Citations

Abstract α-PD-1 checkpoint blockade is a promising immunotherapeutic approach for many solid tumors; however, this strategy is minimally effective for GBM patients as a monotherapy. One potential reason why α-PD-1 checkpoint blockade is ineffective is the tumor microenvironment and systemic derangements of the immune system which are prevalent in GBM patients. We have successfully modeled peripheral immune derangements in experimental murine GBM models. These include low peripheral blood CD4 T cell counts, reduced MHC class II expression on monocytes, and atrophy of primary immune organs in animals harboring gliomas. We therefore hypothesized that extended half-life IL-2, a potent cytokine which promotes the proliferation, differentiation, and killing activity of T cells, could overcome immune derangements and could potentially synergize with α-PD-1 checkpoint blockade therapy. In cohorts of C57Bl/6 mice, we supplemented α-PD-1 checkpoint blockade with multiple bio-engineered extended half-life IL-2 molecules to treat GL261 and CT2A orthotopic glioma models which are normally resistant to monotherapy. We observe a statistically significant increase in survival in GL261-bearing animals receiving the combination of extended half-life IL-2 reagents and αPD-1 therapy relative to control-treated mice. Some animals receiving this combination therapy had a reduction in tumor burden to levels below detection. These long-term survivors underwent a rechallenge experiment with a second inoculation of GL261-Luc and effectively cleared tumor without further therapeutic intervention. This intervention causes a significant shift in the immune profile, including the formation of mature T cell responses, as well as restoring the diminished peripheral immune cell counts in GL261-bearing animals. Finally, combining extended half-life IL-2 with α-PD-1 checkpoint blockade is effective independently of the CD8 T cell response. Together, these data suggest that combination immunotherapies employing extended half-life IL-2 fusion proteins are translational to the clinic and do not require the identification of tumor specific antigens for efficacy

Abstract OBJECTIVE This study aimed to analyze the hemorrhagic risk of melanoma brain metastases following SRS. METHODS A retrospective analysis was conducted using a prospective institutional database between 1990 and 2021. Lesional hemorrhage was categorized as definite or possible, and hemorrhage severity was graded using CTCAE. RESULTS The study identified 291 patients with 1083 lesions. The mean age of patients was 60 ± 15 years, with 61% being male. Median follow-up was 11 months, corresponding to 581 patient-years. Among the patients, 82 (28%) experienced 135 lesional hemorrhages (13%). Of these, 88 lesions in 61 patients were grade 1-2 hemorrhages, 42 lesions in 25 patients were grade 3, and five lesions in five patients progressed from grade 1 to 3. Surgical intervention was required for 17 lesions (2%) in 16 patients (5%). Lesional hemorrhage was associated with radiosurgery performed between 2015 and 2021 (OR, 0.373; 95% CI, 0.231-0.60; p < 0.001), increasing marginal dose (OR, 0.89; 95% CI, 0.82-0.98; p = 0.017), antiplatelet use (OR, 0.192; 95% CI, 0.082-0.45; p < 0.001), and WBRT (OR, 0.51; 95% CI, 0.330-0.77; p = 0.0017). The cumulative lesional hemorrhage risk reached 17–20% at 36 months following radiosurgery, with 95-96% of hemorrhages occurring within the initial year. Median OS was 11 months (95% CI, 9-13 months). Patients who received radiosurgery between 2015 and 2021 exhibited a median OS of 17 months (95% CI, 10-24 months; p < 0.001), while those without hemorrhage had a median OS of 12 months (95% CI, 10-14 months; p = 0.054). CONCLUSIONS Definitive hemorrhage risk was 17% for melanoma brain metastases after SRS within the first three years, with 95% of lesional hemorrhages occurring within the initial year. Surgical intervention was necessary in 5% of patients. Hemorrhage risk and overall survival improved after 2015.

