Geldanamycin is a benzoquinone ansamycin antibiotic that binds to Hsp90 (Heat Shock Protein 90) and inhibits its function. HSP90 client proteins play important roles in the regulation of the cell cycle, cell growth, cell survival, apoptosis, angiogenesis and oncogenesis. Hsp90-geldanamycin complex. PDB 1yet Geldanamycin induces the degradation of proteins that are mutated in tumor cells such as v-Src, Bcr-Abl and p53 preferentially over their normal cellular counterparts. This effect is mediated via HSP90. Despite its potent antitumor potential, geldanamycin presents several major drawbacks as a drug candidate (namely, hepatotoxicity) that have led to the development of geldanamycin analogues.