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

Conditions

• Phenylketonuria

Eligibility Criteria

Sex

ALL

Age

18 Years - N/A

Healthy Volunteers

Not accepted

Interventions

• JNT-517 Tablet — DRUG
  JNT-517: 75 mg BID
• JNT-517 Tablet — DRUG
  JNT-517: 150 mg BID
• Placebo Tablet: BID — DRUG
  Placebo Tablet: BID

Study Details

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

Key Dates

Start date

Oct 20, 2025

Status verified

Apr 2026

Primary completion

Mar 1, 2028

Completion

Apr 1, 2028

Study Design

Enrollment

120 participants (estimated)

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

Arms

• Experimental: Drug: JNT-517 - 150 mg BID (Tablet)
• Experimental: Drug: JNT-517 - 75 mg BID (Tablet)
• Placebo Comparator: Placebo - BID
  One-third (1/3) of participants in the study will be assigned to placebo twice daily (BID) during Treatment Period Part 1. After 6 weeks, these participants will transition to Treatment Period Part 2 and receive JNT-517 at 150 mg BID for 46 weeks.

Primary Outcome Measure

Absolute Change in Plasma Phenylalanine (Phe) From Baseline to the Mean of Weeks 2, 4, and 6 in the JNT-517 150 mg BID Dose Group at End of Period 1 [ Time Frame: Baseline to End of Period 1 (Week 6) ]

Central Contacts

• Otsuka Call Center
  844-687-8522
  [email protected]

Locations (10)

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