This is a multicenter, randomized, double-blind, placebo-controlled phase IIa study, designed to evaluate the efficacy and safety of ZM-H1505R in combination with Baraclude versus Baraclude monotherapy in adult CHB subjects with HBV DNA <2000 IU/mL but ≥ 50 IU/mL and who have received ETV (0.5 mg, once daily [QD)] monotherapy for at least 12 months.

The study is planned to enroll 90 adult CHB subjects who have received ETV monotherapy for at least 12 months and are still receiving ETV monotherapy (0.5 mg, QD) continuously. Eligible subjects will be randomized in a 1:1:1 ratio into 3 treatment groups. Both HBeAg positive and negative subjects will be included. There will be 20 HBeAg positive subjects and 10 HBeAg negative subjects in each treatment group.

After 48 weeks of treatment with the corresponding regimen, subjects will continue to take Baraclude 0.5 mg QD, as a monotherapy for a 12-week follow-up period for observation of efficacy and safety of ZM-H1505R.

This is a multicenter, randomized, double-blind, placebo-controlled phase IIa study, designed to evaluate the efficacy and safety of ZM-H1505R in combination with Baraclude versus Baraclude monotherapy in adult CHB subjects with HBV DNA <2000 IU/mL but ≥ 50 IU/mL and who have received ETV (0.5 mg, once daily [QD)] monotherapy for at least 12 months.

The study is planned to enroll 90 adult CHB subjects who have received ETV monotherapy for at least 12 months and are still receiving ETV monotherapy (0.5 mg, QD) continuously. Eligible subjects will be randomized in a 1:1:1 ratio into 3 treatment groups. Both HBeAg positive and negative subjects will be included. There will be 20 HBeAg positive subjects and 10 HBeAg negative subjects in each treatment group. The treatment regimens in each group are as follows:

Group A: ZM-H1505R 50 mg QD + Baraclude 0.5 mg QD Group B: ZM-H1505R 100 mg QD + Baraclude 0.5 mg QD Group C: ZM-H1505R placebo QD + Baraclude 0.5 mg QD After 48 weeks of treatment with the corresponding regimen, subjects will continue to take Baraclude 0.5 mg QD, as a monotherapy for a 12-week follow-up period for observation of efficacy and safety of ZM-H1505R.

Inclusion criteria

• 1.Able to understand and sign the written informed consent form (the informed consent should be obtained prior to any study procedure);
• 2.Males and females aged 18-65 (inclusive);
• 3.Have been used ETV (0.5 mg, QD) monotherapy for at least 12 months at the time of screening; and able to provide evidence of existing HBV infection (e.g., HBsAg and/or HBV DNA positive), or HBsAg positive at screening;
• 4.Plasma HBV DNA < 2000 IU/mL but ≥ 50 IU/mL in 2 consecutive tests at least 30 days apart during the screening period (serum samples will be delivered to the designated central laboratory for testing)
• 5.Women of childbearing potential or males with female partners of childbearing potential must agree to voluntarily use the contraceptive methods specified in the protocol from screening to 28 days after the last dose of the study (see Appendix 1).

Exclusion criteria

• 1.Progressive fibrosis or cirrhosis detected at screening, or progressive fibrosis or cirrhosis defined as follows: Metavir ≥ 3 or Ishak fibrosis score ≥ 4 by liver biopsy within 1 year prior to screening; or in the absence of an appropriate liver biopsy, liver stiffness test (FibroScan)

  ≥ 9 kPa within 3 months prior to screening;

• 2.History of hepatocellular carcinoma (HCC); or serum alpha-fetoprotein (AFP) ≥ 50 ng/mL at screening, or imaging examination such as abdominal ultrasound, CT (computed tomography) or MRI (magnetic resonance imaging) suggesting possible HCC;

• 3.Subjects meeting any of the following clinical laboratory parameters at screening:

  1. Hemoglobin < 120 g/L (for males) or < 110 g/L (for females);
  2. Platelet count < 100 × 109/L;
  3. Neutrophil count < 1.5 × 109/L;
  4. Alanine aminotransferase (ALT) > 3 × upper limit of normal (×ULN);
  5. International normalized ratio (INR) of prothrombin time > 1.3;
  6. Albumin < 35 g/L;
  7. Total bilirubin > 2 × ULN, and direct bilirubin > 1.5 × ULN;
  8. Estimated glomerular filtration rate < 60 mL/min/1.73 m2 (calculated using the CKD-MDRD formula, see Appendix 2).

• 4.Abnormal result of electrocardiogram (ECG) at screening and inappropriate for the study participation judged by the investigator; Or QTcF (QT corrected using the Fridericia formula): > 450 ms for males, > 470 ms for females at screening;

• 5.Co-infection with human immunodeficiency virus (HIV), hepatitis A virus (HAV), hepatitis C virus (HCV), hepatitis D virus (HDV) or hepatitis E virus (HEV); Note: Subjects with positive HCV antibody (Ab) but negative HCV RNA and subjects with positive HEV immunoglobulin M (IgM) but negative HEV RNA will NOT be excluded.

• 6.Other malignancy unless the subject's malignancy has been cured by surgical resection (e.g., basal cell skin cancer); Note: Subjects who are suspected of having malignancy must be excluded regardless of evidence of local recurrence or metastasis.

• 7.History of chronic liver disease with a non-HBV etiology, such as alcoholic liver disease, autoimmune liver disease, hereditary liver disease, non-alcoholic fatty liver disease, except for simple fatty liver disease;

• 8.Other concurrent severe systemic diseases or clinical manifestations, for which the investigator considers not suitable to participate in this study, including but not limited to:

  1. Circulatory system diseases: such as unstable angina, myocardial infarction, congestive heart failure, and poorly controlled or refractory hypertension (for example, after medication treatment, systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 100 mmHg);
  2. Respiratory system diseases: such as severe chronic obstructive pulmonary disease;
  3. Primary or secondary renal diseases (such as chronic renal decompensation and renal diseases associated with diabetes, hypertension, and vascular diseases);
  4. Endocrine system diseases: such as poorly controlled diabetes or thyroid disease;
  5. Autoimmune diseases: such as systemic lupus erythematosus, idiopathic thrombocytopenic purpura, rheumatoid arthritis, inflammatory bowel disease, sarcoidosis, autoimmune hemolytic anemia, and psoriasis;
  6. Neuropsychiatric diseases: such as epilepsy, schizophrenia, and depression;

• 9.Use of any investigational product or drug not approved by regulatory authorities within 3 months prior to screening;

• 10.History of persistent alcohol comsumption (alcohol consumption exceeding 40 g ethanol for males or 20 g ethanol for females per day on average) within 6 months prior to screening;

• 11.History of drug dependence or drug abuse;

• 12.Pregnant or breastfeeding women;

• 13.Known hypersensitivity to the active ingredient or formulation excipients of the investigational drug;

• 14.Inappropriate for the study participation for any reason not otherwise listed as judged by the investigator.