McBrayer, Samuel K.

Abstract Background IDH-mutant astrocytomas are classified as WHO grade 4 in the presence of conventional high-grade histologic features and/or homozygous CDKN2A/B deletion in the 5th edition of the WHO Classification of Central Nervous System Tumour guidelines. However, work over the past decade has indicated a number of other molecular alterations that warrant consideration as potential prognostic markers. Methods We used univariate Kaplan-Meier and multivariate Cox proportional hazards regression analysis to evaluate the prognostic effects of homozygous CDKN2A/B deletion, CDK4 amplification, CCND2 amplification, PDGFRA amplification/mutation, PIK3R1 mutation, PIK3CA mutation, MYCN amplification, EGFR amplification/mutation, TERT promoter mutation, and grade 4 histologic features in two independent cohorts of WHO grade 2-4 IDH-mutant astrocytoma (n = 840 and n = 367). Results The presence of CDK4 amplification, CCND2 amplification, PDGFRA alteration, PIK3R1 mutation, MYCN amplification, and EGFR alteration were each associated with reduced overall survival compared to WHO grade 2/3 astrocytomas without these molecular features. 17.7% (148/837) of otherwise grade 2/3 astrocytomas had one or more of these molecular criteria, with resulting intermediate clinical outcome in terms of overall survival (median survival of 67.3-82.0 months) compared to grade 2/3 astrocytomas without these molecular features (median survival of 135.0-140.7 months) and grade 4 astrocytomas (median survival of 35.3-45.0 months). Conclusions The presence of CDK4, CCND2, PDGFRA, PIK3R1, MYCN, and EGFR alterations result in an intermediate patient survival in IDH-mutant astrocytoma. Adding these molecular alterations should be considered in future diagnostic classification systems to improve stratification of high-risk patients.

Abstract IDH mutant gliomas depend on glutaminase for glutamate/glutathione generation from glutamine because R-2-hydroxyglutarate inhibits branched chain amino acid transaminase mediated glutamate biosynthesis. Telaglenastat (CB-839 HCl) is a potent glutaminase-1 specific inhibitor which depletes tumor glutamate in orthotopic IDH mutant glioma PDX models and extends survival in these orthotopic models when added to radiation/temozolomide. NCI-10218 (NCT03528642) is a phase I clinical trial investigating the safety and tolerability of telaglenastat administered orally concurrently with standard doses of radiation (50.4 Gy, grade 2; 59.4 Gy, grade 3) and temozolomide (75 mg/m2 orally daily) in patients (age 16+) with previously untreated IDH mutant grade 2/3 astrocytoma. Telaglenastat dose was escalated in cohorts (400-800 mg twice daily) based on a standard 3 + 3 design to determine the recommended phase 2 dose (RP2D). Toxicities were graded per CTCAE v5.0. An expansion cohort additionally incorporated a seven-day run-in of telaglenastat monotherapy at RP2D prior to radiation to evaluate the pharmacodynamic impact of telaglenastat on plasma and tumor metabolites. 23 patients with IDH mutant astrocytoma (WHO grade 2, n = 5; WHO grade 3, n = 18) were accrued between December 2018 and January 2022 (Dose Escalation: 16; Dose Expansion: 7). Median age was 32 years (range 23-69 years). 61% were male and 70% were ECOG 0. No dose-limiting toxicities were observed. Grade 3/4 adverse events (independent of attribution) included: lymphopenia (3), neutropenia (2), leukocytosis (2), alanine transaminase elevation (2), thrombocytopenia (1), leukopenia (1), maculopapular rash (1), hyperglycemia (1), hyponatremia (1). The RP2D of concurrent telaglenastat was defined as 800 mg twice daily. Following peak absorption on Day 15 at RP2D, the mean (%CV) terminal elimination half-life in the plasma was 4.2 (53.5%) hours (range 2.1-7.1 hours). The Cmax, Tmax, oral clearance, and AUC were 1496 ng/mL, 4.0 hr, 93.6 L/hr/m2, and 7430 ng/mL*hr, respectively.

Abstract Isocitrate dehydrogenase (IDH) mutant gliomas are the most common adult, malignant primary brain tumors diagnosed in patients younger than 50, constituting an important cause of morbidity and mortality. In recent years, there has been significant progress in understanding the molecular pathogenesis and biology of these tumors, sparking multiple efforts to improve their diagnosis and treatment. In this consensus review from the Society for Neuro-Oncology (SNO), the current diagnosis and management of IDH-mutant gliomas will be discussed. In addition, novel therapies, such as targeted molecular therapies and immunotherapies, will be reviewed. Current challenges and future directions for research will be discussed.

