Alnylam Receives Issued U.S. Patent Broadly Covering RNAi Therapeutics; Tuschl II Patent Covers Methods of Making Small Interfering RNAs to Silence Any and All Disease Targets.

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today that a key fundamental patent from its exclusively held "Tuschl II" patent series was issued by the United States Patent and Trademark Office (USPTO). The U.S. patent (U.S. Patent No. 7,056,704) broadly covers methods of making small interfering RNAs (siRNAs), the molecules that mediate RNAi. The issued patent is exclusively licensed to Alnylam for RNAi therapeutics on a worldwide basis through an agreement with Garching Innovation GmbH, the licensing agent for the Max Planck Society.

The new patent stems from groundbreaking research published in 2001 in the journal Nature by Thomas Tuschl, Ph.D., a founder of Alnylam. This work provided the first peer-reviewed published evidence that RNAi is mediated by small double-stranded RNAs with defined structural features and that synthetic siRNAs, with or without chemical modification, can be used to achieve RNAi in mammalian cells.

"We believe that the issuance of the Tuschl II patent represents a defining event in Alnylam's consolidation of intellectual property that is fundamental to the development and commercialization of RNAi therapeutics," said John Maraganore, Ph.D., President and Chief Executive Officer of Alnylam Pharmaceuticals. "Importantly, the new patent describes the methods for making siRNAs toward any disease target in a mammalian cell, thereby providing significant scope for RNAi therapeutics. As such, the new Tuschl II patent, where we have exclusive, worldwide therapeutic rights, solidifies our leadership position in the field of RNAi and bolsters our ability to build value from the advancement of RNAi therapeutics as a potential new class of drugs."

"We expect that this new patent, together with other Alnylam-held intellectual property assets, will strengthen our continued efforts to create value through partnerships and license agreements with major pharmaceutical companies, biotechnology companies, and research product suppliers," continued Dr. Maraganore. "Indeed, the strength of our patent estate supports a track record of business execution with over 20 current partners and licensees that have provided in excess of $100 million in funding to date, and a source of committed and sustainable funding for the future."

The claims for U.S. Patent No. 7,056,704 cover the preparation of 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 of a length of 19-25 nucleotides; and,

--One or more 3'-overhangs at the ends of the double-stranded molecule.

The claims cover such siRNAs for mediating cleavage of a messenger RNA, or mRNA, in mammalian cells, and therefore cover siRNAs with the above mentioned structural elements that are directed toward any and all target genes expressed in mammalian cells.

"We are gratified that the USPTO has acknowledged the pioneering contributions of Professor Tuschl's work which was performed at the Max Planck Institute and disclosed in the Tuschl II patent series," said Robert Millman, Chief Intellectual Property Counsel of Alnylam Pharmaceuticals. "Virtually all patent offices around the world have recognized the pioneering nature of the Tuschl II series of patents, and we are optimistic that similar claims will issue in other countries in which the Tuschl II applications are pending."

In addition to the newly issued Tuschl II patent, Alnylam's intellectual property estate includes certain "fundamental" patents and patent applications that claim the broad structural and functional properties of synthetic RNAi therapeutic products. These include the recently allowed claims of a separate Tuschl II series patent application 10/832,248, and other pending applications from the same Tuschl II series. They also include the Kreutzer-Limmer I and II patents, acquired through the Ribopharma merger: EP Patent No. 1144623, covering methods, medicaments and uses of siRNAs with up to 25 nucleotides complementary to a target gene; EP Patent No. 1214945, covering compositions, methods, and uses of siRNAs with a length between 15 and 49 nucleotides; and EP Patent No. 1352061, covering therapeutic compositions, methods, and uses of siRNA and derivatives directed toward over 125 disease targets. Additional fundamental patents and patent applications licensed to Alnylam on an exclusive or non-exclusive basis include those of Crooke (U.S. Patent Nos. 5,898,031 and 6,107,094), Fire and Mello (U.S. Patent No. 6,506,559), Glover et al. (EP Patent No. 1230375), and Tuschl et al. (Tuschl I, patent pending), among others. In addition, Alnylam alone has a worldwide license for RNAi therapeutics from Isis Pharmaceuticals, Inc., for more than 150 issued patents pertaining to the chemical modification of oligonucleotides used to introduce "drug-like" properties in siRNAs.

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. One method to activate RNAi is with 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.

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 achievement. For more information, visit www.alnylam.com.

Alnylam Forward-Looking Statements

Various statements in this release concerning our future expectations, plans and prospects, including our views with respect to the timing and the future issuance of patents and the importance and scope of our intellectual property rights, 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 products; the successful development of our product candidates, 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 quarterly report on Form 10-Q 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.