Fasenra injection may be used to treat severe eosinophilic asthma in adults and children aged 6 years and older or eosinophilic granulomatosis with polyangiitis (EGPA) in adults. Fasenra's mechanism of action (MOA) involves specifically targeting eosinophils, which are white blood cells associated with inflammation found in the airways of people with asthma and tissues of people with EGPA.