Programed cell death protein 1 (PD-1) is a cell surface receptor. PD-1 and its ligand PD-L1 are crucial immune checkpoints to downregulate T cell activation, tolerance and immunopathology. Several types of cancer cells overexpress PD-L1 in order to escape from the PD-1/PD-L1 immunosurveillance mechanism.
Human PD-L1 inhibitor III is a peptide-based molecule. It binds to human PD-1 and inhibits PD-1/PD-L1 binding. This peptide, hPDL-1 inhibitor III has anchor residues (underlined), TEKDYRHGNIRMKLAYDL that influence binding of hPD-L1 to hPD-1. Developing inhibitors specifically blocking the PD-1/PD-L1 pathway has become a popular approach toward cancer treatment.