PDCD1 and cancer: At least nine of these inhibitors are under investigation in phase I or phase II clinical studies involving patients with cancer (e.g., CFI-402411, NDI-101150, GRC-54276, BGB-15025, PRJ1-3024, FB-849, BB-3008, RGT-264, and BGB-26808), either as monotherapy or in combination with immunotherapy, such as programmed cell death 1/programmed cell death-ligand 1 (PD-1/PD-L1) blockade.