Rituximab as an immunosuppressant in antineutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND Rituximab has been used in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) since 2003. Our objective was to describe outcomes and adverse events following rituximab since that time in an inception cohort. METHODS Patients with AAV (diagnosed 1991-2012) who received rituximab (n = 120) were evaluated and incidence per person-year (PPY) with 95% confidence interval was calculated for relapse and infections. Time to remission and relapse by number of rituximab infusions given per treatment course (≤2 versus >2) and by ever having been exposed to cyclophosphamide were compared using Kaplan-Meier curves. Rituximab-treated patients were characterized in comparison with AAV patients treated with cyclophosphamide but not exposed to rituximab (n = 351) using Fisher's exact or rank tests. RESULTS Rituximab resulted in 86% achieving remission and 41% having a subsequent relapse in a median of 19 months (range 9-29). Time to remission and relapse were similar between rituximab infusion courses (≤2 versus >2; remission P = 0.86 and relapse P = 0.78, respectively). Incidence of relapse was 0.22 PPY (0.14, 0.31) and of severe infection was 0.12 PPY (0.08, 0.24). Time to relapse was shorter in those never exposed to cyclophosphamide (n = 20): 50% by 8 months versus 50% by 24 and 30 months for those with prior or concurrent exposure to cyclophosphamide (n = 100). Compared with those who never received rituximab, rituximab-treated patients were younger (P < 0.001), more likely to have granulomatosis with polyangiitis (P = 0.001) and had more upper airway (P = 0.01) and less kidney involvement (P = 0.007). CONCLUSIONS Rituximab is beneficial when prescribed outside of a trial setting. Response to treatment and relapse is similar regardless of infusion number. Rituximab without cyclophosphamide may result in a shorter time to relapse supporting combination of these therapies.