This is a study for adults and children ≥ 14 years old who have Phenylketonuria (PKU) with uncontrolled plasma Phe levels. No clinical intervention or study drug is provided by BioMarin in this study.

Inclusion Criteria:

• Male and female subjects with diagnosis of PKU which is a condition characterized by PAH deficiency
• Ability and willingness to maintain dietary protein intake consistent with baseline intake
• Willingness and capable per investigator opinion to comply with study procedures and requirements
• Plasma Phe Levels > 600umol/L

Exclusion Criteria:

• Clinically significant liver dysfunction or disease
• Prior treatment with gene therapy
• Any condition that, in the opinion of the investigator or Sponsor, would prevent the subject from fully complying with the requirements of the study

PKU Patients 14 years or older with uncontrolled plasma Phe levels