Treatments of refractory eosinophilic lung diseases with biologics

Biologics targeting the molecules associated with type 2 inflammation have significantly improved the outcomes of patients with severe eosinophilic asthma and chronic rhinosinusitis with nasal polyps (CRSwNP). Chronic eosinophilic airway/lung diseases including chronic eosinophilic pneumonia, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic bronchitis, and eosinophilic granulomatosis with polyangiitis share clinical features with eosinophilic asthma and CRPwNP, which are mostly adult-onset and may develop simultaneously or consecutively. These eosinophilic airway/lung diseases respond well to initial treatment with systemic corticosteroids, but often recur when the corticosteroids are tapered. The management of these "refractory" cases is an unmet need for clinicians. We first reviewed the standard treatments for these chronic eosinophilic airway/lung diseases, followed by the definition and prevalence of refractory diseases and the role of biologics in their management. The available evidence varies from case reports and case series to randomized control trials, depending on the type of disease; however, these studies provide not only a direction for clinical practice, but also insights into the pathophysiology of each disease. Physicians should discuss the efficacy and costs of biologics in patients with refractory eosinophilic airway/lung diseases to minimize not only the current symptoms, but future risks as well.