Similar to our observations in the MYCN-amplified neuroblastoma cell lines, delivery of Cas9D10A targeting an amplified loci in combination with CHK1i appreciably improved the cell-killing efficacy of Cas9D10A at lower concentrations for BT474 and NCI-H716 cells (Supplementary Fig. 26A–C) whereas delivery of Cas9D10A in combination with ATRi was more variable in its effect on cell killing (Supplementary Fig. 26D–F). Here, MYCN is linked to neuroblastoma.