Taveos' unraveling accelerates as UK joins global regulatory retreat

A rare autoimmune vasculitis treatment has lost its UK authorization after regulators concluded that data underpinning its approval can no longer be trusted. The Medicines and Healthcare products Regulatory Agency (MHRA) announced on September 1, 2026 that it has suspended the use, supply, and sale of avacopan (Avacopan Vifor, previously known as Tavneos) to new patients, citing questions about the integrity and reliability of data from the pivotal clinical study on which the medicine's UK authorization was based.

The MHRA concluded, following advice from the Commission on Human Medicines (CHM) and representations from patients and healthcare professionals, that the pivotal study can no longer be relied upon to demonstrate avacopan's efficacy. With that evidentiary foundation removed, the agency determined that the available evidence no longer supports a positive benefit-risk balance for the medicine. The suspension took effect from September 1, 2026, under Regulations 69 and 71 of the Human Medicines Regulations 2012.

Avacopan Vifor, a complement C5a receptor inhibitor, was authorized in the UK on May 6, 2022, for use in combination with a rituximab or cyclophosphamide regimen in adults with severe, active granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) — rare autoimmune diseases affecting small blood vessels. Existing patients will be permitted to continue receiving supply during a six-month managed withdrawal period, after which the MHRA intends to revoke the UK marketing authorization on March 1, 2027. The marketing authorization holder has guaranteed supply to cover that transition.

Healthcare professionals have been advised not to initiate treatment in new patients and to review those currently receiving avacopan at the earliest opportunity, considering alternative treatment options. Patients should not discontinue treatment without first consulting their specialist. Existing risk minimization measures remain in effect, including monitoring of liver function — for which the recommended testing frequency was recently increased — as well as white blood cell count monitoring and assessment for serious infections.

The UK action follows a parallel regulatory move in the EU. The European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) recommended revocation of avacopan's EU marketing authorization in June 2026, citing the same data integrity concerns. Across the Atlantic, Amgen submitted data to the US FDA in July 2026 challenging a proposed withdrawal of Tavneos, requesting a formal hearing as regulators in multiple jurisdictions reassess the medicine's evidentiary basis.

The regulatory actions stem from concerns over how data from the pivotal Phase III ADVOCATE trial were handled before approval. The US FDA has said unblinded study personnel selected patient data for readjudication and reanalysis after the original prespecified analysis failed to show a statistically significant treatment effect, resulting in analyses that made avacopan appear effective. The agency also said the original application contained inaccurate statements regarding database lock, unblinding, and the analyses used to evaluate the study. European regulators subsequently concluded that the integrity concerns meant ADVOCATE could no longer reliably establish efficacy, while additional postmarketing concerns over serious liver injury have further weighed on the medicine's benefit-risk assessment.

For GPA and MPA patients in the UK, the suspension removes a treatment option for these conditions and will require treating physicians to manage transitions to existing standard-of-care regimens ahead of the March 2027 revocation deadline.

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