Avacopan is effective in inducing remission for MPA/GPA, regardless of changes in serum C5a levels: a single-center study in Japan.

BACKGROUND: Avacopan, a selective oral C5a receptor antagonist, was approved for the treatment of microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) in 2021. However, there are still limited reports on its efficacy and safety in real-world settings, specifically regarding its impact on the Vasculitis Damage Index (VDI), and its effects on serum biomarkers are poorly understood. This study aimed to evaluate the efficacy and safety of avacopan in remission induction therapy for MPA/GPA in a real-world setting, as well as its effect on serum C5a levels. METHODS: This retrospective study investigated patients with MPA/GPA who received remission induction therapy with a 6-month follow-up at our institution, comparing those who received avacopan with those who did not. Efficacy and safety were evaluated by comparing the remission rate, changes in Birmingham Vasculitis Activity Score (BVAS) and VDI score after 6 months, daily glucocorticoid (GC) dose, and incidence of adverse events (AEs). Changes in serum C5a levels, measured using ELISA, were compared between both groups at baseline and 3 months. RESULTS: A total of 66 patients with MPA/GPA were included, with 14 and 52 patients in the avacopan and non-avacopan groups, respectively. The remission rate and decrease in BVAS was comparable between both groups. However, those who received avacopan had a significantly smaller increase in VDI score, significantly lower daily GC dose at 1, 3, and 6 months, and significantly lower incidence of GC-related AEs within 6 months. Serum C5a levels did not significantly change in the avacopan group but significantly decreased in the non-avacopan group. Remission was achieved in the avacopan group regardless of whether serum C5a decreased or increased. CONCLUSIONS: Treatment with avacopan appears to effectively suppress the increase in VDI score, enable reduced GC dosage, and lower the incidence of GC-related AEs during remission induction therapy for MPA/GPA in a real-world setting. Furthermore, avacopan may suppress disease activity regardless of serum C5a levels. CLINICAL TRIAL NUMBER: Not applicable.