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BackgroundPreclinical studies have suggested that mTOR pathway signaling may be a potential therapeutic target for childhood ependymoma.MethodsA phase II clinical trial (ClinicalTrials.gov identifier: NCT02155920) of single-agent everolimus was performed to test the hypothesis that mTOR pathway inhibition would result in tumor responses for children with recurrent and/or progressive ependymomas.ResultsEleven subjects [sex: 4 females (36.4%); median age: 8 years (range: 2-15 years); race: 9 white; prior therapies: median 6 (range: 3-9)] were enrolled on the study. Ten primary tumors were located in the posterior fossa and one primary tumor was located in the spinal cord. Eight of 9 tumors were PF-A subtype epenydmomas. All subjects were treated with oral everolimus 4.5 mg/m2/day (each cycle = 28 days) that was titrated to achieve serum trough levels of 5-15 ng/ml. Overall, everolimus was well tolerated; except for a single event of grade 3 pneumonia, all adverse events were grade 1-2. No objective tumor responses were observed. Participating subjects experienced tumor progression and discontinued therapy after a median of 2 cycles of therapy (1 cycle = 2; 2 cycles = 6; 3, 4, and 8 cycles = 1 each).ConclusionsEverolimus does not appear to have activity for children with recurrent or progressive PF-A ependymoma.

Background Recurrent atypical teratoid/rhabdoid tumor (AT/RT) is, most often, a fatal pediatric malignancy with limited curative options. Methods We conducted a phase II study of Aurora kinase A inhibitor alisertib in patients aged Results SD (n = 8) and partial response (PR) (n = 1) were observed among 30 evaluable patients. Progression-free survival (PFS) was 30.0% ± 7.9% at 6 months and 13.3% ± 5.6% at 1 year. One-year overall survival (OS) was 36.7% ± 8.4%. Two patients continued treatment for >12 months. PFS did not differ by AT/RT molecular groups. Neutropenia was the most common adverse effect (n = 23/30, 77%). The 22 patients who received liquid formulation had a higher mean maximum concentration (Cmax) of 10.1 ± 3.0 µM and faster time to Cmax (Tmax = 1.2 ± 0.7 h) than those who received tablets (Cmax = 5.7 ± 2.4 µM, Tmax = 3.4 ± 1.4 h). Conclusions Although the study did not meet predetermined efficacy end point, single-agent alisertib was well tolerated by children with recurrent AT/RT, and SD or PR was observed in approximately a third of the patients.

BACKGROUND Sporadic optic pathway/hypothalamic gliomas represent a unique entity within pediatric low-grade glioma. Despite favorable survival, location makes treatment difficult and local progression debilitating. This study is a longitudinal assessment of visual acuity (VA) among children treated within the last 2 decades. METHODS Clinical characteristics were abstracted for patients treated from 2000 to 2018 at Texas Children's Cancer Center in Houston. Ophthalmologic data taken at 3- to 6-month intervals were examined with age-appropriate VA metrics converted to the LogMAR (logarithm of the minimum angle of resolution) scale. Kaplan-Meier blindness-free survival (BFS) curves, calculated as time-to-bilateral functional blindness (LogMAR ≥0.8 in both eyes), were calculated for patients receiving early radiation therapy (RT; upfront or as first-line salvage treatment) or chemotherapy (CT) and evaluated using the log-rank test. RESULTS Thirty-eight patients with a median follow-up of 8.5 years (range, 2-17 years) were identified. Median age at diagnosis was 3 years (interquartile range

Purpose: Genomic aberrations in cell cycle and PI3K pathways are commonly observed in pediatric brain tumors. This study determined the MTD/recommended phase II dose (RP2D) of ribociclib and everolimus and characterized single-agent ribociclib concentrations in plasma and tumor in children undergoing resection. Patients and Methods: Patients were enrolled in the phase I study according to a rolling 6 design and received ribociclib and everolimus daily for 21 and 28 days, respectively. Surgical patients received ribociclib at the pediatric RP2D (350 mg/m2) for 7–10 days preoperatively followed by enrollment on the phase I study. Pharmacokinetics were analyzed for both cohorts. Results: Sixteen patients were enrolled on the phase I study (median age, 10.3 years; range, 3.9–20.4) and 6 patients in the surgical cohort (median age, 11.4 years; range: 7.2–17.1). Thirteen patients were enrolled at dose level 1 without dose-limiting toxicities (DLT). Two of the 3 patients at dose level 2 experienced DLTs (grade 3 hypertension and grade 4 alanine aminotransferase). The most common grade 3/4 toxicities were lymphopenia, neutropenia, and leukopenia. The RP2D of ribociclib and everolimus was 120 and 1.2 mg/m2 for 21 and 28 days, respectively. Steady-state everolimus exposures with ribociclib were 2.5-fold higher than everolimus administered alone. Ribociclib plasma, tumor concentrations, and cerebrospinal fluid (CSF) samples were collected. The mean tumor-to-plasma ratio of ribociclib was 19.8 (range, 2.22–53.4). Conclusions: Ribociclib and everolimus were well-tolerated and demonstrated pharmacokinetic properties similar to those in adults. Potential therapeutic ribociclib concentrations could be achieved in CSF and tumor tissue, although interpatient variability was observed.

Background Genomic aberrations in the cell cycle and PI3K/Akt/mTOR pathways have been reported in diffuse intrinsic pontine glioma (DIPG) and high-grade glioma (HGG). Dual inhibition of CDK4/6 and mTOR has biologic rationale and minimal overlapping toxicities. This study determined the recommended phase 2 dose (RP2D) of ribociclib and everolimus following radiotherapy in children with DIPG and HGG. Methods Patients were enrolled according to a Rolling-6 design and received ribociclib and everolimus once daily for 21 and 28 days, respectively. All patients with HGG and biopsied DIPG were screened for retinoblastoma protein presence by immunohistochemistry. Pharmacokinetics were analyzed. Results Nineteen patients enrolled (median age: 8 years [range: 2-18]). Three patients enrolled at each dose level 1 and 2 without dose-limiting toxicities (DLT). Thirteen patients were enrolled at dose level 3, with one patient experiencing a DLT (grade 3 infection). One patient came off therapy before cycle 9 due to cardiac toxicity. The most common grade 3/4 toxicities were neutropenia (33%), leucopenia (17%), and lymphopenia (11%). Steady-state everolimus exposures in combination were 1.9 ± 0.9-fold higher than single-agent administration. Median overall survival for 15 patients with DIPG was 13.9 months; median event-free survival for four patients with HGG was 10.5 months. Two longer survivors had tumor molecular profiling identifying CDKN2A/B deletion and CDK4 overexpression. Conclusion The combination of ribociclib and everolimus following radiotherapy in children with newly diagnosed DIPG and HGG was well tolerated, with a RP2D of ribociclib 170 mg/m2 and everolimus 1.5 mg/m2. Results will inform a molecularly guided phase II study underway to evaluate efficacy.

Many immunotherapies act by enhancing the ability of cytotoxic T cells to kill tumor cells. Killing depends on T cell recognition of antigens presented by class I major histocompatibility complex (MHC-I) proteins on tumor cells. In this study, we showed that medulloblastomas lacking the p53 tumor suppressor do not express surface MHC-I and are therefore resistant to immune rejection. Mechanistically, this is because p53 regulates expression of the peptide transporter Tap1 and the aminopeptidase Erap1, which are required for MHC-I trafficking to the cell surface. In vitro, tumor necrosis factor (TNF) or lymphotoxin-β receptor agonist can rescue expression of Erap1, Tap1 and MHC-I on p53-mutant tumor cells. In vivo, low doses of TNF prolong survival and synergize with immune checkpoint inhibitors to promote tumor rejection. These studies identified p53 as a key regulator of immune evasion and suggest that TNF could be used to enhance sensitivity of tumors to immunotherapy.

