This study is being done to compare two strategies to deliver HCV treatment to persons with hepatitis C virus (HCV) who also use drugs and are participating in an outpatient opioid treatment program (OTP). Participants will be randomized into one of two treatment groups:

1. Test and treat plus peer-mentors: This treatment group will be offered 8 weeks of glecaprevir/pibrentasvir (an FDA approved HCV treatment) within days of HCV diagnosis at the OTP. Participants in this group will receive treatment adherence support from a peer-mentor who is someone who has been cured of HCV infection.
2. Standard of care HCV treatment referral: This treatment group will be referred to an offsite HCV treatment location. This is the usual care for anyone who tests positive for HCV at the OTP who is not participating in this study.

Inclusion Criteria:

• Ability and willingness of participant to provide written informed consent
• Men and women age ≥18 to ≤70 years at study entry
• HCV antibody positive/detectable HCV RNA
• HCV treatment naïve (no prior treatment with an approved or investigational oral Direct-Acting Antivirals (DAA) therapy
• Negative pregnancy test at screening or at the day of treatment initiation (females of childbearing potential only)
• If co-infection with Human Immunodeficiency Virus (HIV) is documented, the subject must be anti-retroviral treatment (ART) naïve with CD4 T cell count >500 cells/mm3 OR on a stable ART regimen (containing only permissible ART - Raltegravir; dolutegravir; Rilpivirine; Elvitegravir/cobicistat; Tenofovir disoproxil fumarate; Tenofovir alafenamide; Emtricitabine; Lamivudine and/or Abacavir, bictegravir)

Exclusion Criteria:

• Women who are pregnant or breastfeeding, or considering becoming pregnant during the study and for 30 days after the last dose of study drug
• Known allergy/sensitivity or any hypersensitivity to components of study drugs or their formulation
• Current or history of decompensated liver disease (including but not limited to encephalopathy, variceal bleeding, or ascites) prior to study entry
• History of hepatocellular carcinoma (HCC)
• Any history of active Hepatitis B or positive HBsAg test
• Platelet count < 150,000/mm3
• HCV RNA undetectable
• History of clinically significant abnormalities or co-morbidities that make the subject an unsuitable candidate for this study, in the opinion of the investigator.
• Women of childbearing potential that are not practicing at least one specified method of birth control that is effective from Study Day 1 through at least 30 days after the last dose of study drug.
• Subject is currently taking any of the following prohibited medications: red yeast rice (monacolin K), St. John's Wort, carbamazepine, dabigatran, efavirenz, phenytoin, pentobarbital, phenobarbital, primidone, rifabutin, rifampin.
• Subject is not able or willing to safely discontinue the prohibited medications or supplements listed below at least 14 days prior to the first dose of GLE/PIB: some HMG-CoA reductase inhibitors, astemizole, cisapride, terfenadine, ethinyl estradiol.

Participants who were eligible for treatment initiation based on protocol criteria, excluding two participants from the analysis due to randomization error. Analyses were conducted with a modified intention to treat of approach, which excluded randomized participants who were found on testing to have an undetectable HCV RNA, HBsAg positive or a platelet count <150,000.

Treatment day 1 up to 30 days post treatment initiation

All Grade 3 or higher and all SAEs related to the use of Glecaprevir/pibrentasvir (GLE/PIB) in intervention arm or prescribed DAA course in SOC arm were to be collected.