First generation hydroxamic acid based HDAC inhibitors and one cyclic depsipeptide have been approved by the FDA for the treatment of hematological malignancies (cutaneous T-cell lymphoma, peripheral T-cell lymphoma, multiple myeloma), including Vorinostat (a.k.a. SAHA; hydroxamic acid), Belinostat (PXD-101; hydroxamic acid), Panobinostat (LBH589; hydroxamic acid) and Romidepsin (FK-228; cyclic depsipeptide). This evidence concerns the gene HDAC9 and plasma cell myeloma.