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In two trials involving patients with hepatitis C in whom previous treatment with direct-acting antiviral agents failed, treatment for 12 weeks with sofosbuvir, velpatasvir, and voxilaprevir achieved high rates of sustained virologic response. The majority of patients who are chronically infected with hepatitis C virus (HCV) can now be successfully treated with drugs that directly target viral replication. 1 , 2 Combination regimens of direct-acting antiviral agents (DAAs) provide rates of sustained virologic response exceeding 90%, regardless of HCV genotype, disease stage, or treatment history. 3 The proportion of patients who do not have a sustained virologic response to treatment with approved regimens is small, but given the size of the infected population — estimates range up to 150 million people worldwide 4 — the absolute number of such patients is substantial and will increase as more . . .

In patients with HCV genotypes 2 and 3, sofosbuvir plus ribavirin was administered for 12 weeks in patients with genotype 2 and for 24 weeks in those with genotype 3. Rates of sustained virologic response were 93% in patients with genotype 2 and 85% in those with genotype 3. Of the six main genotypes of the hepatitis C virus (HCV), genotypes 2 and 3 account for approximately 30% of chronic infections worldwide. 1 Although these two genotypes have historically been grouped together in treatment guidelines and clinical trials, 2 , 3 accumulating evidence suggests that there are important clinical differences between them. 1 , 4 , 5 HCV genotype 3 infection is associated with a higher incidence of hepatic steatosis, more rapid progression of fibrosis, and possibly a greater risk of hepatocellular carcinoma than is HCV genotype 2 infection. 6 Moreover, patients with HCV genotype 3 infection are less responsive to peginterferon-based treatment than are patients . . .

In previously untreated patients with HCV genotype 1 infection without cirrhosis, the rate of sustained virologic response was 94% with 8 weeks of ledipasvir–sofosbuvir, 93% with 8 weeks of ledipasvir–sofosbuvir plus ribavirin, and 95% with 12 weeks of ledipasvir–sofosbuvir. More than 3 million people in the United States are chronically infected with the hepatitis C virus (HCV). 1 , 2 Although the number of new infections has been declining for decades, HCV-related morbidity and mortality are projected to continue rising for another 20 years. 3 One half to three quarters of persons currently infected with HCV have not received a diagnosis and are untreated; many will have progression to decompensated cirrhosis, hepatocellular carcinoma, and other liver complications. 3 , 4 Early diagnosis and treatment are essential to improve long-term health outcomes in this population. New guidelines from the Centers for Disease Control and Prevention . . .

Background. Sofosbuvir (SOF) exhibits a high barrier to resistance, with no S282T NS5B substitution or phenotypic resistance detected in phase 3 registration studies. Methods. Here, emergence of the NS5B variants L159F and V321A and possible association with resistance was evaluated in 8 studies of SOF (NEUTRINO, FISSION, POSITRON, FUSION, VALENCE, PHOTON-1, PHOTON-2, and P7977-2025) and 5 studies of combination ledipasvir (LDV) and SOF (LDV/SOF; LONESTAR, ELECTRON [LDV/SOF arms], ION1, ION2, and ION3), using deep sequencing. Results. Deep sequencing detected L159F in 15% (53 of 353) and V321A in 5% (17 of 353) of patients with virologic failure in the SOF studies. Intensification of SOF treatment with LDV reduced the emergence of L159F or V321A to 2% (1 of 50 each) at virologic failure. L159F and V321A did not influence the outcome of retreatment with SOF, ribavirin, and pegylated interferon. At baseline, L159F was detected only in genotype 1-infected patients (1%) and was only associated with increased virologic failure in patients treated for short durations with SOF and ribavirin. Conclusions. Deep-sequencing analysis confirmed that NS5B variants L159F and V321A emerged in a subset of patients treated with SOF at virologic failure. These variants had no impact on retreatment outcome with SOF, ribavirin, and pegylated interferon. Baseline L159F in genotype 1 did not affect the treatment outcome with LDV/SOF.

