bluuebunny/crossref_metadata_2025 huggingface dataset:
CTIM-25. NEOADJUVANT ANTI-PD1 IMMUNOTHERAPY FOR SURGICALLY ACCESSIBLE RECURRENT GLIOBLASTOMA: CLINICAL AND MOLECULAR OUTCOMES OF A STAGE 2 SINGLE-ARM EXPANSION COHORT
Authors: Ricardo McFaline-Figueroa J , Prins Robert , Qiao Yu , Sun Lu , Li Gang , Kim Jiyoon , Lee Eudocia , Nayak Lakshmi , Chukwueke Ugonma , Beroukhim Rameen , Batchelor Tracy , Chiocca E Antonio , Doherty Lisa , Stefanik Jennifer , Partridge Kathryn , Spearman Amanda , Lavallee Maria , Myers Alexa , Laforest-Roys Corey , Garcia Rachel Fox , Bi Wenya Linda , Arnaout Omar , Peruzzi Pierpaolo , Cosgrove G Rees , Ligon Keith , Arrillaga-Romany Isabel , Clarke Jennifer , Reardon David A , Cloughesy Timothy , Wen Patrick Y
Published: November 2022

Glioblastoma is immunologically “cold”, with little clinical response to single-agent immune-checkpoint inhibitors (ICI). Our previous randomized study of neoadjuvant and adjuvant pembrolizumab versus adjuvant pembrolizumab in recurrent glioblastoma identified a molecular signature for ICI and suggested that neoadjuvant pembrolizumab improved survival (PMID30742122). We extended these original findings with a single-arm expansion cohort of glioblastoma patients at first or second relapse undergoing surgical resection for recurrent disease. Eligibility was identical to the original study. Patients receiving > 4mg dexamethasone, or with prior immunotherapy or anti-angiogenic therapy were excluded. The primary objective was to determine the effect of neoadjuvant pembrolizumab on cell cycle/cancer proliferation genes. Secondary objectives were PFS-6 and OS. Twenty-five patients received neoadjuvant pembrolizumab followed by tumor resection and adjuvant pembrolizumab until progression or unacceptable toxicity. The median age of participants was 60 years and median KPS was 90. Ninety-six percent of tumors were IDH wild-type and 48% were MGMT promoter methylated. Neoadjuvant pembrolizumab continued to induce alterations in the tumor microenvironment (T-cell/IFN upregulation, cell cycle downregulation; molecular responders (MR)), but the proportion of MR in this trial was 36% compared with 70% in the original treatment cohort. Median OS was 6.8 months. There were no CTCAE grade 4-5 AEs attributable to pembrolizumab. Further analysis of prognostic differences between stage 1 and 2 subjects is underway, as are additional immune and genotypic correlates to further define molecular changes induced by pembrolizumab. Anti-PD1 monotherapy triggers an intra-tumoral genetic signature associated with interferon-γ response and suppression of cell cycle/cancer proliferation in recurrent glioblastoma, though does not extend OS. This surgical window-of-opportunity paradigm allows for attribution of molecular effects to single agents. Future work will evaluate the differences in patient population, tumor characteristics, and address additional immune checkpoints and/or signaling pathways that can be targeted to augment the effectiveness of anti-PD1 in glioblastoma.
CTIM-32. FIRST-IN-CHILDREN PHASE 1 TRIAL OF INDOXIMOD-BASED CHEMO-IMMUNOTHERAPY FOR PATIENTS WITH PEDIATRIC BRAIN TUMORS: ANALYSIS OF SAFETY, TOLERABILITY, AND 5-YEAR OUTCOME
Authors: Johnson Theodore , Pacholczyk Rafal , Aguilera Dolly , Al-Basheer Ahmad , Bajaj Manish , Bandopadhayay Pratiti , Berrong Zuzana , Bouffet Eric , Castellino Robert , Dorris Kathleen , Eaton Bree , Esiashvili Natia , Foreman Nicholas , Fridlyand Diana , Giller Cole , Heger Ian , Kadom Nadja , Kennedy Eugene , Manoharan Neevika , Martin William , McDonough Colleen , Parker Rebecca , Ramaswamy Vijay , Ring Eric , Rojiani Amyn , Sadek Ramses , Smith Amy , Smith Chris , Vaizer Rachel , Yeo Kee Kiat , MacDonald Tobey , Munn David
Published: November 2022

BACKGROUND

Recurrent brain tumors are the leading cause of cancer death in children. We conducted a first-in-children, two-institution, Phase 1 open-label dose-confirmation study using a 3 + 3 design, with expansion cohorts, to determine the recommended pediatric dose of the IDO pathway-inhibitor indoximod (NCT02502708). DESIGN/

METHODS

Eligible patients were 3-22 years old with either recurrent malignant brain tumor or newly-diagnosed diffuse intrinsic pontine glioma (DIPG). Palliative radiation, surgery or dexamethasone were allowed as needed for patient management. Separate dose-finding arms were performed for indoximod plus temozolomide (200 mg/m2/day orally for 5 days of each 28-day cycle) and for indoximod plus conformal radiation (in patients for whom re-irradiation was planned as standard-of-care). At progression, patients who were otherwise clinically stable were offered crossover to indoximod plus a second-line chemotherapy regimen (cyclophosphamide 2.5 mg/kg/day orally and etoposide 50 mg/m2/day orally for 21 days of each 28-day cycle).

RESULTS

Between December 2015 and January 2019, the study enrolled 81 brain tumor patients, including newly-diagnosed DIPG (n = 13) or recurrent ependymoma (n = 27), glioblastoma/high-grade glioma (n = 19), medulloblastoma (n = 13), or other CNS tumors ( n= 9). Median follow-up was 52 months (range 39-77 months). No dose-limiting toxicities were observed, and the pediatric indoximod dose was determined (19.2 mg/kg/dose, given twice daily). Indoximod was well tolerated and did not affect the ability to deliver chemotherapy or radiation as planned. Median overall survival was 13.6 months (n = 81). Median overall survival was 34.7 months for the subset of patients who continued indoximod with second-line chemotherapy after progression on indoximod plus temozolomide (n = 18).

