'Recycling' of knowledge is clearly a major factor influencing the NP profiles of Clinical candidates, as shown by the target examples (Figures ). Most striking is the fact that as few as 176 NP fragments account for, on average, 63% of the heavy (non-H) atoms in the Murcko scaffold structures of Clinical compounds disclosed since 2008. Further, just 58 NP fragments (Figure ) cover 90.5% of all Clinical compound NP fragment space. We therefore extend the questions already raised regarding the necessity for novel ring systems in drugs to ask if application of NP fragments is a preferred strategy for success, instead of hunting for diversity amongst the vast numbers of less-used and virtual non-NP ring systems and scaffolds. The rapid growth in Clinical PNPs has probably occurred largely unknowingly because the PNP concept, disclosed in 2020, is too new to have had significant impact on Clinical compound design.