Stable disease for four years in metastatic malignant melanoma treated with the heat shock protein inhibitor 17-AAG

Heat shock proteins, including HSP90, contribute to the stabilization of a number of key molecules implicated in proliferative pathways in cancer. Geldanamycin and related compounds are competitive inhibitors of HSP90 at the N-terminal ATP binding site. The geldanamycin derivative 17-allylamino, 17-demethoxygeldanamycin (17-AAG) was the first HSP90 inhibitor to enter clinical development. Here we describe a patient with metastatic malignant melanoma treated with 17-AAG. She enjoyed a period of stable disease for a period of 49 months on treatment. Prolonged disease stabilization may prove to be a clinically meaningful outcome for many molecularly targeted agents and the design of phase II studies of these novel therapies needs to consider the use of progression-free survival as a valid endpoint.