ATM Inhibitor-11 (Compound 1) is an inhibitor for ATM with an IC 50 of 0.32 nM. ATM Inhibitor-11 inhibits the KAP1 phosphorylation with an IC 50 of 0.97 nM. ATM Inhibitor-11 exhibits high exposure in the brain, heart and plasma of ICR mouse. ATM Inhibitor-11 exhibits anti-tumor efficacy in NCI-H441 xenograft mouse model.