Isocitrate Dehydrogenase Research Articles

BIOM-17. EVALUATION OF CARBONIC ANHYDRASE TYPE IX (CA IX) EXPRESSION AS TARGET FOR RADIOLIGAND THERAPY IN GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma represents an unmet need in neuro-oncology. Radioligand therapies are effective and approved in extracranial malignancies such as prostate cancer and neuroendocrine tumors, but data on their use is limited in brain tumors. In addition, rational target selection in gliomas is complicated by tumor heterogeneity. In extracranial tumors, clinical trials of radionuclide treatments targeting carbonic anhydrase IX (CA IX) are ongoing. METHODS Tumor samples of glioblastoma (isocitrate dehydrogenase [IDH]-wildtype) were retrieved from the Neuro-Biobank of the Medical University of Vienna. Formalin-fixed, paraffin-embedded tissue specimen were stained using rabbit anti-CA IX antibody (clone EP161, Cell Marque) on a Ventana Benchmark Ultra platform (Roche Diagnostics). CA IX expression was assessed semiquantitatively. RESULTS Overall, 29 patient samples were included in this study. Median age at surgery was 65 years (range: 55 – 74), and 22/29 (75.9%) were male. Median overall survival (OS) reached 11.6 months (95% confidence interval: 7.3 – 16.3). In total, 24/29 (82.8%) of specimen were positive for CA IX, of whom 20/29 (69.0%) exhibited moderate to high membranous CA IX expression and 4/29 (13.8%) showed weak immunoreactivity. CA IX staining displayed pronounced spatial heterogeneity, as positive areas were primarily seen in pseudo-palisading tumor cells around necrotic foci. Patients with stronger CA IX staining tended to have longer OS (median: 14.2 months) compared to those with absent or weak CA IX expression (median OS: 6.2 months; p = 0.075). Inclusion of further samples of different glioma subtypes is ongoing. CONCLUSIONS CA IX could represent a promising target for radioligand therapy in glioblastoma given the strong CA IX immunoreactivity in most samples. Intratumoral heterogeneity in CA IX expression should be considered in the design of appropriate compounds and the choice of optimal radionuclides to maximize efficacy.

NIMG-28. HYPERPOLARIZED13C IMAGING OF D-2-HYDROXYGLUTARATE-INDUCED DOWNREGULATION OF PYRUVATE DEHYDROGENASE ACTIVITY PROVIDES AN EARLY READOUT OF RESPONSE TO VORASIDENIB IN MUTANT IDH GLIOMAS

Abstract Mutations in isocitrate dehydrogenase (IDHm) define a distinct class of gliomas. IDHm converts a-ketoglutarate (a-KG) to D-2-hydroxyglutarate (D-2HG), which inhibits a-KG-dependent histone/DNA demethylases and induces epigenetic alterations that drive tumorigenesis. The IDHm inhibitor vorasidenib extends progression-free survival in IDHm glioma patients and is expected to be widely used for this patient population. However, not all patients respond to vorasidenib, and magnetic resonance imaging (MRI) does not assess whether a patient is responding to vorasidenib. Therefore, the goal of this study was to identify metabolic alterations induced by D-2HG that can be leveraged for non-invasive imaging of IDHm gliomas. Using clinically relevant patient-derived models (BT257, BT142, BT54, SF10417, SF10602), we show that D-2HG downregulates the activity of pyruvate dehydrogenase (PDH), the rate-limiting enzyme for oxidation of glucose-derived pyruvate via the tricarboxylic acid cycle, by multiple mechanisms. Drug affinity target stability assays show that D-2HG directly binds to and inhibits PDH activity. D-2HG also inhibits a-KG-dependent prolyl hydroxylases that target hypoxia-inducible factor 1-a (HIF-1a) for degradation. As a result, D-2HG stabilizes HIF-1a and drives expression of pyruvate dehydrogenase kinase 3, which phosphorylates and inhibits PDH activity. Suppressing D-2HG using vorasidenib upregulates PDH activity in IDHm glioma cells and intracranial tumors. Next, we examined whether hyperpolarized 13C-MRS, which is an advanced MRI-based method of imaging metabolic activity, monitors PDH activity in IDHm gliomas. Following administration of hyperpolarized [2-13C]-pyruvate, metabolic conversion to [5-13C]-glutamate provides a readout of PDH activity. Our studies indicate that [5-13C]-glutamate production from hyperpolarized [2-13C]-pyruvate is upregulated in IDHm glioma cells treated with vorasidenib. Importantly, [5-13C]-glutamate production is elevated within 5 days of treatment with vorasidenib in rats bearing intracranial BT257 or BT142 xenografts, when changes cannot be observed by MRI. Collectively, our studies identify hyperpolarized [2-13C]-pyruvate as a unique probe of D-2HG-induced metabolic rewiring and highlight its ability to assess IDHm glioma response to therapy, which is a challenge in the clinic.

