Tokyo, Japan, November 26 2025 — Renalys Pharma has announced positive topline results from its Phase III clinical study evaluating sparsentan in Japanese patients with IgA nephropathy (IgAN), demonstrating a substantial reduction in proteinuria and a favourable safety profile. As IgAN remains one of the most common primary glomerular diseases in Japan, these findings highlight sparsentan’s potential to become an important therapeutic option for patients needing more effective, kidney-protective treatment. The Phase III study evaluated sparsentan, a dual endothelin angiotensin receptor antagonist (DEARA), in adult Japanese patients with biopsy-proven IgAN. At week 36, patients receiving sparsentan achieved a 58.54% reduction in the 24-hour urine protein-to-creatinine ratio, a key indicator of treatment benefit in IgAN. These results echo prior global findings and support Renalys Pharma’s plan to advance regulatory submissions in Japan. With IgAN frequently progressing to chronic kidney disease and, eventually, renal failure, sparsentan’s performance in this population establishes important clinical evidence for addressing a significant unmet need in nephrology.
Science Significance
IgA nephropathy is a progressive autoimmune kidney disease characterized by immune-complex deposition in the glomeruli, leading to inflammation, protein leakage, and long-term structural damage. Elevated proteinuria is strongly correlated with disease progression, making reduction a primary therapeutic objective. Sparsentan’s mechanism — simultaneously blocking endothelin-1 and angiotensin II pathways — targets the hemodynamic and inflammatory drivers of glomerular injury more comprehensively than traditional single-pathway inhibitors.
The Japanese Phase III data reinforce the scientific rationale behind dual-pathway inhibition. Not only did sparsentan achieve a highly meaningful reduction in proteinuria, but early results suggest potential slowing of kidney function decline. These outcomes contribute to a growing body of evidence establishing sparsentan as a promising candidate for long-term renoprotection in IgAN populations worldwide.
Regulatory Significance
Renalys Pharma has confirmed its intention to file a New Drug Application (NDA) in Japan in 2026, supported by this robust dataset. IgAN remains a disease with limited approved treatment options in many countries, and Japan has historically faced a heavy burden of IgAN-associated kidney failure. The strong Phase III results fulfil regulatory expectations for demonstrating clinically relevant proteinuria reduction and consistent safety. As global approvals increasingly prioritise early detection and slowing of kidney decline, sparsentan’s performance will likely support favourable regulatory consideration. The programme’s alignment with chronic kidney disease management initiatives also situates the therapy within emerging global regulatory interest in renoprotective agents.
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Business Significance
The Phase III success significantly strengthens Renalys Pharma’s commercial and strategic profile in the Japanese pharmaceutical market. IgA nephropathy is more prevalent in Japan than in Western countries, creating strong market potential for innovative therapeutics that outperform existing standard-of-care options. Sparsentan’s differentiation as a dual-pathway inhibitor gives Renalys a competitive advantage as payers and clinicians seek treatments with meaningful kidney-preserving outcomes. Furthermore, the data add value to sparsentan’s global development programme and may encourage international partnerships, licensing opportunities, and expanded regional collaborations. With Japan representing one of the world’s most mature nephrology markets, a successful NDA application could play a pivotal role in the drug’s global adoption trajectory.
Patients’ Significance
For patients, sparsentan offers a significant step forward in the management of IgA nephropathy. Many individuals with IgAN continue to face progression to end-stage renal disease despite current therapies. The ability to achieve more than 50% proteinuria reduction suggests potential to delay dialysis, kidney transplantation, and long-term complications.
Sparsentan’s favourable safety profile also supports long-term use, which is critical in a chronic disease requiring ongoing therapy. These results provide renewed hope for patients seeking effective and tolerable treatment options capable of preserving kidney health and preventing irreversible decline.
Policy Significance
The strong Phase III results arrive at a time when Japan, like many nations, is prioritizing early intervention in chronic kidney disease to reduce healthcare expenditure and improve patient outcomes. A therapy capable of significantly reducing proteinuria aligns with national health policy objectives focused on preventing progression to expensive renal replacement therapies. Sparsentan may also support future policy discussions related to CKD screening, guideline updates, and reimbursement frameworks designed to incentivize long-term kidney preservation rather than late-stage intervention.
Renalys Pharma’s positive Phase III results for sparsentan represent a major advancement for Japanese patients living with IgA nephropathy. By demonstrating substantial proteinuria reduction and reinforcing global evidence, the company is well positioned to move toward regulatory submission and eventual commercialization. As the need for effective IgAN treatments continues to grow, sparsentan may soon offer a new therapeutic option capable of transforming disease management and improving long-term kidney outcomes.
Source: Renalys Pharma press release
