BRD 4354 is a moderately potent inhibitor of HDAC5 and HDAC9, with BRD4354 having half-maximum inhibitory concentrations (IC50) of 0.85 μM and 1.88 μM, respectively. BRD 4354 also inhibits HDACs 4, 6, 7, and 8 at higher concentrations (3.88-13.8 μM) but demonstrates less of an inhibitory effect on other class I HDACs 1, 2, and 3 (IC50>40 μM) .