The primary purpose of this study is to assess the safety and tolerability of single and multiple intravenous (IV) doses of GIGA-2339 in participants with chronic Hepatitis B Virus (HBV) infection.
Hepatitis B envelope antigen (HBeAg) negative chronic HBV infection for ≥ 6 months, defined as presence of Hepatitis B surface antigen (HBsAg) in serum for ≥ 6 months.
Serum HBsAg concentration between ≥ 100 international units per milliliter (IU/mL) and 2000 IU/mL at screening.
Currently on stable dose of nucleot(s)ide analogues (NAs) (≥ 6 months) and expected to continue while participating in the study, or are not received NAs.
Have serum HBV deoxyribonucleic acid (DNA) concentration ≤ 50 IU/mL at screening (for those who are on NAs); or have serum HBV DNA concentration ≤ 2000 IU/mL at screening (for those who are NOT on NAs).
Positive for co-infection with hepatitis C virus (HCV), human immunodeficiency virus (HIV), and/or hepatitis D virus (HDV) at screening.
Participants that weigh less than 50 kilograms (kg) and/or have a body mass index (BMI) less than 18.5.
History of documented liver cirrhosis at screening. Patients under liver cirrhosis evaluation at screening will not be eligible until cirrhosis is ruled out.
Liver stiffness > 8 kilopascal (kPa) at screening.