Iyekegbe, Dennis O.

Abstract GNE-317 is a dual PI3K/mTOR inhibitor with excellent blood-brain barrier penetration. In this study, the efficacy of GNE-317 was evaluated in the Mayo panel of primary glioblastoma multiforme (GBM) xenografts. Based on the concept of oncogene addiction, we hypothesized that GNE-317 would be most efficacious in EGFR-hyper-activated and/or PTEN-deficient lines. In a CyQUANT cell proliferation assay, the inhibitory concentration of 50% cell number (IC50) for GBM6, 10, 22, and 84 were 0.59±0.50, 0.72±0.40, 0.26±0.14, and 3.49±1.64 microM, respectively. In these selected lines, there was a poor correlation between EGFR or PTEN status and in vitro response. The efficacy of GNE-317 also was evaluated in 10 lines in an orthotopic xenograft model. Mice with established tumors were randomized to daily dosing with GNE-317 (30 mg/kg) or placebo until moribund. Similar to in vitro data, there was a spectrum of response to GNE-317 (Table 1). The survival benefit ratio (ratio of median survival) did not correlate with EGFR amplification (P=0.78), EGFR mutation (P=0.25), or PTEN (P=0.55) status when analyzed singly. However, GNE-317 did extend survival in 4 of 5 lines in which either EGFR or PTEN were deregulated. To evaluate potentially clinically relevant combinations, the efficacy of GNE-317 combined with bevacizumab (BEV) was tested in the same orthotopic model in GBM8, 10, and 59. In GBM10, GNE-317/BEV provided a significant increase in survival compared to the most effective single agent (P<0.0001). In GBM8, 10, and 59, the ratio of median survival for GNE-317/BEV vs. placebo were 1.47, 1.75, and 1.74, respectively (all P≤0.01). In conclusion, there may be a correlation between deregulation of the EGFR/PTEN signaling network and GNE-317 efficacy, and the efficacy of GNE-317 in some models can be extended when combined with bevacizumab. Table 1:Molecular Characteristics and Efficacy of GNE-317 in Mayo Primary GBM XenograftsEGFR AmplifiedEGFR vIII MutatedPTEN MutatedGNE-317 Responder*Benefit Ratio** of GNE-317GBM6YesYesWTYes1.35GBM8YesNoYes, HDYes1.19GBM10NoNoYes, HDYes1.47GBM22NoNoWTNo0.85GBM59YesYesYes, HDYes1.27GBM84YesNoYes, del Exon 1No1.02GBM115NoNoTBDNo0.86GBM116NoNoTBDNo1.05GBM117NoNoTBDYes1.38GBM122YesNoTBDNo0.99Abbreviations: HD=homozygous deleted; del=deletion in; TBD=to be determined; WT=wild type.* If in vivo survival difference reached P<0.05 by Log-rank Kaplan-Meier method between the GNE-317 treated and placebo groups, the GBM line was classified as a responder to GNE-317.** The benefit ratio equals to median survival of the GNE-317 treated group, divided by that of the placebo group. Note: This abstract was not presented at the meeting. Citation Format: Terence T. Sio, Jenny L. Pokorny, Ann C. Mladek, Brett L. Carlson, Mark A. Schroeder, Dennis O. Iyekegbe, Katrina Bakken, Laurent Salphati, Heidi Phillips, Jann N. Sarkaria. Preclinical efficacy of GNE-317, a dual PI3K/mTOR inhibitor, with or without bevacizumab in EGFR and/or PTEN-mutated glioblastoma multiforme. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2617. doi:10.1158/1538-7445.AM2014-2617

Abstract Purpose: Wee1 regulates key DNA damage checkpoints, and in this study, the efficacy of the Wee1 inhibitor MK-1775 was evaluated in glioblastoma multiforme (GBM) xenograft models alone and in combination with radiation and/or temozolomide. Experimental Design: In vitro MK-1775 efficacy alone and in combination with temozolomide, and the impact on DNA damage, was analyzed by Western blotting and γH2AX foci formation. In vivo efficacy was evaluated in orthotopic and heterotopic xenografts. Drug distribution was assessed by conventional mass spectrometry (MS) and matrix-assisted laser desorption/ionization (MALDI)-MS imaging. Results: GBM22 (IC50 = 68 nmol/L) was significantly more sensitive to MK-1775 compared with five other GBM xenograft lines, including GBM6 (IC50 >300 nmol/L), and this was associated with a significant difference in pan-nuclear γH2AX staining between treated GBM22 (81% cells positive) and GBM6 (20% cells positive) cells. However, there was no sensitizing effect of MK-1775 when combined with temozolomide in vitro. In an orthotopic GBM22 model, MK-1775 was ineffective when combined with temozolomide, whereas in a flank model of GBM22, MK-1775 exhibited both single-agent and combinatorial activity with temozolomide. Consistent with limited drug delivery into orthotopic tumors, the normal brain to whole blood ratio following a single MK-1775 dose was 5%, and MALDI-MS imaging demonstrated heterogeneous and markedly lower MK-1775 distribution in orthotopic as compared with heterotopic GBM22 tumors. Conclusions: Limited distribution to brain tumors may limit the efficacy of MK-1775 in GBM. Clin Cancer Res; 21(8); 1916–24. ©2015 AACR.