Current prodrug design for drug discovery

Prodrugs are inactive compounds which are metabolized either chemically or enzymatically in a controlled or predictable manner to the parent active drug inside the body. Prodrugs can enhance the therapeutic efficacy and/or reduce adverse effects via different mechanisms, including increased solubility, improved permeability and bioavailability, prolonged half-life, and tissue-targeted delivery. Besides the prodrug itself, optimization of vehicles and other enhancement techniques is important as well. Strategies to improve the oral bioavailability and achieve tumor-specific targeting have been the most important developments in prodrug design during the last 5 years. This review describes recent developments in orally administered and tumor-targeted prodrugs. Pharmacokinetic and pharmacodynamic evaluations of these prodrugs are systematically introduced in this review.