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The treatment of hepatitis C virus (HCV) has made significant advances with the development of new direct-acting antivirals. Nucleotide polymerase inhibitors are one class of these new medications that have been shown to be highly effective, safe and well tolerated as part of an antiviral regimen. Sofosbuvir has become the first drug in this class to be approved for clinical use, supported by results from extensive phase II and phase III clinical trials. This review will further discuss nucleotide polymerase inhibitors, including the data supporting their use as part of interferon-free HCV treatment regimens.

BACKGROUND: Although the addition of the HCV NS3/4A protease inhibitors boceprevir and telaprevir to pegylated interferon (peginterferon) alfa plus ribavirin has improved sustained virological response (SVR) in treatment-naive and treatment-experienced patients infected with hepatitis C virus (HCV) genotype 1, the regimens have a high pill burden and are associated with increased rates and severity of adverse events, such as anaemia and rash. The efficacy and safety of the combination of simeprevir, a one pill, once-daily, oral HCV NS3/4A protease inhibitor, plus peginterferon alfa 2a plus ribavirin were assessed in treatment-naive patients with HCV genotype 1 infection. METHODS: In QUEST-1, a phase 3, randomised, double-blind multicentre trial undertaken in 13 countries (Australia, Europe, North America, Puerto Rico, and New Zealand), 394 patients (aged >/=18 years) with chronic HCV genotype 1 infection and no history of HCV treatment, stratified by HCV subtype and host IL28B genotype, were randomly assigned in a 2:1 ratio with a computer-generated allocation sequence to receive simeprevir (150 mg once daily, orally) plus peginterferon alfa 2a plus ribavirin for 12 weeks, followed by peginterferon alfa 2a plus ribavirin (simeprevir group), or placebo orally plus peginterferon alfa 2a plus ribavirin for 12 weeks, followed by peginterferon alfa 2a plus ribavirin (placebo group). Treatment duration was 24 weeks or 48 weeks in the simeprevir group according to criteria for response-guided therapy (ie, HCV RNA <25 IU/mL [undetectable or detectable] at week 4 and <25 IU/mL undetectable at week 12) and 48 weeks in the placebo group. Patients, study personnel, and the sponsor were masked to the treatment group assignment. The primary efficacy endpoint was sustained virological response 12 weeks after the planned end of treatment (SVR12) and was assessed with an intention-to-treat analysis. The results of the primary analysis (week 60) are presented for safety and SVR12. This trial is registered with ClinicalTrials.gov, number NCT01289782. FINDINGS: Treatment with simeprevir, peginterferon alfa 2a, and ribavirin was superior to placebo, peginterferon alfa 2a, and ribavirin (SVR12 in 210 [80%] patients of 264 vs 65 [50%] of 130, respectively, adjusted difference 29.3% [95% CI 20.1-38.6; p<0.0001). Adverse events in the first 12 weeks of treatment led to discontinuation of simeprevir in two (<1%) patients and discontinuation of placebo in one patient (<1%); fatigue (106 [40%] vs 49 [38%] patients, respectively) and headache (81 [31%] vs 48 [37%], respectively) were the most common adverse events. The prevalences of anaemia (42 [16%] vs 14 [11%], respectively) and rash (72 [27%] vs 33 [25%]) were similar in the simeprevir and placebo groups. Addition of simeprevir did not increase severity of patient-reported fatigue and functioning limitations, but shortened their duration. INTERPRETATION: Simeprevir once daily with peginterferon alfa 2a and ribavirin shortens therapy in treatment-naive patients with HCV genotype 1 infection without worsening the adverse event profiles associated with peginterferon alfa 2a plus ribavirin. FUNDING: Janssen Infectious Diseases-Diagnostics.

BACKGROUND & AIMS: Interferon-based treatment of chronic hepatitis C virus (HCV) infection can negatively affect patient-reported outcomes (PROs) and work productivity (WP). We assessed these factors in patients with chronic hepatitis C treated with sofosbuvir and ribavirin, with or without pegylated interferon. METHODS: The HCV-specific Quality of Life (Chronic Liver Disease Questionnaire-HCV version [CLDQ-HCV]), Functional Assessment of Chronic Illness Therapy-Fatigue, and Work Productivity and Activity Index: Specific Health Problem questionnaires were completed before, during, and after treatment of patients infected with HCV genotypes 2 or 3 who received sofosbuvir and ribavirin for 16 or 12 weeks (the FUSION study, n = 201) or patients infected with HCV genotype 1 who received pegylated interferon, sofosbuvir, and ribavirin for 12 weeks (the NEUTRINO study, n = 327). RESULTS: Patients in each group of the FUSION study had similar PRO and WP scores at each time point (all comparisons, P > .05). Compared with baseline, patients had modest reductions in fatigue, HCV-specific quality of life, and WP and Activity Index scores during treatment (P = .02 to <.0001). However, by 4 weeks after treatment, all scores returned to baseline levels or higher. Subjects in the NEUTRINO study had greater reductions in these scores during treatment; most remained significant through 4 weeks after treatment (P < .05). Significant improvements in PROs were observed among patients with sustained virologic responses 12 weeks after treatment in the FUSION and NEUTRINO studies (all P < .05). In multivariate analyses after adjustment for confounders, interferon therapy was independently associated with worse PROs after 12 weeks of treatment. CONCLUSIONS: On the basis of an analysis of 2 large clinical trials (FUSION and NEUTRINO), patient outcome and productivity are more negatively affected by the inclusion of pegylated interferon in treatment than by interferon-free regimens. Patients with sustained virologic responses 12 weeks after treatment had significant improvements in PROs in both studies.

OBJECTIVE: To investigate in this phase 2a study (ZENITH) the safety, tolerability, and antiviral activity of VX-222, a selective, non-nucleoside inhibitor of hepatitis C virus (HCV) NS5B polymerase, combined with various telaprevir-based regimens for treatment of genotype 1 HCV. METHODS: In total, 152 treatment-naive patients received VX-222+telaprevir ('DUAL' regimen; n=47), with ribavirin ('TRIPLE' regimen; n=46), or with peginterferon+ribavirin ('QUAD' regimen; n=59) for 12 weeks. Patients with detectable HCV RNA at weeks 2 and/or 8 received peginterferon+ribavirin for 24 (DUAL and TRIPLE) or 12 (QUAD) additional weeks. RESULTS: VX-222 (100 or 400 mg twice daily) was well tolerated, with an increased rate of gastrointestinal adverse events observed with the higher dose. Across VX-222 400-mg twice-daily regimens, the QUAD was associated with the highest frequency of grade 3/4 adverse events. The DUAL was discontinued because of high viral breakthrough before week 12. Sustained virologic response (SVR) 24 weeks after end of treatment (SVR24), including patients treated with 12 or 24 additional weeks of peginterferon+ribavirin, was 67% for TRIPLE (VX-222 400 mg twice daily) and 79 and 90% for QUAD (VX-222 100 and 400 mg twice daily, respectively). CONCLUSION: These results provide valuable information regarding the safety, tolerability, and efficacy of telaprevir combined with a non-nucleoside polymerase inhibitor, as dual therapy or with ribavirin without or with peginterferon. Telaprevir and VX-222, alone or with ribavirin without or with peginterferon, were generally well tolerated, with improved tolerability without peginterferon. SVR24 rates achieved with TRIPLE and QUAD regimens containing telaprevir and VX-222 were comparable to those observed with telaprevir-based therapy.