Diffuse intrinsic pontine glioma (DIPG) is a lethal childhood brain tumor. Radiotherapy remains the standard of care, but tumors recur due to radioresistance. Tumor hypoxia contributes to radioresistance, and evidence of oxidative metabolism and hypoxia-associated transcriptomic programs suggests that hypoxia may be relevant in DIPG. We therefore investigated the FDA-approved mitochondrial inhibitor atovaquone as a strategy to target oxidative metabolism and enhance radiation response in DIPG. Methods: Patient-derived DIPG cell lines were used to evaluate atovaquone by extracellular flux analysis, hypoxia and reactive oxygen species assays, clonogenic survival assays, metabolomics, and RNA sequencing. To improve brain exposure, an amorphous solid dispersion (ASD) atovaquone formulation was evaluated and tested in an orthotopic DIPG model. Results: In patient-derived DIPG cultures, atovaquone suppressed mitochondrial respiration, reduced hypoxia-associated readouts, decreased HIF-1α expression in 3D models, and enhanced radiation response. At higher concentrations, atovaquone also increased oxidative stress and enhanced the radiosensitivity of DIPG monolayers. Transcriptomics analysis revealed disruption of cell-cycle and mitotic pathways, supporting additional treatment-associated effects beyond hypoxia reduction alone. Commercial and ASD formulations showed comparable in vitro activity. In vivo, ASD atovaquone combined with radiation prolonged survival in an orthotopic DIPG model. Conclusions: Targeting mitochondrial metabolism enhances radiosensitivity in DIPG and supports mitochondrial metabolism as a potential therapeutic weakness in this disease. Its effects are associated with reduced hypoxia-related signaling and broader metabolic and transcriptional changes.
Mudassar et al. (Mon,) studied this question.