DIPG-56. Development and application of a novel antibody against CD99 as a therapeutic strategy in Diffuse Midline Glioma

BACKGROUND: There is an unmet need to identify novel targeted therapies for Diffuse Midline glioma (DMG) which is currently a refractory disease. Recently, we identified high expression of a cell surface antigen, CD99 in H3K27M-mutant expressing DMGs compared to other normal brain counterparts. We developed a novel chimeric CD99 antibody and tested the anti-tumor efficacy of this antibody in vitro and in vivo. METHOD: Bio-legend cell-surface screening was performed in H3K27M-mutant and WT DMG cells. Functional role of CD99 was studied using CD99 proficient and depleted tumors. Designed and synthesized CD99 antibody with a new binding sequence on a human IgG scaffold and performed cell toxicity and growth-inhibitory studies using DMG tumor and normal cells. We also performed these studies in combination with radiation. Multiple patient-derived orthotopic DMG xenograft models was used to test the antibody efficacy. Different antibody delivery routes, that are clinically relevant were investigated. RESULTS: CD99 expression is transcriptionally regulated by H3K27M and is enriched on the cell surface of K27M tumors compared to WT DMG tumors. Our new CD99 antibody (10D1 clone) significantly reduced DIPG tumor cell proliferation in vitro. Intravenous infusion of this antibody in DIPG tumor bearing mice showed complete clearance of tumor that prolonged animal survival suggesting the enhanced anti-tumor efficacy of 10D1-CD99 and importantly, its ability in crossing the blood-brain-barrier and reaching the pons target site. Loco-regional administration of 10D1 showed similar anti-tumor effects even at much reduced antibody concentrations while toxicity to CD99-expressing T cells was minimum. Radiation increased CD99 expression and enhanced the cytotoxic effect of 10D1-CD99. CONCLUSION: We have developed a novel CNS penetrant CD99 antibody that is an attractive therapeutic strategy in treating DMG. 10D1 is currently in development as a therapeutic.

MODL-31. Novel in vivo models of post-radiation recurrent pediatric high-grade glioma show increased susceptibility to MAPK inhibition

BACKGROUND: Pediatric high-grade glioma (pHGG) is the most common cause of childhood cancer mortality, with median survival of less than one year. The standard of care for pHGG includes radiation therapy (RT), but almost all patients who respond initially relapse with aggressive, radiation-resistant disease. Matched primary/recurrent models and effective therapies for recurrent pHGG have not been adequately developed. METHODS: Orthotopic patient derived xenograft (PDX) models of radiation-resistant pHGG were developed by implanting BT245 (H3K27M) and HSJD-GBM-001 (GBM1, H3-wt) cells into mice. Resultant tumors were irradiated at 8Gy (4Gy x 2d) and allowed to regrow. Recurrent, radiation-resistant tumors (BT245MR and GBM1MR) and initial tumors (BT245M and GBM1M) were collected for bulk RNA-Seq analysis and ex vivo cell culture. Dose-response experiments were conducted in explant cells to identify drugs with increased effectiveness against recurrent (MR) cell lines versus wild-type cell lines. RESULTS: In both BT245 and GBM1 explant cells, geneset enrichment analysis (GSEA) showed upregulated mesenchymal (BT245MR: NES=3.4, FDR=0; GBM1MR: NES=2.4, FDR<0.002) and hypoxia-related (BT245MR: NES=3.6, FDR=0; GBM1MR: NES=3.4, FDR=0) pathways. GBM1MR tumors also showed enrichment in MAPK signaling (NES=4.7, FDR=0). RNA processing (NES=-6.5, FDR=0) and translation (NES=-5.8, FDR=0) pathways were depleted in BT245MR cells, and DNA repair pathways (NES=-5.8, FDR=0) were depleted in GBM1MR cells. The MAPK inhibitor trametinib demonstrated increased effectiveness in BT245MR and GBM1MR cell lines versus wild-type controls (BT245 IC50 158.7nM (wt) vs. 56.0 (MR), p<0.05; GBM1 IC50 150.7 (wt) vs. 53.4 (MR), p<0.05). BT245MR and GBM1MR cells reliably form PDX tumors after injection into mice. CONCLUSION: BT245MR and GBM1MR represent novel in vivo models of radiation-resistant pHGG, with gene expression alterations consistent with an irradiated phenotype. GSEA and in vitro dose-response data suggest MAPK inhibition may be effective in radiation-resistant pHGG. We are currently conducting in vivo experiments to validate increased trametinib sensitivity in these models.

