mRNA-3139

mRNA-3139 is an investigational messenger RNA (mRNA) therapeutic being developed by Moderna for the treatment of phenylketonuria (PKU). PKU is a rare inherited metabolic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase (PAH), which is responsible for the conversion of phenylalanine to tyrosine. A lack of functional PAH leads to toxic accumulations of phenylalanine in the blood and brain. mRNA-3139 is designed to deliver mRNA encoding the functional PAH enzyme into the patient's hepatocytes using lipid nanoparticle (LNP) technology. Once delivered, the cellular machinery translates the mRNA into functional PAH protein, potentially restoring the metabolic pathway and reducing phenylalanine levels. The drug is part of Moderna's rare disease intracellular therapeutics pipeline and represents a protein replacement approach using mRNA technology.