Discovery of Macrocycle-Based HPK1 Inhibitors for T-Cell-Based Immunotherapy.

Hematopoietic progenitor kinase 1 (HPK1) is a negative regulator of T-cell activation, and targeting HPK1 is considered a promising strategy for improving responses to antitumor immune therapies. The biggest challenge of HPK1 inhibitor design is to achieve a higher selectivity to GLK, an HPK1 homology protein as a positive regulator of T-cell activation. Herein, we report the design of a series of macrocycle-based HPK1 inhibitors via a conformational constraint strategy. The identified candidate compound exhibited HPK1 inhibition with an IC value of 0.8 nM and 101.3-fold selectivity against GLK. Compound also displayed good oral bioavailability ( = 27-49%) in mice and beagles and favorable metabolic stability ( > 186.4 min) in human liver microsomes. More importantly, compound demonstrated a clear synergistic effect with anti-PD-1 in both MC38 (MSI) and CT26 (MSS) syngeneic tumor mouse models. These results showed that compound i has a great potential in immunotherapy.