Drug regulatory committees within the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) are recommending that Amgen remove Tavneos (avacopan) from the market. An independent investigation – which concluded earlier this year – revealed that data from the drug’s phase 3 trial had previously been altered by staff of ChemoCentryx (the drug’s initial developers) to make the drug seem more effective. With the integrity of the research brought into question, the trial report has now been retracted.
Avacopan is a small molecule inhibitor used to treat vasculitis – an inflammatory condition that restricts blood flow. ChemoCentryx developed the drug, receiving FDA approval in October 2021 and EU authorisation in January 2022. Amgen bought the company in October 2022 for $3.7 billion (£2.8 billion).
Meanwhile, ChemoCentryx shareholders filed a lawsuit for alleged securities fraud, prompting an independent investigation. According to the FDA, the inquiry’s results – released in May 2025 – unexpectedly revealed that data from the clinical trial was manipulated, making the drug ‘look effective when the original analysis did not support that conclusion’.
The report found that ChemoCentryx altered results from nine trial participants after initial blinded analysis, including changing outcomes for five patients who received avacopan. ‘ChemoCentryx personnel confirmed that changing the remission outcomes for the five avacopan patients would change the study results,’ notes a letter from the FDA to Amgen. These ‘changes changed the study result from not statistically significant to statistically significant,’ bringing the integrity of the trial into question as this is a breach of good clinical practice.
The FDA has also raised concerns over the safety of the drug, owing to some patients having fatal liver-based side effects, which are more severe than those identified during clinical trials. There has been a disproportionate number of severe liver-related cases in Japan, with Amgen suggesting that this ‘could be due to genetic differences, use of concomitant treatments or differences in monitoring’.
Owing to both factors, the FDA’s Centre for Drug Evaluation and Research is proposing that avacopan should be withdrawn from the market. Equally, the EMA’s Committee for Medicinal Products for Human Use (CHMP) has reached the same conclusion. After conducting its own review of avacopan, the CHMP found that the drug’s ‘benefits are no longer proven to outweigh its risks’. The committee recommends that the drug should no longer be sold in the EU and that doctors switch existing patients to alternatives. However, the European Commission will need to confirm this recommendation.
Kissei Pharmaceutical, which markets avacopan in Japan, briefly recommended that doctors pause prescribing the drug to new patients. The company later agreed with regulators to maintain approval for the drug, but with additional safety warnings on the label, and regular mandatory liver function tests.
The New England Journal of Medicine has now retracted the trial report as it ‘is inconsistent with proper research conduct’. Amgen told Chemistry World that it takes ‘scientific integrity seriously and respects the role of journals in upholding the peer review process’.
Amgen has now ‘proactively initiated’ its own independent re-view of the initial trial results, which is being conducted by the Duke Clinical Institute, US. The company will share the results from this investigation by the end of July as part of an FDA hearing.
