Akkermansia Probiotics Plus Anti-PD-1 Monoclonal Antibody in MSS/pMMR Advanced Colorectal Cancer

Inclusion Criteria: * • Age 18-75 years * ECOG performance status score of 0-2 * Histopathologically confirmed colorectal cancer; tumor tissue immunohistochemistry or genetic testing showing pMMR or MSS/MSI-L type * Metastatic colorectal adenocarcinoma that has failed standard treatments (including irinotecan, oxaliplatin, fluorouracil, bevacizumab, cetuximab, etc.) * No prior use of immunotherapy (such as immune checkpoint inhibitors, adoptive cell immunotherapy, etc.) * At least one evaluable lesion according to RECIST version 1.1 criteria * No intestinal obstruction and good oral compliance * Adequate bone marrow, liver, and kidney function to receive treatment * Signed informed consent Exclusion Criteria: * • History of allergic diseases, severe drug allergies, or known allergies to probiotic drugs * Use of antibiotics or probiotic drugs/health products within the last 3 months * History of other malignancies with a disease-free interval of less than 5 years (except for cured basal cell carcinoma of the skin, cured cervical carcinoma in situ, and gastrointestinal tumors cured by endoscopic mucosal resection) * Presence of any active autoimmune disease or history of autoimmune disease * Current use of immunosuppressants or hormone therapy, continued within 2 weeks prior to enrollment * Concurrent severe infections * Congenital or acquired immune deficiency, or active hepatitis * Concurrent severe complications