Usability of mepolizumab single-use prefilled autoinjector for patient self-administration.

Objective: To evaluate usability of mepolizumab as a liquid drug product self-administered via a single-use prefilled autoinjector (AI) by patients with severe eosinophilic asthma (SEA), or their caregivers, in-clinic and at home. Methods: This open-label, single-arm, Phase IIIa study (NCT03099096; GSK ID: 204959) included patients aged ≥12 years with SEA who were either receiving mepolizumab (100 mg subcutaneously [SC]) every 4 weeks (Q4W) for ≥12 weeks before screening or not receiving mepolizumab but met criteria indicative of SEA. Patients/caregivers self-administered mepolizumab (100 mg SC) via an AI Q4W for 12 weeks. The first (Week 0) and third (Week 8) doses were observed in-clinic; the second dose (Week 4) was administered unobserved at home. Primary and secondary endpoints were the proportion of patients who successfully self-administered their third and second doses, respectively (determined by investigator/site staff). Patient experience, mepolizumab trough concentrations, blood eosinophil count (BEC), and safety were also assessed. Results: Of 159 patients/caregivers who self-administered ≥1 dose of mepolizumab, 157 completed the study. Nearly all patients successfully self-administered their third mepolizumab dose in-clinic and second dose at home (≥98% and ≥96%, respectively); this was further confirmed by mepolizumab trough concentrations/BEC. At study end, ≥88% of patients were "very" or "extremely" confident about using the AI correctly. Incidence of on-treatment drug-related adverse events (AEs) was low (3%); no fatal AEs occurred. Conclusions: Patients/caregivers successfully self-administered mepolizumab via the AI both in-clinic and at home; no new safety concerns were identified.