RecruitingPHASE3INTERVENTIONAL

A Study of JNT-517 in Participants With Phenylketonuria (PKU)

This research study is for adults (18 and over) with a condition called Phenylketonuria (PKU). We are testing a new tablet medicine, JNT-517, to see if it's safe to use, how well it helps control PKU, and how your body reacts to it. You will either receive the new medicine or a 'dummy' tablet (placebo) without knowing which one, and there's a good chance you'll get the real medicine during the first part of the study. After about six weeks, everyone continuing in the study will receive JNT-517 for many months. Taking part will involve regular check-ups, keeping a food diary, and occasionally collecting urine samples. The study could last for about 400 days in total.

At a glance

Status

Recruiting

Phase

PHASE3

Sponsor

Otsuka Pharmaceutical Development & Commercialization, Inc.

Enrolment target

120

Start

20 Oct 2025

Estimated completion

01 Apr 2028

Phenylketonuria

What is this study about?

This study is designed to explore a new tablet medicine called JNT-517 for people living with Phenylketonuria, often called PKU. PKU is a lifelong condition that affects how the body breaks down a substance found in food, called phenylalanine. If not managed properly, high levels of phenylalanine can lead to health problems.

The main aim of this study is to find out if JNT-517 is a safe and effective way to help manage PKU in adults. We also want to understand how your body processes this new medicine. We're especially interested in how it affects your phenylalanine levels. By carefully studying JNT-517, we hope to contribute to new ways of helping people with PKU live healthier lives.

This important stage of research, called Phase 3, means the medicine has already been tested in smaller groups and shown some promise. Now, it's being tested in a larger group of people to confirm these findings and gather more information before it could potentially become widely available.

Key takeaways

This study is testing a new PKU tablet, JNT-517, in adults.
It aims to check the medicine's safety and how well it works.
You might take JNT-517 or a dummy pill (placebo) at first.
Participation involves regular check-ups, keeping a food diary, and taking the study medicine twice daily.
The total study time could be around 400 days.
You can stop participating at any time.

Who may be eligible?

To join this study, you need to be an adult (18 years old or over) with a formal diagnosis of PKU. Your phenylalanine levels in your blood also need to be above a certain level during the screening checks.

If you are currently taking other medicines for PKU, such as sapropterin or special amino acid supplements, you might still be able to join, but your dose must have been stable for at least 4 weeks before the study starts and stay stable throughout. If you've been on a medicine called pegvaliase, you would need to have stopped taking it at least 4 weeks before screening.

You also need to be willing and able to stick to a stable PKU diet, and be able to adjust it if needed during the study. There are also specific requirements for women who could become pregnant, including using effective birth control methods.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you 18 years old or older?
Do you have a diagnosis of PKU?
Are your phenylalanine levels typically above a certain level?
Are you able and willing to maintain a stable PKU diet?
If you might become pregnant, are you willing to use two effective forms of birth control during the study?

Answer every question to see your result.

What does participation involve?

If you decide to take part, you'll first have a screening period that could last up to 35 days. This is to make sure your diet is stable and your phenylalanine levels meet the study's requirements.

After screening, you'll take either JNT-517 or a placebo (dummy pill) twice a day for about 365 days. In the first six weeks, there's a 2 in 3 chance you'll receive JNT-517. After that, if you continue, you will definitely receive JNT-517, but at one of two possible doses, for an additional 46 weeks.

Throughout the study, you'll have regular check-ups, either by visiting a clinic or having a nurse come to your home. You'll also be asked to collect urine samples at home and bring them to the clinic on specific days. For 3 days before each study visit, you'll need to keep a food diary. The total time you could be involved in the study is up to 400 days.

Potential risks and benefits

Taking part in any medical study has potential benefits and risks. The potential benefit of this study is that JNT-517 might help manage your PKU more effectively. However, it's also possible you might not experience any direct benefits, especially if you are in the placebo group initially. As with any new medicine, there could be side effects, which the study will carefully monitor. You will be told about all known possible side effects. Remember, joining this study is completely voluntary, and you are free to withdraw at any time without giving a reason, and it will not affect your usual medical care.

Locations (25)

University of California Los Angeles (UCLA) School of Medicine
Verified postcode
Los Angeles, United States· Recruiting
University of Florida (UF) Health Shands Hospital
Verified postcode
Gainesville, United States· Recruiting
University of South Florida
Verified postcode
Tampa, United States· Recruiting
Ann & Robert H. Lurie Children's Hospital of Chicago
Verified postcode
Chicago, United States· Recruiting
Oregon Health and Science University
Verified postcode
Portland, United States· Recruiting
University of Pittsburgh Medical Center (UPMC) - Children's Hospital of Pittsburgh
Verified postcode
Pittsburgh, United States· Recruiting
Vanderbilt University Medical Center
Verified postcode
Nashville, United States· Recruiting
University of Texas Southwestern
Verified postcode
Dallas, United States· Recruiting
University of Texas Health (UTHealth) Science Center at Houston
Verified postcode
Houston, United States· Recruiting
Utah Health - The University of Utah Hospital
Verified postcode
Salt Lake City, United States· Recruiting
Royal Adelaide Hospital
Verified postcode
Adelaide, Australia· Recruiting
Royal Melbourne Hospital
Verified postcode
Parkville, Australia· Recruiting

Common questions

What is Phenylketonuria (PKU)?

PKU is a genetic condition where your body can't properly process a substance called phenylalanine, which is found in many foods. If not managed, it can build up and cause health problems.

What is JNT-517?

JNT-517 is a new tablet medicine being tested to help control phenylalanine levels in adults with PKU.

What is a 'placebo'?

A placebo is a 'dummy' tablet that looks like the study medicine but contains no active drug. It helps researchers compare the effects of the new medicine.

Will I know if I'm taking JNT-517 or the placebo?

No, you won't know initially. This is called 'blinding' and helps ensure the study results are fair. Everyone who continues after the first six weeks will receive JNT-517.

How long will the study last?

Including screening, your participation could last for up to 400 days, which is just over a year.

How to find out more

Otsuka Call Center

otsuka-professionalservices@otsuka-us.com 844-687-8522 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.