Trials For Glioblastoma Research Articles

Simulating photodynamic therapy for the treatment of glioblastoma using Monte Carlo radiative transport.

Glioblastoma (GBM) is a rare but deadly form of brain tumor with a low median survival rate of 14.6 months, due to its resistance to treatment. An independent simulation of the INtraoperative photoDYnamic therapy for GliOblastoma (INDYGO) trial, a clinical trial aiming to treat the GBM resection cavity with photodynamic therapy (PDT) via a laser coupled balloon device, is demonstrated. To develop a framework providing increased understanding for the PDT treatment, its parameters, and their impact on the clinical outcome. We use Monte Carlo radiative transport techniques within a computational brain model containing a GBM to simulate light path and PDT effects. Treatment parameters (laser power, photosensitizer concentration, and irradiation time) are considered, as well as PDT's impact on brain tissue temperature. The simulation suggests that 39% of post-resection GBM cells are killed at the end of treatment when using the standard INDYGO trial protocol (light fluence = at balloon wall) and assuming an initial photosensitizer concentration of . Increases in treatment time and light power (light fluence = at balloon wall) result in further cell kill but increase brain cell temperature, which potentially affects treatment safety. Increasing the p hotosensitizer concentration produces the most significant increase in cell kill, with 61% of GBM cells killed when doubling concentration to and keeping the treatment time and power the same. According to these simulations, the standard trial protocol is reasonably well optimized with improvements in cell kill difficult to achieve without potentially dangerous increases in temperature. To improve treatment outcome, focus should be placed on improving the photosensitizer. With further development and optimization, the simulation could have potential clinical benefit and be used to help plan and optimize intraoperative PDT treatment for GBM.

Leveraging external control data in the design and analysis of neuro-oncology trials: Pearls and perils.

Randomized controlled trials have been the gold standard for evaluating medical treatments for many decades but they are often criticized for requiring large sample sizes. Given the urgent need for better therapies for glioblastoma, it has been argued that data collected from patients treated with the standard regimen can provide high-quality external control data to supplement or replace concurrent control arm in future glioblastoma trials. In this article, we provide an in-depth appraisal of the use of external control data in the context of neuro-oncology trials. We describe several clinical trial designs with particular attention to how external information is utilized and address common fallacies that may lead to inappropriate adoptions of external control data. Using 2 completed glioblastoma trials, we illustrate the use of an assessment tool that lays out a blueprint for assembling a high-quality external control data set. Using statistical simulations, we draw caution from scenarios where these approaches can fall short on controlling the type I error rate. While this approach may hold promise in generating informative data in certain settings, this sense of optimism should be tampered with a healthy dose of skepticism due to a myriad of design and analysis challenges articulated in this review. Importantly, careful planning is key to its successful implementation.

Small Molecule Immunomodulators as Next-Generation Therapeutics for Glioblastoma.

Glioblastoma (GBM), the most aggressive astrocytic glioma, remains a therapeutic challenge despite multimodal approaches. Immunotherapy holds promise, but its efficacy is hindered by the highly immunosuppressive GBM microenvironment. This review underscores the urgent need to comprehend the intricate interactions between glioma and immune cells, shaping the immunosuppressive tumor microenvironment (TME) in GBM. Immunotherapeutic advancements have shown limited success, prompting exploration of immunomodulatory approaches targeting tumor-associated macrophages (TAMs) and microglia, constituting a substantial portion of the GBM TME. Converting protumor M2-like TAMs to antitumor M1-like phenotypes emerges as a potential therapeutic strategy for GBM. The blood-brain barrier (BBB) poses an additional challenge to successful immunotherapy, restricting drug delivery to GBM TME. Research efforts to enhance BBB permeability have mainly focused on small molecules, which can traverse the BBB more effectively than biologics. Despite over 200 clinical trials for GBM, studies on small molecule immunomodulators within the GBM TME are scarce. Developing small molecules with optimal brain penetration and selectivity against immunomodulatory pathways presents a promising avenue for combination therapies in GBM. This comprehensive review discusses various immunomodulatory pathways in GBM progression with a focus on immune checkpoints and TAM-related targets. The exploration of such molecules, with the capacity to selectively target key immunomodulatory pathways and penetrate the BBB, holds the key to unlocking new combination therapy approaches for GBM.

