CNS Tumors Research Articles

Establishment of a Brain Tumor Consortium of Africa: Advancing Collaborative Research and Advocacy for Brain Tumors in Africa

Abstract Background Brain tumors represent a significant global health challenge, with rising incidence and mortality impacting individuals worldwide and contributing to cancer-related morbidity and mortality. In Africa, this burden is exacerbated by limited access to advanced diagnostics, treatment options, and multi-disciplinary care, compounded by the absence of standardized cancer registration and tumor biobanking. The introduction of molecular diagnostics, as outlined in the 2021 WHO CNS tumor classification, adds complexity to brain tumor management, particularly in regions with scarce resources. Methods To address these issues, the Brain Tumor Consortium for Africa (BTCA) was established in 2023, bringing together experts to improve CNS tumor diagnosis, patient care, and research. The initial project, conducted via an electronic questionnaire, aimed to assess neuro-oncology capacity across SSA. Results The study revealed significant gaps, with a limited number of institutions incorporating molecular subtyping into their diagnostic algorithms. The consortium’s efforts focus on enhancing local data use, informing public policy, and promoting collaboration to advance neuro-oncology practices in Africa. By fostering a network enlisting the expertise of collaborators in the field of neurosurgery, neurology, neuropathology, anatomic pathology, and medical and radiation oncology, the BTCA seeks to improve brain tumor management through better diagnostics, infrastructure and policy advocacy. Future directions include expanding molecular diagnostic capabilities, standardizing brain tumor biobanking, enhancing data collection, and advocating for improved brain tumor care in national health agendas. Conclusion The BTCA represents a pioneering model of collaboration and innovation in addressing the unique challenges of brain tumor care in Africa.

Maternal illnesses during pregnancy and the risk of childhood cancer: A medical-record based analysis (UKCCS).

Often relying on mother's recollections of past events, the possible relationship between maternal illness in pregnancy and risk of malignancy in their offspring has long been a focus of research. Free from recall bias, this study of childhood cancer (0-14 years) examined these associations using data abstracted from mothers' primary-care (1623 cases, 2521 controls) and obstetric (2721 cases, 5169 controls) records. Maternal infections and other illnesses in pregnancy were examined for any possible associations with childhood leukaemia, lymphoma, CNS or embryonal tumours using pooled information from the two medical record sources (2885 cases and 5499 controls), accounting for potential confounders. Maternal anaemia was associated with childhood acute myeloid leukaemia (AML) (odds ratio, OR = 2.07, 95%CI [1.40-3.08]). Anaemia during pregnancy was also recorded more frequently in the notes of mothers of children with medulloblastoma, retinoblastoma and embryonal rhabdomyosarcoma: ORs 2.36 [1.36-4.11], 1.83 [1.01-3.33] and 2.91 [1.64-5.16] respectively. Other associations included urinary tract infections (UTIs) and non-Hodgkin lymphoma (NHL); preeclampsia and NHL; and polyhydramnios with both AML and NHL. No evidence was found to suggest that influenza during pregnancy impacted on childhood leukaemia risk. In conclusion, our findings are supportive of an association between maternal anaemia in pregnancy and childhood AML, and maternal anaemia and embryonal tumours; underscoring the need for further research exploring the potential causes and roles of iron and vitamin deficiencies. Due to small numbers and lack of corroborative evidence, the associations observed for UTIs, preeclampsia, and polyhydramnios must be treated cautiously.

BIOM-71. EXPANDING THE SPECTRUM OFTERT PROMOTER NON-CANONICAL SEQUENCE VARIANTS IN CNS TUMORS: A CASE SERIES

Abstract Most TERT promoter (TERTp) clinically relevant sequence variants in CNS tumors are the canonical C228T and C250T mutations. Non-canonical TERTp mutations have been reported mainly in non-CNS tumors. We describe 12 CNS tumors with non-canonical TERTp variants interpreted as clinically relevant. Using clinical targeted NGS panels (2020-2024), we detected c.-100_-79dup (n=2), c.-92_-91insGGCGGCCCCGCCCCTTCCTTTC (n=1), c.-118_-117insTCCCCGGCCCAGCCCCTTCCGGG (n=1), c.-123_-76dup (n=1), c.-110_-89dup (n=2), and c.-57A>C (n=5). Most cases had chromosomal microarray (n=11) and/or methylation array data analyzed using the NCI/Bethesda v.2 classifier (n=9). All non-canonical TERTp variants occurred at a variant allele frequency suggestive of somatic clonal origin (mean, 34%; range, 18-46), and in adults (mean age, 60 years; range, 36-88). Except for the c.-57A>C variant, all non-canonical TERTp variants occurred in tumors with histological and/or molecular diagnostic features of glioblastoma, IDH-wildtype (GBM), often epigenetically aligning to this tumor type. All five tested cases matched to superfamily glioblastoma (score ≥ 0.9), with three to class GBM_RTK_I (>0.9 in 2, 0.86 in 1) and two to GBM_RTK_II (>0.9). The size and sequence of such variants suggest that these may be functionally equivalent to canonical mutations or generate favorable TERTp activation motif conformations like previously reported activating duplications. The c.-57A>C variant is a well-established oncogenic mutation observed in other cancer types but has not been reported in CNS tumors. We describe five cases with the c.-57A>C variant: one GBM matching to methylation class GBM_MES_TYP (0.99); two oligodendroglioma, IDH-mutant and 1p/19q-codeleted, one of which had methylation data matching to class O_IDH (0.99); one diffuse glioma, IDH-mutant, which was partially 1p/19q-codeleted and matched to class O_IDH (0.99); and one anaplastic meningioma, aligning to superfamily meningioma (0.99)/MNG_MAL (0.79). Our findings show that non-canonical TERTp variants typically occur in tumor types that often harbor TERTp canonical mutations, expanding the spectrum of TERTp clinically relevant variants that are molecular biomarkers in CNS tumors.