CONCLUSIONS

Indoximod was well tolerated and could be combined with a variety of standard treatments for pediatric brain tumors. Preliminary anti-tumor activity and overall survival suggest that indoximod with standard therapy should be further evaluated in pediatric brain tumors, and potentially other pediatric solid tumors.
CTIM-33. SEXUAL DIMORPHISM OF HUMAN IMMUNE SYSTEM PREDICTS CLINICAL OUTCOMES IN GLIOBLASTOMA IMMUNOTHERAPY: A SYSTEMATIC REVIEW AND META-ANALYSIS
Authors: Shireman Jack , Ammanuel Simon , Eickhoff Jens , Dey Mahua
Published: November 2022

Biological differences based on sex have been documented throughout scientific literature. Glioblastoma, the most common primary malignant brain tumor in adults, has a male sex incidence bias, however, no clinical trial data examining differential effects of treatment between sexes currently exist. We analyzed genomic data, as well as clinical trials, to delineate the effect of sex on the immune system and glioblastoma outcome following immunotherapy. We found that, in general females possess enriched immunological signatures on gene set enrichment analysis, that also stratified patient survival when delineated by sex. Female glioblastoma patients treated with immunotherapy had a statistically significant survival advantage at the 1-year compared to males (RR = 1.15; p = 0.0241). This effect was even more pronounced in vaccine-based immunotherapy, (RR = 1.29; p = 0.0158). Our study shows a meaningful difference in the immunobiology between males and females that also influences overall response to immunotherapy in the setting of glioblastoma. Our study adds to a growing body of literature examining sex differences in male and female immunology. We demonstrate both using large scale omic data sets, as well as clinical trials, that female sexually dimorphic genes are tied to immunological responses, and that females have better outcomes during GBM immunotherapy treatments. This data is critical to better inform treatment practices and further crystalizes the need for balanced trial design and prospective reporting of sex as a variable across all GBM clinical trials.
CTNI-28. SYSTEMATIC REVIEW OF PHASE III TRIALS IN NEWLY DIAGNOSED GLIOBLASTOMA 2005-2021
Authors: Oster Christoph , Lazaridis Lazaros , Feldheim Jonas , Schmidt Teresa , Kleinschnitz Christoph , Kebir Sied , Glas Martin
Published: November 2022

BACKGROUND

Despite a plethora of studies since the EORTC/NCIC trial in 2005, glioblastoma (GBM) prognosis remains poor. We here identify and compare glioblastoma phase III trials in terms of efficacy and baseline characteristics in an attempt to summarize the experience of the past 16 years.

METHODS

A systematic literature search using PubMed and ClinicalTrials.gov was conducted to provide an overview of clinically relevant GBM phase III trials (years 2005-2021) of adult patients younger than 70 years of age. Search results were screened according to predefined inclusion criteria and either excluded or included in further analysis on study design, baseline characteristics, and survival results.

RESULTS

Eleven trials from the literature and clinical trial database fulfilled the search criteria. Among these trials, a total of three GBM phase III trials reported overall survival (OS) benefit, including the EORTC/NCIC study (NCT00006353), EF-14 (NCT00916409) and CeTeG/NOA09 (NCT01149109). All three studies demonstrate similar hazard ratios, which translate into risk reduction of about 40%. Furthermore, low toxicity profile and mostly preserved quality of life were attributed to the treatments tested. Looking at the study designs, eight out of eleven trials were open label randomized trials, including all of the positive ones, and only three negative trials employed treatment blinding and a placebo control. Canonical baseline characteristics (extent of resection, age, gender, MGMT promoter methylation status) did not significantly differ between positive and negative trials. IDH mutation status was analyzed in only two trials, each showing a small percentage of IDH-mutant tumors only.

CONCLUSION

This analysis on GBM phase III trials conducted between 2005 and 2021 revealed that the majority of trials did not show a significant improvement in overall survival. CeTeG/NOA-09 and EF-14 are the only two studies with positive overall survival outcome since the EORTC/NCIC trial in 2005.
CTNI-48. TRIAL UPDATE -RESULTS OF A PHASE I WINDOW OF OPPORTUNITY TRIAL EVALUATING A FIRST-IN-CLASS CD29 INHIBITOR, OS2966, IN RECURRENT HIGH-GRADE GLIOMA
Authors: Liu James , Carbonell Anne-Marie , Nwagwu Chibueze , Immidisetti Amanda , Vogelbaum Michael
Published: November 2022

BACKGROUND

OS2966 is a first-in-class, humanized, and deimmunized anti-CD29 (β1integrin) monoclonal antibody. CD29 is a mechanosignaling receptor prominently upregulated in glioblastoma. Preclinical studies in mice and non-human primates have demonstrated safety and encouraging efficacy. A phase I clinical trial was therefore initiated to evaluate the safety and feasibility of delivering OS2966 directly to the site of disease via convection-enhanced delivery (CED) in recurrent high-grade glioma patients.

METHODS

This study employs a 2-part design: In part 1, patients undergo stereotactic tumor biopsy followed by placement of a CED catheter(s) for delivery of OS2966 to the bulk contrast-enhancing tumor. Subsequently, in part 2, patients undergo a clinically-indicated tumor resection followed by placement of CED catheter(s) and delivery of OS2966 to the surrounding tumor-infiltrated brain. Co-convection of gadolinium enables real-time monitoring of therapeutic delivery. A concentration-based accelerated titration design is utilized for dose escalation. Given availability of pre and post-infusion samples, pharmacodynamic data will be analyzed to explore mechanism of action of OS2966.

