Selective and brain-penetrant lanosterol synthase inhibitors target glioma stem-like cells by activating a shunt pathway that generates the toxic metabolite 24(S),25-epoxycholesterol

Glioblastoma (GBM) is a common and aggressive adult brain cancer with few treatment options due in part to the challenges of identifying brain-penetrant drugs. Here, we investigated the mechanism of a tetracyclic dicarboximide (referred to as MM0299) identified in a screen for compounds with anti-glioblastoma activity. MM0299 inhibits lanosterol synthase (LSS) and diverts sterol flux away from cholesterol into a “shunt” pathway that culminates in 24(S),25-epoxycholesterol (EPC). EPC synthesis following MM0299 treatment is both necessary and sufficient to block the growth of mouse and human glioma stem-like cells by depleting cellular cholesterol. In comparison to a known LSS inhibitor, MM0299 exhibits superior selectivity for LSS over other sterol biosynthetic enzymes. Critical for its application in the brain, we report an MM0299 derivative that is orally bioavailable, brain-penetrant and induces the production of EPC in orthotopic GBM tumors but not normal mouse brain. These studies have implications for the development of an LSS inhibitor to treat GBM or other neurologic indications. Overall design: Spontaneous glioblastoma tumors from genetically engineered mouse model were pooled together to generate mouse GBM Mut6 cell line. Mut6 cells were treated with DMSO or 100 nM MM0299 for 24 hours. Total RNA was collected from these samples.