ONC201 in combination with paxalisib for the treatment of H3K27-altered diffuse midline glioma

Diffuse midline gliomas (DMG), including diffuse intrinsic pontine gliomas (DIPGs), are the most lethal of all childhood cancers. Palliative radiotherapy is the only proven life-prolonging treatment, with patient survival 9-11 months. ONC201 shows preclinical and emerging clinical efficacy in DIPG. Currently, little is known about the mechanisms of sensitivity/resistance of DIPGs to ONC201, or whether recurring genomic features influence response. Using a systems-biological approach, we show ONC201 elicits potent agonism of the mitochondrial protease, CLPP, driving proteolysis of electron transport chain (ETC) and tricarboxylic acid (TCA) cycle proteins. DIPGs harboring TP53-mutations show reduced sensitivity to ONC201. Molecular mechanisms identify metabolic adaptation and resistance to ONC201 regulated by redox-activated PI3K/Akt signaling, counteracted using the brain penetrant PI3K/Akt inhibitor, paxalisib, in both wt-TP53 and TP53-mutant DIPGs. The discoveries described within, coupled with the powerful anti-DIPG/DMG pharmacokinetic and pharmacodynamic properties of ONC201 and paxalisib inform the DIPG/DMG phase II combination clinical trial NCT05009992.