Long-term safety of mepolizumab for up to ∼10 years in patients with severe asthma: open-label extension study

OBJECTIVES: Long-term safety monitoring of mepolizumab is necessary to support real-world use for the treatment of severe asthma. This Long-Term Access Program assessed the safety and benefit:risk of mepolizumab in pediatric, adolescent, and adult patients with severe asthma. MATERIALS AND METHODS: This was a multicenter, Phase IIIb safety, open-label extension study of multiple prior studies assessing mepolizumab in addition to standard of care (Aug 2015 - Aug 2022). Adults/adolescents (≥12 years of age) received mepolizumab 100 mg subcutaneously (SC) every 4 weeks until mepolizumab was commercialized. Pediatric patients (6-11 years of age) received mepolizumab 40 mg or 100 mg SC (bodyweight <40 or ≥40 kg, respectively) every 4 weeks. Safety was assessed every 4 weeks and benefit:risk every 12 weeks. RESULTS: Of the 514 patients enrolled, 57% were female and the mean age was 51.1 (standard deviation: 14.9) years; 24 (5%) patients were 6-17 years of age. Total cumulative mepolizumab exposure across all mepolizumab studies included in this analysis was 1500.59 patient-years; median exposure was 2.03 (range, 0.08 to 9.97) years. Overall, 37 (7%) patients experienced on-treatment serious adverse events (SAEs): 34/502 (7%) in the 100 mg SC group and 3/7 (43%) in the 40 mg SC pediatric group. Two patients experienced SAEs considered to be treatment-related by the investigator. Infections were the most common SAEs of special interest (9 2% patients). Physician-assessed benefit:risk of mepolizumab supported continued treatment over the study period. CONCLUSIONS: This long-term safety analysis of mepolizumab was consistent with previous reports, with no emerging safety concerns; most patients had a favorable benefit:risk up to ∼10 years. CLINICAL TRIAL IDENTIFIER: NCT00244686 (GSK ID 201956).