JNT-517 treatment for adults with phenylketonuria (PKU)

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This Phase 3, randomized, double-blind study gives adults with PKU either JNT-517 or placebo for an initial ~6-week blinded period with about a 2 in 3 chance of receiving active drug. After that, participants who continue will receive one of two JNT-517 doses for an additional 46 weeks, and total participation can last up to ~400 days including screening. Dosing is oral JNT-517 75 mg or 150 mg twice daily (BID) or matching placebo, with clinic visits or mobile nurse home visits for monitoring, safety labs, and pharmacokinetic sampling. The study requires dietary stabilization and multiple fasting plasma phenylalanine measurements during screening to confirm eligibility and stable dietary intake.

Why it matters

Who can join: the full rules

Inclusion Criteria:

1. Male or female participants aged 4 years or older.
2. Diagnosed with phenylketonuria.
3. Have phenylalanine levels that meet study requirements.
4. Meet study-specific requirements regarding current treatment for phenylketonuria.
5. Willing and able to follow study dietary requirements.
6. Weigh at least 12.5 kilograms.
7. If able to become pregnant or father a child, willing to follow the study's contraception requirements.
8. Any ongoing mental health condition must be stable before entering the study.
9. Able to provide informed consent (or have consent provided by a parent or legal guardian, when applicable) and comply with study procedures.

Exclusion Criteria:

Participants will be excluded from the study if any of the following criteria are met:

1. Significant medical condition that, in the investigator's opinion, could make participation unsafe or interfere with study participation.
2. Significant liver disease or impaired kidney function.
3. Certain eye conditions, including significant cataracts.
4. Active infection requiring medical evaluation.
5. History of certain cancers within the past 5 years.
6. Allergy or hypersensitivity to JNT-517 or its ingredients.
7. Prior treatment with JNT-517.
8. Recent participation in another investigational study or receipt of an investigational treatment that does not meet study requirements.
9. Use of medications that are not permitted during the study.
10. Abnormal laboratory or heart test results that would make study participation inappropriate.
11. Conditions that could affect the absorption of oral study medication.
12. History of recent substance or alcohol abuse.
13. Unwillingness to follow study requirements, including restrictions on intentional weight loss.

Where it's running

• University of California Los Angeles (UCLA) School of Medicine
  Los Angeles, California, United States Recruiting
• University of Florida (UF) Health Shands Hospital
  Gainesville, Florida, United States Recruiting
• University of South Florida
  Tampa, Florida, United States Recruiting
• Ann & Robert H. Lurie Children's Hospital of Chicago
  Chicago, Illinois, United States Recruiting
• Oregon Health and Science University
  Portland, Oregon, United States Recruiting
• University of Pittsburgh Medical Center (UPMC) - Children's Hospital of Pittsburgh
  Pittsburgh, Pennsylvania, United States Recruiting

Study contacts

• Study coordinator: Otsuka Call Center
• Email: Otsuka-ProfessionalServices@otsuka-us.com
• Phone: 844-687-8522

Similar studies

Other studies for the same condition or treatment. Recruiting studies are listed first.

• Impact of a Phenylalanine-Restricted Diet on Gut Health in Children with PKU

  This study looks at how a Phe-restricted diet, with or without sapropterin or sepiapterin, might affect gut health in kids with PKU.

  Recruiting Birmingham Women's and Children's NHS Foundation Trust · Birmingham · NCT07728032

• How Repinatrabit is processed in adults with liver or kidney impairment versus normal function

  This study tests how Repinatrabit is handled by the body in adults with moderate liver impairment or severe kidney impairment compared to adults with normal liver function.

  Recruiting Phase 1 Otsuka Pharmaceutical Development & Commercialization, Inc. · Miami, Florida · NCT07713758

• Eating disorders in people with phenylketonuria

  This study looks at whether eating disorders and BMI issues are more common in people with phenylketonuria who are followed at a French hospital.

  Recruiting Central Hospital, Nancy, France · Nancy · NCT07698743

• GenSci144 tablets early-dose study for phenylketonuria treatment

  This early-phase trial tests a single dose of GenSci144 tablets in healthy adults to see if it is safe and tolerable, while also looking at how the body processes the drug.

  Recruiting Phase 1 Changchun GeneScience Pharmaceutical Co., Ltd. · Jinan, Shandong · NCT07685210

• Immune Modulation During Palynziq Treatment in Adults

  This study tests whether adding low-dose methotrexate can help people with PKU tolerate Palynziq better and achieve better blood levels of phenylalanine.

  Recruiting at 10 sites Phase 4 BioMarin Pharmaceutical · Los Angeles, California and 11 other locations · NCT07477691

• AG-181 safety and tolerability in people with phenylketonuria

  This trial will test AG-181 for safety and tolerability in people with PKU who have high blood phenylalanine and at least one R408W PAH mutation.

  Recruiting at 5 sites Phase 1 Agios Pharmaceuticals, Inc. · Indianapolis, Indiana and 4 other locations · NCT07241234

How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.