Featured Trial

A Study to Evaluate the Safety and Efficacy of JNT‑517 in Participants With Phenylketonuria (PKU)

Study Identifier:

JNT517-301

ClinicalTrials.gov Identifier:

NCT06971731

EudraCT Identifier:

N/A

Study Contact Information:

844-687-8522 or [email protected]

Will Be Recruiting

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Trial Details

A Phase 3, Double-Blind, Randomized, Two-Period, Multicenter, Placebo-Controlled, Efficacy and Safety Study of Repinatrabit (Ruh-pi-nah-tra-bit) (JNT-517) for the Treatment of Participants with Phenylketonuria (Fen-il-key-toe-NU-ree-uh).

The goal of this Phase 3 randomized study is to assess the safety and efficacy. Approximately 120 participants will be included in this study.

The study requires a screening period of up to 35 days to run the necessary tests to ensure study eligibility (for example, amino acid levels) and to ensure a consistent diet. Enrolled participants will be in the study for up to 14 months.

Estimated Enrollment

120

Trial Dates

Aug 2025 - Nov 2026

Study Drug

Drug: JNT-517 Tablet

Drug: Placebo Tablet: BID

Phase

Phase 3

Type

Interventional

Therapeutic Area

Phenylketonuria (PKU)

Trial Participation

Take Repinatrabit (JNT-517) 75 mg or Repinatrabit (JNT-517) 150 mg, or a placebo BID (twice daily) for approximately 6 weeks. Followed by treatment with Repinatrabit (JNT-517) 75 mg or 150 mg for the remaining 46 weeks (Total= approximately 365 days).
Visit the clinic and have the option for a mobile health nurse visit your home for checkups and tests (including some blood draws).
Collect urine samples at home and bring them to the clinic on specified days.
Keep a food diary 3 days before each study visit.

Trial Participant requirements

Age

18+ years

Sex

Female & Male

Healthy Volunteers

Inclusion and Exclusion Criteria

Males and females >= 18 years of age on Day 1
Diagnosis of PKU
3 plasma Phe levels (after >= 4 hour fast) during Screening period of >= 360 μmol/L (20%) or >=600 μmol/L
Not on pegvaliase (Palynziq) or sepiapterin (Sephience) for four weeks prior to screening

Any acute or uncontrolled chronic medical condition that would prevent the participant from complying with the procedures or place the participant at risk if they participate in the study.
Any history of cataracts or more than minimal cataracts observed during the Screening ophthalmologic examination. Minimal cataracts are defined as changes similar to lens opacities classification system III (LOCS III), lens grade C1, N1 or P1.
Any history of malignancy of any organ system (other than non-melanoma skin cancer or in situ cervical cancer), treated or untreated, within the past 5 years, regardless of whether there is evidence of local recurrence or metastases.
Any history of significant liver disease.

Requirements information

Inclusion criteria

Inclusion Criteria:
Males and females ≥18 years of age on Day 1
Clinical diagnosis of PKU
Average of at least 3 plasma Phe levels (after \>4-hour fast) during Screening period of ≥360 μmol/L
Not on pegvaliase within 4 weeks prior to Screening
If on sapropterin or large neutral amino acids, such as PheBloc®, NeoPhe®, and PreKunil® at Screening, must be on a stable dose 4 weeks prior to Screening and for the entire study duration.
Willing and able to maintain a stable diet in Phe and total protein (intact protein and medical food protein) and able to adjust diet through the duration of the study according to the Dietary Management Guidelines
Body weight \>45 kg
If biologically female of childbearing potential:
Must have a negative serum pregnancy test at Screening and a negative urine pregnancy test by Day 1
Must practice sexual abstinence, or if involved in any sexual intercourse that could lead to pregnancy, must agree to use 2 highly effective contraceptive methods from Screening until at least 30 days after the last study drug administration
If taking estrogen- or progesterone-based oral contraceptives, must agree to use 2 other highly effective methods of contraception or must agree to sexual abstinence during the study
Must refrain from donating ova during the course of the study and for 30 days after the last dose of the study drug.
If a biologically female not of childbearing potential or postmenopausal, defined as follows:
Has had surgical sterilization (hysterectomy, bilateral oophorectomy, or bilateral salpingectomy)
Has had amenorrhea for minimum of 1 year with confirmation by levels of follicle stimulating hormone testing
Has not achieved menarche (has not had first menstrual period). If a female achieves menarche during the study, she will need to follow the contraception requirement for females of childbearing potential
If biologically male, must practice sexual abstinence, or if involved in any sexual intercourse that could lead to pregnancy, must agree to use highly effective contraceptive methods from Day 1 until at least 30 days after the last study drug administration and must refrain from donating sperm during the course of the study and for 30 days after the last dose of the study drug NOTE: No restrictions are required for biological males who have undergone a documented vasectomy at least 4 months prior to Screening. If the vasectomy procedure is not documented or was performed less than 4 months prior to Screening, males must follow the same contraception as for non-vasectomized participants.
Participants with psychiatric illness must be well-controlled for the last 6 months prior to the Screening visit and if on medication, on stable medications for the last 3 months.
Capable of giving signed informed consent or parent/legal guardian to provide informed consent and the participant to give assent and confirm able to comply with study procedures
Exclusion Criteria:
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About PKU

Phenylketonuria, also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine or Phe to build up in the body. PKU is caused by a change in the phenylalanine hydroxylase (PAH) gene. This gene helps create the enzyme needed to break down phenylalanine.

Without the enzyme necessary to break down phenylalanine, a dangerous buildup can develop when a person with PKU eats foods that contain protein or products that contain aspartame, an artificial sweetener. This can eventually lead to serious health problems.

The accumulation of the amino acid Phe, a building block of protein found in your food, in people with PKU can cause learning difficulties, trouble with decision making, difficulty concentrating or focusing, feeling nervous, and trouble following rules. People with PKU require a special low-protein diet and/or pharmacologic treatment to prevent neurological and developmental complications.

Study Locations

No locations found.

July 2025 01US25EUC0279