Orally bioavailable and blood–brain barrier-penetrating ATM inhibitor (AZ32) radiosensitizes intracranial gliomas in mice

Jeremy Karlin, Jasmine Allen, Syed F. Ahmad, Gareth Hughes, Victoria Sheridan, Rajesh Odedra, Paul Farrington, Elaine B. Cadogan, Lucy C. Riches, Antonio Garcia-Trinidad, Andrew G. Thomason, Bhavika Patel, Jennifer Vincent, Alan Lau, Kurt G. Pike, Thomas A. Hunt, Amrita Sule, Nicholas C.K. Valerie, Laura Biddlestone-Thorpe, Jenna KahnJason M. Beckta, Nitai Mukhopadhyay, Bernard Barlaam, Sebastien L. Degorce, Jason Kettle, Nicola Colclough, Joanne Wilson, Aaron Smith, Ian P. Barrett, Li Zheng, Tianwei Zhang, Yingchun Wang, Kan Chen, Martin Pass, Stephen T. Durant, Kristoffer Valerie

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Inhibition of ataxia-telangiectasia mutated (ATM) during radiotherapy of glioblastoma multiforme (GBM) may improve tumor control by short-circuiting the response to radiation-induced DNA damage. A major impediment for clinical implementation is that current inhibitors have limited central nervous system (CNS) bioavailability; thus, the goal was to identify ATM inhibitors (ATMi) with improved CNS penetration. Drug screens and refinement of lead compounds identified AZ31 and AZ32. The compounds were then tested in vivo for efficacy and impact on tumor and healthy brain. Both AZ31 and AZ32 blocked the DNA damage response and radiosensitized GBM cells in vitro. AZ32, with enhanced blood–brain barrier (BBB) penetration, was highly efficient in vivo as radiosensitizer in syngeneic and human, orthotopic mouse glioma model compared with AZ31. Furthermore, human glioma cell lines expressing mutant p53 or having checkpoint-defective mutations were particularly sensitive to ATMi radiosensitization. The mechanism for this p53 effect involves a propensity to undergo mitotic catastrophe relative to cells with wild-type p53. In vivo, apoptosis was >6-fold higher in tumor relative to healthy brain after exposure to AZ32 and low-dose radiation. AZ32 is the first ATMi with oral bioavailability shown to radiosensitize glioma and improve survival in orthotopic mouse models. These findings support the development of a clinical-grade, BBB-penetrating ATMi for the treatment of GBM. Importantly, because many GBMs have defective p53 signaling, the use of an ATMi concurrent with standard radiotherapy is expected to be cancer-specific, increase the therapeutic ratio, and maintain full therapeutic effect at lower radiation doses.

Original languageEnglish (US)
Pages (from-to)1637-1647
Number of pages11
JournalMolecular cancer therapeutics
Volume17
Issue number8
DOIs
StatePublished - Aug 2018
Externally publishedYes

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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