BIOM-20. EVALUATING THE POTENTIAL OF PSMA TARGETING IN CNS TUMORS: INSIGHTS FROM LARGE-SCALE TRANSCRIPTOME PROFILING

Abstract PURPOSE Prostate-specific membrane antigen (PSMA) is a well-established target in prostate cancer therapy that has shown potential as a theranostic target across non-central nervous system (CNS) and CNS tumor types. We aimed to investigate the pan-tissue expression pattern of the PSMA-encoding gene FOLH1 to assess whether transcriptome profiling can inform tumor theranostics. EXPERIMENTAL DESIGN We assessed FOLH1 expression from the Open Pediatric Cancer Project (OpenPedCan, n = 2132 specimens), The Cancer Genome Atlas (TCGA, n = 10411 specimens), and the Genotype Tissue Expression Project (GTEx, n = 17382 specimens) in relation to published reports of PSMA radionuclide uptake. RESULTS When comparing FOLH1 expression across tumor versus normal tissues, we found that non-CNS tumors exhibiting elevated expression of at least two-fold (FDR < 0.05) were reported to have successful PSMA radionuclide uptake in contrast to tumors with less than a two-fold elevation or with lower expression of FOLH1 relative to normal. Notably, CNS tumors universally exhibited lower expression of FOLH1 relative to normal brain tissue, but we observed considerable variation in the expression of blood-tumor barrier (BTB) components associated with reports of BTB integrity and uptake of PSMA radiotracers. CONCLUSIONS Large-scale transcriptomics data may help guide the application of PSMA-based radionuclide therapies in non-CNS tumors, but care should be taken to account for BTB effects in CNS tumors when assessing the potential for radionuclide success. Our analysis demonstrated that FOLH1 showed a lack of tumor-specific expression for both adult and pediatric CNS tumors when compared to normal brain tissue, suggesting that PSMA is not a desirable target in this disease type. This study highlights the utility of utilizing large-scale molecular data to guide the selection of theranostic targets.

CTIM-15. LOCOREGIONAL ADMINISTRATION OF B7-H3-CAR T CELLS EXPRESSING 41BB LIGAND FOR PEDIATRIC PATIENTS WITH PRIMARY CNS TUMORS: PRELIMINARY RESULTS FROM A PHASE I STUDY

Abstract Outcomes for pediatric patients with diffuse midline glioma (DMG) and relapsed/refractory CNS malignancies remain poor. Loc3CAR is an ongoing, first-in-human, phase I clinical trial (NCT05835687) evaluating intracranial delivery of B7-H3-CAR T cells expressing 41BB ligand (B7-H3-CAR-T) for patients ≤21 years old with i) relapsed/refractory B7-H3+ CNS tumors (Cohort A), or ii) DMG post-radiation (Cohort B). Treatment included 6 intracerebroventricular B7-H3-CAR-T infusions administered over 7 weeks. Primary and secondary outcomes were safety and disease response, respectively. To date, 84% (21/25) of tumors screened were B7-H3+ (median H-score 200; range 0-300). CAR-T products were successfully manufactured for all patients enrolled on the collection/manufacture phase of the trial (n=11). Eight patients (7 cohort A; 1 cohort B) were treated with a total of 42 infusions on dose level 1 (1x107/3x107 CAR+ T cells/dose). Post-infusion, multiple participants exhibited neurologic findings suggestive of on-tumor CAR-T activation, including seizure, dysphasia, and localized pain. One patient, with a large tumor burden and high B7-H3 expression (H-score = 300), experienced a dose limiting toxicity with unresponsiveness and decorticate posturing approximately 16 hours post-infusion #1. Their clinical status rapidly improved following CSF removal and intravenous dexamethasone. Common adverse events attributable to B7-H3-CAR-T included headache (8/8), fever (7/8), and nausea/vomiting (5/8). Two of 7 (29%) evaluable patients achieved clinical benefit with stable disease at week 8. B7-H3-CAR-T and inflammatory cytokines were detected in the CSF from all patients evaluated. Circulating tumor DNA (ctDNA) was measured using a novel DNA methylation-based sequencing pipeline and detected in the CSF from 6/8 patients. For 2 patients, ctDNA abundance increased post-infusion, followed by clearance, suggesting subclinical antitumor activity. Single cell RNAseq of immune cells in the CSF from 1 patient analyzed to date, demonstrated abundant Tregs post-infusion #4, suggesting B7-H3-CAR-T may induce local anti-inflammatory responses. Overall, intracranially administered B7-H3-CAR-T have an acceptable safety profile and warrant continued exploration for pediatric patients with CNS tumors.

