Abstract 2200: Development and optimization of cost-effective non-human primate in vitro assays for immunogenicity screening and functional evaluation of immuno-oncology drug candidates

A surge in demand and a decrease in supply of non-human primate (NHP) test subjects have caused acritical shortage and a major price hike for biomedical research. Therefore, researchers are actively lookinginto refinement and/or alternatives to studies using NHP. The development of cost-effective NHP in vitroassays with predictive value for the assessment of unwanted immunogenicity as well as the functionalityof drug candidates can provide useful tools in this context. For instance, PBMCs isolated from blood,sourced from Cynomolgus Macaques, can be cryopreserved and thawed thereafter on multiple separateoccasions to be used for isolation of immune cell subsets of interest.The development of customized in vitro assays based on cynomolgus monkey PBMCs can be used for thepre-selection of drug candidates and therefore reduce the number of NHP that are required for in vivostudies. For instance, cynomolgus PBMCs can be used to evaluate the unwanted immunogenicity of testcompounds in vitro. Here, it was shown that ATR-107, an anti-IL21R antibody and Bococizumab triggeredsignificant proliferation of cynomolgus PBMCs. Furthermore, using immunopeptidomics (in collaborationwith ImmuneSpec) Infliximab-derived peptide fragments that are known to be immunogenic in humanwere found to be presented at the surface of cynomolgus dendritic cells after their incubation withInfliximab during their maturation.We previously reported the development of cynomolgus monkey PBMC-derived in vitro assays that canbe used for the functional evaluation of new drug candidates (e.g., macrophage reprogramming, cytokinerelease, M2-suppression assay, ADCP etc.), target binding studies as well as Cynomolgus Macaque PBMCx human dendritic cell (DC) mixed lymphocyte reactions (MLR). Continuous efforts to optimize these assayscan additionally minimize the requirements of cynomolgus monkey material. For instance, it was shownthat by adapting the cell culture conditions for the generation of cynomolgus macrophages, cell yields canbe substantially improved, reducing the number of required PBMC samples, and allowing to perform largerassays for a given amount of NHP material.With our expanding portfolio and continuous optimization of Cynomolgus Macaque assays we aim to aidbiomedical drug development and to refine/reduce NHP usage. Citation Format: Christoph Schifflers, Vlaming Martijn, Emmanuelle Sidot, Jezabel Lefevre, Elise Pepermans, Ellen Boelen, Sofie Pattyn. Development and optimization of cost-effective non-human primate in vitro assays for immunogenicity screening and functional evaluation of immuno-oncology drug candidates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2200.