Assessment of viral RdRp activity in a plasmid-based minireplicon reporter system confirmed dose-dependent inhibition of RdRp by JMN3-003 also in a sub-infection setting, since luciferase reporter expression was fully blocked at compound concentrations of approximately 100 nM (figure 7C). Taken together, these data suggest indirect inhibition of the viral polymerase complex through interaction of the compound with a cellular cofactor required for RdRp activity as the basis for the antiviral effect of JMN3-003.