A potent, selective and ATP-competitive inhibitor of ATM Kinase (Ki = 2.2 nM; IC₅₀ = 13 nM). Inhibits DNA-PK, mTOR, PI 3-K, PI 4-K, and ATR at much higher concentrations (IC₅₀ = 2500, 9300, 16600, >100000 and >100000 nM, respectively).