Momenta Pharmaceuticals, Inc.
Jun 28, 2004

Momenta Pharmaceuticals Announces Exercise of Over-Allotment Option

CAMBRIDGE, MA - June 28, 2004 – Momenta Pharmaceuticals, Inc. (NASDAQ:
MNTA) announced today that the underwriters of the Company's recent initial public
offering of 5,350,000 shares of common stock exercised in full their over-allotment option
to purchase an additional 802,500 shares of common stock at the initial public offering
price of $6.50 per share. The net proceeds to the Company from the over-allotment option
are approximately $4.85 million.

The managing underwriters for the offering were SG Cowen & Co., LLC and Banc of
America Securities LLC, acting as joint book-running managers, and CIBC World Markets
Corp. and ThinkEquity Partners LLC, acting as co-managers.

Copies of the final prospectus relating to the offering may be obtained from either SG
Cowen & Co., LLC, Prospectus Department, 1221 Avenue of the Americas, 6th Floor, New
York, NY 10020 or Banc of America Securities LLC, 9 West 57th Street, New York, NY
10019.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor
shall there be any sale of these securities in any state or jurisdiction in which such an offer,
solicitation or sale would be unlawful prior to registration or qualification under the
securities laws of any such state or jurisdiction.

About Momenta


Momenta Pharmaceuticals, Inc. is a biotechnology company specializing in the detailed
structural analysis and design of complex sugars for the development of improved versions
of existing drugs, the development of novel drugs and the discovery of new biological
processes. Momenta is also utilizing its ability to sequence sugars to create technologyenabled
generic products. Through detailed analysis of the molecular structure of complex
sugars, our proprietary technology provides a more complete understanding of the roles
that sugars play in cellular function, disease and drug action. Based on Momenta's
understanding of complex sugars, the Company has developed a diversified pipeline of
novel discovery and development candidates and near-term product opportunities.
Momenta was founded in 2001 and is headquartered in Cambridge, MA.

Contact: Valerie Threlfall, Momenta Pharmaceuticals, Inc., 617-395-5116