In the third part of the study, patients with metastatic colorectal cancer (CRC) will receive the best dose of the study drug determined from the first part of the study and will be followed to see what side effects and effectiveness the study drug has, if any, in treating the cancer. Approximately 25 patients with KRAS mutation (Active, not recruiting) and 15 patients with BRAF mutation (Active, not recruiting) from the US will be enrolled in Part 3.