Inclusion Criteria:
1. Positive for HBsAg for at least 6 months, either HBeAg (+) or HBeAg (-), and ALT ≤ 10X ULN at screening;
2. Interferon naïve;
3. Quantitative HBsAg Level \< 5,000 IU/mL at screening; HBV DNA \< 2,000 IU/mL (patients are either under NUC treatment or not);
4. Adults ≥20 years of age; patients who are over 70 years of age must be in generally good health depending upon the Investigator's judgment;
5. Laboratory test results before study entry: WBC ≥ 3,000/mm3; ANC ≥ 1,500/mm3; Platelet ≥ 90,000/mm3; Hemoglobin ≥ 10g/dL; e-GFR ≥ 60mL/min;
6. ECG without clinically significant abnormalities before study entry;
7. Be able to attend all scheduled visits and to comply with all study procedures;
8. Patients with anti-HDV (+) can be enrolled;
9. Patients with fibrosis stage \< F3 can be enrolled;
10. Willing to provide written informed consent;
Exclusion Criteria:
1. Clinically significant illness or surgery that might interfere with study participation;
2. Clinically significant vital sign abnormalities or fever \[body temperature \>38℃\]);
3. History of significant alcohol or drug abuse within 6 months prior to the screening visit (alcohol consumption of more than 14 units of alcohol per week \[1 Unit = 150 mL of wine, 360 mL of beer, or 45 mL of 40% alcohol\]) or refusal to abstain from alcohol or illicit drugs throughout the study;
4. Any history or presence of poorly controlled or clinically significant medical conditions that are not suitable to receive interferon-based treatment, at the discretion of the investigator: major psychiatric (including but not limited to those with severe depression, severe bi-polar disorder, schizophrenia, suicidal ideation or history of suicidal attempt), neurological, cardiovascular (i.e. uncontrolled hypertension, congestive heart failure (≥ NYHA class 2), serious cardiac arrhythmia, significant coronary artery stenosis, unstable angina) or recent stroke or myocardial infarction), pulmonary, hematologic, immunologic, autoimmune diseases, thyroid or other endocrine diseases, metabolic (e.g. diabetes mellitus with HbA1C \> 8.0%) or other uncontrolled systemic disease, coagulation disorders or blood dyscrasias;
5. Pregnant patient, female patient or the spouse of male patient, with child-bearing potential who is unwilling or unable to practice adequate contraception, defined as vasectomy in men, tubal ligation in women, or use of condoms and spermicides, or birth control pills, or intrauterine devices throughout the study;
6. History of severe allergic or hypersensitivity reactions, e.g. hypersensitivity to the active substance or to any of the excipients of Ropeginterferon alfa-2b (P1101), bronchospasm, angioedema, asthma, or anaphylaxis;
7. Therapy with any systemic anti-viral treatment, anti-neoplastic, or immunomodulatory treatment (including supraphysiologic doses of steroids and radiation) within 1 month (3 months for those with long elimination half-lives) prior to the first dose of study drug;
8. A depot injection or an implant of any drug within 3 months prior to administration of study medication, other than contraception or hyaluronic acid injections in joints for osteoarthritis;
9. Body organ transplant or taking immunosuppressant;
10. Use investigational drug of other clinical trials within 4 weeks prior to the first dose of the study drug;
11. History of malignancy diagnosed or treated within 5 years prior to screening (except for localized treatment of squamous or non-invasive basal cell skin cancers; cervical carcinoma in situ);
12. History of opportunistic infection (e.g., invasive candidiasis or pneumocystis pneumonia);
13. Serious localized infection (e.g., cellulitis, abscess) or systemic and life-threatening infection (e.g., septicemia) within 3 months prior to screening;
14. Clinically significant medical conditions known to interfere absorption, distribution, metabolism or excretion of the study drugs;
15. Decompensated liver disease, which includes but not limited to the following: total bilirubin≥2 mg/dL (except in Gilbert syndrome), direct bilirubin ≥2X ULN, albumin level \< 3.5 g/dL, INR ≥1.5; clinical evidence of ascites, liver decompensation, hepatic encephalopathy, oesophageal varices or cirrhosis as identified by ultrasound or any other examination before study entry;
16. Significant steatohepatitis by ultrasound or other examination at the discretion of investigator;
17. Other form of significant chronic liver diseases, except those mentioned above (e.g. HBV, HDV);
18. Significant or major fundoscopic findings at screening including but not limited to retinal exudates, hemorrhage, detachment, neovascularization, papilledema, optic atrophy, microaneurysms and macular changes;
19. Positive for anti-HIV or anti-HCV;
20. Prior therapy with anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, anti-CTLA-4 antibody, or any other antibody or drug specifically targeting T-cell co-stimulation or immune checkpoint pathway;
21. Any contraindication to receiving anti-PD-1 antibody (e.g. active or a history of life-threatening autoimmune conditions, corticosteroids treatment required) or hypersensitivity to the constituents of anti-PD-1 antibody;
22. Patients under monotherapy by telbivudine or any other combination therapy with telbivudine.