RESULTS

Four patients have completed treatment in both study parts. No dose-limiting toxicity or adverse events related to treatment with OS2966 or CED catheter placement have been reported at the first 3 dose levels (ie, doses up to 0.6 mg/mL). For the four patients treated an average of 4.2 mL and 3.2 mL were infused in study parts 1 and 2 respectively. The Vd/Vi ratio ranged from 0.6 to 1.6 in part 1, and from 2.0 to 4.3 in Study Part 2. Analysis of tissue samples collected during the trial has demonstrated decreased VEGF expression post-treatment, with preinfusion samples showing > 50% VEGF expression and post-infusion samples showing 10% expression. Additional pharmacodynamic analysis via tissue-level biomarkers is ongoing and will be presented.

CONCLUSION

Initial data demonstrate the safety and feasibility of direct intracranial delivery of OS2966.
CTNI-56. A MULTI-INSTITUTIONAL RETROSPECTIVE SERIES OF ADULT-ONSET MEDULLOBLASTOMA
Authors: Bonm Alipi , Rutenberg Michael , Therkelsen Kate , Ruiz Amber , McGranahan Tresa , Cimino Patrick , Nagpal Seema , Taylor Lynne
Published: November 2022

Adult-onset medulloblastoma is a rare tumor for which limited data exists. Current treatment is based on data from childhood medulloblastoma. We present a retrospective cohort of 130 consecutive patients age ≥ 18 years and treated at the University of Washington (N = 61), University of Florida (N = 50), and Stanford University (N = 19), from 2000-2021. Median duration of follow-up was 57.3 months. Patients were 57.7% male (75/130), with median age at diagnosis of 29 years. 5 and 10-year overall survival were 78.9% and 67.6% and no recurrence was seen beyond 10 years. 31/130 (23.8%) patients had Chang M1 or greater disease and molecular typing was available for 41/130 patients. There was no improvement in progression-free survival (PFS) or overall survival (OS) either in patients who received proton therapy or those who received concurrent vincristine. There was a trend favoring longer OS in patients receiving radiotherapy within 6 weeks of surgery. A trend towards shorter OS in patients receiving a higher craniospinal radiation dose ( > 30Gy) likely reflected accurate clinical risk stratification. There was no improvement in OS or PFS for adjuvant chemotherapy overall, but patients receiving ≥ 5 cycles had improved PFS (HR 2.10, 95% CI = 1.19 - 3.90, p = 0.038) and a trend to improved OS (HR 2.07, 95%CI = 0.81-5.25, p = 0.125). After first progression, median OS was 20.7 months and both 5 and 10-year survival were 24.8%. We conclude that surveillance past 10 years may be unnecessary and that 1 in 4 patients achieve long-term survival after first relapse. Within the confines of a retrospective study, these data suggest equivalence between proton and photon radiotherapy, no benefit to concurrent vincristine, and that at least 5 cycles of adjuvant chemotherapy are required to delay progression.
CTNI-64. FOCUSED ULTRASOUND MEDIATED BLOOD-BRAIN BARRIER PENETRANCE TO ENABLE CELL-FREE DNA (CFDNA) AS A LIQUID BIOPSY IN RECURRENT PRIMARY BRAIN TUMORS
Authors: Miller Alexandra , Ramamurthy Bhaskar , Pike Luke , Keralapura Mallika , Hofius Jonathan , Marshall Jack , Jones Marvin , Lee Chi-Yin , Stember Joseph , Brennan Cameron , Kaley Thomas , Dittamore Ryan , Mellinghoff Ingo
Published: November 2022

The WHO recommends molecular characterization of CNS tumors. (Louis et al., 2021, 2016). However, many patients at diagnosis and recurrence, do not have tissue accessible for genomics. Blood-based liquid biopsy tests, provide a non-invasive means to obtain genomic data. Liquid biopsy tests are widely adopted to avoid side effects related to invasive biopsies in other solid tumors. However, for primary brain tumors, most patients have cfDNA concentrations below the Limit-of-Detection (LOD) of the tests. The primary contributor to low yield is the blood-brain barrier (BBB) which prevents free passage of tumor analytes into the circulatory system. BBB opening mediated by Focused Ultrasound (FUS) oscillation of microbubbles (MB) has led to an increase of tumor-derived circulating biomarkers in pre-clinical models and in human GBM (Zhu et al 2018, Meng et al 2021). Cordance Medical is developing a non-invasive, portable FUS platform that can enable clinic-based BBB opening treatments. The Cordance device utilizes three transducer types, a Type 1 transducer for non-invasive BBB opening localization obtains Doppler images of the Circle-of-Willis through the temporal lobe. The Doppler images align to the existing MRI using CoW as the fiducial. An array of Type 2 transducers for BBB opening to generate sufficient acoustic pressure to safely oscillate MBs to open the BBB. Finally, Type 3 transducers for safety monitoring receive echo signals from the MBs. Signals are analyzed for harmonic content which enables safety monitoring. The primary endpoint, we will be examining the Cordance platform's ability to increase the concentration of circulating biomarkers following a safe BBB opening. We will recruit patients with recurrent GBM. Patients will receive a baseline blood draw, a BBB opening treatment with the Cordance device, followed by a blood draw after the treatment. Liquid biopsy tests to be examined include the MSK ACCESS test and tumor-informed ddPCR MRD test.
DNAR-06. LOSS OF HISTONE H3 THREONINE 45 PHOSPHORYLATION DECREASES H3K36ME3 TO ABROGATE THE RADIATION-INDUCED DNA DAMAGE IN GLIOBLASTOMA MULTIFORME
Authors: Parwani Kiran , Spangle Jennifer , McSwain Leon , Javadi Ramona Haji Seyed , Kenney Anna , Yu David
Published: November 2022

