Severe Eosinophilic Asthma: From Immunopathology to Pharmacological Treatment

Background: Asthma is a heterogeneous chronic airway disease characterized by inflammation, airflow obstruction, hyperresponsiveness, and remodeling. Severe eosinophilic asthma is driven by eosinophilic inflammation, which contributes to tissue damage, recurrent exacerbations, and progressive impairment of airway structure and function. Eosinophils play a central role through the release of cytokines, cytotoxic granule proteins, and extracellular traps, and their persistence in the airways is sustained by type 2 inflammatory pathways, particularly interleukin-5-mediated signaling. A better understanding of eosinophil biology has promoted the development of targeted therapies, including anti-interleukin-5/interleukin-5 receptor agents and biologics that indirectly modulate eosinophilic inflammation, such as anti-interleukin-4 receptor alpha and anti-thymic stromal lymphopoietin antibodies. Aim: This narrative review summarizes the immunopathology of eosinophilic asthma and links eosinophil biology to current and emerging pharmacological strategies. We discuss biologics that directly target the IL-5/IL-5 receptor axis, as well as agents that indirectly modulate eosinophilic inflammation, including IL-4 receptor alpha and TSLP blockade. We also review the clinical positioning of available biologics, focusing on blood eosinophils, FeNO, exacerbation history, oral corticosteroid exposure, lung function, type 2 comorbidities, treatment response, remission and switching. Conclusions: Overall, eosinophilic inflammation remains a central therapeutic target and a key component of precision medicine in severe asthma, but biologic selection should be individualized and reassessed through multidomain clinical outcomes.