Furaprofen (R803) is an effective HCV replication inhibitor. Furaprofen (R803) is substantially more potent against genotype 1a and 1b replicons ( EC 50 , ~30 nM) than against the genotype 2a replicon (EC 50 , ~1,000 nM). In Vitro Furaprofen (R803) is potent and highly specific for HCV replication. The antiviral activity of Furaprofen has been determined by a reporter replicon assay with multiple repeats to be 29.88±8.05 nM, an ~3-fold improvement over the activity of the parent compound, R706. The potency of Furaprofen against the replicon is also confirmed by both Western blotting and TaqMan RT-PCR to be about 37 nM and 54.67±4.11 nM, respectively. To assess the general effect of Furaprofen on cell proliferation, a panel of primary cells and transformed human cell lines are treated with increasing doses of Furaprofen for 48 h, and the effect on cell proliferation is measured by an MTS-based cell viability assay. The the concentration that caused a 50% reduction in cell numbers in the absence of virus infection (CC 50 ) of Furaprofen is found to range from 2 μM to ≥10 μM, depending on the cell type and proliferation status. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:EC50: ~30 nM (HCV genotype 1a and 1b replicons), ~1000 nM (HCV genotype 2a replicon)