Promising Phase I Data for Antisoma's AS1411 Revealed at ASCO

Antisoma Plans to Reopen Study in Renal and Lung Cancers


LONDON and ORLANDO, Fla., May 16, 2005 (PRIMEZONE) -- American Society of Clinical Oncology Meeting -- Cancer drug developer Antisoma (LSE:ASM) announces the presentation at ASCO of promising phase I data on its anti-nucleolin aptamer drug AS1411 (formerly AGRO100). Among seventeen patients with various spreading, advanced cancers unresponsive to prior therapies, seven showed stable disease for 2 months or more after treatment and one patient had a near-complete response, as detailed below. AS1411 was remarkably well tolerated, with no toxicity of any type related to drug administration in any of the patients.

There were three renal cell carcinoma patients in the study. One had stable disease for 9 months and then progressed. A second is still stable more than 10 months after receiving the drug and the third, with a large abdominal tumour that grew after removal of a cancerous kidney, has a near-complete response 10 months after treatment, with his tumour reduced in size from around 19 cm before treatment to less than 1cm in April.

In light of the encouraging findings from the phase I trial and an expanding base of preclinical data, Antisoma is planning a programme of further clinical trials covering multiple cancer indications. In order to make a rapid start in assessing AS1411 in specific cancers, Antisoma plans to reopen the phase I trial but to restrict recruitment to patients with renal and non-small cell lung cancers.

The ASCO presentation was made by the phase I study's Principal Investigator, Dr. Damian Laber, from the Brown Cancer Center at the University of Louisville, Kentucky. Speaking after the presentation, Dr. Laber said, "For a phase I trial, with very sick patients, the findings with AS1411 really are impressive. We're very keen to start treating patients again in Louisville, and are delighted that the programme is being expanded."

Antisoma's CEO Glyn Edwards said: "AS1411 has proved to be a valuable addition to our pipeline, taking us into a novel area of cancer therapy where we now have a leading position. The drug's promising phase I data provide an ideal platform for studies in specific cancers, and we look forward to findings from the first such study in renal and lung cancers."

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.

AS1411

AS1411 is the first aptamer drug to be tested for the treatment of cancer in human clinical trials. Aptamers are oligonucleotides that can fold into a stable, three-dimensional structure capable of interacting with a particular target protein. AS1411 binds with high specificity to the protein nucleolin, which is found on the surface of cancer cells. When AS1411 binds to cell-surface nucleolin, it is internalised and has been shown to kill cancer cells in a range of models. Preclinical data on AS1411 were presented at the TIDES meeting on 3rd May 2005 (press release issued 4th May 2005).

Background on Antisoma

Based in London, U.K., 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. Please visit www.Antisoma.com for further information about Antisoma.

Enquiries:

CONTACT:  Antisoma plc
          Glyn Edwards, CEO
          Daniel Elger, Director of Communications 
          +44 (0)7909 915068 

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

          De Facto Communications (ex-U.K. enquiries)
          Richard Anderson 
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