FDA Warns of Liver Injury Cases Linked to Amgen's Rare Disease Drug

• The FDA identified 76 liver injury cases with 8 deaths, including 7 cases of vanishing bile duct syndrome, a rare condition causing permanent liver damage, with median onset of 46 days after starting treatment
• In January 2024, the FDA asked Amgen to voluntarily withdraw Tavneos due to concerns about primary endpoint data from 9 of 331 patients in the approval trial, but Amgen declined
• Both European and Australian labels warn of vanishing bile duct syndrome cases, but U.S. prescribing information currently does not include this warning

Summary

The FDA issued a safety warning on March 31 regarding Amgen's Tavneos, a drug approved in 2021 for treating ANCA-associated vasculitis—a group of rare autoimmune diseases. The agency identified 76 cases of drug-induced liver injury with evidence linking them to Tavneos, including seven cases of vanishing bile duct syndrome, a rare condition causing permanent liver damage. Eight deaths were reported among these cases.

The FDA is urging healthcare providers to closely monitor patients taking Tavneos and discontinue treatment immediately if liver damage is suspected. The median time to onset of liver injury was 46 days after starting treatment.

This warning intensifies regulatory scrutiny of the drug. In January 2024, the FDA requested Amgen voluntarily withdraw Tavneos following concerns during re-evaluation of primary endpoint data for nine of 331 patients in the late-stage trial supporting its approval. Amgen declined, maintaining confidence in the drug's benefit-risk profile and stating no awareness of data integrity issues.

Notably, while European and Australian labels mention post-marketing cases of vanishing bile duct syndrome, U.S. prescribing information currently lacks this warning. The European Medicines Agency also began reviewing Tavneos in January due to data integrity questions.

Market Implications: This development poses significant regulatory and commercial risks for Amgen. The safety concerns, combined with ongoing data integrity questions from both U.S. and European regulators, could lead to label restrictions, market withdrawal, or reduced prescribing—all potentially impacting Tavneos revenue and Amgen's reputation in the rare disease treatment space.