The landscape of immune checkpoint inhibitor clinical trials in glioblastoma: A systematic review

Abstract Background Glioblastoma is characterized by rapid tumor growth and high invasiveness. The tumor microenvironment of glioblastoma is highly immunosuppressive with both intrinsic and adaptive resistance mechanisms that result in disease recurrence despite current immunotherapeutic strategies. Methods In this systematic review of clinical trials involving immunotherapy for glioblastoma using ClinicalTrials.gov and PubMed databases from 2016 and onward, we explore immunotherapeutic modalities involving immune checkpoint blockade (ICB). Results A total of 106 clinical trials were identified, 18 with clinical outcomes. ICB in glioblastoma has failed to improve overall survival compared to the current standard of care, including those therapies inhibiting multiple checkpoints. Among all immune checkpoint trials, targets included programmed cell death protein-1 (PD-1) (35/48), PD-L1 (12/48), cytotoxic T-lymphocyte-associated protein-4 (6/48), TIGIT (2/48), B7-H3 (2/48), and TIM-3 (1/48). Preliminary results from combination immunotherapies (32.1% of all trials) demonstrated improved treatment efficacy compared to monotherapy, specifically those combining checkpoint therapy with another immunotherapy modality. Conclusions Clinical trials involving ICB strategies for glioblastoma have not demonstrated improved survival. Comparison of therapeutic efficacy across trials was limited due to heterogeneity in the study population and outcome operationalization. Standardization of future trials could facilitate comparison across immunotherapy modalities for robust meta-analysis. Current immunotherapy trials have shifted focus toward combination strategies; preliminary results suggest that they are more encouraging than mono-modality immunotherapies. Given the intrinsic heterogeneity of glioblastoma, the utilization of immune markers will be key for the development of future immunotherapy approaches.

CTNI-16. USE OF PREDICTIVE SCORE-BASED HISTORICAL CONTROL DATA IN SINGLE-ARM TRIALS

Abstract Even though the randomized controlled trials (RCTs) are still the preferred approach to evaluate the effects of treatments, single-arm study designs have been traditionally used in Phase II oncology clinical trials. The single-arm studies using historical control or external control might be inevitable and even fatal when concurrent controls are impractical or unethical in rare and high-risk diseases. Due to recruiting difficulty, ethical and economic reasons, the single-arm trials can be a good option to test the experimental efficacy with the external control data of historical control rates for early efficacy phase 2 trials in glioblastoma. The FDA guidelines on external control data focus on the use of patient-level data from other clinical trials or real-world data (RWD), and so there is no guidance for summary-level historical control. Furthermore, there exist methodological issues to use historical data like identification of relevant data, amount of discounting (time difference and dissimilarity), prior robustness or operating characteristics. In this study, we propose a synthetic data based predictive scoring method optimally to match the historical control data with the characteristic conditions of the experimental studies. We consider both a binary (PFS on six months) and survival (median PFS) endpoints as surrogates for Phase 2 single-arm trials in newly diagnosed and recurrent glioblastoma patients. We perform meta-analysis to summarize the endpoints and the related socio-demographic, treatment and genetic factors from the summary-level historical data. Then we generate the synthetic patients based on the meta-summarized data. The generalized boosted regression models will be used to identify significant characteristics affecting the survival of GBM patients using the synthetic data. Finally the predictive score-based historical data model will be developed to provide the optimal matching with the characteristics of the experimental studies. This study will be validated using existing patient-level data as well as cross-validation methods.

IMMU-39. EFFICACY OF IMMUNE CHECKPOINT INHIBITORS IN GLIOBLASTOMA FROM REAL-WORLD DATA ANALYSIS

Abstract Immune checkpoint inhibitors (ICIs) failed to show efficacy in a randomized trial in glioblastoma (GBM). We utilized the patient-led XCELSIOR platform (NCT03793088) to evaluate ICIs in real-world GBM treatment. XCELSIOR centralizes EMR data from all care sites, creating longitudinal, source-verified data. Identity verification permits accurate overall survival (OS) calculations. As of 6/8/2023, 726 GBM patients were enrolled in XCELSIOR. Median diagnosis date was 1/13/2021 and median age was 56. Seventy-five patients (10%) received ICIs: 53 received pembrolizumab (71%) and 26 received nivolumab (35%) including 12 with ipilimumab (16%). Median days from diagnosis to ICI initiation was 263 days with 22 patients treated at 1st line, 39 at 2nd line, and 14 at 3rd line or later. Data was annotated for 71 patients treated with ICIs and 394 patients not treated with ICIs (no-ICI). Median OS (mOS) from diagnosis for all ICI patients vs. no-ICI was 4.95 years (95% CI 2.18-NR) vs. 1.75 years (1.56-2.03, p < 0.0001). Key features in the ICI cohort were 46% methylated MGMT, 47% gross total resection, 61% exposed to non-SOC agents besides ICI. Creating a propensity score matched cohort for these features, ICI vs. no-ICI had a numerically increased but non-significant mOS of 2.58 years (1.78-NR, n=62) vs. 2.05 years (1.76-2.61, n=113) but a 5-year survival rate of 44% for ICI vs. 16% for no-ICI. Optune use was similar, 39% ICI and 29% no-ICI. Common non-SOC agents used in the ICI cohort were everolimus (11%), osimertinib (8%), lenvatinib (7%), abemaciclib (7%), and neoantigen peptide vaccines (7%). Among unmethylated MGMT patients, mOS was 1.78 years for ICI vs. 1.8 years for no-ICI. These data suggest activity of ICIs for a subset of GBM patients, but do not support use in patients with unmethylated MGMT. Next steps will focus on discrete combination regimens in this evolving data.

