SLN.L Regulatory News (SLN)

10 Sep 2007 07:00

Silence Therapeutics RNAi Lead Compound Atu027 Successfully Completes 28-Day Toxicology Studies

London, UK, 10 September 2007 - Silence Therapeutics plc ("the Company"), a leading European RNAi therapeutics company, announces that its lead compound, Atu027, has successfully completed pre-clinical, 28-day toxicology studies.

Silence Therapeutics has identified a dose range for Atu027, a systemically delivered RNAi compound, at which additional pre-clinical studies will be conducted prior to an anticipated regulatory submission in 2008 to enable human studies.

The Company also confirms that, following discussions with the United States Patent and Trademark Office, it is progressing its core AtuRNAi patent application in the USA. Silence Therapeutics was granted its core chemistry patent (EP 1527176) by the European Patent Office in January 2007.

"These results represent a significant step for us in the development of our systemically delivered, proprietary AtuRNAi molecules," said Jeff Vick, Chief Executive Officer of Silence Therapeutics. "The delivery of siRNA molecules as a whole, and systemic delivery in particular, is an important challenge upon which the industry is focussed. We are delighted that we have been able to announce our progress and look forward to working independently and with our pharmaceutical partners to bring our proprietary siRNA molecules, combined with proprietary delivery technologies, into the clinic in 2008 and beyond. In addition we anticipate that our products and technologies will have broad international patent protection."

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Notes to Editors

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

Silence Therapeutics plc 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 one of its proprietary compounds, AKIi-5, based on AtuRNAi technology 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 in 2008.

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

About RNAi

RNA interference (RNAi), a Nobel Prize winning technology, is 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.

Enquiries:

For further information, please contact the following:

Silence Therapeutics plc Investor Relations +44(0)20 7307 1620 Citigate Dewe Rogerson Jeff Vick, CEO +44(0)20 7638 9571 Iain Ross, Executive Chairman Valerie Auffray David Dible Nominated Adviser Grant Thornton Corporate Finance +44 (0) 20 7383 5100 Gerry Beaney Colin Aaronson