carryforwards        Carryforwards
                                     -------------------------------------
     2002                                $  2,500,000         $     73,000
     2003                                   4,807,000              346,000
     2004                                   6,642,000              408,000
     2005                                   6,707,000              681,000
     2006                                   7,533,000              595,000
     2007-2020                             77,465,000            2,373,000
                                         ------------         ------------
     Total                               $105,654,000         $  4,476,000
                                         ============         ============

     The deferred tax asset consists of the following:

                                                      Year Ended March 31,
                                                    2001                2000
                                               --------------------------------
Temporary differences ..................       $  6,738,000        $  3,416,000
Operating loss carryforwards ...........         40,307,000          40,540,000
Tax credit carryforwards ...............          4,476,000           4,585,000
                                               ------------        ------------
                                                 51,521,000          48,541,000
Valuation allowance ....................        (51,521,000)        (48,541,000)
                                               ------------        ------------
                                               $         --        $         --
                                               ============        ============

     A full  valuation  allowance has been  provided,  as it is uncertain if the
Company will realize the deferred tax asset.


                                      F-11



3.   Shareholder's Equity

     (a)  Common Stock & Warrants

     On July 24,  2000,  Repligen  issued to a third party a warrant to purchase
50,000 shares of common stock at $7.125 per share exercisable  through July 2003
in partial  consideration for a licensing agreement entered into with such third
party.  The Company  recorded the value of this  warrant,  as  determined  using
Black-Scholes option pricing model, as research and development expense.

     On May 10, 2000, pursuant to a patent purchase  agreement,  Repligen issued
to Tolerance  Therapeutics LLC ("Tolerance"),  in partial  consideration for the
assignment by Tolerance to Repligen of a U.S.  patent  application  claiming the
use of CTLA4-Ig in treatment of diseases of the immune system,  30,000 shares of
Repligen  common  stock.  The  Company  recorded  the  value of these  shares as
research and development expense.

     On April 7, 2000, Repligen issued to each of its investor relation firm and
public  relations firm, in  consideration  for services,  a warrant  exercisable
through July 2001 to purchase 10,000 shares of common stock of Repligen at $8.56
per share. The Company  recorded the value of this warrant,  as determined using
Black-Scholes  option  pricing  model,  as selling,  general and  administrative
expense.

     On April 7, 2000,  Repligen  issued a warrant to purchase  2,900  shares of
common stock at $9.00 per share to an existing  shareholder  exercisable through
July 2000.  This warrant  expired during fiscal 2001.  The Company  recorded the
value of this warrant, as determined using  Black-Scholes  option pricing model,
as selling, general and administrative expense.

     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.  Repligen  engaged  Paramount  Capital,  Inc.
("Paramount")  to  act  as  placement  agent  for  this  transaction.  For  this
transaction,  Repligen  paid  Paramount  approximately  $1.57  million  for  its
services,  plus related transactional expenses, and issued to Paramount warrants
to purchase up to 129,946 shares of common stock at $9.49 per share.

     In July  1999,  Repligen  engaged  Paramount  as a  nonexclusive  financial
adviser for an initial  period of 12 months from the date  thereof.  In exchange
and as consideration  for these 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.  Each  warrant is
exercisable at $2.75 per share at any time prior to July 15, 2004. Repligen also
agreed to pay Paramount  additional fees upon the consummation of certain equity
financing  transactions.  The Company  valued  these  warrants at fair value and
recorded an expense of $188,285 during fiscal 2000 relating to this issuance. In
March 2000,  Repligen terminated the financial advisory agreement with Paramount
for an additional payment of $200,000 in cash. All payments were expensed in the
accompanying  statement of  operations  as selling,  general and  administrative
expense for the year ended March 31, 2000.

     Pursuant  to stock  purchase  agreements  dated  April 30, 1999 and May 14,
1999, respectively, Repligen issued to certain accredited investors in a private
placement an  aggregate  of 3,600,000  shares of common stock at $2.50 per share
for an aggregate  purchase price of approximately  $9 million,  resulting in net
proceeds to Repligen of approximately $8.9 million.

     In March 1999,  the Company  entered into an agreement  for legal  services
relating to a complaint filed against  Bristol-Myers  Squibb Company.  Under the
terms of the  agreement,  the  Company is required to pay $50,000 in annual fees
for three years, and, if successful in the


                                      F-12



litigation,  a portion of any  financial  recovery will be paid and a warrant to
purchase  100,000 shares of common stock at an exercise price of $1.63 per share
will be issued. The Company will value this warrant at the time of issuance.  In
addition, the Company issued a fully vested warrant to legal counsel to purchase
100,000  shares of common  stock at an  exercise  price of $1.63 per share.  The
Company valued this warrant at fair value, as determined using the Black-Scholes
option pricing model and recorded  legal expense of $126,270  during fiscal 1999
relating to this issuance. In March 2000, this warrant was exercised pursuant to
the "net exercise"  provision in the warrant.  Repligen  issued 83,184 shares of
common  stock upon  exercise of the warrant and  received no proceeds  from such
transaction.

