Synergism of combination of talazoparib and romidepsin in vitro. Isoblogram analysis of the effect of fixed molar ration combinations of talazoparib with vorinostat (A), romidepsin (B), bexarotene (C), methotrexate (D), pralatrexate (E), and bortezomib (F) during 24 hours of treatment, assessed by XTT assay. The diagonal line indicates equipotent drug combinations that results in 50% effect level if effects are additive. The red dot represents the real-life result of the drug combination. If the red dot falls beneath the line, it represents synergism; if it falls above the line, it represents antagonism. Combination index (CI) is a numeric measure of synergy. A combination index of 0.30 to 0.70 indicates synergism; 0.70 to 0.84 indicates moderate synergism; 0.85 to 0.90 indicates slight synergism; 0.90 to 1.10 indicates nearly additive effects; and >1.00 indicates antagonism.