Efficacy In Glioblastoma Research Articles

Synergistically Enhancing Immunotherapy Efficacy in Glioblastoma with Gold-Core Silica-Shell Nanoparticles and Radiation.

Glioblastoma is a highly aggressive brain tumor with universally poor outcomes. Recent progress in immune checkpoint inhibitors has led to increased interest in their application in glioblastoma. Nonetheless, the unique immune milieu in the brain has posed remarkable challenges to the efficacy of immunotherapy. We aimed to leverage the radiation-induced immunogenic cell death to overcome the immunosuppressive network in glioblastoma. We developed a novel approach using the gold-core silica-shell nanoparticles (Au@SiO2 NPs) in combination with low-dose radiation to enhance the therapeutic efficacy of the immune checkpoint inhibitor (atezolizumab) in brain tumors. The biocompatibility, immune cell recruitment, and antitumor ability of the combinatorial strategy were determined using in vitro assays and in vivo models. Our approach successfully induced the migration of macrophages towards brain tumors and promoted cancer cell apoptosis. Subcutaneous tumor models demonstrated favorable safety profiles and significantly enhanced anticancer effects. In orthotopic brain tumor models, the multimodal therapy yielded substantial prognostic benefits over any individual modalities, achieving an impressive 40% survival rate. In summary, the combination of Au@SiO2 NPs and low-dose radiation holds the potential to improve the clinical efficacy of immune checkpoint inhibitors. The synergetic strategy modulates tumor microenvironments and enhances systemic antitumor immunity, paving a novel way for glioblastoma treatment.

IMMU-04. LOW-INTENSITY PULSED ULTRASOUND ENHANCES CAR T CELL THERAPY BY INDUCING TWO-WAY IMMUNE CELL TRAFFICKING – T CELL INTO TUMOR AND MYELOID CELL INTO PERIPHERY IN A SYNGENEIC MOUSE GLIOBLASTOMA MODEL

Abstract Chimeric Antigen Receptor (CAR) T-cell therapy has been successful against hematological malignancies. However, it has not established efficacy in glioblastoma (GBM) patients. Significant challenges currently limiting the effectiveness of CAR T-cell therapy for patients with GBM include poor CAR-T cell trafficking to GBM due to the blood-brain barrier, and the presence of highly immunosuppressive and pro-tumoral tumor-associated macrophages (TAMs) in the tumor microenvironment. Furthermore, the heterogeneous expression of target antigens in GBM can lead to antigen escape and therapeutic resistance. Low-intensity pulsed ultrasound with microbubbles (LIPU/MB) has been shown to enhance CAR T-cell trafficking and improve survival in immunocompromised xenograft mice GBM models. In this study, we investigated whether multiple rounds of LIPU/MB can improve not only CAR T-cell but also endogenous T-cell infiltration into the tumors and induce myeloid cell trafficking into lymph nodes (LNs), thus enhancing CAR T-cell therapy against GBM in the immunocompetent syngeneic mice model. We recently developed a novel immunocompetent transgenic (Tg) mouse that expresses an anti-EGFRvIII CAR on T-cells and enables us to investigate the interaction between CAR T-cells and the endogenous immune environment. C57BL6/J mice bearing intracerebral EGFRvIII+ GBM received an intravenous administration of anti-EGFRvIII CAR T-cells derived from Tg-mice. The mice were stratified to receive single-LIPU (1 min before CAR T-cells administration) or triple-LIPU/MB (1 min before CAR T-cells administration, then two and four days later). Triple-LIPU/MB significantly suppressed tumor growth and improved survival and was associated with increased CAR T-cells and endogenous T-cells infiltration into the tumors compared with single-LIPU/MB or without LIPU. Furthermore, draining cervical LNs showed increased macrophages trafficking after triple-LIPU/MB. Moreover, TAMs isolated from triple-LIPU/MB mice brains showed higher levels of MHC-II expression. These results suggest that LIPU/MB may promote the tumor antigen presentation to endogenous T-cells and enhance the efficacy of CAR T-cell therapy for GBM.

Delivery versus Potency in Treating Brain Tumors: BI-907828, a MDM2-p53 Antagonist with Limited BBB Penetration but Significant In Vivo Efficacy in Glioblastoma.

