CTSB and neoplasm: To overcome this limitation, Moreno et al., (2014) have devised a pro-cytotoxic system based on mitoparan conjugated to poly(l-glutamic acid) PGA polymer through specific cleavage sequences that are cleaved by overexpressed tumor proteases, such as the metalloproteinase-2 or cathepsin B, in which the conjugated mitoparan becomes active only when it reaches cancer cells, then is cleaved and released by the tumor proteases [118].