ATLANTA – Rituximab (Rituxan) is superior to azathioprine (Imuran) for preventing ANCA-associated vasculitis relapses in patients with histories of previous relapses, according to a randomized trial of 170 patients presented at the annual meeting of the American College of Rheumatology.
Rituximab has been previously shown to be the superior remission maintenance option in the French MAINRITSAN trial (), but mostly in newly diagnosed patients after cyclophosphamide induction. The results expand the finding to those with relapsing disease who previously had remission induced with rituximab, said lead investigator , a clinical lecturer at Cambridge (England) University.
Subjects in the RITAZAREM(rituximab versus azathioprine as therapy for maintenance of remission for antineutrophil cytoplasmic antibody [ANCA]–associated vasculitis) were enrolled during a relapse of either granulomatosis with polyangiitis or microscopic polyangiitis and underwent remission induction with rituximab 375 mg/m2 per week for 4 weeks coupled with prednisone, either 1 or 0.5 mg/kg per day at provider discretion.
After successful induction – defined as a Birmingham Vasculitis Activity Score for Wegener’s Granulomatosis of 1 point or less on no more than 10 mg/day prednisone – 85 patients were randomized to rituximaband 85 to azathioprine 2 mg/kg per day for 20 months, followed by a taper. Prednisone was tapered per protocol to discontinuation at 20 months.
Eleven rituximab patients (13%) relapsed during the 20-month maintenance phase; two relapses were major. There were 32 relapses (38%) in the azathioprine group, 12 of them (38%) major (hazard ratio for rituximab versus azathioprine, 0.3; 95% CI, 0.15-0.60; P less than .001). ANCA type, glucocorticoid induction regimen, and severity of the enrollment relapse did not affect the outcomes.
Also, “there was an increase in the proportion of patients who became ANCA negative” in the rituximab arm, while “there was really no change” with azathioprine. In short, “rituximab is superior to azathioprine for prevention of disease relapse,” Dr. Smith said.
Her audience had a few questions about the rituximab regimen. The French MAINRITSAN trial dosed rituximab every 6 months instead of every 4, for a cumulative dose of 2.5 g, not 5 g, which an audience member said is the standard approach.
Dr. Smith explained that she and her colleagues have seen relapses with rituximab maintenance at 5 and 6 months, so they wanted to move to a shorter schedule. As for the higher dose, they wanted to “achieve complete B-cell depletion for the duration of the treatment period” to see if it translates into longer lasting remissions. “We will hopefully be able to address that question” with further analysis, she said.
There were no new safety signals; 19 rituximab patients (22%) and 31 azathioprine subjects (36%) had at least one serious adverse event; an infection requiring hospitalization occurred in 7 rituximab patients (8%) and 11 azathioprine patients (13%). Twenty-five (29%) rituximab and 21 (25%) azathioprine subjects developed hypogammaglobulinemia (IgG less than 5 g/L), and about half of each group developed an infection that required antibiotics, but not hospitalization.
There was one death in the azathioprine arm from malignancy, and three in the rituximab group, one from infection and two as of yet unclassified.
The groups were well balanced. Subjects were a median of 59 years old, with a median disease duration of 5.3 years. Refractory patients – those who had not achieved remission during a previous relapse – were excluded, as were patients who had received a B cell–depleting treatment in the previous 6 months and those with eosinophilic granulomatosis with polyangiitis or a malignancy in the past 5 years. Among patients in the study, 72% had tested positive for anti–proteinase 3 ANCA, and 28% for myeloperoxidase ANCA.
The work was funded by Versus Arthritis (formerly Arthritis Research UK), the National Institutes of Health, and the makers of rituximab, Roche/Genentech. Dr. Smith reported ties to Roche, Sanofi, and MedImmune.
SOURCE: Smith R et al. Arthritis Rheumatol. 2019;71(suppl 10), .