Ion Channel Modulator DPI-201-106 Significantly Enhances Antitumor Activity of DNA Damage Response Inhibitors in Glioblastoma

Background: Glioblastoma, a lethal high-grade glioma, has not seen improvements in clinical outcomes in nearly 30 years. Ion channels are increasingly associated with tumorigenesis, and there are hundreds of brain-penetrant drugs that inhibit ion channels, representing an untapped therapeutic resource. The aim of this exploratory drug study was to screen an ion channel drug library against patient-derived glioblastoma cells to identify new treatments for brain cancer.

Methods: Seventy-two ion channel inhibitors were screened in patient-derived glioblastoma cells, and cell viability was determined using the ViaLight Assay. Cell cycle and apoptosis analysis were determined with flow cytometry using PI and Annexin V staining, respectively. Protein and phosphoprotein expression was determined using mass spectrometry and analyzed using gene set enrichment analysis. Kaplan-Meier survival analyses were performed using intracranial xenograft models of GBM6 and WK1 cells.

Results: The voltage-gated sodium channel modulator, DPI-201-106, was revealed to reduce glioblastoma cell viability in vitro by inducing cell cycle arrest and apoptosis. Phosphoproteomics indicated that DPI-201-106 may impact DNA damage response (DDR) pathways. Combination treatment of DPI-201-106 with the CHK1 inhibitor prexasertib or the PARP inhibitor niraparib demonstrated synergistic effects in multiple patient-derived glioblastoma cells both in vitro and in intracranial xenograft mouse models, extending survival of glioblastoma-bearing mice.

Conclusions: DPI-201-106 enhances the efficacy of DDR inhibitors to reduce glioblastoma growth. As these drugs have already been clinically tested in humans, repurposing DPI-201-106 in novel combinatorial approaches will allow for rapid translation into the clinic.