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Sirna granted patent covering RNAi-mediated inhibition of gene expression

Sirna Therapeutics, Inc. (San Francisco, CA) the leading clinical-stage RNAi therapeutics company, announced that the United Kingdom Patent Office has issued a broad patent covering RNA interference (RNAi) mediated inhibition of gene expression using short-interfering ribonucleic acids (siRNA). The patent claims, which are not limited to a specific siRNA sequence or structure, broadly cover any siRNA molecule which targets conserved sequences within a virus or a gene. This patent is important because it enables increased therapeutic potential of RNAi technology. First, it allows an siRNA therapeutic to target the conserved region of a virus thus targeting multiple strains of the virus as well as preventing escape mutants. Second, the patent allows an siRNA therapeutic to target more than one gene in a biological pathway to increase therapeutic effect of an siRNA.

Together, these claims provide important coverage for the development of siRNA therapeutics to treat RNA viruses such as Hepatitis C virus (HCV), human immunodeficiency virus (HIV), respiratory syncytial virus (RSV), influenza virus, bird flu virus, and severe acute respiratory syndrome (SARS) as well as other viral or gene targets where targeting a conserved region would provide therapeutic benefit.

"To effectively develop RNAi-based therapeutics against certain RNA viruses, it is critical to target conserved sequences of the viral RNA," stated Barry Polisky, PhD, Senior Vice President and Chief Scientific Officer at Sirna. "These viruses mutate at a high frequency and can become resistant to single agent therapies. However, not all regions of the virus mutate at the same rate. The conserved viral regions are those that mutate at a lower rate thus targeting this region decreases the likelihood that the virus can mutate to escape the action of a therapeutic. By targeting conserved sequences of an RNA virus, such as HCV or RSV, we can have a potent therapeutic effect on a wide range of viral variants."

The patent also addresses the potential for siRNA therapeutics targeting one or more genes in a biological pathway. Targeting conserved sequences which are shared between two or more genes offers a unique therapeutic approach to diseases such as age-related macular degeneration (AMD). For example, Sirna is investigating the regulation of angiogenesis in AMD by targeting multiple VEGF receptors -- VEGFR1 and VEGFR2 -- using a single siRNA molecule. Instead of designing a separate therapeutic modality against each of these two receptors, it is possible to design a single siRNA to reduce the expression of both VEGF receptors by targeting common sequences shared by the two.

Issued on September 21, 2005, the patent entitled "RNA Interference Mediated Inhibition of Gene Expression Using Short Interfering Nucleic Acid (siNA)" (GB 2396616) further strengthens Sirna's portfolio and the company's leadership position in developing siRNA-based therapeutics. The patent covers short interfering RNA (siRNA) molecules that target more than one gene using conserved shared target sequences. These siRNAs can be used to target multiple genes having conserved sequences. As such, siRNAs can be used to inhibit the expression of multiple genes involved in a disease process for increased therapeutic effect.

The claims in this patent are not limited to any specific gene target sequence or structure and are broadly applicable to inhibiting gene targets sharing conserved or homologous sequences. To date, Sirna has filed over 125 patents in multiple countries around the world on mammalian genes and viruses responsible for neurological, cardiovascular, infectious, metabolic, ocular, oncology and respiratory human diseases.

The issuance of the patent follows three target patents and one broad-spectrum siRNA patent secured earlier this year by Sirna in the United Kingdom. The UK patents, which address the Hepatitis C Virus, Vascular Endothelial Growth Factor and Vascular Endothelial Growth Factor Receptor-1, broadly cover siRNAs against these targets. The company was also issued a broad patent covering the chemical and structural modifications of siRNAs necessary for the creation of viable siRNA-based therapeutics. In the coming months Sirna expects that patents with similar scope and breadth will be issued in other major countries.

Sirna has both in-licensed patents with third parties and filed patents on technology discovered inside the company. Sirna's internal scientific work has resulted in 44 issued patents and over 250 pending patents. These patents include: 10 pending patents for siRNAs & micro-RNAs, one granted and 10 pending patents for "No-Ribo" siNAs, 5 pending patents for Multifunctional siRNAs, 23 issued and over 70 filed patents for Oligonucleotide Chemistry and Delivery, 15 issued and 25 filed patents for Oligonucleotide Manufacturing, and three granted and over 100 patents pending for fully enabled siRNAs against specific gene targets. To ensure that Sirna can bring RNAi-based therapeutics to the market, the company has pursued an in-licensing strategy to provide itself total freedom to do so in all disease areas. Sirna's in-licensing strategy has encompassed several key patents, including the Tuschl Patent from the University of Massachusetts which covers the seminal RNA interference technology covering siRNA for uses relating to human and veterinary therapeutic, prophylactic, diagnostic and healthcare applications, as well as, Carnegie Patent from the Carnegie Institution of Washington and UMASS. The Carnegie Patent is based on the pioneering work of Drs. Andrew Fire and Craig Mello in C. elegans governing genetic inhibition of genes by double-stranded RNA via RNAi.

Sirna has filed enabling patents for over 125 important mammalian disease targets including: alpha-synuclein (Parkinson'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), NOGO & NOGO Receptors (spinal cord injury), PTP-1B (diabetes, obesity), RSV (Respiratory Syncytial virus), and VEGF (angiogenesis, AMD, diabetic retinopathy, cancer, kidney disease).

Sirna 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 has presented interim Phase 1 clinical trial data for its most advanced compound, Sirna-027, a chemically optimized siRNA targeting the clinically validated vascular endothelial growth factor pathway to treat AMD. The results to date, demonstrate that Sirna-027 for AMD is safe and well tolerated. Visual acuity has stabilized in 100 percent of patients treated and clinically significant improvement, of three lines or greater on the ETDRS eye chart, has been observed in 25 percent of the patients tested. Sirna Therapeutics has collaborations with Eli Lilly and Company, Targeted Genetics, Archemix Corporation and Protiva Biotherapeutics. Sirna has a leading intellectual property portfolio in RNAi with 44 issued patents and over 250 pending applications worldwide.

Sirna Therapeutics, Inc.
+1-303-449-6500
www.sirna.com