Zaky, Wafik

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Pediatric Central Nervous System Cancers provide multidisciplinary diagnostic workup, staging, and treatment recommendations for diffuse high-grade gliomas and medulloblastomas in children and adolescents. This article summarizes the studies and panel discussion that serve as the rationale for comprehensive care recommendations included in the NCCN Guidelines for Pediatric Central Nervous System Cancers.

ABSTRACT Background Diffuse intrinsic pontine glioma (DIPG) carries a poor prognosis with a median survival of less than 12 months. Key molecular features include histone H3 mutation (K27M) and AKT pathway dysregulation. There is currently no curative treatment. Methods This is a Phase I study of vorinostat and temsirolimus in newly diagnosed (Stratum 1) and progressive (Stratum 2) DIPG (NCT02420613). The primary aims are to determine the safety, maximum tolerated dose (MTD), and toxicities. A modified 3 + 3 design was used to establish the MTD, where the first three patients were assigned the first dose level regardless of stratum. Stratum 1 received radiotherapy with vorinostat, followed by up to 10 cycles of vorinostat and temsirolimus. Stratum 2 received up to 12 cycles of vorinostat and temsirolimus. Vorinostat was administered at a fixed dose of 230 mg/m 2 daily on Days 1–8, and temsirolimus was administered on Days 1 and 8 at 25 mg/m 2 (Dose level 1) or 35 mg/m 2 (Dose level 2). Results Six patients were enrolled, three in each stratum. No dose‐limiting toxicity was observed, and most adverse effects were limited to Grades 1 or 2, including fatigue, myelosuppression, hyperlipidemia, hyperglycemia, elevated creatinine, nausea, vomiting, and headache. One patient experienced Grade 3 leukopenia. In the study, the MTD with acceptable toxicity was vorinostat 230 mg/m 2 and temsirolimus 35 mg/m 2 . Conclusions Overall, the combination of temsirolimus and vorinostat is well‐tolerated and safe, prompting the need for larger studies to investigate its efficacy.

Abstract BACKGROUND Diffuse intrinsic pontine glioma (DIPG) carries a poor prognosis with a median survival of less than 12 months. Histone mutation, K27M, and AKT pathway dysregulation play key roles in tumorigenesis. There is no curative treatment with radiation therapy, which currently remains the standard treatment. METHODS This is a phase I study of vorinostat and temsirolimus in newly diagnosed (stratum 1) and progressive (stratum 2) DIPG. The primary aims are to determine the safety, maximum tolerated dose, and toxicities (NCT02420613). Stratum 1 received radiation concurrently with vorinostat, followed by vorinostat and temsirolimus for up to 10 cycles. Stratum 2 received vorinostat and temsirolimus for up to 12 cycles. In stratum 1, vorinostat was administered daily at 230 mg/m2. The maintenance phase (both strata) included concurrent vorinostat 230 mg/m2 daily and temsirolimus 25 or 35 mg/m2 (Days 1 and 8). RESULTS Six patients were enrolled, three in each stratum. Three of the six patients had confirmed H3 K27M mutations. No dose-limiting toxicity was observed, and most adverse effects were limited to grades 1 or 2, including fatigue, nausea, vomiting, myelosuppression, hyperlipidemia, hyperglycemia, elevated liver enzymes, and creatinine. However, one patient experienced grade 3 leukopenia. Two of the three patients in stratum 1 showed evidence of radiographic response after the chemoradiation phase, of whom one patient had progression-free survival of 12 months and completed the 10 maintenance cycles. All patients at stratum 2 had disease progression with no radiographic response. CONCLUSION Overall, the combination of temsirolimus and vorinostat is well tolerated and safe, prompting the need for larger studies to investigate its efficacy. Due to the small number of patients, the study’s findings are limited, and trends in efficacy should be interpreted with caution.

Abstract Background This study evaluated the safety and pharmacokinetics (PK) of oral ONC201 administered twice-weekly on consecutive days (D1D2) in pediatric patients with newly diagnosed DIPG and/or recurrent/refractory H3 K27M glioma. Methods This phase 1 dose-escalation and expansion study included pediatric patients with H3 K27M-mutant glioma and/or DIPG following ≥1 line of therapy (NCT03416530). ONC201 was administered D1D2 at 3 dose levels (DLs; −1, 1, and 2). The actual administered dose within DLs was dependent on weight. Safety was assessed in all DLs; PK analysis was conducted in DL2. Patients receiving once-weekly ONC201 (D1) served as a PK comparator. Results Twelve patients received D1D2 ONC201 (DL1, n = 3; DL1, n = 3; DL2, n = 6); no dose-limiting toxicities or grade ≥3 treatment-related adverse events occurred. PK analyses at DL2 (D1-250 mg, n = 3; D1-625 mg, n = 3; D1D2-250 mg, n = 2; D1D2-625 mg, n = 2) demonstrated variability in Cmax, AUC0–24, and AUC0–48, with comparable exposures across weight groups. No accumulation occurred with D1D2 dosing; the majority of ONC201 cleared before administration of the second dose. Cmax was variable between groups but did not appear to increase with D1D2 dosing. AUC0–48 was greater with D1D2 than once-weekly. Conclusions ONC201 given D1D2 was well tolerated at all DLs and associated with greater AUC0–48.