BACKGROUND AND PURPOSE: Diffuse intrinsic pontine glioma is a lethal childhood brain cancer with dismal prognosis and MR imaging is the primary methodology used for diagnosis and monitoring. Our aim was to determine whether advanced diffusion, perfusion, and permeability MR imaging metrics predict survival and pseudoprogression in children with newly diagnosed diffuse intrinsic pontine glioma. MATERIALS AND METHODS: A clinical trial using the poly (adenosine diphosphate ribose) polymerase (PARP) inhibitor veliparib concurrently with radiation therapy, followed by maintenance therapy with veliparib + temozolomide, in children with diffuse intrinsic pontine glioma was conducted by the Pediatric Brain Tumor Consortium. Standard MR imaging, DWI, dynamic contrast-enhanced perfusion, and DSC perfusion were performed at baseline and approximately every 2 months throughout treatment. ADC histogram metrics of T2-weighted FLAIR and enhancing tumor volume, dynamic contrast-enhanced permeability metrics for enhancing tumors, and tumor relative CBV from DSC perfusion MR imaging were calculated. Baseline values, post-radiation therapy changes, and longitudinal trends for all metrics were evaluated for associations with survival and pseudoprogression. RESULTS: Fifty children were evaluable for survival analyses. Higher baseline relative CBV was associated with shorter progression-free survival (P = .02, Q = 0.089) and overall survival (P = .006, Q = 0.055). Associations of higher baseline mean transfer constant from the blood plasma into the extravascular extracellular space with shorter progression-free survival (P = .03, Q = 0.105) and overall survival (P = .03, Q = 0.102) trended toward significance. An increase in relative CBV with time was associated with shorter progression-free survival (P

The overall survival of children with acute lymphoblastic leukemia (ALL) is over 90%. Much of this success comes from the daily use of 6-mercaptopurine (6-MP) during maintenance therapy [1]. Mercap...

Many immunotherapies act by enhancing the ability of cytotoxic T cells to kill tumor cells. Killing depends on T cell recognition of antigens presented by class I major histocompatibility complex (MHC-I) proteins on tumor cells. Here we show that medulloblastomas lacking the p53 tumor suppressor do not express surface MHC-I, and are therefore resistant to immune rejection. Mechanistically, this is because p53 regulates expression of the peptide transporter Tap1 and the aminopeptidase Erap1, which are required for MHC-I trafficking to the cell surface. In vitro, tumor necrosis factor (TNF) or lymphotoxin-β receptor agonist (LTβRag) can rescue expression of Erap1, Tap1 and MHC-I on p53-mutant tumor cells. In vivo, low doses of TNF prolong survival and synergize with immune checkpoint inhibitors to promote tumor rejection. These studies identify p53 as a key regulator of immune evasion, and suggest that TNF could be used to enhance sensitivity of tumors to immunotherapy.

Ependymoma (EPN) is the third most common brain tumor in children and frequently recurs. Here, we report an integrated longitudinal analysis of epigenetic, genetic and tumorigenic changes in 30 patient-matched repeated relapses obtained from 10 pediatric patients to understand the mechanism of recurrences. Genome-wide DNA methylation analysis revealed stable molecular subtypes and convergent epigenetic reprogramming during serial relapses of the 5 RELA and 5 PFA EPNs that paralleled with elevated patient-derived orthotopic xenograft (PDOX) (13/27) formation in the late relapses. Differentially methylated CpGs (DMCs) preexisted in the primary tumors and persisted in the relapses (driver DMCs) were detected, ranging from 51 hypo-methylated in RELA to 148 hyper-methylated DMCs in PFA tumors; while newly acquired DMCs sustained in all the relapses but was absent in the primary tumors (booster DMCs) ranged from 38- 323 hyper-methylated DMCs in RELA and PFA EPNs, respectively. Integrated analysis of these DMC associated DNA methylation regions (DMRs) and RNAseq in both patient and PDOX tumors identified a small fraction of the differentially expressed genes (4.6±4.4% in RELA and 4.5±1.1% in PFA) as regulated by driver DMRs (e.g., up-regulated CACNA1H, SLC12A7, RARA in RELA and HSPB8, GMPR, ITGB4 in PFA) and booster DMRs (including the sole upregulated PLEKHG1 in RELA and NOTCH, EPHA2, SUFU, FOXJ1 in PFA tumors). Most these genes were novel to EPN relapses. Seven DMCs in RELA and 22 in PFA tumors were also identified as potential relapse predictors. Finally, integrating DNA methylation with histone modification identified LSD1 as a relapse driver gene. Combined treatment of a novel inhibitor SYC-836 with radiation significantly prolonged survival times in two PDOX models of recurrent PFA. This high-resolution epigenetic and genetic roadmap of EPN relapse and our 13 new PDOX models should significantly facilitate biological and preclinical studies of pediatric EPN recurrences.

BACKGROUND The outcome for pediatric patients with high-grade glioma (HGG) remains poor. Veliparib, a potent oral PARP1/2 inhibitor, enhances the activity of radiotherapy and DNA-damaging chemotherapy. Preclinical data indicates that veliparib crosses the blood-brain-barrier and enhances the efficacy of radiotherapy and temozolomide in IDH mutant and wild-type HGG models. ACNS1721 was a single-arm, non-randomized phase 2 clinical trial designed to determine whether treatment with veliparib and radiotherapy, followed by the poly (ADP-ribose) polymerase (PARP) inhibitor veliparib and temozolomide, improves progression-free survival (PFS) in pediatric patients with newly diagnosed HGG without H3 K27M or BRAF mutations compared to patient level data from historical cohorts with closely matching clinical and molecular features. METHODS Following surgical resection, newly diagnosed children with non-metastatic HGG were screened by rapid central pathology review and molecular testing. Eligible patients without somatic H3 K27M or BRAF mutations were enrolled on Stratum 1 (IDH wild-type) or Stratum 2 (IDH mutant). Protocol radiochemotherapy consisted of involved field radiotherapy with concurrent veliparib at 65 mg/m2 twice daily. Adjuvant chemotherapy consisted of up to 10 cycles of veliparib 25 mg/m2 twice daily and temozolomide 135 mg/m2 once daily for 5 days every 4 weeks. RESULTS Both strata were closed to accrual for futility after planned interim analyses. Among the 23 eligible patients who enrolled on Stratum 1 and received protocol therapy, the 1-year progression-free survival (PFS) was 0.29 (SE = 0.09) and 1-year overall survival (OS) was 0.67 (SE = 0.10). Among the 14 eligible patients who enrolled on Stratum 2 and received protocol therapy, the 1-year PFS was 0.57 (SE = 0.15) and 1-year OS was 0.90 (SE = 0.09). CONCLUSION Rapid central pathology review and molecular testing was feasible. The protocol therapy was well tolerated but failed to improve outcome compared to clinically and molecularly matched historical control cohorts.

BACKGROUND RAF alterations are oncogenic drivers found in most pediatric low-grade gliomas (LGGs). Tovorafenib is an investigational, oral, selective, CNS-penetrant, small molecule, type II pan‑RAF inhibitor. METHODS FIREFLY-1 (NCT04775485) is a multicenter phase 2 study evaluating the safety and efficacy of tovorafenib monotherapy. Registrational arm 1 enrolled patients with recurrent/progressive LGG harboring an activating BRAF alteration. Patients aged 6 months–25 years who progressed following ≥ 1 prior line of systemic therapy were eligible. Tovorafenib 420 mg/m2 (≤ 600 mg) was administered weekly (tablet or liquid suspension formulation) until progression or for ≥ 26, 28-day cycles. The primary endpoint (arm 1) was overall response rate, as defined by RANO criteria, per independent review. RESULTS As of April 14, 2022, 25 patients were enrolled to arm 1 and had ≥ 6 months of follow-up. Median age at enrollment was 8 years (range 3–18). Most patients had astrocytomas (92%), 48% with optic pathway involvement. Patients were heavily pretreated (56% with ≥ 3 prior lines of therapy), and 72% previously received MAPK pathway-targeted agents. Tumors harbored BRAF fusions (84%) or BRAF V600E mutations (16%). Per independent assessment, partial responses (1 unconfirmed) were seen in 14 (64%) of 22 evaluable patients, with 6 additional patients having stable disease, and a clinical benefit rate of 91%. Responses were achieved in tumors with BRAF fusions and V600E mutations. Most treatment-emergent adverse events (AEs) were grade 1 or 2 (96%). The most common grade ≥ 3 AEs were anemia (12%), vomiting, increased blood creatinine phosphokinase and maculopapular rash (8% each). Seven patients (28%) required dose modification for treatment-related AEs; no patients discontinued tovorafenib due to AEs. Updated results, including efficacy per RAPNO assessments will be presented. CONCLUSIONS Tovorafenib was generally well tolerated and showed encouraging evidence of antitumor activity in children with pretreated BRAF-altered LGG.

