The Food and Drug Administration approved Travere Therapeutics’ drug Filspari for the treatment of focal segmental glomerulosclerosis (FSGS), a rare and potentially fatal kidney disease, according to an announcement on April 14. This approval makes Filspari the first drug available for this indication.
FSGS affects around seven out of every one million people, causing scarring in the small blood vessels of the kidneys. The condition can lead to hypertension, swelling, kidney failure, and may be fatal if untreated. Until now, there were no approved therapies specifically targeting this disorder.
The FDA granted approval to Filspari despite results from a Phase 3 trial that showed it did not outperform Sanofi’s Avapro in improving kidney function after 108 weeks. However, more patients on Filspari achieved partial remission from proteinuria compared to those taking Avapro. Data from an earlier Phase 2 study also demonstrated that Filspari reduced proteinuria by more than twofold versus Avapro.
Travere CEO Eric Dube said in a prepared statement that the decision is a “historic milestone” for patients with FSGS and confirmed that “Filspari will be available ‘immediately’ for doctors to prescribe.” Analysts at Jefferies said they expect a strong launch due to the urgency of treating this faster-progressing disease and noted Travere’s established commercial presence. They also projected limited competition over at least three years before other potential challengers reach the market.
Market projections vary: Guggenheim Partners estimated peak annual sales could exceed $2 billion before patent protections expire in 2033, while Jefferies expects about 20,000 eligible patients could create a total addressable market near $960 million by 2032. In IgA nephropathy—a different kidney disorder—Filspari saw its accelerated approval converted to traditional approval in September 2024 and reported significant revenue growth afterward.
Broader implications of this decision include providing hope for thousands living with an otherwise untreatable condition and opening up new opportunities within rare disease therapeutics.
