Abstract 1537: Anti-CD19 ARTEMIS™ T cells prevent excessive inflammatory cytokine release, including IL-6, in a co-culture model of CRS
Authors: Liu Hong , Horan Lucas H. , Grupp Stephan A. , Barrett David M. , Liu Cheng 
Published: August 2018

Abstract
We designed the ARTEMISTM T-cell signaling platform to be a safer ACT therapy by relying on endogenous T-cell signaling factors. We show evidence that the ARTEMISTM receptor disentangles efficacy from CRS and holds the potential to be a clinically safer therapy by preventing ACT-triggered CRS. Despite the remarkable curative potential of anti-CD19-CAR T cells the therapy continues to trigger a potentially life threatening cytokine release syndrome (CRS) that is characterized by excessive concentrations of inflammatory cytokines. We reasoned that by redesigning the T-cell activating antigen receptor to require signaling through the endogenous CD3 complex the T-cell could better regulate its cellular responses and thus reduce the risk of CRS when used as an adoptive T-cell transfer (ACT) therapy. Through protein engineering, we developed the ARTEMIS™ signaling platform which when coupled with Eureka's human anti-CD19 antibody, ET190L1, and expressed on primary T-cells, results in a significant reduction of cytokine release during antigen specific T-cell activation. When CAR vs. ARTEMIS™ comparisons were tested in vitro, ET190L1-ARTEMISTM T-cells and ET190L1-CD28z-CAR T-cells specifically lysed multiple CD19+ leukemia and lymphoma cell lines with similar potencies. However, during the 16 hour in vitro killing assays, ARTEMIS™ T-cells secreted demonstrably less IL-2, IFN-γ, GM-CSF, and TNFα as compared to CAR T-cells. ARTEMISTM T-cells also accumulated less PD-1, LAG3, and TIM3 on their surface during culturing and following in vitro killing, indicating a diminished propensity for exhaustion compared to corresponding CAR T-cells. The ability of the anti-IL6 antibody tocilizumab to mitigate toxicity in patients that develop severe CRS in the clinic suggests that limiting IL-6 expression could improve the safety of adoptive T-cell therapies. However, T-cells are not efficient expressors of IL-6 and the vast majority of elevated IL-6 is produced by monocytes in response to activated CAR T-cells. To assay the effects of T-cell cytotoxicity on upregulation of cytokine expression within monocytes as a model for CRS, we co-cultured T-cells with CD19-positive ALL tumor cells on one side of a transwell and monocytes on the other side. After tumor cell lysis, RNA expression levels were measured from both T-cells and monocytes. Using ET190L1-ARTEMIS™ T-cells to kill NALM-6 tumor cells resulted in dramatically reduced levels of IL-6 and IL-5 mRNA upregulation within monocytes compared to that observed with CAR transduced T-cells. When tested in vivo against CD19+ xenografts mouse models, intravenous administration of ET190L1-ARTEMISTM T-cells caused efficient tumor regression. In agreement with the in vitro data, mice treated with ARTEMISTM T-cells released significantly lower levels of cytokines in their blood at 24 hours post dosing than mice treated with CAR T-cells.
Citation Format: Hong Liu, Lucas H. Horan, Stephan A. Grupp, David M. Barrett, Cheng Liu. Anti-CD19 ARTEMIS™ T cells prevent excessive inflammatory cytokine release, including IL-6, in a co-culture model of CRS [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 1537.