Chugai has submitted an NDA in Japan for sparsentan to treat IgA nephropathy. The filing is supported by Japanese Phase III and global PROTECT trial data showing significant proteinuria reduction and long-term kidney protection.
Written By: Nalam Karthik, PharmD
Reviewed By: Pharmacally Editorial Team
Chugai Pharmaceutical Co., Ltd. has filed a New Drug Application (NDA) in Japan for sparsentan for the treatment of immunoglobulin A nephropathy (IgA nephropathy; IgAN), a chronic kidney disease that can progressively lead to kidney failure.
The submission is supported by data from a Japanese Phase III study and the global Phase III PROTECT trial (NCT03762850), both of which demonstrated significant reductions in proteinuria and supported the therapy’s potential to slow disease progression.
IgA Nephropathy Remains a Significant Unmet Need
IgA nephropathy is characterized by the accumulation of abnormal immunoglobulin A (IgA) deposits in the kidneys, leading to inflammation and gradual loss of kidney function. Patients commonly experience hematuria and proteinuria, with excess protein in the urine serving as a key marker of kidney damage and disease progression.
Despite current supportive therapies, including renin-angiotensin system inhibitors, many patients continue to experience declining kidney function. Approximately 20% to 40% of patients may progress to end-stage renal disease within 20 years of diagnosis, requiring dialysis or kidney transplantation.
Japanese Phase III Study Met Primary Endpoint
The Japanese Phase III study enrolled 35 patients with IgA nephropathy and evaluated the percentage change from baseline in the 24-hour urine protein-to-creatinine ratio (UPCR) at Week 36.
The study met its primary endpoint, demonstrating a least-squares geometric mean reduction in UPCR of 58.5% at Week 36 (95% CI: -68.75% to -45.00%). Sparsentan was generally well tolerated, and no new safety signals were identified in Japanese patients.
PROTECT Trial Demonstrated Durable Renal Benefits
Additional support for the filing comes from the global Phase III PROTECT study, a randomized, double-blind, active-controlled trial conducted across 156 sites in 18 countries.
The efficacy analysis included 281 patients randomized to receive either sparsentan or irbesartan. Sparsentan achieved significantly greater reductions in proteinuria at Week 36 and subsequently demonstrated a slower rate of kidney function decline over two years compared with irbesartan, supporting its potential to provide long-term renal protection.
Sparsentan’s Dual Mechanism
Sparsentan is an oral, once-daily therapy that simultaneously blocks the endothelin receptor type A (ETAR) and angiotensin II type 1 receptor (AT1R), targeting two pathways implicated in kidney disease progression. The drug is marketed as FILSPARI® in several countries and is the first dual endothelin receptor and angiotensin receptor antagonist approved for IgA nephropathy.
Global Regulatory Progress
Sparsentan received full approval from the U.S. Food and Drug Administration in September 2024 for the treatment of IgA nephropathy following positive long-term results from the PROTECT study. The therapy also received European Commission marketing authorization in April 2025.
Chugai obtained exclusive rights to develop and commercialize sparsentan in Japan, South Korea, and Taiwan through its acquisition of Renalys Pharma.
What This Means for Patients
For people living with IgA nephropathy, sparsentan may offer a new treatment option aimed at reducing proteinuria and slowing the loss of kidney function. If approved in Japan, the therapy could address a significant unmet need for patients at risk of progressing to kidney failure despite existing treatments.
The NDA filing marks an important step toward expanding access to a therapy that has demonstrated clinically meaningful kidney benefits in both Japanese and global studies.
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About the Writer
Nalam Karthik (LinkedIn) is a healthcare writer and PharmD graduate with interests in pharmacovigilance, drug safety, clinical data analysis, and quality assurance. He is passionate about translating clinical and pharmaceutical knowledge into accessible healthcare content while staying engaged with advancements in drug development and patient safety initiatives.