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Objective: Mepolizumab is a humanized IgG1 monoclonal antibody that blocks human IL-5 from binding to the IL-5 receptor, which is mainly expressed on eosinophils. Eosinophils are key cells in the inflammatory cascade of various diseases, including asthma. This study investigated the pharmacokinetic (PK)/pharmacodynamic (PD) relationship between exposure of mepolizumab subcutaneous (SC) administration and blood eosinophil reduction compared with intravenous (IV) administration in adult subjects with asthma. Methods: In this multi-center, randomized, open-label, parallel-group, repeat-dose study, 70 adult subjects received one of four possible treatment regimens: mepolizumab 12.5, 125, or 250 mg SC or 75 mg IV. In addition to analyzing the dose and PK/PD relationship, absolute bioavailability, safety, tolerability, and incidence of anti-mepolizumab antibodies were evaluated. Results: Blood eosinophil levels decreased in a dose-dependent manner with the lowest (12.5 mg) dose clearly differentiating from the other doses. A non-linear inhibition Imax model based on blood eosinophil levels at week 12 identified that the SC doses providing 50% and 90% of maximal blood eosinophil inhibition were 11 mg (95% confidence interval (CI): 5.19 – 16.85) and 99 mg (95% CI: 47 – 152), respectively. The route of administration did not affect the exposure-response relationship. The estimated mepolizumab SC absolute bioavailability (arm) was 74% (90% CI: 54 – 102%). The safety profile of mepolizumab was favorable. Conclusions: A dose-dependent reduction in blood eosinophils across all mepolizumab doses investigated was observed. The subcutaneous absolute bioavailability was 74%. The route of administration did not affect the mepolizumab exposure eosinophil response relationship.

ABSTRACT

Objectives There are no published reports for anti‐interleukin‐5 therapy in children <12 years with asthma. The primary objective of this study was to characterize the pharmacokinetics and pharmacodynamics of mepolizumab following subcutaneous (SC) administration in children 6 to 11 years‐of‐age with severe eosinophilic asthma. Hypothesis Mepolizumab SC pharmacokinetics and pharmacodynamics in children with severe eosinophilic asthma are comparable with adults. Study Design Multinational, nonrandomised, open‐label (NCT02377427). Patient Selection Children 6 to 11 years‐of‐age with severe eosinophilic asthma (blood eosinophil count ≥150 cells/µL at screening or ≥300 cells/µL <12 months of screening) and ≥2 exacerbations in the prior year. Methodology Children received mepolizumab SC 40 mg (bodyweight <40 kg) or 100 mg (≥40 kg) every 4 weeks for 12 weeks. Results Thirty‐six children received mepolizumab (40 mg, n = 26; 100 mg, n = 10). Mepolizumab exposures were higher and apparent clearance lower than predicted based on prior existing data. Derived mepolizumab exposures normalized to mean bodyweight for the 40 mg and 100 mg dose groups were 454 μg * day/mL and 675 μg * day/mL, respectively. At week 12, blood eosinophils were reduced by 89% and 83% from baseline to 42 and 55 cells/µL, respectively. Mepolizumab was well tolerated; no new safety signals were observed compared with previous adult/adolescent studies. Conclusion In children 6 to 11 years‐of‐age with severe eosinophilic asthma, mepolizumab SC 40 or 100 mg provided bodyweight‐adjusted drug exposure within twofold of target adult exposure as well as marked reductions to blood eosinophil counts similar to adults, and although not designed to evaluate efficacy outcomes, demonstrated a positive clinical profile.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• IL-13 can recapitulate the key pathological and clinical features of asthma.• Exhaled NO (FeNO) concentrations are elevated under conditions of pulmonary inflammation, including asthma.• Therapies that inhibit signalling by both IL-13 and the functionally redundant cytokine IL-4 have demonstrated reductions in FeNO, although relationship to dose was not reported. WHAT THIS STUDY ADDS• This study provides the first report of the safety and pharmacokinetics of GSK679586, a novel humanized monoclonal antibody that prevents IL-13 from binding its two known receptors.• This is the first report of the effects on FeNO of a therapy targeting IL-13 alone. Inhibition of IL-13 signalling by GSK679586 produces dose-and time-dependent reductions in FeNO in mild intermittent asthmatics. Thus, FeNO appears to be a dose-and time-responsive clinical biomarker of IL-13 inhibition in mild asthma. AIMSIL-13 is implicated as an important mediator of the pathology of asthma. This first clinical study with GSK679586, a novel humanized anti-IL-13 IgG1 monoclonal antibody, evaluated the safety, pharmacokinetics and pharmacodynamics of escalating single and repeat doses of GSK679586. METHODSIn this randomized, double-blind study, healthy subjects received single intravenous infusions of GSK679586 (0.005, 0.05, 0.5, 2.5, 10 mg kg) or placebo and mild intermittent asthmatics received two once monthly intravenous infusions of GSK679586 (2.5, 10, 20 mg kg -1 ) or placebo. RESULTSGSK679586 displayed approximately linear pharmacokinetics (based on AUC and Cmax) with limited accumulation upon repeat administration. In mild intermittent asthmatics, treatment with GSK679586 produced an increase in serum total IL-13 concentrations, indicative of GSK679586-IL-13 complex formation. Additionally, mean levels of exhaled nitric oxide (FeNO), a marker of pulmonary inflammation, were reduced relative to baseline at 2.5, 10 and 20 mg kg -1 doses of GSK679586 at both 2 weeks (19%, 44% and 52% decreases) and 8 weeks (29%, 55% and 42% decreases) after the second infusion. GSK679586 was well tolerated; the incidence of AEs was comparable across all presumed biologically active doses and there were no treatment-related SAEs. CONCLUSIONSGSK679586 demonstrated dose-dependent pharmacological activity in the lungs of mild intermittent asthmatics. These findings, together with the favourable safety profile and advantageous PK characteristics of a monoclonal antibody (e.g. a long half-life supporting less frequent dosing), warrant further investigation of GSK679586 in a broader asthma patient population.