The LSD1 inhibitor tranylcypromine (TCP, 41) combined with all-trans-retinoic acid 37 (Fig. 3) is now in clinical trials for the treatment of adult patients with acute myeloid leukemia (AML) and myelodisplastic syndrome (MDS) (NCT02273102) and patients with relapsed or refractory AML (NCT02261779) in non-acute promyelocytic leukemia (APL) AMLs when treatment with all-trans-retinoic acid 37 is not effective. The gene discussed is KDM1A; the disease is acute promyelocytic leukemia.