Notably,after the cleavage of the peptide by intracellular cathepsin B, 128 activated the PDT activity of 124, as theamino group is uncaged, while releasing HCPT, therefore effectivelyinducing apoptosis of 4T1 cells and shrinking the size of the 4T13D tumor spheroids through the combined effects of PDT and chemotherapy.This work reported a novel strategy for constructing cathepsin B-activatedPSs and building a promising antitumor platform. The gene discussed is CTSB; the disease is neoplasm.