PRAD50: a novel and clinically applicable pharmacodynamic biomarker of both ATM and ATR inhibition identified using mass spectrometry and immunohistochemistry. Issue 10 (13th November 2018)

• Record Type: Journal Article
• Authors: Jones, Gemma; Rooney, Claire; Griffin, Nicola; Roudier, Martine; Young, Lucy A.; Garcia-Trinidad, Antonio; Hughes, Gareth; Whiteaker, Jeffrey; Wilson, Zena; Odedra, Rajesh; Zhao, Lei; Ivey, Richard; Howat, William; Harrington, Elizabeth; Barrett, J.; Ramos-Montoya, Antonio; Lau, Alan; Paulovich, Amanda; Cadogan, Elaine; Pierce, Andrew
• Is Part Of: British journal of cancer. Volume 119:Issue 10(2018)
• Page Start: 1233
• Page End: 1243
• Publication Date: 2018-11-13
• Subjects: Cancer -- Periodicals; Cancer -- Research -- Periodicals; Tumors -- Periodicals; 616.994
• DOI: 10.1038/s41416-018-0286-4
• Languages: English
• ISSNs: 0007-0920

Abstract

Abstract Background AZD0156 and AZD6738 are potent and selective inhibitors of ataxia-telangiectasia-kinase (ATM) and ataxia-telangiectasia-mutated and Rad3-related (ATR), respectively, important sensors/signallers of DNA damage. Methods We used multiplexed targeted-mass-spectrometry to select pRAD50(Ser635) as a pharmacodynamic biomarker for AZD0156-mediated ATM inhibition from a panel of 45 peptides, then developed and tested a clinically applicable immunohistochemistry assay for pRAD50(Ser635) detection in FFPE tissue. Results We found moderate pRAD50 baseline levels across cancer indications. pRAD50 was detectable in 100% gastric cancers (n = 23), 99% colorectal cancers (n = 102), 95% triple-negative-breast cancers (TNBC) (n = 40) and 87.5% glioblastoma-multiformes (n = 16). We demonstrated AZD0156 target inhibition in TNBC patient-derived xenograft models; where AZD0156 monotherapy or post olaparib treatment, resulted in a 34–72% reduction in pRAD50. Similar inhibition of pRAD50 (68%) was observed following ATM inhibitor treatment post irinotecan in a colorectal cancer xenograft model. ATR inhibition, using AZD6738, increased pRAD50 in the ATM-proficient models whilst in ATM-deficient models the opposite was observed, suggesting pRAD50 pharmacodynamics post ATR inhibition may be ATM-dependent and could be useful to determine ATM functionality in patients treated with ATR inhibitors. Conclusion Together these data support clinical utilisation of pRAD50 as a biomarker of AZD0156 and AZD6738 pharmacology to elucidate clinical pharmacokinetic/pharmacodynamic relationships, thereby informing recommended Phase 2 dose/schedule.