BACKGROUND: Dual inhibition of CDK4/6 and mTOR in DIPG and pediatric HGG has strong biologic rationale, given prevalent genetic alterations resulting in upregulated cell cycle and PI3K/mTOR pathways in these diseases, as well as non-overlapping agent toxicities. This study sought to evaluate safety/tolerability and determine the recommended phase 2 dose (RP2D) of ribociclib and everolimus among children with newly diagnosed DIPG and HGG post-radiotherapy. METHODS: Patients were enrolled according to a Rolling-6 design and received oral ribociclib and everolimus once daily for 21 and 28 days, respectively, starting 2-4 weeks post-completion of radiotherapy. All HGG and biopsied DIPG patients were screened for RB protein presence by immunohistochemistry. Pharmacokinetics and survival data were analyzed. RESULTS: Nineteen patients enrolled (median age: 8 years [range: 2-18]). Three patients enrolled at each of dose levels 1 and 2 without dose-limiting toxicities (DLTs). Thirteen patients enrolled at dose level 3, with one patient experiencing a DLT (grade 3 infection). One patient came off therapy prior to cycle 9 due to cardiac toxicity. The most common grade 3/4 toxicities were neutropenia (33%), leucopenia (17%), and lymphopenia (11%). Steady-state everolimus exposures in combination were 1.9±0.9-fold higher than single-agent administration. Median overall survival (OS) for 15 patients with DIPG was 13.9 months, with 12-, 24-, and 36-month OS of 53.3%, 38.9%, and 38.9%. Median event-free survival for four patients with HGG was 10.5 months. Among patients with tumor molecular profiling, two longer survivors (OS: 20, >37 months) had evidence of cell cycle upregulation with CDKN2A/B deletion and CDK4 overexpression identified. CONCLUSIONS: The combination of ribociclib and everolimus was well-tolerated post-radiotherapy in children with newly diagnosed DIPG and HGG, with a RP2D of ribociclib 170 mg/m2 days 1-21 and everolimus 1.5 mg/m2 days 1-28. Results will inform a molecularly-guided phase II study currently underway to evaluate efficacy.

BACKGROUND RAS/RAF/MEK/ERK pathway activation is the primary driver for most pediatric low-grade gliomas (pLGG). MEK162 (binimetinib) is an orally bioavailable MEK1/2 inhibitor with superior brain penetration in a preclinical model. The primary objective of this multi-institutional phase II and target validation study was to assess stratum-specific efficacy of binimetinib in progressive pLGG. METHODS Eligible children aged 1-18 years with previously treated radiographically progressive pLGG were enrolled and treated with binimetinib, starting dose 32mg/m2/dose twice daily. Stratum 1 included patients with pLGG with documented BRAF fusion; stratum 2, neurofibromatosis 1 (NF1)-associated pLGG; stratum 3, sporadic pLGG without documented BRAF fusion; and stratum 4, patients undergoing planned tumor biopsy who began binimetinib preoperatively. Partial and minor responses (PR and MR) were defined as ≥50% and ≥25% decrease in maximal two-dimensional measurements. RESULTS Of 86 patients enrolled, 85 were evaluable for response. Of these, 48 (56%) showed a radiographic response (30 PR and 18 MR) in the first year of treatment. Response rate for stratum 1 (n=28) was 50% (12 PR and 2 MR); 12 (43%) had stable disease (SD) and 2 (7%) progressive disease (PD). Stratum 2 (n=21) response rate was 43% (5 PR, 4 MR), with 12 (57%) SD and no PD. Stratum 3 (n=29) response rate was 69% (10 PR, 10 MR), 4 (14%) SD and 5 (17%) PD. Stratum 4 (n=7) include 3 PR, 2 MR, 2 SD. Nineteen (22%) discontinued treatment for toxicity (most commonly dermatologic), and an additional 42 (49%) required dose reduction. Median dose at the time of PR/MR was 28mg/m2; responses were seen at doses as low 16mg/m2. CONCLUSION Binimetinib is highly effective in the treatment of both NF1-associated and sporadic pLGG, with or without documented BRAF fusion. Modified dosing strategies to improve tolerability may be considered in future trials.

INTRODUCTION: Panobinostat is an oral HDAC inhibitor with pre-clinical activity against DIPG. The phase I study in children with progressive DIPG (stratum 1) defined the maximum-tolerated dose (MTD) as 10 mg/m2 administered 3x/week, 3 weeks on/1 week off. Herein, we report results of stratum 2, involving children with non-progressive DIPG/DMG using an alternative schedule. Primary objectives were to describe the toxicity profile and define the MTD; secondary objectives were to describe progression-free survival (PFS) and overall survival (OS). PATIENTS AND METHODS: Patients with non-progressive DIPG or H3K27M-mutated thalamic DMG were eligible >14 days following standard radiation therapy only. Panobinostat was given every other day, 3x/week, on alternate weeks. Patients who received at least one dose of panobinostat were evaluable for toxicity. Four dose levels (DL) were evaluated: DL1 (16mg/m2/dose), DL2 (22 mg/m2/dose), DL3 (28 mg/m2/dose) and DL4 (36 mg/m2/dose). Dose escalation was determined by a continuous reassessment method. Correlative studies included pharmacokinetics obtained on course 1, day 1, and day 3 prior to subsequent dosing. RESULTS: Thirty-four eligible patients (median age, 7.6 [3-16] years) were enrolled with 29 evaluable for dose finding; DL1, n=3; DL2, n=10; DL3, n=11; DL4, n=5. The primary toxicities were myelosuppression and gastrointestinal. Eight DLTs occurred: DL2, Grade 3 thrombocytopenia (n=1); DL3, Grade 4 neutropenia (n=3), Grade 4 neutropenia and Grade 4 thrombocytopenia, (n=1); DL4, Grade 2 nausea (n=1), Grade 3 increased ALT (n=1), Grade 4 thrombocytopenia (n=1). Median PFS from drug initiation was 4.4 (1-11.2) months; median OS from diagnosis was 11.7 (4.5-25) months. These did not significantly differ from the PBTC historical cohort (PFS, p-value 0.4967; OS, p-value 0.6457). CONCLUSION: The MTD of panobinostat administered on this schedule to children with non-progressive DIPG/DMG is 22 mg/m2/dose. The primary DLT was myelosuppression. There was no significant improvement in PFS or OS in this cohort.

