R132H Mutation Research Articles

IDH1 R132H and TP53 R248Q Mutations Modulate Glioma Cell Migration and Adhesion on Different ECM Components

Mutations in IDH1 and TP53 have a significant impact on glioma prognosis and progression; however, their roles in tumor cell invasion in terms of interactions with particular components of the extracellular matrix (ECM) are still unclear. Using gene editing protocol based on CRISPR-Cas 9 with cytidine deaminase, we introduced point mutations into U87MG glioblastoma cells to establish modified cell lines with heterozygous IDH1 R132H, homozygous TP53 R248Q and heterozygous IDH1 R132H, homozygous TP53 R248Q genotypes. A comparative study of cell migration on major ECM components was carried out by high-content microscopy. IDH1 R132H mutation introduced to U87MG glioblastoma cells was shown to decrease the migration speed on Matrigel and collagen IV substrates compared to the wild-type. This data were supported by cell adhesion quantification via the lateral shift assay performed by atomic force microscopy (AFM). TP53 R248Q mutation increased cell adhesion to various substrates and significantly promoted cell migration on hyaluronic acid and chondroitin sulfate but did not change the migration rates on laminin and collagens IV and I. A double-mutant genotype produced by consequently introducing IDH1 R132H and TP53 R248Q to parental glioblastoma cells was characterized by the highest migration among all the cell lines, with particularly faster motility on chondroitin sulfate. These findings underscore the complex interactions between glioma cells, with the most important driver mutations and specific ECM components regulating cancer cell migration, offering valuable insights for potential therapeutic targets in glioma treatment.

PATH-18. CURRENT STATUS OF CANCER GENOMIC PROFILING (CGP) TESTS IN BRAIN TUMOR TREATMENT - COMPLEMENTING BRAIN TUMOR PATHOLOGICAL DIAGNOSIS WITH CGP-

Abstract INTRODUCTION Cancer genomic profiling (CGP) tests are currently used in the search for therapeutic targets and have become an auxiliary tool in diagnosis according to the new WHO classification (WHO 2021), which requires the integration of pathomorphological and molecular diagnostics. Here, we report on brain tumor cases at our institution that underwent CGP testing. METHODS From May 2020 to the present, 27 brain tumor cases that underwent CGP testing at our institution were included in this study. There were 14 males and 13 females, ranging from 18 to 70 years (average 48.4 years). The tests conducted included Foundation One CDx, GeneMineTop, and NCC OncoPanel. RESULTS The cases that underwent CGP testing included 13 cases of glioblastoma IDH-wildtype, 3 cases of astrocytoma, IDH-mutant, grade 4, 4 cases of astrocytoma IDH-mutant, grade 3, 3 cases of oligodendroglioma, 1p/19q codeleted, grade 3, 1 case of astrocytoma, IDH-mutant, grade 2, 1 case of ependymoma, 1 case of pilocytic astrocytoma and 1 case of PitNEC. CGP testing enabled molecular diagnostics such as IDH mutation and TERTp mutation. Based on the results, therapeutic suggestions were possible for 5 out of 25 cases (20%) (BRAF V600E mutation 1 case, IDH1 R132H mutation 1 case, TMB high 3 cases). Checkpoint inhibitors were used in a case with high TMB. Genetic risk assessment by a genetic counselor was conducted for all cases, and one high TMB case was diagnosed as hereditary cancer. A germline pathogenic variant in MSH6 was detected, leading to a diagnosis of Lynch syndrome. CONCLUSION Molecular diagnostics through CGP testing served as an aid in diagnosis according to WHO2021. Cases where drug suggestions were feasible underwent treatment with targeted molecular therapies and checkpoint inhibitor. We experienced cases where hereditary cancer syndromes such as Lynch syndrome were diagnosed through the detection of germline pathogenic variants.

CNSC-63. THE COMPLEX RELATIONSHIP BETWEEN GENETIC ETIOLOGIES OF GLIOBLASTOMA AND PATIENT SURVIVAL: A RETROSPECTIVE ANALYSIS

Abstract Data Analysis was done using the NIH GDC Data Portal with glioblastomas being the only selected primary diagnosis (n=1381). Kaplan Meier plots were generated for various genes and mutations and the survival data was compared between carriers and non-carriers. Median survival was 14 months post diagnosis when all patients are clustered together. Survival Plot of patients with IDH1 R132H mutation (n=35) vs without IDH1 R132H mutation (n=538) reveals that carriers have longer survival compared to non-carriers. The next seven cases with the highest number of specific mutations were a variation between TP53 and EGFR, both genes implicated in various cancers due to their roles in cancer suppression and proliferation respectively. The ten most frequent specific mutations observed were all missense mutations. Furthermore, patients without PTEN mutations (n=98) had better survival compared to patients who had PTEN mutations (n=623), particularly observed after one year. For specific mutations, IDH1 R132H was detected in 35 patients. All other specific mutation groups had less than 30 patients, therefore, a larger cohort would be beneficial in understanding the survival outcomes of various specific mutations. In terms of total number of mutations per gene, PTEN had the highest followed by TP53 and EGFR. In understanding the survival data, the best target for therapies can be narrowed, regardless of the increasingly evident polygenic pathology of glioblastoma.

