Silence Therapeutics deepens diverse portfolio of RNAi intellectual property

Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company") announces the issuance of United States patent 7,723,316, titled Compositions and Methods of RNAi Therapeutics For Treatment of Cancer and Other Neovascularization Disease, by the United States Patent and Trademark Office (USPTO).  The issued patent, which deepens the Company's diverse portfolio of RNA interference (RNAi) intellectual property, is broadly directed to a double-stranded short interfering RNA (siRNA) sequence that targets vascular endothelial growth factor receptor 2 (VEGFR2).  VEGFR2 has been demonstrated to play an important role in the vasculogenic and angiogenic activities that contribute to the development and progression of tumors associated with a broad range of cancers.  The issued subject matter is not limited to the VEGFR2 compositions and also includes methods for reducing tumor growth.

"Silence is compiling a powerful portfolio of intellectual property with value tied to the unique scope of its issued claims and not simply a large number of owned patents.  Today's patent issuance fits perfectly with this strategy, as in our opinion, there are few disease targets with IP value comparable to VEGFR2," stated Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics.  "With its demonstrated connection to a broad host of cancers, among other disease areas, VEGFR2 is a target that we expect to help drive the expansion of Silence's RNAi therapeutics pipeline.  We view today's milestone as more than just another patent issuance; it is a development that significantly enhances the fundamental usefulness and functionality of our growing RNAi IP estate."

The specific composition of matter and method claims for the issued patent include but are not limited to:

• A double stranded, double blunt ended siRNA molecule against VEGFR2
• The siRNA associated with nucleic acid delivery vehicle optionally including PEG and/or targeting moiety
• The siRNA associated with one or more additional nucleic acid molecules
• The siRNA including at least one chemically modified nucleotide for stabilization
• Methods for reducing neovascularization

Silence Therapeutics is executing a proactive strategy to continue to build and strengthen a diverse and competitive intellectual property portfolio that provides the company and its partners with a strong proprietary position in the RNAi therapeutics space.  The company believes that it will continue to make significant progress in these efforts throughout 2010 as it expects a number of additional valuable RNAi patents to be issued in both the United States and Europe during the year.  This consistent and meaningful IP portfolio growth reinforces Silence's belief that the company can sustain its position as a partner-of-choice in RNAi therapeutics. At present, Silence's global patent portfolio contains issued patents and pending applications covering strategic areas of RNAi therapeutic development including multiple proprietary siRNA delivery technologies, potent siRNA sequences specific for high-value disease targets and key RNAi sequence and chemical modifications.