Dddr-13. st-401, a brain penetrating microtubule targeting agent that kills glioblastoma in interphase and by disrupting mitochondria function

The development of small molecular entities that can effectively penetrate the blood-brain barrier and kill glioblastoma (GBM) is crucial in Neuro-Oncology. ST-401, a unique microtubule depolymerizer, has shown remarkable potential as a therapeutic agent for GBM in PD-GBM isolates (nanomolar potencies) and in vivo preclinical GBM models (potencies DNA-damaging agents). This study aims to investigate the novel mechanism of action of ST-401 and its impact on GBM cell death. We recently showed that increasing concentrations of ST-401 disrupts mitochondrial function, leading to cell death initially in interphase and then in mitosis. Through single-cell RNA sequencing analysis, significant changes in mRNA related to mitochondrial functions were observed, including ribosomal proteins and OXPHOS genes. The study focuses on the role of mitochondria in GBM tumorigenesis and explores how ST-401 affects mitochondrial OXPHOS function. We identified three GBM cell lines (U251, SNB-19, and SF-539) with increasing vulnerability to ST-401, respectively, as measured by using WST-1, an index of mitochondria OXPHOS. Further investigation using the Seahorse platform demonstrated that SF-539 cells treated with ST-401 exhibited a loss of spare capacitance and significantly reduced mitochondrial function, including basal and maximal OXPHOS response, as well as ATP production. In conclusion, our results emphasize the existence of specific subtypes of GBM that show vulnerability or resistance to the antitumor effects of ST-401. Identifying these subtypes is crucial for advancing precision Neuro-Oncology and facilitating human trials. Our results also suggest that ST-401's inhibition of microtubule function and induction of cell death in interphase are associated with the loss of mitochondrial respiratory function. Given the limited treatment options for brain tumors and the challenges in delivering drugs across the blood-brain barrier, the development of brain-penetrant drugs like ST-401 holds great promise. Funded by NIH (CA244213 to NS and NS106924 to NS).