Activity of a first-in-class oral HIF2-alpha inhibitor, PT2385, in patients with first recurrence of glioblastoma

INTRODUCTION

Hypoxia inducible factor 2-alpha (HIF2α) mediates cellular responses to hypoxia and is over-expressed in glioblastoma (GBM). PT2385 is an oral HIF2α inhibitor with in vivo activity against GBM.

METHODS

A two-stage single-arm open-label phase II study of adults with GBM at first recurrence following chemoradiation with measurable disease was conducted through the Adult Brain Tumor Consortium. PT2385 was administered at the phase II dose (800 mg b.i.d.). The primary outcome was objective radiographic response (ORR = complete response + partial response, CR + PR); secondary outcomes were safety, overall survival (OS), and progression free survival (PFS). Exploratory objectives included pharmacokinetics (day 15 Cmin), pharmacodynamics (erythropoietin, vascular endothelial growth factor), and pH-weighted amine- chemical exchange saturation transfer (CEST) MRI to quantify tumor acidity at baseline and explore associations with drug response. Stage 1 enrolled 24 patients with early stoppage for ≤ 1 ORR.

RESULTS

Of the 24 enrolled patients, median age was 62.1 (38.7-76.7) years, median KPS 80, MGMT promoter was methylated in 46% of tumors. PT2385 was well tolerated. Grade ≥ 3 drug-related adverse events were hypoxia (n = 2), hyponatremia (2), lymphopenia (1), anemia (1), and hyperglycemia (1). No objective radiographic responses were observed; median PFS was 1.8 months (95% CI 1.6-2.5) and OS was 7.7 months (95% CI 4.9-12.6). Drug exposure varied widely and did not differ by corticosteroid use (p = 0.12), antiepileptics (p = 0.09), or sex (p = 0.37). Patients with high systemic exposure had significantly longer PFS (6.7 vs 1.8 months, p = 0.009). Baseline acidity by pH-weighted CEST MRI correlated significantly with treatment duration (R2 = 0.49, p = 0.017). Non-enhancing infiltrative disease with high acidity gave rise to recurrence.

CONCLUSIONS

PT2385 monotherapy had limited activity in first recurrent GBM. Drug exposure was variable. Signals of activity were observed in GBM patients with high systemic exposure and acidic lesions on CEST imaging. A second-generation HIF2α inhibitor is being studied.

DDEL-11. DETERMINING THE DOSE OF REGADENOSON MOST LIKELY TO TRANSIENTLY ALTER THE INTEGRITY OF THE BLOOD-BRAIN BARRIER IN PATIENTS WITH GLIOMAS

BACKGROUND

The blood brain barrier (BBB) is a major obstacle to the delivery of chemotherapy to the CNS. Regadenoson is an FDA approved adenosine A2 agonist used for cardiac stress tests. In murine models, it transiently increases BBB permeability to a 70KD dextran. This multi-institutional, NIH funded, Adult Brain Tumor Consortium trial was designed to discover a dose of regadenoson that substantially increases vascular permeability in normal appearing white matter (NAWM) where drug delivery is particularly challenging.

METHODS

Adults ages 18-45 with supratentorial gliomas at low-risk for regadenoson complications were recruited (n = 7). One patient was treated at each of seven dose levels (from 0.05 to 1.4 mg) that are known to be safe in humans. The primary outcome measure is change in vascular permeability via dynamic contrast enhanced (DCE) perfusion MRI estimates of Ktrans. The primary outcome measure was a 10-fold higher Ktrans in NAWM than reported in literature (Ktrans > 0.04 min-1). Contrast-enhanced T1 subtraction map estimates of change in contrast enhancement and other measurements in normal brain and non-enhancing tumor were quantified.

RESULTS

Ktrans measures in NAWM averaged 1.13x10-3 ± 0.44x10-3 (SEM) min-1, lower than the target of 0.04 min-1. Normalized, contrast enhanced T1-weighted MR signal intensity in NAWM increased an average of 74.0 ± 22.4% min-1 (SEM) min-1, which was significantly higher than zero (P = 0.0163). Data available from this limited sample failed to meet the target goal in Ktrans increase or change in contrast enhancing signal intensity.

CONCLUSION

Administration of regadenoson at seven different doses did not significantly elevate Ktrans for gadolinium in NAWM. This data suggests that single doses of regadenoson are unlikely to substantially increase the delivery of therapeutic agents in non-enhancing brain tissue. This trial design is appropriate for further human testing of other regadenoson schedules and other novel approaches aimed at transiently modifying BBB permeability.

NIMG-34. QUANTIFICATION OF GLYCOLYTIC FLUX REDUCTION IN RECURRENT GLIOBLASTOMA AFTER EGFR INHIBITION USING MOLECULAR MR-PET

In recently published work, we demonstrated that acute inhibition of the EGFR – the most frequently altered oncogene in GBM – can rapidly reduce glycolysis in a subset of GBM. To quantify this effect, we propose a new combination metabolic MR-PET imaging biomarker that combines 18F-FDG PET, DSC perfusion MRI, diffusion MRI, and pH- and oxygen-sensitive amine CEST-SAGE-EPI. Specifically, this “glycolytic index” or GI, can be defined as elevated glucose uptake (18F-FDG standard uptake value), elevated tumor acidity (MTRasym@3ppm), and lower oxygen utilization (relative cerebral metabolic rate of oxygen, rCMRO2, defined as R2’ x rCBF/rCBV from oxygen-sensitive SAGE-EPI and DSC perfusion), normalized to cell density (using ADC from diffusion MRI). In the current study, we explored the use of Tagrisso® (Osimertinib or AZD9291), which has very high brain to plasma ratios (> 1) and has proven effective in CNS metastasis of EGFR mutant lung cancer, as a potential treatment for EGFR amplified recurrent GBM. We have conducted a clinical trial (NCT03732352) to determine whether we observe similar metabolic imaging changes in EGFR mutated or amplified recurrent glioblastoma patients after treatment with osimertinib. Consistent with prior in vitro and in vivo results, treated patients exhibited a reduced glycolytic flux as indicated by reduction in 18F-FDG PET uptake (-3% change in SUV), tumor acidity (-19% change in MTRasym@3ppm) on pH-weighted CEST MRI, and glycolytic index (GI) (-25% change) in EGFR amplified recurrent GBM within 24 hours of treatment. Preliminary data suggests early change in GI correlates with and predicts both PFS (Pearson correlation, R2=0.3463, P=0.0441; Log-rank, P=0.0467) and OS (R2=0.6368, P=0.0019; Log-rank, P=0.0192). These preliminary data establish the scientific premise that a “glycolytic index” created using 18F-FDG PET, DSC perfusion, diffusion MRI, and pH- and oxygen-weighted amine CEST-SAGE-EPI may be an important tool for quantifying and visualizing glycolytic flux in GBM.

QOL-12. “I’M JUST LIKE A BASKET FULL OF PROBLEMS”: QUALITATIVE STUDY OF COGNITIVE DYSFUNCTION AND QUALITY OF LIFE IN GLIOMA SURVIVORS

For glioma survivors, cognitive impairment can be a central determinant of quality of life, but we need better understanding of their unique challenges and supportive care needs. In this qualitative study, we aimed to explore the post-treatment experiences of cognitive and functional challenges and their impact on quality of life from the perspectives of glioma survivors. Glioma survivors in an observational study were invited to participate in an in-depth qualitative interview. Using a semi-structured interview guide, interviews were audio-recorded and transcribed verbatim. Data were analyzed using a reflexive thematic analysis approach to develop key themes to inform clinical practice. Participants (n=9) ranged in age from 29 to 72 years, and were at least 4 years post-diagnosis. Under the overarching survivorship theme, three key themes were developed. The first theme, “Learning what my brain can and can’t handle,” centered on functional challenges related to cognitive impairments, including difficulties at work and managing home and family responsibilities. In response, participants described generating their own strategies to manage cognitive limitations in daily activities. The second theme, “Such an important crossroads”, reflected the significant emotional impact of persisting impairments (e.g., frustration, disappointment, reduced self-esteem, acceptance), increased anxiety around an uncertain future, and a shift in personal values towards an increased sense of gratitude, crystalizing of intentions, and focus on things of greatest importance. The final theme, “A solid foundation of people around me”, referred to the necessity of social support, in both emotional and instrumental terms. Many expressed a desire for and appreciation of coping tools and support for the support people in their lives. Nearly all participants expressed interest in cognitive rehabilitation – whether or not they were experiencing significant cognitive problems. These findings have implications for clinical practice and can inform the development of effective patient-centered supportive care interventions in this population.

NIMG-48. MULTI-ECHO SPIN-AND-GRADIENT ECHO (SAGE) PERFUSION MRI TO EVALUATE BRAIN TUMOR MICROSTRUCTURE AND MICROVASCULATURE

BACKGROUND

In a classic DSC perfusion sequence, T1 and T2* leakage effects compete in determining the post-bolus signal, and are influenced by tissue geometry (i.e. cell density, cell size). Different DSC sequences can be variously influenced by these effects, depending on the different degree of T1 weighting and the pre-bolus administration. Multi-echo spin-and-gradient echo (SAGE) perfusion MRI enables to disentangle T2* and T1 components that contribute to the classic DSC curve, and to simultaneously compute DSC and DCE perfusion metrics.

METHODS

We retrospectively selected patients with: diagnosis of primary brain tumor, availability of SAGE-based DSC perfusion and DWI datasets, availability of histopathological images from targeted biopsies located within contrast-enhancing tissue. Post-processing allowed to distinguish the pure T2* component from the pure T1 component, and to perform a DCE analysis on the latter. Quantitative perfusion MRI measurements were then evaluated with respect to underlying histopathology.

RESULTS

Histopathological images were available for 22 targeted biopsies (across 10 patients) meeting the inclusion criteria. The following novel MRI quantitative maps were successfully computed voxelwise: ΔR2* at steady state (reflecting T2* leakage effects), ΔR1 at steady state (reflecting T1 leakage effects), transverse relaxivity at tracer equilibrium (TRATE, reflecting the combination of T2* and T1 leakage effects). In addition, Ve and ktrans were computed from the DCE analysis, and the percentage of signal recovery (PSR) was computed from the second echo of the multi-echo DSC (comparable to a classic single-echo DSC sequence).

CONCLUSIONS

Histopathological validation will assess the usefulness of these novel multi-echo derived quantitative maps for the non-invasive prediction of tumor microstructure. This would be particularly relevant for: 1) differential diagnosis between brain tumors with different cell size and cell density (e.g. lymphoma vs glioblastoma); 2) treatment response assessment (as pre-existing studies proved that cell shrinkage is an early event in treatment response).

