A Study of Sepiapterin in Participants With Phenylketonuria (PKU)

Last updated: June 4, 2025
Sponsor: PTC Therapeutics
Overall Status: Active - Recruiting

Phase

3

Condition

Phenylketonuria

Treatment

Sepiapterin

Clinical Study ID

NCT06302348
PTC923-PKU-401
2024-514435-20-00
  • Ages < 12
  • All Genders

Study 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.

Eligibility Criteria

Inclusion

Key Inclusion Criteria:

For all participants:

  • Women of childbearing potential must have a negative pregnancy test at screening andagree to abstinence or the use of at least one highly effective form ofcontraception for the duration of the study, and for up to 90 days after the lastdose 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 1 blood Phe measurement ≥600 micromoles (μmol)/liter (L) as documented in themedical history.

  • For participants ≥1 month of age at Screening: A minimum of 1 documented blood Phemeasurement <480 μmol/L within 1 month prior to Screening.

  • For participants ≥1 month of age at Screening: Two screening blood Phe concentrationvalues 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 <12 years of age:

  • Baseline FSIQ score ≥80.

Exclusion

Key Exclusion Criteria:

  • History of allergies or adverse reactions to any of the ingredients or excipients ofsynthetic tetrahydrobiopterin (BH4) or sepiapterin.

  • Serious neuropsychiatric illness (for example, major depression) not currently undermedical control or other concurrent disease or condition that, in the opinion of theinvestigator or sponsor, would interfere with the participant's ability toparticipate in the study or increase the risk of participation for that participant.

  • Treatment with BH4 supplementation (sapropterin, KUVAN) within 3 months prior toScreening.

  • Current participation in another investigational drug study or use of anyinvestigational agent within 30 days prior to Screening.

  • Confirmed diagnosis of a primary BH4 deficiency as evidenced by biallelic pathogenicmutations in 6-pyruvoyltetrahydropterin synthase, recessiveGuanosine-5'-triphosphate (GTP) cyclohydrolase I, sepiapterin reductase, quinoiddihydropteridine 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 laboratoryfindings 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.

Note: Other protocol-defined inclusion and exclusion criteria may apply.

Study Design

Total Participants: 56
Treatment Group(s): 1
Primary Treatment: Sepiapterin
Phase: 3
Study Start date:
March 04, 2024
Estimated Completion Date:
February 28, 2031

Study 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.

Connect with a study center

  • Indiana University

    Indianapolis, Indiana 46202
    United States

    Active - Recruiting

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