2.8 Dose-response curve (DRC) analysis with SARS-CoV-2-Nluc
A549-ACE2-TMPRSS2 cells (1.2 x 104 cells per well) were plated into white 384-well µClear plates (Greiner Bio-One). On the next day, the cells were treated with 2-fold serial dilution of the compound prepared in DMSO and infected with SARS-CoV-2-Nluc (MOI 0.01) (Rihn et al., 2021). After incubation at 37°C for 24 hours, nanoluciferase substrates (Promega) were added to each well and luciferase signals were measured using a VICTOR3TM multilabel plate reader (PerkinElmer). Cell viability was measured using the CellTiter-Glo Luminescent Cell Viability Assay (Promega, Madison, WI, USA) according to the manufacturer instructions. The relative luciferase signals of the compound-treated groups were normalized to that of non-infection control (set as 0%) and DMSO-treated groups (set as 100%). The DRCs were generated using Prism6 software (GraphPad, San Diego, CA), and IC50 (half-maximal inhibitory concentration) and CC50 (half-maximal cytotoxic concentration) values were calculated using a nonlinear regression model.