Eight different fragment libraries were chosen as building blocks for LigBuilder, including the available default library, four commercial libraries (one epigenetic-focused), DNMT1 inhibitors, food chemicals from FooDB, and natural products. These were selected considering the sources of the training sets used before with alvaBuilder (Table ). Notably, fragments from DNMT1 inhibitors, FooDB, and natural products were obtained from the fragmentation of the corresponding curated chemical libraries with the RECAP algorithm. Table summarizes the sources and number of compounds of the eight libraries.