HSP70 Interactome‐Mediated Proteolysis Targeting Chimera (HSP70‐PROTAC) for Ferroptosis‐Driven Cancer Treatment

Abstract Targeted protein degradation (TPD) represents a transformative therapeutic paradigm that harnesses the cellular degradation machinery to pharmacologically eliminate disease‐causing proteins with aberrant expression. This work here reports the first design of an HSP70 interactome‐mediated proteolysis targeting chimera (HSP70‐PROTAC) for the degradation of the intracellular therapeutically relevant proteins via dual processes of ubiquitin‐proteasomal degradation (UPS) and chaperone‐mediated autophagy (CMA). By hijacking the highly expressed heat shock cognate protein (Hsc70) isoform complex in tumor tissues to glutathione peroxidase 4 (GPX4) protein, this work successfully develops an HSP70‐PROTAC molecule GDAz‐3 that potently and rapidly eliminates GPX4 in HT1080 cells, thereby triggering ferroptosis with high selectivity. Correspondingly, GDAz‐3 exhibits a remarkable tumor‐inhibitory effect in the HT1080 xenograft tumor mouse model without obvious toxicity. In addition, this work demonstrates the versatility of HSP70‐based PROTACs by effectively degrading additional endogenous bromodomain‐containing protein 4 (BRD4) in cancer cells. More importantly, the degradation of GPX4 mediated by GDAz‐3 occurs with comparable efficiency in CRBN/VHL‐knockdown cells and 786‐O cells intrinsically lacking VHL expression, which facilitates expanding the application scope and overcoming drug resistance of traditional PROTAC. These findings suggest that HSP70‐PROTAC is a novel and feasible strategy for the future development of TPD technology.