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Antisoma Announces Further Data From ASA404 Ovarian Cancer Trial

LONDON, 12 July 2007 - Cancer drug developer Antisoma plc (LSE: ASM, US OTC: ATSMY) today announces new data from its phase II trial of ASA404 in recurrent, platinum-sensitive ovarian cancer. This trial compares patients receiving ASA404 plus chemotherapy (n=37) with patients receiving chemotherapy alone (n=38). The main findings are as follows:

* There was no advantage in median time to tumour progression in the ASA404 arm compared with the control arm * One-year survival rates were 74% for the ASA404 arm and 92% for the control arm. Since the majority of patients in both arms were alive after one year, median survival values have not been determined * Independently-determined response rates were consistent with those previously reported from investigator assessment and showed a higher response rate in the ASA404 arm * Addition of ASA404 to chemotherapy was generally well tolerated.

Based on these data, development in ovarian cancer will not be a priority.

Antisoma has been testing ASA404 in several cancer types and previously reported a 5-month increase in median survival when the drug was added to chemotherapy in non-small cell lung cancer.

Antisoma licensed ASA404 to Novartis in April 2007. Novartis plans to start enrolling patients into a phase III trial in non-small cell lung cancer early in 2008 and to explore the potential benefits of the compound in various other solid tumours.

Glyn Edwards, Antisoma's CEO said, "Our ovarian cancer trial has not produced positive results like those seen with ASA404 in lung cancer. More broadly, we're very pleased with the progress made by Novartis to date with ASA404 in lung cancer and look forward to working with them to fully evaluate the drug in other cancers."

Enquiries: Glyn Edwards, Chief Executive Officer Daniel Elger, Director of Communications +44 (0) 7909 915068 Antisoma plc

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

Brian Korb +1 646 378 2923 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.

Details of the ASA404 trial in ovarian cancer The ASA404 trial in ovarian cancer included women with ovarian cancer that had recurred six months or more after treatment with platinum chemotherapy. Patients were randomised to receive either ASA404 plus carboplatin and paclitaxel chemotherapy or the chemotherapy drugs alone.

Endpoints measured in the trial included response (a measure of tumour shrinkage), which was assessed both by the doctors participating in the trial and by an independent analysis of patient scans; time to tumour progression (a measure of the time between treatment and the resumption of tumour growth); and survival.

Thirty-seven patients were treated in the ASA404 arm and 38 received chemotherapy alone. One patient in the ASA404 arm was excluded from the analysis of survival and one patient in the chemotherapy-alone arm was excluded from the independent analyses of response and time to tumour progression.

The data from the ovarian cancer study will be presented by Prof Hani Gabra of Imperial College, London, at the ECCO (European Cancer Conference) in Barcelona on September 26th 2007. This will be a poster presentation in the Gynaecological Cancer session (1400-1700 CET; title: Update of phase II study of DMXAA (AS1404) combined with carboplatin and paclitaxel in recurrent ovarian cancer).

Background on ASA404 ASA404 (DMXAA, formerly AS1404) 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) in August 2001. Antisoma signed a worldwide development and marketing agreement for ASA404 with Novartis 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.

Posted: July 2007

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