HDAC6 and glioblastoma: There is an increasing number of reports of small molecule inhibitors of HDAC6 in development; some of these inhibitors (e.g., ACY-738, ACY-1083) have been shown to cross the blood–brain barrier [13,14], while others enhance the effects of TMZ and irradiation therapy in GBM cells in vitro [2,5,6,7,8,15,16].