PATH-19. DIAGNOSTIC UTILITY OF MOLECULAR PROFILING IN ADULT DIFFUSE GLIOMA

Abstract INTRODUCTION With the publication of World Health Organization Classification of the Central Nervous System Tumors (WHO CNS5), molecular profiling has become essential for the diagnosis of CNS tumors. To test for the diagnostic molecular alterations, we developed a targeted DNA sequencing panel (Nakashima et al. 2024) to analyze 113 genes, chromosomal abnormalities, and MGMT promoter methylation. This study aimed to evaluate our diagnostic approach using the targeted sequencing panel. PATIENTS AND METHODS We included 72 cases of diffuse adult gliomas diagnosed at our institute between June 2023 and May 2024. We analyzed the tumor diagnoses based on the pathological and immunohistochemical findings as well as the targeted sequencing panel findings. RESULTS The tumor diagnoses were as follows: glioblastoma, IDH-wildtype: 32 cases, astrocytoma, IDH-mutant: 17 cases, oligodendroglioma, IDH-mutant and 1p/19q-codeleted: 15 cases, others: 8 cases. Among 32 cases of IDH1/2 mutations, 28 cases (87.5%) with IDH1 R132H mutation were diagnosed by immunohistochemistry using anti-IDH1 R132H antibody, whereas 4 (12.5%) (3 with IDH2 mutation, and 1 with IDH1 R132S) were diagnosed by the targeted sequencing panel. Of the 32 glioblastoma cases, 6 (18.8%) did not show necrosis or microvascular proliferation and were diagnosed based on either TERT promoter mutation, EGFR amplification, or chromosome 7/chromosome 10 abnormalities. Moreover, 24 out of 26 resected cases (92.3%) were diagnosed morphologically, whereas 4 of 6 biopsy cases (66.7%) were diagnosed molecularly (p=0.0056). Among the 17 cases of astrocytoma, IDH-mutant, 2 (11.8%) showed homozygous deletion of CDKN2A/B. There were 4 cases (5.6%) out of 72 that did not satisfy the diagnostic criteria for glioblastoma, astrocytoma, oligodendroglioma. CONCLUSION Approximately 95% of cases were diagnosed based on WHO CNS5 criteria with molecular profiling. We also demonstrate molecular profiling is useful in glioblastoma diagnostics, especially in biopsy cases where morphological diagnostic evidence is not recognized.

Blood and cerebrospinal fluid biomarkers in neuro-oncology.

The purpose of this review is to discuss the value of blood and CSF biomarkers in primary CNS tumors. Several analytes can be assessed with liquid biopsy techniques, including circulating tumor cells, circulating cell-free tumor DNA, circulating cell-free RNA, circulating proteins and metabolites, extracellular vesicles and tumor-educated platelets. Among diffuse gliomas of the adult, ctDNA in blood or CSF has represented the most used analyte, with the detection of molecular alterations such as MGMT promoter, PTEN, EGFRVIII, TERT promoter mutation and IDH R132H mutation. In general, CSF is enriched for ctDNA as compared with plasma. The use of MRI-guided focused ultrasounds to disrupt the blood-brain barrier could enhance the level of biomarkers in both blood and CSF. The detection of MYD88 L265P mutation with digital droplet PCR and the detection of ctDNA with next generation sequencing represent the best tools to diagnose and monitoring CNS lymphomas under treatment. In meningiomas, the low concentration of ctDNA is a limiting factor for the detection of driver mutations, such as NF2, AKTs, SMO, KLF4, TRAF7, SMARCB1, SMARCE1, PTEN, and TERT; an alternative approach could be the isolation of ctDNA through circulating extracellular vesicles. Liquid biopsies are being used extensively for diagnosis and surveillance of diffuse midline gliomas, in particular with the detection of the driver mutation H3K27M. Last, specific methylome patterns in CSF may allow the distinction of glioblastomas from CNS lymphomas or meningiomas. This review summarizes the current knowledge and future perspectives of liquid biopsy of blood and CSF for diagnosis and monitoring of primary CNS tumors.

