CTNI-11. DEEP PHENOTYPING OF MULTI DRUG RESPONSES IN PATIENTS WITH GLIOMAS USING TUMOR-EMBEDDED MICRODEVICES

The lack of reliable predictive biomarkers to guide effective therapy is a major obstacle for the advancement of therapy for high grade gliomas (HGG), and particularly glioblastoma (GBM), one of the few cancers whose prognosis has not improved over the past several decades. With this pilot clinical trial we provide first in human evidence that drug-releasing intratumoral microdevices (IMD) can be safely and effectively used to obtain patient-specific, high throughput molecular and histopathological data to inform selection of drugs based on their observed antitumor effect in situ. The use of IMD is seamlessly integrated in standard surgical practice during tumor resection. None of the six enrolled patients experienced adverse events related to the IMD, and the retrieved tissue was usable for downstream analysis for 11 out of 12 retrieved specimens. Molecular analysis of the specimens provided, for the first time in humans, preliminary evidence of the robustness of the readout, with strong correlation between IMD analysis and clinic-radiological responses to temozolomide. From an investigational aspect, the amount of information obtained with IMD allows unprecedented characterization of tissue effects of any drugs of interest, within the physiological context of the intact tumor.

PATH-15. THE PROGNOSTIC IMPLICATION OF MGMT PROMOTER METHYLATION IN IDH-MUTANT GLIOMAS

BACKGROUND

MGMT promoter methylation in IDH-mutant gliomas was associated with improved survival in a recent study (PMID 35386566) but did not account for the updated WHO classification of CNS tumors. We evaluated the prognostic value of MGMT methylation in IDH-mutant gliomas incorporating the 2021 WHO classification.

METHODS

We retrospectively identified 431 patients with IDH-mutant gliomas treated at a single institution from 2010-2020. Kaplan-Meier method was used to estimate OS and PFS rates. Log-Rank test was used to evaluate differences between groups.

RESULTS

Median age was 36.2 years. MGMT promoter was methylated in 49.6%, unmethylated in 17.2%, partially methylated in 6.7%, and untested in 26.5%. Histological diagnosis was consistent with astrocytoma in 45.7%, oligodendroglioma in 33.9%, glioblastoma in 16.4%, and oligoastrocytoma in 4%. After accounting for 1p/19q and CDKN2A statuses, 190 patients had an integrated diagnosis of astrocytoma, grade 2 or 3; 94 had astrocytoma, grade 4; and 147 had oligodendroglioma, grade 2 or 3. There were 101 death events. Median OS was 33.36 years and median PFS was 5.67 years in MGMT methylated gliomas, compared to median OS of 12.54 years (p=0.0064) and median PFS of 3.91 years (p=0.0034) in unmethylated tumors. Upon univariate subgroup analysis, MGMT methylation was associated with significantly longer OS in histological astrocytomas, grade 2 or 4. However, when stratifying patients according to 2021 WHO classification of CNS tumors, there was no significant difference in OS between MGMT methylated and unmethylated astrocytomas or oligodendrogliomas, irrespective of WHO grade.

CONCLUSION

MGMT promoter methylation was associated with prolonged OS in histological astrocytomas, IDH-mutant. However, MGMT status did not impact survival after incorporating 2021 WHO classification of CNS tumors, suggesting that 1p/19q co-deletion and CDKN2A homozygous deletion are stronger prognostic factors in our cohort. The number of survival events was limited; larger datasets are required for more definitive conclusions.

EXTH-61. RPP25L IS A NOVEL DEPENDENCY IN GLIOBLASTOMAS WITH LOW RPP25 EXPRESSION

Genetic redundancy is a property whereby two or more genes encode for the same biological function, and inactivation of one redundant gene has little effect on the overall phenotype. In recent years, genetic redundancy has been exploited as a cancer therapeutic strategy, as individual paralogs of essential genes are occasionally lost in cancers because of genomic deletions. Inactivation of the non-deleted paralog can therefore be selectively toxic to tumor cells. To identify cancer cells that may become reliant on the non-methylated paralog of essential genes, we performed an in-silico analysis of the correlation between DNA methylation and genetic dependency across large scale CRISPR knockout screens that revealed novel paralog dependencies. Through this analysis, we identified glioblastoma cell lines with hypermethylation of the RPP25 promoter and with sensitivity to loss of RPP25L. RPP25 is a known structural component of RNAse P, a key enzyme involved in tRNA maturation. While the biological function of RPP25L is unknown, it has significant sequence homology to RPP25. We used CRISPR editing and CRISPR interference to inactivate RPP25L in a panel of glioblastoma cell lines and demonstrated that cell lines that do not express RPP25 (SF295, GB1, LN18) exhibit a rapid reduction in viability upon RPP25L loss, whereas cell lines with retained RPP25 expression or re-expressed RPP25 are not affected. RPP25L dependency is associated with a marked reduction in nascent polypeptide formation as determined by click chemistry. Lastly, we validated RPP25L dependency in glioblastoma patient-derived neurospheres with loss of RPP25 expression. These results indicate that RPP25L is a promising novel therapeutic target in glioblastomas with hypermethylation of the RPP25 promoter.

