Silence Therapeutics Issued Novel RNAi Patent Covering High-Value Cancer Target in United States

LONDON, May 26 /PRNewswire/ -- 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.

About Silence Therapeutics plc (www.silence-therapeutics.com)

Silence Therapeutics plc (AIM: SLN) is a leading global biotechnology company dedicated to the discovery, development and delivery of targeted, systemic RNA interference (RNAi) therapeutics for the treatment of serious diseases.  The company possesses multiple proprietary siRNA delivery technology platforms including AtuPLEX™, a system that enables the functional delivery of siRNA molecules to targeted diseased tissues and cells, while increasing their bioavailability and intracellular uptake.  A second, complementary delivery technology known as PolyTran™ uses a library of novel peptide-based biodegradable polycationic polymers for systemic siRNA administration.  Additionally, the company has a platform of novel short interfering RNA (siRNA) molecules, AtuRNAi, which provide a number of advantages over conventional siRNA molecules, including increased stability against nuclease degradation.  Silence's unique RNAi assets also include structural features for a next generation of RNAi molecules and additional proprietary siRNA sequences against more than 50 highly valued oncology and other disease targets.

The company's strong and diverse intellectual property portfolio includes exclusive licenses from the University of Massachusetts on three patent families associated with the Zamore "Design Rules," which cover broad structural features of siRNA design for more potent next generation siRNA sequences.

Silence Therapeutics is headquartered in London, UK, with research and development operations in Berlin and Palo Alto, CA.

Forward-Looking Statements

This press release includes forward-looking statements that are subject to risks, uncertainties and other factors. These risks and uncertainties could cause actual results to differ materially from those referred to in the forward-looking statements. All forward-looking statements are based on information currently available to Silence Therapeutics and Silence Therapeutics assumes no obligation to update any such forward-looking statements.

SOURCE Silence Therapeutics plc