For myxovirus infection, the viral RdRp complex mediates both genome transcription and replication to express viral proteins and generate progeny genomes, respectively. Replication occurs through generation of an antigenome of positive polarity, which then serves as template for negative strand genome synthesis [1] . To directly test whether JMN3-003 affects viral RdRp activity in the context of virus infection, we determined the copy numbers of MeV-Alaska mRNA and antigenome in infected, compoundtreated cells relative to vehicle-treated controls by quantitative RT-PCR. Presence of JMN3-003 caused a dose-dependent reduction in viral RNA levels (figure 7A). At a concentration of 100 nM, for instance, we observed a .100-fold reduction of viral [35] , was required to achieve comparable mRNA and antigenome reduction levels ( figure 7A ).