SAR3419 (coltuximab ravtansine), an antibody-drug conjugate of maytansinoid DM4 and anti-CD19 antibody, has proven its efficacy preclinically in B-ALL and infant mixed-lineage leukemia (MLL) immune-deficient (NOD/SCID) mice xenografts. The gene discussed is CD19; the disease is precursor B-cell acute lymphoblastic leukemia.