Alnylam Granted Broad European Patent Covering Compositions, Methods and Uses for RNAi Therapeutics; New Grant For Kreutzer-Limmer Patent Covers siRNAs With a Length That is Critical For RNAi Therapeutics.

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that the European Patent Office has granted Alnylam a new patent (EP Patent No. 1214945) with broad claims covering short interfering RNAs (siRNAs), the molecules that mediate RNA interference (RNAi). The new patent significantly extends the claims of the original Kreutzer-Limmer patent, a pioneering patent in the RNAi field, which Alnylam acquired in the July 2003 merger with Ribopharma AG. The claims of the newly granted patent cover therapeutic compositions, methods, and uses of siRNAs and derivatives with a length between 15 and 49 nucleotides.

"The claims in the new Kreutzer-Limmer patent are very broad and cover both research and pharmaceutical commercial applications of synthetic RNAi products in the world's second largest market," said John Maraganore, Ph.D., President and Chief Executive Officer of Alnylam Pharmaceuticals. "While we are aware of the potential competitive responses associated with a newly-granted patent under European patent law, we believe that this patent, together with the previously granted patent in the same series, exemplifies Alnylam's IP leadership in the RNAi field and will significantly reinforce our strategy of building value today from our IP assets through licensing and major alliances."

The newly granted patent includes 84 claims on siRNAs with a length between 15 and 49 nucleotides, a length that is a critical feature for siRNAs to be used in mammalian systems for harnessing the endogenous RNAi mechanism. These new claims support and extend the claims of the original Kreutzer-Limmer patent (EP Patent No. 1144623) covering siRNAs having a sequence complementary to a target gene of up to 25 nucleotides in length. In addition to the Kreutzer-Limmer patent, Alnylam's intellectual property leadership is comprised of multiple fundamental issued patents and pending patent applications in the RNAi field, including those of Crooke (US Patent No.'s 5,898,031 and 6,107,094), Fire and Mello (US Patent No. 6,506,559), Glover et al. (AU Patent No. 774285), Tuschl et al. ("Tuschl 1" and "Tuschl 2"), and others. Alnylam has applied its intellectual property assets to create significant value today through alliances with Merck and Co., Inc. and Medtronic, Inc. and license agreements with multiple companies including Invitrogen Corporation, Benitec Ltd., GeneCare Research Institute Co., Ltd., Cenix Bioscience GmbH, and others.

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 and regulate such genes selectively through RNAi could provide a means to treat a wide range of human diseases. The discovery of RNAi has been heralded by many as a major breakthrough, and the journal Science named RNAi the top scientific achievement of 2002, as well as one of the top 10 scientific advances of 2003.

About Alnylam

Alnylam is a biopharmaceutical company seeking to develop and commercialize novel therapeutics based on RNA interference, or RNAi. Growing from its foundation as the world's first company focused on RNAi therapeutics, the company's leadership in the field of RNAi is supported by its preeminent founders and advisors and its strengths in fundamental patents, technology, and know-how that underlie the commercialization of RNAi therapeutics. Alnylam is developing a pipeline of RNAi products using Direct RNAi(TM) to treat ocular, central nervous system, and respiratory diseases and Systemic RNAi(TM) to treat a broad range of diseases, including oncology, metabolic, and autoimmune diseases. The company's global headquarters are in Cambridge, Massachusetts. For additional information, please visit www.alnylam.com.

Alnylam Forward Looking Statements

Various statements in this release concerning our future expectations, plans, prospects and future operating results 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; our ability to obtain additional funding to support our business activities; our dependence on third parties for development, manufacture, marketing, sales and distribution of our products; the successful development of products, 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; obtaining, maintaining and protecting intellectual property utilized by our products; and our short operating history; as well as those risks more fully discussed in the "Certain Factors That May Affect Future Results" section of our Annual Report on Form 10-K for 2004 filed 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. We do not assume any obligation to update any forward-looking statements.