Administering mouse Pah mRNA packaged in LNPs through repeated intravenous injection into a PKU (Pahenu2) mouse model produced therapeutic PAH protein, reduced Phe levels in the liver, serum, and brain, and reversed the progression of the disease.234,235 These findings suggest Pah mRNA formulated in LNPs offers an alternative therapeutic option for PKU patients who eliminates the need for a lifelong Phe-restricted diet. The gene discussed is PAH; the disease is pulmonary arterial hypertension.