Safety and Efficacy of Switching to Tenofovir Alafenamide (TAF) From Tenofovir Disoproxil Fumarate (TDF) and/or Other Oral Antiviral Treatment (OAV)

Key Inclusion Criteria:

All Participants (Parts A and B):

- Ability to understand and sign a written informed consent form; consent must be
obtained prior to initiation of study procedures

- Adult male or non-pregnant female individuals

- Documented evidence of chronic HBV infection

- ALT ≤ 10 × upper limit of normal (ULN)

Part A Only (renal impairment):

- Maintained on TDF and/or other OAV treatment(s) for chronic hepatitis B (CHB) for at
least 48 weeks and with viral suppression (HBV DNA < LLOQ) for ≥ 6 months prior to
screening

- All individuals must have HBV DNA < 20 IU/mL at screening by central laboratory

- Both HBeAg positive and negative individuals are eligible to participate

- Moderate renal impairment (30 mL/min ≤ eGFRcg ≤ 59 mL/min), severe renal impairment
(15 mL/min ≤ eGFRcg < 30 mL/min) or end stage renal disease (ESRD) (eGFR < 15 mL/min)
maintained on hemodialysis (HD)

- Stable renal function (for participants with moderate or severe impairment): serum
creatinine measured at least once within three months prior to Screening. The
measurement difference between the value measured within three months prior to
Screening versus the Screening value must be ≤ 25% of the Screening value

Part B Only (hepatic impairment):

- Maintained on TDF and/or other OAV(s) for CHB for at least 48 weeks and with viral
suppression (HBV DNA < LLOQ) for ≥ 6 months prior to screening

- All individuals must have HBV DNA < 20 IU/mL at screening by central laboratory

- Both HBeAg positive and negative individuals are eligible to participate

- CPT score of 7-12 (inclusive) OR a past history of CPT score ≥ 7 and any CPT score ≤
12 at screening

- eGFRCG ≥ 30 mL/min using the Cockcroft-Gault equation

Key Exclusion Criteria:

All Individuals (Parts A & B):

- Women who are breastfeeding or who believe they may wish to become pregnant during the
course of the study

- 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 HCV, HIV, or HDV

- Prior Interferon (IFN) use within 6 months of screening

- Evidence of hepatocellular carcinoma

- Received solid organ or bone marrow transplant

- Significant cardiovascular, pulmonary, or neurological disease

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

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

- Known hypersensitivity to study drugs, metabolites, or formulation excipients

- Current alcohol or substance abuse judged by the investigator to potentially interfere
with individual's 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.

Part A Only (Renal Impairment):

- Current or historical evidence of clinical hepatic decompensation (e.g., ascites,
encephalopathy or variceal hemorrhage)

- Abnormal hematological and biochemical parameters, including:

- Hemoglobin < 9 g/dL

- Absolute neutrophil count < 750/mm^3

- Platelets ≤ 50,000/mm^3

- Aspartate aminotransferase (AST) > 10 × ULN

- Albumin < 3.0 g/dL

- Total bilirubin > 2.5 × ULN

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

- Individuals with ESRD (i.e. eGFRcg < 15 mL/min) not on HD, or those on other forms of
renal replacement therapy (i.e. peritoneal dialysis)

Part B Only (Hepatic Impairment):

- Active variceal bleeding within 6 months or prior placement of a portosystemic shunt
(such as transjugular intrahepatic portosystemic shunt [TIPS])

- History of hepatorenal syndrome, hepatopulmonary syndrome, Grade 3 or Grade 4 hepatic
encephalopathy, or spontaneous bacterial peritonitis within 6 months of screening

- Grade 2 hepatic encephalopathy at screening

- MELD score ≥ 30

- Abnormal hematological and biochemical parameters, including

- Absolute neutrophil count < 750/mm^3

- Platelets < 30,000/mm^3

- Hemoglobin < 8.0 g/dL

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