GT1a Patients Research Articles

Evolution of hepatitis C virus genotype 1a vs. 1b distribution inGermany between 2004 and 2018 - An analysis of 17093 patients from different real world registries

Hepatitis C virus (HCV) genotype (GT) 1 is the most common HCV GT in Western and Central Europe. Themain focus of this present work is to analyze the change of baseline characteristics of 17 093 HCV-patients with genotype 1a/1b with antiviral therapy in Germany between 2004 and 2018. We analyzed five periods: (i) 2004-2007, (ii)2008-2010, (iii) 2010-2013, (iv) 2014-2016, (v) 2017-2018. The present analysis is based on five German non-interventional registry studies and comprises data on 17 093 HCV-GT1 patients documented between 2004 and 2018 [ML17071, ML19464, ML21645, ML25724 (Peginterferon alfa-2a® non-interventional study [PAN]) and the German Hepatitis C-Registry (DHC-R). Overall, 7662 patients were infected with HCV GT1a and 9431 patients with HCV GT1b. GT1a patients were younger (46.5 years vs. 51.2 years) and more often male (70 % vs. 52 %). Previous or ongoing drug abuse was documented more frequently for GT1a patients throughout the study periods with highest frequencies in the most recent period (2017-2018; 44 % for GT1a and 10.3 % for GT1b). Metabolic comorbidities, such as those who are overweight and those with diabetes mellitus, were associated with HCV GT1b-infected women. The GT1a ratio increased from 33.6 % (2004-2007) to 50 % (2017-2018). A relevant change in the GT1a/1b ratio was observed over time in men (2004-2007: 38 %/63 %; 2017-2018: 59 %/41 %). In contrast, only 30 % of women had GT1a infection throughout all study periods without relevant changes. There were no regional differences within Germany in HCV GT1a/1b distribution despite a higher proportion of GT1b-infected women in East Germany in 2004-2007 (86 %). A marked increase of GT1a infection associated with drug use was observed in men, but not women, in Germany between 2004 and 2018. The present data show a fundamental change in HCV epidemiology, which has an impact on therapy management and general care of hepatitis C patients in Germany.

Efficacy and Safety of Ombitasvir/Paritaprevir/Ritonavir in Patients With Hepatitis C Virus Genotype 1 or 4 Infection and Advanced Kidney Disease

IntroductionHepatitis C virus (HCV) infection is common in patients with end-stage renal disease. We investigated the safety and efficacy of ombitasvir (OBV)/paritaprevir (PTV)/ritonavir (r) ± dasabuvir (DSV) ± ribavirin (RBV) in 2 phase 3, open-label, multicenter studies in patients with stage 4 or 5 chronic kidney disease (CKD).MethodsRUBY-I, Cohort 2 enrolled treatment-naïve or -experienced patients with HCV genotype (GT) 1a or 1b infection, with or without cirrhosis. Patients received 12 weeks (24 weeks for GT1a patients with cirrhosis) of OBV/PTV/r + DSV; all GT1a patients received RBV. RUBY-II enrolled treatment-naïve patients with GT1a or GT4 infection without cirrhosis. All patients received 12 weeks of RBV-free treatment: OBV/PTV/r + DSV for GT1a-infected patients; OBV/PTV/r for GT4-infected patients. The primary endpoint was sustained virologic response at posttreatment week 12 (SVR12).ResultsRUBY-I, Cohort 2 and RUBY-II enrolled 66 patients, including 50 (76%) on dialysis; 15 (23%) had compensated cirrhosis. Overall, the SVR12 rate was 95% (63/66); 1 patient had virologic failure. There were 3 discontinuations due to adverse events. Seventy-three percent (27/37) of patients receiving RBV had adverse events leading to RBV dose modification. The RBV-free RUBY-II study had no hemoglobin-associated adverse events.ConclusionTreatment with OBV/PTV/r ± DSV ± RBV was well tolerated and patients with HCV GT1 or 4 infection and stage 4 or 5 CKD had high SVR12 rates, including patients with compensated cirrhosis and/or prior treatment experience.

Integrated pharmacokinetic/viral dynamic model for daclatasvir/asunaprevir in treatment of patients with genotype 1 chronic hepatitis C.

