IgA nephropathy (IgAN) is a chronic progressive kidney disease, and long-term control of proteinuria and prevention of relapse are crucial for delaying disease progression. Patients with IgAN who achieve proteinuria remission after receiving Nefecon for 9 months or longer still face the risk of proteinuria relapse after treatment discontinuation. This study is to evaluate the efficacy and safety of Nefecon 8 mg treatment for 15 months as a maintenance therapy for prevention of proteinuria relapse in proteinuria-remitted patients.

Inclusion Criteria:

• Diagnosed primary IgAN with biopsy verification.
• Female or male participants ≥18 years of age.
• Completion of 9 months of Nefecon 16 mg QD at the Baseline visit.
• Proteinuria ≥ 1g/d prior to initiation of Nefecon
• Proteinuria<0.5 g/day (or UPCR <0.5 g/g) at screening
• eGFR ≥30 ml/min/1.73m² at screening
• On stable treatment with supportive treatment（including RAASi, SGLT2i, ERA） for at least 1 month prior to the Baseline visit

Exclusion Criteria:

• Systemic diseases that may cause mesangial immunoglobulin A deposition, including but not limited to IgAVN, systemic lupus erythematosus, dermatitis herpetiformis, ankylosing spondylitis, and others;
• Presence of other glomerulopathies (e.g., C3 glomerulopathy, nephrotic syndrome and/or diabetes nephropathy), active infection, severe hepatic impairment (Child-Pugh Class C), congestive heart failure, and a history of malignant tumor within the past 5 years.
• On current or planned dialysis or kidney transplantation;
• Participants who have been treated with systemic glucocorticoids and immunosuppressive agents within the past 3 months, including mycophenolate mofetil, hydroxychloroquine, cyclophosphamide, azathioprine, leflunomide, calcineurin inhibitors, and Chinese traditional medicines with immunosuppressive effects (such as Tripterygium wilfordii, Sinomenium acutum, Tripterygium Glycosides Tablets, Kunxian Capsules, Kunming Shanhaitang Tablets, etc.); treatment with B-cell targeted biological agents (such as telitacicept, etc.); complement pathway inhibitors, etc.;
• Poorly controlled diabetes mellitus (HbA1c>8%）
• Poorly controlled hypertension （≥160/100mmHg）
• Participants taking potent inhibitors of cytochrome P450 (CYP) 3A4.
• Females who are pregnant, breastfeeding, or plan to become pregnant in the trial period.
• Any other conditions that, in the investigator's judgment, make the patient ineligible for this clinical study.