QL1203 In Combination With Chemotherapy for Metastatic Colorectal Cancer to Determine Efficacy and Safety

Inclusion Criteria: * Diagnosed as metastatic colorectal adenocarcinoma and is not suitable for local treatment such as radical resection, radiotherapy, radiofrequency and so on. * Man or woman at least 18 years old. * At least one measurable lesion can be evaluated according to Response Evaluation Criteria In Solid Tumors 1.1（RECIST1.1） criteria. * Eastern Cooperative Oncology Group (ECOG) performance status should be 0-1 before randomization. * The level of organ function must meet the requirements before randomization. * Prior to randomization, the damage caused by other treatments had recovered to \< grade 2 (CTCAE version 4.03). Exclusion Criteria: * Prior systemic or local chemotherapy for colorectal cancer，except in the following cases: the interval between the last dose of neoadjuvant or adjuvant therapy and recurrence\> 6 months。 * Prior epithelial growth factor receptor(EGFR)-targeted drugs for colorectal cancer. * Presence of central nervous system (CNS) metastases before the informed consent was signed, except for those who had stabilized CNS metastases for more than 4 weeks and had no symptoms after treatment. * History of malignancies other than colorectal cancer within 5 years prior to randomization, excluding cutaneous basal cell carcinoma, cervical carcinoma in situ, and thyroid papillary adenocarcinoma of non-melanoma after radical treatment. * History of interstitial lung disease. * Existing intestinal obstruction before randomization, active inflammatory bowel disease. * Patients with non-healing abdominal fistula and gastrointestinal perforation before randomization. * There were severe active infections or uncontrollable infections that required systemic treatment and could not be enrolled at the decision of the investigator within 14 days before randomization.