Alnylam to Present Phase I Data for ALN-RSV01, an RNAi Therapeutic for the Treatment of RSV, at the 2006 Pediatric Academic Societies' Annual Meeting.

CAMBRIDGE, Mass. -- Results to be Reported from First Clinical Trials Evaluating an RNAi Therapeutic for Viral Infectious Disease 

Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that Alnylam and collaborators will present data from its Phase I trials with ALN-RSV01, an RNAi therapeutic for the treatment of respiratory syncytial virus (RSV) infection, at the 2006 Pediatric Academic Societies' (PAS) Annual Meeting being held in San Francisco April 29 - May 2 at the Moscone West Convention Center.

The Phase I trials, conducted in the U.S. and in Europe, were designed to assess the safety and pharmacology of ALN-RSV01 in healthy volunteers. Data to date from these trials will be presented on Sunday, April 30, 2006 at 4:15 p.m. PT during the State of the Art Plenary Session #3810 titled "RNA Interference, Technological Development of siRNAs and Potential Treatments for Childhood Diseases" to be held in Moscone West, Room 3016-3018.

In addition, the results will be discussed on Monday, May 1, 2006 at the PAS/PIDS platform session #4130 titled "Infectious Diseases II" which begins at 8:00 a.m. PT in the Moscone West, Room 3001.

About Respiratory Syncytial Virus (RSV)

RSV is a highly contagious virus that causes infections in both the upper and lower respiratory tract. RSV infects nearly every child at least once by the age of two years and is a major cause of hospitalization due to respiratory infection in children and people with compromised immune systems, and others. RSV infection typically results in cold-like symptoms but can lead to more serious respiratory illness such as croup, pneumonia, bronchiolitis, and in extreme cases, death. RSV infection in the pediatric population accounts for more than 100,000 hospitalizations per year in the U.S. The development of childhood asthma is also known to occur after childhood RSV infection. As a result, there is a significant need for novel therapeutics to treat patients who become infected with RSV.

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. RNAi is activated by 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. Alnylam's initial drug development programs are focused on Direct RNAi(TM) therapeutics which are siRNAs administered directly to diseased parts of the body. In parallel, the company is developing Systemic RNAi(TM) therapeutics that travel through the bloodstream to reach diseased parts of the body.

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, and Novartis. 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 corporate achievement. For more information, please visit www.alnylam.com.

Alnylam Forward-Looking Statements

Various statements in this release concerning our future expectations, plans, and prospects, 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 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; 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-K 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.