A non-redundant data set comprising 771 approved drugs was derived from the ChEMBL DrugStore database47 (link). The selected compounds were all (i) marketed drugs, (ii) classified as small molecular weight therapeutics (i.e. no nutritional supplements, diagnostic agents or biologics), (iii) of specified molecular structure, (iv) composed of at least six atoms, (v) dependent on a biological macromolecule for their mode of action (i.e. exclude chelators and buffers), (vi) orally administered, (vii) systemically absorbed (i.e. exclude compounds whose site of action is in the gastro-intestinal (GI) tract e.g. orlistat targets gastric lipase, acarbose targets enteric alpha glucosidase).