Glioblastoma multiforme (GBM) is the most common and fatal adult brain tumour. As radioresistance is a common occurrence and contributes to poor patient prognosis, exploiting the mechanistic basis of GBM radioresistance to develop new therapeutic approaches remains an unmet clinical need. Chromatin post-translational modifications (PTMs) can augment cancer radioresistance. Several chromatin PTMs are regulated by PI3K/AKT, which is frequently hyperactivated in GBM. Previous research demonstrated that the PI3K effector AKT phosphorylates histone H3 at threonine 45 (pH3T45) in response to DNA damage. To genetically dissect the function of H3T45 phosphorylation in the DNA damage response, we engineered the PI3K pathway-activated U87MG GBM cell line to stably overexpress wildtype H3, or a phospho-null H3T45A mutant. We show that in both the presence and absence of irradiation, cells harbouring the phospho-null H3T45A mutant decreases H3K36me3 on free and nucleosome-incorporated histones, which may suggest a deficiency in DNA repair protein recruitment. By surveying irradiation-induced 53BP1 foci formation, we demonstrate that loss of pH3T45 compromises damage repair through NHEJ by delaying the onset of repair signaling. We also observe a defect in DNA damage resolution, which enhances apoptosis to reduce cell clonogenicity and proliferative capacity. Irradiation does not further reduce clonogenicity and proliferation in the phospho-null H3T45A-expressing cells. Taken together, these data suggest a critical function for PI3K-directed H3T45 phosphorylation in DNA damage repair and that loss of pH3T45 may contribute to GBM radioresistance. We anticipate that further characterization of this phosphorylation event will inform the understanding of GBM radioresistance and may suggest novel therapeutic strategies.
DDEL-01. ANIMAL STUDIES WITH A NEW CNS DRUG DELIVERY DEVICE TO EFFECTIVELY TREAT LEPTOMENINGEAL CARCINOMATOSIS PATIENTS
Authors: Kumthekar Priya , Benatti Hector , Taghian Toloo , Gormley William B , Nagpal Seema , Baker William C , Patel Rajan , Brown Emma , Glicksman Marcie , Gray-Edwards Heather
Published: November 2022

Background

Appropriate drug distribution is needed for effective treatment of brain metastases and leptomeningeal carcinomatosis. Lack of proper drug bioavailability in the CNS contributes to the poor outcome in these patients. EnClear Therapies has developed a device delivering intrathecal therapeutics utilizing the active control of CSF flow through an external pump. Herein, we look at intrathecal drug delivery of methotrexate with EnClear’s system and its impact of drug concentration in sheep and non-human primates.

METHODS

The EnClear device utilizes two implantable catheters (intracranial in the ventricular system and lumbar thecal sac) and an extracorporeal pump that controls the speed and direction of CSF flow. Software monitors the output from sensor arrays for pressure, respiration, and heart rate. Gadolinium and MRI were used to determine the CSF flow characteristics. Administration of Methotrexate via the EnClear system was compared to current two standards of delivery, intracerebroventricular or lumbar intrathecal administration. Methotrexate levels were measured with Liquid Chromatography/Mass Spectrometry in CSF, blood, and multiple CNS and peripheral tissues.

RESULTS

There was a two-fold increase in methotrexate levels in multiple regions of the brain including deeper brain structures including the striatum using the EnClear's system, compared to traditional lumbar intrathecal and intracerebroventricular delivery. Higher peak levels of methotrexate were reached in the CSF with the use of EnClear’s system, with simultaneous reduction in the peripheral nerves and systemic tissues – a potential source of toxicity.

Conclusions

In large animal studies, the EnClear device has for the first time, demonstrated increased brain parenchymal drug levels via intrathecal delivery. In addition to the drug parenchyma, drug delivery with this novel device has shown improved distribution throughout CNS and leptomeninges as compared to traditional intrathecal drug delivery and decreased peripheral distribution.
DDEL-08. NOVEL COMBINATION THERAPY USING PI3KINASE INHIBITION AND IMMUNE BASED THERAPY FOR THE TREATMENT OF GLIOBLASTOMA MULTIFORME
Authors: Fonkem Ekokobe , Rogers Karen newell , Tobin Richard , Das Mita , Bowen Sara , Tadipatri Ramya , Healey Debbie , Quarles Christopher , Clark John
Published: November 2022

Hurdles to effective treatments for glioblastoma multiforme (GBM), the most aggressive form of brain cancer, are resistance to chemotherapy, radiation, and immune checkpoint inhibitors. GBMs, like other “difficult to treat” tumors, often over-utilize the phosphatidyl inositol 3 kinase (PI3K) pathway for survival, cell growth, and cell division, conferring both chemotherapy and radiation resistance. Furthermore, the PI3K pathway has been shown to modulate expression of Major Histocompatibility Complex (MHC) molecules, key components of immune recognition. Based on these observations, we examined the potential of a novel, small molecule PI3K inhibitor GCT.Glio.1 (NPT520-337), which was designed to cross the blood brain barrier, to increase the sensitivity of GBM to immune based therapies and radiation. We hypothesized that targeting PI3K would result in growth arrest and increase cell surface expression of MHC molecules and the PD-L1 checkpoint target. Treatment of GL261 mouse and human U251 GBM cell lines with GCT.Glio.1 caused growth arrest at the G2/M checkpoint, increased the cell surface expression of PD-L1 and MHC class II, and synergized with radiation to cause growth arrest and cell death. Based on these results we designed and performed in vivo animal studies, implanting luciferase-flagged GL261 into the caudate nucleus of C57BL6 mice. We treated the animals orally with GCT.Glio.1 followed 24 hours later by anti-PD1 therapy in repeating cycles. The treatments significantly delayed progression of the tumor when compared to no treatment or either treatment alone, with several animals exhibiting complete regression as measured by MRI and bioluminescence. In conclusion, these results indicate that GCT.Glio.1 may sensitize GBM to immune checkpoint inhibitor and/or radiation therapies. Based on our encouraging pre-clinical data and early results from pre-clinical pharmacology and safety studies, we anticipate filing a pre-Investigational New Drug application (pre-IND) as the next step toward our goal of a clinical trial using this combination therapy.
DDEL-19. TREATMENT ADHERENCE OF SELUMETINIB AMONG PATIENTS DIAGNOSED WITH NEUROFIBROMATOSIS TYPE I AND PLEXIFORM NEUROFIBROMA IN THE UNITED STATES
Authors: Yang Xiaoqin , Gao Chi , Ahsan Sama , Dettling Theresa , Gu Yuqian , Banatwala Azeem , Cheng Wendy
Published: November 2022

INTRODUCTION

Selumetinib is the only FDA-approved (April 2020) treatment for pediatric patients with neurofibromatosis type 1 (NF1) and symptomatic inoperable plexiform neurofibroma (PN). Real-world information on selumetinib treatment patterns is lacking. Our study assessed treatment adherence among pediatric patients prescribed selumetinib using a large health claims database.