In order to develop an integrated pharmacokinetic/viral dynamic (PK/VD) model to predict long-term virological response rates to daclatasvir (DCV) and asunaprevir (ASV) combination therapy in patients infected with genotype 1 (GT1) chronic hepatitis C virus (HCV), a systematic publication search was conducted for DCV and ASV administered alone and/or in combination in healthy subjects or patients with GT1 HCV infection. On the basis of a constructed meta-database, an integrated PK/VD model was developed, which adequately described both DCV and ASV PK profiles and viral load time curves. The IC50 values of DCV and ASV were estimated to be 0.041 and 2.45 μg/L, respectively, in GT1A patients. A sigmoid Emax function was applied to describe the antiviral effects of DCV and ASV, depending on the drug concentrations in the effect compartment. An empirical exponential function revealed that IC50 changing over time described drug resistance in HCV GT1A patients during DCV or ASV monotherapy. Finally, the PK/VD model was evaluated externally by comparing the expected and observed virological response rates during and post-treatment with DCV and ASV combination therapy in HCV GT1B patients. Both the rates were in general agreement. Our PK/VD model provides a useful platform for the characterization of pharmacokinetic/pharmacodynamic relationships and the prediction of long-term virological response rates to aid future development of direct acting antiviral drugs.

Pegylated-interferon plus ribavirin treatment does not alter the prevalence of resistance-associated substitutions to direct-acting antivirals in HCV genotype 1a patients.

BackgroundDirect-acting antiviral (DAA) resistance-associated substitutions (RASs) can jeopardize the effectiveness of DAAs in patients with hepatitis C virus (HCV). The selection pressure by pegylated-interferon (Peg-IFN) plus ribavirin (P/R) treatment may enhance HCV genome variation. However, whether P/R treatment alters the rate of change of RASs is still unclear.Materials and methodsWe retrieved the genomic sequences of HCV genotype (GT) 1a patients from GenBank, which included patients naïve to P/R (pre-IFN group) and those previously treated with P/R (post-IFN group). The sequences were aligned and analyzed by using MEGA 6.0 software. Clinically relevant RASs were summarized from the current medical literature.ResultsIn the cross-sectional study, the total prevalence of clinically relevant RASs was high, independent of the treatment group (pre-IFN: 219/403 [54.34%] vs post-IFN: 67/131 [51.15%]). The high prevalence was mainly detected in the NS3 region RAS at Q80 (40.69% vs 36.64%). The RASs in the NS5A region, such as M28, Q30, L31 and Y93, were uncommon (0%–5%). Similarly, all RASs showed no difference between the two groups. One exception was the RAS at I170 in the NS3 region, which was significantly higher in the post-IFN group than in the pre-IFN group. In the longitudinal study, similar results were observed. However, no difference in RAS at I170 was observed between the two groups. Finally, no clinically relevant RASs were detected in response to the DAA regimens approved for GT 1a patients treated with P/R.ConclusionOur results suggest that previous P/R treatment failure was not favorably associated with an increase in DAAs RASs present in GT1a patients. Our results support the American Association for the Study of Liver Diseases’ recommendations of DAA intervention in P/R-treated GT1a patients.

Unraveling the structural basis of grazoprevir potency against clinically relevant substitutions in hepatitis C virus NS3/4A protease from genotype 1a

Grazoprevir is a potent pan-genotype and macrocyclic inhibitor of hepatitis C virus (HCV) NS3/4A protease and was developed for treating chronic HCV infection. In HCV genotype (GT) 1a, grazoprevir maintains potent activity against a majority of NS3 resistance-associated amino acid substitutions, including the highly prevalent and naturally occurring Q80K polymorphism that impacts simeprevir, another NS3/4A protease inhibitor. The basis for an unexpected difference in the clinical impact of some NS3 substitutions was investigated. Phenotypic analysis of resistance-associated substitutions identified in NS3 from GT1a-infected patients who failed therapy with grazoprevir (in combination with elbasvir, an inhibitor of HCV NS5A protein) showed that positions 56, 156, and 168 in NS3 were most impactful because they diminished protein-inhibitor interactions. Although an amino acid substitution from aspartic acid to alanine at position 168 (D168A) reduced the potency of grazoprevir, its combination with R155K unexpectedly nullified this effect. Molecular dynamics and free-energy surface studies indicated that Asp-168 is important in anchoring Arg-155 for ligand binding but is not critical for Lys-155 because of the inherent flexibility of its side chain. Moreover, modeling studies supported a strong direct cation-heterocycle interaction between the Lys-155 side chain of the double substitution, R155K/D168A, and the lone pair on the quinoxaline in grazoprevir. This unique interaction provides a structural basis for grazoprevir's higher potency than simeprevir, an inhibitor to which the double substitution confers a significant reduction in potency. Our findings are consistent with the detection of R155K/D168A in NS3 from virologic failures treated with simeprevir but not grazoprevir.

