Avacopan Safety Data Bolstered by New Interim Trial Results
New study findings may help the vasculitis drug remain on the U.S. market.
1Interim Trial Results
Interim findings from the AvacoStar trial suggest that avacopan, a treatment for antineutrophil cytoplasmic antibody-associated vasculitis, may avoid total market withdrawal. Reported by Bernhard Hellmich at the American College of Rheumatology, the study evaluated safety outcomes in 504 patients across Britain and Germany, comparing the drug against standard rituximab or cyclophosphamide regimens.
2Liver Injury Findings
Patients receiving avacopan experienced a fourfold higher rate of liver abnormalities compared to those on conventional alternatives. Despite this elevated incidence rate ratio of 4.03, the absolute rate remained low at 0.07 per patient-year. Most liver events occurred within the first six months and were generally resolved without causing severe clinical complications.
3Regulatory Context
The drug faced severe scrutiny after revelations that original developer ChemoCentryx readjudicated pivotal trial data to meet primary endpoints. Following these findings, the FDA requested a voluntary market withdrawal. While European and British regulators revoked marketing authorization in 2024, Amgen has resisted the FDA's request to pull the drug from the U.S. market.
4Comparative Safety Profile
Beyond liver concerns, avacopan showed no significant increase in other adverse events compared to standard care. Serious infections occurred at a rate of 0.14 per patient-year for avacopan, lower than the 0.18 observed in the control group. Cardiac events and malignancies were reported at identical rates across both treatment arms during the study.
5Study Design Details
Launched in 2023 by Vifor Fresenius Medical Care Renal Pharma, the trial enrolled 504 patients with highly active AAV. Participants were split into 254 receiving avacopan and 250 receiving conventional therapies. As of September 2025, over 95% of patients remained on their original therapy, providing a robust dataset for ongoing safety analysis.
6Clinical Resolution Rates
Of the 22 liver events identified, 12 were considered possibly or definitely related to avacopan. Clinicians noted that 20 of these cases resolved before the interim data cutoff. One remaining case was deemed clinically irrelevant, while another resolved later, suggesting that the liver issues are manageable under current clinical monitoring protocols.
7Limitations and Bias
Bernhard Hellmich cautioned that the trial design, which allowed investigators to choose treatments based on clinical judgment, introduces potential residual bias. Furthermore, the study is ongoing with a final completion date scheduled for 2030. Future results with longer treatment durations may reveal safety risks that are not yet apparent in current data.
8Market Future Outlook
The combination of these new safety findings and a recent Italian study confirming efficacy provides a potential lifeline for avacopan in the United States. While the drug remains under intense regulatory pressure, these data points offer a basis for Amgen to maintain availability for patients who require alternatives to traditional corticosteroid-based treatments.
Original article: MedPage Today — Avacopan Safety Data Bolstered by New Interim Trial Results