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

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. 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. Peak serum concentrations of belimumab (Cmax) were obtained within the 1-h infusion. Geometric mean Cmax, 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− naive, CD20+/CD69+ active, CD20+/CD138+ plasmacytoid, CD19+/CD27BRIGHT/CD38BRIGHT 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. 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. ClinicalTrials.gov identifier, NCT02880852.