Alnylam Announces Achievement of Key Milestone in Collaboration Agreement.

- Alnylam Advances RNAi Therapeutic Program into IND-Enabling Studies using Isis Intellectual Property -

CAMBRIDGE, Mass. -- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY) announced today the achievement of an important milestone in its strategic alliance with Isis Pharmaceuticals, Inc. (Nasdaq: ISIS). Alnylam has initiated IND-enabling studies with an RNAi therapeutic clinical candidate that utilizes technology and intellectual property licensed exclusively from Isis. Under the 2004 strategic alliance agreement, Alnylam obtained an exclusive license to Isis intellectual property for double-stranded oligonucleotide therapeutics that mediate RNAi, such as small interfering RNAs (siRNAs), in return for upfront cash payments, milestone payments, and royalties. The achievement of the development milestone demonstrates the importance of Isis technology for the advancement of RNAi therapeutics.

"The advancement of RNAi therapeutics into development stages has occurred at a rapid pace, in part due to the pioneering work of Isis across virtually all categories of oligonucleotide therapeutics," said Barry Greene, Chief Operating Officer of Alnylam. "Isis technology and intellectual property have proven to be critical components in developing siRNAs with needed 'drug-like' properties."

"Our exclusive strategic alliance with Alnylam highlights the significance of the Isis intellectual property estate and technology for the development and commercialization of oligonucleotide therapeutics, including those that function through an RNAi mechanism," said Lynne Parshall, Executive Vice President and Chief Financial Officer of Isis. "We view Alnylam as the leader in RNAi, and our agreement provides a unique opportunity for Isis to benefit in the continued progress in the entire field of RNAi therapeutic products as we focus our primary efforts on single-stranded antisense oligonucleotides."

About Isis Intellectual Property (IP) Licensed to Alnylam for RNAi Therapeutics

Isis controls more than 150 issued patents pertaining to chemical modification of oligonucleotides for therapeutic applications. These patents have been exclusively licensed to Alnylam for double-stranded RNAi therapeutics and include, but are not limited to:

* The Crooke Patents: U.S. 5,898,031 and U.S. 6,107,094 cover compositions, methods, and uses of modified oligonucleotides to inactivate a target mRNA mediated by a double-stranded RNase;

* Phosphorothioate and 2'-O-methyl modifications (Buhr, U.S. Patent No. 6,476,205); and,

* 2'-Ribose modifications (Cook, U.S. Patent Nos. 5,670,633; 6,005,087; 6,531,584; and 7,138,517).

About Alnylam Intellectual Property (IP)

Alnylam's IP estate includes issued or granted fundamental patents in many of the world's major pharmaceutical markets that claim the broad structural and functional properties of synthetic RNAi therapeutic products. As it applies to the U.S. and Europe, these include:

* The Tuschl II '704 patent (U.S. Patent No. 7,056,704) issued in June 2006 and exclusively licensed to Alnylam, which broadly covers methods of making siRNAs to silence any and all disease targets;

* The Tuschl II '196 patent (U.S. Patent No. 7,078,196) issued in July 2006 and exclusively licensed to Alnylam, which broadly covers methods of making siRNAs with or without chemical modifications;

* The Kreutzer-Limmer I '623 patent (EP 1144623) granted in August 2002, upheld in June 2006 and owned by Alnylam, covering methods, medicaments, and uses of siRNAs having, among other structural features, a length of 15-21 base pairs;

* The Kreutzer-Limmer I '945 patent (EP 1214945) granted in June 2005 and owned by Alnylam, covering compositions, methods, and uses of siRNAs with a length between 15 and 49 nucleotides;

* Additional fundamental patents and patent applications licensed to Alnylam on an exclusive or non-exclusive basis, including those of Fire and Mello (U.S. Patent No. 6,506,559) and Glover et al. (EP 1230375); and,

* Several divisional patent applications pending of the aforementioned issued or granted patents and additional patent applications pending including Tuschl I.

About RNA Interference (RNAi)

RNA interference (or RNAi) is a naturally occurring mechanism within cells for selectively silencing and regulating specific genes. The discovery of RNAi has been widely acknowledged as a major breakthrough in biology, and the technology was recognized for its potential broad impact in medicine with the award of the 2006 Nobel Prize for Physiology or Medicine. Since many diseases are caused by the inappropriate activity of specific genes, the ability to silence genes selectively through RNAi has accelerated the understanding of these genes and their related pathways. Additionally, 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 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 II human clinical trials for the treatment of respiratory syncytial virus (RSV) infection. RSV infects nearly every child at least once by the age of two and accounts for more than 125,000 hospitalizations annually in the U.S. pediatric population. RSV infection also poses a great risk to the elderly and other adults with compromised immune systems. 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, Novartis, and Biogen Idec. The company, founded in 2002, maintains global headquarters in Cambridge, Massachusetts, and has an additional operating unit in Kulmbach, Germany. 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 without limitation, statements concerning the importance and use of Isis intellectual property and technology in the development of RNAi therapeutics, 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 utilized by Alnylam's products; 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; the successful development of Alnylam's product candidates, all of which are in early stages of development; 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.