METHODS

Eligible patients aged 2-21 years with ≥ 1 selumetinib prescription fill in 4/2019-1/2022 (1st fill defines index date), ≥ 6 months of eligibility pre index (baseline), ≥ 3 months of eligibility post index (observation period) and no clinical trial participation were identified from the Clarivate® DRG® Real World Data Repository. Baseline patient characteristics were summarized. Adherence to selumetinib during observation period was evaluated using medication possession ratio (MPR) among patients with ≥ 2 prescription fills and proportion of days covered (PDC) over fixed time periods. Proportion of adherent patients (≥ 80% MPR or PDC) were reported.

RESULTS

73 eligible patients were identified with mean age of 13.0 (standard deviation [SD]: 4.7) years, 54.8% male, 65.8% with commercial insurance, and 31.5% with Medicaid. The most common baseline treatment was pain medication (23.3%). The mean (SD) Quan Charlson Comorbidity Index was 0.9 (1.3) and the most common NF1 PN-related comorbidities were attention-deficit hyperactivity disorder (11.0%) and headaches (6.8%). The mean (SD) MPR was 86.0% (19.8%) and 71.2% of patients were adherent (MPR ≥ 80%). At 60, 90 and 120 days, the mean PDC was 79.6%, 73.0% and 68.4%, respectively; and the proportion of adherent patients (PDC ≥ 80%) was 56.2%, 56.2% and 48.6%, respectively. Analyses assessing PDC at 150 and 180 days indicated slightly under half of patients remained adherent.

CONCLUSION

Mean adherence to selumetinib was high; about half to three-quarters of NF1 PN pediatric patients were adherent to selumetinib--a clinically important finding given the generally low medication adherence rates in pediatric patients.
DDDR-06. NEUROFIBROMATOSIS TUMOR SUPPRESSORS COOPERATIVELY DRIVE TUMOR DE-DIFFERENTIATION AND MEK INHIBITOR RESISTANCE IN PERIPHERAL NERVOUS SYSTEM TUMORS
Authors: Vasudevan Harish , Payne Emily , Delley Cyrille , Sale Matthew , Liu S John , Lastella Sydney , Lucas Calixto-Hope , Eaton Charlotte , Casey-Clyde Tim , Magill Stephen , Chen William , Reddy Alyssa , Braunstein Steve , Perry Arie , Jacques Line , Pekmezci Melike , Abate Adam , McCormick Frank , Raleigh David
Published: November 2022

Schwann cell derived tumors comprising schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors (MPNSTs) are the most common cancers of the peripheral nervous system and often arise in patients with neurofibromatosis type-1 (NF-1) or type-2 (NF-2). NF-1 is caused by loss of NF1, a negative regulator of Ras signaling, and NF-2 is caused by loss of NF2, a pleiotropic tumor suppressor with numerous functions including inhibition of PAK signaling. However, whether functional interactions exist between the NF1 and NF2 tumor suppressors remain unclear. More broadly, there are currently no effective molecular therapies for patients with Schwann cell tumors beyond the MEK inhibitor selumetinib to treat neurofibromas in patients with NF-1. Here, we integrate DNA methylation profiling, whole exome sequencing, bulk and single-cell RNA sequencing, biochemistry, and pharmacology across human samples, cell lines, and mouse xenografts to identify cellular de-differentiation as a driver of malignant transformation and selumetinib resistance. Single nuclear RNA-sequencing of human neurofibromas (n = 3) or MPNSTs (n = 3) revealed a total of 13 cell types with increased proliferating, de-differentiated tumor cell populations in MPNST samples. Single cell RNA-sequencing of MPNST mouse xenografts revealed persistence of de-differentiated cell populations in selumetinib treated samples compared to vehicle control, suggesting cellular de-differentiation underlies treatment resistance. A genome-wide CRISPRi screen for mediators of selumetinib response in NF1 deficient neurofibroma cells revealed NF2 loss drives selumetinib resistance. Consistently, NF2 suppression in NF1 deficient neurofibroma cells caused Schwann cell de-differentiation and activation of PAK, a serine threonine kinase. Translationally, a small molecule PAK inhibitor in combination with selumetinib formed an effective therapy in mouse MPNST xenografts. In sum, we elucidate a paradigm of de-differentiation driving malignant transformation and treatment resistance in Schwann cell tumors, uncovering a functional link between the NF1 and NF2 tumor suppressors that sheds light on a novel therapeutic vulnerability.
DDDR-10. INHIBITING INSULIN SIGNALING REVERSES RESISTANCE TO PI3K-MTOR INHIBITORS IN AGGRESSIVE PEDIATRIC HIGH-GRADE GLIOMAS
Authors: Gatesman Taylor , Halligan Katharine , Halbert Matthew , Stanton Ann-Catherine , Cruz Andrea , Golbourn Brian , Pollack Ian F , Mack Stephen C , Agnihotri Sameer
Published: November 2022

