Obinutuzumab treatment for antineutrophil cytoplasmic antibody-associated vasculitis.

Background: Anti-CD20 therapy with rituximab serves as the cornerstone of both induction and maintenance treatment for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Obinutuzumab, a humanized type II anti-CD20 monoclonal antibody, is designed for more potent and sustained B-cell depletion with improved tolerability. Due to the paucity of clinical evidence of obinutuzumab in AAV, we undertook this study to assess its efficacy and safety profile. Methods: Twelve consecutive patients with AAV who received first obinutuzumab treatment between September 2022 and December 2024 were included in this retrospective study. Clinical and pathological data were collected at predefined time points. Results: Four patients received obinutuzumab for induction therapy, and 8 for maintenance therapy. The median follow-up duration after obinutuzumab administration was 17.5 months. Among the 4 patients receiving obinutuzumab for induction therapy, one patient progressed to end-stage kidney disease after infection, while the other 3 achieved sustained remission. Among the 8 patients receiving obinutuzumab for maintenance therapy, no relapse occurred. Among all the patients, three experienced at least one severe adverse event following obinutuzumab therapy. B-cell reconstitution typically began 9-12 months after obinutuzumab administration, with one patient showing no reconstitution at 24 months of follow-up. Concomitant with B-cell depletion, ANCA levels gradually declined in most patients and became undetectable in half. Notably, ANCA levels continued to decrease for up to one year after obinutuzumab administration, even after B-cell reconstitution began. Conclusion: Obinutuzumab was effective and well-tolerated in AAV patients, supporting its potential as an alternative anti-CD20 therapy for AAV.