Predictive modelling and simulation for taming the chance and luck in biologics drug discovery

Three Pillars of Survival paradigm in the pharmaceutical drug discovery stipulates that a drug candidate is more likely to reach Phase III if it meets the following criteria: 1) it reaches the required tissue compartment, 2) engages the desired target, 3) triggers the desired downstream pharmacological effect. This paper describes the progress made along this track for biologics, in the first instance for monoclonal antibodies, their fragments and therapeutic proteins in general. Cross­species/cross­modality physiologically­based pharmacokinetics (PBPK) framework aims to provide the first principle quantitative predictions for the first two of the declared Pillars. The approach is based on two­pore hypothesis of extravasation, further developed with PBPK in mind and parameterized for fractional tissue lymph flow rates using rodent data. The biologics PBPK framework is validated by accurately predicting the tissue distribution and elimination properties of normal and modified antibodies and their fragments in primate and human studies

Modelling bispecific monoclonal antibody interaction with two cell membrane targets indicates the importance of surface diffusion

We have developed a mathematical framework for describing a bispecific monoclonal antibody interaction with two independent membrane-bound targets that are expressed on the same cell surface. The bispecific antibody in solution binds either of the two targets first, and then cross-links with the second one whilst on the cell surface, subject to rate-limiting lateral diffusion step within the lifetime of the monovalently engaged antibody-antigen complex. At experimental densities, only a small fraction of the free targets is expected to lie within the reach of the antibody binding sites at any time. Using ordinary differential equation and Monte Carlo simulation-based models, we validated this approach against an independently published anti-CD4/CD70 DuetMab experimental data set. As a result of dimensional reduction, the cell surface reaction is expected to be so rapid that, in agreement with the experimental data, no monovalently bound bispecific antibody binary complexes accumulate until cross-linking is complete. The dissociation of the bispecific antibody from the ternary cross-linked complex is expected to be significantly slower than that from either of the monovalently bound variants. We estimate that the effective affinity of the bivalently bound bispecific antibody is enhanced for about four orders of magnitude over that of the monovalently bound species. This avidity enhancement allows for the highly specific binding of anti-CD4/CD70 DuetMab to the cells that are positive for both target antigens over those that express only one or the other We suggest that the lateral diffusion of target antigens in the cell membrane also plays a key role in the avidity effect of natural antibodies and other bivalent ligands in their interactions with their respective cell surface receptors

Toward systems-informed models for biologics disposition: covariates of the abundance of the neonatal Fc Receptor (FcRn) in human tissues and implications for pharmacokinetic modelling

Biologics are a fast-growing therapeutic class, with intertwined pharmacokinetics and pharmacodynamics, affected by the abundance and function of the FcRn receptor. While many investigators assume adequacy of classical models, such as allometry, for pharmacokinetic characterization of biologics, advocates of physiologically-based pharmacokinetics (PBPK) propose consideration of known systems parameters that affect the fate of biologics to enable a priori predictions, which go beyond allometry. The aim of this study was to deploy a systems-informed modelling approach to predict the disposition of Fc-containing biologics. We used global proteomics to quantify the FcRn receptor [p51 and β2-microglobulin (B2M) subunits] in 167 samples of human tissue (liver, intestine, kidney and skin) and assessed covariates of its expression. FcRn p51 subunit was highest in liver relative to other tissues, and B2M was 1–2 orders of magnitude more abundant than FcRn p51 across all sets. There were no sex-related differences, while higher expression was confirmed in neonate liver compared with adult liver. Trends of expression in liver and kidney indicated a moderate effect of body mass index, which should be confirmed in a larger sample size. Expression of FcRn p51 subunit was approximately 2-fold lower in histologically normal liver tissue adjacent to cancer compared with healthy liver. FcRn mRNA in plasma-derived exosomes correlated moderately with protein abundance in matching liver tissue, opening the possibility of use as a potential clinical tool. Predicted effects of trends in FcRn abundance in healthy and disease (cancer and psoriasis) populations using trastuzumab and efalizumab PBPK models were in line with clinical observations, and global sensitivity analysis revealed endogenous IgG plasma concentration and tissue FcRn abundance as key systems parameters influencing exposure to Fc-conjugated biologics

