A Study Evaluating Treatment Regimens Containing Vebicorvir (ABI-H0731) in Participants With Chronic Hepatitis B Infection

The purpose of this study is to determine if vebicorvir (VBR, ABI-H0731) in combination with AB-729 is safe and effective in participants with chronic hepatitis B infection (cHBV) receiving a standard of care nucleos(t)ide/reverse transcriptase inhibitor (SOC NrtI).

The initial cohort of participants will be enrolled in 3 treatment groups receiving 1) VBR + AB-729 + SOC NrtI, 2) VBR + SOC NrtI, or 3) AB-729 + SOC NrtI for up to 48 weeks. At Week 48, all participants will have an assessment of Treatment Stopping Criteria. Any participant who meets the Treatment Stopping Criteria, will discontinue their assigned treatment including NrtI and will remain in follow-up through Week 96. The participants who do not meet the Treatment Stopping Criteria will continue treatment with NrtI alone and will remain in follow-up through Week 96. Up to an additional 2 cohorts may be added to the study in future protocol amendments.

Eligibility Criteria:
Inclusion Criteria:

* Body mass index (BMI) 18 to 36 kg/m\^2 and a minimum body weight of 45 kg (inclusive)
* Female participants must be non-pregnant and have a negative serum pregnancy test at Screening and a negative urine pregnancy test at Day 1
* Chronic Hepatitis B defined as HBV infection documented for ≥6 months prior to Screening
* Hepatitis B 'e' antigen (HBeAg) negative at least 3 months prior to Screening Visit (historical documentation) AND at the Screening Visit
* Virologically suppressed on SOC NrtI therapy with nonquantifiable HBV DNA for at least 6 months prior to Screening
* On a stable SOC NrtI regimen of ETV, TDF, or TAF for \>12 months
* HBsAg ≥100 international units/mL at Screening
* Lack of bridging fibrosis or cirrhosis
* Agreement to comply with protocol-specified contraceptive requirements
* In good general health, except for cHBV, in the opinion of the Investigator
* Able to take oral medication and willing to receive subcutaneous injections of AB-729.

Exclusion Criteria:

* Co-infection with human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis D virus (HDV), acute hepatitis A virus (HAV), or acute hepatitis E virus (HEV)
* Females who are lactating or wish to become pregnant during the course of the study
* History of liver transplant or evidence of advanced liver disease, cirrhosis, or hepatic decompensation at any time prior to, or at the time of Screening
* History of persistent alcohol abuse or illicit drug abuse within 3 years prior to Screening
* Clinically significant diseases or conditions, such as cardiac disease, including poorly-controlled or unstable hypertension; pulmonary disease; chronic or recurrent renal or urinary tract disease; liver disease other than cHBV; endocrine disorder; autoimmune disorder; poorly controlled diabetes mellitus; neuromuscular, musculoskeletal, or mucocutaneous conditions requiring frequent treatment, seizure disorders requiring treatment; ongoing infection or other medical conditions requiring frequent medical management or pharmacologic or surgical treatment that, in the opinion of the Investigator or the Sponsor, makes the subject unsuitable for study participation
* History of hepatocellular carcinoma (HCC)
* History of malignancy other than HCC unless the subject's malignancy has been in complete remission off chemotherapy and without additional medical or surgical interventions during the 3 years before Screening
* History or presence at Screening of electrocardiogram (ECG) abnormalities deemed clinically significant, in the opinion of the Investigator
* History of hypersensitivity or idiosyncratic reaction to any components or excipients of the investigational drugs
* History of any significant food or drug-related allergic reactions such as anaphylaxis or Stevens-Johnson syndrome
* Exclusionary laboratory results at Screening:

  1. Platelet count \<100,000/mm\^3
  2. Albumin \<3 g/dL
  3. Direct bilirubin \>1.2× upper limit of normal (ULN)
  4. ALT ≥5× ULN
  5. Serum alpha fetoprotein (AFP) ≥100 ng/mL. If AFP at Screening is \> ULN but \<100 ng/mL, the subject is eligible if hepatic imaging prior to initiation of study drug reveals no lesions indicative of possible HCC
  6. International Normalized Ratio (INR) \>1.5× ULN
  7. Estimated creatinine clearance (CrCl) \<50 mL/min (using the Cockcroft-Gault method) based on serum creatinine and actual body weight at Screening
  8. Any other laboratory abnormality deemed clinically significant by the Investigator
* Current or prior use of prohibited (per protocol) concomitant medications from 28 days prior to Day 1.
* Current or prior treatment for cHBV with:

  * Lamivudine, telbivudine or adefovir (any duration)
  * HBV core inhibitor (any duration)
  * siRNA or other oligonucleotide therapeutic (any duration)
  * Interferon in the 6 months prior to Screening
  * Any investigational agent for cHBV in the 6 months prior to Screening.
* Participation in another clinical study of a drug or device whereby the last investigational drug/device administration is within 60 days or 5 half-lives prior to study start.