MDM2-p53 inhibition may be effective in glioblastoma (GBM). This study evaluates the pharmacokinetics/pharmacodynamics of BI-907828, a potent antagonist of MDM2, in GBM, and demonstrates a translational paradigm with a focus on a unified "Delivery - Potency - Efficacy" relationship in drug development for central nervous system(CNS) tumors. BI-907828 was tested for cytotoxicity and MDM2-p53 pathway inhibition. Systemic pharmacokinetics and transport mechanisms controlling CNS distribution were evaluated in mice. BI-907828 free fractions in cell media, mouse and human specimens were measured to determine "active" unbound concentrations. Efficacy measures, including overall survival and target expression were assessed in mouse orthotopic GBM xenografts. BI-907828 exhibited potent inhibition of MDM2-p53 pathway and promoted cell death in GBM TP53 wild-type cells. MDM2-amplified cells are highly sensitive to BI-907828, with an effective unbound concentration of 0.1 nmol/L. The CNS distribution of BI-907828 is limited by blood-brain barrier (BBB) efflux mediated by P-gp, resulting in a Kp,uu_brain of 0.002. Despite this seemingly "poor" BBB penetration, weekly administration of 10 mg/kg BI-907828 extended median survival of orthotopic GBM108 xenografts from 28 to 218 days (P < 0.0001). This excellent efficacy can be attributed to high potency, resulting in a limited, yet effective, exposure in the CNS. These studies show that efficacy of BI-907828 in orthotopic models is related to high potency even though its CNS distribution is limited by BBB efflux. Therefore, a comprehensive understanding of all aspects of the "Delivery - Potency - Efficacy" relationship is warranted in drug discovery and development, especially for treatment of CNS tumors.

EPIC-1042 as a potent PTRF/Cavin1-caveolin-1 interaction inhibitor to induce PARP1 autophagic degradation and suppress temozolomide efflux for glioblastoma.

Temozolomide (TMZ) treatment efficacy in glioblastoma is determined by various mechanisms such as TMZ efflux, autophagy, base excision repair (BER) pathway, and the level of O6-methylguanine-DNA methyltransferase (MGMT). Here, we reported a novel small-molecular inhibitor (SMI) EPIC-1042 (C20H28N6) with the potential to decrease TMZ efflux and promote PARP1 degradation via autolysosomes in the early stage. EPIC-1042 was obtained from receptor-based virtual screening. Co-immunoprecipitation and pull-down assays were applied to verify the blocking effect of EPIC-1042. Western blotting, co-immunoprecipitation, and immunofluorescence were used to elucidate the underlying mechanisms of EPIC-1042. In vivo experiments were performed to verify the efficacy of EPIC-1042 in sensitizing glioblastoma cells to TMZ. EPIC-1042 physically interrupted the interaction of PTRF/Cavin1 and caveolin-1, leading to reduced secretion of small extracellular vesicles (sEVs) to decrease TMZ efflux. It also induced PARP1 autophagic degradation via increased p62 expression that more p62 bound to PARP1 and specially promoted PARP1 translocation into autolysosomes for degradation in the early stage. Moreover, EPIC-1042 inhibited autophagy flux at last. The application of EPIC-1042 enhanced TMZ efficacy in glioblastoma in vivo. EPIC-1042 reinforced the effect of TMZ by preventing TMZ efflux, inducing PARP1 degradation via autolysosomes to perturb the BER pathway and recruitment of MGMT, and inhibiting autophagy flux in the later stage. Therefore, this study provided a novel therapeutic strategy using the combination of TMZ with EPIC-1042 for glioblastoma treatment.

LMAP-07 POTENTIAL MECHANISM OF IMMUNE ESCAPE RELATED TO TUMOR-ASSOCIATED MACROPHAGE IN GLIOBLASTOMA AFTER COMBINED THERAPY WITH RADIOTHERAPY AND IMMUNE CHECKPOINT BLOCKER

