BMS-1 is an inhibitor of the PD-1/PD-L1 protein/protein interaction (IC₅₀ between 6 and 100 nM)^[1][2]. IC50 & Target: PD1-PDL1^[1] In Vitro: Since PD-1 mediated the exhaustion of natural killer (NK) cell by binding to its ligand PD-L1, BMS-1 (PD-1/PD-L1 inhibitor 1) (1 μM, 3 days) is used to disturb the interaction between PD-1 and PD-L1. Dexamethasone induced increase of PD-1 expression and decrease of cytotoxicity of the co-cultured NK92 cells are reversed by BMS-1^[1]. BMS-1, a small-molecule immune checkpoint inhibitor of PD-1/PD-L1, can be used as a therapeutic strategy for tumor immunotherapy^[2]. In Vivo: BMS-1 (500 μg/mL; 100 μL; i.p.) significantly slows down tumor growth and prolongs the survival rates in BALB/c mice^[3].