Phase I/II Study of Enhanced CD33 CAR T Cells in Subjects With Relapsed or Refractory Acute Myeloid Leukemia

Subjects will be pretreated with chemotherapy prior to infusion of CAR T cells: about 5 days before cells transfusion, the patients who planned to reinfuse CAR T cells were treated with fluorodarabine 30 mg/m\^2( body surface area) and cyclophosphamide 250 mg/m\^2( body surface area) for 3 days. Then this study will be using the Bayesian optimal interval phase I/II (Boin12) trial design. The protocol preset 2 dose levels: Dose 1 (DL-1) was 5×10\^5 (±20%) CAR T cells/kg, and dose 2 (DL-2) was 1×10\^6 (±20%) CAR T cells/kg. If the above dose cannot be met, subjects can still enter the study upon investigator consideration but require documentation of dosing. The lowest dose is 1×10\^5 CAR T cells/kg (±20%), and the highest dose is 1×10\^6 CAR T cells/kg (±20%). If the dose is out of the range mentioned above, entry into the trial will not be considered.