Efficacy, safety and pharmacokinetics of simeprevir and TMC647055/ritonavir with or without ribavirin and JNJ-56914845 in HCV genotype 1 infection

BackgroundA Phase 2a, open-label study (NCT01724086) was conducted to assess the efficacy and safety of a once-daily, 2-direct-acting-antiviral-agent (2-DAA) combination of simeprevir + TMC647055/ritonavir ± ribavirin and of the 3-DAA combination of simeprevir + TMC647055/ritonavir + JNJ-56914845 in chronic hepatitis C virus genotype (GT)1-infected treatment-naïve and prior-relapse patients.MethodsThe study comprised four 12-week treatment panels: Panel 1 (n = 10; GT1a) and Panel 2-Arm 1 (n = 12; GT1b): simeprevir 75 mg once daily + TMC647055 450 mg once daily/ritonavir 30 mg once daily + ribavirin 1000–1200 mg/day; Panel 2-Arm 2 (n = 9; GT1b): simeprevir 75 mg + TMC647055 450 mg/ritonavir 30 mg without ribavirin; Panel 3: simeprevir 75 mg + TMC647055 600 mg/ritonavir 50 mg with (Arm 1: GT1a; n = 7) or without (Arm 2: GT1b; n = 8) ribavirin; Panel 4: simeprevir 75 mg + TMC647055 450 mg/ritonavir 30 mg + JNJ-56914845 30 mg once daily (Arm 1: n = 22; GT1a/GT1b) or 60 mg once daily (Arm 2: n = 22; GT1a/GT1b). Primary endpoint was sustained virologic response 12 weeks after end of treatment (12 weeks of combination treatment; SVR12).ResultsIn Panel 1 and Panel 2-Arm 1, 5/10 and 6/12 (50%) GT1a/GT1b + ribavirin patients achieved SVR12, versus 3/9 (33%) GT1b without ribavirin patients in Panel 2-Arm 2. In Panel 3-Arm 1 and Panel 3-Arm 2, 6/7 (86%) GT1a + ribavirin and 4/8 (50%) GT1b without ribavirin patients, respectively, achieved SVR12. In Panel 4, 10/14 (71%) and 14/15 (93%) GT1a patients in Arms 1 and 2 achieved SVR12 compared with 8/8 and 7/7 (100%) GT1b patients in each arm, respectively. No deaths, serious adverse events (AEs), Grade 4 AEs or AEs leading to treatment discontinuation occurred.ConclusionsThe 2- and 3-DAA combinations were well tolerated. High SVR rates of 93% and 100% in GT1a- and GT1b-infected patients, respectively, were achieved in this study by combining simeprevir with JNJ-56914845 60 mg and TMC647055/ritonavir.Trial registrationNCT01724086 (date of registration: September 26, 2012)

Effect of Baseline Resistance-Associated Variants on SVR with the 3D Regimen with and without RBV in GT1a and GT1b-Infected Patients

Effect of Baseline Resistance-Associated Variants on SVR with the 3D Regimen with and without RBV in GT1a and GT1b-Infected Patients

Clinical Resistance to Velpatasvir (GS-5816), a Novel Pan-Genotypic Inhibitor of the Hepatitis C Virus NS5A Protein