Abstract Background: IDH mutated gliomas are critically dependent on glutaminase for glutamate biosynthesis. CB-839 is a novel glutaminase-1 inhibitor which has demonstrated efficacy in both genetically engineered and patient derived IDH mutated glioma cells, especially in combination with radiation. These preclinical studies evaluate the pharmacodynamic and pharmacokinetic impact of combining CB-839 with TMZ in patient derived xenograft (PDX) glioma models. Methods: GBM164 is a PDX model derived from an IDH1 mutant, 1p/19q non-codeleted glioma. D- and L-2HG levels in untreated GBM164 tumors were compared to GBM6 tumors (IDH wildtype glioma PDX) by GC/MS. Athymic nude mice bearing GBM164 flank tumors were treated with CB-839 (200 mg/kg PO BID x 9 doses) and/or temozolomide (50 mg/kg PO daily x 5 doses) and sacrificed four hours after the last dose to harvest plasma, normal brain and flank tumor. Tumor metabolomics were assessed by GC/MS. DNA damage signaling in tumors was assessed by Western blotting for KAP1 / Chk1 / Chk2 phosphorylation and H2AX / Rad51. Tumor, plasma and brain pharmacokinetics were assessed by LC/MS/MS. Results: Total 2HG levels in GBM164 were 18-fold higher than GBM6. CB-839 monotherapy reduced tumor glutamate (18% reduction, p = 0.15) and aspartate (30% reduction, p = 0.06) when compared to vehicle, however these changes did not reach statistical significance. The combination of CB-839 and TMZ more significantly reduced both tumor glutamate (30% reduction, p = 0.03) and aspartate (34% reduction, p < 0.001) when compared to TMZ monotherapy. CB-839 did not significantly increase DNA damage compared to vehicle, and the combination of CB-839 and TMZ did not significantly increase DNA damage compared to TMZ monotherapy. The mean tumor: plasma ratios of CB-839 concentrations were 0.68 and 0.58 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. The mean brain: plasma ratios of CB-839 concentrations were 0.07 and 0.12 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. Conclusion: The addition of CB-839 to TMZ significantly reduces glioma aspartate and glutamate in an IDH1 mutant PDX glioma model, without any impact on DNA damage. Survival studies are in progress to assess the efficacy of CB-839 when used in combination with RT and/or TMZ. Citation Format: Sani Haider Kizilbash, Danielle M. Burgenske, Samuel McBrayer, Sandhya Devarajan, Shiv K. Gupta, Taro Hitosugi, Lihong He, Mark A. Schroeder, Brett L. Carlson, Marina Gelman, Charles A. Kunos, Joel M. Reid, Alex A. Adjei, Jann N. Sarkaria. The addition of CB-839 to temozolomide significantly reduces glioma aspartate and glutamate in an IDH mutated patient derived glioma xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3870.

TPS2075 Background: IDH mutant astrocytomas express high levels of 2-hydroxyglutarate (2-HG), an oncogenic metabolite which drives gliomagenesis. Excess 2-HG inhibits branched chain amino acid transaminase, which catalyzes glutamate synthesis from branched chain amino acids. This defect causes these tumors to become more reliant on glutaminase for glutamate biosynthesis from glutamine. CB-839 (telaglenastat) is a novel glutaminase inhibitor which is well tolerated in humans. McBrayer et al have recently demonstrated that CB-839 further depletes intracellular glutamate and glutathione in IDH mutant glioma cells, and enhances RT (radiation therapy) efficacy in an orthotopic glioma model. Methods: NCI #10218 is a CTEP supported phase I clinical trial investigating the safety and tolerability of CB-839 when combined with RT/TMZ (temozolomide) in patients with previously untreated IDH mutant grade II/III astrocytoma. Patients with grade II and III astrocytomas will be treated with 50.4 and 59.4 Gy of RT, respectively, with standard doses of concurrent TMZ. CB-839 will also be administered orally concurrently with RT, with doses escalated in cohorts based on a standard 3+3 design. After defining the maximum tolerated dose (MTD) of CB-839, an expansion cohort will evaluate the pre- and post-CB-839 therapy metabolome of patients with IDH mutant astrocytoma. Enrollment to this cohort will require measurable disease and patients will additionally be treated with a 7 day run-in of CB-839 at MTD prior to RT. The effect of CB-839 on the metabolome will be studied in both plasma (LC/MS/MS) and tumor (magnetic resonance spectroscopy), along with PK to confirm adequacy of systemic exposure. Preliminary data on neurocognitive endpoints will also be acquired. NCI #10218 is currently activated for enrollment to cohort 1. Clinical trial information: NCT03528642.