Background. The development of direct-acting antivirals in recent years has dramatically enhanced rates of viral eradication to >90% in patients with chronic hepatitis C virus (HCV) infection. To determine true treatment efficacy and define the most appropriate retreatment, it is important to distinguish virologic relapse from reinfection when patients in whom HCV is eradicated during treatment become infected with a new HCV strain after treatment. Methods. We investigated the prevalence of late recurrent viremia (patients with sustained virologic response 12 weeks after the end of treatment but detectable HCV RNA at follow-up week 24) and used refined phylogenetic analysis of multiple HCV genes to distinguish virologic relapse from reinfection. Results. Across 11 phase 3 clinical trials of ledipasvir–sofosbuvir (SOF) and SOF, only 12 of 3004 patients had detectable HCV RNA following sustained virologic response 12 weeks after the end of treatment. Of these 12 patients with late recurrent viremia, 11 had the same HCV genotype/subtype at baseline and at recurrence. Phylogenetic analysis demonstrated that 58% (7 of 12) of these patients were successfully treated with the SOF-based regimen, with HCV eradication achieved, but became reinfected with a different HCV strain after treatment. The remaining 5 patients with late recurrent viremia had virologic relapse in which the HCV present at baseline persisted in the liver or another compartment and reemerged in the blood 24 weeks after treatment. Conclusions. The incidence of late recurrent viremia was low. Distinguishing reinfection from virologic relapse has implications for determining true treatment efficiency and selecting optimal retreatment strategies.

Background. Sofosbuvir is a chain-terminating nucleotide analogue inhibitor of the hepatitis C virus (HCV) NS5B RNA polymerase that is efficacious in subjects with HCV genotype 1–6 infection. Sofosbuvir resistance is primarily conferred by the S282T substitution in NS5B. Methods. NS5B sequencing and susceptibility testing of HCV from subjects infected with genotypes 1–6 who participated in phase 2 and 3 sofosbuvir clinical trials was performed. Results. No NS5B variants present at baseline among 1645 sofosbuvir-treated subjects were associated with treatment failure; sofosbuvir susceptibility was within 2-fold of reference. Among 282 subjects who did not achieve sustained virologic response, no novel sofosbuvir resistance–associated variants were identified, and the NS5B changes observed did not confer significant reductions in sofosbuvir susceptibility. In 1 subject with S282T observed at relapse 4 weeks after sofosbuvir monotherapy, the resistant variant (13.5-fold reduced sofosbuvir susceptibility, replication capacity <2% of control) became undetectable by deep sequencing 12 weeks after treatment. L159F and V321A were identified as treatment-emergent variants but did not confer resistance to sofosbuvir in the replicon system. Conclusions. These data demonstrate a uniform susceptibility of subject-derived HCV to sofosbuvir, and also show that selection of sofosbuvir-resistant HCV is exceedingly rare and is associated with a significant reduction in viral fitness.

The development of resistance to direct-acting antivirals (DAAs) targeting the hepatitis C virus (HCV) can compromise therapy. However, mechanisms that determine prevalence and frequency of resistance-conferring mutations remain elusive. Here, we studied the fidelity of the HCV RNA-dependent RNA polymerase NS5B in an attempt to link the efficiency of mismatch formation with genotypic changes observed in vivo. Enzyme kinetic measurements revealed unexpectedly high error rates (approximately 10-3 per site) for G:U/U:G mismatches. The strong preference for G:U/U:G mismatches over all other mistakes correlates with a mutational bias in favor of transitions over transversions. Deep sequencing of HCV RNA samples isolated from 20 treatment-naïve patients revealed an approximately 75-fold difference in frequencies of the two classes of mutations. A stochastic model based on these results suggests that the bias toward transitions can also affect the selection of resistance-conferring mutations. Collectively, the data provide strong evidence to suggest that the nature of the nucleotide change can contribute to the genetic barrier in the development of resistance to DAAs.

