Evaluating Large Neutral Amino Acids for Treating Phenylketonuria

Safety and Efficacy of Treatment With Large Neutral Amino Acids in Patients With Classical Phenylketonuria

Not applicable Interventional Rigshospitalet, Denmark · NCT06337864

This study is testing if Large Neutral Amino Acids can be a better treatment for adults with Phenylketonuria than the usual diet that limits phenylalanine.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment30 (estimated)
Ages18 Years to 50 Years
SexAll
SponsorRigshospitalet, Denmark Academic / other
Locations2 sites (Copenhagen and 1 other locations)
Trial IDNCT06337864 on ClinicalTrials.gov

What this trial studies

This study aims to assess the effectiveness of Large Neutral Amino Acids (LNAA) as an alternative treatment for adults with classical Phenylketonuria (PKU), compared to the traditional phenylalanine-restricted diet. It will investigate the impact of LNAA on cerebral dopamine synthesis, cognitive function, and mental health. The study will utilize a randomized, open-label, crossover design, allowing participants to experience both treatment approaches. Additionally, a healthy control group will be included to establish baseline measures, and participants may have the option to continue in an open-label extension study for long-term evaluation.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18 and older with classical PKU confirmed by genetic testing or historical evidence of elevated phenylalanine levels.

Not a fit: Patients who are unable to adhere to study requirements or have serious neuropsychiatric conditions may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a more manageable and effective alternative to the strict dietary restrictions currently required for PKU patients.

How similar studies have performed: While the use of LNAA in PKU management is a novel approach, similar studies have shown promise in exploring alternative treatments for metabolic disorders.

Eligibility criteria

Show full inclusion / exclusion criteria
Patients ≥ 18 years of age with Classical PKU molecularly confirmed via the finding of two pathogenic variants in the phenylalanine hydroxylase (PAH) gene and/or historical evidence of Phe concentrations ≥1200 μmol/L in the medical history

Inclusion Criteria:

* Treatment initiation within the first month of life
* Intelligence quotient over 84, based upon the baseline neuropsychological evaluation
* Conventional dietary treatment up to minimum 15 years of age
* Signed informed consent
* Willing and able to comply with the protocol and study procedures

Exclusion Criteria:

* Unable or unwilling to adhere to the requirements of the study
* A female who is pregnant or breastfeeding or planning to get pregnant during the study period
* Concomitant medication that may interfere with the PET analysis, as judged by the investigator
* A serious neuropsychiatric disease that could interfere with the subject's ability to participate in the study at the discretion of the investigator
* Concomitant treatment with BH4 supplementation (sapropterin) or Pegvaliase-pqpz (PALYNZIQ)
* Failing to submit at least one blood Phe home sample during the year before study initiation
* Standard MRI contraindications
* Body weight over 110 kg

Where this trial is running

Copenhagen and 1 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Brain DiseasesBrain Diseases, MetabolicBrain Diseases, Metabolic, InbornGenetic Diseases, InbornMetabolism, Inborn ErrorsAmino Acid Metabolism, Inborn ErrorsMetabolic DiseasePhenylketonurias
Last reviewed 2026-06-09 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.