B cell-driven reduced-dose rituximab as induction therapy for 2 patients with ANCA-associated renal vasculitis: A case series.

Objective: Antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV), a multisystem autoimmune disorder, deteriorates small vessels. Kidney involvement occurs in most affected patients and is the most common cause of rapidly progressive glomerulonephritis (RPGN). Rituximab (RTX), an anti-CD20 antibody, has been used in the induction and maintenance therapy of AAV as a non-inferior alternative to cyclophosphamide. Administration of 4 once-weekly doses of 375 mg/m is the common dose in remission induction therapy, referred to as a conventional regimen. Recently, it was shown that the cumulative complete remission (CR) rates did not differ between low-dose RTX (2 once-weekly doses of 375 mg/m) and the conventional RTX regimen. We aimed to explore the effect of the B cell-driven RTX dosing regimen.

Case Reports: Herein, we reported B cell-driven reduced-dose RTX therapies in a 71-year-old male de novo patient (case 1) and a 60-year-old female patient (case 2). Case 1, de novo diagnosed based on kidney biopsy, received 3 once-semimonthly doses of 300 mg RTX as induction therapy. Case 2, who was clinically diagnosed with ANCA-associated renal vasculitis 4 years before receiving treatment at our hospital, accepted 4 once-monthly doses of 300 mg RTX as induction therapy. Further dosages were dependent on peripheral CD19+ B-cell levels.

Results: During the course of treatment, peripheral B-cell counts of both patients turned 0, and symptoms of both patients improved, complete remission occurred in case 1, with a Birmingham vasculitis activity score (BVAS) of 0.

Conclusion: B cell-driven reduced-dose RTX might be also effective in induction therapy for AAV. Further study is warranted to confirm the efficacy, safety, and risk of relapse of a reduced-dose RTX regimen.