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04/06/2006

Antisoma's AS1404 shows early promise in ovarian cancer trial

Atlanta, Georgia, and London, UK: 4 June 2006 - Antisoma announces the presentation today at ASCO of initial findings from a phase II trial of AS1404 (DMXAA) in ovarian cancer. The study randomised patients with recurrent ovarian cancer to receive AS1404 plus chemotherapy or chemotherapy alone. With initial data available from 62 patients, those receiving AS1404 had a tumour response rate of 61.3%, compared with 54.8% for those receiving chemotherapy alone.

Safety findings from the trial show that, to date, AS1404 has been well tolerated and has not exacerbated the side effects of chemotherapy. Patients continue to be followed up to assess the effect of AS1404 on time to tumour progression and survival.

The ovarian cancer study is one of three randomised controlled phase II trials of AS1404. A separate announcement has been made today concerning data from a trial in non-small cell lung cancer, where addition of AS1404 to chemotherapy was associated with a higher response rate, longer time to progression and enhanced projected survival compared with chemotherapy alone. A third trial, in hormone-refractory prostate cancer, is also ongoing.

Antisoma announced with the lung cancer findings that it had regained all rights to AS1404 from its partner Roche. Antisoma plans to start a phase III trial in non-small cell lung cancer in parallel with completing the phase II studies in ovarian and prostate cancers.

Prof Hani Gabra of Imperial College London, an investigator in the study and the presenter of the AS1404 ovarian cancer trial at ASCO, said, “These early data are interesting and I look forward to seeing the results from the other measures of efficacy in this trial.”

Glyn Edwards, CEO of Antisoma said, “In the context of the positive findings from our lung cancer trial, it is very encouraging to see promising early data in another cancer indication. Because AS1404 works by disrupting tumour blood vessels, it could potentially provide benefit to patients with a wide variety of cancers.”

Enquiries:

Glyn Edwards, CEO		+44 (0)7909 915 068
Daniel Elger, Director of Communications
Antisoma plc
Mark Court/Lisa Baderoon/ Rebecca Skye Dietrich		+44 (0)20 7466 5000
Buchanan Communications

Antisoma 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.

The AS1404 phase II trial in ovarian cancer

For full details of the data presented from the ovarian cancer study of AS1404, the ASCO poster is available at www.antisoma.co.uk. The response data currently available are from 62 of 77 patients enrolled in the trial, and are based on use of RECIST (Response Evaluation Criteria In Solid Tumours), a standard means of assessing the impact of therapies on tumour growth The response rates quoted are the sum of complete and partial responses to treatment for each arm of the trial, as reported by investigators in the study. Most responses are confirmed but these preliminary findings also include a number of unconfirmed responses.

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.co.uk for further information about Antisoma.