ABSTRACT
The goal in most drug development processes is the design of agents that are optimally effective in curing a defined illness with minimum or no side effects. For a traditional (nontargeted) delivery system, only a minor fraction of the total administered drug reaches the target site. Therefore a considerable portion of the administered therapeutic agent may interact with nontarget sites, resulting in inefficient drug delivery and/or undesirable side effects. A drug delivery system that has the ability to target a drug to a particular site (such as a specific tissue, organ, cell, enzyme, bacterium, or virus) would optimize therapy and minimize or eliminate possible drug toxicity. One approach to the site-specific delivery of a parent drug to a certain tissue involves the design of drug delivery systems targeted to specific drug carrier proteins and/or enzymes. Among molecular modification strategies, the prodrug approach would be useful for site-specific delivery of the drug.
