This is a open-label to assess the efficacy and safety of IM19 CAR-T cells in R/R B-cell Acute Lymphoblastic Leukemia.

Inclusion Criteria:

• Relapsed or refractory B-ALL, defined as：1）Not chieving a CR after 1 cycle of standard chemotherapy for relapsed leukemia. 2）Any relapse after HSCT and must be ≥ 6 months from HSCT at the time of IM19 CAR-T cells infusion. 3）Primary refractory as defined by not achieving a CR after 2 cycles of a standard chemotherapy regimen.
• Patients with Ph+ ALL are eligible if they are intolerant to or have failed two lines of TKI ± chemotherapy ；Ph + all patients with T315I mutation are not required to receive at least two TKI ± chemotherapy in the absence of effective TKI therapy.
• Morphological evidence of disease in bone marrow (at least 5% blasts).
• Aged 3 to 70 years.
• Estimated life expectancy >3 months.
• ECOG performance status of 0 or 1(age ≥ 16 years) or Lansky (age < 16 years).
• Women of childbearing age who had a negative blood pregnancy test before the start of the trial and agreed to take effective contraceptive measures during the trial period until the last follow-up; male subjects with fertility partners agreed to take effective contraceptive measures during the trial period until the last follow-up.
• Adequate organ function.
• Volunteer to participate in this trial and sign on the informed consent.

Exclusion Criteria:

• Subjects with lsolated extramedullary disease relapse.
• Subjects with Burkitt's lymphoma.
• Subjects has obvious symptoms of central nervous system invasion and needs targeted treatment.
• Subjects has previously received gene product therapy.
• Subjects has graft-versus-host response（GVHD） and need to use immunosuppressants or GVHD ≥ grade 2 or being treated with anti GVHD or suffering from autoimmune diseases.
• Subjects has received chemotherapy or radiotherapy within 3 days before leukapheresis.
• Subjects received systemic steroids within 5 days prior to leukapheresis.
• Subjects received drugs that stimulated the production of hematopoietic cells in the bone marrow for 5 days prior to leucapheresis.
• Subjects has participated in other clinical studies within 1 month before screening or plan to participate in other drug clinical trials during this study.
• Subjects received allogeneic cell therapy within 6 weeks before leukapheresis.
• Subjects with History or presence of CNS disorder.
• Subjects with HBV, HCV, HIV ,EBV,ECV or syphilis infection at the time of screening.
• Pregnant or lactating, or planning pregnancy within 180 days after the end of CAR-T cells infusion, or male patients whose partners plan pregnancy 180 days after their CAR-T cell infusion.
• Subjects with other tumors in the past 5 years.
• Within 14 days before enrollment, there were active or uncontrollable infections requiring systemic treatment.