The compound, XL418 is an inhibitor of protein kinase B (PKB or AKT) and S6 Kinase (S6K), key components of the phosphoinosotide-3 kinase (PI3K) signaling pathway. Activation of these kinases is a frequent event in human tumors, promoting cell growth, survival and resistance to chemotherapyterm and radiotherapy.

   "One of our drug development strategies is to systematically target key nodes in signaling pathways that are frequently deregulated in human tumors. An important component of this strategy is our focus on signaling downstream of PI3K," said Gisela Schwab, senior vice president at Exelixis.