CLRM-14 INTRATUMORAL EXTRACELLULAR METABOLIC IMPACT OF DFMO AND AMXT 1501 IN LIVE HUMAN GLIOMAS

Gliomas may leverage alternate metabolic pathways in response to metabolism-targeted therapeutic intervention, all of which remain unexplored in the live human glioma, in situ. Defining emergent mechanisms of metabolic resistance in response to therapeutic challenge can help guide rational combinatorial therapies. To date, the metabolic response of gliomas in response to therapeutic intervention has remained poorly understood due to the relative inaccessibility of the live human tumor, in situ. Microdialysis is an underutilized tool that could be leveraged to overcome this longstanding challenge. Data from our ongoing intraoperative microdialysis trial have revealed an upregulation of polyamine metabolism and a novel glioma-associated metabolite, guanidinoacetate (GAA) -- a metabolite co-produced with ornithine, which is required for polyamine synthesis. In a Phase 0 trial, we will evaluate in situ glioma responses to polyamine depletion (difluoromethylornithine, DFMO) with or without blockade of polyamine uptake (AMXT 1501) to identify candidate extracellular biomarkers of target engagement and cytotoxicity in fifteen post-operative patients who have undergone a standard-of-care planned subtotal resection for high-grade glioma. Intraoperatively, high-molecular-weight catheters will be implanted into the residual tumor and brain adjacent to the resection cavity for post-operative longitudinal monitoring of extracellular metabolites via microdialysis. Polyamines and guanidinoacetate, a candidate biomarker of glioma-upregulated polyamine synthesis, will be monitored throughout therapeutic intervention from post-operative day (POD) 1 to POD5 via longitudinal microdialysis to determine live in situ glioma pharmacodynamic responses to polyamine depletion. Catheters will be removed on post-operative day five prior to discharge. We hypothesize that GAA will reflect local tumor production of polyamine metabolism. Additionally, in situ microdialysis in Phase 0 trials will allow for pharmacodynamic and pharmacokinetic, in addition to metabolic, monitoring, an opportunity which is rarely afforded in most clinical trials due to lack of access to the CNS.