Background:

ETP-46464 is a potent and selective inhibitor for ATR (IC50 = 25 nM).

ATR (ATM- and Rad3-related) is a member of PIKK (phosphatidylinositol 3-kinase-like kinases) that regulates the DNA damage response pathways. It is a DNA damage sensor that is activated upon genotoxic stresses (e.g. ionizing radiation, UV radiation and DNA replication stalling) and phosphorylates its downstream substrates (e.g. p53, BRCA1 and CHEK1).

ETP-46464 abolished the G2/M checkpoint. It caused the presence of micronuclei or completely fragmented nuclei in cells under ionizing radiation. Cells treated simultaneously with hydroxyurea and ETP-46464 exhibited elevated ATM and Chk2 phosphorylation. In U2OS cells, ETP-46464 promoted the breakage of stalked replication forks. [1]

Reference:
1. Toledo LI, Murga M, Zur R et al.  A cell-based screen identifies ATR inhibitors with synthetic lethal properties for cancer-associated mutations. Nat Struct Mol Biol. 2011 Jun;18(6):721-7.