To determine if NA808 has a synergic effect with DAAs, we examined combination treatment with NS5B nucleoside inhibitor, RO-9187,13 NS5B polymerase non-nucleoside inhibitor, HCV-796, or NS3/4A protease inhibitor, telaprevir, in HCV genotype 1a- or 1b-infected chimeric mice. Oral administration of once-daily 1000 mg/kg RO-9187, 100 mg/kg HCV-796, or 400 mg/kg telaprevir had only very limited effects or no apparent effects on serum HCV-RNA levels

during the 14 days of treatment (Figure 4B, C, and D). However, the combination therapy of NA808 with RO-9187, HCV-796, or telaprevir led to decreases in serum HCV-RNA levels of about 2.6-log, 3.5-log, and 2.5-log, respectively, within 14 days ( Figure 4B, C, and D); these reductions were all in excess of viral www.selleckchem.com/products/z-vad-fmk.html load reductions achieved by treatment with NA808 (5 mg/kg) alone. After 28 days of combination treatment with NA808 and telaprevir, serum HCV-RNA levels were reduced by 104-fold (data not shown). These data suggest that NA808 has synergistic antiviral effects with HCV enzyme-targeted drugs in vivo, regardless

of the targeted enzyme. The combination therapy of NA808 with telaprevir and HCV-796 resulted in up to a 4.7-log reduction of serum HCV-RNA within 14 days ( Figure 4D). At the end of the treatment, hepatic HCV-RNA levels were also reduced, correlating with the reduction of serum HCV-RNA ( Figure 4E). We measured the plasma concentration of NA808 in humanized-liver mice at

24 hours after 14 days of treatment. The plasma concentrations of NA808 at trough level were 0.510 ± 0.517 Alpelisib nmol/L (1.5 mg/kg), 0.446 ± 0.163 nmol/L (3 mg/kg), and 1.44 ± 1.07 nmol/L (5 mg/kg), respectively (Table 3). Obvious toxicological findings in general conditions Alanine-glyoxylate transaminase were not observed at any doses. We selected 1.4 nmol/L as an effective trough level of NA808 in vivo. The current treatment regimen for HCV infection is combination therapy with PEG-IFN and RBV; however, this combination therapy has limited efficacy and is not well tolerated in many patients due to its systemic side-effect profile.3 and 4 Although the HCV NS3/4A protease inhibitors telaprevir and SCH503034 (boceprevir) have been recently approved for the treatment of chronic HCV infection, these compounds need to be combined with the current standard of care.5 Therefore, the ultimate goal of developing a therapy for chronic hepatitis C is likely to combine HCV enzyme-targeting agents without the use of IFN or RBV. Currently, combination therapies of DAAs, such as NS3/4 serine protease inhibitors, NS5B RNA-dependent RNA polymerase inhibitors, and NS5A inhibitors, are being tested in clinical trials; however, the emergence of resistance mutations limits the efficacy of these therapies.8 and 9 In addition, the antiviral activities of DAAs are reduced for certain HCV genotypes.