Cambridge, MA, April 7, 2010 - Momenta Pharmaceuticals, Inc. (Nasdaq:MNTA), a biotechnology company specializing in the characterization and engineering of complex mixture drugs, today announced that the results of the M118 EMINENCE clinical trial have published in Circulation. The paper, entitled Evaluation of a New Heparin Agent in Percutaneous Coronary Intervention: Results of the Phase 2 Evaluation of M118 in Percutaneous Coronary Intervention (EMINENCE) Trial published in the April 5, 2010 "Publish Ahead of Print" online edition of the peer-reviewed journal Circulation: Journal of the American Heart Association (http://circ.ahajournals.org). Circulation is a preeminent publication with a readership of approximately 23,900 cardiologists, cardiovascular surgeons, electrophysiologists, internists, nurses and others interested in cardiovascular medicine. The Impact Factor of Circulation ranks first among journals in the cardiac & cardiovascular systems, hematology and peripheral vascular disease categories according to Journal Citation Reports(R) 2009, published by Thomson Scientific.

The key conclusion in the paper is that in this study M118 was well-tolerated and provided further evidence of feasibility for use as an anticoagulant in patients undergoing elective percutaneous coronary intervention. The authors further conclude the data provides the basis for further investigations of M118 in ischemic heart disease. The first author was Sunil V. Rao, M.D., co-principal investigator for the EMINENCE trial. Dr. Rao is an Assistant Professor of Medicine at the Duke University Medical Center and Director of the Cardiac Catheterization Laboratories at the Durham, NC Veterans Affairs Medical Center.

About EMINENCE

The EMINENCE trial was designed to evaluate the utility of M118 in patients with stable angina undergoing an elective PCI. Patients scheduled to undergo elective PCI, who met study eligibility criteria and for whom use of a glycoprotein IIb/IIIa inhibitor (GPI) was not intended, were randomly assigned to treatment with 1 of 3 doses (50 IU/kg, 75 IU/kg, or 100 IU/kg) of intravenous (IV) M118, or a standard unfractionated heparin (UFH) dose of 70 U/kg. Patients were also treated with at least 325 mg of aspirin and at least 300 mg of clopidogrel before PCI. The study was originally planned to include 150 patients in each arm, for a total of 600 patients. Enrollment into the lowest dose (50 IU/kg) was discontinued based on a recommendation by the Data Safety Monitoring Board, and consequently, approximately 500 patients in total were enrolled (44, 152, 156, patients enrolled in the 50 IU/kg, 75 IU/kg, and 100 IU/kg M118 arms respectively, and 151 patients in the 70 U/kg UFH arm).

The primary objective of EMINENCE was to evaluate the safety and feasibility of utilizing M118 as an anticoagulant in the target population of patients with stable CAD undergoing a PCI. A secondary objective was to evaluate the effect of M118 on procedural indices, including procedure success, abrupt closure, post-procedural Thrombosis in Myocardial Infarction (TIMI) flow grade, and catheter thrombus.

About M118

M118 is a novel anticoagulant that has been rationally engineered using Momenta's proprietary technology and analytical methods to provide anticoagulant therapy to patients with acute coronary syndrome (ACS). M118 was designed to interact at multiple points in the coagulation cascade by selectively binding to both anti-thrombin III and thrombin, two critical factors involved in the formation of clots. Preclinical and phase 1 studies have shown that M118 is a potent inhibitor of multiple factors in the blood that lead to clot formation, that its anticoagulant effects can be neutralized and that its activity can be monitored with standard point-of-care assays. An anticoagulant possessing these properties has the potential to satisfy a currently unmet medical need within the ACS patient population by capturing, in a single anticoagulant therapy, the positive attributes of both UFH (reversibility, monitorability and broad inhibition of the coagulation cascade) and low molecular weight heparins (adequate bioavailability and predictable pharmacokinetics to allow for convenient subcutaneous administration). M118 is designed to be an anticoagulant that could potentially be used in multiple settings, including initial medical management of ACS, angioplasty or coronary artery bypass surgery.

About Momenta

Momenta Pharmaceuticals is a biotechnology company, headquartered in Cambridge, MA, specializing in the detailed structural analysis of complex mixture drugs. Momenta is applying its technology to the development of generic versions of complex drug products, as well as to the discovery and development of novel drugs.

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 management's future expectations, beliefs, intentions, goals, strategies, plans or prospects relating to the future clinical development and feasibility or utility of M118 may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. In particular, statements in this press release regarding the results of the study data and its implications for future clinical trials, its implications regarding the feasibility and tolerability of M118, its potential to address unmet medical needs in multiple settings, including initial medical management of ACS, angioplasty or coronary artery bypass surgery, and the timing of any future trials are forward-looking statements that are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements and future development and commercialization will be dependent on securing a collaborative partner to finance future clinical trials. These statements are subject to the risk that further analyses of the study data may lead to different (including less favorable) interpretations of the data and/or may identify important implications of the study data that are not reflected in these statements. Clinical trial data are subject to differing interpretations, and regulatory agencies, medical and scientific experts and others may not share the Company's views of the study data, or its implications for the remaining clinical trials, and the future development and commercialization of M118. Such forward-looking statements involve known and unknown risks, uncertainties and other factors referred to in the Company's Quarterly Report on Form 10-K for the year ended December 31, 2009 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. As a result of such risks, uncertainties and factors, the Company's actual results may differ materially from any future results, performance or achievements discussed in or implied by the forward-looking statements contained herein. Momenta is providing the information in this press release as of this date and assumes no obligation to update the information included in this press release or revise any forward-looking statements, whether as a result of new information, future events or otherwise. Our logo, trade names and service marks are the property of Momenta Pharmaceuticals, Inc. Other trademarks or service marks appearing in this press release are the property of their respective owners and are not the property of Momenta Pharmaceuticals, Inc. or its subsidiaries.