The development of new methods to treat cancer is greatly needed. The Hsp90 protein folding machinery has been the target of significant interest for the development of anti-cancer agents. However, Hsp90 is responsible for the folding of ~300 protein folding substrates, which may lead to undesired on-target toxicity and may be responsible for many of the Hsp90-targeted drugs that have failed in clinical trials. Through a structure-based approach, an isoform-selective inhibitor of Hsp90 has been identified and shown to exhibit good selectivity and affinity against particular cancers. Consequently, the goal of this application is to optimize this new inhibitory scaffold for great affinity/efficacy, to evaluate the role of a specific Hsp90 isoform in cancer, and to validate this isoform as a target for the treatment of bladder cancer.