The transformative potential of mRNA vaccines for glioblastoma and human cancer: technological advances and translation to clinical trials.

Originally devised for cancer control, mRNA vaccines have risen to the forefront of medicine as effective instruments for control of infectious disease, notably their pivotal role in combating the COVID-19 pandemic. This review focuses on fundamental aspects of the development of mRNA vaccines, e.g., tumor antigens, vector design, and precise delivery methodologies, - highlighting key technological advances. The recent, promising success of personalized mRNA vaccines against pancreatic cancer and melanoma illustrates the potential value for other intractable, immunologically resistant, solid tumors, such as glioblastoma, as well as the potential for synergies with a combinatorial, immunotherapeutic approach. The impact and progress in human cancer, including pancreatic cancer, head and neck cancer, bladder cancer are reviewed, as are lessons learned from first-in-human CAR-T cell, DNA and dendritic cell vaccines targeting glioblastoma. Going forward, a roadmap is provided for the transformative potential of mRNA vaccines to advance cancer immunotherapy, with a particular focus on the opportunities and challenges of glioblastoma. The current landscape of glioblastoma immunotherapy and gene therapy is reviewed with an eye to combinatorial approaches harnessing RNA science. Preliminary preclinical and clinical data supports the concept that mRNA vaccines could be a viable, novel approach to prolong survival in patients with glioblastoma.

Lisavanbulin (BAL101553), a novel microtubule inhibitor, plus radiation in patients with newly diagnosed, MGMT promoter unmethylated glioblastoma.

Background: Lisavanbulin (BAL101553) is a small, lipophilic, oral microtubule destabilizer with promising antitumoral activity observed in preclinical glioblastoma (GBM) models. Methods: This multicenter phase 1 study sought to determine the MTD of oral Lisavanbulin in combination with standard RT (60 Gy/30 fractions) but without temozolomide in patients with newly diagnosed MGMT promoter unmethylated GBM (uGBM). Dose escalation followed a modified 3 + 3 design. Secondary objectives included estimation of OS and PFS and pharmacokinetic analysis. Results: Twenty-six patients with uGBM (median age, 63 years, 42.3% male, 61.5% with gross total resection, median Karnofsky performance status 80) were enrolled; 2 tumors had an IDH1 mutation. Predefined dose levels of Lisavanbulin, administered daily concomitantly with RT, were: 4 mg (5 pts), 6 mg (5 pts), 8 mg (7 pts), 12 mg (5 pts), and 15 mg (4 pts). The initial starting dose was 8 mg. Due to grade 4 aseptic meningoencephalitis in the first patient, the dose was decreased to 4 mg. Dose escalation resumed and continued to 15 mg with dose-limiting toxicities of grade 2 confusion and memory impairment observed at 12 mg. Avanbulin exposures increased in a relatively dose-proportional manner with increasing oral dose of Lisavanbulin from 4 to 15 mg. Conclusions: Lisavanbulin in combination with RT was considered safe up to the highest predefined oral dose level of 15 mg daily.

No drug holidays in BRAFV600E glioma patients: An argument for dose reduction of targeted therapies.

Background: Combined BRAF and MEK inhibition is effective for some BRAFV600E-altered gliomas, a cancer for which there are few effective therapies. While recent clinical trials demonstrate objective response rates of 30%-40%, tolerable adverse event rates are 70%-90%, and 12%-15% of patients stop therapy for toxicity. There are no clear guidelines regarding the timing and reinitiation of BRAF-targeted therapies following drug holidays. Here, we describe 4 patients with rapid disease progression during periods of treatment interruption. All patients experienced a response upon resumption of targeted therapy. Methods: This is a multi-institutional, retrospective review of 4 patients. Results: Three patients were diagnosed with BRAFV600E mutated anaplastic pleomorphic xanthoastrocytoma (aPXA) and 1 with epithelioid glioblastoma. The age range was 32 to 46; 3 patients were female and one patient was male. All patients were initially treated with radiation and were subsequently treated with BRAF/MEK inhibitors after disease progression. All patients with aPXA required the targeted therapy to be held due to toxicity and 1 patient held the therapy prior to transitioning to a novel BRAF-targeted agent. All patients were restarted on BRAF/MEK inhibitors after a drug holiday. Three patients required a dose reduction and all improved clinically following reinitiation. Conclusions: Clinical and radiographic progression may occur rapidly upon holding BRAF-targeted therapy, warranting judicious dose reductions and minimization of drug holidays.

