Tavneos' Defense: Can Steroid-Sparing Benefit Outweigh Liver Toxicity and Flawed ADVOCATE Trial Data?

Amgen Defends Tavneos Against FDA Withdrawal Request

Amgen is vigorously defending its rare kidney disease drug, Tavneos, against a proposed FDA withdrawal due to liver toxicity concerns. The company has requested a hearing with the FDA, submitting a data package including real-world evidence from over 2,200 patients and a re-adjudication of the pivotal ADVOCATE trial. Amgen argues Tavneos has a favorable benefit-risk profile for ANCA-associated vasculitis, citing its role in reducing steroid reliance and high remission rates, despite acknowledging serious hepatic adverse events and patient deaths in Japan.

• The FDA initiated withdrawal proceedings in January, citing liver toxicity issues, which were exacerbated by reports of 20 patient deaths in Japan, mostly due to vanishing bile duct syndrome (VBS). This led to recommendations for withdrawal from both the FDA and EMA, and the retraction of a key study from The New England Journal of Medicine.
• Amgen's comprehensive defense strategy includes submitting a data and analyses package to the FDA, requesting a hearing, and presenting 71 published real-world studies from over 2,200 patients. The company also emphasized patient perspectives and testimonials, highlighting the drug's importance in managing ANCA-associated vasculitis and reducing reliance on corticosteroids.
• An independent re-adjudication of the ADVOCATE trial confirmed Tavneos's efficacy for remission at week 26, sustained at week 52, comparable to prednisone, while achieving an 81% mean reduction in glucocorticoid use. Post-marketing safety data showed 31 serious hepatic adverse events per 1,000 patient years, mostly reversible, with some VBS-related deaths, particularly in Japanese patients over 65.

Tavneos's Safety Profile Under Regulatory Scrutiny

Published safety and tolerability data for Tavneos (avacopan) are derived from both pivotal clinical trials and expanding real-world evidence. While the overall profile supports a glucocorticoid-sparing strategy, post-marketing surveillance and studies in specific patient populations have identified key safety signals that warrant ongoing scrutiny and careful patient monitoring.

• In the pivotal 52-week ADVOCATE trial, the incidence of serious adverse events (excluding worsening vasculitis) was comparable between treatment arms, occurring in 37.3% of patients receiving avacopan and 39.0% of those in the prednisone group.

• Post-marketing surveillance using the FDA Adverse Event Reporting System (FAERS) from Q3 2021 to Q4 2024 identified 7,141 adverse events in 3,135 patients. Signal mining from this database revealed previously unrecognized potential adverse events, including alopecia, sepsis, pulmonary hemorrhage, hypertransaminasemia, deafness, and insomnia.

• Infection and hepatotoxicity have emerged as key safety considerations. A real-world review reported a 14% rate of serious infection at 6 months, while a study in 15 patients with diffuse alveolar hemorrhage observed two serious infections, one of which was a fatal opportunistic infection. Furthermore, a signal for hepatotoxicity has been identified, with a particularly pronounced incidence in Japanese populations.

• In specific populations, such as patients with end-stage kidney disease (ESKD) on hemodialysis, avacopan demonstrated good tolerability in a Phase 1 study. Adverse events in this cohort were reported as mild to moderate and were consistent with the drug's established safety profile.

The Unmet Needs in ANCA-Associated Vasculitis Treatment

Despite significant advances in immunosuppressive therapy that have markedly improved survival in ANCA-associated vasculitis (AAV), substantial gaps remain in achieving durable remission without excessive toxicity. Current approaches are hampered by a lack of individualization, uncertainty around treatment duration, and the persistent burden of both disease- and treatment-related morbidity. These limitations underscore the need for better biomarkers, refined diagnostic criteria, and glucocorticoid-sparing strategies.

• Relapse remains common and largely unresolved: Despite therapeutic advances that have reduced mortality, 30–50% of patients still relapse; in one Chinese cohort, relapse occurred in 32.7% of patients who achieved remission, and treatment resistance was seen in 10.7%. Notably, over 25 years, the risk of relapse has not meaningfully changed even as ESRD/death rates have declined (P = 0.45 for trend).

• Glucocorticoid toxicity is a major unresolved issue: Long-term glucocorticoid (GC) use drives significant treatment-related morbidity, including infections, malignancy, and cardiovascular disease. Patients on oral GCs for >12 weeks showed a trend toward more serious infections (21% vs. 7%; P = 0.06) versus shorter courses, and corticosteroid use is strongly associated with both infection and multi-comorbidity burden.

• Infection, not vasculitis, is the leading cause of early mortality: Broad-spectrum immunosuppression leaves patients vulnerable to infection, which remains the greatest driver of early death and a persistent long-term problem. In a real-world cost analysis, 71% of hospital costs were attributable to infections and 60% to multi-comorbidity—both linked to corticosteroid exposure, exceeding the cost burden of relapses.

• Lack of individualized, biomarker-guided therapy: Current treatment strategies are not tailored to individual risk, resulting in over-treatment of some patients and under-treatment of others. Robust predictors of relapse, immunological quiescence, and optimal treatment duration remain lacking, limiting the ability to personalize immunosuppressive intensity.