Velpatasvir (VEL, GS-5816) is a novel pan-genotypic hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor with activity against genotype 1 (GT1) to GT6 HCV replicons. In a phase 1b 3-day monotherapy study, patients treated with a 150-mg dose of GS-5816 had a mean maximal HCV RNA decline of ≥3.3 log10 IU/ml in GT1a, -1b, -2, -3, and -4. This report characterizes virologic resistance to VEL in these patients. NS5A resistance-associated substitutions (RASs) were detected by deep sequencing (1% cutoff) pretreatment in 22/70 patients, i.e., 10/35 (29%) patients with GT1a, 1/8 (13%) with GT1b, 4/8 (50.0%) with GT2, 5/17 (29.4%) with GT3, and 2/2 (100.0%) with GT4. In GT1a and GT3 patients, pretreatment RASs were associated with a slightly reduced HCV RNA response compared to that of patients without pretreatment RASs; among patients with GT1b, GT2, and GT4, no significant difference in response was observed in those with or without pretreatment RASs. Following treatment, the pattern of emergent RASs was more complex for GT1a than for the other genotypes. In GT1a, substitutions emerged at positions M28, Q30, L31, P32, H58, E92, and Y93, with the most prevalent substitutions at positions Y93, M28, and L31. RASs were observed at two positions in GT1b and GT2 (Y93 and L31), three positions in GT3 (Y93, L31, and E92), and four positions in GT4 (L28, M31, P32L, and Y93). RASs that were present pretreatment persisted through the 48-week follow-up period; however, RASs emerging during treatment were more likely to decline both in prevalence and in frequency within the viral population during follow-up. (This study has been registered at ClinicalTrials.gov under registration no. NCT01740791.).

Clinical relevance of the HCV protease inhibitor-resistant mutant viral load assessed by ultra-deep pyrosequencing in treatment failure

BackgroundThe detection of low frequency mutants in patients with hepatitis C virus (HCV) receiving direct-acting antivirals (DAAs) is still debated. The clinical relevance of the mutant viral load has not yet been evaluated. ObjectivesTo assess the viral load of resistance associated variants (RAVs) in patients at different time points, including the baseline, virological failure and one year after the cessation of therapy. Study designThe study included 22 patients who were previously treated with protease inhibitors (PI) (with telaprevir and boceprevir). For each patient, three time points were assessed using ultra-deep pyrosequencing (UDPS). ResultsBaseline mutations were observed in 14/22 patients (64%). At virological failure, RAVs were detected in 18/22 patients (82%). Persistent RAVs were observed in four HCV GT 1a patients (18%). Persistence mutations were found only in HCV GT 1a patients. The baseline relative V36M, R155K, R155T and A156T mutation load of patients with persistent RAVs was significantly higher (P<0.001) than those of patients without persistent RAVs. ConclusionThe UDPS follow-up analysis demonstrated that the presence of BOC or TLP-RAVs persist one year after therapy cessation only in HCV GT 1a patients. The relative mutant viral load should be considered prior to any PI based re-treatment. This concept of the baseline mutation viral load must be validated using current therapy and must be validated on a larger cohort.

SAT-125 - Higher Genetic Barrier Revealed in HCV GT-1b/2/4/6 Subjects than GT-1a Patients – A Proof of Concept Trial of TG-2349 (Furaprevir)

SAT-125 - Higher Genetic Barrier Revealed in HCV GT-1b/2/4/6 Subjects than GT-1a Patients – A Proof of Concept Trial of TG-2349 (Furaprevir)

LBP503 - Effect of Baseline Resistance-Associated Variants on SVR with the 3D Regimen with and without RBV in GT1A and GT1B-Infected Patients

LBP503 - Effect of Baseline Resistance-Associated Variants on SVR with the 3D Regimen with and without RBV in GT1A and GT1B-Infected Patients

Clinical and In Vitro Resistance to GS-9669, a Thumb Site II Nonnucleoside Inhibitor of the Hepatitis C Virus NS5B Polymerase

Treatment with GS-9669, a novel nonnucleoside inhibitor (site II) of hepatitis C virus (HCV) nonstructural 5B (NS5B) polymerase, resulted in significant antiviral activity in HCV genotype (GT) 1 patients dosed at 50 and 500 mg once daily (QD) and at 50, 100, and 500 mg twice daily (BID) for 3 days. This report characterizes the virologic resistance to GS-9669 in vitro and in GT1 HCV-infected patients from a phase I clinical study. An in vitro resistance selection study with GS-9669 revealed substitutions at several NS5B residues that conferred resistance. The M423 variants were selected at low drug concentrations (5× the 50% effective concentration [EC50]), and the L419, R422, and I482 variants were selected at higher drug concentrations (20× the EC50). During the phase I clinical study, substitutions at NS5B residues 419, 422, and 486 were the predominant changes associated with GS-9669 monotherapy. Substitutions at position 423 were observed only in GT1a patients in the low-dose groups (50 and 100 mg BID). Interestingly, four HCV patients had substitutions at position 423 at baseline. Consistent with the low resistance level at this position, three patients with M423I or M423V at baseline achieved >2-log10 reductions of HCV RNA when treated with 100 mg BID or with 500 mg QD or BID of GS-9669. The fourth patient, who had the M423V substitution at baseline, had a 4.4-log10 reduction of HCV RNA with 500 mg BID of GS-9669. Phenotypic analyses demonstrated that the viral isolates with multiple GS-9669 resistance-associated variants have reduced susceptibility to GS-9669 and lomibuvir (VX-222) but are not cross-resistant to other classes of HCV inhibitors. (This study has been registered at ClinicalTrials.gov under registration no. NCT01431898.).

