Silence Therapeutics Adds New Patent to Industry Leading Structural Modification Intellectual Property Portfolio

LONDON, Aug. 11 /PRNewswire/ -- Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company") announces the issuance of United States patent 7,772,203, titled "Methods and Compositions for Controlling Efficacy of RNA Silencing," by the United States Patent and Trademark Office (USPTO). The issued patent generally claims methods of enhancing RNA silencing with a double stranded RNA interference (RNAi) agent. The patent's RNA silencing method claims include coverage for the administering of a pharmaceutical composition containing short interfering RNA (siRNA), micro RNA (miRNA), pre-miRNA or short hairpin (shRNA) molecules. Silence believes the proprietary structural modification techniques covered in this patent will play a key role in increasing the potential therapeutic efficacy of RNAi therapeutics.

"We are convinced that our growing portfolio of issued patents will have significant value for other companies in the RNAi space, particularly the 'Zamore Design Rule' patents. We believe that the Zamore technology is fundamental for the development and commercialization of RNAi therapeutics with enhanced efficacy and we expect there will be increased interest for licensing deals from a number of companies working in this area," stated Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics. "Importantly, our efforts to continue to build value around the Zamore patent estate are not limited to the U.S. We expect to add additional protection to the Zamore technology with the issuance of a European patent directed to the 'Zamore Design Rules.'"

The issued patent is the fourth patent to issue from the three "Zamore Design Rule" patent families for which Silence owns exclusive licenses in the human healthcare field from the University of Massachusetts Medical School. These patent families disclose various efficacy-enhancing methods and structural elements for RNAi therapeutics, informally known as the "Zamore Design Rules" and are based on the seminal research of Phillip D. Zamore, Ph.D. at the University of Massachusetts Medical School. Dr. Zamore is a Howard Hughes Medical Institute Investigator, the Gretchen Stone Cook Chair of Biomedical Sciences, and Professor of Biochemistry & Molecular Pharmacology at University of Massachusetts Medical School. He also serves as co-director of the RNA Therapeutics Institute at the University of Massachusetts Medical School. Silence expects additional patent issuances related to the Zamore portfolio.

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 a number of additional valuable 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