Pediatric high-grade glioma (pHGG) is an incurable disease with a median survival of less than 6 months post-progression and no effective targeted therapy. PDGFRA is commonly altered in pHGG, but targeting PDGFRA in this disease has been unsuccessful, likely due to poor central nervous system (CNS) penetrance. Avapritinib is a novel and CNS-penetrant PDGFRA/KIT inhibitor that is FDA-approved for adults with unresectable or metastatic PDGFRA exon 18-mutant gastrointestinal stromal tumor (GIST) and is being studied in CNS tumors. We performed a pre-clinical and clinical assessment to determine the potential suitability of avapritinib therapy in PDGFRA-driven glioma. A multi-institutional cohort genetic analysis revealed PDGFRA amplification and mutation in 10.2% and 6.1% of pHGG, respectively. Additionally, PDGFRA expression in the absence of genetic events was significantly increased in H3K27-altered diffuse midline glioma (DMG) compared to H3-wildtype pHGG. Avapritinib performed well in: (i) mutant PDGFRA enzyme inhibition and wildtype inhibition at high dose, (ii) minimal off-target kinase inhibition, (iii) brain penetration (peak 10 µM), and (iv) proliferation/pPDGFRA reduction in PDGFRA-amplified and mutant pHGG cell lines. Avapritinib treatment in an aggressive PDX model of pHGG resulted in significant survival benefit. We pursued treatment of eight pediatric and young adult HGG patients with avapritinib across seven institutions. Patients were a mixture of local (N = 4) and metastatic disease (N = 4); all patients were post-initial radiation, with 7/8 having progressed on prior treatment. 7/8 patients had PDGFRA amplifications or mutations, and 7/8 had H3K27M mutations. Therapy was generally well-tolerated. 4/8 patients showed radiographic response to avapritinib, with one patient demonstrating complete response of target lesion and remains on therapy. Avapritinib levels in patients’ CSF and brain tumor tissue reached micromolar levels. These results demonstrate that avapritinib is a potent, selective, and CNS-penetrant PDGFRA/KIT inhibitor that is promising for further study in pHGG with relevant alterations.
H3K27M-mutated diffuse midline glioma (H3K27M DMG) are an almost universally fatal disease with a median survival of less than 6 months post progression and no effective therapy. PDGFRA-signaling has shown to promote and sustain a subset of oligodendrocyte precursor-like tumor cells that are responsible for tumor propagating potential and high proliferation rates. However, first attempts to target PDGFRA in adult glioblastoma with dasatinib/imatinib or pediatric refractory brain tumors with sunitinib were not successful. We report on the first experience in two patients receiving avapritinib, a highly potent, selective, brain penetrant PDGFRA/KIT inhibitor under a compassionate use program. Our first patient with spinal H3K27M DMG developed supratentorial metastases ten months after initial diagnosis. Molecular profiling revealed de novo PDGFRA and KIT amplifications and treatment with dasatinib was initiated. Due to disease progression and novel metastases, therapy was switched to avapritinib showing near complete resolution of the previously unirradiated frontal lesion with additional disease stabilization of other metastatic sites. Following re-resection and irradiation of progressing cerebellar lesions, the patient remains clinically stable on avapritinib therapy over 12 months. The second patient with diffuse intrinsic pontine glioma showed disease progression nine months after diagnosis and was treated with focal re-irradiation (30Gy). As the tumor harbored a PDGFRA R841del alteration, avapritinib was initiated seven weeks after radiation upon further tumor progression resulting in partial response. Pharmacokinetic sampling of cerebrospinal fluid (CSF) detected an increasing CSF/plasma ratio over time and up to 4 µM avapritinib in tumor tissue. Avapritinib CSF levels in both patients were distinctly higher than dasatinib levels. Avapritinib was generally well tolerated besides lower limb edema, elevated LDH and liver enzymes. Hence, effective CNS penetration of avapritinib at pharmacologically relevant brain tumor concentrations resulted in clinical response in two patients with rapidly progressive H3K27M DMG.
