Prodrugs: Some thoughts and current issues.

The prodrug approach to resolving formulation, delivery, and toxicity limitations on problematic drugs has had its proponents and detractors. Over the last 10 years or so, about 20% of all new small molecule NCEs have been prodrugs-a number that will surprise some. As chemists begin to explore new chemical spaces, larger and more complex molecules present greater drug delivery challenges. Prodrugs provide a means of solving these challenges, but also have their limitations. Prodrugs are becoming an integral part of the drug discovery paradigm in some large pharma companies, and a number of small biotech companies have been built around the design and application of prodrugs to improve drug candidates. Some issues facing the area of prodrug research and the commercialization of prodrugs are discussed.