bluuebunny/crossref_metadata_2025 huggingface dataset:
DDEL-05. BLOOD-BRAIN BARRIER DISRUPTION AND ENHANCED RADIOSENSITIZERS EXTRAVASATION UPON FOCUSED ULTRASOUND FOR TREATMENT OF DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Hart Elvin ‘t , Derieppe Marc , Bruin Maaike , Besse Helena , Haumann Rianne , Hoving Eelco , Huitema Alwin , Ries Mario , van Vuurden Dannis
Published: December 2020

Poor prognosis of diffuse midline glioma, including diffuse intrinsic pontine glioma (DIPG), reflects the low efficacy of current treatment strategies, mainly due to (1) a largely intact blood-brain barrier (BBB) and (2) the proficiency of tumour tissues to upregulate multiple DNA repair genes, resulting into radio-resistance. In vitro studies showed therapeutic benefit by combining radiotherapy and radiosensitizers, while pre-clinical and clinical studies evidenced safe and transient opening of the BBB using microbubble mediated focused ultrasound (FUS). Previously, we demonstrated the enhanced extravasation of olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor in the mouse pons. Local drug delivery was applied using an in-house built X-ray image-guided FUS system with a 1 MHz mono-element transducer delivering a tone-burst pulse with a mechanical index of 0.4. Tissue/blood drug concentrations were analysed by LC-MS/MS, 30 minutes after intraperitoneal injection of 10 mg/kg olaparib. The FUS system allowed for precise treatment of the pons, proven by local extravasation of Evans Blue-conjugated albumin. A significant 5.1 fold median increase was observed in absolute concentrations in the pons after FUS intervention compared to the control and a 4.9 fold increase of the median tissue-blood ratio (*p<0.05). No significant differences were detected in brain regions outside the ultrasound focus and other organs, confirming the local intervention. With this, the 299 nM equivalent olaparib concentration found in the pons will facilitate PARP inhibition in future murine patient-derived xenograft tumour models, thus leading to a greater therapeutic effect when in combination with radiotherapy treatment of DIPG.
DDEL-07. A PHASE I STUDY EXAMINING THE FEASIBILITY OF INTERMITTENT CONVECTION-ENHANCED DELIVERY (CED) OF MTX110 FOR THE TREATMENT OF CHILDREN WITH NEWLY DIAGNOSED DIFFUSE MIDLINE GLIOMAS
Authors: Zacharoulis Stergios , Szalontay Luca , Higgins Dominic , Englander Zachary , Jin ZhenZhen , Garvin James , Zylber Rebecca , Stark Eileen , Maddocks Alexis , Sethi Chankrit , Canoll Peter , Dammnett Steve , Cook Craig , Feldstein Neil , Bruce Jeffrey
Published: December 2020

Convection-enhanced delivery (CED, the infusion of drugs under controlled pressure to the brain parenchyma via targeted micro-catheters, allows accurate anatomical targeting and delivery of higher (therapeutic) drug concentrations through clinically relevant volumes of brain tissue or tumor. Histone deacetylase inhibitors have been found in vitro to be the most active agents against Diffuse Midline Gliomas (DMGs) Using a novel device (implantable subcutaneous pump connected with catheter directly implanted into the pons/thalamus) we are performing a Phase I safety study of repeated infusions of MTX110 (MTX110, Midatech) in a dose escalation manner. Eligible patients include 3–18 years of age with newly diagnosed DMGs following radiation therapy without evidence of hemorrhage or cysts with intact organ function. Patients undergo a tumor biopsy and a single catheter (Spetzler lumbar shunt catheter, Integra, Plainsboro, NJ) is placed stereotactically into the geometric center of the tumor. A second catheter is inserted subcutaneously with the distal tubing connected to the infusion pump, (SynchroMed II (Medtronic)), also inserted subcutaneously. The infusion pump is prefilled with MTX110 and administered using wireless N’Vison Clinical programmer into two 24-hour infusions, consisting of 20 hours of drug infusions at 0.2mL/hr. The pulse is completed 7 days later. This is a dose escalation study with the infusate consisting of gadolinium and MTX110 (30, 60, or 90 microM). The study describing the first use in children of this device for direct-to-tumor drug delivery is open to recruitment (January 2020) and the preliminary data will be available for presentation by June 2020.
DDEL-08. CONVECTION-ENHANCED DELIVERY OF NIMUSTINE HYDROCHLORIDE (ACNU) AGAINST PEDIATRIC DIFFUSE INTRINSIC PONTINE GLIOMAS
Authors: Saito Ryuta , Kanamori Masayuki , Tominaga Teiji
Published: December 2020

Diffuse intrinsic pontine gliomas (DIPGs) are amongst the most challenging tumors to treat. Surgery is not an option, the effects of radiation therapy are temporary, and no chemotherapeutic agent has demonstrated significant efficacy. Intracerebral infusion technique of convection-enhanced delivery (CED) for patients with brain tumors could offer a novel approach for effective chemotherapy. We have been working to develop an effective chemotherapy using nimustine hydrochloride (ACNU) with this drug delivery method. After several studies targeting supratentorial recurrent malignant gliomas and recurrent gliomas affecting brainstem, we conducted phase 1 study to evaluate the safety of combination of convection-enhanced delivery of nimustine hydrochloride and systemic temozolomide against recurrent gliomas affecting brainstem. In this study, we demonstrated the safety and feasibility of CED of ACNU as well as real time monitoring of drug distribution by mixing ACNU with contrast agent; Gd-DOTA. We also defined the maximum tolerable concentration in this study and proceeded to phase 2 trial against recurrent gliomas affecting brain stem. However, these trials revealed the difficulty of treating pediatric DIPG at the time of recurrence. Therefore, we decided to treat pediatric DIPG cases at their initial diagnosis in the subsequent study. Aiming at obtaining Shonin approval both for intraparenchymal infusion catheter and drug to infuse into brain parenchyma, we are now conducting Phase II physician-led trial against initially diagnosed pediatric DIPG cases.
DDEL-10. A NANOPARTICLE PLATFORM FOR INTRATHECAL DELIVERY OF THE HISTONE DEACETYLASE INHIBITOR (HDACi) PANOBINOSTAT IN METASTATIC OR RECURRENT MEDULLOBLASTOMA
Authors: Chaudhuri Sauradip , Mohammad Afroz S , Zhang Wenqui , Baker Cassandra , Broughton Colton W , Fowler Martha J , Stabenfeldt Sarah E , Wechsler-Reya Robert J , Sandberg David I , Elmquist William F , Sirianni Rachael W
Published: December 2020

