Sunjong Ji

Patients with H3K27M-mutant diffuse midline glioma (DMG) have no proven effective therapies. ONC201 has recently demonstrated efficacy in these patients, but the mechanism behind this finding remains unknown. We assessed clinical outcomes, tumor sequencing, and tissue/cerebrospinal fluid (CSF) correlate samples from patients treated in two completed multisite clinical studies. Patients treated with ONC201 following initial radiation but prior to recurrence demonstrated a median overall survival of 21.7 months, whereas those treated after recurrence had a median overall survival of 9.3 months. Radiographic response was associated with increased expression of key tricarboxylic acid cycle-related genes in baseline tumor sequencing. ONC201 treatment increased 2-hydroxyglutarate levels in cultured H3K27M-DMG cells and patient CSF samples. This corresponded with increases in repressive H3K27me3 in vitro and in human tumors accompanied by epigenetic downregulation of cell cycle regulation and neuroglial differentiation genes. Overall, ONC201 demonstrates efficacy in H3K27M-DMG by disrupting integrated metabolic and epigenetic pathways and reversing pathognomonic H3K27me3 reduction. SIGNIFICANCE: The clinical, radiographic, and molecular analyses included in this study demonstrate the efficacy of ONC201 in H3K27M-mutant DMG and support ONC201 as the first monotherapy to improve outcomes in H3K27M-mutant DMG beyond radiation. Mechanistically, ONC201 disrupts integrated metabolic and epigenetic pathways and reverses pathognomonic H3K27me3 reduction. This article is featured in Selected Articles from This Issue, p. 2293.

BACKGROUND: Diffuse Midline Glioma (DMG) with the H3K27M mutation is a lethal childhood brain cancer, with patients rarely surviving 2 years from diagnosis. METHODS: We conducted a multi-site Phase 1 trial of the imipridone ONC201 for children with H3K27M-mutant glioma (NCT03416530). Patients enrolled on Arm D of the trial (n = 24) underwent serial lumbar puncture for cell-free tumor DNA (cf-tDNA) analysis and patients on all arms at the University of Michigan underwent serial plasma collection. We performed digital droplet polymerase chain reaction (ddPCR) analysis of cf-tDNA samples and compared variant allele fraction (VAF) to radiographic change (maximal 2D tumor area on MRI). RESULTS: Change in H3.3K27M VAF over time ("VAF delta") correlated with prolonged PFS in both CSF and plasma samples. Nonrecurrent patients that had a decrease in CSF VAF displayed a longer progression free survival (P = .0042). Decrease in plasma VAF displayed a similar trend (P = .085). VAF "spikes" (increase of at least 25%) preceded tumor progression in 8/16 cases (50%) in plasma and 5/11 cases (45.4%) in CSF. In individual cases, early reduction in H3K27M VAF predicted long-term clinical response (>1 year) to ONC201, and did not increase in cases of later-defined pseudo-progression. CONCLUSION: Our work demonstrates the feasibility and potential utility of serial cf-tDNA in both plasma and CSF of DMG patients to supplement radiographic monitoring. Patterns of change in H3K27M VAF over time demonstrate clinical utility in terms of predicting progression and sustained response and possible differentiation of pseudo-progression and pseudo-response.

