Study Design

In this popPK/PD analysis, PK data from 688 individuals from three studies [phase I: BEL116119 and BEL114448 (n = 134); phase III: BEL112341 [10] ({"type":"clinical-trial","attrs":{"text":"NCT01484496","term_id":"NCT01484496"}}NCT01484496; n = 554)] and PD data from BEL112341, for which the methods and results have been described previously [10, 12, 14], were analyzed using a popPK/PD approach (Table 1). The primary efficacy endpoint for Study BEL112341 was the SLE responder index 4 (SRI4), a composite index that includes a ≥4-point reduction in the Safety of Estrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index (SELENA-SLEDAI) [10].

Studies included in the belimumab population pharmacokinetic/pharmacodynamic (PK/PD) analysis

CD cluster of differentiation, dsDNA double-stranded DNA, IgG immunoglobulin G, IV intravenous, SAEs serious adverse events, SC subcutaneous, SELENA-SLEDAI Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus, SLE systemic lupus erythematosus, SRI systemic lupus erythematosus responder index

All subjects with evaluable dosing, actual sampling time, and belimumab concentration data were included in the popPK dataset and analysis. All subjects and placebo subjects with evaluable PD efficacy/safety data were included in the popPK/PD dataset and analysis.

Serum concentrations of belimumab were determined by a validated electrochemiluminescence‐based immunoassay with a lower limit of quantitation of 100 ng/mL of belimumab in human serum.