INTRODUCTION

Panobinostat is a histone deacetylase inhibitor (HDACi) that is a clinical candidate for treatment of pediatric medulloblastoma and diffuse intrinsic pontine glioma. Panobinostat is poorly water-soluble and experiences a number of barriers to effective delivery. Here, we developed a novel drug delivery system consisting of β-cyclodextrin-poly(β-amino ester). These cyclodextrin-networks (CDNs) self-assemble into nanoparticles encapsulating a high quantity of HDACi for slow release. We sought to test the hypothesis that panobinostat-loaded CDNs would demonstrate a differentiated pharmacokinetic profile compared to free panobinostat in mice after direct administration to cerebrospinal fluid.

METHODS

CDNs were synthesized via Michael addition and engineered to encapsulate a library of HDACi drugs. Nanoparticles were characterized for size, surface charge, loading, controlled release, and stability. CDNs or fluorescent surrogate nanoparticles were administered to the cisterna magna of mice. Tissues were collected for LC-MS/MS (pharmacokinetics [PK]: 1, 4, 8, 24, and 48 hrs) or microscopy (localization: 2, 6, 24, and 48 hrs, 1 and 3 wks).

RESULTS

Intravital and confocal microscopy demonstrate that nanoparticles distribute rapidly in subarachnoid space and can localize with metastases, persisting for > 3 weeks. Nanoparticle panobinostat is released over weeks and is better tolerated than free drug. CDN-panobinostat delivery tended to be higher in the cerebellum and lower in the spinal cord at both early and late time points compared to freely administered drug.

CONCLUSIONS

We present a nanoparticle platform for HDACi delivery with a differentiated PK profile in the CSF compared to free drug. Additional PK and therapeutic studies are ongoing.
DDEL-14. SAFETY OF INTERVENTRICULAR METHOTREXATE ADMINISTRATION FOLLOWING RADIATION IN PEDIATRIC PATIENTS WITH MALIGNANT BRAIN TUMORS
Authors: Rosales Kristofer , Maher Ossama , Fader Maggie , Gallegos Natalie , Niazi Toba , Ragheb John , Khatib Ziad
Published: December 2020

BACKGROUND

Methotrexate has been used for intrathecal administration in leukemia as well as embryonal CNS tumors in children. Concerns about neurologic side effects including leukoencephalopathy, demyelination, and seizures have limited the use of methotrexate following exposure to focal radiation.

OBJECTIVE

To evaluate and determine safety of Intraventricular administration of Methotrexate in pediatric patients with recurrent malignant brain tumors along with systemic Topotecan and Cyclophosphamide after exposure to prior radiation therapy. DESIGN/METHOD: Patients with recurrent cerebellar embryonal tumors after standard treatment that included radiation were enrolled on this IRB approved phase 2 study. An Ommaya reservoir was inserted in the lateral ventricle and used to administer 4 daily doses of methotrexate (2 mg/dose) along with (Topotecan [0.75mg/m2/day] and Cyclophosphamide [250 mg/m2/day]). A neurological evaluation was performed at baseline and daily during the intraventricular administration of the Methotrexate, this evaluation was repeated prior to each subsequent cycle and at completion of the protocol.

RESULTS

Three patients (age range 3–20) received 2–3 cycles of intra-Ommaya Methotrexate and Topotecan/Cyclophosphamide. No MRI demyelination or white matter changes were seen after completion of the intraventricular Methotrexate therapy. None of the patients enrolled on this trial had adverse effects related to the therapy regimen received. Clinical neurological status was unchanged during the entire course of the treatment and upon completion of the scheduled therapy.

CONCLUSION

Intraventricular administration of daily low dose Methotrexate is well tolerated in children with recurrent embryonal CNS tumors who had prior exposure to radiation.
DIPG-02. USEFULNESS OF BEVACIZUMAB IN MAINTAINING QUALITY OF LIFE AT THE TIME OF DIFFUSE INTRINSIC PONTINE GLIOMA RELAPSE
Authors: Gomi Akira , Uchiyama Taku , Oguma Hirofumi , Yamaguchi Takashi , Kawai Kensuke
Published: December 2020

INTRODUCTION

Even in the age of molecular diagnosis, diffuse intrinsic pontine glioma (DIPG) is still a dismal disease. The usefulness of bevacizumab for DIPG relapse is reported.

SUBJECTS AND METHODS

The treatment and outcomes of 10 patients with DIPG who were treated at our institute since 2001 were retrospectively reviewed. All patients were diagnosed with DIPG by MRI imaging and underwent radiation therapy first. Three cases did not receive chemotherapy at the time of relapse (Untreated Group). In 7 cases, chemotherapy was performed at the time of relapse with ACNU/vincristine or interferon beta (Other Treatment Group), and 2 cases with bevacizumab (Bv Group). The change in the Karnofsky Performance Status Scale (KPS) from the time of relapse was compared.

RESULTS

The average overall survival (OS) for all 10 cases was 10.0 months. No prolongation of OS by bevacizumab was observed. However, it was only in the Bv Group that the KPS increased from the time of relapse. Comparison of the KPS at the time of relapse and the KPS after 4 months showed that the Bv Group remained unchanged or increased, while the Untreated Group and the Other Treatment Group decreased. In the Other Treatment Group, hospitalization was required for treatment, and side effects of bone marrow suppression were observed. However, in the Bv Group, outpatient treatment was possible, there were no side effects, and all could be observed at home.

