The past two decades have witnessed the emergence of macrocycles, including macrocyclic peptides, as a promising yet underexploited class of de novo drug candidates. Both rational/computational design and in vitro display systems have contributed tremendously to the development of cyclic peptide binders of either traditional targets such as cell-surface receptors and enzymes or challenging targets such as protein−protein interaction surfaces. mRNA display, a key platform technology for the discovery of cyclic peptide ligands, has become one of the leading strategies that can generate natural-product-like macrocyclic peptide binders with antibody-like affinities. On the basis of the original cell-free transcription/translation system, mRNA display is highly evolvable to realize its full potential by applying genetic reprogramming and chemical/ enzymatic modifications. In addition, mRNA display also allows the follow-up hit-to-lead development using high-throughput focused affinity maturation. Finally, mRNA-displayed peptides can be readily engineered to create chemical conjugates based on known small molecules or biologics. This review covers the birth and growth of mRNA display and discusses the above features of mRNA display with success stories and future perspectives and is up to date as of August 2018.

There is a lack of current treatment options for ovarian clear cell carcinoma (CCC) and the cancer is often resistant to platinum‐based chemotherapy. Hence there is an urgent need for novel therapeutics. The transcription factor hepatocyte nuclear factor 1β (HNF1β) is ubiquitously overexpressed in CCC and is seen as an attractive therapeutic target. This was validated through shRNA‐mediated knockdown of the target protein, HNF1β, in five high‐ and low‐HNF1β‐expressing CCC lines. To inhibit the protein function, cell‐permeable, non‐helical constrained proteomimetics to target the HNF1β–importin α protein–protein interaction were designed, guided by X‐ray crystallographic data and molecular dynamics simulations. In this way, we developed the first reported series of constrained peptide nuclear import inhibitors. Importantly, this general approach may be extended to other transcription factors.

Stapled peptides have great potential as modulators of protein–protein interactions (PPIs). However, there is a vast landscape of chemical features that can be varied for any given peptide, and identifying a set of features that maximizes cellular uptake and subsequent target engagement remains a key challenge. Herein, we present a systematic analysis of staple functionality on the peptide bioactivity landscape in cellular assays. Through application of a “toolbox” of diversified dialkynyl linkers to the stapling of MDM2-binding peptides via a double-click approach, we conducted a study of cellular uptake and p53 activation as a function of the linker. Minor changes in the linker motif and the specific pairing of linker with peptide sequence can lead to substantial differences in bioactivity, a finding which may have important design implications for peptide-based inhibitors of other PPIs. Given the complexity of the structure–activity relationships involved, the toolbox approach represents a generalizable strategy for optimization when progressing from in vitro binding assays to cellular efficacy studies.

We combined mRNA display technology with lipid-nanodisc based selections and identified high-affinity ligands targeting the integral membrane sensor domain of the histidine kinase AgrC as potent inhibitors of Staphylococcus aureus...