Kizilbash, Sani H

Abstract Tesevatinib is a potent oral brain penetrant EGFR inhibitor currently being evaluated for glioblastoma therapy. Tesevatinib distribution was assessed in wild-type (WT) and Mdr1a/b(-/-)Bcrp(-/-) triple knockout (TKO) FVB mice after dosing orally or via osmotic minipump; drug–tissue binding was assessed by rapid equilibrium dialysis. Two hours after tesevatinib dosing, brain concentrations in WT and TKO mice were 0.72 and 10.03 μg/g, respectively. Brain-to-plasma ratios (Kp) were 0.53 and 5.73, respectively. With intraperitoneal infusion, brain concentrations were 1.46 and 30.6 μg/g (Kp 1.16 and 25.10), respectively. The brain-to-plasma unbound drug concentration ratios were substantially lower (WT mice, 0.03–0.08; TKO mice, 0.40–1.75). Unbound drug concentrations in brains of WT mice were 0.78 to 1.59 ng/g. In vitro cytotoxicity and EGFR pathway signaling were evaluated using EGFR-amplified patient-derived glioblastoma xenograft models (GBM12, GBM6). In vivo pharmacodynamics and efficacy were assessed using athymic nude mice bearing either intracranial or flank tumors treated by oral gavage. Tesevatinib potently reduced cell viability [IC50 GBM12 = 11 nmol/L (5.5 ng/mL), GBM6 = 102 nmol/L] and suppressed EGFR signaling in vitro. However, tesevatinib efficacy compared with vehicle in intracranial (GBM12, median survival: 23 vs. 18 days, P = 0.003) and flank models (GBM12, median time to outcome: 41 vs. 33 days, P = 0.007; GBM6, 44 vs. 33 days, P = 0.007) was modest and associated with partial inhibition of EGFR signaling. Overall, tesevatinib efficacy in EGFR-amplified PDX GBM models is robust in vitro but relatively modest in vivo, despite a high brain-to-plasma ratio. This discrepancy may be explained by drug-tissue binding and compensatory signaling.

Posterior fossa (PF) diffuse gliomas in pediatric patients frequently harbor the H3 K27M mutation. Among adults, PF diffuse gliomas are rare, with limited data regarding molecular features and clinical outcomes. We identified 28 adult PF diffuse glioma patients (17 males; median: 50 y, range: 19 to 78 y), with surgery performed at our institution (13 brainstem; 15 cerebellum). Histologic subtypes included anaplastic astrocytoma (n=21), glioblastoma (n=6), and diffuse astrocytoma (n=1). Immunohistochemistry was performed for H3 K27M (n=26), IDH1-R132H (n=28), and ATRX (n=28). A 150-gene neuro-oncology-targeted next-generation sequencing panel was attempted in 24/28, with sufficient informative material in 15 (51.7%). Tumors comprised 4 distinct groups: driver mutations in H3F3A (brainstem=4; cerebellum=2), IDH1 (brainstem=4; cerebellum=4), TERT promotor mutation (brainstem=0; cerebellum=3), and none of these (n=5), with the latter harboring mutations of TP53 , PDGFRA , ATRX , NF1 , and RB1 . All TERT promoter–mutant cases were IDH-wild-type and arose within the cerebellum. To date, 20 patients have died of disease, with a median survival of 16.3 months, 1-year survival of 67.5%. Median survival within the subgroups included: H3F3A =16.4 months, IDH mutant=113.4 months, and TERT promoter mutant=12.9 months. These findings suggest that PF diffuse gliomas affecting adults show molecular heterogeneity, which may be associated with patient outcomes and possible response to therapy, and supports the utility of molecular testing in these tumors.

