LILRB4 (ILT3)

Class

Monoclonal antibody (IgG1)

Pathway

High-affinity LILRB4 binding depletes LILRB4-positive monocytic leukemia cells via antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP)

LILRB4 (also called ILT3) is an inhibitory receptor found on cells of the myeloid lineage, including monocytes and macrophages, and is also expressed on the surface of certain leukemic blasts, particularly in monocytic subtypes of acute myeloid leukemia. Under normal physiology, LILRB4 dampens immune activation by delivering inhibitory signals that help maintain tolerance and limit excessive inflammation. In monocytic leukemias, malignant cells co-opt this receptor to suppress surrounding T cells and evade immune surveillance, while the receptor's restricted expression pattern makes it a useful marker for distinguishing tumor cells from most normal tissues. A monoclonal antibody directed against LILRB4 exploits this selective expression: by binding tightly to the receptor on leukemic cells, it flags them for destruction through two natural immune mechanisms, antibody-dependent cellular cytotoxicity, in which immune effector cells kill the antibody-coated target, and antibody-dependent cellular phagocytosis, in which those cells are engulfed and degraded by phagocytes. This dual mode of action allows for direct elimination of the malignant population without relying on chemotherapy. The approach is relevant to hematologic malignancies where monocytic differentiation and LILRB4 expression are prominent, offering a targeted alternative or complement to broader cytotoxic regimens.