A cell-permeable p-tolylbenzamide and a Histone Deacetylase (HDAC) Inhibitor IV (Cat. No. 382170) analog that acts as a selective inhibitor against class I HDAC1/2/3 (IC₅₀ = 0.15/0.76/0.37 µM with 15/30/180 min preincubation), while exhibiting much lower acitivity against class I HDAC8 (IC₅₀ ≥ 5µM with 3 h preincubation) and no activity against class II HDAC4/5/7 even at concentrations as high as 180µM. Although the mode of inhibition is mechanistically competitive and reversible, due to the slow- and tight-binding nature, long preincubation is often required for effective in vitro enzyme inhibition, while 106-induced cellular H3 hyperacetylation is shown to persist for more than 6 hours after inhibitor removal by washing in GM15850 culture. 106 is reported to be less cytotoxic than TSA (Cat. No. 647925), MS-275, and SAHA (EC₅₀ = 6.3, 0.328, 0.768, and 1.5 µM, respectively, in GM15850 killing).