Sarkaria, Jann N.

7073 Background: In preclinical studies, combinations of bortezomib and RT result in synergistic tumor killing (Cancer Chemother Pharmacol. 2007;59:207-15). Our group reported the results from the phase I portion of this study previously (J Clin Oncol. 200;28 (suppl; abstr 7085)). Based on these data, we undertook a phase II study of bortezomib in combination with paclitaxel/CBCDA and RT. Methods: Based on results from our previously reported phase I trial, systemic therapy included bortezomib (1.2 mg/m² IV days 1,4,8,11), paclitaxel (175 mg/m² IV day 2), and carboplatin (CBCDA; AUC=6 day 2) given every 3 weeks for 2 cycles. Thoracic radiotherapy (RT) included 60Gy/30 daily fractions starting day 1. The primary endpoint was the 12-month survival rate. If 41 or more of these 60 patients (68%) were alive at least 12 months after study entry, the trial would be deemed as positive and further study would be warranted. Results: 27 pts were enrolled to the phase II portion: M/F=17/10; stage IIIA/IIIB=13/14; ECOG PS 0/1=9/18; and median age: 58 (range 43-79). 18 pts (67%) completed therapy per protocol. At a planned interim analysis, 23 of 26 evaluable patients (88.5%, 95% CI: 70-98%) survived for at least 6 months, which exceeded the boundary of 21 or more needed to continue to full accrual. This trial could have continued per protocol, but was closed early due to slow accrual. With a median follow-up of 15.0 months in the 17 patients still alive, the 12-month survival rate was 71% (95% CI: 49 – 85). The median OS was 19 months (95% CI: 11 – no upper). Grade 3 or higher adverse events (regardless of attribution) were reported in 22 (82%) patients. Grade 4/5 adverse events were reported in 15 (56%) patients. There was one grade 5 event (pneumonitis). The most common (5 or more patients) grade 3/4 adverse events were fatigue (22%), leukopenia (63%), neutropenia (67%), and thrombocytopenia (44%). Conclusions: The addition of bortezomib resulted in high levels of severe hematologic toxicity, but also demonstrated evidence of activity with a 12-month survival rate of 71% and a median OS of 19 months. Further testing of this regimen in a larger study appears warranted.

2032 Background: Dasatinib is a potent oral ATP competitive multi-targeted kinase inhibitor of multiple members of the Src kinase family, known to be involved in gliomagenesis and invasion. N0877 is a phase I/randomized phase II trial evaluating the combination of dasatinib, radiation (RT) and temozolomide (TMZ) in newly diagnosed GBM. The phase I portion has been completed and is the focus of this report. Methods: A cohorts-of-3 design was used to assess the safety of dasatinib in combination with RT and concomitant TMZ, and establish the phase II dose of the combination. Dasatinib was given orally for 42 days, beginning with the first day of RT (total dose 60 Gy) and first dose of TMZ (75 mg/m2/d). A 24 - 42 day rest (cycle 2) followed the RT/TMZ/dasatinib. Patients (pts) were observed for DLT to the end of cycle 2. Patients then received 6 cycles (28 day cycles) of dasatinib (once daily) and TMZ (days 1-5). At the completion of 6 cycles of TMZ + dasatinib, pts stay on dasatinib only (28 day cycles) until progressive disease. Results: Phase I component is complete with 13 patients (3 at dose level 0, 3 at dose level 0-A, 7 at dose level 1). One patient in dose level 1 had to be replaced due to the development of unrelated medical issues. One DLT (grade 4 pancytopenia) was observed in 1 patient at dose level 0 (50mg bid) and one DLT (grade 3 rash) was observed in 1 patient at dose level 1 (150mg qd). MTD of dasatinib was determined to be 150mg daily. Most common adverse events throughout the entire study period were hematologic with the most common toxicity being lymphopenia (grade 3 in 69% of patients, grade 4 in 8%). Other toxicities attributed to treatment and occurring in > 10% of patients included anemia (31%), neutropenia (15%), and fatigue(15%). Best response was stable disease in 10 patients, progressive disease in 1 patient, and not evaluable in 2. Conclusions: MTD for dasatinib in combination with TMZ and RT in newly diagnosed GBM patients is 150mg daily. Toxicity was primarily hematologic with minimal non-hematologic events. This dose is currently being used in the ongoing placebo-controlled, randomized phase II trial.

