Potent Cyclic Peptide Inhibitors of FXIIa Discovered by mRNA Display with Genetic Code Reprogramming

J Med Chem. 2021 Jun 10;64(11):7853-7876. doi: 10.1021/acs.jmedchem.1c00651. Epub 2021 May 27.


The contact system comprises a series of serine proteases that mediate procoagulant and proinflammatory activities via the intrinsic pathway of coagulation and the kallikrein-kinin system, respectively. Inhibition of Factor XIIa (FXIIa), an initiator of the contact system, has been demonstrated to lead to thrombo-protection and anti-inflammatory effects in animal models and serves as a potentially safer target for the development of antithrombotics. Herein, we describe the use of the Randomised Nonstandard Peptide Integrated Discovery (RaPID) mRNA display technology to identify a series of potent and selective cyclic peptide inhibitors of FXIIa. Cyclic peptides were evaluated in vitro, and three lead compounds exhibited significant prolongation of aPTT, a reduction in thrombin generation, and an inhibition of bradykinin formation. We also describe our efforts to identify the critical residues for binding FXIIa through alanine scanning, analogue generation, and via in silico methods to predict the binding mode of our lead cyclic peptide inhibitors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Factor XIIa / antagonists & inhibitors*
  • Factor XIIa / metabolism
  • Gene Library
  • Genetic Code
  • Humans
  • Inhibitory Concentration 50
  • Kallikreins / chemistry
  • Kallikreins / metabolism
  • Molecular Dynamics Simulation
  • Partial Thromboplastin Time
  • Peptides, Cyclic / chemistry*
  • Peptides, Cyclic / metabolism
  • Protein Stability
  • Prothrombin Time
  • Puromycin / chemistry
  • RNA, Messenger / chemistry
  • RNA, Messenger / metabolism*
  • Serine Proteinase Inhibitors / chemistry*
  • Serine Proteinase Inhibitors / metabolism
  • Structure-Activity Relationship


  • Peptides, Cyclic
  • RNA, Messenger
  • Serine Proteinase Inhibitors
  • Puromycin
  • Kallikreins
  • Factor XIIa