GSK-LSD1 is a highly potent, specific and irreversible inhibitor of Lysine Specific Demethylase-1 (LSD1). It inhibits LSD1 in biochemical assay with an IC50 ~16 nM, and is > 1000 fold selective over other closely related FAD utilizing enzymes (i.e. LSD2, MAO-A, MAO-B). GSK-LSD1 induces gene expression changes in cancer cell lines (average EC50 < 5 nM) and inhibits cancer cell line growth (average EC50 < 5 nM).