The overexpression of Hsp90 and its higher affinity for ATP in cancer cells provide a basis for selective targeting of malignantly transformed cells.10,11 Unfortunately, the first discovered Hsp90 inhibitor, geldanamycin,12 was too unstable and potentially toxic for clinical use.13,14 However, optimized analogs like 17-AAG and 17-DMAG have entered clinical trials. The gene discussed is HSP90AB1; the disease is cancer.