Joan R. Butterton

Grazoprevir–Elbasvir Combination Therapy for Treatment-Naive Cirrhotic and Noncirrhotic Patients With Chronic Hepatitis C Virus Genotype 1, 4, or 6 Infection: A Randomized Trial

Context Various oral interferon- and ribavirin-free regimens are becoming available to treat chronic hepatitis C virus (HCV) infection. A grazoprevirelbasvir combination regimen has shown promise in phase 2 trials. Contribution This phase 3 trial found a once-daily grazoprevirelbasvir regimen to be effective and well-tolerated in patients with HCV genotype 1, 4, or 6 infection. Outcomes were similar in patients with and without cirrhosis. Caution The study did not include an active comparator, so how this regimen compares with others is unknown. Implication Grazoprevirelbasvir represents a new therapeutic option for chronic HCV infection. Chronic hepatitis C virus (HCV) infection remains a growing cause of cirrhosis, hepatocellular carcinoma, hepatic decompensation, and liver transplantation (1). Effective therapy for HCV infection diminishes long-term liver-related complications and mortality (2). Convenient, oral, direct-acting antiviral regimens are being investigated for chronic HCV infection (3). Grazoprevir is an NS3/4A protease inhibitor that has high potency in vitro against HCV genotype (GT) 1, GT2, GT4, GT5, and GT6 but is less active against GT3 (4). Grazoprevir retains substantial activity against resistance-associated variants (RAVs) commonly detected after failed therapy with first-generation protease inhibitors (4, 5). Elbasvir is an NS5A inhibitor active against GT1, GT2a, GT3, GT4, GT5, and GT6, even in the presence of RAVs associated with failure of other NS5A inhibitors, such as daclatasvir and ledipasvir (6, 7). Grazoprevirelbasvir has been evaluated in an extensive phase 2 clinical development program (5, 810). The C-WORTHY study indicated that grazoprevirelbasvir with or without ribavirin for 12 weeks provided efficacious and well-tolerated therapy for monoinfected and HIVco-infected patients, treatment-naive and treatment-experienced patients, and noncirrhotic and cirrhotic patients (9, 10). The objective of the phase 3 C-EDGE Treatment-Naive trial was to evaluate the efficacy and safety profile of a once-daily, fixed-dose, oral, 12-week regimen of grazoprevirelbasvir without interferon or ribavirin in treatment-naive monoinfected patients with and without cirrhosis and with GT1, GT4, or GT6 infection. Methods Study Design The C-EDGE Treatment-Naive study was an international, randomized, blinded, placebo-controlled, parallel-group trial of a fixed-dose combination of grazoprevir 100 mg/elbasvir 50 mg for treatment-naive cirrhotic and noncirrhotic patients with chronic HCV GT1, GT4, or GT6 infections. A historical SVR12 rate was used as the comparator for efficacy. A deferred-treatment group was included as a concurrent placebo group to assess safety; after the follow-up period, placebo recipients received open-label grazoprevirelbasvir so that all participants would receive therapy during the study. Recruitment of Study Participants Patients were recruited from general medical clinics at 60 trial centers: 4 in Australia, 4 in the Czech Republic, 5 in France, 5 in Germany, 5 in Israel, 3 in Puerto Rico, 3 in South Korea, 4 in Sweden, 3 in Taiwan, and 24 in the United States. Patients who fulfilled inclusion criteria were asked to participate in the trial. Selected clinical sites were experienced in the management and care of HCV-infected patients, with a history of successful study conduct and the capability for rapid enrollment. Sites were chosen to allow a wide geographic distribution and to ensure that requirements for minority representation, enrollment of patients with cirrhosis, and genotype distribution were met. Eligibility Criteria Adults (aged >18 years) with HCV RNA levels greater than 104 IU/mL were eligible. Hepatic fibrosis was staged by biopsy or noninvasive assessment (Appendix 1) (11). Exclusion criteria were decompensated liver disease, hepatocellular carcinoma, HIV or hepatitis B virus co-infection, uncontrolled diabetes mellitus (hemoglobin A1c level >10%), elevated prothrombin time unrelated to anticoagulation, creatinine clearance less than 50 mL/min, hemoglobin level less than 95 g/L, thrombocytopenia (platelet count <50109 cells/L), aminotransferase levels more than 10 times the upper limit of normal, or hypoalbuminemia (albumin level <30 g/L). Enrollment was constrained to meet the following targets: 20% of the participants having cirrhosis and 15% having GT4 or GT6 infection. All participants provided written informed consent. The study was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Independent ethics committees reviewed and approved the protocol and applicable amendments for each institution. Randomization and Masking After stratification by presence or absence of cirrhosis and GT1, GT4, or GT6, patients were randomly assigned in a 3:1 ratio to receive immediate or deferred therapy with grazoprevirelbasvir through a central interactive