Efficacy and Safety of All-Oral Combination of Narlaprevir/Ritonavir and Sofosbuvir in Treatment-naïve Patients With Chronic Hepatitis C Genotype 1

Inclusion Criteria: * Are willing and able to provide written informed consent. * Have confirmed chronic HCV infection as documented by: positive anti-HCV antibody (Ab) test or positive HCV RNA or positive HCV genotyping test at least 6 months prior to the Baseline/Day 1 visit * Have HCV genotype 1 at screening as determined by the Central Laboratory. Any nondefinitive results must exclude the subject from study participation. * Minimum HCV-RNA level of ≥ 10,000 IU at baseline; * Treatment-naive patients to be enrolled into 8 week cohort must have HCV-RNA level \<1,000,000 IU/L at baseline; * No evidence of cirrhosis; availability at Baseline of at least one of the following tests negative results: 1. Liver biopsy within 2 years of screening showing absence of cirrhosis 2. Fibroscan® with a result of ≤ 12.5 kilopascal (kPa) within 6 months of baseline/Day1 3. FibroTest® score of ≤ 0.48 AND Aspartate aminotransferase (AST)-to-Platelet Ratio Index (APRI) of ≤ 1 performed during screening In the absence of a definitive diagnosis of the presence or absence of cirrhosis by the above criteria, a liver biopsy was required. Liver biopsy results supersede the results obtained by Fibroscan® or FibroTest® * Have a screening electrocardiogram (ECG) without clinically significant abnormalities (P wave \< 0.1 s; PQ interval 0,12-0,2 s; QRS complex 0,06-0,1 s; QT interval 0,35-0,49 s). * Must have the following laboratory parameters at screening: 1. alanine aminotransferase (ALT) ≤ 10 x the upper limit of normal (ULN) 2. AST ≤ 10 x ULN 3. Hemoglobin ≥ 12g/dL for male, ≥ 11g/dL for female subjects 4. Platelets ≥ 50,000cells/mm\^3 (for patients in 8-week study treatment group - ≥ 150,000 cells/mm3) 5. International normalized ratio (INR) ≤ 1.5 x ULN unless subject has known hemophilia or is stable on an anticoagulant regimen affecting INR 6. Albumin ≥ 3 g/dL; 7. Direct bilirubin ≤ 1.5 x ULN; 8. Hemoglobin A1c (HbA1c) ≤10%; 9. Creatinine clearance (CLcr) ≥ 60 mL/min, as calculated by the Cockcroft-Gault equation. * Have not been treated with any investigational drug or device within 30 days of the screening visit. * A female subject is eligible to enter the study if it is confirmed that she is: 1. Not pregnant or nursing; 2. Of nonchildbearing potential (i.e., women who have had a hysterectomy, both ovaries removed, or medically documented ovarian failure, or are postmenopausal women \>50 years of age with cessation \[for ≥ 12 months \] of previously occurring menses), or 3. Of childbearing potential (i.e., women who had not had a hysterectomy, both ovaries removed, or medically documented ovarian failure). Women ≤ 50 years of age with amenorrhea are considered to be of childbearing potential. These women must have a negative serum pregnancy test at screening and a negative urine pregnancy test on the baseline/Day 1 visit prior to enrollment. They must also agree to one of the following from the screening until 6 months after last dose of the investigational drugs: * Complete abstinence from intercourse. Periodic abstinence from intercourse (e.g., calendar, ovulation, symptothermal, post-ovulation methods) is not permitted. * Consistent and correct use of 1 of the following methods of birth control listed below in addition to a male partner who correctly uses a condom from the date of screening until 6 months after the last dose of the investigational drugs. Women of childbearing potential must not rely on hormone-containing contraceptives as a form of birth control during the study. Female subjects using a hormone-containing contraceptive prior to screening must stop their contraceptive regimen use from the date of screening until 6 months after their last dose of investigational drugs. * intrauterine device (IUD) with a failure rate of \< 1 %; * female barrier method: cervical cap or diaphragm with spermicidal agent * tubal sterilization * vasectomy in male partner * All male study participants must agree to consistently and correctly use a condom, while their female partner agrees to use either 1 of the nonhormonal methods of birth control listed above or a hormone-containing contraceptive listed below, from the date of screening until 6 months after their last dose of investigational drugs: * implants of levonorgestrel * injectable progesterone * oral contraceptives (either combined or progesterone only) * contraceptive vaginal ring * transdermal contraceptive patch * Male subjects must agree to refrain from sperm donation for at least 6 months after the last dose of investigational drugs. * Are in generally good health as determined by the investigator. * Are able to comply with the dosing instructions for study drug administration and are able to complete the study schedule of assessments. Exclusion Criteria: * Had prior exposure to Interferon (IFN), ribavirin (RBV), or other approved or experimental Direct-acting Antivirals (DAA) targeting the HCV. * Had prior exposure to amiodarone within 24 months before the screening * Are pregnant or nursing female or male with pregnant female partner. * Chronic liver disease of a non-HCV etiology (e.g., hemochromatosis, Wilson's disease, α1-antitrypsin deficiency, cholangitis). * Are infected with hepatitis B virus (HBV) or human immunodeficiency virus(HIV). * Have history of malignancy diagnosed or treated within 5 years; subjects under evaluation for malignancy are not eligible. * Have chronic use of systemically administered immunosuppressive agents (e.g., prednisone equivalent \> 10 mg/day). * Have clinically relevant drug or alcohol abuse within 12 months of screening. A positive drug screen must exclude subjects unless it can be explained by a prescribed medication; the diagnosis and prescription must be approved by the investigator. * Have excessive alcohol consumption, defined as more than 3 drinks on any single day and more than 7 drinks per week for females, and \> than 4 drinks on any single day and more than 14 drinks per week for males. * Have history of solid organ transplantation. * Have history of clinically significant illness or any other major medical disorder that may interfere with subject treatment, assessment, or compliance with the protocol by Investigators' opinion. * Have history of a gastrointestinal disorder (or postoperative condition) that can interfere with the absorption of the study drug. * Have history of difficulty with blood collection and/or poor venous access for the purposes of phlebotomy. * Usage of any prohibited concomitant medications as described in the protocol (Appendix 1 - list of drugs with expected drug-drug interactions due to concomitant ritonavir usage) * Have known hypersensitivity to the study investigational medicinal product, the metabolites, or formulation excipients.