BACKGROUND: The outcome for pediatric patients with high-grade glioma (HGG) remains poor. Veliparib, a potent oral PARP1/2 inhibitor, enhances the activity of radiotherapy and DNA-damaging chemotherapy. Preclinical data indicates that veliparib crosses the blood-brain-barrier and enhances the efficacy of radiotherapy and temozolomide in IDH mutant and wild-type HGG models. ACNS1721 was a single-arm, non-randomized phase 2 clinical trial designed to determine whether treatment with veliparib and radiotherapy, followed by the poly (ADP-ribose) polymerase (PARP) inhibitor veliparib and temozolomide, improves progression-free survival (PFS) in pediatric patients with newly diagnosed HGG without H3 K27M or BRAF mutations compared to patient level data from historical cohorts with closely matching clinical and molecular features. METHODS: Following surgical resection, newly diagnosed children with non-metastatic HGG were screened by rapid central pathology review and molecular testing. Eligible patients without somatic H3 K27M or BRAF mutations were enrolled on Stratum 1 (IDH wild-type) or Stratum 2 (IDH mutant). Protocol radiochemotherapy consisted of involved field radiotherapy with concurrent veliparib at 65 mg/m2 twice daily. Adjuvant chemotherapy consisted of up to 10 cycles of veliparib 25 mg/m2 twice daily and temozolomide 135 mg/m2 once daily for 5 days every 4 weeks. RESULTS: Both strata were closed to accrual for futility after planned interim analyses. Among the 23 eligible patients who enrolled on Stratum 1 and received protocol therapy, the 1-year progression-free survival (PFS) was 0.29 (SE = 0.09) and 1-year overall survival (OS) was 0.67 (SE = 0.10). Among the 14 eligible patients who enrolled on Stratum 2 and received protocol therapy, the 1-year PFS was 0.57 (SE = 0.15) and 1-year OS was 0.90 (SE = 0.09). CONCLUSION: Rapid central pathology review and molecular testing was feasible. The protocol therapy was well tolerated but failed to improve outcome compared to clinically and molecularly matched historical control cohorts.

Brain tumors are the leading cause of cancer-related death in children. Tazemetostat is an FDA-approved enhancer of zeste homolog (EZH2) inhibitor. To determine its role in difficult-to-treat pediatric brain tumors, we examined EZH2 levels in a panel of 22 PDOX models and confirmed EZH2 mRNA over-expression in 9 GBM (34.6 ± 12.7-fold) and 11 medulloblastoma models (6.2 ± 1.7 in group 3, 6.0 ± 2.4 in group 4) accompanied by elevated H3K27me3 expression. Therapeutic efficacy was evaluated in 4 models (1 GBM, 2 medulloblastomas and 1 ATRT) via systematically administered tazemetostat (250 and 400 mg/kg, gavaged, twice daily) alone and in combination with cisplatin (5 mg/kg, i.p., twice) and/or radiation (2 Gy/day × 5 days). Compared with the untreated controls, tazemetostat significantly (Pcorrected

BACKGROUND Patients with chiasmatic-hypothalamic low-grade glioma (CHLGG) have frequent MRIs with gadolinium-based contrast agents (GBCA) for disease monitoring. Cumulative gadolinium deposition in the brains of children is a potential concern. The purpose of this study is to evaluate whether MRI with GBCA is necessary for determining radiographic tumor progression in children with CHLGG. METHODS Children who were treated for progressive CHLGG from 2005 to 2019 at Texas Children's Cancer Center were identified. Pre- and post-contrast MRI sequences were separately reviewed by one neuroradiologist who was blinded to the clinical course. Three dimensional measurements and tumor characteristics were evaluated. Radiographic progression was defined as a 25% increase in size (product of two largest dimensions) compared with baseline or best response after initiation of therapy. RESULTS A total of 28 patients with progressive CHLGG were identified with a total of 683 MRIs with GBCA reviewed (mean 24 MRIs/patient; range, 11-43 MRIs). Radiographic progression was observed 92 times, 91 (99%) on noncontrast and 90 (98%) on contrast imaging. Sixty-seven progressions necessitating management changes were identified in all (100%) noncontrast sequences and 66 (99%) contrast sequences. Tumor growth > 2 mm in any dimension was identified in 184/187 (98%) noncontrast and 181/187 (97%) with contrast imaging. Metastatic tumors were better visualized on contrast imaging in 4/7 (57%). CONCLUSION MRI without GBCA effectively identifies patients with progressive disease. When imaging children with CHLGG, eliminating GBCA should be considered unless monitoring patients with metastatic disease.

Background Both intensity-modulated radiotherapy (RT) and passively scattered proton therapy have a risk of secondary malignant neoplasm (SMN) in children. To determine the influence of RT modality on the incidence of SMN after craniospinal irradiation (CSI), the authors compared the incidence of SMN in children who had medulloblastoma treated with either photon CSI plus an intensity-modulated RT boost (group I) or passively scattered proton CSI plus a boost (group II). Methods From 1996 to 2014, 115 children with medulloblastoma (group I, n = 63; group II, n = 52) received CSI followed by a boost to the tumor bed. Most patients had standard-risk disease (63.5%). The median follow-up was 12.8 years for group I and 8.7 years for group II. Results The 5-year and 10-year overall survival (OS) rates were 88.8% and 85.1%, respectively, for standard-risk patients and 63.1% and 57.3%, respectively, for high-risk patients, with no OS difference by RT modality (P = .81). Six SMNs were identified (4 in group I, 2 in group II). The 5-year and 10-year SMN incidence rates were 1.0% and 6.9%, respectively (0.0% and 8.0%, respectively, in group I; 2.2% and 4.9%, respectively, in group II; P = .74). Two SMNs occurred in the clinical target volume in the brain, 2 occurred in the exit dose region from the photon spinal field, 1 occurred in the entrance path of a proton beam, and 1 occurred outside the radiation field. There were no reported cases of secondary leukemia. Conclusions This analysis demonstrates no difference in OS or SMN incidence between patients in groups I and II 10 years after RT. Lay summary One hundred fifteen children with medulloblastoma received radiotherapy (RT) with either photon craniospinal irradiation (CSI) and an intensity-modulated RT boost (group I; n = 63) or passively scattered proton CSI and a boost (group II;, n = 52). The majority of children had standard-risk disease (63.5%). The 5-year and 10-year overall survival rates were 88.8% and 85.1% for standard-risk patients, respectively, and 63.1% and 57.3% for high-risk patients, respectively, with no difference in overall survival by RT group (P = .81). The 5-year and 10-year second malignant neoplasm incidence rates were 1.0% and 6.9%, respectively, with no difference in second malignant neoplasm incidence according to RT group (P = .74).

BackgroundDisruption of cell-cycle regulators is a potential therapeutic target for brain tumors in children and adolescents. The aim of this study was to determine the maximum tolerated dose (MTD) and describe toxicities related to palbociclib, a selective cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in pediatric patients with progressive/refractory brain tumors with intact retinoblastoma protein.MethodsPalbociclib was administered orally starting at 50mg/m2 daily for the first 21 days of a 28-day course. Dose escalation was according to the Rolling-6 statistical design in less heavily (stratum I) and heavily pretreated (stratum II) patients, and MTD was determined separately for each group. Pharmacokinetic studies were performed during the first course, and pharmacodynamic studies were conducted to evaluate relationships between drug levels and toxicities.ResultsA total of 21 patients were enrolled on stratum I and 14 patients on stratum II. The MTD for both strata was 75mg/m2 . Palbociclib absorption (mean Tmax between 4.9 and 6.6 h) and elimination (mean half-life between 11.3 and 19.5 h) were assessed. The most common toxicity was myelosuppression. Higher palbociclib exposure was associated with grade 3/4 neutropenia and leukopenia. Dose limiting toxicities included grade 4 neutropenia and grade 3 thrombocytopenia and dehydration. No patients had an objective response to palbociclib therapy.ConclusionsPalbociclib was safely administered to children and adolescents at a dosage of 75mg/m2 for 21 consecutive days followed by seven days of rest in both strata. Future studies will establish its optimal utilization in pediatric patients with brain tumors.

