The drug is a small molecule inhibitor of phosphoinositide-3 kinase (PI3K). Activation of PI3K is a frequent event in human tumors, promoting tumor cell growth, survival, and resistance to chemotherapy and radiotherapy.
Exelixis is evaluating multiple compounds that inhibit distinct components of the PI3K pathway. The company has already filed applications for two other compounds targeting this pathway, and believes that the strategy has the potential to treat multiple cancers.