EMA looks into 'data integrity' issue with Amgen's Tavneos

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Bottle of Tavneos with two pills in front of it

The EMA's human medicines committee has started a review of oral complement C5 inhibitor Tavneos, prompted by information that the regulator says raises questions about the integrity of the data from the pivotal ADVOCATE study.

ADVOCATE was the main study submitted in support of the EU approval of Tavneos (avacopan) in 2022 as a treatment for severe, active granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), two rare inflammatory conditions of the blood vessels.

Originally developed by ChemoCentryx, which was acquired by Amgen for $3.7 billion in 2022, Tavneos is licensed by CSL Vifor in Europe, which has not commented yet on the development.

In a statement, the EMA said that its concerns "relate to how the data for the ADVOCATE study was handled before Tavneos was authorised, which may have impacted the findings on the medicine's effectiveness." It added that the review has been started at the request of the European Commission.

Tavneos was first approved in the US for the same two indications in 2021, becoming the first orally-active drug that targets the complement C5 receptor. That decision came despite earlier scepticism at the FDA about the design of the phase 3 trial, and an advisory committee meeting that was split down the middle on the question of whether the drug's efficacy data supported approval.

It has since turned into one of Amgen's fastest-growing products, with US sales more than doubling to $283 million in 2024 and rising another 49% to $301 million in the first nine months of 2025. CSL Vifor records revenues from the drug outside the US under an agreement with ChemoCentryx that predated Amgen's acquisition, but does not break out sales specifics.

"EMA will now review all available data to assess whether this emerging information has an impact on the balance of benefits and risks of Tavneos," said the EU regulator. "The agency will then issue a recommendation on whether the marketing authorisation in the EU should be maintained, amended, suspended, or revoked."

Prior to the approval of Tavneos, patients with GPA and MPA were typically treated with the anti-CD20 antibody rituximab combined with corticosteroids, a regimen that can have serious side effects when administered over prolonged periods.

GSK's IL-5 inhibitor Nucala (mepolizumab) has also been approved in some markets, including EU member states and the US, as an add-on treatment for adults with GPA associated with high levels of blood eosinophils.