voice-response system according to a computer-generated random allocation schedule. Patients took 1 fixed-dose combination tablet of grazoprevirelbasvir (immediate-treatment group) or matching placebo (deferred-treatment group) once daily at approximately the same time, without regard to food, for 12 weeks. Patients, clinical site, and sponsor personnel were blinded to treatment assignment (except for a separate unblinded medical team that monitored virologic failures and serious adverse events). Four weeks after completion of therapy, treatment allocation was unblinded, and patients in the deferred-treatment group then received open-label grazoprevirelbasvir for 12 weeks. All patients were to be followed for 24 weeks after cessation of active study therapy (Figure 1). Figure 1. Diagram of study design. DFW = deferred follow-up week; DTW = deferred-treatment week; FU = follow-up; FW = follow-up week; GZREBR = grazoprevirelbasvir; TW = treatment week. Outcome Measures This report describes the efficacy among patients enrolled in the immediate-treatment group through 12 weeks after treatment and the safety findings among patients enrolled in both groups through 14 days after the end of therapy in the initial treatment period. Efficacy and safety results for both groups through follow-up week 24 are still being collected and will be presented in a future report. The primary efficacy outcome variable was the proportion of patients in the immediate-treatment group achieving unquantifiable HCV RNA 12 weeks after the end of study treatment (SVR12). Virologic failures encompassed breakthrough viremia (confirmed HCV RNA level at or above the lower limit of quantification [LLOQ] during treatment after previously being below the LLOQ) and relapse (confirmed HCV RNA level at or above the LLOQ subsequent to cessation of study therapy after becoming undetectable at the end of treatment). Viral and Resistance Assays Plasma HCV RNA levels were measured by the COBAS AmpliPrep/COBAS TaqMan HCV test, version 2.0 (Roche Molecular Diagnostics, Branchburg, NJ), with an LLOQ of 15 IU/mL. Specimens for viral load measurements were collected at screening; baseline; treatment weeks 4, 8, and 12; and follow-up weeks 4, 12, and 24. Circulating viral quasi-species at baseline or at the time of virologic failure underwent population sequencing with a detection limit for variants of approximately 25% prevalence (12). The complete NS3 and NS5A genes were amplified from samples with RNA levels of 1000 IU/mL or greater by using reverse transcription polymerase chain reaction (5, 12, 13). Resultant amino acid sequences were compared with wild-type GT1a (H77; accession number NC004102), GT1b (Con1; AJ238799), GT4a (ED43; GU814265), or GT6a (EUHK2; Y12083) reference sequences. To assess the effect of baseline NS3 variants, specific amino acid loci prone to selection by early-generation NS3/4A protease inhibitors (positions 36, 54, 55, 56, 80, 107, 122, 132, 155, 156, 158, 168, 170, and 175) were studied in replicon cell lines encoding mutations in a GT1a backbone (5, 14). These substitutions were categorized according to whether they conferred a greater than 5-fold reduced susceptibility to grazoprevir. Likewise, to assess the effect of baseline NS5A variants, amino acid loci selected by NS5A inhibitors (positions 28, 30, 31, 58, and 93) were categorized according to whether they conferred a greater than 5-fold reduced susceptibility to elbasvir in the replicon assay. Statistical Analysis The C-EDGE Treatment-Naive study was designed to randomly assign approximately 400 patients, with 300 patients in the immediate-treatment group and 100 patients in the deferred-treatment group (which served as the placebo control group for the first 12 weeks). After a 4-week follow-up period, placebo recipients were unblinded at study week 16 and received open-label grazoprevirelbasvir. The primary efficacy hypothesis exclusively applied to patients in the immediate-treatment group. Assuming a response rate of 85% or greater, the study had more than 99% power to demonstrate an SVR12 rate superior to the reference rate of 73% at an overall 1-sided value of 0.025. The historical reference rate of 73% was derived from phase 3 trials of simeprevir/peginterferon + ribavirin in treatment-naive monoinfected patients, after adjustment for the expected proportion of cirrhotic patients and the anticipated improved tolerability with an interferon-free regimen (Appendix 1) (15, 16). The primary efficacy and safety analyses were performed on the full data set, which included all patients receiving at least 1 dose of the study treatment. The primary efficacy end point was prespecified as the proportion of patients with an HCV RNA level below the LLOQ 12 weeks after the end of treatment (SVR12) (17). Missing outcome data were imputed as failures unless the values immediately before and after the missing result were both successes, in which case the absent value was imputed as a success. The 95% CIs were computed by the conservative ClopperPear

