The in vivo fitting of the PK profile is the gold standard in antibody PK assays, since it permits the PK parameters to be determined separately for non-specific and target-dependent elimination. The findings presented herein demonstrate that the in vitro liver NPC assay using flow cytometry is a useful tool to determine the binding and uptake of biologics and to predict the PK. The concentration-dependent binding and uptake was measured to determine the PK parameters using monkey NPC, the FcγRIIB-expressing fraction of which was identified by CD31 and CD45. This approach was also extended to NPC from monkeys. A titration assay was performed to determine the PK parameters, and the obtained parameter was comparable to that determined by the fitting of the in vivo PK. In mice, the FcγRIIB-expressing cells were identified in the CD146-positive and CD45-negative fraction by flow cytometry. This study reports on the development of a cell-based assay for evaluating the binding and uptake of such an antibody using liver NPC of mice and monkeys. However, there is currently no in vitro quantitative assay using NPC.
Evaluation of the binding and uptake of an antibody in liver non-parenchymal cells (NPC), including liver sinusoidal endothelial cells, is important for revealing its pharmacokinetic (PK) behavior, since NPC has important roles in eliminating an antibody from the blood via the Fc fragment of IgG receptor IIB (FcγRIIB).
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