Press releases 17 /05 /2010 Antisoma Interim Management Statement London, UK, and Cambridge, MA: 17 May 2010 – Cancer drug developer Antisoma plc (LSE: ASM; USOTC: ATSMY) today publishes its Interim Management Statement for the period from 1 January to 16 May 2010. Antisoma’s CEO, Glyn Edwards, said: “We have two promising cancer drugs, AS1413 and AS1411, both of which we expect to report key trial data during the next year. Having taken measures to reduce our costs, we expect our cash resources to take us well past these trial results.” Joint Chairman and CEO’s statement We are determined to bounce back strongly from the recent disappointment over ASA404 , centred on the termination in March of a phase III trial evaluating the drug as a first-line treatment for lung cancer. We recognise that ASA404 was considered the Company’s most significant asset, but we are confident that Antisoma’s strategy of investment in a diversified portfolio of products remains sound. We have had to make tough decisions in light of the ASA404 result, but believe that we have the product assets, people and financial resources to build value for the future. AS1413 – rapid recruitment continues in phase III trial AS1413 is a novel chemotherapy treatment that we are testing in a large, multi-country, randomised phase III trial in patients with secondary acute myeloid leukaemia (secondary AML). The trial, known as ACCEDE, has now recruited over 75 % of its target of 450 patients, putting us on course to complete enrolment this calendar year. Following collection and processing of data, we expect to announce results of the study during the first half of 2011. There is interest from potential licensing partners for AS1413. We have decided to take a pragmatic stance to realising the value of this drug, and have therefore widened our partnering discussions to include US rights, which we had previously planned to retain. However, we will only strike a deal ahead of the phase III data if the terms are sufficiently favourable. We believe that AS1413 could ultimately find application in a number of blood cancer settings, with potential sales running to hundreds of millions of dollars annually. A presentation at the American Association of Cancer Research (AACR) Annual Meeting during April reinforced the differentiation of AS1413 from currently available leukaemia treatments and its potential to provide unique benefits for patients. Three presentations with relevance to AS1413 will be made at the American Society of Clinical Oncology (ASCO) Annual Meeting in June; abstracts will be available on the ASCO website ( www.asco.org ) from 20 May. AS1411 – phase IIb trial now underway AS1411 is the most advanced aptamer in trials for cancer. It is now in a 90- patient phase IIb study in patients with AML. This trial follows an earlier randomised phase II trial in AML, which reported positive results at the 2009 ASCO meeting: in that study, two different doses of AS1411 in combination with cytarabine chemotherapy produced response rates of around 20 %, whereas the response rate in patients receiving chemotherapy alone was 5 %. Addition of AS1411 to chemotherapy was not associated with any significant additional side-effects. Headline data from the phase IIb study are expected in the first half of next year. Recent and forthcoming conference presentations highlight the broad potential of AS1411. Non-clinical data presented at AACR in April showed activity in a model of colorectal cancer and positive findings when AS1411 was combined with a number of approved treatments for blood cancers. At the ASCO meeting we will have three presentations on AS1411 , including updated findings from the first phase II clinical trial in AML and data from a phase II clinical trial in renal cancer. DCAM auto-immune programme progressing towards partnering We have an important pre-clinical programme in auto-immune diseases. This comprises a series of molecules collectively known as DCAMs (dendritic cell auto-immune modulators). They are highly specific, small-molecule inhibitors of wild-type Flt3 , and are designed for oral treatment of various auto-immune conditions. Positive results have already been achieved in animal models of inflammatory bowel disease and rheumatoid arthritis, and we are now working towards establishing a licensing partnership for further development of the programme. Cash conservation measures enacted We are no longer anticipating further revenues from the ASA404 programme, and have therefore taken steps to reduce our cash utilisation and ensure that our funds take us comfortably through key clinical data on AS1413 and AS1411. We announced on 29 March that our unaudited cash position as of the end of February 2010 was GBP 45.1 million. Board and management changes Regrettably, we have had to restructure the business and make headcount reductions as part of our effort to conserve cash resources. As part of the restructuring, our former Chief Operating Officer, Dr Ursula Ney, has left the Company and the Antisoma Board. Ursula made a very significant contribution to the development of Antisoma, and we wish her well with future ventures. Two other members of the Senior Management Team, Julio Gagne and Kevin Kissane, have also left the Company, and our total headcount has now been reduced to around seventy-five. Outlook We look forward to a number of important clinical milestones in the near term, notably phase III data on AS1413 and phase IIb data on AS1411 , both of which we expect during the next year. Enquiries: Glyn Edwards, CEO Daniel Elger, VP, Marketing & Communications + 44 (0) 7909 915068 Antisoma plc Mark Court/Lisa Baderoon/Catherine Breen + 44 (0)20 7466 5000 Buchanan Communications Seth Lewis + 1 617 583 1308 The Trout Group |