Effect of Kunxian capsule, a novel Tripterygium wilfordii preparation, on reducing proteinuria and slowing renal function decline in diabetic kidney disease: a 48–week randomized controlled trial

Background Diabetic kidney disease (DKD), a leading cause of chronic kidney disease, remains a clinical challenge despite renin–angiotensin system blockade. This study evaluated the efficacy and safety of adding Kunxian capsule to standard therapy with irbesartan in patients with DKD.Methods Eighty patients with DKD were randomly assigned to either the experimental group (standard therapy with irbesartan plus Kunxian capsule) or the control group (standard therapy with irbesartan) for 48 weeks. Primary outcomes included the proteinuria remission rate, degree of proteinuria reduction, and median time to remission. Secondary outcomes included the slope of eGFR decline and the incidence of renal composite hard endpoint. Safety was assessed by monitoring adverse events. This trial was registered in ClinicalTrials.gov on March 2, 2021 (No. NCT04981613).Results In the intention–to–treat analysis, the experimental group had a higher proteinuria remission rate (57.50% vs. 25.00%), a shorter median time to remission (5 months vs. not reached), and a greater reduction in 24–hour urinary protein than the control group. A lower incidence of renal composite hard endpoint was observed in the experimental group (10.00% vs. 32.50%), accompanied by a slower eGFR decline. No significant differences in the incidence of adverse events were observed between the two groups. Inflammatory markers, including C–reactive protein and erythrocyte sedimentation rate, were significantly reduced in the experimental group.Conclusions Adding Kunxian capsule to standard therapy with irbesartan improved the proteinuria remission rate and attenuated renal function decline in patients with DKD, supporting its potential as a promising adjunctive therapy.