Silence Therapeutics and Dainippon Sumitomo Expand siRNA Delivery Collaboration

Companies to Examine Delivery of RNAi Therapeutics to Additional Disease Targets

LONDON, March 30, 2010 - Silence Therapeutics plc (AIM: SLN) today announced that the company and
Dainippon Sumitomo Pharma Co., Ltd. have agreed to an expansion of their
ongoing small interfering RNA (siRNA) delivery collaboration. Under this
collaboration, which was originally entered into in August 2009, the
companies are leveraging Silence's proprietary siRNA molecules and multiple
lipid delivery and targeting technologies to demonstrate functional delivery
of RNA interference (RNAi) therapeutics to specific disease targets in the
body. Under the terms of the expansion, the companies will examine delivery
to additional disease targets selected by Dainippon Sumitomo. The financial
details of the original collaboration and this extension have not been
disclosed.

"We believe that the decision to expand this collaboration less than
eight months after its initiation and within three months of the merger
between Silence and Intradigm provides clear evidence that both Silence and
Dainippon Sumitomo are not only pleased with the progress already achieved
through this partnership but also with its future potential," stated Philip
Haworth, Ph.D., chief executive officer of Silence Therapeutics. "While we at
Silence have long believed in the significant value and potential of our
proprietary technologies, it is gratifying to have a partner support our
activities with a rapid expansion of this key collaboration."

Several of Silence Therapeutics' proprietary assets are being leveraged
as part of this collaboration. These include the company's AtuRNAi, a novel
siRNA molecule which is chemically modified to improve stability, reduce
manufacturing costs and increase yields, all of which are key considerations
in the emerging RNAi therapeutics space. Additionally, a number of the
company's proprietary lipid delivery and targeting technologies for siRNAs,
including AtuPLEX, are also being used as part of the collaborative research
efforts.

The challenges of systemic siRNA delivery are well documented and include
numerous biological barriers that limit RNAi therapeutics' ability to reach
targets safely and effectively. Successfully solving this delivery problem
and enabling siRNA molecules to safely and effectively reach various tissue
sites within the body is essential to realizing the vast therapeutic
potential of RNAi.

Silence Therapeutics has been advised by Summit Pharmaceuticals
International which represents and markets the technologies, products and
expertise of Silence Therapeutics in Japan.

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) uses a
library of novel peptide-based biodegradable polycationic polymers for
systemic siRNA administration. 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
exclusive licenses from the University of Massachusetts on three patent
families associated with the Zamore "Design Rules," which cover 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.

About Dainippon Sumitomo Pharma (www.ds-pharma.co.jp/english)

Dainippon Sumitomo Pharma Co., Ltd. is a multi-billion dollar, top-ten
listed pharmaceutical company in Japan with more than 7,000 employees
worldwide. The company has a diverse portfolio of pharmaceutical, animal
health and food and specialty products. The company aims to produce
innovative new drugs in the CNS area and the specialty area.

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 Tim Brons (media), tbrons at vidacommunication.com, or Stephanie Diaz (investors), sdiaz at vidacommunication.com, both of Vida Communication, +1-415-675-7400, for Silence Therapeutics; or Richard Potts or Jonathan Senior, both of Nomura Code Securities, +44(0)20-7776-1200