This is a Phase II, multicenter, open-label study. Eligible subjects who have completed the HSK39297-202 study will be enrolled.Starting dose is 200 mg QD.Dose may be increased to 300 mg QD after 8-12 weeks of stable 200 mg QD therapy if 24-h urine protein excretion (UPE) remains >1 g/24 h and no Grade ≥3 treatment-related adverse events (AEs) occur.After the treatment period, subjects will enter the 4-week safety follow-up period.

Inclusion Criteria:

1. Completed the HSK39297-202 study and assessed by the investigator to have a favorable benefit-risk profile for 200 mg QD HSK39297.

2. eGFR ≥30 mL/min/1.73 m² at screening (calculated by CKD-EPI 2021 equation).

3. Able to maintain optimized, stable background therapy with RAS blockers, SGLT2 inhibitors, endothelin receptor antagonists, or hydroxychloroquine during the study.

4. Vaccinated against Neisseria meningitidis and Streptococcus pneumoniae as required in the previous study (booster if needed).

5. Fertile females: negative serum pregnancy test; highly effective contraception from signing informed consent until 30 days after last dose.

   Fertile males: highly effective contraception from signing informed consent until 90 days after last dose.

6. Voluntarily provided written informed consent and able to comply with study procedures

Exclusion Criteria:

1. Known or suspected hereditary or acquired complement deficiency.
2. Active primary or secondary immunodeficiency.
3. History of bone marrow / hematopoietic stem cell or solid organ transplantation.
4. Malignancy within the past 5 years (except cured basal cell carcinoma of the skin or carcinoma in situ of the cervix).
5. History of recurrent invasive infections caused by encapsulated bacteria (e.g., N. meningitidis, S. pneumoniae) or Mycobacterium tuberculosis.
6. Severe concomitant diseases judged by the investigator to be incompatible with study participation.
7. Suspected hypersensitivity to the investigational product or its class.
8. Pregnant or lactating females.
9. Other conditions that may interfere with the study or increase subject risk.