HDAC9 and diffuse large B-cell lymphoma: Three schemes for designing HDAC inhibitors include drug design based on zinc-binding groups, selective inhibitors targeting different subtypes of HDAC, and dual mechanism or multitarget HDAC inhibitors.1340 Many HDAC inhibitors have been synthesized based on these schemes, with more than ten entering clinical trials.1341 For example, abexinostat, a potent oral pan-HDAC inhibitor designed based on ZBG, is currently undergoing phase II clinical trials for recurrent/refractory DLBCL and follicular lymphoma as a single-drug treatment (NCT03936153 and NCT03934567).