Amgen is standing behind a rare disease drug that the FDA wants off the market due to safety concerns and alleged clinical trial manipulation, and its defense will include a new analysis of the pivotal data that supported the product’s initial approval five years ago.
The pharmaceutical company disclosed the independent review in a letter to the FDA requesting a hearing regarding the agency’s proposal to withdraw approval of the drug, Tavneos. The Amgen letter was dated June 1, the FDA’s deadline for Amgen to request a hearing. The FDA made the letter public on Thursday.
Tavneos was originally developed by ChemoCentryx, which Amgen acquired for $3.7 billion in 2022. This oral small molecule is designed to inhibit the C5a receptor of the complement system, a part of the immune system. Tavneos is one of a limited number of treatments for antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, a group of inflammatory disorders that causes inflammation leading to blood vessel and organ damage, particularly to the kidneys. But the FDA became increasingly concerned that the drug can damage the liver.
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Liver toxicity is a known risk of Tavneos that has been on its label since its 2021 approval, but in the warnings and precautions section and not in a more stringent black box warning. Questions about the drug’s clinical trial integrity came to the FDA’s attention last year from securities fraud litigation against ChemoCentryx. In the FDA’s notice proposing withdrawal of Tavneos’s approval, the agency said an expert report filed with the court in that case said statistical analysis of Tavneos’s pivotal study found that the treatment group did not meet the main trial goal. The report added that ChemoCentryx personnel picked nine trial participants for readjudication, including five whose clinical outcomes were changed from “not in sustained remission” to “sustained remission.” The FDA said ChemoCentryx submitted Tavneos’s new drug application without disclosing these changes.
Last July, the FDA asked Amgen to respond. According to the agency, the company’s response confirmed key factual allegations in the court report. Amgen also contended that the data in Tavneos’s submission were accurate and the readjudications were appropriate. The FDA disagrees.
“The Division Director did not know that the facts on which he was relying were untrue — that absent manipulation, the study results were not statistically significant on the superiority analysis at week 52, and the procedures in place to ensure trial quality were violated,” the FDA said in its proposal. “Had the Division Director known these facts, he would not have recommended approval.”
In February, Amgen disclosed that the FDA asked Amgen to voluntarily withdraw Tavneos from the U.S. market, citing safety concerns and readjudicated trial data. Amgen said it was confident in the risk-benefit profile for its drug and would keep selling it. The FDA raised the stakes in late March, issuing a safety alert to patients and clinicians about cases of serious liver injury, some fatal, associated with Tavneos. Most of these cases were in Japan. The FDA described these problems as a new safety concern. On April 27, the FDA’s Center for Drug Evaluation and Research issued a proposal to withdraw Tavneos’s approval.
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FDA procedures permit a drug company to request a hearing on a drug withdrawal proposal, which Amgen did with its June 1 letter. Tavneos will remain available to patients while the process continues. The contract research organization (CRO) that handled Tavneos’s Phase 3 clinical trial was Medpace. The independent trial analysis commissioned by Amgen will come from the Duke Clinical Research Institute (DCRI), a part of the Duke University School of Medicine that operates as a full-service CRO.
The DCRI analysis and all other supporting documents in support of Amgen’s hearing request are due by June 29. That’s also the deadline for public comments. Many of them submitted so far are from people who say they are patients who have benefited from Tavneos. Clinicians have also commented in support of Tavneos, some saying that given the limited treatment options for ANCA-associated vasculitis, the drug should remain available until more definitive information is known about the liver injury risk.
Tavneos is not yet a big revenue driver for Amgen, but sales are growing. The company reported $459 million in global Tavneos revenue for 2025, a 62% increase from the prior year. While ChemoCentryx had projected Tavneos as having potential applications in a wide range of inflammatory disorders, the only clinical program for the drug listed in Amgen’s pipeline is an ongoing Phase 3 trial that could support expanding the current approval to children.
In early June, Amgen issued a statement to clinicians about Tavneos stating it remains confident in the overall benefit-risk profile of the drug based on the clinical data, post-marketing safety surveillance, and real world evidence from more than 8,000 treated patients.
“Collectively, the evidence demonstrates the impact of Tavneos on supporting remission, reducing relapse risk, and improving kidney function and quality of life measures, all while reducing glucocorticoid exposure and associated toxicity,” the company said.
Photo: Patrick T. Fallon/Bloomberg, via Getty Images