Usability of mepolizumab single-use prefilled syringe for patient self-administration

Objective: A liquid mepolizumab formulation in a single-use prefilled syringe (PFS) is under development. We evaluated the usability of mepolizumab self-injected via PFS by patients with severe eosinophilic asthma (SEA), or their caregivers, in clinic and at home. Methods: This open-label, single-arm, Phase IIIa study included patients with SEA, aged >= 12 years, and receiving mepolizumab (100 mg subcutaneously) every 4 weeks for >= 12 weeks prior to screening. Patients with SEA not receiving mepolizumab at screening who met additional criteria were also included. Patients/caregivers self-administered mepolizumab (100 mg subcutaneously) via PFS every 4 weeks for 12 weeks. The first (Week 0) and third (Week 8) dose were observed in clinic; the second dose (Week 4) was unobserved at home. Primary and secondary endpoints were the proportion of patients who successfully self-administered their third and second doses, respectively. Injection success was determined by investigator/site staff. Patient experience, mepolizumab trough concentrations, blood eosinophil counts, and safety were also assessed. Results: Of the 56 patients/caregivers who self-administered >= 1 dose of mepolizumab, 55 completed the study. All patients were reported to have successfully self-administered their third mepolizumab dose in clinic (N = 55, 100%); this was further evidenced by trough concentrations/blood eosinophil counts. Most patients/caregivers found the PFS easy and convenient to use with 75% (n = 42) expressing little/no anxiety about using the device at home. Incidence of on-treatment drug-related adverse events was low (4%); none were fatal. Conclusions: Patients/caregivers successfully self-administered mepolizumab via the PFS both in clinic and at home, with no new safety concerns identified.