Evaluating the Efficacy of Chidamide in the Treatment of Initial Unresectable Metastatic Colorectal Cancer With High Expression of SULF1

Inclusion Criteria 1. This study intends to enroll patients diagnosed with advanced colorectal cancer who are treated at Sir Run Run Shaw Hospital, Zhejiang University School of Medicine. 2. Age ≥ 18 years. 3. Voluntary participation in this study and signing of the informed consent form. 4. Confirmed by definitive histological evidence as colon or rectal adenocarcinoma. 5. ECOG performance status score of 0-1. 6. Tumor SULF1 high expression as determined by immunohistochemistry. 7. Confirmed by CT or MR assessment as distant metastasis of colon or rectal adenocarcinoma or unresectable locally advanced disease, and according to RECIST v1.1 criteria, at least one measurable lesion confirmed by independent central imaging review, and after multidisciplinary discussion, it is considered that local treatment (surgery, intervention, radiotherapy, etc.) is not feasible currently or within the near future (within 2 months). 8. Patients with metastatic colorectal cancer who have previously received first-line standard regimen therapy, including at least oxaliplatin or irinotecan. 9. The following laboratory test values obtained within 7 days before treatment on Day 1 of each treatment cycle, with adequate organ function: Hemoglobin ≥ 90 g/L, neutrophil count ≥ 1.5 × 10\^9/L, platelet count ≥ 75 × 10\^9/L, serum total bilirubin ≤ 1.5 × upper limit of normal (ULN), aspartate aminotransferase ≤ 2 × ULN, alanine aminotransferase ≤ 3 × ULN, serum creatinine ≤ 1.5 × ULN. 10. Willing and able to comply with the study protocol and visit schedule. 11. Life expectancy of at least 12 weeks. Exclusion Criteria Patients meeting any of the following criteria will be excluded from the study: 1. The patient has severe infection, obstruction, active bleeding, or perforation and requires emergency surgery or stent placement. 2. Previous or concurrent other active malignancy (except malignancies that have been treated with curative intent and have had no recurrence for more than 5 years, or carcinoma in situ that can be cured with adequate treatment). 3. Major surgery such as laparotomy, thoracotomy, or laparoscopic organ resection, or severe trauma within the previous 2 weeks. 4. Active coronary artery disease, severe/unstable angina, newly diagnosed angina, or myocardial infarction within 12 months before study participation. 5. Thrombotic or embolic events within the previous 6 months, such as cerebrovascular accident (including transient ischemic attack), pulmonary embolism, or deep vein thrombosis. 6. New York Heart Association (NYHA) class II or higher congestive heart failure. 7. Known human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS)-related disease, or active hepatitis B or hepatitis C. 8. Active inflammatory bowel disease or other colorectal diseases causing chronic diarrhea. 9. Any unresolved CTCAE grade 2 or higher toxicity caused by prior treatment (except anemia, alopecia, and skin pigmentation). 10. History of known or suspected allergy to any relevant drug used in the study. 11. Patients scheduled to undergo local treatment (surgery, intervention, radiotherapy, etc.) in the near future (within 2 months). 12. Any medical condition that is unstable or may affect patient safety and study compliance. 13. Receipt of radiotherapy within \< 4 weeks before the first dose of study drug, or receipt of chemotherapy, biological therapy, endocrine therapy, or small-molecule targeted therapy before the first dose of study drug (enrollment is permitted if the washout period is ≥ 5 half-lives from the first dose of study drug). 14. Insufficient hematopoietic function or organ function (blood products such as transfusion are not permitted to correct this within ≤ 14 days before the first dose of study drug). 15. Vulnerable populations, including individuals with mental illness, cognitive impairment, critically ill patients, minors, pregnant women, illiterate individuals, etc.