Sibeprenlimab held kidney function steady in IgA nephropathy's confirmatory trial

Sibeprenlimab kept kidney function almost completely stable over two years in people with IgA nephropathy, according to the final analysis of the phase 3 VISIONARY trial — the read-out that was supposed to answer the question its accelerated approval left open [s1]. When the FDA cleared the drug, sold as Voyxact, it did so on proteinuria alone and said plainly that an effect on kidney-function decline had not been established. This analysis supplies that missing evidence [s1].

IgA nephropathy is an autoimmune kidney disease in which a faulty form of the antibody immunoglobulin A inflames the kidney's filtering units, leaks protein into the urine, and slowly erodes the estimated glomerular filtration rate (eGFR), the standard gauge of kidney function. It is the most common primary disease of the kidney's filters and a frequent cause of kidney failure in younger adults. Sibeprenlimab is a monoclonal antibody that blocks APRIL, a protein that tells B cells to make the disease-driving antibody — cutting off the supply at its source rather than mopping up the damage downstream [s1].

What the trial did

VISIONARY is a randomised, double-blind, placebo-controlled phase 3 trial funded by Otsuka, which markets the drug [s1][s2]. It enrolled 510 adults with biopsy-confirmed IgA nephropathy at risk of progression despite standard therapy, assigning 259 to subcutaneous sibeprenlimab 400 mg every four weeks and 251 to placebo [s1]. An earlier interim analysis had already shown the drug roughly halved protein leakage at nine months — the basis for approval. This final analysis tested the endpoint that matters more: the annualised rate of eGFR decline over 24 months [s1].

What it found

The slope of kidney decline was essentially flat on the drug. The annualised eGFR slope was 0.3 mL/min per 1.73 m² per year with sibeprenlimab (95% confidence interval −0.4 to 0.9) against −4.2 with placebo (95% CI −4.9 to −3.6) [s1]. The between-group difference of 4.5 mL/min per 1.73 m² per year (95% CI 3.6 to 5.4; P<0.001) means placebo patients lost kidney function at the expected pace of a progressive disease while treated patients barely lost any [s1]. Measured differently, the gap in eGFR change from baseline to two years was 9.2 mL/min per 1.73 m² in the drug's favour (95% CI 7.1 to 11.4; P<0.001) [s1].

That translated into far fewer hard events. A composite kidney endpoint — a confirmed sustained fall in eGFR, kidney failure, or death — occurred in a single patient (0.4%) on sibeprenlimab versus 28 (11.2%) on placebo, a hazard ratio of 0.029 (95% CI 0.004 to 0.214; P<0.001) [s1].

Safety was unremarkable. Adverse events occurred in 90.7% of the drug group and 90.0% of the placebo group; serious adverse events were less frequent on the drug (8.1% versus 12.7%), as were serious infections (1.9% versus 4.0%) [s1]. No deaths were reported [s1].

How to read it

The surrogate-to-outcome gap that hangs over accelerated approvals has now closed for this drug. A flat eGFR slope sustained over two years is the result nephrologists wanted, and the near-elimination of the composite kidney endpoint is the kind of effect size that is hard to explain away [s1]. The confidence intervals around the slope are tight and well clear of zero [s1].

Two cautions temper the enthusiasm. First, a hazard ratio of 0.029 rests on very few events — one versus 28 — so the point estimate is dramatic but its interval is correspondingly wide, and two years is short against a disease that unfolds over decades [s1]. Second, VISIONARY, like every trial in this crowded field, compared its drug to placebo on top of standard care, not against the other new agents. A near-identical confirmatory story has just emerged for atacicept, whose ORIGIN 3 trial reported significant eGFR benefit and a lower progression rate, and against older options such as the endothelin blocker atrasentan. How these drugs rank, and whether they can be combined, remains unanswered [s1].

What to watch

The immediate consequence is regulatory: a stable two-year eGFR slope and a near-absent composite endpoint are the evidence that converts an accelerated approval into a full one [s1]. Beyond that, the field now has several drugs with broadly similar effects on proteinuria and eGFR but different mechanisms and dosing, and the practical work of sequencing and combining them has barely begun [s1]. For patients, the near-term upshot is that a disease with almost no targeted options a few years ago now has a drug shown to all but halt kidney decline over two years — with the usual caveat that longer follow-up is needed to confirm the benefit holds across the decades the disease actually runs [s1].

This article describes research and regulatory context and is not medical advice. Treatment of IgA nephropathy is a decision for treating clinicians.