CTNI-52. EXPEDITED CHEMORADIATION AFTER LASER INTERSTITIAL THERMAL THERAPY (LITT) IS FEASIBLE AND SAFE IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA

Abstract BACKGROUND High-grade gliomas (HGG) are incurable primary brain tumors. Laser Interstitial Thermal Therapy (LITT) has emerged as an alternative to surgery for select patients. Hyperthermia can improve the efficacy of radiation and chemotherapy. Shortening the time between LITT and chemoradiation may maximize their biological and clinical benefits. This clinical trial evaluated the safety and feasibility of expediting chemoradiation after biopsy and LITT in patients with newly-diagnosed HGG. METHODS Patients with suspected HGG were enrolled. Those with pathologic confirmation of HGG and deemed appropriate candidates for LITT and chemoradiation were considered evaluable. Participants underwent 6 weeks of adjuvant chemoradiation within seven days of LITT. Endpoints were assessed until the completion of radiation, and included the occurrence of wound dehiscence; new, treatment-refractory seizures; cerebral edema; and completion of planned radiotherapy. RESULTS Fifteen patients with suspected HGG were enrolled and ten were considered evaluable. All ten patients were diagnosed with glioblastoma (GBM, IDHwt). Five patients were deemed unevaluable: four patients with other CNS tumors and one GBM patient who developed grade 4 postoperative edema. Of ten evaluable patients, the median age was 60.2 years (IQR: 51.0, 69.4), and median preoperative KPS was 90 (IQR: 90, 80). The median time between LITT and the initiation of chemoradiation was seven days. There were no occurrences of significant protocol-related adverse events. CONCLUSIONS Accelerated initiation of chemoradiation after biopsy and LITT is safe and feasible for patients with newly diagnosed HGG. A larger study is needed to assess potential synergy of hyperthermia and chemoradiation to improve survival.

BIOM-61. CSF CTDNA ANALYSIS OF PATIENTS WITH DIFFUSE GLIOMAS REVEALS DIAGNOSTIC MOLECULAR ALTERATIONS

Abstract There is a critical need for better strategies to diagnose and monitor patients with diffuse gliomas. Liquid biopsies are less invasive than tissue biopsies and are amenable to serial collection at multiple timepoints. However, analysis of circulating tumor DNA (ctDNA) in cerebrospinal fluid (CSF) in patients with diffuse gliomas remains underutilized in clinical practice due to technical challenges and a scarcity of studies demonstrating clinical utility. We evaluated ctDNA in 49 CSF samples from patients with various types of diffuse gliomas with a next generation sequencing (NGS) panel interrogating 613 cancer-related genes. Cell-free DNA concentration obtained from CSF (0.4-5mL) ranged from 0.009 to 60ng/µL. Input DNA concentration ranged from 0.12-30ng. Mutations were detected in 29/49 (59.2%) samples including 22/49 (44.9%) with single nucleotide changes, 14/49 (28.6%) with copy number changes, and 1 fusion (2.0%). The majority of samples without mutations detected (n=20) had suboptimal DNA input (<30ng): 17/20 (85%). We identified diagnostic alterations in CSF including mutations in IDH1 (3/5 IDH-mutant gliomas), TERTp and EGFR amplification (7/34 glioblastomas), H3-3A (4/6 pediatric high-grade gliomas). Some of these mutations, in combination with other clinical parameters, allowed us to identify specific CNS tumor types based on the 2021 WHO classification of CNS tumors, resulting in the reclassification of 2 patients. Matched tumor tissue sequencing results were available for 23/49 (46.9%) patients and the results showed good concordance with CSF ctDNA analysis. In summary, our results suggest that the NGS analysis of CSF-ctDNA can provide clinically relevant information in patients with diffuse gliomas.

DDEL-14. NOVEL BLOOD BRAIN BARRIER PENETRATING BI-SPECIFIC ANTIBODY THERAPY FOR BREAST CANCER BRAIN METASTASIS

Abstract Breast cancer is the second leading cause for brain metastasis after lung cancer. While Her2 +ve tumors respond to her2 targeted antibody therapy, these antibodies are unable to cross the blood brain tumor barrier to effectively target metastases hidden in the ‘CNS sanctuary’. To overcome this hurdle, we have modified Her2 targeting Herceptin to create a CNS penetrating antibody that is transported in a unidirectional fashion into brain tumors. The modified BBB penetrating Herceptin is processed by the tumor specific microenvironment after crossing the BBB, such that the modified antibody is then trapped in the tumor ECM. This has the potential to increase tumor retention and reduce systemic toxicity. The BBB penetrant anti Her2 antibody (Herceptin) binds to Her2 on breast cancer cells and suppresses activation of Her2 signaling in vitro. Western blot analysis shows reduction of Her2 phosphorylation and down stream signaling with both unmodified and BBB modified Herceptin. This permits recruitment and retention of the antibody into the CNS tumors. Using fluorescence imaging and IHC of intracranial tumors we have validated that the BBB modified Herceptin is localized into intracranial tumors. We are currently evaluating the safety and therapeutic benefit of this approach in mice bearing intracranial tumors.