NIMG-77. MRI PHENOMENON OF PUNCTATE ENHANCING LESIONS IN PATIENTS TREATED WITH IDH INHIBITORS

Abstract BACKGROUND Magnetic Resonance Imaging (MRI) response assessment is essential in isocitrate dehydrogenase (IDH)-mutant gliomas and provides evidence of treatment efficacy. Ivosidenib, a mutant IDH1 inhibitor, and vorasidenib, a pan-mutant IDH inhibitor, may induce imaging stabilization or improvement. We describe an imaging phenomenon of punctate enhancing lesions in patients receiving ivosidenib or vorasidenib. METHODS From October 2020 to December 2023, we identified patients treated with IDH inhibitors who developed punctate enhancing lesions on imaging during their treatment course. We report their clinical and imaging characteristics. RESULTS In our cohort (n=5), patients age range was 29-47 years. Diagnoses included astrocytoma grades 2 (n=2) or 3 (n=1), and oligodendroglioma grades 2 (n=1) or 3 (n=1). Beside all having a prior resection, two had prior radiation therapy and temozolomide, one had prior temozolomide only and two were treatment-naïve. Before initiation of IDH inhibitor, all patients had some evidence of enhancement, albeit small (<1 cm) for most. Four patients received ivosidenib (500mg daily) and one received vorasidenib (40mg daily). The median time to develop punctate lesions from treatment initiation was 16 months (range 1-28 months). All but one lesion was < 1 cm and adjacent to the original tumor locations. Four had FLAIR correlation, and two had high DWI signal without associated restricted diffusion. Punctate lesions resolved on subsequent imaging, within 1-2 months, for all grade 2 tumors. Punctate lesions persisted in the grade 3 tumors, without further progression. Four patients remain on therapy. One discontinued treatment due to this enhancement, which resolved on subsequent imaging. CONCLUSIONS Punctate enhancing lesions may develop in patients on IDH inhibitors. We advocate for close interval imaging monitoring in these cases since they may not universally require treatment discontinuation. Future advanced imaging and tissue evaluations of punctate enhancement, to differentiate between inflammatory response and progression, would be of interest.

INNV-37. REAL-WORLD OUTCOMES AMONG HIGH GRADE IDH1-MUTANT GLIOMA PATIENTS TREATED WITH AN IDH INHIBITOR

Abstract BACKGROUND Isocitrate dehydrogenase (IDH) inhibitors are transforming the treatment of patients with non-enhancing grade 2 IDH-mutant gliomas. Uncertainty remains on the utility of IDH-inhibitors in high-grade IDH-mutant glioma patients that had prior therapies and have progressive disease. METHODS From October 2020 to December 2023, we identified high-grade IDH1-mutant patients treated with off-label ivosidenib, a mutant IDH1 inhibitor. We report their clinical and imaging characteristics. RESULTS In our cohort (n=18), the patient age range was 29-68 years with male predominance (n=11). Diagnoses included astrocytoma grades 3 (n=9) or 4 (n=2), and oligodendroglioma grade 3 (n=7). The median number of progressions prior to ivosidenib initiation was 2 (range 1-7). Fifteen patients had prior surgical resection, three had biopsy. Prior treatment exposures included radiation therapy (n=15), temozolomide (n=18), lomustine (n=5), bevacizumab (n=3), etoposide (n=1), optune (n=1) and a clinical trial (n=1). Mean time from diagnosis to ivosidenib treatment was 9.6 years (95% CI, 6.7 to 16.4 years). Karnofsky performance-status score upon initiation was 80 (n=6) or 90 (n=12). Thirteen patients had >1 cm enhancing disease, five had non-enhancing disease. Ivosidenib was initiated due to enhancing disease progression (n=11), non-enhancing disease progression (n=4), a combination of both (n=2) or temozolomide intolerance (n=1). Best radiographic responses per RANO criteria were partial response (n=2), minor response (n=3), stable disease (n=7), and progressive disease (n=6). Nine patients continue ivosidenib without disease progression, with a median treatment duration of 27.5 months (95% CI, 18.0 to 33.0 months). All had FLAIR stabilization/improvement and 45% (n=4) had improved enhancing disease. Nine patients discontinued ivosidenib due to progression, with a median treatment duration of 7 months (95% CI, 3 to 9 months). CONCLUSIONS These data suggest that treatment with an IDH inhibitor can provide disease control for some high-grade IDH-mutant glioma patients who had prior therapies and progressive disease. Future studies are needed to investigate this patients population.

PATH-66. MOLECULAR FEATURES RELATED TO LONG-TERM SURVIVAL IN GLIOBLASTOMA

Abstract Glioblastoma Multiforme (GBM) remains the most common malignant primary brain tumor in adults, with a dismal prognosis that rarely exceeds beyond 2 years of survival despite multimodal treatment. While small fractions of GBM patients seem to display extended survival, the underlying mechanisms for this peculiarity remain largely unknown. Previously published investigations of long-term survivors (LTS) usually incorporate small numbers of patients, non-uniform definition of LTS and rarely provide a comprehensive molecular analysis. With advances in multi-omics technologies and their integration with disease diagnostics, numerous prognostic molecular markers have been proposed. So far, only O6-methylguanine-DNA-methyltransferase (MGMT) gene promotor hypermethylation was linked to outcome and therapy response. We aim to investigate omics characteristics associated with LTS. Molecularly confirmed Isocitrate Dehydrogenase (IDH) wildtype GBM patients, >18 years old, operated and treated at our institution between 2013 and 2020 and living ≥5 years post-diagnosis (LTS = 62) or 1-2 years (STS = 62) were identified. Clinical and demographic characteristics were matched. Tumor tissues was analyzed with targeted next generation sequencing (NGS) and compared between LTS and STS. In addition, methylation analysis was done for all LTS. Results will be presented. We hope to shed a broader light on the molecular drivers behind the LTS in GBM patients, that will provide prognostic markers and potential targets for novel treatments.

