MRI and Lung Function Measures of Benralizumab Response in Asthma

Inclusion Criteria: * People with eosinophilic asthma meeting the National Institute for Health and Clinical Excellence (NICE) criteria for benralizumab therapy based on eosinophil count and exacerbation rates will be offered the chance to participate in this study. Exclusion Criteria: * Any medical illness that in the opinion of the investigator is likely to significantly impact on the response to benralizumab or the outcome of the MRI and lung function testing. * Non-concordance with routine asthma therapies (this would be assessed as a mandatory part of NICE-based criteria). * Any additional significant lung illness that would impact on likelihood of response to benralizumab. Of note, trivial stable bronchiectasis that in the opinion of the patient's clinician is not clinically significant nor likely to result in either recurrent exacerbations or impairment of interpretation of investigation results will not be exclusion criteria. Part of the initial inclusion regarding eligibility by NICE criteria include an assessment of a likely eosinophilic asthmatic phenotype with probability of treatment response, and potential subjects with complex lung disease would be unlikely to be eligible. * Current cigarette smoking, or cigarette smoking within the past 6 months * Significant lifetime smoking history of ≥20 pack years * Previous use of another biologic therapy targeting eosinophils within 6 months of enrollment * Pregnancy, planning pregnancy, or breast feeding. Women of childbearing potential must use effective contraception (concordant use of hormonal contraceptive, intrauterine device, total abstinence), and urine pregnancy tests will be performed before scans. * Abnormal renal function (eGFR \<30), to avoid risks from Gadolinium chelate MRI contrast agents.