A method for treating acute myeloid leukemia (AML), such as poor risk AML, by administering to a subject in need thereof an effective amount of a mitochondrial activity inhibitor, for example a class A electron transport chain (ETC) complex I inhibitor such as Mubritinib or a pharmaceutically acceptable salt thereof, is disclosed. The AML to be treated may be characterized by certain features, such as high level of expression of one or more Homeobox (HOX)-network genes, high and/or low expression of specific genes, the presence of one or more cytogenetic or molecular risk factors such as intermediate cytogenetic risk, Normal Karyotype (N?), mutated NPM1, mutated CEBPA, mutated FLT3, mutated DNMT3A, mutated TET2, mutated IDH1, mutated IDH2, mutated RUNX1, mutated WT1, mutated SRSF2, intermediate cytogenetic risk with abnormal karyotype (intern(abnK)), trisomy 8 (+8) and/or abnormal chromosome (5/7), and/or a high leukemic stem cell (LSC) frequency.