CTIM-11. SINGLE-CENTER, OFF-LABEL NEOADJUVANT PEMBROLIZUMAB FOR TREATMENT OF RECURRENT GBM AT UCLA

Neoadjuvant drug administration provides a window of opportunity for developing novel therapies. Specifically, neoadjuvant pembrolizumab (PD1 checkpoint inhibitor) has the potential for improving understanding of immunomodulatory effects on the tumor microenvironment and for treating recurrent GBM. It is known that a functional immune deficit exists within the tumor T-lymphocyte compartment. As pembrolizumab promotes lymphocyte infiltration, it may contribute to antitumor effects in the neoadjuvant setting. Our previous randomized clinical trial (RCT) suggested that neoadjuvant pembrolizumab improved survival for recurrent GBM patients with 1-2 relapses. Here, we sought to extend our original findings and analyze the role of off-label neoadjuvant pembrolizumab in patients with multiple recurrences. We identified a retrospective 22-patient cohort at UCLA. Every patient had a GBM tissue diagnosis, received standard treatment, and had one to five recurrences. Each received off-label neoadjuvant pembrolizumab and surgical resection within 7-21 days. Progression-free (PFS) and overall survival (OS) for our cohort of neoadjuvant-treated patients were calculated as days from surgical resection and compared to historical control data from the original RCT (n = 15 neoadjuvant, 15 adjuvant). Results show that administration of neoadjuvant pembrolizumab in our cohort significantly increased median PFS compared to our historical adjuvant control (114 vs 75 days, p = 0.03). The OS of our neoadjuvant cohort was 294 days as compared to 192 days in the historical control. Both PFS and OS in our neoadjuvant cohort were not statistically different than the historical neoadjuvant cohort (PFSp = 0.08, OSp = 0.13). Since our cohort was not limited to initial recurrences, this data suggests that patients with more advanced recurrences could also benefit from neo-adjuvant therapy. Ongoing work will evaluate the microenvironmental genetic signature induced by pembrolizumab and assess pre-surgical tumor volume so that adequate comparisons can be made with other trials. We believe this promising finding offers novel therapeutic options for those patients with multiple recurrences.

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).

CTNI-49. EARLY SIGNAL OF ACTIVITY FROM A PHASE 2 STUDY OF ST101, A FIRST-IN-CLASS PEPTIDE ANTAGONIST OF CCAAT/ENHANCER-BINDING PROTEIN Β (C/EBPΒ), IN RECURRENT GLIOBLASTOMA (GBM)

BACKGROUND

C/EBPβ is a transcription factor that is active during embryofetal development but held in an inactive state in most mature cells (Zahnow 2009). C/EBPβ activates a proliferation/survival gene signature in multiple cancers, where it inversely correlates with disease prognosis and survival. ST101 is a cell-penetrating peptide antagonist of C/EBPβ. ST101 exposure leads to selective tumor cell death in multiple human cancer cell lines, including GBM, without impacting normal cell viability. In vivo, ST101 displays rapid uptake into multiple organs, the ability to cross the blood-brain barrier, and a long plasma half-life due to its resistance to degradation. It has potent anti-tumor activity in multiple GBM models, as a single agent or in combination, which supported moving into clinical development. TRIAL DESIGN: This phase 2 study is enrolling adult patients with GBM that has recurred or progressed after one standard treatment regimen (surgery, radiotherapy +/-temozolomide). Patients require measurable disease at baseline and at least 3 months from prior radiotherapy. Subjects receive the recommended phase 2 dose of ST101 (500mg IV weekly). Recruitment in the phase 2 portion of this trial began in January, 2022.

RESULTS

As of June 1, 2022, 14 GBM patients were enrolled. One patient has a confirmed mRANO partial response (PR) after 18 weeks of therapy, seven patients have not reached the first on-study assessment and six patients progressed. The median duration of therapy was 5 weeks. ST101 has a favorable safety profile with minor infusion related reactions being the most common adverse event. Based on the confirmed PR, the GBM cohort will be expanded.

CONCLUSION

This first-in-class C/EBPβ inhibitor, ST101, showed an early signal of activity in recurrent GBM. More extensive follow-up and clinical experience will be presented as this trial expands and matures.

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.

NIMG-14. RADIOLOGIC ASSESSMENT OF BRAIN METASTASES UNDERGOING LASER INTERSTITIAL THERMAL THERAPY (LITT)

BACKGROUND

Laser Interstitial Thermal Therapy (LITT) is a novel treatment for brain metastases (BMs), and data regarding radiologic changes and long-term efficacy is sparse. This study explored volumetric changes in responding and non-responding BMs and their associations with lesion-specific progression-free survival (PFS-L).

METHODS

Patients with BMs treated with LITT were retrospectively enrolled. 3D volumes-of-interest of the contrast-enhancing BM tissue (CE) on pre-, post-LITT, and follow-up MRI scans were obtained. BMs were followed until progression or censoring. PFS-L was determined using the modified RANO criteria to assess treatment efficacy on each lesion.

RESULTS

Thirty-one BMs (from 30 patients) were preliminarily analyzed. 2 BMs had no follow-up scans. Median follow-up for 29 BMs was 248 days (range 28-2200). Median time to response was 430 days (responders n=7/29), median time to progression was 176 days (progressive disease n=7/29). Pre-LITT CE volume was a predictor of PFS-L (p=0.001), with BMs> 2.5 cc being 14 times more likely to undergo progression. Differences in age and primary tumor site did not impact PFS-L, whereas PFS-L tended to be longer in females (p=0.059), and in frontal and deep grey matter BMs (p=0.11). Post-LITT CE volume was higher than pre-LITT (p< 0.0001, median increase 59%), with no significant differences among responders, stable disease, and progressive disease. In each responding BM, the CE volume shrinkage over time was described by an exponential decay (R2 ranging 0.92-1.0 and half-life ranging 16.55-204 days). All responding BMs showed a pooled exponential decay with R2=0.88 and half-life=75.6 days.

CONCLUSIONS

Our data suggest that smaller BMs may have improved outcomes from LITT treatment. CE volumes may increase in the early post-procedural scans, possibly due to both inflammatory changes and thermal damage. The characterization of the volumetric changes across time for responding lesions may be useful for an early detection of BMs at risk for progression.

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.

NIMG-50. ASSOCIATION BETWEEN SALINITY, ACIDITY, DIFFUSIVITY, AND HYPOXIA IN HUMAN GLIOMAS USING MULTI-NUCLEAR MRI

INTRODUCTION

Sodium MRI has been recently explored in brain tumors to potentially reveal complementary information with proton MRI about the tumor microenvironment. However, there remains limited investigation combining sodium and quantitative proton MRI techniques. This pilot study explored the associations of sodium MRI with diffusion-, pH-, and hypoxia-weighted MRI biomarkers in gliomas.

METHODS

Eleven patients with gliomas (n=8 IDH-wild-type; n=3 IDH-mutant) who obtained sodium, anatomical, diffusion-, pH-, and hypoxia-weighted MRI were studied. All images were obtained on a 3T Siemens Prisma with a dedicated multi-nuclear head coil. Regions-of-interest were segmented on the contrast-enhancing (CE) (n=10), FLAIR (n=11), and necrotic regions (n=9). Sodium values were normalized to the mean values of the eyes. Median sodium, apparent diffusion coefficient (ADC), ADC(L) from bimodal histogram analyses, MTRasym (acidity), and R2’ (hypoxia) values were obtained.

RESULTS

There was increased sodium in necrosis compared to FLAIR regions (mean difference=0.24; P/i>< 0.05) and compared to CE regions (mean difference=0.17; P/i>=0.07). There were significant positive correlations between sodium and ADC in CE (R=0.94; P/i>< 0.0001) and FLAIR regions (ρ=0.77; P/i>< 0.01), but not in necrosis (R=0.44; P/i>=0.24). There was also a significant positive correlation with ADC(L) in CE regions (R=0.90; P< 0.001) but not in FLAIR regions (ρ=0.50; P/i>=0.12). Furthermore, there was a significant positive correlation between sodium and MTRasym in necrosis (R=0.74; P/i>< 0.05) and a positive trend in CE regions (R=0.55; P=0.10). There was also a negative trend between sodium and R2’ in FLAIR regions (ρ=-0.58; P/i>=0.11).

CONCLUSIONS

Because ADC and ADC(L) are inversely related to cell density, increased sodium in gliomas may reflect increased extracellular space stemming from lower cell density, as sodium concentration is higher extracellularly. Positive associations between sodium and acidity as well as negative associations between sodium and hypoxia may reflect alterations in coupled sodium-pH and sodium-hypoxia homeostasis in gliomas.

CTIM-24. NUTMEG: A RANDOMIZED PHASE II STUDY OF NIVOLUMAB AND TEMOZOLOMIDE VERSUS TEMOZOLOMIDE ALONE IN NEWLY DIAGNOSED ELDERLY PATIENTS WITH GLIOBLASTOMA

BACKGROUND

Nivolumab is a PD-1 inhibitor with known safety profile. An increase in mutations as we age is well documented in glioblastoma and other cancers. Higher mutational load is associated with increased response to nivolumab in extracranial malignancies. NUTMEG examined the activity of nivolumab added to temozolomide in glioblastoma patients aged ≥ 65 years.

METHODS

NUTMEG was an international multicenter phase II trial for newly diagnosed glioblastoma patients aged ≥ 65 years, randomized 2:1 to experimental (40Gy/15 fractions with temozolomide 75mg/m2, then 6 cycles of temozolomide 150-200mg/m2 D1-5 Q28D + nivolumab 240mg D1,15 Q28D C1-4 and 480mg D1 Q28D C5-6) versus standard arm (40Gy/15 fractions with temozolomide 75mg/m2, then 6 cycles of temozolomide alone 150-200mg/m2 D1-5 Q28D), stratified by age, ECOG status, MGMT status and resection extent.

RESULTS

103 patients were enrolled (69 in experimental arm, 34 in standard arm). Median age was 73 years, 36% ECOG 0, 57% MGMT-unmethylated and 51% gross macroscopic resection. Median follow-up is 31 months to date, with 77 deaths (surviving patients to continue follow-up and final results will be presented). Median overall survival was 11.8 months in the experimental arm versus 12.0 months in the standard arm (HR 0.95 95%CI 0.59-1.53 for experimental relative to control). Six-month progression-free survival rate using mRANO was 64% in the experimental arm versus 49% in the standard arm (HR 0.81 95%CI 0.51-1.26). Grade 3/4 adverse events were reported in 46% of experimental arm (7% lung infection, 7% thromboembolic events, 6% fatigue, 6% muscle weakness) and in 29% of control arm (9% fatigue, 6% seizure, 6% thromboembolic events).

