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. Here, HDAC6 is linked to AL amyloidosis.