Abstract Atypical Teratoid/Rhabdoid Tumors (ATRTs) are malignant tumors of the central nervous system in children. They are almost universally characterized by genetic loss of SWI/SNF Related, Matrix Associated, Actin Dependent Regulator of Chromatin Subfamily member B1 (SMARCB1) - a core subunit of the ATP-dependent SWI/SNF chromatin remodeling complex, and dysregulation of lineage restricted enhancers. Here, we show that tumor subgroup-specific upregulation of a distant member of the transforming growth factor-β (TGF-β), bone morphogenic factor (BMF) family of proteins drives insensitivity to NK-mediated cytolysis in vitro and in vivo. Mechanistically, subgroup-specific loss of chromatin occupancy by the RE1 Silencing Transcription Factor (REST) to its consensus RE1 motif, allowed deposition of enhancer-specific histone H3 lysine4 (K4) mono-methylation and histone H3K27 acetylation marks to activate an enhancer-promoter interaction. Restoration of REST binding or BET-domain inhibition resulted in a significant reduction in the enhancer marks and enhancer-promoter interaction and involved histone H3K27me3 deposition at the REST binding site, to facilitate gene silencing and sensitization of ATRTs to NK-mediated cytolysis. Thus, our study has identified a novel function for REST as a modulator of tumor-intrinsic enhancer activity and tumor-extrinsic immune microenvironment. Of equal significance, we highlight a role of REST in recruiting the polycomb repressive complex-2 (PRC2) in gene silencing in ATRTs.

Abstract Background Medulloblastoma in adults is rare and treatment decisions are largely driven from pediatric literature. We sought to characterize recurrent medulloblastoma in adults. Methods From a single-institution dataset of 200 adult patients diagnosed with medulloblastoma during 1978–2017, those with recurrence were analyzed for clinical features, treatment, and outcome. Results Of the 200 patients, 82 (41%) with median age of 29 years (18–59) had recurrence after a median follow-up time of 8.4 years (95% CI = 7.1, 10.3). Of these, 30 (37%) were standard-risk, 31 (38%) were high-risk, and 21 (26%) had unknown-risk diseases at the time of initial diagnosis. Forty-eight (58%) presented with recurrence outside the posterior fossa, of whom 35 (43%) had distant recurrence only. Median Progression-free survival (PFS) and OS from initial surgery were 33.5 and 62.4 months, respectively. Neither PFS nor OS from initial diagnosis differed between the standard-risk and high-risk groups in those who experience recurrence (P = .505 and .463, respectively). Median OS from first recurrence was 20.3 months, also with no difference between the standard-risk and high-risk groups (P = .518). Recurrences were treated with combinations of re-resection (20 patients; 25%), systemic chemotherapy (61 patients; 76%), radiation (29 patients; 36%), stem cell transplant (6 patients; 8%), and intrathecal chemotherapy (4 patients; 5%). Patients who received radiation at recurrence had better OS (32.9 months) than those who did not (19.2 months) (P = .034). Conclusions Recurrent medulloblastoma in adults has a poor prognosis irrespective of initial risk stratification. Recurrence commonly arises outside the posterior fossa years after initial diagnosis.

Abstract Background ONC201, a dopamine receptor D2 (DRD2) antagonist and caseinolytic protease P (ClpP) agonist, has induced durable tumor regressions in adults with recurrent H3 K27M-mutant glioma. We report results from the first phase I pediatric clinical trial of ONC201. Methods This open-label, multi-center clinical trial (NCT03416530) of ONC201 for pediatric H3 K27M-mutant diffuse midline glioma (DMG) or diffuse intrinsic pontine glioma (DIPG) employed a dose-escalation and dose-expansion design. The primary endpoint was the recommended phase II dose (RP2D). A standard 3 + 3 dose escalation design was implemented. The target dose was the previously established adult RP2D (625 mg), scaled by body weight. Twenty-two pediatric patients with DMG/DIPG were treated following radiation; prior lines of systemic therapy in addition to radiation were permitted providing sufficient time had elapsed prior to study treatment. Results The RP2D of orally administered ONC201 in this pediatric population was determined to be the adult RP2D (625 mg), scaled by body weight; no dose-limiting toxicities (DLT) occurred. The most frequent treatment-emergent Grade 1-2 AEs were headache, nausea, vomiting, dizziness and increase in alanine aminotransferase. Pharmacokinetics were determined following the first dose: T1/2, 8.4 h; Tmax, 2.1 h; Cmax, 2.3 µg/mL; AUC0-tlast, 16.4 hµg/mL. Median duration of treatment was 20.6 weeks (range 5.1-129). Five (22.7%) patients, all of whom initiated ONC201 following radiation and prior to recurrence, were alive at 2 years from diagnosis. Conclusions The adult 625 mg weekly RP2D of ONC201 scaled by body weight was well tolerated. Further investigation of ONC201 for DMG/DIPG is warranted.