CONCLUSIONS

There was insufficient evidence of clinical benefit with nivolumab in this population. No new safety signals were identified. Central imaging review is underway and correlative studies will characterize the immune landscape, including mutational load, neoantigen and other immune markers. NCT04195139.

Regional Cerebral Small Vessel Disease (rCSVD) Score: A clinical MRI grading system validated in a stroke cohort

BACKGROUND

Current methods for quantitative assessment of cerebral small vessel disease (CSVD) ignore critical aspects of the disease, namely lesion type and regionality. We developed and tested a new scoring system for CSVD, "regional Cerebral Small Vessel Disease" (rCSVD) based on regional assessment of magnetic resonance imaging (MRI) features.

METHODS

141 patients were retrospectively included with a derivation cohort of 46 consecutive brain MRI exams and a validation cohort of 95 patients with known cerebrovascular disease. We compared the predictive value of rCSVD against existing scoring methods. We determined the predictive value of rCSVD score for all-cause mortality and recurrent strokes.

RESULTS

46 (44 male) veteran patients (age: 66-93 years), were included for derivation of the rCSVD score. A non-overlapping validation cohort consisted of 95 patients (89 male; age: 34-91 years) with known cerebrovascular disease were enrolled. Based on ROC analysis with comparison of AUC (Area Under the Curve), "rCSVD" score performed better compared to "total SVD score" and Fazekas score for predicting all-cause mortality (0.75 vs 0.68 vs 0.69; p = 0.046). "rCSVD" and total SVD scores were predictive of recurrent strokes in our validation cohort (p-values 0.004 and 0.001). At a median of 5.1 years (range 2-17 years) follow-up, Kaplan-Meier survival analysis demonstrated an rCSVD score of 2 to be a significant predictor of all-cause-mortality.

CONCLUSION

"rCSVD" score can be derived from routine brain MRI, has value in risk stratification of patients at risk of CSVD, and has potential in clinical trials once fully validated in a larger patient cohort.

P11.65.B GBM AGILE: A global, phase 2/3 adaptive platform trial to evaluate multiple treatment 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. It is a collaboration between academic investigators, patient organizations and industry, under the sponsorship of the non-profit organization, Global Coalition for Adaptive Research, to support new drug applications for newly diagnosed and recurrent GBM.

Material and Methods

The primary objective of GBM AGILE is to identify therapies that effectively improve overall survival in patients with newly diagnosed 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 companies to be evaluated simultaneously and/or over time against a common control arm. Based on performance, a drug may graduate and move to a Stage 2 (Phase 3) within the trial, and the totality of the data can be used for a new drug application and registration process. New experimental therapies are added as information about promising new drugs is identified while other 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 such as risk-based monitoring and enhanced remote activities. With its adaptable structure, GBM AGILE has continued trial activation, inclusion of new investigational therapies, and enrollment globally through the challenges of a global pandemic.GBM AGILE provides an efficient mechanism to screen and develop robust information regarding the efficacy of proposed novel therapeutics and associated biomarkers for GBM and to quickly move therapies and biomarkers into clinic. GBM AGILE received initial approval from the United States FDA in April 2019, and in Europe through the Voluntary Harmonization Procedure (VHP) in April, 2021. As of 2022, AGILE has screened over 1000 patients studying multiple investigational treatments. Enrollment rates are 3 to 4 times greater than traditional GBM trials, with active sites averaging 0.75 to 1 patients/site/month.

Currently, there are 41 sites activated in the US, 4 in Canada and 2 in Switzerland and an estimated 24 sites yet to open in Germany, France, Switzerland, Italy and Austria. In addition to the continued expansion in Europe, effort is undergoing to extend the trial to China and Australia as well. Clinical trial information: NCT03970447

NIMG-44. PROGNOSTIC VALUE OF PH- AND OXYGEN-SENSITIVE MRI IN GLIOMA PATIENTS

Hypoxia and tissue acidosis are two key features of the glioma microenvironment, both associated with a more aggressive phenotype through promotion of invasion, angiogenesis, and resistance to a vast number of therapies. In the current study, we demonstrate that higher levels of acidity and hypoxia in glioma are associated with worse prognosis by using simultaneous pH- and oxygen-sensitive amine chemical exchange saturation transfer spin-and-gradient echo echo-planar imaging (CEST-SAGE-EPI). A total of 159 histologically confirmed adult glioma patients (WHO grade II: N = 42; grade III: N = 38; grade IV, N = 79) were retrospectively evaluated. All patients were scanned with a custom amine CEST-SAGE-EPI MRI pulse sequence at 3T. Magnetization transfer ratio asymmetry (MTRasym) at 3ppm was used as a measure of relative acidity, R2’ was used as a surrogate of hypoxia, and their product MTRasym×R2' was used to quantify the degree of both acidity and hypoxia. Cox regression was performed to evaluate prognostic factors for OS and PFS. Univariate results suggested higher hypoxia, R2' (HR = 1.44, p = 0.0002), and higher combined measure of acidity and hypoxia, MTRasym×R2' (HR = 1.14, p = 0.0008), were associated with a shorter OS. When considering age, treatment status, and IDH mutation status as covariates, R2' and MTRasym×R2' remained significantly associated with patient OS (R2': HR = 1.27, p = 0.045; MTRasym×R2': HR = 1.17, p = 0.002). Within the treatment naïve patients, tumor acidity MTRasym, was also associated with OS (HR = 3.72, p = 0.003). R2' and MTRasym×R2' were significantly associated with PFS, both using univariate (R2': p < 0.0001; MTRasym×R2': p < 0.0001) and multivariate analyses including clinical factors (R2': p = 0.010; MTRasym×R2': p < 0.0001). In summary, tumor acidity and hypoxia measured using pH- and oxygen-sensitive metabolic MRI are significant prognostic factors in glioma.

CTNI-14. EVALUATING METABOLIC ALTERATIONS IN PATIENTS WITH EGFR ACTIVATED RECURRENT GLIOBLASTOMA (RGBM) BY INHIBITING EGFR WITH OSIMERTINIB

BACKGROUND

EGFR activated GBM is highly metabolically active and effective targeting with EGFR TKis in human-tumor models rapidly attenuates glucose metabolism engaging apoptotic machinery. Rapid changes in glucose uptake using 18F-FDG-PET is an effective predictive biomarker of therapeutic response in these models. Clinical 18F-FDG-PET may allow investigators to obtain early readout on EGFR TKi in this patient population. We explore this approach using osimertinib in EGFRamp/p53wt rGBM.

METHODS

EGFRamp/p53wt rGBM patients were treated with oral osimertinib 240mg for three days followed by 160mg/day until progression. F18-FDG-PET scan was obtained as a double baseline, 24 hours apart, prior to dosing with osimertinib. Third scan was obtained after 3 doses of 240mg. Primary objective defines test-retest variance of tumor FDG uptake before osimertinib and to evaluate if osimertinib significantly decreases glucose utilization after three doses. Study-drug and funding provided by AstraZeneca.

RESULTS

12 pts were evaluated, 10 female, median age 57.5 years (44-61). Volumetric mRANO showed no responses, 6 SD, 5 PD, and one NE. Median PFS was 31 days, no patient achieved 6-month-PFS and median OS was 5.5 months. No new adverse event signal appeared. Double baseline PET SUV mean was 0.97 (normalized to whole cerebellum) with upward trend from first to second scan with mean percent change of 2.8 and 95% CI(0.7,5.1). Change in PET from 2nd to 3rd showed mean percent change -3.2 with 95% CI (-11.1,4.8). Preclinical models suggest 15-20% attenuation is needed to predict improved outcomes in patients treated with EGFR-TKi.

CONCLUSION

F18-FDG-PET has little variance with test-retest showing upward trend with second scan. Post osimertinib F18-FDG-PET shows limited attenuation of tumor FDG uptake. No clinical signal was seen in study. Deeper attenuation of FDG uptake may be needed to show clinical effect from EGFR inhibitors. F18-FDG-PET can be used to evaluate change in tumor glucose utilization.

NIMG-24. RANO CRITERIA DETECTS EARLY PROGRESSION SOONER THAN MODIFIED RANO CRITERIA IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA

BACKGROUND

Accurate response criteria are crucial for determining treatment efficacy. The response assessment in neuro-oncology (RANO) criteria was developed to standardize response assessment in neuro-oncology. Modified RANO (m-RANO) criteria were recently proposed to address some limitations of the initial criteria including the use of a post-radiation baseline and an additional scan to confirm progression. We sought to identify differences in the association of progression-free survival (PFS) and overall survival (OS) using RANO and m-RANO criteria.

METHODS

We conducted a retrospective review of newly diagnosed glioblastoma (GBM) patients treated at Dana-Farber Cancer Institute from January 2013 until December 2019. Patients with available clinical and imaging data obtained before initiation of treatment, after radiation completion and at intervals of 1 to 3 months were included. MRIs were evaluated by two independent readers, and PD dates determined using RANO and m-RANO criteria.

RESULTS

552 patients were included. 97.1% of the tumors were IDH wild-type. MGMT promoter was unmethylated in 51.4%, methylated in 35.1% and undetermined in 8.5%. Median OS among patients was 18.1 months. 72 patients (13%) did not have PD at the end of the study. 83 patients had treatment change while being clinically stable and without a confirmation scan and were excluded from the final analysis. PFS was 8.2 months with RANO and 8.4 months with mRANO. Difference in PD dates between RANO and m-RANO was detected in 76 patients (14%), where PFS was 3.5 months with RANO and 5.1 months with m-RANO. These patients had a worse median OS than those with identical RANO and m-RANO PD dates (15.2 vs. 22.4 months, p< 0.0001).

CONCLUSION

RANO and m-RANO criteria resulted in identical PFS for most patients. 14% of patients had discordant PD dates and a worse prognosis. These patients progressed early, and their PD was identified sooner with RANO criteria.

