FDA Approves Travere's Filspari for Focal Segmental Glomerulosclerosis

The FDA has approved Travere Therapeutics' sparsentan (Filspari) to reduce proteinuria in adults and children 8 years and older with focal segmental glomerulosclerosis (FSGS) who do not have nephrotic syndrome, The American Journal of Managed Care reported, citing the company's April 13 announcement.

FSGS is a rare kidney disorder in which scarring of the glomeruli, the kidney's filtering units, lets protein leak into the urine and often leads to kidney failure, Pharmaceutical Executive reported. Until now, patients have largely relied on off-label treatments, including long-term steroids, the publication said. Travere described Filspari as the first and only FDA-approved medicine for the disease.

"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, Travere's president and chief executive, as quoted by both publications.

The DUPLEX trial

The approval is based on the Phase 3 DUPLEX trial (NCT03493685), a randomized, double-blind study that compared sparsentan with the maximum labeled dose of irbesartan, an angiotensin receptor blocker, in patients aged 8 to 75 with biopsy-proven FSGS or a genetic mutation associated with the disease. Sparsentan was titrated to a target of 800 mg a day and irbesartan to 300 mg a day, according to AJMC.

At week 108, proteinuria fell 46% from baseline with sparsentan and 30% with irbesartan in the overall population (P = .0299). In patients without nephrotic syndrome, the group covered by the new label, the reductions were 48% and 27% (P = .0075). Mean estimated glomerular filtration rate, a measure of kidney function, fell by 11.3 mL/min/1.73 m2 with sparsentan and 12.4 mL/min/1.73 m2 with irbesartan, AJMC reported. Pharmaceutical Executive said the safety profile was generally comparable to irbesartan in adult and pediatric patients and that two-year results were published in the New England Journal of Medicine.

Review extension and earlier approvals

The decision came after the FDA in January extended its target action date for Travere's supplemental new drug application to April 13, 2026. AJMC reported that the agency said it needed the time to further characterize the drug's clinical benefit and did not raise questions about safety or manufacturing.

Sparsentan blocks both the endothelin A receptor and the angiotensin II receptor. It received accelerated approval in February 2023 to reduce proteinuria in IgA nephropathy and full approval in September 2024 to slow kidney function decline in that disease, according to AJMC.

Travere estimates that more than 30,000 people in the US have FSGS without nephrotic syndrome and that more than 100,000 people in the US have either FSGS or IgA nephropathy. The company said the drug is available for nephrologists to prescribe immediately.