STEM-12. A NEURONAL STEM-LIKE PHENOTYPE IN GRADE 4 IDH-MUTANT ASTROCYTOMA WITH CDKN2A/B LOSS IS ASSOCIATED WITH CUX2 DEFICIENCY

Abstract Diffuse gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, the loss of CDKN2A/B in IDH-mutant astrocytoma confers an aggressive high grade phenotype and is the strongest implicated molecular alteration associated poor clinical survival, thus is now sufficient to define a grade 4 tumor regardless of histologic grade. However, there remains no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with RNA sequencing data and found the increased expression of regulators of embryonic nervous system development and signaling concurrent with CDKN2A/B loss. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and cell-lines harboring CDKN2A/B homozygous deletion, we stably re-expressed p14ARF, p15INK4B, and p16INK4A using a Tet-inducible system. IDH-mutant cell lines with re-expression of p14, p15, or p16 displayed differential transcription factor activation, impaired neurosphere capability, decreased colony formation, and lower neurosphere proliferation. Intriguingly, RNA-seq data revealed CUX2, a transcription factor known to control neuronal precursor behavior, as the likely candidate regulating the differential expression profile across CDKN2A/B status. We observed increased CUX2 expression in cell lines stably re-expressing p14, p15, and p16. We validated the CUX2 signature across publicly available datasets of IDH-mutant astrocytoma where CUX2 expression negatively correlated with loss of CDKN2A/B in patient tumors. Together our work suggests CUX2 deficiency in IDH-mutant astrocytoma with CDKN2A/B deletion enables an increased neuronal stem-like phenotype in these grade 4 tumors.

NCOG-27. HIGHER LEVELS OF SERUM ICAM-1 AND IL-10 ARE ASSOCIATED WITH COGNITIVE DYSFUNCTION IN BOTH IDH-WILDTYPE AND IDH-MUTANT GLIOMA

Abstract BACKGROUND Cognitive dysfunction is common among glioma patients, but the contribution of specific mechanisms to the development of cognitive symptoms is unclear. Circulating levels of proteins linked to neurodegeneration, inflammation, and vascular damage have been associated with cognitive symptoms in neurological diseases and aging, but their prognostic value in glioma is unknown. Here, we examined associations between cognitive symptoms and serum levels of protein biomarkers in glioma patients. METHODS Cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA, scores ≤ 25 = cognitive dysfunction). Cytokines (interleukin-1β [IL-1β], IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, interferon-γ [IFN-γ], tumor necrosis factor-α [TNF-α]), and neurodegeneration (neurofilament light chain [NfL], tau, glial fibrillary acidic protein [GFAP]), and vascular damage markers (Serum amyloid A [SAA], C-reactive protein [CRP], vascular cell adhesion molecule 1 [VCAM-1], and intercellular adhesion molecule 1 [ICAM-1]) were measured using ultrasensitive assays (Meso Scale Discovery). RESULTS Patients (n=73) were predominantly male (58%), white (74%), with a median age of 44 (range=24,74). Cognitive dysfunction was found in 53% of the patients. Levels of NfL (p=0.035), IL-6 (p=0.006), IL-10 (p=0.007), TNF-α (p=0.035), IFN-γ (p=0.011), CRP (p=0.016), VCAM-1 (p=0.012), and ICAM-1 (p<0.001) were higher in patients with cognitive dysfunction when compared to those with normal cognition. After adjusting for isocitrate dehydrogenase (IDH) tumor mutation status, age, tumor grade, and number of surgeries, higher levels of ICAM-1 and IL-10, but not other markers, remained associated with cognitive dysfunction. MoCA scores were negatively correlated with GFAP (r=-0.24, p=0.038), IFN-γ (r=-0.31, p=0.008), IL-6 (r=-0.29, p=0.014), IL-10 (r=-0.24, p=0.039), and ICAM-1 (r=-0.39, p<0.001). CONCLUSIONS ICAM-1 and IL-10 levels were higher in patients with MOCA determined cognitive dysfunction, suggesting an association between cognitive symptoms and inflammation and vascular impairment in glioma patients. Future analyses in larger longitudinal cohorts are warranted to assess the predictive value of protein biomarkers.

Vorasidenib (Voranigo) for low-grade glioma.

The FDA has approved vorasidenib (Voranigo – Servier), an oral isocitrate dehydrogenase (IDH)inhibitor, for treatment of grade 2 astrocytoma or oligodendroglioma in patients ≥12 years old with an IDH1 or IDH2 mutation. It is the first systemic treatment to be approved in the US for this indication.

