13 COMBINATION OF THE NS5A INHIBITOR, GS-5885, THE NS3 PROTEASE INHIBITOR, GS-9451, AND PEGYLATED INTERFERON PLUS RIBAVIRIN IN TREATMENT EXPERIENCED PATIENTS WITH GENOTYPE 1 HEPATITIS C INFECTION

Introduction:Uncovering the rapid dynamics of HCV under pegylated-interferon/ribavirin (pegIFN/riba) treatment has provided critical information on the mechanism of HCV clearance and viral eradication.With the use of protease-inhibitors in patients often insensitive (or partially-sensitive) to interferonadministration, the study of early viral kinetics may disclose, and predict, viral dynamics underlying drug-resistance development.Methods: HCV-RNA decay was assessed (detection-limit=15 IU/ml) under telaprevir-treatment (baseline-1h-2h-3h-4h-5h-6h-8h-12h-24h-28h-48h-1w-2w-4w-8w-12w) and modeled according to Neumann et al., Science 1998.NS3-protease sequences were obtained at different time-points (baseline-8h-24h-48h) during telaprevir-treatment by population-sequencing.For 6 patients, viral quasispecies evolution at the same time-points was assessed by ultradeep 454-pyrosequencing (UDPS).Results: Twelve HCV-1 infected patients (HCV-1b=9; HCV-1a=3) received telaprevir+pegIFN-2a/riba after previous failure to pegIFN/riba-treatment (null-responders=7; partial-responders=1; relapsers=4).The median (IQR) follow-up time was 6 (4-8) weeks.Viral-load decay within the first 48h was similar in previous nonresponders (median[IQR] RNA-decay=2.6[2.6-2.9]logUI/ml) and relapsers (median[IQR] RNA-decay=2.6[2.2-3.1]logIU/ml;p = 0.788), and independent from 1a/b HCV-genotype (2.6[2.3-3.3]logIU/ml in HCV-1a vs. 2.7[2.5-2.8]logIU/ml in HCV-1b; p = 0.921).HCV-RNA decay tended to be biphasic, with an initial drop at 8h since first-dose (median[IQR] RNA-decay=1.2[0.7-2.1]logIU/ml).The mathematical model set a therapy-effect delay-time (t 0 ) of 7.2h.Within the first 24h, the median[IQR] RNA-decay was 2.3[2.1-2.5]logIU/ml, with the exception of a single patient carrying the T54S RAV at baseline, who showed a slower decay (1.6 logIU/ml).Virion clearance (c) was 0.33•day -1 , with a rate of cell-death (d) of 0.0182•day -1 .By UDPS-analysis, the prevalent prototypic strain remained invariant (in sequence and prevalence, >98%) in all patients until the end of treatment observation (48h).By contrast, minorityquasispecies rearranged in all patients, yet without appearance of telaprevir/boceprevir resistance-mutations.In one HCV-1a patient, the macrocyclic-PI resistance-mutation Q80L significantly increased in prevalence from baseline (210/2063[10.2%]reads)to 48h (264/1060[24.9%]reads;p < 0.001).Conclusions: A very rapid kinetics of HCV-RNA was observed starting from early hours after treatment-initiation; it was not related to HCV-1 genotype and to previous response to pegIFN/ribatreatment (thus suggesting to be mediated mostly by telaprevir effect).The wide rearrangement of viral minority strains even in absence of resistance development, may suggest a different sensitivity/fitness of intra-host quasispecies to telaprevir-based therapy, not necessarily regulated by presence/appearance of primary mutations.