Alnylam Awarded $23 Million U.S. Government Contract to Develop RNAi Therapeutics for Biological Threats.

Funding over a Four-Year Term to Support Alnylam Biodefense(TM) Efforts

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health (NIH), has awarded the company a contract to advance the development of a broad spectrum RNAi anti-viral therapeutic against hemorrhagic fever virus, including the Ebola virus. The federal contract (No. HHSN266200600012C) will provide Alnylam with $23 million in funding over a four-year period to develop small interfering RNAs (siRNAs), the molecules that mediate RNAi, as anti-viral drugs targeting the Ebola virus. The Ebola virus can cause a severe, often fatal infection, and poses a potential biological safety risk and bioterrorism threat.

With this new contract, the company is establishing Alnylam Biodefense(TM), an initiative to build a robust platform for developing RNAi therapeutics targeting threats of bioterrorism. Funding for this program, as with Alnylam's pandemic flu program, represents an example of broad public health and federal interest in the potential of RNAi technology to treat and prevent disease from these, and other serious and life-threatening viruses. U.S. Government funding for development of RNAi therapeutics for Ebola virus extends Alnylam's anti-viral pipeline, including programs for treatment of respiratory syncytial virus with ALN-RSV01, currently in Phase I clinical trials; pandemic influenza with ALN-FLU01 in a partnership with Novartis; and, JC virus in a recently announced partnership with Biogen Idec.

"We are pleased to receive this contract to develop an anti-viral RNAi therapeutic for Ebola, enabling us to launch efforts on our Alnylam Biodefense platform. We view this project as an important opportunity to strengthen our nation's capabilities to counter serious biological security threats," said Barry Greene, Chief Operating Officer of Alnylam. "In terms of our overall business strategy, funding for Alnylam Biodefense efforts will strengthen our platform capabilities and its applications for discovery of RNAi therapeutics for traditional clinical indications. Moreover, we believe that successful advancement of our Alnylam Biodefense efforts could create the potential for nearer-term product opportunities as a result of possible accelerated paths to approval and revenues from government stockpiling contracts."

As part of a public sector-private sector partnership with its Ebola program, Alnylam is working with the United States Army Medical Research Institute of Infectious Diseases (USAMRIID), an organization which is uniquely experienced in the handling, safety, and security requirements of specialized biological agents. Alnylam will be producing drug candidates which will be sent to USAMRIID for in vitro and in vivo testing against the Ebola virus.

About RNA Interference (RNAi) RNA interference, or RNAi, is a naturally occurring mechanism within cells for selectively silencing and regulating specific genes. Since many diseases are caused by the inappropriate activity of specific genes, the ability to silence genes selectively through RNAi could provide a new way to treat a wide range of human diseases. RNAi is induced by small, double-stranded RNA molecules. One method to activate RNAi is with chemically synthesized small interfering RNAs, or siRNAs, which are double-stranded RNAs that are targeted to a specific disease-associated gene. The siRNA molecules are used by the natural RNAi machinery in cells to cause highly targeted gene silencing.

About USAMRIID USAMRIID, located at Fort Detrick, Maryland, is the lead medical research laboratory for the U.S. Biological Defense Research Program, and plays a key role in national defense and in infectious disease research. The Institute's mission is to conduct basic and applied research on biological threats resulting in medical solutions (such as vaccines, drugs and diagnostics) to protect the warfighter. USAMRIID is a subordinate laboratory of the U.S. Army Medical Research and Materiel Command. The information contained in this press release does not necessarily reflect the position or the policy of the Government and no official endorsement should be inferred.

About Alnylam Alnylam is a biopharmaceutical company developing novel therapeutics based on RNA interference, or RNAi. The company is applying its therapeutic expertise in RNAi to address significant medical needs, many of which cannot effectively be addressed with small molecules or antibodies, the current major classes of drugs. Alnylam is building a pipeline of RNAi therapeutics; its lead program is in Phase I human clinical trials for the treatment of respiratory syncytial virus (RSV) infection, which is the leading cause of hospitalization in infants in the U.S. The company's leadership position in fundamental patents, technology, and know-how relating to RNAi has enabled it to form major alliances with leading companies including Merck, Medtronic, Novartis, and Biogen Idec. The company, founded in 2002, maintains global headquarters in Cambridge, Massachusetts, and has an additional operating unit in Kulmbach, Germany. Alnylam is honored to be the "emerging/mid-cap" company recipient of the 2006 James D. Watson Helix Award, the biotechnology industry's award for outstanding achievement. For more information, visit www.alnylam.com.

Alnylam Forward-Looking Statements Various statements in this release concerning our future expectations, plans, and prospects, including our plans with respect to the discovery and development of an RNAi therapeutic for the Ebola virus, constitute forward-looking statements for the purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including risks related to: our approach to discover and develop novel drugs, which is unproven and may never lead to marketable products; obtaining, maintaining and protecting intellectual property utilized by our products; our ability to enforce our patents against infringers and to defend our patent portfolio against challenges from third parties; our ability to obtain additional funding to support our business activities; our dependence on third parties for development, manufacture, marketing, sales, and distribution of products; the successful development of our product candidates, all of which are in early stages of development; obtaining regulatory approval for products; competition from others using technology similar to ours and others developing products for similar uses; our dependence on collaborators; and our short operating history; as well as those risks more fully discussed in the "Risk Factors" section of our most recent report on Form 10-Q on file with the Securities and Exchange Commission. In addition, any forward-looking statements represent our views only as of today and should not be relied upon as representing our views as of any subsequent date. Alnylam does not assume any obligation to update any forward-looking statements.