Molecules are fragmented using extended connectivity fragments, and the fragment score is calculated as a sum of contributions of all fragments in the molecule divided by the number of fragments in the molecule. The fragment frequency is related to their synthetic accessibility and hence easy-to-prepare substructures are present in molecules quite often. The complexity score is calculated as the sum of ring complexity (i.e., ring bridge atoms and spiro atoms), the number of stereocenters, large rings (i.e., ring size greater than eight, molecular complexity increases), and molecule size. The SA score was calculated for all epigenetic-focused libraries.