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 (AUC(0–t)), and AUC from time zero to infinity (AUC(0–∞)) 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, AUC(0–t), and AUC(0–∞) 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.