Combinatorial efficacy of ACY738 and ibrutinib in CLL cells in vitro. (A) CellTiter-Blue assay was performed to detect cell kill synergy in CLL cell lines treated with ACY738 and ibrutinib. (B) CellTiter-Blue assay was performed to detect cell kill in CLL patient peripheral B cells with unmutated or mutated IGVH status after 48 hours of indicated treatments (n = 8 patients per group). All error bars correspond to standard deviations. *P < .05, **P < .005.