RNAI Sirna Therapeutics

Long-awaited ruling on Kreutzer-Limmer patent validates objections filed by Sirna Therapeutics, sanofi-aventis, Atugen, and others SAN FRANCISCO, June 23 /PRNewswire-FirstCall/ -- Sirna Therapeutics, Inc. (NASDAQ:RNAI), a leading RNAi-based therapeutics company, announced today that its objections to the Kreutzer-Limmer patent in Europe were accepted by the European Patent Office, resulting in both a significant narrowing of the patent claims and substantial limitations on the commercial utility of that patent. "We contended from the very beginning that the Kreutzer-Limmer patent would not stand up to scientific and legal scrutiny and that its true commercial and scientific value in the field of RNA medicines has been miscast and misunderstood," stated Howard W. Robin, President and Chief Executive Officer of Sirna Therapeutics. "We will continue to oppose unsubstantiated patent claims while growing our own intellectual property estate to seek to ensure that we have the freedom to advance both our own and our partners' RNAi-based therapies through the clinic and into the market." European patent No: EP1144623B1 (the Kreutzer-Limmer patent), which was opposed by Sirna, AstraZeneca PLC, Atugen (SR Pharma PLC), Janssen Pharmaceutica N.V., and sanofi-aventis, was significantly narrowed and now only covers methods of making and using double stranded RNA with lengths and structures of limited usefulness as RNAi-based therapeutics. "The claims of the Kreutzer-Limmer patent as granted are now limited to chemical structures, that in our experience, are obsolete and essentially ineffective as viable RNAi-based therapeutics," stated Bharat Chowrira, Ph.D., J.D. Chief Patent Counsel of Sirna Therapeutics. "We believe, therefore, that this patent has no impact on our current or future programs, and perhaps more importantly, that it does not provide any meaningful intellectual property protection in the field of RNAi-based therapeutics." Sirna believes that its issued and pending patents in siRNA design, chemistry, synthesis, delivery and manufacturing together with its target patents and microRNA patents, give the company a dominant intellectual property portfolio in the field of RNAi-based therapeutics. About RNA interference RNA interference (RNAi) is a natural, selective process for turning off genes. RNAi is triggered by short interfering RNA (siRNA) molecules that engage a group of cellular proteins, known as RISC (RNA induced silencing complex). The RISC guides the siRNA to its target messenger RNA (mRNA, the messenger between DNA and proteins) by complementary base pairing for the targeted break-up of the mRNA, thus halting protein expression or viral replication. The RISC-siRNA-complex binds and cleaves multiple mRNA molecules in a catalytic fashion. About Sirna Therapeutics Sirna Therapeutics is a clinical-stage biotechnology company developing RNAi-based therapies for serious diseases and conditions, including age-related macular degeneration (AMD), hepatitis B and C, dermatology, asthma, Huntington's disease, diabetes and oncology. Sirna Therapeutics completed its Phase 1 clinical trial for Sirna-027 in AMD in 2005 and with its strategic partner, Allergan, Inc., expects to move Sirna-027 into Phase 2 clinical trials in 2006. Sirna has selected a clinical compound for hepatitis C virus, Sirna-034, which the Company plans to bring into Phase 1 clinical trials by the end of 2006. Sirna has established an exclusive multi-year strategic alliance with GlaxoSmithKline for the development of siRNA compounds for the treatment of respiratory diseases. Sirna has a leading intellectual property portfolio in RNAi covering over 250 mammalian gene and viral targets and over 200 issued or pending patents covering other major aspects of RNAi technology, including microRNA technology. More information on Sirna Therapeutics is available on the Company's web site at http://www.sirna.com/. Safe Harbor Statement Statements in this press release which are not strictly historical are "forward-looking" statements which should be considered as subject to many risks and uncertainties. Patent applications may not result in issued patents, and issued patents may not be enforceable or could be invalidated. In addition, because our research and development and the surrounding legal environment can change, it is difficult to predict the effect that patents held by others, including the Kreutzer-Limmer patent, could potentially have on our programs. Other risks and uncertainties include, among others, Sirna's early stage of development and short operating history, Sirna's history and expectation of losses and need to raise capital, Sirna's need to obtain clinical validation and regulatory approval for Sirna-027, Sirna-034 and Sirna's other product candidates, any of which could have negative results, Sirna's need to engage collaborators, Sirna's need to obtain and protect intellectual property, and the risk of third-party patent infringement claims. These and additional risk factors are identified in Sirna's Securities and Exchange Commission filings, including its Forms 10-K and 10-Q and in other SEC filings. Sirna undertakes no obligation to revise or update any forward- looking statements in order to reflect events or circumstances that may arise after the date of this release. Contacts: Greg Weaver, SVP & Chief Financial Officer, Sirna Therapeutics, Inc., 415-512-7200 Alan Zachary, McKinney/Chicago, 312-944-6784 x 316 DATASOURCE: Sirna Therapeutics, Inc. CONTACT: Greg Weaver, SVP & Chief Financial Officer of Sirna Therapeutics, Inc., +1-415-512-7200; or Alan Zachary of McKinney-Chicago, +1-312-944-6784 x 316, for Sirna Therapeutics, Inc. Web site: http://www.sirna.com/

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