Among the six KMT1A inhibitors, chaetocin significantly suppressed the cell propagation (inhibition ratio: 65%–88%, IC50 = 24.4–32.5 nM), induced apoptosis (2–5-fold), and caused G1 phase cell cycle arrest (68.9 vs 55.5%) of bladder cancer (BC) cells, without influencing normal bladder epithelial cells. Here, SUV39H1 is linked to urinary bladder cancer.