Clinical Study of Universal CD19 CAR-γδ T Cell Infusion in the Treatment of Relapsed/Refractory Acute B Lymphoblastic Leukemia

Inclusion Criteria:

* Age \> 14 years, gender unrestricted;
* Clinically diagnosed with relapsed/refractory acute B-lymphoblastic leukemia, with bone marrow blast/immature lymphocyte proportion ≥5% (morphology) (excluding cases with isolated extramedullary involvement), meeting any of the following criteria:

  1. Failure to achieve CR after 2 cycles of standard chemotherapy;
  2. Initial induction achieved CR, but CR duration ≤12 months;
  3. Relapsed/refractory B-ALL refractory to first or multiple salvage therapies;
  4. Post-hematopoietic stem cell transplantation relapse, including hematological relapse and minimal residual disease (MRD) positivity;
  5. Patients for whom no standard therapy exists.
* Cytology or histology confirms tumor cell immunophenotype as CD19-positive;
* Expected survival time exceeding 3 months;
* Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2;
* Key organ functions meeting the following criteria: left ventricular ejection fraction ≥50% by echocardiography; serum creatinine ≤1.5 × upper limit of normal (ULN); alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤3 × ULN; total bilirubin ≤1.5 × ULN;
* Negative pregnancy test for women of childbearing potential; both males and females agree to use effective contraception during treatment and for 1 year thereafter;
* Toxicity from prior anti-tumor therapy ≤ Grade 1 (according to CTCAE v5.0) or at an acceptable level per inclusion/exclusion criteria;
* No significant hereditary diseases;
* Able to comprehend the trial requirements and procedures, and willing to participate in the clinical study as required;
* Signed informed consent form for the trial

Exclusion Criteria:

* Presence of central nervous system (CNS) involvement or a clinically significant history of CNS diseases, such as epilepsy and cerebrovascular diseases;
* Pregnant or lactating women, or women who disagree to use effective contraception during treatment and within 1 year after treatment;
* Other malignancies that are not in remission;
* Patients with primary immunodeficiency or autoimmune diseases requiring immunosuppressive therapy;
* Patients who have received allogeneic immune cell therapy within 6 months before enrollment, or donor lymphocyte infusion within 6 weeks before enrollment;
* Confirmed positive anti-FMC63 and DSA responses in the patient's serum;
* Patients who have participated in other clinical trials within 4 weeks before enrollment;
* Uncontrolled infectious diseases or other serious conditions, including but not limited to infections (human immunodeficiency virus, acute or chronic active hepatitis B or C), congestive heart failure, unstable angina, arrhythmia, or conditions considered by the treating physician to pose unpredictable risks;
* History of stroke or intracranial hemorrhage within 3 months before enrollment;
* Major surgery or trauma within 28 days before enrollment, or main side effects not yet recovered;
* History of allergy to any component of the cell product;
* Inability to understand or unwillingness to sign the informed consent form;
* Other reasons deemed by the researchers as unsuitable for the clinical trial.