CTIM-17. EO2401 THERAPEUTIC VACCINE FOR PATIENTS WITH RECURRENT GLIOBLASTOMA: PHASE 1/2 ROSALIE STUDY (NCT04116658)

EO2401 includes microbial-derived, synthetically produced HLA-A2 restricted peptides with molecular mimicry to antigens (IL13Rα2, BIRC5 and FOXM1) upregulated in glioblastoma, and the CD4 helper peptide UCP2. Patients with glioblastoma at first progression received EO2401 (300µg/peptide, q2weeks x4 then q4weeks), EO2401+nivolumab (3mg/kg q2weeks), or E02401+nivolumab+bevacizumab (10mg/kg q2weeks). Cohort-1 included EO2401x2 then EO2401+nivolumab. EO2401+nivolumab was evaluated in Cohort-2a, as adjuvant treatment in Cohort-2b, and as neoadjuvant/adjuvant treatment in Cohort-2c. Cohort-3 assessed EO2401+nivolumab+bevacizumab. Part 1 included 40 patients (Cohort-1/3, Cohort-2a/23, Cohort-2b/3, Cohort-3/11). Part 2 allowed low-dose-bevacizumab (5mg/kg q2weeks) for symptomatic edema and enrolled 38 patients (Cohort-1/18, Cohort-2a/15, Cohort-2b/3; and recruiting Cohort-2c/2 target 6, Cohort-3/0 target 15).Safety assessment of part 1 showed EO2401+nivolumab+/-bevacizumab to be well tolerated with EO2401 associated toxicity limited to local administration site reactions (48%; all grade 1-2). The nivolumab-/bevacizumab-toxicity was consistent with historical single-agent data. Strong CD8 T cell ELISPOT responses against the 3 vaccine peptides and cross-reactivity against targeted antigens was demonstrated in the majority of evaluable patients. Immune response was confirmed with tetramer staining of specific CD8 either ex vivo or after in vitro stimulation. For part 1, median progression-free survival (mPFS), and median survival (mOS) for EO2401+nivolumab (Cohorts-1/2/2b, n=29 median follow-up [mFU] 14.0 months) were 1.8 and 10.6 months. Patients on EO2401+nivolumab+bevacizumab (n = 11 mFU 9.6 m) had mPFS 5.5 months and 9 patients alive 7-12.4 months. Objective Response Rate/Disease Control Rate for EO2401+nivolumab and EO2401+nivolumab+bevacizumab was 10%/34% and 55%/82%.Median treatment duration for Cohort-2a part 1 was 6.1 weeks (1/23 on treatment), while it was 10.0 weeks (8/15 on treatment) for Cohort-2a part 2. Overall, in part 2, 36% received low-dose-bevacizumab.EO2401 generated strong immune responses and was well tolerated. Addition of standard bevacizumab to EO2401+nivolumab improved PFS and tumor response. Symptom driven low-dose-bevacizumab supported longer treatment durations. Outcome of study part 2 will be presented.

BIOM-37. EVALUATION OF TEMPORALIS MUSCLE THICKNESS WITH TOXICITY AND SURVIVAL IN GLIOBLASTOMA PATIENTS RECEIVING CHEMORADIATION

BACKGROUND

Treatment-related toxicity is common in patients with glioblastoma (GBM) receiving chemotherapy and radiotherapy (RT). Temporalis muscle thickness (TMT) is a biomarker associated with sarcopenia and worse clinical outcomes in GBM, however its relation to treatment toxicity is less studied. We hypothesize that TMT may predict toxicity and survival in GBM patients.

METHODS

We reviewed consecutive patients with IDH-wildtype GBM treated from 2014-2019 at a single academic center. TMT was retrospectively assessed on T1-weighted MRI scans and dichotomized based upon previously validated sex-specific cutoff values. TMT was measured on baseline MRI scan at time of diagnosis. Cox regression multivariable analysis (MVA) was used to assess survival.

RESULTS

We evaluated 351 patients with median age of 60y (range 20-94) and median follow-up of 14mo. Most patients were male (59%), baseline KPS >70 (95%), and MGMT unmethylated (55%). After maximal safe resection, most patients received standard (90%) or hypofractionated (10%) RT with concurrent systemic therapy (89%). On MVA, baseline low TMT (HR 1.93, p=0.01), age >65y, baseline KPS, and MGMT-unmethylated status were associated with worse OS. On MVA, baseline low TMT (HR 1.95, p=0.01), age >65y, MGMT-unmethylated status, and discontinuing systemic therapy were associated with worse profession-free survival (PFS). 21 patients did not complete anticipated treatment course of chemoradiation and adjuvant systemic therapy due to toxicity, primarily thrombocytopenia, associated with worse OS on MVA (HR 1.99, p< 0.01). Low TMT was associated with higher risk of stopping treatment due to adverse events (OR 5.25, p< 0.01) independent of age, sex, extent of resection, RT dose on MVA.

CONCLUSION

Baseline low TMT was associated with worse PFS and OS, and it was associated with treatment interruption due to treatment toxicity in GBM patients. While further validation is needed, TMT may help identify patients who will benefit from aggressive symptom management or treatment deintensification.

DISP-14. DEFINING INTERVENTIONS AND METRICS TO IMPROVE DIVERSITY IN CNS CLINICAL TRIAL PARTICIPATION: A SNO AND RANO EFFORT

Despite major strides in cancer research, care, and therapy, these advances have not been equitable across race and ethnicity. Groups underrepresented in medicine (URM) are more likely to have inadequate preventive screening, increased delays in diagnosis, and poor representation in clinical trials. Notably, Black and Latino Americans represent 29% of the population but only reflect 8% of oncology clinical trial participants. Recent studies have shown that this disparity is also present in neuro-oncology as women, Black, and Latino Americans remain under-accrued in clinical trials. Brain tumor patients already face unique barriers to clinical trial enrollment and completion due to disease-specific conditions–such as impaired motor function, cognition, language deficits, and caregiver dependency–which pose additional difficulties in clinical trial consent, enrollment, and adherence. As part of this collaborative initiative, we evaluated the impact of how a lack of diversity in cancer research is detrimental to scientific discovery and propose interventions focused on improving URM engagement with clinical research. Recommendations include the creation of inclusive trial design at the onset, decreasing barriers to care, expanding trial eligibility, and equitable access to tumor profiling for personalized medical trials. Additionally, setting reasonable metrics and goals for accrual and engagement with patient and community stakeholders will ultimately help to diversify trial participants. Lastly, diversification and inclusion practices within the neuro-oncology workforce, including all personnel involved in clinical research, will help to minimize bias, promote concordant care, and assist with developing sustainable solutions. The diversification of participation in neuro-oncology clinical trials is imperative. The lack of diversity in clinical trials can contribute to improper generalizability of treatment efficacy, resulting in potentially harmful practices. Equitable access and inclusion of URM brain tumor patients will not only enhance research discoveries but will also result in improved patient care for all cancer patients.

