Travere undercuts key rival in rare kidney disease IgAN

Shortly after claiming FDA approval for its Filspari therapy for rare kidney disease IgA Nephropathy (IgAN), Travere Therapeutics has said it will price the drug at a discount to a recently-approved rival therapy from Calliditas Therapeutics.

Travere has set a list price for Filspari (sparsentan) of $9,900 per month, roughly $118,800 per year, which is less than the $170,000 annual price of Calliditas’ corticosteroid-based Tarpeyo (budesonide) therapy, which became the first FDA-approved therapy for IgAN in 2021.

IgAN is considered a rare disease, with about 150,000 in the US diagnosed with the autoimmune disease, also known as Berger’s disease. It occurs when antibodies accumulate in the kidneys, causing inflammation and scarring, and it can develop into chronic kidney disease (CKD). Symptoms include blood and protein in the urine that can make it appear dark brown and foamy.

Like Tarpeyo, Filspari has been granted accelerated approval on the strength of its ability to reduce protein levels in the urine of IgAN patients, and neither drug has yet been shown to slow kidney function decline over time.

An ongoing phase 3 trial called PROTECT is testing Filspari’s ability to slow kidney function decline, with results due in the fourth quarter of this year, a little after Calliditas is due to report results from the second, confirmatory stage of its late-stage NefIgArd study.

The positive verdict on the dual endothelin angiotensin receptor antagonist comes after a three-month delay at the FDA, caused by a request to include liver monitoring in its risk evaluation and mitigation strategy (REMS) for the drug.

Filspari has been approved with a boxed warning about liver toxicity and the potential to harm unborn children, which means access is limited to prescribers, pharmacists, and patients enrolled into a restricted programme.

Travere’s chief executive Eric Dube said Filspari will be a “transformative treatment” for patients with IgAN, as it is a “first-of-its-kind, non-immunosuppressive therapy” for the disease. The company estimates that approximately 30,000 to 50,000 IgAN patients will be eligible for treatment with the drug.

Tarpeyo – which was approved with no REMS programme requirement – made $12 million in sales in the third quarter of this year and is predicted to make $35 million to $40 million for the full year, a little ahead of analyst expectations. Jefferies is predicting Filspari will reach $35 million in sales this year, and $745 million at peak.

More competition is on the way, meanwhile. Chinook Therapeutics is in direct pursuit of Travere with its endothelin antagonist atrasentan, while Novartis is also testing its oral complement factor B inhibitor iptacopan in IgAN. Top-line phase 3 results for both drugs are due later this year.

Meantime, Travere is looking to expand the label for its drug into another rare kidney disease, focal segmental glomerulosclerosis (FSGS), with results from the late-stage DUPLEX study due in the second quarter of this year.