SW620 (ATCC) cells were selected as the cell line for in vitro activity detection experiments. 2000 cells were inoculated into each well of a 96-well cell culture plate and cultured for 20-24 hours. The antibody-drug conjugate prepared according to the method in Example 3 was formulated with L15 cell culture medium containing 10% FBS into 11 concentration gradients of test solution: 1000, 166.7, 55.6, 18.6, 6.17, 2.06, 0.69, 0.23, 0.08, 0.008 and OnM. 100 ul of the diluted test solution per well was added to the culture plate containing the inoculated cells and incubated in a 37°C, 5% CO, incubator for 144 hours. Then, CellTiter-Glo® Luminescent Cell Viability Assay Reagent (50 ul/well) was added, and the mixture was shaken at 500 rpm at room temperature for 10 minutes. The data were read using a SpectraMaxL microplate reader (OD570nm, with 2-second interval readings), and the IC53 results were calculated.

SK-BR-3 (ATCC) cells were selected as the cell line for in vitro activity detection experiments. 2000 cells were inoculated into each well of a 96-well cell culture plate and cultured for 20-24 hours. The antibody-drug conjugate prepared according to the method in Example 3 was formulated with L15 cell culture medium containing 10% FBS into 11 concentration gradients of test solution: 1000, 166.7, 55.6, 18.6, 6.17, 2.06, 0.69, 0.23, 0.08, 0.008 and OnM. 100 ul of the diluted test solution per well was added to the culture plate containing the inoculated cells and incubated in a 37°C, 5% CO, incubator for 144 hours. Then, CellTiter-Glo® Luminescent Cell Viability Assay Reagent (50 ul/well) was added, and the mixture was shaken at 500 rpm at room temperature for 10 minutes. The data were read using a SpectraMaxL microplate reader (OD570nm, with 2-second interval readings), and the IC50 results were calculated.