PENETRATION ENHANCEMENT FOR POLYPEPTIDES THROUGH EPITHELIA .D. ROUTES OF DELIVERY - CASE-STUDIES .5. ORAL ABSPORTION OF PEPTIDES AND PROTEINS

Many approaches to achieve oral absorption of a wide variety of peptide and protein drugs are currently under investigation. Progression from demonstration of oral pharmacologic activity, in animal models, to achievement of clinically and commercially attractive delivery systems still presents significant challenges for most novel approaches. Recent advances in our understanding of the transport properties of cellular barriers and our ability to establish these barriers in vitro, has, however, provided new tools for designing mechanism-based strategies and for evaluating the basis of pragmatic approaches. In this review we examine the status of these approaches against our current understanding of specific routes and mechanisms of transport across cells of the gastrointestinal epithelium. The feasibility of exploiting such pathways for the oral delivery of specific peptides and for achieving effective, safe and commercializable delivery systems will be discussed.