PI3K and mTOR inhibitors: a new generation of targeted anticancer agents.

Epidemiological and experimental studies support an important role of the phosphoinosite 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway in the biology of human cancers. Over the past few years a number of components of this signaling cascade have been the subject of intense drug discovery activities. This article summarizes progress made in the identification of kinase inhibitors of PI3K and mTOR, with an emphasis placed on drugs currently undergoing clinical trials. Potential combination strategies, safety concerns, and resistance mechanisms for this new generation of anticancer agents are also discussed.