Background: Recurrent glial tumors of the brain continue to be one of the most challenging malignancies to treat, and median survival for patients with recurrent disease is approximately 6 months for glioblastoma multiforme (GBM). The front-line therapy for GBM - temozolomide (TMZ) - is subject to resistance by DNA repair protein O⁶-methylguanine-DNA methyltransferase (MGMT), leading to poor prognoses for patients with recurrent GBM. Dianhydrogalactitol (VAL-083)is a first-in-class bi-functional N⁷ DNA alkylating agent shown to cross the blood-brain barrier, accumulate in brain tissue, and have activity against GBM. Studies suggest that VAL-083 overcomes MGMT-driven drug resistance in vitro and targets cancer stem cells. The purpose of this study is to determine the maximal tolerated dose (MTD) of VAL-083 in patients with recurrent GBM or progressive secondary brain tumor, and explore the safety, pharmacokinetics and tumor responses to treatment. Methods: Open-label phase I/II dose-escalation study of VAL-083 in patients with histologically confirmed primary WHO grade 4 malignant GBM, now recurrent, previously treated for GBM with surgery and/or radiation, if appropriate, and have failed both bevacizumab and temozolomide; or progressive secondary brain tumor, has failed standard brain radiotherapy, and has brain tumor progression after at least one line of systemic therapy. The study uses a 3 + 3 dose escalation design, until reaching the MTD or maximum specified dose. Patients receive IV VAL-083 on days 1, 2, and 3 of each 21-day treatment cycle. In phase II, additional patients are treated at the MTD (or selected optimum dose) to measure tumor responses. Results: Cohort 1 (3 patients) and cohort 2 (4 patients) were completed without any DLT’s. Adverse events (AEs) have all been grade 1/2, with only 1 grade 3 AE, unrelated to treatment. Cohort 3 currently has 4 patient enrolled, without reaching the MTD. 1/7 (14.3%) patients in cohorts 1and 2 has prolonged stable disease (15+ cycles) on VAL-083 treatment. Conclusions: VAL-083 up to the 2nd dose level was well tolerated without any safety signals. Dose escalation is continuing. Clinical trial information: NCT01478178.