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

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.