Abstract INTRODUCTION Extracellular Vesicles (EVs) are lipid bilayer particles present in almost all biofluids and carry tumor-specific molecular cargo. Plasma EVs are promising sources of biomarker discovery for glioblastoma (GBM). The clinical relevance of non-neoplastic plasma EVs in GBM remains unclear. In this study, we determine if associations exist between plasma EV subpopulation frequencies in GBM and clinical factors. METHODS Platelet-free plasma samples of 63 GBM, 43 Grade 2 glioma, and 45 healthy donors were included. All glioma plasma samples were collected before surgery. Plasma EV subpopulation frequency based on surface expression of EV-associated tetraspanins (CD9/CD81/CD63) and markers of cell origin (CD45/CD41a/CD11b/CD31) was determined by spectral flow cytometry. Clinical information including age, surgery, MGMT methylation status, corticosteroid usage, tumor volume, and overall survival data was recorded. RESULTS Compared to normal donors, GBM patients had increased CD9+, CD63+, CD81+, and CD11b+ EVs but decreased CD41a+ EVs. GBM patients also had the highest frequency of myeloid-derived CD9+CD11b+ EVs (20.17%) followed by grade 2 gliomas (13.78%) and normal donors (2.76%, p< 0.001). More GBM patients (29/63, 46.0%) received preoperative corticosteroids than grade 2 glioma patients (9/43, 20.9%; p = 0.008). Corticosteroid use was not associated with differences in EV subpopulation frequencies in GBM or grade 2 glioma patients. Pearson correlation analysis showed weak but statistically significant correlations between GBM total tumor volume and CD9+ EVs (p = 0.014), CD41a+ EVs (p = 0.037), and CD9+/CD63-/CD81- EVs (p = 0.007). In GBM patients, younger age (< 60 yrs, p = 0.01), gross total resection (p = 0.02), MGMT methylation (p = 0.002), high CD9+ EV expression (p = 0.011), low CD9+CD63-CD81- EV expression (p = 0.009) and low CD9+CD11b+ EV expression (p = 0.006) correlated with longer overall survival. CONCLUSION Differentially expressed non-neoplastic plasma EV subpopulations have significant clinical relevance in GBM including association with tumor volume and predicting survival. Validation of those markers in larger cohorts could reveal new prognostic biomarkers for GBM.

Abstract 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 PDX cultures with vehicle, temozolomide, MLN4924, or arsenic trioxide. EVs were isolated from culture supernatants using size exclusion chromatography and then analyzed by mass spectrometry (proteomics) and RNA sequencing to characterize and compare cargo profiles for each condition. We found that at the proteome level, FDFT1 and FARSB were detected only in temozolomide EVs across all cell lines. In addition, there were drug-agnostic indications of exposure, including decreased abundance in all treated EV conditions of SLC3A2, C3, PLG, and A1BG, and increased abundance of GSTP1. These cargo changes were further validated by western blotting and ExoView immunofluorescence on isolated EVs. At the EV-transcriptome level, 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. Thus, these results indicate that EV cargo post-treatment may be a novel pharmacodynamic reporter in GBM. To allow immunoprecipitation of patient GBM-derived EVs with the selective interrogation, the potential biomarkers, including PTPRZ1, B7H3, IL13RA2, and EGFR 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.