BIOM-18. MAPPING TUMOR HABITATS IN IDH-WILD TYPE GLIOBLASTOMA: INTEGRATING MR IMAGING, PATHOLOGIC, AND RNA DATA FROM IVY GLIOBLASTOMA ATLAS PROJECT

Abstract BACKGROUND To identify biologic correlates and spatially validate intratumoral subregions (tumor habitat) using diffusion-weighted and dynamic susceptibility contrast-imaging on a comprehensive pathology map of the isocitrate dehydrogenase (IDH)-wild type whole glioblastoma sample using the Ivy Glioblastoma Atlas Project (Ivy GAP). METHODS Complete data of 20 patients with 168 slides of IDH-wild type glioblastoma were obtained from the IvyGAP (http://glioblastoma.alleninstitute.org/). On MRI, tumor habitats were defined using voxel-wise clustering of apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) maps for contrast-enhancing lesion (CEL) and peritumoral non-enhancing lesion (NEL). On pathology slides, normalized areas of leading edge (LE), infiltrating tumor (IT), cellular tumor (CT), hypervascular lesion (CThypervascular), and perinecrotic lesion (CTperinecrotic) were obtained. Gross specimen pictures were co-registered on MRI images for co-localization and correlation between MRI tumor habitats. Pathologic areas were calculated using Pearson’s correlation coefficient. RNA sequencing of 67 RNA-seq samples was assessed using 4 Neftel subtypes and further correlated with pathology. RESULTS Six tumor habitats were correlated: hypervascular, hypovascular cellular, and hypovascular hypocellular habitats for CEL and NEL. CT was strongly correlated with hypovascular cellular habitat in CEL (C2, r = 0.238, p =.005). IT was strongly correlated with hypovascular cellular habitat in NEL (C5, r = 0.294, p =.017). CThypervascular was correlated with hypervascular habitat in NEL (r = 0.195, p =.023). CTperinecrotic was correlated with imaging necrosis (r = 0.199, p =.005). Astrocyte-like subtypes were positively correlated with IT (r = 0.256, p <.001), while mesenchymal-like subtypes were positively correlated with CTperinecrotic area (r = 0.246, p <.001). CONCLUSION Pathologically matched tumor subregions were cellular tumor with hypovascular cellular habitat in CEL and infiltrative tumor with hypovascular cellular habitat in NEL. Identification of the most aggressive tumor portion, and infiltrative tumor portion using non-invasive imaging can be achieved using MRI tumor habitats.

CTNI-66. IDH-MUTANT GLIOMA PATIENTS TREATED WITH VORASIDENIB: ONGOING DATA FROM THE VORASIDENIB EXPANDED ACCESS PROGRAM

Abstract BACKGROUND Vorasidenib (VOR) is an oral, brain-penetrant dual inhibitor of mutant isocitrate dehydrogenase 1/2 (mIDH1/2) demonstrating clinical efficacy and safety in patients with mIDH1/2 glioma in the phase 3 INDIGO study (NCT04164901). Servier launched an expanded access program (EAP, NCT05592743) in November 2022 designed to provide access to VOR for patients with mIDH1/2 glioma. Early clinical outcomes of patients treated in this EAP are presented. METHODS Eligible participants were aged ≥12 years with mIDH1/2 glioma and, in the opinion of the treating oncologist, would potentially benefit from treatment with VOR. Safety assessments occur every two weeks for the first two 28-day cycles, then monthly for the duration of treatment. RESULTS As of the March 31, 2024 data cutoff, 71 participants have initiated treatment with VOR. Mean (SD) age was 42.7 (14.8) years; 39 (55%) were male; and 34 (48%) with astrocytoma. mIDH mutation status was 46 (65%) mIDH1. One participant had separate tumors with either mIDH1 or mIDH2 identified. The majority of participants had grade 2 gliomas (n=51 [72%]) and non-contrast–enhancing disease (n=49 [69%]). As of the data cutoff, 62 (87%) participants remain on treatment, with the majority initiating treatment within the past 6 months (n=49 [69%]). Nine (13%) participants have discontinued treatment due to: radiographic progressive disease (n=3); clinical progressive disease (n=4); adverse event (AE) unrelated to treatment (n=1); or other reason (n=1). Three participants have died (disease progression [n=2], unrelated infection [n=1]). At least one AE of any grade was seen in 35 (49%) participants, with 4 (6%) experiencing unrelated serious AEs. Eight (11%) patients had AEs of special interest (defined as grade 2 or higher ALT/AST elevations). Ten (14%) patients had AEs that led to dose interruption and one (1%) patient had dose reduction. Additional treatment duration and various subgroup analyses will be presented.

TMET-29. TARGETING IDH1-MUTATED OLIGODENDROGLIOMA WITH ACID CERAMIDASE INHIBITORS

Abstract BACKGROUND Currently, an estimated 14,950 people lives with oligodendroglioma in the United States. Oligodendroglioma is genetically defined as a tumor harboring isocitrate dehydrogenase 1 or 2 mutations (IDH1mut/IDH2mut). Previously, we reported that in IDH1mut gliomas, D-2HG, the product of IDH1 mutant enzyme produces an increase in monounsaturated fatty acid levels that are incorporated into ceramides, tilting the S1P-to-ceramide rheostat toward apoptosis. Herein, we exploited this imbalance to further induce and IDHmut-specific glioma cell death. METHODS TCGA and CCGA data were used to explore the association between acid ceramidase (AC) gene expression and patient survival. CCK8 viability assays were carried out to measure the sensitivity of glioma cell lines to acid ceramidase inhibitors. Western blot and liquid chromatography-mass spectrometry analyses were performed for studying the mechanism of action of acid ceramidase inhibitors. The in vivo efficacy of the SABRAC drug, an irreversible inhibitor of AC, was evaluated in an orthotopic oligodendroglioma xenograft mice model using TS603 patient-derived oligodendroglioma cells. RESULTS. We report for the first time that the inhibition of acid ceramidase (AC) induces apoptosis and increases the survival of mice with IDH1mut oligodendroglioma. We demonstrated an IDH1mut-specific cytotoxicity of SABRAC, in patient-derived oligodendroglioma cells. Exploring the mechanism of action of this drug, we found that SABRAC activates both extrinsic and intrinsic apoptosis in an ER stress-independent manner, pointing to a direct action of AC-related ceramides in mitochondria permeability. The activation of apoptosis detected under SABRAC treatment was associated with up to a 30-fold increase in some ceramide levels and its derivatives from the salvage pathway. CONCLUSIONS We propose AC as a novel therapeutic target in oligodendroglioma with IDH1mut and we are conducting additional preclinical testing.

