RNAI Sirna Therapeutics

Patent Covers Any Chemically Modified siRNA Sequence Used Against the Targeted Gene and Sets Precedent for Sirna Therapeutics' Substantial Target Patent Portfolio in the U.S. SAN FRANCISCO, April 3 /PRNewswire-FirstCall/ -- Sirna Therapeutics, Inc. (NASDAQ:RNAI) a leading RNAi therapeutics company, announced today that the United States Patent and Trademark Office (USPTO) will issue Sirna U.S. Patent No. 7,022,828 on April 4, 2006. This is the first siRNA target patent issued in the United States and sets an important precedent for Sirna's entire target patent portfolio. The patent covers any chemically modified siRNA targeting I Kappa B kinase-gamma (IKK-gamma). Importantly, the claims of the patent are not limited to a specific siRNA sequence but cover any siRNA sequence used against the gene. In addition, the claims of this patent are not limited to a specific type of chemical modification or structure but cover any chemical modification that can be made to the siRNA. The patent covers blunt-ended siRNAs as well as those with one or more nucleotide overhangs. IKK-gamma is an activator of the NF-kappaB pathway (NF-kb), an important mediator in a host of diseases, such as asthma, arthritis, cancer, chronic inflammation, neurodegenerative diseases and heart disease. "We are gratified that the US Patent Office has issued the first broad siRNA target patent to Sirna," said Bharat Chowrira, Ph.D., Vice President, Legal Affairs and Chief Patent Counsel. "We have put tremendous effort into the creation of a fully enabling target patent portfolio. The formation of this target patent estate required the design, synthesis and evaluation of hundreds of siRNAs per target. The issuance of this patent provides further validation of our patent strategy and gives us confidence that our other patents covering over 250 targets will issue in a similar fashion." Sirna is the first company to file enabling patents for over 250 important mammalian disease targets including: alpha-synuclein (Parkinson's disease), BACE (Alzheimer's disease), HBV (hepatitis B), HCV (hepatitis C), HD (Huntington's disease), HIV (human immunodeficiency virus), HR (hairless gene), IL-4, IL-13, IL-4 Receptors, IL-13 Receptors (asthma, respiratory diseases), influenza virus (flu virus), NOGO & NOGO Receptors (spinal cord injury), p38 (inflammation), PTP-1B (diabetes, obesity), retinoblastoma 1 (hearing loss), RSV (reparatory syncytial virus) and VEGF (angiogenesis, AMD, diabetic retinopathy, cancer, kidney disease). "The issuance of this patent changes the IP landscape in the field of RNAi," stated Howard W. Robin, President and CEO of Sirna Therapeutics. "We believe that the combination of our target patents with our patents in siRNA design, chemistry, synthesis, and manufacturing gives Sirna Therapeutics a dominant intellectual property estate in the field of RNAi-based therapeutics." 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., will 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 175 issued or pending patents covering other major aspects of RNAi 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. For example, no single patent issuance predicts the likelihood of the rest of the pending Sirna patent estate issuing. Patent applications may not result in issued patents, and issued patents may not be enforceable or could be invalidated. In addition, most drug candidates do not become approved drugs. The development of Sirna-027 and Sirna-034 as well as Sirna's other programs are still at a relatively early stage, are subject to significant unknowns, and require significant funding. Other risks and uncertainties include 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 the company'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 the 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: Rebecca Galler Robison, Senior Director, Corporate Strategy, Sirna Therapeutics, Inc., 303-449-6500 Alan Zachary, McKinney Chicago, 312-944-6784 x316 DATASOURCE: Sirna Therapeutics, Inc. CONTACT: Rebecca Galler Robison, Senior Director, Corporate Strategy of Sirna Therapeutics, Inc., +1-303-449-6500; or Alan Zachary of McKinney Chicago, +1-312-944-6784, ext. 316, for Sirna Therapeutics, Inc. Web site: http://www.sirna.com/

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