Discovery of a New and Selective HPK1 PROTAC for Enhancing Tumor Immunotherapy through Eliminating GLK Degradation

HPK1 is an attractive therapeutic target for tumor immunotherapy. Nevertheless, the formidable challenge selectivity over GLK and limited antitumor efficacy of HPK1 inhibitors and PROTACs impeded their developments. Here, we demonstrated that blocking GLK alone or simultaneous blocking both GLK and HPK1 could reduce immune activation through siRNA, which underscores the necessity for designing selective HPK1 degraders. Given the differences in spatial tolerance between HPK1 and GLK, we successfully obtained a degrader, designated E3, which exhibits a DC₅₀ of 3.16 nM for HPK1 and demonstrates at least a 1000-fold selectivity over GLK. Notably, E3 displayed a superior capacity for promoting immune activation. Oral administration of E3 combined with PDL-1 antibody showed significant antitumor activity. In conclusion, the availability of E3 provides a structural foundation for the development of selective HPK1 PROTACs.