Alnylam to Webcast Conference Call Discussing First Quarter 2005 Financial Results.

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), the leading therapeutic RNA interference (RNAi) company, today announced that it will report financial results for the first quarter of 2005 on Wednesday, May 11, 2005, after the U.S. financial markets close.

Management will provide an update on the company, discuss first quarter results and discuss expectations for the future via conference call on Wednesday, May 11, 2005, at 5:00 pm EDT. To access the call, please dial 800-701-0682 (domestic) or 617-213-8030 (international) five minutes prior to the start time and provide the passcode 28432824. A replay of the call will be available from 6:30 pm EDT on May 11, 2005 until May 18, 2005. To access the replay, please dial 888-286-8010 (domestic) or 617-801-6888 (international), and provide the access code 51159485.

A live audio webcast of the call will also be available on the "Investors" section of the company's website, www.alnylam.com. An archived webcast will be available on the Alnylam website approximately two hours after the event and will be archived for 14 days.

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 oncologic, metabolic, and autoimmune diseases. The company's global headquarters are in Cambridge, Massachusetts. For additional information, please visit http://www.alnylam.com.

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 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.