The therapeutic landscape for anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) has been thrown into turmoil. Avacopan (Tavneos), an oral C5a complement inhibitor once hailed as a breakthrough treatment, is now the subject of a deepening medical and regulatory crisis. A new study, published Monday in Arthritis & Rheumatology, provides sobering real-world evidence of significant hepatotoxicity, adding substantial weight to the FDA’s ongoing push to have the drug removed from the U.S. market.
This latest report, utilizing data from the American College of Rheumatology’s (ACR) RISE registry, highlights not only the potential for drug-induced liver injury (DILI) but also a concerning gap in clinical adherence to safety monitoring protocols. The findings arrive as Amgen, the pharmaceutical giant that acquired the U.S. rights to the drug, remains locked in a standoff with regulators, refusing to voluntarily pull the product despite a global climate of intense scrutiny.
A Chronology of Controversy
The trajectory of avacopan from a promising therapy to a pariah in the rheumatological community has been rapid and unprecedented. The following timeline captures the disintegration of the drug’s regulatory standing:
- October 2021: The FDA grants approval to avacopan for the treatment of AAV. The drug is positioned as a novel oral alternative to traditional therapies, generating significant interest in the medical community.
- February 2026: The regulatory climate shifts dramatically. The FDA announces that it has identified severe liver risks that exceed the warnings already included on the drug’s label. Simultaneously, the agency reveals concerns regarding the integrity of data within the ADVOCATE trial—the pivotal randomized study that supported the drug’s initial approval. Amgen is formally advised to withdraw the product from the U.S. market.
- March 2026: The FDA escalates its warning, confirming that eight patients have died from liver injury linked to avacopan, alongside dozens of nonfatal, yet serious, cases of DILI.
- June 2026: The New England Journal of Medicine (NEJM) takes the rare and drastic step of retracting the primary ADVOCATE trial paper. The retraction followed a request from the paper’s two lead academic authors, who discovered that data had been surreptitiously altered after unblinding—an act attributed to individuals affiliated with ChemoCentryx, the original developer of the drug.
- Early 2027: The European Union formally revokes marketing authorization for Tavneos. Despite this international precedent, Amgen maintains its refusal to withdraw the drug in the United States, citing its ongoing internal review and the therapeutic value the drug provides to specific patient populations.
Supporting Data: The RISE Registry Findings
The report published in Arthritis & Rheumatology provides the most systematic look to date at how avacopan behaves in the "real world," outside of the controlled environment of a clinical trial. Led by Eric T. Roberts, PhD, MPH, of the University of California San Francisco, the research team combed through the ACR’s RISE registry—a massive database covering approximately 25% of all U.S. rheumatology practices and 3.5 million patients.
Researchers identified 238 patients diagnosed with AAV who were prescribed avacopan between October 2021 and March 2025. Among this cohort, 14 instances of clinically significant liver enzyme elevations were identified. Crucially, two of these cases were classified as drug-induced liver injury (DILI) that was deemed "highly likely" to be caused by the medication.
The DILI Experience
The two confirmed cases of DILI involved middle-aged women suffering from granulomatosis-with-polyangiitis, a severe subtype of AAV. Both patients developed hepatotoxicity approximately nine weeks into their treatment regimen. Using the RUCAM scoring form—a standardized tool used to calculate the likelihood of drug-induced injury—both cases received a score of 9, the highest possible rating, indicating a near-certain link between the drug and the liver damage.
While both patients recovered within two months of cessation and avoided the catastrophic outcome of vanishing bile duct syndrome (VBDS), the findings are significant. VBDS, a condition in which the bile ducts are permanently destroyed, has been a looming fear among clinicians tracking adverse event reports. The fact that overt DILI was identified in a registry cohort suggests that the risks are not merely anecdotal but are present in standard clinical practice.
Clinical Oversight and Monitoring Gaps
One of the most alarming revelations in the Roberts report is not just the toxicity of the drug, but the failure of the medical community to adhere to the FDA’s stringent safety monitoring requirements.
The FDA mandate for avacopan is clear: clinicians should perform liver panels every two weeks during the first month of treatment and continue monthly monitoring through the end of the sixth month. However, the study found that the median time to the first liver test was 32 days, with some patients waiting significantly longer. Furthermore, the median interval for subsequent testing stretched to 125 days.
In practical terms, this means that roughly one-quarter of the rheumatologists surveyed waited more than two months for an initial check, and another quarter allowed intervals between safety tests to extend beyond six months. The researchers noted that these gaps in surveillance represent a systemic failure that leaves patients dangerously exposed to asymptomatic liver injury, which can progress to failure if not caught in the early, reversible stages.
Official Responses and Corporate Strategy
Amgen remains in a precarious position. The company has publicly defended the drug, emphasizing its utility as an alternative for patients who may not respond to or cannot tolerate traditional, more toxic immunosuppressants. By generating an estimated $459 million in global sales last year, avacopan represents a significant revenue stream, yet the reputational cost of the data integrity scandal is mounting.
The FDA, meanwhile, finds itself in an awkward position. While the agency has issued strong recommendations and identified the drug as a significant safety risk, it has yet to issue a formal, mandatory withdrawal order. This hesitation may stem from the legal complexity of forcing a product off the market when a manufacturer is actively resisting, particularly in the wake of the ADVOCATE trial retraction, which has essentially invalidated the primary evidence base for the drug’s efficacy/safety profile.
For the rheumatology community, the message from regulators and researchers is increasingly unified: the current clinical trial data is compromised, the real-world safety profile is suspect, and the current monitoring practices are inadequate.
Implications for the Future of AAV Treatment
The ongoing saga of avacopan serves as a cautionary tale for both the pharmaceutical industry and the regulatory bodies that govern it. The retraction of the NEJM paper regarding the ADVOCATE trial highlights the dangers of "data manipulation" in an era where rapid approval processes are becoming the norm.
For clinicians, the implications are immediate. The Roberts study suggests that while avacopan may have a role in treating AAV, the "benefit-risk ratio" has shifted dramatically. Any physician currently prescribing avacopan must, at a minimum, reconcile their monitoring protocols with the FDA’s strict recommendations.
However, many in the field are now questioning whether the risks inherent in the drug—and the lack of trustworthy clinical data—outweigh its benefits. The decision to keep the drug on the market, in the face of eight confirmed deaths and a global regulatory rejection, is placing an immense burden on the shoulders of the rheumatologists who must explain these risks to their patients.
As the legal and medical debate continues, the case of avacopan will likely be remembered as a pivotal moment in the history of drug regulation. It underscores the vital importance of transparent data, the necessity of rigorous post-market surveillance, and the uncomfortable reality that when a pharmaceutical product’s foundations are built on compromised data, the patient is always the one who pays the highest price.
Whether the FDA will take the final, decisive step of mandating a withdrawal remains the central question. Until then, the medical community must grapple with the knowledge that one of their modern tools for treating AAV comes with a price tag that goes far beyond its wholesale cost.
