Human peptide transporters: therapeutic applications

Peptide transporters are epithelial solute carriers. Their functional role has been characterised in the small intestine and proximal tubules, where they are involved in absorption of dietary peptides and peptide reabsorption, respectively. Currently, two peptide transporters, PepT1 and PepT2, which possess transport activity, have been identified. The transporters are not drug targets per se, but due to uniquely broad substrate specificity they have proven to be relevant in drug therapy at the level of drug transport. Therapeutic agents such as orally active beta-lactam antibiotics, bestatin, prodrugs of acyclovir and gancyclovir have oral bioavailabilities, which are largely a result of their interaction with PepT1. The transporters have therefore received considerable attention in relation to drug delivery. The aim of the present review is to highlight structural requirements for binding to peptide transporters, as well as their role in drug delivery and in potential future drug design and targeted tissue delivery of peptides and peptidomimetics.