Researchers tested to see if arsenic trioxide (ATO) was effective in combination with all-trans retinoic acid (ATRA) in in both the mouse model of acute myeloid leukemia (AML) and in human AML cells in the lab, and determined that the combination proved 'powerfully and exquisitely effective' against a subset of AML. The combo could serve as the foothold researchers need to overcome resistance to therapy — a common challenge in treating AML.