Safety and Antiviral Activity of a Monoclonal Hepatitis B Antibody (The SAMBA Study)

Inclusion Criteria: * Age ≥ 18 to ≤ 70; * HBV infection confirmed by positive HBsAg for ≥6 months; * On HBV-active nucleos(t)ide therapy for ≥6 months without change in NRTI in the previous 3 months; * The following laboratory values 49 days prior to study entry (day 0): * HBV DNA below lower limit of quantification; * HBs antibody negative; * HBeAg negative; * Ability and willingness to provide informed consent. * For participants who can become pregnant (i.e., participants who have not been post-menopausal for at least 24 consecutive months, who have had menses within the preceding 24 months, or who have not undergone surgical sterilization, specifically hysterectomy and/or bilateral oophorectomy or bilateral salpingectomy), negative serum or urine pregnancy test at screening and on day 0 (study entry). * Participants who can become pregnant must agree to use two methods of contraception, one of which must be from the highly effective methods for contraception listed below. Barrier methods of contraception are permitted for the second method of contraception. Contraception must be used from 10 days prior to study entry and during study follow up. Acceptable methods of contraception include: * Contraceptive subdermal implant; * Intrauterine device or intrauterine system; * Combined estrogen and progestogen oral contraceptive; * Injectable progestogen; * Contraceptive vaginal ring; * Percutaneous contraceptive patches; * Partner sterilization with documentation of azoospermia prior to the participant\'s entry into the study, and this partner is the sole partner for that participant. The documentation of partner sterility can come from the site personnel\'s review of medical records or medical history interview provided by the participant or the partner. Self-reported documentation of reproductive potential should be entered in the source documents. * Participants who can impregnate a partner and who are engaging in sexual activity that could lead to pregnancy must agree to use condoms from 10 days prior to study entry and during study follow up to avoid impregnating a partner who can get pregnant. Exclusion Criteria: * Clinical symptoms, imaging studies or liver histology suggestive of advanced fibrosis (exclude fibrosis grade 3 and 4 by FibroScan) (Fibroscan®\< 9 kpa) 12 months prior to entry or done at the pre-infusion visit. Note: If FibroScan results are not available, imaging will be performed at the preinfusion visit. * Presence of a LI-RADS4 or 5 liver lesion on imaging 12 months prior to entry or done at pre-infusion visit, if prior results not available. * Alpha fetoprotein \>20 ng/ml. Note: Alpha-fetoprotein (AFP) above normal but \< 20 is acceptable for entry if earlier AFP levels (older than 6 months) are within normal range and imaging is negative in last 3 months). * HIV-1, HCV or hepatitis delta virus infection 12 months prior to entry or done at screen, if prior results not available; * History of hematopoietic stem cell transplant or solid organ transplant; * Any confirmed significant allergic reactions (urticaria or anaphylaxis) against any drug, monoclonal antibody or vaccine, or multiple drug allergies (non-active hay fever is acceptable); * History of cardiovascular disease (e.g., cardiac insufficiency, coronary artery disease, cardiomyopathy, congestive heart failure, family history of congenital long QT syndrome, family history of sudden death); * History or presence of clinically significant Electrocardiogram (ECG) abnormalities based on the average of the triplicate ECG recordings (e.g., PR interval \>210 ms, QT corrected for heart rate using the Fridericia's correction factor \[QTcF\] \> 450 ms for males and QTcF \>470 ms for females); * History of systemic corticosteroids, immunosuppressive anti-cancer, systemic interferons or interleukins 6 months prior to entry; * History of chronic liver disease from another cause, ICD, or autoimmune diseases that in the opinion of the investigator would preclude participation; * Any significant acute infection (e.g. influenza, COVID-19) or any other clinically significant illness 2 weeks prior to entry. * Laboratory abnormalities in the parameters listed below: * Absolute neutrophil count \<1,000 /mm3 * Hemoglobin \<10 gm/dL (6.21 mmol/L) * Platelet count \<150,000 /mm3 * ALT \>2.0 x Upper normal limit (ULN) * AST \>2.0 x ULN * Total bilirubin \>1.5 ULN (except individuals with known Gilbert\'s) * Albumin \<3.5 gm/dL * Estimated glomerular filtration rate (eGFR) \<70 mL/min * INR ≥1.2 * Pregnancy or lactation; * Any vaccination 2 weeks prior to entry; * Receipt of anti-HBV mAb therapy of any kind in the past (including HBIG); * Participation in another clinical study of an investigational product currently or 12 weeks prior to, or expected participation during this study