Recent advances in retrometabolic drug design and targeting approaches.

A number of representative, recent advances achieved within the field of retrometabolic drug design are briefly summarized. For the soft drug approach, some of the results of recent in vivo studies of loteprednol etabonate, a soft corticosteroid approved by the FDA in 1998, are reviewed. For the chemical delivery system (CDS) approach, the latest advances achieved in the brain targeting of peptides such as kyotorphin and TRH analogues are described.