Precision medicine for the discovery of treatable mechanisms in severe asthma.

Although the complex disease of asthma has been defined as being heterogeneous, the extent of its endophenotypes remains unclear. The pharmacological approach to initiating treatment has, until recently, been based on disease control and severity. The introduction of antibody therapies targeting the Type 2 inflammation pathway for patients with severe asthma has resulted in the recognition of an allergic and an eosinophilic phenotype, which are not mutually exclusive. Concomitantly, molecular phenotyping based on a transcriptomic analysis of bronchial epithelial and sputum cells has identified a Type 2 high inflammation cluster characterized by eosinophilia and recurrent exacerbations, as well as Type 2 low clusters linked with IL-6 trans-signalling, interferon pathways, inflammasome activation and mitochondrial oxidative phosphorylation pathways. Systems biology approaches are establishing the links between these pathways or mechanisms, and clinical and physiologic features. Validation of these pathways contributes to defining endotypes and treatable mechanisms. Precision medicine approaches are necessary to link treatable mechanisms with treatable traits and biomarkers derived from clinical, physiologic and inflammatory features of clinical phenotypes. The deep molecular phenotyping of airway samples along with noninvasive biomarkers linked to bioinformatic and machine learning techniques will enable the rapid detection of molecular mechanisms that transgresses beyond the concept of treatable traits.