An HDAC inhibitor that preferentially inhibits HDAC2 (IC50 = 30 nM) and HDAC3 (IC50 = 16 nM) over HDAC1, 4, 6, 7, and 8 (IC50s = 4.8, 5, >10, 4.1, and >10 μM, respectively). At 0.1-0.4 μM, it induces differentiation and promotes apoptosis of acute myeloid leukemic cell lines U937, HL60, and Kasumi-1.