SUMMARY A patient with recurrent multifocal glioblastoma received chimeric antigen receptor (CAR)–engineered T cells targeting the tumor-associated antigen interleukin-13 receptor alpha 2 (IL13Rα2). Multiple infusions of CAR T cells were administered over 220 days through two intracranial delivery routes — infusions into the resected tumor cavity followed by infusions into the ventricular system. Intracranial infusions of IL13Rα2-targeted CAR T cells were not associated with any toxic effects of grade 3 or higher. After CAR T-cell treatment, regression of all intracranial and spinal tumors was observed, along with corresponding increases in levels of cytokines and immune cells in the cerebrospinal fluid. This clinical response continued for 7.5 months after the initiation of CAR T-cell therapy.

Purpose A first-in-human pilot safety and feasibility trial evaluating chimeric antigen receptor (CAR) engineered, autologous primary human CD8+ cytolytic T lymphocytes (CTLs) targeting IL13Rα2 for the treatment of recurrent glioblastoma (GBM). Experimental Design Three patients with recurrent GBM were treated with IL13(E13Y)-zetakine CD8+ CTL targeting IL13Rα2. Patients received up to twelve local infusions at a maximum dose of 108 CAR-engineered T cells via a catheter/reservoir system. Results We demonstrate the feasibility of manufacturing sufficient numbers of autologous CTL clones expressing an IL13(E13Y)-zetakine CAR for redirected HLA-independent IL13Rα2-specific effector function for a cohort of patients diagnosed with GBM. Intracranial delivery of the IL13-zetakine+ CTL clones into the resection cavity of three patients with recurrent disease was well-tolerated, with manageable temporary CNS inflammation. Following infusion of IL13-zetakine+ CTLs, evidence for transient anti-glioma responses was observed in two of the patients. Analysis of tumor tissue from one patient before and after T cell therapy suggested reduced overall IL13Rα2 expression within the tumor following treatment. MRI analysis of another patient indicated an increase in tumor necrotic volume at the site of IL13-zetakine+ T cell administration. Conclusion These findings provide promising first-in-human clinical experience for intracranial administration of IL13Rα2-specific CAR T cells for the treatment of GBM, establishing a foundation on which future refinements of adoptive CAR T cell therapies can be applied.

Little is known about how leukemia cells alter the bone marrow (BM) niche to facilitate their own growth and evade chemotherapy. Here, we provide evidence that acute myeloid leukemia (AML) blasts remodel the BM niche into a leukemia growth-permissive and normal hematopoiesis-suppressive microenvironment through exosome secretion. Either engrafted AML cells or AML-derived exosomes increased mesenchymal stromal progenitors and blocked osteolineage development and bone formation in vivo. Preconditioning with AML-derived exosomes ‘primed’ the animals for accelerated AML growth. Conversely, disruption of exosome secretion in AML cells through targeting Rab27a, an important regulator involved in exosome release, significantly delayed leukemia development. In BM stromal cells, AML-derived exosomes induced the expression of DKK1, a suppressor of normal hematopoiesis and osteogenesis, thereby contributing to osteoblast loss. Conversely, treatment with a DKK1 inhibitor delayed AML progression and prolonged survival in AML-engrafted mice. In addition, AML-derived exosomes induced a broad downregulation of hematopoietic stem cell-supporting factors (for example, CXCL12, KITL and IGF1) in BM stromal cells and reduced their ability to support normal hematopoiesis. Altogether, this study uncovers novel features of AML pathogenesis and unveils how AML cells create a self-strengthening leukemic niche that promotes leukemic cell proliferation and survival, while suppressing normal hematopoiesis through exosome secretion.

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.