Based on our findings of increased dependence on MCL-1 or BCL-XL, sequestration of the apoptosis activator BIM upon venetoclax treatment and synergistic activity in BCP-ALL cell lines, we extended our analyses and evaluated anti-leukemia activity of combined BCL-2 and MCL-1 or BCL-XL inhibition in primary patient-derived xenograft ALL samples. This evidence concerns the gene MCL1 and leukemia.