PD-1/PD-L1-IN-32 (compound A56) is a potent PD-1/PD-L1 inhibitor ( IC 50 =2.4 nM), with anticancer activity. PD-1/PD-L1-IN-32 significantly inhibits tumor growth in hPD-L1 MC38 humanized mouse model, without obvious toxicity against mouse normal ability.