Study of Bepirovirsen in Nucleos(t)Ide Analogue-treated Participants With Chronic Hepatitis B (B-Well 1)

This study is intended to confirm the efficacy, safety, pharmacokinetic (PK) profile, and the durability of hepatitis B virus surface antigen (HBsAg) suppression observed with bepirovirsen for 24 weeks (with loading doses) as compared to the placebo arm. This study will have 4 stages: a) Double-blind treatment (bepirovirsen or placebo) for 24 weeks. b) Nucleos(t)ide analogue (NA) treatment for 24 weeks. c) NA cessation stage OR Continue NA for 24 weeks. d) Durability of response and follow up for further 24 weeks for participants who stopped NA treatment at Week 48. The arms will be stratified based on HBsAg level (HBsAg greater than or equal to \[≥\] 100 international unit per milliliter \[IU/mL\] to less than or equal \[≤\]1000 IU/mL or greater than \[\>\] 1000 IU/mL to ≤3000 IU/mL) at screening. The total duration of the study, including screening (up to 60 days), the double-blind treatment stage (24 weeks), the On NA only stage (24 weeks), and the NA cessation and durability stages (48 weeks) is up to approximately 104 weeks at maximum for each participant.