Mepolizumab Pharmacokinetics Among Patients With Severe Asthma

Asthma is a chronic disease characterized by inflammation and obstruction of the airways. Understanding the biological effects of the corticosteroids allowed to identify and to define the type 2 inflammation present in nearly 80% of patients with asthma. Monoclonal antibodies (MAb) in severe asthma target type-2 inflammation. Mepolizumab is a humanized IgG1 kappa subclass monoclonal antibody directed specifically against interleukin 5 (IL-5). It acts specifically on eosinophil homeostasis, since IL-5 is a key interleukin in eosinophil maturation. Poor MAb responses can hypothetically arise in situations of poor treatment compliance. And after excluding the latter, several biological mechanisms have been mentioned: i) insufficient bioavailability of the MAb to reach the eosinophils of the bronchial compartment; ii) he development of autoimmunity with the formation of circulating immune complexes; and iii) immunization against mepolizumab, with the formation of neutralizing anti-drug antibodies (ADA). ADA were detected in up to 20% of a treated population and were rarely neutralizing. Interestingly, these ADA could also be detected in naïve populations, suggesting a possible cross-immunization related to previous exposure to MAbs and/or to insufficient assay specificity. In any case, all three possibilities have a common outcome, i.e. decreased circulating concentrations of the MAb in the blood. The investigators propose to measure the concentrations of mepolizumab in the serum of asthmatic patients treated with this mAb. The investigators hypothesize that the individual pharmacokinetics (PK) of mepolizumab may differ between clinical responders and non-responders.