Remdesivir is a direct-acting antiviral that inhibits RNA-dependent RNA polymerase from severe acute respiratory syndrome coronavirus 2 with high potency

J Biol Chem. 2020 May 15;295(20):6785-6797. doi: 10.1074/jbc.RA120.013679. Epub 2020 Apr 13.


Effective treatments for coronavirus disease 2019 (COVID-19) are urgently needed to control this current pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Replication of SARS-CoV-2 depends on the viral RNA-dependent RNA polymerase (RdRp), which is the likely target of the investigational nucleotide analogue remdesivir (RDV). RDV shows broad-spectrum antiviral activity against RNA viruses, and previous studies with RdRps from Ebola virus and Middle East respiratory syndrome coronavirus (MERS-CoV) have revealed that delayed chain termination is RDV's plausible mechanism of action. Here, we expressed and purified active SARS-CoV-2 RdRp composed of the nonstructural proteins nsp8 and nsp12. Enzyme kinetics indicated that this RdRp efficiently incorporates the active triphosphate form of RDV (RDV-TP) into RNA. Incorporation of RDV-TP at position i caused termination of RNA synthesis at position i+3. We obtained almost identical results with SARS-CoV, MERS-CoV, and SARS-CoV-2 RdRps. A unique property of RDV-TP is its high selectivity over incorporation of its natural nucleotide counterpart ATP. In this regard, the triphosphate forms of 2'-C-methylated compounds, including sofosbuvir, approved for the management of hepatitis C virus infection, and the broad-acting antivirals favipiravir and ribavirin, exhibited significant deficits. Furthermore, we provide evidence for the target specificity of RDV, as RDV-TP was less efficiently incorporated by the distantly related Lassa virus RdRp, and termination of RNA synthesis was not observed. These results collectively provide a unifying, refined mechanism of RDV-mediated RNA synthesis inhibition in coronaviruses and define this nucleotide analogue as a direct-acting antiviral.

Keywords: COVID-19; Ebola virus; Lassa virus; MERS; RNA polymerase; RNA-dependent RNA polymerase (RdRp); SARS; SARS-CoV-2; coronavirus (CoV); drug action; drug development; drug discovery; favipiravir; plus-stranded RNA virus; remdesivir; replication; ribavirin; sofosbuvir.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Monophosphate / analogs & derivatives*
  • Adenosine Monophosphate / pharmacology
  • Alanine / analogs & derivatives*
  • Alanine / pharmacology
  • Animals
  • Antiviral Agents / pharmacology*
  • Betacoronavirus / enzymology*
  • Betacoronavirus / physiology
  • Models, Molecular
  • RNA-Dependent RNA Polymerase / antagonists & inhibitors*
  • SARS-CoV-2
  • Sf9 Cells
  • Spodoptera
  • Virus Replication / drug effects*


  • Antiviral Agents
  • remdesivir
  • Adenosine Monophosphate
  • RNA-Dependent RNA Polymerase
  • Alanine

Associated data

  • PDB/4WTD
  • PDB/6NUR

Grant support