CTNI-27. MULTI-CENTER, PHASE 2 STUDY EVALUATING THE PHARMACOKINETICS, SAFETY AND PRELIMINARY EFFICACY OF PAXALISIB IN NEWLY DIAGNOSED ADULT PATIENTS WITH UNMETHYLATED GLIOBLASTOMA (GBM)

NCT03522298 was an open-label, multi-center, 2-stage trial designed to establish the maximum tolerated dose (MTD) for once-daily (QD) paxalisib dosing (Stage 1), then evaluate pharmacokinetics(PK) and safety and explore efficacy (Stage 2). Eligible patients had undergone surgical resection and chemoradiotherapy (EORTC 26981–22981/NCIC CE3), had a life expectancy of ³ 12 weeks and were progression free before starting adjuvant paxalisib. Stage 1 used a standard 3 + 3 dose-escalation design to determine the MTD. Stage 2 was a two-arm, open-label, expansion cohort with patients randomized 1:1 to receive paxalisib at the MTD under fed or fasted conditions. In both stages, treatment comprised daily paxalisib administered in continuous 28-day cycles, until disease progression or unacceptable toxicity. Patients (n = 30; 70.0% males, mean age 58.5 years, mean 3.75 months since diagnosis) received paxalisib for a mean duration of 99 (9-833) days. In Stage 1 (n = 9), an MTD of 60mg was established on the dose-limiting toxicities of hyperglycemia (n = 1) and stomatitis (n = 1) at 75mg. Paxalisib was well-tolerated with no unexpected safety signals. Adverse events (37%) or progressive disease (33%) were the primary reasons for treatment discontinuation. At the MTD, the PK profile was linear and dose-proportional with no differences in Tmax and elimination half-life under fed/fasted conditions. Ten patients underwent FDG-PET imaging, 8 (80%) had a decrease in FDG uptake on Day 3 and/or Day 7 in Cycle 1; 4 (40%) had a metabolic partial response. From date of diagnosis, progression free survival (mRANO, investigator review) was 8.6 months and overall survival was 15.7 months. Primary study outcomes (1) MTD of 60mg was established for QD dosing and (2) PK and safety were consistent with prior clinical experience. Preliminary efficacy signals were encouraging and further investigation of paxalisib 60mg QD in newly diagnosed and recurrent GBM is ongoing in a pivotal trial (GBM AGILE, NCT03970447).

CTIM-25. NEOADJUVANT ANTI-PD1 IMMUNOTHERAPY FOR SURGICALLY ACCESSIBLE RECURRENT GLIOBLASTOMA: CLINICAL AND MOLECULAR OUTCOMES OF A STAGE 2 SINGLE-ARM EXPANSION COHORT

Glioblastoma is immunologically “cold”, with little clinical response to single-agent immune-checkpoint inhibitors (ICI). Our previous randomized study of neoadjuvant and adjuvant pembrolizumab versus adjuvant pembrolizumab in recurrent glioblastoma identified a molecular signature for ICI and suggested that neoadjuvant pembrolizumab improved survival (PMID30742122). We extended these original findings with a single-arm expansion cohort of glioblastoma patients at first or second relapse undergoing surgical resection for recurrent disease. Eligibility was identical to the original study. Patients receiving > 4mg dexamethasone, or with prior immunotherapy or anti-angiogenic therapy were excluded. The primary objective was to determine the effect of neoadjuvant pembrolizumab on cell cycle/cancer proliferation genes. Secondary objectives were PFS-6 and OS. Twenty-five patients received neoadjuvant pembrolizumab followed by tumor resection and adjuvant pembrolizumab until progression or unacceptable toxicity. The median age of participants was 60 years and median KPS was 90. Ninety-six percent of tumors were IDH wild-type and 48% were MGMT promoter methylated. Neoadjuvant pembrolizumab continued to induce alterations in the tumor microenvironment (T-cell/IFN upregulation, cell cycle downregulation; molecular responders (MR)), but the proportion of MR in this trial was 36% compared with 70% in the original treatment cohort. Median OS was 6.8 months. There were no CTCAE grade 4-5 AEs attributable to pembrolizumab. Further analysis of prognostic differences between stage 1 and 2 subjects is underway, as are additional immune and genotypic correlates to further define molecular changes induced by pembrolizumab. Anti-PD1 monotherapy triggers an intra-tumoral genetic signature associated with interferon-γ response and suppression of cell cycle/cancer proliferation in recurrent glioblastoma, though does not extend OS. This surgical window-of-opportunity paradigm allows for attribution of molecular effects to single agents. Future work will evaluate the differences in patient population, tumor characteristics, and address additional immune checkpoints and/or signaling pathways that can be targeted to augment the effectiveness of anti-PD1 in glioblastoma.

