HDAC9 and mature T-cell and NK-cell non-Hodgkin lymphoma: Treatment options for relapsed or refractory PTCL include alemtuzumab (Campath), bortezomib (Velcade), gemcitabine, dose-adjusted EPOCH, or novel agents such as pralatrexate (Folotyn) and romidepsin (Istodax)—the first histone deacetylase (HDAC) inhibitor (class I selective) approved for the treatment of PTCL (Celgene, 2014; NCCN, 2015).