title: Bicyclization and tethering to albumin yields long-acting peptide antagonists.
abstract: Proteolytically stable peptide architectures are required for the development of long-acting peptide therapeutics. In this work, we found that a phage-selected bicyclic peptide antagonist exhibits an unusually high stability in vivo and subsequently deciphered the underlying mechanisms of peptide stabilization. We found that the bicyclic peptide was significantly more stable than its constituent rings synthesized as two individual macrocycles. The two rings protect each other from proteolysis when linked together, conceivably by constraining the conformation and/or by mutually shielding regions prone to proteolysis. A second stabilization mechanism was found when the bicyclic peptide was linked to an albumin-binding peptide to prevent its rapid renal clearance. The bicyclic peptide conjugate not only circulated 50-fold longer (t(1/2) = 24 h) but also became entirely resistant to proteolysis when tethered to the long-lived serum protein. The bicyclic peptide format overcomes a limitation faced by many peptide leads and appears to be suitable for the generation of long-acting peptide therapeutics.
authors.affiliation: Institute of Chemical Sciences and Engineering,  Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Angelini
authors.forename: Julia
authors.initials: J
authors.lastname: Morales-Sanfrutos
authors.forename: Philippe
authors.initials: P
authors.lastname: Diderich
authors.forename: Shiyu
authors.initials: S
authors.lastname: Chen
authors.forename: Christian
authors.initials: C
authors.lastname: Heinis
mesh_terms: D000818:Animals; D001643:Bridged Bicyclo Compounds / Q000097:blood / Q000737:chemistry / Q000494:pharmacology*; D003500:Cyclization; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000097:blood / Q000737:chemistry / Q000494:pharmacology*; D012709:Serum Albumin / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013329:Structure-Activity Relationship; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors*
chemical_list: D001643:Bridged Bicyclo Compounds; D010456:Peptides, Cyclic; D012709:Serum Albumin; D014568:Urokinase-Type Plasminogen Activator