DDDR-14. IMPROVED ANTI-GLIOBLASTOMA EFFICACY BY BRG399, A NOVEL ORAL MICROTUBULE BINDING AGENT

Abstract Glioblastoma (GBM) is a highly malignant form of brain tumor with a poor prognosis despite advances in treatments. Therapeutic resistance/relapse remains a significant challenge necessitating the development of novel approaches. BRG399 is a brain permeant, non P-gp substrate, microtubule-targeting agent that displays anti-cancer activity in vitro and in vivo. BRG399 was well tolerated in rat and dog toxicology studies. Anti-cancer activity (IC50) of BRG399 in in vitro models of GBM was assessed to have potency ranging from 42nm to 89nM in the 3 cell lines tested. Here, in vivo tumor activity of BRG399 was assessed in Sprague Dawley rats implanted with 3x105 C6 rat glioma cells into the right entorhinal cortex/subiculum region. 14 days post successful implantation tumors were assessed by MRI, rats were randomized to receive vehicle (2% Labrasol) or BRG399 (5, 10, 20 mg/kg groups) twice daily by oral gavage for 16 days, and MRIs were performed on survivors on days 31 and 45 post implantation. BRG399 administration resulted in a marked improvement in survival (from 7.7 ± 2.6 days to 25.5 ± 15.6 days, log-rank test, p:0.007) compared to controls. Six animals receiving BRG399 remained alive beyond day 60 of post-treatment initiation. To assess biodistribution of BRG399 in the brain, rats were implanted with C6 cells and tumor establishment assessed 12 days later by MRI. Animals were treated with vehicle or BRG399 (10, 20, 25 mg/kg) and plasma and brains were collected for bioanalytical assessment. Tissue single cell biodistribution was performed using TIMSTOF FLEX spatial OMICS. These results demonstrate a therapeutic effect of BRG399 on intracranial glioma-bearing rats with survival of the BRG399 treatment groups of strong statistical significance over the control group. Analysis of drug levels in plasma and brain will serve as guidance for dose and scheduling decisions for further therapeutic development.