AT13387 is a potent and selective non-natural product inhibitor of Hsp90 derived from the Company’s Pyramid^TM platform. In tumour cells Hsp90 acts as a "molecular chaperone" stabilising and preventing the breakdown of key cancer forming (oncogenic) proteins. These so-called client proteins and their association with different tumour types include HER2 (the target for Herceptin^® in breast cancer), the androgen receptor (the target for hormone therapy in prostate cancer), mutant B-raf (melanoma), c-kit (the target for Gleevec^® in gastro-intestinal tumours) and mutant EGFr (the target for Tarceva^® and Iressa^® in the treatment of non-small cell lung cancers). The functional role of Hsp90 means that AT13387 has the potential to control the proliferation of multiple solid tumours and haematological malignancies where uncontrolled cell growth is dependent on interaction between Hsp90 and its client proteins. These include tumour types which have become resistant to initial therapy.

Astex announced that it had received IND approval from the FDA for AT13387 in February 2008. The compound is now in Phase I clinical trials.

Patents filed.

Astex is currently evaluating partnering options with respect to its HSP90 inhibitors which are wholly owned assets of Astex.