Study finds low rate of liver injury from avacopan amid FDA approval review

A study in *Arthritis & Rheumatology* shows a low 0.8% rate of drug-induced liver injury among 238 U.S. patients treated with avacopan. This finding contrasts with a March 2026 FDA safety communication that flagged 76 cases globally, mostly in Japan. The study arrives as the FDA seeks to withdraw approval of avacopan, alleging original manufacturer ChemoCentryx manipulated trial data, a claim denied by current owner Amgen. Researchers also note that U.S. clinicians are under-monitoring patients' liver enzymes.

U.S. avacopan liver injury incidence

• ▪In the Arthritis & Rheumatology study of 238 U.S. patients, two patients developed drug-induced liver injury, with both recovering with appropriate monitoring and care.
• ▪Among the U.S. cohort in the Arthritis & Rheumatology study, five patients had elevated AST, three had elevated ALT, four had elevated alkaline phosphatase, and two had elevated total bilirubin.
• ▪The Arthritis & Rheumatology study analyzed data from the Rheumatology Informatics System for Effectiveness Registry for patients receiving avacopan between October 2021 and March 2025.
• ▪A study published in Arthritis & Rheumatology found that only 0.8% of 238 U.S. patients treated with avacopan developed drug-induced liver injury.

FDA approval withdrawal proceedings

• ▪The U.S. Food and Drug Administration is seeking to withdraw its approval of avacopan, alleging that original manufacturer ChemoCentryx manipulated efficacy trial data and made false statements.
• ▪Amgen, which acquired ChemoCentryx in 2022, has denied the U.S. Food and Drug Administration's allegations of data manipulation regarding avacopan.

Japan hepatotoxicity cases

• ▪Lead researcher Eric T. Roberts stated that candidate hypotheses for the higher rate of avacopan-associated liver injury in Japan include differences in genetics, clinical practices, comorbidities, or concomitant medications.
• ▪A March 2026 U.S. Food and Drug Administration safety communication identified 76 cases of drug-induced liver injury causally linked to avacopan, including 66 cases in Japan and eight fatalities.

Liver enzyme monitoring practices

• ▪In the analyzed U.S. cohort of the Arthritis & Rheumatology study, the median time to the first liver enzyme screening was 32 days, with average subsequent testing intervals of 125 days.
• ▪The Arthritis & Rheumatology study found that U.S. patients prescribed avacopan did not have their hepatic enzymes monitored as frequently as recommended by the U.S. Food and Drug Administration.