SOUTH SAN FRANCISCO--Exelixis announced that it has signed a Cooperative Research and Development Agreement with the US National Cancer Institute to elucidate how NCI anti-cancer compounds work. In the three-year collaboration, Exelixis will use its proprietary model system genetics technology to identify the mechanism of action for NCI compounds that have a demonstrated in vivo or in vitro anti-cancer activity. NCI will work with Exelixis to characterize and further develop the compounds for clinical therapeutic potential.