Design of Gallinamide A Analogs as Potent Inhibitors of the Cysteine Proteases Human Cathepsin L and Trypanosoma cruzi Cruzain

J Med Chem. 2019 Oct 24;62(20):9026-9044. doi: 10.1021/acs.jmedchem.9b00294. Epub 2019 Oct 4.


Gallinamide A, originally isolated with a modest antimalarial activity, was subsequently reisolated and characterized as a potent, selective, and irreversible inhibitor of the human cysteine protease cathepsin L. Molecular docking identified potential modifications to improve binding, which were synthesized as a suite of analogs. Resultingly, this current study produced the most potent gallinamide analog yet tested against cathepsin L (10, Ki = 0.0937 ± 0.01 nM and kinact/Ki = 8 730 000). From a protein structure and substrate preference perspective, cruzain, an essential Trypanosoma cruzi cysteine protease, is highly homologous. Our investigations revealed that gallinamide and its analogs potently inhibit cruzain and are exquisitely toxic toward T. cruzi in the intracellular amastigote stage. The most active compound, 5, had an IC50 = 5.1 ± 1.4 nM, but was relatively inactive to both the epimastigote (insect stage) and the host cell, and thus represents a new candidate for the treatment of Chagas disease.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimicrobial Cationic Peptides / chemistry*
  • Antimicrobial Cationic Peptides / pharmacology*
  • Cathepsin L / antagonists & inhibitors*
  • Cysteine Endopeptidases
  • Cysteine Proteinase Inhibitors / chemistry*
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Drug Design*
  • Humans
  • Kinetics
  • Molecular Docking Simulation
  • Protozoan Proteins / antagonists & inhibitors*
  • Trypanosoma cruzi / enzymology*


  • Antimicrobial Cationic Peptides
  • Cysteine Proteinase Inhibitors
  • Protozoan Proteins
  • gallinamide A
  • Cysteine Endopeptidases
  • cruzain, Trypanosoma cruzi
  • Cathepsin L