CNSC-70. THE ROLE OF MAP4K4 IN TUMOR CELL INVASION OBSERVED IN A 3D IN VITRO MODEL OF PEDIATRIC GLIOBLASTOMA

Abstract Several CNS tumors such as pediatric glioblastoma (pGBM), diffuse midline glioma (DMG), and medulloblastoma (MB) are characterized by local invasive spread and dissemination of tumor cells into surrounding brain tissue. As identified by our group in a genome-wide CRISPR screen and several others, MAP4K4 is a mediator of cell invasion in several cancers, including glioblastoma and medulloblastoma. Recently, we validated the pro-invasive role of MAP4K4 in a panel of pGBM cell lines. To further validate this finding in the context of pGBM cellular invasion, we performed 3D Matrigel timelapse invasion assays. We performed single- and multi-spheroid encapsulation to track spheroid invasion and cell-to-cell interactions between multiple spheroids. Tumor spheroids were cultured in a round-bottom, non-adherent well plate encapsulated in a Matrigel matrix and treated with a MAP4K4 small molecule inhibitor (PF06260933 dihydrochloride) or had a MAP4K4 knockout performed with Cas9 editing. Cell invasion was recorded over 72 hours and three-dimensional structures were stained for actin and imaged 10 days post-initial seeding. We show that MAP4K4 KO (p ~ 0.00033), small-molecule inhibition in the presence of a TGFB receptor agonist (SRI-011381), (p ~ 0.001) and with drug alone (p ~ 0.013) decreased spheroid invasion and prevented single-cell invasion of pGBM cells (SF188) into the matrix. More surprisingly, abrogation of MAP4K4 prevented individual spheroids in a multi-spheroid co-culture, from forming integrated glioma networks through the formation of tube-like structures in the matrix. Based on our initial findings, it appears that MAP4K4 is necessary for single-cell invasion into a three-dimensional matrix. It also appears that MAP4K4 is required for cell-to-cell connections to form between spheroids in the 3D environment to allow for the formation of higher-ordered and spatially organized structures. Future directions include studying how MAP4K4 allows for the formation of glioma tumor networks in pediatric GBM.

CTNI-58. A PHASE 0/2 TRIAL OF ABEMACICLIB PLUS LY3214996 IN RECURRENT GLIOBLASTOMA

Abstract BACKGROUND This Phase 0/2 study (NCT04391595) evaluates tumor pharmacokinetics (PK), tumor pharmacodynamics (PD), and clinical efficacy of abemaciclib, a CDK4 and 6 inhibitor, plus LY3214996, an ERK 1/2 inhibitor, in recurrent glioblastoma (rGBM). METHODS Adult rGBM patients (n=42) with intact RB, >30% pERK expression, and CDKN2A/B deletion or CDK4/6 amplification received six days of abemaciclib plus LY3214996 prior to a planned resection. Time-escalation cohorts (3-5 and 7-9 hour intervals from last dose to tumor resection) identified the optimal time interval (OTI). Subsequent Phase 0 patients had tumor tissue (gadolinium [Gd]-enhancing and nonenhancing regions), cerebrospinal fluid (CSF), and plasma collected at the OTI. Total and unbound drug concentrations were measured using validated LC-MS/MS methods. Tumor PD was compared to matched archival or pre-treatment biopsied tissue. A PK ‘trigger’ (i.e., unbound concentration > 5 x IC50) was set for each drug. Gd-nonenhancing tumor demonstrating PK response to both drugs qualified patients for the Phase 2 component of the study. RESULTS Forty two patients were accrued to Phase 0 and no dose-limiting toxicities were observed. Median unbound concentrations in Gd-nonenhancing tumor regions were 31 nM and 10 nM for abemaciclib and LY3214996, respectively. Tumor RB, RSK phosphorylation, and tumor proliferation (MIB-1) decreased in (47.5%), (25%) and (72.5%) patients, respectively. Nine of the 40 (22.5%) patients exceeded PK thresholds for both abemaciclib (12 nM) and LY3214996 (25 nM), qualifying them for Phase 2. Here, median PFS and median OS were 2.4 and 7.2 months, respectively. CONCLUSION Abemaciclib and LY3214996 achieved pharmacologically-relevant concentrations in Gd-non-enhancing GBM tissue in 80% and 30% of the patients, respectively. Suppression of the RB pathway and tumor proliferation, but not ERK pathway was observed. Inadequate CNS penetration and tumor PD modulation by LY3214996 contributed to the unremarkable clinical efficacy profile of this drug combination. Targeted ERK inhibition remains an unmet need in experimental GBM therapy.