Systematic Review of Cerebrospinal Fluid Biomarker Discovery in Neuro-Oncology: A Roadmap to Standardization and Clinical Application.

Effective diagnosis, prognostication, and management of CNS malignancies traditionally involves invasive brain biopsies that pose significant risk to the patient. Sampling and molecular profiling of cerebrospinal fluid (CSF) is a safer, rapid, and noninvasive alternative that offers a snapshot of the intracranial milieu while overcoming the challenge of sampling error that plagues conventional brain biopsy. Although numerous biomarkers have been identified, translational challenges remain, and standardization of protocols is necessary. Here, we systematically reviewed 141 studies (Medline, SCOPUS, and Biosis databases; between January 2000 and September 29, 2022) that molecularly profiled CSF from adults with brain malignancies including glioma, brain metastasis, and primary and secondary CNS lymphomas. We provide an overview of promising CSF biomarkers, propose CSF reporting guidelines, and discuss the various considerations that go into biomarker discovery, including the influence of blood-brain barrier disruption, cell of origin, and site of CSF acquisition (eg, lumbar and ventricular). We also performed a meta-analysis of proteomic data sets, identifying biomarkers in CNS malignancies and establishing a resource for the research community.

All-trans retinoic acid induces durable tumor immunity in IDH-mutant gliomas by rescuing transcriptional repression of the CRBP1-retinoic acid axis.

Diffuse gliomas are epigenetically dysregulated, immunologically cold, and fatal tumors characterized by mutations in isocitrate dehydrogenase (IDH). Although IDH mutations yield a uniquely immunosuppressive tumor microenvironment, the regulatory mechanisms that drive the immune landscape of IDH mutant (IDHm) gliomas remain unknown. Here, we reveal that transcriptional repression of retinoic acid (RA) pathway signaling impairs both innate and adaptive immune surveillance in IDHm glioma through epigenetic silencing of retinol binding protein 1 (RBP1) and induces a profound anti-inflammatory landscape marked by loss of inflammatory cell states and infiltration of suppressive myeloid phenotypes. Restorative retinoic acid therapy in murine glioma models promotes clonal CD4 + T cell expansion and induces tumor regression in IDHm, but not IDH wildtype (IDHwt), gliomas. Our findings provide a mechanistic rationale for RA immunotherapy in IDHm glioma and is the basis for an ongoing investigator-initiated, single-center clinical trial investigating all-trans retinoic acid (ATRA) in recurrent IDHm human subjects.

Intrathecal bivalent CAR T cells targeting EGFR and IL13Rα2 in recurrent glioblastoma: phase 1 trial interim results.

Recurrent glioblastoma (rGBM) remains a major unmet medical need, with a median overall survival of less than 1 year. Here we report the first six patients with rGBM treated in a phase 1 trial of intrathecally delivered bivalent chimeric antigen receptor (CAR) T cells targeting epidermal growth factor receptor (EGFR) and interleukin-13 receptor alpha 2 (IL13Rα2). The study's primary endpoints were safety and determination of the maximum tolerated dose. Secondary endpoints reported in this interim analysis include the frequency of manufacturing failures and objective radiographic response (ORR) according to modified Response Assessment in Neuro-Oncology criteria. All six patients had progressive, multifocal disease at the time of treatment. In both dose level 1 (1 ×107 cells; n = 3) and dose level 2 (2.5 × 107 cells; n = 3), administration of CART-EGFR-IL13Rα2 cells was associated with early-onset neurotoxicity, most consistent with immune effector cell-associated neurotoxicity syndrome (ICANS), and managed with high-dose dexamethasone and anakinra (anti-IL1R). One patient in dose level 2 experienced a dose-limiting toxicity (grade 3 anorexia, generalized muscle weakness and fatigue). Reductions in enhancement and tumor size at early magnetic resonance imaging timepoints were observed in all six patients; however, none met criteria for ORR. In exploratory endpoint analyses, substantial CAR T cell abundance and cytokine release in the cerebrospinal fluid were detected in all six patients. Taken together, these first-in-human data demonstrate the preliminary safety and bioactivity of CART-EGFR-IL13Rα2 cells in rGBM. An encouraging early efficacy signal was also detected and requires confirmation with additional patients and longer follow-up time. ClinicalTrials.gov identifier: NCT05168423 .

An immunosuppressive vascular niche drives macrophage polarization and immunotherapy resistance in glioblastoma.

