HCC 1954, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.

NCI-N87, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.

BT-474, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.

SK-OV-3, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.

MCF-7, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.

MDA-MB-468, 1000cell/well was added to the designated 384-well cell culture plate in the appropriate growth media. The ADCs stock solution was diluted in series in a ratio of 1:3 to produce 10 diluted solutions with different concentrations (the compound stock solution was an L-His buffer salt solution with a concentration of about 2 mg/mL, which was diluted with PBS, and the initial maximum concentration at test point was about 500 mg/mL). 4ul of the compound diluted solutions with different concentrations was distributed into a 384-well plate. After 96 hours, the plate was taken from the incubator and equilibrated at room temperature for 10 minutes. 40uL of CellTiter-Glo reagent was added to each well to be tested (the ratio of CellTiter-Glo reagent to medium was 1:1).the plate was then placed at room temperature for 30 minutes, and then reading was carried out on an EnSpire reader for cell counting.