EXTH-63. Repurposing itraconazole and pyrimethamine as a combinatorial treatment for glioblastoma

BACKGROUND Glioblastoma (GBM) is marked by a poor median overall survival of 14-16 months, highlighting the need for improving treatment. Drug repurposing leverages existing, safe compounds to provide more effective, cost-efficient cancer treatments. Based on the principle of Multidrug Adjunctive Cancer Treatment (MDACT), this study explores the potential of combining repurposed agents itraconazole and pyrimethamine as a treatment for GBM. MATERIAL AND METHODS 2D and 3D CellTiter-Glo assays were used to assess the effects of single and combination treatments on the viability of GBM patient-derived stem cell lines (PDSCL; N = 9) and ex vivo GBM tumor tissue fragments (TTF; N = 2), respectively. Bulk RNA-sequencing was performed on PDSCL after 48h of treatment to reveal molecular mechanisms of action. The orthotopic, syngeneic F98 GBM rat model was used for in vivo validation. RESULTS Both itraconazole and pyrimethamine, at clinically relevant concentrations, caused marked reductions in cell viability across a heterogeneous population of PDSCL. Bliss synergy analysis revealed mainly additive effects between both compounds. A significant decrease in cell viability of patient-derived and rat F98 TTF was observed after combinatorial treatment. On the molecular level, itraconazole induced upregulation of genes related to apoptosis and cholesterol homeostasis, while pyrimethamine reduced the expression of genes involved in G2/M checkpoint regulation and mitotic spindle assembly. In vivo, combinatorial treatment with 37.5 mg/kg itraconazole (b.i.d.) and 10 mg/kg pyrimethamine led to a significant increase in survival (P = 0.0334), compared to vehicle control (N = 6/group). No significant changes in body weights were observed, indicating treatment safety. CONCLUSION These data demonstrate potent anti-cancer effects when combining itraconazole and pyrimethamine in relevant preclinical GBM models, highlighting its potential as a combinatorial treatment for GBM. [This work was funded by a fellowship and project grant from “Fonds voor Wetenschappelijk Onderzoek” (FWO), grant number 1SH3H24N and S000825N]