Su1053 Virological Response in Treatment-Naïve Patients With Chronic HCV Genotype-1 Infection Receiving Faldaprevir Plus Pegylated Interferon α-2A and Ribavirin Is Unaffected by Ribavirin Dose Reduction

Background: Optimal duration of interferon-free HCV treatment continues to be examined in clinical trials. The SOUND-C2 and -C3 studies assessed the efficacy and safety of 16, 24, 28 and 40 weeks (W) of the interferon-free combination of faldaprevir, deleobuvir ± ribavirin in treatment-naive patients infected with HCV genotype (GT)-1. Relapse was higher in HCV GT-1a-infected patients treated for 16W with this regimen compared with GT-1b. We examined the relationship between duration of undetectable HCV RNA and virological response in SOUND-C2 and -C3. Methods: Patients received faldaprevir 120 mg QD plus deleobuvir 600 mg BID or TID. A ribavirin-free arm was investigated in SOUND-C2. The relationship between duration of undetectable HCV RNA to the end of treatment and SVR12 was assessed. Results: SVR rates among patients with undetectable HCV RNA at the last ontreatment visit, based on duration of undetectable HCV RNA, are shown (Table). GT-1binfected patients may require less time at undetectable HCV RNA (8-12W) compared with GT-1a patients (>16W) in order to achieve SVR. Regression analysis indicated that duration of undetectable HCV RNA was significantly associated with SVR. Conclusions: Duration of undetectable HCV RNA to end of treatment with this two DAA regimen was associated with SVR. These data suggest that the optimal treatment duration in GT-1b-infected patients is between 8W and 12W plus the time required to reach undetectable HCV RNA. There were

Faldaprevir combined with pegylated interferon alfa-2a and ribavirin in treatment-naïve patients with chronic genotype1 HCV: SILEN-C1 trial

Faldaprevir (BI 201335) is a potent, hepatitis C virus (HCV) NS3/4A protease inhibitor with pharmacokinetic properties supportive of once-daily (QD) dosing. Four hundred and twenty-nine HCV genotype (GT)-1 treatment-naïve patients without cirrhosis were randomized 1:1:2:2 to receive 24 weeks of pegylated interferon alfa-2a and ribavirin (PegIFN/RBV) in combination with placebo, faldaprevir 120 mg QD with 3 days of PegIFN/RBV lead-in (LI), 240 mg QD with LI, or 240 mg QD without LI, followed by an additional 24 weeks of PegIFN/RBV. Patients in the 240 mg QD groups achieving maintained rapid virologic response (mRVR; viral load [VL] <25 IU/mL at week 4 and undetectable at weeks 8-20) were rerandomized to cease all treatment at week 24 or continue receiving PegIFN/RBV up to week 48. VL was measured by Roche TaqMan. Sustained virologic response (SVR) rates were 56%, 72%, 72%, and 84% in the placebo, faldaprevir 120 mg QD/LI, 240 mg QD/LI, and 240 mg QD groups. Ninety-two percent of mRVR patients treated with faldaprevir 240 mg QD achieved SVR, irrespective of PegIFN/RBV treatment duration. Eighty-two percent of GT-1a patients who received faldaprevir 240 mg QD achieved SVR versus 47% with placebo. Mild gastrointestinal disorders, jaundice resulting from isolated unconjugated hyperbilirubinemia, and rash or photosensitivity were more common in the active groups than with placebo. Discontinuations resulting from adverse events occurred in 4%, 11%, and 5% of patients treated with 120 mg QD/LI, 240 mg QD/LI, and 240 mg QD of faldaprevir versus 1% with placebo. Faldaprevir QD with PegIFN/RBV achieved consistently high SVR rates with acceptable tolerability and safety at all dose levels. The 120 and 240 mg QD doses are currently undergoing phase 3 evaluation. (HEPATOLOGY 2013;57:2143-2154).

