Two clinical trials investigating combination therapy with HDAC inhibitors are currently active: 1) a phase 1 trial with panobinostat and the proteasome inhibitor marizomib (NCT04341311) for children with DIPG, and 2) PNOC’s phase 1, target validation trial of the dual HDAC/PI3K inhibitor fimepinostat for children with DIPG, HGG, or medulloblastoma (NCT03893487). Here, HDAC9 is linked to medulloblastoma.