     In  March  1999,  the  Company   acquired  all  rights  to  certain  patent
applications  relating to the use of secretin in the  treatment  of autism.  The
rights were acquired pursuant to a Patent Purchase Agreement whereby the Company
paid  $150,000 in cash,  issued a warrant to purchase  350,000  shares of common
stock with an exercise  price of $1.59 per share,  and issued  262,500 shares of
common  stock  (see Note 5).  The  Company  valued  the  shares  and  warrant in
accordance  with ETIF 96-18  using the  Black-Scholes  option-pricing  model and
recorded a charge of $1,035,000.  As of March 31, 2001,  225,000 of these shares
of common  stock  underlying  this  warrant were  exercised.  Repligen  received
$357,750 of proceeds from this exercise.

     At March 31, 2001, common stock reserved for issuance is as follows:

Reserved for                                                            Shares
- ------------                                                            ------
Incentive and nonqualified stock option plans                         3,254,619
Warrants granted in connection with the Patent Purchase Agreement       125,000
Warrants granted in connection with Licensing Agreement                  50,000
Warrants granted for payment of services                                249,946
                                                                      ---------
                                                                      3,679,565
                                                                      =========

     (b)  Stock Options

     The Company's  stock option plan  authorizes the grant of either  incentive
stock options or nonqualified stock options. Incentive stock options are granted
to employees at the fair market value at the date of grant.  Nonqualified  stock
options are granted to employees or  nonemployees.  The options  generally  vest
over four or five years and expire no more than 10 years from the date of grant.
As of March 31, 2001, the Company had 1,775,178 shares of common stock available
for grant.

     A summary of stock option activity under all plans is as follows:



                                                                      Years Ended March 31,
                                                     2001                       2000                       1999
                                           ------------------------------------------------------------------------------
                                                          Weighted                   Weighted                   Weighted
                                                           Average                    Average                    Average
                                            Number of     Price per    Number of     Price per    Number of     Price per
                                              Shares        Share        Shares        Share        Shares        Share
                                           ----------    ----------   ----------    ----------   ----------    ----------
                                                                                             
Outstanding at beginning of period          1,288,041    $     1.81    1,289,291    $     1.78      740,291    $     2.05
Granted                                       258,400          6.59      169,908          2.86      568,500          1.38
Exercised                                     (34,200)         0.72      (64,458)         2.30           --            --
Forfeited                                     (32,800)         3.73     (106,700)         1.44      (19,500)         1.18
                                           ----------    ----------   ----------    ----------   ----------    ----------
Outstanding at end of period                1,479,441    $     2.64    1,288,041    $     1.82    1,289,291    $     1.78
                                           ----------    ----------   ----------    ----------   ----------    ----------
Exercisable at end of period                  894,941    $     1.92      694,941    $     1.96      529,691    $     2.33
                                           ==========    ==========   ==========    ==========   ==========    ==========



                                      F-13





                                                    Options Outstanding         Options Exercisable
                                                    -------------------         -------------------
                                                  Weighted
                                                   Average      Weighted                      Weighted
                                                  Remaining     Average                       Average
                                    Number       Contractual  Exercise Price      Number    Exercise Price
                                 Outstanding         Life       Per Share      Outstanding    Per Share
                                 -----------     -----------  --------------   -----------  --------------
                                                                               
        $.05-$1.00                   89,541           5.16      $    0.60         89,541      $    0.60
       $1.03-$1.63                  897,500           6.35      $    1.38        619,400      $    1.36
       $2.75-$2.91                  160,000           5.05      $    2.76        113,600      $    2.75
       $3.00-$4.13                  128,900           8.90      $    3.77         32,400      $    3.05
       $6.13-$7.19                   55,500           7.38      $    6.60         15,000      $    6.56
      $7.64-$12.45                  148,000           7.83      $    8.97         25,000      $   12.45
- -------------------------------------------------------------------------------------------------------
                                  1,479,441           6.55      $    2.64        894,941      $    1.92
                                  =========      =========      =========      =========      =========


     The Company  accounts for its stock-based  compensation  under SFAS No. 123
Accounting   for   Stock-Based   Compensation.   The  Company  has  adopted  the
disclosure-only alternative for employee grants and, accordingly,  will continue
to account for stock-based compensation for employees under APB Opinion No. 25.

