Renalys Pharma Announces Positive Topline Results from Phase III Study of Sparsentan in Japanese Patients with IgA Nephropathy

– In a Phase 3 clinical study evaluating the efficacy and safety of sparsentan in Japanese patients with IgA nephropathy (N=35), the percent change from baseline in the 24-hour urine protein-to-creatinine ratio at Week 36, which was the study's primary endpoint, was -58.54%. Sparsentan was well-tolerated with a profile consistent with other global trials and no new safety risks specific to Japanese patients were observed.

– Based on the results of this study, Renalys Pharma plans to submit a New Drug Application for sparsentan in Japan in 2026.

TOKYO, Nov. 26, 2025 /PRNewswire/ -- Renalys Pharma, Inc. (Headquarters: Chuo-ku, Tokyo; "Renalys") today announced positive topline results from its Phase III clinical study of sparsentan (development code: 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, MD, PhD, 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."

About sparsentan

Sparsentan is an oral dual endothelin and angiotensin II receptor antagonist (DEARA) developed by Travere Therapeutics, Inc. ("Travere").  Renalys has an exclusive license for development and commercialization of sparsentan in Japan and several Asian territories.  In 2024, Travere received full FDA approval in the U.S. for sparsentan (U.S. brand name: FILSPARI®) to slow kidney function decline in adults with primary IgA nephropathy (IgAN) who are at risk of disease progression*.  Full approval is based on positive long-term confirmatory results from the PROTECT Study demonstrating that FILSPARI® significantly slowed kidney function decline over two years compared to irbesartan.  In the PROTECT Study, 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.  In Europe, FILSPARI® received standard EU approval for the IgA nephropathy indication in 2025.  In 2025, the FDA accepted for review Travere's supplemental new drug application (sNDA) for FILSPARI® for the treatment of focal segmental glomerulosclerosis (FSGS).

*FILSPARI® (sparsentan) U.S. Indication:

FILSPARI is an endothelin and angiotensin II receptor antagonist indicated to slow kidney function decline in adults with primary IgA nephropathy (IgAN) who are at risk of disease progression.

About IgA Nephropathy

The management of patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) has become a social issue that places a heavy burden on the Japanese healthcare system.  IgA nephropathy is widely known as one of the main causes of kidney failure and is considered to develop when abnormal IgA proteins are deposited in kidney tissue, inhibiting kidney function and causing inflammation.  IgA nephropathy is a rare intractable disease (designated as an intractable disease 66) with many unresolved mechanisms of onset and severity.  Currently, there is significant unmet need for approved treatment for IgA nephropathy in Japan.

About Renalys Pharma, Inc.

Renalys Pharma, a privately held late-stage clinical biopharmaceutical company based in Japan, is committed to the development of innovative therapeutics targeting unmet needs in the management of renal disease for Japanese and Asian patients.  Founded by Catalys Pacific and SR One, the company aims to address the growing "drug loss" in the region by catalyzing access to new treatments for kidney disease patients.

Company Name: Renalys Pharma, Inc.
Address: 3-11, Nihonbashi-honcho 2-chome, Chuo-ku, Tokyo, Japan
Representative: BT Slingsby, MD, PhD, MPH
URL: https://renalys.com/

[Disclaimer]

Information concerning pharmaceutical products (compound under development) contained herein is not intended as advertising or as medical advice, but intended for disclosure of management information.

Renalys Pharma is scheduled to become a wholly owned subsidiary of Chugai Pharmaceutical Co., Ltd. on November 27, 2025.

For details, please refer to the following press release:
"Notice Regarding the Absorption-type Merger of Renalys Pharma, Inc. as a Wholly Owned Subsidiary"
https://www.chugai-pharm.co.jp/news/detail/20251118173000_1531.html 

Reference

1. Proteinuria reduction as a surrogate endpoint for clinical study of IgA nephropathy in Japanese patients: data from the J-CKD-DB-Ex.
   Naoki Kashihara. Clin Exp Nephrol. 2025 Nov 18. doi: 10.1007/s10157-025-02788-4.

SOURCE Renalys Pharma, Inc.