• Patients who volunteer to participate in this clinical trial and fully understand this study and sign the informed consent form (ICF), and willing to follow and capable of completing all testing procedures.

• Male or female aged 18-75 at the time of signing the ICF.

• Patients with histopathological confirmed primary colon adenocarcinoma

• MSS/RAS mutation patients with clinical stages T3N1-2 and T4N0-2

• an ECOG score of 0 or 1

• At least 1 measurable lesion according to RECIST 1.1 requirements.

• Patients must provide tumor tissue that meets the requirements for MSI/MMR testing.

• Expected survival period of at least 3 months.

• Negative hepatitis B surface antigen (HBsAg) and hepatitis B core antibody (HBcAb) (-). If HBsAg (+) or HBcAb (+), hepatitis B virus deoxyribonucleic acid (HBV-DNA) must be \<2500 copies/mL or 500 IU/mL before inclusion.

• Negative HCV antibody or HCV-RNA. If HCV-RNA is positive, the patient must have alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 × ULN to be included. Patients with co-infection of hepatitis B and hepatitis C should be excluded (HBsAg or HBcAb test is positive, and HCV antibody test is positive).

• Sufficient organ and bone marrow function confirmed by laboratory examinations within 7 days prior to the first use of the study medication, without severe hematopoietic abnormalities, heart, lung, liver, kidney dysfunction, and immune deficiency \[no blood transfusion, albumin, recombinant human thrombopoietin, or colony stimulating factor (CSF) treatment was received within 14 days prior to the first use of the study medication\]:

‣ Absolute value of neutrophils ≥ 1.5 × 109/L, platelet ≥ 100 × 109/L, hemoglobin concentration ≥ 9g/dL);

⁃ Liver function test: bilirubin ≤ 1.5 × ULN; aspartate transaminase and glutamate transaminase ≤ 2.5 × ULN; if there is liver metastasis, AST and ALT ≤ 5 × ULN;

⁃ Renal function test: serum creatinine ≤ 1.5 × ULN, or creatinine clearance rate (CCr) ≥ 60ml/min;

⁃ Coagulation: international standardized ratio (INR) ≤ 1.5 × ULN, prothrombin time (PT) and activated partial thromboplastin time (APTT) ≤ 1.5 × ULN;

⁃ Thyroid function: thyroid stimulating hormone (TSH) ≤ ULN; Should there be abnormalities, the levels of FT3 and FT4 should be examined. If the levels of FT3 and FT4 are normal, the patients can be included;

• Women of childbearing age must undergo a serum pregnancy test within 14 days before treatment, and the result is negative. And they are willing to use medically recognized effective contraceptive methods (such as intrauterine devices, contraceptives, or condoms) during the study period and within 3 months after the last dose of the study medication. For male subjects with partners of childbearing age, surgical sterilization is required, or it is recommended to use effective contraceptive methods during the study period and within 3 months after the last dose of the study medication.