CONCLUSION

From the above results, bevacizumab appears useful for palliative treatment for maintaining quality of life after DIPG relapse.
DIPG-03. THERAPEUTIC TARGETING OF TRANSCRIPTIONAL ELONGATION IN DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Katagi Hiroaki , Takata Nozomu , Aoi Yuki , Zhang Yongzhan , Rendleman Emily J , Blyth Gavin T , Eckerdt Frank D , Tomita Yusuke , Sasaki Takahiro , Saratsis Amanda M , Kondo Akihide , Goldman Stewart , Becher Oren J , Smith Edwin , Zou Lihua , Shilatifard Ali , Hashizume Rintaro
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is highly aggressive brain stem tumor and needed to develop novel therapeutic agents for the treatment. The super elongation complex (SEC) is essential for transcription elongation through release of RNA polymerase II (Pol II). We found that AFF4, a scaffold protein of the SEC, is required for the growth of H3K27M-mutant DIPG cells. In addition, the small molecule SEC inhibitor, KL-1, increased promoter-proximal pausing of Pol II, and reduced transcription elongation, resulting in down-regulate cell cycle, transcription and DNA repair genes. KL-1 treatment decreased cell growth and increased apoptosis in H3K27M-mutant DIPG cells, and prolonged animal survival in our human H3K27M-mutant DIPG xenograft model. Our results demonstrate that the SEC disruption by KL-1 is a novel therapeutic strategy for H3K27M-mutant DIPG.
DIPG-04. THERAPEUTIC STRATEGY FOR DIFFUSE MIDLINE GLIOMAS. A SINGLE CENTER EXPERIENCE
Authors: Yamanaka Takumi , Takahashi Yoshinobu , Morisako Tamaki , Nagai Toshiki , Tanigawa Seisuke , Umebayashi Daisuke , Takeuchi Hayato , Tatsuzawa Kazunori , Miyachi Mitsuru , Yagyu Shigeki , Iehara Tomoko , Hosoi Hajime , Hashimoto Naoya
Published: December 2020

INTRODUCTION

Diffuse midline gliomas have unfavorable prognoses due to the difficulty of surgery and chemo-radiation resistances. The purpose of this study is to overview our surgical experiences and prognoses of this challenging neoplasm.

MATERIALS AND METHODS

Five patients of diffuse midline gliomas who were treated between 2016 and 2019 were enrolled. Tumor locations, surgical procedures, molecular diagnoses, and prognoses were retrospectively reviewed.

RESULTS

There were 3 male and 2 female patients, and the median age was 15 years ranged from 7 to 21 years. Tumors were located at the basal ganglia in 1 patient, thalamus in 1, brain stem in 2, and cervical spine in 1. Mutations of H3 K27M genes were detected in 4 surgically treated patients, except for 1 patient, who were radiologically diagnosed as diffuse intrinsic pontine glioma (DIPG). Focal irradiation of ranged 35 to 54Gy were administered in all cases along with temozolomide in 2 cases and bevacizumab in 2 cases. The median survival time was 13 months ranged from 4 to 18 months.

DISCUSSION

Supratentorial tumors were maximumly resected, whereas just biopsies were performed in cases of exophytic brain stem and spinal tumors. Diagnosis of DIPG was made without using surgical specimens. Therapeutic strategies should be discussed with a concern to the patients’ qualities of life for this tumor entity with dismal prognosis.
DIPG-05. HISTONE H3.3 K27M IMPAIRS SER31 PHOSPHORYLATION, RESULTING IN CHROMOSOMAL INSTABILITY, LOSS OF CELL CYCLE CHECKPOINT CONTROL, AND TUMOR FORMATION
Authors: Day Charles , Langfald Alyssa , Grigore Florina , Fadness Sela , Sepaniac Leslie , Stumpff Jason , Vaughan Kevin , Robinson James , Hinchcliffe Edward
Published: December 2020

Diffuse midline gliomas with the H3.3 K27M mutation are lethal brain tumors in children. H3 K27M causes global loss of Lys27 triple methylation (Lys27me3), inducing epigenetic reprograming. Here we show that H3.3 K27M also causes decreased H3.3 Ser31 phosphorylation on mitotic chromosomes. We show that H3.3 K27M DIPG cells have reduced pericentromeric phospho-Ser31 and increased rates of chromosome missegregation compared to normal, diploid human cells. CRISPR-editing K27M to M27K restored phospho-Ser31 to WT levels and dramatically decreased the rate of chromosome missegregation. We confirm that Chk1 is the H3.3 Ser31 kinase: K27M mutant H3.3 protein exhibits ~60% reduced Chk1 phosphorylation of Ser31 in vitro. Chk1 knockdown completely abolishes phospho-Ser31 in cells and these have increased rates of chromosome missegregation. In normal, diploid cells, expression of K27M or an S31A non-phosphorylatable mutant increased chromosome missegregation; this is suppressed by expressing a phosphomimetic double mutant (K27M/S31E) that restores phospho-Ser31. WT cells arrest following chromosome missegregation. However, cells expressing H3.3 K27M or S31A fail to arrest - despite having WT p53. Finally, we expressed H3F3AS31A and PDGFb in an RCAS/TVA mouse model of DIPG and ~80% developed diffuse high-grade brain tumors and show significantly decreased survival. Our results suggest that loss of phospho-Ser31 alone is oncogenic because H3.3 S31A-expressing cells are WT for K27me3. Our results demonstrate that H3.3 K27M inhibits Ser31 phosphorylation both in vitro and in vivo, leading to both chromosome missegregation and loss of subsequent G1 arrest – thus creating diffuse midline gliomas with both dynamic, complex karyotypes and epigenetic reprogramming.
DIPG-08. ELECTRONIC SEQUENCING PROVIDES OPTIMIZED QUANTIFICATION OF SERIAL, MULTI-GENE MOLECULAR RESPONSE IN THE CSF OF CHILDREN WITH HIGH-GRADE GLIOMA
Authors: Bruzek Amy , Muruganand Ashwath , Ravi Karthik , Wadden Jack , Babila Clarissa , Tunkle Leo , Wierzbicki Kyle , Stallard Stefanie , Cantor Evan , Qin Tingting , Wolfe Ian , Mody Rajen , Muraszko Karin , Franson Andrea , Robertson Patrica , Maher Cormac , Garton Hugh , Koschmann Carl
Published: December 2020

BACKGROUND

For pediatric high-grade glioma (pHGG), non-invasive methods for diagnosis and surveillance are needed. Tumors release DNA (tDNA) into cerebrospinal fluid (CSF), allowing for detection of tumor-associated mutations by CSF sampling. We hypothesized that direct, electronic analysis of tDNA with a novel, hand-held platform (Oxford Nanopore MinION) could quantify patient-specific CSF tDNA variant allele fraction (VAF) with improved speed and limit of detection compared to established methods.

