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

The goal of this Phase 3, randomized study is to assess the safety, efficacy, tolerability, and pharmacokinetics (PK) of oral JNT-517 in adults (18 years of age or older) with PKU. Participants will receive either JNT-517 or placebo and will be blinded to their treatment assignment. Participants will have a 2 in 3 (or approximately 67%) chance of receiving JNT-517 during the first part of the study which will last approximately six weeks. During the second part of the study every participant who continues in the study will receive one of two doses of JNT-517 for an additional 46 weeks. The study requires a screening period of up to 35 days to ensure dietary stabilization and amino acid levels required to meet study eligibility. In total, participation in the study could last for up to 400 days. Participants will: Take 75 mg JNT-517 or 150 mg JNT-517, or a placebo BID (2x per day) for approximately 365 days; Visit the clinic or have a mobile health nurse visit your home for checkups and tests; Collect urine sample at home and bring to clinic on specified days; Keep a food diary 3 days before each study visit

NCT Number	NCT06971731
Lead Sponsor	Otsuka Pharmaceutical Development & Commercialization, Inc.
Conditions	Phenylketonuria
Enrollment	120 participants
Start Date	2025-10-20
Primary Completion	2028-03-01 (estimated)
Study Completion	2028-04-01 (estimated)
Updated on ClinicalTrials.gov	2026-07-08