Madalena M. A. Peyroteo1, Patrick Weber2, Philippe B. Pierrillas1, Christian Heichinger1, Henry Kao1, Antoine Soubret1, Christine McIntyre3, Cristina Santini1, Laura Codarri Deak2
1Roche Pharma Research and Early Development (pRED), Roche Innovation Center Basel, 2Roche Pharma Research and Early Development (pRED), Roche Innovation Center Zurich, 3Roche Pharma Research and Early Development (pRED), Roche Innovation Center Welwyn
INTRODUCTION: Tobemstomig is a 1+1 PD1-LAG3 bispecific antibody aiming to reinvigorate tumor-specific T-cells and overcome LAG3-mediated resistance to current checkpoint inhibitors (CPIs) by a preferential binding to T-cells that co-express PD-1 and LAG-3. Maximal blockade of both PD-1 and LAG-3 is required for the intended therapeutic effect. Therefore, understanding the binding dynamics of the molecule to each receptor is key to optimizing its potential. Tobemstomig has been evaluated in patients with solid tumors including non-small cell lung cancer. OBJECTIVES: Assess the binding dynamics and affinity of tobemstomig to PD-1 and LAG-3 receptors on activated CD4+ T cells, and determine the potency and selectivity gain using a novel competition binding mechanistic model; Investigate the dose-dependent targeting of T cells by tobemstomig, accounting for tumoral cell density and the molecule’s binding kinetics; Determine the minimal dose required to achieve > 90% targeting of T cells expressing PD-1 and/or LAG-3. METHODS : Tobemstomig’s binding dynamics are assessed by flow cytometry in a binding assay, using activated CD4+ T cells from healthy donors exposed to increasing concentrations of compound in presence or absence of anti-PD-1 or anti-LAG-3 competing antibodies to assess the potency of each binding arm and the avidity driven selectivity gain. The binding affinity to each receptor has been estimated by fitting the experimental data to a novel mechanistic model. Subsequently, a range of tobemstomig doses have been simulated using a minimal physiologically-based pharmacokinetic (mPBPK) model [1], describing both systemic and intratumoral concentrations of tobemstomig to identify the necessary dose for optimal receptor blockade of PD-1 and LAG-3. The mPBPK model incorporates the binding dynamics estimated from the in vitro data and patient variability in PK parameters and tumoral cell density of PD1 and/or LAG3 expressing cells. RESULTS : The mechanistic model that best fits the data identified five unique binding behaviors of tobemstomig, depending on receptor type and T-cell expression of PD-1 and LAG-3. As expected, it was found that tobemstomig has a higher affinity for PD-1 than for LAG-3 and preferentially binds to T-cells co-expressing both PD-1 and LAG-3 in a dose-dependent manner. Applying these findings in a mPBPK model and simulating the receptor occupancy (RO) of PD-1 and LAG-3 on TILs across a range of tobemstomig doses lead to the identification of the minimal required dose for maximal receptor blockade. Results indicate that TILs expressing only PD-1 or LAG-3 require a 100-fold increase in dose compared to TILs co-expressing both receptors. CONCLUSIONS : This study provides a detailed understanding of tobemstomig’s binding behavior, strengthening confidence in the kinetic parameters used in the mPBPK model and its dose-dependent binding profile. This approach offers a highly comprehensive and informative way to describe the binding dynamics of bispecific molecules, essential for optimizing their therapeutic potential.
[1] Li et al. Clin Pharmacol Ther. 2021 Jul;110(1):200-209
Reference: PAGE 33 (2025) Abstr 11555 [www.page-meeting.org/?abstract=11555]
Poster: Drug/Disease Modelling - Oncology