HDAC6 and plasma cell myeloma: ACY-241, a second-generation HDAC6 selective inhibitor, has been studied in combination with various agents in multiple cancers such as paclitaxel in solid tumor models; anti-PD-L1, pomalidomide, and daratumumab in multiple myeloma (MM); JQ1 in head and neck cancer; nivolumab in advanced non-small cell lung cancer; and erlotinib in pancreatic cancer [18,19,20,21,22,23,55].