1509 Background: Lack of MGMT methylation in GBM tumors is associated with a worse outcome with combined radiation (RT) and temozolomide (TMZ) therapy, and it is unclear whether non-methylated tumors benefit from TMZ treatment. Methods: The potential benefits of concomitant or adjuvant TMZ relative to methylation status were evaluated in 10 GBM tumors established from patient samples and maintained by serial passage in mice. For each tumor line, 32 mice with established orthotopic xenografts were randomized to A) placebo, B) TMZ PO daily × 5 (120 mg/kg or 66 mg/kg, as indicated) C) RT, 2 Gy bid × 10 fx., D) combined TMZ and RT, and mice were followed until moribund. Efficacy was evaluated by regression modeling and Kaplan-Meier statistical analyses. Results: Six lines with non-methylated MGMT (GBM10, 14, 26, 28, 36, 43) and 4 with methylated MGMT (GBM8, 12, 16, 34) were evaluated, and complete results are available in 6 lines. In all tumor lines and at both dose levels, there was a significant benefit for TMZ relative to placebo (p<0.003). Both methylated tumors (GBM8 and 12) and one non-methylated tumor (GBM14) were markedly sensitive to TMZ with greater than a 50 day extension in survival with monotherapy. Individually and in a pooled analysis, there was no evidence for a synergistic interaction between TMZ and RT in the non-methylated tumors (p=0.91 for pooled analysis). In contrast, there was a striking degree of synergy in GBM12 (p<0.001) and at least additive effects of combined treatment in GBM8 (5 of 8 mice still surviving in the RT/TMZ arm). In a pooled analysis of these 2 MGMT methylated tumors, there was a trend towards synergy (p=0.11). Conclusions: TMZ treatment did not sensitize MGMT non-methylated tumors to radiation, and with one exception, these non-methylated tumors were only modestly sensitive to TMZ alone. In contrast, treatment with TMZ appears to sensitize MGMT-methylated tumors to radiation and monotherapy is associated with marked and significant benefit. [Table: see text] No significant financial relationships to disclose.

2038 The effects of combining histone deacetylase (HDAC) inhibitors and proteasome inhibitors were evaluated in both established glioblastoma multiforme (GBM) cell lines and short-term cultures derived from the Mayo Clinic xenograft GBM panel. Co-exposure of LBH589 (LBH) and botezomib (btzmb) results in a striking induction of apoptosis, at minimally toxic doses of either drug alone, in established U251, U87, and D37 GBM cell lines, as well as in GBM8 (G-8), GBM10 (G-10), GBM12 (G-12), GBM14 (G-14), and GBM56 (G-56) cells, which have been developed from the Mayo xenograft GBM panel and maintained in short-term cultures. Synergism of apoptosis induction was also observed in U251 cells when co-exposing other HDAC inhibitors, including LAQ824 (LAQ) and trichostatin A (TSA), with another proteasome inhibitor MG132, demonstarting a class effect. In U251 cells, btzmb alone or in combination with LBH decreased Raf-1 levels and inactivated Akt and Erk. Either LBH589 or bortezomib alone increased expression of the cell cycle regulators p21 and p27. Additionally, the combination, but not the individual agents, markedly increased JNK activation. In addition, cell death after exposure to LBH589 and bortezomib is associated with cytochrome c release, Bax translocation, as well as caspase and PARP cleavage. Bax translocation may contribute to the synergistic cytotoxicity of the combination of LBH and btzmb in glioma cells since Bax translocation to mitochondria is known to precede cytochrome c release and apoptosis, but other pathways are likely to be involved. This combination regimen warrants further preclinical and possible clinical study for glioma patients. No significant financial relationships to disclose.

