Asthma and COPD are the most prevalent chronic inflammatory lung diseases worldwide. The development of airway and lung inflammation is the result of complex interactions between the epithelial barrier, the innate and the adaptive immune system. Deep phenotyping approaches identify heterogeneous patient populations with regard to dysregulation in this “triangle”. These discoveries resulted in the identification of different phenotypes or endotypes. In terms of asthma, the most prevalent endotype is defined by the presence of T-helper (Th) 2 T-cells, Eosinophils and IgE production (eosinophilic phenotype). Furthermore, patients suffering from non-eosinophilic asthma can be further subdivided into several other phenotypes. A similar approach has been performed for patients suffering from COPD. These phenotypes now require tailored therapeutic approaches, which advanced with the development of novel targeted therapies such as antibodies against IL-5 and IL-5 receptors, TSLP, IL-25 and other key molecules. The selection of such tailored therapeutic approaches requires the identification of the phenotypes using biomarkers. Currently only a few biomarkers are available to classify this heterogeneous patient population and future direction of research is aiming to identify, characterise and validate novel biomarkers which are better suited for phenotyping and endotyping.
