Japanese Phase 1 Study of Mepolizumab

Asthma is a disease characterised by chronic airway inflammation, bronchial hyper-reactivity and variable airflow obstruction. Eosinophils are usually prominent in the airway inflammation seen in asthma and are considered a central cause in the pathogenesis of asthma. The expression of interleukin (IL)-5 is elevated in bronchoalveolar lavage (BAL) fluid and bronchial biopsies in patients with asthma. Moreover, the level of IL-5 in BAL fluid and the bronchial mucosa correlates with disease severity. The cytokine IL-5 promotes eosinophil differentiation, recruitment and survival. Thus a therapeutic strategy which blocks IL-5, thereby suppressing eosinophilic inflammation, may have therapeutic benefit in asthma. SB-240563 (mepolizumab) is a humanized monoclonal antibody that blocks human interleukin 5 (hIL-5) from binding to its receptor. Initial clinical studies investigated the safety and efficacy of SB-240563 for the treatment of asthma and atopic dermatitis (AD). SB-240563 consistently and significantly reduced peripheral and tissue eosinophils in patients with these atopic conditions, including asthma, and in healthy volunteers. SB-240563 is currently under development for severe refractory asthma and a Phase IIB dose-ranging study using the IV route of administration is currently ongoing. This study will be a single-blind, placebo-controlled, parallel group, dose ascending, single dose study in Japanese healthy male subjects. Since this is the first study conducted in Japanese subjects, doses of SB-240563 will be administered in an ascending order. In studies conducted in non-Japanese subjects, SB-240563 has been well-tolerated following single and repeated intravenous dose up to 750 mg (SB-240563/006, SB-240563/036 and MEE103226). Intravenous repeated doses of 75 mg, 250 mg and 750 mg are being administered to non-Japanese asthma patients in an on-going Phase II study. In consideration of the above facts, single intravenous administration of 4 doses (10 mg, 75 mg, 250 mg and 750 mg) of SB-240563 will be administered in this study. A single intravenous dose of 10 mg will be administered in order to explore the effect of a lower dose of SB-240563 than previously studied on blood eosinophil counts. This low dose is expected to help further characterize the concentration-response relationship based on blood eosinophils. This study is designed as a randomized, parallel group, placebo-controlled, single-blind study to evaluate the pharmacokinetics, pharmacodynamics, safety and tolerability of SB-240563 in Japanese male subjects.