This study will assess the efficacy, safety, and tolerability of elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide (E/C/F/TAF) fixed-dose combination (FDC) in human immunodeficiency virus (HIV)/hepatitis B virus (HBV) coinfected adults.

Participants will be enrolled into two cohorts:

• Cohort 1: HIV/HBV coinfected adults who are HIV treatment-naive and HBV treatment-naive
• Cohort 2: HIV/HBV coinfected adults who are HIV-suppressed

Key Inclusion Criteria:

• Both Cohorts 1 and 2:

  • The ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study procedures

  • HIV/HBV co-infected adult males and non-pregnant and non-lactating females

  • No evidence of hepatocellular carcinoma (HCC) or clinical or imaging evidence of cirrhosis (ascites, variceal bleeding, encephalopathy).

    --- Subjects should have documentation of an abdominal ultrasound in the 12 months prior to screening, or an abdominal ultrasound at screening, demonstrating the absence of cirrhosis and HCC.

  • Acute Hepatitis A virus (HAV) immunoglobulin M (IgM) negative

  • Hepatitis C virus (HCV) Ab negative, or HCV Ab positive with negative HCV RNA

  • Hepatitis D virus (HDV) Ab negative, or HDV Ab positive with negative HDV RNA

  • Estimated glomerular filtration rate (eGFR) ≥ 50 mL/min according to the Cockcroft-Gault formula

  • CD4+ count of > 200 cells/μL

  • Chronic HBV infection as defined by

    • HBsAg positive for ≥ 6 months Or

    • HBsAg positive at screening and either hepatitis B e antigen (HBeAg) or HBV DNA positive ≥ 6 months Or

    • At screening: positive total hepatitis B core antibody (HBcAb) and negative immunoglobulin M antibody to hepatitis B core antigen (HBcIgM) antibody, and

      • HBsAg positive, or
      • HBeAg positive, or
      • HBV DNA positive

• Cohort 1 (HIV and HBV treatment naive) only:

  • No current or prior anti-HIV treatment, including antiretroviral medications received for prevention (PrEP), or post exposure prophylaxis (PEP)
  • No current or prior anti-HBV treatment
  • Plasma HIV-1 RNA level ≥ 500 copies/mL at screening
  • Screening HBV DNA ≥ 3 log10 IU/mL and < 9 log10 IU/mL

• Cohort 2 (HIV suppressed) only:

  • Receiving current antiretroviral regimen for at least 4 consecutive months
  • No current or prior regimen containing 3 active anti-HBV agents (i.e. cannot be on tenofovir alafenamide (TDF)/emtricitabine (FTC)/Entecavir or TDF/lamivudine(3TC)/Entecavir)
  • Maintained plasma HIV-1 RNA < 50 copies/mL for 6 consecutive months prior to and at the time of the screening visit. Unconfirmed virologic evaluation of ≥ 50 copies/mL after previously reaching viral suppression (transient detectable viremia, or "blip") and prior to screening is acceptable
  • Documented positive HIV antibody test
  • Screening HBV DNA < 9 log10 IU/mL

Key Exclusion Criteria:

• Females who are breastfeeding
• Positive serum pregnancy test (female of childbearing potential)
• Have an implanted defibrillator or pacemaker
• Current alcohol or substance use
• A history of malignancy within the past 5 years (prior to screening) or ongoing malignancy other than cutaneous Kaposi's sarcoma (KS), basal cell carcinoma, or resected, non-invasive carcinoma.
• Received solid organ or bone marrow transplant
• Any history of, or current evidence of, clinical hepatic decompensation (e.g., ascites, encephalopathy or variceal hemorrhage).
• Significant bone disease (e.g., osteomalacia, chronic osteomyelitis, osteogenesis imperfecta, osteochondroses), or multiple bone fractures
• Active, serious infections (other than HIV-1 infection) requiring parenteral antibiotic or antifungal therapy within 30 days prior to Day 1
• Subjects on hemodialysis, other forms of renal replacement therapy, or on treatment for underlying kidney diseases (including prednisolone, and dexamethasone)
• Any other clinical condition or prior therapy that, in the opinion of the Investigator, would make the subject unsuitable for the study or unable to comply with the dosing requirements
• Investigational agents (unless approved by Gilead Sciences). Participation in any other clinical trial without prior approval from the sponsor is prohibited while participating in this trial

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Qualified external researchers may request IPD for this study after study completion. For more information, please visit our website at http://www.gilead.com/research/disclosure-and-transparency.

18 months after study completion

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