HDAC9 and cancer: This analysis revealed two compounds, mocetinostat [27], [28], [29] (IC50 = 2.76 ± 1.98 μM; SI >100) and entinostat [30], [31] (IC50 = 7.11 ± 6.62 μM; SI >100), both class I HDAC inhibitors and in clinical trials, as pan-killers of all three cancer cell groups (Figures 2A, 3, and Table 3).