A selective cyclic peptide inhibitor of β-Factor XIIa was engineered within a cyclotide scaffold, combining ultrapotent anti-clotting activity with the exceptional stability of plant-derived cyclotide structures.
Ultrapotent + ultrastableCyclotide scaffold provides exceptional protease resistance and cell permeability while the engineered inhibitor loop delivers ultrapotent Factor XIIa selectivity
What the researchers found
Engineered cyclotide containing a Factor XIIa inhibitor loop achieved ultrapotent and selective inhibition of human β-Factor XIIa while maintaining the cyclotide scaffold's proteolytic stability and cell permeability.
Why it matters
Factor XII drives pathological blood clotting (thrombosis) without being needed for normal wound healing — making it an ideal anticoagulant target. A cyclotide-based inhibitor could be more stable than existing peptide anticoagulants.
The numbers in context
>10^12 library; pM Ki for FXIIa; >1,000-fold selectivity; MCoTI-II scaffold; co-crystal structure
How the study worked
Peptide engineering study. Factor XIIa inhibitor sequence grafted into cyclotide scaffold. Potency and selectivity profiling against coagulation factors. Stability and cell permeability assessment.
Who was studied
N/A (in vitro peptide engineering)
What this study cannot tell us
In vitro potency and selectivity study. In vivo anti-thrombotic efficacy not tested. Cyclotide manufacturing at pharmaceutical scale is challenging. Immunogenicity of plant-derived scaffold in humans unknown.
How to read the evidence
Low-to-moderate evidence: thorough in vitro characterization with potency and selectivity data, but no in vivo anticoagulant testing.
When this study was published
Published 2021. Cyclotide-based drug design is advancing with multiple therapeutic applications in development.
The bigger picture
Cyclotides as drug scaffolds represent one of the most exciting developments in peptide therapeutics. Their inherent stability solves the major weakness of peptide drugs (rapid degradation), and their engineerability allows insertion of diverse bioactive sequences.
Questions still open
- Would this cyclotide prevent thrombosis in vivo without bleeding risk?
- Can cyclotide scaffolds deliver other anti-clotting or anti-inflammatory peptides?
- Would oral delivery of cyclotide anticoagulants be possible given their stability?
Common questions
What is a cyclotide?
Why target Factor XIIa for anticoagulation?
Read the original research
An Ultrapotent and Selective Cyclic Peptide Inhibitor of Human β-Factor XIIa in a Cyclotide Scaffold.
Journal of the American Chemical Society, 143(44), 18481-18489
Citation
Liu, Wenyu; de Veer, Simon J; Huang, Yen-Hua; Sengoku, Toru; Okada, Chikako; Ogata, Kazuhiro; Zdenek, Christina N; Fry, Bryan G; Swedberg, Joakim E; Passioura, Toby; Craik, David J; Suga, Hiroaki. (2021). An Ultrapotent and Selective Cyclic Peptide Inhibitor of Human β-Factor XIIa in a Cyclotide Scaffold.. Journal of the American Chemical Society, 143(44), 18481-18489. https://doi.org/10.1021/jacs.1c07574