Fig. 1.

Median IC50 value of the drugs in VeroE6 cells

Median IC50 (left axis) of (A) remdesivir, (B) nirmatrelvir, and (C) molnupiravir. Vero E6 cells were infected with indicated SARS-CoV-2 variants at 0.1 multiplicity of infection for 1 h. Subsequently, seven concentrations of the drugs were treated with two-fold serial dilution (remdesivir and nirmatrelvir [antiviral component of Paxlovid]: 20 to 0.31 μM, molnupiravir: 40 to 0.62 μM) for 48 h. The cell infectivity ratio between the drug treatment and virus only-treated groups was assessed through high-content imaging analysis to determine the number of infected cells (N protein-expressing cells) using immunofluorescence images with viral N-specific antibody and total cells (number of nuclei) using DAPI staining. The IC₅₀ values were determined from dose-response curves and median IC₅₀ value was calculated. The experiments were performed in triplicate (the reference strain for remdesivir [n = 21], nirmatrelvir [n = 13], and molnupiravir [n = 12]).