A notable exception has been in the treatment of patients with acute promyelocytic leukemia (APL) with the introduction of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), drugs targeted at the specific molecular aberration causative of the disease [the PML-RARA fusion product of t(15;17) translocation, pathognomonic for the disease]. This evidence concerns the gene PML and acute promyelocytic leukemia.