 Increasing doses of AT13387 will be administered to groups of 3 to 6 patients at each dose level. The pharmacokinetic profile of AT13387 following a one hour intravenous infusion will be determined and the effect of AT13387 on predefined biomarkers in blood plasma and circulating white blood cells will be established. Patients will be closely monitored for the development of side effects which would preclude further dose escalation. 