Phenotyping severe asthma: a rationale for biologic therapy

Introduction: Asthma is a complex disease with heterogeneity in etiology, triggers, clinical characteristics and different responses to pharmacological therapies. Areas covered: Patients with severe uncontrolled asthma constitute a relatively small percentage, ranging from 5 to 10% of all asthmatics. These patients can benefit from targeted biological therapies developed in recent years. In fact, a better understanding of the etiopathological mechanisms of different phenotypes and endotypes of severe asthma have led to the availability of innovative biological therapies, able to modify the natural history of the disease by targeting molecules involved in airway inflammation. Several phenotypes based on clinical and physiologic variables and on inflammatory markers have been reported. Expert opinion: The priority is to define the molecular process underlying the disease. In this context the recognition of T2 and non T2 inflammatory pathways, so called molecular phenotypes, represents the most reliable approach to drive the use of novel biological therapies. For this purpose, several biomarkers have been validated for identifying severe asthma phenotypes and for guiding the choice of the most appropriate treatment. The purpose of this review is to discuss the current knowledge about the molecular phenotypes of severe asthma, as well as the rationale underlying the use of existing biological drugs.