In an R/R AML PDX model, both CAR cell types led to CAR-T cell in vivo activation and clonal expansion, but only ADCLEC.syn1 administration resulted in complete remissions; moreover, mice relapsing with AML after CD33-CAR-T treatment were still successfully treated by ADCLEC.syn1, achieving second remission. The gene discussed is CD33; the disease is acute myeloid leukemia.