This is a multicenter, single-arm, open-label, phase IIIb extension clinical trial designed to evaluate the long-term safety and tolerability of GST-HG141 (nerlecovir, 50 mg BID) in combination with nucleos(t)ide analogues (NAs) in patients with chronic hepatitis B (CHB) who completed 48 weeks of treatment in the phase III study (GST-HG141-III-01), did not discontinue prematurely, had an overall medication compliance rate of ≥80%, and were willing to continue treatment.

A maximum of 578 eligible participants will be enrolled at 64 centers, including those who completed the preceding study, had ALT ≤5× upper limit of normal (ULN), and had no severe comorbidities (e.g., decompensated cirrhosis, other viral infections, or malignant tumors)

Inclusion Criteria:

1. Participants who received the study treatment of the phase III clinical trial of GST-HG141 (GST-HG141-III-01) in accordance with the protocol requirements (participants without early withdrawal and with overall medication compliance ≥ 80%), and had ALT ≤ 5×ULN;
2. Participants were willing to participate in the study and were judged by the investigator to be suitable for long-term treatment with GST-HG141 combined with NAs;
3. Male participants with female partners of childbearing potential or female participants of childbearing potential voluntarily adopted effective contraceptive measures from screening to 28 days after study withdrawal ;
4. Signed the informed consent form prior to the trial and were able to complete the study in accordance with the requirements of the trial protocol.

Exclusion Criteria:

1. Presence of severe systemic infection requiring treatment;

2. Suffering from clinically significant acute or chronic liver diseases not caused by HBV infection;

3. Participants with a history of liver cirrhosis; or currently diagnosed or suspected decompensated liver cirrhosis, including but not limited to hepatic encephalopathy, hepatorenal syndrome, esophagogastric variceal bleeding, splenomegaly, ascites, etc.; or participants with significant progression of liver fibrosis;

4. Primary liver cancer; suspected malignant space-occupying liver lesions suggested by imaging examination; combined with other malignant tumors (except cured basal cell carcinoma or squamous cell carcinoma of the skin and carcinoma in situ of the cervix);

5. Impaired gastrointestinal function or gastrointestinal diseases that may affect the absorption of oral drugs as judged by the investigator;

6. Combined with severe diseases of the circulatory, respiratory, urinary, hematological, metabolic, immune, psychiatric, neurological, renal and other systems, and judged by the investigator to be ineligible for continued participation in the study;

7. Participants with major trauma or major surgery within 3 months prior to screening; or those planning to undergo surgery during the study period;

8. Laboratory test abnormalities:

   1. Platelet count < 100×10^9/L;
   2. White blood cell count < 3.0×10^9/L;
   3. Absolute neutrophil count < 1.3×10^9/L;
   4. Serum total bilirubin > 2×ULN;
   5. Albumin < 35 g/L;
   6. Estimated glomerular filtration rate (eGFR) ≤ 60 ml·min-¹·(1.73m²)-¹ ;
   7. International Normalized Ratio (INR) of prothrombin time > 1.5;

9. Lactating females or participants with a positive pregnancy test;

10. Participants with any other conditions deemed inappropriate for participation in this trial by the investigator.