SURG-18. INNOVATIVE DRUG-DEVICE COMBINATION FOR THE PHOTODYNAMIC TREATMENT OF PRIMARY GLIOBLASTOMA (GBM) PATIENTS

Abstract Despite advances in neurosurgical technology and techniques, the survival rate of GBM patients has remained relatively unchanged. The main treatments for GBM are associated with difficulties resulting from incomplete tumor resection and recurrence. In such situations, Photodynamic Therapy (PDT) is increasingly popular as an advanced therapeutic strategy, characterized by fewer side effects, minimal toxicity, and more controlled treatment. 5-aminolevulinic acid hydrochloride, (5-ALA HCl) has been used for years as a photosensitizing drug for the intraoperative visualization of GBM tumor tissue, enabling a more complete tumor resection. We demonstrated that, after such fluorescence-guided surgery, a laser light of specific 635 nm wavelength can additionally induce specific tumor cell death via the production of reactive oxygen species. This 5-ALA HCl–based PDT provides an antitumor effect within the tumor resection margins where recurrences occur in almost all patients. After performing pilot studies in over 20 patients with primary GBM, leading to positive safety and survival signals, we designed a new drug-device combination for this specific PDT procedure. It consists of Pentalafen ®, 5-ALA HCl administered orally to the patient before surgery, combined to Heliance®, a balloon device, inflated intraoperatively into the resection cavity, and connected to a controller (laser system) via an optical fiber to produce the light that illuminates the resection margins. A dedicated algorithm enables the duration of the illumination to be automatically computed from the tumor volume. This procedure adds an average of 30 minutes to the neurosurgery and can thus be fully integrated into the standard of care for primary GBM. This new drug-device combination is currently evaluated in a US phase 1 trial (NCT05736406) evaluating the feasibility of different light regimen treatments with the aim of delaying GBM recurrence and improving overall survival. If data is confirmed, it could be applicable to other CNS and solid tumors.

CSIG-33. CERAMIDE-1-PHOSPHATE/CERK ARE REGULATORS OF ETMR GROWTH AND POTENTIAL THERAPEUTIC TARGETS

Abstract Embryonal tumor with multilayered rosettes (ETMR) is a highly aggressive CNS neoplasm which occurs almost exclusively in infants and is associated with an extremely poor prognosis. To identify functional signaling lipids that contribute to the aggressive nature of ETMR and that can be targeted therapeutically, we carried out mass spectrometry imaging on human ETMR patient samples, the patient-derived cell line BT183, and normal neural stem cells. We identified an accumulation of ceramide-1-photphate (C1P) within the rapidly proliferating embryonal tumor cells in patient samples and the cell model. We also detected high accumulation of C1P within the aberrant vascular proliferations in patient samples. Ceramide-1-phosphate is a pleiotropic bioactive signaling lipid that controls cell fate. C1P and its synthesizing enzyme, ceramide kinase (CERK), are known mitogens that have been shown to regulate cell proliferation in several non-CNS cancers. C1P is known to mediate the upregulation of PI3K/Akt/mTOR, MAPK/MEK/ERK1/2, Rho kinase, JNK, to promote cell survival and migration. After spatially mapping C1P accumulation in patient samples and our in vitro 3D models, we next carried out IHC to correlate lipid accumulation with its synthesizing enzyme, CERK. CERK was found to be abundantly accumulated in both endothelial and tumor cells within the tumor microenvironment of patient samples. Western blot analysis of CERK demonstrated a significant increase in the ETMR 3D tumorspheres compared to the NSC neurospheres. Treatment of the ETMR 3D tumorspheres with the CERK inhibitor, NVP-231, potently reduced cell growth and viability. Western blot analysis of ETMR tumorspheres at 8 and 24 hours post-treatment demonstrated a time-dependent decrease in N-MYC and a subsequent increase in p53. Studies are ongoing to validate these findings in vivo and to elucidate the signaling pathways that C1P/CERK regulate in both the vascular and tumor cells in ETMR.

EXTH-77. INFANT-TYPE HEMISPHERIC GLIOMAS WITH INITIAL RESPONSE FOLLOWED BY RESISTANCE ON TARGETED AGENTS

Abstract Pediatric-type Diffuse High Grade Gliomas (pHGG) are a rare brain tumor with high mortality and need for more effective treatment options. pHGG’s make up only about 10% of CNS tumors but are responsible for a majority of the deaths. Infant-type Hemispheric Gliomas are a subtype of pHGG with tyrosine kinase alterations in genes such as ROS1, ALK, MET, and NTRK1-3. Despite advances in categorization and targeted therapies, the natural history of patients with infant HGG treated with targeted therapy over time needs to be better characterized, including the durability of objective responses. We present a retrospective case series involving two patients diagnosed with Infant-type Hemispheric Gliomas at Arkansas Children’s Hospital from 2022-2024. Each diagnosis was determined based on histology, targeted tumor sequencing, and methylation profiling. Both patients were initially treated with primary surgical resection and systemic chemotherapy. Each patient experienced disease progression. Actionable pathogenic mutations were identified in both patients (a MET alteration in patient 1 who was then started on Cabozantinib, an ALK fusion in patient 2 subsequently treated with Lorlatinib) with an objective disease response in both patients. In both cases, further relapse occurred while on targeted inhibition. Relapse specimen was not available for patient 1, but for patient 2, recurrent tumor sequencing revealed similar genetics from the diagnostic specimen except for a MET copy number gain suggesting the mechanism of resistance in this patient. Infant-type Hemispheric Gliomas with targetable alterations can show meaningful responses to pathway inhibition. Relapse after initial response may warrant additional surgical sample to identify new alterations which can lead to changes in therapy. Larger prospective cohorts are needed to study targeted agents in this population, and early integration during radiation or after initial diagnosis may be needed.

