A Travere Therapeutics drug for a rare disease that can progress to kidney failure has converted its status to full FDA approval, strengthening the product’s case to compete against two other therapies that received affirmative regulatory decisions in the past year, one of them a Novartis drug recently awarded accelerated approval.
The Travere drug, Filspari, treats immunoglobulin A nephropathy (IgAN), a disease in which a patient’s immune system produces excessive amounts of antibodies that damage the kidney. Filspari’s accelerated FDA approval last year relied on data showing the drug reduced proteinuria, levels of urine proteins that are a sign of kidney disease. The full approval announced late Thursday is based on long-term results showing the San Diego-based biotech’s once-daily pill significantly slowed kidney function decline measured over the course of two years.
Filspari overcame what was initially a failure of its confirmatory study. Last September, Travere released results from the Phase 3 test, which compared the drug to irbesartan, a generic blood pressure drug that is used to treat nephropathy. According to results in estimated glomerular filtration rate (eGFR), a measure of kidney function, the trending improvement in the Filspari arm fell just short of statistical significance. Travere did not run another confirmatory study. The full FDA approval is based on a modified analysis that evaluates data from all study participants, regardless of whether they discontinued treatment. These results were statistically significant.
The Funding Model for Cancer Innovation is Broken — We Can Fix It
Closing cancer health equity gaps require medical breakthroughs made possible by new funding approaches.
The full approval expands the population of IgAN patients addressable by Filspari. The initial approval permitted use of the drug in patients whose disease reached a specified proteinuria threshold. The full approval removes this threshold. Leerink Partners analyst Joseph Schwartz said in a note sent to investors that Filspari’s initial label made 30,000 to 50,000 IgAN patients eligible for treatment with the drug. Removing the proteinuria threshold expands the addressable population to greater than 70,000, he said. Schwartz also noted that draft IgAN guidelines from Kidney Disease: Improving Global Outcomes, an organization that sets guidelines for kidney care, lower the proteinuria targets for the disease, lower the threshold for defining patients at risk of progressive function kidney loss, and recommend that patients at risk of progressive kidney function loss be treated with Filspari.
“Taken together, these adjustments should open up the market opportunity for Filspari, with more patients fitting the criteria for additional treatment to lower levels of proteinuria,” Schwartz said.
Filspari is a small molecule designed to selectively block two pathways associated with IgAN progression. Travere touts it as the only non-immunosuppressive therapy for the disorder. The first FDA-approved therapy for IgAN was Calliditas Therapeutics drug Tarpeyo, a corticosteroid whose broad immunosuppressive effects go beyond the kidney. Last December, Tarpeyo converted its 2021 accelerated approval to a full approval. Novartis is in the mix with Fabhalta, a drug that won accelerated approval in August for IgAN. Fabhalta is a small molecule designed to block a complement system pathway whose activation is thought to be associated with IgAN progression.
Filspari’s label still carries a black box warning for liver toxicity. The drug is made available only under a Risk Evaluation and Mitigation Strategies (REMS) program that informs clinicians and patients about that risk. The label advises clinicians to monitor for liver enzymes that indicate potential liver toxicity. Travere said it expects to submit a supplemental new drug application to potentially modify the liver-monitoring REMS.
Transforming Patient Care: The Role of AI-Powered Assistants
The progress in artificial intelligence (AI) is reshaping patient care, across various dimensions, from facilitating faster discharge to curating treatment plans and suggesting lifestyle changes.
Travere reported $46.9 million in Filspari revenue in the first half of this year. Sales are poised to grow as the drug gains approvals in other markets. The European Commission granted Filspari conditional marketing authorization in April. CSL Vifor holds the rights to commercialize the drug in Europe, Australia, and New Zealand. Renalys Pharma holds right to the drug in certain Asian markets. Results from a pivotal study in Japan are expected in the second half of 2025. Travere is eligible for up to $910 million in milestone payments plus royalties from sales from these partners, the company said in an investor presentation.
Image: peterschreiber.media, Getty Images