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Study of pegvaliase injections compared to diet control in adolescents aged 12-17 with phenylketonuria (PKU)

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on adolescents with Phenylketonuria (PKU), a genetic condition where the body cannot properly break down an amino acid found in protein-rich foods. The study will test a medication called Palynziq (pegvaliase), which is given as an injection under the skin. The purpose is to evaluate if this treatment is safe and effective for young patients aged 12-17 years who have not achieved good control of their PKU with diet alone.

The treatment involves receiving subcutaneous injections of Palynziq at different doses (2.5 mg, 10 mg, or 20 mg) using pre-filled syringes. Some participants will receive the medication while others will continue with dietary management only. The study will last approximately 215 days, during which participants will need regular medical check-ups and blood tests to monitor their condition.

Throughout the study, healthcare providers will monitor participants' health through various tests and examine how well the medication helps control blood protein levels. An adult must be present to observe the participant for at least one hour after each injection. The study will also track how the treatment affects participants' ability to include more protein in their diet.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Your blood will be tested to confirm phenylketonuria (PKU) diagnosis and measure blood phenylalanine levels

    A physical examination, laboratory tests (blood and urine), and heart test (ECG) will be performed to assess your general health

  2. Step 2

    Study medication introduction

    You will receive Palynziq as an injection under the skin (subcutaneous injection)

    The medication comes in pre-filled syringes with different strengths: 2.5 mg, 10 mg, or 20 mg

    An adult (18 years or older) must be present during injection and for one hour afterward

  3. Step 3

    Dietary monitoring

    A study dietician will help monitor and adjust your protein intake from food and medical supplements

    Regular assessments of your dietary protein intake will be recorded

  4. Step 4

    Ongoing monitoring

    Regular blood tests to check phenylalanine levels

    Blood samples will be taken to measure medication levels in your body

    Regular health assessments including physical examinations and laboratory tests

    Monitoring for any side effects or reactions to the medication

  5. Step 5

    Study duration

    The study continues until August 2027

    Regular visits to the study center will be required throughout the study period

Who can join the trial?

11 criteria

  • Age requirement: 12-17 years old for US participants, or 12-15 years old for participants outside the US
  • Must have PKU diagnosis and be unable to maintain recommended blood phenylalanine levels despite previous treatments (both diet and medication)
  • Must have at least two blood phenylalanine measurements above 600 µmol/L during screening (taken 7-10 days apart)
  • Must have average blood phenylalanine levels above 600 µmol/L over the past 12 months
  • Must be willing to maintain and adjust protein intake according to study requirements under supervision
  • If taking medications for ADHD (attention deficit hyperactivity disorder), depression, or other psychiatric conditions, must be on stable doses for at least 8 weeks before joining
  • Must have an adult (18 years or older) who can observe the participant during treatment and for one hour afterward
  • Must be able to follow all study procedures
  • Must be in good general health, confirmed by physical exam, laboratory tests, and heart tests (ECG)
  • Both males and females can participate
  • Female participants who can become pregnant must have negative pregnancy tests and agree to additional pregnancy testing during the study

Who cannot join the trial?

15 criteria

  • Age below 12 years or above 18 years
  • Previous participation in clinical trials with pegvaliase (an enzyme replacement therapy)
  • Currently pregnant or breastfeeding women
  • History of severe allergic reactions to any medications
  • Significant liver or kidney problems (organ dysfunction)
  • Current use of other experimental treatments
  • Inability to follow dietary restrictions required for the study
  • Mental health conditions that could interfere with study participation
  • Uncontrolled medical conditions like hypertension (high blood pressure) or diabetes
  • Use of medications that could interact with the study drug
  • History of substance abuse within the past year
  • Unable to provide informed consent or follow study procedures
  • Blood disorders that could affect study results
  • Recent major surgery (within 3 months)
  • Active infections or serious illness
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Investigated drugs

Pegvaliase is a medication used to treat phenylketonuria (PKU), a rare genetic condition that causes an amino acid called phenylalanine to build up in the body. This medication is given as an injection under the skin (subcutaneous injection). It works by helping the body break down phenylalanine, which can help reduce its levels in the blood. This treatment is being studied as an alternative or supplement to the traditional dietary management of PKU in adolescent patients. Diet-only control represents the traditional treatment approach for PKU, which involves following a strict diet that limits the intake of foods containing phenylalanine. This typically means avoiding foods high in protein such as meat, fish, eggs, dairy products, nuts, and some grains.

What is already known about the treatment

Pegvaliase - A therapeutic enzyme administered through subcutaneous injections, specifically designed for treating Phenylketonuria (PKU), a rare genetic disorder affecting the body's ability to break down phenylalanine. This medication works by replacing the deficient enzyme in PKU patients, helping to reduce phenylalanine levels in the blood to a manageable range. Pegvaliase belongs to the class of enzyme replacement therapies and represents a significant advancement in PKU treatment, offering an alternative to strict dietary management. The medication is currently being studied in Phase 3 clinical trials for adolescent patients aged 12-17 years, with promising results in improving quality of life for individuals with PKU.

Investigated diseases

Phenylketonuria (PKU) - A genetic disorder that affects the body's ability to process an amino acid called phenylalanine, which is found in many foods containing protein. When a person has PKU, phenylalanine builds up in the body because an enzyme needed to break it down is missing or not working properly. The condition is present from birth and is inherited in an autosomal recessive pattern, meaning both parents must pass on the defective gene. Without dietary management, phenylalanine accumulates in the blood and can lead to various developmental issues. The disorder affects how the body processes protein and requires careful monitoring of protein intake through diet.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2024-510875-39-00Protocol code165-306Estimated enrolment62 patientsSponsorBiomarin Pharmaceutical Inc.

sourced from the EU Clinical Trials Register and site verification

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