OBJECTIVES: Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is a rare, heterogeneous, life-threatening, autoimmune condition. This study aimed to evaluate the cost-utility of avacopan in combination with rituximab or cyclophosphamide compared with glucocorticoids (GC) and cyclophosphamide or rituximab for the treatment of severe, active AAV from the Spanish National Health System perspective.

METHODS: A 9-state Markov model was developed to reflect clinical practice for induction of remission and sustained maintenance in patients with AAV over a lifetime horizon, comprising an active disease state where patients start, three remission and three relapse states, end-stage renal disease (ESRD) and death. Clinical data were obtained from the phase 3 ADVOCATE trial and were validated by a panel of Spanish clinical experts, and included disease remission at 26, 52 and 60 weeks, change in estimated glomerular filtration rate and health-related quality of life. Transition probabilities to ESRD were sourced from literature. Costs (€, 2022) were sourced from national databases, including drug acquisition, management of AAV, ESRD and adverse events. Health outcomes were expressed as quality-adjusted life years (QALYs). Sensitivity analyses were performed to examine the robustness.

RESULTS: Preliminary results were highly sensitive to the assumptions of progression to ESRD, and available related data varied according to ESRD management and AAV treatment. Considering an average annual progression to ESRD of 2.0%-9.8%, a regimen including avacopan compared to GC, as an add on to cyclophosphamide (35%) and rituximab (65%), respectively, was more effective (5.77-6.63 vs 5.59-6.32 QALYs), and resulted in an incremental cost (€8,918-14,191), yielding an incremental cost-utility ratio between €29,020-78,142 per additional QALY gained.

CONCLUSIONS: Avacopan is a new cost-effective option for AAV patients in Spain since it reduces the risk of ESRD, considering a threshold for orphan drugs of €30,000-100,000/QALY gained. This model facilitates the approach to economic evaluation of orphan drugs where the evidence is scarce.