Fig. 4.

Time-of-addition analysis of the antiviral activity of molnupiravir. (A) Schematic illustration of the time-of-addition experiment. (B), (C) and (D) Caco2 or A549 cells were infected with HCoV-NL63, HCoV-229E or HCoV-OC43 at an MOI of 0.1 for 2 h (0–2 h) respectively. 5 μM molnupiravir was introduced at different time points, designated as virucidal, pretreatment (pre), during treatment (during) or post-treatment (post). The inhibitory effect of molnupiravir in each group was determined by qRT-PCR. Data represent as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001. HCoV: human coronavirus.