TPS350 Background: Mutations in isocitrate dehydrogenase 1 (mIDH1) are found in approximately 20-30% of patients with intrahepatic cholangiocarcinoma (CCA), and less commonly in glioma, chondrosarcoma, and other gastrointestinal malignancies. Despite documented clinical activity of mIDH1 inhibition in solid tumors, there are no approved targeted therapies for this patient population. LY3410738 is a potent, selective, and covalent inhibitor of mIDH1 R132. LY3410738 is differentiated from prior mIDH1 inhibitors by 1) its unique covalent binding mode, 2) its increased potency, and 3) its unique binding site outside of the dimer interface, which enables activity in the setting of known common second-site IDH1 mutations. Methods: This is an open-label, multicenter, global phase 1 study with oral LY3410738 currently enrolling patients with advanced CCA and other solid tumor types (NCT04521686). A dose escalation cohort will be followed with 4 exploratory expansion cohorts. The primary objective for dose escalation is determination of the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D). The primary objective for dose expansion is to assess the preliminary anti-tumor activity by ORR of LY3410738 when administered alone or in combination with cisplatin plus gemcitabine. Secondary objectives include evaluating safety and tolerability, pharmacokinetics, pharmacodynamics, progression free survival, and overall survival. Key inclusion criteria include any solid tumor with the presence of mIDH1 R132, ECOG performance status ≤1, and adequate organ function. Any prior treatment including an IDH1 inhibitor is allowed in the dose escalation cohort. Exclusion criteria include presence of active central nervous system metastases, leptomeningeal disease, and active or uncontrolled infection. CCA patients must not have had locoregional therapy within 4 weeks prior to the initial study dose, history of hepatic encephalopathy or refractory ascites, ongoing cholangitis, or mixed hepatocellular-CCA histology. Dose escalation will follow a 3+3 design and will allow patient back-fill to dose levels previously cleared for safety. Each cycle will be 28 days (4 weeks). Once the RP2D is determined, LY3410738 will be evaluated as monotherapy in expansion cohorts 1-3, and in combination with cisplatin plus gemcitabine in expansion cohort 4. Cohort 1 will enroll CCA patients with measurable disease who have received prior chemotherapy. Cohort 2 will enroll patients with advanced solid tumors except CCA who have measurable disease and received standard therapies. Cohort 3 will enroll patients with advanced solid tumors who have non-measurable disease and received standard therapies. Cohort 4 will enroll CCA patients with measurable disease who are treatment naïve for advanced disease. Clinical trial information: NCT04521686.

2025 Background: Although adjuvant radiation has demonstrated a clear survival benefit in anaplastic astrocytomas (AA), the role of concurrent temozolomide (TMZ) remains controversial. Methods: All adult patients diagnosed with AA from 2001 to 2011 and treated with standard doses of adjuvant radiation were identified retrospectively using the neuro-oncology database at the Mayo Clinic (Rochester, MN). Clinical data was extracted from the electronic medical record. IDH mutation status was also determined by obtaining either IDH1R132H immunostain on existing unstained slides or paraffin block sections, or by sequencing. Cumulative survival probabilities were estimated using the Kaplan-Meier method. Univariable and multivariable Cox proportional hazards regression models were fit to compare patients who did/did not receive TMZ. Results: 218 patients were identified that met inclusion criteria. 34 patients were excluded due to missing data on adjuvant chemotherapy. 146 patients had received adjuvant TMZ while 38 had not. Of these, IDH mutation status was determined on 124 patients who received TMZ and 33 of those who had not. The median duration of follow up was 36.4 months. On univariable analysis, adjuvant TMZ demonstrated a trend towards improved median survival from 35.2 to 53.1 months (p=0.06). As an independent variable, patients with IDH mutations had longer median survivals (111.7 months) when compared to IDH wild-type patients (23.3 months) (p<0.001). On multivariable analysis, five-year-survival was significantly impacted by receipt of adjuvant TMZ (HR = 0.56, p=0.03) and IDH mutation status remained a significant prognostic factor (HR = 0.19, p < 0.001) (see Table). Conclusions: IDH mutation strongly predicts a favorable outcome in patients with AA. Secondarily, concurrent TMZ is also associated with improved survival in patients with AA who are receiving adjuvant radiotherapy. [Table: see text]

