Dactolisib (BEZ235, NVP-BEZ235) is a dual ATP-competitive PI3K and mTOR inhibitor for p110α/γ/δ/β and mTOR(p70S6K) with IC50 of 4 nM /5 nM /7 nM /75 nM /6 nM in cell-free assays, respectively. Inhibits ATR with IC50 of 21 nM in 3T3TopBP1-ER cell.
BEZ235 significantly reduces the phosphorylation levels of the mTOR activated kinase p70S6K. BEZ235 results in a reduction of S235/S236P-RPS6 levels with IC50 of 6.5 nM. The activity of BEZ235 against mTOR is determined using a biochemical mTOR K-LISA assay with IC50 of 20.7 nM. BEZ235 shows slightly lower activity against its β paralogue with IC50 of 75 nM. The PI3K/Akt/mTOR pathway is often constitutively activated in human tumor cells. BEZ235 blocks PI3K and mTOR kinase activity by binding to the ATP-binding cleft of these enzymes. Both PTEN-null cell lines PC3M and U87MG show a dose-dependent reduction in cell proliferation when treated with increasing concentrations of BEZ235 with an average GI50 of 10-12 nM.  BEZ235 is an mTORC1/2 catalytic inhibitor.