Chemical structures of molecules in the training and test mixtures were standardized and curated following our canonical data curation practices using ChemAxon Standardizer version 20.9 . Briefly, salts and solvents were stripped from all compounds followed by removal of counterions, large organic compounds (Da ≥ 2000), mixtures, and inorganic compounds. Specific chemotypes such as aromatic, nitro groups, sulfo groups, tautomers, and protonation state were standardized using ChemAxon Standardizer software ().