TMET-14. ENOLASE 2 IS A UNIQUE METABOLIC VULNERABILITY INDUCED BY THE 1P19Q CODELETION IN OLIGODENDROGLIOMAS

Abstract Gliomas are devastating primary brain tumors in adults. The presence of an isocitrate dehydrogenase mutation combined with a chromosomal 1p/19q codeletion discriminates oligodendrogliomas from astrocytomas. The goal of this study was to leverage metabolic vulnerabilities induced by the 1p/19q codeletion for oligodendroglioma therapy. The 1p19q codeletion results in loss of enolase 1 (ENO1), which converts 2-phosphoglycerate to phosphoenolpyruvate during glycolysis. Here, we show that enolase 2 (ENO2) is upregulated in patient-derived oligodendroglioma (SF10417, BT88, BT54) models relative to astrocytoma (BT142, SF10602) and normal human astrocytes. ENO2 is also elevated in oligodendroglioma patient biopsies relative to astrocytoma or gliosis. Mechanistic studies indicate that inhibiting MEK1 or ERK1 abrogates ENO2 expression, suggesting that the MAPK pathway upregulates ENO2 in oligodendrogliomas. Next, we examined the therapeutic potential of targeting ENO2 in oligodendrogliomas. Genetic ablation of ENO2 or pharmacological inhibition using POMHEX inhibited the viability of SF10417 and BT88 cells with IC50 values of ~50 nM. In contrast, the IC50 for BT142 and SF10602 astrocytoma cells was ~5-8 uM, highlighting the exquisite dependence of oligodendrogliomas on ENO2. However, ENO2 inhibition did not lead to cytotoxicity in patient-derived oligodendroglioma cells or intracranial tumor xenografts. To assess the metabolic consequences of ENO2 inhibition and identify potential compensatory alterations, we traced [U-13C]-glucose metabolism in vivo in mice bearing intracranial SF10417 tumors. Although POMHEX abrogated glycolytic metabolism downstream of 2-phosphoglycerate, it shunted glucose towards biosynthesis of serine, glycine, methionine and purine nucleotides, an effect that was driven by phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme for serine biosynthesis. Importantly, the novel PHGDH inhibitor PHGDH-D8 was synthetically lethal in combination with POMHEX in oligodendroglioma cells and the combination induced apoptosis in mice bearing intracranial SF10417 tumors. Collectively, we exploit a mechanistic understanding of metabolic vulnerabilities induced by the 1p19q codeletion to identify combined inhibition of ENO2 and PHGDH as a novel therapeutic opportunity for oligodendrogliomas.

DDDR-24. REAL WORLD EXPERIENCE USING THE IDH INHIBITOR IVOSIDENIB IN IDH MUTANT GLIOMA: TOLERABILITY AND OUTCOMES

Abstract BACKGROUND Mutant isocitrate dehydrogenase (IDHm) inhibitors represent a novel therapeutic strategy for treating IDHm glioma, though their optimal use outside of clinical trials remains undefined. This study describes real world utilization of the IDH1 inhibitor, ivosidenib, in patients with IDHm glioma. METHODS We retrospectively reviewed clinical and radiographic data from IDHm glioma patients treated with ivosidenib monotherapy at Dana-Farber Cancer Institute and Massachusetts General Hospital from 2020-2024. Patients with a baseline MRI at ivosidenib initiation and at least 2 subsequent scans while on ivosidenib were included in radiographic response analysis (452 scans). RESULTS This cohort included 77 patients (39 males) age 17-75 years (median 41). Thirty-eight patients (49%) had astrocytomas and 39 (51%) had oligodendrogliomas; 48 (62%) had grade 2, 26 (34%) grade 3, and 3 (4%) grade 4 gliomas. Twenty-four patients (31%) received ivosidenib as first-line therapy and 53 (69%) received ivosidenib after failing prior treatments. Among those in the radiographic analysis, 4 (6%) demonstrated partial response, 4 (6%) minor response, 44 (62%) stable disease, and 19 (27%) progressive disease (PD). Significantly higher PD rates were seen in those with enhancing disease (p<0.001) or received ivosidenib as subsequent-line therapy (p=0.002); PD rate was similar between grades 2 and 3 in the first-line group (p=0.64). One-year progression free survival was 100% in the first-line group and 66% in the subsequent-line group. At the time of our analyses, 4 patients (5%) had died (all in the subsequent-line group). Infrequent side effects included CK elevation, QTc prolongation, transaminitis, and diarrhea. One patient (1%) was dose reduced and 3 (4%) discontinued drug due to side effects. CONCLUSIONS In this real world IDHm glioma cohort, ivosidenib was well-tolerated. Better response rates were seen in patients without enhancing disease at ivosidenib initiation and those who received the drug as first-line therapy.