     The Company has computed the pro forma disclosures  required under SFAS No.
123 for all stock options  granted to employees in 2001, 2000 and 1999 using the
Black-Scholes  option-pricing  model prescribed by SFAS No. 123. The assumptions
used and the weighted  average  information  for the years ended March 31, 2001,
2000 and 1999 are as follows:



                                                                        Year ended March 31,
                                                                  2001              2000             1999
                                                          -----------------------------------------------
                                                                                     
Risk-free interest rates                                   5.28%-6.33%       5.08%-6.03%      4.54%-5.61%
Expected dividend yield                                             --                --               --
Expected lives                                                 7 years           7 years         10 years
Expected volatility                                               108%               70%              93%
Weighted average grant date fair value of options
    granted during the period                                    $6.59             $2.86            $1.38
Weighted average remaining contractual life of
    options outstanding                                      6.6 years         7.0 years        7.7 years


If compensation  expense for the Company's stock option plan had been determined
consistent  with  SFAS No.  123,  the pro  forma net loss and net loss per share
would have been as follows:

                                        Year Ended March 31
Net loss-                      2001             2000             1999
                         ------------------------------------------------
As reported.               ($5,278,867)     ($3,816,383)     ($2,543,933)
Pro forma                  ($5,681,311)     ($4,103,293)     ($2,768,827)

Basic and diluted net loss per share-
As reported                    $ (0.20)         $ (0.18)         $ (0.14)
Pro forma                      $ (0.21)         $ (0.19)         $ (0.15)

                                      F-14



4.   Commitments and Contingencies

     The Company  leases  their  facilities.  Obligations  under  noncancellable
operating leases as of March 31, 2001 is approximately as follows:

                     Year Ending March 31,
                     ---------------------
                  2002......................        $181,000
                  2003......................          13,000
                                                    --------
                  Total minimum lease payments      $194,000
                                                    --------

     Rent expense charged to operations under operating leases was approximately
$377,000,  $296,000 and  $281,000  for the years ended March 31, 2001,  2000 and
1999, respectively.

5.   Certain Technologies and Product Candidates

     In December 2000, the Company  purchased from the University of California,
San Diego (UCSD) a right to a U.S. patent application covering novel methods for
the treatment of mitochondrial disease.  Under terms of the agreement,  Repligen
received  the  exclusive  right under the license to  commercialize  products to
treat  mitochondrial  disease and paid UCSD an up-front fee.  Repligen will also
pay UCSD clinical  development  milestones and royalties on product  sales.  The
Company has expensed the purchase price as research and  development  expense as
the realizability of the patent is subject to the outcome of additional research
and development and the successful prosecution of the patent.

     In May 2000,  the Company  purchased from  Tolerance  Therapeutics  LLC the
rights  to a  U.S.  patent  application  claiming  the  use of  CTLA4-Ig  in the
treatment of diseases of the immune system.  Under terms of the  agreement,  the
Company  paid cash and issued stock for the  purchase.  The Company has expensed
the purchase price as research and development  expense as the  realizability of
the patent is subject to the outcome of additional  research and development and
the successful prosecution of the patent.

     In  October  1999,  the  Company  acquired  the  commercial  rights  to two
diagnostic  products based on synthetic forms of porcine and human secretin from
ChiRhoClin,  Inc. a private company.  Both of these products have been evaluated
in  clinical  trials for their  safety and  efficacy  in  diagnosing  pancreatic
function and gastrinoma.  A New Drug Application (NDA) for each product has been
filed with the United States Food and Drug Administration  (FDA). In March 2000,
the FDA issued an "approvable  letter" for the use of synthetic porcine secretin
in the diagnosis of pancreatic function. A second "approvable letter" was issued
in November 2000, which contained numerous questions  concerning the manufacture
and quality control of the synthetic  porcine product.  Final approval to market
this product will be based on a satisfactory response to questions raised by the
FDA by ChiRhoClin.

     Under terms of the  licensing  agreement,  Repligen  paid  $1,000,000  upon
execution of the agreement  and, if the NDAs are  approved,  the Company will be
required to pay future  royalties  and  milestones  in cash and to issue  common
stock. This $1,000,000  payment is included in research and development  expense
in the  accompanying  statement of operations for the year ended March 31, 2000.
The Company  expensed the $1 million  payment during fiscal 2000, as the Company
believes that the net  realizable  value of such license fee is uncertain  until
such time as the NDA approval is obtained.

