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16/11/2005

Extended follow-up of renal cancer patients provides new support for Antisoma’s AS1411

Philadelphia, US and London, UK: 16 November 2005 - Cancer drug developer Antisoma plc (LSE: ASM) announces the presentation of long-term follow-up data from the phase I trial of its aptamer drug AS1411. The new data extend results presented at the ASCO meeting in May, where promising signs of anti-cancer activity were reported in the trial’s three renal cancer patients. At that time, one of these patients had shown a near-complete response, having experienced dramatic shrinkage of a large tumour. This patient is still in remission 16 months after treatment. The other two renal cancer patients had shown prolonged stable disease, one for 9 months and one ongoing at the time of ASCO. The latter patient is now known to have remained stable for 15 months before relapse. This update will be presented today at the AACR-NCI-EORTC meeting in Philadelphia by Professor Donald Miller, a co-inventor of AS1411 and Director of the Brown Cancer Center at the University of Louisville, where the trial was conducted.

Tomorrow, two further presentations at the same meeting will highlight ongoing scientific work on AS1411. Scientists from Antisoma will confirm that AS1411 kills a wide range of solid and blood cancer cells in culture. Various renal cancer lines are amongst those susceptible to AS1411. The drug’s co-inventor Dr Paula Bates will show that AS1411 inhibits lung tumour formation in a mouse model of metastatic (spreading) cancer.

The phase I trial of AS1411 has now reopened and is focusing on patients with renal and non-small cell lung cancers. Prof. Miller said: “Recruitment is progressing well and we look forward to presenting more results in the near future.”

Glyn Edwards, Chief Executive Officer of Antisoma, said: “AS1411 clearly has potential against a number of cancers and the updated findings from renal cancer patients are particularly encouraging.”

Enquiries:

Glyn Edwards, CEO
Daniel Elger, Director of Communications
+44 (0)7909 915 068
Antisoma plc

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

Disclaimer

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.

Background on AS1404

AS1404 (chemical name DMXAA) is a small-molecule derived from xanthenone acetic acid. A member of the class of drugs known as ‘vascular disrupting agents’, it is the only representative of its subclass in clinical trials and is the first of these drugs to report efficacy data from a controlled study (for full details see announcement of 17 October 2005). AS1404 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 Technologies) in August 2001.

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. In 2002, Antisoma formed a broad strategic alliance with Roche to develop and commercialise products from Antisoma’s pipeline. AS1404 is included within the Roche alliance. Please visit www.antisoma.com for further information about Antisoma.

Background on the AACR-NCI-EORTC conference

The AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics: Discovery, Biology, and Clinical Applications, is a joint conference held by the American Association for Cancer Research, US National Cancer Institute and European Organization for Research and Treatment of Cancer.