We reported the earlier development of EV-based therapeutic formulations using the exogenous loading of naïve EVs with a number of potent therapeutic proteins, including the antioxidant enzyme catalase [19]; brain-derived neurotrophic factor (BDNF) [22]; and tripeptidyl peptidase-1 (TPP1), a therapeutic enzyme for the treatment of a lysosomal storage disorder, Batten disease [21]. Here, TPP1 is linked to lysosomal storage disease.