This multi-center, open-label, non-randomized, non-placebo-controlled, Phase I study will define the safety profile and tumor response profile of the multi-kinase inhibitor BAY73-4506 as oral treatment in combination with the chemotherapy regimen mFOLFOX6 or FOLFIRI in patients with metastatic CRC. It will also determine the impact of the combined administration on the concentration of drugs over time (pharmacokinetics) of BAY73-4506, oxaliplatin, 5 FU, and irinotecan.

This study will be conducted at approximately 5 - 8 study centers in Germany. Up to 60 patients will be enrolled into this study to ensute that at least 12 - 15 patients for each combination regimen can be evaluated for safety and pharmacokinetics. For this reason a minimum of 20 patients will receive mFOLFOX6 in combination with BAY73-4506 and at least 20 patients will receive FOLFIRI in combination with BAY73-4506.

Inclusion Criteria:

• Histological or cytological documentation of adenocarcinoma of the colon or rectum.
• At least 1 measurable lesion as per RECIST
• ECOG Performance Status of 0 - 1
• Life expectancy of at least 12 weeks.
• Adequate bone marrow, liver, and renal function

Exclusion Criteria:

• More than 1 previous chemotherapy for Colorectal Cancer. Adjuvant chemotherapy for Colorectal Cancer (Stage I, II, II) is permitted, if the adjuvant therapy ended >6 month before screening.
• Previous FOLFOX treatment for patients who will be included in the mFOLFOX6 cohort apart from FOLFOX treatment in an adjuvant setting.
• Previous FOLFIRI treatment for patients who will be included in the FOLFIRI cohort.