METHODS

We integrated required multi-timepoint (0, 2, and 6 months) correlate lumbar punctures (LP) in two ongoing pHGG clinical trials. Using Nanopore technology, we performed amplicon-based PCR on CSF tDNA for recurrent mutations from patient samples (n=19) and normal controls. VAF were determined via MinKNOW, Guppy, MiniMap2, and Integrated Genome Browser.

RESULTS

Nanopore CSF tDNA demonstrated improved sensitivity (91%) when compare to NGS sequencing (50%). Nanopore analysis of serially diluted CSF sample demonstrated significantly lower limit of detection (attomolar) than typical NGS sample requirement (nanomolar). H3K27M mutation was reliably detected with 1,000x depth sequencing, which was achieved in less than 15 minutes of sequencing after amplification. Multiplexed Nanopore analysis of H3F3A and HIST1H3B was employed when H3 status was unknown. Serial CSF tDNA analysis confirmed multi-gene (H3F3A K27M, PIK3CA, and TP53) molecular remission in a 17-year-old with thalamic diffuse midline glioma that correlated with sustained clinical response to ONC201 (14 months and ongoing).

CONCLUSIONS

Use of a hand-held, electronic DNA analysis platform allows quantification of multi-gene molecular response with improved speed and limit of detection in the CSF of children with high-grade glioma.
DIPG-11. A PHASE I DOSE ESCALATION STUDY OF BXQ-350 IN CHILDREN AND YOUNG ADULTS WITH RELAPSED SOLID TUMORS
Authors: Setty Bhuvana , Cripe Timothy , Schottmiller Mariko DeWire- , Curry Richard , AdelBaki Mohamed
Published: December 2020

BXQ-350 is a novel agent composed of the multifunctional, lysosomal activator protein Saposin C (SapC) and dioleoyl- phosphatidylserine (DOPS). BXQ-350 demonstrated antitumor effects in vitro and in vivo. Many tumors, including diffuse intrinsic pontine glioma (DIPG), and cells of tumor vasculature have aberrantly-exposed PS-rich domains on the cell surface. BXQ-350 is an anti-tumor agent in development from Bexion Pharmaceuticals, Inc. that selectively targets tumor cell PS, particularly those translocated to the outer leaflet of the plasma membrane in tumor cells. BXQ-350 activates and participates in various cellular processes, including apoptosis and necrosis, and may also exhibit novel mechanisms leading to cell death that require further investigation. An adult Phase I trial with BXQ-350 completed enrollment in 2019 having dosed 86 recurrent solid tumor patients, including glioblastoma, with only one serious infusion-related reaction. The highest planned dose of 2.4 mg/kg was achieved and seven patients remain on study with multiple cases demonstrating an objective response. A Phase I pediatric dose escalation trial in recurrent solid tumors, including central nervous system (CNS) tumors, also completed enrollment in 2019. The highest planned dose of 3.2 mg/kg was achieved and there have been no BXQ-350 related serious adverse events. Eight patients (7 CNS and 1 non-CNS) completed at least one cycle with one DIPG patient completing cycle five. A pediatric Phase I trial in newly diagnosed DIPG and diffuse midline glioma (DMG) is planned for 2nd quarter 2020.
DIPG-12. TARGETING EPIGENETIC MODIFIERS TO INDUCE IMMUNE SIGNALING IN DIPG
Authors: Tetens Ashley , Martin Allison , Arnold Antje , Novak Orlandi , Eberhart Charles , Feinberg Andrew , Raabe Eric , Koldobskiy Michael
Published: December 2020

DIPG is a universally fatal pediatric brainstem tumor with no effective therapy. Recent work has shown that over 80% of DIPG cases harbor the H3K27M mutation leading to global loss of the repressive H3K27 trimethylation mark, global DNA hypomethylation, and a distinct gene expression signature. We sought to exploit epigenetic vulnerabilities in DIPG through the use of DNA methyltransferase inhibitors and histone deacetylase (HDAC) inhibitors. We find that treatment with low-dose 5-aza-2’-deoxycytidine (decitabine), alone and in combination with HDAC inhibitors, elicits profound genome-wide demethylation in DIPG patient-derived neurosphere cell lines, impairs proliferation, and induces apoptosis. We show that this treatment induces immune activation, with induction of type I interferon signaling, increased expression of major histocompatibility complexes, and expression of tumor antigens. These results suggest that the immunogenicity of DIPG may be modulated by epigenetic therapies, suggesting the possibility of novel combination approaches to immunotherapy of DIPG in the future.
DIPG-13. TARGETING HYPOXIA AND MITOCHONDRIA WITH REPURPOSED METABOLIC DRUGS AS AN APPROACH TO RADIOSENSITIZATION FOR DIFFUSE INTRINSIC PONTINE GLIOMAS (DIPG)
Authors: Shen Han , Chang Cecilia , Gee Harriet , McKelvey Kelly , O’Neill Geraldine , Prior Victoria , Blackburn Anneke , Hau Eric
Published: December 2020