Gaining Insight into the Catalytic Mechanism of the R132H IDH1 Mutant: A Synergistic DFT Cluster and Experimental Investigation.

Human isocitrate dehydrogenase 1 (IDH1) is an enzyme that is found in humans that plays a critical role in aerobic metabolism. As a part of the citric acid cycle, IDH1 becomes responsible for catalyzing the oxidative decarboxylation of isocitrate to form α-ketoglutarate (αKG), with nicotinamide adenine dinucleotide phosphate (NADP+) as a cofactor. Strikingly, mutations of the IDH1 enzyme have been discovered in several cancers including glioblastoma multiforme (GBM), a highly aggressive form of brain cancer. It has been experimentally determined that single-residue IDH1 mutations occur at a very high frequency in GBM. Specifically, the IDH1 R132H mutation is known to produce (D)2-hydroxyglutarate (2HG), a recognized oncometabolite. Using the previously determined catalytic mechanism of IDH1, a DFT QM model was developed to study the mechanistic properties of IDH1 R132H compared to wild type enzyme. Validating these insights, biochemical in vitro assays of metabolites produced by mutant vs wild type enzymes were measured and compared. From the results discussed herein, we discuss the mechanistic impact of mutations in IDH1 on its ability to catalyze the formation of αKG and 2HG.

Clinical utility of plasma cell-free DNA (cfDNA) in diffuse gliomas for the detection of IDH1 R132H mutation

Liquid biopsy for CNS tumors is in its nascent phase, hindered by the low levels of circulating tumor DNA (ctDNA). Overcoming this challenge requires highly sensitive molecular techniques. DD-PCR emerges as a standout technique due to its ability to identify rare mutations, copy number variations, and circulating nucleic acids, making it one of the best methods for identifying somatic mutations in cell-free DNA (cfDNA). Despite promising results from various studies demonstrating the feasibility of obtaining informative ctDNA profiles from liquid biopsy samples, challenges persist, including the need to standardize sample collection, storage, and processing methods, define clear assay positivity thresholds, and address the overall low assay sensitivity. Our two-phase study began by assessing DD-PCR efficacy in FFPE tissues, revealing robust concordance with immunohistochemistry. In Phase 1 (85 cases), DD-PCR on FFPE tissues demonstrated 100 % sensitivity and specificity for IDH1 R132H mutations. In Phase 2 (100 cases), analysis extended to cfDNA, maintaining high specificity (100 %) with moderate sensitivity (44.2 %). Overall concordance with immunohistochemistry was 61 %, highlighting liquid biopsy's potential in glioma management. The findings emphasized DD-PCR's clinical utility in both tissue and liquid biopsy, underscoring its role in early detection, diagnosis, and therapeutic monitoring of diffuse gliomas.

Clinical outcome, radiological findings, and genetic features of IDH-mutant brainstem glioma in adults.

With the recent advent of genetic testing, IDH-mutant glioma has been found among adult brainstem gliomas. However, the clinical outcome and prognosis of IDH-mutant brainstem gliomas in adults have not been elucidated. This study aimed to investigate the clinical outcome, radiological findings, and genetic features of adult patients with IDH-mutant diffuse brainstem gliomas. Data from adult patients with brainstem glioma at Hokkaido University Hospital between 2006 and 2022 were retrospectively analyzed. Patient characteristics, treatment methods, genetic features, and prognosis were evaluated. Of 12 patients with brainstem glioma with proven histopathology, 4 were identified with IDH mutation. All patients underwent local radiotherapy with 54 Gray in 27 fractions combined with chemotherapy with temozolomide. Three patients had IDH1 R132H mutation and one had IDH2 R172G mutation. The median progression-free survival and overall survival were 68.4months and 85.2months, respectively, longer than that for IDH-wildtype gliomas (5.6months and 12.0months, respectively). At the time of initial onset, contrast-enhanced lesions were observed in two of the four cases in magnetic resonance imaging. As some adult brainstem gliomas have IDH mutations, and a clearly different prognosis from those with IDH-wildtype, biopsies are proactively considered to confirm the genotype.

Ultra-Rapid Droplet Digital PCR Enables Intraoperative Tumor Quantification.

