Glioblastoma (GBM) is the most common and aggressive primary brain tumor, with poor prognosis due to its high recurrence rate and resistance to therapy. Standard treatment includes surgical resection followed by radiotherapy and temozolomide chemotherapy, yet 80–90% of patients relapse. This is largely driven by GBM’s extensive genetic and cellular heterogeneity, including a subpopulation of tumor-initiating cells (TICs) that promote resistance and disease recurrence.

We propose repurposing FDA-approved drugs to target shared vulnerabilities across diverse TIC populations, independent of tumor-specific mutations. Using patient-derived 3D TIC cultures and orthotopic xenograft (PDX) models, we focus on essential cellular processes such as apoptosis, cell cycle control, protein synthesis, and DNA damage response.

A high-throughput screen of 2,702 FDA-approved compounds was conducted on three heterogeneous TIC models: two derived from matched primary and recurrent GBMs, and one from an independent recurrent tumor. Only 2% of the compounds (66 in total) showed significant anti-tumor activity across all models. From this subset, we prioritized three candidates: Homoharringtonine, a protein synthesis inhibitor; Ixazomib Citrate, a proteasome inhibitor; and Panobinostat, a histone deacetylase inhibitor. Notably, Homoharringtonine and Ixazomib have not been previously tested in GBM, offering novel therapeutic potential. While Panobinostat has been explored in prior studies, it exhibited efficacy across all tested models.

These results highlight our TICs panel as a valuable screening platform for real-time therapy monitoring and for identifying promising TIC-targeting drugs for GBM treatment. Future work will explore resistance mechanisms using single-cell transcriptomic and epigenomic profiling, and develop rational combination therapies.