Calliditas wins over FDA for full approval, broader label on kidney disease drug Tarpeyo

Two years after securing an accelerated approval for its primary immunoglobulin A nephropathy (IgAN) therapy Tarpeyo (budesonide), Calliditas Therapeutics has scored a full FDA endorsement for the oral, delayed-release drug.

Tarpeyo becomes the first treatment fully approved in the United States specifically for the chronic autoimmune kidney condition, also known as Berger’s disease.

While some graduations from accelerated to full approval are ceremonial, this endorsement carries extra weight as it expands the label for Tarpeyo, allowing it to be accessed by all patients with IgAN. Previously, the FDA limited the med's use to those at risk for rapid disease progression.

The expansion was facilitated by a confirmatory trial, which was the first phase 3 IgAN study to show significant improvement in estimated glomerular filtration rate (eGFR), which is the most reliable measure of kidney function. The results showed that Tarpeyo can reduce the time to kidney failure by 30%, potentially delaying clinical outcomes by 12.8 years, compared to standard of care blood pressure treatments.

Previously, in marketing Tarpeyo with its accelerated approval, the company could only point to the symptomatic improvements the drug could provide. But the full nod and the broadened label gives Calliditas more ammunition in winning over doctors and patients, which often isn’t easy with a corticosteroid such as Tarpeyo.

“We can talk to physicians about kidney function, which we haven’t really been able to do,” Calliditas CEO Renee Aguiar-Lucander said in an interview. “And also obviously from a payer perspective, payers are always a little bit more comfortable with drugs that have a standard approval.”

There are 130,000 to 150,000 people who have IgAN in the U.S. Over time, their kidneys can no longer remove waste from the blood, leaving them at risk of progressing to end-stage renal disease (ESRD), which requires hemodialysis or kidney transplant.

Calliditas believes the disease forms in the small intestine, creating IgA antibodies that enter through systemic circulation, triggering an autoimmune response that leads to the formation of immune complexes that deposit in the kidneys. As an immunosuppressant, Tarpeyo is designed to halt the formation of the antibodies.

Sales of Tarpeyo have been trending positively. In the third quarter, the drug generated revenue of 284 million Swedish krone ($26 million), which was an uptick of 130% year over year. The figure brought the drug's total sales sales since launch to $68.8 million.

In Europe, where the drug was approved in July of 2022 and is dubbed Kinpeygo, Stada serves as Calliditas’ commercial partner. In China, where IgAN is more prevalent as the most common primary glomerular disease, Hong Kong-based Everest Medicines will handle its commercialization. Kinpeygo is under a priority review in China, with a decision expected next year.

Calliditas will continue to market Tarpeyo in the United States.

“We felt that the best way of delivering shareholder value long term really was for us to build our own kind of commercialization effort in the U.S.,” Aguiar-Lucander said. “We really didn't have the resources or the people to build it up on a global basis, so we really had to pick one market.”

Rolling out the drug initially presented many challenges, Aguiar-Lucander said, noting that IgAN previously wasn’t listed on the World Health Organization’s ICD-10 registry of diseases, which is a starting point for patients, physicians and drugmakers to find, prescribe and market drugs.  

“This was obviously the very first time that there was a drug approved in this indication,” Aguiar-Lucander said. “It meant that we've had to kind of start from ground zero in terms of identifying the right physicians and working under quite a basic level with a lot of mapping and market research to try and get going in terms of building this market.”

While Calliditas might have a stronghold on the market for now, that could change in the next few years as several companies advance IgAN medicines.

One of the competitors, Travere’s non-immunosuppressive agent sparsentan, has gained approval for IgAN in Europe. In February, the FDA gave the drug an accelerated nod, but that is under threat because a phase 3 confirmatory trial has come up just short.

Earlier this year, Novartis took a $3.2 billion plunge on Chinook, largely to acquire IgAN candidate atrasentan. Interim results from a phase 3 trial have shown it provided significant reductions in proteinuria—a measure of protein in the urine which is a symptom of kidney disease. Novartis says it will file for an FDA accelerated approval next year.

Novartis has another candidate in Fabhalta (iptacopan), which gained FDA approval earlier this month in paroxysmal nocturnal hemoglobinuria (PNH). The drug has scored in a phase 3 trial in IgAN, also showing the ability to reduce proteinuria.

IgAN is a tough nut to crack. Regeneron and Alnylam’s cemdisiran showed promise in a phase 2 trial before the companies ended their efforts with the drug last year. Two months ago, Omeros halted a phase 3 trial of its hopeful narsoplimab when it became evident that the study would fail.