To calculate these scores, we determined scaffolds of each generated molecule and each input validation molecule with Chem.Scaffolds.MurckoScaffold function from RDKit. Then, the type of transformation for each generated molecule was found by comparing its scaffold to the scaffold of the respective input validation molecule. If the two scaffolds were the same (but the molecules were different), then the transformation was classified as "R-group change". If the two scaffolds were different, then the transformation was classified as "scaffold change". The cases of each transformation type were counted over the whole set of generated molecules. (Note that the sum of the number of scaffold change transformations and the number of R-group change transformations may be slightly less than the total number of successfully generated molecules because of the rare cases when input and output molecules were identical.) The number of unique scaffolds refer to the total number of unique scaffolds in the set of generated molecules. The number of new scaffolds refer to those unique scaffolds that were absent from the training or input validation sets.