Abstract Immune checkpoint blockers (ICBs) have revolutionized the treatment of cancer. Radiotherapy (RT) has been demonstrated to increase the survival benefit of ICBs in some cancers through its local and systemic immunomodulation, although its efficacy in glioblastoma (GBM) is very limited. With a thorough investigation of the immune responses to single and dual treatment utilizing single-cell RNA-seq analyses on the synergy of RT and anti-PD-L1 antibody (aPD-L1), we studied the potential mechanism of immune escape in GBM even when RT and ICB are combined. Our findings demonstrated a statistically significant longer survival of mice treated with RT and aPD-L1 combined than either single modality of treatment in an orthotopic syngeneic GBM model achieving a 70% cure rate. In the tumor tissues collected from the mouse brain that failed dual treatment, i.e., immune escaped, immune cell profiling still demonstrated much lower T regulatory cells and higher CD8+ cytotoxic T cells infiltrated to tumor, and elevated CD8+/CD4+ and CD8+/Treg ratios in the dual therapy group compared to single therapies, as expected with synergistic effects of dual treatment. RT with aPD-L1 markedly reduced CD8+ and CD4+ T exhaustion cells and elevated T-memory cells in comparison to single modality groups. Nevertheless, compared to the RT alone or no treatment control group, dual therapy failed to decrease the proportion of Arginase1-positive glioma-associated macrophages (GAM) in macrophage/monocytes in tumor microenvironment, which were considerably increased if treated with aPD-L1 only. Moreover, the combination of RT with aPD-L1 did not alter immunosuppressive gene expression in the macrophage/monocyte groups. In conclusion, our research demonstrated that RT and aPD-L1 together may elicit a potent and durable antitumor immune response in the GBM mouse model through regulating lymphocytes but not macrophages. Our findings point to the urgent need for research into GAM-modulating drug and their potential to prevent immunological escape.

Glioblastoma vascular plasticity limits effector T-cell infiltration and is blocked by cAMP activation.

Glioblastoma (GBM) is the deadliest form of brain cancer, characterized as a highly angiogenetic and immunosuppressive malignancy. Although immune checkpoint blockades have revolutionized cancer therapy, their therapeutic efficacy in GBM has been far less than expected or even ineffective. Here, we reveal that the genomic signature of glioma-derived endothelial cells (GdECs) correlates with an immunosuppressive state and poor prognosis of glioma patients. In vitro model of GdECs differentiation is established for drug screening, and we identify that cAMP activators could effectively block the GdECs formation by inducing oxidative stress. cAMP activator impairs the GdECs differentiation in vivo, normalizes the tumor vessels, and alters the immune profile, especially increasing the influx and function of CD8+ effector T cells. The dual blockade of GdECs and PD-1 induces tumor regression and establishes anti-tumor immune memory. Our study reveals that endothelial transdifferentiation of GBM shapes an endothelial immune cell barrier and supports the clinical development of combining GdECs blockade and immunotherapy for GBM.

Lysine methylation promotes NFAT5 activation and determines temozolomide efficacy in glioblastoma

Temozolomide (TMZ) therapy offers minimal clinical benefits in patients with glioblastoma multiforme (GBM) with high EGFR activity, underscoring the need for effective combination therapy. Here, we show that tonicity-responsive enhancer binding protein (NFAT5) lysine methylation, is a determinant of TMZ response. Mechanistically, EGFR activation induces phosphorylated EZH2 (Ser21) binding and triggers NFAT5 methylation at K668. Methylation prevents NFAT5 cytoplasm interaction with E3 ligase TRAF6, thus blocks NFAT5 lysosomal degradation and cytosol localization restriction, which was mediated by TRAF6 induced K63-linked ubiquitination, resulting in NFAT5 protein stabilization, nuclear accumulation and activation. Methylated NFAT5 leads to the upregulation of MGMT, a transcriptional target of NFAT5, which is responsible for unfavorable TMZ response. Inhibition of NFAT5 K668 methylation improved TMZ efficacy in orthotopic xenografts and patient-derived xenografts (PDX) models. Notably, NFAT5 K668 methylation levels are elevated in TMZ-refractory specimens and confer poor prognosis. Our findings suggest targeting NFAT5 methylation is a promising therapeutic strategy to improve TMZ response in tumors with EGFR activation.

A Trojan-Horse-Like Biomimetic Nano-NK to Elicit an Immunostimulatory Tumor Microenvironment for Enhanced GBM Chemo-Immunotherapy.

