HDAC-IN-37 is a potent HDAC inhibitor with IC 50 s of 0.0551 μM, 1.24 μM, 0.948 μM and 34.2 μM for HDAC1 , HDAC3 , HDAC8 and HDAC6 , respectively. HDAC-IN-37 induces histone acetylation in a slow-off manner. HDAC-IN-37 prevents cell transition from G1 phase to S phase and induces early cell apoptosis.