Current standard-of-care for glioblastoma (GBM) includes surgery, radiation and temozolomide. Most tumors recur within a year from diagnosis and median survival for recurrent GBM (rGBM) is 3-9 months. Unmethylated promoter status for O6-methylguanine-DNA-methyltransferase (MGMT) is a validated biomarker for temozolomide-resistance, exhibited by most GBM patients. VAL-083 is a DNA-targeting agent with a mechanism-of-action that is independent of MGMT. VAL-083 overcomes temozolomide-resistance in GBM cell-lines, cancer stem cells, and in vivo models. VAL-083 readily crosses the blood-brain barrier and accumulates in brain-tumor tissue. We recently completed a VAL-083 dose-escalation trial in temozolomide- and bevacizumab-refractory rGBM and determined that 40mg/m2/day given intravenously on days 1,2,3 of a 21-day cycle is generally well-tolerated. This dosing regimen was selected for subsequent GBM trials, including an ongoing single-arm, biomarker-driven Phase 2 trial (N=48) in temolozomide-refractory, bevacizumab-naïve rGBM , MGMT-unmethylated (Clinicaltrials.gov:NCT02717962). The primary objective of this study is to determine if VAL-083 improves OS compared to a historical control of 7.15 months for MGMT-unmethylated rGBM patients treated with lomustine (EORTC26101). In addition, another single-arm, biomarker-driven, Phase 2 study (N=25) of VAL-083 in combination with radiotherapy in newly diagnosed GBM, MGMT-unmethylated is ongoing (Clinicaltrials.gov:NCT03050736). This trial aims to determine a dose for further study of VAL-083 in combination with radiotherapy and explore if VAL-083 improves PFS and OS compared to historical results in newly diagnosed GBM. Enrollment and safety data updates will be provided at the meeting. The results of these studies, if successful, may support VAL-083 as part of a new chemotherapeutic treatment paradigm for GBM.