Tavneos Approval Faces a Rare FDA Reversal Over Trial Data

The FDA wants to pull its approval of Tavneos, a drug used for a rare autoimmune form of vasculitis. The regulator says the treatment won approval based on manipulated study data, while Amgen insists the drug works and should remain available.

The dispute reaches beyond one medication. It raises questions about how regulators judge drugs when clinical evidence looks promising but the study behind it has weaknesses, and what happens when questions about that evidence emerge after approval.

A narrow approval built on uncertain evidence

In May 2021, the US Food and Drug Administration released a lengthy briefing document on an experimental medication for ANCA-associated vasculitis, or AAV. The disease is an umbrella term for rare conditions in which the immune system mistakenly attacks its own blood vessels, often damaging the kidneys and lungs.

The FDA was on the fence about approval and asked an independent advisory committee to weigh in. Participants in the study, conducted by the California biotechnology company ChemoCentryx, appeared to have slightly higher rates of symptom remission after one year. But the FDA said the study design was less than optimal, making the results hard to interpret.

Some advisory committee members shared that concern. One said the effect of the drug “is just not well verified by this study.” At the same time, many patients and some physicians saw a potentially helpful medication in the data. The committee voted narrowly to recommend approval, and the FDA followed that advice on October 7, 2021.

Marketed as Tavneos, the drug then started making its way into clinics. A year after approval, Amgen acquired ChemoCentryx. The treatment costs $220,000 per year, according to Drugs.com, and sales reached nearly half a billion dollars in fiscal year 2025.

Why the FDA now wants Tavneos withdrawn

That financial success unfolded alongside a long-roiling investor lawsuit. The lawsuit uncovered what the FDA now believes is evidence that ChemoCentryx employees manipulated data in the pivotal trial submitted to the agency.

In April of this year, the FDA issued a letter proposing that Tavneos be withdrawn from the US market. The letter cited reports of serious, sometimes fatal, liver injury and argued that the drug no longer has “substantial evidence” showing that it works.

Other developments have added pressure to the case. This summer, the New England Journal of Medicine retracted a paper describing the clinical trial. Tavneos was taken off the market in the European Union, and the United Kingdom announced that it, too, will remove the product.

Amgen has pushed back against its critics. The company insists that, whatever the details of ChemoCentryx’s data handling, Tavneos works as advertised and should stay on the market. In July, Amgen submitted a 104-page document to the FDA stating that “the totality of the evidence supports the continued availability of TAVNEOS.”

Some patients and academic experts also view Tavneos as an important treatment option. Eric Roberts, an epidemiologist at the University of California, San Francisco, co-authored an independent registry study of Tavneos. He said, “This appears to be an efficacious medication,” adding another voice to the debate over whether the drug’s evidence should be judged only through the disputed pivotal trial.

What the fight means for patients

For patients with AAV, the stakes are personal. Chloe Cusano was a 20-year-old college student when unbearable pain struck her legs this past December. She also experienced bouts of breathlessness during routine tasks, including walking upstairs or bending down to retrieve her dog’s water dish.

After going to the emergency room, Cusano spent more than two weeks in the hospital and received a diagnosis of AAV. When the condition was first identified, it was usually fatal. Over the past four decades, scientists have developed drugs that allow many AAV patients to live a relatively normal lifespan.

Because AAV can lead to organ failure, particularly in the kidneys and lungs, patients are immediately started on a high dose of steroids to tamp down inflammation. They also typically receive slower-acting medications aimed at the underlying disease process. Steroids, however, have severe side effects, which helps explain why patients and physicians may see value in another treatment option even when its evidence is under review.

Reshma Ramachandran, a physician and co-director of the Yale Collaboration for Regulatory Rigor, Integrity, and Transparency, says the dispute reflects the FDA’s longstanding struggle to regulate drugs with uncertain efficacy. “We’re just going to be living in uncertainty in terms of whether or not these drugs actually work,” she said.

For American consumers, the Tavneos saga raises questions about the safeguards meant to protect the integrity of drug approvals. The FDA approved the drug after a narrowly favorable advisory vote, then moved toward withdrawal after allegations about the study data, reports of liver injury, and the retraction of a clinical trial paper.

On October 29, a court hearing is expected to proceed over Zoom to consider a proposed $69 million settlement for the investor lawsuit. The hearing will not erase the disagreement over Tavneos, but it will mark another step in a dispute that now involves regulators, patients, researchers, a pharmaceutical company, and courts.

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