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Abstract BACKGROUND Neurofibromatosis type 2-related schwannomatosis (NF2) is an autosomal dominant tumor-predisposition syndrome characterized by bilateral vestibular schwannomas (VS) as well as other nervous system tumors. Management decisions for NF2-related VS are typically predicated on tumor size, associated symptoms, patient age, and comorbidities. Observation, surgical resection, and stereotactic radiosurgery can be viable options. In patients with VS associated with NF2, vascular endothelial growth factor A (VEGF-A) inhibitor, bevacizumab, is a systemic treatment option. In this single institution study, we review our clinical experience in patients with NF2 who received bevacizumab for VS and evaluate the effect of bevacizumab treatment on VS growth and symptom progression. MATERIAL AND METHODS This is a retrospective analysis of patients seen at the Mayo Clinic Rochester Multidisciplinary NF2 Clinic. Three-dimensional volumetric data for VS were measured using manual segmentation with Visage PACS software under the direct supervision of a board-certified neuroradiologist. RESULTS Out of 76 patients with NF2 evaluated in the past 3 years, we identified 19 that received treatment with bevacizumab. Median age of NF2 diagnosis was 19 years (range 0.5-61) with a median NF2 phenotype severity score of 2 (range 1-3). Thirteen of these patients have discontinued bevacizumab, accounting for a median duration of 12.2 months (range 3.3-88 months) of bevacizumab treatment. Bevacizumab was discontinued due to hypertension (n=5), proteinuria and renal dysfunction (n=3), tumor progression (n=2), fatigue or other intolerance (n=2), or non-compliance (n=1). The remaining 6 patients are currently receiving bevacizumab treatment for a median duration of 9.4 months as of March 2023 (range 3.7-48.3 months). Fifteen patients had brain MRI data available to evaluate VS change during bevacizumab treatment, with partial response observed in 5 patients, stable disease in 8, and progression in 2. Ten of the 13 patients who stopped bevacizumab had MRI data to evaluate VS change following treatment termination. Within 6 months of bevacizumab discontinuation, 6 patients had rebound growth of their VS between 21-95% from their previous tumor volume, while 4 did not. Three patients with rebound growth went on to have surgery or irradiation for VS management. CONCLUSION Our single institution experience confirms that bevacizumab can slow progression of VS and symptoms associated with VS growth. However, we note that there is the potential for rapid VS growth following bevacizumab discontinuation, for which we propose heightened surveillance imaging and symptom monitoring for at least 6 months upon stopping anti-VEGF therapy.

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 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.

OBJECTIVE The aim of this study was to report the treatment course of histologically confirmed metastases to the pituitary gland (pituitary metastasis). METHODS The Mayo data explorer was used to find patients with pituitary metastasis. Twenty-one patients were identified between the years 2001 and 2021, and their data were retrospectively collected. RESULTS The most common primary cancer origin was lung in men (45%) and breast in women (33%). The median age was 66 years (IQR 56–68 years). Patients presented with headache (67% [14/21]), vision problems (86% [18/21]), anterior hypopituitarism (71% [15/21]), and arginine vasopressin deficiency (38% [8/21]). Pituitary metastases were found before the diagnosis of the primary cancer in 5 patients (24%). The mean ± SD tumor size was 2.0 ± 0.7 cm, and 90% (19/21) presented as a solitary pituitary mass with no other intracranial metastatic lesions. Common radiological features were pituitary stalk thickening (90% [19/21]), cavernous sinus involvement (71% [15/21]), and constriction at the diaphragma sellae (52% [11/21]). Transsphenoidal surgery was performed in 20 patients, and subtotal resection was most frequently attained (76% [16/21]). Fourteen patients (67%) had adjuvant radiation therapy, and 15 patients (71%) were treated with systemic therapy. The median time from surgery to the initiation of radiation therapy was 16 days (IQR 11–21 days), and that from surgery to the initiation of systemic therapy was 5.0 months (IQR 1.5–14 months). During management, headaches improved in 57% (8/14) and vision problems improved in 61% (11/18) of cases; new hypopituitarism occurred in 5 patients. Six patients developed recurrence, and the median progression-free survival was 24 months (95% CI 5.4–43 months). After recurrence, 1 patient with adenoid cystic carcinoma was treated with rescue radiotherapy twice, and 4 patients responded well to systemic therapy. The median overall survival (OS) was 25 months (95% CI 7.1–43 months). The mean OS was better in patients with neuroendocrine lung tumor (261 months) and papillary thyroid carcinoma (80 months) and worse in patients with small cell lung cancer (4 months) and unknown origin (5 months). CONCLUSIONS Surgery with or without adjuvant radiotherapy is effective for mass reduction, rapid symptomatic improvement of vision and headaches, and definitive diagnosis. Even after local tumor control failure, some patients still benefit from radiation and/or systemic therapy.

