The HDAC inhibitors that are being developed for cancer treatments can be divided into four chemical classes: cyclic tetrapeptides, including depsipeptide, apicidin and trapoxin; the hydroxamic acids, including suberoylanilide hydroxamic acid (SAHA), scriptaid, trichostatin A (TSA), pyroxamide and oxamflatin; short-chain fatty acids, including valproic acid (VPA), phenylbutyrate and butyrate (BT); and benzamides, such as MS-275 (21). The gene discussed is HDAC9; the disease is cancer.