NIMG-41. PH-WEIGHTED MOLECULAR MRI AS AN EARLY BIOMARKER OF METABOLIC RESPONSE TO IDH INHIBITION IN IDH MUTANT GLIOMAS

The current study tested the hypotheses that (1) pH-weighted MRI measurements of tumor acidity reflect glycolytic activity in human gliomas, (2) that tumor acidity, and thus glycolytic activity, differs between human IDH mutant (mIDH) and wild type gliomas, and (3) that an increase in tumor acidity, suggestive of increased glycolytic activity, occurs after inhibition of mutant IDH enzyme activity and reduction in 2HG, an oncometabolite. To test these hypotheses, we employed a custom pH-weighted amine chemical exchange saturation transfer echoplanar (CEST-EPI) technique in 152 patients with IDH mutant or wildtype glioma prior to surgery and 11 patients before and after treatment with AG120 or AG881 enrolled at our institution in a phase 1 perioperative study in patients with recurrent, non-enhancing, IDH mutant low-grade gliomas (NCT03343197). Results from image-guided biopsies in more than 100 patients demonstrated a significant correlation between MTRasym at 3ppm, a measure of tumor acidity from pH-weighted amine CEST-EPI, and expression of key glycolytic proteins including GLUT3 (R2=0.2188,P=0.0105), HK2 (R2=0.1788,P=0.0314), LDHA (R2=0.1111,P=0.0071), and MCT1 (R2=0.1228,P=0.0039) as well as ex vivo extracellular flux analysis estimates of ATP consumption from glycolysis (R2=0.6684,P=0.0021). Data suggests a significantly lower acidity (MTRasym@3ppm) within non-enhancing tumor in IDH mutant gliomas when compared to IDH wild type gliomas (P< 0.0001). Patients in a phase 1 perioperative study showed a shift toward higher tumor acidity (i.e. higher glycolytic activity) following inhibition of IDH based on 2HG suppression in resected tumors, but at levels below that of IDH wild type gliomas. Levels of 2HG within the tumor after IDH inhibition were inversely correlated with post-treatment tumor acidity (R2=0.6342, P=0.0180). Overall, results suggest mIDH gliomas have low levels of glycolytic activity, and successful inhibition of the mutant IDH enzyme results in reduction in 2HG and a measurable metabolic shift toward elevated glycolysis as evidenced using pH-weighted molecular MRI.

NIMG-33. VOLUMETRIC TUMOR MEASUREMENTS ARE SUPERIOR TO 2D BIDIRECTIONAL MEASUREMENTS IN THE EVALUATION OF IDH INHIBITION IN DIFFUSE GLIOMAS: EVIDENCE FROM A PROSPECTIVE PHASE I TRIAL OF IVOSIDENIB

Since IDH mutant (mIDH) low-grade gliomas (LGGs) progress slowly and patients have a relatively long survival, testing of new therapies in clinical trials based solely on survival can take more than 20 years. Guidance on therapeutic evaluation using LGG RANO criteria recommends serial bidirectional (2D) measurements on a single slice; however, questions remain as to the best approach for evaluating LGGs in clinical trials including use of volumetric (3D) measurements, which would theoretically allow for more accurate measurements of irregular shaped lesions and allow readers to better assess areas of change within these tumors. A total of 21 (out of 24) non-enhancing, recurrent mIDH LGGs with imaging pre- and post-treatment enrolled in a phase I, multicenter, open-label study to assess the safety and tolerability of oral ivosidenib (NCT02073994) were included in this exploratory ad hoc analysis. 2D bidirectional and 3D volumetric measurements were centrally evaluated by one of 3 radiologists at an imaging CRO using a paired read and forced adjudication paradigm. The effects of 2D vs. 3D measurements on progression-free survival (PFS), growth rate measurement variability, and reader concordance and adjudication rates were then quantified. 3D volumetric measurements had significantly longer estimates of PFS (P=0.0181), more stable (P=0.0063) and considerably lower measures of tumor growth rate (P=0.0037), the highest inter-reader agreement (weighted Kappa=0.7057), and significantly lower reader discordance rates (P=0.0002) with comparable recommended LGG RANO 2D approaches. In summary, 3D volumetric measurements are better for determining response assessment in LGGs due to longer PFS and more stable measures of tumor growth rates (i.e. less “yo-yo-ing” of measurements over time causing fewer erroneous calls of progression and more accurate growth rates), highest inter-reader agreement, and lowest reader discordance rates. Future studies will focus on validating this in a larger cohort and determining whether these measurements better reflect clinical benefit.

CTNI-18. PHASE I AND PRELIMINARY PHASE 0 RESULTS OF ABTC 1801: A MULTI-ARM CLINICAL TRIAL OF THE PARP INHIBITOR PAMIPARIB (BGB290) WITH VERY LOW DOSE METRONOMIC TEMOZOLOMIDE IN RECURRENT IDH MUTANT GLIOMAS

BACKGROUND

Preclinical studies have demonstrated that IDH1-mutant (IDHmt) gliomas harbor a BRCAness phenotype with a defect in homologous recombination that confers PARP inhibitor sensitivity. Pamiparib (BeiGene BGB-290) is an effective PARP-trapping PARP inhibitor with demonstrated favorable brain penetration in animal models.

METHODS

ABTC 1801 is a study examining the safety, pharmacokinetics, and efficacy of the combination of pamiparib with low dose metronomic temozolomide in recurrent IDHmt gliomas. The Phase I component utilized a 3 + 3 design with a target DLT rate ≤ 33%. Pamiparib dose was 60 mg BID and temozolomide dose 20 mg daily, with dose de-escalation levels for anticipated hematological toxicity.

RESULTS

Seven patients were enrolled on the Phase I portion at dose level 1; one patient was replaced for inadequate dosing secondary to non-compliance. All patients had prior radiotherapy and temozolomide; 4/7 had received multiple lines of alkylator therapy including nitrosoureas. Median age was 45, KPS 90, and number of prior relapses 3. Four patients had anaplastic astrocytoma, 2 anaplastic oligodendroglioma, and 1 glioblastoma. One of 6 patients (16.7%) experienced DLT during the first cycle (grade 3 neutropenia and thrombocytopenia). Two additional patients had grade 2 neutropenia. Two patients remain on study treatment at 12+ and 10+ months, while a third progressed at 10.1 months (PFS-6 43%). Tumor tissue was collected from two patients in the surgical arm. In enhancing and non-enhancing tumors, the mean unbound pamiparib concentrations were 198 and 160 nmol/L (or nmol/kg), respectively, which were > 20-fold the in vitro IC50 for PARP inhibition; mean unbound tumor-to-plasma ratios were 0.65 and 0.38.

CONCLUSIONS

Phase I results support pamiparib 60 mg BID with temozolomide 20 mg daily as the dosages for the Phase II study. Preliminary Phase 0 data suggest that pamiparib likely achieves sufficient pharmacologically active concentrations in both enhancing and non-enhancing brain tumors.

NIMG-45. DIFFUSION MRI AS AN EARLY BIOMARKER OF OVERALL SURVIVAL BENEFIT IN RECURRENT GLIOBLASTOMA TREATED WITH IMMUNE CHECKPOINT INHIBITORS

Diffusion magnetic resonance imaging (MRI) estimates of the apparent diffusion coefficient (ADC) has been revealed to be useful for predicting treatment response in patients with glioblastoma (GBM), with an increase in ADC indicating tumor cell death. The aim of the current study was to investigate whether quantitative changes in diffusion MRI after treatment with immune checkpoint inhibitors (ICI) could predict OS in patients with recurrent GBM. A total of 61 patients were included in this retrospective study with the following inclusion criteria: (i) diagnosis of recurrent GBM treated either with pembrolizumab or nivolumab and (ii) availability of diffusion data in pre- and post-ICI MRI. Tumor volume and median relative apparent diffusion coefficient (rADC) within enhancing tumor with respect to normal-appearing white matter were calculated. Median OS for all patients was 7.6 months (range, 1.0–30.6 months). Results showed that higher post-treatment rADC was associated with significantly longer OS (median, 372 days for rADC ≧ 1.42 versus 211 days for rADC < 1.42; P = 0.01, log-rank test), whereas tumor volume and pre-treatment rADC were not significantly associated with OS. Cox regression analysis revealed post-treatment rADC significantly influences OS (P = 0.02, univariate analysis), even after controlling for age, sex, and IDH status (P = 0.007, multivariate analysis), and additionally controlling for whether surgery was performed after ICI treatment (P = 0.049, multivariate analysis). In conclusion, a high post-treatment rADC may be an early imaging biomarker for identifying OS benefit in recurrent GBM patients receiving ICI treatment.

NIMG-36. VISUALIZATION OF TUMOR HETEROGENEITY AND PREDICTION OF ISOCITRATE DEHYDROGENASE MUTATION STATUS FOR HUMAN GLIOMAS BY USING MULTIPARAMETRIC PHYSIOLOGIC AND METABOLIC MRI

Preoperative prediction of isocitrate dehydrogenase mutation status is clinically meaningful, but remains challenging. This study aimed to predict the isocitrate dehydrogenase (IDH) status of gliomas by using the machine learning voxel-wise clustering method of multiparametric physiologic and metabolic magnetic resonance imaging (MRI) and to show the association of the created cluster labels with the glucose metabolism status of the tumors. Sixty-nine patients with diffuse glioma were scanned by pH-sensitive MRI, diffusion-weighted imaging, fluid-attenuated inversion recovery, and contrast-enhanced T1-weighted imaging at 3 T. An unsupervised two-level clustering approach, including the generation of a self-organizing map followed by the K-means clustering, was used for voxel-wise feature extraction from the acquired images. The logarithmic ratio of the labels in each class within tumor regions was applied to a support vector machine to differentiate IDH mutation status. Bootstrapping and leave-one-out cross-validation were used to calculate the area under the curve (AUC) of receiver operating characteristic curves, accuracy, sensitivity, and specificity for evaluating performance. Targeted biopsies were performed for 14 patients to explore the relationship between clustered labels and the expression of key glycolytic proteins determined using immunohistochemistry. The highest prediction performance to differentiate IDH status was found for 10-class clustering, with a mean AUC, accuracy, sensitivity, and specificity of 0.94, 0.91, 0.90, and 0.91, respectively. The tissues with labels 7 + 8 + 9 + 10 showed high expression levels of hypoxia-inducible factor 1-alpha, glucose transporter 3, and hexokinase 2, which are typical of IDH wild-type glioma, whereas those with labels 1 showed low expression of these proteins. Our machine learning model successfully predicted the IDH mutation status of gliomas, and the resulting clusters properly reflected the metabolic status of the tumors.