Cancer immunity is subjected to spatiotemporal regulation by leukocyte interaction with neoplastic and stromal cells, contributing to immune evasion and immunotherapy resistance. Here, we identify a distinct mesenchymal-like population of endothelial cells (ECs) that form an immunosuppressive vascular niche in glioblastoma (GBM). We reveal a spatially restricted, Twist1/SATB1-mediated sequential transcriptional activation mechanism, through which tumor ECs produce osteopontin to promote immunosuppressive macrophage (Mφ) phenotypes. Genetic or pharmacological ablation of Twist1 reverses Mφ-mediated immunosuppression and enhances T cell infiltration and activation, leading to reduced GBM growth and extended mouse survival, and sensitizing tumor to chimeric antigen receptor T immunotherapy. Thus, these findings uncover a spatially restricted mechanism controlling tumor immunity and suggest that targeting endothelial Twist1 may offer attractive opportunities for optimizing cancer immunotherapy.

Integrating imaging and genomic data for the discovery of distinct glioblastoma subtypes: a joint learning approach.

Glioblastoma is a highly heterogeneous disease, with variations observed at both phenotypical and molecular levels. Personalized therapies would be facilitated by non-invasive in vivo approaches for characterizing this heterogeneity. In this study, we developed unsupervised joint machine learning between radiomic and genomic data, thereby identifying distinct glioblastoma subtypes. A retrospective cohort of 571 IDH-wildtype glioblastoma patients were included in the study, and pre-operative multi-parametric MRI scans and targeted next-generation sequencing (NGS) data were collected. L21-norm minimization was used to select a subset of 12 radiomic features from the MRI scans, and 13 key driver genes from the five main signal pathways most affected in glioblastoma were selected from the genomic data. Subtypes were identified using a joint learning approach called Anchor-based Partial Multi-modal Clustering on both radiomic and genomic modalities. Kaplan-Meier analysis identified three distinct glioblastoma subtypes: high-risk, medium-risk, and low-risk, based on overall survival outcome (p < 0.05, log-rank test; Hazard Ratio = 1.64, 95% CI 1.17-2.31, Cox proportional hazard model on high-risk and low-risk subtypes). The three subtypes displayed different phenotypical and molecular characteristics in terms of imaging histogram, co-occurrence of genes, and correlation between the two modalities. Our findings demonstrate the synergistic value of integrated radiomic signatures and molecular characteristics for glioblastoma subtyping. Joint learning on both modalities can aid in better understanding the molecular basis of phenotypical signatures of glioblastoma, and provide insights into the biological underpinnings of tumor formation and progression.

Repeated peripheral infusions of anti-EGFRvIII CAR T cells in combination with pembrolizumab show no efficacy in glioblastoma: a phase 1 trial.

We previously showed that chimeric antigen receptor (CAR) T-cell therapy targeting epidermal growth factor receptor variant III (EGFRvIII) produces upregulation of programmed death-ligand 1 (PD-L1) in the tumor microenvironment (TME). Here we conducted a phase 1 trial (NCT03726515) of CAR T-EGFRvIII cells administered concomitantly with the anti-PD1 (aPD1) monoclonal antibody pembrolizumab in patients with newly diagnosed, EGFRvIII+ glioblastoma (GBM) (n = 7). The primary outcome was safety, and no dose-limiting toxicity was observed. Secondary outcomes included median progression-free survival (5.2 months; 90% confidence interval (CI), 2.9-6.0 months) and median overall survival (11.8 months; 90% CI, 9.2-14.2 months). In exploratory analyses, comparison of the TME in tumors harvested before versus after CAR + aPD1 administration demonstrated substantial evolution of the infiltrating myeloid and T cells, with more exhausted, regulatory, and interferon (IFN)-stimulated T cells at relapse. Our study suggests that the combination of CAR T cells and PD-1 inhibition in GBM is safe and biologically active but, given the lack of efficacy, also indicates a need to consider alternative strategies.

Exploiting Iron Metabolism as a Therapeutic Vulnerability in Glioblastoma.

In this CCR Translations, we discuss pharmacologic ascorbate as a novel therapeutic for glioblastoma (GBM). Aberrant iron metabolism in GBM can be assessed noninvasively by MRI and exploited to potentially improve the efficacy of chemoradiotherapy. We contextualize the study's results and discuss the next steps to further develop this paradigm. See related article by Petronek et al., p. 283.