     In  March  1999,  the  Company   acquired  all  rights  to  certain  patent
applications  relating to the use of secretin in the  treatment  of autism.  The
rights were acquired pursuant to a patent purchase agreement.  In addition,  the
Company has agreed to make  minimum  annual  royalty  payments  of $500,000  and
certain  milestone  payments  upon  (a)  the  Company's  filing  of a  new  drug
application with the FDA for a clinical  indication  covered by the intellectual
property rights  transferred by the purchase agreement and (b) upon the approval
by the FDA of a product


                                      F-15



covered by the intellectual  property rights transferred to the Company pursuant
to the purchase  agreement.  These milestone  payments,  in the aggregate sum of
$700,000, will be largely credited against certain royalty payments in the event
the  Company  is  able  to  derive  sales  and/or  license   revenues  from  the
intellectual property rights acquired pursuant to the purchase agreement.

     In order for the  Company to  commercialize  secretin  as a  treatment  for
autism,  the Company  will need to expend a  substantial  amount in research and
development,  preclinical testing and clinical trials, regulatory clearances and
manufacturing,  distribution and marketing arrangements, the outcome of which is
uncertain.  The cost and time to complete the  development  of the technology is
significant  and difficult to estimate given the  uncertainties  of research and
development and regulatory process. Accordingly, the net realizable value of the
patent rights acquired is uncertain. Approximately $1,035,000 was charged to the
accompanying 1999 statement of operations as a research and development expense.

6.   Accrued Expenses

     Accrued expenses consist of the following:

                                               Year Ended March 31,
                                              2001             2000
                                            ------------------------
Research & development costs                $321,850        $ 80,083
Payroll & payroll related cost               255,811         166,989
Professional and consulting costs             71,795         235,712
Other accrued expenses                        74,864         109,289
Manufacturing costs                            2,590         179,447
                                            --------        --------
                                            $726,910        $771,520
                                            ========        ========

7.   Selected Quarterly Financial Data (Unaudited)

     The following table contains  Statement of Operations  information for each
quarter  of fiscal  2000 and  2001.  The  Company  believes  that the  following
information  reflects  all normal  recurring  adjustments  necessary  for a fair
presentation of the information for the period presented.  The operating results
for any quarter are not necessarily indicative of results for any future period.


                                      F-16




                                                Q4         Q3         Q2         Q1         Q4         Q3         Q2         Q1
                                               FY01       FY01       FY01       FY01       FY00       FY00       FY00       FY00
                                             -------    -------    -------    -------    -------    -------    -------    -------
                                                                                                  
Revenues:
   Product                                   $   588    $   615    $   324    $   556    $   671    $   558    $   579    $   233
   Research and development                       12          3        127         30         92        160        232        379
   Other                                          --          2         15         75         14         14         15         31
                                             -------    -------    -------    -------    -------    -------    -------    -------
Total revenues                                   600        620        466        661        777        732        826        643
                                             -------    -------    -------    -------    -------    -------    -------    -------

Costs and expenses:
    Research and development                   1,580      1,781      1,343      1,083        668      1,865        733        488
    Selling, general and administrative          536        568        658        731        844        443        767        426
    Cost of products sold                        448        393        229        330        332        292        287        196
                                             -------    -------    -------    -------    -------    -------    -------    -------
Total costs and expenses                       2,564      2,742      2,230      2,144      1,844      2,600      1,787      1,110
                                             -------    -------    -------    -------    -------    -------    -------    -------

Loss from operations                          (1,964)    (2,122)    (1,764)    (1,483)    (1,067)    (1,868)      (961)      (467)
                                             -------    -------    -------    -------    -------    -------    -------    -------
Investment income                                450        539        552        513        213        131        156         47
                                             -------    -------    -------    -------    -------    -------    -------    -------
Net loss                                     $(1,514)   $(1,583)   $(1,212)   $  (970)   $  (854)   $(1,737)   $  (805)   $  (420)
                                             =======    =======    =======    =======    =======    =======    =======    =======
Net loss per common share                    $ (0.06)   $ (0.06)   $ (0.05)   $ (0.04)   $ (0.04)   $ (0.08)   $ (0.04)   $ (0.02)
Weighted average common shares outstanding    26,599     26,576     26,560     26,456     23,295     22,194     21,868     18,745
                                             =======    =======    =======    =======    =======    =======    =======    =======


8.   Valuation and Qualifying Accounts



                                       Balance at
                                      Beginning of                                   Balance at End
                                         Period        Additions      Deletions        of Period
                                         ------        ---------      ---------        ---------
                                                                            
Allowance for Doubtful Accounts:
          1999                           $25,000            --            --            $25,000
          2000                           $25,000            --            --            $25,000
          2001                           $25,000            --            --            $25,000



                                      F-17