Convection-enhanced delivery of dexamethasone in glioma suppresses myeloid inflammation while avoiding systemic toxicities.

Dexamethasone is widely used to control cerebral edema and inflammation in glioblastoma, but its benefits are limited by systemic toxicities and adverse prognostic associations. We evaluated local administration via convection-enhanced delivery (CED) to maximize intratumoral anti-inflammatory effects by increasing local corticosteroid exposure while minimizing systemic exposure. In a syngeneic glioma mouse model, continuous intraparenchymal infusion of dexamethasone was well tolerated and associated with a modest but significant survival benefit versus vehicle. Single-nucleus RNA sequencing (snRNA-seq) and immunohistochemistry showed attenuation of glioma-associated inflammation with downregulation of reactive microglial/macrophage programs and reduced tumor-infiltrating myeloid cells with a morphology consistent with a less activated state. Experiments in human induced pluripotent stem cell (iPSC)-derived microglia confirmed that dexamethasone directly suppresses inflammatory gene expression, indicating a conserved mechanism across species. Pharmacokinetic analyses supported preferential intratumoral distribution and reduced systemic exposure with CED compared with systemic dosing. These findings suggest that localized dexamethasone delivered by CED reprograms the glioma immune microenvironment and achieves steroid-sparing control of inflammation without the systemic adverse effects associated with standard therapy. This clinically translatable strategy may improve symptom management and provide a platform for integrating local immunomodulation with future glioblastoma therapies.