Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Here we have investigated whole-body pharmacokinetics (PK) of exogenously administered T cells in a mouse model of melanoma and have developed a physiologically based pharmacokinetic (PBPK) model to quantitatively characterize the data. T cells were isolated from the spleen of tumor-bearing mice, activated, and labeled with chromium-51 to facilitate the quantification. Labeled T cells were injected in the tumor-bearing mice, and PK was measured in 19 different tissues. It was found that T cells disappear from the blood rapidly after administration and accumulate in the tissues to various extents. Spleen, liver, lung, kidney, bone, and lymph nodes accounted for more than 90% of T cells in the body. The distribution of T cells in solid tumors was found to be very low, hovering below 1%ID/g (percent of injected dose per gram of tissue) during the entire study. However, this observation may differ for targeted TCR-T and CAR-T cells. Observed PK profiles also suggest that T-cellbased therapies may be more successful in treating cancers of the lymphatic system and bone marrow metastases compared to solid tumors. A PBPK model was developed to characterize the whole-body PK of T cells, which incorporated key processes such as extravasation, elimination, and recirculation of T cells via lymph flow. Retention factors were incorporated into the spleen, liver, and kidney compartment to adequately capture the PK profiles. The model was able to characterize observed PK profiles reasonably well, and parameters were estimated with good confidence. The PK data and PBPK model presented here provide unprecedented insight into the biodistribution of exogenously administered T cells.

Age‐related central neurodegenerative diseases, such as Alzheimer's and Parkinson's disease, are a rising public health concern and have been plagued by repeated drug development failures. The complex nature and poor mechanistic understanding of the etiology of neurodegenerative diseases has hindered the discovery and development of effective disease‐modifying therapeutics. Quantitative systems pharmacology models of neurodegeneration diseases may be useful tools to enhance the understanding of pharmacological intervention strategies and to reduce drug attrition rates. Due to the similarities in pathophysiological mechanisms across neurodegenerative diseases, especially at the cellular and molecular levels, we envision the possibility of structural components that are conserved across models of neurodegenerative diseases. Conserved structural submodels can be viewed as building blocks that are pieced together alongside unique disease components to construct quantitative systems pharmacology (QSP) models of neurodegenerative diseases. Model parameterization would likely be different between the different types of neurodegenerative diseases as well as individual patients. Formulating our mechanistic understanding of neurodegenerative pathophysiology as a mathematical model could aid in the identification and prioritization of drug targets and combinatorial treatment strategies, evaluate the role of patient characteristics on disease progression and therapeutic response, and serve as a central repository of knowledge. Here, we provide a background on neurodegenerative diseases, highlight hallmarks of neurodegeneration, and summarize previous QSP models of neurodegenerative diseases.

Lu et al. show that tackling obesity with bispecific molecules that antagonize/ agonize GIPR/GLP-1R pathways decreases body weight and metabolic parameters in obese mice and monkeys. Mechanistic studies suggest that such molecules bind to GIPR and GLP-1R simultaneously and trigger receptor internalization, amplifying endosomal cAMP signaling in cells expressing both receptors.

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In this investigation, we test the hypothesis that treatment with sorafenib, an anti-angiogenic agent, decreases tumor vascularization and, consequently, hinders the delivery of monoclonal antibodies (mAb) to xenograft tumors. Severe combined immunodeficiency mice bearing carcinoembryonic antigen (CEA) expressing tumor xenografts were divided into control and sorafenib-treated groups. Sorafenib was administered to the latter group at 50 mg/kg IP every 48 h, starting 4 days post-tumor implantation. When tumors attained a size of 200-300 mm(3), mice were evaluated for (a) tumor microvessel density (using immunohistochemical analysis), (b) tumor macromolecular extravasation (using Evans Blue Dye (EBD)), (c) pharmacokinetics of an anti-CEA mAb, T84.66, following an intravenous dose of 10 mg/kg, and (d) intra-tumoral spatial distribution of T84.66 (using autoradiography). Sorafenib treatment resulted in a substantial reduction in tumor growth rate, a visible reduction in tumor microvessel density, and in a 46.4% decrease in EBD extravasation in tumor tissue (p < 0.0455). For control and treated mice, no significant difference was found for the area under the mAb plasma concentration-time curve (AUC(0-7d): 1.67 × 10(3) ± 1.28 × 10(2) vs. 1.76 × 10(3) ± 1.75 × 10(2) nM × day, p = 0.51). However, tumor AUC(0-7d) was reduced by 40.8% in sorafenib-treated mice relative to that observed in control mice (5.61 × 10(2) ± 4.27 × 10(1) vs. 9.48 × 10(2) ± 5.61 × 10(1) nM × day, p < 0.001). Sorafenib therapy was also found to markedly alter mAb tumor spatial distribution. The results collectively suggest that sorafenib treatment causes a significant reduction in mAb delivery to, and distribution within, solid tumors.