Treatment of CD19 Chimeric Antigen Receptor T Cells for Pediatric Patients With CD19-positive B-cell Acute Lymphoblastic Leukemia Who Are Indicated for Hematopoietic Stem Cell Transplantation

Inclusion Criteria:

• Subject eligibility criteria include individuals who are under the age of 25 at thetime of SNUH-CD19-CAR-T administration. Confirmation of B-cell acute lymphoblasticleukemia diagnosed at the initial assessment by a treating physician for the firstdiagnosis is required. Immunophenotypic analysis of CD19 expression on leukemia cellsmust be confirmed through immune profiling at the time of the initial diagnosis ofB-cell acute lymphoblastic leukemia. In patients experiencing hematologic relapse ofB-cell acute lymphoblastic leukemia, CD19 expression should also be confirmed at thetime of relapse confirmation. Patients must achieve hematologic complete remission defined as less than 5% blasts in thebone marrow after the first-line or second-line chemotherapy (first salvage therapy).Eligible patients for hematopoietic stem cell transplantation, defined by indications fortransplantation, include those meeting at least one of the following criteria:

1. Philadelphia chromosome-positive due to t(9;22)(q34;q11) translocation.
2. Hypodiploidy defined by fewer than 44 chromosomes.
3. E2A-HLF gene fusion due to t(17;19) translocation.
4. Detection of minimal residual disease (MRD) positive at 0.01% or higher bynext-generation sequencing confirmed after consolidation therapy and maintenancetherapy.
5. Failure of the first-line therapy.
6. Cases not meeting any of the above criteria but deemed eligible for hematopoietic stemcell transplantation based on the investigator's judgment.

Exclusion Criteria:

• Patients who have undergone hematopoietic stem cell transplantation.
• Individuals for whom an adequate or sufficient leukapheresis product suitable for theproduction of SNUH-CD19-CAR-T cannot be obtained or is unavailable.
• Those known to be infected with the human immunodeficiency virus (HIV).
• Presence of uncontrolled active infections, determined by the investigator'sassessment. If appropriate treatment has been administered for the infection, andthere are no signs of progression at the time of enrollment, it is consideredcontrolled. Persistent fever without other symptoms is not interpreted as progressiveinfection.
• Women who are pregnant or breastfeeding.
• Individuals deemed clinically inappropriate for participation in the clinical trialbased on the investigator's clinical judgment.