Sarkaria, Jann N.

Abstract BACKGROUND The microenvironment of glioblastoma is complex and defined in part by protumorigenic metabolic changes. Within this microenvironment, blood-brain barrier disruption is often associated with the most aggressive portions of the tumor. To date, the metabolic tumor microenvironments of enhancing, blood-brain barrier (BBB) disrupted portions of gliomas, as compared to BBB-intact tumor, remain poorly understood. Specifically, it is unclear if the associated blood-brain barrier disruption merely reflects or functionally supports tumor aggressiveness. METHODS Intra-operative high-molecular weight microdialysis was utilized under an investigational device exemption (NCT NCT04047264) to sample the extracellular metabolome of radiographically diverse regions during fifteen neurosurgical resections. The global extracellular metabolome of recovered microdialysate from contrast-enhancing and non-enhancing tumor, as well as brain adjacent to tumor, was evaluated via ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) on the Metabolon platform and assessed using enrichment and correlation analyses. RESULTS Among 162 named metabolites identified via ultra-performance liquid chromatography tandem mass spectrometry, a novel glioma-associated metabolite, guanidinoacetate (GAA), was 126.32x higher in enhancing tumor than in adjacent brain and 13.63x higher in non-enhancing tumor than brain. Forty-eight additional metabolites were 2.05-10.18x more abundant in enhancing tumor than brain, including carnitine family members and all nine large neutral amino acids. Except for GAA and 2-hydroxyglutarate in IDH-mutant gliomas, differences between non-enhancing tumor and brain microdialysate were comparatively modest and less consistent, suggesting heterogeneity in the glioma metabolic microenvironment of blood-brain barrier (BBB) intact areas as compared to BBB-disrupted portions of gliomas. Interestingly, the enhancing but not the non-enhancing glioma metabolome was significantly enriched for plasma-associated metabolites, largely comprising amino acids and carnitines. CONCLUSION Our patient-derived data suggest that the BBB-disrupted metabolome of high-grade gliomas is characterized by metabolite diffusion from circulation into the tumor microenvironment. Further studies are ongoing to determine how this alteration in the glioma extracellular metabolome impacts glioma behavior and how it could be therapeutically targeted via BBB-modulating drugs.

Abstract Glioblastoma (GBM) is a lethal brain tumor with limited treatment options, due in part to the low blood-brain-barrier (BBB) penetrance of many anti-cancer compounds. Development of a non-invasive test that can measure drug delivery and target engagement in GBM represents an opportunity to enhance knowledge during early phase clinical trials of a new compound’s pharmacological suitability and potential efficacy. We present here data supporting that the cargo within extracellular vesicles (EV) can potentially serve as a liquid biopsy that reports on the pharmacodynamics of GBM therapeutics. We treated short-term cell cultures established from four patient-derived xenografts with vehicle, temozolomide, MLN4924, or arsenic trioxide. EVs were isolated from culture supernatants using size exclusion chromatography and then analyzed by RNA sequencing and mass spectrometry (proteomics) to characterize and compare cargo profiles for each condition. We found that depending on treatment, there were shared alterations in EV cargo between models in the expression of long non-coding RNAs, genes that are overrepresented in biological processes such as cytoplasmic translation and cellular macromolecule biosynthesis, and circular RNAs. Mass spectrometry of protein cargo further demonstrated both upregulated and downregulated peptide abundances with treatment compared to vehicle. Thus, our preliminary results indicate that EV cargo post-treatment may be a novel pharmacodynamic reporter in GBM. To allow for the selective interrogation of patient GBM-derived EVs, we have simultaneously pursued the identification of biomarkers to allow for immunoprecipitation of EVs from patient biofluids. Potential biomarkers, including PTPRZ1, B7H3, and IL13RA2, were screened across isolated EVs from both pre-clinical and clinical patient samples. Future efforts are focused on evaluating immunoprecipitated GBM-EVs from longitudinally collected patient biofluids. Overall, we anticipate that the results of this study will lead to development of a clinical test that reflects BBB penetration and tumor response, which will likely aid in novel drug development efforts.

