Silence Therapeutics Receives Notice of Allowance for RNA Interference (RNAi) Patent Covering Novel Cancer Target

LONDON and PALO ALTO, California, February 8 - Silence Therapeutics plc (AIM: SLN) today announced that the United
States Patent and Trademark Office (USPTO) has issued the company a notice of
allowance on a patent application directed to methods of treatment using a
high-value therapeutic target in the area of oncology. Known as PKN-3, the
target is a protein kinase C-related molecule that is believed to play an
important role in the growth of cancer cells, as well as metastasis
formation. The allowed subject matter is directed to, among other things,
methods of treating cancer with small interfering RNA (siRNA) or antisense
molecules that target the PKN-3 messenger RNA (mRNA). The claims cover the
siRNA molecule in Silence's lead clinical compound, Atu027, an RNAi
therapeutic which targets PKN-3 for the treatment of advanced solid tumors.

"This action by the USPTO is the latest step in Silence's establishment
of a proprietary and compelling RNAi therapeutic franchise which includes
PKN-3 for the treatment of cancer. This development strengthens our dominant
intellectual property position surrounding PKN-3, while specifically
enhancing our global protection for Atu027, our Phase I candidate," said
Philip Haworth, Ph.D., chief executive officer of Silence Therapeutics. "At
the same time, this milestone serves to supplement our already broad and
diverse global RNAi intellectual property portfolio and enhances the
significant proprietary position that this portfolio affords."

Silence has built a strong and diverse intellectual property portfolio
covering all essential areas of RNAi therapeutic development including
multiple proprietary siRNA delivery technologies, potent siRNA sequences and
key siRNA sequence and chemical modifications, as well as specific high-value
disease targets.

About Atu027

Silence's lead internal product, Atu027, is a proprietary AtuRNAi(TM)
molecule in clinical 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.
In June 2009 the company initiated an open-label, single-centre,
dose-escalation Phase I study with Atu027 in patients with advanced solid
(malignant) tumors involving single, as well as, repeated intravenous
administration.

About Silence Therapeutics plc (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 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. A
second, complementary delivery technology known as PolyTran(TM) offers safe
and effective systemic administration using a library of novel peptide-based
biodegradable polycationic polymers. Additionally, the company has 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. 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 strong and diverse intellectual property portfolio includes
an exclusive license to the Zamore patent family from the University of
Massachusetts, which covers broad structural features of siRNA design for
more potent next generation siRNA sequences.

Silence Therapeutics is headquartered in London, UK, with research and
development operations in Berlin and Palo Alto, CA.

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.

Phil Haworth of Silence Therapeutics, +1-650-855-1514, p.haworth at silence-therapeutics.com; or Richard Potts or Jonathan Senior, both of Nomura Code Securities, +44-20-7776-1200; or media, Tim Brons, tbrons at vidacommunication.com, or investors, Stephanie Diaz, sdiaz at vidacommunication.com, both of Vida Communication for Silence Therapeutics, +1-415-675-7400