HDAC9 and hematopoietic and lymphoid cell neoplasm: To date, the following four HDAC inhibitors have been approved by the FDA for treatment of hematologic cancers: vorinostat, romidepsin, belinostat, and panobinostat (West and Johnstone, 2014; Shi et al., 2015; Manal et al., 2016; Yoon and Eom, 2016).