HGG-20. PRMT5 promotes the formation and growth of pediatric high-grade glioma by maintaining tumor stem cell populations

BACKGROUND: Pediatric high-grade gliomas (PHGG) are aggressive, undifferentiated CNS tumors comprising two broad subtypes: diffuse midline glioma with H3K27M mutations (DMG) and cortical high-grade glioma (H3K27-wild-type (wt) PHGG). During normal development, PRMT5 promotes stem cell self-renewal through methylation of arginine residues in histone tails. We hypothesized that PRMT5 controls self-renewal essential to the proliferation of PHGG tumor initiating cells (TICs). METHODS: We identified PRMT5 as potentially oncogenic in PHGG through a screen of 4,139 shRNAs targeting 406 genes with epigenetic activity. To elucidate PRMT5’s activity, we used lentiviral shRNA delivery to knock down (KD) PRMT5 expression in four DMG and one H3K27-wt PHGG cell lines. We performed in vitro growth, cell cycle, apoptosis, limiting dilution and bulk RNA-Seq assays to determine the phenotypic effects of PRMT5 KD. To identify PRMT5’s gene targets, we performed cleavage under targets & release using nuclease (CUT&RUN) followed by qPCR and are currently performing CUT&RUN-Seq. We orthotopically implanted PRMT5 KD PHGG cells into mice and tracked survival, tumor growth and tumor histological characteristics. RESULTS: In vitro, PRMT5 KD reduced cell growth (p&lt;0.001), slowed cell cycle progression and increased apoptosis. PRMT KD also slowed neurosphere formation, demonstrating reduced self-renewal (p&lt;7E-9). Geneset expression analysis showed PRMT5 KD reduced expression of self-renewal genes and increased expression of differentiation genes (FDR&lt;0.0001). In vivo, PRMT5 KD reduced tumor growth, as monitored by bioluminescence and MRI, and aggressiveness, based on Ki-67 staining (p&lt;0.05), leading to increased survival (p&lt;0.001). CUT&RUN-qPCR results showed PRMT5 KD led to decreased expression and H3K4me3 promoter occupancy at PAX3, and decreased expression and increased H3K27me3 occupancy at S100A6. PAX3 and S100A6 are oncogenes that preserve TIC self-renewal. CONCLUSION. In vitro experiments show that PRMT5 KD epigenetically reduces TIC self-renewal. In vitro and in vivo, PRMT5 KD reduced PHGG tumor cell growth and aggressiveness.

RONC-05. Peri-transplant Radiation Therapy for Young Children Treated with High-Dose Chemotherapy for Primary Brain Tumors

PURPOSE: The role of peri-transplant radiation therapy (RT) in young children with primary brain tumors is unclear. We characterized our institutional practice patterns and patient outcomes. MATERIALS AND METHODS: The cohort included all patients treated with high-dose chemotherapy for primary brain tumors at our institution from 2011-2017. Rates of local control (LC), progression-free survival (PFS), overall survival (OS), and radiation-associated injury were assessed. RESULTS: Of 37 eligible patients, 29 (78%) received peri-transplant RT at a median age of 4 years. Patients treated with RT were more likely to have metastatic (p=0.0121) and incompletely resected (p=0.056) disease, and to have high-risk histologies including atypical teratoid rhabdoid tumor, nongerminomatous germ cell tumor, pineoblastoma, primitive neuro-ectodermal tumor, glioneuronal tumor and group 3 medulloblastoma. Of those treated with RT, 13 (45%) received craniospinal irradiation (CSI) and 16 (55%) received focal RT. The median CSI dose was 23.4 Gy (IQR: 18-36; boost median 54 Gy [IQR: 53.7-55.8]) and focal RT dose was 50.4 Gy (IQR: 50.4-54.5). Compared to the focal RT group, patients treated with CSI were older (p=0.0499) and more likely to have metastatic disease (p=0.0004). For the complete cohort, at a median follow-up of 3.8 years, the 2-year rate of LC was 82% (95% CI: 70-96%), PFS was 63% (95% CI: 49-81%), and OS was 65% (95% CI: 51-82%). These rates did not differ significantly between patients treated with and without peri-transplant RT. Two cases of fatal myelopathy were observed after spinal cord doses within the highest tertile (41.4 CGE and 36 Gy); both cases occurred in patients who received RT before high-dose chemotherapy. CONCLUSION: Peri-transplant RT was used for high-risk disease. Oncologic outcomes after RT were encouraging. However, 2 cases of grade 5 myelopathy were observed. If used cautiously, RT may contribute to durable remission in patients at high risk of relapse.

