A fully humanized monoclonal antibody against killer-cell immunoglobulin-like receptors (KIR), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, lirilumab binds to KIR, thereby preventing the binding of KIR ligands to KIR on natural killer (NK) cells. By blocking these inhibitory receptors, NK cells become activated and attack cancer cells leading to tumor cell death. KIR, a member of the immunoglobulin superfamily, is expressed on the surface of NK cells.