Locoregional delivery of IL-13Rx2-targeting CAR-T cells in recurrent high-grade glioma: a phase 1 trial

Diffuse high-grade glioma (HGG), particularly glioblastoma (GBM), is a highly aggressive and lethal cancer with poor response to standard-of-care (SOC) therapies. Tumor recurrence is inevitable and uniformly fatal. Chimeric antigen receptor T cell (CAR-T) therapy is an emerging treatment strategy. Several clinical trials have explored the feasibility and safety of CAR-T therapy targeting various tumor-associated antigens in gliomas, including IL-13Ra2, HER2, EGFRvIII, GD2, and B7H3. While showing promise in improving quality-of-life and survival in some patients, larger studies are needed to determine efficacy and resistance factors. IL-13Rα2, a cancer-testis antigen expressed by most HGGs, is a promising CAR-T target due to its association with poor prognosis and absence of expression in normal brain tissue. This study reports the findings of a phase I trial of IL-13Rα2-targeted CAR-T cells, the largest clinical study conducted to date on this approach.

The literature review section is implicitly present within the introduction and discussion sections. The introduction highlights existing research on CAR-T therapy for HGG and the promise of IL-13Rα2 as a target. The discussion section compares the findings of this trial to previous studies, referencing specific publications on CAR-T therapy and the tumor microenvironment in gliomas.

This single-center, non-randomized, five-arm, dose-escalation phase I study evaluated memory-enriched IL-13Rα2-CAR-T cells in recurrent HGG patients. The trial enrolled heavily pretreated patients with no restrictions on tumor size, multifocality, prior bevacizumab, or recurrence number. Patients received weekly infusions and were evaluated for dose-limiting toxicities (DLTs). The study evolved through five arms, testing three locoregional administration routes (intratumoral (ICT), intraventricular (ICV), and dual ICT/ICV) and two manufacturing platforms (central memory T cells (Tcm) and naive/stem cell memory/central memory T cells (Tn/mem)). Toxicity, disease response, overall survival (OS), cytokine dynamics, and tumor immune contexture biomarkers were monitored. The manufacturing process involved isolating peripheral blood mononuclear cells (PBMCs) from patients, enriching for specific T cell subsets, stimulating, transducing with lentivirus encoding the IL-13Rα2-CAR, and propagating to clinically relevant cell numbers. Imaging (MRI, FDG-PET) was used to assess disease response using modified RANO criteria. Quality of life (QOL) was evaluated using EORTC QLQ-C30. Immunohistochemistry (IHC) analyzed tumor samples for IL-13Rα2 and CD3 expression. Flow cytometry analyzed CAR-T cell products and samples from the central nervous system (CSF, tumor cavity fluid) and blood. Cytokine profiling used a 30-plex panel. qPCR measured CAR-T cell persistence. In vitro and in vivo models assessed CAR-T cell activity.

The study demonstrated that locoregional IL-13Rα2-targeted CAR-T cell therapy is feasible and safe with no dose-limiting toxicities. A maximum feasible dose of 200 × 10⁶ CAR-T cells per infusion cycle was achieved. Grade 3+ toxicities were rare (one grade 3 encephalopathy and one grade 3 ataxia). Stable disease or better was observed in 50% (29/58) of patients, including two partial responses and two complete responses. Median OS for all patients was 8 months (7.7 months for recurrent glioblastoma (rGBM)). Arm 5 demonstrated improved OS (10.2 months) compared to other arms. Central nervous system increases in inflammatory cytokines (IFNγ, CXCL9, CXCL10) were associated with CAR-T cell bioactivity. Pretreatment intratumoral CD3 T cell levels positively correlated with survival. The Tn/mem manufacturing platform yielded superior CAR-T cell products with a less differentiated memory phenotype, potentially contributing to improved outcomes in arm 5. CAR-T cells persisted in CSF and TCF and trafficked to the periphery. The IFNγ pathway emerged as a potential biomarker for CAR-T cell activity.

This study provides the largest dataset on CAR-T cell therapy in brain tumors. The findings highlight the safety and feasibility of locoregional IL-13Rα2-CAR-T cell administration. While overall survival benefit was modest, a subset of patients demonstrated clinical benefit, including improved OS in arm 5, which utilized a dual delivery method and an optimized Tn/mem manufacturing platform. The correlation between pretreatment intratumoral T cell levels and survival suggests that the tumor microenvironment is a critical determinant of response. The identification of the IFNγ pathway as a potential biomarker could help predict treatment response. These results support further exploration of IL-13Rα2-targeted CAR-T cell therapy, particularly with optimization of delivery and manufacturing to enhance efficacy and expand the population of patients who benefit from treatment.

This phase I trial demonstrates the safety and feasibility of locoregional IL-13Rα2-targeted CAR-T cell therapy for recurrent high-grade glioma. Arm 5, using dual ICT/ICV delivery and the Tn/mem platform, showed superior overall survival, suggesting potential for optimization to improve clinical outcomes. Further research should focus on identifying predictive biomarkers and strategies to overcome resistance.

This study was a single-center, non-randomized trial with a heterogeneous patient population. The multiple arms and evolving protocol design may affect comparative analysis. The relatively small sample size limits the statistical power of some analyses. The lack of randomization prevents definitive conclusions on the relative efficacy of the different delivery routes and manufacturing platforms.