The purpose of this study is to learn how 12 weeks of HCV treatment with elbasvir and grazoprevir (brand name Zepatier) impacts your kidney function.

Prospective data collection of 25 Genotype 1 or 4 HCV-infected women from the San Francisco Women's Interagency HIV Study (WIHS) site and 25 Genotype 1 or 4 HCV-infected men from the San Francisco VA Medical Center who are initiated on Zepatier for 12 weeks (Total n=50). For women and men with HCV genotype 1a infection, only those without baseline NS5A resistance mutations will be included. Blood/urine samples will be collected before initiation of treatment, 4 weeks after treatment initiation, 12 weeks after treatment initiation (end of treatment), 24 weeks after treatment initiation to determine Sustained Virological Response (SVR), and at 48 weeks after treatment initiation.

Inclusion Criteria:

1. Active Genotype 1 or 4 HCV infection (If with Genotype 1a infection, only those without baseline NS5A resistance mutation will be included; Genotype 4 HCV infection is uncommon in both study populations). Subjects with HIV coinfection are included. We will not exclude patients who have severe Chronic Kidney Disease, are on dialysis, or have undergone kidney transplant.

Exclusion Criteria:

1. HCV genotype 2, 3, 5, or 6 infection
2. Previous virologic failure to regimens containing an NS5A inhibitor
3. Decompensated liver disease (Child-Pugh Class B or C)
4. Albumin below 3g/dL
5. Platelet count below 75,000
6. Any condition that the investigator considers a contraindication to study participation including limited life expectancy
7. Pregnant or breastfeeding woman
8. Hepatitis B virus (HBV) surface antigen positive (Note: Patients positive for the HBV core antibody will not be excluded, but will have HBV DNA levels checked and will be monitored while on Direct Acting Antivirals (DAA) therapy and medically managed as considered appropriate)
9. Documented ongoing nonadherence to prescribed medications or medical treatment, failure to complete HCV disease evaluation appointments and procedures or unable to commit to scheduled followup/monitoring for the duration of treatment
10. Poor venous access not allowing screening laboratory collection
11. Known hypersensitivity to elbasvir/grazoprevir
12. Co-administration with drugs that are 1) strong CYP3A inducers (e.g., phenytoin, carbamazepine, rifampin); 2) OATP1B1/3 inhibitors (e.g., cyclosporine, darunavir, atazanavir, tipranavir, lopinavir or saquinavir) or 3) efavirenz

25 Genotype 1 or 4 HCV-infected women from the San Francisco WIHS site and 25 Genotype 1 or 4 HCV-infected men from the San Francisco VA Medical Center