Alnylam Initiates Phase I Clinical Study of ALN-VSP in Patients with Liver Cancer.

- ALN-VSP Represents Company's First Clinical Program with a Systemically Delivered RNAi Therapeutic -

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, today announced that it has initiated a Phase I human clinical trial of ALN-VSP to evaluate its safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced liver cancers, including hepatocellular carcinoma and other solid tumors with liver involvement. ALN-VSP is an RNAi therapeutic comprised of two small interfering RNAs (or siRNAs, the molecules that mediate RNAi) formulated in a lipid nanoparticle developed by Tekmira Pharmaceuticals Corporation and designed to target two genes critical in the growth and development of cancer cells: kinesin spindle protein, or KSP, required for tumor proliferation; and vascular endothelial growth factor, or VEGF, required for tumor growth. Pre-clinical data in mouse tumor model studies have demonstrated robust efficacy of ALN-VSP, including suppression of targeted genes, demonstration of an RNAi mechanism of action, tumor reduction, and extension of survival.

"We are excited to have initiated this Phase I trial as it represents an important milestone in Alnylam's efforts to advance RNAi therapeutics for the treatment of cancer. ALN-VSP is also Alnylam's first clinical program employing systemic delivery. Moreover, in this program we are targeting two well-validated genes critical for tumor proliferation and survival, an attractive strategy for the advancement of novel anti-cancer medicines," said Akshay Vaishnaw, M.D., Ph.D., Senior Vice President, Clinical Research at Alnylam. "More than one million liver cancer patients are diagnosed annually, and currently have limited therapeutic options and extremely poor survival rates. Over time and as we aim to demonstrate safety and efficacy for ALN-VSP, we hope that our efforts will provide patients a meaningful treatment option for their disease."

The Phase I trial, conducted in the U.S., is a multi-center, open label, dose escalation study designed to enroll approximately 55 patients with advanced solid tumors with liver involvement, who have failed to respond to or have progressed after standard treatment. The primary objective is to evaluate the safety, tolerability, and pharmacokinetics of intravenous ALN-VSP, including demonstration of the maximum tolerated dose. Other exploratory objectives include the assessment of tumor response through Response Evaluation Criteria for Solid Tumors (RECIST), a set of published guidelines that define when cancer patients' disease improves, stabilizes or progresses during treatment; change in tumor blood flow or vascular permeability measured by DCE-MRI; and, change in plasma biomarkers of angiogenesis. In addition, the analysis of pharmacodynamic effects of ALN-VSP on tumors will be measured in patients electing to proceed with voluntary pre- and post-treatment biopsies.

"RNAi therapeutics represent an encouraging new modality that has the potential to create a new benchmark in the treatment of cancer," said Charles Fuchs, M.D., M.P.H., Director for the Gastrointestinal Cancer Center at Dana-Farber Cancer Institute in Boston. "The ALN-VSP pre-clinical data have demonstrated the ability of an RNAi therapeutic to simultaneously target two key disease pathway genes implicated in primary and secondary liver cancer. The application of this RNAi-based approach may hold promise for other cancers as well."

About Liver Cancers

Cancer affecting the liver, known as either primary or secondary liver cancer, is associated with one of the poorest survival rates in oncology and represents a major unmet medical need affecting a large number of patients worldwide. Primary liver cancer, or hepatocellular carcinoma (HCC), is one of the most common cancers worldwide, with more than 600,000 people diagnosed each year. Secondary liver cancer, also known as metastatic liver cancer, is cancer that spreads to the liver from another part of the body due to other common cancers like colon, lung, or breast cancer. Worldwide, more than 500,000 people are diagnosed with secondary liver cancer each year.

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 and is partnered with Cubist and Kyowa Hakko. In addition, the company is developing RNAi therapeutics for the treatment of a wide range of disease areas, including liver cancers, hypercholesterolemia, Huntington's disease, and TTR amyloidosis. 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, Roche, Takeda, Kyowa Hakko, and Cubist. To reflect its outlook for key scientific, clinical, and business initiatives, Alnylam established "RNAi 2010" in January 2008 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 and Isis are joint owners of Regulus Therapeutics Inc., a company focused on the discovery, development, and commercialization of microRNA therapeutics. Founded in 2002, Alnylam maintains headquarters in Cambridge, Massachusetts. For more information, please visit www.alnylam.com.

Alnylam Forward-Looking Statements

Various statements in this release concerning Alnylam's 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 the company's ability to successfully research and develop products, such as ALN-VSP for the treatment of liver cancers, whether ALN-VSP will be safe or effective, and whether the Phase I clinical trial of ALN-VSP will yield positive results, as well as those risks more fully discussed in the "Risk Factors" section of its most recent quarterly report on Form 10-K 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.