Vorinostat (SAHA) and quisinostat were included as reference inhibitors. As expected from the parasite growth inhibition assays, SAHA exhibited lower inhibition (54%) of the plasmodial target than quisinostat (72%) and 18b (76%). Since 18b showed high inhibitory activity against PfHDAC1 at 1 µM, we further characterized the compound by determining the IC50 value in concentration-response experiments. Vorinostat was included as a reference inhibitor. Figure shows the concentration-response curve of 18b and Figure shows the curve for SAHA. For 18b, an IC50 of 37 nM was calculated by non-linear regression, which outperformed again the inhibitory potency of SAHA (IC50 = 79 nM).