EPID-10. Creation, use, and effectiveness of a primary provider education tool for timely pediatric CNS tumor diagnosis based on HeadSmart

BACKGROUND: Patients of minority race and ethnicity and lower socioeconomic status experience poorer survival of pediatric CNS tumors in the US. These disparities arise in part from differences in stage of disease at diagnosis, suggesting they could be mitigated by earlier diagnosis. HeadSmart is a campaign in the UK to increase awareness of pediatric CNS tumor symptoms among primary care practitioners and the public that has led to a significant decrease in time to diagnosis. METHODS: We created a 30-minute workshop, based on HeadSmart, to educate primary care providers on the presentation, common symptoms, work-up, and diagnosis of pediatric CNS tumors. We publicized the workshop throughout Colorado and delivered it via live webinar or online video recording. We collected demographic, specialty, and practice setting data from participants via optional survey. Participants could also take a 10-question, multiple-choice assessment of their knowledge on pediatric CNS tumor symptoms, work-up, and diagnosis before and after the workshop. RESULTS: We have now delivered the workshop to more than 400 providers in Colorado and the US. 39 providers participated in the survey; 19 completed both the pre- and post-workshop assessments. The mean pre-workshop score was 4.5 correct out of 10 (range 0-7); the mean post-workshop score was 5.4 (range 3-7) (unpaired t-test p=0.04). The mean improvement was 1.1 (paired t-test p=0.007). The majority of participants who completed the survey were pediatricians (n=30). Family practice (FP) physicians and pediatric/FP advance practice practitioners also participated. There was no significant difference in improvement for pediatricians vs. other providers. CONCLUSIONS: An educational tool based on the HeadSmart campaign was widely disseminated and is effective at increasing understanding of the timely diagnosis of pediatric CNS tumors among primary providers in Colorado. Further study, refinement, and dissemination have the potential to help mitigate disparities in pediatric CNS tumor outcomes.

IMMU-23. Novel gene-edited CAR-T cell therapy against Diffuse Intrinsic Pontine Glioma

BACKGROUND: We identified high expression of CD99 in DIPG tumors and developed a CAR using our newly identified single chain variable fragment (scFv) targeting CD99 incorporating a 4-1BB co-stimulatory domain. This CD99 CAR demonstrated the ability to dramatically shrink the established orthotopic DIPG tumor, however tumor recurrence remains an obstacle to cure, due to a loss of the CAR-T cells as they also express the target antigen, CD99 (fratricide). To overcome this obstacle, we modified these CAR-T by editing out CD99. METHODS: CD99 was knocked-out from the human T cells using CRISPR-cas9 gene-editing and subsequently transduced with our CD99 CAR-encoding virus, and isolated the pure population of CD99KO T-cells. These novel, gene-edited T-cells expressing CD99 CAR (“CD99KO CARs”) and the un-edited ones (“CD99 CAR”) were tested for tumor-lysis function when co-cultured with DIPG cells. DIPG tumor-bearing mice infused with a one-time dose of CD99KO CAR-T cells or CD99 CAR- or CD19 control CAR-T cells and were monitored for changes in the tumor burden. At the endpoint spleen and bone marrow were isolated to test for CAR+ cell persistence. RESULTS: The CD99KO CAR-T cells demonstrated effective tumor-lysis when co-cultured with DIPG cells. CD99KO CAR-T cells targeting CD99 showed complete clearance of DIPG tumor in orthotopic DIPG mouse models, and no tumor recurrence was seen well-beyond the time frame of expected tumor recurrence after treatment with un-edited CD99 CAR-T cells. There was an un-precedented increase in the xenograft survival, &gt; 200 days, in mice treated with CD99KO CARs and at which time point sustained persistence of CAR+ cells were evident in the animal spleen and bone marrow. CONCLUSIONS: We have generated a new and promising CAR-T cell therapy that is effective against DIPG with enhanced persistence in animal models which is critical for clinical translation.