Liver-Targeting of Interferon-Alpha with Tissue-Specific Domain Antibodies

PMCID: PMC3581439This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Pharmacokinetic Characteristics, Pharmacodynamic Effect and In Vivo Antiviral Efficacy of Liver-Targeted Interferon Alpha

Work carried out by JM was funded by the National Institutes of Health (NIH). NIH contract number is HHSN272201000039I/HHSN27200001/ A19

Application of quantitative protein mass spectrometric data in the early predictive analysis of membrane-bound target engagement by monoclonal antibodies

ABSTRACTModel-informed drug discovery advocates the use of mathematical modeling and simulation for improved efficacy in drug discovery. In the case of monoclonal antibodies (mAbs) against cell membrane antigens, this requires quantitative insight into the target tissue concentration levels. Protein mass spectrometry data are often available but the values are expressed in relative, rather than in molar concentration units that are easier to incorporate into pharmacokinetic models. Here, we present an empirical correlation that converts the parts per million (ppm) concentrations in the PaxDb database to their molar equivalents that are more suitable for pharmacokinetic modeling. We evaluate the insight afforded to target tissue distribution by analyzing the likely tumor-targeting accuracy of mAbs recognizing either epidermal growth factor receptor or its homolog HER2. Surprisingly, the predicted tissue concentrations of both these targets exceed the Kd values of their respective therapeutic mAbs. Physiologically based pharmacokinetic (PBPK) modeling indicates that in these conditions only about 0.05% of the dosed mAb is likely to reach the solid tumor target cells. The rest of the dose is eliminated in healthy tissues via both nonspecific and target-mediated processes. The presented approach allows evaluation of the interplay between the target expression level in different tissues that determines the overall pharmacokinetic properties of the drug and the fraction that reaches the cells of interest. This methodology can help to evaluate the efficacy and safety properties of novel drugs, especially if the off-target cell degradation has cytotoxic outcomes, as in the case of antibody-drug conjugates

Analysis of IFN inducible gene expression in liver by mIFNα2-dAb fusions.

<p>Targeted mIFNα2 and non-targeted mIFNα2 were administered at 2μg/kg and 20μg/kg via intravenous injection. Vehicle control was also included. Levels of invariant and IFN inducible gene expression were analysed by TaqMan. Data shown are mean n = 4 animals. Error bars represent 95% CI.</p

Quantitative analysis of mIFNα2 and mIFNα2-dAb biodistribution.

<p>Quantitative analyses of ¹¹¹In labelled mIFNα2 and fusion protein levels were carried out 3 hours after intravenous administration in BALB/c mice via tail vein injection of approximately 0.5 MBq radiolabeled compound. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057263#s3" target="_blank">Results</a> show accumulation of radiolabelled mIFNα2-dAb fusions in mouse liver is considerably higher than that observed with mIFNα2. Data also shows increased hepatic accumulation of mIFNα2-DOM26h-196-61 compared to mIFNα2-DOM26h-V_HD2 isotype control. Error bars shown represent standard deviation of the mean, n = 4 (n = 3 in the case of mIFNα2).</p

<i>In vitro</i> activity of mIFNα2 formatted as dAb fusions.

<p>Activity of the mIFNα2-dAb fusion proteins was tested in the B16-Blue™ assay and compared to unfused mIFNα2 standard. Error bars are not visible as they are smaller than the data points, but represent standard error of the mean of 3 independent experiments. mIFNα2-DOM26h-196-61 (dashed line, closed circles) and mIFNα2-V_HD2 isotype control (dotted line, closed diamonds) showed comparable activity to the H₆-mIFNα2 standard (solid line, closed squares), with only minor increases in the EC₅₀.</p