BIOS-07. GRADUAL METABOLIC ALTERATIONS RESTRUCTURE THE SPATIAL ARCHITECTURE AND IMMUNITY IN GLIOBLASTOMA

Abstract The organized layered structure of the human neocortex contrasts sharply with the chaotic architecture of malignant CNS tumors. The heterogenous nature of glioblastoma (GBM) poses significant challenges to research and treatment, given that effective strategies require consistent biological patterns. Here, we leverage recent advances in spatial biology, integrating spatially resolved transcriptomics and metabolomics to identify drivers of GBM-specific architectural evolution. We performed spatial metabolomics (MALDI) and transcriptomics (Visium n=43 and MERFISH n=25) on glioblastoma patients, with computational analysis conducted using the SPATA2 R package. Our findings reveal that most spatial recurrent patterns in glioblastoma emerge in a gradient-like organization, particularly influenced by proximity to areas of necrosis and hypoxia. Samples without hypoxic regions demonstrated less spatial organization. Metabolomic and transcriptomic profiling indicated enhanced responses to hypoxia, reduced cell proliferation, and elevated expression indicative of the S phase in cell division near necrotic regions. The vicinity to hypoxic areas was associated with increased extracellular matrix remodeling and epithelial-to-mesenchymal transition, suggesting that the invasive capabilities of GBM cells originate from these hypoxic niches. By further integrating spatially resolved TCR-sequencing, we identified that hypoxic gradients drive defined T cell responses with a higher likelihood of T cell dysfunction within a distance of 235 µm (sd: 132 µm) to hypoxia. This suggests that the presence of necrosis, hypoxia, and hypoxia-associated metabolites could serve as potential predictive markers for T-cell behavior and exhaustion in glioblastoma. Our study offers an in-depth analysis of the influence of two prevalent niches in glioblastoma: necrosis and hypoxia. We reveal that the complex architecture of glioblastoma is not solely dictated by genetic randomness and stochastic occurrences but is significantly influenced by spatial proximity to key factors like necrosis and hypoxia. This insight contributes to an evolving model that seeks to unravel the intricate biology underpinning this formidable disease.

DDDR-32. EXPLORING ANDROGENIC MODULATION IN GLIOBLASTOMA: POTENCY AND SELECTIVITY OF NOVEL NORETHINDRONE DERIVATIVES

Abstract BACKGROUND Glioblastoma (GBM) represents the most frequently diagnosed malignant CNS tumor in adults and remains incurable. Despite the identification of several oncogenic drivers contributing to tumor formation, targeted therapy with brain-penetrant inhibitors has afforded little progress in survival outcomes. Interestingly, gender has been shown to increase the incidence of GBM, with men having roughly a 50-60% increase in incidence compared to women in the US. This statistic led to research on the involvement of and subsequent inhibition of androgen synthesis and signaling in cell culture models and tumor samples. METHODS To further investigate the potential involvement of steroidal hormones in GBM proliferation, our lab synthesized a series of norethindrone (NE) derivatives with varied molecular weights, steric bulk, and lipophilicity to modulate the androgenic activity of NE. The small library was tested in several GBM cell lines, including U87, A172, and T98G cells, using cell viability assays. RESULTS One derivative, a lipophilically modified version of NE synthesized via a one-pot click reaction, was shown to have improved potency compared with parental NE (>5-fold). The lipophilic NE derivative had IC50 value of 22 uM, 15 uM, and 35 uM in the U87, A172, and T98G cells, respectively. This molecule was tested in immortalized normal human astrocyte (NHA) cells and found to have an IC50 value of 34 uM suggesting some selectivity. DISCUSSION Given this derivative’s activity in GBM models and modest selectivity, we plan to screen it in additional GBM cell lines (LN-18 and U251) and eventually in glioma stem cell models. Future research will focus on identifying key targets involved in the mechanism of action, including the impact of lipophilic addition to the steroid nucleus and its effect on androgenic activity and downstream signaling. We will investigate these effects using RPPA and co-treatments with androgen receptor antagonists and 5-alpha reductase inhibitors.

