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Antisoma plc (SRC)

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Monday 04 June, 2007

Antisoma plc

Positive data from ASA404 prostate cancer trial...






London, UK & Chicago, IL: 3 June 2007 - Antisoma plc (LSE: ASM, US
OTC: ATSMY) announces the presentation today at ASCO of new, positive
data from its randomised phase II trial testing the addition of
ASA404 (formerly AS1404) to first-line docetaxel chemotherapy in
hormone-refractory prostate cancer.

Final PSA data show that ASA404 greatly increased PSA response rate -
the proportion of patients showing a sustained 50% reduction in blood
levels of the prostate cancer biomarker PSA. Seventy patients were
evaluable for PSA response. The response rate was 59% in men treated
with ASA404 plus docetaxel versus 37% in the control group, who
received docetaxel alone. The proportion of patients showing
progression by PSA was 16% in the ASA404 group and 37% in the control
group, a more marked difference than that seen in preliminary
findings from the trial.

PSA reductions were more profound and of more rapid onset in patients
who received ASA404. PSA fell by a median of 79% in the ASA404 group
and 36% in the control group. Among patients whose PSA fell, maximum
reduction was achieved in a median of 96 days in the ASA404 group and
120 days in the control group.

Today's presentation also includes safety findings from the trial.
These remain consistent with earlier reports in showing that addition
of ASA404 to chemotherapy was generally well tolerated.

Data are presented by Dr Roberto Pili of Johns Hopkins University and
Professor Mark Rosenthal of the Royal Melbourne Hospital, Victoria,
Australia. Professor Rosenthal said: "These PSA data clearly suggest
that activity is improved when ASA404 is added to first-line
docetaxel therapy in patients with hormone-refractory prostate
cancer. We will very soon see whether the PSA effect translates into
progression and survival benefits."

Further data from the prostate cancer trial, including 1-year
survival findings, will be available before the end of October, as
will further data from two other studies in ovarian and lung cancers.
Final data from a randomised study in lung cancer were reported in
2006. These showed a 5.2-month extension in median survival when
ASA404 was added to carboplatin and paclitaxel.

ASA404 was recently licensed to Novartis AG, who will be conducting
all further development including a phase III trial in lung cancer
scheduled to start patient recruitment early in 2008.

Glyn Edwards, CEO of Antisoma, said: "This is a really exciting time
with ASA404. We have already seen impressive survival data in lung
cancer and have forged a strong partnership with Novartis to take the
drug forward. The latest data from the prostate cancer trial are very
encouraging as we look forward to seeing survival data from this and
other studies over the next few months."

Prostate cancer is among the most prevalent cancers in the developed
world. It often responds initially to hormonal therapies, but each
year some 200,000 men across the US, Europe and Japan develop
'hormone-refractory' disease.  The taxane drug docetaxel has become
an important treatment for such hormone-refractory prostate cancer.
ASA404 has shown synergistic anti-cancer effects in combination with
docetaxel and other taxanes in preclinical tests.

A copy of the poster presented at ASCO is available at
www.antisoma.com.


Enquiries:

Glyn Edwards, Chief Executive Officer
Daniel Elger, Director of Communications          +44 7909 915 068
Antisoma plc

Mark Court/Lisa Baderoon/Rebecca Skye
Dietrich                                          +44 (0)20 7466 5000
Buchanan Communications

Brian Korb                                        +1  212 477 9007
The Trout Group


Antisoma disclaimer
Certain matters discussed in this statement 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.

PSA and PSA responses
PSA is a protein, prostate-specific antigen. Levels of PSA in the
blood are used in the diagnosis of prostate cancer and the tracking
of responses to its treatment. PSA is one of the most widely
recognised disease markers in oncology, and PSA responses have been
related to clinical outcomes in numerous studies.

PSA response is defined as a 50% or greater reduction in PSA level
from baseline and progression by PSA is defined as a 25% or greater
increase from the lower of baseline or PSA nadir. This is in
accordance with the Bubley criteria (Eligibility and response
guidelines for phase II clinical trials in androgen-independent
prostate cancer: recommendations from the Prostate-Specific Antigen
Working Group. Journal of Clinical Oncology 1999, Volume 17, pp
3461-67).

Background on ASA404
ASA404 (DMXAA) is a small-molecule vascular disrupting agent which
targets the blood vessels that nourish tumours. The drug was
discovered by Professors Bruce Baguley and William Denny and their
teams at the Auckland Cancer Society Research Centre, University of
Auckland, New Zealand. It was in-licensed by Antisoma from Cancer
Research Ventures Limited (now Cancer Research Technology), the
development and commercialisation company of the Cancer Research
Campaign (now Cancer Research UK), in August 2001. CRUK had supported
two phase I studies in the UK and New Zealand. ASA404 has shown a
substantial survival benefit in patients with non-small cell lung
cancer when added to paclitaxel-based chemotherapy in a randomised
phase II study. Worldwide rights to the drug were licensed to
Novartis AG in April 2007.

Background on Antisoma
Based in London, UK, Antisoma is a biopharmaceutical company that
develops novel products for the treatment of cancer. Antisoma fills
its development pipeline by acquiring promising new product
candidates from internationally recognised academic or cancer
research institutions. Its core activity is the preclinical and
clinical development of these drug candidates. Please visit
www.antisoma.com for further information.

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