Silence Therapeutics' Atu027 Demonstrates Promising Antitumor Activity in Phase I Study Presented at ASCO

LONDON, June 6, 2011 /PRNewswire-FirstCall/ -- Silence Therapeutics plc (AIM: SLN) ("Silence" or the "Company"), a leading global RNA interference (RNAi) therapeutics company, announces positive updated data from its ongoing Phase I study of Atu027, one of the most clinically advanced RNAi therapeutics in the area of oncology, in patients with advanced solid tumors. Study results show that nine of the 24 patients treated with Atu027 to date achieved stable disease after repeated treatment with six of these cases confirmed at study end (three months after treatment initiation) and three other patients continuing to receive treatment with Atu027 under compassionate use. Among the patients who achieved stable disease, one individual with neuroendocrine cancer achieved disease stabilization for nine months with a second neuroendocrine cancer patient showing partial regression of pulmonary metastases. An additional patient with breast cancer experienced a slight regression in liver metastases. Interim study data, which include results for the 24 patients who have received the study's first eight escalating doses of Atu027, are being presented today in a poster presentation at the 2011 American Society of Clinical Oncology ("ASCO") Annual Meeting in Chicago.

In addition to the encouraging antitumor activity, study results show Atu027 to be well tolerated with no observed dose-limited toxicities or evidence of cytokine activation. Favorable pharmacokinetic (PK) data showed dose-dependent increases in siRNA and lipid levels, suggesting no evidence of drug accumulation during repeat treatment. Additionally, the maximum tolerated dose for Atu027 has not been reached yet, further supporting the tolerability of the treatment and providing the opportunity to examine the possibility of enhanced efficacy at higher doses. Dose escalation and patient enrollment is continuing in the study with the goal of evaluating a total of 11 escalating doses of Atu027 in approximately 33 patients. Silence expects to complete the ongoing open label, single-center, dose-finding Phase I trial in the second half of 2011.

"The next step in translating the promising science of RNA interference into meaningful therapeutics with the potential to help patients is the gathering and presentation of positive clinical study data. We believe that the combination of antitumor activity, impressive PK results and the clean safety profile that has been demonstrated by Atu027 in this study so far, represents significant clinical progress not just for Silence but for the entire field of RNAi therapeutics," said Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics. "The Atu027 data presented today provide valuable validation for Silence's foundational RNAi technology platform, as well as our AtuPlex delivery technology, which is the only systemic lipid-based siRNA delivery technology in clinical trials that does not require suppression of the immune system prior to treatment. We look forward to completing this ongoing study and reporting final data once available."

"We are clearly optimistic by the results that indicate activity in this study so far, particularly the impressive tolerability and safety being displayed by Atu027," stated the study's principal investigator, Dirk Strumberg, M.D., Professor of Medicine and Director, Department of Hematology and Medical Oncology, University of Bochum, Marienhospital Herne. "For an early-stage study, it is pleasantly surprising to see some patients who are suffering with difficult-to-treat tumours experience prolonged disease stabilization."

Data from Silence's ongoing Phase I study of Atu027 were presented today at the ASCO meeting in a poster titled "First-in-human phase I study of Atu027, a liposomal small interfering RNA formulation, targeting protein kinase N3 (PKN3) in patients with advanced solid tumors."

About Atu027

Atu027 is a liposomal siRNA formulation targeting PKN3 for the treatment of advanced solid cancer. PKN3 is a key regulator during angiogenesis and lymphangiogenesis, while also acting as a major regulator of metastasis and motility during pathological processes. Accordingly, Silence believes that inhibition of PKN3 with Atu027 may lead to a reduction in nutrient and oxygen supply to solid tumors, as well as interfering with tumor formation, endothelial cell motility and metastasis.

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(TM), 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 more than 50 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, as well as, 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.

SOURCE Silence Therapeutics Plc