🏛️ Verified NIH Record • Updated 2026-06-19

A Long-Term Safety Study of PTC923 in Participants With Phenylketonuria (NCT05166161)

A Phase 3 Open-Label Study of PTC923 (Sepiapterin) in Phenylketonuria

🔵 Active, Not Recruiting Phase3 💊 Investigational Drug / Biologic Sponsor: PTC Therapeutics

🩺 Plain-English Summary (8th-Grade Level)

The main purpose of this study is to evaluate the long-term safety of PTC923 in participants with phenylketonuria, and to evaluate the changes from baseline in dietary phenylalanine (Phe)/protein consumption.

Who can join: To join this study, participants generally need to meet the listed inclusion criteria (4 items) and avoid the listed exclusions (13 items).

Location: Children's Hospital Colorado — Aurora, Colorado

🧪 Interventions in This Study

📋 "Do I Qualify?" — 1-Minute Self Screener

Instant Checklist

Check every box below. If you can check all of them, you may meet the study's basic screening requirements (final eligibility is confirmed by the site team).

Usually NOT eligible if any of the following apply:

  • Exclusion Criteria:
  • Inability to tolerate oral medication.
  • A female who is pregnant or breastfeeding, or considering pregnancy.
  • Serious neuropsychiatric illness (for example, major depression) not currently under medical control, that in the opinion of the investigator or PTC, would interfere with the participant's ability to participate in the study or increase the risk of participation for that participant.
  • Past medical history and/or evidence of renal impairment and/or condition including moderate/severe renal insufficiency (glomerular filtration rate \[GFR\] \<60 milliliters \[mL\]/minute \[min\] min as estimated most recently during qualifying participation in a feeder study) and/or under care of a nephrologist.
  • Any other condition that in the opinion of the investigator or PTC, would interfere with the participant's ability to participate in the study or increase the risk of participation for that participant.
  • Requirement for concomitant treatment with any drug known to inhibit folate synthesis (for example, methotrexate).
  • Concomitant treatment with tetrahydrobiopterin (BH4) supplementation (for example, sapropterin dihydrochloride, KUVAN) or pegvaliase-pqpz (PALYNZIQ). Additional criteria for non-feeder participants who did not participate in a feeder study:
  • Gastrointestinal disease (such as irritable bowel syndrome, inflammatory bowel disease, chronic gastritis, and peptic ulcer disease, etc) that could affect the absorption of study drug.
  • History of gastric surgery, including Roux-en-Y gastric bypass surgery or an antrectomy with vagotomy, or gastrectomy.
  • History of allergies or adverse reactions to synthetic BH4 or sepiapterin.
  • Any clinically significant laboratory abnormality as determined by the investigator.

🔍 Extracted verbatim from the official NIH eligibility criteria. Always confirm with the study coordinator.

📍 All Participating Trial Locations (46 Sites)

Showing the first 25 of 46 sites.

  • Children's Hospital Colorado — Aurora, Colorado
  • UF College of Medicine, Department of Pediatrics Division of Genetics and Metabolism — Gainesville, Florida
  • Indiana University School of Medicine Department of Medical and Molecular Genetics — Indianapolis, Indiana
  • Boston Children's Hospital — Boston, Massachusetts
  • Icahn School of Medicine at Mount Sinai (ISMMS) — New York, New York
  • UPMC Children's Hospital of Pittsburgh — Pittsburgh, Pennsylvania
  • University of Utah — Salt Lake City, Utah
  • The Queensland Children's Hospital — South Brisbane, Brisbane
  • Westmead Hospital — Westmead, New South Wales
  • PARC Clinical Research — Adelaide, South Australia
  • Royal Children's Hospital — Parkville, Victoria
  • Hospital de clinicas de Porto Alegre — Porto Alegre, Rio Grande do Sul
  • Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo — Ribeirão Preto, São Paulo
  • Metabolics and Genetics in Calgary (MAGIC) Clinic, Ltd. — Calgary, Alberta
  • McMaster Children's Hospital Hamilton Health Sciences — Hamilton, Ontario
  • The Hospital for Sick Children University of Toronto Adult Clinic: The Fred A Litwin Family Centre in Genetic Medicine University Health Network & Mt. Sinai Hospital — Toronto, Ontario
  • Fakultní nemocnice Královské Vinohrady Klinika dětí a dorostu Ambulance pro léčbu PKU a HPA — Prague,
  • Copenhagen University Hospital, Rigshospitalet — Copenhagen,
  • Hôpital Necker-Enfants Malades - Centre de Référence des Maladies Héréditaires du Métabolisme — Paris,
  • Medical Genetics and Laboratory Diagnostics Center — Tbilisi,
  • University Children's Hospital Hamburg Eppendorf (Kinder-UKE) Klinik für Kinder- und Jugendmedizin (Kinder-UKE) — Hamburg,
  • Universitätsklinikum Heidelberg / Zentrum für Kinder- und Jugendmedizin / Sektion für Neuropädiatrie & Stoffwechselmedizin — Heidelberg,
  • Universitätsklinikum Münster — Münster,
  • Azienda Ospedaliera-Universita Padova — Padua, Veneto
  • Department of Human Neuroscience, Child and Adolescent Neuropsychiatry, Policlinico Umberto I — Rome,

💰 Cost, Insurance & Patient Rights

  • 100% Free Items: The investigational treatment and protocol-required procedures are supplied at zero cost by the sponsor.
  • Routine Patient Care: Under federal law (ACA § 2709) and many state statutes, routine care costs are covered during participation.
  • Voluntary Participation: You may withdraw at any time without affecting your standard medical care.

More studies in Phenylketonuria

Explore by condition: All Phenylketonuria clinical trials

💡 How to Participate

  1. Check the checklist above to see if you may qualify.
  2. Review the official NIH record below to find the coordinating site.
  3. Ask about the visit schedule, what is covered at no cost, and any travel support.
  4. Confirm with your own doctor before making a decision.
🏛️ View Official NIH Record ↗