Although the chemo- and immuno-therapies have obtained good responses for several solid tumors, including those with brain metastasis, their clinical efficacy in glioblastoma (GBM) is disappointing. The lack of safe and effective delivery systems across the blood-brain barrier (BBB) and the immunosuppressive tumor microenvironment (TME) are two main hurdles for GBM therapy. Herein, a Trojan-horse-like nanoparticle system is designed, which encapsulates biocompatible PLGA-coated temozolomide (TMZ) and IL-15 nanoparticles (NPs) with cRGD-decorated NK cell membrane (R-NKm@NP), to elicit the immunostimulatory TME for GBM chemo-immunotherapy. Taking advantage of the outer NK cell membrane cooperating with cRGD, the R-NKm@NPs effectively traversed across the BBB and targeted GBM. In addition, the R-NKm@NPs exhibited good antitumor ability and prolonged the median survival of GBM-bearing mice. Notably, after R-NKm@NPs treatment, the locally released TMZ and IL-15 synergistically stimulated the proliferation and activation of NK cells, leading to the maturation of dendritic cells and infiltration of CD8+ cytotoxic T cells, eliciting an immunostimulatory TME. Lastly, the R-NKm@NPs not only effectively prolonged the metabolic cycling time of the drugs in vivo, but also has no noticeable side effects. This study may offer valuable insights for developing biomimetic nanoparticles to potentiate GBM chemo- and immuno-therapies in the future.

EPIC-0307-mediated selective disruption of PRADX-EZH2 interaction and enhancement of temozolomide sensitivity to glioblastoma via inhibiting DNA repair and MGMT.

Temozolomide (TMZ) treatment efficacy in glioblastoma (GBM) has been limited by resistance. The level of O-6-methylguanine-DNA methyltransferase (MGMT) and intrinsic DNA damage repair factors are important for the TMZ response in patients. Here, we reported a novel compound, called EPIC-0307, that increased TMZ sensitivity by inhibiting specific DNA damage repair proteins and MGMT expression. EPIC-0307 was derived by molecular docking screening. RNA immunoprecipitation (RIP), and chromatin immunoprecipitation by RNA (ChIRP) assays were used to verify the blocking effect. Chromatin immunoprecipitation (ChIP) and co-immunoprecipitation (Co-IP) assays were performed to explore the mechanism of EPIC-0307. A series of in vivo and in vitro experiments were designed to evaluate the efficacy of EPIC-0307 in sensitizing GBM cells to TMZ. EPIC-0307 selectively disrupted the binding of PRADX to EZH2 and upregulated the expression of P21 and PUMA, leading to cell cycle arrest and apoptosis in GBM cells. EPIC-0307 exhibited a synergistic inhibitory effect on GBM when combined with TMZ by downregulating TMZ-induced DNA damage repair responses and epigenetically silencing MGMT expression through modulating the recruitment of ATF3-pSTAT3-HDAC1 regulatory complex to the MGMT promoter. EPIC-0307 demonstrated significant efficacy in suppressing the tumorigenesis of GBM cells, restoring TMZ sensitivity. This study identified a potential small-molecule inhibitor (SMI) EPIC-0307 that selectively disrupted the PRADX-EZH2 interaction to upregulate expressions of tumor suppressor genes, thereby exerting its antitumor effects on GBM cells. EPIC-0307 treatment also increased the chemotherapeutic efficacy of TMZ by epigenetically downregulating DNA repair-associate genes and MGMT expression in GBM cells.

Development and validation of a GC-MS method for determination of metformin in normal brain and in glioblastoma tissues

Metformin hydrochloride (MH) has recently been repurposed as an anticancer agent, showing antiproliferative activity in vitro and in vivo. In particular, experimental evidence has suggested its potential clinical efficacy in glioblastoma (GBM), a very aggressive tumor frequently characterized by gloomy prognosis. Unfortunately, the published literature concerning experimental applications of MH in glioblastoma animal models report no data on metformin levels reached in the brain, which, considering the high hydrophilicity of the drug, are likely very low. Therefore, new sensitive analytical methods to be applied on biological tissues are necessary to improve our knowledge of MH in vivo biodistribution and biological effects on tumors. In this research work, a GC-MS method for MH quantification in brain tissues is proposed. MH has been derivatized using N-methyl-bis(trifluoroacetamide), as already described in the literature, but the derivatization conditions have been optimized; moreover, deuterated MH has been selected as the best internal standard, after a comparative evaluation including other internal standards employed in published methods. After ascertaining method linearity, its accuracy, precision, specificity, repeatability, LOD and LOQ (0.373 µM and 1.242 µM, respectively, corresponding to 0.887 and 2.958 pmol/mg of wet tissue) have been evaluated on mouse brain tissue samples, obtained through a straightforward preparation procedure involving methanolic extraction from lyophilized brain homogenates and solid phase purification. The method has been validated on brain samples obtained from mice, either healthy or xenografted with GBM cells, receiving metformin dissolved in the drinking water. This analytical method can be usefully applied in preclinical studies aiming at clarifying MH mechanism of action in brain tumors.