Although interferon-free regimens are approved for patients co-infected with HIV and genotype-2 or genotype-3 hepatitis C virus (HCV), interferon-based regimens are still an option for those co-infected with HIV and HCV genotypes 1 or 4. These regimens are limited by clinically significant toxic effects and drug interactions with antiretroviral therapy. We aimed to assess the efficacy and safety of an interferon-free, all-oral regimen of sofosbuvir plus ribavirin in patients with HIV and HCV co-infection. We did this open-label, non-randomised, uncontrolled, phase 3 study at 45 sites in seven European countries and Australia. We enrolled patients (aged ≥18 years) co-infected with stable HIV and chronic HCV genotypes 1–4, including those with compensated cirrhosis. Once-daily sofosbuvir (400 mg) plus twice-daily ribavirin (1000 mg in patients with bodyweights <75 kg and 1200 mg in those with weights ≥75 kg) was given for 24 weeks to all patients except treatment-naive patients with genotype-2 HCV, who received a 12-week regimen. The primary efficacy endpoint was sustained virological response 12 weeks after treatment. We did analysis by modified intention to treat. This study is registered with ClinicalTrials.gov, number NCT01783678. Between Feb 7, 2013, and July 29, 2013, we enrolled 275 eligible patients, of whom 262 (95%) completed treatment; 274 patients were included in the final analysis. Overall rates of sustained virological response 12 weeks after treatment were 85% (95% CI 77–91) in patients with genotype-1 HCV, 88% (69–98) in patients with genotype-2 HCV, 89% (81–94) in patients with genotype-3 HCV, and 84% (66–95) in patients with genotype-4 HCV. Response rates in treatment-naive patients with HCV genotypes 2 or 3 (89% [95% CI 67–99] and 91% [81–97], respectively) were similar to those in treatment-experienced patients infected with those genotypes (83% [36–100] and 86% [73–94], respectively). There was no emergence of sofosbuvir-resistance mutations in patients with HCV viral relapse. Six (2%) patients discontinued treatment because of adverse events. The most common adverse events were fatigue, insomnia, asthenia, and headache. Four (1%) patients had serious adverse events regarded as related to study treatment. Additionally, four (1%) patients receiving antiretroviral treatment had a transient HIV viral breakthrough; however, none required changes in antiretroviral regimen. Sofosbuvir and ribavirin provided high rates of sustained virological response after 12 weeks of treatment in treatment-naive and treatment-experienced patients co-infected with HIV and HCV genotypes 1–4. The characteristics of this interferon-free combination regimen make sofosbuvir plus ribavirin a useful treatment option for this patient population. Gilead Sciences.

Hepatitis C virus (HCV) is currently classified into 8 genotypes and 86 subtypes. The objective of this study was to characterize novel HCV subtypes and to investigate the impact of subtypes on treatment outcome. Full-genome sequencing was performed on HCV plasma samples with <85% sequence homology of NS3, NS5A, and/or NS5B to HCV genotype (GT) 1-8 reference strains. A total of 14 653 patients with GT1-6 HCV infection were enrolled in clinical studies of sofosbuvir-based regimens. For the majority of the patients, a specific subtype could be assigned based on a close genetic relationship to previously described subtypes. However, for 19 patients, novel subtypes were identified with <85% homology compared with previously described subtypes. These novel subtypes had the following genotypes: 9 in GT2, 5 in GT4, 2 in GT6, and 1 each in GT1, GT3, and GT5. Despite the presence of polymorphisms at resistance-associated substitution positions, 18 of the 19 patients treated with sofosbuvir-containing therapy achieved SVR12. Nineteen novel HCV subtypes were identified, suggesting an even greater genetic diversity of HCV subtypes than previously recognized.

In this phase 3 study involving patients with HCV genotype 1, 2, 4, 5, or 6 infection, including those with compensated cirrhosis, treatment with 12 weeks of sofosbuvir and velpatasvir resulted in a sustained virologic response in 99% of patients. The hepatitis C virus (HCV), a single-stranded RNA virus of the family Flaviviridae with six major genotypes, infects up to 150 million people worldwide. 1 , 2 Chronic HCV infection causes progressive liver fibrosis, which can lead to cirrhosis, hepatic decompensation, and hepatocellular carcinoma. 3 , 4 As many as half a million people die annually from liver disease associated with chronic HCV infection. 5 In recent years, the development of drugs that directly interfere with HCV replication has revolutionized HCV treatment. There are now effective combinations of direct-acting antiviral agents for most patients, but in choosing an appropriate regimen, clinicians must take into account . . .