Multicenter Phase II Trial of the Heat Shock Protein 90 Inhibitor, Retaspimycin Hydrochloride (IPI-504), in Patients With Castration-resistant Prostate Cancer

Heat shock protein 90 inhibition with IPI-504 administered as a single agent had a minimal effect on the PSA level or tumor burden and was associated with unacceptable toxicity in several patients. Therefore, additional evaluation in CRPC patients is not warranted. IPI-504 is being investigated at less-intensive doses and schedules in other tumor types.