Current treatment for Glioblastoma (GBM) involves radiotherapy which provides some tumour control and can extend survival by a few months. Unfortunately, due to the resistant nature of GBM cells to therapy, tumours always recur. The identification of BCL-XL [Pro-Survival Molecule] as a potential target for radio-sensitisation provides a potential route to a novel therapy with a clear translational pathway using the blood brain barrier penetrant inhibitor A1331852. This project aims to test the efficacy of A1331852 in combination with targeted Radiotherapy in a pre-clinical mouse model of GBM. To explore this opportunity further and allow development of the therapy for patient use, funding has been requested to undertake a large pre-clinical study.