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 thisstudy:

1. Voluntarily participate in this study and provide a signed and dated writteninformed 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 (withcomplete pathological report provided), including:Advanced solid tumors thathave 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 whichaccessible treatments have failed, or for which the investigator deems thepatient intolerant to accessible treatments based on comprehensive risk-benefitassessments (intolerance defined as ≥Grade 3 adverse reactions post-treatment,or reactions below Grade 3 but persistent or recurrent, impacting continuedtreatment). All related adverse reactions must resolve to ≤Grade 1 or return tobaseline before screening or the first dose.Primary malignant peritoneal tumorsconfirmed by pathology and/or histology, including primary peritoneal cancer,peritoneal mesothelioma, etc., with failed or intolerable standardtherapy;Other solid tumors with peritoneal metastasis judged by theinvestigator to lack standard treatment options.

4. Clear systemic treatment plan for primary and metastatic lesions, with noanticipated 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 measurablelesion (per iRECIST criteria); or evaluable malignant peritoneal effusion viaultrasound (per WHO criteria);

7. Willingness to provide recent FFPE tissue samples, pathological slides (8consecutive unstained slides), or ascites tumor cells for B7-H3 expressiontesting, with confirmed B7-H3 positivity;

8. No intraperitoneal drug injections (including hyperthermic intraperitonealchemotherapy) within 1 month before signing the informed consent, exceptdiagnostic 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 chronicconditions 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 metastasespresent).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 (exceptalopecia);

13. Fertile males and females must agree to use contraception from informed consentuntil 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 fromintraperitoneal therapy; 3. MSI-H/dMMR colorectal cancer patients notpreviously treated with immunotherapy; 4. Extensive liver metastases (>70%liver involvement); 5. Confirmed portal vein thrombosis; 6. Bowel obstructionwithin 4 weeks before dosing; 7. Conditions limiting drug diffusion (e.g.,compartmentalized or gelatinous ascites); 8. Surgery or radiotherapy within 4weeks before the first dose; 9. Systemic steroids (excluding replacementtherapy) or immunosuppressants within 1 week before treatment; 10.Participation in other drug trials within 4 weeks before screening; 11. PriorB7-H3-targeted therapy (antibody/ADC/cell therapy) without confirmed B7-H3positivity via biopsy; 12. Severe allergy to any component of theinvestigational drug or biologics; 13. Concurrent malignancies (except curedcervical carcinoma in situ or basal cell carcinoma); 14. Severe autoimmunediseases; 15. Prior allogeneic tissue/organ transplant; 16. Live vaccineswithin 2 weeks before cell therapy or planned during the study; 17. Active HBV,HCV (unless RNA-negative), HIV, syphilis, EBV, or CMV infection; 18. Activesystemic infection or coagulation disorders; 19. Severe cardiac (NYHA ClassIII+), hepatic (Child-Pugh C+), renal (CKD ≥Stage 4), or pulmonaryinsufficiency; 20. Pregnancy or lactation; 21. Any condition deemed unsuitableby the investigator