A Phase 1b, Open-label, Multicenter, Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics Study of AG-181 in Subjects With Phenylketonuria
The primary purpose of this study is to assess the safety and tolerability of AG-181 in subjects with Phenylketonuria (PKU).
• Diagnosis of PKU, defined as documented presence of 2 mutant alleles in the phenylalanine hydroxylase (PAH) gene, of which at least 1 is the R408W mutation, as determined during Screening per the genotyping performed by the study central genotyping laboratory.
• At least 1 plasma Phe concentration greater than (\>) 600 micromoles per liter (μmol/L) in the 52 weeks before providing informed consent.
• Average concentration of plasma Phe \> 600 μmol/L in Phe samples taken during Screening, with no individual assessment below 360 μmol/L. Any Phe samples taken after Day -20 will not be included.
• Body mass index (BMI) greater than or equal to (≥) 18.0 kilograms per meter square (kg/m\^2) to lesser than or equal to (≤) 35.0 kg/m\^2 and weight ≥ 50 kilograms (kg) at any time during the Screening Period.
• Documented approval from a dietitian confirming that the subject can maintain their diet consistent in protein and Phe intake throughout the study as outlined in the Diet Manual.