Last December, Chloe Cusano was 20 and in college. Then came pain in her legs she could not bear, and breathlessness from small tasks: climbing stairs, bending down for her dog’s water dish. She spent more than two weeks in hospital and left with a diagnosis of ANCA-associated vasculitis, or AAV, a group of rare diseases in which the immune system turns on the body’s own blood vessels. When doctors first identified the condition, it usually killed.
Four decades of medicine have changed that, and many patients now live roughly normal lives. Because the disease can quickly destroy the kidneys and lungs, though, treatment opens with heavy doses of steroids. Within six weeks Cusano had put on 40 pounds. Her moods lurched from deep sadness to anger. She struggled to fall asleep, and when she did, nightmares came. “I did not like it at all,” she said.
A pill called Tavneos was meant to spare people like her some of that. Five years after it was approved, the US Food and Drug Administration says the evidence behind it was manipulated. As Sara Talpos reported for Undark, republished by Ars Technica, pulling a drug off the market turns out to be much harder than letting it on.
A narrow vote
In May 2021 the FDA was undecided. It published a long briefing document on the drug, developed by ChemoCentryx, a small California biotech company, and asked an independent advisory committee for its view. Patients on the drug seemed to reach remission slightly more often after one year, but the agency said the trial’s design made the result hard to read.
David Pisetsky, a rheumatologist at Duke University School of Medicine, voted no. Many patients in the comparison group, he said, got just one round of rituximab, a slower-acting drug, on top of steroids, when in ordinary practice they would have got two. Mike Putman of the Medical College of Wisconsin later argued much the same in the journal Rheumatology, while granting that the standard of care at the time was “somewhat debate-able.”
Walter Kraft, a clinical pharmacologist at Thomas Jefferson University, voted yes. “I felt the evidence, though limited, met the societal and therapeutic goals,” he told the meeting. Demanding a second trial could have held the drug back for years. The committee narrowly recommended approval, and on October 7, 2021, the FDA granted it.
The small house and the large one
A year later Amgen, one of the world’s biggest drugmakers, bought ChemoCentryx for nearly $4 billion. Drugs.com lists the price of Tavneos at $220,000 a year, and in fiscal 2025 its sales came close to half a billion dollars.
This is now the usual pattern. Sean Nicholson, an economist at Cornell, says large companies increasingly leave the science to “nimble, small startup biotechs” and then buy or partner with them. David Ridley, a health economist at Duke’s Fuqua School of Business, describes what pushes the small firms: “Small companies have more to lose. The entire company can be at stake. That urgency can drive them to work harder and move faster.” Then he added: “In rare cases, they might cut corners.”
A large company has many drugs in development. A small one may live or die by one trial. One can see in that imbalance an old story about power: the risk sits with the weak party, and the strong one buys the result once it looks safe.
What the lawsuit found
ChemoCentryx’s share price collapsed as soon as the 2021 briefing document came out, and shareholders sued for securities fraud. Four years later, a report filed in that case alleged that the company’s own analysis had first found no better one-year remission on Tavneos than on standard treatment.
The FDA’s drug center took this up. On April 27, 2026, it proposed withdrawing approval. It said “unblinded study personnel manipulated the results of the pivotal clinical study so the drug looked effective,” and that the company never disclosed the original analysis to regulators, in breach of FDA rules. The agency also cited cases of serious drug-induced liver injury, some of them fatal. Its conclusion went beyond most regulatory language: it “can no longer conclude that there is, or has ever been, a valid demonstration that TAVNEOS is effective.”
Other institutions followed. The New England Journal of Medicine retracted its paper on the trial this summer. In August, CSL and its Vifor unit announced that the European Commission had revoked the drug’s licence across the EU and EEA. In Britain, according to Vasculitis UK, the regulator stopped supply to new patients from September 1, will keep existing patients on it through a six-month managed withdrawal, and intends to revoke the licence on March 1, 2027.
For the shareholders, ChemoCentryx agreed to pay $69 million, Bloomberg Law reported, while denying the allegations. The settlement’s own website set a final approval hearing for October 29 before Judge Jon S. Tigar. No ruling has yet been reported.
The defence
Amgen has not backed down. In July it sent the FDA a 104-page submission arguing that “the totality of the evidence supports the continued availability of TAVNEOS.” According to Fierce Pharma, the centrepiece is a re-analysis by the Duke Clinical Research Institute that Amgen says confirms the drug’s results. The company has asked for a hearing, and while that request stands, Tavneos stays on American pharmacy shelves.
Amgen has some outside support. “This appears to be an efficacious medication,” said Eric Roberts, a University of California, San Francisco epidemiologist who co-wrote an independent registry study of the drug. Some patients agree.
Reshma Ramachandran, a physician and co-director of the Yale Collaboration for Regulatory Rigor, Integrity, and Transparency, sees the case as part of the FDA’s long struggle with drugs whose benefit was never firmly proven. Without more rigorous studies, she warned, “we’re just going to be living in uncertainty in terms of whether or not these drugs actually work.”
Kraft, who voted yes in 2021, now qualifies that vote. It was, he said, “based upon an assumption that the sponsor was following the rules of the road.”
So the drug stays on sale on one side of the Atlantic and is being withdrawn on the other. The same trial data now lead to opposite answers depending on which agency reads them. Patients who take it for months or years are left to wait for the outcome. In the United States, the FDA says Tavneos remains available until ChemoCentryx withdraws it or the Commissioner orders it removed, possibly after a hearing.