Discovery of Novel Celastrol Derivatives as Hsp90–Cdc37 Interaction Disruptors with Antitumor Activity

To develop novel and efficient heat shock protein 90–cell division cycle 37 (Hsp90–Cdc37) interaction disruptors, several lipophilic fragments were introduced into celastrol (CEL) to synthesize 48 new CEL derivatives. Among all the target compounds, 41 was screened with superior antiproliferative activity on related cancer cells (IC₅₀: 0.41–0.94 μM) and 41 could decrease the level of the Hsp90–Cdc37 complex in A549 cells. The capability to disrupt the Hsp90–Cdc37 interaction was stronger than that of CEL. Furthermore, pull-down assay, UV assay, and molecular docking analysis all showed that 41 might disrupt the interaction of the Hsp90–Cdc37 complex by preferentially binding to Cdc37 in cancer cells. Further studies showed that 41 could significantly regulate the levels of Hsp90–Cdc37 clients, thereby inducing the apoptosis of cancer cells. Together, 41 is a novel Hsp90–Cdc37 disruptor by binding to Cdc37 (hydrogen bond and/or covalent bond). Our results may provide reference for the discovery of effective Hsp90–Cdc37 disruptors.