The US Food and Drug Administration (FDA) has issued a warning to Amgen centred around Tavneos (avacopan), after the agency found "reasonable evidence of a causal association" between 76 cases of drug-induced liver injury (DILI) from around the world and the drug.
The cases included 54 hospitalisations and eight deaths, with the vast majority of cases being reported in Japan.
The FDA identified seven cases of vanishing bile duct syndrome (VBDS), a serious liver reaction in which the bile ducts are destroyed, which it has said it thinks is related to the use of Tavneos. Three of these cases resulted in deaths.
Tavneos is used to treat two forms of ANCA-associated vasculitis (granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA)) and was approved for use in the US in 2021.
The drug came to Amgen in 2022, when the pharma company dropped $3.7bn to acquire ChemoCentryx. It is one of Amgen's fastest-growing drugs, with sales last year reaching $459m, up 62%.
The FDA has identified DILI and VBDS as new safety concerns associated with Amgen's product, while the drugmaker claims that liver toxicity, including VBDS, is "a known infrequent risk of Tavneos treatment."
The FDA has recommended comprehensive liver panel testing in patients taking the drug during the first five months of treatment, with immediate discontinuation of dosing if liver damage biomarkers or DILI symptoms are detected.
The FDA also emphasised that patients taking avacopan should contact a healthcare professional if they experience unusual fatigue, itching, nausea, vomiting, light-colored stools, yellowing of the skin or eyes, or dark urine, swelling in the stomach or abdomen, or pain in the upper right abdomen.
This new warning comes on the heels of a separate disagreement between the FDA and Amgen around the drug's overall benefits and risks, as well as how some of the original clinical trial data was handled.
In January, the agency asked Amgen's ChemoCentryx unit to voluntarily withdraw Tavneos from the US market. Amgen has denied the FDA's request to suspend the distribution of Tavneos, stating that it remains "confident that Tavneos is an important and effective treatment for severe ANCA-associated vasculitis, based on robust clinical data and real-world evidence demonstrating its effectiveness and favourable benefit-risk profile."
The FDA's safety notice, published on Tuesday, did not provide updates on its discussions with Amgen concerning the withdrawal of Tavneos.