Intermediate, where the previous K-Means clustering was also applied, but only to those compounds coming from ChEMBL (Figure ). In order for this schema to have a test set of comparable size with the others, only one data source was used. We chose MUV dataset since it was designed to be challenging, as seen in the Introduction, while data architectural design of the original DUD is not that well suited for this problem. In Figures , S4 and S5 of the Supporting Information, the proportion of actives/inactives for each target in each splitting set is depicted for random, clustering, database-based and intermediate cross-validation strategies, respectively.