9093 Background: Pembrolizumab interrupts PD-1/-L1 interaction and is efficacious in many cancers. However, resistance invariably emerges in the majority of patients. Potential mechanisms include activation of compensatory pathways. The inhibition of sonic hedgehog signaling (sHH) was previously shown to induce intra-tumoral (IT) infiltration by CD4+, CD8+ and HLA-DR class II cells. Our preclinical data showed sHH inhibitor enhanced IT penetration by monoclonal antibodies and induced PD-L1 expression. We conducted a phase I study using a novel sequential pulse dosing of sonedegib followed by pembrolizumab in aST with an expansion cohort to determine the maximum tolerated dose (MTD), tolerability and preliminary efficacy. Methods: The dose escalation utilized a 3+3 design to determine the MTD and proceeded to expansion cohort upon determination of the MTD. Patients enrolled to each dose level were observed for dose limiting toxicities (DLTs) during the 1st cycle. The expansion cohort consisted of NSCLC and head/neck squamous cell carcinoma (HNSCC) previously treated by anti-PD1/-L1. The recommended phase 2 dose (RP2D) was determined following the review of the toxicity profile of the combination from all cycles. The study treatment consisted of sonidegib oral daily from day 1 to 8 and pembrolizumab I.V. 200 mg on day 8 on an every 3-week cycle. The sonidegib dose levels explored were 400, 600 and 800 mg. Archival tumor and blood specimens were collected for correlative studies. Adverse events (AEs) were categorized and graded per CTCAE v5.0, and tumor response by RECIST v1.1. Results: The study enrolled a total of 33 patients and 29 received treatment (13 in escalation and 16 in expansion), including patients with NSCLC, HNSCC, skin cancer, gastric cancer and melanoma. The enrollment to the NSCLC cohort is complete and HNSCC continues. No DLT was encountered during dose escalation and the MTD was not reached. The highest planned dose level was selected to proceed to expansion (sonidegib 800mg days 1-8 in combination with pembrolizumab I.V. 200 mg on day 8 on an every 3-week cycle). The expansion cohort proceeded to enroll 15 patients evaluable for AEs (10 NSCLC and 5 HSNCC). Grade 3 and above treatment-related AEs across all patients were hyperglycemia, fatigue, dyspepsia, abdominal pain. The mature efficacy data will be reported at the meeting. Conclusions: The study successfully determined the RP2D of sonidegib when dosed sequentially with pembrolizumab in advanced solid tumors. The AE profile of the combination is similar to that for respective agents given individually. The efficacy data among anti-PD1/-PDL1-treated NSCLC will be reported at the meeting. Clinical trial information: NCT04007744 .

