CD33 and acute myeloid leukemia: Inspiringly, a 44-year-old male patient with refractory AML (AML-M4, normal karyotype, TP53 mutation) converted to MRD− disease when a dose of 7 × 105/kg CLL-1-CD33 CAR-T cells was firstly used after T cell-depleting conditioning therapy with fludarabine 30 mg/m2 and cyclophosphamide 500 mg/m2 for 3 consecutive days.