• Documented chronic hepatitis B virus (HBV) infection and documented human immunodeficiency virus (HIV)-1 infection greater than equal to (\>=) 12 months prior to Screening.

• Must be on uninterrupted antiretroviral therapy (ART) containing at least tenofovir disoproxil (TDF) or tenofovir alafenamide (TAF) plus lamivudine (3TC) or emtricitabine (FTC) for greater than (\>)12 months, with no planned changes to the stable regimen over the duration of the study.

• o Switch in ART is permitted \>=6 months prior to Screening for reasons not related to loss of HIV or HBV control (e.g., change in formulary, tolerability, side effects).

• Documented evidence of at least 2 plasma HIV-1 ribonucleic acid (RNA) measurements less than (\<) 50 copies per milliliter (copies/mL) are required in the 12 months prior to Screening: 1 within 6 to 12 months prior to Screening and 1 within 6 months prior to Screening.

• Plasma or serum HBV deoxyribonucleic acid (DNA) concentration must be adequately suppressed, defined as plasma or serum HBV DNA \<90 international units per milliliter (IU/mL).

• Plasma or serum HBsAg concentration \>100 IU/mL and \<=3000 IU/mL.

• Plasma HIV-1 RNA concentration must be undetectable, defined as plasma HIV 1 RNA \<50 copies/mL.

• Cluster of differentiation 4 (CD4) count \>=350 cells per cubic millimeter (cells/mm\^3).

• Alanine aminotransferase (ALT) \<=2 times upper limit of normal (ULN).