EXTH-11. TELOMERASE INHIBITION IS AN EFFECTIVE THERAPEUTIC STRATEGY IN TERT PROMOTER-MUTANT GLIOBLASTOMAS MODELS WITH LOW TUMOR BURDEN

Glioblastoma targeted therapeutics have been challenging to develop due to significant inter- and intra-tumoral heterogeneity. While many activated oncogenes in glioblastoma are subclonal, TERT promoter mutations commonly occur as clonal events and are found in up to 80% of IDH-wildtype glioblastomas. Given the high prevalence and clonal nature of TERT promoter mutations in glioblastoma, telomerase is considered a promising therapeutic target for this deadly cancer. Prior studies have validated this hypothesis, demonstrating that knockout of the transcription factor GABPA, which selectively binds to the mutant TERT promoter, as well as base editing-mediated correction of TERT promoter mutations, are selectively toxic to TERTpromoter mutant glioblastomas. However, an important limitation of this strategy is that cancer cell death does not occur immediately after telomerase ablation, but rather after several cell divisions required to reach critically short telomeres. We therefore hypothesize that telomerase inhibition would only be effective in low tumor burden glioblastomas. In this study, we used CRISPR interference to knock down TERT expression in TERT promoter-mutant glioblastoma cell lines and patient derived models. We then measured cell viability and assessed for features of telomere crisis by measuring telomere length and chromatin bridge formation. Lastly, we used a doxycycline inducible CRISPR interference system to knock down TERT expression in vivo early and late in the tumor formation process. We demonstrated that TERT promoter-mutant glioblastoma cells are sensitive to telomerase inhibition and undergo telomere crisis. In vivo, tumor formation is only inhibited when TERT knockdown is induced shortly after tumor implantation, but not when tumor burden is high. This work supports the idea that telomerase inhibition would be a suitable therapeutic strategy for glioblastoma patients with low tumor burden, for example in the adjuvant setting after surgical debulking and chemoradiation.

TMIC-10. IDENTIFICATION, VALIDATION AND BIOLOGICAL CHARACTERIZATION OF NOVEL GLIOBLASTOMA TUMOUR MICROENVIRONMENT SUBTYPES: IMPLICATIONS FOR PRECISION IMMUNOTHERAPY

New precision medicine therapies are urgently required for glioblastoma (GBM). However, to date, efforts to subtype patients based on molecular profiles, have failed to direct treatment strategies. We hypothesized that interrogation of the GBM tumor microenvironment (TME) and identification of novel TME-specific subtypes could inform new precision treatment strategies. To this end, a refined and validated microenvironment cell population (MCP)-counter method was applied to > 800 GBM patient tumours and validated by multiplex-immunohistochemistry. The MCP-counter deconvolution method interrogates the TME composition from transcriptomic data. Using this refined method, we classified the GLIOTRAIN(www.gliotrain.eu) IDHwt GBM cohort (n=123) into 3 novel clusters characterised by differences in TME composition and subsequently validated findings in the TCGA (n=69), CGGA (n=72) and DUKE (unpublished)(n=162) cohorts. TMEHigh tumours (30%) displayed elevated immune populations, functional orientation markers, immune checkpoint genes, and upregulated immunoregulatory pathways. Moreover, tertiary lymphoid structures were a feature of TMEHigh/mesenchymal+ patients. TMEMed (46%) tumours displayed heterogeneous immune populations and upregulated neuronal signalling pathways. TMELow (24%) tumours represented an ‘immune-desert’ group, high EGFR mutation frequency and upregulated EGFR signalling pathways. Longitudinal analysis of the GLASS cohort revealed TME-subtype transitions upon recurrence, influenced by TME composition changes. Finally, assessment of three GBM immunotherapy clinical trial cohorts revealed that TMEHigh patients treated with neo-adjuvant anti-PD1 have a significantly improved survival (P=0.04). Moreover, TMEHigh patients treated with anti-PD1 and an oncolytic virus (PVSRIPO) in the adjuvant setting, showed a trend towards improved survival (P=0.15 and P=0.056 respectively). Overall, we have established a novel TME-based classification system for application in intracranial malignancies. This system may be used to better inform a precision targeting approach in the brain tumour setting. For example, we hypothesise that patients bearing TMELow tumours may be amenable to neoadjuvant anti-TIM3 + EGFR inhibitor, TMEMed to anti-angiogenic immunotherapy, and TMEHigh patients to neoadjuvant anti-PD1 + anti-CTLA4.

BIOM-47. PREDICTORS OF SEIZURE AT ONSET USING A FUNCTIONAL VARIANT ANALYSIS OF TARGETED NEXT GENERATION SEQUENCING IN GBM

BACKGROUND

Adverse events (AE) including seizures cause significant morbidity in patients with GBM. We propose a novel method for assessing genomic predictors of AEs using results from a clinical targeted sequencing platform with variant function analysis.

METHODS

We identified 1,011 consecutive adult patients with newly diagnosed, histologically confirmed IDH-wildtype GBM with targeted exome NGS (Oncopanel) at Dana-Farber Cancer Institute from 2013-2019. Seizure at presentation was retrospectively identified as an AE. Biologic function (high loss, low loss, neutral, low gain and high gain) was assigned to variants using a three-tiered approach leveraging a genetic variant database (OncoKB), followed by analysis using protein prediction tools (Sift, Polyphen2 and Provean). Univariate logistic regression was performed for each relevant altered gene against the outcome of interest with false-discovery rate correction. Genes associated with seizure at presentation were included iteratively in a multivariate logistic model including other predictors of the outcome.

RESULTS

Our analysis included 470 GBM patients with 107 genes and 12 whole chromosome or arm level candidate variants covered by all versions of Oncopanel and with >10% alteration. Seizure at presentation occurred in 143/463 patients (31%) and was associated with EGFR amplification (high gain) (OR: 2.76, 95% CI: 1.4-5.3, p = 0.04). In a multivariate analysis (including age, sex, and preoperative tumor volume), EGFR amplification remained statistically significant (OR: 1.5, 95% CI: 1.0-2.2, p = 0.03).

CONCLUSION

Genomic biomarkers based on functional variant analysis of a routine clinical panel may predict adverse events in GBM. Seizure at presentation was independently associated with EGFR amplification. Our ongoing analysis will look at predictors of myelosuppression, thromboembolism, pseudoprogression and early progression using a similar approach. Identifying molecular risk factors could improve the management of patients through supportive care and consideration of prophylactic therapies.