Recent Developments in Blood Biomarkers in Neuro-oncology.

PURPOSE OF REVIEW: Given the invasive and high-risk nature of brain surgery, the need for non-invasive biomarkers obtained from the peripheral blood is greatest in tumors of the central nervous system (CNS). In this comprehensive review, we highlight recent advances in blood biomarker development for adult and pediatric brain tumors. RECENT FINDINGS: We summarize recent blood biomarker development for CNS tumors across multiple key analytes, including peripheral blood mononuclear cells, cell-free DNA, cell-free RNA, proteomics, circulating tumor cells, and tumor-educated platelets. We also discuss methods for enhancing blood biomarker detection through transient opening of the blood-brain barrier. Although blood-based biomarkers are not yet used in routine neuro-oncology practice, this field is advancing rapidly and holds great promise for improved and non-invasive management of patients with brain tumors. Prospective and adequately powered studies are needed to confirm the clinical utility of any blood biomarker prior to widespread clinical implementation.

Adding Value to Liquid Biopsy for Brain Tumors: The Role of Imaging.

Clinical management in neuro-oncology has changed to an integrative approach that incorporates molecular profiles alongside histopathology and imaging findings. While the World Health Organization (WHO) guideline recommends the genotyping of informative alterations as a routine clinical practice for central nervous system (CNS) tumors, the acquisition of tumor tissue in the CNS is invasive and not always possible. Liquid biopsy is a non-invasive approach that provides the opportunity to capture the complex molecular heterogeneity of the whole tumor through the detection of circulating tumor biomarkers in body fluids, such as blood or cerebrospinal fluid (CSF). Despite all of the advantages, the low abundance of tumor-derived biomarkers, particularly in CNS tumors, as well as their short half-life has limited the application of liquid biopsy in clinical practice. Thus, it is crucial to identify the factors associated with the presence of these biomarkers and explore possible strategies that can increase the shedding of these tumoral components into biological fluids. In this review, we first describe the clinical applications of liquid biopsy in CNS tumors, including its roles in the early detection of recurrence and monitoring of treatment response. We then discuss the utilization of imaging in identifying the factors that affect the detection of circulating biomarkers as well as how image-guided interventions such as focused ultrasound can help enhance the presence of tumor biomarkers through blood-brain barrier (BBB) disruption.

Optimizing CAR-T Therapy for Glioblastoma.

Chimeric antigen receptor T-cell therapies have transformed the management of hematologic malignancies but have not yet demonstrated consistent efficacy in solid tumors. Glioblastoma is the most common primary malignant brain tumor in adults and remains a major unmet medical need. Attempts at harnessing the potential of chimeric antigen receptor T-cell therapy for glioblastoma have resulted in glimpses of promise but have been met with substantial challenges. In this focused review, we discuss current and future strategies being developed to optimize chimeric antigen receptor T cells for efficacy in patients with glioblastoma, including the identification and characterization of new target antigens, reversal of T-cell dysfunction with novel chimeric antigen receptor constructs, regulatable platforms, and gene knockout strategies, and the use of combination therapies to overcome the immune-hostile microenvironment.

RNA fusion transcript panel identifies diverse repertoire of fusions in adult glioma patients with therapeutic implications.

Background: Recurrent gliomas are therapeutically challenging diseases with few treatment options available. One area of potential therapeutic vulnerability is the presence of targetable oncogenic fusion proteins. Methods: To better understand the clinical benefit of routinely testing for fusion proteins in adult glioma patients, we performed a retrospective review of 647 adult patients with glioma who underwent surgical resection at our center between August 2017 and May 2021 and whose tumors were analyzed with an in-house fusion transcript panel. Results: Fifty-two patients (8%) were found to harbor a potentially targetable fusion with 11 (21%) of these patients receiving treatment with a fusion-targeted inhibitor. The targetable genes found to be involved in a fusion included FGFR3, MET, EGFR, NTRK1, NTRK2, BRAF, ROS1, and PIK3CA. Conclusions: This analysis demonstrates that routine clinical testing for gene fusions identifies a diverse repertoire of potential therapeutic targets in adult patients with glioma and can offer rational therapeutic options for patients with recurrent disease.

Small-molecule toosendanin reverses macrophage-mediated immunosuppression to overcome glioblastoma resistance to immunotherapy.