The diagnosis and treatment of tumors often depends on molecular-genetic data. However, rapid and iterative access to molecular data is not currently feasible during surgery, complicating intraoperative diagnosis and precluding measurement of tumor cell burdens at surgical margins to guide resections. To address this gap, we developed Ultra-Rapid droplet digital PCR (UR-ddPCR), which can be completed in 15 minutes from tissue to result with an accuracy comparable to standard ddPCR. We demonstrate UR-ddPCR assays for the IDH1 R132H and BRAF V600E clonal mutations that are present in many low-grade gliomas and melanomas, respectively. We illustrate the clinical feasibility of UR-ddPCR by performing it intraoperatively for 13 glioma cases. We further combine UR-ddPCR measurements with UR-stimulated Raman histology intraoperatively to estimate tumor cell densities in addition to tumor cell percentages. We anticipate that UR-ddPCR, along with future refinements in assay instrumentation, will enable novel point-of-care diagnostics and the development of molecularly-guided surgeries that improve clinical outcomes.

IDH1 mutation predicts seizure occurrence and prognosis in lower-grade glioma adults

Epileptic seizures are frequently the first symptom in glioma patients. However, the causal relationship between glioma and epilepsy is not yet fully understood, as it cannot be explained solely by tumor mass effect or peritumoral factors. In this study, we retrospectively enrolled 320 patients with grade 2–4 glioma who received treatment between January 2019 and July 2022, and explored the biomarkers of seizure occurrence and seizure outcome prediction using univariate and multivariate logistic regression analyses. Our results showed that IDH1 R132H mutation was an independent risk factor for seizure occurrence in lower-grade glioma (LGG) patients (OR = 4.915, 95%CI = 1.713 – 14.103, P = 0.003). Additionally, IDH1 R132H mutation predicted higher seizure-free ratios in LGG patients with intact ATRX expression (OR = 6.793, 95%CI = 1.217 – 37.923, P = 0.029) one year after diagnosis. Therefore, our findings suggest that IDH1 mutation can predict seizure occurrence and control in LGG patients, providing further insights into the relationship between glioma and epilepsy.

Reliable detection of genetic alterations in cyst fluid DNA for the diagnosis of brain tumors.

Liquid biopsy of cyst fluid in brain tumors has not been extensively studied to date. The present study was performed to see whether diagnostic genetic alterations found in brain tumor tissue DNA could also be detected in cell-free DNA (cfDNA) of cyst fluid in cystic brain tumors. Cyst fluid was obtained from 22 patients undergoing surgery for a cystic brain tumor with confirmed genetic alterations in tumor DNA. Pathological diagnoses based on WHO 2021 classification and diagnostic alterations in the tumor DNA, such as IDH1 R132H and TERT promoter mutation for oligodendrogliomas, were detected by Sanger sequencing. The same alterations were analyzed by both droplet digital PCR (ddPCR) and Sanger sequencing in cyst fluid cfDNA. Additionally, multiplex ligation-dependent probe amplification (MLPA) assays were performed to assess 1p/19q status, presence of CDKN2A loss, PTEN loss and EGFR amplification, to assess whether differentiating between astrocytomas and oligodendrogliomas and grading is possible from cyst fluid cfDNA. Twenty-five genetic alterations were found in 22 tumor samples. All (100%) alterations were detected in cyst fluid cfDNA by ddPCR. Twenty of the 25 (80%) alterations were also detected by Sanger sequencing of cyst fluid cfDNA. Variant allele frequency (VAF) in cyst fluid cfDNA was comparable to that of tumor DNA (R = 0.62, Pearson's correlation). MLPA was feasible in 11 out of 17 (65%) diffuse gliomas, with close correlation of results between tumor DNA and cyst fluid cfDNA. Cell-free DNA obtained from cyst fluid in cystic brain tumors is a reliable alternative to tumor DNA when diagnosing brain tumors.

MODL-46. RECAPITULATING CELLULAR HETEROGENEITY AND TREATMENT-SPECIFIC EFFECTS THROUGH SINGLE-CELL ANALYSIS OF PATIENT-DERIVED TUMOR SLICE CULTURE MODELS

