HDAC6 and cancer: Combinations of HDACi, such as ACY-241 (a moderately selective HDAC6 inhibitor) or Entinostat (a class I inhibitor) with anti PD-1/PD-L1 antibodies have been tested in several clinical trials to treat various cancers (e.g. clinical trial reference: NCT02635061, NCT02915523, NCT02697630) (22).