Biological Therapies of Severe Asthma and Their Possible Effects on Airway Remodeling

Asthma-one of the most common chronic, non-communicable diseases in children and adults-is characterised by variable respiratory symptoms and variable airflow limitation. Asthma is a consequence of complex gene-environment interactions, with heterogeneity in clinical presentation and the type and intensity of airway inflammation and remodelling. The goal of asthma treatment is to achieve good asthma control-ie, to minimise symptom burden and risk of exacerbations. Anti-inflammatory and bronchodilator treatments are the mainstay of asthma therapy and are used in a stepwise approach. Pharmacological treatment is based on a cycle of assessment and re-evaluation of symptom control, risk factors, comorbidities, side-effects, and patient satisfaction by means of shared decisions. Asthma is classed as severe when requiring high-intensity treatment to keep it under control, or if it remains uncontrolled despite treatment. New biological therapies for treatment of severe asthma, together with developments in biomarkers, present opportunities for phenotype-specific interventions and realisation of more personalised treatment. In this Seminar, we provide a clinically focused overview of asthma, including epidemiology, pathophysiology, clinical diagnosis, asthma phenotypes, severe asthma, acute exacerbations, and clinical management of disease in adults and children older than 5 years. Emerging therapies, controversies, and uncertainties in asthma management are also discussed.

Asthma is one of the most common chronic immunological diseases in humans, affecting people from childhood to old age. Progress in treating asthma has been relatively slow and treatment guidelines have mostly recommended empirical approaches on the basis of clinical measures of disease severity rather than on the basis of the underlying mechanisms of pathogenesis. An important molecular mechanism of asthma is type 2 inflammation, which occurs in many but not all patients. In this Opinion article, I explore the role of type 2 inflammation in asthma, including lessons learnt from clinical trials of inhibitors of type 2 inflammation. I consider how dichotomizing asthma according to levels of type 2 inflammation--into 'T helper 2 (TH2)-high' and 'TH2-low' subtypes (endotypes)--has shaped our thinking about the pathobiology of asthma and has generated new interest in understanding the mechanisms of disease that are independent of type 2 inflammation.

Many patients with asthma have uncontrolled disease despite treatment with inhaled glucocorticoids. One potential cause of the variability in response to treatment is heterogeneity in the role of interleukin-13 expression in the clinical asthma phenotype. We hypothesized that anti-interleukin-13 therapy would benefit patients with asthma who had a pretreatment profile consistent with interleukin-13 activity. We conducted a randomized, double-blind, placebo-controlled study of lebrikizumab, a monoclonal antibody to interleukin-13, in 219 adults who had asthma that was inadequately controlled despite inhaled glucocorticoid therapy. The primary efficacy outcome was the relative change in prebronchodilator forced expiratory volume in 1 second (FEV(1)) from baseline to week 12. Among the secondary outcomes was the rate of asthma exacerbations through 24 weeks. Patient subgroups were prespecified according to baseline type 2 helper T-cell (Th2) status (assessed on the basis of total IgE level and blood eosinophil count) and serum periostin level. At baseline, patients had a mean FEV(1) that was 65% of the predicted value and were taking a mean dose of inhaled glucocorticoids of 580 μg per day; 80% were also taking a long-acting beta-agonist. At week 12, the mean increase in FEV(1) was 5.5 percentage points higher in the lebrikizumab group than in the placebo group (P = 0.02). Among patients in the high-periostin subgroup, the increase from baseline FEV(1) was 8.2 percentage points higher in the lebrikizumab group than in the placebo group (P = 0.03). Among patients in the low-periostin subgroup, the increase from baseline FEV(1) was 1.6 percentage points higher in the lebrikizumab group than in the placebo group (P = 0.61). Musculoskeletal side effects were more common with lebrikizumab than with placebo (13.2% vs. 5.4%, P = 0.045). Lebrikizumab treatment was associated with improved lung function. Patients with high pretreatment levels of serum periostin had greater improvement in lung function with lebrikizumab than did patients with low periostin levels. (Funded by Genentech; ClinicalTrials.gov number, NCT00930163 .).