A novel class of TMPRSS2 inhibitors potently block SARS-CoV-2 and MERS-CoV viral entry and protect human epithelial lung cells

Proc Natl Acad Sci U S A. 2021 Oct 26;118(43):e2108728118. doi: 10.1073/pnas.2108728118.


The host cell serine protease TMPRSS2 is an attractive therapeutic target for COVID-19 drug discovery. This protease activates the Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and of other coronaviruses and is essential for viral spread in the lung. Utilizing rational structure-based drug design (SBDD) coupled to substrate specificity screening of TMPRSS2, we have discovered covalent small-molecule ketobenzothiazole (kbt) TMPRSS2 inhibitors which are structurally distinct from and have significantly improved activity over the existing known inhibitors Camostat and Nafamostat. Lead compound MM3122 (4) has an IC50 (half-maximal inhibitory concentration) of 340 pM against recombinant full-length TMPRSS2 protein, an EC50 (half-maximal effective concentration) of 430 pM in blocking host cell entry into Calu-3 human lung epithelial cells of a newly developed VSV-SARS-CoV-2 chimeric virus, and an EC50 of 74 nM in inhibiting cytopathic effects induced by SARS-CoV-2 virus in Calu-3 cells. Further, MM3122 blocks Middle East respiratory syndrome coronavirus (MERS-CoV) cell entry with an EC50 of 870 pM. MM3122 has excellent metabolic stability, safety, and pharmacokinetics in mice, with a half-life of 8.6 h in plasma and 7.5 h in lung tissue, making it suitable for in vivo efficacy evaluation and a promising drug candidate for COVID-19 treatment.

Keywords: COVID-19; PS-SCL; antiviral; protease inhibitor; structure-based drug discovery.

Publication types

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

MeSH terms

  • Animals
  • Benzamidines / chemistry
  • Benzothiazoles / pharmacokinetics
  • Benzothiazoles / pharmacology*
  • COVID-19 / genetics
  • COVID-19 / virology
  • COVID-19 Drug Treatment*
  • Cell Line
  • Drug Design
  • Epithelial Cells / drug effects
  • Epithelial Cells / virology
  • Esters / chemistry
  • Guanidines / chemistry
  • Humans
  • Lung / drug effects
  • Lung / virology
  • Mice
  • Middle East Respiratory Syndrome Coronavirus / drug effects
  • Middle East Respiratory Syndrome Coronavirus / pathogenicity
  • Oligopeptides / pharmacokinetics
  • Oligopeptides / pharmacology*
  • SARS-CoV-2 / drug effects*
  • SARS-CoV-2 / pathogenicity
  • Serine Endopeptidases / drug effects
  • Serine Endopeptidases / genetics*
  • Serine Endopeptidases / ultrastructure
  • Small Molecule Libraries / pharmacology
  • Substrate Specificity / drug effects
  • Virus Internalization / drug effects


  • Ac-GQFR-kbt
  • Benzamidines
  • Benzothiazoles
  • Esters
  • Guanidines
  • Oligopeptides
  • Small Molecule Libraries
  • camostat
  • Serine Endopeptidases
  • TMPRSS2 protein, human
  • benzothiazole
  • nafamostat