Otsuka Opens New Chapter in IgA Nephropathy With ‘Improvement’ in Kidney Function Decline

Otsuka’s immunoglobulin A (IgA) nephropathy treatment Voxact succeeded in stabilizing patients’ kidney function at levels comparable to those of healthy adults in a phase 3 clinical trial, marking the first such result worldwide.

According to biotech publication Fierce Pharma on the 3rd local time, Otsuka presented the 2-year results from the phase 3 Visionary trial of sibeprenlimab (brand name Voxact) at the GlomCon 2026 conference in Hawaii.

In the study, Voxact recorded an annual change in estimated glomerular filtration rate (eGFR), a measure of kidney function, of +0.3 mL/min/1.73m² over 2 years. This suggests that kidney function actually improved slightly. The placebo group recorded -4.2 mL/min/1.73m² over the same period, indicating worsening kidney function.

Voxact’s results met the KDIGO guideline benchmark for the age-related decline in eGFR among healthy people, defined as less than 1 mL/min/1.73m² per year. It is the first case in which kidney function decline in patients with IgA nephropathy was limited to a level comparable to that of healthy people.

John Kraus, Otsuka’s chief medical officer (CMO), said in an interview with Fierce Pharma, “The stable maintenance of eGFR over 2 years in patients with IgA nephropathy is a highly meaningful result,” emphasizing that “preserving kidney function is incredibly important in a disease that can lead to dialysis or transplantation.”

The results represent a substantial improvement over the annual eGFR decline of -3 mL/min/1.73m² recorded in the first-year interim analysis. The earlier results fell short of expectations and raised concerns about antidrug antibodies (ADAs), causing disappointment, but the 2-year data demonstrated long-term efficacy and reversed the sentiment.

The gap with competing drugs also widened. TrueTACNA, Vera Therapeutics’ APRIL/BAFF dual inhibitor, recorded an annual eGFR change of -0.6 mL/min/1.73m² over 96 weeks in a phase 2b trial. Voxact therefore showed an advantage in preserving kidney function.

Voxact targets APRIL, a signaling protein that supports B-cell survival and antibody production. Its safety profile was similar to that of placebo (35% vs. 33%), while the infection rate was 1.9%, lower than the 4% reported in the placebo group.

Based on the data, Otsuka plans to submit an application to the U.S. Food and Drug Administration (FDA) to convert Voxact’s accelerated approval to full approval. The company also plans to add an autoinjector to the existing prefilled syringe formulation.

Voxact has shown steep sales growth since receiving accelerated approval in November 2025. It recorded sales of 17.1 billion yen (approximately $110 million, 16.5 billion won) in the first half of this year alone. As a result, Otsuka more than doubled its sales forecast for the year, raising it from 25 billion yen to 60 billion yen.