title: In vitro evaluation of N-methyl amide tripeptidomimetics as substrates for the human intestinal di-/tri-peptide transporter hPEPT1.
abstract: Oral absorption of tripeptides is generally mediated by the human intestinal di-/tri-peptide transporter, hPEPT1. However, the bioavailability of tripeptides is often limited due to degradation in the GI-tract by various peptidases. The aim of the present study was to evaluate the general application of N-methyl amide bioisosteres as peptide bond replacements in tripeptides in order to decrease degradation by peptidases and yet retain affinity for and transport via hPEPT1. Seven structurally diverse N-methyl amide tripeptidomimetics were selected based on a principal component analysis of structural properties of 6859 N-methyl amide tripeptidomimetics. In vitro extracellular degradation of the selected tripeptidomimetics as well as affinity for and transepithelial transport via hPEPT1 were investigated in Caco-2 cells. Decreased apparent degradation was observed for all tripeptidomimetics compared to the corresponding natural tripeptides. However, affinity for and transepithelial transport via hPEPT1 were only seen for Gly-Sar-Sar, AsnPsi[CONCH(3)]PhePsi[CONCH(3)]Trp, and Gly-Sar-Leu. This implies that tripeptidomimetics originating from tripeptides with neutral side chains are more likely to be substrates for hPEPT1 than tripeptidomimetics with charged side chains. The results of the present study indicate that the N-methyl amide peptide bond replacement approach for increasing bioavailability of tripeptidomimetic drug candidates is not generally applicable to all tripeptides. Nevertheless, retained affinity for and transport via hPEPT1 were shown for three of the evaluated N-methyl amide tripeptidomimetics.
authors.affiliation: Molecular Biopharmaceutics, Department of Pharmaceutics and Analytical Chemistry, The Danish University of Pharmaceutical Sciences, 2-Universitetsparken, DK-2100 Copenhagen, Denmark.
authors.forename: Rikke
authors.initials: R
authors.lastname: Andersen
authors.forename: Carsten Uhd
authors.initials: CU
authors.lastname: Nielsen
authors.forename: Mikael
authors.initials: M
authors.lastname: Begtrup
authors.forename: Flemming Steen
authors.initials: FS
authors.lastname: Jørgensen
authors.forename: Birger
authors.initials: B
authors.lastname: Brodin
authors.forename: Sven
authors.initials: S
authors.lastname: Frokjaer
authors.forename: Bente
authors.initials: B
authors.lastname: Steffansen
mesh_terms: D000577:Amides / Q000138:chemical synthesis / Q000378:metabolism*; D018938:Caco-2 Cells; D015195:Drug Design; D004355:Drug Stability; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology; D007700:Kinetics; D008745:Methylation; D015394:Molecular Structure; D009842:Oligopeptides / Q000138:chemical synthesis / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D000074011:Peptide Transporter 1; D025341:Principal Component Analysis; D013329:Structure-Activity Relationship; D027981:Symporters / Q000378:metabolism*
chemical_list: D000577:Amides; D009842:Oligopeptides; D000074011:Peptide Transporter 1; C082186:SLC15A1 protein, human; D027981:Symporters; C007874:glycyl-sarcosyl-sarcosine; D010447:Peptide Hydrolases