KRAS and cancer: It is estimated that over 30% of all human cancers are driven by mutations in RAS genes,2 but with the notable exception of KRAS G12C mutant RAS proteins, RAS proteins have mostly resisted drug development efforts.3,4 RAS proteins connect growth factor signaling to multiple downstream pathways, including the RAF-MEK-ERK pathway (also known as the mitogen activated protein kinase (MAPK) pathway) and the PI3K pathway.