Inflammation Following Mepolizumab and Oral Corticosteroids in Asthma

Inclusion Criteria: * Age ≥ 18 and ≤ 80 years at consent. * Able and willing to provide written informed consent and to comply with the study protocol. * Severe asthma diagnosis confirmed after assessment by an asthma specialist. * Suitable for mepolizumab as per NICE/SMC Clinical Guidelines. Exclusion Criteria: * Maintenance oral corticosteroid treatment within the past four weeks. * Acute exacerbation requiring oral corticosteroids in the four weeks prior to consent. * Other clinically significant medical disease or uncontrolled concomitant disease despite treatment that is likely, in the opinion of the investigator, to require a change in therapy or impact the ability to participate in the study or be significantly worsened by oral corticosteroids. * 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. * Treatment with an investigational agent within 30 days of Visit 1 (or five half-lives of the investigational agent, whichever is longer). * Women of child-bearing potential who are pregnant, lactating, planning pregnancy during the study period or are unwilling to use a highly effective form of contraception. * Known hypersensitivity to prednisolone or its excipients. * Previous psychiatric adverse reactions to steroid therapy in the past. * Concomitant medication with systemic anti-fungals such as ketoconazole, retinoids, tetracycline, other systemic immunosuppressants e.g. ciclosporin, azathioprine, mycophenolate and live vaccines during the crossover trial.