A Study of ALG-125755 to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics After Single Doses in Healthy Volunteers, and Single and Multiple Doses in CHB Subjects

Inclusion Criteria for All Subjects: 1. Female subjects must have a negative serum pregnancy test at screening 2. Subjects must have a 12-lead electrocardiogram (ECG) that meets the protocol criteria Inclusion Criteria for Healthy Subjects: 1. Male or female between 18 and 55 years of age, extremes included. 2. Subjects must have a body mass index (BMI) of 18.0 to 32.0 kg/m2, extremes included. Inclusion Criteria for CHB Subjects (Parts 2 and 3): 1. Subjects must be 18 to 70 years of age, inclusive of extremes. 2. Subjects may have a BMI of 18.0 to 35.0 kg/m2, extremes included. 3. For virally suppressed subjects, must be currently receiving HBV NA treatment for ≥6 months prior to screening. For currently not treated or treatment naïve subjects, must have never received treatment OR have not been on treatment within 6 months prior to randomization Exclusion Criteria for All Subjects: 1. Subjects with any current or previous illness that, in the opinion of the Investigator, might confound the results of the study or pose an additional risk in administering study drug to the subject or that could prevent, limit, or confound the protocol specified assessments or study results' interpretation 2. Subjects with a past history of cardiac arrhythmias, risk factors for Torsade de Pointes syndrome (e.g., hypokalemia, family history of long QT Syndrome) or history or clinical evidence at screening of significant or unstable cardiac disease etc. 3. Subjects with a history of clinically significant drug allergy 4. Subject with current or history of clinically significant (as determined by the Investigator) skin disease requiring intermittent or chronic treatment 5. Excessive use of alcohol defined as regular consumption of ≥14 standard drinks/week for women and ≥21 standard drinks/week for men 6. Subjects with Hepatitis A, B, C, D, E or HIV-1/HIV-2 infection or acute infections such as SARS- CoV-2 infection Exclusion Criteria for Healthy Volunteers (Part 1): 1. Unwilling to abstain from alcohol use for 48 hours prior to start of study through end of study follow up. 2. Subjects with renal dysfunction \[e.g., estimated creatinine clearance \<90 mL/min/1.73 m2 at screening, calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula\] Exclusion criteria for CHB subjects (Parts 2 and 3): 1. Subjects who are positive for anti-HBs antibodies. 2. Subject with any history or current evidence of hepatic decompensation such as: variceal bleeding, spontaneous bacterial peritonitis, ascites, hepatic encephalopathy, or active jaundice (within the last year). 3. History or current evidence of cirrhosis. 4. Subjects with liver fibrosis that is classified as Metavir Score ≥F3 liver disease 5. Subjects must have absence of signs of hepatocellular carcinoma