DIPG is the leading cause of brain tumor-related death in children. Currently, radiation is the only treatment that offers transient benefit. Compared to normal brain tissue, DIPGs are hypoperfused with tumors being exposed to hypoxia, a potent barrier to effective radiotherapy. Biguanides are hypoglycemic agents that can reduce the oxygen consumption rate (OCR) in mitochondria, thereby reducing hypoxia. Our previous study has shown that metformin significantly improves the radiosensitivity of DIPG and extends survival in a patient-derived xenograft (PDX) model. In the present study, phenformin, a second biguanide derivative, demonstrated even greater anti-DIPG activity and radiosensitising effect in vitro. As a single agent, phenformin dose-dependently inhibited OCR and increased extracellular acidification rate (ECAR). Low-dose phenformin reduced mitoATP/glycoATP ratio, whereas high doses significantly suppressed net ATP production. To attenuate the phenformin-induced ECAR, phenformin was combined with dichloroacetate (DCA), a clinically relevant pyruvate dehydrogenase kinase inhibitor that can suppress the elevated glycolytic rate of cancers. This combination significantly blocked the phenformin-induced ECAR and killed DIPG cells synergistically by inducing apoptosis, DNA damage and metabolic catastrophe. Moreover, protein expression of HIF-1α and c-Myc, two master regulators that collaboratively enhance the metabolic capacity of tumor cells through increased glycolysis thereby contributing to radioresistance, were also suppressed by phenformin-DCA treatment in vitro. This combination therapy upregulated genes inhibiting cell proliferation while downregulating genes for DNA repair. The triple combination of phenformin, DCA and irradiation demonstrated the most potent efficacy in vitro and is currently being tested in our PDX cohort in vivo.
DIPG-31. MOLECULAR MECHANISMS AND FUNCTIONAL IMPACT OF ABERRANT SPLICING IN DIFFUSE MIDLINE GLIOMAS
Authors: Naqvi Ammar , Gaonkar Krutika , Zhu Yuankun , Brown Miguel , Zhang Bo , Ennis Brian , Storm Phillip , Resnick Adam , Rokita Jo Lynne
Published: December 2020

Fewer than 1% of children diagnosed with diffuse-midline glioma (DMG) survive for more than 5 years, because no effective therapies exist for these patients. Here, we sought to identify and characterize mechanisms of aberrant splicing (AS) in primary DMG tumors. We observed transcriptome-wide AS (9,805 differential splicing variations in 4,734 genes), and identified a DMG-specific splicing signature, that included known cancer genes. We hypothesize that AS of cancer genes play a role in DMG tumor formation. Assessing whether splicing factor dysregulation impacted known cancer transcripts, we discovered several splicing factors, including SRRM4, SRRM3 and RBFOX3 to be down-regulated in DMG. Additionally, we found an enrichment of binding motifs for these proteins within flanking regions of these mis-spliced exons. We also observed recurrent significant exon inclusion in tumor suppressor SMARCA4, an integral member of the SWI/SNF family of proteins involved in chromatin remodeling. Further, we identified AS in 16 of the 27 members of the SWI/SNF complex, including increased skipping of exon 7 in DPF2, representing a complete mRNA transcript switch in DMG. Since SRRM4, SRRM3 and RBFOX3 are known regulators for neural-specific microexons, we focused on microexon splicing changes, hypothesizing that these regulators may be driving microexon mis-splicing in these tumors. We identified 245 known microexons lost or gained in DMG. Moreover, a quarter of which were observed in known cancer genes, with the most frequent splice event causing gain of a clathrin-binding site in the tumor suppressor BIN1 with a concurrent loss of an out-of-frame microexon in the oncogene BAK1, presumably activating it. Altogether, our results suggest that aberrant splicing may be an alternative mechanism driving DMG tumorigenesis and we are currently molecularly validating a subset of these events with the overall goal of identifying novel therapeutic targets for DMG tumors.
DIPG-35. BIOLOGICAL MEDICINE FOR DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG) ERADICATION: RESULTS OF THE THREE ARM BIOMARKER-DRIVEN RANDOMIZED BIOMEDE 1.0 TRIAL
Authors: Grill Jacques , Teuff Gwenael Le , Nysom Karsten , Blomgren Klas , Hargrave Darren , MacCowage Geoff , Bautista Francisco , Van Vuurden Dannis , Dangouloff-Ros Volodia , Puget Stephanie , Varlet Pascale , Debily Marie-Anne , Vassal Gilles , Deley Marie-Cecile Le
Published: December 2020

Despite 50 years of clinical trials, no improvement of survival has been observed in DIPG and most children die within 2 years of diagnosis. Only radiotherapy transiently controls disease progression. The study was conceived as a randomized multi-arm multi-stage program. It started with an open-label phase-II trial comparing three drugs (everolimus, dasatinib, erlotinib) combined with irradiation, allocated according to the presence of their specific targets (PTEN-loss, EGFR-overexpression) defined with a stereotactic biopsy after central confirmation of the diagnosis (presence of histone H3K27M mutation or loss of K27 trimethylation). Targeted therapies were started concomitantly with radiotherapy and were continued until disease progression. No biopsy-related death was reported and diagnostic yield was excellent, with only 5 non-informative biopsies. Biopsy excluded the diagnosisof DIPG in 8% of the cases. At the 3rd interim analysis, based on 193 randomized patients, the IDMC concluded that the study was unlikely to show a difference of OS between the 3 drugs even if 250 patients would be randomized. The median OS from the time of diagnosis was 11.9, 10.5 and 10 months for everolimus, dasatinib and erlotinib. Treatment was discontinued due to toxicity in 2%, 13%, and 15%, respectively. BIOMEDE shows the feasibility of biologically-driven treatment in DIPG on a large international scale. Based on the better toxicity profile and the slightly better efficacy, although not statistically significant, the steering committee proposed that everolimus should be used as the control arm for the next BIOMEDE 2.0 trial.
DIPG-44. A GAIN OF FUNCTION Ezh2 MUTATION DELAYS DIFFUSE INTRINSIC PONTINE GLIOMA PROGRESSION
Authors: Dhar Swati , Gadd Samantha , Brat Daniel , Becher Oren
Published: December 2020

BACKGROUND

Diffuse Intrinsic Pontine Glioma (DIPG) remains an incurable pediatric brain cancer. The oncohistone H3K27M implicated in 80% of the cases, is also predicted to target Enhancer of Zeste Homolog 2 (Ezh2), the catalytic component of the Polycomb Repressor Complex 2 (PRC2). There are no reported mutations of Ezh2 and its function in DIPG is not fully determined. This work aims to address the role of Ezh2 in DIPG.

METHODS

Brainstem tumors were established by intracranial injections of Nestin;Tv-a; Ezh2Y641F/+ (NTv-a; Ezh2Y641F/+) neonatal pups using Replication Competent Avian Sarcoma leucosis virus long terminal repeat with splice acceptor (RCAS) viruses, expressing PDGF-B, p53 shRNA, and RCAS-CRE/Y. Immunohistochemical staining for Ki-67 and H3K27me3 were performed on the Discovery ULTRA (Ventana).

