Developing a PBPK/PD/Tox Modelling Framework for NANOBODY® Drug Conjugates
Soroush Safaei (1), Wilhelmus E. A. de Witte (2), Christelle Nonne (1), Tom Van Bogaert (1), Patrick Lécine (1), Veronique De Brabandere (1), Maria Laura Sargentini-Maier (1)
(1) Sanofi R&D, Ghent, Belgium (2) esqLABS GmbH, Saterland, Germany
Introduction: Sanofi R&D, Ghent, Belgium has initiated a project towards the rational design of NANOBODY®-Drug Conjugates (NDCs). NDCs are molecular constructs that consist of a NANOBODY® molecule, a linker and a small-molecule payload. NANOBODY® molecules consist of variable domains (around 14 kDa) derived from heavy-chain only antibodies as produced by camelids. These molecules can have an albumin binding domain that greatly increases their plasma half-life [1]. The aim of NDC development is to generate a molecule that binds specifically to a tumor target, which results in internalisation, degradation of the protein and intracellular release of the cytotoxic payload. The payload can kill the cells or stop their proliferation and can, depending on its physicochemical properties, diffuse through the cell membranes and kill neighbouring, non-target expressing cells known as the “bystander effect”.
This project aims to elucidate the NANOBODY® properties that influence the safety and efficacy of the NDCs. To that end, a series of tool compounds with strongly different values of a predefined properties (affinity, size, internalisation rate, isoelectric point, half-life) have been developed to study the impact of the NANOBODY® properties on plasma and tumor disposition, safety, and efficacy in several in vivo studies in mice. Integration of all these data in a PBPK/PD/Tox model is planned to quantify the impact of each parameter on efficacy and toxicity and to allow the prediction of efficacy and toxicity for new/hypothetical NDCs.
Objectives: The overall goal of this work is to develop a PBPK/PD/Tox framework to allow an integrated analysis of PK/PD, efficacy, and toxicity of a wide range of NDC molecules. This encompasses three specific objectives:
- To develop a functional model structure in MoBi® [2] that incorporates the relevant parameters to optimise NANOBODY® molecules for NDCs.
- To systematically investigate the model structure and the impact of relevant parameters to gain a better understanding of behavior of the biological system model.
- To evaluate and refine the model parameter values based on observed data with respect to plasma pharmacokinetics, distribution and tumor targeting, efficacy and toxicity in mice.
Methods: For PBPK/PD/Tox framework development, we extended the default PK-Sim® v11 [3] model for large molecules in MoBi® of the Open Systems Pharmacology Suite [4] to incorporate additional features of NDCs, including 3 NDC deconjugation pathways, tumor growth and shrinkage, with corresponding release of tumor content in plasma. We have also developed a two-region tumor module (exposed and deep regions to represent areas close and far from the vasculature) to replicate the “bystander effect”.
Each of these NDC constructs is modelled as a large molecule. Upon NDC clearance in the endosomes and NDC-target complex internalisation, the same deconjugation product will be released intracellularly for all NDC construct, which consists of a payload and a part of the payload-NANOBODY® linker. This molecule and potentially its main metabolite are modelled as a small molecule in the same model.
Results: Using the PBPK/PD/Tox framework, we performed sensitivity analysis and model characterisation to determine model sensitivity of plasma PK (NDC and toxophore), tumor PK (NDC and toxophore) and tumor growth inhibition for the following parameters: NDC dose, target concentration in tumor/other organs, target binding affinity, internalisation rate constant, FcRn binding, hydrodynamic radius, isoelectric point, elimination half-life, distribution kinetics between exposed and deep tumor compartment, tumor growth inhibition potency, toxicity EC50.
Conclusion: A PBPK/PD/Tox framework is developed which allows an integrated analysis of the in vivo data to evaluate the PK/PD and toxicity of a wide range of NDC molecules. We determined the model sensitivity of plasma PK, tumor PK and tumor growth inhibition for several parameters. The next step of this work is to perform sensitivity analysis towards NANOBODY® molecule optimisation for the following parameters: target concentration in tumor/other organs, target binding affinity, internalisation rate constant, FcRn binding, hydrodynamic radius, and elimination half-life.
References:
[1] Hoefman, Sven, Ingrid Ottevaere, Judith Baumeister, and Maria Sargentini-Maier. 2015. “Pre-Clinical Intravenous Serum Pharmacokinetics of Albumin Binding and Non-Half-Life Extended Nanobodies®.” Antibodies 4 (3): 141–56.
[2] Niederalt, C., Kuepfer, L., Solodenko, J., Eissing, T., Siegmund, H.U., Block, M., Willmann, S. and Lippert, J., 2018. A generic whole body physiologically based pharmacokinetic model for therapeutic proteins in PK-Sim. Journal of pharmacokinetics and pharmacodynamics, 45, pp.235-257.
[3] Willmann, S., Lippert, J., Sevestre, M., Solodenko, J., Fois, F. and Schmitt, W., 2003. PK-Sim®: a physiologically based pharmacokinetic ‘whole-body’ model. Biosilico, 1(4), pp.121-124.
[4] Lippert, J., Burghaus, R., Edginton, A., Frechen, S., Karlsson, M., Kovar, A., Lehr, T., Milligan, P., Nock, V., Ramusovic, S. and Riggs, M., 2019. Open systems pharmacology community - an open access, open source, open science approach to modeling and simulation in pharmaceutical sciences. CPT: pharmacometrics & systems pharmacology, 8(12), p.878.