Efficacy of tPBM on ADHD symptoms and Executive Function Deficits in Adults with high-functioning Autism Spectrum Disorder

Introduction

Executive function (EF) deficits are often associated with Autism Spectrum Disorder (ASD), even in the absence of Attention Deficit Hyperactivity Disorder (ADHD) diagnosis. To date, no approved medication treatments exist for EF deficits associated with ASD.

Objectives

To assess the efficacy of transcranial photobiomodulation (tPBM) on EF in adults with ASD.

Methods

Adults (18-59) with high-functioning (HF)-ASD received twice a week tPBM for 8 weeks in an open-label single group design. ASD and EF deficits were assessed by clinician-rated Clinical Global Impression Scale and patient-rated scales of Behavior Rating Inventory of Executive Function-Adult (BRIEF-A).

Results

Eleven participants were enrolled. Ten participants completed the study. Nine participants who completed the study had comorbid ADHD diagnosis. All 10 participants were included in efficacy analyses of EF deficits. Statistically significant improvements in executive function deficits were found in BRIEF-A total score and in subdomains of Inhibition, Emotional Control, Planning and Organization, Organization of Materials, Behavioral Regulation, Metacognitive Index and Global Executive Control. All participants were found to have mild to moderate improvement in their ADHD symptom severity per clinician rated CGIs. Statistically significant improvements in ADHD symptoms were noted in self-rated scales. No adverse events required changes in tPBM protocol.

Conclusions

tPBM is a safe and feasible treatment approach that has the potential to treat core features of ASD. Further research is necessary and warranted.

Disclosure

This work is funded by Alan and Lorraine Bressler Clinical and Research Program for Autism Spectrum Disorder and the MGH Pediatric Psychopharmacology Council Fund.

Absolute calibration of Fujifilm BAS-TR image plate response to laser driven protons up to 40 MeV

Image plates (IPs) are a popular detector in the field of laser driven ion acceleration, owing to their high dynamic range and reusability. An absolute calibration of these detectors to laser-driven protons in the routinely produced tens of MeV energy range is, therefore, essential. In this paper, the response of Fujifilm BAS-TR IPs to 1-40 MeV protons is calibrated by employing the detectors in high resolution Thomson parabola spectrometers in conjunction with a CR-39 nuclear track detector to determine absolute proton numbers. While CR-39 was placed in front of the image plate for lower energy protons, it was placed behind the image plate for energies above 10 MeV using suitable metal filters sandwiched between the image plate and CR-39 to select specific energies. The measured response agrees well with previously reported calibrations as well as standard models of IP response, providing, for the first time, an absolute calibration over a large range of proton energies of relevance to current experiments.

Rural residents' emotions, beliefs, and sources that influenced those beliefs regarding sex offender policies, practice, and the efficacy of treatment

Public perceptions regarding a sex offender's likelihood to reoffend and the efficacy of sex offender policies and practices is often inconsistent with the extant literature in academia. Thus, there is a critical need to better understand what influences those beliefs regarding sex offender policies and practices. We collected data from 284 residents from government defined rural counties and sought to examine: (1) the sources that were most influential in shaping their beliefs regarding sex offender policies and practices; (2) what characteristics the "influential sources" had; and (3) the residents' emotional response when they think about "sex offenders". The majority of participants were supportive of registration, community notification, and use of the polygraph. Further, the results suggest that "academics and peer review articles" rarely influence beliefs. Rather, "personal experiences" and the emotions "rage" and "sadness" (but not anger or disgust) may be important in influencing rural residents' beliefs regarding sex offender treatment, castration, execution, and misconceptions regarding juveniles with a sex offense. We conclude by discussing: (1) potential factors that may affect why academics are not perceived as influential sources; and (2) possibilities for how scientists can influence rural residents' beliefs by utilizing personal experiences and anecdotal information that may spark emotion.

