ATR kinase inhibitors NVP-BEZ235 and AZD6738 effectively penetrate the brain after systemic administration

Guido Fròsina, Aldo Profumo, Daniela Marubbi, Diana Marcello, Jean Louis Ravetti, Antonio Daga

Research output: Contribution to journalArticle

Abstract

Ataxia Telangiectasia and Rad3 related protein (ATR) is a central mediator of the response to DNA damage that may cause the quiescent resistance of cancer initiating cells to genotoxic radiotherapy. NVP-BEZ235 is a dual PI3K/mTOR inhibitor that also effectively targets ATR with IC50 =21×10-9 M in cells. AZD6738 does not target significantly PI3K/mTOR-related kinases but specifically inhibits ATR with IC50 =74×10-9 M in cells. Both drugs have been proposed as radiosensitizers of different tumors including glioblastoma (GB), the most malignant brain tumor. In order to study the radiosensitizing properties of ATR inhibitors NVP-BEZ235 and AZD6738 towards GB, we have preliminarily investigated their capacity to penetrate the brain after systemic administration. Tumor-free CD-1 mice were inoculated i.p. with 25 mg/Kg body weight of NVP-BEZ235 or AZD6738. 1, 2, 6 and 8 h later, blood was collected by retro-orbital bleeding after which the mice were euthanized and the brains explanted. Blood and brain samples were then extracted and NVP-BEZ235 and AZD6738 concentrations determined by High Performance Liquid Chromatography/Mass Spectrometry. We found for NVP-BEZ235 and especially for AZD6738, elevated bioavailability and effective brain penetration after intraperitoneal administration. Albeit low drug and radiation dosages were used, a trend to toxicity of NVP-BEZ235 followed by ionizing radiation (IR) towards mice bearing primary glioma initiating cells (GIC)-driven orthotopic tumors was yet observed, as compared to AZD6738+IR and vehicle+IR. Survival was never improved with median values of 99, 86 and 101 days for vehicle+IR, NVP-BEZ235+IR and AZD6738+IR-treated mice, respectively. Although the present results indicate favorable pharmacokinetics properties of ATR inhibitors NVP-BEZ235 and AZD6738, they do not lend support to their use as radiosensitizers of GB.

Original languageEnglish
Article number76
JournalRadiation Oncology
Volume13
Issue number1
DOIs
Publication statusPublished - Apr 23 2018

Keywords

  • Ataxia Telangiectasia and Rad3 related protein
  • Blood brain barrier
  • Pharmacokinetics

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging

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