DDEL-13. ENHANCING THE EFFICACY OF THE BBB-PENETRANT PEPTIDE-DRUG CONJUGATE PT(IV)-M13 WITH THE KINASE INHIBITOR BIA TO IMPROVE INTRA-TUMORAL DELIVERY AND INHIBIT DNA REPAIR

Abstract The blood-brain and blood-tumor barriers (BBB and BTB) constitute major obstacles to effective GBM therapy. These barriers impede the penetration of the great majority of pharmacological agents into brain tumors. This study introduces a dual-modality approach aimed at enhancing drug delivery to GBM through manipulating BTB permeability and facilitating targeted drug delivery through a novel BBB penetrant drug conjugate. First, we investigated the effects of the broad specificity kinase inhibitor 6-bromo-indirubin-3’-acetoxime (BIA), a derivative of the natural medicinal indirubin, on BTB integrity. These studies revealed that BIA diminishes trans-endothelial electrical resistance and reduces the expression of VE-cadherin in human cerebral microvascular endothelial cells (hCMEC/D3), indicating a loosening of tight junctions. This effect was also observed in mouse GBM models, suggesting a BIA-induced increase in BTB permeability, enhancing the intra-tumoral accumulation and efficacy of non-brain-penetrant therapeutic agents in murine GBM models. Secondly, we have developed Pt(IV)-M13, a perfluoroaryl stapled variant of the cell-penetrating peptide TP10 conjugated to Pt(IV), a prodrug form of cisplatin. This conjugate demonstrates an ability to penetrate the BBB, enhancing drug delivery while limiting exposure to healthy brain tissue, Pt(IV)-M13 exhibits a promising cytotoxic effect on GBM cells, sparing non-tumorous cells, and increases the survival of GBM tumor-bearing mice significantly compared to controls. Our data includes quantitative analysis of platinum accumulation in tumor tissues versus non-targeted regions, highlighting the specificity and potential of this approach. Furthermore, we have found that BIA synergizes with Pt(IV)-M13 in vitro, via inhibition of DNA repair, and are currently investigating the safety and efficacy of administering BIA in conjunction with Pt(IV)-M13 in vivo. This novel strategy holds potential to significantly impact the clinical management of GBM, emphasizing the importance of targeting the BTB in future therapeutic strategies.