Asthma is a chronic inflammatory disorder of the airways in which many cell types play a role, in particular tissue mast cells, circulating eosinophils and T lymphocytes. In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness and cough, particularly at night and/or in the early morning. These symptoms are usually associated with airflow limitation that is at least partly reversible either spontaneously or with treatment.
According to the National Institute of Allergy and Infectious Diseases (NIAID), approximately 7% of Americans currently suffer from asthma. Both prevalence and mortality rates have risen since 1982. There are approximately500,000 hospital admissions and 1.8 million emergency visits attributed to this disease each year in the U.S. Almost 7 million asthmatics are under the age of 18 and there are more than 3,000 deaths from asthma annually. Despite the prevalence and significant medical and economic consequences of asthma, relatively few novel therapies have been introduced in the last 10 years.