T cell-based immunotherapy holds promise for treating solid tumors, but its therapeutic efficacy is limited by intratumoral immune suppression. This immune suppressive tumor microenvironment is largely driven by tumor-associated myeloid cells, including macrophages. Here, we report that toosendanin (TSN), a small-molecule compound, reprograms macrophages to enforce antitumor immunity in glioblastoma (GBM) in mouse models. Our functional screen of genetically probed macrophages with a chemical library identifies that TSN reverses macrophage-mediated tumor immunosuppression, leading to enhanced T cell infiltration, activation, and reduced exhaustion. Chemoproteomic and structural analyses revealed that TSN interacts with Hck and Lyn to abrogate suppressive macrophage immunity. In addition, a combination of immune checkpoint blockade and TSN therapy induced regression of syngeneic GBM tumors in mice. Furthermore, TSN treatment sensitized GBM to Egfrviii chimeric antigen receptor (CAR) T cell therapy. These findings suggest that TSN may serve as a therapeutic compound that blocks tumor immunosuppression and circumvents tumor resistance to T cell-based immunotherapy in GBM and other solid tumors that warrants further investigation.

Distinguishing Progression from Pseudoprogression in Glioblastoma Using 18F-Fluciclovine PET.

Accurate differentiation between tumor progression (TP) and pseudoprogression remains a critical unmet need in neurooncology. 18F-fluciclovine is a widely available synthetic amino acid PET radiotracer. In this study, we aimed to assess the value of 18F-fluciclovine PET for differentiating pseudoprogression from TP in a prospective cohort of patients with suspected radiographic recurrence of glioblastoma. Methods: We enrolled 30 glioblastoma patients with radiographic progression after first-line chemoradiotherapy for whom surgical resection was planned. The patients underwent preoperative 18F-fluciclovine PET and MRI. The relative percentages of viable tumor and therapy-related changes observed in histopathology were quantified and categorized as TP (≥50% viable tumor), mixed TP (<50% and >10% viable tumor), or pseudoprogression (≤10% viable tumor). Results: Eighteen patients had TP, 4 had mixed TP, and 8 had pseudoprogression. Patients with TP/mixed TP had a significantly higher 40- to 50-min SUVmax (6.64 + 1.88 vs. 4.11 ± 1.52, P = 0.009) than patients with pseudoprogression. A 40- to 50-min SUVmax cutoff of 4.66 provided 90% sensitivity and 83% specificity for differentiation of TP/mixed TP from pseudoprogression (area under the curve [AUC], 0.86). A maximum relative cerebral blood volume cutoff of 3.672 provided 90% sensitivity and 71% specificity for differentiation of TP/mixed TP from pseudoprogression (AUC, 0.779). Combining a 40- to 50-min SUVmax cutoff of 4.66 and a maximum relative cerebral blood volume of 3.67 on MRI provided 100% sensitivity and 80% specificity for differentiating TP/mixed TP from pseudoprogression (AUC, 0.95). Conclusion: 18F-fluciclovine PET uptake can accurately differentiate pseudoprogression from TP in glioblastoma, with even greater accuracy when combined with multiparametric MRI. Given the wide availability of 18F-fluciclovine, larger, multicenter studies are warranted to determine whether amino acid PET with 18F-fluciclovine should be used in the routine posttreatment assessment of glioblastoma.

Clinical utility of plasma cell-free DNA in gliomas.

Noninvasive molecular profiling of tumors using plasma-based next-generation sequencing (NGS) is increasingly used to aid in diagnosis, treatment selection, and disease monitoring in oncology. In patients with glioma, however, the plasma cell-free DNA (cfDNA) tumor fraction, defined as the fractional proportion of circulating tumor-derived DNA (ctDNA) relative to total cfDNA, is especially low, in large part due to the blood-brain barrier. As a result, commercial plasma-based NGS assays, designed to screen for a small number of actionable genomic alterations, are not sensitive enough to guide the management of patients with glioma. As this has been long recognized in neuro-oncology, significant research efforts have been undertaken to improve the sensitivity of plasma ctDNA detection in patients with glioma and to understand the biology and clinical relevance of non-tumor-derived cfDNA, which makes up most of the total cfDNA pool. Here, we review key recent advances in the field of plasma cfDNA analysis in patients with glioma, including (1) the prognostic impact of pre-treatment and on-treatment total plasma cfDNA concentrations, (2) use of tumor-guided sequencing approaches to improve the sensitivity of ctDNA detection in the plasma, and (3) the emergence of plasma cfDNA methylomics for detection and discrimination of glioma from other primary intracranial tumors.