Brain Tumor Immunotherapy Research Articles

Abstract 2272: Identification of predictive biomarkers for immunotherapy of brain and solid tumors by studying inter-cellular immune networks

Abstract Immune checkpoint molecules (ICMs) make up the immune suppressive network (ISN) that blocks spontaneous or therapy-induced anti-tumoral immune responses. A decade of research into checkpoint inhibitors (CPIs) has identified only few predictive biomarkers for single-agent CPI therapy. Those discovered show mediocre predictive capability. A considerable fraction of predicted non-responders demonstrate response and vice versa. It is unlikely that current biomarker discovery tools based on single antigen immunohistochemistry or whole-tumor genomics/transcriptomics will uncover predictive biomarkers for therapy with CPI combinations. Brain tumors, specifically glioblastoma, are almost uniformly lethal. Preclinical studies have shown that more than one agent is needed to relieve the strong immunosuppression in these tumors. No rational approach to select the right combination of agents is currently available. We have developed several unique methodologies that delineate the ISN formed between all immune and tumor cell subsets within individual human brain tumors. Our current ISN models incorporate cell-level data, frequency of all intratumoral immune subsets (up to 13 immune subsets), and gene-expression data with each subset's deep-sequenced transcriptome. We produce transcriptomes from all intratumoral immune subsets (as few as 100 cells) and tumor cells that are sorted using elaborate multicolor flow cytometric panels. These transcriptomes reveal each subset's full immune state: expression of all ICMs, all inter-cellular functional and communication molecules (e.g. cytokines, chemokines, receptors, ligands), and its active pathways. The collected data is integrated using systems-biology tools to generate models of the ISN which delineate the interactions that each cell subset has with all other immune or tumor cell subsets within a tumor. Individual ISN data can be evaluated in respect to each patient's response to CPI treatment to determine which ISN patterns correlate with response, or lack of response, to CPI treatment. Emerging results may retrospectively explain the failure of some CPI clinical trials conducted on glioblastoma, and reveal new targets. Studying the relationship between ISN patterns and clinical responses to checkpoint inhibition may enable identification of much needed predictive biomarkers. A systematic evaluation of the suppressive components found to be frequently active in many patients' ISNs may guide rational decisions in planning of clinical trials with improved chances to succeed. This methodology may, in the future, guide physicians in selecting reagents to treat an individual patient's tumor, bringing about the age of personalized medicine to the field of immuno-oncology. Citation Format: Ilan Volovitz, Gil Diamant, Marina Roitman, Nati Shapira, Roni Hagai, Barak Bensimhon, Merav Lustgarten, Rachel Grossman, Zvi Ram. Identification of predictive biomarkers for immunotherapy of brain and solid tumors by studying inter-cellular immune networks [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2272.

Correlating Radiographical and Pathological Response to Immunotherapy in Primary Brain Tumors (P4.157)

Correlating Radiographical and Pathological Response to Immunotherapy in Primary Brain Tumors (P4.157)

Radiological evaluation of response to immunotherapy in brain tumors: Where are we now and where are we going?

Radiological evaluation of response to immunotherapy in brain tumors: Where are we now and where are we going?

Limiting glioma development by photodynamic therapy-generated macrophage vaccine and allo-stimulation: an in vivo histological study in rats.

Immunotherapy of brain tumors involves the stimulation of an antitumor immune response. This type of therapy can be targeted specifically to tumor cells thus sparing surrounding normal brain. Due to the presence of the blood-brain barrier, the brain is relatively isolated from the systemic circulation and, as such, the initiation of significant immune responses is more limited than other types of cancers. The purpose of this study was to show that the efficacy of tumor primed antigen presenting macrophage (MaF98) vaccines can be increased by: (1)photodynamic therapy (PDT) of the priming tumor cells and (2)intracranial injection of allogeneic glioma cells directly into the tumor site. Experiments were conducted in an in vivo brain tumor development model using Fischer rats and F98 (syngeneic) and BT4C (allogeneic) glioma cells. The results showed that immunization with Ma (acting as antigen-presenting cells), primed with PDT-treated tumor cells (MaF98), significantly slowed but did not prevent the growth of F98-induced tumors in the brain. Complete suppression of tumor development was obtained via MaF98 inoculation combined with direct intracranial injection of allogeneic glioma cells. No deleterious effects were noted in any of the animals during the 14-day observation period.

