Kevin Bielamowicz

Pediatric-type diffuse high-grade gliomas (pHGGs) tend to have a dismal prognosis. Some of these gliomas feature alterations in genes such as ROS1, ALK, MET, and NTRK1–3. Despite development of targeted agents, the therapeutic application of these agents in pHGGs is still unclear. The aim of this retrospective case series is to report the outcome of two patients with pHGGs who were treated at Arkansas Children’s Hospital with targeted agents (Cabozantinib for a MET fusion in patient 1 and Lorlatinib for an ALK fusion in patient 2) with an initial, objective response followed by treatment resistance. Each diagnosis was determined based on histology, targeted tumor sequencing, and methylation profiling. In both cases, relapse occurred while on targeted inhibition. Recurrent tumor sequencing for patient 2 revealed a MET copy gain suggesting a mechanism of resistance in this patient. Pediatric high-grade gliomas with targetable alterations can show objective responses to pathway inhibition. Relapse after initial response may warrant additional surgical samples to identify new alterations which can lead to changes in therapy. Larger prospective cohorts are needed to study targeted agents in this population, and earlier integration of these agents may be beneficial.

Background: Novel therapies are needed for children, adolescents, and young adults with relapse/refractory leukemia or solid tumors. The proteasome inhibitor carfilzomib has demonstrated pre-clinical activity against several pediatric malignancies when used alone or in combination. Therefore, a multicenter dose-escalation phase 1 study of carfilzomib administered in combination with cyclophosphamide and etoposide was conducted. Methods: Study eligibility included an age of 6 months to 2/day, etoposide 100 mg/m²/day, and carfilzomib was administered every 28 days with growth factor support. The carfilzomib starting dose was 11 mg/m²/day, and dose escalation followed a rolling-six design, managed independently for each stratum. Dose-limiting toxicity (DLT) was assessed during the first cycle, and disease response was assessed after one cycle (stratum A) or two cycles (stratum B). Results: Thirty-eight patients were treated (14 in stratum A; 24 in stratum B). For stratum A, the maximum tolerated dose (MTD) for carfilzomib was 11 mg/m²/day. Three DLTs were observed: thrombocytopenia, pericarditis, and posterior reversible encephalopathy syndrome (PRES). Most patients received one cycle. For stratum B, an MTD was not reached. The highest dose level administered and recommended in phase 2 (RP2D) was 20 mg/m²/days 1–2 and 36 mg/m²/days 3–5 for cycle 1, then 36 mg/m² for days 1–5 of all subsequent cycles. There was a single DLT of PRES. A dose expansion for additional toxicity data was conducted. Overall, twenty patients received ≥ 2 cycles (range, 2–14). Conclusions: A 5-day schedule of carfilzomib/cyclophosphamide/etoposide was well-tolerated in patients with solid tumors. Patients with sarcomas benefited most, warranting further evaluation.

Background: Novel therapies are needed for children, adolescents, and young adults with relapse/refractory leukemia or solid tumors. The proteasome inhibitor carfilzomib has demonstrated pre-clinical activity against several pediatric malignancies when used alone or in combination. Therefore, a multicenter dose-escalation phase 1 study of car-filzomib administered in combination with cyclophosphamide and etoposide was con-ducted. Methods: Study eligibility included age 6 months to < 30 years with re-lapsed/refractory leukemia (stratum A) or relapsed/refractory non-CNS solid tumor (stratum B), Karnofsky/Lansky score ≥ 50, and adequate organ function. A 5-day regimen of cyclophosphamide 440 mg/m2/day, etoposide 100 mg/m2/day, and carfilzomib was administered every 28 days with growth factor support. The carfilzomib starting dose was 11 mg/m2/day and dose escalation followed a rolling-six design, managed inde-pendently for each stratum. Dose-limiting toxicity (DLT) was assessed during the first cycle and disease response was assessed after one cycle (stratum A) or two cycles (stra-tum B). Results: Thirty-eight patients were treated (14 in stratum A; 24 in stratum B). For stratum A, the maximum tolerated dose (MTD) for carfilzomib was 11 mg/m2/day. Three DLTs were observed: thrombocytopenia, pericarditis, and posterior reversible enceph-alopathy syndrome (PRES). Most patients received one cycle. For stratum B, an MTD was not reached. The highest dose level administered and recommended phase 2 dose was 20 mg/m2/days 1-2 and 36 mg/m2/days 3-5 for cycle 1, then 36 mg/m2 for days 1-5 of all subsequent cycles. There was a single DLT of PRES. A dose expansion for additional toxicity data was conducted. Overall, twenty patients received > 2 cycles (range, 2–14). Conclusions: A 5-day schedule of carfilzomib/cyclophosphamide/etoposide was well tolerated in patients with solid tumors. Patients with sarcomas benefited most, war-ranting further evaluation.