BACKGROUND: The B-cell-specific Moloney murine leukemia virus integration site-1 (BMI-1) protein, implicated in self-renewal and DNA-damage signaling, is highly expressed in DIPG and HGG. Preclinically, BMI-1 modulation by unesbulin (PTC596 [which mediates hyperphosphorylation and subsequent degradation of BMI-1]) leads to DIPG/HGG cell proliferation blockade, mitotic abnormalities, and tumor cell sensitization to radiation-induced DNA damage. METHODS: This phase Ib study sought to determine the maximally tolerated dose/ recommended phase 2 dose (RP2D) of unesbulin administered concurrently with radiotherapy and adjuvantly in children with newly diagnosed DIPG or HGG. Patients were enrolled according to a Rolling-6 design and received oral unesbulin twice weekly during radiotherapy and as maintenance therapy. RESULTS: Twenty-seven patients enrolled (median age: 8.5 years [range: 2-18]), including 18 patients with DIPG and nine patients with HGG. Unesbulin was administered in capsule formulation in the first nine patients, then tablet formulation for subsequent patients. Within the capsule formulation group, three dose-limiting toxicities (DLTs) were observed in two patients on dose level 2 (grade 4 neutropenia). Within the tablet formulation group, four DLTs were experienced by three patients on dose level 2 (grade 3 ALT elevation, grade 3 dehydration/vomiting, grade 3 decreased ejection fraction, grade 4 neutropenia). Dose level 1 was declared the RP2D, and six additional patients enrolled in the expansion cohort at this dose without DLTs. Most common drug-related grade 3/4 toxicities were neutropenia (48%), leucopenia (35%), and elevated ALT (26%). Similar pharmacokinetic profiles were observed for capsule and tablet formulations, consistent with adult data. Survival outcomes and genomics results will be shared at time of presentation. CONCLUSIONS: The RP2D of unesbulin in children newly diagnosed with DIPG or HGG is 200mg/m2 twice weekly, concurrent with and following radiotherapy. The recently opened surgical cohort will assess intratumoral pharmacokinetics and inhibition of tumor BMI-1 signaling, with results forthcoming.

Brain tumor is a leading cause of cancer related death in children. In addition to replicating histopathology, animal models faithfully replicating genetic/epigenetic abnormalities, molecular subtypes and broad inter-tumoral heterogeneities are needed. Through direct implantation of patient surgical or autopsied tumor tissues into matching locations in the brains of SCID mice, we developed a panel of 150 PDOX mouse models. Here, we report the analysis of 74 of the 150 PDOX models, 45 matching patient tissues and 60 non-tumorigenic samples to a well-annotated reference cohort of 2,801 methylation profiles of primary brain tumors. Our data showed that the lack of tumorigenicity was neither correlated with molecular subtypes nor predicted by low cell viabilities of the patient samples. Methylation profiling identified PDOX models representing nearly a full spectrum of molecular subtypes of pediatric brain tumors including GBM, medulloblastoma, ependymoma and ATRT. Direct comparison with the original patient tumors confirmed the replication of molecular subtypes. ONCOplot [FB1] analysis of PDOX models derived from matching pairs of primary and recurrent tumors (n=8) revealed close clustering with the patient tumors. Investigation of metastatic properties was performed in 13 MB models by harvesting and sub-transplanting matching PDOX primary tumors in the cerebella and metastatic tumors in the spinal cords. To confirm the potential and power of PDOX models in preclinical drug testing, we applied fractionated radiation (2 Gy/day x 5 days) and optimized multi-agent combinatory chemotherapies in MB models of the four major subgroups. High-throughput combination drug screening with ~ 8,000 drugs in PDOX-derived GBM cell lines and primary cultures of MB PDOX cells identified a library of ~ 3,500 drugs that were active in pediatric brain tumors. In summary, this study provides detailed information on molecular subclassification of a uniquely large cohort of PDOX models to serve as essential tools for brain tumor research.

INTRODUCTION: Autophagy is a highly conserved process by which intracellular components are degraded and recycled promoting cell survival. Preclinically, autophagy has been implicated as a resistance mechanism in BRAF-mutant glioma cells treated with MAPK-pathway inhibitors. HCQ, an oral autophagy inhibitor, has been evaluated preclinically and clinically to overcome resistance. METHODS: PBTC-055 (NCT04201457) is a phase I/II trial of HCQ combined with trametinib (BRAF-fusion or NF1-associated gliomas) or trametinib and dabrafenib (BRAFV600E gliomas) in patients < 30 years with progressive glioma. Prior treatment with RAF and/or MEK inhibitor with sub-optimal response (no response or response followed by progression on therapy) was required. Here, we present phase I data combining trametinib with HCQ utilizing a rolling-6 design. HCQ was administered at escalating dose levels (8, 15, or 20 mg/kg/day divided BID) in combination with standard pediatric trametinib dosing. All patients received prior MEK inhibitor therapy; 5/18 (28%) exhibited no response and 13/18 (72%) progressed on active therapy. RESULTS: Eighteen eligible/evaluable subjects were enrolled. Median age was 9.6 years (2.5-20.4 years); 10 were male. There were 2 dose-limiting toxicities (both grade 3 rash one each at DL1 and DL3). The highest dose level of HCQ (20 mg/kg/day divided BID) was declared the RP2D. Grade 3 adverse events possibly related to therapy included skin infection, rash, cardiac ejection fraction decrease, weight loss, and anorexia. There were no grade 4 or 5 attributable toxicities. Preliminarily, combination pharmacokinetic assessment revealed similar metabolism of trametinib to that reported as a single agent; HCQ demonstrated more rapid clearance compared to adults. Pharmacodynamic assessments are ongoing. CONCLUSIONS: The combination of trametinib and HCQ is safe with a RP2D of HCQ of 20 mg/kg/day divided BID. Currently, subjects are enrolling on the phase II portion evaluating the efficacy of this novel combination.

BACKGROUND: Despite being the most common central nervous system tumor in children, ≤5% of pediatric low grade gliomas (pLGG) present with metastases. Due to their rarity, there is a paucity of clinical and molecular data in metastatic pLGGs. To address the need, we analyzed a cohort of 22 patients with pLGG followed at Texas Children’s Hospital who presented with metastatic disease. RESULTS: The predominant histology was pilocytic astrocytoma (16/22, 73%); average age at diagnosis was 4 years 11 months. The most common sites of primary disease were optic pathway/chiasm (7/22, 32%) and suprasellar (5/22, 23%). Metastatic disease was most commonly noted in the leptomeninges (12/22, 55%). 16/22 patients (73%) were treated with up-front medical therapy following tumor biopsy/resection, the majority with carboplatin-based therapy; the remaining 6 patients received only surgery up-front. Only 2/22 patients (9%) did not progress after their initial treatment with an average follow-up of 42 months. 14 patients (14/22, 64%) had continued disease progression after at least 2 therapeutic interventions; however, only 3 patients (3/22, 14%) eventually received craniospinal radiation. 10 patients (10/22, 45%) received treatment with an agent targeting the mitogen-activated protein kinase (MAPK) pathway. 20/22 patients (91%) were alive at last follow-up (average 72 months). 4/21 patients (19%) harbored a BRAF V600E mutation while 7/20 (35%) had a BRAF::KIAA1549 duplication/fusion. 8/20 patients (40%) were wildtype for both analyzed molecular alterations in BRAF. 8 patients had germline whole exome sequencing performed and all were negative for pathogenic/likely-pathogenic variants related to their clinical phenotype. Methylation analyses are pending on patients with available tumor tissue. CONCLUSION: In our cohort of patients with metastatic pLGG, most tumors progressed despite numerous therapeutic regimens, but the overall survival was >90%. 40% of patients were wild type for the 2 most common MAPK alterations seen in pLGG.

Background Pediatric low-grade gliomas (pLGGs) are the most common childhood brain tumor. Progression-free survival (PFS) is much lower than overall survival, emphasizing the need for alternative treatments. Sporadic (without neurofibromatosis type 1) optic pathway and hypothalamic gliomas (OPHGs) are often multiply recurrent and cause significant visual deficits. Recently, there has been a prioritization of functional outcomes. Methods We present results from children with recurrent/progressive OPHGs treated on a PBTC (Pediatric Brain Tumor Consortium) phase II trial evaluating efficacy of selumetinib (AZD6244, ARRY-142886) a MEK-1/2 inhibitor. Stratum 4 of PBTC-029 included patients with sporadic recurrent/progressive OPHGs treated with selumetinib at the recommended phase II dose (25mg/m2/dose BID) for a maximum of 26 courses. Results Twenty-five eligible and evaluable patients were enrolled with a median of 4 (1-11) previous therapies. Six of 25 (24%) had partial response, 14/25 (56%) had stable disease, and 5 (20%) had progressive disease while on treatment. The median treatment courses were 26 (2-26); 14/25 patients completed all 26 courses. Two-year PFS was 78 ± 8.5%. Nineteen of 25 patients were evaluable for visual acuity which improved in 4/19 patients (21%), was stable in 13/19 (68%), and worsened in 2/19 (11%). Five of 19 patients (26%) had improved visual fields and 14/19 (74%) were stable. The most common toxicities were grade 1/2 CPK elevation, anemia, diarrhea, headache, nausea/emesis, fatigue, AST and ALT increase, hypoalbuminemia, and rash. Conclusions Selumetinib was tolerable and led to responses and prolonged disease stability in children with recurrent/progressive OPHGs based upon radiographic response, PFS, and visual outcomes.

