CD274 and neoplasm: Programmed death protein-1 (PD-1)/programmed death ligand-1 (PD-L1) blockade has revolutionized the treatment of cancer1; however, although several tumor types are responsive to PD-1-/PD-L1-targeted monotherapy, response rates are low in multiple tumor types and many patients that do respond subsequently acquire resistance.2-8 The discovery of novel immune checkpoints in addition to PD-1/PD-L1 has prompted interest in investigating whether agents designed to inhibit these additional checkpoints as single agents or in combination might address the unmet need for enhanced antitumor effects.8-10