Novel Immunotherapeutic Approaches for the Treatment of Glioblastoma.

Glioblastoma is highly aggressive and remains difficult to treat despite being the most common malignant primary brain tumor in adults. Current standard-of-care treatment calls for maximum resection of the tumor mass followed by concurrent chemotherapy and radiotherapy and further adjuvant chemotherapy if necessary. Despite this regimen, prognosis remains grim. Immunotherapy has shown promising success in a variety of solid tumor types, but efficacy in glioblastoma is yet to be demonstrated. Barriers to the success of immunotherapy in glioblastoma include: a heterogeneous tumor cell population, a highly immunosuppressive microenvironment, and the blood-brain barrier, to name a few. Several immunotherapeutic approaches are actively being investigated and developed to overcome these limitations. In this review, we present different classes of immunotherapy targeting glioblastoma, their most recent results, and potential future directions.

Assessment of The Impact of Oncolytic Virotherapy on The Immunopeptidome Profile of Tumor by Utilizing GEMM Derived Immunocompetent GBM Models

Abstract Immunotherapy clinical trials have not shown efficacy in glioblastoma (GBM), arguably the deadliest of all cancers. A microenvironment, characterized by a paucity of T cells recognizing tumor peptides displayed on major histocompatibility complexes of tumor cells is one of the main reasons for GBM’s evasion. Virotherapy provides the opportunity to reshape the GBM TME towards pro-inflammatory phenotype. Data from a recent clinical trial with herpes simplex-1 based oncolytic virus (oHSV) have shown that the administration of these agents leads to a rapid influx of CD8 T cells, and activation of myeloid cells, suggesting that oHSV may offer an in-situ vaccination approach to increase availability of actionable antigens. C57BL/6-derived GBM models do not mimic the outcome observed with patient derived tumors in terms of virus replication. To decipher the impact of oHSV on tumor antigen specific responses, better immunocompetent models are needed. To assess whether oHSV treatment modulates the immunopeptidome profile (IP) of tumor, we used two transplantable GEMM-derived GBM models, 1620 and 1694. Both have wild type human EGFR, loss of Pten and Cdkn2a in BALB/c background. These models were more receptive to infection than CT2A. In vivo, virus persisted in tumors for up to 6 days, but not for 4 days in CT2A. IP analyses revealed that oHSV promotes epitope presentation on tumor cells and in TME. Moreover, low dose of virus efficiently induced antigen availability in both models though it differentially modulated the MHC ligandome. Using two new GBM models, we showed that an oncolytic virus used in clinical trial with recurrent GBM (NCT03152318) modulates IP of tumors, and low dose of virus is sufficient to induce the presentation of tumor epitopes. This project is supported by Bridge Fund given to Drs. Chiocca and White and P01 CA236749 to Dr. Chiocca.

Minimally Invasive Treatments for Glioblastoma: A Review of Current and Emerging Surgical Technologies

Glioblastoma (GBM) is malignant, primary intracranial neoplasm associated with poor outcomes. Maximal, safe cytoreduction remains an important component of effective treatment for patients with this disease; however, some patients are not candidates for resection due to comorbid status, tumor location, or other factors. In this review, we aimed to describe minimally invasive surgical techniques that are emerging as important tools for improving safety and efficiency in GBM cytoreduction, including for patients with previously unresectable lesions. Specifically, we aimed to describe the commercially available tubular retractor systems and describe the available data regarding the benefits, risks, and utility of these retractors for patients with GBM. Additionally, we aimed to describe laser interstitial thermal therapy (LITT) and its use in GBM, including a description of the mechanism of action, commercially available systems, the steps in surgical implantation, available outcomes data, and future directions for the technology in this context. Finally, we aimed to review the use of MRI-guided high-intensity focused ultrasound (MRgHIFU) in GBM, including a description of its mechanism and data regarding efficacy in GBM. The availability and use of tubular retractors, LITT, and MRgHIFU provide clinically effective alternative methods for cytoreduction in GBM and are also emerging as important tools for the expansion of treatment to GBM that previously may have been classified as nonresectable. This review will assist in the development of an intimate knowledge of the use and utility of these techniques and is important for clinicians caring for patients with GBM.

PHGDH Inhibition Overcomes Glioblastoma Resistance to T-cell Therapy.

Phosphoglycerate dehydrogenase (PHGDH) inhibition improves T-cell therapy efficacy in glioblastoma.

