Study of Simtuzumab in HIV and/or Hepatitis C- Infected Adults With Liver Fibrosis

Key Inclusion Criteria: * HIV-infected individuals must have positive serologies with viral load suppressed below 400 copies/mL * HCV-infected individuals must have: * Chronic HCV infection with HCV RNA ≥ 2000 IU/ml AND at least 1 of the following: * Been null responder to previous pegylated interferon and ribavirin therapy OR * Failed to achieve sustained virologic response (SVR) on a regimen containing a direct-acting antiviral (DAA) in addition to pegylated interferon and ribavirin OR * Are unwilling to receive or have contraindications to interferon therapy for HCV * HIV/HCV co-infected individuals must have: * Positive HIV serologies with viral load suppressed below 400 copies/mL * Chronic HCV infection with HCV RNA ≥ 2000 IU/ml AND at least 1 of the following: * Been null responder to previous pegylated interferon and ribavirin therapy OR * Failed to achieve SVR on a regimen containing a direct-acting antiviral (DAA) in addition to pegylated interferon and ribavirin OR * Are unwilling to receive or have contraindications to interferon therapy for HCV * Willing to allow blood and tissue samples to be stored for future use to study HIV infection, immune function, liver disease and additional mechanisms involved in liver fibrosis among patients with HIV and/or HCV, which may not be related directly to the specific objectives of this study protocol * Have a primary care physician Key Exclusion Criteria: * Cause of liver fibrosis other than HCV or long-term antiretroviral therapy (ART) treatment for HIV * Currently being treated for HCV * Evidence of active Hepatitis A, B or D infections * History or evidence of hepatocellular carcinoma * Unwillingness to undergo a liver biopsy pre-treatment and post-treatment, or to undergo all other protocol required tests/procedures or return to the site for required visits * Presence of contraindications to magnetic resonance imaging (e.g., presence of any metal in the body, cardiac or neural pacemaker, aneurysm clip, cochlear implant, claustrophobia)