CAY10747 is an inhibitor of the protein-protein interaction between heat shock protein 90 (Hsp90) and cell division cycle 37 (Cdc37) and a derivative of celastrol .1It decreases protein levels of the Hsp90-Cdc37 complex and the Hsp90-Cdc37 clients phosphorylated Akt and Cdk4 in A549 cells when used at a concentration of 5 μM. CAY10747 inhibits proliferation of A549, MCF-7, HOS, and HepG2 cells (IC50s = 0.41, 0.64, 0.9, and 0.94 μM, respectively) and induces apoptosis in A549 cells.