The selective BCL-2 inhibitor, ABT199 (venetoclax), which has shown promise in clinical trials against chronic lymphocytic leukemia and other hematopoietic malignancies (227–229), was effective both in vitro and in xenograft models against MLL-r leukemias in combination with cytotoxic chemotherapies and with a DOT1L inhibitor. Here, KMT2A is linked to leukemia.