Finerenone in Primary IgA Nephropathy: A Matched Case-Control Study

This study aimed to evaluate whether supplementation of finerenone to renin-angiotensin system inhibitor (RASi) therapy confers additional renoprotective benefit versus RASi therapy only in clinical IgA nephropathy (IgAN).

Primary IgAN patients administered RASi therapy at Ruijin Hospital from January 2023 to December 2023 were retrospectively enrolled, with an estimated glomerular filtration rate (eGFR) ≥25 mL/min/1.73 m². IgAN patients treated with steroids or immunosuppressants were excluded. The analyzed patients were divided into the finerenone and RASi groups based on finerenone use status. Patients were selected via 1:1 propensity score matching (PSM) based on age, sex, 24-hour urine protein, eGFR, and sodium-dependent glucose transporter-2 inhibitor (SGLT2i) use status. The primary endpoint was the change in urinary protein at 9 months compared to baseline. Secondary endpoints included eGFR decline and safety outcomes, with additional data collection at 12 months.

After PSM, 62 patients were included, with 31 in each group. The finerenone group showed a greater reduction in urinary protein (-29.03% vs. 41.47%, p < 0.001) and a slower least squares mean eGFR slope (1.87 vs. -4.13 mL/min/1.73 m², p = 0.03) at 9 months compared with the RASi group. Subgroup analysis suggested a trend toward greater improvement with SGLT2i addition, but the interaction was not statistically significant (p = 0.31), likely due to the limited sample size. Extended follow-up at 12 months confirmed these findings, demonstrating a sustained reduction in proteinuria (p = 0.001). Hyperkalemia rates remained similar in both groups at 4, 9, and 12 months.

The combination of finerenone with RASi is associated with a greater reduction in urinary protein and potentially better stabilization of eGFR compared with RASi alone in IgAN patients. However, these findings require further validation in prospective studies.