Ltd. is a new class I biologic drug, which is currently undergoing a randomized controlled clinical study in Hospital 307 for the treatment of metastatic colorectal cancer that has failed second-line or higher treatment. The basic requirements for enrolling patients in this trial are: 1. age ≥ 18 years, regardless of gender; 2. patients with metastatic colorectal cancer; 3. previous chemotherapy with irinotecan and oxaliplatin-based regimens; 4. no combined serious systemic diseases (other than cardiovascular, uncontrolled hypertension, diabetes, heart failure, severe arrhythmias, severe autoimmune diseases, severe psychological or psychiatric abnormalities, drug or alcohol dependence, uncontrolled heart failure, or other diseases). drug or alcohol dependency, uncontrolled thoracic ascites).