The pre-training set was generated starting from ChEMBL v31 . Fine-tuning datasets were extracted from LIT-PCBA . All sets were generated by (a) retaining molecules containing selected atoms (C, H, O, N, S, P, F, Cl, Br, and I), (b) removing salts and disconnected structures, as well as stereochemistry annotations and charge, (c) retaining molecules whose canonicalized SMILES strings contained 100 tokens or less. After sanitization, canonicalization, label encoding, and padding (to 100), molecules were randomly split into training, validation, and test sets. For ChEMBL, this led to a training set of 1,900,000, and a validation and a test set of 100,000 and 23,680 molecules, respectively. The number of compounds for each fine-tuning campaign is reported in Table .