Positive topline results announced from Phase III study of sparsentan in Japanese patients with IgA nephropathy – Renalys Pharma/Chugai

Chugai and Renalys Pharma, Inc. announced positive topline results from its Phase III clinical study of sparsentan (RE 021), an orally administered dual endothelin and angiotensin II receptor antagonist (DEARA), in Japanese patients with IgA nephropathy (IgAN). Based on these results, the company plans to submit a New Drug Application in Japan in 2026.

The primary endpoint of the study assessed the percent change from baseline in the 24-hour urine protein-to-creatinine ratio (UPCR) after 36 weeks of oral administration of sparsentan in Japanese IgAN patients (N=35). The least-squares geometric mean percent change (95% CI) was –58.54% (–68.75%, –45.00%), confirming the efficacy of sparsentan in this patient population. Sparsentan was well-tolerated in the study with a safety profile consistent with other global trials and no new safety risks specific to Japanese patients were observed.

BT Slingsby, Chairman, CEO, and Co-Founder of Renalys, commented: “In Japan, treatment options for IgAN remain limited, and unmet medical needs are extremely high. Sparsentan has already been approved in the United States and Europe, and from the perspective of addressing the drug lag, it is imperative that we deliver this therapy to Japanese patients who need it as soon as possible.”

Ryutaro Shimazaki, Chief Development Officer of Renalys, commented: “This Phase III study in Japan was able to be conducted as a small-scale bridging study following extensive discussions with the PMDA, enabling the use of data from large-scale overseas clinical trials. The study included both adult and pediatric patients aged 10 years and older, and strong reductions in proteinuria consistent with international trial results were observed across all age groups. We extend our deepest gratitude to the patients, investigators, and all those involved in conducting this study.”

Naoki Kashihara, President of Japan Kidney Association, commented: “For rare kidney diseases such as IgAN, progress in developing effective therapies had long been limited. It is encouraging to see accelerated drug development in this field. Sparsentan has demonstrated strong proteinuria-lowering effects and a favorable safety profile, as shown in both large global clinical trials and this clinical study in Japanese patients. Furthermore, sparsentan is expected to have potential not only for rare kidney diseases such as FSGS and Alport syndrome but also more broadly for chronic kidney disease (CKD), which is one of the unique advantages of this therapy. Prior to this clinical study in Japanese patients, the Japanese Society of Nephrology used its large patient database to clarify the relationship between proteinuria and renal outcomes in Japanese patients with IgAN. ¹ We will continue working with related academic societies and contribute to evaluating appropriate clinical endpoints, including in international initiatives.”