FLT3, CD3

Class

Bispecific T-cell engaging antibody

FLT3 (also called CD135) is a cell-surface receptor found on early blood-forming (myeloid) progenitor cells and, importantly, on the malignant blasts of most cases of acute myeloid leukemia (AML). CD3 is a signaling component of the T-cell receptor complex present on essentially all mature T cells, the immune system's cytotoxic effector cells. A bispecific T-cell engaging antibody is built with two binding arms: one that grips FLT3 on the leukemic cell and one that grips CD3 on a nearby T cell. By physically bridging the two, the molecule forces an artificial immune synapse, activating the T cell and directing its killing machinery at the FLT3-positive cell irrespective of the T cell's own native antigen specificity. This strategy is attractive in AML because it can eliminate leukemic cells whether or not they carry specific driver mutations, broadening applicability beyond genotype-restricted small-molecule kinase inhibitors. The general rationale for this class of mechanism is to co-opt the patient's own T-cell compartment as a targeted cytotoxic weapon against a tumor-associated surface marker, a strategy used across several hematologic malignancies and, increasingly, solid tumors where a sufficiently tumor-restricted surface antigen exists.