Abstract
Chimeric antigen receptor T cell (CAR-T) therapy is an emerging strategy to improve treatment outcomes for recurrent high-grade glioma, a cancer that responds poorly to current therapies. Here we report a completed phase I trial evaluating IL-13Rα2-targeted CAR-T cells in 65 patients with recurrent high-grade glioma, the majority being recurrent glioblastoma (rGBM). Primary objectives were safety and feasibility, maximum tolerated dose/maximum feasible dose and a recommended phase 2 dose plan. Secondary objectives included overall survival, disease response, cytokine dynamics and tumor immune contexture biomarkers. This trial evolved to evaluate three routes of locoregional T cell administration (intratumoral (ICT), intraventricular (ICV) and dual ICT/ICV) and two manufacturing platforms, culminating in arm 5, which utilized dual ICT/ICV delivery and an optimized manufacturing process. Locoregional CAR-T cell administration was feasible and well tolerated, and as there were no dose-limiting toxicities across all arms, a maximum tolerated dose was not determined. Probable treatment-related grade 3+ toxicities were one grade 3 encephalopathy and one grade 3 ataxia. A clinical maximum feasible dose of 200 × 106 CAR-T cells per infusion cycle was achieved for arm 5; however, other arms either did not test or achieve this dose due to manufacturing feasibility. A recommended phase 2 dose will be refined in future studies based on data from this trial. Stable disease or better was achieved in 50% (29/58) of patients, with two partial responses, one complete response and a second complete response after additional CAR-T cycles off protocol. For rGBM, median overall survival for all patients was 7.7 months and for arm 5 was 10.2 months. Central nervous system increases in inflammatory cytokines, including IFNγ, CXCL9 and CXCL10, were associated with CAR-T cell administration and bioactivity. Pretreatment intratumoral CD3 T cell levels were positively associated with survival. These findings demonstrate that locoregional IL-13Rα2-targeted CAR-T therapy is safe with promising clinical activity in a subset of patients. ClinicalTrials.gov Identifier: NCT02208362.
Main
Diffuse high-grade glioma (HGG) is an intractable cancer that responds poorly to standard-of-care (SOC) therapy of maximal surgical resection, focal radiation and chemotherapy1. Glioblastoma (GBM), defined as an isocitrate dehydrogenase (IDH)-wildtype World Health Organization (WHO) grade 4 astrocytoma, is the most aggressive type having the worst prognosis of HGGs. Despite intensive SOC treatment, tumor recurrence is inevitable and remains uniformly lethal with no current effective treatments2,3.
Chimeric antigen receptor T cell (CAR-T) therapy is being explored in early-stage clinical trials as a strategy to improve treatment outcomes for HGG. So far, the feasibility and safety of CAR-T therapy targeting a range of tumor-associated antigens in gliomas, including IL-13Rα2 (refs. 4,5,6), HER2 (refs. 7,8), EGFRvIII (refs. 9,10), GD2 (ref. 11) and B7H3 (ref. 12), have been reported. Encouragingly, a subset of patients in many of these early clinical trials have reported improved quality-of-life (QOL), objective responses, and noteworthy survival benefit. One case report from our institution demonstrated that locoregional delivery of IL-13Rα2-CAR-T cells mediated a complete response (CR) in a patient with multifocal recurrent GBM (rGBM)6,13. While these initial findings are encouraging, larger-scale clinical studies with more comprehensive correlative analyses are needed to better understand determinants of both antitumor potency and tumor resistance.
IL-13Rα2 is a cancer-testis antigen that is expressed by the majority of HGG, and in GBM is associated with a mesenchymal gene signature and poor prognosis14,15. The potential of IL-13Rα2 as a CAR-T target is further strengthened by the absence of expression in the normal brain tissue. Our group has optimized an IL-13 cytokine-directed CAR mutated at a single site (E12Y) and incorporating a 4-1BB costimulatory domain, which demonstrates preferential recognition of the intended target, IL-13Rα2, over IL-13Rα1, a low-affinity receptor that is more ubiquitously expressed16,17. In this Article, we report findings from a phase I trial of IL-13Rα2-targeted CAR-T cells for rGBM and other HGGs, representing the largest clinical study completed so far.