• Diagnostic and prognostic uncertainty persists: There is no established diagnostic criteria for AAV, and prognostic markers remain limited—serum creatinine at baseline remains one of the only validated predictors of ESRD or death (HR 1.11 per 1 mg/dl; 95% CI 1.04–1.18, P = 0.002), highlighting the need for earlier detection and more sophisticated biomarkers.

• Residual disease activity is difficult to distinguish from damage: Existing remission definitions may underestimate ongoing disease activity, and interpreting residual symptoms in the absence of overt inflammation remains clinically challenging, complicating decisions about therapy tapering or escalation.

• Targeted therapies have shown mixed results: While rituximab and combination cyclophosphamide-rituximab induction regimens (with rapid GC tapering) have demonstrated high remission rates (96%) and low relapse (5% over 2.9 years), other targeted approaches—such as infliximab added to standard therapy—failed to improve remission, adverse events, damage scores, relapse rates, or biomarker levels in a cohort of 33 patients.

• Pathophysiological understanding remains incomplete: Elucidation of the genetic background of AAV and the role of granulomatous lesions in granulomatosis with polyangiitis are still needed to fully understand disease mechanisms and inform more targeted therapeutic strategies.

• Quality-of-life considerations remain under-addressed: Beyond survival, factors such as eligibility for renal transplantation and successful pregnancy outcomes for young women are critical to patients' quality of life, yet are not consistently integrated into treatment planning alongside disease control metrics.

Re-evaluating Tavneos's Efficacy in ANCA-Associated Vasculitis

Rituximab remains the most extensively characterized approved therapy in ANCA-associated vasculitis (AAV), with response rates that have proven durable across multiple cohorts and study designs. In pivotal comparative data, complete remission rates with rituximab reached 64% at 6 months versus 53% with cyclophosphamide-azathioprine, with rituximab meeting noninferiority criteria (P<0.001) and demonstrating superiority in relapsing disease at 6 and 12 months. Earlier foundational studies reported complete remission in 75% of patients with refractory disease, though 57% subsequently relapsed at a median of 11.5 months, underscoring the need for retreatment strategies—repeat rituximab courses induced or maintained complete remission in 84% of cases. More recent combination approaches pairing cyclophosphamide with rituximab for induction have pushed remission rates to 96%, with a median time-to-remission of 77 days and a relapse rate of just 5% over nearly three years of follow-up. Glucocorticoid-sparing regimens have also matured: the 2025 LoVAS trial data showed reduced-dose prednisolone combined with rituximab achieved comparable relapse rates to high-dose regimens (13.0% vs. 7.6%, p=0.311) while significantly reducing serious adverse events (27.5% vs. 46.2%, p=0.025) and enabling prednisolone discontinuation in nearly 90% of patients.

Avacopan, as a complement C5a receptor inhibitor, has emerged as a corticosteroid-sparing alternative with favorable efficacy signals. In the ADVOCATE trial, avacopan achieved remission in 65.7% of patients compared to 54.9% in the prednisone-tapering arm, while the CLEAR trial demonstrated that 86.4% of avacopan-treated patients achieved a ≥50% improvement in Birmingham Vasculitis Activity Score versus 70% with prednisone. Avacopan has shown sustained remission benefits at 12 months relative to high-dose glucocorticoids, with no major safety concerns reported, positioning it as an effective strategy for minimizing cumulative steroid exposure. In contrast, plasma exchange (PLEX) has not demonstrated a consistent mortality or renal benefit when added to standard induction therapy; a large meta-analysis of 1,235 patients found no significant reduction in mortality at 3 or 12 months, and while time-to-event analysis suggested a lower incidence of end-stage renal disease (HR 0.71, 95% CI 0.55–0.92), overall mortality remained similar between groups (HR 0.96, 95% CI 0.72–1.29)—findings that do not support routine PLEX use in clinical practice. Belimumab, targeting B-cell survival factors, also failed to demonstrate meaningful benefit, with no significant reduction in protocol-specified events or vasculitis relapse when added to azathioprine and glucocorticoids.

Survival outcomes in AAV continue to be shaped by both disease-related and treatment-related morbidity. A large Chinese cohort of 398 patients reported an overall mortality rate of 33.9% over a median follow-up of 25.5 months, with the majority of deaths occurring within the first year, predominantly due to secondary infection (39.3%), while cardiovascular events became the leading cause of death beyond 12 months. Independent predictors of mortality included age, secondary infection, pulmonary involvement, and baseline renal function. Age-related vulnerability is particularly notable in patients over 75 years, where one-year mortality reached 20% overall, ranging from 10% with rituximab-cyclophosphamide combination therapy to 26% with low-dose rituximab, alongside substantial rates of serious infection requiring hospitalization (27% overall). Encouragingly, broader improvements in earlier diagnosis—facilitated by more reliable ANCA testing—combined with advances in induction and remission-maintenance strategies have reduced acute disease-related mortality, shifting clinical attention toward long-term morbidities such as chronic kidney disease and cardiovascular disease as the primary determinants of long-term prognosis in AAV.