HDAC6 and plasma cell myeloma: The lack of activity may be related to pharmacokinetics; the clinical HDAC6 candidate ricolinostat (ACY-1215) was recently reported to lack sufficient serum concentration to directly induce anti-multiple myeloma activity in vivo.17 However, at the cellular level, the HDAC6 inhibitor HPOB, while possessing potent HDAC6 deacetylase activity, does not modulate autophagy.17,18