Abstract 90: In vitro functional evaluation of immuno-oncology drug candidates in customized bioassays

Abstract Increased understanding of the complex tumor microenvironment and its interactors has boosted therapeutic interest and highlighted the importance of the development of innovative in vitro bioassays to represent all the players of the cancer immune response and thereby potentially provide pivotal information on the functional dynamics of candidate therapeutics. Regulatory T cells play an important role by downregulating the anti-tumor response. Their regulation mechanisms constitute an important target for new therapeutics. To study these mechanisms in a human model, suppressive Treg bioassays, mimicking the suppressive action of these cells, were developed and optimized. We further highlight the study of neutrophil function in vitro using flow-cytometry or the Incucyte® live imaging system to monitor neutrophil functions such as antibody-dependent cell-mediated cytotoxicity (ADCC), Neutrophil Extracellular Traps (NETs) formation and the release of Reactive Oxygen Species (ROS). Additionally, multiplex cytokine and peroxidase enzyme analysis after activation and stimulation of neutrophils can be evaluated using ELISA or Luminex technology. Moreover, to refine/reduce non-human primate (NHP) usage, we aimed to develop cost-effective NHP in vitro assays with predictive value for in vivo studies. We isolated Cynomolgus Macaque monocytes and successfully differentiated/polarized them into M0- and M2-like macrophages with a cell surface phenotype comparable to that of their human counterparts. We further developed a Cynomolgus Macaque PBMC x human dendritic cell (DC) mixed lymphocyte reaction (MLR) assay for functional evaluation of test compounds, effectively generated Cynomolgus Macaque immature DCs and implemented Cynomolgus Macaque cytokine release assays. Using high quality primary human immune cells from our own biobank, in vitro bioassays have been developed with superior robustness and reproducibility to screen candidate Immuno-Oncology therapeutics. Citation Format: Martijn Vlaming, Emmanuelle Sidot, Jezabel Lefèvre, Ellen Boelen, Sofie Pattyn. In vitro functional evaluation of immuno-oncology drug candidates in customized bioassays abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 90.