RTID-04. GLUGLIO - A PHASE IB/II RANDOMIZED DRUG REPURPOSING TRIAL OF GLUTAMATE SIGNALING INHIBITORS IN COMBINATION WITH CHEMORADIOTHERAPY IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA (NCT05664464)

Abstract

Abstract Glioblastoma synthesizes and secretes large quantities of the excitatory neurotransmitter glutamate, driving epilepsy, neuronal death, tumor growth and invasion. Several brain-penetrating drugs that have obtained clinical approval in other pathologic conditions can inhibit glutamate synthesis, secretion and signalling, respectively, including (i) the anti-seizure drug gabapentin, which inhibits the glutamate synthesis enzyme, branched chain amino acid transaminase 1, (ii) the anti-inflammatory drug sulfasalazine, which inhibits glutamate secretion by blocking the cystine-glutamate exchanger system Xc, and (iii) the cognitive enhancer memantine, which can prevent glutamate-driven, calcium-induced neuronal death and tumor cell invasion by blocking N-methyl-D-aspartate (NMDA) type glutamate receptors. The multi-centre, open-label, parallel-group, two-arm, 1:1 randomized, phase Ib/II trial GLUGLIO explores the efficacy of a triple-combination of daily oral gabapentin, sulfasalazine and memantine in combination with standard chemoradiotherapy compared to chemoradiotherapy alone. Dosing of either drug will be sought up to the maximum approved dose and will be reevaluated in an interim safety analysis after 20 patients have been randomized into the experimental arm. The primary endpoint is progression-free survival at 6 months (PFS-6). The sample size of N = 120 patients was calculated to detect an increase in PFS-6 from 50% to 70% with a power of 80% performing exploratory hypothesis testing at a one-sided significance level of 10%. Secondary endpoints include progression-free, overall and seizure-free survival, response rate, quality of life of patients and caregivers, symptom burden, cognitive functioning, tumor glutamate levels by magnetic resonance spectroscopy as well as anti-convulsant and steroid use. Surgical tissues as well as peripheral blood and electroencephalography recordings will also be sampled longitudinally for translational analyses. Recruitment is ongoing and foreseen to be completed by mid 2026. The simultaneous targeting of glutamate synthesis, secretion and signalling will clarify whether glutamate should be further explored as a clinical target in glioblastoma patients.