People who inject drugs (PWID) have higher rates of hepatitis C virus (HCV) than do other groups. Effective, safe new treatments called direct-acting antiviral agents (DAAs) have been developed recently. Unfortunately, PWID rarely get these treatments. The drugs are expensive, so insurers often do not cover the cost of DAAs. Sometimes providers hesitate to prescribe DAAs because they are concerned that PWID won't take their medication or that these patients might become reinfected.

Several good models for treating PWID exist. One of them is to provide directly observed treatment (DOT). Another model provides treatment to PWID with the support of patient navigators (PN), public health workers who offer support and education to patients. Though both the DOT and PN models have been successful, we still don't know which model works best.

In this study, the investigators will study both DOT and PN models for treating HCV in PWID. The investigators' goal is to find out which model produces the best results and is preferred by patients. Up to 1,000 HCV-infected PWID will participate in the study in eight sites around the country. Patients will be randomized into either the PN or the DOT groups. Patients who end up in the PN group will get a biweekly blister pack of medication to take home. Their PN will provide education and support. The investigators will find out whether patients adhered to medication using an electronic adherence monitoring system. Patients who are randomly assigned to the DOT group will take their medication in front of a staff member.

This is a multi-site national study (8 U.S. cities), where up to 1000 HCV-infected PWIDs (injecting illicit substances within the last 3 months) will be randomized to either PN plus biweekly blister pack dispensation versus mDOT. Among patients who go on to initiate HCV treatment (n=600 targeted) with a once-daily combination regimen, a comparison will be conducted of the proportion of patients in each arm who: (a) optimally adhere (>=80%), (b) complete treatment, (c) achieve SVR, and (d) develop resistance. The primary outcome will be SVR. The 8 sites offer geographic and policy diversity: New York City, Baltimore, Providence, Boston, Morgantown, Seattle, San Francisco, and Albuquerque.

Participants will be recruited from diverse venues: OAT clinics, community health centers, syringe exchange programs, community-based organizations, homeless programs, and cohorts established by research studies. The clinical sites will determine eligibility based on clinical records, or on-site testing including for HCV tests (anti-HCV and HCV viremia) and drug toxicology testing as needed. Study participants will be screened, consented and enrolled on-site at OAT and non-OAT clinic settings.

Patients will be randomized to one of two models of care: patient navigation (PN) vs. modified directly observed treatment (mDOT). Patients enrolled from OAT clinics who are receiving methadone and randomized to mDOT will receive doses of once daily medication at the same time as they receive methadone. Patients enrolled from community health settings and randomized to mDOT may receive observed doses in a range of settings including: at their clinic, at home, a community site (e.g. at a coffee shop or other gathering place), or using a mobile health app on a smartphone. Subjects randomized to PN will receive a standardized PN intervention and additional support through a peer-led support group.

Participants will be followed for up to 140 weeks: 12 weeks of pre-treatment evaluation, 12 weeks of treatment, 12 weeks of follow-up to determine SVR12, and 104 weeks of follow-up to determine long-term SVR and reinfection. Data sources will include clinical lab and imaging results from medical records, blood tests (HCV viral load during long-term follow-up and resistance assays), urine toxicology, questionnaires, electronic monitors for assessing adherence, and interview.

Inclusion Criteria:

• HCV infection
• Actively injecting drugs (any substance within 3 months)
• Not previously treated with HCV direct-acting antiviral medications
• Age 18 - 70
• Willing to receive HCV treatment with sofosbuvir/velpatasvir
• Willing to be randomized to either PN vs mDOT
• If receiving methadone, be attending methadone clinic a minimum of 5 times per week
• Able to provide informed consent
• English or Spanish fluency

Exclusion Criteria:

• Pregnant or breast feeding
• Hepatocellular carcinoma

mITT, modified intention-to-treat population, which included participants who were randomly assigned and initiated treatment;

The adverse event data were collected from baseline to the last visit week, which was 168 weeks after baseline. Therefore, the time frame for the adverse event data collections was 168 weeks, that is slightly longer than 3 years.

An adverse event will be considered serious when the outcome is:

• Death
• Life-threatening
• Hospitalization (initial or prolonged)
• Disability or permanent damage
• Congenital Anomaly/Birth Defect
• Required intervention to prevent permanent impairment or damage (devices)
• Other serious important medical event