Pharmacokinetic interaction between the hepatitis C virus protease inhibitor boceprevir and cyclosporine and tacrolimus in healthy volunteers

The hepatitis C virus protease inhibitor boceprevir is a strong inhibitor of cytochrome P450 3A4 and 3A5 (CYP3A4/5). Cyclosporine and tacrolimus are calcineurin inhibitor immunosuppressants used to prevent organ rejection after liver transplantation; both are substrates of CYP3A4. This two‐part pharmacokinetic interaction study evaluated boceprevir with cyclosporine (part 1) and tacrolimus (part 2). In part 1, 10 subjects received single‐dose cyclosporine (100 mg) on day 1, single‐dose boceprevir (800 mg) on day 3, and concomitant cyclosporine/boceprevir on day 4. After washout, subjects received boceprevir (800 mg three times a day) for 7 days plus single‐dose cyclosporine (100 mg) on day 6. In part 2A, 12 subjects received single‐dose tacrolimus (0.5 mg). After washout, they received boceprevir (800 mg three times a day) for 11 days plus single‐dose tacrolimus (0.5 mg) on day 6. In part 2B, 10 subjects received single‐dose boceprevir (800 mg) and 24 hours later received boceprevir (800 mg) plus tacrolimus (0.5 mg). Coadministration of boceprevir with cyclosporine/tacrolimus was well tolerated. Concomitant boceprevir increased the area under the concentration‐time curve from time 0 to infinity after single dosing (AUCinf) and maximum observed plasma (or blood) concentration (Cmax) of cyclosporine with geometric mean ratios (GMRs) (90% confidence interval [CI]) of 2.7 (2.4‐3.1) and 2.0 (1.7‐2.4), respectively. Concomitant boceprevir increased the AUCinf and Cmax of tacrolimus with GMRs (90% CI) of 17 (14‐21) and 9.9 (8.0‐12), respectively. Neither cyclosporine nor tacrolimus coadministration had a meaningful effect on boceprevir pharmacokinetics. Conclusion: Dose adjustments of cyclosporine should be anticipated when administered with boceprevir, guided by close monitoring of cyclosporine blood concentrations and frequent assessments of renal function and cyclosporine‐related side effects. Administration of boceprevir plus tacrolimus requires significant dose reduction and prolongation of the dosing interval for tacrolimus, with close monitoring of tacrolimus blood concentrations and frequent assessments of renal function and tacrolimus‐related side effects. (HEPATOLOGY 2012;56:1622–1630)

Pharmacokinetic Interactions Between the Hepatitis C Virus Protease Inhibitor Boceprevir and Ritonavir-Boosted HIV-1 Protease Inhibitors Atazanavir, Darunavir, and Lopinavir

BACKGROUND Boceprevir represents a new treatment option for hepatitis C (HCV)-infected patients, including those with HCV/human immunodeficiency virus coinfection; however, little is known about pharmacokinetic interactions between boceprevir and antiretroviral drugs. METHODS A randomized, open-label study to assess the pharmacokinetic interactions between boceprevir and ritonavir-boosted protease inhibitors (PI/r) was conducted in 39 healthy adults. Subjects received boceprevir (800 mg, 3 times daily) for 6 days and then received PI/r as follows: atazanavir (ATV) 300 mg once daily, lopinavir (LPV) 400 mg twice daily, or darunavir (DRV) 600 mg twice daily, each with ritonavir (RTV) 100 mg on days 10-31, plus concomitant boceprevir on days 25-31. RESULTS Boceprevir decreased the exposure of all PI/r, with area under the concentration-time curve [AUC] from time 0 to the time of the last measurable sample geometric mean ratios of 0.65 (90% confidence interval [CI], .55-.78) for ATV/r; 0.66 (90% CI, .60-.72) for LPV/r, and 0.56 (90% CI, .51-.61) for DRV/r. Coadministration with boceprevir decreased RTV AUC during a dosing interval τ (AUC(τ)) by 22%-36%. ATV/r did not significantly affect boceprevir exposure, but boceprevir AUC(τ) was reduced by 45% and 32% when coadministered with LPV/r and DRV/r, respectively. Overall, treatments were well tolerated with no unexpected adverse events. CONCLUSIONS Concomitant administration of boceprevir with PI/r resulted in reduced exposures of PI and boceprevir. These drug-drug interactions may reduce the effectiveness of PI/r and/or boceprevir when coadministered.