NIMG-42. DURABLE OVERALL RESPONSE RATE (ORR) TARGETS FOR RECURRENT GLIOBLASTOMA (RGBM) CLINICAL TRIALS BASED ON THE HISTORIC ASSOCIATION BETWEEN ORR AND MEDIAN OVERALL SURVIVAL (MOS)

Durable overall response rate (ORR) remains a meaningful endpoint in recurrent GBM; however, the target ORR for single arm recurrent GBM trials has not been based on historic information or tied to patient outcomes. The current study reviewed past trials in recurrent GBM in order to judiciously define target ORRs for use in recurrent GBM trials. After reviewing 69 treatment arms comprising 4,971 patients, ORR was 6.1%[95% CI 4.23; 8.76%] for cytotoxic chemotherapies (ORR=7.59% for CCNU, 7.57% for TMZ, 0.64% for CPT-11, and 5.32% for other agents), 3.37% for biologic agents, 7.97% for immunotherapies (select trials), and 26.8% for anti-angiogenic agents. ORRs were significantly correlated with median overall survival (mOS) across chemotherapy (R2=0.4078, P< 0.0001), biologics (R2=0.4003, P=0.0003), and immunotherapy trials (R2=0.8994, P< 0.0001), but not anti-angiogenic agents (R2=0, P=0.8937). Pooling data from chemotherapy, biologics, and immunotherapy trials, a meta-analysis indicated a strong correlation between ORR and mOS (R2=0.3164, P< 0.0001; mOS[weeks]=0.6xORR+28.9), suggesting an ORR >20% results in an mOS of > 40.9 weeks, which is double the survival estimate of a treatment with ORR=0% and ≥ 2 months longer than treatments with ORR=5%. Assuming an ineffective therapy (control) has ORR=5%, a trial of 32 patients with a target ORR=20% leads to the 95% confidence interval higher than the control group. We conclude that single arm phase II studies in recurrent GBM with ≥ 32 patients should have a target ORR ≥ 20%. This was associated with a median OS of approximately 1 year. Importantly, durability of response should also be considered and was not assessed in the current meta-analysis.

CTNI-61. CLINICAL EFFICACY AND PREDICTIVE BIOMARKERS OF ONC201 IN H3K27M-MUTANT DIFFUSE MIDLINE GLIOMA

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.

CTIM-18. PHASE 2 STUDY OF PD-1 BLOCKADE WITH PEMBROLIZUMAB PLUS RE-IRRADIATION FOR RECURRENT GLIOBLASTOMA (RGBM) (NCT03661723)

Re-irradiation is therapeutically considered for select rGBM patients and may induce immunogenic cell death to stimulate anti-tumor immune responses. Our phase 2 study of re-irradiation with pembrolizumab among rGBM patients evaluated the efficacy and safety of this regimen.

METHODS

Adult rGBM patients with KPS ≥ 70, a maximum supratentorial tumor diameter of 6 cm who were on ≤ 2mg dexamethasone/day and were ≥ 6 months from initial conventional radiation therapy were eligible. Cohort A (bevacizumab [BEV]-naïve) had ≤ 2 prior progressions while cohort B (BEV-refractory) allowed unlimited progressions but only one on prior BEV. Re-irradiation included 35 Gy over 10 fractions to residual enhancing (cohort A) as well as enhancing + non-enhancing (cohort B) disease. Pembrolizumab was administered at 200 mg every three weeks beginning within one week of re-irradiation start. BEV was administered at 15 mg/kg every three weeks for cohort B only.

RESULTS

Sixty patients enrolled (n = 30 per cohort) with a median age of 61 years (range 20-76), 47% were female and 53% enrolled after 2 or more progressions. Grade 3 events deemed at least possibly related to study therapy in > one patient for cohort A included headache (n = 2) and for cohort B included elevated ALT (n = 2) and hypertension (n = 5). No grade 4 events occurred in more than single patients per cohort and no grade 5 events occurred. Median PFS and PFS-6 were 4.9 months (95% CI: 3.5, 5.6) and 26.0% (95% CI: 12.3%, 43.0%) for cohort A and 4.14 months (95% CI: 3.45, 5.42) and 16.9% (95% CI: 5.4, 33.7) for cohort B. Median survival for cohorts A and B were 11.5 months (95% CI: 9.6, 14.1) and 7.6 months (95% CI 5.5, 9.3), respectively.

CONCLUSIONS

Re-irradiation with pembrolizumab was overall well tolerated and achieved comparable efficacy to historical salvage therapy established with lomustine.

CTNI-26. SURGICAL WINDOW OF OPPORTUNITY TRIAL OF NAVTEMADLIN (KRT 232; AMG232) IN PATIENTS WITH RECURRENT GLIOBLASTOMA

BACKGROUND

KRT232 is an orally bioavailable, selective small molecule inhibitor of MDM2 that blocks the protein-protein interaction between MDM2 and p53. We performed a surgical window of opportunity trial of KRT232 in patients with recurrent GBM.

METHODS

The primary endpoint was to determine the tumor tissue concentration of KRT232. Prior to surgery, patients received KRT232 at either 120mg (n = 10, minimal dose that is consistently associated with alterations in serum MIC-1) or 240mg (n = 10; recommended phase 2 dose as monotherapy) for two days prior to surgical resection. Surgery was performed 3-6 hours following the last administration of KRT232. Tissue was analyzed for KRT232 concentration by LC/MS and for correlative studies. Participants with TP53 wild-type tumors were eligible to continue KRT232 following recovery from surgery at the RP2D of 240mg QD x 7 days q3weeks.

