I'm LongbridgeAI, I can summarize articles.Amgen's rare-disease drug Tavneos faces UK withdrawal after regulators suspended new prescriptions and plan to revoke authorization by March 2027, citing unreliable efficacy data. While CSL Vifor holds the UK marketing rights, Amgen disagrees with the decision. Concurrently, the US FDA has proposed withdrawing Tavneos due to safety and efficacy concerns. Despite Q2 sales of $150 million, the drug represents a small portion of Amgen's revenue, though the US regulatory outcome remains critical for its commercial value.
Rare-disease drug Tavneos is facing withdrawal from the U.K. market after regulators suspended its use for new patients and set a path toward revoking its authorization in March 2027.
Importantly, CSL Vifor, not Amgen , is the marketing authorization holder for Tavneos in the U.K. and is leading interactions with the Medicines and Healthcare Products Regulatory Agency, according to Amgen. Amgen acquired Tavneos developer ChemoCentryx for $3.7 billion in 2022, but the U.K. regulatory process is being handled by CSL Vifor.
Tavneos, or avacopan, treats adults with severe forms of ANCA-associated vasculitis, a group of rare autoimmune diseases that inflame small blood vessels and can damage organs including the kidneys and lungs.
The MHRA said the pivotal study supporting Tavneos could no longer be relied upon to demonstrate efficacy. New patients cannot receive the drug beginning September 1, while existing patients have a six-month transition period before the agency intends to revoke authorization on March 1, 2027.
Amgen said it disagrees with the regulator's decision.
We disagree with the MHRA's decision to withdraw TAVNEOS from the UK market and are deeply concerned about the impact this decision may have on rare disease patients, an Amgen spokesperson said.
The company added that it believes the regulator's interpretation does not fully recognize the broader evidence supporting Tavneos, including clinical-trial data, real-world studies and secondary endpoints involving reduced steroid exposure and improvements in kidney function.
As the marketing authorization holder for TAVNEOS in the UK, CSL Vifor is leading interactions with MHRA and working to understand the implications of this decision for patients and healthcare providers across Europe, the spokesperson said.
Amgen reported $150 million in Tavneos sales during Q2, up 36% year over year, while full-year 2025 sales reached $459 million, up 62%.
Separately, Tavneos is also facing regulatory scrutiny in the United States. The FDA has proposed withdrawing the drug, citing concerns involving the reliability of efficacy data and safety issues including serious liver injury. Tavneos remains available in the U.S. while that process continues.
Investors Takeaway
For Amgen investors, the U.K. decision should not be viewed as direct regulatory action against Amgen, because CSL Vifor holds the U.K. marketing authorization and is responsible for the MHRA process.
The more direct Amgen-specific catalyst is the FDA proceeding in the United States. Amgen submitted additional analyses in July and requested a hearing as it seeks to preserve the drug's U.S. approval.
Investors should therefore watch the FDA process, Tavneos sales and any additional regulatory developments affecting markets where Amgen holds commercial rights.
Because Tavneos represents a relatively small portion of Amgen's overall revenue, even a significant disruption would not threaten the company's broader financial profile. However, the U.S. regulatory outcome remains important for the future commercial value of the rare-disease treatment and Amgen's return on its ChemoCentryx acquisition.