HPK1-IN-22 (compound ZYF0033) is a hematopoietic progenitor kinase 1 (HPK1) inhibitor with an IC50 less than 10 nM based on the phosphorylation inhibition of MBP protein. HPK1-IN-22 decreases the phosphorylation of SLP76 (serine 376). HPK1-IN-22 promotes anticancer immune responses.HPK1-IN-22 inhibits tumor growth and caused increases intratumoral infiltration of DCs, NK cells, and CD107a+CD8+ T cells but decreased infiltration of regulatory T cells, PD-1+CD8+ T cells, TIM-3+CD8+ T cells, and LAG3+CD8+ T cells in the 4T-1 syngeneic mouse model.