CTNI-53. A GLOBAL, RANDOMIZED, DOUBLE-BLINDED, PHASE 3 STUDY OF VORASIDENIB VERSUS PLACEBO IN PATIENTS WITH ADULT-TYPE DIFFUSE GLIOMA WITH AN IDH1/2 MUTATION (INDIGO): UPDATED EFFICACY RESULTS

Abstract INTRODUCTION The Phase 3 INDIGO study (NCT04164901) evaluated vorasidenib, an oral, brain-penetrant, dual inhibitor of mutated isocitrate dehydrogenase 1/2 (mIDH1/2), in patients with mIDH1/2 diffuse glioma. The primary endpoint of progression-free survival (PFS) per blinded independent review committee (BIRC), and key secondary endpoint of time to next intervention (TTNI), were met in the positive, preplanned second interim analysis (IA2). The study was unblinded in March 2023 following independent data monitoring committee recommendation. Here, we present results after an additional 6 months of follow-up between the database lock for IA2 (September 6, 2022) and study unblinding (March 7, 2023). METHODS Patients with residual/recurrent grade 2 mIDH1/2 oligodendroglioma or astrocytoma were enrolled (≥12 years; Karnofsky Performance Status ≥80; measurable non-enhancing disease; surgery as only prior treatment; no immediate need of chemoradiotherapy). Patients were randomized 1:1 to vorasidenib 40 mg or placebo daily in 28-day cycles. RESULTS Overall, 331 patients were randomized (median age: 40.0 years; oligodendroglioma: 172; astrocytoma: 159). As of March 7, 2023, 123/168 (73%) patients remained on vorasidenib and 72/163 (44%) remained on placebo. PFS per BIRC remained in favor of vorasidenib (HR, 0.35; 95% CI, 0.25–0.49), and was consistent with PFS per investigator assessment (HR, 0.34; 95% CI, 0.23–0.50). Median PFS per BIRC: vorasidenib, not estimable (NE; 95% CI, 22.1–NE); placebo, 11.4 months (95% CI, 11.1–13.9). TTNI also remained in favor of vorasidenib (HR, 0.25; 95% CI, 0.16–0.40). Median TTNI: vorasidenib, NE (95% CI, NE–NE); placebo, 20.1 months (95% CI, 17.5–27.1). No new safety signals emerged. CONCLUSIONS Vorasidenib is a targeted therapy for patients with predominantly non-enhancing mIDH1/2 diffuse glioma following surgical intervention, as shown in the INDIGO population. These additional 6 months of follow-up confirm the previously reported statistically significant and clinically meaningful improvements in PFS and TTNI with vorasidenib.

PATH-55. RAMAN-BASED MACHINE LEARNING PLATFORM REVEALS UNIQUE METABOLIC DIFFERENCES BETWEEN IDHMUT AND IDHWT GLIOMA

Abstract BACKGROUND Formalin-fixed, paraffin-embedded (FFPE) tissue slides are routinely used in cancer diagnosis, clinical decision-making, and stored in biobanks, but their utilization in Raman spectroscopy-based studies has been limited due to the background coming from embedding media. METHODS Spontaneous Raman spectroscopy was used for molecular fingerprinting of FFPE tissue from 46 patient samples with known methylation subtypes. Spectra were used to construct tumor/non-tumor, IDH1WT/IDH1mut, and methylation-subtype classifiers. Support vector machine and random forest were used to identify the most discriminatory Raman frequencies. Stimulated Raman spectroscopy was used to validate the frequencies identified. Mass spectrometry of glioma cell lines and TCGA were used to validate the biological findings. RESULTS Here we develop APOLLO (rAman-based PathOLogy of maLignant glioma) – a computational workflow that predicts different subtypes of glioma from spontaneous Raman spectra of FFPE tissue slides. Our novel APOLLO platform distinguishes tumors from nontumor tissue and identifies novel Raman peaks corresponding to DNA and proteins that are more intense in the tumor. APOLLO differentiates isocitrate dehydrogenase 1 mutant (IDH1mut) from wildtype (IDH1WT) tumors and identifies cholesterol ester levels to be highly abundant in IDHmut glioma. Moreover, APOLLO achieves high discriminative power between finer, clinically relevant glioma methylation subtypes, distinguishing between the CpG island hypermethylated phenotype (G-CIMP)-high and G-CIMP-low molecular phenotypes within the IDH1mut types. CONCLUSIONS Our results demonstrate the potential of label-free Raman spectroscopy to classify glioma subtypes from FFPE slides and to extract meaningful biological information thus opening the door for future applications on these archived tissues in other cancers.

