title: Phage selection of cyclic peptide antagonists with increased stability toward intestinal proteases.
abstract: The oral delivery of protein and peptide drugs is limited by their proteolytic degradation and the poor absorption across the intestinal epithelia. In this work, we exposed a phage library of small bicyclic peptides (<1.5 kDa) to a pancreatic extract of proteases prior to affinity selection to enrich binders with higher stability in the intestinal environment. Panning with the therapeutic target plasma kallikrein yielded potent inhibitors (K(i)s between 5.6 and 336 nM) wherein bicyclic peptides isolated with proteolytic pressure were more stable. A proline residue found in a specific position of several resistant bicyclic peptides proved to be a 'protective mark', rendering the bicyclic peptides resistant to significantly higher concentrations of intestinal proteases while retaining essentially their inhibitory activity.
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Baeriswyl
authors.forename: Christian
authors.initials: C
authors.lastname: Heinis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007422:Intestines / Q000201:enzymology*; D008969:Molecular Sequence Data; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D020842:Plasma Kallikrein / Q000037:antagonists & inhibitors*; D011392:Proline; D055550:Protein Stability; D059748:Proteolysis; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D013552:Swine
chemical_list: D019151:Peptide Library; D010456:Peptides, Cyclic; D015842:Serine Proteinase Inhibitors; D011392:Proline; D020842:Plasma Kallikrein