e14608 Background: Beyond curative surgery, the optimal treatment for early stage pancreatic cancer is still a matter of debate. We conducted a comparative survival analysis between patients with resectable pancreatic cancer who received adjuvant treatment with either gemcitabine or 5-fluorouracil based chemotherapy and chemoradiation regimens. Methods: The Surveillance, Epidemiology and End Results (SEER)-Medicare database was used to identify patients with pancreatic cancer diagnosed from 1998 to 2005 who received curative surgery and adjuvant chemotherapy with either 5-fluorouracil or gemcitabine. These groups were subdivided by treatment with radiotherapy. Patients were followed until death, study endpoint or a maximum of five years after diagnosis. Results: 359 patients received 5-fluorouracil and 346 received gemcitabine. Compared to chemoradiation with 5-fluorouracil, outcomes for patients who received chemoradiation with gemcitabine did not differ. Patients who received gemcitabine without radiation had increased hazards (hazard ratio (HR) = 1.50 for high grade tumors (HGT), HR = 1.32 for low grade tumors (LGT)). However, outcomes of patients who received 5-fluorouracil without radiation varied with tumor grade. In LGT, patients had better outcomes with 5-fluorouracil when compared with chemoradiation with 5-fluorouracil (HR = 0.43). In HGT, the opposite was true (HR 2.10). Conclusions: Patients with low grade resectable pancreatic cancer may have better outcomes with 5-fluorouracil based chemotherapy without radiation when compared to 5-fluorouracil with radiation.

Abstract Panobinostat (PBST) is a histone deacetylase inhibitor with biologic rationale in the treatment of gliomas harboring H3 K27M mutation. METHODS We performed a retrospective medical record review of adult patients with H3 K27M mutant diffuse midline glioma treated with PBST at Mayo Clinic (Rochester, MN). RESULTS Four patients were identified with a mean age 40 years (range 22–62 years). Tumor location was: spinal cord (thoracic n=1, cervical n=1), brainstem (n=1), and thalamus (n=1).Two patients underwent biopsy alone while two underwent a partial resection. Three patients were treated with radiation (36–54 Gy) immediately prior to PBST monotherapy, and one patient was treated with PBST monotherapy without preceding radiation. All patients were otherwise chemotherapy naïve and did not receive any concurrent chemotherapy with PBST. PBST was dosed at either 10 mg (n=1) or 20mg (n=3) administered on days 1, 3, 5, 8, 10 and 12 of 21 day cycles. The mean duration of PBST therapy was 5 months (range 2–11 months). PBST was well tolerated overall. One patient experienced an objective response per RANO criteria. Two patients continue on therapy (5 cycles, 12 cycles) with stable disease. One patient rapidly progressed after 2 cycles of PBST therapy. In contrast with the patients who derived benefit from PBST, this patient was younger (22) and had multifocal disease with leptomeningeal involvement at treatment onset. The average progression free survival post PBST initiation was 8 months. CONCLUSION This single institution case series shows promise that PBST may have therapeutic benefit in adult patients with H3 K27M mutant diffuse midline glioma.

Abstract BACKGROUND High-grade gliomas (HGGs) of the brainstem represent a rarer subtype of central nervous system tumors compared to their supratentorial counterpart. Predictors of survival and patterns of care have not yet been established on a national, multi-institutional scale. METHODS The National Cancer Database was queried for adult cases surgically diagnosed with brainstem high-grade glioma. An array of patient demographics, comorbidities, tumor characteristics and treatment parameters were captured. Predictors of survival were investigated using multivariable Cox proportional hazards regression analysis adjusting for age, insurance status, Charlson comorbidity score, tumor grade, tumor size and type of treatment. RESULTS A total of 422 patients (median 51 years, 60% males) were analyzed. Two hundred eighty one received postoperative radiation with chemotherapy (66.6%), thirty-nine had radiation alone (9.2%), while the remaining had no adjuvant treatment (24.2%). Median radiation dosage was 54Gy. Overall median survival was 9.8 months (95% CI 8.8–12). Survival was significantly longer (p< .001) in the chemotherapy+radiation group (median: 14.2 months, 95% CI 11.7–17.1) compared to radiation alone (median: 5.7 months, 95% CI 3.7–12) and no adjuvant treatment (median:1.8 months, 95% CI 1.4–4). In multivariable analysis, increasing age (HR 1.87, 95% CI 1.47–2.37, p< .001) was associated with worse survival, whereas radiation with chemotherapy (HR 0.67, 95% CI 0.46–0.98, p=0.038) were associated with lower hazards of death compared to radiation alone. In subgroup analysis, the effect of adjuvant chemotherapy with radiation remained significant for grade IV (HR 0.46, 95% CI 0.28–0.76, p=0.003), but not for grade III tumors (HR 0.87, 95% CI 0.48–1.58, p=0.65). CONCLUSION Findings of the present analysis demonstrate the effectiveness of radiation with chemotherapy for adult patients with high-grade brainstem gliomas, particularly grade IV. Further research should aim on identifying specific patient profiles and molecular subgroups that are more likely to benefit from multimodality therapy.