Brain tumor is the leading cause of cancer related death in children. Clinically relevant animals are critical for new therapy development. To address the potential impact of animal gender on tumorigenicity rate, xenograft growth and in vivo drug responses, we retrospectively analyzed 99 of our established patient derived orthotopic xenograft mouse models (orthotopic PDX or PDOX). From 27 patient tumors, including 5 glioblastomas (GBMs), 11 medulloblastomas (MBs), 4 ependymomas (EPNs), 4 atypical teratoid/rhabdoid tumors (ATRTs) and 3 diffuse intrinsic pontine gliomas (DIPGs), that were directly implanted into matching locations in the brains of approximately equal numbers of male and female animals (n = 310) in age-matched (within 2-week age-difference) SCID mice, the tumor formation rate was 50.6 ± 21.5% in male and 52.7 ± 23.5% in female mice with animal survival times of 192.6 ± 31.7 days in male and 173.9 ± 34.5 days in female mice (P = 0.46) regardless of pathological diagnosis. Once established, PDOX tumors were serially subtransplanted for up to VII passage. Analysis of 1,595 mice from 59 PDOX models (18 GBMs, 18 MBs, 5 ATRTs, 6 EPNs, 7 DIPGs and 5 PENTs) during passage II and VII revealed similar tumor take rates of the 6 different tumor types between male (85.4 ± 15.5%) and female mice (84.7 ± 15.2%) (P = 0.74), and animal survival times were 96.7 ± 23.3 days in male mice and 99.7 ± 20 days in female (P = 0.25). A total of 284 mice from 7 GBM, 2 MB, 1 ATRT, 1 EPN, 2 DIPG and 1 PNET were treated with a series of standard and investigational drugs/compounds. The overall survival times were 106.9 ± 25.7 days in male mice, and 110.9 ± 31.8 days in female mice (P = 0.41), similar results were observed when different types/models were analyzed separately. In conclusion, our data demonstrated that the gender of SCID mice did not have a major impact on animal model development nor drug responses in vivo, and SCID mice of both genders are appropriate for use.

Preclinical studies suggested that the mTOR signaling pathway could be a potential therapeutic target in childhood ependymomas. As a result, a phase II clinical trial (ClinicalTrials.gov identifier: NCT02155920) of single-agent everolimus was performed to test the hypothesis that inhibition of the mTOR pathway would result in tumor responses for children with recurrent and/or progressive ependymoma. Eleven patients [sex: 4 females (36.4%); median age: 8 years (range: 2 – 15 years); race: 9 white and 2 other; prior therapies: median 6 (range: 3 – 9)] were enrolled on the study. The primary tumor location for 10 participants was the posterior fossa; the primary location of the remaining tumor was the cervical spine. All patients were treated with oral everolimus 4.5 mg/m2/day (each cycle = 28 days) that was titrated to achieve serum trough levels of 5 – 15 ng/mL. Overall, everolimus was well tolerated; adverse events were grade 1 – 2 and consistent with its previously established safety profile in children. No objective tumor responses were observed. All patients discontinued therapy due to tumor progression after a median of 2 cycles of therapy (1 cycle = 2; 2 cycles = 6; 3, 4, and 8 cycles = 1 each). This study does not support the use of everolimus for children with recurrent or progressive ependymoma.

Medulloblastoma is among the most common malignant brain tumors in children. Recent studies have identified at least four subgroups of the disease that differ in terms of molecular characteristics and patient outcomes. Despite this heterogeneity, most patients with medulloblastoma receive similar therapies, including surgery, radiation, and intensive chemotherapy. Although these treatments prolong survival, many patients still die from the disease and survivors suffer severe long-term side effects from therapy. We hypothesize that each patient with medulloblastoma is sensitive to different therapies and that tailoring therapy based on the molecular and cellular characteristics of patients' tumors will improve outcomes. To test this, we assembled a panel of orthotopic patient-derived xenografts (PDX) and subjected them to DNA sequencing, gene expression profiling, and high-throughput drug screening. Analysis of DNA sequencing revealed that most medulloblastomas do not have actionable mutations that point to effective therapies. In contrast, gene expression and drug response data provided valuable information about potential therapies for every tumor. For example, drug screening demonstrated that actinomycin D, which is used for treatment of sarcoma but rarely for medulloblastoma, was active against PDXs representing Group 3 medulloblastoma, the most aggressive form of the disease. Functional analysis of tumor cells was successfully used in a clinical setting to identify more treatment options than sequencing alone. These studies suggest that it should be possible to move away from a one-size-fits-all approach and begin to treat each patient with therapies that are effective against their specific tumor. Significance: These findings show that high-throughput drug screening identifies therapies for medulloblastoma that cannot be predicted by genomic or transcriptomic analysis.

Background Central nervous system (CNS) malignancies are the most common solid tumors among children, and novel therapies are needed to help improve survival. Pomalidomide is an immunomodulatory agent that displays antiangiogenic and cytotoxic activity, making it an appropriate candidate to explore in pediatric CNS tumors. Methods A phase 1 first in pediatric trial of pomalidomide was conducted in children with recurrent, progressive, and refractory CNS tumors. The primary objective was to determine the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) when given orally once daily for 21 consecutive days of a 28-day cycle. Once the MTD was established, 12 additional patients were enrolled on expansion cohorts based on age and steroid use. Results Twenty-nine children were enrolled and 25 were evaluable for dose-limiting toxicity (DLT). The MTD was 2.6 mg/m2 (dose level 2). Four DLTs were observed in three patients at dose level 3 (3.4 mg/m2 ) includeding grade 3 diarrhea, grade 3 thrombocytopenia, grade 3 lung infection, and grade 4 neutropenia. The most common adverse events were grade 1 and 2 myelosuppression. One patient with an oligodendroglioma had stable disease for nine cycles, and a second patient with an anaplastic pleomorphic xanthoastrocytoma achieved a sustained partial response. Immunologic analyses suggested that pomalidomide triggers immunomodulation. Conclusions The MTD of pomalidomide is 2.6 mg/m2 . It was well tolerated, and immune correlates showed a serum immune response. These data led to an industry-sponsored phase 2 trial of pomalidomide monotherapy in children with recurrent brain tumors (NCT03257631).

Brain tumor is the leading cause of cancer related death in children. Clinically relevant animals are critical for new therapy development. To address the potential impact of animal gender on tumorigenicity rate, xenograft growth and in vivo drug responses, we retrospectively analyzed 99 of our established patient derived orthotopic xenograft mouse models (orthotopic PDX or PDOX). From 27 patient tumors, including 5 glioblastomas (GBMs), 11 medulloblastomas (MBs), 4 ependymomas (EPNs), 4 atypical teratoid/rhabdoid tumors (ATRTs) and 3 diffuse intrinsic pontine gliomas (DIPGs), that were directly implanted into matching locations in the brains of approximately equal numbers of male and female animals (n = 310) in age-matched (within 2-week age-difference) SCID mice, the tumor formation rate was 50.6 ± 21.5% in male and 52.7 ± 23.5% in female mice with animal survival times of 192.6 ± 31.7 days in male and 173.9 ± 34.5 days in female mice (P = 0.46) regardless of pathological diagnosis. Once established, PDOX tumors were serially subtransplanted for up to VII passage. Analysis of 1,595 mice from 59 PDOX models (18 GBMs, 18 MBs, 5 ATRTs, 6 EPNs, 7 DIPGs and 5 PENTs) during passage II and VII revealed similar tumor take rates of the 6 different tumor types between male (85.4 ± 15.5%) and female mice (84.7 ± 15.2%) (P = 0.74), and animal survival times were 96.7 ± 23.3 days in male mice and 99.7 ± 20 days in female (P = 0.25). A total of 284 mice from 7 GBM, 2 MB, 1 ATRT, 1 EPN, 2 DIPG and 1 PNET were treated with a series of standard and investigational drugs/compounds. The overall survival times were 106.9 ± 25.7 days in male mice, and 110.9 ± 31.8 days in female mice (P = 0.41), similar results were observed when different types/models were analyzed separately. In conclusion, our data demonstrated that the gender of SCID mice did not have a major impact on animal model development nor drug responses in vivo, and SCID mice of both genders are appropriate for use.

