• Fully understand this study and voluntarily sign the informed consent form;

• Age between 18-75 years inclusive;

• Patients with histologically confirmed unresectable locally advanced, recurrent, or metastatic colorectal adenocarcinoma;

• Failure of standard second-line systemic treatment with measurable lesions;

• Tumor tissue tested for microsatellite stability (MSS) or low microsatellite instability (MSI-L) by PCR, or confirmed pMMR by immunohistochemistry for DNA mismatch repair (MMR) protein (including MLH1, MSH2, MSH6, and PMS2 protein expression);

• ECOG performance status of 0-2, with no deterioration within 7 days;

• BMI≥18;

• Expected survival ≥3 months;

• Major organ functions meet the following requirements (no use of any blood components and growth factors within 14 days before enrollment):

‣ Absolute neutrophil count ≥1.5×109/L, white blood cells ≥4.0×109/L;

⁃ Platelets ≥100×109/L;

⁃ Hemoglobin ≥90g/L;

⁃ Total bilirubin TBIL ≤1.5 times ULN;

⁃ ALT and AST ≤5 times ULN;

⁃ Urea/BUN and creatinine (Cr) ≤1.5×ULN (and creatinine clearance (CCr) ≥ 50mL/min);

⁃ Left ventricular ejection fraction (LVEF) ≥50%;

⁃ Corrected QT interval by Fridericia's formula (QTcF) \<470 milliseconds.

⁃ INR ≤1.5×ULN, APTT ≤1.5×ULN.

⁃ Women of childbearing age must use effective contraception;

⁃ Good compliance and cooperation with follow-up.