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Nielsen DS, Shepherd NE, Xu W, Lucke AJ, Stoermer MJ, Fairlie DP. Orally Absorbed Cyclic Peptides. Chem Rev 2017; 117:8094-8128. [PMID: 28541045 DOI: 10.1021/acs.chemrev.6b00838] [Citation(s) in RCA: 266] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Peptides and proteins are not orally bioavailable in mammals, although a few peptides are intestinally absorbed in small amounts. Polypeptides are generally too large and polar to passively diffuse through lipid membranes, while most known active transport mechanisms facilitate cell uptake of only very small peptides. Systematic evaluations of peptides with molecular weights above 500 Da are needed to identify parameters that influence oral bioavailability. Here we describe 125 cyclic peptides containing four to thirty-seven amino acids that are orally absorbed by mammals. Cyclization minimizes degradation in the gut, blood, and tissues by removing cleavable N- and C-termini and by shielding components from metabolic enzymes. Cyclization also folds peptides into bioactive conformations that determine exposure of polar atoms to solvation by water and lipids and therefore can influence oral bioavailability. Key chemical properties thought to influence oral absorption and bioavailability are analyzed, including molecular weight, octanol-water partitioning, hydrogen bond donors/acceptors, rotatable bonds, and polar surface area. The cyclic peptides violated to different degrees all of the limits traditionally considered to be important for oral bioavailability of drug-like small molecules, although fewer hydrogen bond donors and reduced flexibility generally favored oral absorption.
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Affiliation(s)
- Daniel S Nielsen
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
| | - Nicholas E Shepherd
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
| | - Weijun Xu
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
| | - Andrew J Lucke
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
| | - Martin J Stoermer
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
| | - David P Fairlie
- Division of Chemistry and Structural Biology, and ‡Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Institute for Molecular Bioscience, The University of Queensland , Brisbane, QLD 4072, Australia
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