Despite numerous clinical studies using chemotherapeutic agents, novel biologics and immunotherapeutic agents, the overall survival of patients with high grade gliomas has not changed drastically over the last decade . The clinical impact of many cytotoxic agents has likely been limited in patients with malignant gliomas by their inability to cross the BBB. This poses an issue not only for primary brain tumors but also for metastatic brain disease. Unfortunately, while systemic therapy options have improved over the years for solid tumors, metastatic tumor cells are able to invade the CNS and proliferate with shelter from an impermeable BBB. Thus, with a lack of effective drug entry of varied chemotherapy agents, there has been no improvements in the overall survival of both malignant glioma and metastatic brain tumors. With this small clinical study, we evaluated regadenoson as a tool to facilitate CNS entry of a mildly permeable agent, temozolomide, from the proposed mechanism of enabling transient BBB disruption.