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 5i exhibited HPK1 inhibition
with an IC50 value of 0.8 nM and 101.3-fold selectivity
against GLK. Compound 5i also displayed good oral bioavailability
(F = 27–49%) in mice and beagles and favorable
metabolic stability (T1/2 > 186.4 min)
in human liver microsomes. More importantly, compound 5i 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 5i has a great potential in immunotherapy.