CTNI-65. INVESTIGATING SAFETY AND EFFICACY OF TTFIELDS PRIOR AND CONCOMITANT TO RADIOTHERAPY IN NEWLY DIAGNOSED GLIOBLASTOMA - FIRST RESULTS OF THE PRICOTTF PHASE I/II TRIAL

Abstract BACKGROUND A synergistic inhibiting effect on glioblastoma cell proliferation was reported for the combination of TTFields and radiotherapy. Based on these preclinical findings, we performed the phase I/II PriCoTTF trial in adult nGBM patients to investigate the safety and efficacy of TTFields therapy initiated prior and concomitant to radiochemotherapy. Material and METHODS In this phase I/II trial, TTFields therapy was initiated following surgery and continued throughout radiochemotherapy and adjuvant chemotherapy for a total of approximately 9 months. TTFields rechallenge was allowed at recurrence. Radiotherapy was conducted with arrays applied on the patients’ scalp. Safety and tolerance are the study’s primary endpoint, determined by a selection of pre-specified treatment-limiting toxicities (TLTs). RESULTS A total of 33 patients have been enrolled. Patients' characteristics were mostly typical for glioblastoma, except for a rather low fraction of patients with gross total resection (GTR, 22.5%). The distribution of adverse events of ≥ common toxicity criteria (CTC) grade 3 was comparable to that of established glioblastoma trials. Notably, skin toxicity of ≥ CTC grade 3 was uncommon (n = 2, 6%). No patient developed TLTs. Median TTFields treatment duration was 8.4 months. Overall survival data was not mature enough (event rate 48%) to allow for a definite conclusion. Notably, on multivariable Cox regression, the number of days with TTFields adherence >23 hours was independently associated with overall survival (HR 0.96, 95% confidence interval 0.93 - 0.99, p = 0.008). CONCLUSION The PriCoTTF trial met its primary endpoint indicating that combined TTFields and radiotherapy is safe and well tolerated. High-grade skin toxicity was quite uncommon and the patients with high TTFields adherence seem to perform particularly well. An extended follow-up is required to provide first estimates regarding putative efficacy. At that point in time, the reduced overall TTFields duration and fraction of patients with GTR need to be factored in.

GLIOMA-05 A NOVEL CONCEPT FOR TREATMENT OF GLIOBLASTOMA: VAGUS NERVE ELECTRICAL STIMULATION FOR SUPPRESSION OF CYTOKINE (IL-6) SIGNALING

Abstract Glioblastoma is an aggressive, incurable cancer. Innovative approaches are urgently needed. There is resurgent interest in harnessing the power of the immune system (O’Rourke DM, 2017; Liau LM, 2023). Glioblastoma is a key target for cytokine reprogramming of the tumor microenvironment involving macrophages, monocytes, lymphocytes, and myeloid-derived cells. Furthermore, as with other cancers, the incidence and poor prognosis is linked to the age of the patient, and chronic, low-grade inflammation, or “inflammaging” (Franceschi, 2014). There is strong clinical, genomic (Coppola, 2014), preclinical data linking the progression of glioblastoma to the cytokine, IL-6. Yi Fan and colleagues (Wang, 2018; Yang, 2021) showed that blockade of IL-6 increases survival in mouse models of glioblastoma, an effect enhanced with the use of immune checkpoint blockade (ICB). These results were validated and extended by others (Tsukamoto, 2018; Lamano,2019). Taken together, we translated the findings to a prospective, multicenter clinical trial (NRG BRAIN-010, NCT04729959; PI, Stephen Bagley) for recurrent glioblastoma, combining stereotactic radiosurgery, IL-6R blockade (tocilizumab) and ICB (atezolizumab). To date, the regimen is well-tolerated with an acceptable safety profile. Vagus nerve stimulation is FDA-approved for control of medically refractory epilepsy. It is currently being evaluated in a multicenter, pivotal trial to treat advanced rheumatoid arthritis (RESET-RA, NCT04539964). Electrical stimulation of the vagus nerve activates the inflammatory reflex (Kelly, 2022), with a reduction of inflammatory cytokines, including IL-6 (Koopman, 2016). Electrical stimulation of the vagus nerve uses the ‘inflammatory reflex’ and exploits the cholinergic effect on T-cells (Levine, 2020). Taken together, we now propose a clinical trial to assess the safety and efficacy of vagal nerve stimulation for patients with glioblastoma and are in discussion with industry (SetPoint Medical) to design a prospective, clinical trial for treatment of glioblastoma.

