Renalys Pharma announced on October 10, 2025, that it has completed data collection for the primary endpoint in its Phase III clinical trial of sparsentan (development code: RE-021) for IgA nephropathy in Japan. The primary endpoint evaluated was the urine protein creatinine ratio using 24-hour urine collection at 36 weeks, with data now collected for all eligible patients.
The Tokyo-based biopharmaceutical company will proceed with analyses of efficacy and safety through 36 weeks of treatment, as well as comparisons with global Phase III trial results, in preparation for submitting a New Drug Application (NDA) to Japanese regulatory authorities.
Sparsentan's Clinical Development and Regulatory Success
Sparsentan is an oral dual endothelin and angiotensin II receptor antagonist originally developed by Travere Therapeutics. Renalys holds an exclusive license for development and commercialization of sparsentan in Japan and several Asian territories.
The drug achieved significant regulatory milestones in 2024 when Travere received full FDA approval for sparsentan (U.S. brand name: FILSPARI®) to slow kidney function decline in adults with primary IgA nephropathy who are at risk of disease progression. This full approval was based on positive long-term confirmatory results from the PROTECT Study, which demonstrated that FILSPARI significantly slowed kidney function decline over two years compared to irbesartan.
In the PROTECT Study, described as the only head-to-head study in IgA nephropathy versus an active comparator, FILSPARI demonstrated a significant reduction in proteinuria, preservation of kidney function and a well-tolerated safety profile compared with active control irbesartan. The drug also obtained standard EU approval for the IgA nephropathy indication in 2025.
Expanding Treatment Applications
Beyond IgA nephropathy, sparsentan's therapeutic potential continues to expand. In 2025, the FDA accepted Travere's supplemental new drug application (sNDA) for FILSPARI for the treatment of focal segmental glomerulosclerosis (FSGS), indicating broader applications in kidney disease management.
Addressing Unmet Medical Need in Japan
IgA nephropathy represents a significant healthcare challenge in Japan, where the management of patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) has become a social issue placing a heavy burden on the healthcare system. The condition is widely recognized as one of the main causes of kidney failure and develops when abnormal IgA proteins are deposited in kidney tissue, inhibiting kidney function and causing inflammation.
The disease is designated as an intractable disease (intractable disease 66) in Japan, with many unresolved mechanisms of onset and severity. Currently, there is significant unmet need for approved treatment for IgA nephropathy in Japan, making Renalys's development program particularly important for Japanese patients.
Company Background and Mission
Renalys Pharma, founded by Catalys Pacific and SR One in 2023, is a privately held late-stage clinical biopharmaceutical company committed to developing innovative therapeutics targeting unmet needs in renal disease management for Japanese and Asian patients. The company aims to address the growing problem of "drug loss" by catalyzing access to new treatments for kidney disease patients in Japan and other Asian regions.
Led by BT Slingsby, MD, PhD, MPH, Renalys is focused on improving the lives of patients in Japan and across Asia by developing innovative therapies for kidney disease, with a primary focus on delivering sparsentan to patients as quickly as possible.
