Apolline Lefevre1, Omar Abdelmotaleb2, Zinnia P. Parra-Guillen1, Iñaki F. Troconiz1, Anneliese Schneider2, Christophe Boetsch2, Nicolas Frances2
1 Pharmacometrics & Systems Pharmacology, Department of Pharmaceutical Science, School of Pharmacy and Nutrition, University of Navarra, 2Roche Pharma Research and Early Development (pRED), Pharmaceutical Sciences PS, Roche Innovation Center Basel
Introduction: CD3 T-cell Bispecific (TCB) antibodies, which redirect T-cells towards tumor cells showed promising results in the clinic. However, Cytokine Release Syndrome (CRS) remains a challenge for their clinical development. Several studies [1], [2] highlight the therapeutic window offered by TCB, where they can be effective without causing severe side effects like CRS. The primary objective of this work is to identify the optimal TCBs design that maximizes the therapeutic window, considering both potency (EC50) and maximal effect (Emax). The second objective is to leverage the formation of trimeric complexes (TC) between the T-cell, tumor cell and TCB to understand differences in cytokine release and tumor killing across various TCB constructs and assay conditions [3]. TC formation follows a bell-shape curve relative to TCB concentration. As such, there exists a TCB concentration at which the maximal number of TC is observed. Beyond this, the formation of dimers is favored, reducing the amount of TC and ultimately, pharmacological activity. This approach enables the investigation of how changes in TCB concentration, binding affinities and target receptor density impact the pharmacological effect and help in the interpretation of complex data. Methods: In this study, eight TCB constructs were generated, designed to target CEACAM5 (via bivalent binding) on tumor cell surface and CD3 (via monovalent binding) on T-cell surface. Two target binders with high or low affinity (0.1nM – 4.99nM), and four CD3 binders with affinities ranging from very low to high (52.40 to 0.93nM), were used [4]. Tumor cell killing and cytokine release were measured in-vitro using healthy donors PBMC, two different cell lines (with varying receptor densities) and ranging concentration up to 5’000pM for cytokine release and 50’000pM for tumor cell killing. The potency values and change of Emax were compared for each TCB construct in order to identify the design which maximizes the therapeutic window. The TC concentrations were simulated using ordinary differential equations (ODE) describing the binding processes for each experiment involving the different TCB constructs and target cell lines. The pharmacological activity (killing or cytokine release) was plotted in function of the amount of trimeric complexes formed. Modeling, simulations and data visualization were performed in Rstudio [5], using rxode2 package [6]. Results: Maximal effects on tumor killing and cytokine release were observed with high-affinity constructs to both target and CD3 arms. Changing the CD3 affinity increased the therapeutic window. In particular, intermediate binding affinity allowed to maintain similar levels of killing while significantly decreasing the amount of cytokine released, as described in [4]. The bell shape was observed mostly in the killing experiment, potentially explained by higher TCB concentrations tested compared to the cytokine release experiments. Additionally, the bell shape was more pronounced with high-affinity CD3 binders, aligning with trimeric complexes findings that lower concentration of TCB are needed to reach the maximum concentration of TC compared to low affinity (0.37nM vs 2.67nM respectively; high affinity target binder). Similar killing and cytokine release dynamics were observed for the different constructs when the effect was expressed in function of the TC. Indeed, from the quantitative framework, the relationship between the response from all experiments (TCB constructs and target cell lines) and the simulated trimeric complexes was observed and followed a sigmoidal function. Conclusion: Modification of the TCB’s binding affinity has direct impacts on the amount of TC formed and on the effect (tumor killing and cytokine release) observed in-vitro. The variability in the response was elucidated through the use of TC, and the same relationship between effect and TC was established for all experiments.
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Reference: PAGE 33 (2025) Abstr 11530 [www.page-meeting.org/?abstract=11530]
Poster: Drug/Disease Modelling - Oncology