Alnylam Added to NASDAQ Biotechnology Index.

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that it will be added to the NASDAQ Biotechnology Index (Nasdaq: NBI), effective with the U.S. market open on Monday, November 14, 2005.

"We are proud to be selected to join the NASDAQ Biotechnology Index," said John Maraganore, Ph.D., President and Chief Executive Officer of Alnylam Pharmaceuticals. "We believe our inclusion in this index reflects the increased awareness in the investment community of the potential of RNAi for therapeutic applications, and the importance of translating this breakthrough in biology into innovative medicines."

The NASDAQ Biotechnology Index was launched in 1993 and includes biotechnology and pharmaceutical companies listed on the NASDAQ National Market that meet minimum requirements for market value, average daily share volume and seasoning as a public company. The NASDAQ Biotechnology Index is ranked on a semi-annual basis in May and November and serves as the basis for the iShares NASDAQ Biotechnology Index Fund(SM) (AMEX:IBB). For more information about the NASDAQ Biotechnology Index, including eligibility criteria, visit www.nasdaq.com.

About Alnylam

Alnylam is a biopharmaceutical company developing novel therapeutics based on a breakthrough in biology known as RNA interference, or RNAi. The company, founded in 2002 by scientific pioneers in the field of RNAi, maintains a leadership position in fundamental patents, technology, and know-how relating to RNAi. Alnylam is applying its expertise in RNAi to address multiple therapeutic opportunities that cannot effectively be addressed with small molecules or antibodies, the two current major classes of drugs. The company's expertise in designing and optimizing RNAi therapeutics has enabled Alnylam to form major alliances with leading companies including Merck, Medtronic, and Novartis. The company's global headquarters are in Cambridge, Massachusetts, with an additional operating unit in Kulmbach, Germany. For more information, please visit www.alnylam.com.

Alnylam Forward-Looking Statements

Various statements in this release concerning our future expectations, plans and prospects, such as the company's inclusion in the NASDAQ Biotechnology Index, 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; our dependence on collaborators; 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 most recent quarterly 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. We do not assume any obligation to update any forward-looking statements.