Pharmacokinetic Evaluation of the Interaction between Hepatitis C Virus Protease Inhibitor Boceprevir and 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitors Atorvastatin and Pravastatin

ABSTRACT Boceprevir is a potent orally administered inhibitor of hepatitis C virus and a strong, reversible inhibitor of CYP3A4, the primary metabolic pathway for many 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Thus, the aim of the present study was to investigate drug-drug interactions between atorvastatin or pravastatin and boceprevir. We conducted a single-center, open-label, fixed-sequence, one-way-crossover study with 20 healthy adult volunteers. Subjects received single-dose atorvastatin (40 mg) or pravastatin (40 mg) on day 1, followed by boceprevir (800 mg three times daily) for 7 to 10 days. Repeat single doses of atorvastatin or pravastatin were administered in the presence of steady-state boceprevir. Atorvastatin exposure increased in the presence of boceprevir, with atorvastatin area under the concentration-time curve from time zero to infinity after single dosing (AUCinf) increasing 2.3-fold (90% confidence interval [CI], 1.85, 2.90) and maximum observed concentration in plasma (Cmax) 2.7-fold (90% CI, 1.81, 3.90). Pravastatin exposure was slightly increased in the presence of boceprevir, with pravastatin AUCinf increasing 1.63-fold (90% CI, 1.03, 2.58) and Cmax 1.49-fold (90% CI, 1.03, 2.14). Boceprevir exposure was generally unchanged when the drug was coadministered with atorvastatin or pravastatin. All adverse events were mild and consistent with the known safety profile of boceprevir. The observed 130% increase in AUC of atorvastatin supports the use of the lowest possible effective dose of atorvastatin when coadministered with boceprevir, without exceeding a maximum daily dose of 40 mg. The observed 60% increase in pravastatin AUC with boceprevir coadministration supports the initiation of pravastatin treatment at the recommended dose when coadministered with boceprevir, with close clinical monitoring.

Pharmacokinetics and safety of twice-daily atazanavir 300 mg and raltegravir 400 mg in healthy individuals.

BACKGROUND Atazanavir plus raltegravir 300/400 mg twice daily is being explored as a ritonavir- and nucleoside-sparing treatment strategy. The pharmacokinetics and safety of this combination in healthy individuals were evaluated. METHODS A total of 22 healthy individuals received raltegravir 400 mg on days 1-5, atazanavir 300 mg on days 6-12 and atazanavir plus raltegravir 300/400 mg on days 13-26, twice daily with a light meal. Serial blood samples were collected 12 h after the morning dose on days 5, 12 and 26; safety assessments, clinical laboratory data and serial electrocardiograms (ECGs) at 0, 2 and 6 h were obtained. RESULTS Raltegravir coadministration reduced atazanavir geometric mean maximum plasma concentration (C(max)), area under the plasma concentration-time curve from 0 to 12 h post-dose (AUC(0-12)) and trough plasma concentration (C(min)) by 11%, 17% and 29%, respectively, compared with atazanavir alone. Geometric mean atazanavir C(min) was 817 ng/ml (range 250-1,550) with raltegravir coadministration. Atazanavir increased raltegravir geometric mean C(max), AUC(0-12) and C(min) by 39%, 54% and 48%, respectively. All adverse events were of mild or moderate intensity. Hyperbilirubinaemia and ECG PR increases with atazanavir were similar to those of atazanavir/ritonavir once daily. No corrected QT prolongations were noted. Mean QRS increase from baseline was 11.0 ms (range 2-25) after receiving atazanavir for 7 days; no further QRS increase was noted and no QRS interval was >120 ms with raltegravir coadministration. No ECG changes were observed with raltegravir alone. CONCLUSIONS Coadministration of atazanavir and raltegravir 300/400 mg twice daily decreased atazanavir AUC(0-12) and C(min) relative to atazanavir alone, and increased AUC(0-12) of raltegravir relative to raltegravir alone. Atazanavir and raltegravir alone and coadministered appeared safe and well-tolerated.

