KRAS and colon carcinoma: This redundancy mechanism has been blamed for the failure of FTase inhibitors (e.g., tipifarnib) to demonstrate significant clinical efficacy in the intended treatments of pancreatic (90% K-Ras mutations), lung, and colon carcinomas (~30% K-Ras mutations) (Lerner et al., 1997; Sparano et al., 2009).