Importance: Patient perceptions regarding the risks of obtaining in-person ophthalmic care during the coronavirus disease 2019 (COVID-19) pandemic may affect adherence to recommended treatment plans and influence visual outcomes. A deeper understanding of patient perspectives will inform strategies to optimize adherence with vision-preserving therapies. Objective: To evaluate perceptions of COVID-19 exposure risk and their association with appointment attendance among patients at high risk of both reversible and irreversible vision loss from lapses in care. Design, Setting, and Participants: This survey study included a nonvalidated telephone survey designed in April and May of 2020 and a retrospective medical record review conducted in parallel with survey administration from May 22 to August 18, 2020. Participants were recruited from 2 tertiary eye care centers (Emory Eye Center in Atlanta, Georgia, and W.K. Kellogg Eye Center in Ann Arbor, Michigan). The study included a random sample of patients with diagnoses of exudative age-related macular degeneration (AMD) or diabetic retinopathy (DR) who received an intravitreal injection between January 6 and March 13, 2020, and were scheduled for a second injection between March 13 and May 6, 2020. Main Outcomes and Measures: Association between perceptions regarding COVID-19 risks and loss to follow-up. Results: Of 1004 eligible patients, 423 (42%) were successfully contacted, and 348 (82%) agreed to participate (participants' mean [SD] age, 75 [12] years; 195 women [56%]; 287 White [82%] patients). Respondents had a mean (SD) of 2.7 (1.1) comorbidities associated with severe COVID-19, and 77 (22%) knew someone with COVID-19. Of all respondents, 163 (47%) were very concerned or moderately concerned about vision loss from missed treatments during the pandemic. Although 208 (60%) believed the COVID-19 virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), exposure at the eye clinic was extremely unlikely or unlikely, 49 (14%) believed it was extremely likely or likely. Seventy-eight participants (22%) were lost to follow-up. Concern regarding COVID-19 exposure during clinic visits (odds ratio [OR], 3.9; 95% CI, 1.8-8.4) and diagnosis of DR (vs AMD) (OR, 8.130; 95% CI, 3.367-20.408) were associated with an increase in likelihood of loss to follow-up. Conclusions and Relevance: Among patients at high risk for vision loss from lapses in care, many expressed concerns regarding the effect of the pandemic on their ability to receive timely care. Survey results suggest that fear of SARS-CoV-2 exposure was associated with a roughly 4-fold increase in the odds of patient loss to follow-up. These results support the potential importance of clearly conveying infection-control measures.

The humanized bone marrow-liver-thymus (BLT) mouse model harbors a nearly complete human immune system, therefore providing a powerful tool to study human immunology and immunotherapy. However, its application is greatly limited by the restricted supply of human CD34 + hematopoietic stem cells and fetal thymus tissues that are needed to generate these mice. The restriction is especially significant for the study of human immune systems with special genetic traits, such as certain human leukocyte antigen (HLA) haplotypes or monogene deficiencies. To circumvent this critical limitation, we have developed a method to quickly propagate established BLT mice. Through secondary transfer of bone marrow cells and human thymus implants from BLT mice into NSG (NOD/SCID/IL-2Rγ −/− ) recipient mice, we were able to expand one primary BLT mouse into a colony of 4–5 proBLT (propagated BLT) mice in 6–8 weeks. These proBLT mice reconstituted human immune cells, including T cells, at levels comparable to those of their primary BLT donor mouse. They also faithfully inherited the human immune cell genetic traits from their donor BLT mouse, such as the HLA-A2 haplotype that is of special interest for studying HLA-A2-restricted human T cell immunotherapies. Moreover, an EGFP reporter gene engineered into the human immune system was stably passed from BLT to proBLT mice, making proBLT mice suitable for studying human immune cell gene therapy. This method provides an opportunity to overcome a critical hurdle to utilizing the BLT humanized mouse model and enables its more widespread use as a valuable preclinical research tool.

Pediatric high-grade glioma (pHGG), including both diffuse midline glioma (DMG) and non-midline tumors, continues to be one of the deadliest oncologic diagnoses (both henceforth referred to as “pHGG”). Targeted therapy options aimed at key oncogenic receptor tyrosine kinase (RTK) drivers using small-molecule RTK inhibitors has been extensively studied, but the absence of proper in vivo modeling that recapitulate pHGG biology has historically been a research challenge. Thankfully, there have been many recent advances in animal modeling, including Cre-inducible transgenic models, as well as intra-uterine electroporation (IUE) models, which closely recapitulate the salient features of human pHGG tumors. Over 20% of pHGG have been found in sequencing studies to have alterations in platelet derived growth factor-alpha (PDGFRA), making growth factor modeling and inhibition via targeted tyrosine kinases a rich vein of interest. With commonly found alterations in other growth factors, including FGFR, EGFR, VEGFR as well as RET, MET, and ALK, it is necessary to model those receptors, as well. Here we review the recent advances in murine modeling and precision targeting of the most important RTKs in their clinical context. We additionally provide a review of current work in the field with several small molecule RTK inhibitors used in pre-clinical or clinical settings for treatment of pHGG.