A Study of Sepiapterin in Participants With Phenylketonuria (PKU)

NCT ID: NCT06302348

Last Updated: 2025-09-12

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: PHASE3
• Total Enrollment: 56 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-03-04
• Study Completion Date: 2031-02-28

Brief Summary

The main purpose of this trial is to evaluate the long-term efficacy of sepiapterin on preserving neurocognitive functioning in children with PKU when treatment is initiated in early childhood.

Detailed Description

The study includes 2 parts: Part 1 and 2. Part 1 is an open-label sepiapterin-responsiveness test, and Part 2 is an open-label treatment period.

Conditions

Phenylketonuria

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

Sepiapterin

Participants will receive age- and weight-adjusted doses of sepiapterin orally once daily for up to 6 years.

Group Type: EXPERIMENTAL

Sepiapterin

Intervention Type: DRUG

Sepiapterin powder for oral use will be suspended in water or apple juice prior to administration.

Interventions

Sepiapterin

Sepiapterin powder for oral use will be suspended in water or apple juice prior to administration.

Intervention Type: DRUG

Other Intervention Names

PTC923; Sephience

Eligibility Criteria

Inclusion Criteria

For all participants:

• Women of childbearing potential must have a negative pregnancy test at screening and agree to abstinence or the use of at least one highly effective form of contraception for the duration of the study, and for at least 90 days after the last dose of the study drug.
• Willing to maintain prescribed daily protein/Phe during Screening and Part 1.
• Established diagnosis of PKU with hyperphenylalaninemia (HPA) evidenced by at least 2 blood Phe measurement ≥600 micromoles (μmol)/liter (L) as documented in the medical history.
• For participants ≥1 month of age at Screening: A minimum of 1 documented blood Phe measurement <480 μmol/L within 1 month prior to Screening.
• For participants ≥1 month of age at Screening: Two screening blood Phe concentration values must be in the range ≥120 to ≤480 μmol/L.

For participants <1 month of age at the time of informed consent/assent only:

• Blood Phe at newborn screening ≥600 μmol/L.

For participants ≥30 months to <10 years of age:

• Baseline FSIQ score ≥80.

Exclusion Criteria

• History of allergies or adverse reactions to any of the ingredients or excipients of synthetic tetrahydrobiopterin (BH4) or sepiapterin.
• Serious neuropsychiatric illness (for example, major depression) not currently under medical control or other concurrent disease or condition that, in the opinion of the investigator or sponsor, would interfere with the participant's ability to participate in the study or increase the risk of participation for that participant.
• Treatment with BH4 supplementation (sapropterin, KUVAN®) within 3 months prior to Screening.
• Current participation in another investigational drug study or use of any investigational agent within 30 days prior to Screening.
• Confirmed diagnosis of a primary BH4 deficiency as evidenced by biallelic pathogenic mutations in 6-pyruvoyltetrahydropterin synthase, recessive Guanosine-5'-triphosphate (GTP) cyclohydrolase I, sepiapterin reductase, quinoid dihydropteridine reductase, or pterin 4-alphacarbinolamine dehydratase genes.
• Any clinically significant laboratory abnormality as determined by the investigator.
• Any past medical history of an abnormal physical examination and/or laboratory findings indicative of signs or symptoms of renal disease, including calculated (Bedside Schwartz Equation) glomerular filtration rate (GFR) <60 milliliters (mL)/minute (min)/1.73 square meter (m^2).
• Major surgery within 90 days prior to Screening visit.

• Maximum Eligible Age: 10 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

PTC Therapeutics

INDUSTRY

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Locations

Indiana University

Indianapolis, Indiana, United States

Site Status: RECRUITING

Countries

United States

Central Contacts

Patient Advocacy

Role: CONTACT

medinfo@ptcbio.com

1-866-562-4620

Facility Contacts

Susan Romie

Role: primary

Other Identifiers

2024-514435-20-00

Identifier Type: OTHER

Identifier Source: secondary_id

PTC923-PKU-401

Identifier Type: -

Identifier Source: org_study_id