News Release

CAMBRIDGE, Mass., Mar 31, 2010 (BUSINESS WIRE) --Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that the Japanese Patent Office has granted claims in a second patent application (JP Application Number 2006-317758) for the Tuschl II patent series, entitled "RNA Interference Mediating Small RNA Molecules." In May 2008, the Japanese Patent Office granted a related set of claims in the Tuschl II patent series (JP 4 095 895). The Tuschl II patent series provides broad exclusivity for small interfering RNAs (siRNAs), the molecules that mediate RNAi, in the world's top pharmaceutical markets, which include the U.S. (U.S. Patent Nos. 7,056,704 and 7,078,196), the European Union (EP 1407044), China (01820900.9), and Japan. The Tuschl II patent is exclusively licensed to Alnylam for RNAi therapeutics on a worldwide basis through an agreement with Max Planck Innovation GmbH, the licensing agent for the Max Planck Society.

"We are very pleased with the grant of this second Tuschl II patent application in Japan, which continues to further extend Alnylam's leadership on intellectual property for RNAi therapeutics," said Barry Greene, President and Chief Operating Officer of Alnylam. "The grant of this new patent broadens the scope of our fundamental patent and patent applications, including those related to the Crooke, Kreutzer-Limmer, Glover, Tuschl I, and Tuschl II patent series. Further, we continue to expect that several additional patents owned or licensed exclusively to Alnylam will be awarded, continuing to extend the breadth of our patent portfolio for all RNAi therapeutics."

"We are gratified that the Japanese Patent Office has decided to grant these new claims from Tuschl II," said Dr. Joern Erselius, Managing Director, Max Planck-Innovation GmbH. "The successful worldwide examination of the Tuschl II patent series highlights that this invention is seminal for RNAi, demonstrating the importance of the work performed by Professor Tuschl and other co-inventors at the Max Planck Institute."

The newly granted patent includes 38 claims broadly covering compositions, methods, uses, and systems for double-stranded RNAs having key structural elements that are widely recognized as important for the therapeutic activity of siRNAs, including:

• a double-stranded region formed from two RNA strands with a length of 19-23 nucleotides;
• at least one 3'-nucleotide overhang at the ends of the double-stranded molecule with a length of 1-3 nucleotides; and,
• one strand of the RNA molecule consisting of a sequence with less than full complementarity to a target mRNA.

Alnylam's IP position is comprised of fundamental, chemistry, delivery, and target patents and patent applications that the company believes are necessary for the development and commercialization of RNAi therapeutics. In aggregate, Alnylam owns or has in-licensed over 1,800 active patent cases, of which over 700 have issued or been granted worldwide, and over 300 have issued or been granted in the U.S., Europe, or Japan, the world's largest pharmaceutical markets.

About Alnylam Intellectual Property (IP)

Alnylam's IP estate includes issued, allowed, or granted fundamental patents in many of the world's major pharmaceutical markets that claim the broad structural and functional properties of RNAi therapeutic products. These include, but are not limited to:

