Actively Recruiting
A Study of JNT-517 in Participants With Phenylketonuria (PKU)
Led by Otsuka Pharmaceutical Development & Commercialization, Inc. · Updated on 2026-05-04
120
Participants Needed
25
Research Sites
127 weeks
Total Duration
On this page
AI-Summary
What this Trial Is About
The goal of this Phase 3, randomized study is to assess the safety, efficacy, tolerability, and pharmacokinetics (PK) of oral JNT-517 in adults (18 years of age or older) with PKU. Participants will receive either JNT-517 or placebo and will be blinded to their treatment assignment. Participants will have a 2 in 3 (or approximately 67%) chance of receiving JNT-517 during the first part of the study which will last approximately six weeks. During the second part of the study every participant who continues in the study will receive one of two doses of JNT-517 for an additional 46 weeks. The study requires a screening period of up to 35 days to ensure dietary stabilization and amino acid levels required to meet study eligibility. In total, participation in the study could last for up to 400 days. Participants will: Take 75 mg JNT-517 or 150 mg JNT-517, or a placebo BID (2x per day) for approximately 365 days; Visit the clinic or have a mobile health nurse visit your home for checkups and tests; Collect urine sample at home and bring to clinic on specified days; Keep a food diary 3 days before each study visit
CONDITIONS
Official Title
A Study of JNT-517 in Participants With Phenylketonuria (PKU)
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Males and females 18 years of age or older on Day 1
- Clinical diagnosis of phenylketonuria (PKU)
- Average of at least 3 plasma phenylalanine (Phe) levels ≥360 µmol/L after a >4-hour fast during screening
- No pegvaliase treatment within 4 weeks prior to screening
- Stable dose of sapropterin or large neutral amino acids if taking these for at least 4 weeks prior to screening and throughout the study
- Willing and able to maintain a stable diet in phenylalanine and total protein throughout the study
- Body weight greater than 40 kilograms
- If biologically female and of childbearing potential: negative pregnancy tests at screening and Day 1, agreement to use two highly effective contraceptive methods or sexual abstinence during the study, and agreement to not donate ova during the study and 30 days after last dose
- If biologically female and not of childbearing potential or postmenopausal (surgical sterilization, amenorrhea for at least 1 year with hormonal confirmation, or no menarche), must follow contraception requirements if menarche occurs during study
- If biologically male, agreement to use highly effective contraception or sexual abstinence during the study and not donate sperm during the study and 30 days after last dose unless vasectomy was done at least 4 months prior
- Psychiatric illness must be well-controlled for at least 6 months and on stable medications for 3 months prior to screening
- Capable of giving informed consent or have parent/legal guardian consent and be able to comply with study procedures
You will not qualify if you...
- Any acute or uncontrolled chronic medical condition that could interfere with study participation or safety
- Positive for hepatitis B, hepatitis C, or HIV
- History of malignancy within past 5 years except non-melanoma skin cancer or in situ cervical cancer
- History of significant liver disease
- History or presence of cataracts beyond minimal lens changes as defined
- Medical or surgical conditions affecting drug absorption, distribution, metabolism, or excretion
- Estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m2
- Participation in another investigational drug trial within 30 days or 5 half-lives of the drug (whichever is longer), with exceptions for gene therapy
- Alcohol consumption within 5 days of randomization or unwillingness to limit alcohol to 1 drink per day until after 6-month visit
- History of drug or alcohol abuse within the last year
- Use of certain medications affecting cytochrome P450 or drug transporters within 4 weeks prior to randomization and unwillingness to avoid during study
- Current or recent active viral or bacterial infection within 2 weeks prior to and during screening
- Unable to tolerate oral medication or conditions interfering with absorption of JNT-517
- Allergy to JNT-517 or any of its components
- Abnormal laboratory values at screening including elevated liver enzymes, bilirubin (except Gilbert Syndrome), low hemoglobin, high white blood cell count, or low platelets
AI-Screening
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Trial Site Locations
Total: 25 locations
1
University of California Los Angeles (UCLA) School of Medicine
Los Angeles, California, United States, 90024
Actively Recruiting
2
University of Florida (UF) Health Shands Hospital
Gainesville, Florida, United States, 32608
Actively Recruiting
3
University of South Florida
Tampa, Florida, United States, 33606
Actively Recruiting
4
Ann & Robert H. Lurie Children's Hospital of Chicago
Chicago, Illinois, United States, 60611
Actively Recruiting
5
Oregon Health and Science University
Portland, Oregon, United States, 97239
Actively Recruiting
6
University of Pittsburgh Medical Center (UPMC) - Children's Hospital of Pittsburgh
Pittsburgh, Pennsylvania, United States, 15201
Actively Recruiting
7
Vanderbilt University Medical Center
Nashville, Tennessee, United States, 37232
Actively Recruiting
8
University of Texas Southwestern
Dallas, Texas, United States, 75390
Actively Recruiting
9
University of Texas Health (UTHealth) Science Center at Houston
Houston, Texas, United States, 77030-1501
Actively Recruiting
10
Utah Health - The University of Utah Hospital
Salt Lake City, Utah, United States, 84112
Actively Recruiting
11
Royal Adelaide Hospital
Adelaide, Australia, 5000
Actively Recruiting
12
Royal Melbourne Hospital
Parkville, Australia
Actively Recruiting
13
Mater Health - Mater Hospital Brisbane
South Brisbane, Australia, 4104
Actively Recruiting
14
M.A.G.I.C Clinic
Calgary, Alberta, Canada, T2E 7H7
Actively Recruiting
15
Fakultní nemocnice Královské Vinohrady
Prague, Czechia
Actively Recruiting
16
Centre Hospitalier Régional Universitaire (CHRU) de Tours - Hôpital Bretonneau
Tours, France
Actively Recruiting
17
Universitätsklinikum Münster
Münster, Germany
Actively Recruiting
18
Nihon University Hospital
Chiyoda-ku, Japan
Actively Recruiting
19
Fujita Health University
Kutsukake-cho, Japan
Actively Recruiting
20
Osaka Metropolitan University Hospital
Osaka, Japan
Actively Recruiting
21
Universitair Medisch Centra (AMC)- Amsterdam
Amsterdam, Netherlands
Actively Recruiting
22
Beatrix Children's Hospital
Groningen, Netherlands
Actively Recruiting
23
Pomorski Uniwersytet Medyczny w Szczecinie
Szczecin, Poland
Actively Recruiting
24
Hospital Universitario Ramón y Cajal
Madrid, Spain
Actively Recruiting
25
Hospital Clinico Universitario de Santiago de Compostela
Santiago de Compostela, Spain
Actively Recruiting
Research Team
O
Otsuka Call Center
CONTACT
How is the study designed?
Study Type
INTERVENTIONAL
Masking
QUADRUPLE
Allocation
RANDOMIZED
Model
PARALLEL
Primary Purpose
TREATMENT
Number of Arms
3
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