Abstract INTRODUCTION Malignant brain tumors are almost universally fatal despite standard-of-care (SOC) therapy with radiation (XRT) and temozolomide (TMZ). Low Grade Glioma (LGG) is a subclass of malignant glioma that can harbor an R132H mutation in Isocitrate Dehydrogenase 1 (IDH1). Extensive clinical trials have explored the clinical utility of IDH1 R132H mutation small molecule inhibitors such as ivosidenib and vorasidenib; however, the direct intracellular and intercellular effects of IDH1 R132H inhibition relative to SOC remain largely unknown. Objective This study examines these issues by developing a novel patient-specific tumor slice culture model to study the effects of both SOC and IDH1 R132H inhibition on IDH1 mutant glioma. Method En-bloc tumor samples from a patient with IDH mutant LGG undergoing surgery were sectioned into 400 um thick slices using a vibratome and cultured on porous microwell inserts for up to 14 days. Tumor slices were then either left untreated or treated with SOC (XRT/TMZ) or ivosidenib and harvested at various time points. Samples were hashed, and single-cell RNA sequencing was performed and analyzed. Result: Patient-derived tumor slice cultures were able to grow and were observed to contain heterogeneous cell populations, including tumor cells, astrocytes, neurons, oligodendrocytes, and microglia. When slice cultures were treated with SOC and ivosidenib treatment, separate tumor subpopulations were shown to be sensitive to either treatment. Furthermore, scRNA analysis revealed unique subpopulations that were insensitive to either treatment. We further demonstrate that slice cultures treated with Ivosidenib enriched for gene signatures related to protein translation and antigen processing. Intriguingly, we find that tumor cultures treated with ivosidenib abrogated the Notch signaling pathways between tumor-tumor and tumor-immune clusters. CONCLUSION Herein, we demonstrate that patient-derived tumor slice cultures are a viable strategy for understanding drug effects and tumor sensitivity to different therapies.

PATH-27. DROPLET DIGITAL PCR ENHANCES DETECTION OF HOTSPOT MUTATIONS IN CIRCULATING TUMOR DNA FROM CEREBROSPINAL FLUID OF PATIENTS WITH HIGH-GRADE GLIOMA

Abstract Molecular profiling of circulating tumor DNA (ctDNA) from cerebrospinal fluid (CSF) has the potential to enhance diagnosis, prognosis, and longitudinal monitoring for glioma patients through a minimally invasive approach. We previously detected somatic mutations from gliomas in CSF samples using MSK-IMPACT™, a 505-gene FDA-authorized next-generation DNA sequencing panel, and detected tumor-derived mutations in 50% of samples of patients with high-grade gliomas (HGG). To investigate whether we could enhance sensitivity of CSF ctDNA profiling and biomarker detection, we tested MSK-IMPACT™ pre-capture NGS residual DNA libraries from 43 CSF ctDNA samples by droplet digital PCR (ddPCR) for detection of key recurrent alterations in IDH1, BRAF, TERT, H3F3A, and TP53 using previously validated probes. Residual libraries contained a median of 18.0ng of DNA library (range, 0.0153-18.0ng). Of the 7 samples positive for IDH1 R132H, TERT C228T, or TERT C250T mutations in MSK-IMPACT™, we found that ddPCR accurately detected all mutations (7/7, 100%), confirming sensitivity of ddPCR in CSF ctDNA. We also tested 36 mutation-negative samples by MSK-IMPACT™ for the corresponding undetected mutations, of which 7 were tested for two mutations. Overall, ddPCR detected 41.9% (18/43) of previously undetected mutations. Specifically, we found that ddPCR rescued hotspot mutations such as BRAF V600E (2/3, 66.7%), IDH1 R132G/H (3/8, 37.5%), TERT C228T (11/26, 42.3%), and TERT C250T (2/4, 50.0%). Collectively, our results suggest that a combined-modality approach involving MSK-IMPACT™ and ddPCR enables comprehensive assessment of limited CSF ctDNA samples with high sensitivity and provides a minimally invasive methodology to molecularly profiling glioma.

IMMU-15. INTERPLAY BETWEEN ATRXAND IDH1 MUTATIONS GOVERNS INNATE IMMUNE RESPONSES IN DIFFUSE GLIOMAS

Abstract Stimulating the innate immune system has been explored as a therapeutic option for the treatment of gliomas. Inactivating mutations in alpha-thalassemia retardation X-linked (ATRX) are defining molecular alterations in IDH-mutant astrocytomas and have been implicated in dysfunctional immune signaling. However, little is known about the interplay between ATRX loss and IDH mutation on innate immunity. To explore this interaction, we used both CRISPR and the RCAS/tva system to generate murine models of ATRX-deficient glioma, in the presence and absence of the IDH1 R132H mutation. We found that ATRX-deficient glioma cells were exquisitely sensitive to dsRNA-based innate immune agonism, displaying increases in inflammatory gene expression and profound cytokine release in vitro, while mice bearing ATRX KO tumors displayed increased T-cell infiltration and improved survival. The presence of IDH1 R132H dampened baseline expression of key innate immune genes and cytokines, with genetic and pharmacological inhibition of IDH1 R132H partially rescuing this suppression. Despite the suppression observed at baseline, IDH1 R132H expression did not interfere with the ATRX KO-mediated sensitivity to dsRNA agonism. These results demonstrate that ATRX loss primes cells for recognition of and activation against dsRNA, while IDH1 R132H reversibly masks this priming. Thus, this study suggests that innate immunity is a potential therapeutic vulnerability of astrocytoma. Further studies are in progress to validate the influence of ATRX loss on immune signaling and tumor-immune coevolution within human tumors.

