Sparsentan Outperforms Irbesartan in Reducing Proteinuria in FSGS-Regardless of Baseline Levels

Sparsentan, marketed under the brand name Filspari, has achieved a landmark milestone in the treatment of focal segmental glomerulosclerosis (FSGS), a rare and often devastating kidney disease. On April 13, 2026, the U.S. Food and Drug Administration (FDA) approved sparsentan as the first-ever therapy specifically for reducing proteinuria in adults and pediatric patients aged 8 years and older with FSGS who do not have nephrotic syndrome.

This approval marks a significant advancement for patients with FSGS, who previously had no FDA-approved treatment options for this condition. The decision was based on robust data from the phase 3 DUPLEX study, the largest head-to-head clinical trial conducted to date in FSGS.

The DUPLEX study demonstrated that sparsentan significantly outperformed irbesartan, a commonly used angiotensin II receptor antagonist, in reducing proteinuria. By week 108, patients treated with sparsentan experienced a 46% reduction in proteinuria from baseline, compared to a 30% reduction in those treated with the maximum labeled dose of irbesartan. Among patients without nephrotic syndrome, the reduction was even more pronounced, with sparsentan achieving a 48% reduction versus a 27% reduction with irbesartan.

the study found a treatment difference in estimated glomerular filtration rate (eGFR) of 1.1 mL/min/1.73 m² in favor of sparsentan over irbesartan in this subgroup. These results align with guidance from Kidney Disease: Improving Global Outcomes (KDIGO), which emphasizes proteinuria reduction as a key strategy to slow disease progression, particularly in patients without active nephrotic syndrome.

Sparsentan’s safety profile was generally comparable to that of irbesartan, and the drug was well tolerated among both adult and pediatric patients. The approval also provides nephrologists with a new FDA-approved option for managing FSGS, a disease that can lead to kidney failure and significantly impact quality of life.

Travere Therapeutics, the developer of sparsentan, announced that the drug will be available for immediate prescribing. The company also noted that patients and clinicians will have access to its existing patient support program, which offers education, prescription access, insurance navigation, and required monitoring.

“Today marks a historic milestone for people living with FSGS, who for the first time have an FDA-approved medicine for this rare and devastating condition,” said Eric Dube, PhD, president and chief executive officer of Travere Therapeutics. “This approval reflects the power of innovation in nephrology and our commitment to delivering transformative therapies for patients in need.”

Kirk Campbell, MD, president of the National Kidney Foundation, echoed the significance of the approval, stating that it provides nephrologists with a new tool to better manage FSGS and potentially improve patient outcomes.

FSGS is characterized by scarring in parts of the kidney’s filtering units, leading to protein leakage into the urine (proteinuria) and, over time, kidney failure. The approval of sparsentan offers renewed hope for patients and their families, as well as for clinicians seeking effective treatments for this challenging condition.

As with any new therapy, ongoing monitoring and further research will be essential to fully understand its long-term benefits and risks. However, the FDA’s decision represents a major step forward in the fight against FSGS and underscores the importance of continued investment in nephrology research.