Inclusion Criteria:
1. Age ≥18 years and ≤75 years.
2. Voluntarily sign informed consent form.
3. Patients with histologically or cytologically confirmed advanced solid tumors.
4. Histologically or cytologically confirmed malignant pleural/peritoneal effusion requiring drainage; or, in the absence of histologic/cytologic evidence, pleural effusion with clear imaging evidence of malignant pleural/peritoneal lesions on chest/abdominal CT and diagnosed as malignant pleural/peritoneal tumor in clinical practice.
5. Have received standard systemic therapy and developed clinical symptoms of serous cavity metastasis.
6. ECOG performance status: 0-2 points. Patients with ECOG 3 may be included if, in the investigator's judgment, removal of the effusion could improve the score to 2 or above.
7. Life expectancy ≥3 months.
8. Adequate major organ function.
9. Able to tolerate thoracentesis/abdominocentesis and catheter placement, or already have a functional thoracic/abdominal drainage catheter in place, and agree to receive study drug treatment via this route.
Exclusion Criteria:
1. Participation in any other interventional clinical trial within 4 weeks prior to the first dose of study drug.
2. Received local intracavitary therapy for pleural/peritoneal effusion (excluding diagnostic or symptom-relieving puncture/drainage) within 2 weeks prior to the first dose of study drug.
3. Received extra-thoracic/extra-abdominal radiotherapy within 2 weeks prior to the first dose of study drug, or received radical radiotherapy to pleural/peritoneal or pulmonary/abdominal lesions within 8 weeks prior to enrollment (palliative radiotherapy to chest/abdomen is permitted).
4. Underwent major thoracic or abdominal surgery within 4 weeks prior to the first dose of study drug and not fully recovered, or planned to undergo elective major surgery during the study period.
5. Any toxicity from prior anti-tumor therapy has not recovered to ≤ Grade 1 at the start of study treatment.
6. Symptomatic, uncontrolled central nervous system (CNS) metastases or leptomeningeal metastases that, in the investigator's judgment, make the patient unsuitable for enrollment.
7. Known human immunodeficiency virus (HIV) infection, active hepatitis B, active hepatitis C, or active syphilis infection.
8. Active, uncontrolled infection requiring systemic antibiotics, antivirals, or antifungal therapy.
9. Pregnant or breastfeeding women.
10. Definite history of severe mental or cognitive disorders that, in the investigator's opinion, may affect study compliance or safety assessment.
11. Presence of any active autoimmune disease, or history of autoimmune disease requiring systemic immunosuppressive therapy (topical glucocorticoids or inhaled/intra-articular steroids are permitted).
12. Require systemic corticosteroids or other immunosuppressants within 2 weeks prior to the first dose of study drug, and expected to require long-term use during the study.
13. Have poorly controlled or severe cardiovascular disease.
14. Have poorly controlled metabolic disease or complete/severe gastrointestinal obstruction requiring intervention.
15. Hypersensitivity to the investigational drug, any of its excipients, liposomal formulations, or kanamycin.
16. Have had a major thromboembolic event within 6 months prior to the first dose, or have a clear bleeding tendency.
17. Active local infection at the administration site.
18. Uncorrectable coagulation dysfunction that would pose a high risk for thoracentesis/abdominocentesis or catheter placement.
19. Have any other concurrent, serious, and/or uncontrolled medical condition.
