MT027 in Patients With Advanced Peritoneal Malignancies or Abdominal Metastatic Solid Tumors

Inclusion Criteria: * Patients must meet all of the following inclusion criteria to be enrolled in this study: 1. Voluntarily participate in this study and provide a signed and dated written informed consent form before undergoing any study-specific procedures, sampling, or analyses; 2. Aged 18-70 years (inclusive), regardless of gender; 3. Diagnosed with primary malignancy confirmed by pathology and/or histology (with complete pathological report provided), including:Advanced solid tumors that have failed ≥2 lines of prior standard therapy;Advanced solid tumors (e.g., gastric cancer, colorectal cancer, platinum-resistant advanced ovarian cancer, fallopian tube cancer, etc.) with no standard treatment available, or for which accessible treatments have failed, or for which the investigator deems the patient intolerant to accessible treatments based on comprehensive risk-benefit assessments (intolerance defined as ≥Grade 3 adverse reactions post-treatment, or reactions below Grade 3 but persistent or recurrent, impacting continued treatment). All related adverse reactions must resolve to ≤Grade 1 or return to baseline before screening or the first dose.Primary malignant peritoneal tumors confirmed by pathology and/or histology, including primary peritoneal cancer, peritoneal mesothelioma, etc., with failed or intolerable standard therapy;Other solid tumors with peritoneal metastasis judged by the investigator to lack standard treatment options. 4. Clear systemic treatment plan for primary and metastatic lesions, with no anticipated changes during the study; 5. Confirmed peritoneal metastasis via biopsy, cytology, CT, or prior evidence; 6. Enhanced CT shows intraperitoneal space-occupying lesions with ≥1 measurable lesion (per iRECIST criteria); or evaluable malignant peritoneal effusion via ultrasound (per WHO criteria); 7. Willingness to provide recent FFPE tissue samples, pathological slides (8 consecutive unstained slides), or ascites tumor cells for B7-H3 expression testing, with confirmed B7-H3 positivity; 8. No intraperitoneal drug injections (including hyperthermic intraperitoneal chemotherapy) within 1 month before signing the informed consent, except diagnostic paracentesis; 9. Expected survival ≥3 months; 10. ECOG performance status (PS) score of 0-2; 11. Laboratory results during screening meeting the following criteria: Blood tests (within 14 days): WBC ≥3.0×10\^9/L; ANC ≥1.5×10\^9/L; Lymphocytes ≥0.8×10\^9/L; Platelets ≥90×10\^9/L; Hemoglobin ≥90 g/L (transfusions or erythropoietin allowed). Patients requiring repeated transfusions due to active bleeding or chronic conditions must be discussed with the sponsor. Liver function (within 7 days): Total bilirubin ≤1.5×ULN; ALT/AST ≤2.5×ULN (≤5×ULN if liver metastases present). Renal function (within 7 days): Serum creatinine ≤1.5×ULN; or CrCL ≥30 mL/min (Cockcroft-Gault formula). Coagulation (within 7 days): INR/PT ≤1.3×ULN; APTT ≤1.5×ULN. 12. Recovery of prior systemic treatment toxicity to ≤Grade 1 or baseline (except alopecia); 13. Fertile males and females must agree to use contraception from informed consent until 180 days post-last MT027 cell infusion. Exclusion Criteria: * 1\. Known allergy to the investigational drug or its excipients; 2. Contraindications to peritoneal puncture or deemed unlikely to benefit from intraperitoneal therapy; 3. MSI-H/dMMR colorectal cancer patients not previously treated with immunotherapy; 4. Extensive liver metastases (\>70% liver involvement); 5. Confirmed portal vein thrombosis; 6. Bowel obstruction within 4 weeks before dosing; 7. Conditions limiting drug diffusion (e.g., compartmentalized or gelatinous ascites); 8. Surgery or radiotherapy within 4 weeks before the first dose; 9. Systemic steroids (excluding replacement therapy) or immunosuppressants within 1 week before treatment; 10. Participation in other drug trials within 4 weeks before screening; 11. Prior B7-H3-targeted therapy (antibody/ADC/cell therapy) without confirmed B7-H3 positivity via biopsy; 12. Severe allergy to any component of the investigational drug or biologics; 13. Concurrent malignancies (except cured cervical carcinoma in situ or basal cell carcinoma); 14. Severe autoimmune diseases; 15. Prior allogeneic tissue/organ transplant; 16. Live vaccines within 2 weeks before cell therapy or planned during the study; 17. Active HBV, HCV (unless RNA-negative), HIV, syphilis, EBV, or CMV infection; 18. Active systemic infection or coagulation disorders; 19. Severe cardiac (NYHA Class III+), hepatic (Child-Pugh C+), renal (CKD ≥Stage 4), or pulmonary insufficiency; 20. Pregnancy or lactation; 21. Any condition deemed unsuitable by the investigator