An Open-Label Study to Evaluate the Long-Term Safety of JNT-517 in Participants With Phenylketonuria
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.
• If on sapropterin or large neutral amino acids at Screening, must be on a stable dose for 4 weeks prior to Screening.
• Willing and able to maintain a diet consistent in Phe content from the Screening period through the duration of the study, unless otherwise directed by a dietician as allowed in the protocol.
• Body weight ≥ 12.5 kg.
• If female of childbearing potential:
∙ Must have a negative serum pregnancy test at Screening and a negative urine pregnancy test by Day 1.
‣ Must practice sexual abstinence, or if involved in any sexual intercourse that could lead to pregnancy, must agree to use 2 different contraceptive methods, where at least 1 method must be highly effective, from Screening until at least 30 days after the last study drug administration.
‣ Must refrain from donating ova during the course of the study and for 30 days after the last dose of the study drug.
• Is a female not of childbearing potential or postmenopausal, defined as follows:
∙ Has had surgical sterilization (hysterectomy, bilateral oophorectomy, or bilateral salpingectomy).
‣ Has had amenorrhea for minimum of 1 year with confirmation by levels of follicle stimulating hormone testing.
‣ Has not achieved menarche (has not had first menstrual period). If a female achieves menarche during the study, she will need to follow the contraception requirement for females of childbearing potential.
⁃ If male, must practice sexual abstinence, or if involved in any sexual intercourse that could lead to pregnancy, must agree to use 2 different contraceptive methods, where at least 1 method must be highly effective, from Day 1 until at least 30 days after the last study drug administration and must refrain from donating sperm during the course of the study and for 30 days after the last dose of the study drug.
⁃ Note: No restrictions are required for males who have undergone a documented vasectomy at least 4 months prior to Screening. If the vasectomy procedure is not documented or was performed less than 4 months prior to Screening, males must follow the same contraception as for non-vasectomized participants.
⁃ Capable of giving signed informed consent, or parent/legal guardian to provide informed consent and pediatric participant to give assent, and be able to comply with study procedures.
⁃ Participants with psychiatric illness must be well-controlled for the last 3 months prior to screening visit and, if on medication, on stable medications for the last 3 months.