Cyclic Peptide Screening Methods for Preclinical Drug Discovery

Abstract

Cyclic peptides are among the most diverse architectures for current drug discovery efforts. Their size, stability, and ease of synthesis provide attractive scaffolds to engage and modulate some of the most challenging targets, including protein–protein interactions and those considered to be “undruggable”. With a variety of sophisticated screening technologies to produce libraries of cyclic peptides, including phage display, mRNA display, split intein circular ligation of peptides, and in silico screening, a new era of cyclic peptide drug discovery is at the forefront of modern medicine. In this perspective, we begin by discussing cyclic peptides approved for clinical use in the past two decades. Particular focus is placed around synthetic chemistries to generate de novo libraries of cyclic peptides and novel methods to screen them. The perspective culminates with future prospects for generating cyclic peptides as viable therapeutic options and discusses the advantages and disadvantages currently being faced with bringing them to market.

High‐throughput screening and biological display technology: Applications in molecular imaging

“…Cyclic peptides generally have a higher stability and longer half-life than linear peptides. Until now, the Food and Drug Administration (FDA) has approved 20 cyclic peptides either for cancer therapy and diagnosis or as antibiotic and antifungal drugs [12].…”

“…Antibody fragmentsThe Geyer group designed a phage display Fab library with a framework derived from the HER2 monoclonal F I G U R E 3 In vivo near-infrared imaging using E8 Nb-IR800 probes (bottom) and control probe IR800 (top) at different time points(3,6,12, and 24 h). E8 Nb-IR800 probes emit stronger tumor signals, persisting for 12-24 h, than IR800 (n = 3).…”

An Efficient, Site‐Selective and Spontaneous Peptide Macrocyclisation During in vitro Translation

“…Macrocyclic peptides are a promising class of compound for drug development, with their large interaction surface able to bind in a similar mode to antibodies while the conformational constraints both reduce the entropic cost of binding and improve protease stability [1] . Peptide display technologies, such as phage or mRNA display, offer a means to discover new macrocyclic peptides, [2] but these need macrocyclisation chemistry that is compatible with both the display platform and subsequent scale up by solid‐phase peptide synthesis (SPPS) [3] . Current cyclisations offer at best limited regioselectivity and are predominantly cysteine‐based, meaning that peptides with multiple cysteines either give a mix of isomers or give the smallest macrocycle (further discussed below).…”

“…[1] Peptide display technologies, such as phage or mRNA display, offer a means to discover new macrocyclic peptides, [2] but these need macrocyclisation chemistry that is compatible with both the display platform and subsequent scale up by solid-phase peptide synthesis (SPPS). [3] Current cyclisations offer at best limited regioselectivity and are predominantly cysteine-based, meaning that peptides with multiple cysteines either give a mix of isomers or give the smallest macrocycle (further discussed below). Cysteine is uniquely convenient in its reactivity among the canonical amino acids, and so offers a convenient handle for further modification of (mRNA-displayed) peptides.…”

Beyond 20 in the 21st Century: Prospects and Challenges of Non-canonical Amino Acids in Peptide Drug Discovery

“…8 While ncAAs are established in small molecule and peptidomimetic drug discovery, 9 not until recently have advances in affinitybased hit-finding platforms, such as mRNA display, provided a means to generate >10 12 unique de novo ncAA-containing macrocyclic peptides (ncAA-MPs) in a single round of screening. 10 laboratories have enabled ncAA incorporation into mRNA display screening libraries; 11,12 however, limitations on codon table modifications remain, providing rich opportunities for drug hunters to further optimize the hits to lead-like chemical matter. As one can imagine, the chemical space of ncAAs for medicinal chemists to explore can be limitless; nevertheless, inspiration from NRPs and RiPPs, such as cyclosporin A, darobactin A, and tryglysin A, have provided several common strategies to design and optimize peptidic structures (Figure 1B).…”