London, England and Freemont, CA. July 31, 2007 – Silence Therapeutics plc and Quark Pharmaceuticals, Inc. (“Quark”), announced today an expansion of their current strategic technology licensing agreement.

In April 2005 the Companies signed an Option and Licence Agreement, which provided Quark with access to Silence Therapeutics’ novel proprietary siRNA technology, AtuRNAi. The first outcome of Companies’ relationship was the development of the AtuRNAi technology-based compound RTP801i, which was licensed to Pfizer Inc in 2006 by Quark and is currently in a phase 1 clinical trial in patients with wet age related macular degeneration. Quark’s product portfolio includes one additional siRNA molecule with a structure covered by patents licensed from Silence Therapeutics.

The expanded agreement provides Quark with options to non-exclusive licenses to develop additional molecules against 3 specific targets using Silence Therapeutics’ proprietary AtuRNAi technology. The terms of the amendment signed today will entitle Silence Therapeutics to milestone payments and a royalty on product sales after exercise of the options by Quark. Further financial details were not disclosed.

Danny Zurr, Chief Executive Officer of Quark Pharmaceuticals: “We are pleased to extend our relationship with Silence Therapeutics. We believe extending this relationship provides Quark with opportunities to further develop its pipeline of clinical product candidates targeted at indications with significant unmet medical needs.”

Iain Ross, Chairman of Silence Therapeutics stated: “This is a long-standing relationship for us and we are pleased we have been able to broaden it. The goal in the RNAi sector is to advance clinical development and Quark has already proven it can utilise our proprietary AtuRNAi technology and take products into the clinic. This agreement forms part of our continuing strategy of signing target-specific collaboration and license agreements with pharmaceutical and biotech companies which will lead to a broader clinical application of our AtuRNAi product platform outside of our internal programs for systemic applications in oncology.”

 

Quark Pharmaceuticals is a clinical-stage biopharmaceutical company focused on discovering and developing novel therapeutics based on its proprietary gene discovery science and technology, with an initial focus on drug candidates that work through the natural mechanism in the cell known as RNA interference, or RNAi, for the treatment of diseases associated with oxidative stress. Quark believes that its proprietary target gene discovery platform, BiFARTM, combined with its ability to design and successfully deliver synthetic molecules of the new class of RNAi therapeutics known as small-interfering RNA, or siRNA, to specific organs in the body, enables the Company to rapidly develop drug candidates. Quark has two internally discovered and developed lead product candidates: RTP801i-14 in phase 1 clinical trial for the treatment of wet age-related macular degeneration, and AKIi-5 for the prevention of acute renal failure. The Company has licensed RTP801i-14 to Pfizer on an exclusive worldwide basis. Quark corporate product development teams are based in Fremont, CA and research facilities in Ness-Ziona, Israel. Additional information is available at www.quarkpharma.com

Silence Therapeutics plc (LSE:SLN) is a leading RNAi company. RNA interference (RNAi) can selectively ”silence” genes linked to the onset of disease.

Silence Therapeutics has developed novel, proprietary short interfering RNA (“siRNA”) molecules, AtuRNAi, which provide a number of advantages over conventional siRNA molecules as they show increased stability against nuclease degradation. In addition, the Company has developed a proprietary systemic delivery system, AtuPLEX. This enables the delivery of siRNA molecules to targeted diseased tissues and cells, whilst increasing their bioavailability and intracellular uptake.

In July 2007, Silence Therapeutics formed a research and development collaboration with Astra Zeneca to develop AtuRNAi against five targets in respiratory indications. The Group’s AtuRNAi technology has also been sublicensed to Pfizer by Quark Pharmaceuticals, through Quark’s license 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. Quark Pharmaceuticals, Inc. has developed a further compound, AKIi-5, having AtuRNAi structure under the existing licence from Silence Therapeutics. This compound has been granted an IND for acute kidney injury and is expected to enter the clinic in 2007. In addition, Silence Therapeutics expects to begin the clinical development of its proprietary AtuRNAi therapeutic molecules for systemic cancer indications, such as gastrointestinal and non-small lung cancer, in 2008.

Silence Therapeutics is based in London, UK, and Berlin, Germany, and is listed on AIM. Additional information is available at www.silence-therapeutics.com