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Study details

Study of PTC923 (Sepiapterin) for People With Phenylketonuria

This Phase 3 study looked at whether PTC923, also called sepiapterin, could help lower blood phenylalanine levels in people with PKU. The study has been completed, but it remains important because it helped evaluate a treatment approach designed to support phenylalanine control in a broad PKU population.

Study type
Interventional clinical trial
Recruitment status
Completed
Recruitment geography
International / multi-country study
Jump to:
Overview Who may qualify Canadian site Therapy background History & publications Official record
Study overview

Official study title: A Phase 3 Study of PTC923 in Subjects With Phenylketonuria

Condition: Phenylketonuria

Intervention / therapy / focus: Drug: PTC923 (sepiapterin); comparator: placebo

Sponsor: PTC Therapeutics, Inc.

Collaborators: None listed

Study phase: Phase 3

Study type: Interventional

ClinicalTrials.gov ID: NCT05099640

Last checked by CanPKU+: March 11, 2026

If you notice that this information is out of date, please let us know at website@canpku.org.

Who may qualify

ClinicalTrials.gov describes this as a study for people with a clinical diagnosis of PKU who had elevated blood phenylalanine levels on current therapy. The study included both children and adults, with age-based dosing built into the protocol. Because this study is completed, new participants are not being enrolled, but the eligibility summary may still be helpful for families reviewing the type of participants included in the research.

Important: Final eligibility is always determined by the study team.

Canadian site information

Current CanPKU+ classification: Completed / past

Canadian site listed on ClinicalTrials.gov: No Canadian site confirmed in the current ClinicalTrials.gov summary reviewed by CanPKU+.

Canadian site note: No Canadian site confirmed at the time of review in the current ClinicalTrials.gov record for this completed study. Families interested in ongoing access to sepiapterin-related research should review the related open-label extension and sponsor study pages for newer site listings.

For sites outside Canada: Please use the official study record below for the most current list of locations.

Therapy background

PTC923, also called sepiapterin, is an oral treatment approach being studied for PKU. It is designed to affect the tetrahydrobiopterin pathway, which is involved in phenylalanine metabolism.

This Phase 3 study evaluated whether sepiapterin could reduce blood phenylalanine levels over a short double-blind treatment period after an initial run-in period that tested responsiveness.

For families, this study is important because it contributed to the evidence base for sepiapterin in a broad PKU population, including participants with different ages and disease severity.

History and publications

This section can include earlier studies and publications related to this therapy, observation, or research program.

Earlier and related studies

Previous study / phase: A Long-Term Safety Study of PTC923 in Participants With Phenylketonuria

Status: Active, not recruiting

ClinicalTrials.gov ID: NCT05166161

This open-label extension follows participants after earlier sepiapterin studies and focuses on long-term safety and changes in dietary phenylalanine and protein intake.

View official study record

Additional related study: No additional related CanPKU+ study listing identified at the time of review.

Status: Not applicable

ClinicalTrials.gov ID: Not applicable

The main directly connected follow-up study identified during review was the open-label extension above.

Publications and presentations

  • Effects of oral sepiapterin on blood Phe concentration in a broad range of patients with phenylketonuria (APHENITY): results of an international, phase 3, randomised, double-blind, placebo-controlled trial.
    Read publication or abstract
  • Interim results from the APHENITY extension study reported improved dietary phenylalanine tolerance with sepiapterin in follow-up participants.
    View source
  • No additional publications were identified by CanPKU+ during this review that needed to be added here separately.
    View source

If you notice that this section is missing a publication or no longer reflects the latest study history, please let us know at website@canpku.org.

Official study record and links

For the most current status, full site list, and eligibility details, use the official study record.