Photobac derived from bacteriochlorophyll-a shows potential for treating brain tumor in animal models by photodynamic therapy with desired pharmacokinetics and limited toxicity in rats and dogs

Photobac is a near infrared photosensitizer (PS) derived from naturally occurring bacteriochlorophyll- a, with a potential for treating a variety of cancer types (U87, F98 and C6 tumor cells in vitro). The main objective of the studies presented herein was to evaluate the efficacy, toxicity and pharmacokinetic profile of Photobac in animals (mice, rats and dogs) and submit these results to the United States Food and Drug Administration (US FDA) for its approval to initiate Phase I human clinical trials of glioblastoma, a deadly cancer disease with no long term cure. The photodynamic therapy (PDT) efficacy of Photobac was evaluated in mice subcutaneously implanted with U87 tumors, and in rats bearing C6 tumors implanted in brain. In both tumor types, the Photobac-PDT was quite effective. The long-term cure in rats was monitored by magnetic resonance imaging (MRI) and histopathology analysis. A detailed pharmacology, pharmacokinetics and toxicokinetic study of Photobac was investigated in both non-GLP and GLP facilities at variable doses following the US FDA parameters. Safety Pharmacology studies suggest that there is no phototoxicity, cerebral or retinal toxicity with Photobac. No metabolites of Photobac were observed following incubation in rat, dog, mini-pig and human hepatocytes. Based on current biological data, Photobac-IND received the approval for Phase-I human clinical trials to treat Glioblastoma (brain cancer), which is currently underway at our institute. Photobac has also received an orphan drug status from the US FDA, because of its potential for treating Glioblastoma as no effective treatment is currently available for this deadly disease.

IMAGING HABITAT CHANGES AFTER PREOPERATIVE RADIOTHERAPY FOR GLIOBLASTOMA: UTILISATION OF A BIOINFORMATICS AND MACHINE LEARNING PIPELINE TO CHARACTERISE REGIONAL TREATMENT RESPONSE

Abstract AIMS Imaging of tumour habitats is a novel technique to assess regional treatment response by defining tumour ‘habitats’, which are regions with shared imaging characteristics. Here, we describe a novel pipeline to characterise imaging habitats in glioblastoma using bioinformatics and machine learning. We apply this pipeline to glioblastoma patients in the Preoperative Brain Irradiation in Glioblastoma (POBIG) trial that received preoperative radiotherapy for the first time. METHOD Glioblastoma patients underwent preoperative diffusion/perfusion MRI. A two- stage clustering pipeline was developed to define imaging habitats using relative cerebral blood volume (rCBV) and apparent diffusion co- effcient (ADC). 6 habitats were defined that occupied 10.6-21.5% of tumour volume. Treatment response was evaluated using Ktrans permeability. RESULTS In newly diagnosed cases the commonest habitats included those with a medium and high rCBV. In contrast, recurrent cases had significantly greater proportion of low rCBV habitats (p = 0.026). Two patients in the POBIG trial received 8 Gy preoperative radiotherapy. Within 24 hours of treatment there was a global decrease in vascularity with a decrease in high rCBV habitats (-3.7%) and increase in low rCBV habitats (+8.2%) in irradiated regions. Habitats demonstrated a heterogeneous response to preoperative radiotherapy, with a greater increase in Ktrans in high rCBV habitats (mean +83%) versus low rCBV habitats (mean +40%). CONCLUSIONS We have developed a unique pipeline to delineate imaging habitats in glioblastoma and applied it to a novel trial. Imaging habitats can allow regional monitoring of treatment response and could allow more targeted treatment in future.

