Effect of finerenone on nephrotic syndrome in patients with diabetic kidney disease

Diabetic kidney disease (DKD) is an important complication of diabetes as it results in end-stage renal disease; hence, several drugs have been developed for its treatment. However, even with treatment with renin-angiotensin system inhibitors and sodium-glucose cotransporter-2 inhibitors, the residual risk of DKD remains. While this risk is an issue, the renoprotective effects of finerenone, a novel non-steroidal mineralocorticoid receptor antagonist, are becoming evident. High proteinuria increases the risk of cardiovascular death as well as renal failure. Hence, it is especially important to address cases of urine protein to nephrotic levels in DKD, however, no previous studies have assessed the safety and efficacy of finerenone in patients with DKD and nephrotic syndrome. Therefore, this study aimed to assess whether finerenone has a renoprotective effect in advanced DKD complicated by nephrotic syndrome. Nine patients with DKD and nephrotic syndrome who received 10–20 mg/day of finerenone were retrospectively analyzed. The average observation period was 9.7±3.4 months. Patients with serum potassium levels greater than 5.0 mEq/L at the start of finelenone were excluded. Changes in urinary protein levels, estimated glomerular filtration rate (eGFR), and serum potassium levels were studied before and after finerenone administration. The mean changes in the urinary protein creatinine ratio (UPCR) at baseline were 6.6±2.0. After finerenone treatment, the mean UPCR decreased to -0.6±3.9; however, this change was not statistically significant. The eGFR decline slope also tended to decrease with finerenone treatment (before vs. after: -3.1±4.9 vs. -1.7±3.2 mL/min/1.73 m2. Furthermore, finerenone did not increase serum potassium levels. Patients treated with finerenone showed decreased UPCR; hence, it is suggested that finerenone may be effective in treating nephrotic syndrome in patients with DKD. These findings may be applicable to real-world clinical settings. Nonetheless, it is important to note that this study was a retrospective analysis of a single-center cohort and had a limited sample size, highlighting the need for additional large-scale investigations.