Silence Therapeutics Issued New U.S. Patent Covering Fundamental RNA Interference Technology Currently in Several Clinical Trials

LONDON, Feb. 23, 2011 /PRNewswire/ -- Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company") announces the issuance of United States patent 7,893,245, titled "Interfering RNA Molecules," by the United States Patent and Trademark Office (USPTO).  The issued patent, which represents a continuation of previously issued U.S. Patent Number 7,452,987, covers chemically modified RNAi molecules with defined positional modifications including siRNA molecules that are blunt ended, as well as molecules with one or more overhangs.  Importantly, this latest patent broadens Silence's protection of these RNAi molecules to those with a chemically modified core length between 17 and 29 nucleotides including the company's portfolio of 25mer siRNA sequences.  This patented siRNA technology forms the foundation for AtuRNAi, Silence's propriety RNAi molecules. Various therapeutics incorporating Silence's AtuRNAi technology are currently being studied in five ongoing clinical trials conducted by Silence Therapeutics and other industry leaders.

"The extended protection for our RNAi technology, particularly the expanded coverage of our AtuRNAi platform, reinforces the meaningful advances Silence Therapeutics is making in the field of RNAi therapeutics.  The AtuRNAi technology is actively being advanced in multiple Phase II clinical studies by Quark and in our own Phase I trial and to date more than 200 patients have been dosed with AtuRNAi with no reported safety issues," stated Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics.  "The value of the AtuRNAi technology is an essential component of all of our internal and partnered programs.  With the extended protection for the AtuRNAi technology, which can be combined with our broadly protected structural modification technology (the 'Zamore Design Rules,'), we and our partners are able to invest in product development more aggressively."  

In related intellectual property news, Silence also announces the issuance of United States patent 7,893,243, titled "Composition and Methods of RNAi Therapeutics for Treatment of Cancer and Other Neovascularization Diseases," by the United States Patent and Trademark Office (USPTO).  This issued patent is broadly directed to a double stranded, double blunt ended siRNA sequence against the validated cancer target vascular endothelial growth factor (VEGF).  VEGF has been demonstrated to play an important role in the underlying causes of various cancers including abnormal angiogenesis and uncontrolled cell division.  The active pharmaceutical ingredient covered by the issued patent is a potent 25mer siRNA, with or without chemical modification, further demonstrating Silence's continued ability to secure meaningful intellectual property protection for its portfolio of 25mer sequences.  

Silence Therapeutics is executing a proactive strategy to continue to build and strengthen a global, 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 Japan, the United States and Europe during 2011.  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 reduced cytokine induction and decreased manufacturing costs.  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 lead internal drug candidate is Atu027, a liposomal AtuRNAi formulation in clinical development for systemic cancer indications and one of the most clinically advanced RNAi therapeutics in the area of oncology. Silence is currently conducting an open-label, single-centre, dose-escalation Phase I study with Atu027 in patients with advanced solid tumors involving single, as well as, repeated intravenous administration. The study is expected to be completed in the second half of 2011.

The Company's RNAi therapeutic platform has received key validation through multiple partnerships with pharmaceutical companies including AstraZeneca, Dainippon Sumitomo, Pfizer, and Quark. Silence is actively pursuing the establishment of additional partnerships.

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