Characterization of Resistance to the Protease Inhibitor GS-9451 in Hepatitis C Virus-Infected Patients

GS-9451, a novel hepatitis C virus (HCV) nonstructural 3/4a (NS3/4a) protease inhibitor, is highly active in patients infected with HCV genotype 1 (GT 1). The aim of this study is to characterize the clinical resistance profile of GS-9451 in GT 1 HCV-infected patients in a phase 1, 3-day monotherapy study. The full-length NS3/4A gene was population sequenced at baseline, on the final treatment day, and at follow-up time points. NS3 protease domains from patient isolates with emerging mutations were cloned into an NS3 shuttle vector, and their susceptibilities to GS-9451 and other HCV inhibitors were determined using a transient replication assay. No resistance mutations at NS3 position 155, 156, or 168 were detected in any of the baseline samples or in viruses from patients treated with 60 mg of GS-9451 once daily. Among patients who received 200 mg and 400 mg of GS-9451, viruses with mutations at position D168 (D168E/G/V) and R155 (R155K), which confer high-level resistance to GS-9451, were detected in those with GT 1b and GT 1a virus, respectively. Viruses with D168 mutations were no longer detected in any GT 1b patient at day 14 and subsequent time points. In GT 1a patients, R155K mutants were replaced by the wild type in 57% of patients at week 24. These NS3 clinical mutants were sensitive to NS5B and NS5A inhibitors, as well as alpha interferon (IFN-α) and ribavirin. The lack of cross-resistance between GS-9451 and other classes of HCV inhibitors supports the utility of combination therapy.

1228 CHARACTERIZATION OF NOVEL, HIGHLY POTENT NS5A INHIBITORS WITH QD DOSING POTENTIAL AND ROBUST ACTIVITY IN AN HCV CHIMERIC ANIMAL MODEL

Background: This study monitored for resistance for up to 12 weeks of treatment with danoprevir (DNV) plus low-dose ritonavir (r) in combination with PegIFNa-2a/RBV in genotype (GT) 1 treatmentnaive patients and prior null responders. Materials and Methods: Three cohorts of treatment-naive HCV GT1 patients were randomised to receive DNV/r (n = 31) or placebo/r + PegIFNa-2a/RBV (n =3) for 15 days with DNV/r regimens of 100/100mg q12h (cohort 1), 200/100mg q24h (cohort 2), and 200/100mg q12h (cohort 3). A fourth cohort (n = 24) included prior null responder GT1 patients who received 100/100mg q12h DNV/r or placebo/r + PegIFNa-2a/RBV for 12 weeks. The NS3/4A and/or NS3 protease coding region was amplified and population sequence was performed on all baseline samples. Population sequence and phenotypic analyses were performed on on-treatment and follow up samples from DNV/r/PegIFNa-2a/RBV-treated patients that experienced: i. viral load rebound, ii. non response or iii. partial response. Results: Low-dose DNV/r + PegIFNa-2a/RBV provided robust virological response in all cohorts. No viral breakthrough was observed in treatment-naive patients (cohorts 1–3, 22 GT1a and 9 GT1b) after 2 weeks of DNV combination therapy. Of the 24 (8 GT1a and 16 GT1b) prior null responder patients treated with DNV/r for up to 12 weeks, four GT1a patients experienced a viral breakthrough (two patients by week 3, one by week 4 and one by week 8 of treatment). This was associated with the selection of R155K in the NS3 protease region and ~250-fold EC50 shift compared to the baseline samples. The R155K resistance mutation persisted for up to 12 weeks after cessation of therapy. Viral breakthrough was observed in one GT1b patient. Population sequence of the NS3/4A region of 58 patients at baseline did not show any DNV resistance mutations. Conclusions: DNV/r + PegIFNa-2a/RBV provided a robust virological response in GT1b and GT1a treatment-naive patients with no viral breakthrough observed. In prior null responders, robust response was observed in GT1b patients whereas resistance related viral breakthrough was observed in 4/8 GT1a patients. R155K mutation persisted for 12 weeks after the cessation of therapy, emphasising the need for a second direct-acting antiviral agent in this population.

