TMIC-25. SMAC Mimetic Targets Glioblastoma Stem Cells and Reprograms the Associated Tumor Microenvironment

Abstract Glioblastoma (GBM) is a highly treatment-resistant malignancy characterized by its poor prognosis and intrinsic resistance to therapy, driven largely by glioblastoma stem cells (GSCs) and an immunosuppressive tumor microenvironment (TME). This dual resistance plays a significant role in the failure of current treatment strategies. Consequently, there is an urgent need for novel therapeutic approaches that can effectively target GSCs while simultaneously reshaping the TME to promote anti-tumor immunity. In this study, we investigated the dual therapeutic potential of Xevinapant, a lead SMAC mimetic, through a combination of in vitro, in vivo, and single-cell transcriptomic analyses. We found that Xevinapant demonstrated potent anti-tumor activity through inducing dose-dependent apoptosis and significantly reduced cell viability in both human and mouse GSCs. In vivo administration of Xevinapant led to significant tumor suppression and extended overall survival in orthotopic models. Notably, our single-cell RNA sequencing result revealed that Xevinapant activated immune effector cell responses, contributing to the reprogramming of the immunosuppressive TME. Immune cell activation (both lymphoid and myeloid lineages) was further validated by flow cytometry using tumor-derived cells. To overcome potential therapeutic resistance, we derived Xevinapant-specific gene expression signatures and queried the LINCS database to identify small molecules with synergistic effects. Our analysis identified a promising compound ST-059620 that, when used in combination with Xevinapant, enhanced therapeutic efficacy and overcame resistance. Taken together, our findings highlight the dual mechanism of action of Xevinapant in targeting both tumor-intrinsic and microenvironmental resistance mechanisms. These results support the continued clinical development of Xevinapant and provide a strong rationale for combination strategies aimed at improving treatment efficacy in GBM.