Inclusion Criteria:
1. Aged 1-12 years with weight≥10kg, male or female;
2. The child and/or guardian has signed the informed consent form (ICF) and has the ability to comply with the study requirements.
3. Diagnosed with relapsed/refractory neuroblastoma. Clinical diagnostic criteria and first-line standard treatment can refer to the NCCN guidelines:
1. Relapsed neuroblastoma: New lesions appear at the primary site or other locations 4 weeks after achieving complete remission through first-line standard treatment.
2. Refractory neuroblastoma: Failure to achieve complete remission after standard treatment protocols, which include induction chemotherapy, surgery, and radiotherapy targeting the primary tumor and residual metastatic sites;
4. Prior to enrollment, appropriate measures can be implemented to ensure that the subject's disease status is either partial remission (PR) or stable disease (SD).
5. According to the INRC efficacy criteria, there must be at least one lesion whose efficacy can be assessed through functional imaging (123I-MIBG) and/or bone marrow examination (bone marrow aspiration or biopsy). If soft tissue lesions are present, the longest diameter of the target lesion should be ≤2 cm.
6. Tumor tissue sections or paraffin blocks can be provided, and it has been confirmed through immunohistochemistry (IHC) that the tumor tissue expresses B7-H3.
7. Lansky score\>60；
8. Estimated life expectancy \> 12 weeks;
9. Adequate organ and bone marrow function, and the laboratory test value meets the following requirements within 7 days before enrollment, as follows:
(1)Blood Routine Test: Absolute neutrophil count(ANC)≥1.5×10\^9/L;Absolute lymphocyte count (ALC)≥0.2×10\^9/L；Platelet count ≥75×10\^9/L; Haemoglobin≥90g/L; (2)Heart: Left ventricular ejection fraction (LVEF)≥50%;Cardiac function Grade I-II; (3)Pulmonary function: indoor oxygen saturation≥92%. (4)Hepatic function：Total bilirubin≤3×ULN; Aspartate aminotransferase (AST) or alanine aminotransferase (ALT)≤5×ULN; (5)Renal function: Serum creatinine≤2×ULN, or Creatinine clearance rate (CCR)≥60 mL/min (Cockroft-Gault formula); 10.All toxic responses originating from previous radiotherapy, chemotherapy, or other treatments (occurring within 4 weeks or 5 half-lives of anti-tumor drugs therapy \[including but not limited to chemotherapy, targeted therapy, immunotherapy, Chinese herbal medicine\]) have returned to NCI CTCAEV5.0 Grade≤1 (except for hair loss).
Exclusion Criteria:
1. Suffering from malignant tumors or diagnosed within 5 years before enrollment, excluding radical skin basal cell carcinoma, skin squamous cell carcinoma, thyroid cancer, breast cancer (ductal carcinoma in situ) and / or radical resection of carcinoma in situ.
2. Participants with symptomatic central nervous system (CNS) metastasis confirmed by imaging or pathological examination.
3. Participants with MIBG non-avid disease.
4. Participants with a history of organ transplantation（excluding stem cell transplantation）;
5. Participants with active autoimmune diseases requiring systemic treatment (such as the use of disease-modifying drugs, corticosteroids, or immunosuppressants) are considered. The use of replacement therapies (such as thyroxine, insulin, or physiological corticosteroids for adrenal or pituitary insufficiency) is permitted. A known history of primary immunodeficiency is also noted. For patients who only test positive for autoimmune antibodies, the presence of autoimmune disease must be confirmed based on the investigator's judgment.
6. Uncontrolled or irreparable systemic diseases, metabolic disorders, or other non-malignant organ diseases or cancer sequelae, which may lead to higher medical risks and/or uncertainties in survival assessment.
7. Active pulmonary tuberculosis (TB), who is receiving anti-tuberculosis treatment or has received anti-tuberculosis treatment within 1 year before enrollment; human immunodeficiency virus (HIV) infection, known syphilis infection.
8. Severe infections that are either active or poorly controlled clinically within 4 weeks prior to enrollment, including but not limited to hospitalization due to infections, bacteremia, or severe pneumonia complications (excluding mild urinary tract infections and upper respiratory tract infections).
9. Received radiotherapy, chemotherapy (excluding lymphodepletion), molecular targeted therapy, immune checkpoint inhibitors, or other anti-tumor treatments within 4 weeks or 5 half-lives (whichever is shorter) before cell infusion..
10. Participants who have undergone major surgery (craniotomy, thoracotomy, or laparotomy) within 4 weeks prior to the initiation of the study, or have severe unhealed wounds, ulcers, or fractures.
11. Participants who have received treatment from other clinical trials within 4 weeks prior to the initiation of the study.
12. Participants who receive attenuated live vaccines within 4 weeks prior to the initiation of the study.
13. Participants who have used any gene therapy products prior to cell infusion.
14. Allergic to components of CNK-UT injection.
15. Participants suffer from known mental or substance abuse disorders, which may interfere with their ability to comply with research requirements.
16. Participants considered by the investigator to have other potentially life-threatening serious complications that may interfere with the evaluation of this study..
17. Other situations that the participant is identified by the investigator as unsuitable to participate in the study.