• the Crooke Patents (U.S. Patent Nos. 5,898,031, 6,107,094, 7,432,249, 7,432,250, 7,629,321 and EP 0928290) issued in over 15 countries and licensed exclusively from Isis Pharmaceuticals, Inc. to Alnylam for RNAi therapeutics, which cover compositions, methods, and uses of modified oligonucleotides, including double stranded RNAs, to inactivate a target mRNA mediated by a double stranded RNase, such as "RISC," which is the cellular enzyme complex that mediates RNAi;
• the Glover '375 patent (EP 1230375), granted in July 2005, licensed exclusively to Alnylam from Cancer Research Technologies, Ltd., and currently under appeal, which covers therapeutic uses of double-stranded RNA expressed from endogenous templates or expression vectors to mediate RNA interference in mammalian cells;
• the Kreutzer-Limmer I '719 patent (EP 1550719), owned by Alnylam and where the company has received a notification of 'intent to grant', which covers siRNAs comprising 15-21 nucleotides in length stabilized by chemical linkages;
• the Kreutzer-Limmer I '235 patent (DE 10066235), granted in January 2008 and owned by Alnylam, which covers methods, uses, and medicaments of siRNAs, with a length between 15 and 49 nucleotides, expressed through a vector;
• the Kreutzer-Limmer I '945 patent (EP 1214945) granted in June 2005, currently under appeal, and owned by Alnylam, which covers compositions, methods, and uses of siRNAs with a length between 15 and 49 nucleotides;
• the Kreutzer-Limmer I '167 patent (DE 10080167) granted in October 2007, currently under appeal, and owned by Alnylam, which covers pharmaceutical compositions and uses of siRNAs with a length between 15 and 49 nucleotides that target certain broad categories of mammalian genes;
• the Kreutzer-Limmer II '061 patent (EP 1352061), granted in May 2006 and owned by Alnylam, which covers therapeutic compositions, methods, and uses of siRNA and derivatives directed toward approximately 130 disease targets;
• the Tuschl I patent (EP 1309726), granted in December 2009, and exclusively licensed to Alnylam from the Max Planck Society, the Massachusetts Institute of Technology, and Whitehead Institute, which covers methods for using certain dsRNAs for RNAi;
• the Tuschl II '704 patent (U.S. Patent No. 7,056,704) issued in June 2006 and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers methods of making siRNAs to silence any and all disease target genes;
• the Tuschl II '196 patent (U.S. Patent No. 7,078,196) issued in July 2006 and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers methods of making siRNAs with or without chemical modifications;
• the Tuschl II '044 patent (EP 1407044), granted in January 2008 and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers compositions, methods, and uses of siRNAs;
• the Tuschl II patent (JP 4 095 895) granted in May 2008 in Japan and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers compositions, methods, uses, and systems of siRNAs;
• the Tuschl II patent (JP Application No. 2006-317758) granted in March 2010 in Japan and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers compositions, methods, uses, and systems of siRNAs;
• the Tuschl II patent (Application No. 01820900.9) in China which received an intent to grant in April 2009 and exclusively licensed to Alnylam from the Max Planck Society, which broadly covers compositions, methods, uses, and systems for siRNAs;
• the Kay & McCaffrey patent (AU patent application no. 2002326410) granted in February 2009 in Australia and exclusively licensed to Alnylam from Stanford University, which broadly covers methods and composition for RNAi therapeutics including siRNAs and shRNAs; and,
• many divisional and continuing patent applications pending of the aforementioned issued or granted patents and additional patent applications pending, including patents and patent applications covering inventions by Crooke, Fire & Mello (U.S. Patent No. 6,506,559), Kreutzer & Limmer, Glover, Li & Kirby, Pachuk, Tuschl, Hannon, Giordano, and Kay & McCaffrey, amongst others.

In addition to fundamental patents, Alnylam is the exclusive licensee in the field of RNAi therapeutics for more than 175 issued chemistry patents owned or controlled by Isis Pharmaceuticals, Inc. broadly covering chemical modifications, including motifs and patterns of modifications of oligonucleotides, including RNAi therapeutics. These patents include:

• 2'-Ribose modifications of oligonucleotides (Cook, U.S. Patent Nos. 5,670,633; 6,005,087; 6,531,584; and 7,138,517);
• chemical conjugates of oligonucleotides (Manoharan, U.S. Patent No. 6,153,737); and,
• "overhang," "blunt-end," and nucleotide pairing design motifs (Woppmann et al., UK 2417727), which is owned by Alnylam.

In addition to fundamental and chemistry patents, Alnylam is also the exclusive licensee in the field of RNAi therapeutics for certain delivery patents, including those owned and controlled by Tekmira Pharmaceuticals Corporation, broadly covering delivery of oligonucleotides, including RNAi therapeutics, with liposomal formulations. These patents include:

• formulations of oligonucleotides, including siRNAs, in cationic liposomes (Wheeler, U.S. Patent Nos. 5,976,567 and 6,815,432; and Semple, U.S. Patent No. 6,858,225); and,
• chemically modified siRNAs with "drug-like" properties for in vivo delivery (Soutschek and Manoharan, U.S. patent application 10/916,185 /Allowed).

Alnylam is also contributing on a royalty-free/non-profit basis its technology and more than 1,500 issued or pending patents from its RNAi patent estate to the patent pool initiated by GlaxoSmithKline in 2009. The patent pool was formed to aid in the discovery and development of new medicines for the treatment of 16 neglected tropical diseases (NTD), as defined by the U.S. Food and Drug Administration, in the world's least developed countries. In January 2010, BIO Ventures for Global Health (BVGH) was chosen as administrator of patent pool. In this role, BVGH will organize disease-specific meetings that identify the gaps in expertise and intellectual property that currently exist in product development for NTDs, and will help global health researchers work with industry to fill these gaps to create medicines for NTDs faster and more efficiently.

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. Small interfering RNAs (siRNAs), the molecules that mediate RNAi and comprise Alnylam's RNAi therapeutic platform, target the cause of diseases by potently silencing specific 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 liver cancers, TTR-mediated amyloidosis (ATTR), hypercholesterolemia, 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, Roche, Takeda, Kyowa Hakko Kirin, and Cubist. Alnylam and Isis are joint owners of Regulus Therapeutics Inc., a company focused on the discovery, development, and commercialization of microRNA-based therapeutics. Founded in 2002, Alnylam maintains headquarters in Cambridge, Massachusetts. For more information, please visit www.alnylam.com.

Alnylam Forward-Looking Statement

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 and to successfully prosecute and enforce its patents around the world, as well as those risks more fully discussed in the "Risk Factors" section of its most recent annual 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.

SOURCE: Alnylam Pharmaceuticals, Inc.

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