Intracranial Cannula Implantation for Serial Locoregional Chimeric Antigen Receptor (CAR) T Cell Infusions in Mice

Pediatric CNS tumors are responsible for the majority of cancer-related deaths in children and have poor prognoses, despite advancements in chemotherapy ...

Children’s Hospital of Philadelphia

Proteasome inhibitors have garnered interest as novel chemotherapeutic agents based on their ability to inhibit the growth of cancer cells by altering the balance of intracellular proteins. Initial clinical trials of this drug class focused on bortezomib, a reversible inhibitor of the 20S proteasome, with promising results for the treatment of adult hematologic malignancies, including multiple myeloma and non-Hodgkin lymphoma.

The role of proteasome inhibition in the treatment of malignant and non-malignant hematologic disorders.

Immunotherapy for the treatment of cancer has advanced at a tremendous pace over the last decade. In this review, we provide an overview of recent progress in immunotherapy for the treatment of leukemia, focusing on antibody-drug conjugates (ADC), bi-specific T-cell engagers (BiTE), and chimeric antigen receptor (CAR) T cells.

New developments in immunotherapy for pediatric leukemia.

T cells made with messenger RNA (mRNA) encoding chimeric antigen receptor (CAR) offer a safe alternative to those transduced with viral CARs by mitigating the side effects of constitutively active T cells. Previous studies have shown that mRNA CAR T cells are transiently effective but lack persistence and potency across tumor types. It was hypothesized that the efficacy of mRNA CARs could be improved by utilizing recent advancements in RNA technology, such as incorporating a modified nucleoside, 1-methylpseudouridine, into the mRNA and applying a novel purification method using RNase III to eliminate dsRNA contaminants. T cells electroporated with nucleoside-modified and purified mRNA encoding CD19 CAR showed an initial twofold increase in CAR surface expression, as well as a twofold improvement in cytotoxic killing of leukemia cells that persisted up to 5 days. T cells generated with nucleoside-modified and purified CAR mRNA also showed reduced expression of checkpoint regulators and a differential pattern of genetic activation compared to those made with conventional mRNA. In vivo studies using a leukemia mouse model revealed that the most robust 100-fold suppression of leukemic burden was achieved using T cells electroporated with purified mRNAs, regardless of their nucleoside modification. The results provide a novel approach to generate mRNA for clinical trials, and poise mRNA CAR T cells for increased efficacy during testing as new CAR targets emerge.

Purification of mRNA Encoding Chimeric Antigen Receptor Is Critical for Generation of a Robust T-Cell Response.

Adoptive T cell therapy is a form of cellular therapy that utilizes human immune cells, often empowered by the expression of recombinant proteins, to attack selected targets present on tumor or infected cells. T cell-based immunotherapy has been progressing over the past several decades, and reached a milestone with the recent US Food and Drug Administration (FDA) approval of chimeric antigen receptor T cell therapy for relapsed and refractory leukemia and lymphoma. Although most studies have used viral vectors, a growing number of researchers have come to appreciate in vitro-transcribed (IVT) mRNA for the development, testing, and application of T cell-based immunotherapeutics. IVT mRNA offers inherent safety features, highly efficient recombinant protein translation, and the ability to control pharmacokinetic properties of the therapy. In this review, we discuss the history of IVT mRNA in adoptive T cell therapy, from tumor-infiltrating lymphocytes and T cell receptor-based therapies to chimeric antigen receptor therapy and gene-editing techniques, as well as prior and ongoing clinical trials.

The Emerging Role of In Vitro-Transcribed mRNA in Adoptive T Cell Immunotherapy.

The field of cancer immunotherapy has progressed at an accelerated rate over the past decade. Pediatric brain tumors thus far have presented a formidable challenge for immunotherapy development, given their typically low mutational burden, location behind the blood-brain barrier in a unique tumor microenvironment, and intratumoral heterogeneity. Despite these challenges, recent developments in the field have resulted in exciting preclinical evidence for various immunotherapies and multiple clinical trials. This work reviews the history and advances in active immunotherapy, checkpoint blockade, and adoptive T-cell therapy for pediatric brain tumors, including ongoing clinical trials.

Immunotherapy for pediatric brain tumors: past and present.

 (partner and localizer of BRCA2) gene encodes a protein that colocalizes with  in nuclear foci and likely permits the stable intranuclear localization and accumulation of  plays a critical role in maintaining genome integrity through its role in the Fanconi anemia and homologous recombination DNA repair pathways. It has a known loss-of-function disease mechanism. Biallelic  pathogenic variants have been described in autosomal recessive Fanconi anemia. Heterozygous pathogenic variants in  are associated with increased risk for female and male breast cancer and pancreatic cancer ( 324: 217;  71: 2222-2229;  371: 497-506). Heterozygous germline  mutations have also been observed in patients with medulloblastoma ( 19: 785-798). However, -related cancer predisposition to high-grade gliomas has not been reported. Here we report a germline  pathogenic variant (c.509_510delGA, p.Arg170Ilefs*14, NM_024675.3) found in a pediatric patient with high-grade glioma. This variant was first identified by tumor sequencing using the Children's Hospital of Philadelphia (CHOP) Comprehensive Solid Tumor Panel and then confirmed to be a germline change using the CHOP Comprehensive Hereditary Cancer Panel on DNA from a blood sample of this patient. Parental studies showed that this variant was paternally inherited. Further studies are needed to illustrate if pathogenic variants in  convey increased risk to developing brain tumor. This case also highlights the potential of identifying germline mutation through tumor sequencing.

