After raw data were normalized, scaled to z-scores, and summarized, we found that 321 data points (out of a total of 8960 data points representing the 2240 compounds tested at 4 concentrations) had an ISRE activity z-score $2 ( Figure 4A ). This data set represented 285 individual compounds, as some compounds had an ISRE activity z-score $2 at more than one dose. Of these 285 compounds, 64 hit compounds (2.9% of the total compound library) were selected for validation based on a combination of dose-response characteristics and inter-replicate reproducibility. This approach captured all 20 of the compounds with the highest z-scores. In support of re-purposing as a drug discovery strategy, the 64 screening hits were found in a broad range of drug classes ( Figure 4B ).