High-grade glial tumors represent the most morbid form of brain cancer

Purpose Central nervous system (CNS) embryonal tumors are a diverse group of malignant tumors typically affecting pediatric patients that recently have been better defined, and this paper describes evolution of a unique type of embryonal tumor at relapse. Methods Two pediatric patients with CNS embryonal tumors with EWSR1-PLAGL1 rearrangements treated at Arkansas Children’s Hospital with histopathologic and molecular data are described. Results These two patients at diagnosis were classified as CNS embryonal tumors with EWSR1-PLAGL1 rearrangements based on histologic appearance and molecular data. At relapse both patient’s disease was reclassified as atypical teratoid rhabdoid tumor (ATRT) based on loss of INI-1, presence of SMARCB1 alterations, and methylation profiling results. Conclusion CNS embryonal tumors with EWSR1-PLAGL1 rearrangements acquire or include a population of cells with SMARCB1 alterations that are the component that predominate at relapse, suggesting treatment aimed at this disease component at diagnosis should be considered.

Purpose of Review: This review will discuss the challenges facing chimeric antigen receptor (CAR)-T cell application for solid tumors and opportunities to overcome these obstacles. In addition, this review will examine therapies that are in development for pediatric solid tumors. Recent Findings: The similar success of CAR-T cell treatment for hematological malignancies has not been observed in solid tumors because of the hostile tumor microenvironment and tumor heterogeneity. Most strategies developed to combat these limitations emphasize combinatorial techniques that still require further testing. Preliminary results of multiple clinical trials, including GD2- and HER2-CAR-T cells, are encouraging but must be reproduced and validated on a larger scale. Summary: CAR-T cell application in solid tumors remains challenging, and most research is in development. Several clinical trials are ongoing for pediatric solid tumors. Early results are promising but demonstrate the need for CAR-T cell modification to prevent tumor recurrence.

Pharmacogenomics (PGx) is a growing field within precision medicine. Testing can help predict adverse events and sub-therapeutic response risks of certain medications. To date, the US FDA lists over 280 drugs which provide biomarker-based dosing guidance for adults and children. At Arkansas Children’s Hospital (ACH), a clinical PGx laboratory-based test was developed and implemented to provide guidance on 66 pediatric medications for genotype-guided dosing. This PGx test consists of 174 single nucleotide polymorphisms (SNPs) targeting 23 clinically actionable PGx genes or gene variants. Individual genotypes are processed to provide per-gene discrete results in star-allele and phenotype format. These results are then integrated into EPIC- EHR. Genomic indicators built into EPIC-EHR provide the source for clinical decision support (CDS) for clinicians, providing genotype-guided dosing.

Glioblastoma (GBM) is the most common primary malignant brain cancer, and is currently incurable. Chimeric Antigen Receptor (CAR) T-cells have shown promise in GBM treatment. While we have shown that combinatorial targeting of two glioma antigens offsets antigen escape and enhances T-cell effector functions, the inter-patient variability in surface antigen expression between patients hinders the clinical impact of targeting two antigen pairs. This study addresses targeting 3 antigens using a single CAR T-cell product for broader application. We analyzed the surface expression of 3 targetable glioma antigens (HER2, IL13Rα2 and EphA2) in 15 primary GBM samples. Accordingly, we created a trivalent T-cell product armed with three CAR molecules specific for these validated targets encoded by a single universal (U) tricistronic transgene (UCAR T-cells). Our data showed that co-targeting HER2, IL13Rα2 and EphA2 could overcome inter-patient variability by a tendency to capture near 100% of tumor cells in most tumors tested in this cohort. UCAR T-cells made from GBM patients’ blood uniformly expressed all three CAR molecules with distinct antigen specificity. UCAR T-cells mediated robust immune synapses with tumor targets forming more polarized microtubule organizing centers (MTOC) and exhibited improved cytotoxicity and cytokine release over best monospecific and bispecific CAR T-cells per patient tumor profile. Lastly, low doses of UCAR T-cells controlled established autologous GBM patient derived xenografts (PDX) and improved survival of treated animals. UCAR T-cells can overcome antigenic heterogeneity in GBM and lead to improved treatment outcomes.

Glioblastoma (GBM) is the most aggressive primary brain tumor. Combination therapy with surgery, radiation, and chemotherapy is not curative at present and carries a significant risk of toxicity. Advancements in the knowledge of tumor biology and tumor microenvironment have led to the development of novel targeted therapies for glioblastoma. In the past 15 years, a vast amount of pre-clinical data has been generated for glioblastoma immunotherapy. Translating these promising results into the clinic is, however, still an evolving process. Early clinical trials have demonstrated the feasibility and safety of several such approaches in patients with recurrent as well as newly diagnosed glioblastoma. Both passive as well as active immunotherapeutic modalities have also shown potential clinical benefit in at least a subset of these patients. This brief review discusses 'why' and 'how' various types of immunotherapies are being employed to treat glioblastoma.