Dive Brief:

• The Food and Drug Administration on Tuesday granted the first product approval for the progressive kidney condition focal segmental glomerulosclerosis, unlocking what’s believed to be a blockbuster opportunity for the drug’s developer, Travere Therapeutics.
• Known as Filspari, the treatment has been cleared to treat adults and children at least eight years of age with FSGS but not a related condition called nephrotic syndrome. Travere estimates there to be more than 30,000 individuals in the U.S. eligible for treatment. 
• Filspari has been on the market since 2023 for another kidney disease known as IgA nephropathy. There, however, Filspari faces growing competition from drugmakers advancing alternative options, threatening its revenue outlook. Shares climbed by more than 34% in Tuesday trading, pushing the company’s market value close to $4 billion.

Dive Insight:

Filspari has undergone an unusual regulatory journey on its way to an approval in FSGS, a disease that causes progressive kidney scarring and, ultimately, organ failure. 

Travere originally licensed the drug in 2012, when it was known as Retrophin and run by Martin Shkreli. Filspari’s path was straightforward in IgAN, where testing led to an accelerated approval and steady growth since. The drug generated $322 million in U.S. net product sales last year, more than doubling its numbers from the prior year. 

But Filspari missed the main goal of a Phase 3 trial in FSGS in 2023, failing to meaningfully improve kidney function compared to an available treatment after two years. That result clouded Filspari’s future, but Travere pushed forward in FSGS nonetheless, highlighting instead the drug’s ability to reduce excess protein levels in the urine. This “proteinuria” is believed to be an important marker of kidney health, and U.S. regulators have since become more supportive of its use as a study goal. 

Still, an approval wasn’t a sure bet. The FDA has been under heightened scrutiny for recent regulatory decisions, many of them negative, involving rare disease drugmakers. The agency in January also extended its review by three months, heightening investor concerns about Filspari’s chances. 

The approval issued Monday, then, marks a “significant payoff” that opens up a major expansion for the therapy and shifts investor attention away from a competitive IgAN space, wrote Leerink Partners analyst Joseph Schwartz. 

In a separate note, Jefferies analyst Maury Raycroft estimated that the prescribing information covers about 80% of patients. He expects a strong launch due to the “urgency” to treat a “faster-progressing disease” like FSGS. 

Cantor analyst Prakhar Agrawal predicted that Filspari could generate more than $2 billion in sales in FSGS alone, and noted how Travere could benefit greatly due to a major overlap between IgAN and FSGS prescribers. 

“We expect uptake to be very rapid,” Agrawal wrote, after multiple checks with treating physicians.