CTIM-03. IMMUNE CHECKPOINT INHIBITOR NIVOLUMAB IN PEOPLE WITH RECURRENT SELECT RARE CNS CANCERS: RESULTS OF INTERIM ANALYSIS IN A NON-HEAVILY PRETREATED COHORT

Abstract BACKGROUND There is a paucity of salvage therapies for patients with rare CNS tumors. Nivolumab (PD-1 inhibitor) is approved for a variety of systemic cancers. We developed a multisite basket Phase II trial to evaluate Nivolumab for patients with recurrence of one of 12 selected rare CNS cancers. Efficacy is measured by Disease Control Rate (DCR; confirmed CR/PR or durable SD for ≥ 6 months) in 2 cohorts: heavily and non-heavily pretreated (≥ 3 prior therapies, vs. ≤ 2; including radiation and/or standard or experimental drugs). Cohort 1 has been completed. We report efficacy results and safety data of a preplanned interim analysis in Cohort 2 (non-heavily pretreated). METHODS In addition to progressive disease, eligibility includes available tumor tissue; age ≥ 18; KPS ≥ 70; no steroids at trial entry. Planned accrual: 75 in each cohort. Nivolumab dose: 240 mg IV every 2 weeks (4 doses), followed by 480 mg every 4 weeks (14 additional doses). Interim analysis was planned when the sample size reached 32 in each cohort. RESULTS As of December 1, 2023, among 27 evaluable patients treated in the non-heavily pretreated cohort, 10 achieved SD ≥ 6 months (DCR 37%; 95% CI 19.4%,57.6%) – 6 high-grade meningiomas; 1 each: myxopapillary ependymoma with lung metastases; solitary fibrous tumor, gliomatosis (astrocytoma IDH mutant WHO grade 2), chordoma. A total of 56 Grade 3-5 AEs occurred; 13 (Grade 3-4) related to nivolumab, including Grade 3 gait disturbance (3); cerebral edema, cognitive disturbance, colitis, headache, hypotension, hypoxia, lymphopenia, pain, and pruritus (1 each), and one Grade 4 cerebral edema. The three Grade 5 AEs were disease-related. CONCLUSION Preliminary efficacy analysis exceeded the “go” boundary (i.e., > 5 responders) in the non-heavily pretreated cohort. Nivolumab showed an acceptable safety profile. Cohort 2 will continue to complete a planned accrual of 75 patients.

PATH-57. CLINICAL AND MOLECULAR FEATURES OF METHYLATION CLASS DIFFUSE LEPTOMENINGEAL GLIONEURONAL TUMOR

Abstract Genome-wide DNA methylation profiling can help identify rare CNS tumors, including diffuse leptomeningeal glioneuronal tumor (DLGNT). Due to the infrequency of this entity, DLGNT remains poorly understood. To help resolve uncertainty regarding DLGNT, we examined epidemiologic, histologic, and molecular features of 32 (21 newly profiled, 11 publicly available) tumors matching to DLGNT by the DKFZ classifier (v12, score >=0.85). Of these tumors, 25 matched to DLGNT subtype 1 and seven to subtype 2. Subject median age was 12 years in subtype 1 and 22 years in subtype 2 (14.5 overall, range 2-44), with equal numbers of females and males (n=16 each). Spinal cord was the most frequently involved site (n=21), but intracranial lesions were observed (n=6). Leptomeningeal involvement was noted in only four of 11 tumors with available imaging descriptions. In the subset of cases available for histologic review (n=19), oligodendrocyte-like morphology was present in over half (n=11). Microvascular proliferation was uncommon (n=5). Chromosome 1p loss was observed in 29 (91%), and 1p/19q co-deletion was observed in 18 tumors (56%). Gains of 1q and 7q were each observed in 12 (38%), and whole chromosome 7 gain was observed in eight (25%). Loss of 22q was seen in 12 (38%). In the subset of tumors with fusion testing (n=15), KIAA1549::BRAF fusion was present in 12 (80%), and one showed a QKI::RAF1 fusion. Five tumors harbored BRAF mutations, and one harbored a break-point in BRAF without a known fusion partner. In nine subjects with clinical follow-up, there was one death after 3.1 years, and the remaining subjects were alive with a median follow-up of 6.4 years (maximum 19 years). Progression-free survival (PFS) was available for six subjects with a median PFS of 6 years. Presentation of DLGNT without noted leptomeningeal involvement appears common. Further characterization of subject outcomes will help clarify the clinical behavior of DLGNT.

CTIM-17. INDIVIDUALIZED MULTIMODAL IMMUNOTHERAPY (IMI) FOR ADULTS WITH DIFFUSE MIDLINE GLIOMA OR DIFFUSE HEMISPHERIC GLIOMA