Abstract CN02-02: Immunotherapy for central nervous system cancers

Abstract CN02-02: Immunotherapy for central nervous system cancers

Immunotherapy for Pediatric Brain Tumors.

Malignant brain tumors are the most common cause of solid cancer death in children. New targeted therapies are vital to improve treatment outcomes, but must be developed to enable trafficking across the blood brain barrier (BBB). Since activated T cells cross the BBB, cancer immunotherapy can be harnessed to unlock the cytotoxic potential of the immune system. However, standard of care treatments (i.e., chemotherapy and radiation) applied concomitant to pediatric brain tumor immunotherapy may abrogate induction of immunotherapeutic responses. This review will discuss the development of immunotherapies within this paradigm using emerging approaches being investigated in phase I/II trials in children with refractory brain tumors, including checkpoint inhibitors, vaccine immunotherapy, and adoptive cell therapy.

Validation of an Immunohistochemistry Assay for Detection of CD155, the Poliovirus Receptor, in Malignant Gliomas.

- The oncolytic polio-rhinovirus recombinant (PVSRIPO) has demonstrated promise in currently ongoing phase I/II clinical trials against recurrent glioblastoma and was granted breakthrough therapy designation by the Food and Drug Administration/Center for Biologics Evaluation and Research. A reliable clinical assay to document expression of the poliovirus receptor, CD155, in routinely available patient tumor samples is needed for continued clinical development of PVSRIPO oncolytic immunotherapy in primary brain tumors and beyond. - To validate a novel anti-CD155 antibody for immunohistochemistry and develop a robust, reliable, and specific protocol for detecting CD155 expression in glioblastoma formalin-fixed, paraffin-embedded (FFPE) tissue samples. To characterize the expression of CD155 in human glioblastoma cells as well as to evaluate the influence of CD155 expression levels on tumor cell susceptibility to PVSRIPO infection and killing. - Immunohistochemical staining on glioblastoma FFPE tissue sections and immunoblot of corresponding frozen tissues were performed. Positive controls were confirmed sites of poliovirus propagation, spinal cord anterior horn, and tonsils; negative controls were vascular smooth muscle in patient samples and FFPE sections from a confirmed CD155-negative Burkitt lymphoma line (Raji). - We succeeded in developing a reliable assay to specifically detect CD155 by immunohistochemistry in glioblastoma FFPE sections. Our data suggest widespread, virtually universal expression of CD155 in glioblastoma cells at levels commensurate with susceptibility to PVSRIPO infection and killing. - Anti-CD155 antibody D3G7H achieves monospecific detection of CD155 in immunoblots of tumor homogenates and immunohistochemistry of tumor FFPE sections. Our assay has utility in defining appropriate use of PVSRIPO in oncolytic immunotherapy against malignant glioma and other cancer histotypes.

Clinical Trials Investigating Immune Checkpoint Blockade in Glioblastoma.

Immune checkpoint inhibitors have changed the landscape of cancer immunotherapy and are being integrated into the standard of care for a variety of solid and hematologic malignancies. Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and carries a grave prognosis despite advances in surgical resection, chemotherapy, and radiation therapy. Implementing immunotherapy for brain tumors mandates additional considerations due to the unique structural and immunologic milieu of the central nervous system (CNS). Nevertheless, strong data from preclinical studies have driven clinical trials of immune checkpoint blockade for newly diagnosed and recurrent GBM. The focus of this review is to discuss the ongoing clinical trials of checkpoint inhibitors in GBM and review the immunologic rationale for ongoing and future trial designs.

Immunotherapy for Brain Tumors.

Glioblastoma (GBM) is the most lethal form of brain tumor and remains a large, unmet medical need. This review focuses on recent advances in the neurosciences that converge with the broader field of immuno-oncology. Recent findings in neuroanatomy provide a basis for new approaches of cellular therapies for tumors that involve the CNS. The ultimate success of immunotherapy in the CNS will require improved imaging technologies and methods for analysis of the tumor microenvironment in patients with GBM. It is likely that combinatorial approaches with targeted immunotherapies will be required to exploit the vulnerabilities of GBM and other brain tumors.

A combinatorial immunotherapy for malignant brain tumors: D2C7 immunotoxin and immune checkpoint inhibitors.

