The goal of this Phase 3, open-label study is to evaluate the long-term safety of JNT-517 in pediatric and adult participants with Phenylketonuria (PKU) after completion of either Study JNT517-101 (NCT05781399) or JNT517-201 (NCT06637514) as well as participants who have not participated in a prior JNT-517 study. In this trial, all participants will receive JNT-517 using age- and weight-banded dosing as outlined in the protocol, regardless of any dose received in a previous study.
Diagnosis of phenylketonuria (ie, PAH deficiency) by either molecular testing or biochemical criteria consistent with the applicable regional guidelines.
Participants 4 years of age and older, inclusive, at time of Screening.
Not on pegvaliase within 4 weeks of Screening.
Not on sepiapterin within 2 weeks of Screening.
Participation in this study is not considered safe and/or feasible in the opinion of the Investigator.
Participants have not completed a previous JNT-517 study and are eligible for another active JNT-517 trial at the site, unless approval is obtained from the medical monitor.
Any acute or chronic medical condition that would prevent the participant from complying with the procedures or place the participant at risk if they participate in the study.
Positive for hepatitis B or C or human immunodeficiency virus.