Study of Bepirovirsen in Participants Living With Human Immunodeficiency Virus and Chronic Hepatitis B Virus Infection (B-Focus)

Inclusion Criteria:

1. Documented chronic hepatitis B virus (HBV) infection and documented humanimmunodeficiency virus (HIV)-1 infection greater than equal to (>=) 12 months priorto Screening.

2. Must be on uninterrupted antiretroviral therapy (ART) containing at least tenofovirdisoproxil (TDF) or tenofovir alafenamide (TAF) plus lamivudine (3TC) oremtricitabine (FTC) for greater than (>)12 months, with no planned changes to thestable regimen over the duration of the study. o Switch in ART is permitted >=6 months prior to Screening for reasons not relatedto loss of HIV or HBV control (e.g., change in formulary, tolerability, sideeffects).

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

4. Plasma or serum HBV deoxyribonucleic acid (DNA) concentration must be adequatelysuppressed, defined as plasma or serum HBV DNA <90 international units permilliliter (IU/mL).

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

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

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

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

Exclusion Criteria:

1. History of or suspected liver cirrhosis and/or evidence of cirrhosis.

2. Diagnosed or suspected hepatocellular carcinoma (HCC).

3. History of extrahepatic disorders possibly related to HBV immune conditions (e.g.,nephrotic syndrome, any type of glomerulonephritis, polyarteritis nodosa,cryoglobulinemia, uncontrolled hypertension).

4. Coinfection with:

5. Hepatitis C virus (HCV) with positive HCV antibody and detectable HCV RNA atScreening. I. HCV treatment should have completed >12 months prior to Screening.

6. Hepatitis D virus (HDV) defined as positive or equivocal HDV antibodyregardless of HDV RNA level.

7. Clinically significant abnormalities, aside from HIV-1 infection and chronic HBVinfection in medical history (e.g., moderate severe liver disease other than chronicHBV/HIV, acute coronary syndrome within 6 months of Screening, major surgery within 3 months of Screening, significant/unstable cardiac disease, uncontrolled diabetes,bleeding diathesis coagulopathy) or clinically significant physical examinationfindings.

8. Untreated syphilis infection (positive rapid plasma reagin [RPR] at Screeningwithout clear documentation of treatment) are excluded unless they completetreatment during the Screening period and 7 days prior to randomization.

9. History of malignancy within the past 5 years with the exception of specific cancersthat are cured by surgical resection (e.g., skin cancer). Participants underevaluation for possible malignancy are not eligible.

10. History of vasculitis or presence of symptoms and signs of potential vasculitis (e.g., vasculitic rash, skin ulceration, repeated blood detected in urine withoutidentified cause), current or history of an autoimmune condition or history/presenceof other diseases that may be associated with vasculitis condition (e.g., systemiclupus erythematosus, rheumatoid arthritis, relapsing polychondritis, mononeuritismultiplex).

11. Participants who in the investigator's judgment, have a significant risk of suicideor self-harm.

12. Alcohol or drug abuse/dependence

13. Currently taking, or took within 3 months of Screening, any immunosuppressing drugs (e.g., prednisone), other than a short course of therapy (<=2 weeks) ortopical/inhaled steroid use.

14. Participants to whom immunosuppressive treatment, including therapeutic doses ofsteroids, is contraindicated should not be considered for enrolment in the study.

15. Currently taking, or has taken within 12 months of Screening, any interferoncontaining therapy.

16. Participants requiring anti coagulation therapies (e.g., warfarin, Factor Xainhibitors) or anti platelet agents (including but not limited to clopidogrel oraspirin) unless treatment can safely be discontinued throughout duration of studyintervention, by the discretion of the investigator. Occasional use is permitted.

17. Treatment with an HIV-1 immunotherapeutic vaccine within 90 days of Screening.

18. Prior treatment with any oligonucleotide or small interfering ribonucleic acid (siRNA) within 12 months prior to the first dosing day.

19. Prior treatment with bepirovirsen.