conformational flexibility

Cyclic peptides are polypeptide chains taking cyclic ring structure, which exhibit diverse biological activities, such as antibacterial activity, immunosuppressive activity and anti-tumor activity. Cyclic peptides, with the features of good binding affinity, target selectivity and low toxicity, show great success as therapeutics. Multiple cyclic peptides are currently in clinical use, for examples, gramicidin and tyrocidine with bactericidal activity, cyclosporin A with immunosuppressive activity, and vancomycin with antibacterial activity. Furthermore, cyclic peptides usually have the sufficient size and a balanced conformational flexibility/rigidity for binding to flat protein-protein interaction (PPI) interfaces, which have potential to develop PPI drugs.

MCE offers a unique collection of 96 cyclic peptides, all of which have good bioactivities. MCE Cyclic Peptide Library is a powerful tool for drug discovery and PPI inhibitor screening.

Seven-membered rings are privileged medium-sized scaffolds with distinct twist-chair conformations and greater 3D diversity than five- and six-membered rings. Their flexible conformations allow induced-fit protein binding and precise pharmacophore positioning. They also modulate Fsp³, pKa and logP to enhance solubility and permeability. Azepanes, oxepanes and benzodiazepines serve as bioisosteres for hit discovery against GPCRs, ion channels and kinases.

Widely found in plant and microbial alkaloids, seven-membered heterocycles show excellent biocompatibility and target affinity. They underpin many approved drugs for CNS, cancer and infectious diseases, including diazepam, imipramine and carbamazepine. Clinical candidates further highlight their unique value. However, high transannular strain and synthetic difficulty limit their availability, leaving them rare in standard screening libraries.

MCE 7 Membered Scaffold Library contains 2,792 structurally diverse, lead-like molecules covering azepanes, oxepanes, benzodiazepines and dibenzazepines. With varied substitutions, chiral centers and synthetic accessibility, it fills the shortage of medium-ring scaffolds. Ideal for HTS, virtual screening and SAR studies, these novel, patent-clear compounds offer a distinctive starting point for drug discovery in CNS disorders, oncology, antivirals and challenging targets such as PPIs.

Unlike highly conserved orthosteric sites, allosteric sites exhibit low conservation, high hydrophobicity, weak polarity, confined geometry, and dynamic cryptic properties. Rather than rigid keyhole-like cavities, they typically appear as flexible grooves, subunit interface clefts, or shallow depressions formed by protein conformational changes.

Based on the dynamic, hydrophobic, and elongated nature of allosteric pockets, MCE has carried out targeted fragment modification and screening under strict physicochemical criteria: MW 120–280 Da, HBD ≤ 2, HBA ≤ 3, PSA 30–80 Ų, rotatable bonds ≤ 2, cLogP 1–3.5. High 3D diversity was further ensured by PMI analysis, yielding fragments with excellent shape complementarity to allosteric pockets.

This library contains 1,800 structurally diverse, drug-like fragments, this library supports allosteric drug development and pocket optimization. It significantly improves screening hit rates and enables efficient, precise early-stage R&D of allosteric drugs.