SLN.L Regulatory News (SLN)

21 Jan 2009 07:00

Silence Therapeutics announces its successful opposition to second European

Patent in Kreutzer-Limmer patent family.

London, UK, 21 January 2009 - Silence Therapeutics plc , the leading European biopharmaceutical company focused on RNA interference (RNAi), welcomes the announcement today that a second member of the Kreutzer-Limmer patent family has been revoked in its entirety.

Following an oral hearing, the Opposition Division of the European Patent Office announced its decision yesterday to revoke European Patent EP 1 214 945 in its entirety. This patent, which is held by Alnylam Europe AG, is a divisional of European patent EP 1 144 623, which was itself revoked in its entirety by the Technical Board of Appeal on December 09, 2008.

The patent was opposed by Silence Therapeutics AG, Sirna Therapeutics, Quark Biotech Inc. and Abbott Laboratories.

Dr. John Lucas, General Counsel & Vice President, Intellectual Property, at Silence Therapeutics, said: "The decision of the Opposition Division confirms our view that the entire Kreutzer-Limmer RNAi patent family is vulnerable and may be successfully challenged. This is now the second European patent of this family to be revoked. As all of the members of the Kreutzer-Limmer RNAi patent family suffer from the same shortcomings in terms of disclosure, we expect the European Patent Office will take the same position with any further patents in this patent family"

- Ends -

For further information, please contact the following:

Silence Therapeutics plc Powerscourt +44(0)20 7307 1620 +44(0)20 7250 1446 Iain Ross, Chairman & CEO Paul Durman John Lucas, General Counsel & Vice Kay Larsen President Intellectual Property Nominated Advisers Nomura Code Securities Limited +44(0)20 7776 1200 Richard Potts Notes to Editors:

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

Silence Therapeutics plc (AIM: SLN) is a leading European RNAi-focused biotechnology company.

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.

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.

Following the granting of its patents in Europe, the USA and Australia, Silence Therapeutics is one of only two companies worldwide with a proprietary position on composition of matter for siRNA therapeutics.

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 made a regulatory filing in 2008 and expects to commence clinical trials for Atu027 in 2009.

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.

Silence Therapeutics has granted a licence to AstraZeneca to develop novel AtuRNAi therapeutics against five specific targets. 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 a phase II clinical study in July 2008. 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.

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.

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