GSK-LSD1 is a potent and selective inhibitor of lysine specific demethylase 1 (LSD1). GSK-LSD1 2HCl irreversibly inhibits LSD1 with IC₅₀ value of 16 nM and is > 1000 fold selective over LSD2, MAO-A and MAO-B, which were related to FAD utilizing enzymes. GSK-LSD1 potently inhibits proliferation of varies cancer cell lines by changing gene expression patterns.