Exhibit 99.1


REPLIGEN ANNOUNCES $9 MILLION PRIVATE PLACEMENT

ADDITIONAL CAPITAL TO SUPPORT CLINICAL TRIALS OF SECRETIN IN AUTISM
REPLIGEN ANNOUNCES $9 MILLION PRIVATE PLACEMENT

NEEDHAM, MA -- May 17, 1999 -- Repligen Corporation (Nasdaq: RGEN) announced
today that it has entered into definitive agreements to raise $9 million through
a private placement of Repligen's common stock. The Company will issue 3.6
million shares at $2.50 per share.

         The primary use of the proceeds of this financing will be to fund
clinical trials of secretin in autism. Anecdotal reports have indicated that
secretin may produce improvements in gastrointestinal function, language, social
behavior and sleep in autistic children. In March 1999, Repligen acquired the
rights to patent applications for the use of secretin in autism. The Company
plans to manufacture a synthetic, human form of secretin and initiate a
controlled clinical trial by years' end.

         "This financing will increase our cash position to approximately $12
million," stated Walter C. Herlihy, President and CEO of Repligen. "We expect
that this capital will enable us to aggressively pursue the clinical development
of human secretin for autism for at least two years without the need for
additional financing."

         Participants in the financing included funds managed by Wellington
Management Company, LLP. Paramount Capital acted as a financial advisor to the
Company. The financing will close upon the effectiveness of a registration
statement which the Company plans to file with the SEC within 20 days.

         Repligen Corporation develops new drugs for autism, organ transplant
and cancer. The Company also manufactures and markets a set of patented products
based on Protein A which are used by the pharmaceutical industry to produce
therapeutic antibodies. Its corporate headquarters are located at 117 Fourth
Avenue, Needham, MA 02494. Additional information may be requested from
www.repligen.com. 


         This press release contains forward-looking statements based on 
current management expectations. There are certain key factors which could 
cause future results to differ materially from those anticipated by 
management. Such factors include, but are not limited to: uncertainty in the 
realization of future revenues, the uncertain timeline for clinical activity, 
results of pending or future clinical trials, the Company's ability to 
continue to establish collaborative arrangements with third parties; the 
Company's ability to maintain financial stability; the technical risks 
associated with development and manufacture of products; the fact that there 
can be no assurances that patents relating to the Company's potential 
products will afford adequate protection to the Company, the risks of 
technological change and competition, and the competitive environment of the 
biotechnology and pharmaceutical industries. These factors are more fully 
discussed in the Company's periodic filings with the Securities and Exchange 
Commission.


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