Real-world safety and effectiveness of mepolizumab for patients with eosinophilic granulomatosis with polyangiitis in Japan: long-term observation of the MARS study.

Objectives: To provide long-term, real-world safety and effectiveness data for mepolizumab treatment in eosinophilic granulomatosis with polyangiitis in Japan.

Methods: MARS (NCT04551989) was a real-world, observational study of patients who had previously completed the PMS study (NCT03557060; ≥96 weeks of mepolizumab treatment before study entry [baseline]) and continued receiving four-weekly mepolizumab 300 mg subcutaneously for a further 96 weeks. Safety outcomes were assessed from baseline to Week 96 (observation period); clinical outcomes were assessed pre-mepolizumab initiation (retrospective period) and during the observation period.

Results: Of 118 patients enrolled in the study, 58% (69/118) experienced adverse events and 22% (26/118) experienced serious adverse events over the observation period; none were mepolizumab-related. Over the study (pre-mepolizumab period; baseline; end of observation period) the proportion of patients with no clinical symptoms increased (6%, to 27%, to 32%, respectively), median oral glucocorticoid dose decreased (6.9, to 3.0, to 2.0 mg/day, respectively) and the proportion of oral glucocorticoid-free patients increased (8%, to 31%, to 36%, respectively).

Conclusions: Long-term MARS study data are consistent with the known safety profile of mepolizumab. Over 192 weeks (pre-mepolizumab-observation), mepolizumab was well tolerated, with improvements in eosinophilic granulomatosis with polyangiitis disease control and reductions in oral glucocorticoid use.