Pharmacokinetics, Pharmacodynamics and Safety of Belimumab in Chinese Patients with Systemic Lupus Erythematosus: A Phase I, Open-Label Study

INTRODUCTION: The B cell survival factor B lymphocyte stimulator (BLyS) is elevated in patients with systemic lupus erythematosus (SLE) and associated with disease activity. Belimumab, a monoclonal antibody specific for soluble BLyS, is approved for the treatment of adults with active, autoantibody-positive SLE receiving standard therapy. Ethnicity is one of the factors that can potentially affect the pharmacokinetics (PK) of therapeutic monoclonal antibodies, and therefore their efficacy and safety. METHODS: This phase 1, open-label study (200909) evaluated the pharmacokinetics (PK, primary objective), pharmacodynamics (PD), and safety (secondary objectives) of belimumab in Chinese patients with SLE (N = 20). Blood samples were taken up to 84 days after a single intravenous (IV) dose of belimumab 10 mg/kg. RESULTS: Peak serum concentrations of belimumab (C(max)) were obtained within the 1-h infusion. Geometric mean C(max), area under the concentration–time curve (time 0 to last quantifiable concentration), terminal half-life, systemic clearance, and volume of distribution were 221 μg/mL, 2395 day·μg/mL, 14.6 days, 4.06 mL/day/kg, and 85.7 mL/kg, respectively. Decreases in CD20(+), CD20(+)/CD27(−) naïve, CD20(+)/CD69(+) active, CD20(+)/CD138(+) plasmacytoid, CD19(+)/CD27(BRIGHT)/CD38(BRIGHT) SLE subset, and CD20(−)/CD138(+) plasma B Cells post-dose were accompanied by an increase in CD20(+)/CD27(+) memory B cells. Four cases of upper respiratory tract infection (three mild, one moderate) and one case of mild pharyngitis were possibly drug-related; all resolved during the study. CONCLUSION: PK of a single belimumab 10 mg/kg IV dose in Chinese patients with SLE were similar to those observed previously in Japanese and American (white and African-American) patients with SLE. PD results were consistent with belimumab inhibiting BLyS, and belimumab was well tolerated. These data support the use of belimumab in Chinese patients with SLE. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02880852. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40744-020-00193-9) contains supplementary material, which is available to authorized users.