HDAC9 and plasma cell myeloma: Drugs approved for clinical use for multiple myeloma and mantle cell lymphoma based upon this mechanism of action include proteasome inhibitors (bortezomib/carfilzomib) [64], E3-ubiquitin ligase inhibitors (thalidomide/lenalidomide) [65], and HDAC inhibitor (panobinostat) [66,67].