Molecule pre-processing. The molecular structures were standardized with the MOE "wash" procedure (MOE v.2018.01, default settings) before computing molecular descriptors and performing target prediction. As in our previous study, prior to LSTM training, molecular structures were encoded as canonical SMILES 52 strings using the RDKit package (v.2018.03, www.rdkit.org); stereochemical information was removed and only SMILES strings with a length of up to 140 SMILES characters were retained.