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A Phase 3b Open-Label Study of Long-Term Neurocognitive Outcomes in Children With Phenylketonuria Treated With Sepiapterin
Led by PTC Therapeutics · Updated on 2026-05-06
56
Participants Needed
8
Research Sites
N/A
Total Duration
On this page
AI-Summary
What this Trial Is About
Researchers are evaluating the long-term effects of sepiapterin on maintaining brain function in children with Phenylketonuria (PKU) when treatment starts in early childhood. This Phase 3b open-label study aims to understand how sepiapterin impacts neurocognitive abilities over several years in young children with PKU, a condition affecting the body's processing of phenylalanine. The study has two parts: the first is an open-label test to see if participants respond to sepiapterin, and the second is a treatment phase where children receive daily oral doses of sepiapterin adjusted for their age and weight for up to six years. The medication is provided as a powder mixed with water or apple juice. Participants will be monitored regularly with intelligence tests at baseline, 2 years, and 4 years to observe changes in cognitive function. Quality of life and blood phenylalanine levels will also be assessed throughout the study, which may last up to six years. Safety and adherence will be tracked closely to evaluate the treatment’s impact over time.
CONDITIONS
Brief Title
A Study of Sepiapterin in Participants With Phenylketonuria (PKU)
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Women of childbearing potential must have a negative pregnancy test at screening and agree to use effective contraception or abstinence during the study and for at least 90 days after the last dose
- Willingness to maintain prescribed daily protein and phenylalanine intake during screening and Part 1
- For participants aged 1 month or older: established diagnosis of PKU with hyperphenylalaninemia confirmed by at least two blood phenylalanine measurements ≥600 micromoles per liter
- At least one documented blood phenylalanine measurement below 480 micromoles per liter within one month prior to screening
- Two screening blood phenylalanine values between 120 and 480 micromoles per liter
- For participants younger than 1 month: blood phenylalanine at newborn screening ≥600 micromoles per liter
- For participants aged 30 months to under 10 years: baseline full-scale intelligence quotient (FSIQ) score of 80 or higher
You will not qualify if you...
- History of allergies or adverse reactions to synthetic tetrahydrobiopterin (BH4) ingredients or sepiapterin
- Serious neuropsychiatric illness not currently under medical control or other diseases that could interfere with study participation or increase risk
- Treatment with BH4 supplements such as sapropterin (KUVAN) within 3 months prior to screening
- Participation in another investigational drug study or use of investigational agents within 30 days prior to screening
- Confirmed diagnosis of primary BH4 deficiency with specific genetic mutations
- Clinically significant laboratory abnormalities
- History or signs of renal disease with glomerular filtration rate below 60 mL/min/1.73 m2
- Major surgery within 90 days before screening
- Previous treatment with sepiapterin for longer than 6 weeks
AI-Screening
AI-Powered Screening
Complete this quick 3-step screening to check your eligibility
Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
1 visit (in-person)
Duration - Not specified
Participants undergo an open-label sepiapterin-responsiveness test to assess initial reaction to the drug.
1 visit (in-person)
Duration - Up to 6 years
Participants receive age- and weight-adjusted doses of sepiapterin orally once daily for up to 6 years.
Periodic visits for assessments during treatment
Trial Site Locations
Total: 8 locations
1
Indiana University School of Medicine
Indianapolis, Indiana, United States, 46202
Actively Recruiting
2
Women and Children Hospital
North Adelaide, Australia, SA 5006
Actively Recruiting
3
The Royal Children's Hospital
Parkville, Australia, VIC 3052
Actively Recruiting
4
Centre Hospitalier Régional Universitaire (CHRU) de Tours - Hôpital Clocheville
Tours, France, 37044
Actively Recruiting
5
Children's Health Ireland (CHI)
Dublin, Ireland, D01 YC67
Actively Recruiting
6
Pomorski Uniwersytet Medyczny w Szczecinie
Szczecin, Poland, 70-204
Actively Recruiting
7
Instytut Matki i Dziecka
Warsaw, Poland, 01-211
Actively Recruiting
8
Birmingham Women's and Children's NHS Foundation Trust
Birmingham, United Kingdom, B4 6NH
Actively Recruiting
Research Team
P
Patient Advocacy
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
NA
Model
SINGLE_GROUP
Primary Purpose
TREATMENT
Number of Arms
1
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