102 Background: Immunotoxins can induce direct and rapid cytotoxicity by targeting specific tumor antigens. D2C7 is a unique recombinant immunotoxin targeting EGFRwt/EGFRvIII, two frequently overexpressed proteins on gliomas, and is currently being tested in a phase I/II clinical trial (NCT02303678) for recurrent malignant gliomas. Immunotoxins have also been shown to induce a secondary antitumor immune response via stimulation of cytotoxic T lymphocytes (CTLs). Immune checkpoint inhibitors, which have successfully treated several advanced tumors by promoting the antitumor function of CTLs, may further enhance this immunotoxin-induced antitumor response. Thus, we hypothesize that combining D2C7 with immune checkpoint inhibitors will promote long-term tumor regression due to primary cytotoxicity and enhanced anti-tumor immunity. Methods: We developed a CT2A-mD2C7 mouse glioma cell line with robust in vitro cytotoxicity of D2C7 (IC50= 0.47 ng/mL). In vivo anti-tumor efficacy was evaluated by intratumoral injection of D2C7 combined with intraperitoneal injection of anti-CTLA4 or anti-PD1 antibodies in single-side and bilateral subcutaneous (SC) CT2A-mD2C7 glioma models in C57BL/6 immunocompetent mice. Results: In the single-side model, D2C7 monotherapy and combinatorial therapy showed a significant tumor growth delay (P < 0.01). Complete regression ( ≥ 40%) was only observed in combinatorial therapy groups. All cured mice rejected the rechallenging of CT2A parental cells in the contralateral flank and the subsequent rechallenging of CT2A-mD2C7 cells in the brain. In the bilateral model, the larger right tumors were treated with D2C7/anti-CTLA4/anti-PD1 monotherapy or D2C7+anti-CTLA4/PD1 combinatorial therapy, while the left tumors were untreated by D2C7. In the groups where the right tumors were treated with monotherapy or combinatorial therapy, the left untreated tumors also grew much slower. Furthermore, the combinatorial therapy led to the most significantly delayed growth of the left untreated tumors (P < 0.05). Conclusions: Immune checkpoint inhibitors can enhance D2C7-induced anti-tumor immunity to achieve a synergistic long-term tumor regression.

Abstract A53: Establishment of a brain tumor model with dysfunctional tumor immunity in mice as a platform for immunotherapeutic evaluation and PD-1 immunotherapy

Abstract Several clinical trials are currently underway for patients with newly diagnosed and recurrent glioblastoma to reinvigorate tumor immunity using immune-checkpoint blockade. However, the CNS is immunologically unique in its maintenance of an immunosuppressive environment, to protect brain cells from autoimmunity and inflammation. Thus, immunotherapy of brain tumors requires novel regimens to overcome tumor immuno-suppression. Suitable preclinical animal models with exhausted tumor-specific immunity are currently not available. We thus hypothesized that a chronic LCMV (cLCMV) strain that induces T cell exhaustion in mice may be co-opted to model the impaired immunity that characterizes brain tumors. In this model, naïve and cLCMV-infected mice failed to reject a challenge with glioma in brain when murine glioma cells express one of LCMV antigens (VA-glioma) that are presented via MHC-I. In contrast, mice preimmunized with the acutely-controlled LCMV (aLCMV) strain did reject VA-glioma. In fact, in vitro co-culture of lymphocytes and glioma cells, and in vivo TIL analyses suggested that VA-glioma failed to induce CD8+ T cell responses in cLCMV-mice, in contrast to the robust CD8+ T cell response in aLCMV-mice. Furthermore, cLCMV-specific CD8 T cells lacked a central memory T cell phenotype (CD44+, CD62L-, CD127-) and expressed significantly high levels of PD-1. Thus, treatment with anti-PD1, but not isotype control antibody, successfully reinvigorated and restored antitumor immunity in cLCMV-mice that received VA-glioma cells. PD-1 blockade led to significantly improved survival. However, this treatment did not show a therapeutic effect in cLCMV-mice that received parental glioma cells that don't express the viral antigen. These data strongly suggest that PD-1 blockade is effective in brain tumors that induce impaired tumor-specific T cell immunity. In conclusion, this novel mouse model may be useful to screen for novel immune checkpoint inhibitors and combination regimes in the setting of a single dysfunctional CD8 T cell response. Citation Format: Hiroshi Nakashima, Quazim Alayo, Pablo Penaloza, Dan Barouch, Ennio Antonio Chiocca. Establishment of a brain tumor model with dysfunctional tumor immunity in mice as a platform for immunotherapeutic evaluation and PD-1 immunotherapy. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A53.

