In Vitro Selection of Macrocyclic α/β 3 -Peptides against Human EGFR.

Here, we report ribosomal construction of thioether-macrocyclic α/β 3 -peptide libraries in which β-homoglycine, β-homoalanine, β-homophenylglycine, and β-homoglutamine are introduced by genetic code reprogramming. The libraries were applied to the RaPID (Random nonstandard Peptides Integrated Discovery) selection against human EGFR to obtain PPI (protein-protein interaction) inhibitors. The resulting peptides contained up to five β 3 -amino acid (β 3 AA) residues and exhibited outstanding binding affinity, PPI inhibitory activity, and proteolytic stability, which were attributed to the β 3 AAs included in the peptides. This showcase work has demonstrated that the use of such β 3 AAs enhances the drug-like properties of peptides, providing a unique platform for the discovery of de novo macrocycles against a protein of interest.