Design, synthesis, and biological evaluation of 2,4-diaminopyrimidine inhibitors of hematopoietic progenitor kinase 1

Cancer immunotherapy is an emerging anti-cancer strategy that enhances immune circulation by targeting the immune system. Among the various targets, HPK1, a member of the mammalian Ste20-like protein serine/threonine kinase family, serves as a crucial negative regulator of immune-mediated mechanisms, positioning it as a promising target for immunotherapy. Herein, based on the reported HPK1 inhibitors characterized by 2,4-diaminopyrimidine components, four series of derivatives were obtained through structural optimization methods. Compound 10c demonstrates significant inhibitory effects on HPK1 kinase, with an IC₅₀ of 0.09 nM. Additionally, it markedly inhibits the phosphorylation of the downstream adaptor protein SLP76, with an IC₅₀ of 33.74 nM, and effectively stimulates the secretion of the T cell activation marker IL-2, exhibiting an EC₅₀ of 84.24 nM. These findings suggest that compound 10c holds considerable promise for applications in immunotherapy.