RESULTS

Twenty-one patients were enrolled from July 2018 to April 2020. One patient was deemed ineligible after surgery due to non-GBM tumor. Study met the prespecified criteria of target intra-tumor drug concentration of ≥ 25nM in contrast enhancing tissue in more than 50% of the patients in the 120mg cohort (67.1 ± 42.7nM in 8/10 patients) and 240mg (328.7 ± 468.1nM in 10/10 patients) cohort. Serum MIC-1 fold-changes from baseline (FCB) approximately 24 hours after a single dose of KRT232 were higher in the 240mg cohort (9.1 ± 4.1-FCB) than the 120mg cohort (3.6 ± 2.0-FCB). CDKN1A (p21), a downstream marker of p53, was significantly upregulated in analyzed participants whose GBM was TP53 wildtype, but not in TP53 mutant GBM or control samples (GBM treated with standard of care).

CONCLUSION

KRT232 at both 120mg and 240mg achieves adequate tumor tissue penetration and affects downstream pathways in TP53 wildtype GBM. The study has moved to Alliance to complete a phase 1 study of radiation + KRT232 in patients with newly diagnosed MGMT unmethylated GBM.

NIMG-59. EVALUATION OF THE RESPONSE ASSESSMENT CRITERIA IN NEWLY DIAGNOSED AND RECURRENT GLIOBLASTOMA

BACKGROUND

We sought to compare the Response Assessment in Neuro-Oncology (RANO), modified RANO (mRANO), and immunotherapy RANO (iRANO) in a large population of patients with newly diagnosed (nGBM) and recurrent (rGBM) glioblastoma.

METHODS

Bidimensional measurements of enhancing disease and FLAIR sequence evaluation were performed by two independent readers on brain MRIs of consecutive patients with IDH-wildtype nGBM and rGBM treated at a single institution. Discrepancies were evaluated by a third reader. Dates of disease progression (PD) were identified using RANO, mRANO, iRANO, and other response assessment criteria variations. Spearman’s correlations between PFS and OS were calculated using iterative multiple imputations for censored observations.

RESULTS

526 nGBM and 580 rGBM cases were included. Spearman’s correlations were not significantly different between RANO and mRANO in nGBM (0.69 [95% CI 0.62 to 0.75] vs. 0.67 [0.60, 0.73]) and rGBM (0.48 [0.40, 0.55] vs. 0.50 [0.42, 0.57]). Evaluation of FLAIR did not improve the correlation in patients who received antiangiogenic therapy. Acquisition of confirmation scans was associated with increased correlation only when PD was identified within 12 weeks of completion of radiation in nGBM. The use of the post-radiation MRI as a baseline was associated with increased correlation compared to use of the pre-radiation MRI in nGBM (0.67 [0.60, 0.73] vs. 0.53 [0.42, 0.62]). The correlation with iRANO was similar to RANO and mRANO among 98 patients with nGBM and 175 patients with rGBM who received immunotherapy.

CONCLUSIONS

RANO and mRANO demonstrated similar correlations between PFS and OS. The evaluation of FLAIR can be omitted, while confirmation scans were only beneficial in nGBM in the first 12 weeks after completion of radiation. There was a trend in favor of the post-radiation MRI as the baseline scan in nGBM. The use of iRANO criteria did not add a significant benefit in patients who received immunotherapy.

CTNI-38. UPDATE ON GBM AGILE: A GLOBAL, PHASE 2/3 ADAPTIVE PLATFORM TRIAL TO EVALUATE MULTIPLE REGIMENS IN NEWLY DIAGNOSED AND RECURRENT GLIOBLASTOMA

BACKGROUND

GBM AGILE (Glioblastoma Adaptive, Global, Innovative Learning Environment) is a biomarker based, multi-arm, international, seamless Phase 2/3 response adaptive randomization platform trial designed to rapidly identify experimental therapies that improve overall survival and confirm efficacious experimental therapies and associated biomarker signatures to support new drug approvals and registration. GBM AGILE is a collaboration between academic investigators, patient organizations and industry to support new drug applications for newly diagnosed and recurrent GBM.

METHODS

The primary objective of GBM AGILE is to identify therapies that effectively improve the overall survival in patients with ND or recurrent GBM. Bayesian response adaptive randomization is used within subtypes of the disease to assign participants to investigational arms based on their performance. Operating under a Master Protocol, GBM AGILE allows multiple drugs from different pharmaceutical/biotech companies to be evaluated simultaneously and/or over time against a common control. New experimental therapies are added as information about promising new drugs is identified while therapies are removed as they complete their evaluation. The master protocol/ trial infrastructure includes efficiencies through an adaptive trial design, shared control arm and operational processes to serve the goal of helping patients receive optimal care in a fast and efficient manner. GBM AGILE has screened over 1200 patients and enrollment rates are 3 to 4 times greater than traditional GBM trials, with active sites averaging 0.75 to 1 patients/sites/month. There are 41 active sites in the US, 4 active sites in Canada and 3 active sites in Europe with more sites anticipated to open across 5 countries in Europe. Expansion to China and Australia are under progress. Through the use of improved and flexible processes, GBM AGILE serves as a global trial that supports the efficient and rapid incorporation and evaluation of new experimental therapies for patients with GBM.Clinical trial information: NCT03970447.

CTIM-09. ENRICHED TCR/BCR VDJ REARRANGEMENTS CORRELATE WITH MRI AND SURVIVAL OUTCOMES IN PATIENTS WITH RECURRENT HIGH-GRADE GLIOMA TREATED WITH CAN-3110

BACKGROUND

CAN-3110 (rQNestin34.5v2) is an HSV-1 oncolytic viral immunotherapy with one copy of the inflammatory ICP34.5 gene under transcriptional control of the Nestin glioma-specific promoter. We completed a phase 1 sequential dose-escalation trial of CAN-3110 in recurrent high-grade glioma (rHGG).

METHODS

CAN-3110 was injected intratumorally starting at 1x106 plaque forming units (pfu) and dose- escalated by half log up to 1x1010 pfu in biopsy confirmed rHGG. An expansion cohort of 12 patients was then accrued at 1x109 pfus. Blood and post-injection rHGG were collected.

