Abstract Patients with H3K27M-mutated diffuse midline glioma (DMG) have no proven effective therapies beyond radiation. ONC201, a DRD2 antagonist and mitochondrial ClpP agonist, has shown promise in this population. Clinical and genetic variables associated with ONC201 response in H3K27M-mutant DMG continue to be investigated. A combined clinical and genetic study evaluated patients with H3K27M-DMG treated with single-agent ONC201 at the established phase 2 dose. Clinical outcomes of patients treated on two recently completed multi-site clinical studies (NCT03416530 and NCT03134131, n = 75) were compared with historical control data from patients with confirmed H3K27M-DMG (n = 391 total, n = 119 recurrent). Patients treated with ONC201 monotherapy following initial radiation, but prior to recurrence, demonstrated a median overall survival (OS) of 25.6 months from diagnosis and recurrent patients demonstrated a median OS of 16.2 months from recurrence, both of these more than doubling historical outcomes. Using a Cox model to correct for age, gender and tumor location, OS of ONC201-treated patients with H3K27M-mutant tumors remained significantly better than non-ONC201-treated historical controls (p = 0.0001). A survival and radiographic analysis based on tumor location, revealed stronger responses in thalamic patients. In patients with thalamic tumors treated after initial radiation (n = 16), median OS was not reached with median follow up of 22.1 months (historical control median OS of 12.5 months, n = 83, p = 0.0001). Significant correlations were found between baseline cerebral blood flow (CBF) on perfusion imaging and OS (Pearson’s r = 0.75, p = 0.003) and between nrCBF and PFS (r = 0.77, p = 0.002). Baseline tumor sequencing from treated patients (n = 20) demonstrates EGFR mutation (n = 3) and high EGFR expression as a marker of resistance and improved response in tumors with MAPK-pathway alterations (n = 5). In conclusion, ONC201 demonstrates unprecedented clinical and radiographic efficacy in H3K27M-mutant DMG with outcomes enriched in patients with thalamic tumors, treatment prior to recurrence, MAPK-pathway alterations, and patients with relatively high CBF.
e13540 Background: Mutations in the histone genes H3.3 and H3.1 are driver events in pediatric and adult gliomas and carry diagnostic and prognostic importance for tumors originating from midline structures. Patients with tumors affected by these mutations are notoriously difficult to treat, and the prevalence and molecular correlates of H3 mutations in a large glioma population have not been systematically reported. We aim to survey a large cohort of gliomas for H3-mutations. Methods: Consecutive gliomas submitted for tumor profiling at Caris Life Sciences from 2015- 2018 were analyzed. NextGen sequencing was done on 592 genes (NextSEQ Illumina); MGMT promoter methylation was tested by pyrosequencing; and EGFRvIII and gene fusions were tested by RNA-sequencing (ArcherDx FusionPlex). Results: Of the 1763 tumors analyzed, 41 harbored H3F3A alterations, including 33 with the K27M mutation (4 arose from the spinal cord, 1 from cerebellum, 1 from brain stem, 4 from thalamus, and 23 from brain, NOS). Eight G34R mutations were identified. A HIST1H3B-K27M was detected in a tumor from the brain stem. Overall, H3 mutations were more prevalent in pediatric tumors (8 of 26, 31%) than adult tumors (34 of 1737, 2%). All H3 mutations seen in pediatric tumors were from grade IV tumors. Among the 34 H3-mutated adult tumors, histology differed. There were 2 grade II tumors (diffuse astrocytoma), 1 low grade glioma from the spinal cord, 1 anaplastic ganglioglioma and 2 anaplastic astrocytomas. In the investigated cohort, H3-mutations were mutually exclusive of IDH1/2 mutations and EGFR alterations. Significantly higher mutation rates were seen in H3-mutated tumors for TP53 (69%. Vs. 37%), ATRX (46% vs. 24%), NF1 (23% vs. 12%) , PDGFRA (17% vs. 1%), FGFR1 (12% vs. 1%), FBXW7 (5% vs. 0), BLM (3% vs. 0) and TSC2 (2% vs.0) compared with H3-WT (p < 0.05). The H3-WT tumors were more enriched for MGMT-methylation (53% vs. 26%) and PTEN mutation (22% vs. 7%) (p < 0.05). In H3-mutated tumors that were MGMT-methylated (n = 10), most H3-mutations seen were G34R (n = 8) while K27M (n = 2) was largely exclusive. Conclusions: This survey of a large cohort of gliomas revealed a heterogeneous distribution of H3 mutations. The co-occurring molecular alterations seen in H3-mutated tumors further support the hypothesis that these tumors are a distinct molecular entity. By better characterizing these associations, we are closer to developing more insight into novel treatment strategies for a class of tumors with historically dismal prognosis.
