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

Launched by OTSUKA PHARMACEUTICAL DEVELOPMENT & COMMERCIALIZATION, INC. · May 7, 2025

Keywords

ClinConnect Summary

This clinical trial is studying a new oral medication called JNT-517 to see how safe and effective it is for adults with Phenylketonuria (PKU), a genetic condition that affects how the body processes a specific amino acid called phenylalanine. In this study, participants will take either JNT-517 or a placebo (a pill with no active ingredient) for the first six weeks, and those who continue will receive one of two doses of JNT-517 for an additional 46 weeks. The entire study may last up to 400 days, and participants will need to keep a food diary and provide urine samples during their visits to the clinic or have a nurse come to their home for checkups.

To participate, individuals must be at least 18 years old, have a confirmed diagnosis of PKU, and meet specific health criteria, including maintaining stable amino acid levels and following a special diet. Participants should also be willing to follow guidelines regarding contraception if they are capable of becoming pregnant or fathering a child. This trial aims to help researchers understand if JNT-517 can improve the quality of life for people living with PKU.

Gender

ALL

Eligibility criteria

• Inclusion Criteria:
• • 1. Males and females ≥18 years of age on Day 1
• • 2. Clinical diagnosis of PKU
• • 3. Average of at least 3 plasma Phe levels (after \>4-hour fast) during Screening period of ≥360 μmol/L
• • 4. Not on pegvaliase within 4 weeks prior to Screening
• • 5. 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.
• • 6. 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
• • 7. Body weight \>45 kg
• 8. If biologically female of childbearing potential:
• • 1. Must have a negative serum pregnancy test at Screening and a negative urine pregnancy test by Day 1
• • 2. 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
• • 3. 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
• • 4. Must refrain from donating ova during the course of the study and for 30 days after the last dose of the study drug.
• 9. If a biologically female not of childbearing potential or postmenopausal, defined as follows:
• • 1. Has had surgical sterilization (hysterectomy, bilateral oophorectomy, or bilateral salpingectomy)
• • 2. Has had amenorrhea for minimum of 1 year with confirmation by levels of follicle stimulating hormone testing
• • 3. 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
• • 10. 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.
• • 11. 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.
• • 12. 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:
• • -