CCT128930 is a novel potent ATP-competitive, AKT inhibitor with an IC50 of 6 nM. CCT128930 prevents AKT activity in vitro and in vivo and induces marked antitumor responses. CCT128930 showed significantly antiproliferative activity and inhibited the phosphorylation of a range of AKT substrates in multiple tumor cell lines in vitro, consistent with AKT inhibition. CCT128930 caused a G1 arrest in PTEN-null U87MG human glioblastoma cells, in good agreement with AKT pathway blockade.