IMMU-45. MYELOID-ASSOCIATED WILD-TYPE IDH1 PROMOTES IMMUNOSUPPRESSION IN GLIOBLASTOMA

Abstract Tumor-associated myeloid cells (TAMCs) promote immunosuppression in the GBM tumor microenvironment (TME) and resistance to immune checkpoint therapy (ICT). However, the metabolic and epigenetic mechanisms underlying TAMC activation and the therapeutic potential of fine-tuning TAMC activation remain largely unexplored. Our analyses of GBM patient single-cell RNA sequencing (scRNA-Seq) datasets demonstrated that in addition to tumor cells, wild-type isocitrate dehydrogenase (wt-IDH1) is also highly expressed in TAMCs. Using a murine model with myeloid cell-specific deletion of wt-IDH1 (LysM-cre-ERT2; wt-IDH1L/L), we demonstrated that the loss of wt-IDH1 promoted inflammatory myeloid phenotypes, increased CD8+ T cells in the TME, improved survival of GBM tumor-bearing mice, and enhanced anti-tumor effects of PD1 checkpoint blockade. Further, the pharmacological inhibition of wt-IDH1 using systemic administration of a first-in-class wt-IDH1-specific, brain-penetrant small molecule inhibitor or intrathecal delivery of siRNA targeted to wt-IDH1 mirrored the functional phenotype of wt-IDH1-deleted myeloid cells, overcame ICT resistance, and promoted long-term survival and anti-tumor immune memory. Mechanistically, in myeloid cells, the genetic or pharmacological inactivation of wt-IDH1 inhibited oxidative phosphorylation, reduced myeloid cell proliferation, increased their tumoricidal activity, and altered chromatin accessibility of key transcription factors implicated in the regulation of myeloid cell states, including AP-1, IRFs, STAT1/2, NFATs, and CEPBPs. These studies define wt-IDH1 as a metabolic checkpoint of myeloid cell activation and credential the inhibition of wt-IDH1 as a novel immunotherapeutic strategy to increase ICT efficacy for patients with GBM.

DISP-02. SOCIOECONOMIC FACTORS INFLUENCE OVERALL SURVIVAL IN CHEMORADIATION-TREATED NEWLY DIAGNOSED WHO GRADE 4 GLIOBLASTOMA

Abstract Social determinants of health are known to influence health outcomes, yet the interactive effects of patient-specific socioeconomic variables on overall survival remain poorly characterized in patients with glioblastoma (GBM). We aimed to assess socioeconomic factors associated with overall survival in a clinically homogenous GBM population. Patients with newly diagnosed isocitrate dehydrogenase wild-type glioblastoma, who underwent maximal safe resection of contrast-enhanced (CE) and non-contrast enhanced tissue (NC) tissue with adjuvant chemoradiation from 1997-2017 were selected for inclusion. Socioeconomic factors were collected through retrospective chart review. Variables associated with overall survival on univariate cox proportional hazards models (p<0.05) were selected for multivariate analysis. 272 patients (42.6% female, 14.3% minority) were included. On univariate logistic regression, older age (HR: 1.23, p<0.001), greater residual CE tissue (HR: 3.95, p<0.001), were associated with reduced survival. Greater extent of resection NCE tissue (HR 0.94, p=0.028), higher postoperative KPS (HR 0.89, p=0.034), and unemployment (HR: 0.67, p=0.022), were associated with longer overall survival. On multivariate analysis, age was associated with reduced survival (HR: 1.31, p<0.001), while unemployment (HR:0.69, p=0.049) was associated with longer overall survival. Subgroup multivariate analyses was performed dividing patients into those <65 (n=185, 45% female, 11.9% minority, 48% employed) and those ≥65 (n=87, 37% female, 14% minority, 20% employed). In the <65 cohort, protective factors included retirement (HR: 0.49 p=0.004), and unemployment (HR:.57, p=0.006). Older age (HR: 1.03, p=0.004), and greater residual CE tissue (HR: 1.16, p=0.03) continued to be associated with poorer survival. No variables correlated with outcomes in the ≥65 cohort. Active employment was associated with reduced survival in GBM patients treated with standard care, potentially serving as a proxy for access to subsequent treatment.

TMET-25. WILD-TYPE IDH1 INHIBITS FERROPTOSIS IN GLIOBLASTOMA

Abstract De novo lipogenesis and the defense against oxidative lipid damage require large amounts of cytosolic NADPH. Our group has recently found that glioblastoma (GBM) up-regulate wild-type Isocitrate dehydrogenase 1 (referred to hereafter as ‘wt-IDH1high GBM) that, through oxidative decarboxylation of isocitrate, generates large quantities of alpha-ketoglutarate and cytosolic NADPH. We demonstrated that RNAi-mediated knockdown of wt-IDH1, alone and in combination with RT, slows the growth of patient-derived HGG xenografts, while overexpression of wt-IDH1 promotes intracranial HGG growth. Here, we demonstrate that wt-IDH1high GBM produce excess NADPH, which is a rate-limiting reductant that drives de novo fatty acid biosynthesis. Isotope tracer and liquid chromatography-based lipidomic studies indicate that wt-IDH1 supports the de novo biosynthesis of mono-unsaturated fatty acids (MUFAs), promotes the incorporation of monounsaturated, and reduces the abundance of oxidizable polyunsaturated (PUFA) phospholipids in the cell membrane. Conversely, the genetic ablation of wt-IDH1 or the pharmacologic inhibition of wt-IDH1 in tumor cells, using a brain-penetrant wt-IDH1-specific small molecule, revealed a significant increase in PUFA-containing lipid species harboring oxidized arachidonic tails. Of note, two lipid species, (PE16:0_20:4) and (PE18:0_22:4), previously reported to act as substrates for 15-lipoxygenase (15-LOX) - a key enzyme that facilitates lipid peroxidation - are enriched in tumor cells with wt-IDH1 compromise. Further, we found that the enhanced NADPH production in wt-IDH1high GBM, together with heightened biosynthesis of carbon precursors required for glutathione biosynthesis, increased levels of reduced glutathione (GSH), activate the phospholipid peroxidase glutathione peroxidase 4 (GPX4)-driven lipid repair pathway, which scavenges PUFA-containing lipid peroxides, known executioners of ferroptosis. These findings support elevated wt-IDH1 expression, the ensuing effect on the tumor lipidome, redox homeostasis, and protection against lipid peroxidation as contributors to GBM tumor growth and therapy resistance and point to the inhibition of wt-IDH1 as a ferroptosis-inducing strategy for the treatment of GBM.