DEVELOPING 3D PRINTING MODELS OF BRAIN TUMOURS

Abstract AIMS To succeed in clinical trials for glioblastoma we need in vitro models capable of more faithfully replicating dis- ease biology and more accurately predicting patient drug responses. To this end, new bioprinting technologies have the potential to biofabricate clinically relevant biomimetic tissues which can accelerate drug discovery and additionally serve as a platform for personalized medicine. METHOD We evaluated the effect of individual biomaterials and combinations of biomaterials, including decellularised pig brain extracellular matrix (dECM), fibrin, gelatin-methacryloyl (GelMA), hyaluronic acid-methacrylate (HAMA), Matrigel and alginate, on the proliferation and invasion of aggressive brain cancer cells (U87) in vitro. Cell viability was assessed using propidium iodide. Invasiveness was studied employing confocal microscopy. Data generated from Z-stacks was analysed using ImageJ to determine the size and circularity of cells. RESULTS Although Matrigel supports rapid cell proliferation and invasion, it has mechanical properties unsuited to bio- printing. In contrast, HAMA displays a pronounced shear-thinning behaviour and rapid controllable photo- crosslinking. Combinations of HAMA-fibrin provided results comparable to those seen with Matrigel or HAMA- Matrigel. However, high levels of crosslinking affected these biomaterial mixtures, resulting in a decreased ability of cells to grow and spread. CONCLUSIONS Initial results indicate that the addition of fibrin to HAMA promoted the growth and spreading of U87 cells. In further work, we aim to improve our printed constructs by including porcine brain dECM, microglia and recently established cell lines from paediatric patients. The project will test whether these bioprinted models can provide drug testing data with closer results to human disease than current, simpler alternatives.

Trends in Immunotherapy Clinical Trials to Treat Glioblastoma: A Look at Progress and Challenges

We aimed to catalog past and present clinical trials on immunotherapy treatments for glioblastoma (GBM) and discover relevant trends in this field. Former and ongoing clinical trials involving the use of immunotherapy to treat GBM were queried in July 2022 within the clinicaltrials.gov registry (https://clinicaltrials.gov/). Pertinent trials were categorized by variables including immunotherapy classification, tumor type (newly diagnosed vs. recurrent), country of origin, start date, clinical phase, study completion status, estimated subject enrollment, design, publication status, and funding source. A list of 173 trials were identified in total. The number of immunotherapy clinical trials to treat GBM has increased over time. The largest proportion of trials were gene therapies (97 studies; 56.1%) and viral therapies (37 studies; 21.4%). Studies were designated as a biologic (45.1%), drug (43.9%), genetic (2.3%), or procedure (1.2%). Trials spanned 19 countries; China, the second largest contributor (5.8%) after the United States (70.0%), has increased clinical trial development in the past years. The average time to completion was 52.3 months. Trials were primarily funded by academic centers; however, one-fourth of the trials were funded by industry and two were funded by foundations. One-tenth of the trials were active and over one-third were linked to publications. Our findings provide a comprehensive summary of the state of immunotherapy clinical trials for GBM, highlighting the evolving nature and growing scope of this field.

Delineation and agreement of FET PET biological volumes in glioblastoma: results of the nuclear medicine credentialing program from the prospective, multi-centre trial evaluating FET PET In Glioblastoma (FIG) study—TROG 18.06

PurposeThe O-(2-[18F]-fluoroethyl)-l-tyrosine (FET) PET in Glioblastoma (FIG) trial is an Australian prospective, multi-centre study evaluating FET PET for glioblastoma patient management. FET PET imaging timepoints are pre-chemoradiotherapy (FET1), 1-month post-chemoradiotherapy (FET2), and at suspected progression (FET3). Before participant recruitment, site nuclear medicine physicians (NMPs) underwent credentialing of FET PET delineation and image interpretation.MethodsSites were required to complete contouring and dynamic analysis by ≥ 2 NMPs on benchmarking cases (n = 6) assessing biological tumour volume (BTV) delineation (3 × FET1) and image interpretation (3 × FET3). Data was reviewed by experts and violations noted. BTV definition includes tumour-to-background ratio (TBR) threshold of 1.6 with crescent-shaped background contour in the contralateral normal brain. Recurrence/pseudoprogression interpretation (FET3) required assessment of maximum TBR (TBRmax), dynamic analysis (time activity curve [TAC] type, time to peak), and qualitative assessment. Intraclass correlation coefficient (ICC) assessed volume agreement, coefficient of variation (CoV) compared maximum/mean TBR (TBRmax/TBRmean) across cases, and pairwise analysis assessed spatial (Dice similarity coefficient [DSC]) and boundary agreement (Hausdorff distance [HD], mean absolute surface distance [MASD]).ResultsData was accrued from 21 NMPs (10 centres, n ≥ 2 each) and 20 underwent review. The initial pass rate was 93/119 (78.2%) and 27/30 requested resubmissions were completed. Violations were found in 25/72 (34.7%; 13/12 minor/major) of FET1 and 22/74 (29.7%; 14/8 minor/major) of FET3 reports. The primary reasons for resubmission were as follows: BTV over-contour (15/30, 50.0%), background placement (8/30, 26.7%), TAC classification (9/30, 30.0%), and image interpretation (7/30, 23.3%). CoV median and range for BTV, TBRmax, and TBRmean were 21.53% (12.00–30.10%), 5.89% (5.01–6.68%), and 5.01% (3.37–6.34%), respectively. BTV agreement was moderate to excellent (ICC = 0.82; 95% CI, 0.63–0.97) with good spatial (DSC = 0.84 ± 0.09) and boundary (HD = 15.78 ± 8.30 mm; MASD = 1.47 ± 1.36 mm) agreement.ConclusionThe FIG study credentialing program has increased expertise across study sites. TBRmax and TBRmean were robust, with considerable variability in BTV delineation and image interpretation observed.

