Respiratory Syncytial Virus (RSV) Infection

Respiratory Syncytial Virus (RSV) Infection

- ALN-RSV01 Demonstrates Statistically Significant Anti-Viral Activity -
- Complete Results for GEMINI Phase II Study to be Presented at the International Symposium on Respiratory Viral Infections -

CAMBRIDGE, Mass. -- Jan. 23, 2008--Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, today reported positive data for the ALN-RSV01 Phase II experimental infection study, now called "GEMINI." The GEMINI study was designed to evaluate the safety and anti-viral activity of ALN-RSV01, an RNAi therapeutic for the treatment of RSV infection. Top-line results show that ALN-RSV01 was safe and well tolerated and demonstrated statistically significant anti-viral activity. The complete results of the study will be presented at the International Symposium on Respiratory Viral Infections meeting, to be held February 28 - March 2, 2008 in Singapore.

"We are very pleased with the results of GEMINI and look forward to advancing this program to its next stage of development, a Phase II study in naturally infected adult patients which we expect to initiate in the first half of this year," said John Maraganore, Ph.D., Chief Executive Officer of Alnylam. "These new data, to be presented at an upcoming scientific meeting, represent important progress for our RSV program and more generally for RNAi therapeutics, perhaps the biopharmaceutical industry's most promising new approach for innovative medicines."

The GEMINI study was a double-blind, placebo-controlled, randomized study of ALN-RSV01 or placebo in 88 adult subjects experimentally infected with a wild type clinical strain of RSV. The study was designed to measure the safety and anti-viral activity of ALN-RSV01, with efficacy measures including the incidence of viral infection and the effects of treatment on the degree of viral infection and resulting clinical symptoms. The study was performed using ALN-RSV01 or placebo administered intranasally for five consecutive days -- two days prior and three days after viral inoculation.

"ALN-RSV01 offers a potential new therapeutic approach for the treatment of RSV infection, a serious respiratory viral disease that leads to hospitalization in nearly 300,000 pediatric and adult patients annually in the U.S. alone," said John P. DeVincenzo, M.D., Associate Professor of Pediatrics and Infectious Diseases at the University of Tennessee Health Science Center and Principal Investigator for the GEMINI study. "I am very encouraged by these promising new human data which demonstrate anti-viral activity for an RNAi therapeutic in a major respiratory infectious disease, and support continued development of ALN-RSV01 for the treatment of RSV infection."

About RNA Interference (RNAi)

RNAi (RNA interference) is a revolution in biology, representing a breakthrough in understanding how genes are turned on and off in cells, and a completely new approach to drug discovery and development. Its discovery has been heralded as "a major scientific breakthrough that happens once every decade or so," and represents one of the most promising and rapidly advancing frontiers in biology and drug discovery today which was awarded the 2006 Nobel Prize for Physiology or Medicine. RNAi is a natural process of gene silencing that occurs in organisms ranging from plants to mammals. By harnessing the natural biological process of RNAi occurring in our cells, the creation of a major new class of medicines, known as RNAi therapeutics, is on the horizon. RNAi therapeutics target the cause of diseases by potently silencing specific messenger RNAs (mRNAs), thereby preventing disease-causing proteins from being made. RNAi therapeutics have the potential to treat disease and help patients in a fundamentally new way.

About Alnylam Pharmaceuticals

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 leading the translation of RNAi as a new class of innovative medicines with peer-reviewed research efforts published in the world's top scientific journals including Nature, Nature Medicine, and Cell. The company is leveraging these capabilities to build a broad pipeline of RNAi therapeutics; its most advanced program is in Phase II human clinical trials for the treatment of respiratory syncytial virus (RSV) infection. In addition, the company is developing RNAi therapeutics for the treatment of a wide range of disease areas, including hypercholesterolemia, liver cancers, and Huntington's disease. 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 Medtronic, Novartis, Biogen Idec, and Roche. To reflect its outlook for key scientific, clinical, and business initiatives, Alnylam has established "RNAi 2010" which includes the company's plan to significantly expand the scope of delivery solutions for RNAi therapeutics, have four or more programs in clinical development, and to form four or more new major business collaborations, all by the end of 2010. Alnylam is a joint owner of Regulus Therapeutics LLC, a joint venture focused on the discovery, development, and commercialization of microRNA therapeutics. Founded in 2002, Alnylam maintains headquarters in Cambridge, Massachusetts. For more information, visit

Alnylam Forward-Looking Statements

Various statements in this release concerning Alnylam's future expectations, plans and prospects, including, without limitation, statements concerning the timing and scope of clinical trials and studies, the timing and scope of availability of results of clinical trials and studies, the need for novel RSV therapeutics, and our views with respect to the potential for RNAi therapeutics, including ALN-RSV01, 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: Alnylam's approach to discover and develop novel drugs, which is unproven and may never lead to marketable products; obtaining, maintaining and protecting intellectual property; Alnylam's ability to enforce its patents against infringers and to defend its patent portfolio against challenges from third parties; Alnylam's ability to obtain additional funding to support its business activities; Alnylam's dependence on third parties for development, manufacture, marketing, sales and distribution of products; obtaining regulatory approval for products; competition from others using technology similar to Alnylam's and others developing products for similar uses; Alnylam's dependence on collaborators; and Alnylam's short operating history; as well as those risks more fully discussed in the "Risk Factors" section of its most recent quarterly report on Form 10-Q on file with the Securities and Exchange Commission. In addition, any forward-looking statements represent Alnylam's views only as of today and should not be relied upon as representing its views as of any subsequent date. Alnylam does not assume any obligation to update any forward-looking statements.