LSD1-C76 is the most potent and selective Lysine Specific Demethylase-1 (LSD1) inhibitor reported to date. It inhibits LSD1 with an IC50 ~5 nM, but not monoamine oxidase proteins MAO-A and MAO-B (>5 μM). As LSD1 plays an important role in the epigenetic control of gene expression in normal development and cancer progression, LSD1-C76 serves as a very useful chemical probe to study the target biology.