TIPS-22 A TWO-PART, PHASE 1 STUDY OF RHENIUM (186RE) OBISBEMEDA (186RNL) DELIVERED BY CONVECTION ENHANCED DELIVERY (CED) FOR RECURRENT, REFRACTORY, OR PROGRESSIVE CHILDHOOD EPENDYMOMA AND HIGH-GRADE GLIOMA (HGG)

Abstract INTRODUCTION: Childhood ependymoma and HGG are difficult tumors to treat. Recurrent ependymoma is treated with re-resection and multiple rounds of EBRT. HGG is treated with chemoradiation followed by clinical trials, if available. While EBRT remains a central component of management, it is limited by tolerance of the surrounding normal brain tissue. 186RNL permits the selective delivery of beta-emitting radiation with excellent tumor retention. In an adult Phase 1/2 trial for recurrent glioblastoma (NCT01906385), the mean absorbed dose to the tumor was ~300-500 Gy, markedly higher than absorbed doses typically delivered by EBRT. Despite this, no dose-limiting toxicity was observed, and no treatment-related serious adverse events have occurred. Here, we describe the first pediatric trial using a two-part, Phase 1 dose-finding study followed by expansion cohorts to explore efficacy. Enrolling subjects will be 6 to 21 years of age with a diagnosis of recurrent ependymoma or HGG. Subjects will be allowed to enroll either if they have exhausted standard of care options or if they are clinically stable and surgical resection can be deferred by 4 weeks. Part 1 will enroll up to 24 subjects to determine the maximum feasible dose (MFD) of 186RNL administered by CED. Tumor size and concentration of infusate will be escalated in each cohort (A-D) to a maximum tumor diameter of 6 cm (114.1 mL) and a concentration of 2mCi/ml. Up to 4 CED catheters will be used. Part 2 will independently evaluate 186RNL in 2 different expansion cohorts: Cohort 2A: recurrent ependymoma; Cohort B: recurrent HGG. The primary endpoint for Cohort 2A is overall response rate (ORR) by Radiographic Assessment in Pediatric Neuro-Oncology (RAPNO) criteria and the primary endpoint for Cohort 2B is progression free survival. Planned enrollment will begin in early 2023.

MDM2 Inhibition in the Treatment of Glioblastoma: From Concept to Clinical Investigation.

Inhibition of the interaction between MDM2 and p53 has emerged as a promising strategy for combating cancer, including the treatment of glioblastoma (GBM). Numerous MDM2 inhibitors have been developed and are currently undergoing rigorous testing for their potential in GBM therapy. Encouraging results from studies conducted in cell culture and animal models suggest that MDM2 inhibitors could effectively treat a specific subset of GBM patients with wild-type TP53 or functional p53. Combination therapy with clinically established treatment modalities such as radiation and chemotherapy offers the potential to achieve a more profound therapeutic response. Furthermore, an increasing array of other molecularly targeted therapies are being explored in combination with MDM2 inhibitors to increase the effects of individual treatments. While some MDM2 inhibitors have progressed to early phase clinical trials in GBM, their efficacy, alone and in combination, is yet to be confirmed. In this article, we present an overview of MDM2 inhibitors currently under preclinical and clinical investigation, with a specific focus on the drugs being assessed in ongoing clinical trials for GBM patients.