RESULTS

Ezh2 overexpression (Ezh2Y641F/+, RCAS CRE) conferred a survival advantage of approximately 10 days (n=20 mice/group, p<0.001). H3K27me3 levels were significantly upregulated in RCAS CRE group (50% vs 20% in RCAS Y, n=4 tumors/group, p<0.03), with a concomitant lower Ki-67 staining (30% vs. 55% in RCAS Y, n=3 tumors/group, p<0.05). Interestingly, pathological review categorized more RCAS-CRE tumors as ‘atypical’. RNA-sequencing of virus-infected neural precursor cells revealed a suppression of inflammatory/interferon gene signature in the Ezh2 overexpression group. CONCLUSIONS AND FUTURE DIRECTIONS: Enhanced Ezh2 activity appears to delay DIPG pathogenesis. Ongoing work aims to highlight the contribution of differentially expressed gene signatures that contribute to this phenotype.
DIPG-53. CHARACTERIZING THE ROLE OF PPM1D MUTATIONS IN THE PATHOGENESIS OF DIFFUSE INTRINSIC PONTINE GLIOMAS (DIPGS)
Authors: Khadka Prasidda , Reitman Zachary , Lu Sophie , Buchan Graham , Hartley Rachel , Bear Heather , Georgis Yoahnna , Jarmale Spandana , Schoolcraft Kathleen , Miller Peter , Gonzalez Elizabeth , Gionet Gabrielle , Qian Kenin , Melanson Randy , Keshishian Hasmik , Carvalho Diana , Condurat Alexandra , Goodale Amy , Abid Tanaz , Piccioni Federica , Chi Susan , Carr Steven , Haas-Kogan Daphne , Ebert Benjamin , Kieran Mark , Jones Chris , Ligon Keith , Beroukhim Rameen , Phoenix Timothy , Bandopadhayay Pratiti
Published: December 2020

INTRODUCTION

We have previously found that up to 15% of all DIPGs harbor mutations in PPM1D, resulting in the expression of an activated and truncated PPM1D (PPM1Dtr). Here we evaluate the mechanisms through which PPM1Dtr enhances glioma formation and identify its associated therapeutic vulnerabilities.

METHODS

We have developed multiple in vitro and in vivo models of PPM1D-mutant DIPGs and applied quantitative proteomic and functional genomic approaches to identify pathways altered by PPM1Dtr and associated dependencies.

RESULTS

PPM1D mutations are clonal events that are anti-correlated to TP53 mutations. We find ectopic expression of PPM1Dtr to be sufficient to enhance glioma formation and to be necessary in PPM1D-mutant DIPG cells. In addition, endogenous truncation of PPM1D is sufficient to enhance glioma formation in the presence of mutant H3F3A and PDGFRA. PPM1Dtr overexpression attenuates g-H2AX formation and suppresses apoptosis and cell-cycle arrest in response to radiation treatment. Deep scale phosphoproteomics analyses reveal DNA-damage and cell cycle pathways to be most significantly associated with PPM1Dtr. Furthermore, preliminary analysis of genome-wide loss-of-function CRISPR/Cas9 screens in isogenic GFP and PPM1Dtr overexpressing mouse neural stem cells reveal differential dependency on DNA-damage response genes in the PPM1Dtr overexpressing cells. Consistent with PPM1D’s role in stabilizing MDM2, PPM1D-mutant DIPG models are sensitive to a panel of MDM2 inhibitors (Nutlin-3a, RG7388, and AMG232).

CONCLUSION

Our study shows that PPM1Dtr is both an oncogene and a dependency in PPM1D- mutant DIPG, and there are novel therapeutic vulnerabilities associated with PPM1D that may be exploited.
DIPG-55. PATTERNS OF CEREBROSPINAL FLUID DIVERSION AND SURVIVAL IN CHILDREN WITH DIFFUSE INTRINSIC PONTINE GLIOMA: A REPORT FROM THE INTERNATIONAL DIPG REGISTRY
Authors: Cooney Tabitha , DeWire-Schottmiller Mariko , Lane Adam , Saab Raya , Bandopadhayay Pratiti , Dorris Kathleen , Packer Roger , Kilburn Lindsey , Minturn Jane , Dodgshun Andrew , Parkin Sara , Goldman Stewart , Sandler Eric , Greiner Robert , Gottardo Nicholas , Dholaria Hetal , Coven Scott L , Hassall Tim , Hansford Jordan , Samson Yvan , Leary Sarah , Bartels Ute , Bouffet Eric , Tinkle Christopher , Monje Michelle , Fisher Paul G , Ziegler David , Chintagumpala Murali , Wagner Lars , Koschmann Carl , Benito Elisa Carrasquedo , Leach James , Jones Blaise , Chaney Brooklyn , Black Katie , Asher Anthony , Bond Hailey , Fouladi Maryam , Warren Katherine E
Published: December 2020

There is no standard of care for cerebrospinal (CSF) diversion in children with diffuse intrinsic pontine glioma (DIPG), nor understanding of survival impact. We evaluated CSF diversion characteristics in children with DIPG to determine incidence, indications and potential impact on survival. Data was extracted from subjects registered in the International DIPG registry (IDIPGR). IDIPGR team personnel obtained clinical and radiographic data from the registry database and when appropriate, abstracted additional data from individual medical records. Univariable analyses were performed using the Fisher’s exact test or Wilcoxon rank sum test. Survival was estimated using the Kaplan-Meier method. Evaluable patients (n=457) met criteria for DIPG diagnosis by central radiology review. Ninety-two patients (20%) had permanent CSF diversion. Indications for permanent diversion were hydrocephalus (41%), hydrocephalus and clinical symptoms (35%), and clinical symptoms alone (3%). Those with permanent diversion were significantly younger at diagnosis than those without diversion (median 5.3 years vs 6.9 years, p=0.0002), otherwise no significant differences in gender, race, or treatment were found. The progression-free and overall survival of those with permanent CSF diversion compared to those without permanent diversion was 4.5 and 10.9 months vs 6.9 and 11.2 months, respectively (p=0.001, p= 0.4). There was no significant difference in overall survival in patients with or without permanent CSF diversion among a large cohort of DIPG patients. Patients without permanent diversion had significantly prolonged progression free survival compared to those with permanent diversion. The qualitative risks and benefits of permanent CSF diversion need to be further evaluated.
DIPG-62. PRECLINICAL EVALUATION OF IMIPRIDONE-BASED COMBINATION THERAPIES IN PEDIATRIC H3K27M MUTANT DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)
Authors: Borsuk Robyn , Zhou Lanlan , Zhang Yiqun , Prabhua Varun , Allen Joshua , Oster Wolfgang , Tapinos Nikos , Lulla Rishi R , El-Deiry Wafik
Published: December 2020

