RNS Number:7312R
Antisoma PLC
06 November 2003

        Broad potential for R1549 highlighted by favourable tolerability
                     profile in gastric cancer pilot study

London, UK, 6 November 2003: Antisoma plc (LSE:ASM), the biopharmaceutical
company specialising in the development of anti-cancer drugs, today announces
final results from its pilot phase II study of R1549 in gastric cancer. The
trial, which has been funded since November 2002 by Antisoma's co-development
partner, Roche, evaluated the drug in a small group of patients who had received
surgery to treat advanced gastric cancer. Eight patients who received surgery
plus R1549 were compared with seven patients who received surgery alone.
Tolerability findings were comparable to those observed in patients receiving
R1549 for ovarian cancer. As expected, based on the small size of the trial, no
statistically significant differences were observed in survival time between the
treated and untreated patients.

The importance of these results lies in the extension of favourable tolerability
data to a broader patient population than ovarian cancer sufferers. The gastric
study included patients with a different type of tumour, a different surgical
history and for the first time men as well as women. This study makes possible
the future evaluation of R1549 in gastric and other abdominal cancers in the
event of positive results from the drug's pivotal phase III study in ovarian
cancer. Antisoma and Roche expect to announce the principal results of the
ovarian study during the first half of 2004.  A previous phase II study in
ovarian cancer showed a statistically significant increase in survival time,
with enhanced five- and ten-year survival (details of the publications are
provided in Notes to Editors).

An investigator in the study, Dr Bruce Sizer of Essex County Hospital,
Colchester, UK, said, "This trial was a useful first step in evaluating R1549 in
gastric cancer. Further trials will be needed to fully elucidate the value of
the drug in this and other possible abdominal cancer indications."

Glyn Edwards, CEO of Antisoma, said, "This is an exciting time for Antisoma as
we await the results of our pivotal study of R1549 in ovarian cancer. By showing
that R1549 can also be given safely to patients with gastric cancer, today's
results provide a potential springboard for the extension of the development
programme to a range of abdominal cancers."



Enquiries:

Antisoma plc                              Tel: +44 (0)20 8799 8200
Glyn Edwards, Chief Executive Officer

Financial Dynamics                        Tel: +44 (0)20 7831 3113
Jonathan Birt


Except for the historical information presented, 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.


Notes to editors

Gastric cancer

Approximately 875,000 new cases of gastric cancer are diagnosed worldwide each
year. Treatment options are limited and survival rates remain poor, as
approximately 80% of patients present with locally advanced or metastatic
disease. The World Health Organisation estimates that gastric cancer killed
almost 650,000 people worldwide in 2000.

References for ovarian cancer phase II study

*    Hird V. et al. Adjuvant therapy of ovarian cancer with radioactive
     monoclonal antibody. Br J Cancer (1993) 68: 403-406.

*    Epenetos A.A. et al. Long term survival of patients with advanced
     ovarian cancer treated with intraperitoneal radioimmunotherapy. Int J 
     Gynecol Cancer (2000) 10 (suppl 1): 44-46.

*    Nicholson S. et al. Radioimmunotherapy after chemotherapy compared to
     chemotherapy alone in the treatment of advanced ovarian cancer: A matched
     analysis. Oncol Reports (1998) 5: 223-226.

About Antisoma

Based in London, UK, Antisoma is a biopharmaceutical company that develops novel
products for the treatment of cancer. The Company 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. Antisoma forms partnerships
with pharmaceutical companies to bring its products to market.  In November
2002, Antisoma signed a ground-breaking collaboration agreement with Roche to
develop and commercialise products from Antisoma's pipeline. Please visit
www.antisoma.com for further information.


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