To this end, we performed CRISPR-Cas9-mediated RUNX1-RUNX1T1 disruption utilizing our in vitro setup with the four sgRNAs (RX1, RX2, RXT1, RXT2) and showed the specific target site variations in a pre-therapeutic blood sample from one patient (Patient 4) diagnosed with CBF AML with t(8;21)(q22;q22.1). This evidence concerns the gene RUNX1 and acute myeloid leukemia.