OBJECTIVE The objective of this study was to analyze the hemorrhagic risk of melanoma brain metastases after Gamma Knife radiosurgery (GKRS). METHODS A prospective institutional database was retrospectively queried to identify patients who underwent GKRS for melanoma brain metastases between 1990 and 2021. Lesional hemorrhage was defined as definite or possible based on radiologists’ readings, and severity was graded according to Common Terminology Criteria for Adverse Events. RESULTS Two hundred ninety-one patients with 1083 lesions treated in 419 sessions were identified. The mean (± SD) patient age was 60 ± 15 years, and 61% were male. The median follow-up period for overall survival (OS) was 11 (range 0–214) months with 581 patient-years. Definite/possible lesional hemorrhages occurred in 13% of lesions, with grade 3 hemorrhages observed in 4% of lesions. Surgical intervention was required in 2% of cases (5% of patients), and all resected lesions were pathologically consistent with melanoma. A decreased risk of definite/possible lesional hemorrhage was associated with a later time period between 2015 and 2021 (OR 0.45, 95% CI 0.266–0.75, p = 0.0021), increased marginal dose (OR 0.91, 95% CI 0.83–0.99, p = 0.037), antiplatelet use post-GKRS (OR 0.195, 95% CI 0.083–0.46, p < 0.001), and whole-brain radiotherapy (WBRT; OR 0.53, 95% CI 0.344–0.82, p = 0.0042). After 2015, more patients received anticoagulation, B-Raf proto-oncogene inhibitors, and immune checkpoint inhibitors, and fewer received bevacizumab (p < 0.001). The cumulative risk of lesional hemorrhage was 17%–20% at 36 months from GKRS, with 95%–96% of cases occurring within 12 months. The median patient OS was 11 (95% CI 9–13) months, and multivariate Cox regression analysis revealed that antiplatelet agents (hazard ratio [HR] 0.66, 95% CI 0.45–0.96, p = 0.031) and immune checkpoint inhibitors (HR 0.35, 95% CI 0.26–0.48, p < 0.001) were associated with longer OS, while WBRT (HR 1.36, 95% CI 1.02–1.81, p = 0.037) and definite/possible hemorrhage (HR 1.39, 95% CI 1.04–1.85, p = 0.024) were associated with shorter OS. CONCLUSIONS The definite hemorrhage risk of melanoma brain metastases after GKRS was 17% in the first 3 years and 95% of the lesional hemorrhage occurred within the 1st year. Surgical intervention was needed in 5% of patients. Antiplatelet agents and immune checkpoint inhibitors were associated with improved OS, while definite/possible hemorrhage was associated with worse OS.

Abstract Cerebral malaria is the deadliest complication that can arise from Plasmodium infection. CD8 T-cell engagement of brain vasculature is a putative mechanism of neuropathology in cerebral malaria. To define contributions of brain endothelial cell major histocompatibility complex (MHC) class I antigen-presentation to CD8 T cells in establishing cerebral malaria pathology, we developed novel H-2Kb LoxP and H-2Db LoxP mice crossed with Cdh5-Cre mice to achieve targeted deletion of discrete class I molecules, specifically from brain endothelium. This strategy allowed us to avoid off-target effects on iron homeostasis and class I-like molecules, which are known to perturb Plasmodium infection. This is the first endothelial-specific ablation of individual class-I molecules enabling us to interrogate these molecular interactions. In these studies, we interrogated human and mouse transcriptomics data to compare antigen presentation capacity during cerebral malaria. Using the Plasmodium berghei ANKA model of experimental cerebral malaria (ECM), we observed that H-2Kb and H-2Db class I molecules regulate distinct patterns of disease onset, CD8 T-cell infiltration, targeted cell death and regional blood–brain barrier disruption. Strikingly, ablation of either molecule from brain endothelial cells resulted in reduced CD8 T-cell activation, attenuated T-cell interaction with brain vasculature, lessened targeted cell death, preserved blood–brain barrier integrity and prevention of ECM and the death of the animal. We were able to show that these events were brain-specific through the use of parabiosis and created the novel technique of dual small animal MRI to simultaneously scan conjoined parabionts during infection. These data demonstrate that interactions of CD8 T cells with discrete MHC class I molecules on brain endothelium differentially regulate development of ECM neuropathology. Therefore, targeting MHC class I interactions therapeutically may hold potential for treatment of cases of severe malaria.

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 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.