BIMG-11. PHARMACODYNAMIC EVALUATION OF IDH AND EGFR INHIBITION IN HUMAN GLIOMAS USING MOLECULAR MRI

Metabolic differences are inherent to specific glioma subtypes and can be altered using targeted treatments, including IDH and EGFR inhibition. Using a large cohort of patients scanned at UCLA and other centers over the last 5 years, we demonstrate that IDH, 1p19q, and EGFR alterations uniquely contribute to alterations in glycolysis and oxygen utilization using a clinically available molecular MRI technique termed amine chemical exchange saturation transfer spin-and-gradient-echo echoplanar imaging (CEST-SAGE-EPI). Our data shows that CEST-SAGE-EPI estimates of tumor acidity are strongly associated with the degree of glycolysis as evaluated with direct pH measurements, quantitative IHC, bioenergetics experiments, and correlations with 18F-FDG PET images. Data further reveals that IDH wild type gliomas have higher acidity and oxygen utilization compared with IDH mutant gliomas, 1p19q non-codeleted gliomas (astrocytomas) have higher tumor acidity compared to 1p19q codeleted gliomas (oligodendrogliomas), and EGFR amplified gliomas have higher oxygen utilization compared with non-amplified gliomas. Additionally, phase II clinical trial data suggests successful IDH inhibition results in an early and measurable increase in tumor acidity and further reduction in oxygen utilization, signifying suppression of oxidative phosphorylation and/or glutaminolysis in favor of glycolysis. Alternatively, phase II clinical trial data suggests successful EGFR inhibition with brain penetrant agents results in early reductions in tumor acidity and 18F-FDG PET uptake, consistent with a reduction in glycolysis. Data also indicates that continual increases in tumor acidity during routine follow-up after initial therapeutic changes results in uniformly worse outcomes in all tumor subtypes under all mentioned treatment scenarios.

NIMG-28. VALIDATION OF MODIFIED RESPONSE ASSESSMENT IN NEURO ONCOLOGY (mRANO) DETERMINED PFS AS A STRONG PREDICTOR OF OVERALL SURVIVAL IN RECURRENT GLIOBLASTOMA TREATED WITH A TARGETED IMMUNOTOXIN

INTRODUCTION

The current study compared the modified response assessment in neuro-oncology (mRANO)(1), iRANO (2), and standard RANO criteria (3) as well as quantified the association between progression-free (PFS) and overall survival (OS) in an immunotherapy trial in recurrent glioblastoma (rGBM).

METHODS

A total of 47 patients with rGBM were enrolled in a phase II convection-enhanced delivery of an IL4R-targeted immunotoxin (MDNA55-05, NCT02858895). Bidirectional tumor measurements were created by local sites and an independent radiologic faculty (IRF), then standard RANO, iRANO, and mRANO criteria were applied. Differences of PFS and the association between PFS and OS were evaluated.

RESULTS

41 of 47 patients were evaluable for response. Both local site and IRF-determined PFS was significantly shorter using standard RANO compared to iRANO (log-rank, P< 0.0001; HR=0.3) and mRANO (P< 0.0001; HR=0.3). No difference in PFS was observed between iRANO and mRANO (Local, P=0.67; IRF, P=0.59). In patients who died and had confirmed progression on standard RANO, no correlation was observed between PFS and OS (Local, P=0.47; IRF, P=0.34). Using the iRANO, a weak association driven by a few outliers was observed between confirmed PFS and OS via local site measurements (P=0.017), but not central IRF measurements (P=0.18). Importantly, 24 of 41 patients (59%) were censored using iRANO and not included because they did not have confirmation of progression 3 months after initial progression. A strong correlation was observed between mRANO PFS and OS for both local (R2=0.66, P< 0.0001) and IRF-determined reads (R2=0.57, P=0.0007).

CONCLUSION

No correlation between PFS and OS was observed for standard RANO or iRANO, but a strong correlation was identified between both locally-determined and centrally-determined PFS and OS using the mRANO criteria. Also, the iRANO criteria was difficult to implement due to need to confirm progression 3 months after initial progression, censoring more than half the patients.

RTID-11. GBM AGILE: A GLOBAL, PHASE 2/3 ADAPTIVE PLATFORM TRIAL TO EVALUATE MULTIPLE REGIMENS IN NEWLY DIAGNOSED AND RECURRENT GLIOBLASTOMA

Developing new therapies for patients with glioblastoma (GBM) requires focused interaction between industry, academia, nonprofits, patient advocacy, and health authorities, and novel approaches to clinical trials. GBM Adaptive Global Innovative Learning Environment (GBM AGILE) Trial was designed by over 130 global key opinion leaders in consultation with health authorities to provide an optimal mechanism for phase 2/3 development in GBM. The Sponsor of GBM AGILE is the Global Coalition for Adaptive Research, whose mission is to accelerate the development of treatments rare and deadly diseases by serving as sponsor of innovative trials. GBM AGILE is an international platform trial designed to evaluate multiple therapies in newly diagnosed and recurrent GBM. Its goals are to identify effective therapies for GBM and match effective therapies with patient subtypes, with data generated to support regulatory filing for new drug applications. Bayesian response adaptive randomization is used within subtypes of the disease to assign participants to investigational arms based on their performance. The primary endpoint is overall survival. The trial is being conducted under a master Investigational New Drug Application/Clinical Trial Agreement and Master Protocol, allowing multiple drugs from different companies to be evaluated simultaneously and/or over time. The plan is to add experimental therapies as new information is identified and remove therapies as they complete their individual evaluation against a common control. GBM AGILE received IND approval from the FDA in April 2019, screening its first patient in June 2019. As of June 2020 over 200 patients have been screened. Expansion to Canada, Europe, China, and Australia is also underway. There is currently one investigational arm under evaluation in the trial, with two additional arms to be added in Q4 2020/ Q1 2021. Clinical trial information: NCT03970447.

NIMG-49. VALIDATION OF SIMULTANEOUS PH- AND O2-WEIGHTED MOLECULAR MRI USING 18F-FDG PET, IMMUNOHISTOCHEMISTRY, AND BIOENERGETICS

This study aimed to investigate the potential of a novel MRI metric related to aerobic glycolysis in patients with diffuse gliomas. All subjects (Study I–III; 7, 26, and 11 subjects, respectively) were scanned on 3-T systems and underwent pH-weighted amine chemical exchange saturation transfer spin-and-gradient-echo echoplanar imaging (CEST-SAGE-EPI) or CEST-EPI, and perfusion imaging. Relative oxygen extraction fraction (rOEF) was calculated by dividing hypoxia-sensitive R2’ by normalized relative cerebral blood volume (nrCBV); a novel metric that characterizes glycolytic status (aerobic glycolytic index, AGI) was calculated by dividing amine CEST contrast by rOEF. Patients in Study I were additionally scanned by 18F-fluorodeoxyglucose (FDG)-PET. Stereotactic image-guided biopsies were performed on patients in Study II and III, and samples were analyzed by immunohistochemistry (IHC) and extracellular flux bioenergetic analysis, respectively. Pairwise correlation between MR metrics and standardized uptake value of 18F-FDG, IHC metrics, or indices of cellular metabolism was calculated using Spearman’s correlation analysis. In Study I, AGI showed very strong significant correlation with 18F-FDG uptake in glioma (correlation coefficient ρ = 0.86, P =0.014). In Study II, AGI was significantly correlated with glucose transporter 3 (ρ = 0.71; P = 0.0041) and hexokinase 2 (ρ = 0.73; P = 0.0029) in IDH wild-type glioma, while it was significantly correlated with monocarboxylate transporter 1 (ρ = 0.59; P = 0.0094) in IDH mutant glioma. This result may reflect the different glycolytic statuses of these gliomas; specifically, the rate-limiting steps in glycolysis. In Study III, a strong significant correlation with cellular AGI derived from the bioenergetic analysis was found for AGI derived from MRI (ρ = 0.79, P = .036). In conclusion, AGI derived from MRI was correlated with FDG, IHC measurements, and cellular AGI. Future studies investigating the clinical utility of AGI in prediction and evaluation of treatment effects are warranted.

NIMG-52. CHARACTERIZATION OF COGNITIVE FUNCTION IN SURVIVORS OF DIFFUSE GLIOMAS USING MORPHOMETRIC CORRELATION NETWORKS (MCN)

Advanced multimodality treatments have led to improved survival and quality of life for patients with diffuse gliomas, and widespread functional reorganization has been reported to be associated with improved cognitive function. However, investigation of morphological alterations in patients with diffuse gliomas has been problematic, largely due to the tumor resection cavities. This pilot study has overcome these challenges and aims to characterize the relationship between structural plasticity and cognitive function in survivors of diffuse gliomas. High-resolution T1 weighted images were collected from 24 patients with diffuse gliomas (mean age 44.5 ± 11.5) who had completed their treatment within the previous ten years. Interregional correlations of cortical thickness were computed to establish morphometric correlation networks (MCN) for twelve cognitively impaired and twelve non-impaired glioma patients, as well as correlated with self-reported cognitive impairment. Our findings demonstrated that both cognitively impaired (σ=1.5979) and non-impaired (σ=1.3683) glioma patients have a small world architecture in disrupted morphological networks. Although the left fusiform (p=0.0409), left inferior (p=0.0209), and temporal (p=0.0173) gyri were observed to be thicker in non-impaired patients, the robustness of their morphological network was weak and easily vulnerable to pathological attacks and neurological deterioration. Furthermore, regions such as the superior temporal gyrus (p=0.0126) and rostral middle frontal gyrus (p=0.0148) were not only identified as predominant nodes in the MCN of patients but were also found to have greater gray matter thickness, which is associated with better FACT-cognitive function. Together, these results support our hypothesis that a widespread morphological network is altered in survivors of diffuse gliomas. Predominant regions obtained by topological analysis may lead to reliable imaging biomarkers that help evaluate patients’ cognition and ability to function.

CTNI-17. CLINICAL EFFICACY AND PREDICTIVE BIOMARKERS OF ONC201 IN H3 K27M-MUTANT DIFFUSE MIDLINE GLIOMA

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.

RTID-05. INDIGO: A GLOBAL, RANDOMIZED, DOUBLE-BLIND, PHASE 3 STUDY OF VORASIDENIB (AG-881) VS PLACEBO IN PATIENTS WITH RESIDUAL/RECURRENT GRADE II GLIOMA WITH AN ISOCITRATE DEHYDROGENASE 1/2 (IDH1/2) MUTATION

BACKGROUND

Low-grade gliomas (LGGs; WHO grade II) are incurable and ultimately progress to high-grade gliomas. The current treatment options are surgery followed by observation (“watch and wait”) for patients with lower risk for disease progression or postoperative chemoradiotherapy (high-risk population). There are no approved targeted therapies. IDH1 and IDH2 mutations (mIDH1/2) occur in approximately 80% and 4% of LGGs, respectively, and promote tumorigenesis via neomorphic production of D-2-hydroxyglutarate. Vorasidenib, an oral, potent, reversible, brain-penetrant pan-inhibitor of mIDH1/2, was evaluated in 76 patients with glioma in two phase 1 studies (dose escalation and perioperative) and was associated with a favorable safety profile at daily doses below 100 mg. Preliminary clinical activity was observed in non-enhancing glioma patients in both studies, with an objective response rate (ORR) of 18.2% and median progression-free survival of 31.4 months in the dose escalation study.

