Supplementary Material for: Efficacy and Safety of Finerenone in Patients with Idiopathic Membranous Nephropathy (IMN): A Multicenter, prospective-retrospective Real-World Study

Introduction. The efficacy and safety of finerenone in patients with idiopathic membranous nephropathy (IMN) remains unclear, especially given the need for additional supportive therapeutic options. Methods. This prospective-retrospective, multicentre, observational real-world study evaluated the efficacy and safety of finerenone in IMN patients with proteinuria ≥1 g/24h. The primary outcome was the percentage change in proteinuria from baseline to six months with finerenone treatment. Secondary outcomes included the stratified reduction in proteinuria, and changes in estimated glomerular filtration rate (eGFR), serum albumin (ALB), and total cholesterol (TCHO). Safety assessment focused on serum potassium. Data were primarily analysed using linear mixed-effects models. Results. Among 112 IMN patients treated with finerenone, 79 were ultimately analyzed. All of them received tolerated doses of ACEIs or ARBs, and 53.2% (42/79) were treated with immunosuppressive therapy. The median baseline proteinuria was 3212.5 mg/24h (IQR 1977.0 - 7113.6). After six months of finerenone treatment, the geometric mean reduction in proteinuria was -58.5% (95% CI: - 67.7 to - 46.6; P 5 mmol/L) occurring in 5.1% of participants (4/79), no cases exceeded 5.5 mmol/L. Conclusion. In combination with ACEIs or ARBs, finerenone appeared to reduce proteinuria in IMN patients with or without immunosuppressive therapy. Serum potassium did not exceed 5.5 mmol/L in any cases.