Prodrug-loaded semiconducting polymer hydrogels for deep-tissue sono-immunotherapy of orthotopic glioblastoma.

Although immunotherapy has achieved great success in the treatment of a variety of tumors, its efficacy for glioblastoma (GBM) is still limited. Both the immunosuppressive tumor microenvironment (TME) and poor penetration of immunotherapeutic agents into tumors contributed to the poor anti-glioma immunity. Herein, we develop an injectable prodrug-loaded hydrogel delivery system with sono-activatable properties for sonodynamic therapy (SDT)-triggered immunomodulation for GBM treatment. The prodrug alginate hydrogels (APN), which contain semiconducting polymer nanoparticles (SPNs) and the NLG919 prodrug linked by singlet oxygen (1O2)-cleavable linkers, are in situ formed via coordination of alginate solution with Ca2+ in the TME. SPNs serve as sonosensitizers to produce 1O2 upon ultrasound (US) irradiation for SDT. The generated 1O2 not only induce immunogenic cell death, but also break 1O2-cleavable linkers to precisely activate the NLG919 prodrug. Antitumor immunity is significantly amplified due to the reversal of immunosuppression mediated by indolamine 2,3-dioxygenase-dependent tryptophan metabolism. This smart prodrug hydrogel platform potently inhibits tumor growth in orthotopic glioma-bearing mice. Collectively, this work provides a sono-activatable hydrogel platform for precise sono-immunotherapy against GBM.

Ultrasound-excited temozolomide sonosensitization induces necroptosis in glioblastoma

Temozolomide (TMZ) has been determined to be the chemotherapeutic drug with efficacy for glioblastoma (GBM). Thus, potentiating the therapeutic effect of TMZ can undoubtedly yield twice the result with half the effort. In this study, we found for the first time that TMZ can produce reactive oxygen species (ROS) under the influence of ultrasound (US). This property allows TMZ-US therapy to have better efficacy in the treatment of GBM. Given that the increasing use of US in central nervous system (CNS) diseases and the importance of TMZ for GBM therapy, our results will facilitate the development of TMZ-associated glioblastoma therapies. Moreover, we found that chemotherapeutic drugs might have the ability to generate ROS under the excitation of US. On a larger scale, our findings may be applicable to a wide range of known drugs.

A Pt(IV)-conjugated brain penetrant macrocyclic peptide shows pre-clinical efficacy in glioblastoma.

Glioblastoma (GBM) is the most aggressive primary malignant brain tumor, with a median survival of approximately 15months. Treatment is limited by the blood-brain barrier (BBB) which restricts the passage of most drugs to the brain. We previously reported the design and synthesis of a BBB-penetrant macrocyclic cell-penetrating peptide conjugate (M13) covalently linked at the axial position of a Pt(IV) cisplatin prodrug. Here we show the Pt(IV)-M13 conjugate releases active cisplatin upon intracellular reduction and effects potent in vitro GBM cell killing. Pt(IV)-M13 significantly increased platinum uptake in an in vitro BBB spheroid model and intravenous administration of Pt(IV)-M13 in GBM tumor-bearing mice led to higher platinum levels in brain tissue and intratumorally compared with cisplatin. Pt(IV)-M13 administration was tolerated in naïve nude mice at higher dosage regimes than cisplatin and significantly extended survival above controls in a murine GBM xenograft model (median survival 33days for Pt(IV)-M13 vs 24days for Pt(IV) prodrug, 22.5days for cisplatin and 22days for control). Increased numbers of γH2AX nuclear foci, biomarkers of DNA damage, were observed in tumors of Pt(IV)-M13-treated mice, consistent with elevated platinum levels. The present work provides the first demonstration that systemic injection of a Pt(IV) complex conjugated to a brain-penetrant macrocyclic peptide can lead to increased platinum levels in the brain and extend survival in mouse GBM models, supporting further development of this approach and the utility of brain-penetrating macrocyclic peptide conjugates for delivering non-BBB penetrant drugs to the central nervous system.

Impact of CD4 T cells on intratumoral CD8 T-cell exhaustion and responsiveness to PD-1 blockade therapy in mouse brain tumors

BackgroundGlioblastoma is a fatal disease despite aggressive multimodal therapy. PD-1 blockade, a therapy that reinvigorates hypofunctional exhausted CD8 T cells (Tex) in many malignancies, has not shown efficacy in glioblastoma....

