By contrast, the results of the cytotoxicity assays show that the 6F6-ADC significantly decreased CRC spheroid growth in SW620 (by 32%) and Difi cell cultures (by 73%), whereas it had no effect on SW480 cells expressing low levels of CLDN1 (Fig. 5A and Supplementary Fig. 5C). Here, CLDN1 is linked to colorectal carcinoma.