OBJECTIVE Convection-enhanced delivery (CED) and osmotic pump delivery both have been promoted as promising techniques to deliver drugs to pediatric diffuse intrinsic pontine gliomas (DIPGs). Correspondingly, the aim of this study was to understand how infusate molecular weight (MW), duration of delivery, and mechanism of delivery (CED or osmotic pump) affect volume of distribution (V d ) in the brainstem, to better inform drug selection and delivery in future DIPG investigations. METHODS A series of in vivo experiments were conducted using rat models. CED and osmotic pump delivery systems were surgically implanted in the brainstem, and different MW fluorescent dextran beads were infused either once (acute) or daily for 5 days (chronic) in a volume infused (V i ). Brainstems were harvested after the last infusion, and V d was quantified using serial sectioning and fluorescence imaging. RESULTS Fluorescence imaging showed infusate uptake within the brainstem for both systems without complication. A significant inverse relationship was observed between infusate MW and V d in all settings, which was distinctly exponential in nature in the setting of acute delivery across the 570-Da to 150-kDa range. Chronic duration and CED technique resulted in significantly greater V d compared to acute duration or osmotic pump delivery, respectively. When accounting for V i , acute infusion yielded significantly greater V d /V i than chronic infusion. The distribution in CED versus osmotic pump delivery was significantly affected by infusate MW at higher weights. CONCLUSIONS Here the authors demonstrate that infusate MW, duration of infusion, and infusion mechanism all impact the V d of an infused agent and should be considered when selecting drugs and infusion parameters for novel investigations to treat DIPGs.

Abstract BACKGROUND Glioblastomas show marked intra- and inter-tumor heterogeneity and are strongly resistant to both radio- and chemo-therapy, which are standard therapeutic modalities for this tumor. MicroRNAs (miRNAs) have the potential to serve as effective therapeutics for glioblastoma as they modulate the activity of multiple signaling pathways. METHODS Glioblastoma cultures were transfected with miR-34a or control miRNA mimics to assess biological function and therapeutic potential in vitro. miR-34a was packaged into bacterially-derived nanocells and administered intravenously for delivery to orthotopic patient-derived glioblastoma xenografts in mice. RESULTS Overexpression of miR-34a strongly reduced the activation status of the three core signaling networks that have been found to be deregulated in the vast majority of glioblastoma tumors, the receptor tyrosine kinase, p53 and Rb networks. miR-34a transfection also inhibited the survival of multiple established glioblastoma cell lines as well as primary patient-derived xenograft cultures representing the proneural, mesenchymal and classical subtypes. Transfection of miR-34a synergized with temozolomide (TMZ) in in vitro cultures of glioblastoma cells with primary TMZ sensitivity, primary TMZ resistance and acquired TMZ resistance. Intravenous administration of bacterially-derived nanocells carrying miR-34a strongly enhanced TMZ sensitivity in an orthotopic patient-derived xenograft mouse model of glioblastoma. CONCLUSIONS miR-34a strongly sensitizes a wide range of glioblastoma cell cultures to TMZ, suggesting that combination therapy of TMZ with miR-34a may serve as a novel therapeutic approach for the treatment of glioblastoma tumors. Bacterially-derived nanocells are an effective vehicle for the delivery of miR-34a to glioblastoma tumors.

Abstract Purpose: Glioblastoma is the most frequent and lethal primary brain tumor. Development of novel therapies relies on the availability of relevant preclinical models. We have established a panel of 96 glioblastoma patient-derived xenografts (PDX) and undertaken its genomic and phenotypic characterization. Experimental Design: PDXs were established from glioblastoma, IDH-wildtype (n = 93), glioblastoma, IDH-mutant (n = 2), diffuse midline glioma, H3 K27M-mutant (n = 1), and both primary (n = 60) and recurrent (n = 34) tumors. Tumor growth rates, histopathology, and treatment response were characterized. Integrated molecular profiling was performed by whole-exome sequencing (WES, n = 83), RNA-sequencing (n = 68), and genome-wide methylation profiling (n = 76). WES data from 24 patient tumors was compared with derivative models. Results: PDXs recapitulate many key phenotypic and molecular features of patient tumors. Orthotopic PDXs show characteristic tumor morphology and invasion patterns, but largely lack microvascular proliferation and necrosis. PDXs capture common and rare molecular drivers, including alterations of TERT, EGFR, PTEN, TP53, BRAF, and IDH1, most at frequencies comparable with human glioblastoma. However, PDGFRA amplification was absent. RNA-sequencing and genome-wide methylation profiling demonstrated broad representation of glioblastoma molecular subtypes. MGMT promoter methylation correlated with increased survival in response to temozolomide. WES of 24 matched patient tumors showed preservation of most genetic driver alterations, including EGFR amplification. However, in four patient–PDX pairs, driver alterations were gained or lost on engraftment, consistent with clonal selection. Conclusions: Our PDX panel captures the molecular heterogeneity of glioblastoma and recapitulates many salient genetic and phenotypic features. All models and genomic data are openly available to investigators.

