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04/02/2005

Antisoma completes acquisition of Aptamera

London, UK, and Louisville, KY, USA: 4 February 2005 - Further to the announcement made yesterday, Antisoma plc (LSE:ASM) announces the completion of its acquisition of Aptamera Inc. This follows today’s admission to the Official List and to trading on the London Stock Exchange of the shares issued to Aptamera’s shareholders in conjunction with the transaction.

With completion of the acquisition, Dr Mark Rogers has been appointed a non-executive director of Antisoma. The following are Dr Rogers’ disclosable interests under Section 16.4 of the UKLA Listing Rules:

• Current directorships of public companies: Cardiome Pharma Corp (Chairman)
• Public company directorships in past 5 years: Adherex Technologies Inc, Genta Inc.
• Beneficial interest in ordinary Antisoma shares: 6,603,475 (1.99% of issued ordinary shares following the issue of new shares to Aptamera’s shareholders)

Further details about Dr Rogers were provided in an RNS statement released on 10 January.

Enquiries:

Glyn Edwards, CEO, +44 (0)20 8799 8244
Antisoma plc

Neil Mackison, +44 (0)20 7767 1000
ING Corporate Finance

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

Richard Anderson, +44 (0)20 7940 1000
De Facto Communications (mainland European enquiries)

Jonathan Birt, +1 917 941 7341
Financial Dynamics (United States Enquiries)

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 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 November 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.