NPM1 and acute myeloid leukemia: However, arsenic trioxide (As2O3) has recently shown significant efficacy in patients with acute promyelocytic leukemia (APL) and many other malignancies, such as adult T-cell leukemia/lymphoma (ATL) and NPM1 mutant acute myeloid leukemia (AML) (Kchour et al., 2009; Mathews et al., 2011; El Hajj et al., 2015).