Exosomes are extracellular vesicles (EVs) that are produced by almost all cells as part of normal physiology and act as naturally-occurring cellular messengers, transporting proteins and nucleic acids as a form of intercellular communication. At Evox we are engineering exosomes to enable specific loading of therapeutic proteins and nucleic acids, with the aim of using these engineered exosomes as potential therapies in inherited metabolic diseases, such as phenylketonuria (PKU) and arginosuccinic aciduria (ASA). By engineering exosome-associated proteins, we can potentially use exosomes to replace mutated proteins in such diseases, either through direct protein replacement or through the deliver of mRNA to target cells.