Abstract 900: Dianhydrogalactitol (VAL-083) has the potential to overcome major challenges in the treatment of DIPG
Authors: Steino Anne , Zhai Beibei , Bacha Jeffrey A. , Brown Dennis M. , Daugaard Mads , Mueller Sabine 
Published: August 2018

Abstract
Despite decades of clinical trials, children with diffuse intrinsic pontine gliomas (DIPG) continue to have a very poor prognosis and dismal survival. DIPG is inoperable and standard treatment is radiation alone. Major obstacles to the successful treatment of DIPG include 1) an intact blood brain barrier impeding drug penetration, 2) inherent tumor cell resistance mechanisms to conventional chemotherapeutics, and 3) a lack of drug-induced potentiation of radiotherapy. VAL-083 is a structurally unique bi-functional DNA targeting agent that has the potential to overcome these barriers. VAL-083 readily crosses the blood-brain barrier and accumulates in brain tumor tissue where it rapidly forms interstrand DNA crosslinks at guanine-N7, leading to persistent DNA double strand breaks, cell cycle arrest, and cancer cell death. VAL-083 has cytotoxic activity in several pediatric brain tumors as assessed in NCI-sponsored clinical trials, both as a single agent and in combination with other chemotherapeutics. We recently completed a Phase I/II clinical trial in refractory GBM and established a well-tolerated dosing regimen of VAL-083 in adult brain tumor patients. We have previously demonstrated that VAL-083 cytotoxicity is independent of both the primary, DNA repair protein O6-methylguanine DNA methyltransferase (MGMT), and the secondary, DNA mismatch repair (MMR) system, mechanisms of resistance to temozolomide (TMZ) in vitro. TMZ is commonly used in combination with radiation for the treatment of adult brain tumors but has failed to improve the effect of radiation in DIPG. Importantly, VAL-083 potentiates the effect of radiation and overcomes TMZ resistance in TMZ-resistant adult glioblastoma cancer stem cells (CSCs) and non-CSCs at concentrations that are physiologically achievable in the CNS. Additionally, VAL-083 demonstrated synergistic efficacy in prostate and lung cancer cells with topoisomerase (Topo) inhibitors camptothecin and etoposide, commonly used in the treatment of pediatric brain tumors. In conclusion, VAL-083 is able to 1) cross the blood brain barrier, 2) overcome resistance mechanisms to chemotherapeutics commonly used in the treatment of adult gliomas, and 3) potentiate the effects of radiation in adult glioma cells at physiologically achievable concentrations. Thus, VAL-083 may have the potential to overcome major challenges in DIPG treatment as a single agent, in combination with radiotherapy, or as part of a combination regimen with Topo inhibitors. In the present study, we investigated the effects of VAL-083 in combination with radiation, irinotecan (Topo 1 inhibitor), or Wee1 inhibitor AZD1775 in a panel of DIPG cell lines with varying genetic profiles. The results will provide guidance for the design of animal models studying VAL-083 treatment of DIPG, either as part of a chemo-radiation regimen or in combination with Topo or Wee1 inhibitors.
Citation Format: Anne Steino, Beibei Zhai, Jeffrey A. Bacha, Dennis M. Brown, Mads Daugaard, Sabine Mueller. Dianhydrogalactitol (VAL-083) has the potential to overcome major challenges in the treatment of DIPG [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 900.