This is a prospective, open-label, single-arm exploratory clinical trial to evaluate the safety and efficacy of CMTS1215 (Proteus mirabilis) oncolytic bacteria injection for the treatment of solid tumors. The study aims to enroll at least 8 patients with histologically confirmed solid tumors who have failed or are unable to complete conventional first-line, second-line, or third-line anti-tumor therapies.

Oncolytic bacteria are a class of bacteria that can specifically reproduce within tumors and cause tumor cell death while activating the host immune system. CMTS1215 is a Proteus mirabilis strain developed by the research team with demonstrated oncolytic effects in preclinical studies. The bacteria show excellent tumor tropism and have been shown to be safe and effective in mouse and canine models.

This study will evaluate the tumor response rate at 1 week and 4 weeks post-treatment according to RECIST 1.1 criteria, as well as assess the safety profile of the treatment. Patients will receive intratumoral injection of CMTS1215 under direct visualization or endoscopic guidance for up to 6-8 treatment cycles.

Inclusion Criteria:

1. Adults aged 18 years or older, any gender
2. Histologically confirmed solid tumor with measurable lesions according to RECIST 1.1
3. Failed or unable to complete conventional first-line, second-line, or third-line anti-tumor therapies, with multidisciplinary team consensus that no other suitable treatment options are available
4. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
5. Expected survival time > 3 months 6 Voluntary participation with signed informed consent

Exclusion Criteria:

1. Uncontrolled cardiovascular disease (e.g., heart failure NYHA III-IV, coronary artery disease, cardiomyopathy, arrhythmia)
2. Active severe clinical infection (> Grade 2 NCI-CTCAE v5.0), including fungal, viral, or tuberculosis infection
3. Coagulation abnormalities with bleeding tendency (INR outside normal range without anticoagulants within 14 days prior to enrollment); patients on anticoagulants or vitamin K antagonists (warfarin, heparin, or similar)
4. History of immunodeficiency, acquired or congenital immunodeficiency diseases, or organ transplantation
5. Lactating female patients
6. Currently participating in other clinical studies
7. Women of childbearing potential planning pregnancy during the study period
8. Patients with allergies to common antibiotics
9. Patients lacking or with restricted legal capacity
10. Other patients deemed unsuitable for enrollment by the investigator