METHODS

Approximately 366 patients will be randomized 1:1 to vorasidenib (50 mg QD) or matched placebo and stratified by 1p19q status (intact vs co-deleted). Key eligibility criteria: age ≥ 12 years; grade II oligodendroglioma or astrocytoma (per WHO 2016 criteria) not in need of immediate treatment and without high-risk features; centrally confirmed mIDH1/2 status; ≥ 1 surgery for glioma with most recent ≥ 1 year but ≤ 5 years before randomization, and no other anticancer therapy; Karnofsky performance status ≥ 80%; and centrally confirmed measurable, non-enhancing disease evaluable by magnetic resonance imaging. Crossover from placebo to the vorasidenib arm is permitted upon centrally confirmed radiographic progression per RANO-LGG criteria. Primary endpoint: progression-free survival assessed by independent review. Secondary endpoints: safety and tolerability, tumor growth rate assessed by volume, ORR, overall survival, and quality of life. Clinical data will be reviewed regularly by an independent data monitoring committee. The study is currently enrolling patients in the US, with additional countries planned (NCT04164901).

NIMG-17. VALIDATION OF DIFFUSION MRI AS AN IMAGING BIOMARKER FOR BEVACIZUMAB THERAPY IN RECURRENT GLIOBLASTOMA IN A RANDOMIZED PHASE III TRIAL OF BEVACIZUMAB WITH OR WITHOUT VB-111 (GLOBE)

BACKGROUND

Evidence from independent single center as well as multicenter phase II trials have suggested diffusion MRI is a strong predictive imaging biomarker for survival benefit in recurrent glioblastoma (rGBM) treated with anti-VEGF monotherapy, but not systemic chemotherapies or combination therapies with anti-VEGF agents. The current study builds on this body of evidence by evaluating these diffusion MR phenotypes in a large randomized phase III clinical trial.

METHODS

Patients with rGBM were enrolled in a phase III randomized (1:1), controlled trial (NCT02511405) to compare the efficacy and safety of bevacizumab (BV) versus bevacizumab in combination with ofranergene obadenovec (BV+VB-111), an anti-cancer viral therapy. In 170 patients with diffusion MRI available, pre-treatment enhancing tumor volume and ADC histogram analysis were used to phenotype patients as having high (>1.24 um2/ms) or low (< 1.24 um2/ms) ADCL, the mean value of the lower peak in a double Gaussian model of the ADC histogram within the contrast enhancing tumor.

RESULTS

Baseline tumor volume (P=0.3460) and ADCL (P=0.2143) did not differ between treatment arms. Univariate analysis showed that patients with high ADCL had a significant survival advantage when pooling all patients (P=0.0006), as well as when examining the BV (P=0.0159) and BV+VB-111 individually (P=0.0262). Multivariable Cox regression accounting for treatment arm, age, baseline tumor volume and ADCL identified continuous measures of tumor volume (P< 0.0001; HR=1.0212) and ADCL phenotypes (P=0.0012; HR=0.5574) as independent predictors of OS.

CONCLUSION

Baseline diffusion MRI and tumor volume are independent imaging biomarkers of OS in rGBM treated with BV or BV+VB-111. Since ADCL was predictive of OS in combination BV+VB-111, results support the working hypothesis that co-administration of VB-111 with BV may block any VB-111 anti-tumor effect, whereas VB-111 monotherapy or priming may result in higher efficacy of VB-111.

STEM-05. SINGLE CELL SEQUENCING CHARACTERIZES SPATIAL AND TEMPORAL RELATIONSHIPS OF ENHANCING AND NON-ENHANCING REGIONS IN HIGH-GRADE GLIOMA

INTRODUCTION

Treatments of high grade glioma focus on the contrast enhancing (CE) portion of the tumor. However, given the invasive nature of glioma, residual tumor cells responsible for recurrence likely exist in the non-enhancing (NE) region.

METHODS

In 3 patients undergoing surgery for malignant glioma, we used pre-operative magnetic resonance images to prospectively identify biopsy targets in the CE region and locations 0.5-2.0cm beyond the CE edge. We carried out single cell sequencing on image guided biopsy specimens to generate 12,528 RNA profiles.

RESULTS

In all samples, tumor cells clustered into three predominant groups: tumor cells with astrocyte markers (ASC-like), tumor cells with oligodendrocyte markers (ODC-like), and tumor cells with neither marker. This last group consisted of a small proportion of tumor cells and expressed putative stem cell markers (PROM1, NES, SLC1A3, A2B5, ID1). A trajectory analysis consistently positioned this group as branching off into either ASC-like or ODC-like cells. CE regions had different cellular compositions than NE regions, with higher proportions of tumor, endothelial cells, T-cells, and NK cells. Using location and cell density data, we modeled expected tumor burden, predicting tumor cells up to 1.5cm beyond the CE region of the tumor. There were significant differences in gene expression between CE and NE tumor cells, with increased inflammation and hypoxia in the CE region versus increased proliferative markers in the NE region. Tumor cells in the NE region were characterized by increased proliferation, markers of invasion, and markers of self-renewal.

CONCLUSIONS

Single cell sequencing illustrates multiple glioma cell types and suggests a hierarchical relationship between tumor cell types. CE and NE regions exhibit different tumor and non-tumor cell populations as well as different gene expression profiles within individual cell types. There remains a significant tumor cell burden in the NE portion of tumor, including actively proliferating cells.

CSIG-03. RECONCILING TUMOR HETEROGENEITY IN GLIOBLASTOMA USING A PATHWAY-BASED APPROACH

Despite efforts to gain a deeper understanding of its molecular architecture, glioblastoma (GBM) remains uniformly fatal. While genome-based molecular subtyping has revealed that GBMs may be parsed into several molecularly distinct categories, this insight has yielded little progress towards extending patient survival. In particular, the great phenotypic heterogeneity of GBM – both inter and intratumorally – has hindered therapeutic efforts. To this end, we interrogated tumor samples using a pathway-based approach to resolve tumoral heterogeneity. Gene set enrichment analysis (GSEA) was applied to gene expression data and used to provide an overview of each sample that can be compared to other samples by generating sample clusters based on overall patterns of enrichment. The Cancer Genome Atlas (TCGA) samples were clustered using the canonical and oncogenic signatures and in both cases the clustering was distinct from the molecular subtype previously reported and clusters were informative of patient survival. We also analyzed single cell RNA sequencing datasets and uniformly found two clusters of cells enriched for cell cycle regulation and survival pathways. We have validated our approach by generating gene lists from common elements found in the top contributing genesets for a particular cluster and testing the top targets in appropriate gliomasphere patient-derived lines. Samples enriched for cell cycle related genesets showed a decrease in sphere formation capacity when E2F1, out top target, was silenced and when treated with fulvestrant and calcitriol, which were identified as potential drugs targeting this genelist. Conversely, no changes were observed in samples not enriched for this gene list. Finally, we interrogated spatial heterogeneity and found higher enrichment of the proliferative signature in contrast enhancing compared with non-enhancing regions. Our studies relate inter- and intratumoral heterogeneity to critical cellular pathways dysregulated in GBM, with the ultimate goal of establishing a pipeline for patient- and tumor-specific precision medicine.

CTIM-13. CLINICAL EFFICACY OF MDNA55, AN INTERLEUKIN-4 RECEPTOR TARGETED IMMUNOTHERAPY, IN RECURRENT GBM DELIVERED BY CONVECTION ENHANCED DELIVERY (CED)

BACKGROUND

MDNA55 is an IL4R-targeted toxin in development for GBM, a universally fatal disease. IL4R is over-expressed in GBM, the tumor microenvironment, and high expression is associated with poor outcomes in GBM.

METHOD

MDNA55-05 is an open-label, single-arm study of MDNA55 delivered by CED as a single treatment in rGBM patients at 1st or 2nd recurrence with an aggressive form of GBM (de novo GBM, IDH wild-type, not-resectable at recurrence, ~ 50% expressing high levels of IL4R). Primary endpoint is mOS, secondary endpoint includes impact of IL4R status on mOS. A Synthetic Control Arm (SCA) served as an external comparator constructed from patient registries at neurosurgery centers under IRB-approved protocols. Propensity score weighting corrected for imbalances in baseline characteristics between the two groups.

RESULTS

MDNA55 showed an acceptable safety profile at doses up to 240μg. In all evaluable subjects (n=44) mOS was 11.6 and OS-12 was 46%. A sub-population (n=32) consisting of all IL4RHigh subjects + only IL4RLow subjects treated with high dose (median 180µg) showed most benefit: mOS is 15 months, OS-12 is 55%. Tumor control, assessed by mRANO criteria, was seen in 81% (26/32) of this sub-population, including those that had pseudo-progression (15/26). In these subjects, tumor control was associated with longer mPFS (4.7 months) and mOS (15.0 months) than those with progressive disease (mPFS 1.0 month, mOS 7.7 months). Comparison against the SCA demonstrated > 100% increase in mOS: 15.7 months vs 7.2 months (HR 0.52, 95% CI 0.30, 0.91).

CONCLUSIONS

MDNA55 demonstrates improved survival and tumor control in this study design and has potential to benefit all rGBM patients treated at high dose irrespective of IL4R expression. There are no approved therapies for rGBM that can extend survival by 50%; the potential for MDNA55 to extend survival by > 100% is promising for this devastating disease.

Abstract PR13: Adjuvant TLR-3 administration enhances proinflammatory immune responses and is associated with extended survival in glioblastoma patients treated with dendritic cell vaccination

Malignant glioma, associated with a poor prognosis, is the most common primary malignant brain tumor in adults. We and others have documented immune responses following dendritic cell (DC) vaccination as an active immunotherapeutic treatment for these patients. In this phase II clinical trial, we randomized malignant glioma patients to receive autologous tumor lysate pulsed DC vaccination with and without adjuvant Toll-like receptor (TLR) agonists. TLRs are present on dendritic cells and serve to modulate immune responses. Twenty-three patients with WHO grade III or IV glioma were treated with three intradermal injections of autologous tumor lysate-pulsed DC on days 0, 14, and 28 followed by an adjuvant placebo, TLR-7 agonist (resiquimod), or TLR-3 agonist (Poly ICLC). Mass cytometry (CyTOF) was used to analyze immune cell populations of patient peripheral blood mononuclear cells (PBMC) before and following treatment. DC-vaccinated patients who received adjuvant Poly ICLC treatment had a significantly improved median survival of 54 months over placebo (11 months) and adjuvant resiquimod (17 months) groups (P<0.01). CyTOF and single-cell RNA sequencing (scRNseq) gene expression analysis of systemic PBMCs from patients demonstrated increased immune cell activation and expression of proinflammatory genes. Notably, the expansion of a heterogenous myeloid cell population was noted to correlate with increased survival, corroborating preclinical evidence that these cells modulate adaptive immunity in the tumor microenvironment. Overall, these findings suggest that adjuvant Poly ICLC treatment improves outcomes with autologous lysate-pulsed DC vaccine treatment via modulation of proinflammatory pathways.

