Efficacy and Safety of Narlaprevir Used in Combination With Ritonavir in Treatment-Naïve and Failed Prior Treatment With Pegylated Interferon/Ribavirin Patients With Chronic Hepatitis C Genotype 1 (PIONEER - Study)

Inclusion Criteria: * Body weight ≥ 40 and ≤ 125 kg; * Documented infection with HCV genotype 1 (Mixed infections with other genotypes are not eligible): 1. treatment naïve (to interferon and ribavirin); or 2. treatment failure patients (patients must have received interferon/ribavirin at standard doses for a minimum of 12 weeks); * Minimum HCV-RNA level of ≥10,000 IU at baseline; * No evidence of cirrhosis; availability at Baseline of at least one of the following tests negative results: 1. Liver biopsy showing no cirrhosis (not later than within 3 years prior to Baseline) or 2. FibroScan elasticity score \< 12.5 kPa 12 months prior to baseline or 3. FibroTest \< 0.75 12 months prior to baseline and aspartate aminotransferase (AST)/platelet ratio (APRI) of ≤ 1 during screening * Using acceptable contraception methods for both partners from enrollment into the study until 6 months following the end of treatment; * Willingness to give written informed consent. Exclusion Criteria: * Previous treatment with any HCV NS3-specific protease inhibitor and/ or other direct antiviral agents (e.g. HCV polymerase inhibitors); * Treatment for HCV infection 30 days before the enrolment; * Use of prohibited medications within 2 weeks prior to start of study medications (inducers or substrates of CYP3A4); * Findings suspicious for hepatocellular carcinoma (HCC); * Hepatic failure at present or in history; * Auto-immune hepatitis in history; * Anti-nuclear antibodies (ANA) titers \> 1:320; * Evidence of gallstones, choledocholithiasis and calcified gallbladder; * HBsAg positive; * HIV positive; * Serum hemoglobin of \<13g/dL for males and \<12g/dL for females; * Neutrophils \<1500/mm3 (\<1,5х109/L) at Screening; * Platelets \<150000/mm3 (\<150х109/L) at Screening (patients with a platelet count \>100,000/mm3 (\>100х109/L) but less than 150,000/mm3 (150х109/L) can be included in the study in case a Fibroscan or FibroTest or liver biopsy during the study screening period shows no cirrhosis) * Total bilirubin \>1.6 mg/dL (\>27.36 µmol/L) unless history of Gilbert's disease. If Gilbert's disease is the proposed etiology, this must be documented in the subject's chart; * Direct bilirubin \>1.5 x upper limit of normal (ULN) of the laboratory reference range at Screening; * Serum albumin \< lower limit of normal (LLN) of laboratory reference range at Screening; * Serum creatinine \>ULN of the laboratory reference at Screening; * Serum aspartate aminotransferase (AST) / alanine aminotransferase (ALT) \>5 x ULN of the laboratory reference range at Screening; * Thyroid stimulating hormone (TSH) \>1.2 ULN or \<0.8 LLN; * Contraindications to pegylated interferon, ribavirin and/or ritonavir treatment; * Hypersensitivity to any of the study drugs; * Active or suspected cancer; * Psychiatric disease (moderate or severe depression, schizophrenia, bipolar disorder et al); * Previous suicide attempt or suicidal ideation; * Drug addiction; * Opiate agonist substitution therapy; * History of active gout within the past year; * Organ transplant (except of cornea and hair transplant); * Pregnant or nursing women; * Men whose female partners are pregnant or planning pregnancy; * Any medical condition that could interfere with the patient's participation and completion of the study; * Use of other investigational drugs/ participation in other clinical trial within 30 days before the enrolment.