In this work, a series of potent LSD1 inhibitors were synthesized and found to have very potent activity against proliferation of MLL-rearranged leukemia cells MV4-11 and Molm-13 with EC50 values of 10–320 nM, while these compounds had no or considerably weakened activity against proliferation of several other leukemia and solid tumor cells. The gene discussed is KMT2A; the disease is leukemia.