Optimization of IL13Rα2-Targeted Chimeric Antigen Receptor T Cells for Improved Anti-tumor Efficacy against Glioblastoma

Abstract

T cell immunotherapy is emerging as a powerful strategy to treat cancer and may improve outcomes for patients with glioblastoma (GBM). We have developed a chimeric antigen receptor (CAR) T cell immunotherapy targeting IL-13 receptor α2 (IL13Rα2) for the treatment of GBM. Here, we describe the optimization of IL13Rα2-targeted CAR T cells, including the design of a 4-1BB (CD137) co-stimulatory CAR (IL13BBζ) and a manufacturing platform using enriched central memory T cells. Utilizing orthotopic human GBM models with patient-derived tumor sphere lines in NSG mice, we found that IL13BBζ-CAR T cells improved anti-tumor activity and T cell persistence as compared to first-generation IL13ζ-CAR CD8 T cells that had shown evidence for bioactivity in patients. Investigating the impact of corticosteroids, given their frequent use in the clinical management of GBM, we demonstrate that low-dose dexamethasone does not diminish CAR T cell anti-tumor activity in vivo. Furthermore, we found that local intracranial delivery of CAR T cells elicits superior anti-tumor efficacy as compared to intravenous administration, with intraventricular infusions exhibiting possible benefit over intracranial tumor infusions in a multifocal disease model. Overall, these findings help define parameters for the clinical translation of CAR T cell therapy for the treatment of brain tumors.

Mechanisms of resistance to CAR T cell therapy

“…The patient had an impressive clinical response with complete regression of all intracranial and spinal tumours that lasted for 7.5 months 122 . Strategies to optimize IL-13Rα2-targeted strategies include designing a second-generation 4-1BB co-stimulatory domain-containing CAR product using enriched central memory T cells; in orthotopic glioblastoma models, this product was effective irrespective of corticosteroid treatment (a mainstay of glioblastoma therapy) and had higher efficacy with intraventricular infusions than intravenous delivery (and perhaps also than intratumour administration in the multifocal disease setting) 161 . Anti-GD2 CAR T cell therapy for histone H3 lysine 27-methylated (H3K27me) diffuse midline gliomas, a uniformly fatal type of paediatric CNS tumour, is another promising approach 162 .…”

Clinical chimeric antigen receptor‐T cell therapy: a new and promising treatment modality for glioblastoma

“…36 Follow-up animal studies show that IL-13Ra2-CAR-T cell therapy could be combined with dexamethasone without losing efficacy. 43 These results indicate that CAR-T cell effector activity is surprisingly robust, and may even argue against priming or re-priming effects, which can be perturbed by concomitant glucocorticoid therapy. 94 …”

CAR T cells for brain tumors: Lessons learned and road ahead

“…Drawing from work on cytotoxin‐conjugated IL‐13 that defined mutations which increased the specificity of IL‐13 for IL13Rα2 over the more ubiquitously expressed IL13Rα1/IL‐4Rα complex, an E13Y site‐directed mutation was introduced in IL‐13 . In vitro studies showed that CAR T cells were specific to glioma cells, and consistent with the different affinities of the IL‐13(E13Y) mutein for IL‐13 receptor forms, the engineered T cell activity was observed only against cell lines expressing IL13Rα2 . First‐generation IL13Rα2‐targeted CARs, termed IL13‐zetakine, demonstrated anti‐glioma activity in vitro and in vivo in mice, and second‐generation CAR designs with the inclusion of a 4‐1BB costimulatory domain and an optimized spacer domain improved anti‐tumor potency more than 10‐fold against human GBM xenografts …”