LSD1-IN-38 (Compound 23e) is a reversible, orally active inhibitor for lysine specific demethylase 1 ( LSD1 ) with an IC 50 of 1.2 nM. LSD1-IN-38 inhibits the proliferation of cancer cells MV4-11, Kasumi-1 and NCI-H526, with IC 50 of 5, 4 and 11 nM, respectively. LSD1-IN-38 activates CD86 expression with an EC 50 of 0.034 μM, and induces differentiation in MV4−11 cell. LSD1-IN-38 exhibits antitumor efficacy in mouse models.