Currently more than 40 cyclic peptide drugs are in clinical use with the vast majority derived from natural products (e.g. cyclosporine, vancomycin).
Compared to linear peptides, cyclic peptides benefit from enhanced cell permeability, increased target affinity, and resistance to proteolytic degradation. Moreover, cyclic peptides are capable of acting as inhibitors against some of the most challenging targets, including protein-protein interactions (PPIs).
A major obstacle to the discovery of new cyclic peptide drugs is the challenge in synthesising them: Cyclisation of short peptides containing seven or fewer amino acids is especially challenging, with common problems during cyclization including C-terminal epimerization, cyclo-oligomerization and the appearance of side products arising from polymerization. Consequently, there is a pressing need for new macrocyclization strategies that can provide easy access to a variety of cyclic peptide scaffolds.