Sibeprenlimab, an investigational monoclonal antibody targeting APRIL (A PRoliferation-Inducing Ligand), has demonstrated significant efficacy in reducing proteinuria in patients with IgA nephropathy (IgAN) in the largest Phase 3 trial ever conducted for this progressive kidney disease. The 12-month interim analysis from the VISIONARY trial showed a 54.3% placebo-adjusted reduction in proteinuria, with data presented at the American Society of Nephrology Kidney Week 2025 and simultaneously published in The New England Journal of Medicine.
Robust Efficacy Across Multiple Biomarkers
The VISIONARY study (NCT05248646) randomized 510 adults with IgAN across 31 countries to receive either subcutaneous sibeprenlimab 400 mg or placebo every four weeks. At 12 months, sibeprenlimab showed a reduction in 24-hour urine protein-to-creatinine ratio (uPCR-24h) of 56.6% (95% CI, 50.8% to 61.7%) compared with 5.1% for placebo, corresponding to a placebo-adjusted reduction of 54.3% (95% CI, 46.4% to 60.9%).
"This is another look at the proteinuria data, looking at the proteinuria response across different baseline characteristics, but also looking at other biomarkers of improved glomerular health, so the impact on hematuria, the impact on Gd-IgA1, which has not previously been discussed," said Jonathan Barratt, MBChB, PhD, Mayer Professor of Renal Medicine at the University of Leicester.
Beyond proteinuria reduction, sibeprenlimab substantially reduced serum immunoglobulins (IgA, IgG, IgM), APRIL, galactose-deficient IgA1 (Gd-IgA1), and rates of hematuria. The treatment also yielded higher rates of proteinuric remission at 34.3% compared to 12.7% for placebo.
Consistent Safety Profile and Broad Efficacy
The safety profile of sibeprenlimab was favorable and consistent with placebo. At the interim analysis cutoff, the incidence of treatment-emergent adverse events was similar between sibeprenlimab (74.1%) and placebo (82.1%) groups, with the majority being mild to moderate in severity. The most common events were upper respiratory tract infections (14.7% for sibeprenlimab vs. 13.9% for placebo) and nasopharyngitis (12.4% for sibeprenlimab vs. 10.0% for placebo). No deaths occurred during the study period.
Treatment effects remained consistent across prespecified subgroups, including patients with varying baseline proteinuria levels, estimated glomerular filtration rate (eGFR), demographics, and prior immunosuppression. Importantly, 98% of participants were on renin-angiotensin system inhibitors and 39% were also taking SGLT2 inhibitors at baseline, suggesting that sibeprenlimab delivered significant additional benefit beyond optimized standard of care.
Mechanism of Action and Clinical Significance
Sibeprenlimab works by selectively binding to and inhibiting APRIL, a cytokine in the tumor necrosis factor (TNF) family that plays a key role in IgAN pathogenesis. APRIL promotes the survival and class switching of B cells toward IgA-producing cells, particularly the pathogenic galactose-deficient IgA1 (Gd-IgA1) that forms immune complexes in the kidneys.
By inhibiting APRIL, sibeprenlimab reduces the production of Gd-IgA1, which may help slow kidney damage and progression toward end-stage kidney disease (ESKD). The drug is administered as a single-dose prefilled syringe for subcutaneous injection every four weeks, intended for self-administration.
Regulatory Progress and Future Outlook
Otsuka Pharmaceutical has filed a Biologics License Application (BLA) for sibeprenlimab with the U.S. FDA and received Priority Review designation, with a target action date of November 28, 2025. The 9-month interim analysis results were submitted as part of the BLA submission.
"If we can truly arrest loss of kidney function in patients with IGA nephropathy, it will transform the outlook of these young people living with what at the moment is a relentlessly progressive kidney disease," noted one expert commenting on the potential impact.
The VISIONARY study continues in a blinded manner to evaluate the change in kidney function over 24 months as measured by eGFR, with completion expected in 2026. This longer-term data will be crucial for understanding sibeprenlimab's impact on the primary clinical concern in IgAN - preserving kidney function.
"These data give us a fuller picture of where we are with this drug while we're all desperately waiting to see the glomerular filtration rate (GFR) data," said Barratt. "The phase 2 data looked incredibly promising over that initial 12 month treatment period when sibeprenlimab was given."
IgAN is a progressive, immune-mediated chronic kidney disease that typically manifests in adults aged 20-40 years and leads to ESKD over the lifetime of most patients. Despite supportive care, there remains an unmet need for treatments that address the root causes of the condition, making sibeprenlimab's targeted approach particularly significant for this patient population.
