Distinctively, the confirmed hit compounds of two clusters, an oxadiazole scaffold and a pyrimidinone scaffold, stood out from the rest of hits as their IC50 values were in the single-digit micromolar range and the compounds displayed no apparent toxic effects on the HEK-AC1 cells after 2-hour incubation. Results from optimization of the oxadiazole scaffold have since been reported leading to the development of AC10065. The other single-digit micromolar potency scaffold was the pyrimidinone series represented by hit 1 (Figure ) and the concentrationresponse curves for against AC1 and AC8 are presented in Figure .