3109 Background: 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). We report initial results of a first-in-human phase 1 dose-escalation trial (NCT04197934) in patients with EGFR aberrant recurrent HGA and NSCLC. Methods: Adult patients with either recurrent EGFR mutant NSCLC with CNS metastases or recurrent EGFR mutant and/or EGFR amplified HGA were enrolled. WSD0922-Fu was orally administered, and dose escalated in cohorts based on a standard 3+3 design to determine the maximum tolerated dose (MTD). Toxicities were graded per CTCAE v5.0 and preliminary efficacy was based on modified RANO criteria or RECIST 1.1 as appropriate. Results: 25 patients (17 HGA, 8 NSCLC) were enrolled and treated in six cohorts (40 mg once daily to 320 mg twice daily, 28-day cycles). The median age was 57 years (range 39-75 years). 24% were female and 36% were ECOG 0. For patients with HGA, all patients were previously treated with radiation and temozolomide; the median number of prior lines of systemic therapy was 1 (range 1-4). For patients with NSCLC, all patients were previously treated with an EGFR inhibitor (prior osimertinib 88%); the median number of prior lines of systemic therapy was 1.5 (range 1-6). The median duration of exposure to WSD0922-Fu among all patients was 54 days (range 2-258 days). The most common (≥25%) treatment-related adverse events included fatigue (68%), acneiform rash (68%), diarrhea (52%), nausea (48%) and pruritis (28%). The frequency of severe AEs was dose dependent. The most common Grade 3+ AEs (≥10%) included lymphopenia (16%), acneiform rash (12%), headache (12%) and diarrhea (12%). The MTD was defined as 160 mg twice daily. At Cycle 1 Day 15 for patients treated at this dose level, the mean terminal elimination half-life (%CV) in the plasma was 31.6 h (102%) (median 14.5 h; range 6.2-78.7 h). The mean Cmax, Tmax, oral clearance at steady state, and AUC (0-12 h) (%CV) were 4513 ng/mL (50%), 2.0 hr (69%), 6.9 L/hr/m2 (42%), and 28084 h*ng/mL (52%), respectively. Oral clearance at steady state was inversely related with dose, suggesting either inhibition or saturation of clearance processes. Among patients treated at MTD or higher dose levels and with available response data, 100% (5/5) of patients with NSCLC demonstrated clinical benefit (SD + PR) while 60% of patients had partial responses (intracranial and extracranial). Furthermore, prolonged stable disease (9 cycles) was observed in a patient with EGFRvIII mutant GBM. Conclusions: The MTD for WSD0922-Fu monotherapy is 160 mg BID. Preliminary efficacy was observed in patients with osimertinib-resistant NSCLC and EGFRvIII mutant HGA. Enrollment to expansion cohorts is ongoing. Clinical trial information: NCT04197934 .

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 .

TPS2082 Background: No drug has improved survival for patients with high-grade gliomas (HGGs) since temozolomide in 2005. Relatively little is known about the live response of in situ gliomas to therapeutic intervention. Phase 0 studies that leverage access to the live human glioma in situ, including via microdialysis to sample the live glioma microenvironment, provide an attractive and feasible solution to this problem. We performed intraoperative microdialysis to evaluate the extracellular metabolome of divergent regions in 15 HGG resections. Our data revealed a conserved metabolic signature of HGGs and a novel glioma-associated metabolite, guanidinoacetate (GAA). Pathways enriched in this tumor signature included methionine and polyamine metabolism. Although GAA is typically converted to creatine, we hypothesize that the high flux of ornithine through ornithine decarboxylase (ODC) results in excess GAA accumulation. As such, in a Phase 0 trial, we will evaluate in situ glioma responses to polyamine depletion via ODC inhibition (Difluoromethylornithine, DFMO), with or without blockade of polyamine uptake (AMXT 1501), to identify candidate extracellular biomarkers of target engagement and cytotoxicity. Methods: Patients will be recruited who are undergoing a clinically indicated subtotal resection for a known or suspected high-grade glioma (NCT05717153). At the end of the surgery, two microdialysis catheters will be implanted for post-operative microdialysis, one in residual tumor and one in brain adjacent to tumor for an internal control. Beginning on post-operative day (POD) 1, patients will be randomized to one of the following three groups, including administration of vehicle, DFMO (500 mg, PO, BID) and AMXT 1501 (600 mg, PO, BID): 1) DFMO + AMXT 1501 (POD1-5); 2) Vehicle (POD1–POD2), followed by DFMO + AMXT 1501 (POD3-POD5); 3) DFMO alone (POD1–POD2), followed by DFMO + AMXT 1501 (POD3- POD5). Throughout this time, extracellular metabolite levels of polyamines, guanidinoacetate, and glutamate will be quantified from microdialysate collected every two hours from intraoperatively implanted 100 kDA microdialysis catheters. The primary outcome of this study is to determine how polyamine depletion impacts extracellular intratumoral guanidinoacetate abundance. The secondary outcomes of this study are to (1) determine the impact of polyamine depletion on polyamine abundance and the global extracellular metabolome within live human gliomas, in situ, and (2) assess the feasibility of longitudinal microdialysis for pharmacodynamic analysis within live human gliomas in situ in the post-operative setting. Clinical trial information: NCT05717153 .

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 .