This is a single-arm, open-label phase I study to determine the safety, tolerability, and recommended dose (RD) of CAR-T-19 cells for patients with CD19+ relapse/refractory B-ALL under the age of 25.

B-cell acute lymphoblastic leukemia (B-ALL) accounting for 85% of all ALL cases, is a common hematological malignancy in children and adults. CD19 is a widely expressed antigen in both normal B cells and B cells-derived leukemia and lymphomas. This is a single-arm, open-label phase I study of CAR-T-19 (anti CD19 scFv chimeric antigen receptor T) cells for patients with CD19-positive relapse/refractory B-ALL under the age of 25.

Primary endpoint is to determine the safety, tolerability, and recommended dose (RD) of CAR-T-19. Secondary endpoints measure ORR, OS and others.

Inclusion Criteria:

• Patients with relapse/refractory B-ALL.
• Tumor cells from bone marrow or peripheral blood are measured CD19+ with 3 months before enrollment.
• Karnofsky Score ≥ 70 or Lansky Score ≥ 50.
• Patients who have a life expectancy of at least 12 weeks.
• Understand and voluntarily sign informed consent and are willing to comply with laboratory tests and other research procedures.

Exclusion Criteria:

• Patients with extramedullary relapse (EMR).
• Patients with genetic diseases, Burkitt lymphoma and leukemia or other malignancies.
• Patients positive for any of the following: HbsAg, HBV-DNA, HCV-Ab, HCV-RNA, HIV-Ab, TP-Ab, EBV-DNA or CMV-DNA.
• Patients with other uncontrolled infection.
• Patients who received anti-CD19 / anti-CD3 therapy, or any other anti-CD19 therapy.
• Patients with active Grade II-IV GVHD within 3 months prior to screening.
• Tumor cells are detected in cerebrospinal fluid.
• Patients who received HSCT within 3 months prior to screening.
• Anticipated other clinical trials within 4 weeks before this trial
• Pregnant or lactating women.
• Any condition that would, in the investigator's judgment, make it unsuitable for the donors to be enrolled.