Data Sets. Our primary source of SAR data was ChEMBL 27, we collected all the quantitative compound-protein associations from single protein assays, related to the 136 epigenetic targets identified in our previous work (biological activity reported as IC 50 , EC 50 , K i or K d ). In the context of each target, compounds were labeled as "active" when they had unequivocally assigned activities lower than or equal to 10 µM, and as "inactive" in the opposite case. Compounds whose label could not be unequivocally assigned (e.g., activity < 100 µM or activity > 1 µM) were removed from the data set. The remaining compounds were curated using the open-source cheminformatics toolkit RDKit, version 2020.03.1 and the functions Standardizer, LargestFragmentChoser, Uncharger, Reionizer and