London, UK, and Cambridge, MA: 16 December 2009 – Antisoma plc (LSE: ASM; USOTC:
ATSMY) announces that results of its phase II trial of AS1411 as a second-line
treatment for metastatic renal cell carcinoma (RCC; kidney cancer) provide
further evidence that the drug has anti-cancer activity. Safety findings suggest
that AS1411 is exceptionally well tolerated compared to most current cancer
treatments. Data from the trial will be submitted to a forthcoming scientific
meeting.

Antisoma had two aims for this study. One was to decide whether to continue
development in RCC; the second was to inform development in other cancer
settings.

With respect to RCC, the AS1411 phase II data have been evaluated in the context
of findings from a recent phase III study of the new drug everolimus, which was
conducted in a very similar patient population. Independent assessment of scans
from the AS1411 trial suggests single-agent activity comparable with that of
everolimus, although the median progression-free survival was slightly inferior.
Given the approval of everolimus earlier this year and the many other drugs now
available for RCC, Antisoma does not plan to pursue development of AS1411 in
this setting.

With respect to broader development, the AS1411 phase II trial in RCC provides
further evidence of anti-cancer activity and a highly favourable safety profile.
These observations support previous findings suggesting that AS1411 has
potential in various cancers. For the immediate future, development will remain
focused in AML (acute myeloid leukaemia). A randomised phase II trial in this
setting reported positive data earlier this year, and a phase IIb trial in AML
will begin soon.

Glyn Edwards, CEO of Antisoma, said: “We have taken a critical look at the renal
cancer market and decided not to pursue development of AS1411 for this
indication. We are, however, very encouraged to see further evidence of activity
with AS1411, and are now focusing our efforts around this drug on the
forthcoming trial in AML, a setting where we have already reported positive data
from a randomised phase II trial.”

Enquiries:


  Antisoma plc

  Glyn Edwards, CEO

  Daniel Elger, VP Marketing & Communications    +44 (0) 7909 915 068



  Buchanan Communications (media enquiries)

  Mark Court/Lisa Baderoon/Catherine Breen       +44 (0)20 7466 5000



  The Trout Group (US investor enquiries)

  Seth Lewis                                     +1 617 583 1308



Except for the historical information presented, certain matters discussed in
this announcement are forward looking statements that are subject to a number of
risks and uncertainties that could cause actual results to differ materially
from results, performance or achievements expressed or implied by such
statements. These risks and uncertainties may be associated with product
discovery and development, including statements regarding the company's clinical
development programmes, the expected timing of clinical trials and regulatory
filings. Such statements are based on management's current expectations, but
actual results may differ materially.

About the AS1411 phase II trial
Patients in the study had metastatic renal cell carcinoma that had previously
been treated with at least one tyrosine kinase inhibitor (sunitinib or
sorafenib). Thirty-five patients were enrolled at centres in the US. All
received monotherapy treatment with AS1411 at 40mg/kg/day for 4 days of
continuous infusion over one or two cycles. Response rates and progression-free
survival were assessed using tumour scans, and safety and pharmacokinetic data
were collected.

About AS1411
AS1411 belongs to a new type of drug called aptamers. These drugs are short
pieces of DNA or RNA that fold into three-dimensional structures capable of
targeting particular proteins. AS1411 is a DNA aptamer that targets nucleolin, a
protein found on the surface of cancer cells.

AS1411 was originally developed by Dr Paula Bates, Dr John Trent and Prof.
Donald Miller at the University of Alabama and then at the University of
Louisville. Antisoma added AS1411 to its pipeline when it acquired the
Louisville-based company Aptamera Inc. in 2005.

In May 2009, Antisoma reported positive findings from a randomised phase II
trial in which AS1411 was given in combination with high-dose cytarabine to
patients with relapsed and refractory AML (acute myeloid leukaemia). A phase IIb
trial in AML is expected to start in early 2010.

About Antisoma
Antisoma is a London Stock Exchange-listed biopharmaceutical company that
develops novel products for the treatment of cancer. The Company has operations
in the UK and the US. It has two drugs in phase III trials: ASA404, a
tumour-vascular disrupting agent, which is partnered with Novartis and which is
under development for lung and breast cancers; and AS1413, a novel DNA
intercalator being evaluated in secondary AML. Please visit www.antisoma.com
<

http://www.antisoma.com/> for further information about Antisoma.


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