Mepolizumab has clinical benefits including oral corticosteroid sparing irrespective of baseline EGPA characteristics.

Background: The Mepolizumab in Relapsing or Refractory EGPA (MIRRA) trial (GSK ID: 115921/NCT02020889) demonstrated that mepolizumab increased remission time and reduced oral corticosteroid (OCS) use compared with placebo in patients with relapsing or refractory eosinophilic granulomatosis with polyangiitis (EGPA). The present analysis investigated the impact of baseline characteristics on clinical outcomes and characterised the OCS-sparing effect of mepolizumab.

Methods: In a phase 3, randomised controlled trial for patients with EGPA (MIRRA), patients received standard of care plus mepolizumab 300 mg or placebo every 4 weeks for 52 weeks. The accrued duration of remission, the proportion of patients in remission at weeks 36 and 48, and the proportion of patients with clinical benefit (remission, OCS or relapse-related) were assessed according to baseline EGPA characteristic subgroups (). Mepolizumab-related OCS-sparing benefits were also quantified.

Results: Accrued duration of remission and the proportion of patients in remission at weeks 36 and 48 were greater with mepolizumab than placebo across the baseline subgroups of refractory disease, immunosuppressant use, EGPA duration, relapse number and OCS use ≤20 mg·day. The proportion of patients with clinical benefit was greater with mepolizumab placebo (range 76-81% 25-39%), irrespective of immunosuppressant use or EGPA duration. Patients treated with mepolizumab placebo accrued significantly more weeks on OCS ≤4 mg·day (OR 5.06, 95% CI 2.47-10.38) and had a mean of 1423.1 mg less per-patient OCS exposure over 52 weeks.

Conclusions: Mepolizumab treatment provided benefits to patients with EGPA across varying baseline clinical characteristics and can be considered an OCS-sparing treatment in EGPA.