Efficacy of conventional immunosuppressants in relapsing or refractory eosinophilic granulomatosis with polyangiitis: evidence from a Canadian single-centre cohort.

To describe the efficacy of conventional immunosuppressants in disease control of relapsing or refractory eosinophilic granulomatosis with polyangiitis (EGPA) compared to recently published mepolizumab and rituximab studies. A retrospective analysis from the Toronto Vasculitis Clinic was conducted. Patients with relapsing or refractory EGPA with similar entry criteria as the main mepolizumab (MIRRA) or rituximab (case-series) studies, who were started on conventional immunosuppressants, were assessed for remission at 24- and 52-weeks. Remission was defined as a Birmingham Vasculitis Activity Score of 0 and a prednisone dose of ≤4mg/day, ≤7.5mg/day, corresponding to the mepolizumab trial, or any prednisone dose per day, as in the rituximab study. Among 110 cohort patients, 24 with relapsing or refractory EGPA met eligibility criteria. Conventional immunosuppressants used were methotrexate (n=15), azathioprine (n=8) or leflunomide (n=1). Remission rates at 24-weeks were 8.3% with prednisone ≤4mg/day (vs. 28.0% in the mepolizumab trial); 41.6% with prednisone ≤7.5mg/day (vs. 45% in the mepolizumab trial) and 62.5% with any prednisone dose (vs. 34% in the rituximab study). Remission at 52-weeks was 50.0% with any prednisone dose (vs. 49% in the rituximab study), whereas sustained remission at week 52 (as of week 24) was 4.2% with prednisone ≤4mg/day (vs. 19% in the mepolizumab trial), and 33.3% with prednisone ≤7.5mg/day (vs. 24% in the mepolizumab trial). Though our study was small and retrospective, rates of remission observed with conventional immunosuppressants were substantial. This should be kept in mind when interpreting results of placebo-controlled or retrospective studies on biologics in EGPA.