Factors Impacting Response to Olutasidenib in Patients with mIDH1 Acute Myeloid Leukemia

Introduction. Olutasidenib is an FDA-approved, targeted therapy for IDH1-mutated (mIDH1) AML. Among 147 patients with relapsed/refractory mIDH1 AML, 51 (35%) achieved a complete response (CR) or CR with partial hematologic recovery (CRh) after treatment with olutasidenib, with a duration of response of 25.9 months. We conducted sub-analyses to better understand which factors might be predictive of response to therapy. Methods. Patients were divided into groups based on achieving an overall response (CR, CRh, CRi, PR, MLFS) or having best response of stable disease or progression. Groups were compared to determine if there were baseline patient or disease characteristics that might predict attainment of an overall response to olutasidenib. The study was not powered to statistically evaluate subpopulations. Descriptive statistics are provided, and differences of 20% or more between groups were noted. Data cutoff date is June 2021. Results. As of data cutoff, 71 (48%) patients had achieved an overall response; the remaining 76 patients had stable disease (SD), clinical benefit (CB), disease progression (PD) or were not evaluated (due to short time on trial). Composite CR (CR, CRh, CRi) was achieved in 66/71 (93%) of overall responders, with PR and MLFS comprising only 3% of overall responders ( Table 1). With a median follow-up of 10.2 months (range 0.2-38.1), 20 responders were continuing treatment with ongoing responses at the time of data cutoff while 51 had discontinued; reasons for discontinuation were HSCT (n=14 all of whom had ongoing responses), disease progression (n=24), adverse event (n=8), physician decision (n=4) and protocol deviation (1). Responses to olutasidenib therapy were observed across a broad range of patient demographics and disease characteristics, most of which did not appear to impact the rate of response to olutasidenib ( Table 2). Bone marrow blast count at baseline correlated with response, with 63% of patients with baseline counts ≤40% achieving an overall response compared with 34% in those with baseline counts >40%. More patients with R132C (58%) and R132L/G/S (48%) mutations achieved an overall response compared to those with an R132H mutation (26%) However, a previous analysis showed that patients with the R132H mutation were more likely to have a FLT3 and/or NPM1 mutation, which are associated with a poor prognosis (de Botton S, et al, Blood 2021). Although fewer patients in the overall responder groups had FLT3 or NPM1 mutations compared with the non-responder group, 12/38 (32%) with NPM1 and 5/16 (31%) with FLT3 had an overall response. In addition, 2/5 (40%) patients with the TP53 co-mutation had an overall response to olutasidenib. While group outcomes for specific characteristics of disease may suggest a worse prognosis, individual patients treated with olutasidenib may achieve an overall response despite the impact of these negative factors. Two patients in this analysis had mIDH1-R132H mutations as well as FLT3 and NPM1 co-mutations and primary relapsed AML. One achieved a CRh and proceeded to transplant after a DOR of 15.5 months, and the other achieved a CRi lasting 1.3 months and then progressed. The baseline bone blast count was 53% in the first patient and 80% in the second. Two of the responders in this analysis had mIDH1-R132C and a TP53 co-mutation with refractory AML; one achieved a CR and proceeded to transplant after a DOR of 6 months, and the other had a PR and progressed after 3 months. The baseline bone blast count was 25% in the first patient and 65% in the second patient. Conclusions. This post-hoc analysis demonstrated that response to olutasidenib occurred across a wide variety of patient types and disease characteristics, including those generally associated with a poor prognosis. Baseline bone blast count was strongly predictive of response to treatment. Further evaluation of these observations is needed.

Diagnostic Utility of Immunohistochemical Detection of MEOX2, SOX11, INSM1 and EGFR in Gliomas.

Histological identification of dispersed glioma cells in small biopsies can be challenging, especially in tumours lacking the IDH1 R132H mutation or alterations in TP53. We postulated that immunohistochemical detection of proteins expressed preferentially in gliomas (EGFR, MEOX2, CD34) or during embryonal development (SOX11, INSM1) can be used to distinguish reactive gliosis from glioma. Tissue microarrays of 46 reactive glioses, 81 glioblastomas, 34 IDH1-mutant diffuse gliomas, and 23 gliomas of other types were analysed. Glial neoplasms were significantly more often (p < 0.001, χ2) positive for EGFR (34.1% vs. 0%), MEOX2 (49.3% vs. 2.3%), SOX11 (70.5% vs. 20.4%), and INSM1 (65.4% vs. 2.3%). In 94.3% (66/70) of the glioblastomas, the expression of at least two markers was observed, while no reactive gliosis showed coexpression of any of the proteins. Compared to IDH1-mutant tumours, glioblastomas showed significantly higher expression of EGFR, MEOX2, and CD34 and significantly lower positivity for SOX11. Non-diffuse gliomas were only rarely positive for any of the five markers tested. Our results indicate that immunohistochemical detection of EGFR, MEOX2, SOX11, and INSM1 can be useful for detection of glioblastoma cells in limited histological samples, especially when used in combination.