Characterisation of the absorption, distribution, metabolism, excretion and mass balance of doravirine, a non-nucleoside reverse transcriptase inhibitor in humans

Abstract Absorption, distribution, metabolism and elimination of doravirine (MK-1439), a novel non-nucleoside reverse transcriptase inhibitor, were investigated. Two clinical trials were conducted in healthy subjects: an oral single dose [14 C]doravirine (350 mg, ∼200 µCi) trial (n = 6) and an intravenous (IV) single-dose doravirine (100 µg) trial (n = 12). In vitro metabolism, protein binding, apparent permeability and P-glycoprotein (P-gp) transport studies were conducted to complement the clinical trials. Following oral [14 C]doravirine administration, all of the administered dose was recovered. The absorbed dose was eliminated primarily via metabolism. An oxidative metabolite (M9) was the predominant metabolite in excreta and was the primary circulating metabolite (12.9% of circulating radioactivity). Following IV administration, doravirine clearance and volume of distribution were 3.73 L/h (95% confidence intervals (CI) 3.09, 4.49) and 60.5 L (95% CI 53.7, 68.4), respectively. In vitro, doravirine is not highly bound to plasma proteins (unbound fraction 0.24) and has good passive permeability. The metabolite M9 was generated by cytochrome P450 3A (CYP3A)4/5-mediated oxidation. Doravirine was a P-gp substrate but P-gp efflux is not expected to play a significant role in limiting doravirine absorption or to be involved in the elimination of doravirine. In conclusion, doravirine is a low clearance drug, primarily eliminated by CYP3A-mediated metabolism.

No Pharmacokinetic Interaction Between the Hepatitis C Virus Inhibitors Elbasvir/Grazoprevir and Famotidine or Pantoprazole

Use of agents to suppress gastric acid secretion is common among patients with hepatitis C virus (HCV) infection. The aims of this open‐label, three‐period, fixed‐sequence study were to evaluate the effect of famotidine and pantoprazole on the pharmacokinetics and safety of elbasvir/grazoprevir fixed‐dose combination (FDC) in 16 healthy subjects. Elbasvir and grazoprevir each exhibited similar pharmacokinetics following single‐dose administration of elbasvir/grazoprevir with or without famotidine or pantoprazole. Geometric mean ratios (GMRs) of grazoprevir AUC(0,∞), Cmax, and C24 (elbasvir/grazoprevir + famotidine or elbasvir/grazoprevir + pantoprazole vs. elbasvir/grazoprevir) ranged from 0.89–1.17. Similarly, GMRs of elbasvir AUC(0,∞), Cmax, and C24 (elbasvir/grazoprevir + famotidine or elbasvir/grazoprevir + pantoprazole vs. elbasvir/grazoprevir) ranged from 1.02–1.11. These results indicate that gastric acid‐reducing agents do not modify the pharmacokinetics of elbasvir or grazoprevir in a clinically relevant manner and may be coadministered with elbasvir/grazoprevir in HCV‐infected patients without restriction.

Clinical pharmacology profile of boceprevir, a hepatitis C virus NS3 protease inhibitor: focus on drug-drug interactions.

Boceprevir is a potent, orally administered ketoamide inhibitor that targets the active site of the hepatitis C virus (HCV) non-structural (NS) 3 protease. The addition of boceprevir to peginterferon plus ribavirin resulted in higher rates of sustained virologic response (SVR) than for peginterferon plus ribavirin alone in phase III studies in both previously treated and untreated patients with HCV infection. Because boceprevir is metabolized by metabolic routes common to many other drugs, and is an inhibitor of cytochrome P450 (CYP) 3A4/5, there is a high potential for drug–drug interactions when boceprevir is administered with other therapies, particularly when treating patients with chronic HCV infection who are often receiving other medications concomitantly. Boceprevir is no longer widely used in the US or EU due to the introduction of second-generation treatments for HCV infection. However, in many other geographic regions, first-generation protease inhibitors such as boceprevir continue to form an important treatment option for patients with HCV infection. This review summarizes the interactions between boceprevir and other therapeutic agents commonly used in this patient population, indicating dose adjustment requirements where needed. Most drug interactions do not affect boceprevir plasma concentrations to a clinically meaningful extent, and thus efficacy is likely to be maintained when boceprevir is coadministered with the majority of other therapeutics. Overall, the drug–drug interaction profile of boceprevir suggests that this agent is suitable for use in a wide range of HCV-infected patients receiving concomitant therapies.