RESULTS

41 rHGG patients were treated (42 separate interventions): median age 56 years (range 27-74); 21 females, 20 males; median baseline KPS 90 (range 70-100). CAN-3110 administration was well-tolerated with no dose limiting toxicities. Median overall survival (mOS) was 11.9 months. Histologic and molecular analyses showed significantly increased T cell infiltration in post treatment samples with elevated T cell and/or B cell receptor (TCR/BCR) transcripts which correlated with patient survival (HR 0.26 for patients with elevated TCR/BCR rearrangements as compared to patients with low). Volumetric analyses of MRI suggest a trend between reduction in the relative change in tumor growth, TCR/BCRs enrichment and survival in CAN-3110 treated patients.

CLINICAL IMPLICATIONS

Administration of CAN-3110 into rHGG was well tolerated. OS of CAN-3110 treated subjects compare favorably to historical controls. The association of increased TCR/BCR transcripts with survival suggests that CAN-3110 induces T cell responses against rHGG, supporting further clinical development of CAN-3110 viral immunotherapy.

EXTH-19. OPTIMIZING MDM2 INHIBITION FOR THE TREATMENT OF GLIOBLASTOMA

Over 60% of glioblastomas retain wild-type p53, resulting in potential susceptibility to MDM2 inhibitors. These molecules disrupt the interaction between p53 and its negative regulator MDM2, allowing downstream pathway signaling and cell fate decisions including growth inhibition and death resulting from cellular stress. We have analyzed clinical samples from 10 patients newly diagnosed with glioblastoma multiforme (GBM) and treated with the MDM2 inhibitor KRT-232. We detected upregulation of CDKN1A transcript (a target of p53) in all p53 wild-type tumors (8 of 10), but not in p53-mutant tumors (2 of 10). In patient-derived cell lines, treatment with KRT-232 at the clinically detected concentration was only sufficient to stall tumor growth. Cell death via apoptosis can be achieved when MDM2 inhibition is combined with the chemotherapeutic agent temozolomide. As the effects and resistance mechanisms of MDM2 inhibition remain poorly understood in GBM, we have additionally performed genomic and transcriptomic analyses in patient-derived cell lines to better characterize sensitive tumors and identify putative biomarkers of drug response. Dose response curves and growth assays showed that tumors with inactivating p53 mutations are highly resistant to treatment, but those that retain wild-type p53 exhibit various degrees of drug sensitivity. This suggests that other factors, in addition to p53 mutational status, mediate response to MDM2 inhibition in gliomas. Transcriptional analyses of patient samples following drug treatment suggest that cell division, chromatin reorganization, cell differentiation state and immune response programs become deregulated under MDM2 inhibition and in the absence of p53-inactivating mutations.

RTID-01. ONC108: A RANDOMIZED PHASE 3 STUDY OF ONC201 IN PATIENTS WITH NEWLY DIAGNOSED H3 K27M-MUTANT DIFFUSE GLIOMA

BACKGROUND

H3 K27M-mutant diffuse midline glioma is a universally fatal malignancy primarily affecting children and young adults; while radiotherapy (RT) provides transient benefit, no effective systemic therapy is currently available. ONC201, a first-in-class imipridone, is an oral, blood-brain barrier penetrating, selective small molecule antagonist of dopamine receptor D2/3 (DRD2) and agonist of the mitochondrial protease ClpP. An integrated pooled analysis of objective response in ONC201-treated patients enrolled in one of five open-label trials has previously demonstrated efficacy in patients with recurrent disease. This phase 3 trial will be the first randomized, controlled study evaluating ONC201 in patients with H3 K27M-mutant disease.

METHODS

ONC108 is a randomized, double-blind, placebo-controlled, parallel-group, international Phase 3 study of ONC201 in patients with newly diagnosed H3 K27M-mutant diffuse glioma. Patients will be randomized to receive once-weekly ONC201 or placebo following standard frontline radiotherapy. Primary efficacy endpoints are overall survival (OS) and progression-free survival (PFS) in all participants; PFS will be assessed with the response assessment in neuro-oncology-high grade glioma by blind independent central review. Other objectives include assessments of safety, additional efficacy endpoints, clinical benefit, quality of life, pharmacokinetics, biomarkers, and healthcare resource utilization. Eligible patients will have histologically confirmed H3 K27M-mutant diffuse glioma, a Karnofsky/Lanksy performance status ≥ 70, and completed first-line radiotherapy. Eligibility will not be restricted based on age; however, patients must be ≥ 10 kg at time of randomization. Patients with a primary spinal tumor, diffuse intrinsic pontine glioma, leptomeningeal disease, or cerebrospinal fluid dissemination are not eligible.

EPID-11. NATIONAL EPIDEMIOLOGY AND SURVIVAL OF ADULT-TYPE DIFFUSE GLIOMAS IN THE UNITED STATES BY IDH, 1P/19Q, MGMT, AND WHO CNS GRADE

BACKGROUND

Histomolecularly-defined adult-type diffuse gliomas—including IDH-wildtype glioblastoma, IDH-mutant astrocytoma, and IDH-mutant 1p/19q-codeleted oligodendroglioma—were incorporated into U.S. cancer registry reporting for individuals with brain tumors beginning in 2018. We therefore assessed their epidemiology and overall survival (OS) patterns.

METHODS

Individuals histopathologically diagnosed with diffuse gliomas in 2018 and had brain molecular marker data were identified within the National Cancer Database; Surveillance, Epidemiology, and End Results Incidence; and Central Brain Tumor Registry of the United States databases. Age-adjusted incidence rates per 100,000 population with 95% confidence intervals (95CI) were estimated. OS was estimated using Kaplan Meier methods and stratified by WHO CNS grade, age, sex, tumor size, treatment, extent of resection, and MGMT promoter methylation. WHO CNS grade was additionally examined among individuals with IDH-wildtype diffuse astrocytic gliomas.

