SLC6A19 and phenylketonuria: Additional therapies targeting Phe in the gastrointestinal tract are under investigation, such as engineered Escherichia coli Nissle, which expresses Phe ammonia lyase and other Phe-degrading enzymes [16], or inhibitors of the major intestinal absorption pathway for phenylalanine, the epithelial apical membrane amino acid transporter B0AT1 (slc6a19), showing the potentiality of B0AT1 as a target for treating PKU, among other conditions [17,18,19].