Pharmacokinetics and Tolerability of Letermovir Coadministered With Azole Antifungals (Posaconazole or Voriconazole) in Healthy Subjects

Letermovir is a human cytomegalovirus terminase inhibitor for cytomegalovirus infection prophylaxis in hematopoietic stem cell transplant recipients. Posaconazole (POS), a substrate of glucuronosyltransferase and P‐glycoprotein, and voriconazole (VRC), a substrate of CYP2C9/19, are commonly administered to transplant recipients. Because coadministration of these azoles with letermovir is expected, the effect of letermovir on exposure to these antifungals was investigated. Two trials were conducted in healthy female subjects 18 to 55 years of age. In trial 1, single‐dose POS 300 mg was administered alone, followed by a 7‐day washout; then letermovir 480 mg once daily was given for 14 days with POS 300 mg coadministered on day 14. In trial 2, on day 1 VRC 400 mg was given every 12 hours; on days 2 and 3, VRC 200 mg was given every 12 hours, and on day 4 VRC 200 mg. On days 5 to 8, letermovir 480 mg was given once daily. Days 9 to 12 repeated days 1 to 4 coadministered with letermovir 480 mg once daily. In both trials, blood samples were collected for the assessment of the pharmacokinetic profiles of the antifungals, and safety was assessed. The geometric mean ratios (90%CIs) for POS+letermovir/POS area under the curve and peak concentration were 0.98 (0.83, 1.17) and 1.11 (0.95, 1.29), respectively. Voriconazole+letermovir/VRC area under the curve and peak concentration geometric mean ratios were 0.56 (0.51, 0.62) and 0.61 (0.53, 0.71), respectively. All treatments were generally well tolerated. Letermovir did not affect POS pharmacokinetics to a clinically meaningful extent but decreased VRC exposure. These results suggest that letermovir may be a perpetrator of CYP2C9/19‐mediated drug‐drug interactions.

Grazoprevir, Ruzasvir, and Uprifosbuvir for HCV After NS5A Treatment Failure

People with hepatitis C virus (HCV) infection who have failed treatment with an all‐oral regimen represent a challenging treatment population. The present studies evaluated the safety and efficacy of grazoprevir, ruzasvir, and uprifosbuvir, with or without ribavirin, in participants who had failed an NS5A inhibitor‐containing regimen. C‐SURGE (PN‐3682‐021) and C‐CREST Part C (PN‐3682‐011 and ‐012) were open‐label, multicenter studies. Participants who had previously relapsed following an NS5A inhibitor–containing all‐oral regimen were retreated with grazoprevir 100 mg, ruzasvir 60 mg, and uprifosbuvir 450 mg alone for 24 weeks or with ribavirin for 16 weeks. The primary efficacy endpoint was sustained virologic response (HCV RNA below the limit of quantitation [<15 IU/mL]) 12 weeks after treatment completion (SVR12). In C‐SURGE, SVR12 was achieved by 49/49 (100%) and 43/44 (98%) genotype (GT)1 participants in the 24‐week no ribavirin arm and the 16‐week plus ribavirin arm (lost to follow‐up, n = 1), respectively. In C‐CREST Part C, SVR12 was achieved by 23/24 (96%) participants treated for 16 weeks with ribavirin (GT1, 2/2 [100%]; GT2, 13/14 [93%]; GT3, 8/8 [100%]). One participant with GT2 infection discontinued study medication after a single dose of grazoprevir, ruzasvir, and uprifosbuvir plus ribavirin due to serious adverse events of vomiting and tachycardia. The presence of baseline resistance‐associated substitutions had no impact on SVR12. No participant who completed treatment in either study experienced virologic failure. Conclusion: Grazoprevir, ruzasvir, and uprifosbuvir, with or without ribavirin, for 16 or 24 weeks was safe and highly effective in participants with HCV infection who had previously failed NS5A inhibitor–containing therapy. (Hepatology 2017;66:1794–1804)