FDA cleared Filspari for focal segmental glomerulosclerosis on Monday, making Travere Therapeutics’ endothelin blocker the first and only approved drug for a disease that affects roughly seven of every one million people.
The clearance came despite a failed Phase 3 study. Data from the DUPLEX trial showed Filspari didn’t outperform Sanofi’s Avapro at improving kidney function after 108 weeks. But significantly more patients on Filspari hit partial remission from proteinuria, and the Phase 2 DUET study showed a more than twofold decrease in proteinuria versus Avapro. That package, accepted by FDA in May 2025, was enough.
Now the market math: Guggenheim pegs peak FSGS sales at over $2 billion before patent protections expire in 2033. Jefferies is more measured, projecting a $960 million total addressable market by 2032 with around 20,000 eligible patients. Travere’s CEO Eric Dube put the U.S. addressable FSGS population at more than 30,000. Travere shares jumped nearly 40% in pre-market trading Tuesday, hovering around $43.
Jefferies expects limited competition for the foreseeable future, with Travere holding at least a three-year lead over potential challengers BioMarin and Boehringer Ingelheim. Filspari already cleared $322 million in 2025 sales from its IgA nephropathy indication, a 144% year-on-year jump after accelerated approval converted to traditional approval in September 2024.
The review itself wasn’t clean: FDA extended it by three months in January, pushing the original Jan. 13 PDUFA date. Filspari can be prescribed immediately.
— Sarah Chen