A Long-Term Study of JNT-517 in Participants With Phenylketonuria

Exclusion Criteria22

• 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.
• Any history of significant liver disease.
• Any history of cataracts or more than minimal cataracts observed during the Screening ophthalmologic examination.
• Any surgical or medical conditions that may affect study drug absorption, distribution, metabolism, or excretion.
• Estimated glomerular filtration rate < 60 milliliters per minute per 1.73 square meters (mL/min/1.73 m\^2) by 2021 Chronic Kidney Disease Epidemiology Collaboration formula (participants aged 17 years or greater) or by Schwartz formula (participants aged 4 to 16 years of age).
• History of drug or alcohol abuse in the last year.
• Use of any medication that are inhibitors or inducers of cytochrome P450 (CYP)3A4 or inhibitors of the transporter P glycoprotein (P-gp) within 4 weeks prior to the first dose of study drug and unwilling and/or unable to avoid these medications throughout the treatment duration.
• Use of any medications that are a substrate of breast cancer resistance protein (BCRP), multidrug and toxin extrusion (MATE)1, MATE2-K, organic anion transporter 3 (OAT3), or CYP3A4 within 4 weeks prior to the first dose of study drug and unwilling and/or unable to avoid these medications throughout the treatment duration (Appendix A). CYP3A4 substrates may be allowed if reduction in exposure is not expected to impact safety of the participant after consultation with the Medical Monitor.
• NOTE: Participants of childbearing potential will be permitted to continue with estrogen- or progesterone based oral contraceptives, but must agree to use 2 other methods of contraception, where at least 1 must be highly effective, or must agree to sexual abstinence during the study.
• Current, recent, or suspected infection within 2 weeks of Screening of Severe Acute Respiratory Syndrome Coronavirus 2/Coronavirus Disease 2019 (SARS-CoV-2/COVID-19).
• Unable to tolerate oral medication or inability to swallow tablets.
• Allergy to JNT-517 or any component of the investigational product.
• Any of the following laboratory values at the Screening visit:
• Alanine aminotransferase or aspartate aminotransferase values ˃ 1.5 x the upper limit of normal (ULN).
• Total bilirubin ˃ULN unless history of Gilbert Syndrome and then total bilirubin >4 milligrams per deciliter \[mg/dL\] is exclusionary.
• Hemoglobin ˂10.0 g/dL (˂100.0 grams per liter \[g/L\])
• White blood cell count ˃1 x ULN
• Platelet count ˂150 × 109/L (˂150,000/cubic millimeters\[mm\^3\])
• Participation in another investigational drug trial within 30 days (other than for JNT-517) or, if known 5 half-lives of investigational drug (whichever is longer).