Background A Pediatric Brain Tumor Consortium (PBTC) phase I/II trial of veliparib and radiation followed by veliparib and temozolomide (TMZ) was conducted in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG). The objectives were to: (i) estimate the recommended phase II dose (RP2D) of veliparib with concurrent radiation; (ii) evaluate the pharmacokinetic parameters of veliparib during radiation; (iii) evaluate feasibility of intrapatient TMZ dose escalation; (iv) describe toxicities of protocol therapy; and (v) estimate the overall survival distribution compared with historical series. Methods Veliparib was given Monday through Friday b.i.d. during radiation followed by a 4-week rest. Patients then received veliparib at 25 mg/m2 b.i.d. and TMZ 135 mg/m2 daily for 5 days every 28 days. Intrapatient dose escalation of TMZ was investigated for patients experiencing minimal toxicity. Results Sixty-six patients (65 eligible) were enrolled. The RP2D of veliparib was 65 mg/m2 b.i.d. with radiation. Dose-limiting toxicities during radiation with veliparib therapy included: grade 2 intratumoral hemorrhage (n = 1), grade 3 maculopapular rash (n = 2), and grade 3 nervous system disorder (generalized neurologic deterioration) (n = 1). Intrapatient TMZ dose escalation during maintenance was not tolerated. Following a planned interim analysis, it was concluded that this treatment did not show a survival benefit compared with PBTC historical controls, and accrual was stopped for futility. The 1- and 2-year overall survival rates were 37.2% (SE 7%) and 5.3% (SE 3%), respectively. Conclusion Addition of veliparib to radiation followed by TMZ and veliparib was tolerated but did not improve survival for patients with newly diagnosed DIPG. Trial Registration NCT01514201

Purpose To study the efficacy and tolerability of valproic acid (VPA) and radiation, followed by VPA and bevacizumab in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG) or high-grade glioma (HGG). Methods Children 3 to 21 years of age received radiation therapy and VPA at 15 mg/kg/day and dose adjusted to maintain a trough range of 85 to 115 μg/mL. VPA was continued post-radiation, and bevacizumab was started at 10 mg/kg intravenously biweekly, four weeks after completing radiation therapy. Results From September 2009 through August 2015, 20 DIPG and 18 HGG patients were enrolled (NCT00879437). During radiation and VPA, grade 3 or higher toxicities requiring discontinuation or modification of VPA dosing included grade 3 thrombocytopenia (1), grade 3 weight gain (1), and grade 3 pancreatitis (1). During VPA and bevacizumab, the most common grade 3 or higher toxicities were grade 3 neutropenia (3), grade 3 thrombocytopenia (3), grade 3 fatigue (3), and grade 3 hypertension (4). Two patients discontinued protocol therapy prior to disease progression (one grade 4 thrombosis and one grade 1 intratumoral hemorrhage). Median event-free survival (EFS) and overall survival (OS) for DIPG were 7.8 (95% CI 5.6-8.2) and 10.3 (7.4-13.4) months, and estimated one-year EFS was 12% (2%-31%). Median EFS and OS for HGG were 9.1 (6.4-11) and 12.1 (10-22.1) months, and estimated one-year EFS was 24% (7%-45%). Four patients with glioblastoma and mismatch-repair deficiency syndrome had EFS of 28.5, 16.7, 10.4, and 9 months. Conclusion Addition of VPA and bevacizumab to radiation was well tolerated but did not appear to improve EFS or OS in children with DIPG or HGG.

Optimising the conduct of clinical trials for diffuse intrinsic pontine glioma involves use of consistent, objective disease assessments and standardised response criteria. The Response Assessment in Pediatric Neuro-Oncology working group, consisting of an international panel of paediatric and adult neuro-oncologists, clinicians, radiologists, radiation oncologists, and neurosurgeons, was established to address issues and unique challenges in assessing response in children with CNS tumours. A working group was formed specifically to address response assessment in children and young adults with diffuse intrinsic pontine glioma and to develop a consensus on recommendations for response assessment. Response should be assessed using MRI of brain and spine, neurological examination, and anti-inflammatory or antiangiogenic drugs. Clinical imaging standards are defined. As with previous consensus recommendations, these recommendations will need to be validated in prospective clinical trials.

Mutation in isocitrate dehydrogenase 1 (IDH1) occurs in >70% of WHO grade II/III astrocytomas, oligodendrogliomas and secondary glioblastoma. The mutant enzyme catalyzes the reduction of α-ketoglutaric acid to D-2-hydroxyglutaric acid, leading to cancer initiation. In this study, we examined therapeutic efficacy of SYC-435 (1-hydroxypyridin-2-one), a newly developed mutant IDH1inhibitor, in IDH1 mutant gliomas. IDH1 R132H mutation (homozygous) was detected in BT142 anaplastic oligoastrocytoma (AOA) and R132C mutation (mutant allele frequency 39–50%) in V0914AOA by pyrosequencing. Suppression of cell growth by SYC-435 was observed with more sensitive of mutant over wild-type IDH1. Patient-derived orthotopic xenograft mouse models of BT142AOA and V0914AOA were treated with vehicle, SYC-435 (15 mg/kg/day x 28 days), temozolomide (50 mg/kg/day x 5 days)/fractionated radiation (2 Gy/day x 5 days) (standard therapy), and SYC-435/standard therapy starting 2 weeks after intracranial tumor implantation. Log rank analysis showed SYC-435 alone did not alter survival times. Although standard therapy significantly prolonged survival times in both models (P< 0.0005), SYC-435/standard therapy further extended survival times (P< 0.05) in V0914AOA and exhibited similar trend in BT142AOA. Elevation of 2-HG/α-KG ratio and methylation of H3K4/H3K9 in V0914AOA tumor compared to wild-type model was detected at the end of treatments. SYC-435 with/without standard therapy tended to reduce 2-HG/α-KG ratio and dramatically reduced methylation of H3K4/H3K9. RNA-seq analysis showed sirtuin signaling pathway, mitochondrial dysfunction and oxidative phosphorylation pathways with mitochondrial DNA (mtDNA) encoded molecules were highly affected by all treatments. However, mtDNA regulation did not correlate to survival benefits. In conclusion, SYC-435 possesses anti-tumor effects that are more sensitive in IDH1 mutant gliomas and generated strong synergistic activities with standard therapies for survival benefits with reduced methylation of H3K4/H3K9. Treatments significantly affected mtDNA but significance to survival benefits remains to be elucidated. Our data support the clinical testing of SYC-435 in patients with IDH1 mutant glioma.

