A Phase Ib Study of Humanized Anti-VEGF Monoclonal Antibody (Sevacizumab) Injection Plus FOLFIRI in Chinese Patients With Metastatic Colorectal Cancer

Inclusion Criteria: * Histological/cytological confirmed unresectable metastatic colorectal cancer patients who have failed first-line oxaliplatin-based chemotherapy * At least one measurable lesion (according to RECIST 1.1 ) * At least 4 weeks from the last chemotherapy. If patients received anti-tumor biological products, at least four t1/2 of washout period is needed * Toxicity from previous treatment has to restore to ≤ grade 1 (NCI CTC4.0) * ECOG performance status 0-1 * Life expectancy ≥ 3 months * Adequate hematologic function: ANC ≥ 1.5 × 10\^9 /L, HB ≥ 90 g /L (blood transfusion allowed), PLT ≥ 100 ×10\^9 /L; Adequate hepatic function: ALT ≤ 2.5 × ULN, AST ≤ 2.5 × ULN, TBIL ≤ 1.5 × ULN (patients with liver metastases ALT ≤ 5 × ULN, AST ≤ 5 × ULN); Adequate renal function: creatinine ≤ 1 × ULN; Coagulation function: INR ≤ 1.5 × ULN, APTT ≤ 1.5 × ULN * Patients of childbearing potential (male and female) must agree to use reliable methods of contraception until at least 12 weeks after the last dose * Patients signed written inform consent * Willingness and capability to communicate with investigators and to comply with protocol requirements Exclusion Criteria: * HCV, TP or HIV antibody positive * Previously received anti-VEGF protein drugs, such as Bevacizumab,Sevacizumab * Previously treated with irinotecan * History of dihydropyrimidine dehydrogenase deficiency * Patients with alcohol or drug dependence * Participation in other clinical trials within 4 weeks before enrollment * Active or chronic hepatitis B infection with HBV DNA \> 1.0 \* 10\^3 IU/mL * Serious infection requiring intravenous antibiotic therapy * Symptomatic brain metastases * Patients with proteinuria at screening (urine protein ≥ 1+) * History of abdominal fistula, gastrointestinal perforation, abdominal abscess within 6 months prior to enrollment * History of intestinal obstruction, inflammatory bowel disease, or other intestinal diseases with chronic diarrhea as the major symptom * Serious non-healing wounds, ulcers or fractures * Major surgery (excluding biopsy) or significant trauma within 4 weeks prior to enrollment * Active bleeding within 3 months prior to enrollment * Bleeding diathesis or coagulation disorder * History of arterial or venous thrombosis * History of myocardial infarction or stroke within 6 months prior to enrollment * Unstable angina, congestive heart failure, New York Heart Association (NYHA) class II heart failure, uncontrollable arrhythmia, uncontrolled hypertension * Expected to receive surgery during the study or within 1 month after the last dose * The investigators consider the patients are not suitable for this trial * Pregnant and lactating women * Known allergies to any excipient in the study drug * Patients can not complete this study for any other reason