Eradication of Neuroblastoma by T Cells Redirected with an Optimized GD2-Specific Chimeric Antigen Receptor and Interleukin-15

Abstract

Purpose: A delay in encountering the cognate antigen while in the circulation, and the suboptimal costimulation received at the tumor site are key reasons for the limited activity of chimeric antigen receptor-redirected T cells (CAR-T) in solid tumors. We have explored the benefits of incorporating the IL15 cytokine within the CAR cassette to provide both a survival signal before antigen encounter, and an additional cytokine signaling at the tumor site using a neuroblastoma tumor model. Experimental Design: We optimized the construct for the CAR specific for the NB-antigen GD2 without (GD2.CAR) or with IL15 (GD2.CAR.15). We then compared the expansion, phenotype, and antitumor activity of T cells transduced with these constructs against an array of neuroblastoma cell lines in vitro and in vivo using a xenogeneic metastatic model of neuroblastoma. Results: We observed that optimized GD2.CAR.15-Ts have reduced expression of the PD-1 receptor, are enriched in stem cell-like cells, and have superior antitumor activity upon repetitive tumor exposures in vitro and in vivo as compared with GD2.CAR-Ts. Tumor rechallenge experiments in vivo further highlighted the role of IL15 in promoting enhanced CART antitumor activity and survival, both in the peripheral blood and tissues. Finally, the inclusion of the inducible caspase-9 gene (iC9) safety switch warranted effective on demand elimination of the engineered GD2. CAR.15-Ts. Conclusions: Our results guide new therapeutic options for GD2.CAR-Ts in patients with neuroblastoma, and CART development for a broad range of solid tumors.

Monitoring Immune Responses in Neuroblastoma Patients during Therapy

“…Thirdly, immune monitoring in this phase 1 study indicated a correlation between circulating IL-15 levels and GD2 CAR T cell expansion [89]. Circulating IL-15 levels could not only potentially be used as a biomarker for CAR T cell expansion, but a pre-clinical xenograft mouse model transduced with GD2 CAR T cells overexpressing IL-15 also showed improved expansion, enhanced anti-tumor activity and improved survival [93].…”

“…Infused cells can be isolated from PB [82][83][84][85], as well as from tumor tissue (e.g., TILs) [8,20]. In addition, isolated cells can be genetically modified to improve recognition of tumor cells, for example through knock-in of a NBL-specific T cell receptor (TCR) [40,86,87], a chimeric antigen receptor (CAR) [20,[88][89][90][91][92][93][94][95], or a bispecific antibody [96,97] against tumor specific targets such as GD2, PRAME, NY-ESO-1, L1-CAM, B7-H3, and mutated ALK. Very low or even absent surface expression of major histocompatibility complex I (MHC-I) on NBL cells has led to the focus on MHC-I unrestricted ACT-strategies, mainly exploiting NK cell-and CAR therapy (or a combination of both).…”

GD2-targeted chimeric antigen receptor T cells prevent metastasis formation by elimination of breast cancer stem-like cells

“…51 Further engineering will improve the efficacy of GD2-CAR-T, for example by coexpression of IL15. 52 Moreover, GD2-CAR-T effector function might be enhanced with additional immune checkpoint blockade. 53 In conclusion, we report for the first time, that GD2directed immunotherapy by GD2-CAR-T can prevent metastasis formation in a highly aggressive model of TNBC.…”

Chimeric Antigen Receptor Cell Therapy: Overcoming Obstacles to Battle Cancer

“…Finally, the emergence of "Armored CARs" that constitutively secrete cytokines such as IL-12. IL-15 and IL-18 also provided further hope that more sophisticated engineering of CAR-T cells can overcome the persistence issue all together ( Figure 1B) [70][71][72][73].…”