Primary central nervous system (CNS) tumors are now the most common cause of childhood cancer–related deaths. Pediatric high-grade gliomas (pHGGs) are among the most lethal brain tumors with a 5-year survival rate of only 20%. MYCN pHGGs represent one subgroup with an unmet need for therapeutics. MYCN belongs to the family of MYC transcription factors that regulate numerous cancer hallmarks such as proliferation, apoptosis, and metabolism. While no direct inhibitors of MYCN are in clinical trial, current strategies focus on targeting the MYCN mediated transcriptional machinery or cell cycle regulators. Lack of relevant pHGG models for pre-clinical testing contribute to limited therapeutic efficacy. To address these knowledge gaps, we developed a novel mouse model of MYCN pHGG using the FLEx-Cre switch system, whereby neural stem cells are selectively delivered with MYCN cDNA and shRNA targeting the tumor suppressor genes p53 and Pten and form tumors in vivo. We identified that this model harbors hyper-activation of the PI3K/AKT/mTOR signaling pathway. We demonstrate that dual PI3K-mTOR blood brain barrier penetrant inhibitors are effective in reducing pHGG growth and MYCN protein levels. Because treatment-resistance is a fundamental feature of pHGGs, we developed a novel drug-resistance model of MYCN pHGG as a mechanistic tool to identify relevant resistance mechanisms. Using transcriptome analysis, we identified the insulin growth factor signaling pathway as our top mechanism of resistance. We hypothesized that MYCN is a critical driver of pHGG and can be effectively targeted via dual inhibition of PI3K-mTOR and IGF/Insulin signaling pathways. We tested next generation inhibitors of IGF and PI3K/mTOR pathways and performed genetic and pharmacological assays in our MYCN pHGG and human MYCN pHGG cells. Inhibition of both pathways in our MYCN pHGG model and human MYCN cells were synergistic, leading to significant decreases in cell growth and MYCN signaling.
DDDR-11. TREATING DIPG WITH A MITOCHONDRIALLY TARGETED PLATINUM(IV)-BASED PRODRUG
Authors: Raghavan Sudhir , Sharpe Martyn , Baskin David
Published: November 2022

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal childhood cancer of the brain with 5-year survival rates of < 2%. Despite the introduction of conventional chemotherapy and radiotherapy, improvements in survival have been marginal and long-term survivorship is rare. We previously developed MP-Pt(IV), monoamine oxidase B (MAOB) sensitive, mitochondrial targeting platinum-(IV) based prodrug derived from the chemotherapeutic cisplatin. MP-Pt(IV) is well tolerated and is highly effective in a mice xenograft GBM brain tumour model. Unlike in GBM, the expression levels of MAOB in DIPG are unknown. We tested MP-Pt(IV) against DIPG to test whether DIPG exhibit a similar sensitivity to mitochondrially targeted Pt(IV)-based prodrugs.

METHODS

In-vitro cell growth inhibition studies were conducted on DIPG cells using MP-Pt(IV). Labeling studies were carried out with MitoSox, MitoTracker, and H2DCFAM. Oxygen consumption studies were performed to show mitochondrial targeting. Clonogenic survival assay and scratch assay were performed.

RESULTS

MP-Pt(IV) shows potent growth inhibition of DIPG in cell culture studies. Mechanistic studies indicate mitochondrial targeting of the prodrug. Significant increases in cellular super-oxide and hydrogen peroxide levels are observed upon MP-Pt(IV) treatment. Oxygen consumption studies confirm mitochondrial targeting of MP-Pt(IV). MP-Pt(IV) strongly inhibits clonogenic survival and cell migration in treated cells.

CONCLUSIONS

We demonstrate that MP-Pt(IV) is highly effective in DIPG in vitro and is a good candidate for testing in a DIPG xenograft animal model and further development.
DDDR-16. GBP3-STING INTERACTION IN GLIOBLASTOMA COORDINATES AUTOPHAGY, ANTI-OXIDATIVE, AND DNA REPAIR PROGRAMS IN RESPONSE TO TEMOZOLOMIDE
Authors: Li Ming , Chen Clark
Published: November 2022

INTRODUCTION

Guanylate-binding proteins (GBPs) are a group of dynamin-related large (~65 kDa) GTPases expressed in response to interferon and mediate intracellular immunity. In contrast to the Ras- or Rho family of small GTPases (~20 kDa) or the trimeric GTPases, little is known about the function of GBPs beyond their role in innate cellular immunity.

METHODS

Informatic analysis of clinically annotated glioblastoma datasets, laboratory studies of protein-protein interaction, functional characterization after depletion or exogenous expression

RESULTS

Of the seven known members of human GBPs, only GBP3 showed significant up-regulation in response to temozolomide, the standard-of-care DNA-alkylating chemotherapy for glioblastoma. Importantly, high levels of glioblastoma GBP3 expression was associated with worsened survival after temozolomide treatment. Consistent with this observation, exogenous expression of GBP3 induced temozolomide resistance in independent patient-derived glioblastoma neurosphere lines, while GBP3 silencing conferred temozolomide sensitivity, both in vitro and in vivo. This sensitivity was associated with the accumulation of cytoplasmic DNA fragments, suggesting the involvement of STING. Supporting this hypothesis, the N-terminal of GBP3 physically interacted with STING to prevent proteasome-mediated degradation of STING. Since cytoplasmic DNA bound STING activates key transcriptional programs, we profiled transcription programs requiring both GBP3 and STING expression and identified an autophagy program mediated by p62 (autophagy), a defense program against oxidative insults mediated by nuclear factor erythroid 2 like 2 (NFE2L2, NRF2), and a DNA repair program mediated by O6-methylguanine-DNA-methyltransferase (MGMT). These programs were previously shown to play central roles in cellular resistance to DNA alkylating agents.