Neuroimaging of Peptide-based Vaccine Therapy in Pediatric Brain Tumors: Initial Experience.

The potential benefits of peptide-based immunotherapy for pediatric brain tumors are under investigation. Treatment-related heterogeneity has resulted in radiographic challenges, including pseudoprogression. Conventional MR imaging has limitations in assessment of different forms of treatment-related heterogeneity, particularly regarding distinguishing true tumor progression from efficacious treatment responses. Advanced neuroimaging techniques, including diffusion magnetic resonance (MR), perfusion MR, and MR spectroscopy, may add value in the assessment of treatment-related heterogeneity. Observations suggest that recent delineation of specific response criteria for immunotherapy of adult brain tumors is likely relevant to the pediatric population and further validation in multicenter pediatric brain tumor peptide-based vaccine studies is warranted.

Development of a peptide vaccine platform for brain tumor immunotherapy that incorporates adjuvant CD27 stimulation for enhanced T cell immunity

Development of a peptide vaccine platform for brain tumor immunotherapy that incorporates adjuvant CD27 stimulation for enhanced T cell immunity

Immunotherapy for malignant primary brain tumors with ICT-107, a dendritic cell vaccine

ABSTRACTIntroduction: ICT-107 is a dendritic cell vaccine for the treatment of primary malignant brain tumors such as glioblastoma multiforme (GBM). For this immunotherapy treatment, autologous dendritic cells are pulsed with peptides from six tumor-associated antigens expressed on gliomas.Areas covered: Review of phase I and II clinical date is presented. In a phase I clinical trial with ICT-107 treatment in patients with malignant gliomas, the vaccine was found to be safe and tolerable, with encouraging results for overall survival and progression-free survival. A Phase II trial has completed enrollment, while a Phase III trial is currently opened to enrolling patients with newly diagnosed glioblastoma multiforme.Expert opinion: Immunotherapy with ICT-107 might present a therapeutic option for treatment in a subgroup of GBM patients.

TMOD-20. ESTABLISHMENT OF A BRAIN TUMOR MODEL WITH DYSFUNCTIONAL TUMOR IMMUNITY IN MICE AS A PLATFORM FOR IMMUNOTHERAPEUTIC EVALUATION

Several clinical trials are currently underway for patients with newly diagnosed and recurrent glioblastoma to reinvigorate tumor immunity using immune-checkpoint blockade. However, the CNS is immunologically unique in its maintenance of an immunosuppressive environment, to protect brain cells from autoimmunity and inflammation. Thus, immunotherapy of brain tumors requires novel regimens to overcome tumor immuno-suppression. Suitable preclinical animal models with exhausted tumor-specific immunity are currently not available. We thus hypothesized that a chronic LCMV (cLCMV) strain that induces T cell exhaustion in mice may be co-opted to model the impaired immunity that characterizes brain tumors. In this model, naïve and cLCMV-infected mice failed to reject a challenge with glioma in brain when murine glioma cells express one of LCMV antigens (VA-glioma) that are presented via MHC-I. In contrast, mice preimmunized with the acutely-controlled LCMV (aLCMV) strain did reject VA-glioma. In fact, in vitro co-culture of lymphocytes and glioma cells, and in vivo TIL analyses suggested that VA-glioma failed to induce CD8+ T cell responses in cLCMV-mice, in contrast to the robust CD8+ T cell response in aLCMV-mice. Furthermore, cLCMV-specific CD8 T cells lacked a central memory T cell phenotype (CD44+, CD62L-, CD127-) and expressed significantly high levels of PD-1. Treatment with anti-PD1, but not isotype control antibody, successfully reinvigorated and restored antitumor immunity in cLCMV-mice that received VA-glioma cells. PD-1 blockade led to significantly improved survival. However, this treatment did not show a therapeutic effect in cLCMV-mice that received parental glioma cells that don’t express the viral antigen. These data strongly suggest that PD-1 blockade is effective in brain tumors that induce impaired tumor-specific T cell immunity. In conclusion, this novel mouse model may be useful to screen for novel immune checkpoint inhibitors and combination regimes in the setting of a single dysfunctional CD8 T cell response.

CD8 T Cell-Independent Antitumor Response and Its Potential for Treatment of Malignant Gliomas.