Imipridones induce apoptosis in cancer via p53 independent upregulation of TNF-related apoptosis inducing ligand (TRAIL) pathway and its proapoptotic receptor DR5. ONC201, a first-in-class imipridone, is being evaluated alone and with radiotherapy for children with H3K27M mutant diffuse glioma. We sought to determine if ONC201 and its imipridone analogs (ONC206, ONC212) are synergistic with other chemotherapy agents. Seven patient-derived DIPG cell lines, six H3.3K27M mutant (SU-DIPG-IV, SU-DIPG-13, SU-DIPG-25, SU-DIPG-27, SU-DIPG-29, SF8628) and one H3.1K27M mutant (SU-DIPG-36) were grown in culture and exposed to ONC201, ONC206, and ONC212 alone and in combination with histone de-acetylase inhibitors (HDACi) or etoposide. A dose-dependent response to ONC201, ONC206, and ONC212 was demonstrated in all cell lines, with mean IC50 values of 1.46 µM, 0.11 µM, and 0.03 µM respectively. ONC206 and ONC212 induced apoptosis measured by increased expression of cleaved PARP and ISR by increased expression ATF4. In two cell lines, synergy studies revealed combination indices (CI) < 1 for ONC206 and etoposide, with a best CI of 0.62 in SU-DIPG-IV and 0.46 in SU-DIPG-25. Synergy was also observed between ONC201 and etoposide (CI 0.46) and ONC201 and panobinostat (CI 0.01). Imipridones and analogs were superior to panobinostat and etoposide in triggering apoptosis as measured by sub-G1 phase content. Additional synergy and mechanistic analyses are ongoing and will be reported. Our results suggest that H3K27M mutant DIPG cells demonstrate increased sensitivity to imipridone analogs (ONC206 and ONC212) when compared to ONC201. Combinational strategies with etoposide or HDACi should be considered for clinical translation.
DIPG-63. LOSS OF THE H4 LYSINE METHYLTRANSFERASE KMT5B DRIVES INVASION / MIGRATION BY DEPLETING H3K27me3 AT LOCI OTHERWISE RETAINED IN H3K27M MUTANT DIPG CELLS
Authors: Kessler Ketty , Mackay Alan , Molinari Valeria , Tari Haider , Burford Anna , Sottoriva Andrea , Vinci Maria , Jones Chris
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) and other diffuse midline glioma (DMG) are characterised by K27M mutations in histone H3 variants. The major functional consequence is a global loss of the repressive mark H3K27me3, causing a raft of transcriptional changes promoting tumorigenesis, although certain key loci retain trimethylation, such as CDKN2A/B. We recently identified subclonal loss-of-function mutations in the H4 lysine methyltransferase KMT5B to be associated with an enhanced invasion/migration, but the mechanism by which this occurred was unclear. Here we show by ChIP-seq using patient-derived subclonal DIPG models and CRISPR-Cas9 depletion that loss of KMT5B (or KMT5C) causes a paradoxical increase in global levels of H4K20me3 in promoters and regulatory regions, only ablated by knocking out both enzymes. Loss of KMT5B alone further causes loss of the majority of otherwise retained H3K27me3 loci in DIPG cells, although CDKN2A/B itself was spared. De-repression occurred at bivalent loci marked by H3K4me3 and had elevated gene expression by RNAseq; these were significantly enriched for genes involved in chromatin remodelling and invasion/migration, the latter including MMP9/MMP24. Phenotypic assessment of the models in vitro by high-throughput imaging demonstrated significantly increased invasion and migration in association with either KMT5B or KMT5C loss, but not both. Quantitative proteomic assessment of the secretome identified factors by which a minority of KMT5B-deficient cells may signal to promote motility of the neighbouring populations. These data suggest a previously unrecognised trans-histone (H4/H3) interaction in DIPG cells with a potentially profound effect on their diffusely infiltrating phenotype.
DIPG-70. DISORDERED DNA METHYLATION IN DIPG UNDERLIES PHENOTYPIC PLASTICITY
Authors: Koldobskiy Michael , Tetens Ashley , Martin Allison , Eberhart Charles , Raabe Eric , Goutsias John , Feinberg Andrew
Published: December 2020

Diffuse intrinsic pontine glioma (DIPG) is a childhood brainstem tumor with a dismal prognosis and no effective treatment. Recent studies point to a critical role for epigenetic dysregulation in this disease. Nearly 80% of DIPGs harbor mutations in histone H3 encoding replacement of lysine 27 with methionine (K27M), leading to global loss of the repressive histone H3K27 trimethylation mark, global DNA hypomethylation, and a distinct gene expression profile. However, a static view of the epigenome fails to capture the plasticity of cancer cells and their gene expression states. Recent studies across diverse cancers have highlighted the role of epigenetic variability as a driving force in tumor evolution. Epigenetic variability may underlie the heterogeneity and phenotypic plasticity of DIPG cells and allow for the selection of cellular traits that promote survival and resistance to therapy. We have recently formalized a novel framework for analyzing variability of DNA methylation directly from whole-genome bisulfite sequencing data, allowing computation of DNA methylation entropy at precise genomic locations. Using these methods, we have shown that DIPG exhibits a markedly disordered epigenome, with increased stochasticity of DNA methylation localizing to specific regulatory elements and genes. We evaluate the responsiveness of the DIPG epigenetic landscape to pharmacologic modulation in order to modify proliferation, differentiation state, and immune signaling in DIPG cells.
EPCT-01. PHASE I STUDY OF DAY101 (TAK580) IN CHILDREN AND YOUNG ADULTS WITH RADIOGRAPHICALLY RECURRENT OR PROGRESSIVE LOW-GRADE GLIOMA (LGG)
Authors: Wright Karen , Krzykwa Emily , Greenspan Lianne , Chi Susan , Yeo Kee Kiat , Mueller Sabine , Prados Michael , Haas-Kogan Daphne
Published: December 2020

BACKGROUND

We report a phase I study examining pharmacokinetics, safety and recommended dosage of the type 2 RAF inhibitor DAY101 in children/young adults with radiographically recurrent/progressive LGGs harboring MAPK pathway alterations.