This abstract is also being presented as Poster B27.

Citation Format: Joseph P. Antonios, Richard G. Everson, Aaron Mochizuki, Sara Khattab, Horacio Soto, Prashant Romiyo, Matthew Z. Sun, Diana Moughon, Emma Billingslea-Yoon, Sylvia Odesa, Gang Li, Eric Kawaguchi, Alex Salazar, William Yong, Jason Schlossman, Benjamin Ellingson, Anthony C. Wang, Timothy Cloughesy, Robert M. Prins, Linda M. Liau. Adjuvant TLR-3 administration enhances proinflammatory immune responses and is associated with extended survival in glioblastoma patients treated with dendritic cell vaccination [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr PR13.

RBTT-11. NRG ONCOLOGY NRG-BN006: A PHASE II/III RANDOMIZED, OPEN-LABEL STUDY OF TOCA 511 AND TOCA FC WITH STANDARD OF CARE COMPARED TO STANDARD OF CARE IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA

The standard of care (SOC) in newly diagnosed glioblastoma (nGBM) includes resection and chemoradiotherapy. With a median overall survival (OS) of only 16–18 months for well-selected patients in clinical trials, better therapeutic options are needed. Toca 511 (vocimagene amiretrorepvec) is a retroviral replicating vector encoding a codon optimized, heat stabilized cytosine deaminase that converts Toca FC (extended-release 5- fluorocytosine,5-FC) into 5-fluorouracil. Preclinical evidence demonstrates that Toca 511 & 5-FC kill cancer cells and immunosuppressive myeloid cells in the tumor microenvironment, leading to durable antitumor immune responses. Three phase (P) 1 studies in patients with recurrent high grade glioma have demonstrated tolerable safety profile and encouraging efficacy. NRG-BN006 is a randomized P2/3 trial of Toca 511 & Toca FC with SOC versus SOC for patients with nGBM. Optune use is allowed on the SOC arm, but not on the experimental arm. Patients will be stratified by age and KPS score for 1:1 randomization. The primary endpoint is progression-free survival for P2 and OS for P3. The secondary endpoints include objective response rate in patients with measurable disease and safety. Key inclusion criteria include presumptive diagnosis of glioblastoma with anticipated 80% resection, unifocal tumor, and KPS≥70. Immune monitoring and molecular profiling will be performed. P2 has 90% power to detect a hazard ratio (HR)=0.67 in 250 nGBM patients. P3 has 85% power to detect a HR=0.75 in 720 nGBM patients. Since patients are enrolled prior to surgery and confirmatory diagnosis of GBM, approximately 900 patients will be enrolled, and two interim analyses are planned for OS. In addition, two interim safety analyses will be conducted for the experimental treatment, with the first 15 and 30 eligible and analyzable patients randomized to the experimental arm. NRG-BN006 is anticipated to start enrollment in Q4 2019. Supported by grants U10CA180868, U10CA180822 from NCI and Tocagen.

NIMG-34. MULTI-PARAMETRIC MR-PET IMAGING PREDICTS PHARMACOKINETICS AND CLINICAL RESPONSE TO GDC-0084 IN HUMAN RECURRENT HIGH-GRADE GLIOMA

Alterations in the PI3K pathway are found in the majority of malignant gliomas, but lack of efficacy has caused investigators to question the viability of this target, particularly due to lack of brain penetration. GDC-0084 was specifically optimized to penetrate the brain, targeting both PI3K and mTOR. Since these two targets alter tumor vascularity and metabolism, respectively, we hypothesized that multi-parametric MR-PET could be used to quantify the response, estimate pharmacokinetic (PK) parameters, and predict progression-free survival (PFS) in patients with recurrent malignant gliomas. In this first-in-man, multicenter, phase I, dose-escalation study (NCT01547546), we show in 47 patients that the measured maximum concentration (Cmax) of GDC0084 was associated with a decrease in enhancing tumor volume (P=0.0287) and an increase in fractional anisotropy (FA) (P=0.0418). Post-treatment tumor volume, 18F-FDG uptake, Ktrans, and relative cerebral blood volume (rCBV) were all correlated with Cmax. A linear combination of change in 18F-FDG PET uptake, apparent diffusion coefficient (ADC), FA, Ktrans, vp, and rCBV were able to estimate both Cmax (R2=0.4113, P< 0.0001) and drug exposure (AUC) (R2=0.3481, P< 0.0001). Using this composite multi-parametric MR-PET imaging response biomarker to predict PK, patients with an estimated Cmax >0.1 uM and AUC > 1.25 uM*hr demonstrated significantly longer PFS compared with patients with a lower estimated concentration and exposure (P=0.0039 and P=0.0296, respectively). Results from the current study suggest composite biomarkers created from multi-parametric MR-PET imaging targeting metabolic and/or physiologic processes specific to the drug mechanism of action may be useful for subsequent evaluation of treatment efficacy for larger phase II-III studies.

NIMG-47. VOLUMETRIC ANALYSIS OF PHASE 2 AND 3 TRIALS IN RECURRENT GLIOBLASTOMA TREATED WITH VB-111 WITH OR WITHOUT BEVACIZUMAB OR BEVACIZUMAB MONOTHERAPY

VB-111 is a non-replicating adenovirus carrying a pro-apoptotic transgene for TNFR1/Fas under the control of a modified murine promoter to pre-proendothelin 1. The transgene is expressed only in angiogenic endothelial cells, and therefore VB-111 results in targeted apoptosis of neovascular vessels. The current study characterizes the quantitative radiographic results and impact on OS in phase 2 and 3 trials of recurrent glioblastoma (GBM) patients treated with VB-111 with or without bevacizumab (BV) or BV monotherapy. MRI data from a phase 2 (NCT01260506) and randomized, double arm, controlled phase 3 (GLOBE; NCT02511405) trial of VB-111 in recurrent GBM were used in current study: Arm A) VB-111 monotherapy until progression followed by combination VB-111 and bevacizumab (BV) (“Primed Combination”; Phase 2; N=24); Arm B) VB-111 in combination with BV (“Unprimed Combination”; Phase 3; N=124); Arm C) BV monotherapy (“Control”; Phase 3; N=120). Contrast enhanced T1-weighted digital subtraction was used to quantify tumor volume at all time points. Baseline tumor volume was prognostic for OS in all treatment groups when controlling for therapy and age (Cox, P< 0.001, HR=1.02). In patients with smaller tumors (< 25mL), the “primed combination” cohort (Arm A) from the phase 2 trial had a significant OS advantage compared to both upfront combination of VB-111 and BV (Arm B; P=0.0094, HR=0.53; median OS = 7 vs. 15mo) as well as BV alone (Arm C; P=0.025, HR=0.58; median OS=8.5 vs. 15mo). Patients with a radiographic response (>65% reduction) had a significant survival difference from non-responders when controlling for age, baseline tumor volume, and treatment arm (P=0.0014, HR=0.58). Responders to VB-111 monotherapy or combination therapy after priming with VB-111 exhibited characteristic, expansive areas of necrosis in areas of initial disease.

NIMG-60. IDH MUTANT GLIOMAS WITH 1p/19q CO-DELETION ARE LESS ACIDIC THAN NON-CO-DELETED GLIOMAS AS MEASURED WITH PH-WEIGHTED AMINE CEST-MRI AND AMINO ACID PET

1p/19q co-deleted gliomas are known to have slower growth rates and are more sensitive to chemotherapy and radiotherapy. This may be partially explained by the lower tumor acidosis compared to non-co-deleted gliomas, as extracellular acidosis is one of the driving forces toward tumor invasion and resistance to treatments. Amine CEST-EPI is a fast chemical exchange saturation transfer (CEST) imaging technique sensitive to decreased extracellular pH, transverse relaxation rate, and amino acid concentration. In the current study, we demonstrated that 1p/19q co-deleted gliomas are less acidic than non-co-deleted gliomas, using a combination of pH-sensitive amineCEST-EPI, T2 relaxometry, and 18F-FDOPA (18[F] fluorodopa) amino acid PET. 70 histologically-confirmed glioma patients (World Health Organization WHO grade II, N=35; grade III, N=35) received amine CEST-EPI scans. Among them, 16 patients received 18F-FDOPA PET scan and 45 patients received T2 relaxometry quantification. Mann-Whitney u-test is performed to evaluate the differences. Median MTRasym at 3ppm (magnetization transfer ratio asymmetry at amine proton resonance frequency) within T2 hyperintense lesions was significantly lower in 1p/19q co-deleted gliomas compared to non-co-deleted ones (co-deleted 1.19±0.31%; non-co-deleted 1.66±0.45%; p< 0.0001). The significantly lower MTRasym persists when comparing within grade II (p=0.003), grade III (p=0.031), IDH1 mutated gliomas (p=0.002), and gliomas exhibiting classical oligodendroglial histology (p=0.0007). The ROC analysis shows that the prediction of 1p/19q status using MTRasym has area under the curve (AUC) of 0.80 (sensitivity 75.6%. specificity 72.7%). Median FDOPA and T2 in T2-hyperintense lesions were not different between 1p/19q co-deleted and non-co-deleted tumors (FDOPA p=0.84; T2 p=0.63). Results suggest 1p/19q co-deleted gliomas have notably lower acidity compared with non-co-deleted gliomas, as indicated by lower MTRasym and no differences in amino acid concentration or transverse relaxation rate. Further, data indicate the 1p/19q co-deleted gliomas may have distinct metabolic characteristics and tumor microenvironment that can be measured using pH-sensitive amineCEST-MRI at 3T.

ACTR-58. BASELINE REQUIREMENTS FOR NOVEL AGENTS BEING CONSIDERED FOR BRAIN CANCER EFFICACY TRIALS: REPORT OF AN ABTC WORKSHOP

Despite advances in the understanding of molecular pathways, the availability of NGS panels to identify potentially drugable mutations, the proliferation of targeted therapies, and the progress seen in other cancers, only one novel agent (temozolomide) has significantly improved the survival of patients with glioblastoma in the past three decades. A major factor distinguishing brain cancer from other malignancies is the presence of the blood-brain barrier that restricts entry into the central nervous system of over 95% of drugs currently approved by the FDA. Clinical investigators have historically justified glioblastoma efficacy trials with pharmacokinetic data documenting measurable brain concentrations in animals or in contrast enhancing brain tumor specimens from patients. However, the discovery of effective therapeutic agents (whose mechanism of action requires that the drug directly reaches the cancer) will likely require that therapeutic drug concentrations (rather than measurable levels or blood:brain ratios) be delivered to non-contrast enhancing regions of the brain. The importance of delivering therapeutic concentrations of drug to non-enhancing brain is highlighted by knowledge that a gross total resection of all enhancing portions of a glioblastoma provides no chance of cure and limited improvement in overall survival. Utilizing these more stringent emerging criteria to select novel agents for efficacy studies will encourage pre-clinical and phase I studies to define the CNS penetration of new drugs and determine a therapeutic concentration for each agent. This will aid in the rational prioritization of agents selected for phase II studies. A full report of the outcome of the ABTC workshop on this topic will be presented. This will include: 1) methods to determine “therapeutic” drug concentrations for glioblastoma, 2) methods to quantify drug concentrations in non-enhancing brain, 3) pharmacokinetic and pharmacodynamic considerations, and 4) potential shortcomings of this approach.

