Asthma

Asthma is a common respiratory disease with a complex etiology involving a combination of genetic and environmental components. Current asthma management involves a step-up and step-down approach based on asthma control with a large degree of heterogeneity in responses to the main drug classes currently in use: β2-adrenergic receptor agonists, corticosteroids, and leukotriene modifiers. Importantly, asthma is heterogeneous with respect to clinical presentation and the inflammatory mechanisms that underlie it. This heterogeneity likely contributes to variable results in clinical trials, particularly when targeting specific inflammatory mediators. These factors have motivated a drive toward stratified medicine in asthma based on clinical/cellular outcomes or genetics (i.e., pharmacogenetics). Significant progress has been made in identifying genetic polymorphisms that influence the efficacy and potential for adverse effects of all main classes of asthma drugs. Importantly an emerging role for genetics in phase II development of newer therapies has been demonstrated (e.g., anti-IL4). Similarly, the stratification of patients based on clinical characteristics (e.g., blood and sputum eosinophil levels) has been critical in evaluating newer therapies (e.g., anti-IL5). As a proof of concept, anti-IgE is the latest therapy to be introduced into clinical practice, although only for severe, allergic patients (i.e., in a stratified manner). As new asthma genes are identified using genome-wide association, among other technologies, new targets (e.g., IL33/IL33 receptor (IL1RL1)) will emerge and pharmacogenetics in these development programs will be essential. In this chapter we review the current understanding of asthma pathobiology and its clinical presentation, as well as the use of stratified medicine, which holds great promise for maximizing clinical outcomes and minimizing adverse effects in existing and new therapies.