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.

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 IC55 results were calculated.