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Home › Conditions › Phenylketonuria

Phenylketonuria

Part of Brain Diseases, Metabolic, Inborn

2 published articles · Updated continuously

Clinical Trial Landscape

Clinical Trials for Phenylketonuria

19 trials tracked for Phenylketonuria: 9 in phase 3 or 4 and 3 with published results. The most-cited published study has 41 citations.

19Trials tracked
9Phase 3 & 4
0Recruiting
3With published results
Phase distribution
Phase 4 2 Phase 3 7 Phase 2 5 Other / NA 5
  1. Phase 3 Kuvan® in Phenylketonuria Patients Less Than 4 Years Old Completed · 41 cited
  2. Phase 3 A Study of PTC923 in Participants With Phenylketonuria Completed · 37 cited
  3. Phase 3 An Open-Label Phase 3 Study of BMN 165 for Adults With PKU Not Previously Treated w/ BMN 165 Completed · 21 cited
  4. Phase 4 The Effectiveness of Kuvan in Amish PKU Patients Completed
  5. Phase 4 Response to Kuvan® in Subjects With Phenylketonuria (PKU) in a 4 Weeks Testing Period Completed
  6. Phase 3 Effect of Kuvan on Neurocognitive Function, Blood Phenylalanine Level, Safety, and Pharmacokinetics in Children With PKU Completed
Show 13 more trials
  1. Phase 3 Safety and Therapeutic Effects of Sapropterin Dihydrochloride on Neuropsychiatric Symptoms in Phenylketonuria (PKU) Patients Completed
  2. Phase 3 Phase 3 Open-label Study to Evaluate the Response and Safety of Kuvan® in Subjects With Phenylketonuria Completed
  3. Phase 3 Study of Phenoptin in Subjects With Phenylketonuria Who Participated in Protocols PKU-004 or PKU-006 Completed
  4. Phase 2 A Study to Evaluate Subcutaneously Administered rAvPAL-PEG in Patients With Phenylketonuria for 24 Weeks Completed
  5. Phase 2 Dose-Finding Study to Evaluate the Safety, Efficacy, & Tolerability of Multiple Doses of rAvPAL-PEG in Subjects With PKU Completed
  6. Phase 2 Long-Term Extension of Previous rAvPAL-PEG Protocols in Subjects With PKU (PAL-003) Completed
  7. Phase 2 Safety, Tolerability, and Efficacy Study of rAvPAL-PEG Administered Daily in Subjects With Phenylketonuria (PKU) Completed
  8. Phase 2 Kuvan Therapy in Phenylketonuria (PKU): The Effect of Blood Phenylalanine Concentration on Kuvan Response Completed
  9. N/A Nutritional and Neurotransmitter Changes in PKU Subjects on BH4 Completed
  10. N/A Phase 2 Study of Glycomacropeptide Versus Amino Acid Diet for Management of Phenylketonuria Completed
  11. N/A The Brain, Neurological Features and Neuropsychological Functioning in Adults With Phenylketonuria: A Pilot Study Completed
  12. N/A A Phase 3 Substudy to Evaluate Executive Function in Adults With PKU Who Are Participating in the Phase 3 Study, 165-302 Completed
  13. N/A Fluorodeoxyglucose Positron Emission Tomography (FDG PET) Findings in Patients With Phenylketonuria Before and After KUVAN Therapy Completed

Showing the 19 most-cited and recently-updated of 19 trials. Browse the full registry →

Trial data sourced from ClinicalTrials.gov. Counts describe the research landscape and are not a treatment recommendation. Informational only — not medical advice.

What the trials found For clinicians

Phenylketonuria: what the trials found

Kuvan® (sapropterin dihydrochloride) has demonstrated significant efficacy in managing blood phenylalanine (Phe) levels. In a study of 59 participants, 75% achieved at least a 30% reduction from baseline 2. Further analysis showed that across various PKU phenotypes, 69% of patients experienced a 20-30% reduction, while 8% saw less than a 10% reduction 2. In another trial, Kuvan® was associated with a -48.75% change in blood Phe in specific responder groups 11, and a 37.1% improvement in dietary Phe tolerance after 26 weeks 3.

Sapropterin dihydrochloride has also been evaluated for neurocognitive and behavioral outcomes. One study reported Full-Scale Intelligence Quotient (FSIQ) scores ranging from 100.76 to 104.69 following treatment 6. However, significant changes were not observed in ADHD ratings (p=0.085), Global Function Evaluation (p=0.67), or Hamilton Anxiety Rating Scale scores (p=0.669) over a 13-week period 7.

PTC923 showed significant reduction in blood Phe levels in patients with baseline levels $\geq$600 \mu mol/L, with 92.9% achieving target levels below 600 \mu mol/L during the double-blind phase (p<0.0001) 4. Additionally, rAvPAL-PEG was evaluated for immunogenicity; studies showed varying rates of PAL IgG and PEG-IgG antibody positivity among participants [10, 14].

Recent results — preliminary, needs further review

  • • BMN 165 (rAvPAL-PEG) and other sapropterin formulations are currently undergoing investigation regarding efficacy and immunogenicity, but results are not yet corroborated [5, 12].
  • • Studies investigating the impact of Kuvan therapy on BMI, Bone Mineral Density, and Lean Mass have shown statistically significant improvements in BMD (p<0.001) and Lean Mass (p=0.0179) at 12 months 19.

For the clinician treating this condition

  • Kuvan® is established as an effective intervention for reducing blood phenylalanine levels and improving dietary Phe tolerance in patients with PKU [2, 3].
  • Sapropterin dihydrochloride treatment is associated with stable FSIQ scores but did not show statistically significant improvements in anxiety or ADHD symptoms in the studied cohorts [6, 7].
  • PTC923 demonstrated a high success rate (92.9%) in reducing blood Phe levels to below 600 \mu mol/L in patients with high baseline concentrations 4.

AI synthesis of 7 cited trials, updated Jun 25, 2026. Informational only — not medical advice; trial data sourced from ClinicalTrials.gov. How we use AI.

HCP Mode — summaries include clinical detail, trial data, and statistical outcomes.
Patient Mode — summaries use plain language, avoiding clinical jargon.
Sepiapterin reduces blood phenylalanine more than sapropterin in PKU patients
Drug Pipeline RCT
Sepiapterin reduces blood phenylalanine more than sapropterin in PKU patients Sepiapterin beats sapropterin for lowering blood levels
This Phase 3, randomized, crossover trial in 82 children and adults with phenylketonuria compared sepiapterin to sapropterin.
New research shows a specific vitamin treatment works much better than current options for a rare genetic condition.
May 1, 2026
Walking program improves liver enzymes and BMI in children with PKU and NAFLD
Diabetes & Endocrinology RCT
Walking program improves liver enzymes and BMI in children with PKU and NAFLD Walking program shows improvement in liver health markers for children with PKU and fatty liver
An 8-week RCT in 40 overweight/obese children with PKU and NAFLD found that a free walking program significantly improved BMI, ALT, GGT, ALP…
An 8-week walking program improved liver health markers and BMI in children with PKU and fatty liver disease.
Apr 3, 2026