Fasenra (benralizumab) is a prescription biologic medication indicated for the add-on maintenance treatment of patients with severe eosinophilic asthma, typically administered when standard inhaled therapies are not sufficient to control symptoms. It belongs to a class of drugs known as interleukin-5 receptor alpha (IL-5Rα)–directed cytolytic monoclonal antibodies.

Fasenra works by binding to the IL-5 receptor on eosinophils, a type of white blood cell involved in airway inflammation. This action attracts natural killer cells, leading to rapid and near-complete depletion of eosinophils through antibody-dependent cell-mediated cytotoxicity (ADCC). By reducing eosinophil levels, Fasenra helps decrease airway inflammation, improve lung function, and reduce the frequency of asthma exacerbations.

It is administered via subcutaneous injection, typically once every 4 weeks for the first three doses, followed by once every 8 weeks thereafter. Fasenra is not intended for relief of acute asthma symptoms or bronchospasm.

Common side effects may include headache, sore throat, and injection site reactions. As a biologic therapy, it should be used under medical supervision, especially in patients with parasitic infections or hypersensitivity reactions.