{
  "abstract": "Background Multispecific antibody cancer therapies and other Ab-based therapies such as antibody-drug conjugates (ADCs) depend on efficient targeting and internalization of tumor-associated antigens. However, many highly expressed cancer targets internalize at different rates, making the selection of combinations challenging. A mechanistic understanding of the processes involved in targeting and internalization of these multispecifics is critical for designing effective therapeutic strategies. We developed a mechanistic model that describes an exemplar bispecific antibody combination, in which the rapidly internalizing target EphA2, overexpressed in proliferating epithelial cancers facilitates the uptake of the slowly internalizing target ALCAM, which is associated with metastasis and cancer progression.Methods To investigate a guide-effector strategy in bispecific antibody systems, we developed a computational model based on ordinary differential equations (ODEs). This model encompasses key processes, such as the binding of the bispecific antibody to its targets—EphA2 and ALCAM, antigen turnover, the formation of receptor-antibody complexes (both dimers and trimers), and the endocytosis of free and bound receptors. The model simulations were validated using published experimental data. 1 Results Simulations showed that while a monoclonal anti-ALCAM antibody failed to induce ALCAM internalization, the bispecific antibody (3F1/RYR), co-targeting ALCAM with the rapidly internalizing EphA2, induced ALCAM removal at an EphA2: ALCAM ratio of 9.7: ~60% internalization by 1 hour (vs. 52% observed), ~86% by 4 hours (vs. 86% observed), and ~99% by 24 hours (vs. 90% observed) ( figure 1A). Interestingly, ALCAM engagement in the bispecific complex also slowed EphA2’s rapid internalization. At a low EphA2: ALCAM ratio (0.2), simulated bispecific-mediated EphA2 (3F1/RYR) internalization was ~40%, compared to ~60% with a monospecific anti-EphA2 antibody(C10/RYR), aligning well with observed data (figure 1B). These findings highlight the complex interplay between target antigens within this bispecific system.Simulations also revealed that the EphA2: ALCAM surface ratio determined the extent of ALCAM internalization by the bispecific antibody. Higher ratios of EphA2 to ALCAM resulted in greater ALCAM surface removal, as confirmed by experimental results (table 1). Thus, simulation demonstrates that increasing the guide antigen (EphA2) enhances the internalization of the effector antigen (ALCAM).Conclusions Our study establishes a validated mechanistic framework for guide-effector interactions in bispecific antibodies and ADCs. This framework provides a tool to select antigen combinations, optimize antigen internalization and improve payload delivery in cancer treatment.Reference Lee NK, Su Y, Bidlingmaier S, Liu B. Manipulation of cell-type selective antibody internalization by a guide-effector bispecific design. Mol Cancer Ther. 2019 Jun;18(6):1092–1103Abstract 1124 Figure 1Antibody mediated surface internalization of surface ALCAM (A) and surface EphA2 (B) mediated by different antibodies. Abbreviations: 3F1: monocloncal Ab against ALCAM; 3f1/RYR, bispecific Ab against both ALCAM and EphA2; C10/RYR Ab against EphA2Abstract 1124 Table 1Impact of EphA2: ALCAM ratio on ALCAM internalization by bispecific antibody: simulated vs. observed% at 24 hours",
  "authors": [
    {
      "affiliations": [
        "Differentia Biotech P Ltd, South San Francisco, CA, USA"
      ],
      "name": "Rajeev Kumar"
    },
    {
      "affiliations": [
        "Differentia Biotech P Ltd, South San Francisco, CA, USA"
      ],
      "name": "Kalyanasundaram Subramanian"
    }
  ],
  "title": "1124 Optimizing cancer targeting: mechanistic modeling of a bispecific guide-effector strategy",
  "uid": "e96a838b-d9ad-52a4-bd12-110fc7df16eb"
}