In support of a 'natural selection' process occurring in successful drug discovery, the results (Figures , Table ) show that since 2008, Clinical compounds have increased NP property values versus target-matched Reference compounds. Overall in this period, PNPs are 54% more likely to be found in Clinical versus Reference compounds. On the other hand, not all target classes show a NP signal, there is less evidence for a NP property clinical increase prior to 2008, and Clinical and Reference compounds have the same relative abundance in the NPL (NP-like) class in all time frames (Figure ).