title: A rapid in vitro screening for delivery of peptide-derived peptidase inhibitors as potential drug candidates via epithelial peptide transporters.
abstract: Targeting drugs or prodrugs to a specific enzyme by simultaneously targeting cell membrane carriers for efficient transport should provide the highest bioavailability along with specificity at the site of action. The peptide transporters PEPT1 and PEPT2 are expressed in a variety of tissues, including the brush-border membranes of epithelial cells of the small intestine and kidney. The transporters accept a wide range of substrates and are therefore good targets for a transporter-mediated drug delivery. Here, we report a screening procedure for peptidomimetic drug candidates combining two independent expression systems: 1) a competition assay in transgenic Pichia pastoris yeast cells expressing either mammalian PEPT1 or PEPT2 for identifying substrate interaction with the transporter binding site; and 2) a Xenopus laevis-based oocyte expression of the peptide transporter for assessing electrogenic transport of drug candidates. Based on the known oral availability and in vivo efficacy of the dipeptidyl peptidase IV (DPIV) inhibitor isoleucine-thiazolidide and its peptide-like structure, we first tested whether this compound is a substrate of epithelial peptide transporters. Additionally, a series of structurally related inhibitors were analyzed for transport. We identified various compounds that serve as substrates of the intestinal peptide transporter PEPT1. In contrast, none of these DPIV inhibitors showed electrogenic transport by PEPT2, although a variety of the compounds displayed good affinities for competition in peptide uptake in PEPT2-expressing cells, suggesting that they may serve as efficient inhibitors. In conclusion, we have applied an in vitro screening system that predicts efficient intestinal absorption of peptide-derived peptidase inhibitors via PEPT1 in vivo.
authors.affiliation: Institute of Nutritional Sciences, Center of Life and Food Sciences, Technical University of Munich, Hochfeldweg 2, D-85350 Freising-Weihenstephan, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Foltz
authors.forename: Antje
authors.initials: A
authors.lastname: Meyer
authors.forename: Stephan
authors.initials: S
authors.lastname: Theis
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Demuth
authors.forename: Hannelore
authors.initials: H
authors.lastname: Daniel
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D016503:Drug Delivery Systems / Q000379:methods*; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D000074011:Peptide Transporter 1; D011480:Protease Inhibitors / Q000008:administration & dosage / Q000378:metabolism*; D027981:Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D000074011:Peptide Transporter 1; D011480:Protease Inhibitors; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2