AUTHOR=Cacicedo Maximiliano L. , Weinl-Tenbruck Christine , Frank Daniel , Limeres Maria Jose , Wirsching Sebastian , Hilbert Katja , Pasha Famian Mansure Abdollah , Horscroft Nigel , Hennermann Julia B. , Zepp Fred , Chevessier-Tünnesen Frédéric , Gehring Stephan TITLE=Phenylalanine hydroxylase mRNA rescues the phenylketonuria phenotype in mice JOURNAL=Frontiers in Bioengineering and Biotechnology VOLUME=Volume 10 - 2022 YEAR=2022 URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.993298 DOI=10.3389/fbioe.2022.993298 ISSN=2296-4185 ABSTRACT=Phenylketonuria (PKU) is an inborn error of metabolism caused by a deficiency in functional phenylalanine hydroxylase (PAH), resulting in accumulation of phenylalanine (Phe) in patients´ blood and organs. Affected patients encounter severe mental retardation, neurological deficits, and behavioral abnormalities when not treated. Early diagnosis and treatment are extremely important; newborn screening programs have been implemented in most countries to ensure early identification of patients with PKU. Despite available treatment options, several challenges remain: life-long adherence to a strict diet, approval of some medications for adults only, and lack of response to these therapies in a subpopulation of patients. Therefore, there is an urgent need for treatment alternatives. An mRNA-based approach tested in PKU mice showed a fast reduction in the accumulation of Phe in serum, liver and brain, the most significant organ affected. Repeated injections of LNP-formulated mouse PAH mRNA rescued PKU mice from the disease phenotype for a prolonged period of time. An mRNA-based approach could improve the quality of life tremendously in PKU patients of all ages by replacing standard-of-care treatments.