Advances in high-throughput screening of cyclic peptide drugs using mRNA display technology

Cyclic peptides have emerged as a promising therapeutic modality for targeting classically deemed "undruggable" protein that defy conventional small-molecule intervention. Their rigid conformations improve binding affinity, selectivity and proteolytic stability, bridging the gap between low-molecular-weight drugs and large biologics. Early discovery of cyclic peptide relied on natural product isolation. However, display technologies now enable the generation and screening of libraries containing up to 10¹⁵ unique sequences. Among these, mRNA display technology offers a uniquely powerful in vitro platform that covalently links genotype (mRNA) to phenotype (encoded peptide), facilitating the ultrahigh-throughput interrogation of trillions of variants in a single selection cycle. Recent clinical translation of de novo mRNA display-derived cyclic peptides signals the approach's maturation. In this review, we systematically evaluate mRNA display technology by outlining its methodological framework and highlighting its unique advantages for engineering macrocyclic therapeutics. We critically examine its transformative potential as well as its inherent limitations in identifying bioactive cyclic peptides, with particular attention to library diversity and the precision of on-resin screening. Through this analysis, we aim to provide insightful perspectives and strategic recommendations to guide future efforts in exploiting mRNA display for the development of innovative cyclic peptide-based drugs.