Abstract
Prodrugs are bioreversible derivatives of drug molecules used to overcome some barriers to the utility of the parent drug molecule. These barriers include, but are not limited to, solubility, permeability, stability, presystemic metabolism and targeting limitations. The patent literature shows a dramatic increase in numbers of prodrug patents (> 2000% increase in 2002 compared to 1993), with claims for cancer treatment comprising 37% of these. This increase is largely due to the rise from North American-based multinationals and some smaller drug delivery companies mirroring the overall trend. In 2001 and 2002, 14% of all new approved chemical drugs were prodrugs. It appears that prodrugs to overcome barriers to the delivery of problematic drug candidates are becoming an integral part of the drug discovery paradigm.