Actively Recruiting
An Open-Label Study to Evaluate the Long-Term Safety of JNT-517 in Participants With Phenylketonuria
Led by Otsuka Pharmaceutical Development & Commercialization, Inc. · Updated on 2026-05-01
240
Participants Needed
12
Research Sites
13 weeks
Total Duration
On this page
AI-Summary
What this Trial Is About
Researchers are evaluating the long-term safety of JNT-517 in children and adults with Phenylketonuria (PKU), a condition caused by a deficiency in the PAH enzyme. This Phase 3, open-label study includes participants who completed previous JNT-517 studies as well as those new to JNT-517 treatment. The goal is to understand how the drug performs over an extended period when used consistently in this population. All participants will receive JNT-517 orally twice daily with doses adjusted for age and weight. The study will follow a fixed dosing schedule regardless of prior exposure to JNT-517. Participants will be monitored for treatment-emergent adverse events and changes in blood and urine phenylalanine levels, dietary intake, and attention-related symptoms among children previously treated. Participants will attend regular visits for safety assessments, blood tests, dietary evaluations, and symptom rating scales. Plasma drug concentrations will be measured at specific times in younger children to understand drug levels. The study tracks adverse events from screening through two weeks after the last dose. Total participation duration may last up to approximately five years, allowing long-term safety and efficacy monitoring.
CONDITIONS
Brief Title
A Long-Term Study of JNT-517 in Participants With Phenylketonuria
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Diagnosis of phenylketonuria (PAH deficiency) by molecular or biochemical testing
- Age 4 years or older at screening
- Not using pegvaliase within 4 weeks before screening
- Not using sepiapterin within 2 weeks before screening
- Stable dose of sapropterin or large neutral amino acids for 4 weeks before screening if applicable
- Willing and able to maintain a consistent phenylalanine diet during the study
- Body weight of at least 12.5 kg
- For females of childbearing potential: negative pregnancy tests before and at Day 1, use of two contraceptive methods or abstinence from screening through 30 days after last dose, and no egg donation during study and 30 days after last dose
- For females not of childbearing potential or postmenopausal: surgical sterilization, amenorrhea for at least 1 year confirmed by hormone testing, or no menarche; if menarche occurs during study, contraception requirements apply
- For males: use of two contraceptive methods or abstinence from Day 1 through 30 days after last dose, no sperm donation during study and 30 days post-dose; exceptions for documented vasectomy at least 4 months prior
- Able to provide informed consent or have legal guardian consent with pediatric assent
- Psychiatric illness must be well-controlled and on stable medication for 3 months prior to screening
You will not qualify if you...
- Investigator considers participation unsafe or unfeasible
- Not completed prior JNT-517 study if eligible for another active JNT-517 trial without medical monitor approval
- Acute or chronic medical conditions preventing study compliance or increasing risk
- Positive for hepatitis B, hepatitis C, or HIV
- History of significant liver disease
- History or presence of cataracts beyond minimal during screening eye exam
- Surgical or medical conditions affecting drug absorption or metabolism
- Estimated glomerular filtration rate below 60 mL/min/1.73 m²
- History of drug or alcohol abuse within past year
- Use of certain medications affecting cytochrome P450 enzymes or transporters within 4 weeks before dosing and unable to avoid during study
- Recent or suspected COVID-19 infection within 2 weeks before screening
- Unable to tolerate oral medication or swallow tablets
- Allergy to JNT-517 or its components
- Abnormal lab values including elevated liver enzymes, bilirubin, low hemoglobin, abnormal blood counts
- Participation in another investigational drug trial within 30 days prior (except JNT-517) or 5 half-lives of that drug
AI-Screening
AI-Powered Screening
Complete this quick 3-step screening to check your eligibility
Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
screening and enrollment visit
Duration - Long-term until study completion
Participants take JNT-517 orally twice daily with dosing based on age and weight.
Regular visits for safety and efficacy assessments throughout treatment
Duration - 2 weeks
Participants are monitored for safety and outcomes for 2 weeks after the last dose of JNT-517.
Visits during the 2 weeks following treatment completion
Trial Site Locations
Total: 12 locations
1
University of Florida (UF) Health Shands Hospital
Gainesville, Florida, United States, 32608
Actively Recruiting
2
University of South Florida
Tampa, Florida, United States, 33606
Actively Recruiting
3
Oregon Health and Science University
Portland, Oregon, United States, 97239
Actively Recruiting
4
University of Pittsburgh Medical Center (UPMC) - Children's Hospital of Pittsburgh
Pittsburgh, Pennsylvania, United States, 15224
Actively Recruiting
5
Children's Medical Center Dallas
Dallas, Texas, United States, 75235
Actively Recruiting
6
University of Texas Southwestern Medical Center
Dallas, Texas, United States, 75390
Actively Recruiting
7
University of Texas Health (UTHealth) Science Center at Houston
Houston, Texas, United States, 77030
Actively Recruiting
8
Utah Health - The University of Utah Hospital
Salt Lake City, Utah, United States, 84112
Actively Recruiting
9
Children's Health Queensland - Queensland Children's Hospital
South Brisbane, Queensland, Australia, 4101
Actively Recruiting
10
Mater Health - Mater Hospital Brisbane
South Brisbane, Queensland, Australia, 4101
Actively Recruiting
11
Royal Adelaide Hospital
Adelaide, South Australia, Australia, 5000
Actively Recruiting
12
Murdoch Children's Research Institute
Parkville, Victoria, Australia, 3052
Actively Recruiting
Research Team
O
Otsuka Call Center
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
NA
Model
SINGLE_GROUP
Primary Purpose
TREATMENT
Number of Arms
1
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