Previously, we developed novel amide-bearing hydroxamic acid derivatives as class-selective HDAC inhibitors termed SL142 and SL325 (Fig. 1A) and reported that these small molecules show more significant HDAC1, HDAC4 and HDAC6 inhibitory activity in human prostate cancer cells LNCaP than SAHA [17]. The gene discussed is HDAC9; the disease is prostate cancer.