AZISAST Study: AZIthromycin in Severe ASThma Study

Inclusion Criteria: 1. patients who have given written informed consent 2. males or females of any race 3. 18-75 years of age 4. with the diagnosis of persistent asthma ≥ 1 year duration at screening and a history consistent with GINA step 4 or 5 clinical features 5. receiving high dose ICS plus inhaled LABA for at least 6 months prior to screening 6. patients who have suffered multiple (i.e. at least two) independent documented severe asthma exacerbations within the previous 12 months 7. patients must be never-smokers or ex-smokers with a smoking history of ≤ 10 pack-years. Exclusion Criteria: 1. females who are pregnant or who are breastfeeding 2. patients with severe bronchiectasis 3. patients with active tuberculosis or non-tuberculous mycobacterial infections (NTM) 4. patients with significant underlying medical conditions (e.g. infection, hematological disease, malignancy, neurologic, renal, hepatic, coronary heart disease or other cardiovascular disease, endocrinologic or gastrointestinal disease) within the previous 3 months 5. who are unable to perform spirometry or complete a patient diary or complete questionnaires 6. patients with known hypersensitivity to azithromycin or other macrolide antibiotics 7. patients who's heart rate corrected QT interval is prolonged 8. patients who have - in the judgement of the investigator - a clinically relevant laboratory abnormality 9. patients currently treated with macrolide antibiotics or recent macrolide treatment (in the past twelve weeks) 10. anti-IgE treatment