Definition

A humanized, immunoglobulin G1 (IgG1) bispecific antibody directed against the human negative immunoregulatory checkpoint receptors programmed cell death protein 1 (PD-1; PD1; PDCD1; CD279; programmed death 1) and lymphocyte activation gene 3 protein (LAG-3; LAG3; CD223), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-PD-1/LAG-3 bispecific antibody AK129 targets and binds to both PD-1 and LAG-3 expressed on T cells, thereby blocking the interaction of PD-1 to its ligand programmed cell death-ligand 1 (PD-L1; cluster of differentiation 274; CD274) and of LAG-3 to its ligand major histocompatibility complex II (MHCII). This inhibits the PD-1- and LAG-3-mediated downregulation of T-cell activation and proliferation and abrogates downstream immune suppression. This may lead to a cytotoxic T-lymphocyte (CTL)-mediated immune response against tumor cells. PD-1 and LAG-3 play key roles in suppressing T-cell activation and proliferation and promote tumor immune escape.