Abstract Objectives Rituximab (RTX) is a standard maintenance therapy for ANCA-associated vasculitis. Its efficacy in Japan remains unclear, where microscopic polyangiitis (MPA) predominates and clinical characteristics differ from Western-dominated RCT populations. Methods Japanese patients with MPA or granulomatosis with polyangiitis (GPA) enrolled in a nationwide registry were included. Exposure was RTX use during maintenance therapy. The primary endpoint was major relapse-free survival at 104 weeks. The secondary endpoint was any relapse-free survival (major or minor) at 104 weeks. Baseline differences were adjusted using inverse probability of treatment weighting (IPTW) based on key demographic and disease-related covariates. Results A total of 389 patients were analyzed, with 85 in the RTX group. The RTX group included a higher proportion of GPA cases (37/85 vs. 74/304), resulting in baseline imbalance. After IPTW, no major relapses were observed in the RTX group, whereas the major relapse-free survival at 104 weeks was 94.8% in the non-RTX group. The RTX group showed significantly higher any relapse-free survival at 104 weeks (95.4% vs. 83.3%; HR for any relapse, 0.27; 95% CI, 0.09–0.74; p = 0.02). Conclusions Our findings suggest that RTX may be an effective option for remission maintenance in Japanese patients with MPA or GPA.
Takeuchi et al. (Wed,) studied this question.