This trial assesses the efficacy of two different weekly dosing regimens of Sym004 (Arm A: 12 mg/kg/week versus Arm B: 9 mg/kg loading dose followed by 6 mg/kg/week) compared with investigator's choice in terms of overall survival time in subjects with mCRC. Subjects assigned to Arm C will receive best supportive care (BSC), Fluorouracil (5-FU), or Capecitabine, per local standard of care.
Subjects will receive treatment until unacceptable toxicity, disease progression, withdrawal of consent, or until the subject meets any of the criteria for treatment discontinuation or trial discontinuation. Therefore, the duration of treatment will differ among individuals and cannot be fixed in advance.