Malignant brain tumors continue to represent a devastating diagnosis with no real chance for cure. Despite an increasing list of potential salvage therapies, standard-of-care for these patients has not changed in over a decade. Immunotherapy has been seen as an exciting option, with the potential to offer specific and long lasting tumor clearance. The “gold standard” in immunotherapy has been the development of a tumor-specific CD8 T cell response to potentiate tumor clearance and immunological memory. While many advances have been made in the field of immunotherapy, few therapies have seen true success. Many of the same principles used to develop immunotherapy in tumors of the peripheral organs have been applied to brain tumor immunotherapy. The immune-specialized nature of the brain should call into question whether this approach is appropriate. Recent results from our own experiments require a rethinking of current dogma. Perhaps a CD8 T cell response is not sufficient for an organ as immunologically unique as the brain. Examination of previously elucidated principles of the brain’s immune-specialized status and known immunological preferences should generate discussion and experimentation to address the failure of current therapies.

Concepts in glioma immunotherapy.

Immunotherapeutic concepts in neurooncology have been developed for many decades but have mainly been hampered by poor definition of relevant antigens and selective measures to target the central nervous system. Independent of the recent remarkable successes in clinical immunooncology with checkpoint inhibitors and vaccines, immunotherapy of brain tumors in general and gliomas in particular has evolved with novel neurooncology-specific concepts over the past years providing new phase 1 approaches of individualized immunotherapy to first phase three clinical trials. These concepts are driven by a high medical need in the absence of approved targeted therapies and refute the classic dogma that the central nervous system is immune-privileged and hence inaccessible to potent antitumor immunity. Instead, measures have been taken to improve the odds for successful immunotherapies, including rational targeting of relevant antigens and integration of immunotherapies into standard of care primary radiochemotherapy to increase the efficacy of antitumor immunity in a meaningful time window. This review highlights concepts and challenges associated with epitope discovery and selection and trial design.

Brain tumor immunotherapy. What have we learned so far?

Brain tumor immunotherapy. What have we learned so far?

An Update on the Role of Immunotherapy and Vaccine Strategies for Primary Brain Tumors.

Existing therapies for glioblastoma (GBM), the most common malignant primary brain tumor in adults, have fallen short of improving the dismal patient outcomes, with an average 14-16-month median overall survival. The biological complexity and adaptability of GBM, redundancy of dysregulated signaling pathways, and poor penetration of therapies through the blood-brain barrier contribute to poor therapeutic progress. The current standard of care for newly diagnosed GBM consists of maximal safe resection, followed by fractionated radiotherapy combined with concurrent temozolomide (TMZ) and 6-12 cycles of adjuvant TMZ. At progression, bevacizumab with or without additional chemotherapy is an option for salvage therapy. The recent FDA approval of sipuleucel-T for prostate cancer and ipilumimab, nivolumab, and pembrolizumab for select solid tumors and the ongoing trials showing clinical efficacy and response durability herald a new era of cancer treatment with the potential to change standard-of-care treatment across multiple cancers. The evaluation of various immunotherapeutics is advancing for GBM, putting into question the dogma of the CNS as an immuno-privileged site. While the field is yet young, both active immunotherapy involving vaccine strategies and cellular therapy as well as reversal of GBM-induced global immune-suppression through immune checkpoint blockade are showing promising results and revealing essential immunological insights regarding kinetics of the immune response, immune evasion, and correlative biomarkers. The future holds exciting promise in establishing new treatment options for GBM that harness the patients' own immune system by activating it with immune checkpoint inhibitors, providing specificity using vaccine therapy, and allowing for modulation and enhancement by combinatorial approaches.

Immunosuppressive Mechanisms of Malignant Gliomas: Parallels at Non-CNS Sites.

The central nervous system (CNS) possesses powerful local and global immunosuppressive capabilities that modulate unwanted inflammatory reactions in nervous tissue. These same immune-modulatory mechanisms are also co-opted by malignant brain tumors and pose a formidable challenge to brain tumor immunotherapy. Routes by which malignant gliomas coordinate immunosuppression include the mechanical and functional barriers of the CNS; immunosuppressive cytokines and catabolites; immune checkpoint molecules; tumor-infiltrating immune cells; and suppressor immune cells. The challenges to overcoming tumor-induced immunosuppression, however, are not unique to the brain, and several analogous immunosuppressive mechanisms also exist for primary tumors outside of the CNS. Ultimately, the immune responses in the CNS are linked and complementary to immune processes in the periphery, and advances in tumor immunotherapy in peripheral sites may therefore illuminate novel approaches to brain tumor immunotherapy, and vice versa.