Astex Therapeutics Updates on AT13387, its HSP90 Inhibitor, and AT9283, its Multi-Targeted Kinase Inhibitor at the EORTC-NCI-AACR Cancer Conference

Cambridge, UK 14th October, 2008. Astex Therapeutics Limited, the world’s leading fragment-based drug discovery company, today announced that it is to present key findings on two of its wholly owned clinical stage anti-cancer compounds and on one of its earlier stage drug discovery programmes at the 20th EORTC-NCI-AACR1 symposium on “Molecular Targets and Cancer Therapeutics” to be held in Geneva, Switzerland, 21-24 October 2008. Astex’s scientists will present further data on AT13387, the Company’s novel small molecule inhibitor of heat shock protein 90 (HSP90). AT13387, which has options for oral delivery, is currently being administered as an intravenous formulation in a Phase I study in cancer patients with solid tumours at three leading cancer centres in the USA. AT13387 is the third product derived from Astex’s PyramidTM fragment chemistry platform to enter human clinical trials.

Astex will also present the first disclosure of the full chemical structure of AT9283, its multi-targeted kinase inhibitor. AT9283 is currently being tested in multiple Phase I and Phase I/IIa human clinical trials for the treatment of a variety of solid tumours and haematological malignancies. Early evidence of clinical activity has been observed in patients treated with AT9283.

The Company will also present data on its selective JAK2 inhibitor programme, which is targeting the treatment of a number of myeloproliferative diseases. The selective JAK2 inhibitor programme is designed to complement the JAK2 inhibitory activity already observed in myelofibrosis patients treated with AT9283.

1European Organisation for Research and Treatment of Cancer - National Cancer Institute - American Association for Cancer Research

Contacts Jeremy Carmichael, PhD Director of Business Development

Astex Therapeutics Ltd 436 Cambridge Science Park Milton Road, Cambridge CB4 0QA, UK

Tel: +44(0)1223 226289 Fax: +44(0)1223 226201 j.carmichael@astex-therapeutics.com www.astex-therapeutics.com