Abstract Diffuse Midline Glioma (DMG, H3K27 mutant) and Diffuse Hemispheric Glioma (DHG, H3G34 mutant) are rare malignant CNS tumors with dismal prognosis. We retrospectively searched in our database for adults (>18y) with molecularly define DMG/DHG, treated between May 2015 and 2024 with IMI as part of first-line treatment. Amongst 157 IMI-treated malignant glioma patients, four patients fit these restrictions, pointing to scarce experience of IMI for DMG/DHG adult patients. HM (M, 29y) was diagnosed with a DMG in the pons. He received radiochemotherapy, and continued after 2x TMZm with BRAF-MEK-inhibition therapy. He received one IO-Vac® dendritic cell vaccine but showed fast progression thereafter. He died 9 months after diagnosis. GJE (F, 28y) had a DMG at the corpus callosum. She received radiochemotherapy and 6x TMZm, followed by 2x IO-Vac® and 3x maintenance immunogenic cell death (ICD) immunotherapy (NDV injections, sessions of modulated electrohyperthermia), combined with WT1 and H3K27M long-peptide vaccines. She progressed after 20 months, for which a new IO-Vac® and an H3K27M short- and long-peptide vaccine were given. She died 5 months later. Overall Survival (OS) was 26 months after initial diagnosis. JD (F, 27y) was diagnosed with a DMG in C2-C6. She received radiochemotherapy followed by IMI alone, including 2x IO-Vac®, one ICD immunotherapy, and four doses of anti-PD1. She died 17 months later, making OS 27 months after diagnosis. VJ (F, 21y) had a DHG in the left cerebrum. She received radiochemotherapy and 12 cycles of maintenance TMZ (TMZm), between which ICD immunotherapy was inserted each time. Afterwards, she received two IO-Vac®. Finally, she received ICD immunotherapy (6x) combined with checkpoint inhibitors (4x anti-CTLA4, 10x anti-PD1). Thirty months after diagnosis, she is in remission with a stable Health Utility Index of 0.72. IMI might have contributed to a better OS in three out of four DMG/DHG patients, and should be explored further as part of the treatment for these patients.

CTNI-11. A PHASE 1 OPEN-LABEL STUDY OF BRAF INHIBITOR ABM-1310 IN PATIENTS (PTS) WITH RECURRENT BRAF V600-MUTATED PRIMARY CNS TUMORS

Abstract BACKGROUND ABM-1310 is a blood-brain barrier penetrant BRAF inhibitor. Here we report interim results from our phase 1 study of ABM-1310. METHODS This is a dose-escalation plus expansions trial for adult pts with BRAF V600-mutated primary CNS tumors. In the dose-escalation, ABM-1310 is given at 150 or 200 mg twice a day (bid). In the expansion, ABM-1310 150 mg bid is administered. Study objectives include patient safety, maximum tolerated dose (MTD), preliminary efficacy and pharmacokinetics (PK). Clinical trial information: NCT05892653. RESULTS By May 6, 2024, 15 pts (7 male; median age 39 years old) have been treated. In the dose escalation: 4 pts received ABM-1310 150 mg bid, and another 7-pts received ABM-1310 200 mg bid. In the expansion, all 4 pts were given ABM-1310 at 150 mg bid. Among 14 efficacy evaluable pts, 3 had partial response (PR) (including one each of glioblastoma, WHO grade 2 and 3 pleomorphic xanthoastrocytoma) and 9 pts had stable disease as their best responses. Two pts have PR response for > 8 months and continue study treatment. All pts experienced treatment-related AEs. Common AEs were asymptomatic QT prolongation (n=11) and rash (n=10). Seven pts had grade 3 QT prolongation. There was no drug-related SAE. There was no ABM-1310 related dose limiting toxicity although a few pts had study treatment interruption or dose reduction. One patient discontinued prematurely due to asymptomatic Grade 3 QT prolongation. There were no drug-related deaths. The MTD for ABM-1310 was 200 mg bid, the recommended dose was 150 mg bid. In PK assessment, ABM-1310 drug exposure vs. dosage showed a linear proportional relationship. This trial is ongoing. CONCLUSIONS ABM-1310 was generally safe and tolerated. There were no new safety signals. Preliminary efficacy data demonstrate favorable anti-cancer activity in patients with recurrent BRAF V600-mutated primary CNS tumors.

DDEL-07. EFFICACY OF TEMOZOLOMIDE IN MEDULLOBLASTOMA PATIENTS: REVIEW OF SERIES OF TWO ADULT PATIENTS WITH RECENT UPDATES IN LITERATURE

Abstract Medulloblastoma is a primary malignant CNS tumor commonly seen in children and rarely in adults (20% vs 1% of all primary brain tumors). Maximal safe resection and craniospinal irradiation followed by adjuvant chemotherapy have proven to be an effective treatment in children. Due to insufficient data available in adult patients, it is also the usual approach in them despite unclear long-term outcomes. Standard chemotherapeutic regimens consisting of vincristine, cisplatin, and lomustine are known to cause greater toxicity in adults making adequate dose titration a challenge. Temozolomide is a second-generation cytotoxic alkylating agent with favorable CNS penetration. It is a potential alternative that has yielded superior results in treating gliomas and preventing recurrence along with minimal toxicity. We discuss a series of two adult medulloblastoma cases which were given 24 cycles of Temozolomide monotherapy over two years following surgical resection and craniospinal irradiation. Serial MRIs did not report any signs of recurrence rendering one case cancer-free for seventeen years and the other for ten. Minimal toxicity in the form of nausea, vomiting, headache, and reversible, temporary pancytopenia was seen in contrast to other agents. Improved survival with minimal toxicity was demonstrated in both cases proving the efficacy of Temozolomide as adjuvant chemotherapy for adult Medulloblastoma. While a regimen of Temozolomide is recommended for recurrent Medulloblastoma, there is no optimal regimen available for initially diagnosed, localized tumors, especially in adults. Multi-institutional clinical trials are required to study its role as a monotherapy during an early yet critical phase of management.