Novel Compound Designed Using Momenta’s Proprietary Technology

CAMBRIDGE, MA — July 31, 2006 — Momenta Pharmaceuticals, Inc. (Nasdaq: MNTA), a biotechnology company specializing in the characterization and engineering of complex drugs, announced today that it has submitted an electronic Investigational New Drug (IND) application to the U.S. Food and Drug Administration to begin a Phase I human clinical study of M118, the Company’s lead novel development candidate. M118 is an anticoagulant designed specifically to treat acute coronary syndromes (ACS).
Momenta developed M118 using its proprietary technology for the detailed analysis and design of complex sugar therapeutics. By isolating, characterizing and engineering the key sugar structures within heparin that contribute to anticoagulation, Momenta designed a proprietary compound that it believes could provide baseline anticoagulant therapy to treat ACS patients who require a coronary intervention, as well as those ACS patients who are medically managed, or do not require intervention in order to treat their coronary attack. M118 is designed to be a reversible and monitorable anticoagulant that has a pharmacokinetic profile similar to a low molecular weight heparin. Thus, M118 is designed to be a therapeutic option that can be used across a variety of ACS treatment paths.
“M118 has the potential to be a significant future advancement in the treatment and management of ACS,” said Alan Crane, CEO of Momenta. “We are very encouraged by our preclinical studies which show that M118 could be a potent agent that provides consistent, flexible and reversible anticoagulant therapy. We look forward to continuing to advance M118 into Phase I clinical trials in the coming months.”

“M118 illustrates the potential of our technology, particularly our ability to leverage analytics and engineering to create novel drug candidates,” continued Mr. Crane. “The filing of the M118 IND also demonstrates our technology’s capability to generate a large number of product opportunities as we add and advance both complex generic and novel products to our growing pipeline.”

Background on M118

M118 directly leverages Momenta’s technology for characterizing complex mixtures, correlating specific chemical structures to biological activity, and applying these structure-function relationships to design therapies with improved clinical properties. This “rational” engineering process has resulted in a product design that we believe combines in one molecule, the best attributes of existing anticoagulants.
A key unmet need in ACS is the lack of a flexible anticoagulant agent that can be used regardless of whether a patient requires coronary intervention or is treated medically with pharmacological agents. We believe M118 can directly overcome this challenge as it combines the advantageous properties of unfractionated heparin, a preferred agent in ACS because of its ability to be reversed and monitored, with the convenience and predictable pharmacokinetic properties of low molecular weight heparins.
Based on preclinical studies, M118 has been shown to be at least as effective in inhibiting clot formation as unfractionated heparin without causing increased bleeding complications. Moreover, preclinical studies found that M118’s anticoagulant activity was reversible by protamine sulfate, unlike currently marketed low molecular weight heparins or direct thrombin inhibitors. Finally, the preclinical studies also demonstrated that the level of anticoagulation provided by M118 can be readily monitored using standard point-of-care coagulation assays.
Background on Acute Coronary Syndromes
ACS is characteristically used to describe patients experiencing an acute myocardial infarction, or heart attack, as well as patients who present at hospitals with unstable angina, a transient blockage of a coronary artery. According to the National Hospital Discharge Survey, each year, there are more than 1.9 million occurrences of either unstable angina or myocardial infarction requiring medical treatment across the U.S. As part of the treatment of ACS, anticoagulant agents are routinely administered to prevent the accumulation and formation of blood clots which can lead to serious, life-threatening complications.

About Momenta
Momenta Pharmaceuticals is a biotechnology company specializing in the detailed characterization and engineering of complex sugars. Momenta is applying its technology to create technology-enabled generic versions of sugar-based and other complex drug products, develop improved versions of existing drugs, and discover novel drugs and new biological processes. The Company’s most advanced product candidate is M-Enoxaparin, a technology-enabled generic version of Lovenox®. In accordance with its collaboration with Sandoz, the generics business of Novartis AG, an ANDA was submitted to the FDA for M-Enoxaparin in August 2005. Momenta has multiple technology-enabled generic products in its pipeline. Momenta’s first novel drug candidate is M118. The Company is developing other novel drug candidates through its discovery effort focused on understanding sugar-based biological processes. Momenta was founded in 2001 based on technology initially developed at Massachusetts Institute of Technology and is headquartered in Cambridge, MA.

To receive additional information about Momenta, please visit the 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, intentions, goals, strategies, plans or prospects, including statements relating to the Company’s M118 program, including, the design, development, administration and application of such product candidate and the potential for the Company to demonstrate through preclinical and clinical studies that M118 is safe and effective, may 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 Quarterly Report on Form 10-Q for the quarter ended March 31, 2006 filed with the Securities and Exchange Commission 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.

Momenta Contacts:

Michael Lawless
Investor Relations
617-395-5189

Media Inquiries:

Barbara Yates
Yates and Associates
781-258-6153

Press Contact
press@momentapharma.com

Company Fact Sheet

Technology Fact Sheet

Regulatory Fact Sheet