A Phase 3, Multicenter, Open-Label Extension Study of Phenoptin in Subjects With PKU Who Have Elevated Phenylalanine Levels

Inclusion Criteria: 8 years of age and older Prior successful participation in Study PKU-003 Willing and able to provide written informed consent or assent and written informed consent (if required) by a parent or legal guardian For females of child-bearing potential only: Negative urine pregnancy test within 24 hours prior to enrollment. Women using acceptable birth control measures must agree to continue to use those measures while participating in the study Willing and able to comply with study procedures Willing to continue current diet unchanged while participating in the study Exclusion Criteria: Perceived to be unreliable or unavailable for study participation or, if under the age of 18, have parents or legal guardians who are perceived to be unreliable or unavailable Withdrew from, or otherwise did not successfully complete, study PKU-003, except for subjects who were removed from the study because their blood Phe exceeded the alert level Expected to require any investigational agent or vaccine prior to completion of all scheduled study assessments Pregnant or breastfeeding, or planning pregnancy Concurrent disease or condition that would interfere with study participation or safety (e.g., seizure disorder, oral steroid-dependent asthma or other condition requiring oral or parenteral corticosteroid administration, or insulin-dependent diabetes) Requirement for concomitant treatment with any drug known to inhibit folate synthesis (e.g., methotrexate) Concurrent use of levodopa