HDAC inhibitors have been used for the treatmentof various formsof cancer, neurological disorders, and human immunodeficiency virus(HIV) infection.9 There are five HDAC inhibitorscurrently approved by the FDA, with a further 20 in various stagesof clinical trials (Figure 1B).10−12 However, a fundamental issue with current HDAC inhibitortechnologies is the lack of isoform or complex selectivity. This evidence concerns the gene HDAC9 and cancer.