Abstract 4512: Mouse Model for in Vivo Evaluation of Efficacy and Potential Cytokine Release Syndrome of Chimeric Antigen Receptor (CAR) T Cell Therapy

Abstract Chimeric antigen receptor (CAR) T-cell therapy holds great promise as cancer immunotherapy. While impressive responses have been achieved in patients with hematological malignancies there are challenges for CAR T therapy such as toxicity complications due to cytokine release syndrome (CRS) and limitations due to CAR T cell exhaustion. As increasing number of novel CAR T products are in the discovery and preclinical phase of development, preclinical models to assess efficacy as well as potential toxicity of CAR T in vivo are needed. Here, we describe a new NSG™ mice model to examine CAR T cells for efficacy and potential CRS. Immunodeficient NSG™ mice are commonly used to evaluate CAR T functions. However, human T cells can cause acute xeno-GVHD in NSG™ limiting the use of the model system. A system to study human T cell function in the absence of xeno-GVHD is required. A new NSG™ derivative NSG-MHC Class I/II knockout (KO) strain has MHC class I and MHC class II deficiency in addition to B, T and NK cell deficiency. NSG-MHC Class I/II KO mice are known to have a delayed onset of GVHD and can provide a useful background to study human immunity in the absence of GVHD [M. A. Brehm et al., FASEB J. 33, 3137–3151 (2019)]. Human B-cell lymphoma Raji tumor cells express high levels of CD19 and CD22 which are targets for CAR T therapy. Using NSG-MHC Class I/II KO mice and luciferase-tagged Raji-Luc tumor model we found that compared to controls CD22 CAR T and CD19 CAR T showed significant tumor growth inhibition by Xenogen imaging analysis. No body weight loss was observed with the CAR T treatments. As high tumor burdens are usually associated with the potential of causing CRS we examined CD19 CAR T cells on low and high tumor burdens and the data will be presented in context of efficacy. We have established a new mouse model using NSG-MHCI/II KO mice to enable evaluation of CAR T efficacy and propensity to induce cytokines simultaneously in vivo. Furthermore PBMC-humanized NSG-MHCI/II KO mice can also be established and used to examine CAR T cells prepared from the same PBMC donor to mimic autologous CAR T cell therapy. Citation Format: Jing Jiao, Chunting Ye, Danying Cai, Mingshan Cheng, James Keck. Mouse model for in vivo evaluation of efficacy and potential cytokine release syndrome of chimeric antigen receptor (CAR) T cell therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4512.