Results
Trial design and patient characteristics
We conducted a single-center, nonrandomized, five-arm, dose-escalation phase I study to evaluate memory-enriched IL-13Rα2-CAR-T cells for recurrent HGG (rHGG). This trial enrolled heavily pretreated patients with no enrollment restrictions for tumor size, multifocal disease, prior bevacizumab or number of recurrences, with approximately 75% of participants being treated following second recurrence or later and the majority being IDH-wildtype rGBM (41 of 58 response evaluable patients) (Table 1)18. Trial eligibility criteria included confirmed IL-13Rα2 tumor expression, Karnofsky Performance Score (KPS) ≥60 and life expectancy >4 weeks.
Patients were treated at one of three dose schedules of weekly infusions and evaluated for 1 week after the third cycle for dose-limiting toxicities (DLTs) (Fig. 1a,b). Additional infusions were allowed, and patients were followed for toxicities, response and survival until they progressed or required disallowed therapy. After patients went off protocol therapy, they were only followed for toxicities and survival, and not disease-response, since other therapies were allowed19, except for unique patient number (UPN) 109 who was also followed for anti-tumor response on a single-subject protocol (SSP) under NCT02208362 (SSP available in ref. 6).
This study evolved to evaluate five treatment arms testing three routes of locoregional administration and two manufacturing platforms (Fig. 1c). Delivery routes included the following: arm 1, intratumoral following biopsy (ICT-Biopsy); arm 2, intratumoral following maximal surgical resection (ICT-Resection); arm 3, intraventricular (ICV); and arms 4 and 5, ICT and ICV delivery (Dual ICT/ICV). In addition, two manufacturing platforms (Supplementary Fig. 1) were utilized in this trial differing in T cell subsets enriched for CAR engineering: arms 1–4 utilized CD62L+, CD45RA− central memory T cells (Tcm); and arm 5 utilized CD62L+ enriched naive, stem cell memory and central memory T cells (Tn/mem).
The trial opened as a two-arm study treating patients ICT following either biopsy (arm 1) or resection (arm 2). Arms 3–5 were added by protocol amendments based on clinical observations (Methods). ICV delivery (arm 3) was added on the basis of clinical experience with UPN109, in which ICV administered IL-13Rα2-CAR-T cells mediated a CR against multifocal rGBM6, along with preclinical data suggesting ICV was more effective against multifocal tumors16,20. Subsequently, the trial transitioned to dual delivery combining attributes of both ICV and ICT (arms 4 and 5)16,20,21, and after noting that ICV delivery eliminated small, multifocal subpial lesions, whereas large intraparenchymal tumor progressed (Extended Data Fig. 1a). The protocol was amended to include the Tn/mem manufacturing platform (arm 5) based on data suggesting superior activity against hematological malignancies for Tn/mem- versus Tcm-derived CAR-T cell products22,23,24,25,26,27, along with feasibility challenges with generating sufficient Tcm-derived CAR products for the highest dose schedule (DS3) in arm 4 (refs. 22,23,24,25,26,27). Arm 5, (Tn/mem manufacturing and dual ICT/ICV delivery), therefore, represents the foundation for ongoing and future clinical testing (NCT04003649, NCT04510051 and NCT04661384).
A total of 92 patients were enrolled between June 2015 and February 2020. Patients underwent apheresis for CAR manufacturing, and CAR-T products were successfully produced from 97% (89/92) (Fig. 1c). Due to rapid tumor progression, 24 patients did not receive their manufactured CAR-T product. Sixty-five patients received at least one CAR-T infusion (Extended Data Table 1). Fifty-eight patients received at least three CAR-T infusions and were evaluable for disease response (n = 58), overall survival (OS; n = 57) or dose escalation (n = 54) (Figs. 1c and 2a, and Supplementary Table 1). UPN230 was not evaluable for survival due to the extended wait between surgery and CAR-T treatment; and four participants (UPN201, UPN131, UPN260 and UPN409) were not evaluable for dose escalation due to either receipt of <80% of the CAR-T cell dose or disallowed therapy (‘Study design’ section in Methods)…
