Astex Therapeutics Announces New Drug Discovery Alliance with Janssen Pharmaceutica N.V.

Cambridge, UK 9th June, 2008. Astex Therapeutics Limited (“Astex”) today announced that Astex and Janssen Pharmaceutica have entered into a research alliance focused on the research, development and commercialisation of novel drugs for the treatment of cancer. The new agreement grants Janssen Pharmaceutica a worldwide exclusive license to compounds arising from Astex’s novel FGFR inhibitor programme, and the parties are also to establish a new drug discovery alliance focused on the identification of novel inhibitors against a further two cancer drug targets. The highly selective FGFR inhibitors were discovered using Astex’s proprietary fragment-based drug discovery platform, Pyramid™, which will also be employed to drive the new drug discovery programme. Since 2004 Astex has used Pyramid™ to generate one new cancer drug candidate for clinical development each year.

Under the terms of the agreement, Ortho Biotech Research & Development, the research and development arm of Janssen Pharmaceutica, will be responsible for completing all of the preclinical and clinical development of all products arising from the collaboration and for their commercialisation globally. The agreement also grants Astex an option to co-commercialise FGFR products developed under the collaboration in the USA.

The agreement provides for an upfront payment and equity investment in Astex, plus committed research funding, totalling $37.4 million over a two year period, as well as downstream development and regulatory milestones relating to all three programmes. Astex will also receive tiered, double digit, royalties on sales of FGFR inhibitor products discovered and developed under the collaboration and additional royalties on new products generated under the other research programmes. Total payments under the collaboration, excluding royalties, could be worth over $500 million to Astex, assuming one product from each programme is successfully commercialised in all territories.

Harren Jhoti, Chief Executive Officer of Astex Therapeutics, said, “This is another landmark agreement for Astex, and we are delighted to be working with one of the global leaders in oncology drug development on this discovery alliance. This partnership is another testament to Astex’s position as the leader in fragment-based drug discovery and the productivity generated by our platform.”

Contacts Astex Therapeutics Limited Romaine Miles Corporate Communications Email: r.miles@astex-therapeutics.com Tel: +44 (0) 1223 226200 Web: www.astex-therapeutics.com

About Astex

Astex is a UK-based biotechnology company that discovers and develops novel small molecule therapeutics. Using its pioneering fragment-based drug discovery platform Pyramid™, Astex has built a pipeline of five molecularly-targeted oncology drugs, of which three are currently being tested in clinical trials and two are in pre-clinical development.

In addition to its proprietary research programmes, Astex’s productivity in lead discovery has been endorsed through numerous partnerships with major pharmaceutical companies, including Novartis, AstraZeneca, Bayer-Schering and Boehringer Ingelheim.

For further information on Astex please visit the Company’s website at www.astex-therapeutics.com