Biological treatments for severe asthma: A major advance in asthma care

Asthma is a heterogeneous disease with considerable variability noted in disease severity, patterns of airway inflammation, and achievement of disease control on current medications. An absence of disease control is most frequently noted in patients with severe asthma, and is defined as a lack of control while on high dose inhaled corticosteroids (ICS) plus a second controller medication. In part, this lack of control may relate to a diminished effect of current guideline-directed care on the existing pattern of airway inflammation in severe asthma. Airway inflammation in severe asthma has been arbitrarily divided into T (type) 2 high and T2 low. T2 high is characterized by the generation of key cytokines, interleukin (IL)-4, −5 and −13, which generate and regulate airway inflammation. Biomarkers to mark the presence of T2-high inflammation include eosinophils, fractional exhaled nitric oxide (FeNO) and immunoglobulin (Ig) E, whose presence arises from the action of IgE, IL-5, IL-4, and IL-13. In this review, treatment of severe asthma with monoclonal antibodies, i.e. biologics, which are directed against these inflammation generated pathways are reviewed. The available monoclonal antibodies include omalizumab (anti-IgE); mepolizumab, reslizumab and benralizumab (anti-IL-5 pathways), and dupilumab (anti-IL-4/IL-13). The use of these T2-high interventions has led to significant reductions in asthma symptoms, a decreased frequency of exacerbations, and improved lung function in many patients. Not only has the use of these monoclonal antibodies led to improved asthma control in patients with severe disease, their use has provided insight into mechanisms of severe asthma.