The Dublin Zepatier Study

Inclusion Criteria: 1. Subject is ≥18 years of age. 2. Subject must be HCV treatment naive. Subject is willing and able to understand and provide written informed consent prior to participation in this study. 3. Documented chronic HCV infection (RNA positive), HCV RNA levels \> 10x4 IU/ml. 4. Documented HCV genotype 1 and 4. 5. Documented HIV and HBV uninfected (HIV Ab negative, HBsAg negative) 6. A female is eligible to enter and participate in the study if she is of: * non-childbearing potential (i.e., physiologically incapable of becoming pregnant, including any female who is post-menopausal); or, * Child-bearing potential, has a negative pregnancy test (serum β-HCG) at screen and agrees to an acceptable barrier and/or hormonal method of contraception (any contraception method must be used consistently and correctly, i.e., in accordance with both the approved product label and the instructions of a physician): Sterilization (female subject or male partner of female subject). Male and female subjects must agree to 7 months post-treatment contraception if taking ribavirin and one month post- treatment contraception for Zepatier only. 7. Stable attender in the site of enrolment (receiving OST at least 3 months before enrolment and were at least 80 % adherent to OST appointments) 8. Venous access available for blood monitoring. 9. Fibroscan done as per HSE Hepatitis C Advisory Group guidelines. 10. Safety bloods done prior to study including a HGB \> 9.5g/dL, platelets \> 75,000, AST \< 10x ULN, albumin levels \> 30g/L. Exclusion Criteria: 1. 1\. Child Pugh B or C (see Appendix 10.1 for Child-Pugh Classification) 2. HCV non-G1/G4 3. History of decompensated liver disease 4. Laboratory exclusions include platelet count \<75,000, albumin \<30gm/L, Alanine aminotransferase (ALT) \>10 times the upper limit of normal (ULN). 5. Subject is enrolled in one or more investigational drug protocols, which may impact on assessment of HCV treatment with Zepatier (+/-ribavirin). 6. Subject is, in the opinion of the investigator, unable to complete the study dosing period and protocol evaluations and assessments. 7. Patients with alcohol and drug use problems that in the view of investigator will compromise adherence to compliance with the study will be excluded. 8. Subject is either pregnant or breastfeeding. 9. Subject suffers from any serious medical condition (such as pancreatitis, diabetes, congestive heart failure, cardiomyopathy or other cardiac dysfunction), which in the opinion of the Investigator, would compromise the safety of the subject. 10. Subject has a pre-existing mental, physical, or substance abuse disorder that, in the opinion of the Investigator, may interfere with the subject's ability to comply with the dosing schedule and protocol evaluations and assessments. 11. Subject has a history of inflammatory bowel disease or intestinal malignancy, intestinal ischemia, malabsorption, or other gastrointestinal dysfunction, which, in the opinion of the Investigator, may interfere with drug absorption or render the subject unable to take oral medication. 12. Subject has any acute laboratory abnormality at screening, which, in the opinion of the Investigator, would preclude the subject's participation in the study of an investigational compound. If subjects are found to have an acute Grade 4 laboratory abnormality at screening, this test may be repeated once within the 45-day screening window. Any verified Grade 4 laboratory abnormality would exclude a subject from study participation. 13. Subject has received treatment with radiation therapy or cytotoxic chemotherapeutic agents within 28 days prior to Screening, or has an anticipated need for these agents within the study period. 14. Subjects who require treatment with any contraindicated medications (as outlined in the SPC) within 14 days of commencement of investigational product, or an anticipated need during the study. 15. Subject has a history of allergy to any of the treatment products or any excipients therein.