Whole-Body Pharmacokinetics of Antibody in Mice Determined using Enzyme-Linked Immunosorbent Assay and Derivation of Tissue Interstitial Concentrations

Abstract

Here we have reported whole-body disposition of wild-type IgG and FcRn non-binding IgG in mice, determined using Enzyme-Linked Immunosorbent Assay (ELISA). The disposition data generated using ELISA are compared with previously published biodistribution data generated using radiolabelled IgG. In addition, we introduce a novel concept of ABC_IS values, which are defined as percentage ratios of tissue interstitial and plasma AUC values. These values can help in predicting tissue interstitial concentrations of monoclonal antibodies (mAbs) based on the plasma concentrations. Tissue interstitial concentrations derived from our study are also compared with previously reported values measured using microdialysis or centrifugation method. Lastly, the new set of biodistribution data generated using ELISA are used to refine the PBPK model for mAbs.

Keywords: Antibody biodistribution coefficient; Antibody interstitial concentration; Antibody pharmacokinetics; ELISA; Neonatal Fc receptor (FcRn); Tissue biodistribution.

Figure 1.. Observed, total, and interstitial concentrations of IgG and FcRn non-binding IgG in plasma and 11 tissues.

Measured tissue concentrations of IgG (black circle) and FcRn non-binding IgG (black square) are presented. After accounting for residual blood content, total tissue concentration of IgG (grey circle) and FcRn non-binding IgG (grey square) were calculated. Tissue interstitial concentration of IgG (white circle) and FcRn non-binding IgG (white square) were calculated from measured tissue concentrations. PK profiles of IgG and FcRn non-binding IgG in non-target expressing tumor, MDA-MB-468, are also presented.

Figure 2.. Comparison of antibody biodistribution in different studies.

Total tissue concentrations of IgG (black circle) are compared with tissue concentrations of I-125 labelled IgG in wild-type mice from Garg et al. (grey circle) and Chen et al. (white circle) studies. Total tissue concentrations of FcRn non-binding IgG (black square) are compared with tissue concentrations of I-125 labelled IgG in FcRn knockout mice from Garg et al (grey square) and Chen et al. (white square) studies. The reported concentrations in brain from Garg et al. and Chen et al. were corrected with residual blood content, and thus measured tissue concentration of IgG (black circle) and FcRn non-binding IgG (black square) are presented for comparison.

Figure 3.. Percentage change of tissue-to-plasma area under the curve ratios (T/P) between IgG and FcRn non-binding IgG.

Area under the curve (AUC_0-t) were AUC_{0–168 h} and AUC_{0–72 h} for IgG and FcRn non-binding IgG.

Figure 4.. Comparison of the PBPK model-predicted vs. measured concentrations of IgG and FcRn non-binding IgG.

Comparison of the refined platform PBPK model predicted IgG (black solid line) and FcRn non-binding IgG (black dash line) with measured concentrations of IgG (circle) and FcRn non-binding IgG (square). The refined platform PBPK model better characterized the observed data than PK profiles of IgG (grey dash line) and FcRn non-binding IgG (grey dot line) simulated by previously published platform PBPK model.

Figure 5.. Comparison of interstitial tissue concentration of IgG obtained from different studies.

Tissue interstitial concentration of IgG (black circle) calculated from our measured tissue IgG concentrations were compared with Jadhav et al. study (black square), which directly measured interstitial concentrations of IgG by using microdialysis, and Eigenmann et al. study (white circle), which used tissue centrifugation method. Tissue interstitial concentrations of IgG (dashed line) predicted by the refined platform PBPK model are also presented.