Clinical and molecular characteristics of patients with AML with an exceptional response to ivosidenib.

7036 Background: Ivosidenib (IVO) twas approved based on a CR/CRh rate of 31.8% in IDH1 mutant (IDH1m) R/R AML; median duration of CR/CRh (DOR) was 8.2 months (mo). The purpose of this study is to elucidate the clinical and molecular characteristics of exceptional responders to single agent IVO. Methods: We analyzed all patients (pts) with IDH1m R/R AML who received IVO 500mg QD on the phase 1 dose escalation/expansion study and had a DOR of &gt;12 mo. Results: Of 179 pts who received IVO 500 mg QD, 57 (31.8%) achieved a CR/CRh. Of these, 20 (35.1%) had a DOR &gt;12 mo. After excluding 7 pts who went to HSCT, 13 (22.8% of responders, 7.3% of cohort) had DOR &gt;12 mo (exceptional response) and 8 (14% of responders, 4.5% of cohort) had DOR &gt;24 mo. The 13 exceptional responders all achieved CR as best response, and median DOR was 42.6 mo. Median OS was not reached; estimated OS at 48 mo was 67.1%. Median EFS was 44.4 mo. Reasons for discontinuing treatment included relapse (n=4), adverse event unrelated to IVO (n=3), and patient (pt) decision (n=3). Three pts remain on treatment. All pts who relapsed had DOR between 1-2 years; none of the 8 pts with DOR &gt;2 years relapsed. Baseline characteristics are in the table. The most common co-mutations were DNMT3A, ASXL1, SRSF2, and JAK2 (3 each, 23%). Five pts (39%) had a splicing factor mutation. No pts had FLT3 or RTK pathway mutations other than JAK2. Only 1 pt with NPM1 had an exceptional response, and 1 pt had TP53 (VAF 3.6%). Six pts (46%) had an abnormal karyotype, 6 normal (46%), and 1 missing (8%). Most pts had intermediate-risk cytogenetics (10 pts, 77%), 2 poor-risk, and 1 missing. The median IDH1 VAF was 25% (range 10-50%). The median number of co-mutations was 1 (range 0-6). Having 0-1 co-mutations was associated with a longer response. Eleven pts (85%) had an IDH1 R132C mutation; 1 each (7.7%) had R132H and R132L mutations. Mutation clearance of IDH1 was noted in 8 pts (61.5%). Conclusions: A subset of pts with IDH1m R/R AML have prolonged CR on single agent IVO without HSCT (22.8% of CR/CRh responders) and no pts in CR for &gt;2 years (14% of CR/CRh responders) relapsed. A low mutational burden, lack of RTK pathway mutations and canonical AML drivers, and co-occurrence of mutations associated with clonal hematopoiesis appear to be associated with exceptional response. Clinical trial information: NCT02074839 . [Table: see text]

Ivosidenib off-label use for IDH mutant gliomas: The MD Anderson Cancer Center real life experience.

