FDA Moves to Pull Amgen's TAVNEOS After Trial Data Manipulation

Amgen (AMGN) closed at $376.04 on July 23. The FDA is trying to pull one of its drugs off the market, and the reason is not a safety signal or a failed confirmatory trial. It is something far more damaging: clinical trial data manipulation.

On April 27, 2026, the FDA’s Center for Drug Evaluation and Research (CDER) proposed withdrawing approval of TAVNEOS (avacopan), a treatment for ANCA-associated vasculitis. The agency’s case rests on two independent grounds: the drug has not been shown to be effective, and the original marketing application contained untrue statements of material fact. Both stem from the same root cause. Unblinded study personnel manipulated endpoint data in the ADVOCATE Phase 3 trial, the sole registrational study supporting approval, after the initial analysis showed the drug was not statistically significant.

On July 23, Amgen submitted new data and analyses to the FDA and formally requested a hearing to challenge the withdrawal. Reuters reported the submission on July 24. Amgen has until July 29 to submit all supporting materials.

What the FDA Found

According to the FDA’s Notice of Opportunity for Hearing, the ADVOCATE trial database was locked and unblinded on November 5, 2019. After unblinding, ChemoCentryx personnel selected nine subjects for endpoint readjudication. Five of those were avacopan patients whose outcomes were changed from “not in sustained remission” to “sustained remission.” The statistical analysis submitted in the NDA, performed after these changes, returned a p-value of 0.0132 for superiority at 52 weeks. That p-value was not controlled for Type I error, and the applicant never disclosed that fact.

The original analysis, before the readjudication, did not show statistical significance. The FDA only learned of this more than three years after approval, when an independent investigation by Dr. Patrick Walton surfaced the manipulation. The New England Journal of Medicine retracted the ADVOCATE trial publication on June 29, 2026. The European Medicines Agency recommended revoking the drug’s marketing authorization in June 2026, citing unreliable study data.

The FDA is also concerned about safety. A March 31, 2026, FDA safety communication identified 76 cases of serious drug-induced liver injury linked to TAVNEOS, including 8 deaths and cases of vanishing bile duct syndrome.

What Amgen Is Arguing

Amgen strongly disagrees with the FDA. The company’s July 23 submission includes more than 70 real-world studies involving over 2,200 patients supporting the drug’s effectiveness and safety. Amgen also commissioned the Duke Clinical Research Institute to conduct an independent, blinded review of the ADVOCATE trial. Duke found that TAVNEOS matched a steroid treatment regimen at 26 and 52 weeks, though the review did not reproduce the original finding of superiority at 52 weeks.

That is a significant concession. The superiority claim at 52 weeks was the endpoint that the FDA says was manufactured through data manipulation. Duke’s independent review could not confirm it. Amgen is left arguing noninferiority, which is a weaker position than the one that secured approval in 2021.

TAVNEOS remains on the market while the process plays out. The FDA has said the drug will stay available unless Amgen voluntarily withdraws it or the FDA Commissioner orders its removal after a hearing.

Why This Matters for the Stock

TAVNEOS is not a major revenue driver for Amgen. The drug generated $459 million in full-year 2025 sales and $119 million in Q1 2026, growing 32% year-over-year. Against Amgen’s $36.8 billion in 2025 total revenue, TAVNEOS is roughly 1.3% of the top line. The direct financial impact of a withdrawal is modest.

The real risk is precedent. If the FDA succeeds in retroactively pulling a drug based on data manipulation in the registrational trial, it signals that the agency will go back and re-examine approvals where trial integrity is in question. For a biotech industry where clinical trial conduct is under increasing scrutiny, that is a chilling signal. Patient advocacy groups are fighting to keep TAVNEOS available, citing real-world evidence of benefit. But the FDA’s argument is about data integrity, not whether the drug works in practice. Those are two different questions, and the FDA is focused on the first one.

Amgen has a July 29 deadline to submit all supporting data. The FDA Commissioner will then decide whether to hold a public hearing and, following that hearing, whether to withdraw approval. Watch for the hearing scheduling and any Commissioner-level decision in the coming weeks. The stock has not reacted meaningfully to the July 23 submission, but a hearing date or an adverse ruling could change that.