HGG-21. IDENTIFICATION OF SMALL MOLECULE KINASE INHIBITORS WITH SPECIFIC ACTIVITY IN PEDIATRIC GLIOMA

Abstract HYPOTHESIS: We hypothesize that pediatric high-grade glioma (pedHGG) tumors are sustained by pro-survival and pro-growth kinase signaling pathways that are distinct from adult GBM and normal brain, and can thereby be specifically targeted with small molecule inhibitors. METHODS: We performed a high-throughput chemical genetic screen using the GSK-PKISv1 library of 310 small molecule kinase inhibitors. These chemically diverse compounds have been tested in cell-free kinase inhibition assays measuring 203 unique kinases (37% of the human kinome), providing information on their efficacy against common and orphan kinases. We initially screened 5 high-grade glioma cell lines: 2 supratentorial pedHGG (KNS-42, SU-pcGBM2), 1 brainstem pedHGG (SU-DIPG-IV), and 2 adult supratentorial GBM (U251 MG, GBM43). We also screened immortalized normal human astrocytes to control for nonspecific cytotoxicity. In the initial screen, cells were treated at 1 μM for 24h, then measured for changes in viability, cell cycle, and apoptosis. Of the initial 310 compounds, 15 were selected for follow-up screening based on evidence of specific killing of pedHGG. To identify mechanisms underlying each compound’s activity, we leveraged the available cell-free kinome data and cross-referenced this against gene expression data from pedHGG and adult GBM tumors. RESULTS: Follow-up screening in 8 cell lines revealed 6 lead compounds that had efficacy against multiple pedHGG lines while sparing normal astrocytes and multiple adult GBM lines. The 6 lead compounds had diverse chemical backbones and patterns of activity across in cell-free kinase assays. The top targets of these compounds include some well-known glioma oncogenes (i.e. PDGFRA, EGFR), as well as novel targets (i.e. ERBB4, PYK2, HIPK1, LTK). CONCLUSIONS: Our chemical genetic approach identified 6 diverse small molecule kinase inhibitors with evidence of specific activity against pedHGG cell lines. Genetic and pharmacological validation of the putative targets of these compounds is underway to prioritize candidates for clinical translation.