This unique feature, due to the hydrolysable nature of the SG linker, may allow delivery of SN-38 not just to targeted cells but also to surrounding cells (ie, Trop-2 negative tumor cells, stromal cell and endothelial cells), leading to an improved therapeutic index, especially in biologically aggressive CS in which two components are present (i.e. epithelial and sarcomatous). Here, TACSTD2 is linked to Cowden syndrome 1.