• Male or female, age ≥ 18 years old, ≤ 75 years old

• Metastatic colorectal adenocarcinoma confirmed by histology, metastases cannot be removed

• RAS mutation, BRAF V600E wild type, and microsatellite stable

• ECOG 0 to 1

• Life expectancy is at least 12 weeks

• Hematological examination absolute neutrophil count (ANC)\>1.5×109/L, hemoglobin\>8g/dL and platelet\>100×109/L (according to the normal value of clinical trial center)

• Prothrombin time (PT) \< 1.5 times the upper limit of normal value and normal thromboplastin time (APTT) \< 1.5 times the upper limit of normal value

• Laboratory examination, serum creatinine is less than or equal to 1.5 times the upper limit of the normal reference range (if serum creatinine is elevated, 24 hours of urine must be collected, except for 24 hours creatinine clearance \> 50ml/min)

• When there is no liver metastasis, ALT or AST is less than or equal to 2.5 times the upper limit of the normal value reference range, serum total bilirubin is less than or equal to 1.5 times the upper limit of the normal value reference range; for patients with liver metastasis, ALT or AST is less than or equal to 5 times the upper limit of the normal value reference range, serum total bilirubin is less than or equal to 3 times the upper limit of the normal value reference range

⁃ Women of childbearing age must be willing to use adequate contraception during study drug treatment

⁃ Informed consent has been signed

⁃ According to the definition of RECIST 1.1, the investigator determined that the patient had a measurable disease. Tumor lesions located in previous radiotherapy areas are considered measurable if they demonstrate progression.