TPS2085 Background: Glioblastoma (GBM) is the most common and aggressive form of brain tumor in adults. Despite maximal surgical resection, irradiation, and chemotherapy, median overall survival (OS) remains at only 30 weeks for recurrent GBM (rGBM) patients, emphasizing the need for novel treatments. GBM tumors are immunologically ‘cold,’ in that they have an immune-suppressive microenvironment with a low number of tumor-infiltrating lymphocytes (TIL). Interleukin 7 (IL-7) plays a key role in T cell development and survival. The physiological level of IL-7 increases to stimulate T cell expansion in lymphopenic condition. Previous studies have shown that lymphopenic GBM patients have shorter survival. However, their IL-7 levels are unexpectedly low. Efineptakin alfa (NT-I7), a long-acting IL-7, has been shown to increase effector CD8 T cells and reduce suppressor T-regulatory cells in murine GBM models, with subsequently improved OS. Further, we recently completed a Phase I study which showed that NT-I7 is safe, well- tolerated, and increased absolute lymphocyte counts (ALC) in newly diagnosed GBM patients. Phase II dosing was determined through this Phase I study reaching maximum tolerated dose. Thus, we hypothesized that NT-I7 may reverse GBM-associated immune suppression and potentiate the effect of an immune checkpoint inhibitor, leading to an increase in TILs and improved survival. Our preliminary data suggests that combining NT-I7 with pembrolizumab, an anti-PD-1 antibody, improves survival in murine glioma models. The purpose of this study is to evaluate the safety and efficacy of combining NT-I7 and pembrolizumab in rGBM patients. Methods: This is an open-label single arm one-stage Phase II study of NT-I7 and pembrolizumab as neoadjuvant and adjuvant therapy with surgery for adult patients with rGBM. We plan to enroll 30 evaluable patients, including a 6-patient safety run-in. Key eligibility criteria include candidates willing to undergo clinically indicated resection or biopsy, age ≥ 18 years, Karnofsky performance status ≥ 70, and dexamethasone dose > 2 mg/day ≤ 2 days prior to registration. The primary endpoint is a 9-month OS rate. Secondary endpoints include progression-free survival, objective response rate, changes in ALC, and adverse events profile. The correlative endpoints include studies to assess the anti-glioma immune response, changes in T cell subsets, T cell effector function, cytokine analysis, and immunohistochemical analysis of GBM tissue. Longitudinal cerebrospinal fluid proteomics is optional. This study opened on 1/20/2023. Two of the planned 30 patients had been enrolled by submission on 2/14/2023. Clinical trial information: NCT05465954 .

TPS2081 Background: Murine double minute 2 (MDM2) directly regulates the stability of the tumor suppressor p53, and dysregulation of this pathway can critically disrupt cellular response to genomic stress and lead to cell death. BI 907828 is a highly potent inhibitor of the MDM2-p53 interface that triggers accumulation of p53 and subsequent apoptosis in multiple GBM patient-derived xenografts (PDXs) with wild-type p53. Moreover, the combination of BI 907828 and radiotherapy provides significant survival extension in multiple orthotopic GBM PDXs. Methods: An integrated Phase 0/1 trial design is being used to evaluate the potential for BI 907828 to achieve a therapeutic concentration in brain tumor tissue and to test the safety of the combination with radiation. The co-primary endpoints for the Phase 0 study are i) measured total concentration of BI 907828 and ii) calculated unbound concentration of BI 907828 in contrast and non-contrast enhancing regions of tumor. Key inclusion criteria for the Phase 0 study are patients at least 18 years of age, ECOG performance status of 0 or 1, histologic or radiologic new diagnosis of GBM, and planned surgical resection. The first approximately 6 patients enrolled in the Phase 0 will be treated at the starting dose of 30 mg, and the future patients enrolled will be dosed at higher levels (45 mg or 60 mg) provided there are no safety concerns. If dose-limiting toxicities (DLTs) are encountered, then a Bayesian Logistic Regression Model (BLRM) with overdose control will be used to guide the dose level decisions for the additional patients. Multiple, image-registered tumor samples and intra-operative plasma samples will be analyzed for BI 907828 by LC-MS/MS. Intra-tumoral variation in BI 907828 will be correlated with pharmacodynamic effects of MDM2 inhibition (elevation of p53, p21, MDM2, GDF15, PUMA). Those patients completing the Phase 0 study and who meet additional eligibility criteria can enroll on the Phase 1a portion of the study. The pathologic inclusion criteria are TP53 wild-type, IDH1/2 wild-type, MGMT unmethylated GBM. Co-primary endpoints for the Phase 1a trial are i) occurrence of DLTs during and within 21 days after completion of radiation therapy, and ii) occurrence of adverse events throughout the treatment period. Tolerability of inter-patient dose-escalation of BI 907828 (30, 45, 60 mg) combined with radiation therapy (60 Gy in 30 fractions) will be evaluated with dose-escalation guided by a two-parameter BLRM with overdose control. Patients will remain on BI 907828 monotherapy following completion of radiotherapy until progression. To date, two patients have enrolled on the Phase 0 study, and one patient went on to enroll on the Phase 1a portion of the study. Clinical trial information: NCT05376800 .