SLN.L Regulatory News (SLN)

30 Jul 2008 12:00

Silence Therapeutics to receive $1.9m Milestone Payment as Pfizer and Quark

commence Phase II Trial

London - 30 July 2008 - Silence Therapeutics plc (AIM: SLN), a leading European RNAi focused biotechnology company, today announces that its partner, Quark Pharmaceuticals Inc ("Quark") together with Pfizer, has commenced a Phase II clinical trial with RTP-801i-14 (PF-4523655), a small interfering RNA (siRNA) therapeutic product based on Silence's AtuRNAi technology. Its initiation triggers a $1.9 million milestone payment to Silence from Quark.

The study is designed to evaluate the effectiveness of the candidate in improving visual acuity compared to laser treatment in patients with diabetic macular oedema. The Phase II study is being funded and is conducted by Pfizer Inc in collaboration with Quark. Pfizer in-licensed RTP-801i-14 from Quark in a deal announced in 2006 for the treatment of age-related macular degeneration (AMD) and other ophthalmologic and non-ophthalmologic indications.

Diabetic macular oedema results in the macula swelling and surrounding blood vessels dilating to compensate for this. The dilated vessels are generally leaky, resulting in fluid build-up in the macula, which in turn causes the macula to swell and cease to function. Diabetic macular oedema is the most common cause of visual impairment in patients with non-proliferative retinopathy. Approximately 14% of people with diabetes have diabetic macular oedema with prevalence increasing to 29% for people with diabetes who use insulin for more than 20 years.

In December 2004 Quark and Silence Therapeutics AG signed a Collaboration Agreement on the development of siRNA molecules for the gene target RTP-801, which resulted in RTP801i-14, a 19 base pairs long blunt-ended AtuRNAi (siRNA) molecule and also provided Quark with a license to AtuRNAi technology. In addition a second agreement (Option and License Agreement) was signed in April 2005 and expanded in 2007 to provide Quark with options for non-exclusive licenses to develop additional molecules against further specific targets using Silence Therapeutics' proprietary AtuRNAi technology.

Iain Ross, Chairman and CEO of Silence Therapeutics, commenting on today's announcement said, "It is great news that our partners Quark and Pfizer are continuing to make good clinical progress with RTP-801i-14 a compound which we discovered together in our collaboration with Quark. The commencement of the first Phase II clinical trial utilising our chemistry is a very significant milestone for Silence and the advancement of this compound represents a further strong validation of our proprietary AtuRNAi technology."

The Company also announces today that its operating company Silence Therapeutics AG has been awarded a research grant from the German Federal Ministry of Education and Research. The BioChancePlus grant programme provides individual grants to support innovative research initiatives in Germany. The grant, which totals ¢â€š¬1.5 million over three years, was awarded to Silence Therapeutics AG in recognition of the company's pioneering research and development projects in the field of RNAi.

- Ends -

Enquiries:

For further information, please contact the following:

Silence Therapeutics plc European Contacts: +44(0)20 7307 1620 Citigate Dewe Rogerson

Iain Ross, Chairman & Chief Executive Officer +44(0)20 7638 9571

Melvyn Davies, Finance Director David Dible Heather Keohane Silence Therapeutics AG +49(0)30 9489 2800

Thomas Christĩly, Chief Executive Officer Klaus Giese, Chief Scientific Officer Nominated Advisers: U.S. Contacts: Nomura Code Securities Limited LaVoie Group

+44(0)20 7776 1200 +1 - 978.745.4200 Chris Collins Tim Allison x 102 Lisa Rivero x 106 Notes to Editors:

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

Silence Therapeutics plc (AIM: SLN) is a leading European RNAi focused biotechnology company. RNAi can selectively 'silence' genes linked to the onset of disease. RNAi is a Nobel Prize winning technology and one of the most promising areas of drug discovery and development today.

Silence Therapeutics has developed 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. In addition, the Company has developed a proprietary systemic delivery system, AtuPLEX. This system enables the functional delivery of siRNA molecules to targeted diseased tissues and cells, while increasing their bioavailability and intracellular uptake.

Silence's lead internal product, Atu027, is a proprietary AtuRNAi molecule in preclinical development for systemic cancer indications. Atu027 has successfully completed single and repeat dose toxicology and geno-toxicology studies, as well as a 28-day toxicology study using multiple dosing regimens. Silence plans a regulatory filing in 2008 to commence clinical trials for Atu027.

In March 2008, Silence Therapeutics announced a collaboration with AstraZeneca focused on the development of a range of novel delivery approaches for siRNA molecules. Under the terms of the agreement both Silence Therapeutics and AstraZeneca will be allowed to commercialize the truly novel delivery systems that the two partners develop together.

In July 2007, Silence Therapeutics formed its first research and development collaboration with AstraZeneca to develop novel AtuRNAi therapeutics against five specific targets, including those in respiratory indications. This collaboration was the first industry validation of the potential application of Silence Therapeutics' proprietary AtuRNAi molecules and solidified the Company's leadership position in field of RNAi therapeutics.

The Company's AtuRNAi technology also has been sublicensed to Pfizer via Quark's license to them of the compound RTP-801i-14 for the treatment of age-related macular degeneration (AMD) and a number of other indications. This compound entered the clinic in early 2007. Silence Therapeutics also has licensed to Quark rights to the AtuRNAi structure for Quark's proprietary compound, AKIi-5, which is in a Phase I human clinical study for treatment of acute kidney injury. In May 2008 the U.S. Food and Drug Administration (FDA) approved an Investigational New Drug application (IND) from Quark for another siRNA therapeutic product based on Silence's unique proprietary chemistry. The product, DGFi, which uses the same AtuRNAi molecule as AKIi-5, was discovered and is being developed by Quark for use in prevention or treatment of delayed graft function in kidney transplantation.

Silence Therapeutics is based in London, UK, and Berlin, Germany, and is listed on AIM.

About RNAi

RNA interference (RNAi), is a Nobel Prize winning technology and one of the most exciting areas of drug discovery today. It represents a completely new approach to selectively 'silence' or inactivate disease relevant genes and as such it has the potential to create a new class of therapeutic products. RNAi could therefore offer a therapeutic approach to a broad range of diseases (cancer, infectious diseases, inherited diseases), many of which have been regarded as incurable and are not addressed by current therapeutics, therefore providing a large market opportunity.

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.