FLT3 and acute lymphoblastic leukemia: In conclusion, the analyses reported in this study regarding the efficacy of 4G8-SDIE in B-ALL, together with the available data on the favorable safety profile upon application of Fc-optimized FLT3 mAb to AML patients, in our view clearly indicate that 4G8-SDIE constitutes a promising immunotherapeutic compound for treatment of B-ALL.