Silence Therapeutics and Dainippon Sumitomo Expand RNAi Collaboration Just Eight Months After Initiation

Silence Therapeutics and Dainippon Sumitomo Expand RNAi Collaboration Just Eight Months After Initiation

Companies to Examine Delivery of RNAi Therapeutics to Additional Disease Targets

London, March 30, 2010 - Silence Therapeutics plc (AIM: SLN) today announced that the company and Dainippon Sumitomo Pharma Co., Ltd. have agreed to an expansion of their ongoing small interfering RNA (siRNA) delivery collaboration. Under this collaboration, which was originally entered into in August 2009, the companies are leveraging Silence's proprietary siRNA molecules and multiple lipid delivery and targeting technologies to demonstrate functional delivery of RNA interference (RNAi) therapeutics to specific disease targets in the body. Under the terms of the expansion, the companies will examine delivery to additional disease targets selected by Dainippon Sumitomo. The financial details of the original collaboration and this extension have not been disclosed.

"We believe that the decision to expand this collaboration less than eight months after its initiation and within three months of the merger between Silence and Intradigm provides clear evidence that both Silence and Dainippon Sumitomo are not only pleased with the progress already achieved through this partnership but also with its future potential," stated Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics. "While we at Silence have long believed in the significant value and potential of our proprietary technologies, it is gratifying to have a partner support our activities with a rapid expansion of this key collaboration."

Several of Silence Therapeutics' proprietary assets are being leveraged as part of this collaboration. These include the company's AtuRNAi, a novel siRNA molecule which is chemically modified to improve stability, reduce manufacturing costs and increase yields, all of which are key considerations in the emerging RNAi therapeutics space. Additionally, a number of the company's proprietary lipid delivery and targeting technologies for siRNAs, including AtuPLEX, are also being used as part of the collaborative research efforts.

The challenges of systemic siRNA delivery are well documented and include numerous biological barriers that limit RNAi therapeutics' ability to reach targets safely and effectively. Successfully solving this delivery problem and enabling siRNA molecules to safely and effectively reach various tissue sites within the body is essential to realizing the vast therapeutic potential of RNAi.

Silence Therapeutics has been advised by Summit Pharmaceuticals International which represents and markets the technologies, products and expertise of Silence Therapeutics in Japan.

About Silence Therapeutics plc (<>)

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 AtuPLEXTM, 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 PolyTranTM 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.

About Dainippon Sumitomo Pharma (<>)

Dainippon Sumitomo Pharma Co., Ltd. is a multi-billion dollar, top-ten listed pharmaceutical company in Japan with more than 7,000 employees worldwide. The company has a diverse portfolio of pharmaceutical, animal health and food and specialty products.?The company aims to produce innovative new drugs in the CNS area and the specialty area.

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.