Proximal humeral fracture-dislocations: which patterns can be reduced in the emergency department?

BACKGROUND

Shoulder fracture-dislocations can represent a challenging management scenario in the emergency department (ED) because of concern for the presence of occult fractures that may displace during a reduction attempt. The alternative, a closed reduction attempt in the operating room, has the benefit of full paralysis but requires additional resource utilization. There is limited guidance in the literature about the risks of an initial reduction attempt in the ED as a function of fracture pattern to help guide physicians with this decision.

METHODS

This was a retrospective case review of adult patients with shoulder dislocations and fracture-dislocations seen in the ED at a level 1 trauma center over a 10-year period. Imaging and medical records were reviewed to evaluate whether the reduction attempt was successful, unsuccessful without worsening, or unsuccessful with worsening alignment of any fractures, as well as the ultimate clinical outcome.

RESULTS

We identified 165 patients with fracture-dislocations and 484 patients with simple dislocations during the same period. Of the patients with fracture-dislocations, 103 had greater tuberosity fractures, 12 had nondisplaced surgical neck fractures, and 50 had displaced surgical neck fractures. None of the patients with simple dislocations had displacement during an ED reduction attempt, including 100 patients aged >65 years. Of the 103 patients with greater tuberosity fracture-dislocations, only 1 had displacement of a humeral shaft fracture during ED reduction. Displacement occurred in 6 of 8 patients with nondisplaced neck fractures who underwent an initial ED reduction attempt vs. 1 of 4 patients who underwent the initial reduction attempt in the operating room. ED reduction was attempted in 25 of the 50 displaced humeral neck fracture-dislocations and was successful in 10 of these (40%).

CONCLUSIONS

For patients with greater tuberosity fracture-dislocations, there is a low rate of displacement with a reduction attempt in the ED, but an ED reduction attempt in nondisplaced neck fractures is not recommended because of the high rate of displacement. For displaced neck fractures, closed reduction can be successful in select patients. Finally, these data confirm prior reports that closed reduction of simple shoulder dislocations in patients aged >65 years is safe in the ED.

Impact of Noninvasive Respiratory Support in Patients With COVID-19 Requiring V-V ECMO

The impact of the duration of noninvasive respiratory support (RS) including high-flow nasal cannula and noninvasive ventilation before the initiation of extracorporeal membrane oxygenation (ECMO) is unknown. We reviewed data of patients with coronavirus disease 2019 (COVID-19) treated with V-V ECMO at two high-volume tertiary care centers. Survival analysis was used to compare the effect of duration of RS on liberation from ECMO. A total of 78 patients required ECMO and the median duration of RS and invasive mechanical ventilation (IMV) before ECMO was 2 days (interquartile range [IQR]: 0, 6) and 2.5 days (IQR: 1, 5), respectively. The median duration of ECMO support was 24 days (IQR: 11, 73) and 59.0% (N = 46) remained alive at the time of censure. Patients that received RS for ≥3 days were significantly less likely to be liberated from ECMO (HR: 0.46; 95% CI: 0.26-0.83), IMV (HR: 0.42; 95% CI: 0.20-0.89) or be discharged from the hospital (HR: 0.52; 95% CI: 0.27-0.99) compared to patients that received RS for <3 days. There was no difference in hospital mortality between the groups (HR: 1.12; 95% CI: 0.56-2.26). These relationships persisted after adjustment for age, gender, and duration of IMV. Prolonged duration of RS before ECMO may result in lung injury and worse subsequent outcomes.