e14022 Background: Ivosidenib, a small-molecule IDH inhibitor is FDA approved for relapsed or refractory acute myeloid leukemia and cholangiocarcinoma with IDH1 mutation. Early phase clinical trials have shown promising findings for IDH mutant gliomas and results of larger studies of IDH inhibitors in gliomas are still pending. Meanwhile, neuro-oncologists continue to encounter patients with IDH mutant gliomas with limited treatment options. Here, we describe our experience with off-label use of ivosidenib in IDH mutant gliomas. Methods: This is a retrospective case series study in a single cancer care institute. Data points collected include but not limited to patient demographics, type of IDH mutation, treatment history prior to starting ivosidenib, duration of treatment, and progression-free survival. Descriptive statistics were used to summarize patient’s characteristics. The distribution of median progression-free survival (mPFS) was estimated by the Kaplan-Meier method. Results: From August 2018 to December 2022, we identified 13 patients with IDH-mutant glioma prescribed ivosidenib 500mg daily off-label. Four patients did not receive treatment: two were too sick soon after ivosidenib prescribed, and two were not able to get financial coverage. For the nine patients that were treated, median age was 37 (range 25-44). 8 were males and 1 was female. Five have IDH1 R132H mutations, 1p19q intact and four have IDH mutation and 1p19q co-deletion. The highest grade for the tumor is grade 3. Four have non-enhancing disease only. The median lines of therapy prior to starting ivosidenib was 2 (range 0-5). Three patients did not have radiation by the time they started ivosidenib, including two who received this drug as first-line treatment initiated by providers outside of MD Anderson. All patients are still alive as of January 11th, 2023. Disease control rate (all stable disease) was 78%. After a median follow-up of 17.8 (range 15-29) months, mPFS was 3.81 (95% CI: 1.25, 12.78) months. Patients with non-enhancing disease had better PFS than those with enhancing disease, but this was not statistically significant (median PFS: 8.28 vs 3.81 months, p-value = 0.42). Two patients had adverse events: one with grade 1 lethargy, and another patient had a grade 3 surgical wound infection unrelated to the drug requiring a pause in treatment. Conclusions: Ivosidenib was successfully approved by third party payers for treatment of nine patients with IDH mutant gliomas. Ivosidenib was well-tolerated with a modest PFS. Patients with non-enhancing disease may trend toward better PFS than those with enhancing disease. The updated survival data and potential correlation with clinical, molecular, and radiographic data will be presented at the conference.

Case report: Sustained complete remission with ivosidenib in a patient with relapsed, IDH1-mutated acute leukemia

Older patients with acute lymphoblastic leukemia (ALL) have a poor prognosis, with a 5-year overall survival rate of only 10%–20%. This is attributable to patient comorbidities, poor performance status, and high-risk disease biology. The prognosis for patients with relapsed/refractory (R/R) disease remains poor, particularly for patients who are not candidates for therapies targeting CD19 or CD22. Additional treatment options are needed for these patient populations. The patient presented here is a 76-year-old man diagnosed with precursor B-cell ALL with aberrant expression of myeloid markers and lacking significant CD19 or CD22 expression. A 3-year remission was achieved with one cycle of CVP (cyclophosphamide, vincristine, and prednisone) followed by 22 months of maintenance DOMP (dexamethasone, vincristine, methotrexate, and 6-mercaptopurine) prior to relapse. He was then treated with one cycle of salvage CVP, which was complicated by a stroke resulting in hemiparesis. Next-generation sequencing (NGS) was performed on the relapsed bone marrow, which revealed the presence of an R132H mutation in the isocitrate dehydrogenase 1 (IDH1) gene. He was subsequently treated with the IDH1 inhibitor ivosidenib and remained in a second remission for nearly 1 year. IDH1 mutations are present in up to 14% of acute myeloid leukemia (AML) cases but are also seen more rarely in ALL, particularly in cases involving aberrant expression of myeloid markers. Ivosidenib has demonstrated efficacy in patients with IDH1-mutated AML but has not been extensively studied in other hematologic malignancies. This case demonstrates the role of NGS in revealing treatment options in patients with otherwise limited available therapies.

Nanomechanical Signatures in Glioma Cells Depend on CD44 Distribution in IDH1 Wild-Type but Not in IDH1R132H Mutant Early-Passage Cultures

Atomic force microscopy (AFM) recently burst into biomedicine, providing morphological and functional characteristics of cancer cells and their microenvironment responsible for tumor invasion and progression, although the novelty of this assay needs to coordinate the malignant profiles of patients' specimens to diagnostically valuable criteria. Applying high-resolution semi-contact AFM mapping on an extended number of cells, we analyzed the nanomechanical properties of glioma early-passage cell cultures with a different IDH1 R132H mutation status. Each cell culture was additionally clustered on CD44+/- cells to find possible nanomechanical signatures that differentiate cell phenotypes varying in proliferative activity and the characteristic surface marker. IDH1 R132H mutant cells compared to IDH1 wild-type ones (IDH1wt) characterized by two-fold increased stiffness and 1.5-fold elasticity modulus. CD44+/IDH1wt cells were two-fold more rigid and much stiffer than CD44-/IDH1wt ones. In contrast to IDH1 wild-type cells, CD44+/IDH1 R132H and CD44-/IDH1 R132H did not exhibit nanomechanical signatures providing statistically valuable differentiation of these subpopulations. The median stiffness depends on glioma cell types and decreases according to the following manner: IDH1 R132H mt (4.7 mN/m), CD44+/IDH1wt (3.7 mN/m), CD44-/IDH1wt (2.5 mN/m). This indicates that the quantitative nanomechanical mapping would be a promising assay for the quick cell population analysis suitable for detailed diagnostics and personalized treatment of glioma forms.