identification and lead optimization of a series of pyridopyrimidinone derivatives are described as a novel class of efficacious dual PI3K/mTOR inhibitors, resulting in the discovery of 31. Compound 31 exhibited high enzyme activity against PI3K and mTOR, potent suppression of Akt and p70s6k phosphorylation in cell assays, and good pharmacokinetic profile. Furthermore, compound 31 demonstrated in vivo