Purpose: Pediatric glioblastoma multiforme (pGBM) is a highly aggressive tumor in need of novel therapies. Our objective was to demonstrate the therapeutic efficacy of MLN8237 (alisertib), an orally available selective inhibitor of Aurora A kinase (AURKA), and to evaluate which in vitro model system (monolayer or neurosphere) can predict therapeutic efficacy in vivo. Experimental Design: AURKA mRNA expressions were screened with qRT-PCR. In vitro antitumor effects were examined in three matching pairs of monolayer and neurosphere lines established from patient-derived orthotopic xenograft (PDOX) models of the untreated (IC-4687GBM), recurrent (IC-3752GBM), and terminal (IC-R0315GBM) tumors, and in vivo therapeutic efficacy through log rank analysis of survival times in two models (IC-4687GBM and IC-R0315GBM) following MLN8237 treatment (30 mg/kg/day, orally, 12 days). Drug concentrations in vivo and mechanism of action and resistance were also investigated. Results: AURKA mRNA overexpression was detected in 14 pGBM tumors, 10 PDOX models, and 6 cultured pGBM lines as compared with 11 low-grade gliomas and normal brains. MLN8237 penetrated into pGBM xenografts in mouse brains. Significant extension of survival times were achieved in IC-4687GBM of which both neurosphere and monolayer were inhibited in vitro, but not in IC-R0315GBM of which only neurosphere cells responded (similar to IC-3752GBM). Apoptosis-mediated MLN8237 induced cell death, and the presence of AURKA-negative and CD133+ cells appears to have contributed to in vivo therapy resistance. Conclusions: MLN8237 successfully targeted AURKA in a subset of pGBMs. Our data suggest that combination therapy should aim at AURKA-negative and/or CD133+ pGBM cells to prevent tumor recurrence. Clin Cancer Res; 24(9); 2159–70. ©2018 AACR.

Diffuse invasion is the primary cause of treatment failure of glioblastoma (GBM). Previous studies on GBM invasion have long been forced to use the resected tumor mass cells. Here, a strategy to reliably isolate matching pairs of invasive (GBM INV ) and tumor core (GBM TC ) cells from the brains of 6 highly invasive patient‐derived orthotopic models is described. Direct comparison of these GBM INV and GBM TC cells reveals a significantly elevated invasion capacity in GBM INV cells, detects 23/768 miRNAs over‐expressed in the GBM INV cells (miRNA INV ) and 22/768 in the GBM TC cells (miRNA TC ), respectively. Silencing the top 3 miRNAs INV (miR‐126, miR‐369‐5p, miR‐487b) successfully blocks invasion of GBM INV cells in vitro and in mouse brains. Integrated analysis with mRNA expression identifies miRNA INV target genes and discovers KCNA1 as the sole common computational target gene of which 3 inhibitors significantly suppress invasion in vitro. Furthermore, in vivo treatment with 4‐aminopyridine (4‐AP) effectively eliminates GBM invasion and significantly prolongs animal survival times (P = 0.035). The results highlight the power of spatial dissection of functionally accurate GBM INV and GBM TC cells in identifying novel drivers of GBM invasion and provide strong rationale to support the use of biologically accurate starting materials in understanding cancer invasion and metastasis., Using 6 highly invasive glioblastoma (GBM) PDOX models, this study isolates matching pairs of invasive (GBM INV ) and tumor core (GBM TC ) cells, demonstrates an elevated invasion capacity in GBM INV cells, identifies a novel miRNA signature (miRNA INV ) of GBM invasion, and discovers a commonly shared gene, KCNA1, from miRNA INV regulated genes that can be pharmacologically inhibited to block GBM invasion in vivo.

Optimizing the conduct of clinical trials for diffuse intrinsic pontine glioma (DIPG) involves use of consistent, objective disease assessments and standardized response criteria. The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee, an international panel of pediatric and adult neuro-oncologists, clinicians, radiologists, radiation oncologists, and neurosurgeons, was established to address unique challenges in assessing response in children with CNS tumors. A subcommittee of RAPNO was formed to specifically address response assessment in children and young adults with DIPG and to develop a consensus on recommendations for response assessment. Distinct issues related to the response assessment of DIPG include its definition and recent molecular classifications, dearth of imaging response data, the phenomena of pseudoprogression, and measuring response in the era of focal drug delivery. The committee has recommended response be assessed using magnetic resonance imaging (MRI) of brain and spine, neurologic examination, and use of supportive medication, i.e. steroids and anti-angiogenic agents. Clinical imaging standards and imaging quality control are defined. Unique recommendations for DIPG response include an eight-week response duration, a twenty-five percent decrease for partial response, and the distinction of pontine and extra-pontine response for trials that use focal drug delivery. The recommendations presented here represent an initial effort to uniformly collect and evaluate response assessment criteria; these recommendations can now be incorporated into clinical trials to assess feasibility and corroboration with patient outcomes.

BACKGROUND BMI-1 is highly expressed in DIPG. Downregulation leads to inhibition of cell proliferation, cell cycle signaling, self-renewal, telomerase expression, activity, and suppression of DIPG cell migration. Targeted inhibition of BMI-1 sensitizes DIPG cells to radiation and drug-induced DNA damage. PTC596 (formulated by PTC Therapeutics, Inc.) is a novel, orally available drug that inhibits microtubule polymerization, resulting in G2/M cell cycle arrest and post-translational modification of BMI-1 protein and reduced BMI-1 protein levels. OBJECTIVES: To estimate the maximum tolerated dose and describe dose limiting toxicities, pharmacokinetics and pharmacodynamics of PTC596 in children 3–21 years of age with newly diagnosed diffuse intrinsic pontine glioma and high-grade gliomas. METHODS PTC596 is administered twice per week orally during radiotherapy and as maintenance for up to two years. The starting dose of PTC596 was 200 mg/m2, with a subsequent dose level of 260mg/m2/dose. Pharmacokinetics are performed in Cycles 1 and 2. RESULTS This study is currently ongoing. Nine patients (7 with DIPG, 2 with HGG), 8 evaluable, have been enrolled. At dose level 1, 200 mg/m2, three evaluable patients were enrolled and experienced no DLTs. At dose level 2, among 5 evaluable patients, 2 experienced dose-limiting grade 4 neutropenia. PTC596 has been otherwise well tolerated. Five patients remain in Cycles 2–11. CONCLUSION This phase I trial is ongoing. PTC596 is tolerable at dose level 1. We are amending the protocol to introduce tablets that can be dissolved in liquid to allow enrollment of younger patients and those unable to swallow whole tablets.

To identify cellular and molecular changes that driver pediatric low grade glioma (PLGG) progression, we analyzed putative cancer stem cells (CSCs) and evaluated key biological changes in a novel and progressive patient-derived orthotopic xenograft (PDOX) mouse model. Flow cytometric analysis of 22 PLGGs detected CD133+ (

We evaluated circulating levels of immunosuppressive regulatory T cells (Tregs) and other lymphocyte subsets in patients with newly diagnosed medulloblastoma (MBL) undergoing surgery compared to a control cohort of patients undergo craniectomy for correction of Chiari malformation (CM) and further determined the impact of standard irradiation and chemotherapy on this cell population. Eligibility criteria for this biologic study included age 4–21 years, patients with CM undergoing craniectomy (as non-malignant surgical controls) and receiving dexamethasone for prevention of post-operative nausea, and those with newly diagnosed posterior fossa tumors (PFT) undergoing surgical resection and receiving dexamethasone as an anti-edema measure. Patients with confirmed MBL were also followed for longitudinal blood collection and analysis during radiotherapy and chemotherapy. A total of 54 subjects were enrolled on the study [22-CM, 18-MBL, and 14-PFT]. Absolute number and percentage Tregs (defined as CD4+CD25+FoxP3+CD127low/−) at baseline were decreased in MBL and PFT compared to CM [p = 0.0016 and 0.001, respectively). Patients with MBL and PFT had significantly reduced overall CD4+ T cell count (p = 0.0014 and 0.0054, respectively) compared to those with CM. Radiation and chemotherapy treatment in patients with MBL reduced overall lymphocyte counts; however, within the CD4+ T cell compartment, Tregs increased during treatment but gradually declined post therapy. Our results demonstrate that patients with MBL and PFT exhibit overall reduced CD4+ T cell counts at diagnosis but not an elevated proportion of Tregs. Standard treatment exacerbates lymphopenia in those with MBL while enriching for immunosuppressive Tregs over time.