FDA grants full approval to Filspari for focal segmental glomerulosclerosis
The FDA granted full approval to Filspari to reduce proteinuria in patients aged eight and older with FSGS without nephrotic syndrome. The decision was based on Phase III DUPLEX data versus irbesartan.
Travere Therapeutics has received US Food and Drug Administration full approval for Filspari (sparsentan) to reduce proteinuria in adult and paediatric patients aged eight years and above with focal segmental glomerulosclerosis (FSGS) without nephrotic syndrome. The approval makes Filspari the first and only FDA-approved medicine to treat FSGS, expanding its use beyond IgA nephropathy into a second rare kidney condition.
The company's already-marketed endothelin antagonist therapy Filspari (sparsentan) – approved since 2023 for IgA nephropathy – is now also indicated to reduce proteinuria in patients aged eight and over with FSGS who don't have nephrotic syndrome, an advanced form of the disease. Until now, there were no drugs specifically approved by the FDA for the disease.
The approval is based on the results of the Phase III DUPLEX study, said to be the largest comparative trial in FSGS, which compared Filspari to irbesartan. Filspari showed a 46% reduction in proteinuria for the entire study population from baseline to week 108 while irbesartan showed a 30% reduction.
In those without nephrotic syndrome, Filspari resulted in a 48% reduction, compared to 27% for irbesartan. Patients on the therapy also demonstrated a 1.1ml/min/1.73m² mean difference in estimated glomerular filtration rate (eGFR) change versus irbesartan.
Proteinuria wasn't the original primary endpoint for the study, however, and in 2023 Filspari proved no better than irbesartan at improving estimated glomerular filtration rate, a clinical measure that charts kidney function over time. The switch to the proteinuria endpoint was agreed with the FDA, which has awarded Filspari a full approval in FSGS.
Travere estimates that around 30,000 people with FSGS in the US could be eligible for treatment with Filspari. The approval expands the eligible patient population for Filspari to around 100,000 people in the US with FSGS and IgA nephropathy who need better treatment options.