CTSB and cancer: A drug delivery system targeting the extracellular CTSB through a highly selective CTSB inhibitor (NS-629) conjugated with a highly biocompatible liposomal nanocarrier was shown to target CTSB-overexpressing tumor and stromal cells in the tumor microenvironment, resulting in irreversible and selective inactivation of CTSB, achieving CTSB-specific therapy in cancer (70).