A germline  pathogenic variant identified in a pediatric high-grade glioma.

Manufacturing of potent chimeric antigen receptor (CAR) T cells requires phenotypically naive and early memory T cells. We hypothesized lymphatic fluid collected from the thoracic duct of children would serve as a unique reservoir for early T cells, which could then be used for CAR T-cell therapy.

Thoracic duct lymphatic fluid harbors phenotypically naive T cells for use in adoptive T-cell therapy.

Kaposiform lymphangiomatosis (KLA) is a rare lymphatic anomaly primarily affecting the mediastinum with high mortality rate. We present a patient with KLA and significant disease burden harboring a somatic point mutation in the Casitas B lineage lymphoma (CBL) gene. She was treated with MEK inhibition with complete resolution of symptoms, near-complete resolution of lymphatic fluid burden, and remodeling of her lymphatic system. While patients with KLA have been reported to harbor mutations in NRAS, here we report for the first time a causative mutation in the CBL gene in a patient with KLA, successfully treated with Ras pathway inhibition.

Kaposiform lymphangiomatosis effectively treated with MEK inhibition.

Pediatric brain tumors are the leading cause of cancer death in children with an urgent need for innovative therapies. Glypican 2 (GPC2) is a cell surface oncoprotein expressed in neuroblastoma for which targeted immunotherapies have been developed. This work aimed to characterize GPC2 expression in pediatric brain tumors and develop an mRNA CAR T cell approach against this target.

Development of GPC2-directed chimeric antigen receptors using mRNA for pediatric brain tumors.

Diffuse intrinsic pontine glioma (DIPG) remains a fatal brainstem tumor demanding innovative therapies. As B7-H3 (CD276) is expressed on central nervous system (CNS) tumors, we designed B7-H3-specific chimeric antigen receptor (CAR) T cells, confirmed their preclinical efficacy, and opened BrainChild-03 (NCT04185038), a first-in-human phase I trial administering repeated locoregional B7-H3 CAR T cells to children with recurrent/refractory CNS tumors and DIPG. Here, we report the results of the first three evaluable patients with DIPG (including two who enrolled after progression), who received 40 infusions with no dose-limiting toxicities. One patient had sustained clinical and radiographic improvement through 12 months on study. Patients exhibited correlative evidence of local immune activation and persistent cerebrospinal fluid (CSF) B7-H3 CAR T cells. Targeted mass spectrometry of CSF biospecimens revealed modulation of B7-H3 and critical immune analytes (CD14, CD163, CSF-1, CXCL13, and VCAM-1). Our data suggest the feasibility of repeated intracranial B7-H3 CAR T-cell dosing and that intracranial delivery may induce local immune activation.

Intraventricular B7-H3 CAR T Cells for Diffuse Intrinsic Pontine Glioma: Preliminary First-in-Human Bioactivity and Safety.

Central nervous system (CNS) tumors are the most common solid malignancy in the pediatric population. Based on adoptive cellular therapy's clinical success against childhood leukemia and the preclinical efficacy against pediatric CNS tumors, chimeric antigen receptor (CAR) T cells offer hope of improving outcomes for recurrent tumors and universally fatal diseases such as diffuse intrinsic pontine glioma (DIPG). However, a major obstacle for tumors of the brain and spine is ineffective T cell chemotaxis to disease sites. Locoregional CAR T cell delivery via infusion through an intracranial catheter is currently under study in multiple early phase clinical trials. Here, we describe the Seattle Children's single-institution experience including the multidisciplinary process for the preparation of successful, repetitive intracranial T cell infusion for children and the catheter-related safety of our 307 intracranial CAR T cell doses.

Jessica B. Foster

Division of Oncology,
Center for Data Driven Discovery in Biomedicine

Children’s Hospital of Philadelphia

Intracranial Cannula Implantation for Serial Locoregional Chimeric Antigen Receptor (CAR) T Cell Infusions in Mice

Jessica B. Foster

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Division of Oncology,Center for Data Driven Discovery in Biomedicine

Children’s Hospital of Philadelphia

Intracranial Cannula Implantation for Serial Locoregional Chimeric Antigen Receptor (CAR) T Cell Infusions in Mice

Division of Oncology,
Center for Data Driven Discovery in Biomedicine