This study is a multi-center, randomized, double-blind, placebo-controlled clinical study to assess the safety, efficacy, PK and immunogenicity of RBD1016 injection on NAs background treatment in CHB participants.

The study consists of screening period, treatment period, and FU period. It is divided into 3 dose groups, namely 100 mg Q4W, 200 mg Q4W and 200 mg Q12W. Each group will enroll 16 eligible participants, with 12 participants receiving RBD1016 injection and 4 participants receiving placebo.

Inclusion Criteria:

1. Willing and able to give written informed consent for study participation;
2. Male or female participants aged 18-65 years;
3. Body mass index (BMI) within the range of 18-34 kilograms/square meter (kg/m2);
4. Documented history of chronic hepatitis B virus (HBV) infection, by positive HBsAg and/or HBV DNA tests ≥ 6 months before screening;
5. HBeAg positive or negative at screening;
6. On a stable regimen (≥ 12 months before screening) of any approved first-line oral NAs;
7. HBV DNA level <100 IU/mL at screening;
8. HBsAg level ≥50 IU/mL at screening;
9. Serum alanine aminotransferase (ALT) ≤ 1.5 times the upper limit of normal (ULN);
10. Liver transient elastography (FibroScan) results within 12 months before screening or at screening showing that the liver stiffness measurement (LSM) level is less than 9 kPa; or with liver biopsy within 24 months before screening showing that the Metavir score is F0-F2;

Exclusion Criteria:

1. Diagnosed with other liver diseases other than hepatitis B;
2. History of liver cirrhosis or hepatic decompensation (e.g., ascites, varices bleeding, or hepatic encephalopathy) before or at screening;
3. History of organ transplantation or previous or concurrent with hepatocellular carcinoma (HCC), or imaging findings suggesting a possibility of malignant liver lesions;
4. Concurrent hepatitis C virus (HCV), human immunodeficiency virus (HIV), or diagnosis of syphilis, acute hepatitis A or acute hepatitis E;
5. Laboratory results at screening as follows: serum alpha-fetoprotein (AFP) >50 μg/L; serum albumin concentration <3.0 g/dL; international normalized ratio (INR) >1.5; platelet count <90×10^9/L; serum direct bilirubin (DB) >2×ULN; serum creatinine concentration >1.5×ULN or creatinine clearance <60 mL/min (according to the Cockcroft-Gault equation); or any clinically significant laboratory outliers that the investigator believes may interfere with the interpretation of the efficacy and safety data in this study;
6. Those who the investigator believes are not suitable to participate in the study due to other factors.