FLT3 and acute myeloid leukemia: Along the same lines, naked monoclonal antibodies have also been developed for the specific treatment of AML by targeting several antigens expressed on blasts, including, in particular, CD33 (refs. 49, 50), CD123 (refs. 12, 13) and, more anecdotally, CD135 (FLT-3) and CXCR4 (ref. 51).