Washington, DC—Long-term follow-up of the MAINRITSAN trial confirmed primary results of the trial showing the superiority of rituximab compared with azathioprine as maintenance therapy for antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis. At 60 months, the rate of overall survival was 100% for rituximab versus 93% for azathioprine (P = .045). The rate of relapse-free survival was 57.9% versus 37.2%, respectively (P = .012).
“Despite late relapses after the 28-month initial follow-up period, maintenance therapy with rituximab remained significantly superior to azathioprine at 60 months to maintain remission, and was associated with better survival,” said lead investigator Benjamin Terrier, MD, National Referral Center for Rare Systemic Autoimmune Diseases, Hôpital Cochin, AP-HP, Université Paris Descartes, Paris, France.
Primary results of MAINRITSAN were previously published in The New England Journal of Medicine in 2014. For the primary end point, rituximab maintenance therapy was superior at 28 months in maintaining ANCA-associated vasculitis remission following induction therapy with a cyclophosphamide–glucocorticoid regimen versus standard therapy with azathioprine.
MAINRITSAN enrolled 115 newly diagnosed (80%) or relapsing patients (20%) with ANCA-associated vasculitis. Patients who achieved remission with induction therapy were randomized to receive rituximab infusion 500 mg every 6 months for 18 months, or azathioprine for 22 months.
“Following publication of the primary results, some uncertainties remained as to the duration of remission on rituximab. There is a need for therapy that can prevent relapse over the longer term,” Dr Terrier noted during his presentation at the 2016 Annual Meeting of the American College of Rheumatology.
For all relapses, major and minor, rituximab maintained superiority over azathioprine at 60 months. There were 24 events in the rituximab arm; 11 minor relapses and 13 major relapses. There were 36 events in the azathioprine arm; 10 minor relapses and 25 major relapses (plus 1 death). Major relapse-free survival rates were 71.9% for the rituximab arm versus 49.4% for the azathioprine arm (P = .003).
“There was an absolute difference of 12 months favoring rituximab for relapse-free survival,” Dr Terrier said.
Patients treated with rituximab had more serious infections—30 compared with 20 in the azathioprine group. Cardiovascular event rates were similar for both groups.
Time without progression or toxicity was significantly longer in the rituximab arm according to a time without symptoms and toxicity (TWiST) analysis (P <.001). The quality-adjusted TWiST analysis showed significantly longer quality-adjusted time without progression or toxicity in the rituximab arm (P <.001). The cumulative dose of steroids was comparable between treatment groups.
Six cancers were found in the azathioprine arm, including 4 skin cancers, versus 2 in the rituximab arm.
Among patients treated with rituximab, proteinase 3 ANCA antibody positivity or ANCA persistence 12 months after starting maintenance therapy were associated with higher major relapse rates.
“ANCA monitoring seems to be relevant to guide treatment duration,” Dr Terrier said.