Exploration of the Dynamic Changes and Mechanisms of the Immune Microenvironment in Advanced Colorectal Cancer Treated With IBI363 Combination Therapy

Inclusion Criteria: 1. The participant must sign a written informed consent form (ICF) and be able to comply with the protocol-specified visit schedule and related procedures. 2. Age ≥18 years and ≤75 years, with no gender restrictions. 3. Histologically or cytologically confirmed diagnosis of advanced malignant tumors, meeting the following cohort-specific criteria: Cohort 2: * Patients with histopathologically confirmed advanced colorectal cancer (CRC). * Locally confirmed as mismatch repair-proficient (pMMR)/microsatellite instability-low (MSI-L) or microsatellite stable (MSS) based on standard testing. Cohort 9: * Patients with histopathologically confirmed advanced colorectal cancer (CRC). * Locally confirmed as mismatch repair-proficient (pMMR)/microsatellite instability-low (MSI-L) or microsatellite stable (MSS) (if applicable testing results are available). * Baseline imaging must indicate the absence of active liver metastases. Note: Patients with previously treated liver metastases (including surgical resection, microwave or radiofrequency ablation, or stereotactic radiotherapy, but excluding transarterial chemoembolization) are eligible if they received definitive treatment at least 6 months prior to study enrollment and subsequent imaging confirms the absence of liver metastases. Exclusion Criteria: \- 1. Pregnant or breastfeeding women, or women planning to become pregnant before, during, or within 6 months after the last administration of the study drug. 2\. Active or untreated central nervous system (CNS) metastases, confirmed by imaging during screening or previous evaluations (e.g., brain or leptomeningeal metastases). * Patients with asymptomatic brain metastases may participate. * Patients who have received treatment for brain metastases and have been symptomatically stable for ≥2 weeks without evidence of new or enlarging lesions may also be eligible, provided they meet all of the following: * Presence of measurable extracranial disease. * No metastases in the meninges, midbrain, pons, medulla, or spinal cord, and no multiple cerebellar metastases. * No compression of the cerebral aqueduct, third or fourth ventricle, or spinal cord. * Discontinuation of steroid therapy at least 14 days prior to the first dose of study drug. 3\. Active thrombosis, deep vein thrombosis (DVT), or pulmonary embolism within 4 weeks prior to the first administration of the study drug, unless adequately treated and considered stable by the investigator. 4\. Clinically significant cardiovascular or cerebrovascular diseases, including but not limited to: * Ventricular arrhythmias or other uncontrolled cardiac arrhythmias requiring medical intervention (e.g., antiarrhythmic therapy). * Severe conduction disorders (e.g., third-degree atrioventricular block). * QTc interval (corrected by Fridericia's formula) ≥480 ms. * Uncontrolled arterial hypertension despite standard treatment (systolic BP ≥160 mmHg or diastolic BP ≥100 mmHg). * History of myocarditis. * Congestive heart failure requiring ongoing treatment. * Left ventricular ejection fraction (LVEF) \<50%. * New York Heart Association (NYHA) Class III or IV cardiovascular disease. * Acute coronary syndrome (e.g., myocardial infarction, unstable angina), coronary angioplasty, or stent placement within 6 months before the first study drug administration. * Stroke or transient ischemic attack within 6 months before the first study drug administration. * Known active seizures. 5. Interstitial lung disease (ILD), pulmonary fibrosis, pneumoconiosis, drug-induced pneumonitis, radiation pneumonitis requiring steroid treatment, or severe pulmonary dysfunction/restrictive lung disease. 6\. History of allergic diathesis, asthma, or atopic dermatitis. 7. Recurrent or symptomatic pleural, pericardial, or peritoneal effusions requiring repeated drainage. 8\. Active autoimmune diseases requiring systemic therapy within 2 years before the first study drug administration (except for replacement therapies such as thyroid hormone, insulin, or corticosteroids for adrenal or pituitary insufficiency). 9\. History of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation. 10\. Known or suspected hypersensitivity to the study drug or any excipients. 