RGFP-966 decreases HDAC3 activity and is not cytotoxic. RGFP-966 decreases HDAC3 activity and is not cytotoxic. (A) 10 µM of RGFP-966 decreases HDAC3 activity by 65.99 ± 12.2% following 48 h of treatment with RGFP-966. All drug dilutions were done in cell culture media for final DMSO concentration 0.1% (vol/vol). (B) Following 48 h of cell incubation with RGFP-966, the drug did not cause cell death at doses up to 10 µM. ATP levels were measured using a CellTiter-Glo Luminescent Cell Viability Assay (Promega). One-way ANOVA with Tukey’s multiple-comparisons test was used to evaluate the effect of RGFP-966 on HDAC3 activity and cell toxicity. The graph represents mean ± SEM. ****P < 0.0001; ns, not significant; n = 4–5. Karolina J. Janczura et al. PNAS 2018;115:47:E11148-E11157 ©2018 by National Academy of Sciences