1229 GENOTYPIC AND PHENOTYPIC CHARACTERIZATION OF NS3 VARIANTS SELECTED IN HCV-INFECTED PATIENTS TREATED WITH ABT-450

Background: This study monitored for resistance for up to 12 weeks of treatment with danoprevir (DNV) plus low-dose ritonavir (r) in combination with PegIFNa-2a/RBV in genotype (GT) 1 treatmentnaive patients and prior null responders. Materials and Methods: Three cohorts of treatment-naive HCV GT1 patients were randomised to receive DNV/r (n = 31) or placebo/r + PegIFNa-2a/RBV (n =3) for 15 days with DNV/r regimens of 100/100mg q12h (cohort 1), 200/100mg q24h (cohort 2), and 200/100mg q12h (cohort 3). A fourth cohort (n = 24) included prior null responder GT1 patients who received 100/100mg q12h DNV/r or placebo/r + PegIFNa-2a/RBV for 12 weeks. The NS3/4A and/or NS3 protease coding region was amplified and population sequence was performed on all baseline samples. Population sequence and phenotypic analyses were performed on on-treatment and follow up samples from DNV/r/PegIFNa-2a/RBV-treated patients that experienced: i. viral load rebound, ii. non response or iii. partial response. Results: Low-dose DNV/r + PegIFNa-2a/RBV provided robust virological response in all cohorts. No viral breakthrough was observed in treatment-naive patients (cohorts 1–3, 22 GT1a and 9 GT1b) after 2 weeks of DNV combination therapy. Of the 24 (8 GT1a and 16 GT1b) prior null responder patients treated with DNV/r for up to 12 weeks, four GT1a patients experienced a viral breakthrough (two patients by week 3, one by week 4 and one by week 8 of treatment). This was associated with the selection of R155K in the NS3 protease region and ~250-fold EC50 shift compared to the baseline samples. The R155K resistance mutation persisted for up to 12 weeks after cessation of therapy. Viral breakthrough was observed in one GT1b patient. Population sequence of the NS3/4A region of 58 patients at baseline did not show any DNV resistance mutations. Conclusions: DNV/r + PegIFNa-2a/RBV provided a robust virological response in GT1b and GT1a treatment-naive patients with no viral breakthrough observed. In prior null responders, robust response was observed in GT1b patients whereas resistance related viral breakthrough was observed in 4/8 GT1a patients. R155K mutation persisted for 12 weeks after the cessation of therapy, emphasising the need for a second direct-acting antiviral agent in this population.

64 IDENTIFICATION AND CHARACTERIZATION OF A HEPATITIS C VIRUS CAPSID ASSEMBLY INHIBITOR

novel genotypic variant combinations was examined using chimeric sub-genomic replicons. Results: Population sequencing of the NS3 protease and NS5A regions in all baseline isolates revealed the pre-existence of one PI-resistant variant (1a-NS3-K155; ~20-fold increase in BMS650032 EC50). In five of six GT1a patients experiencing VBT, emergent resistance variants to BMS-650032 included substitutions at either NS3–155 (R155K) or NS3–168 (D168E/T/Y). Emergent resistance variants to BMS-790052 included substitutions at NS5A-30 (Q30R), NS5A-31 (L31V/M), and NS5A-93 (Y93C/N). In one patient demonstrating VBT, HCVRNA levels were too low (<100 IU/mL) for analysis. In the one patient who did not respond to the addition of pegIFNa/RBV, the NS3 protease and NS5A resistance variants persisted 4 weeks post-treatment. The patient with a preexisting PI-resistant variant demonstrated rapid viral load decline and remained undetectable throughout the treatment period but relapsed at WK4 post-treatment. Two GT1b patients responded to 2-DAA treatment and demonstrated no relapse 4 weeks posttreatment. Conclusions: HCV NS3 protease and NS5A variants reported to confer resistance to BMS-650032 and BMS-790052, respectively, were selected in prior null responders infected with HCV GT1a during the 2-DAA treatment. These variants were detected at the time of VBT. No VBT was observed in patients infected with GT1b or receiving two DAA with pegIFNa/RBV.