CONCLUSION

In addition to its central role in innate immunity, GBP3 mediates cellular response to DNA damage through coordination of autophagy, anti-oxidative, and DNA repair programs.
DDDR-18. COMPREHENSIVE PROTEOMIC PROFILING OF BRAFV600E GLIOMA CELLS SHOWS UPREGULATION OF GLYCOLYSIS AND TCA CYCLE PROTEINS AFTER COMBINED MTOR AND MAP KINASE PATHWAY BLOCKADE
Authors: Alaali Lujain , Raabe Eric , Maxwell Micah , Eberhart Charles , Zhang Hui
Published: November 2022

Low-grade gliomas (LGG) are slow-growing tumors that affect neurologic function by pressing on the surrounding parts of the brain. Pediatric low-grade glioma (pLGG) is the most common childhood brain tumors. Patients with pLGG often have a significant life-long disabilities. The most common mutations in pLGG are in the mitogen-activated protein kinase (MAPK) pathway including tumor suppressor neurofibromin (NF1), and the oncogene BRAF. BRAF activates MEK1/2, which activates of ERK1/2, leading to tumorigenesis. BRAFV600E mutation results in the activation segment of the kinase “monomeric form of BRAF”, leading to constitutive activation of MAP kinase and mTOR pathways Combination treatment of TAK228 (mTOR inhibitor) and trametinib (MEK1/2 inhibitor), suppressed both mTOR and MAP kinase pathways and inhibited BRAFV600E glioma tumor growth. To further investigate and understand the molecular mechanism of TAK228 and trametinib combinatorial efficacy, we performed comprehensive proteomic analysis of BRAFV600E glioma tumors treated with TAK228 and trametinib. We found increased levels of many proteins in the glycolysis and TCA cycle. Specifically we found increases at the protein level in citrate synthase, aconitase and malate dehydrogenase in the TCA cycle. In glycolysis, we observed increased glucose transporter expression (SLC2A1), increased hexokinase 2, and increased GAPDH. Upregualtion of these proteins may represent attempts to bypass the effects of mTOR and MAP kinase blockade on the activity of these pathways. We are currently performing flux metabolic profiling using uniformly labeled glucose to assess the activity of the pathways after combined mTOR and MAP kinase blockade. Our results may increase our understanding of how glioma cells use glucose and how mTOR and MAP kinase pathway inhibition affects basic metabolic pathways in glioma cells.
DDDR-19. NEXT-GENERATION PI3K INHIBITOR FOR GLIOBLASTOMA TREATMENT
Authors: Hutchings Kasen , Pridham Kevin , Liu Min , Sheng Zhi
Published: November 2022

High-grade gliomas are especially problematic because of the limited treatment options available to patients. The phosphoinositide 3-kinase (PI3K) pathway has become a significant research target within the field of cancer drug discovery due to the pathway’s promotion of cell proliferation and inhibition of apoptosis. While many new PI3K inhibitory medications show promise in preventing cancer growth, many are toxic because they inhibit multiple PI3K catalytic subunit isoforms making these drugs ineffective treatment options. Our novel peptide drug, Selectide-18, overcomes this toxicity by specifically targeting the p110β isoform of PI3K, which was shown to be the most impactful isoform in many cancer types, including several high-grade gliomas. We designed Selectide-18 after discovering an 18-residue motif unique to p110β. Selectide-18 is a mimetic peptide modeled after this motif. Our in silico analyses show that our drug works by binding to the PI3K regulatory subunit, p85α, thus preventing the binding of catalytic subunit p110β and leaving PI3K inactive. These findings were supported by coimmunoprecipitation. Using a PI3K cell-free kinase assay, we confirmed that our drug specifically targets p110β and does not inhibit p110α, p110δ, or p110γ. The IC50 of Selectide-18 was determined to be approximately 100nM using the same PI3K cell-free kinase assay. We tested several drugs in an MTS viability assay, including Selectide-18, a scrambled 18-residue negative control peptide, and PI3K inhibitor GSK2636771 to compare levels of cancer cell viability. Selectide-18 successfully killed glioblastoma cells within lines with high p110β activity. The drug had no effect in cell lines with low p110β activity. In conclusion, Selectide-18 is explicitly tailored for p110β-high gliomas and has shown promise to treat high-grade glioma effectively. We believe this model of peptide drug can usher in a new generation of p110β specific PI3K inhibitors.
DDDR-20. TARGETING THE SELECTIVE VULNERABILITY OF IDH-MUTANT GLIOMA WITH ZOTIRACICLIB
Authors: Pang Ying , Yu Guangyang , Ranjan Alice , Wang Herui , Sergi Zach , Kim Olga , Merchant Mythili , Zhang Meili , Song Hua , Zhang Wei , Davis Dionne , Gilbert Mark , Liu Zhenggang , Wu Jing
Published: November 2022

BACKGROUND

IDH mutations are common in diffuse gliomas and confer an increased dependency on oxidative mitochondrial function. Zotiraciclib, a multi-kinase inhibitor, not only suppresses CDK9-mediated gene transcription process but also causes mitochondrial dysfunction in preclinical models. We investigated the selective activity of zotiraciclib in IDH-mutant gliomas.

METHODS

Cytotoxicity of zotiraciclib was determined in patient-derived glioma cells with/without IDH mutations. Immunoblotting and flow cytometry were used to evaluate the cell death pathways. Real-time ATP production was measured by Seahorse assay.

RESULTS

The EC50 of zotiraciclib in IDH-wt cells was twice as high as in IDH-mutant cells. In low-dose zotiraciclib (15nM)-treated IDH-mutant cells, RNA Pol II phosphorylation and expression of antiapoptotic proteins, including XIAP, MCL-1 and survivin were decreased significantly. Cleaved caspase 3/7, 8, 9 and LC3B were also detected in treated IDH-mutant cells but not in IDH-wt cells, suggesting activation of intrinsic and extrinsic cell apoptosis pathways, and subsequent autophagy of IDH-mutant cells. Low-dose treated IDH-mutant, but not IDH-wt cells, induced decreased expression of a panel of mitochondrial respiration genes, and mitochondrial respiration complexes, cellular ATP depletion and increased ROS production, suggesting a greater disruption of mitochondrial function in zotiraciclib-treated IDH-mutant cells. Zotiraciclib treatment prolonged the survival in mice bearing intracranial IDH-mutant gliomas (30 days in DMSO-treated group vs 33 days in zotiraciclib-treated group, p = 0.01), but not in mice with glioma established with the isogenic IDH-wt glioma cells (18 days in DMSO-treated vs 20 days in zotiraciclib-treated group, p = 0.10).

