The Inflammatory Profile of Exacerbations in Patients With Severe Asthma Receiving Tezepelumab: The TezEx Study

Inclusion Criteria: * Patients who qualify for tezepelumab according to NICE eligibility criteria and yet to begin treatment or those patients within 36 weeks (+/-8 weeks) since their first dose of tezepelumab at the Guy's severe asthma centre. * Age ≥ 18 and ≤ 80 years at tezepelumab initiation. * Able and willing to provide written informed consent and to comply with the study protocol, including being able to attend for assessment during a symptomatic deterioration. Exclusion Criteria: * Other clinically significant medical disease that is likely, in the opinion of the investigator, to require a change in biologic therapy or impact the ability to participate in the study. * History of current alcohol, drug, or chemical abuse or past abuse that would impair or risk the subject's full participation in the study, in the opinion of the investigator. * Other severe eosinophilic lung disease including EGPA, chronic eosinophilic pneumonia and ABPA * Severe bronchiectasis on CT causing daily sputum production * Maintenance therapy with an antibiotic including azithromycin or doxycycline * Inability to give written informed consent