Fig. 5.

Determining the EC₅₀ of E64-D and remdesivir using a SARS-CoV-2-GFP replicon. A, B 293 T cells were transfected with SARS-CoV-2-GFP replicon, E64-D and remdesivir were added to culture media 10 h post transfection or just before transfection respectively, the green fluorescence intensity was determined thirty-six hours post-transfection, and dose responsive curves were drawn and EC₅₀ value of E64-D (A) and remdesivir (B) was calculated by four-parameter nonlinear regression respectively. Cell viability was determined by CCK8 assay in parallel on 293 T cells. The experiments were done in triplicates. C–F Replicon transfection and drug treatment were performed as mentioned in (A, B), thirty-six hours post-transfection, Western blot for tGFP-BlaR expression was carried out with E64-D (C) and remdesivir treated cells (E). EC₅₀ value of E64-D (F) and remdesivir (G) as determined by dose response curves using the ratio of tGFP-BlaR/β-actin gray values with different concentration and calculated by four-parameter nonlinear regression. The experiments were done at least two times.