Both non-nucleoside inhibitors and nucleoside inhibitors of NS5B are currently being tested in clinical

trials, and the most advanced protease inhibitors, such as telaprevir, are linear compounds and are currently on the market; several macrocyclic compounds this website are being tested in clinical trials.11, 22, 23, 24 and 25 Monotherapy with the non-nucleoside polymerase inhibitor, HCV-796, showed less than a 0.5 log10 reduction of serum HCV RNA levels, while a combined treatment with NA808 reduced the HCV titer by 1000-fold from the initial serum levels. This effect was higher than the effect of NA808 alone and higher than the sum of NA808 and HCV-796 monotherapy effects, suggesting synergistic Z-VAD-FMK mouse antiviral efficacy. A similar effect was observed by combination of NA808 with nucleoside polymerase inhibitor, RO-9187, as shown in Figure 4B. The maximum reductions in HCV RNA are mediated by triple combinatorial treatment and the significant in vivo anti-HCV activity with combination treatment is also

observed when NA808 is combined with PEG-IFN. These observations suggest that NA808 may have synergistic antiviral activity with various classes of anti-HCV agents, regardless of their inhibition mechanism, due to the unique host enzyme-targeted mechanism of action. In addition, NA808 could be expected to show a higher barrier to the development of resistant clones. Deep-sequencing analysis showed no evidence for the development of NA808 resistance after 14 passages

in HCV replicon cells, while telaprevir treatment resulted in the selection of known protease resistance mutations (V36A, T54V, and A156T) ( Table 2). The full-genome sequence of HCV obtained see more at day 14 from HCV-infected humanized-liver mice treated with NA808 for 14 days also showed no evidence for the selection of resistance mutations, consistent with the viral load kinetics ( Figure 2B). Host enzyme inhibition might be associated with mechanism-related toxicities or side effects. Although more thorough analyses of toxicity with NA808 are warranted, NA808 did not affect host cell viability in vitro under the assay conditions used (Supplementary Figure 1A), and it was well-tolerated in vivo at the efficacious dose used. The effective plasma concentration of NA808 at trough level was approximately 1.4 nmol/L ( Table 3), around 100 times lower than rats that received 40 mg/kg NA808 at 24 hours after injection (data not shown). No NA808-related changes, including abnormalities of general conditions, body weight decreases, and macroscopic or microscopic changes were observed at this high dose in rats. Homozygous knockout mice for sptlc1 and sptlc2, subunits of SPT, were embryonic lethal, and heterozygous mice showed no phenotype. 26 Mice with conditional sptlc2 knockout showed necrotic lesions in gastrointestinal cells.