Abstract BACKGROUND 177Lu-Dotatate (177Lu-DOTA0-Tyr3-Octreotate) is a beta-particle emitting somatostatin analog recently FDA approved for the treatment of somastatin receptor-positive gastroenteropancreatic neuroendocrine tumors. Somatostatin receptors are highly expressed in almost all meningiomas, therefore 177Lu-Dotatate may be a reasonable treatment strategy for this disease. Furthermore, the short path length of the beta particle should allow for treatment of previously radiated patients with low risk of cerebral radiation necrosis. CASE STUDY: A 61 year-old male presented with a history of atypical meningioma (WHO grade II), recurrent as anaplastic meningioma (WHO grade III). His previous treatments included multiple surgical resections, fractionated radiation therapy, stereotactic radiosurgery, everolimus/octreotide LAR, bevacizumab and hydroxyurea. MRI imaging revealed rapid volumetric progression over the prior nine months with a near tripling in size from 29.9 cm3 to 80.4 cm3. In-111 octreotide confirmed the presence of somatostatin receptors within the tumor. 177Lu-Dotatate was administered intravenously at a dose of 200 millicuries per dose, every eight weeks for four cycles. Treatment was tolerated very well, with no significant adverse events. Tumor volume initially increased to 98.3 cm3 after cycle 1 of treatment, and subsequently decreased to 91.2 cm3 after cycle 2. Eight months after treatment onset, the tumor volume remained stable (93.4 cm3). CONCLUSION 177Lu-Dotatate may be a safe and effective strategy for the treatment of somastatin receptor-positive meningioma. The transient increase in tumor volume after the first dose in this case may have represented delayed treatment effect or pseudoprogression. A phase II clinical trial is currently being activated to determine the progression-free survival associated with 177Lu-Dotatate in patients with recurrent meningioma.

Abstract BACKGROUND The Tumor Treating Fields (TTF) mechanism of action is hypothesized act upon mitosis by disrupting the cell spindle apparatus. However, biomarkers and human tissue correlation of the effect of the TTF device are lacking. CASE: A 41 year-old previously healthy woman was found to have a right frontoparietal glioblastoma after she developed subacute onset of left hemiparesis and headache. The tumor was IDH wild type MGMT promoter unmethylated and TERT mutated. Chromosomal Microarray (CMA) was performed and demonstrated genome wide aneuploidy primarily characterized by hyperdiploidy. She underwent a gross total resection of the enhancing portion of the tumor and subsequent standard chemoradiotherapy (60 Gy IMRT with concomitant temozolomide) followed by initiation of the TTF device and adjuvant temozolomide. Six months after diagnosis, after 72 days of using the TTF device with 75% compliance and completion of the third cycle of temozolomide the patient had radiographic recurrence. She underwent a repeat resection. Pathology demonstrated recurrent tumor. Genetic analysis no longer demonstrated chromosomal losses or gains: the tumor was diploid. DISCUSSION This case may be a demonstration of effect of the TTF device applying a selective pressure to cells with multiple chromosomal gains and losses as the efficiency of mitosis in these cells may already be severely compromised. We are currently performing CMA on all patients with available tissue treated with the TTF device at our institution, with a planned retrospective analysis to explore this hypothesis further. CONCLUSION Repeat resection with detailed genetic analysis of GBM recurrence after therapies may help generate hypotheses regarding mechanisms of resistance, and in this case, mechanisms of action of the TTF.