A Clinical Study to Evaluate the Safety, Tolerability, and Preliminary Efficacy of B019 Injection in Subjects With Relapsed or Refractory B-cell Acute Lymphoblastic Leukemia.

Inclusion Criteria:

1. The patient himself/herself , and/or his/her legal guardian, agree to participate in the trial and sign the informed consent form；
2. Meet the diagnostic criteria for recurrent or refractory acute B cell lymphoblastic leukemia；
3. Documentation of CD19/CD22 tumor expression

3\. Liver, kidney, lung and heart function meet requirements; 4. Expected survival \>3 months; 5. Women of childbearing age and all post-adolescent male participants are willing to use highly effective contraceptive methods within 1 year after the infusion of B019 injection. At the same time, the subject should promise not to donate eggs or sperm for assisted reproduction for 1 year after the cell infusion.

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Exclusion Criteria:

1. Active CNS involvement by malignancy；
2. Isolated extramedullary leukemia recurrence；
3. Subjects with ≥grade 2 acute or moderate to severe chronic graft-versus-host disease (GVHD) within 4 weeks prior to screening;
4. Has had treatment with any prior CAR-T therapy or other therapy abandoned in protocal.

4\. Subjects who received therapy abandoned in protocal before PBMC (peripheral blood mononuclear cells) collection or before B019 injection; 5.Active other malignancy in 5 years. 6. Subjects who are positive for any of HBsAg, HBeAg, HBeAb, HBcAb, HCV-RNA, HIV EBV DNA, CMV DNA, HTLV-ab.

7\. Other situations deemed inappropriate for participation in this study by the investigator.

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