Actively Recruiting
A Phase 3, Double-Blind, Randomized, Two-Period, Multicenter, Placebo-Controlled Study of JNT-517 for Treatment of Phenylketonuria
Led by Otsuka Pharmaceutical Development & Commercialization, Inc. · Updated on 2026-05-04
120
Participants Needed
25
Research Sites
4 weeks
Total Duration
On this page
AI-Summary
What this Trial Is About
Researchers are evaluating the safety, effectiveness, tolerability, and how the body processes (pharmacokinetics) an oral drug called JNT-517 in adults with phenylketonuria (PKU), a rare metabolic condition. This Phase 3 randomized study compares JNT-517 with a placebo, with participants unaware of which treatment they receive. The study is sponsored by Otsuka Pharmaceutical Development & Commercialization, Inc., and includes a screening period to ensure participants have stable diet and amino acid levels. Participants will take either 75 mg or 150 mg of JNT-517, or a placebo, twice daily. The study has two parts: the first lasts about six weeks, where approximately two-thirds receive JNT-517 and one-third a placebo. After this, all participants continuing in the study receive one of two doses of JNT-517 for about 46 more weeks. Some study visits occur at the clinic, while others may be conducted by a mobile health nurse at home. During the study, participants will provide urine samples at home and bring them to the clinic on specific days. They will keep a food diary for three days before each visit to track dietary intake. Regular checkups, tests, and monitoring will be performed to assess changes in blood phenylalanine levels, cognitive and behavioral measures, dietary intake, and safety. Participation may last up to 400 days, including screening and treatment periods.
CONDITIONS
Brief 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 of 360 micromoles per liter or higher during screening
- Not on pegvaliase within 4 weeks prior to screening
- If on sapropterin or large neutral amino acids, must be on a stable dose 4 weeks prior to screening and during the study
- Willing and able to maintain a stable diet in phenylalanine and total protein, with ability to adjust diet during the study
- Body weight greater than 40 kilograms
- If biologically female of childbearing potential: negative pregnancy tests at screening and Day 1, use of 2 highly effective contraceptive methods or sexual abstinence during and 30 days after study, no ova donation during study and 30 days after
- If biologically female not of childbearing potential or postmenopausal, must have surgical sterilization, amenorrhea for 1 year with hormone confirmation, or not yet had first menstrual period
- If biologically male, must use highly effective contraception or sexual abstinence during and 30 days after study, and refrain from sperm donation unless vasectomy documented at least 4 months prior
- Participants with psychiatric illness must be well-controlled for 6 months prior and on stable medications for 3 months
- Capable of giving informed consent or have guardian consent and participant assent to comply with study procedures
You will not qualify if you...
- Any acute or uncontrolled chronic medical condition that prevents compliance or causes risk
- Positive for hepatitis B, hepatitis C, or HIV
- History of malignancy (except certain skin or cervical cancers) within past 5 years
- History of significant liver disease
- History of cataracts more than minimal level on eye exam at screening
- Surgical or medical conditions affecting study 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 that drug
- Alcohol consumption within 5 days of randomization or unwillingness to limit alcohol to 1 drink per day until 6 months
- History of drug or alcohol abuse in past year
- Use of medications that affect cytochrome P450 (CYP3A4), P-glycoprotein, BCRP, MATE1, or MATE2-K within 4 weeks prior to randomization and unable to avoid them
- Current or recent viral or bacterial infection within 2 weeks prior to and during screening
- Unable to tolerate oral medication or conditions interfering with JNT-517 absorption
- Allergy to JNT-517 or its components
- Abnormal lab values at screening including elevated liver enzymes, bilirubin, low hemoglobin, abnormal white blood cell or platelet counts
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.
1 visit (in-person)
Duration - 6 weeks
Participants receive either JNT-517 or placebo tablets twice daily as part of the initial 6-week treatment period.
Weekly visits for up to 6 weeks
Duration - 46 weeks
Participants who received placebo in Part 1 switch to JNT-517 150 mg twice daily, while others continue JNT-517 treatment for an additional 46 weeks.
Monthly visits for up to 46 weeks
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
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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