Mepolizumab as a glucocorticoid-sparing agent in eosinophilic granulomatosis with polyangiitis (EGPA): is a lower dose sufficient?

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare form of small-vessel vasculitis characterized by asthma, hyper-eosinophilia, and progressive multiorgan involvement. EGPA is traditionally treated using glucocorticoids, either alone or in combination with conventional immunosuppressants. Mepolizumab, a novel anti-interleukin (IL)-5 agent, has been approved as an add-on therapy for adult patients with EGPA. The recommended dose of mepolizumab is 300 mg (subcutaneous [SC]) every 4 weeks.The present report discusses three cases of refractory and/or relapsing EGPA in patients regularly taking a stable dose of prednisolone, all of whom were successfully treated with a lower-than-recommended dose of mepolizumab (100 mg SC, every 4 weeks).Treatment with a low dose of mepolizumab enabled us to gradually reduce glucocorticoid doses. In addition, patients treated with low doses of mepolizumab exhibited better asthma control and experienced sustained relapse-free periods. Responses to 100 mg of mepolizumab were comparable to those previously observed in patients taking the recommended dose of 300 mg.Our findings suggest that mepolizumab at a third of the recommended dose can achieve reasonable clinical efficacy in the long-term treatment of EGPA in some patients. Initiation of mepolizumab therapy in the early, eosinophilic phase of EGPA-which is characterized by asthma, marked blood eosinophilia, pulmonary infiltrates, and sinonasal abnormalities-may help to prevent the deleterious side-effects of long-term glucocorticoid use while reducing the cost of EGPA treatment.