Dual Kinase Inhibitors: A Promising Approach for Adult and Pediatric High-Grade Glioma Therapy

High-grade gliomas (HGGs) in both adults and children have a very poor prognosis, with a median survival of less than two years after diagnosis. Genetic changes in receptor tyrosine kinases (RTKs) are common in adult and pediatric glioblastoma. There is frequent amplification of the epidermal growth factor receptor (EGFR) and mutations in the PI3K/AKT/mTOR pathway, which can be targeted by strategies using kinase inhibitors. However, clinical trials that have targeted EGFR or PI3K alone have had minimal effect on the outcomes for patients with HGG. Due to evidence that compensatory kinase activation leads to resistant disease, we have developed therapeutics that target multiple kinases. Using a computational modeling approach, we have designed small molecules that can simultaneously and selectively inhibit both EGFR and PI3K, based on the known binding modes of structurally related ATP binding site inhibitors. A series of new inhibitors have been synthesized and tested for metabolic stability and their ability to inhibit kinases. Six compounds with varying inhibitory effects on EGFR and PI3K were tested on the NCI-60 COMPARE cell line panel, and two compounds, MTX-216 and MTX-241, showed strong activity against human HGG cell lines. These compounds were further evaluated for cytotoxicity in five human glioblastoma (GBM) lines, some with the EGFRvIII mutation, and in three pediatric diffuse intrinsic pontine glioma (DIPG) cell lines. Treatment with MTX-216 or MTX-241 resulted in significant growth inhibition compared to targeting EGFR or PI3K alone with other drugs. The cytotoxic activity was observed at lower concentrations in DIPG patient-derived cell lines compared to adult GBM cell lines, suggesting that lower doses could be used in children, reducing the risk of toxicities. The selectivity of these compounds was also demonstrated against malignant cells compared to normal human astrocytes. Additionally, unique metabolic targeting features were identified in GBM and DIPG lines, indicating suppression of glycolytic pathways and oxidative phosphorylation, which is not observed with other EGFR or PI3K inhibitors. Given the metabolic dependencies of brain tumor cells on glycolytic pathways, future research will explore the possibility of identifying biomarkers for sensitivity to these dual inhibitors. These findings suggest that a single small molecule inhibitor with dual specificity for EGFR and PI3K is a promising treatment strategy for recurrent HGG in both adults and children. Despite the known association of HGG with deregulated EGFR and PI3K activity, there is currently no treatment that targets both of these oncogenes with a single molecule approach.