HDAC9 and primary cutaneous T-cell non-Hodgkin lymphoma: FK228 (romidepsin), which received FDA approval for the treatment of CTCL in 2009, has been described to inhibit the class I HDAC members, HDAC1, 2, and 3, at nanomolar levels while being less effective against HDACs 4, 6, 7, 8, and 9 [55, 56].