CTIM-19. A PHASE 1, SAFETY LEAD-IN AND RANDOMIZED, OPEN-LABEL, PERIOPERATIVE STUDY OF VORASIDENIB COMBINED WITH PEMBROLIZUMAB IN RECURRENT OR PROGRESSIVE ENHANCING IDH-1 MUTANT GLIOMA: TRIAL IN PROGRESS

Abstract BACKGROUND Vorasidenib (VOR) is an oral, brain-penetrant dual inhibitor of isocitrate dehydrogenase 1/2 mutant (mIDH1/2) enzymes. VOR is being investigated in a phase 3 study in residual or recurrent grade 2 non-enhancing gliomas, in which interim analysis showed VOR significantly improved progression-free survival and delayed time to next intervention. A prior neoadjuvant perioperative study in recurrent, non-enhancing grade 2/3 gliomas showed that VOR treatment was associated with interferon signal activation and increased T-cell infiltration, suggesting 2-hydroxyglutarate suppression may prime the tumor immune microenvironment for immune checkpoint blockade. This study (NCT05484622) evaluates the safety and tolerability of VOR+pembrolizumab to determine the recommended combination dose (RCD) of VOR (safety lead-in phase) and evaluates CD3+ T-cell infiltration in tumors following a 28-day preoperative period. METHODS Enrollment: US patients with recurrent or progressive grade 2/3 mIDH1 R132H glioma. Key eligibility: measurable enhancing disease, Karnofsky Performance Status ≥70, resectable (perioperative phase only). Following a March 2024 protocol amendment, inclusion criteria were expanded to include patients with oligodendroglioma in addition to patients with astrocytoma. Safety lead-in dosing: Cohort 1, VOR 40mg QD+pembrolizumab 200mg Q3W in 21-day cycles. The perioperative phase is randomized 1:1:1 to preoperative combination, VOR 40mg QD, or untreated for 28 (+7) days; all patients could opt to receive the VOR RCD in combination with pembrolizumab 200mg Q3W postoperatively. Primary objectives: safety and tolerability of VOR RCD administered with pembrolizumab; CD3+ T-cell infiltration in resected tumors following presurgical treatment with combination compared to untreated tumors. RESULTS Seven patients with recurrent or progressive enhancing grade 2/3 astrocytoma with an mIDH1 R132H were dosed in the safety lead-in phase. No dose-limiting toxicities were detected during this phase. CONCLUSION VOR 40mg QD+pembrolizumab 200mg Q3W was confirmed as the RCD for the perioperative phase. This phase was opened to enrollment in May 2023, and recruitment is ongoing.

CTNI-47. A PHASE 1, RANDOMIZED, PERIOPERATIVE TRIAL OF VORASIDENIB AND IVOSIDENIB IN IDH1-MUTANT DIFFUSE GLIOMA: UPDATED RESULTS

Abstract BACKGROUND Vorasidenib (VOR) and ivosidenib (IVO) showed clinical activity in subjects with isocitrate dehydrogenase mutant (mIDH) gliomas. We evaluated both agents in a phase 1, randomized, open-label perioperative trial (NCT03343197). Pharmacodynamics, pharmacokinetics, and preliminary objective response rate (ORR) data as of 29-April-2020 were previously reported (Mellinghoff et al. Nat Med. 2023). Progression-free survival (PFS) data were not mature at publication time. We report here longer-term follow-up results, including mature PFS. METHODS Participants with grade 2/3 non-enhancing mIDH1 R132H mutant gliomas were randomized to VOR (50 or 10 mg QD), IVO (500 or 250 mg BID), or no treatment (control) for 4 weeks prior to planned surgery, with the option to continue treatment with VOR or IVO post-surgery. Secondary objectives included PFS, ORR assessed by Investigator in the post-surgery period, and safety profile of VOR and IVO. RESULTS Enrollment completed in April-2019. 49 participants were randomized, of which 46 participants (24 oligodendroglioma, 20 astrocytoma, 1 anaplastic oligodendroglioma, 1 anaplastic oligoastrocytoma) received treatment with either VOR (N=24) or IVO (N=22) after surgery. As of 23-September-2023 data cutoff, 11 (46%) and 5 (20%) participants remain on treatment for VOR and IVO, respectively. Median (range) post-operative treatment duration was 44.7 months (0.9–62.7) for VOR, 23.9 months (0–62.7) for IVO. Median (95% CI) PFS was 41.4 months (9.3, NE) for VOR and 38.6 months (18.3, NE) for IVO. ORR per Response Assessment in Neuro-Oncology in low-grade gliomas (RANO-LGG) was 46% for VOR and 27% for IVO. Longer safety follow up will also be presented. CONCLUSION These results provide further evidence of prolonged response using IVO and VOR immediately following surgery in predominantly non-enhancing gliomas. This longer-term follow-up is consistent with Phase 3 INDIGO study results where VOR demonstrated PFS benefit with manageable safety compared with placebo in participants with non-enhancing mIDH gliomas.