The Pharmacokinetics and Relative Bioavailability of Mepolizumab 100 mg Liquid Formulation Administered Subcutaneously to Healthy Participants: A Randomized Trial

This study compared the pharmacokinetic (PK) profile of a new liquid formulation of mepolizumab with the established lyophilized formulation. In this open-label, parallel-group, single-dose study (NCT03014674; GSK ID: 204958), healthy participants were randomized (1:1:1) to receive a single mepolizumab dose (100 mg) administered subcutaneously as liquid in a single-use prefilled syringe or single-use prefilled autoinjector, or as a lyophilized formulation. Maximum plasma concentration, area under the plasma concentration-time curve from time zero (predose) to time of last quantifiable concentration (AUC0-t ), and AUC from time zero to infinity (AUC0-∞ ) as well as additional PK parameters, safety assessments, and blood eosinophil count were evaluated. In total, 244 participants received study drug. All PK parameters were similar across the 3 groups; 90% confidence intervals for maximum plasma concentration, AUC0-t , and AUC0-∞ treatment ratios (liquid prefilled syringe or autoinjector vs lyophilized formulation) were within conventional bioequivalence bounds (0.80-1.25), demonstrating statistical PK comparability. On-treatment adverse event incidence was 29% to 38%. Mepolizumab liquid formulation administered via prefilled syringe or autoinjector had similar PK properties to the lyophilized formulation, with no safety concerns identified.