CTIM-06. EVALUATING THE ASSOCIATION BETWEEN PERIPHERAL BLOOD IMMUNOLOGIC RESPONSE AND THERAPEUTIC RESPONSE TO IMMUNE CHECKPOINT INHIBITION IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA AND GLIOSARCOMA

Abstract Immune checkpoint inhibition (ICI) has failed to demonstrate significant efficacy in glioblastoma. With the underlying hypothesis that generation of an immune response in peripheral is necessary for a brain tumor response, we are enrolling patients with newly diagnosed glioblastoma on an ICI immunotherapy clinical trial with longitudinal monitoring of immune function. The purpose of this work is to improve patient selectivity for response to ICI treatment by identifying peripheral immunologic response via immunophenotyping and functional analyses. Currently, 10 of a planned 48 patients have been treated with combination nivolumab and ipilimumab (NCI-21-C-0015). We analyzed blood samples of the first two patients, from pretreatment through cycle 5 of combination ICI to confirm methods used in this clinical trial. Longitudinal evaluation of immunologic response using comprehensive flow cytometric analysis and an in vitro T cell stimulation paradigm with nivolumab and ipilimumab supplementation, serving as an ex vivo predictor of immune response, are reported. Immunophenotyping via flow cytometry successfully documented patients’ peripheral immune cell phenotypes, and ELISpot and in vitro stimulation assays successfully measured patients’ immune cell functional capacitance. Both patients analyzed have shown increased proportions of effector/memory phenotypes within peripheral T cells, and a decrease in peripheral lymphocyte/monocyte ratio during treatment, potentially indicating lymphocyte sequestration in bone marrow or recruitment to the tumor microenvironment. ELISpot analysis documented interferon-γ production capability of T cell is maintained during treatment. Moreover, preliminary analysis of patients’ T cell proliferative capacity in PBMC utilizing in vitro anti-CD3 stimulation indicated T cells become increased in proliferative capability during treatment. These findings support the feasibility of longitudinal assessments, demonstrating that immunologic responsiveness and functionality can be detected with these blood monitoring strategies. Additional patients’ samples will be tested to allow confirmation of trends in immunologic response, and correlations with patient outcomes will be reported at time of presentation.

CTIM-07. PHASE II RANDOMIZED, BLINDED, PLACEBO-CONTROLLED TRIAL TESTING PP65 CMV MRNA DENDRITIC CELL VACCINE AND TETANUS-DIPHTHERIA TOXOID FOR NEWLY DIAGNOSED GBM (ATTAC II, NCT02465268)

Abstract INTRODUCTION Immunotherapy is limited in efficacy for glioblastoma (GBM). The objective of this study was to evaluate the efficacy and immune effects of the pp65 mRNA dendritic cell (DC) vaccine with the use of lysosomal-associated membrane protein (LAMP) in two different formulations (full-length (fl) and short-length (sh). METHODS Patients who underwent resection of newly diagnosed GBM were enrolled and randomized to one of 3 arms: Arm 1) pp65-shLAMP mRNA DC with GM-CSF, Arm 2) pp65-flLAMP mRNA DC with GM-CSF, Arm 3) Unpulsed peripheral blood mononuclear cells (PBMC). After surgery, patients underwent leukapheresis for PBMC isolation and vaccines generation. Patients were treated with standard radiation and temozolomide followed by dose intensified adjuvant temozolomide at 75-100 mg/m2 x 21 days (aged less than 70) or standard dose at 150-200 mg/m2 x 5 days (patients 70 and older). Immunization started days 22-24 of cycle #1 with vaccines 1-3 delivered at 2 week intervals. All patients received tetanus-toxoid booster prior to vaccine 1. Patients continued to receive monthly vaccines for up to 10 vaccines with tetanus-diphtheria toxoid skin prep prior to vaccines 3, 6 and 9 (arms 1 and 2). Safety, efficacy and immune labs were evaluated. RESULTS Overall DC vaccines were well-tolerated with 2 SAEs possibly attributed to DC vaccination that met criteria as DLTs. Of recorded grade 2 or lower AEs, 2 were possibly attributable to DC vaccination. One patient was removed from the study due to failure to produce DC vaccines that met QA/QC release criteria. CONCLUSION In a large randomized and blinded patient cohort, delivery of CMV LAMP pp65 mRNA DC vaccines is feasible and safe in a multi-institutional setting. The primary endpoint of survival will be analyzed at the conclusion of the study.