A monoclonal antibody directed against the immune inhibitory receptor leukocyte immunoglobulin-like receptor B4 (LILRB4), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-LILRB4 monoclonal antibody IO-202 targets, binds to and inhibits LILRB4 and its downstream signaling pathways. This may restore immune function through the activation of T-cells and T-cell-mediated immune responses against tumor cells, and inhibit tumor infiltration. LILRB4, an immune inhibitory receptor normally expressed on monocytic cells and highly expressed on monocytic acute myeloid leukemia (AML) cells, functions as an immune checkpoint that negatively regulates T-cell activation as its extracellular domain inhibits T-cell activity. It plays an important role in tumor infiltration in leukemias through multiple signaling pathways.