RESULTS

IDH-wildtype glioblastomas’ incidence rate was 1.74 (95CI = 1.69-1.78); as compared to 0.14 (95CI = 0.12-0.15), 0.15 (95CI = 0.14-0.16), and 0.07 (95CI: 0.06-0.08) WHO grade 2, 3, and 4 IDH-mutant astrocytomas. Irrespective of grade, IDH mutation prevalence was highest in adolescents & young adults, and IDH-mutant astrocytomas were more frequently MGMT promoter methylated. For OS analysis, 8,651 individuals were identified: one-year OS was 53.7% for WHO grade 4 IDH-wildtype glioblastomas (95CI = 52.5-54.9); 98.0% (95CI = 96.1-99.0), 92.4% (95CI = 89.6-94.5), and 76.3% (95CI = 70.1-81.3) for grade 2, 3, and 4 IDH-mutant astrocytomas; 97.9% (95CI = 95.9-98.9) and 94.4% (95CI = 90.9-96.6) for grade 2 and 3 IDH-mutant 1p/19q-codeleted oligodendrogliomas. Among IDH-wildtype glioblastomas, median OS was 17.1 months (95CI = 16.1-18.6) and 12.4 months (95CI = 12.0-12.9) for methylated and unmethylated MGMT promoters. IDH-wildtype diffuse astrocytic gliomas reported as WHO grade 2 or 3 demonstrated longer adjusted OS compared to grade 4 tumors (both p < 0.001). A significant association was not observed between chemotherapy and OS (HRadjusted 0.95, 95CI = 0.41-2.22, p = 0.91) for radiotherapy-treated grade 3 IDH-wildtype diffuse astrocytic gliomas.

CONCLUSIONS

Our findings provide the initial U.S. epidemiological estimates for histomolecularly-defined adult-type diffuse gliomas.

NCOG-20. BRAIN ATROPHY IN GLIOBLASTOMA PATIENTS FOLLOWING TREATMENT WITH CHEMORADIATION OR CHEMORADIATION WITH ANTI-ANGIOGENIC THERAPY IN NRG/RTOG 0825 PARTICIPANTS

BACKGROUND

The clinical trial NRG/RTOG 0825 sought to determine if the addition of bevacizumab to temozolomide and radiation improves survival in patients with newly diagnosed glioblastomas. Tertiary objectives included measuring the effect of the addition of bevacizumab to standard chemoradiation on neurocognitive function and quality of life. In this study, we describe brain atrophy changes as measured by ventricular volume expansion.

METHODS

We analyzed longitudinal MRI brain studies obtained from NRG/RTOG-0825. Volume changes in the contralesional (non-tumor) lateral ventricle were measured. Patients were included if they had either a scan at post operative (week 0) or post radiation baseline (week 10). Patients were also required to have at least one follow-up MRI brain scan 6 months or more from their baseline scans (at Week 0 or Week 10). Volumes were delineated using tissue segmentation in Slicer software.

RESULTS

177 patients were identified with eligible baseline scans at Week 0 and 162 patients at Week 10. For participants analyzed at 6 months from the Week 0 scan, mean ventricular volume increased by 54.70% (SEM: 3.21%, t = 6.41, p < 0.001, N = 135). For patients analyzed at 6 months from the Week 10 scan, mean ventricular volume increased by 31.89% (SEM: 2.52%, t = 3.96, p < 0.001, Nf117).

CONCLUSIONS

This study presents evidence of progressive brain volume loss in patients with glioblastoma treated with standard chemoradiation with or without anti-VEGF therapy. This is one of the largest sample sizes of volumetric analysis in real world patients with glioblastoma. These volume changes begin early in the disease course and may precede treatment. Next directions include correlating these volumetric changes with neurocognitive score changes, quality of life scores and analyzing these changes by treatment arm.

Melanoma central nervous system metastases: An update to approaches, challenges, and opportunities

Brain metastases are the most common brain malignancy. This review discusses the studies presented at the third annual meeting of the Melanoma Research Foundation in the context of other recent reports on the biology and treatment of melanoma brain metastases (MBM). Although symptomatic MBM patients were historically excluded from immunotherapy trials, efforts from clinicians and patient advocates have resulted in more inclusive and even dedicated clinical trials for MBM patients. The results of checkpoint inhibitor trials were discussed in conversation with current standards of care for MBM patients, including steroids, radiotherapy, and targeted therapy. Advances in the basic scientific understanding of MBM, including the role of astrocytes and metabolic adaptations to the brain microenvironment, are exposing new vulnerabilities which could be exploited for therapeutic purposes. Technical advances including single-cell omics and multiplex imaging are expanding our understanding of the MBM ecosystem and its response to therapy. This unprecedented level of spatial and temporal resolution is expected to dramatically advance the field in the coming years and render novel treatment approaches that might improve MBM patient outcomes.

Brain metastases: A Society for Neuro-Oncology (SNO) consensus review on current management and future directions

Brain metastases occur commonly in patients with advanced solid malignancies. Yet, less is known about brain metastases than cancer-related entities of similar incidence. Advances in oncologic care have heightened the importance of intracranial management. Here, in this consensus review supported by the Society for Neuro-Oncology (SNO), we review the landscape of brain metastases with particular attention to management approaches and ongoing efforts with potential to shape future paradigms of care. Each coauthor carried an area of expertise within the field of brain metastases and initially composed, edited, or reviewed their specific subsection of interest. After each subsection was accordingly written, multiple drafts of the manuscript were circulated to the entire list of authors for group discussion and feedback. The hope is that the these consensus guidelines will accelerate progress in the understanding and management of patients with brain metastases, and highlight key areas in need of further exploration that will lead to dedicated trials and other research investigations designed to advance the field.