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Abstract 1730: A translational platform using primary human immune cells in vitro, syngeneic and humanized models in vivo to support and advance immuno-oncology drug discovery

Charles River Laboratories (CRL) has established a powerful translational immuno-oncology platform with the capability of progressing biologics or small-molecule modulators of immune response from in vitro to in vivo assays using human and mouse variants of current checkpoint inhibitors and small molecules. Utilizing a blood donor panel, our in vitro platform includes primary human immune cell assays that profile T-cell activation, T cell mediated-cancer cell kill, expansion of T-cell populations, mixed lymphocyte reactions (MLR), T-cell invasion, and antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). The platform is currently being expanded to determine the effect of activated immune cell populations on tumor cell spheroid cultures. It has been validated with standard-of-care chemotherapeutics, including anti-CTLA4, anti-PD1 and a selection of small-molecule inhibitors of targets known to modulate immune responses including IDO inhibitors. Ex vivo analysis of activated mouse splenocyte response to checkpoint inhibitors, measured as cytokine release, and modulation of immune cell populations, as determined by flow cytometry, supports the translation of important compounds from the bench to preclinical models. Syngeneic mouse tumor models have frequently been used to profile immune responses in tumors; CRL has optimized and profiled existing checkpoint inhibitors to support immuno-oncology drug discovery using mouse and rat antibody variants of anti-CTLA4 and anti-PD1. To confirm the translational development of our platform in human tissue, CRL has developed and optimized humanized mouse models using subcutaneous implanted patient-derived xenografts (PDX) with human engraftment via CD34+ haematopoeitic stem cells in NOG mice, which were treated with anti-CTLA4 and anti-PD1. Infiltration of human immune cells and PDL-1 expression was detected by flow cytometry (FC) and immunohistochemistry (IHC) in hematopoietic organs and tumor tissue, supporting the initial in vitro response in primary immune cells. Here we present a screening platform, validated with standard-of-care chemotherapeutics, which will support translation of compounds from in vitro primary immune cell assays to modulation of mouse immune cell population in spleen and tumors, resulting in efficacy and tumor immune cell activation in humanized mouse models. Citation Format: Martin O9Rourke, Shilina Roman, Gary Salmon, Ian Waddell, Julia Schueler, Edgar Wood. A translational platform using primary human immune cells in vitro, syngeneic and humanized models in vivo to support and advance immuno-oncology drug discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1730.