A cell-permeable aryl-morpholino compound that acts as a potent, selective, reversible, and ATP-competitive inhibitor of DNA-PK (IC50 = 120 nM) and PI 3-Kinase catalytic subunit p110β (IC50 = 135 nM). It inhibits DNA-PK-mediated cellular DNA DSB (double strand break) repair (EC50 = 68 μM) and enhances DSB-induced antitumor activity both in vitro and in vivo, while exhibiting no cytotoxic effects (up to 50 μM) in the absence of DSBs. It inhibits PI 3-K p110α, p110γ, and p110δ only at much higher concentrations (IC50 = 1.4, 0.88, and 1.0 μM, respectively) and exhibits no effect against a panel of several other kinases, including, Cdk2, Src, PKA, PKC, Chk1, CK1, ATM, and FKBP12, even at concentrations as high as 100 μM.