Abstract Background Brainstem toxicity after radiation therapy (RT) is a devastating complication and a particular concern with proton radiation (PBT). We investigated the incidence and clinical correlates of brainstem injury in pediatric brain tumors treated with PBT. Methods All patients <21 years with brain tumors treated with PBT at our institution from 2007–2019, with a brainstem Dmean >30 Gy and/or Dmax >50.4 Gy were included. Symptomatic brainstem injury (SBI) was defined as any new or progressive cranial neuropathy, ataxia, and/or motor weakness with corresponding radiographic abnormality within brainstem. Results A total of 595 patients were reviewed and 468 (medulloblastoma = 200, gliomas = 114, ependymoma = 87, ATRT = 43) met our inclusion criteria. Median age at RT was 6.3 years and median prescribed RT dose was 54Gy [RBE]. Fifteen patients (3.2%) developed SBI, at a median of 4 months after RT. Grades 2, 3, 4, and 5 brainstem injuries were seen in 7, 5, 1, and 2 patients respectively. Asymptomatic radiographic changes were seen in 51 patients (10.9%). SBI was significantly higher in patients with age ≤3 years, female gender, ATRT histology, patients receiving high-dose chemotherapy with stem cell rescue, and those not receiving craniospinal irradiation. Patients with SBI had a significantly higher V50–52. In 2014, our institution started using strict brainstem dose constraints (Dmax ≤57 Gy, Dmean ≤52.4 Gy, and V54≤10%). There was a trend towards decrease in SBI from 4.4% (2007-2013) to 1.5% (2014–2019) (P = .089) without affecting survival. Conclusion Our results suggest a low risk of SBI after PBT for pediatric brain tumors, comparable to photon therapy. A lower risk was seen after adopting strict brainstem dose constraints.

Abstract Diffuse Intrinsic Pontine Glioma (DIPG) is an incurable pediatric brain tumor. An almost ubiquitous dominant negative mutation at lysine (K)-27 in genes encoding histone genes HIST1H3B and H3F3A found in patient tumors is a driver of DIPG development. ONC201, a small molecule DRD2 antagonist and ClpP agonist developed by Chimerix Inc, targets the unfolded protein response (UPR) and integrated stress response (ISR) signaling. It is under clinical investigation in patients with recurrent H3K27M DMGs. In adults, single agent studies have shown durable objective responses when administered orally. A multi-arm, non-randomized multi-institutional Phase I clinical trial (NCT03416530) for pediatric patients with H3K27M DMGs is open and accruing. Preliminary results suggest that the drug has a favorable safety profile and holds promise for patients with DIPGs and other midline gliomas. However, the mechanism of action of ONC201 against DIPGs warrants further study. Here, we show that ONC201 is cytotoxic to DIPGs in vitro and in vivo. RNA Seq analyses revealed cell context specific deployment of PERK-activated UPR and calcium signaling-associated RON tyrosine kinase-macrophage stimulating protein (MSP) signaling in DIPGs. Single cell proteomic assays revealed substantial heterogeneity in the sensitivity of DIPG cells to ONC201, and identified stem-like sub-populations of H3K27M DIPGs with intrinsic insensitivity to the drug. ONC201 treatment, which induces cellular stress, also sensitized DIPG cells to cytolytic activity by ex-vivo expanded and activated innate immune cells, in vitro. Ongoing in vivo experiments are expected to support a novel investigational study in patients with midline gliomas.

Abstract ONC201, an anti-cancer DRD2 antagonist and ClpP agonist, is in Phase II trials for adult H3 K27M-mutant diffuse midline gliomas. The recommended phase 2 dose (RP2D) of 625mg ONC201 once a week has been established as a biologically active dose that is well tolerated in adult and pediatric populations. Radiographic regressions with single agent ONC201 have been reported in recurrent H3 K27M-mutant glioma patients. In another study, twice/week dosing was explored in adult patients and deemed to be safe (no DLTs observed). This warranted exploration of twice/week dosing in pediatric patients and will be discussed in this presentation. This multi-arm, dose-escalation and dose-expansion trial (ONC014; NCT03416530) determined the pediatric RP2D of ONC201 administered once per week and twice per week on two consecutive days. ONC201 was orally administered and scaled by body weight. Dose escalation was performed by a 3 + 3 design beginning with two 125mg capsules less than the adult RP2D equivalent. Twelve children (8 females; 4 males) with H3 K27M-mutant gliomas (pons: 8; thalamus: 2; spinal cord: 2) aged 4-19 years have been treated post-radiation: 3 at dose level -1; 3 at dose level 1; 6 as part of the dose expansion cohort on dose level 2. Median KPS was 90 (range 70-100). One treatment cycle was 21 days (6 doses), which also defined the DLT window. Patients were on-treatment for a median length of 4 cycles (range: 2-11). Twice weekly dosing of ONC201 was tolerated well, as observed with weekly dosing, with no instance of DLT. A total of 4 SAEs were reported, none of which were related to the study drug. The most common AEs (regardless of relatedness) included headache, facial nerve disorder, abducens nerve disorder, nausea, fatigue and ataxia. Additional safety data, PK, and clinical outcomes from this arm will be reported.