EXHIBIT 99

                                                Repligen Corporation
                                                41 Seyon Street
RepliGen                                        Building #1, Suite 100
                                                Waltham, Massachusetts 02453
                                                Telephone: 781-250-0111
                                                Telefax:   781-250-0115

FOR IMMEDIATE RELEASE

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CONTACT:
Walter C. Herlihy, Ph.D.                         Laura L. Whitehouse
President and Chief Executive Officer            Sr. Director Market Development
(781) 250-0111, ext. 2000                        (781) 250-0111, ext. 2306

Repligen Announces $12.5 Million Private Placement

WALTHAM, MA - May 2, 2003 - Repligen Corporation (Nasdaq: RGEN) announced today
it has issued and sold to The Riverview Group 2.5 million shares of its common
stock at $5.00 per share in a private placement for gross proceeds of $12.5
million. Rodman & Renshaw, Inc. served as the exclusive placement agent.

"We currently expect to use the net proceeds from this transaction to enable us
to expand our efforts to develop secretin for autism and other indications, to
increase our investment in the process development and manufacturing of CTLA4-Ig
and for working capital, capital expenditures and general corporate purposes"
stated Walter C. Herlihy, President and CEO of Repligen.

About Repligen Corporation

Repligen Corporation is a biopharmaceutical company committed to being the
leader in the development of new drugs for pediatric developmental disorders
including autism, immune and metabolic disorders. Repligen has a Specialty
Pharmaceuticals business comprised of rProtein A(TM) and SecreFlo(TM), the
profits from which will be used to support the development of our proprietary
products. Repligen's corporate headquarters are located at 41 Seyon Street,
Building #1, Suite 100, Waltham, MA 02453. Additional information may be
requested from www.repligen.com.

About The Riverview Group

The Riverview Group is the private equity investment arm of Millennium Partners,
L.P., a New York based investment fund established in 1989. The Riverview Group
specializes in structured private investments in financially and fundamentally
strong public companies with exceptional management teams.

This release contains forward-looking statements which are made pursuant to the
safe harbor provisions of Section 21E of the Securities Exchange Act of 1934.
The forward-looking statements in this release do not constitute guarantees of
future performance. Investors are cautioned that statements in this press
release which are not strictly historical statements, including, without
limitation, statements regarding current or future financial performance,
management's strategy, plans and objectives for future operations, clinical
trials and results and product development and manufacturing plans and
performance such as the anticipated growth in the monoclonal antibody market and
projected growth in product sales, constitute forward-looking statements. Such
forward-looking statements are subject to a number of risks and uncertainties
that could cause actual results to differ materially from those anticipated,
including, without limitation, risks associated with: the success of current and
future collaborative relationships, the market acceptance of our products, our
ability to compete with larger,



better financed pharmaceutical and biotechnology companies, new approaches to
the treatment of our targeted diseases, our expectation of incurring continued
losses, our uncertainty of product revenues and profits, our ability to generate
future revenues, our ability to raise additional capital to continue our drug
development programs, the success of our clinical trials, our ability to develop
and commercialize products, our ability to obtain required regulatory approvals,
our compliance with all Food and Drug Administration regulations, our ability to
obtain, maintain and protect intellectual property rights for our products, the
risk of litigation regarding our intellectual property rights, our limited sales
and manufacturing capabilities, our dependence on third-party manufacturers and
value added resellers, our ability to hire and retain skilled personnel, our
volatile stock price, and other risks detailed in Repligen's filings with the
Securities and Exchange Commission. Repligen assumes no obligation to update any
forward-looking information contained in this press release or with respect to
the announcements described herein.