ABSTRACT
Developing physiologically active substances into pharmaceutical drugs is a challenge with many obstacles, despite recent progress in the design of drug delivery systems. The therapeutic potential of hit and lead compounds is often limited due to poor oral bioavailability, short circulation half-life, and/or a generally diminished ability to penetrate biological barriers. There is a growing body of literature proposing chemical modification and prodrug concepts for overcoming several typical limitations of early drug development candidates, a selection of which is discussed in this chapter.
