Favorable response to asthma-dosed subcutaneous mepolizumab in eosinophilic pneumonia

Introduction: Mepolizumab targets eosinophils in the treatment of asthma. The dose used for asthma is considerably lower than that used for treating eosinophilic granulomatosis with polyangiitis, a recently approved indication. While intravenous mepolizumab use has reported utility in non-asthma eosinophilic disorders, the efficacy of the subcutaneous asthma dosing of the drug for eosinophilic pneumonia is not known. Case study: A middle-aged female was diagnosed with eosinophilic pneumonia. The patient's clinical/radiologic/laboratory findings, response to treatment, and respiratory function studies are described. Results: A woman, born in 1962, had repeated pneumonia hospitalizations from 2007 through 2010. In October 2010, a lung biopsy showed findings consistent with chronic eosinophilic pneumonia and chronic asthma. The patient also had chronic sinusitis. Long term systemic corticosteroids were prescribed but the patient became oxygen dependent by 2014. Omalizumab was administered for 1 year starting in 2015 without improvement in symptoms. In 2016, mepolizumab 100 mg subcutaneously every 4 weeks was initiated. Symptomatic improvement with decreased oxygen and systemic corticosteroid requirements were noted. A chest CT performed in February 2018 showed marked improvement compared to a study in 2016. Interval spirometric improvements were noted. Peripheral blood eosinophils/mm³ prior to mepolizumab were 237, and while on mepolizumab were 10. Conclusion: Parenchymal eosinophilic lung disease may respond to asthma-dosed mepolizumab. Mepolizumab treatment in asthma where concomitant interstitial disease is suspected, may offer an advantage over omalizumab in the ability to reduce eosinophils not only in airways, but also in lung parenchyma.