['hiv', 'hbv']
['e/c/f/taf']

        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.
      