TRLS-09. USE OF A PAN-PEPTIDE CHECKPOINT INHIBITOR IN THE TREATMENT OF CENTRAL NERVOUS SYSTEM TUMORS

Abstract Immunotherapy has revolutionized clinical management of a select group of malignancies by offering a long-term, durable treatment response. Unfortunately, only a small percentage of brain cancers respond. The combination of multiple checkpoint inhibitors may result in serious immune-related adverse events. We have developed a Pan-Immune Checkpoint Ligand that simultaneously controls multiple immune checkpoints. The CD200 immune checkpoint modulates the immune system through a single inhibitory receptor (CD200R1) and multiple activation receptors (CD200ARs). We developed a peptide ligand, CD200AR-L, that targets the CD200ARs, which results in activation of the immune system and suppression of the inhibitory effects of CD200 and other immune checkpoints. Treatment of high-grade glioma in companion dogs with autologous tumor lysate vaccinations and CD200AR-L resulted in a two-year progression-free survival rate of 20% with no significant adverse events. We believe this response is due to the ability of CD200AR-L to modulate multiple immune checkpoints through shared signaling molecules in both the CD200 and PD-1/PD-L1 checkpoint pathways. Our preliminary data demonstrate that CD200R1 and PD-1 mediated immune checkpoint signaling is through SHIP1. CD200AR-L overcomes the immunosuppressive effects of the tumor-derived CD200 and PD-L1 by downregulating these checkpoints on both antigen-presenting cells (APC) and T-cells. CD200AR-L also downregulates PD-1 on APCs and inhibits the upregulation of PD-1 and CTLA4 on T cells. This translational research has led to the initiation of a phase I dose-escalation clinical trial for recurrent glioblastoma in adults (NCT04642937) and the writing of an IND for a pediatric HGG/DIPG trial.

Standardizing the strategy in glioblastoma trials to promote success in cell and gene therapy clinical development.

e13604 Background: Glioblastoma is the most common and aggressive brain tumor, with a high recurrence rate and low survival. We are increasing our understanding of its biology, and more targeted therapeutical agents are available. However, the GBM prognosis has not improved over the last decades. Multiple clinical trials on Cell and Gene Therapies are ongoing but, there is a huge need to define standardized and innovative strategies to promote better patient selection, implement adaptative designs and specific laboratory assays, and tailor the clinical endpoint assessments. Methods: Medical experts panel agreed on the following insights and gave advice to improve the design and conduct of GBM trials. Results: The criteria for selecting patients are not uniform among studies. The 2021 WHO Classification of central nervous system tumors has yet to be universally adopted, and different tumor entities are being treated as GBM according to the prior 2016 classification. Furthermore, the required genetic testing panel is only available in some countries as part of routine testing. A wide range of CGT therapies are being studied with different mechanisms of action and are well suited to be administered as combinatory regimens and multiple-dosing schedules to boost the antitumor effect. The implementation of master protocols offers the possibility to test different schedules to identify the most promising for further investigation during early phase development. There is a lack of biomarkers for the patient- or cancer-specific sensitivity and the efficacy of CGT. This is important not only to target clinical treatments to the appropriate patients and identify responding/non-responding patients early during treatment but also to improve the preclinical models and identify targets for further therapeutic development. Investigators should use standard endpoint criteria when reporting clinical outcomes. It has been common to refrain from introducing any preliminary-effect objective in the early stages. This tendency changes after guidance from experts and regulatory agencies about maximizing early-phase data. Another vital endpoint in the early phases is assessing patient immunogenicity against CG therapy based on humoral and cell virus-specific and tumor-specific immune responses. This is especially important as there are significant concerns in translating preclinical safety results to the clinic due to the species-specificity of different viruses and critical differences between immune systems. Conclusions: Today, the purpose of treatment for GBM is to extend the survival period and to manage the disease while preserving the patient’s quality of life. The goal of CGT is a durable complete response, but to achieve this target, we will need a deep analysis of how we perform clinical trials and move to an expert and tailored research environment.

Abstract LB097: Armored bicistronic CAR T cells with dominant-negative TGF-β receptor II to alleviate antigenic heterogeneity and suppressive immune microenvironment in glioblastoma