Abstract Glioblastoma (GBM) is increasingly recognized as a disease involving dysfunctional cellular metabolism. GBMs are known to be complex heterogeneous systems containing multiple distinct cell populations and are supported by an aberrant network of blood vessels. A better understanding of GBM metabolism, its variation with respect to the tumor microenvironment, and resulting regional changes in chemical composition is required. This may shed light on the observed heterogeneous drug distribution, which cannot be fully described by limited or uneven disruption of the blood–brain barrier. In this work, we used mass spectrometry imaging (MSI) to map metabolites and lipids in patient-derived xenograft models of GBM. A data analysis workflow revealed that distinctive spectral signatures were detected from different regions of the intracranial tumor model. A series of long-chain acylcarnitines were identified and detected with increased intensity at the tumor edge. A 3D MSI dataset demonstrated that these molecules were observed throughout the entire tumor/normal interface and were not confined to a single plane. mRNA sequencing demonstrated that hallmark genes related to fatty acid metabolism were highly expressed in samples with higher acylcarnitine content. These data suggest that cells in the core and the edge of the tumor undergo different fatty acid metabolism, resulting in different chemical environments within the tumor. This may influence drug distribution through changes in tissue drug affinity or transport and constitute an important consideration for therapeutic strategies in the treatment of GBM. Significance: GBM tumors exhibit a metabolic gradient that should be taken into consideration when designing therapeutic strategies for treatment. See related commentary by Tan and Weljie, p. 1231

Abstract INTRODUCTION Neuroimaging dogma for glioblastoma asserts that hyperintensity on T1Gd MRI reveals the bulk of the tumor, while T2/FLAIR signal indicates edema. However, it is unclear whether this edema results from immune response or increased tumor cells. Further, one significant driver of the known sex differences in glioblastoma may be differences in immune response, due to the X-linkage of many immune genes. Based on this, we hypothesized that assumptions regarding tumor cellularity in T2/FLAIR images should be tailored to the biological sex of the patient. METHODS Using a retrospective cohort of 18 primary glioblastoma patients receiving multiple image-localized biopsies (82 total) and standard MRI, we assessed: distance of biopsy from T1Gd and T2 areas; a pathologist’s score of percent tumor cell density; and an imaging-based invasion metric, D/ρ. This metric is derived from the biomathematical Proliferation-Invasion model of glioma growth, which features two parameters, net growth rate (ρ) and net invasion rate (D). Their ratio D/ρ is related to degree of invasion, and is estimated from volumetric measurements of MRI abnormalities. Additionally, 25 patient-derived xenograft models implanted in females were grown until moribund, at which point brains were excised and stained for DAPI (to show all cells) and Lamin (to highlight tumor cells). Image processing of lamin-stained sections defines contours of intensity correlating with cell density. RESULTS Outside both the T1Gd and T2 region, male patient biopsies had higher tumor cell densities than females. Males also tended to have higher invasion metrics. Although each set derived from different patients, preclinical metrics of invasion were positively correlated with clinical invasion in females but negatively correlated in males. CONCLUSION Our preliminary finding that cell distribution patterns correlate with imaging metrics differently between the sexes supports the hypothesis that the degree of tumor cell density represented on certain MRI sequences may be sex-specific.