Abstract 4093: Dual targeted CAR immunotherapy for neuroblastoma using γδ T cells
Authors: Jonus Hunter C. , Lee Jasmine Y. , Silva Jordan A. , Spencer H. Trent , Goldsmith Kelly C. 
Published: April 2023

Abstract
Cellular immunotherapy for aggressive pediatric solid tumors like neuroblastoma (NB) has focused on autologous products of αβ T cells, that so far, have been uniformly unsuccessful. γδ T cells offer a potentially superior, off-the-shelf therapy that is directly cytotoxic towards tumors without alloreactivity. Furthermore, γδ T cell infiltration of the hostile, solid tumor microenvironment is a prognostic marker of favorable disease outcome. Our team recently opened a first-in-child evaluation of unengineered allogeneic γδ T cells in combination with dinutuximab, an anti-GD2 antibody, and chemotherapy (NCT05400603). Our focus now is to optimize a second-generation γδ T-cell therapy by engineering the expression of tumor targeting chimeric antigen receptors (CAR). We hypothesize that CAR-targeting will further enhance γδ T-cell homing and antitumor potency. While anti-GD2 antibodies have been clinically successful immunotherapies for NB, GD2-targeted cell therapies need improvement. Our team recently validated a novel immunotherapy target for NB, protein tyrosine kinase 7 (PTK7), an inactive tyrosine kinase expressed highly amongst all NBs with low to no normal pediatric tissue expression.
We designed a dual-targeting platform directed against both GD2 and PTK7 using γδ T cells, where CARs are separately encoded and dually expressed. Previously optimized transgenes containing GD2 or PTK7 scFv targeting domains followed by a CD8 hinge region, CD28 co-stim/trans-membrane domain, and CD3ζ signalling domain were inserted under the T7 promoter for mRNA production. Purified mRNA was electroporated into γδ T cells following their thaw from cryopreservation. Electroporation titrations were performed to optimize CAR expression to be detected up to 72 hours post-modification, which is compatible with the approximate in vivo lifespan γδ T cells in mice. Simultaneous expression of both CARs appears highest 24 h after electroporation, with ~70% of the target γδ T cell population modified. Anti-GD2/PTK7 γδ T cells are potent against the NB cell line IMR5 (GD2+PTK7+) in a 4 h cytotoxicity assay at effector:target ratios as low as 0.5:1. Importantly, specificity is also shown against NB cell lines genetically engineered to represent the clinical heterogeneity of GD2 and PTK7 expression that may be observed, where the dual CAR therapy is effective against GD2+PTK7+, GD2+PTK7−, and GD2−PTK7+, but not GD2−PTK7− NBs.
In conclusion, we developed a dual CAR-based cellular therapy for NB using γδ T cells as an effector population in place of classical αβ T cells. Early studies demonstrate feasibility for innovative dual CAR expression and show promise for strong anti-NB potency. Future work will optimize CAR signaling domains for maximal efficacy in solid tumors, as well as confirm efficacy and safety in vivo with results rapidly translatable into our established γδ T cell clinical trial pipeline.
Citation Format: Hunter C. Jonus, Jasmine Y. Lee, Jordan A. Silva, H. Trent Spencer, Kelly C. Goldsmith. Dual targeted CAR immunotherapy for neuroblastoma using γδ T cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4093.