CONCLUSIONS

There is selective activity of zotiraciclib in IDH-mutated glioma. Low-dose exposure of zotiraciclib induces cell death and suppresses transcriptional process and mitochondrial biogenesis in IDH-mutant glioma, not in IDH-wt tumors. These findings support a clinical trial testing zotiraciclib in IDH-mutated glioma. The treatment efficacy seen even at low concentrations further supports testing it as a single agent, thereby reducing toxicity concerns.
DDDR-22. TRANSLATION OF THE PDGFRA/KIT INHIBITOR AVAPRITINIB FOR PEDIATRIC HIGH-GRADE GLIOMA
Authors: Mayr Lisa , Trissal Maria , Schwark Kallen , Labelle Jenna , Kong Seongbae , Groves Andrew , Supko Jeffrey , Hack Olivia , Marques Joana , Panditharatna Eshini , Dubois Frank , Greenwald Noah , Bandopadhayay Pratiti , Ligon Keith , Furtner-Srajer Julia , Weiler-Wichtl Liesa , Leiss Ulrike , Rosenmayr Verena , Madlener Sibylle , Stepien Natalia , Lötsch-Gojo Daniela , Dorfer Christian , Dieckmann Karin , Azizi Amedeo , Guntner Armin , Palova Hana , Slaby Ondrej , Pokorná Petra , Beroukhim Rameen , Kramm Christof , Jones David T , Štěrba Jaroslav , Mullauer Leonhard , Haberler Christine , Perez Nisha , Kim Sean , Hsieh Anthony , Dimitrijevic Sasa , Skrypek Mary , Martinez Nina , Bowers Daniel , Filbin Mariella , Gojo Johannes , Koschmann Carl
Published: November 2022

Pediatric high-grade glioma (pHGG) is an incurable disease with a median survival of less than 6 months post-progression and no effective targeted therapy. PDGFRA is commonly altered in pHGG, but targeting PDGFRA in this disease has been unsuccessful, likely due to poor central nervous system (CNS) penetrance. Avapritinib is a novel and CNS-penetrant PDGFRA/KIT inhibitor that is FDA-approved for adults with unresectable or metastatic PDGFRA exon 18-mutant gastrointestinal stromal tumor (GIST) and is being studied in CNS tumors. We performed a pre-clinical and clinical assessment to determine the potential suitability of avapritinib therapy in PDGFRA-driven glioma. A multi-institutional cohort genetic analysis revealed PDGFRA amplification and mutation in 10.2% and 6.1% of pHGG, respectively. Additionally, PDGFRA expression in the absence of genetic events was significantly increased in H3K27-altered diffuse midline glioma (DMG) compared to H3-wildtype pHGG. Avapritinib performed well in: (i) mutant PDGFRA enzyme inhibition and wildtype inhibition at high dose, (ii) minimal off-target kinase inhibition, (iii) brain penetration (peak 10 µM), and (iv) proliferation/pPDGFRA reduction in PDGFRA-amplified and mutant pHGG cell lines. Avapritinib treatment in an aggressive PDX model of pHGG resulted in significant survival benefit. We pursued treatment of eight pediatric and young adult HGG patients with avapritinib across seven institutions. Patients were a mixture of local (N = 4) and metastatic disease (N = 4); all patients were post-initial radiation, with 7/8 having progressed on prior treatment. 7/8 patients had PDGFRA amplifications or mutations, and 7/8 had H3K27M mutations. Therapy was generally well-tolerated. 4/8 patients showed radiographic response to avapritinib, with one patient demonstrating complete response of target lesion and remains on therapy. Avapritinib levels in patients’ CSF and brain tumor tissue reached micromolar levels. These results demonstrate that avapritinib is a potent, selective, and CNS-penetrant PDGFRA/KIT inhibitor that is promising for further study in pHGG with relevant alterations.
DDDR-23. IN SILICO DRUG DISCOVERY REVEALS SUBTYPE-SPECIFIC COMBINATION THERAPIES WITH CASEIN KINASE 2 INHIBITOR CX-4945 IN GLIOBLASTOMA
Authors: Ayad Nagi , Suter Robert , Jermakowicz Anna , Kaeppeli Simon
Published: November 2022

The treatment for glioblastoma (GBM) is maximal safe resection, temozolomide chemotherapy, and radiation therapy. However, with a median survival of only 15 months, new therapies are needed. GBM tumors are highly heterogeneous and three tumor subtypes, namely classical, proneural, and mesenchymal, have been identified. On a single cell level, differences are even more granular. Casein kinase 2 (CK2), which regulates invasion and important pathways including Wnt, Shh, and Notch in GBM, may be a promising target in distinct subpopulations. The CK2 inhibitor CX-4945 (silmitasertib) is in clinical trials for several cancers, including medulloblastoma. We employed single-cell RNA sequencing and analyzed bulk RNA sequencing data of PDX tumors (Brain Tumor PDX national resource at the Mayo Clinic). We found that on the tumor level, CX-4945 may preferentially target mesenchymal subtypes, which are the most invasive. On a single-cell level, CX-4945 was predicted to target cells with Astrocyte-like and Mesenchymal-like transcriptional states, which we show to become enriched upon treatment with the pan-aurora kinase inhibitor alisertib. Thus, CX-4945 in combination with a treatment targeting tumor subtypes and cell populations that evade CK2 inhibition may achieve beneficial clinical results. We identified several promising small molecules that could complement CX-4945 treatment based on the predicted reversal of the transcriptional disease gene expression signatures, which are specific for each subtype. Among these drugs are multiple anti-cancer agents that have shown favorable tolerability and brain penetrance in patients and may be effective in combination therapies. In a next step, we will evaluate the predicted combinations with CX-4945 in vitro and in vivo, with a particular focus on how they influence invasion and migration.