CAMBRIDGE, MA — November 16, 2004 – Momenta Pharmaceuticals, Inc. (Nasdaq: MNTA), a biotechnology company developing drugs based on sugar sequencing technology, today announced the appointment of John E. Bishop, Ph.D. as Vice President, Pharmaceutical Sciences and Manufacturing and Michael A. Lawless as Senior Director, Investor Relations.

Dr. Bishop joins Momenta from Millennium Pharmaceuticals, Inc. where he was most recently responsible for chemical and biologics process development, managing Millennium’s process development group and leading manufacturing efforts for many of Millennium’s small molecule and biologics clinical candidates. Among other projects, Dr. Bishop was chemistry team leader for Velcade© Millennium’s novel multiple myeloma drug, for which he was responsible for all aspects of active pharmaceutical ingredient and drug product development. Prior to Millennium, Dr. Bishop was involved in leading process development efforts on several projects at Dupont Merck Pharmaceuticals. Prior to that, Dr. Bishop worked in medicinal chemistry research. Dr. Bishop received his Ph.D. in Organic Chemistry under Professor Henry Rapoport at the University of California, Berkeley and his M.B.A. from Northeastern University. Joseph E. Tyler, Momenta’s former Vice President, Manufacturing, is retiring after a career of more than 30 years in pharmaceutical manufacturing. Dr. Bishop has assumed responsibility for Momenta’s manufacturing program as of November 15, 2004.

“We are extremely excited to have John Bishop join Momenta’s senior management team. We expect that John’s experience in process development and leading multiple cross-functional product development teams will be invaluable to Momenta as we work towards filing our regulatory application for M-Enoxaparin, our generic version of Lovenox®,” commented Alan Crane, Chairman and Chief Executive Officer of Momenta. “John will also play a critical role in helping to advance our various late stage assets, including applying our technology to glycoproteins, and our preclinical drug candidates.” He added, “We thank Joe Tyler for his efforts in helping position the Company for our next stage of development.”

Momenta also announced the appointment of Michael Lawless as Senior Director, Investor Relations. Mr. Lawless joins Momenta from CTI Molecular Imaging, Inc. where he was Senior Director, Finance and Investor Relations. Prior to CTI, Mr. Lawless worked as an equity research analyst at MFS Investment Management. Mr. Lawless has an M.B.A. from the Tuck School of Business Administration at Dartmouth College.

About Momenta
Momenta Pharmaceuticals, Inc. is a biotechnology company specializing in the sequencing and engineering 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 technology-enabled generic products. The Company’s most advanced product candidate is M-Enoxaparin, a technology-enabled generic version of Lovenox®. Based on its understanding of complex sugars, Momenta has created a diversified pipeline of novel discovery and development candidates. Momenta was founded in 2001 and is headquartered in Cambridge, MA.

To receive additional information about Momenta, please visit our website at www.momentapharma.com, which does not form a part of this press release.

Forward Looking Statements
Statements in this press release regarding Momenta Pharmaceuticals Inc.’s future expectations, beliefs, goals, plans or prospects constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Momenta’s actual results could differ materially from those stated or implied in forward-looking statements due to a number of factors, including those factors contained in Momenta’s final prospectus dated June 21, 2004 filed with the Securities and Exchange Commission in connection with Momenta’s initial public offering under the section “Risk Factors,” as well as other documents that may be filed by Momenta from time to time with the Securities and Exchange Commission. Forward-looking statements include statements regarding Momenta’s expectations, beliefs, intentions or strategies regarding the future and can be identified by forward-looking words such as “anticipate”, “believe”, “could”, “estimate”, “expect”, “intend”, “may”, “should”, “will”, and “would” or similar words. Momenta assumes no obligations to update the information included in this press release.

Our logo, trademarks, and service marks are the property of Momenta Pharmaceuticals, Inc. All other trade names, trademarks, or service marks are property of their respective owners and are not the property of Momenta Pharmaceuticals, Inc.

Contact: Momenta Pharmaceuticals, Inc:
Michael Lawless, Senior Director, Investor Relations, 617-395-5189
Valerie Threlfall, Senior Manager, Strategic Product Development, 617-395-5116

Press Contact
press@momentapharma.com

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