Silence Therapeutics Receives Notice of Allowance for New U.S. Patent Covering Novel Small Interfering RNA (siRNA) Delivery Technology

LONDON, August 3, 2011 /PRNewswire/ --

Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company"), a leading global RNA interference (RNAi) therapeutics company, announces that the United States Patent and Trademark Office has issued the Company a notice of allowance on a patent application directed to the fundamental technology involved in AtuPLEX™, one of Silence's proprietary small interfering RNA (siRNA) delivery systems. The allowable subject matter is directed to AtuFect, the specific proprietary lipid that serves as the basis for the AtuPLEX delivery system, and provides proprietary protection for one of the RNAi industry's most clinically advanced and promising delivery technologies. These claims will cover the delivery system incorporated in Silence's lead clinical compound, Atu027, as well as a number of the Company's other RNAi therapeutic candidates.

"This is a highly valuable patent. Not only does it provide direct protection for AtuPLEX, one of the most advanced and exciting solutions addressing the challenge of delivering siRNAs, but also adds key layers of protection for our pipeline of RNAi therapeutics, including our lead RNAi therapeutic candidate, Atu027," said Max Herrmann, Chief Financial Officer of Silence Therapeutics."This notice of allowance follows the recent presentation of data from our ongoing clinical study of Atu027 at the 2011 American Society of Clinical Oncology conference which showed that the treatment, and therefore the AtuPLEX delivery technology, is safe and well-tolerated in all patients."

At the 2011 American Society of Clinical Oncology annual meeting, Silence presented interim Phase I clinical study results that showed promising antitumor activity associated with Atu027, as well as demonstrating that the treatment is well tolerated with no observed dose-limiting toxicities or evidence of cytokine activation. Favorable pharmacokinetic data showed dose-dependent increases in both siRNA and lipid levels, suggesting no evidence of drug accumulation during repeat treatment. Additionally, the maximum tolerated dose for Atu027 has yet to be reached, further supporting the tolerability of the treatment. These findings provide broad support for AtuPLEX as a safe and effective siRNA delivery technology with the potential to overcome the well-known delivery challenges associated with RNAi therapeutics.

AtuPLEX is the delivery technology incorporated in a number of Silence's partnered and internal RNAi therapeutic candidates. In addition, Silence's non-exclusively partnered DACC delivery system also incorporates the proprietary AtuFect lipid that is the subject of this notice of allowance.  

"The AtuPLEX and DACC delivery systems are key assets for Silence and for our current and future partners," stated Mr. Herrmann. "This latest intellectual property protection for our growing portfolio strengthens our ongoing business development activities that are focused on partnering Atu027 and also our world class delivery systems for individual genes or specific disease areas."

Silence Therapeutics is proactively building and strengthening its global, diverse and competitive intellectual property portfolio. This provides the Company and its partners with a strong proprietary position in the RNAi therapeutics space. The Company expects to make significant further progress in reinforcing its patent portfolio during 2011. At present, Silence's global patent portfolio contains issued patents and pending applications covering strategic areas of RNAi therapeutic development. These include multiple proprietary siRNA delivery technologies, potent siRNA sequences specific for high-value disease targets and key RNAi sequence and chemical modifications.

Notes for editors                    

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

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 short interfering RNA (siRNA) delivery technology platforms including AtuPLEX^™, a system that enables the functional delivery of siRNA molecules to targeted diseased tissues and cells, while increasing their bioavailability and intracellular uptake. Additionally, the company has a platform of novel siRNA molecules, AtuRNAi, which provide a number of advantages over conventional siRNA molecules, including reduced cytokine induction and decreased manufacturing costs. Silence's unique RNAi assets also include structural features for a next generation of RNAi molecules and additional proprietary siRNA sequences against highly valued oncology and other disease targets.

The Company's lead internal drug candidate is Atu027, a liposomal AtuRNAi formulation in clinical development for systemic cancer indications and one of the most clinically advanced RNAi therapeutics in the area of oncology. Silence is currently conducting an open-label, single-centre, dose-escalation Phase I study with Atu027 in patients with advanced solid tumors involving single dose and repeated intravenous administration. The study is expected to be completed in the second half of 2011.

The Company's RNAi therapeutic platform has received key validation through multiple partnerships with pharmaceutical companies including AstraZeneca, Dainippon Sumitomo, Pfizer, and Quark. Silence is actively pursuing the establishment of additional partnerships.

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.

For further information, please contact:

                                         
    Silence Therapeutics                  Singer Capital Markets
    Max Herrmann                          Shaun Dobson/Claes Spång
    +44 20 7491 6520                      +44-20-32057500
    [email protected]   [email protected]
    Vida Communication (US)               [email protected]

                                         
    Tim Brons (media)                   M:Communications (Europe)
    Stephanie Diaz (investors)          Peter Laing / Emma Thompson
    +1 (415) 675-7400                   +44-20-7920-2345 / +44-20-7920-2342
    [email protected]        [email protected]
    [email protected]

SOURCE Silence Therapeutics Plc