['chronic hepatitis b']
['taf', 'tdf', 'taf placebo', 'tdf placebo']

        Key Inclusion Criteria:

          -  Must have the ability to understand and sign a written informed consent form; consent
             must be obtained prior to initiation of study procedures

          -  Adult male and non-pregnant, non-lactating females

          -  Documented evidence of chronic hepatitis B virus (HBV) infection previously

          -  Maintained on tenofovir disoproxil fumarate (TDF) 300 mg once daily for at least 48
             weeks, and as monotherapy for chronic hepatitis B for at least 24 weeks with viral
             suppression (HBV DNA < lower limit of quantitation) for a minimum of 12 weeks prior to
             screening

          -  Adequate renal function

          -  Normal Electrocardiogram

        Key Exclusion Criteria:

          -  Pregnant women or women who are breastfeeding

          -  Males and females of reproductive potential who are unwilling to use an "effective",
             protocol-specified method(s) of contraception during the study.

          -  Co-infection with hepatitis C virus (HCV), hepatitis D virus (HDV), or human
             immunodeficiency virus (HIV)

          -  Evidence of hepatocellular carcinoma

          -  Current evidence of, or recent (≤ 5 year) history of clinical hepatic decompensation

          -  Abnormal hematological and biochemical parameters, including:

               -  Hemoglobin < 10 g/dL

               -  Absolute neutrophil count < 750/mm^3

               -  Platelets ≤ 50,000/mm^3

               -  Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 5 × upper
                  limit of the normal (ULN)

               -  Albumin < 3.0 mg/ dL

               -  International normalized ratio (INR) > 1.5 × ULN (unless stable on anticoagulant
                  regimen)

               -  Total bilirubin > 2.5 × ULN

          -  Received solid organ or bone marrow transplant

          -  Malignancy within 5 years prior to screening, with the exception of specific cancers
             that are cured by surgical resection (eg, basal cell skin cancer). Individuals under
             evaluation for possible malignancy are not eligible.

          -  Currently receiving therapy with immunomodulators (eg, corticosteroids), nephrotoxic
             agents, or agents capable of modifying renal excretion

          -  Individuals receiving ongoing therapy with drugs not to be used with TAF or TDF or
             individuals with a known hypersensitivity to study drugs, metabolites, or formulation
             excipients

          -  Current alcohol or substance abuse judged by the investigator to potentially interfere
             with compliance

          -  Any other clinical condition or prior therapy that, in the opinion of the
             investigator, would make the individual unsuitable for the study or unable to comply
             with dosing requirements.

          -  Use of investigational agents within 3 months of screening, unless allowed by the
             sponsor

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