Abstract WSD0922-Fu is an oral, central nervous system (CNS)-penetrant, small molecule, ATP non-competitive, reversible EGFR inhibitor which potently inhibits EGFR aberrations specific to non-small cell lung cancer (NSCLC) and high-grade astrocytoma (HGA). MC1914 (NCT04197934, sponsored by Wayshine Biopharma and FDA OOPD) is a first-in-human phase 1 dose-escalation trial investigating the safety and tolerability of WSD0922-Fu in patients with EGFR aberrant recurrent HGA and NSCLC. Adult patients with either recurrent EGFR mutant NSCLC with CNS metastases or recurrent EGFR mutant and/or EGFR amplified HGA were initially treated with oral WSD0922-FU, with doses escalated in cohorts based on a standard 3 + 3 design to determine the maximum tolerated dose (MTD). After establishing the MTD, this trial has now activated three dose expansion cohorts. Two of these cohorts evaluate different dose/schedule strategies in independent populations. The NSCLC cohort includes patients with EGFR mutant NSCLC and CNS metastases, and examines the safety, tolerability, plasma pharmacokinetics and preliminary efficacy of continuous WSD0922-Fu dosing (twice daily, seven days per week). The HGA cohort includes patients with EGFRvIII mutant HGA at first recurrence after prior radiation/temozolomide and examines the impact of higher doses of WSD0922-Fu administered intermittently (twice daily, five days per week). The HGA cohort also includes a food-effect study which evaluates the effect of the fed and fasted states on plasma PK. The third cohort (Brain tumor penetration cohort) includes patients with HGA (any EGFR mutation and/or EGFR amplification) who need a surgical resection for recurrent disease. Patients enrolled will be treated pre-operatively with WSD0922-Fu for five days, and tumor PK/PD will be examined in samples obtained from image-registered brain tumor biopsies. WSD0922-Fu therapy will be resumed after post-operative recovery. Patient enrollment to all three dose expansion cohorts is ongoing.

Glioblastomas (GBM) are aggressive tumors that lack effective treatments. Here, we show that the Rho family guanine nucleotide exchange factor Syx promotes GBM cell growth both in vitro and in orthotopic xenografts derived from patients with GBM. Growth defects upon Syx depletion are attributed to prolonged mitosis, increased DNA damage, G2/M cell cycle arrest, and cell apoptosis, mediated by altered mRNA and protein expression of various cell cycle regulators. These effects are phenocopied by depletion of the Rho downstream effector Dia1 and are due, at least in part, to increased phosphorylation, cytoplasmic retention, and reduced activity of the YAP/TAZ transcriptional coactivators. Furthermore, targeting Syx signaling cooperates with radiation treatment and temozolomide (TMZ) to decrease viability in GBM cells, irrespective of their inherent response to TMZ. The data indicate that a Syx-RhoA-Dia1-YAP/TAZ signaling axis regulates cell cycle progression, DNA damage, and therapy resistance in GBM and argue for its targeting for cancer treatment.

Abstract Background Glioblastoma (GBM) is the most common malignant brain tumor and has a poor prognosis. Imaging findings at diagnosis and in response to treatment are nonspecific. Developing noninvasive assays to augment imaging would be helpful. Plasma extracellular vesicles (EVs) are a promising biomarker source for this. Here, we develop spectral flow cytometry techniques that demonstrate differences in bulk plasma EV phenotype between GBM patients and normal donors that could serve as the basis of a liquid biopsy. Methods Plasma EVs were stained for EV-associated tetraspanins (CD9/CD63/CD81), markers indicating cell of origin (CD11b/CD31/CD41a/CD45), and actin/phalloidin (to exclude cell debris). EVs were analyzed using spectral flow cytometry. Multiparametric analysis using t-distributed stochastic neighbor embedding (t-SNE) and self-organizing maps on flow cytometry data (FlowSOM) was performed comparing GBM and normal donor (ND) plasma EVs. Results Size exclusion chromatography plus spectral-based flow cytometer threshold settings enriched plasma EVs while minimizing background noise. GBM patients had increased CD9+, CD63+, CD81+, and myeloid-derived (CD11b+) EVs. Multiparametric analysis demonstrated distinct surface marker expression profiles in GBM plasma EVs compared to ND EVs. Fifteen plasma EV sub-populations differing in size and surface marker expression were identified, six enriched in GBM patients and two in normal donors. Conclusions Multiparametric analysis demonstrates that GBM patients have a distinct nonneoplastic plasma EV phenotype compared to ND. This simple rapid analysis can be performed without purifying tumor EVs and may serve as the basis of a liquid biopsy.

