Binding titration experiments using B16F10-FLT3 transfectants as well as the B-ALL cell lines NALM-16 and SEM—the latter displaying the highest FLT3 expression in our study—revealed that 1 μg/mL 4G8-SDIE was sufficient for saturating target antigen binding. This evidence concerns the gene FLT3 and acute lymphoblastic leukemia.