Discovery and Optimization of Pyrazine Carboxamide AZ3246, a Selective HPK1 Inhibitor

Hematopoietic progenitor kinase 1 (HPK1) is a negative regulator of the T cell receptor signaling pathway and is therefore a target of interest for immunooncology. Nonselective HPK1 inhibitors may affect other kinase components of T cell activation, blunting the beneficial impact of enhanced T cell activity that results from HPK1 inhibition itself. Here, we report the discovery of pyrazine carboxamide HPK1 inhibitors and their optimization through structure-based drug design to afford a highly selective HPK1 inhibitor, compound 24 (AZ3246). This compound induces IL-2 secretion in T cells with an EC50 of 90 nM without inhibiting antagonistic kinases, exhibits pharmacokinetic properties consistent with oral dosing, and demonstrates antitumor activity in the EMT6 syngeneic mouse model.