This is a phase IV, open label, historical controlled comparative study to evaluate the efficacy and safety of Ricovir® in maintaining durability of viral response in CHB patients who have been treated with Viread® and have undetectable HBV DNA in serum by real-time polymerase chain reaction (PCR) assay.

Ricovir® Group

Inclusion Criteria:

• Male or female aged more than 20 years old;
• CHB patients who have been treated with Viread® for more than 1 year;
• Serum HBV DNA level is undetectable (not detected or <20 IU/mL) at screening;
• Informed consent must be obtained before the commencement of any screening procedures or study drugs

Exclusion Criteria:

• Patients with active HCC or other types of malignancy;
• Patients with impaired renal function (defined as eGFR ≦ 30 mL/min/1.73m2);
• Patients with hepatitis A (HAV), hepatitis C (HCV), hepatitis D (HDV) or human immunodeficiency virus (HIV) coinfection;
• Patients with alcohol dependence or addiction;
• Patients with autoimmune hepatitis;
• Patients with primary biliary cholangitis (PBC);
• Pregnancy, planning on getting pregnant, or breast-feeding;
• History of allergy, hypersensitivity, intolerance, or experiencing severe adverse reactions to tenofovir or any ingredient of the study drug;
• Not suitable for participating in this trial at the investigator's discretion.

Historical Control Group

Eligible individuals will be obtained from the TCVGH historical database based on matching (1:1) in terms of age (±5 years) and gender. To be eligible for the study, subjects must meet all of the following criteria:

• Male or female aged more than 20 years old;
• CHB patients who had been treated with Viread® for more than 1 year;
• Patients who had discontinued Viread® therapy for at least 24 weeks during the period from January 2014 to December 2021 and had undetectable HBV DNA (not detected or <20 IU/mL) in serum at the time of discontinuation;
• Patients who have the data of HBV DNA level 24 weeks after the time of discontinuation, with a time window of +4 weeks is allowed;
• The informed consent requirement will be waived based on the approval of IRB.