Inhibition of the interaction between MDM2 and p53 has emerged as a promising strategy for combating cancer, including the treatment of glioblastoma (GBM). Numerous MDM2 inhibitors have been developed and are currently undergoing rigorous testing for their potential in GBM therapy. Encouraging results from studies conducted in cell culture and animal models suggest that MDM2 inhibitors could effectively treat a specific subset of GBM patients with wild-type TP53 or functional p53. Combination therapy with clinically established treatment modalities such as radiation and chemotherapy offers the potential to achieve a more profound therapeutic response. Furthermore, an increasing array of other molecularly targeted therapies are being explored in combination with MDM2 inhibitors to increase the effects of individual treatments. While some MDM2 inhibitors have progressed to early phase clinical trials in GBM, their efficacy, alone and in combination, is yet to be confirmed. In this article, we present an overview of MDM2 inhibitors currently under preclinical and clinical investigation, with a specific focus on the drugs being assessed in ongoing clinical trials for GBM patients.

Glioblastoma (GBM) is a lethal brain cancer with a five-year survival rate of <5%. Approximately half of GBM tumors lack the DNA repair protein O6-methylguanine DNA methyltransferase (MGMT), which reverses O6-alkylguanine (O6G) lesions. Patients presenting MGMT– GBM are treated with surgery followed by radiation therapy and temozolomide (TMZ), an imidazotetrazine prodrug that produces O6-methylguanine (O6MeG) lesions. However, ~50% of these patients will develop TMZ resistance by silencing of the DNA mismatch repair (MMR) pathway. We recently reported that the novel N3-(2-fluoroethyl)imidazotetrazine “KL-50” is efficacious and well-tolerated in murine models of TMZ-resistant GBM (Lin et al. Science 2022, 377, 502). Herein, we rigorously establish that KL-50 generates DNA interstrand crosslinks (ICLs) by DNA alkylation to generate O6-(2-fluoroethyl)guanine (O6FEtG), displacement of fluoride to form an N1,O6-ethanoguanine (N1,O6EtG) intermediate, and ring-opening by the adjacent cytidine. 2-Chloroethylating agents, such as lomustine and mitozolomide (MTZ), generate the same ICL by an analogous mechanism. However, DNA ICLs form >10-fold more slowly from O6FEtG than O6ClEtG, and this slower rate of cross-linking allows MGMT to reverse the initial O6FEtG in healthy tissue while also reducing MGMT–DNA cross-links arising from addition of MGMT to the N1,O6EtG intermediate. KL- 50 is efficacious in an intracranial patient-derived murine xenograft of TMZ-resistant, MGMT–/MMR– GBM (mOS = 205, 28, and 26 d for KL-50, TMZ, and vehicle-treated control, respectively) and in murine models of newly-diagnosed MGMT–/MMR+ GBM, suggesting its use in recurrent and up-front settings, respectively. These studies underscore the significance of considering the rates of chemical DNA modification and biochemical DNA repair in the design of systemic DNA alkylation agents.

Abstract Diffuse midline glioma with H3 K27 alterations (DMG) is the most aggressive primary malignant brain tumor in the pediatric population. Radiation therapy (RT) is the standard-of-care; however, it has not demonstrated a significant improvement in overall survival or stalled disease progression, and children usually succumb to disease within 12-15 months of diagnosis. Consequently, finding efficient treatments for DMG remains one of the most critical unmet needs in modern neuro-oncology. Interleukin 13 receptor subunit alpha 2 (IL-13Rα2) is a cell-surface receptor upregulated in ~80% of DMG versus normal brain, posing a potentially promising therapeutic target. Immunotherapies harnessing IL-13Rα2 to selectively delivery cytotoxic payloads, such as pseudomonas exotoxin A (PE), to tumor cells have been previously demonstrated to be safe in DMG patients and efficacious in preclinical models of DMG with high IL-13Rα2 expression using convection-enhanced delivery (CED). Furthermore, there is evidence that PE-based therapies can sensitize cells to RT. In this study, we utilized in vitro and in vivo models of DMG to evaluate clinically-relevant combination treatments of RT and the IL-13/PE immunotoxin GB-13 (IL13.E13K-PE4E). GB-13 improved the effectiveness of low-dose RT in multiple DMG cell lines by promoting caspase activation, which boosted apoptotic cell death. Intratumoral administration of GB-13 via chronic CED decreased tumor burden and prolonged survival in both DMG patient-derived orthotopic xenograft and genetically engineered mouse models. When GB-13 and RT were administered concurrently, this impact became even more prominent, informing future preclinical and clinical investigation of a potentially efficacious therapeutic approach in a subset of DMG.

