Setting aside romidepsin/depsipeptide/FK228, whose selectivity as a class I-selective HDAC inhibitor is called into question [31], among known class I-selective HDAC inhibitors, entinostat (MS-275) has shown growth inhibitory activity against glioma cells so far, albeit in combination with chemotherapeutic agents or molecular targeting drugs [32,33]. Here, HDAC9 is linked to central nervous system cancer.