Abstract Patients with diffuse midline glioma (DMG) harboring H3 K27M mutation rarely survive longer than two years and have no proven therapies following first-line radiation. ONC201, a bitopic DRD2 antagonist and allosteric ClpP agonist, has shown encouraging efficacy in early phase studies in H3 K27M-mutant DMG. In order to define response rates in H3 K27M DMG patients and to clarify the genomic, anatomic and molecular predictors of response, we performed an integrated pre-clinical and clinical analysis of ONC201 treatment. ONC201 was effective in intra-uterine electroporation (IUE)-generated H3 K27M-mutant murine glioma models with excellent CNS penetration and survival benefit. Patients with H3 K27M-mutant DMG treated with ONC201 on active clinical trials (n=50, 27 thalamic, 23 brainstem) showed an overall survival (OS) of 28.1 (range: 5.9–105) months from diagnosis (enrollment by 4/29/19, data cut-off 12/28/19), compared to historical median OS of 12 months. Median OS for non-recurrent patients has not been reached (n=16, median follow-up: 16.8 from diagnosis). For non-recurrent thalamic patients (n=8), median PFS is 20.1 (range: 9.3–27.6) months from diagnosis (median time on drug: 14.5 months). Best response for thalamic patients by RANO: 1 CR, 5 PR, 7 SD, 8 PD, 6 not reported. Decreased H3 K27M cell-free tumor DNA in plasma and CSF at 6 months correlated with long-term response. Baseline tumor gene expression profiling in patients treated with ONC201 (n=14) identified EGFR and the cortical developmental transcription factor FOXG1 as the strongest biomarkers of radiographic response to ONC201. Analysis of 541 ONC201-treated human cancer cell lines from DepMap, provided evidence for an EGFR-dependent ONC201 resistance mechanism. Analysis of 38 glioma cell lines further supports FOXG1 as a glioma-specific predictive biomarker of ONC201 response. The unprecedented survival results and radiographic responses to ONC201 in H3K27M DMG make a compelling case for later phase and combinatorial studies.
<p>Contains supplementary data and table titles and as well as supplementary figures with associated titles and legends. Fig. S1. Selection method for planned efficacy analysis of ONC201 in patients with H3K27MDMG. Fig. S2. Progression-free survival from diagnosis of trial patients with non-recurrent H3K27MDMG treated with ONC201. Fig. S3. Swimmers’ plot of ONC201 response by recurrence status, tumor location, and ONC201 trial. Fig. S4. ONC201 efficacy is independent of TP53 mutation status and chromosomal instability. Fig. S5. Cox proportional hazard regression to assess the effect of ONC201 after adjusting for confounders. Fig. S6. Survival of patients with H3K27M-DMG treated with ONC201 versus ONC201untreated historical controls. Fig. S7. Survival of patients with H3K27M-DMG treated with ONC201 versus ONC201untreated patients (PNOC003 or HERBY Phase II trials). Fig. S8. Molecular attributes of patients with H3K27M-DMG treated with ONC201. Fig. S9: Survival of H3K27M-DMG mice models treated with ONC201. Fig. S10. Integrative analysis of in vitro and human tumor metabolic gene expression in response to ONC201. Fig. S11. ONC201-mediated L2HG production increases H3K27me3 in H3K27M-DMG cells. Fig. S12. ONC201-induced increase in H3K27me3 is mediated by lactate dehydrogenase. Fig. S13. ONC201 alters genomic chromatin accessibility and H3K27ac distribution in H3K27M-DMG cells. Fig. S14. ONC201 increases global H3K27me3 in patient samples. Fig. S15. ONC201 does not cause hypermethylation leading to a glioma CpG island methylator phenotype.</p>
