biostudies-literatureUnknown33Lang PSanofiPrevious data have suggested an antiviral effect of teriflunomide, including against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the agent underlying the ongoing COVID-19 pandemic. We undertook an <i>in vitro</i> investigation to evaluate the inhibitory activity of teriflunomide against SARS-CoV-2 in a cell-based assay. Teriflunomide was added to Vero (kidney epithelial) cells that had been infected with SARS-CoV-2. A nucleocapsid immunofluorescence assay was performed to examine viral inhibition with teriflunomide and any potential cytotoxic effect. The 50% effective concentration (EC₅₀) for teriflunomide against SARS-CoV-2 was 15.22 μM. No cytotoxicity was evident for teriflunomide in the Vero cells (i.e., the 50% cytotoxic concentration [CC₅₀] was greater than the highest test concentration of 100 μM). The data were supported by additional experiments using other coronaviruses and human cell lines. In the SARS-CoV-2-infected Vero cells, the prodrug leflunomide had an EC₅₀ of 16.49 μM and a CC₅₀ of 54.80 μM. Our finding of teriflunomide-mediated inhibition of SARS-CoV-2 infection at double-digit micromolar potency adds to a growing body of evidence for a broad-ranging antiviral effect of teriflunomide.Biochemistry and biophysics reports101395https://www.ebi.ac.uk/biostudies/studies/S-EPMC9682045biostudies-literature<i>In vitro</i> evaluation of the activity of teriflunomide against SARS-CoV-2 and the human coronaviruses 229E and OC43.PMC9682045Lublin ALGeertsen SSLang PGladysheva TPotter MCGregory JSRufi Pfalse<i>In vitro</i> evaluation of the activity of teriflunomide against SARS-CoV-2 and the human coronaviruses 229E and OC43.Previous data have suggested an antiviral effect of teriflunomide, including against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the agent underlying the ongoing COVID-19 pandemic. We undertook an <i>in vitro</i> investigation to evaluate the inhibitory activity of teriflunomide against SARS-CoV-2 in a cell-based assay. Teriflunomide was added to Vero (kidney epithelial) cells that had been infected with SARS-CoV-2. A nucleocapsid immunofluorescence assay was performed to examine viral inhibition with teriflunomide and any potential cytotoxic effect. The 50% effective concentration (EC₅₀) for teriflunomide against SARS-CoV-2 was 15.22 μM. No cytotoxicity was evident for teriflunomide in the Vero cells (i.e., the 50% cytotoxic concentration [CC₅₀] was greater than the highest test concentration of 100 μM). The data were supported by additional experiments using other coronaviruses and human cell lines. In the SARS-CoV-2-infected Vero cells, the prodrug leflunomide had an EC₅₀ of 16.49 μM and a CC₅₀ of 54.80 μM. Our finding of teriflunomide-mediated inhibition of SARS-CoV-2 infection at double-digit micromolar potency adds to a growing body of evidence for a broad-ranging antiviral effect of teriflunomide.2023-01-01T00:00:00Z2023 Mar2026-05-07T13:22:05.013Z2025-04-19T23:08:07.354ZS-EPMC96820453643796610.1016/j.bbrep.2022.101395