METHODS

Applying a 3 + 3 design, patients < 18 years of age with radiographically recurrent/progressive LGG received oral DAY101 weekly for 4-week cycles up to a maximum of 2 years, if deriving clinical benefit. The starting DAY101 dosage was 280 mg/m2. Dose limiting toxicities were determined after one cycle.

RESULTS

We treated nine eligible patients at 280, 350, and 420 mg/m2. Eight patients had KIAA1549:BRAF fusions. One patient with NF1 did not have a biopsy. There were no DLTs. Weekly administration of DAY101 in children resulted in dose-proportional increases in Cmax and AUC similar to that described in adults. A 2.2-fold mg/kg exposure difference was observed with respect to weight-based dosing and suggested a correlation to best radiographic RANO responses of 2 complete responses, 2 partial responses, 3 stable disease, and 2 progressive disease (independently-reviewed). Median time to response was 10.5 weeks (range: 8–32 weeks).

CONCLUSION

The phase 1A data provide initial pharmacokinetic parameters to describe oral weekly dosing of DAY101 in pediatric patients with radiographically recurrent/progressive LGG. Plasma exposures of DAY101 achieved in adults can be reached in pediatric patients. Oral weekly DAY101 is well-tolerated and possesses anti-tumor activity. The amended protocol will explore additional dose levels and the potential for differential dosing to achieve similar responses across a variety of BSAs.
EPCT-03. A PHASE I TRIAL OF 2-HYDROXYOLEIC ACID IN PEDIATRIC PATIENTS WITH ADVANCED CENTRAL NERVOUS SYSTEM TUMORS
Authors: Hanson Derek
Published: December 2020

2-hydroxyoleic acid (2-OHOA) is the first potential anti-cancer drug to act by modification of cell membrane lipid content. The agent is a derivative of oleic acid, a naturally occurring component of olive oil. Through its unique mechanism of activating sphingomyelin synthase 1, 2-OHOA targets the membrane lipid composition of cancer cells. These lipid changes alter membrane-dependent signaling cascades, such as the Ras/MAPK pathway, that promote tumor cell proliferation. A comprehensive pre-clinical program has characterized the safety and effects of 2-OHOA across a host of animal models. A European phase I/IIa trial of 2-OHOA in adult patients has shown initial promising results with five refractory high-grade glioma patients demonstrating objective clinical benefit by RANO criteria for six or more months. The drug has been very well-tolerated in adult patients with minimal toxicity. This phase I study is the first pediatric investigation of 2-OHOA and focuses on the treatment of relapsed/refractory pediatric central nervous system (CNS) tumors. The trial consists of a dose-escalation phase in up to 18 patients using a standard “3 + 3” design, followed by an expanded safety cohort of up to 10 patients treated at the maximum tolerated dose to confirm the recommended phase II dose. Due to the promising clinical results in adult neuro-oncology patients and the widespread involvement of the Ras/MAPK pathway and other membrane-dependent signaling cascades in the development of pediatric malignancies, we hypothesize that 2-OHOA may be a safe and effective treatment for pediatric patients with several types of advanced CNS tumors.
EPCT-05. A PHASE I TRIAL OF THE CDK 4/6 INHIBITOR PALBOCICLIB IN PEDIATRIC PATIENTS WITH PROGRESSIVE OR REFRACTORY CNS TUMORS: A PEDIATRIC BRAIN TUMOR CONSORTIUM (PBTC) STUDY
Authors: Van Mater David , Gururangan Sridharan , Leary Sarah , Becher Oren , Phillips Joanna , Huang Jie , Campagne Olivia , Poussaint Tina , Goldman Stewart , Baxter Patricia , Dhall Girish , Robinson Giles , DeWire-Schottmiller Mariko , Hwang Eugene , Stewart Clinton , Onar-Thomas Arzu , Dunkel Ira , Fouladi Maryam
Published: December 2020

PBTC-042 was a phase I trial of palbociclib to determine the maximum tolerated dose (MTD) and describe toxicities in children. Palbociclib is an oral, selective cyclin dependent kinase 4/6 inhibitor. METHODS: A rolling-6 design was utilized. Eligible patients were children ≥4 and ≤21 years-old with a progressive/refractory CNS tumor with intact retinoblastoma protein, measurable disease, and ability to swallow capsules. Pharmacokinetic studies were performed during the first course. Here, we report on the heavily pretreated stratum, which included patients who received >4 prior treatment regimens (either chemotherapy or biologic agent), and/or craniospinal irradiation, and/or myeloablative chemotherapy plus stem cell rescue. Palbociclib was initiated at 50 mg/m2/day for 21 consecutive days of a 28-day course. This was one dosage level below the MTD for the less heavily pretreated stratum (75 mg/m2). RESULTS: Fourteen eligible patients were enrolled (median age 12.8 years; male 79%). Eleven patients (79%) had either ependymoma or medulloblastoma. Four eligible and evaluable patients were enrolled at 50 mg/m2 with no DLTs. This prompted a dosage increase to 75 mg/m2. Ten eligible subjects were enrolled and 7 were evaluable for DLT assessment. One of 7 evaluable patients experienced a DLT (grade 3 thrombocytopenia). This established 75 mg/m2 as the MTD for more heavily pretreated patients. Mean ± SD palbociclib apparent oral clearance was 34.6 ± 18.4 L/h/m2. CONCLUSION: The MTD for palbociclib on a 3 week on/1 week off schedule in children with brain tumors is 75 mg/m2 and does not appear to be influenced by the degree of prior therapy.