In the era of precision oncology, rapid molecular profiling as well as continuous monitoring of response to treatment or relapse are of increasing importance. We investigated digital droplet (dd)PCR for cerebrospinal fluid (CSF) derived cell-free (cf)DNA detection as a new method for rapid diagnosing of MYC/MYCN amplification in CNS malignancies - a patient collective with a dismal prognosis. Wet lab validated ddPCR probes for MYC were first investigated in D425 cells, a human medulloblastoma cell line with confirmed MYC amplification. Results of the methylation array of patients with stored CSF/serum samples (-80°C) were screened for patients with MYC/MYCN amplification. Five patients with medulloblastoma (group 3/4) and MYC-amplification and one patient with a diffuse glioma and MYCN-amplification were included in this study. ddPCR was performed on cfDNA isolated from CSF or serum. MYC amplification was detected by ddPCR in 28/33 (85%) CSF samples, with 4/5 negative samples being from one patient, and only one sample showing an unsuccessful analysis. MYC amplification was detectable in all longitudinal samples in 4/5 patients. 1/1 sample from the patient with MYCN amplific ation was positive in ddPCR. We were not able to detect MYC amplification in serum samples. Importantly, a turn-around time of only six hours from sample thawing/acquisition to result generation was easily achievable. Concluding, detection of MYC/MYCN-amplification in CSF by ddPCR is feasible in the clinical setting and allows for a rapid molecular diagnosis. MYC-amplification was constantly detectable in 4/5 patients with longitudinal CSF samples, which is in-line with the tumor burden our patients suffered from. Interestingly, the detectability in the patient’s serum was low, presumably due to the lower percentage of cell-free tumor (ct)DNA in serum when compared to CSF. Our results render ddPCR as a promising tool for bed-side molecular diagnosis and disease monitoring.
To provide an effective alternative to sedation during MRI examinations in pediatric cancer and NF1 patients, the aims of the present study were to (1) exploratively evaluate a behavioral MRI training program, to (2) investigate potential moderators, as well as to (3) assess the patients’ well-being over the course of the intervention. A total of n = 87 patients of the neuro-oncology unit (mean age: 6.83 years) underwent a two-step MRI preparation program, including training inside the scanner, and were recorded using a process-oriented screening. In addition to the retrospective analysis of all data, a subset of 17 patients were also analyzed prospectively. Overall, 80% of the children receiving MRI preparation underwent the MRI scan without sedation, making the success rate almost five times higher than that of a group of 18 children that opted out of the training program. Memory, attentional difficulties, and hyperactivity were significant neuropsychological moderators for successful scanning. The training was associated with favorable psychological well-being. These findings suggest that our MRI preparation could present an alternative to sedation of young patients undergoing MRI examinations as well as a promising tool for improving patients’ treatment-related well-being.
Background Mutations within the telomerase reverse transcriptase promoter (TERTprom) and isocitrate dehydrogenase (IDH) account for the most common genetic alterations in gliomas. Each of these mutations impact clinicopathologic diagnosis and course of diseases. While TERTprom mutations are frequently detected in glioblastoma, IHD mutations are assigned to astrocytoma of grade 2-4, thus mostly associated with better prognosis. In the era of precision oncology, molecular profiling and continuous monitoring of treatment response or relapse are of increasing importance. Accordingly, this study aims to detect TERTprom and IDH mutations in plasma-derived cell-free (cf)DNA of gliomas. The mutant allele frequencies (MAF) will be compared retrospectively to clinico-pathological parameters including extent of resection and tumor progression. Material and Methods Digital droplet PCR (ddPCR) analyses were performed using the QX200TM Digital Droplet System from BioRad. First, to evaluate probes for ddPCR, genomic DNA of several brain tumor cell models (n=6) and tumor tissue (n=1), as well as cfDNA of plasma (n=3) from samples with known TERTprom and IDH mutation status was investigated. For detection of IDH mutations, the unique assay ID dHSaMDV2010055 (IDH1p.R132H) and for TERTprom mutations the TaqMan dPCR Liquid Biopsy Assays for C228T (Hs000000092) and C250T (Hs000000093) were used. The results of ddPCR were analyzed with QuantaSoftTM software and the MAF was calculated Results To validate the detection method for IDH1R132H, we analyzed the MAF in one tissue and corresponding plasma sample of a confirmed IDH1-mutated astrocytoma. In addition, plasma from one astrocytoma grade 2-3 as well as from an IDH1-mutated glioblastoma was tested. Interestingly, both astrocytoma cases exhibited undetectable or very low MAF ranging from 0.1 to 1% in tissue as well as in plasma samples, while in plasma from the high-grade glioblastoma case, IDH1R132H was detected with a frequency of 1.9%. Due to the high GC content of the TERT promoter region, amplification steps are challenging. Accordingly, we first optimized ddPCR conditions for C228T and C250T probes by adding 7-deaza-2-deoxyguanosine-5-triphosphate (7-ddGTP) in varying concentrations to each ddPCR reaction. When using 4µM of 7-ddGTP per sample, a clear separation between mutant and wild-type droplets was reached, detecting MAF between 36-63% in DNA from cell culture models. Conclusion Within this pilot study we optimized the ddPCR method for the detection of IDH1R132H and TERTprom mutations in plasma and tissue samples. Subsequently, we hypothesize that these mutations are suitable liquid biomarkers correlating with extent of resection and tumor progression in gliomas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.