Belinostat (PXD-101) (approved for therapy of peripheral T cell lymphoma (PTCL)), panobinostat (LBH589) (approved for therapy of multiple myeloma) and the compounds recently tested in clinical studies, i.e., givinostat (ITF2357), resminostat (4SC201), abexinostat (PCI24781) and quisinostat (JNJ-26481585), are the pan-HDAC inhibitors. Here, HDAC9 is linked to plasma cell myeloma.