Silence Therapeutics Issued New Patents Covering siRNA Sequences for RNA Interference Therapeutics

LONDON, Sept. 8 /PRNewswire/ -- Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company") announces the issuance of two new patents by the United States Patent and Trademark Office (USPTO) which are broadly directed to double-stranded short interfering RNA (siRNA) sequences against the validated cancer targets epidermal growth factor receptor related protein (EGFR-RP) and vascular endothelial growth factor receptor 1 (VEGFR1).  EGFR-RP and VEGFR1 have been demonstrated to play key roles in the underlying causes of various cancers including abnormal angiogenesis and uncontrolled cell division.  Similar to vascular endothelial growth factor receptor 2 (VEGFR2), VEGFR1 also is implicated in the development and progression of age-related macular degeneration (AMD) and other serious ocular diseases.  The EGFR-RP patent is broadly directed to methods of reducing EGFR-RP with a DNA or RNA molecule, including siRNA molecules.  The sequence covered by the VEGFR1 patent is a potent 25mer siRNA, demonstrating Silence's continued ability to secure meaningful intellectual property protection for its portfolio of 25mer sequences.

"The past several months have seen Silence add a number of high-value patents to its broad RNAi intellectual property portfolio.  Whereas many of these recent issuances have focused on the structural modification of RNAi therapeutics to improve efficacy, today's announcement underscores our efforts to concurrently build critical protection in the equally important areas of siRNA sequences and siRNA delivery," said Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics.  "We are particularly pleased that we have been able to secure an additional patent covering 25mer siRNA sequences, validating our belief that we can build a portfolio of proprietary 25mer siRNA sequences that will provide us an added level of protection in the RNAi space.  Furthermore, the breadth of the issued EGFR-RP patent provides critical value to Silence as it prevents any competitor from developing a siRNA or related therapeutic agent against the EGFR-RP target without our collaboration."

The issued siRNA sequence patents are as follows:

• United States patent 7,786,092, titled, "COMPOSITION AND METHODS OF RNAI THERAPEUTICS FOR TREATMENT OF CANCER AND OTHER NEOVASCULARIZATION DISEASES"
• United States patent 7,781,414 titled, "TARGETS FOR TUMOR GROWTH INHIBITION"

In addition to these two newly issued patents, Silence is also the exclusive licensee to another recently issued United States patent 7,772,201, titled "HIGHLY BRANCHED HK PEPTIDES AS EFFECTIVE CARRIERS OF SIRNA" granted to the University of Maryland, Baltimore.  This patent generally claims methods of transfecting cells with siRNA sequences.  The patent's method claims include coverage for the use of proprietary delivery complexes which include various transport polymers.  The successful delivery of siRNAs into cells remains a critical hurdle in the development of RNAi therapeutics and this new patent adds further versatility to Silence's broad range of siRNA delivery technologies.

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 as it expects additional RNAi patents to be issued in both the United States and Europe during 2010.  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.

Notes for editors

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 short interfering RNA (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 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 Medical School 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 activities in Berlin and operations in Redwood City, 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

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