11. History of significant immune checkpoint inhibitor-related toxicity requiring permanent discontinuation. 12\. Unresolved Grade \>1 toxicity from previous antitumor treatments, except for: * Persistent Grade 2 alopecia, peripheral neuropathy, or hypomagnesemia. * Stable, controlled toxicities (e.g., hypothyroidism managed with hormone replacement or hypertension controlled to \<160/100 mmHg with antihypertensive therapy). 13\. Incomplete recovery from surgery or major surgery within 4 weeks prior to the first study drug administration. 14\. Active, uncontrolled bleeding or known bleeding disorders. 15. Significant gastrointestinal diseases within 6 months before the first study drug administration, including but not limited to: * History of inflammatory bowel disease (IBD). * ≥Grade 2 diarrhea within 2 weeks before the first study drug administration. * Radiation enteritis. 16. Uncontrolled tumor-related pain or symptomatic hypercalcemia. 17. Known HIV infection, active hepatitis B (HBV), hepatitis C (HCV), or active tuberculosis: * HBV-positive patients must undergo HBV DNA testing. Patients are eligible if HBV DNA is ≤2.5 × 10³ copies/mL or ≤500 IU/mL. * HBsAg-positive patients must receive antiviral therapy during the study to prevent reactivation. * Patients with HBcAb(+), HBsAg(-), HBs(-), and HBV DNA(-) do not require antiviral prophylaxis but must be closely monitored for reactivation. * HCV-seropositive patients with negative or undetectable HCV RNA are eligible. * Patients who have completed HCV treatment and achieved an undetectable viral load are eligible. 18\. Severe/uncontrolled infections requiring IV antibiotics within 2 weeks before the first study drug administration or unexplained fever (\>38°C). 19\. Diagnosis of another malignancy within the past 5 years, except for curatively treated basal/squamous cell carcinoma, carcinoma in situ, localized prostate cancer, or papillary thyroid carcinoma. 20\. Prohibited medications and therapies, including but not limited to: * IL-2/IL-15 cytokines (except for their use in adoptive cell therapy or immune modulation in immunocompromised patients). * Chemotherapy or small-molecule targeted therapy within 2 weeks (or 5 half-lives) before first study drug administration, unless no delayed toxicity is expected. Exceptions: * Nitrosoureas and mitomycin C require a 6-week washout period. * Antibody-based therapies within 4 weeks before the first study drug administration. * Participation in another interventional trial within 2 weeks before the first study drug administration. * Palliative radiotherapy within 2 weeks before the first study drug administration. * Live vaccines within 4 weeks before the first study drug administration. * Immunosuppressive therapy or systemic corticosteroids (\>10 mg/day prednisone equivalent) within 2 weeks before the first study drug administration. * Traditional Chinese medicine with known antitumor effects within 1 week before the first study drug administration. 21\. Contraindications for combination therapies, including but not limited to: * UGT1A1\*6/\*6, UGT1A1\*28/\*28, or UGT1A1\*6/\*28 genotypes, which may impact irinotecan metabolism. * Prior extensive abdominal/pelvic radiotherapy, as assessed by the investigator, that may affect bone marrow or gastrointestinal function. 22\. Any condition, treatment, or laboratory abnormality that, in the investigator's judgment, may compromise patient safety, interfere with informed consent, affect compliance, or impact study drug evaluation. 23\. Severe psychiatric disorders, cognitive impairment, or substance abuse that may interfere with the consent process or study compliance. 24\. Any other known or anticipated factors that, in the investigator's opinion, would make the patient unsuitable for the study. Exclusion Criteria for Specific Cohorts Cohort 2: 1. Symptoms or risk of bleeding, perforation, or obstruction at the primary colorectal tumor site. 2. History of significant toxicity requiring permanent discontinuation of bevacizumab, oxaliplatin, capecitabine, or 5-FU. 3. Known allergy to study drugs or excipients. Cohort 9: 1. History of significant toxicity requiring permanent discontinuation of bevacizumab, fruquintinib, or trifluridine/tipiracil, or contraindications to study drugs as assessed by the investigator. 2. Known allergy to study drugs or excipients.