ACTR-61. A RANDOMIZED PHASE 2 TRIAL OF CEDIRANIB IN COMBINATION WITH OLAPARIB VERSUS BEVACIZUMAB IN PATIENTS WITH RECURRENT GLIOBLASTOMA

BACKGROUND

Like most proliferating tumors, GBM relies heavily on accurate DNA repair for maintenance of genome stability. Dysfunction in repair of both single and double strand DNA breaks by PARP inhibition and impairment of homologous recombination, respectively, would be synthetically lethal. In this study we combined the PARP inhibitor olaparib with cediranib, a pan VEGF receptor inhibitor. Cediranib may mediate disruption in the homologous recombination pathway through its antiangiogenic properties.

METHODS

Through the Experimental Therapeutics Clinical Trials Network, we performed an open-label randomized phase II study of bevacizumab (BEV)- naive adult patients with first or second recurrence of glioblastoma after radiation and temozolomide. Patients were randomized 1:1 to receive either olaparib 200 mg by mouth twice daily with cediranib 30 mg by mouth daily or BEV 10 mg/kg IV every 2 weeks. The primary endpoint was progression-free survival at 6 months (PFS6). Secondary endpoints included safety and overall survival. Exploratory objectives included blood, tissue and imaging-based biomarkers of response to treatment.

RESULTS

Seventy patients were enrolled. Median age was 60.5 years (range: 19–79), 39% females, median KPS was 90 (range: 60–100). Baseline characteristics were well balanced. With a data cut-off of 5/2/2019, PFS6 was 14% [95% CI 4–30%] in the cediranib/olaparib arm vs 30.9% [95% CI 12.7–51.2%] in the BEV arm. Median OS was 247 days in the cediranib/olaparib arm vs 201 days in the BEV arm, HR 0.816, 95% CI (0.431, 1.546). Related grade 3, 4 or 5 toxicity was experienced in 29% vs 12% of patients for the cediranib/olaparib vs BEV arm.

CONCLUSION

Treatment with cediranib/olaparib failed to increase PFS and OS in patients with recurrent GBM. Blood, tissue and imaging correlates will be presented to help understand why this treatment combination was unsuccessful.

NCOG-10. RELATIONSHIP BETWEEN COGNITIVE FUNCTION, MOOD, AND FUNCTIONING IN GLIOMA SURVIVORS

Ensuring optimal quality of life and functioning is a clinical priority in treating glioma survivors. Cognitive function and mood symptoms are prevalent in this population after treatment and it’s reasonable to consider these as significant contributors to patients’ functioning at work and in daily life. However, it’s unclear the degree to which these symptoms contribute to such outcomes. To address this question, we examined the relationships between cognitive tests (i.e., a neuropsychological battery) and mood measures (i.e., the Beck Depression Inventory-II, and the Beck Anxiety Inventory) and work and daily functioning (i.e., Work Productivity and Activity Impairment Questionnaire). Partial correlation of cognitive tests and regression models also included age and IQ (i.e., Test of Premorbid Functioning). Of the 11 participants who were currently working, worse work productivity was significantly associated with worse processing speed (Stroop color naming r=-.74,p=.03, Stroop color word r=-.78,p=.02). Similarly, worse ability in daily activities was also associated with worse processing speed and executive function (Stroop color naming, r=-.52,p=.04; Stroop color word, r=-.55,p=.03; Trails B, r=-.53,p=.03). Greater depression symptoms were strongly correlated with both worse work productivity (r=.83,p=.002), and worse ability in daily activities (r=.55,p=.01). Depression symptoms were generally uncorrelated with cognitive scores. In linear regression models that included both depression symptoms and cognitive scores, only depression emerged as a significant predictor of work productivity and ability to conduct daily activities. In sum, glioma survivors face multiple threats to work and daily functioning by way of tumor and treatment related symptoms. Our analyses suggest that both cognitive function and mood symptoms are important to consider in optimizing functioning, but depression appears to vastly outweigh cognitive function in this regard. These preliminary findings highlight the importance of careful attention to these symptoms in survivorship and point to future research directions elaborating on these relationships.

PDCT-12. CLINICAL EFFICACY OF ONC201 IN THALAMIC H3 K27M-MUTANT GLIOMA

ONC201, the first bitopic DRD2 antagonist for clinical oncology, has shown efficacy in H3 K27M-mutant glioma. We performed an integrated preclinical and clinical analysis of ONC201 in thalamic H3 K27M-mutant glioma. ONC201 was effective in mouse intra-uterine electroporation (IUE)-generated H3 K27M-mutant gliomas, with an in vitro IC50 of 500 nM and 50% prolongation of median survival in vivo (p=0.02, n=14). Elevated DRD2 expression was found in the thalamus of non-malignant brain tissue, leading to the hypothesis that thalamic tumors may be a particularly ONC201-sensitive sub-group. We analyzed thalamic H3 K27M-mutant glioma patients treated with ONC201 as of the 05/22/2019 cutoff date, which included patients who had recurrent disease prior to initiating ONC201 (n=20; 15–73 years old) and post-radiation non-recurrent patients (n=11; 5–19 years old). As of 5/22/2019, 10 of 20 recurrent patients and 9 of 11 non-recurrent patients remain on-treatment. Median PFS has not been reached for either cohort: median follow-up of 2.2 months (range: 0.6–37.9) for recurrent patients and 10.6 months (range: 4.3–20.5) from diagnosis for non-recurrent patients. Best response so far by RANO includes 1 CR, 2 PR, 7 SD, 9 PD, 1 NE for recurrent patients and 1 PR, 7 SD, 3 PD for non-recurrent patients. Additionally, 3 recurrent (-66%, -47%, -34%) and 2 non-recurrent (-40%, -10%) patients experienced regressions but are not yet confirmed PRs. For recurrent patients, median onset of response is 3.5 months (range: 2.2–3.8) and median duration of response has not been reached with a median follow-up of 12.5 months (range: 8.1–32.8). Preliminary analyses demonstrated a strong correlation of cell-free tumor DNA in plasma and CSF with MRI response. In summary, ONC201 demonstrates promising clinical efficacy in thalamic H3 K27M-mutant glioma patients, regardless of age. Micro-environmental DRD2 expression may enhance the overall ONC201 response and extend its therapeutic utility beyond H3 K27M-mutant glioma.

NIMG-31. BRAIN CONNECTIVITY PATTERNS CHARACTERIZE COGNITIVE IMPAIRMENT IN LONG-TERM SURVIVORS OF LOW-GRADE GLIOMA (LGG) USING RESTING-STATE FUNCTIONAL MRI (rs-fMRI)

Advanced multimodality treatments that have led to longer survival rates for patients with low-grade gliomas (LGGs) have also resulted in significant changes in cognition and quality of life (QoL). These changes remain poorly understood, largely due to the lack of multifactorial and in-depth studies on cognitive impairment in patients with LGG. Resting-state functional MRI (rs-fMRI) has been widely used as a reliable imaging biomarker to evaluate the treatment outcome by characterizing the cerebral networking alteration associated with a patient’s neurological status. In this preliminary report of an active study, we investigated the cognitive function and cerebral networking connectivity via rs-fMRI in survivors who had completed treatment for LGG within the past 10 years. Survivors were administered a battery of standardized neuropsychological tests. Of the 20 participants enrolled to date (mean age 43 ± 11), 10 participants were categorized as cognitively impaired based on the International Cognition and Cancer Task Force (ICCTF) guidelines, with recommended adjustments considering the number of tests in the battery. Compared to cognitively unimpaired participants, functional connectivity in cognitively impaired patients was lower between memory, visuospatial processing, and primary sensorimotor regions. These preliminary observations suggest there is a potential link between overall cognitive impairment and functional connectivity of various networks as measured using resting-state fMRI.

NIMG-54. DIFFUSION MRI PHENOTYPES PREDICT OVERALL SURVIVAL BENEFIT FROM BEVACIZUMAB IN RECURRENT GLIOBLASTOMA WITH A LARGE TUMOR BURDEN: EVIDENCE FROM CLINICAL PRACTICE AND A MULTICENTER PHASE 3 TRIAL

We have previously shown that diffusion MR characteristics are a predictive imaging biomarker for survival benefit in recurrent glioblastoma treated with anti-VEGF therapy; however, contemporary clinical use of bevacizumab is often limited to patients with very large tumors and/or after multiple recurrences. We hypothesize that diffusion MR characteristics can be used to predict long-term survival benefit in these patients, which may be beneficial for clinical decision-making. The current study identified 83 recurrent glioblastoma patients from our institution who were treated with bevacizumab over the past 5 years with high quality anatomic and diffusion MRI data. Of these 83 patients, 35 had large contrast enhancing tumors (>20cc or >3.4cm diameter, group average). Additionally, we identified 37 recurrent glioblastoma patients from the bevacizumab treated control arm of a recent multicenter phase III trial (NCT02511405) with high quality data and large enhancing tumors for validation. Pre-treatment tumor volume was quantified using T1 subtraction maps and apparent diffusion coefficient (ADC) histogram analysis was used to phenotype patients as having high (> 1.24 um2/ms) or low (< 1.24 um2/ms) ADCL, the mean value of the lower peak using a double Gaussian mixed model. Median overall survival in patients with large volume recurrent glioblastoma was ~5.7 months. High ADCL was associated with significantly longer overall survival (OS) compared with low ADCL in both single center (P=0.0271, HR=0.486, mOS=5.5 vs. 2.8mo) and multicenter phase III data (P=0.0457, HR=0.507, mOS=7.9 vs. 5.7mo). Accounting for absolute tumor volume and age, both cohorts showed that ADCL was an independent prognostic factor for OS (Cox, P< 0.01). In summary, pre-treatment diffusion MR imaging is an independent predictive biomarker for OS in recurrent glioblastoma with a large tumor burden.