Abstract Introduction: We have completed two CAR T cell clinical trials for glioblastoma (GBM) and have identified several key challenges to therapeutic efficacy, including the inherently heterogenous genomic landscape and the immunosuppressive tumor microenvironment (TME) found in GBM. Our previous study showed that EGFR variant III (EGFRvIII)-targeting monovalent CAR T cells reduced target-positive tumor cell populations, but tumor recurrence resulted from target-negative tumor cells, highlighting the limitation of single-target approaches in heterogenous tumors. With regards to the highly immunosuppressive TME in GBM, we found that transforming growth factor-β (TGFβ) was present in the GBM TME as a major driver of suppression of the anti-GBM response in clinical samples. TGFb is consistently highly expressed in both GBM tumor cell lines and patient tumor tissues. Methods: We used two parallel scFv constructs, independently targeting both IL13Rα2 and EGFRvIII, in combination with a truncated dominant negative (dn) TGFβ receptor II. This trivalent construct was designed to explore possible additive effects in both in vitro and in vivo GBM model systems to limit tumor escape and overcome the immunosuppressive GBM TME. The CART-EGFR-IL13Rα2-dnTGFb construct broadened the targeted tumor cell repertoire, blocked TGFβ signaling, and served as a sink for free TGFβ in the GBM TME to overcome the suppressive function of TGFβ. Results: The tri-modular CAR T construct had an enhanced proliferative response when compared with the CART-EGFR-IL13Rα2 construct, in vitro. In co-culture assays, this construct led to reduced PD-1 expression and increased central memory phenotype, when compared to the bicistronic CAR T construct, which suggested a lower fraction of exhausted T cells. Tri-modular CAR T cells blocked the suppressive pSmad2/3 signaling pathway, leading to the increased tumor killing activity in co-culture experiments with both adherent and suspension GBM cell lines. In an immunodeficient mouse model, tri-modular CAR T cells eradicated tumor cells efficiently and mice had a longer median survival when compared those treated with the bicistronic CART-EGFR-IL13Rα2 cells, lacking the dnTGFb receptor II. Conclusion: Overcoming the adaptive changes in the local TME and addressing antigen heterogeneity will be required to improve the clinical efficacy of CAR T-directed strategies. Our combination work showed that bicistronic CART constructs cooperate with truncated TGFβ receptor II efficiently. In summary, the dominant-negative TGFβ RII CART-EGFR-IL13Rα2 structure is a promising strategy to address the clinical challenges of antigenic heterogeneity and the immunosuppressive TME in GBM we have observed in our two GBM CART cell trials at UPenn. Citation Format: Nannan Li, Jesse Rodriguez, Zev Binder, Donald O’Rourke. Armored bicistronic CAR T cells with dominant-negative TGF-β receptor II to alleviate antigenic heterogeneity and suppressive immune microenvironment in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB097.

421 A Phase 1 and Randomized Phase 2 Clinical Trial of Selinexor and Temozolomide in Recurrent Glioblastoma Among Adults: The Product of a Successful Team Science Approach

OBJECTIVES/GOALS: Selinexor is a novel XPO1 inhibitor that blocks nuclear export, thus impairing DNA repair and causing apoptosis. Our goal was to conduct preclinical and clinical studies to test our hypothesis that selinexor’s efficacy is boosted by priming with temozolomide and is associated with a tissue biomarker. METHODS/STUDY POPULATION: We leveraged a team science approach through the NCI Cancer Therapy Evaluation Program (CTEP) to design preclinical experiments, develop a novel RNAseq analysis pipeline, and use pre-existing clinical experience to open an early phase clinical trial for recurrent glioblastoma. Team members included a CTEP medical officer, cancer biologist, pharmacist, industry scientist, translational scientist, and early career clinician scientist mentored by an expert clinician scientist. Based on preclinical results, participants in the clinical trial experimental arm will receive sequential temozolomide 150mg/m2 on days 1-5 and a starting dose of selinexor 60mg on days 8 and 15 of a 28-day cycle. Participants in the control arm will receive monotherapy temozolomide. RESULTS/ANTICIPATED RESULTS: Sequential treatment of U87 cells and intracranial xenografts had superior DNA damage (É£H2A.X, cleaved PARP) and overall survival compared to combination or single-agent (HR 0.25 [95% CI, 0.07-0.84]; p=0.01, log-rank). We used the top-scoring gene pair method to identify an RNAseq signature associated with response to selinexor. We then designed a trial for first recurrent MGMT methylated glioblastoma. Primary objectives are safety and preliminary efficacy. Secondary objectives are overall response rate, efficacy, and validation of a molecular signature. Phase 1 dose finding (n=12) will be followed by a randomized phase 2 (n=72); using proportional hazards regression, RHR 0.5 with p DISCUSSION/SIGNIFICANCE: The NCI CTEP Project Team employs team science as a framework to successfully develop multidisciplinary collaborations, build investigator trial experience, and lead the way to future research opportunities. Our trial addresses a significant unmet need to offer novel therapies and molecular biomarkers in glioblastoma.

CAR T Cell Therapy in Glioblastoma: Overcoming Challenges Related to Antigen Expression

Glioblastoma (GBM) is the most common primary brain tumor, yet prognosis remains dismal with current treatment. Immunotherapeutic strategies have had limited effectiveness to date in GBM, but recent advances hold promise. One such immunotherapeutic advance is chimeric antigen receptor (CAR) T cell therapy, where autologous T cells are extracted and engineered to express a specific receptor against a GBM antigen and are then infused back into the patient. There have been numerous preclinical studies showing promising results, and several of these CAR T cell therapies are being tested in clinical trials for GBM and other brain cancers. While results in tumors such as lymphomas and diffuse intrinsic pontine gliomas have been encouraging, early results in GBM have not shown clinical benefit. Potential reasons for this are the limited number of specific antigens in GBM, their heterogenous expression, and their loss after initiating antigen-specific therapy due to immunoediting. Here, we review the current preclinical and clinical experiences with CAR T cell therapy in GBM and potential strategies to develop more effective CAR T cells for this indication.