Positive preclinical data on Antisoma’s AS1411 presented at AACR

Washington, DC and London, UK: 4 April 2006 Cancer drug developer Antisoma plc (LSE: ASM, US OTC: ATSMY) announces that new data on its aptamer drug AS1411 will be presented today at the American Association of Cancer Research meeting. AS1411 clearly reduced tumour growth in xenograft models of both renal and lung cancers. The effects were statistically significant and seen at doses comparable to those used in clinical trial patients. These findings support Antisoma’s strategy of enrolling additional patients with renal and lung cancers into an extended phase I trial. The positive findings in renal xenografts are also consistent with earlier data from the phase I trial, which reported promising signs of anti-cancer activity among three patients with renal cancer.

Antisoma expects the further clinical development of AS1411 to have two parallel elements: an expedited programme in renal cancer and a more conventional programme in a number of other cancers. Data in the AACR presentation highlight the range of malignancies in which AS1411 has potential. The latest experiments on isolated cancer cells show effective killing of prostate as well as lung cancer cells, in addition to cells from a variety of blood cancer lines (myelomas and lymphomas).

Commenting on the findings, Antisoma’s Chief Executive Officer, Glyn Edwards, said: “The positive preclinical data presented at AACR provide strong support for AS1411 in the indications currently under clinical study and endorse the view that the drug’s potential extends to a considerable variety of other blood and solid 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.


Notes for Editors:

AS1411
Aptamers are short pieces of DNA or RNA that can fold into stable, three-dimensional structures capable of interacting with particular target proteins. AS1411 is the first aptamer to be tested as a treatment for cancer. It binds to the protein nucleolin, which is found on the surface of cancer cells. It is then internalised and has been shown to kill cancer cells from a variety of cell lines. The drug has also shown anti-cancer effects in animal models and promising signs of anti-cancer activity in a phase I study conducted at the Brown Cancer Center, Louisville, Kentucky. AS1411 was originally developed by Dr Paula Bates, Dr John Trent and Prof. Donald Miller at the University of Alabama and then at the University of Louisville. Antisoma added AS1411 to its pipeline when it acquired the Louisville-based company Aptamera Inc. in February 2005.

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. Please visit www.antisoma.com for further information about Antisoma.

Contact Information

Daniel Elger

Director of Communications

Antisoma plc

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