Mal-PEG3-C2-acid can be used to synthesize linker-payload 16 (compound 15) and 20 (compound 18). linker-payload 16 amd 20 is conjugated to DAR1.9 and DAR1.7. ADC 23 and 24 are Neolymphostin ADCs that composes of DAG 1.9 and DAG1.7 linked to PIKK inhibitors with linker-payload 16 and 20, respectively. ADC24 demonstrates cytotoxic activity against BT474 and N87 cell lines with IC 50 of 195 and 202 nM, respectively. ADC23 demonstrates cytotoxic activity against BT474 and N87 cell lines with IC 50 of 286 and 274 nM, respectively.