Abstract An important aspect to determine the efficacy of a targeted macromolecule in treating brain tumors is penetration and activity in tumor across a heterogeneously intact blood-brain barrier. In this study, novel epidermal growth factor receptor (EGFR)-targeted antibody drug conjugates (ADCs) were constructed with a focus on cytotoxicity in glioblastoma (GBM) with an EGFR heterogeneous cell population. Initially, the cytotoxicity of free payloads with multiple mechanisms of cell kill was assessed. These included tesirine (TS, induces DNA cross-links), deruxtecan (Dxd) and SN38 (inhibit topoisomerase I), and an auristatin (MMAE) and maytansinoid (DM1) (inhibit microtubule polymerization). Across four GBM PDXs with varied EGFR expression (GBM6, 39 and 108- EGFRviii amplified; GBM10 - non-amplified), free TS and MMAE were consistently potent with EC50 values ranging from 0.50-45.9 pM and 7.9-229.1 pM, respectively. In contrast, the other free toxins were less potent; EC50 values: Dxd, 0.21-13.1 nM; SN38, 0.87-5.6 nM; DM1, 2.1-19.9 nM. Based on these results, the 40H3 EGFR-specific IgG was used to construct ADCs with TS and MMAE. 40H3-TS had a drug:antibody ratio (DAR) of 2.5 and was potently cytotoxic in GBM6, GBM39 and GBM108, while minimal cytotoxicity was observed in GBM10 or normal astrocyte SVG-A cells. 40H3-MMAE had a DAR of 3 and was similarly effective in GBM6 and GBM39 but less potent in GBM108, GBM10, and SVG-A. Bystander cytotoxicity was evaluated U87 cells expressing eGFP/fLuc2 (U87eGFP/fluc2) or EGFRviii (U87EGFRviii). Using live-cell imaging, U87EGFRviii cells treated with 40H3-TS or 40H3-MMAE had significantly reduced cell confluence relative to control. The same drug treatments in U87eGFP/fLuc2 cells had no effect on growth/confluence. However, in a 1:1 mixed culture, overall confluence was reduced from 89% in control to 35% and 32% after 40H3-TS (p&lt;0.0001) or 40H3-MMAE (p&lt;0.0001) treatment, respectively. This bystander killing of U87eGFP/fLuc2 cells was indicated by a reduction in confluence of green-fluorescent cells from 50% in control versus 29% with 40H3-TS (p&lt;0.0001) and 26% with 40H3-MMAE (p&lt;0.0001) treatment. In GBM39 orthotopic tumors, a single infusion of 10 or 20 µg 40H3-TS via convection enhanced delivery (CED) reduced the bioluminescence signal 7 days post treatment by ~10-fold (p=0.03) as compared to 40H3 control. However, 50% and 80% mortality was observed within a week of infusing 10 and 20 µg 40H3-TS, respectively. Neurotoxicity was associated with neuron loss in treated hemisphere as determined by NeuN staining. In summary, these data highlight the potential for novel EGFR-targeted ADCs to provide potent direct and bystander cytotoxicity to GBM cells. However, further selection and optimization of the conjugated toxins will be required to balance potency and bystander killing with toxicity for EGFR-targeted ADCs. Citation Format: Sonia Jain, Eric Chun Ho, Kendra A. Porath, Antonella Antignani, David J. FitzGerald, Jann N. Sarkaria. Bystander effects of EGFR-targeting 40H3 antibody-drug conjugates in glioblastoma with heterogeneous EGFR expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 556.