Originally developed as a MAO inhibitor to treat mood and anxiety disorders, tranylcypromine (TCP) can inhibit the activity of MAO-A and MAO-B.242,243 In addition, as an irreversible LSD1 inhibitor, TCP also inhibits cancer proliferation and invasion.244 A clinical phase I/II study investigating whether TCP could sensitize ATRA in patients with non-M3 AML or MDS in 2015 was initiated by Michael Luebbert and the University Hospital Freiburg (ClinicalTrials.gov Identifier: NCT02717884). The gene discussed is KDM1A; the disease is cancer.