Alnylam Forms New Agreement with Tekmira Related to the Planned Tekmira-Protiva Business Combination

Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that it has formed a new agreement with Tekmira Pharmaceuticals Corporation (TSX: TKM) related to Tekmira’s planned business combination with Protiva Biotherapeutics, Inc. Upon the effective date for the Tekmira-Protiva transaction, the new agreement will expand Alnylam’s access to key technology and intellectual property (IP) for the delivery of RNAi therapeutics with liposomal delivery technologies. In addition, Alnylam has agreed to make a $5 million equity investment in Tekmira upon completion of the planned Tekmira-Protiva transaction. "We have long valued the technologies and know-how of both Tekmira and Protiva and are pleased that this key technology and IP can now reside in one entity. For quite some time, this has been the right answer for the scientific and clinical advancement of RNAi therapeutics,” said Barry Greene, President and Chief Operating Officer of Alnylam. "Our expanded relationship with the new Tekmira significantly broadens our access to key technologies and IP related to systemic delivery of RNAi therapeutics.” "The business combination between Tekmira and Protiva provides Alnylam with a stronger partner in the delivery of RNAi therapeutics and we will continue to build on the successful relationship we have developed with Alnylam since 2006,” said Timothy M. Ruane, President and Chief Executive Officer of Tekmira. "The Alnylam investment is a strong endorsement of the new company’s undivided and focused commitment to the delivery of RNAi therapeutics and we look forward to working together with Alnylam to advance products into clinical development,” added Dr. Mark J. Murray, Chairman, President and Chief Executive Officer of Protiva, and President and Chief Executive Officer of Tekmira following completion of the business combination. As part of the agreement, Alnylam will make an equity investment of $5.0 million in Tekmira at a price of $2.40 per share upon the closing. This investment is representative of Alnylam’s continued commitment to pursuing novel delivery strategies for RNAi therapeutics. As a result of the new agreement, Alnylam is no longer providing a $5.0 million capital equipment loan to Tekmira. Alnylam maintains its exclusive rights to the Semple (U.S. Patent No. 6,858,225) and Wheeler (U.S. Patent Nos. 5,976,567 and 6,815,432) patents which the company believes are critical for cationic liposomal delivery. Alnylam will also have rights to IP controlled by Protiva prior to the combination and to new IP generated by the combined entity. In addition, Alnylam is granting to the new company InterfeRx™ licenses to discover, develop, and commercialize RNAi therapeutics towards seven gene targets, a number that includes three previously announced InterfeRx licenses granted to Tekmira as part of its January 2007 agreement. The targets covered by these InterfeRx license grants are subject to Alnylam’s consent and any required consent from third parties. In return for these licenses, Alnylam may be eligible to receive milestone fees and royalties. Alnylam created the InterfeRx licensing program to grant licenses under its intellectual property to biotechnology and pharmaceutical companies wishing to pursue RNAi therapeutics against specific targets outside Alnylam’s core strategic interests. Alnylam has retained the option to co-develop and co-commercialize the new company’s PLK1 SNALP program for the treatment of certain cancers, which is one of the seven gene targets for which the new company has received an InterfeRx license. PLK1 SNALP targets the polo-like kinase 1 gene which has been shown to be involved in the growth of certain types of solid tumors and has been shown in pre-clinical studies to selectively kill cancer cells, while sparing normal healthy cells in the same tissue. Alnylam has the right to exercise its option for this program up until the commencement of Phase II clinical trials. Alnylam is developing a systemically delivered RNAi therapeutic, ALN-VSP, for the treatment of liver cancers and potentially other solid tumors. ALN-VSP comprises two siRNAs in a liposomal formulation. These two siRNAs target two separate genes involved in the growth and development of tumors: kinesin spindle protein, or KSP, and vascular endothelial growth factor, or VEGF. Alnylam recently presented data from its ALN-VSP program which were generated using Protiva’s stable nucleic acid-lipid particles, or SNALP, technology. These data were presented at Alnylam’s R&D Day held March 6, 2008 and at the "RNAi, MicroRNA, and Non-Coding RNA” Keystone Symposium held March 25-30, 2008 in Whistler, British Columbia. Alnylam also has rights to use Protiva SNALP formulation technology in the advancement of its other systemically delivered RNAi therapeutic programs, including ALN-PCS for the treatment of hypercholesterolemia. 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 www.alnylam.com. Alnylam Forward-Looking Statements Various statements in this release concerning Alnylam’s future expectations, plans and prospects, including statements regarding Alnylam’s expectations regarding the success of Protiva and Tekmira technology and the importance of Tekmira and Protiva intellectual property, 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 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.