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Completed

NCT Number: NCT05099640

A Study of PTC923 in Participants With Phenylketonuria

The main purpose of this trial is to evaluate the efficacy of PTC923 in reducing blood phenylalanine (Phe) levels in participants with phenylketonuria as measured by mean change in blood Phe levels from baseline to Weeks 5 and 6 (that is, the average of each respective treatment dose 2-week period of double-blind treatment).

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Key information

Conditions

Phenylketonuria Amino Acid Metabolism, Inborn Errors Brain Diseases Brain Diseases, Metabolic Brain Diseases, Metabolic, Inborn Central Nervous System Diseases Congenital, Hereditary, and Neonatal Diseases and Abnormalities Genetic Diseases, Inborn Metabolic Diseases Metabolism, Inborn Errors Nervous System Diseases Nutritional and Metabolic Diseases Phenylketonurias

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 3

Primary location

Westmead Hospital, Westmead, New South Wales, Australia

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About this study

The study includes 2 parts: Part 1 and 2. Part 1 of the study tests for responsiveness to PTC923, with 14 days of open-label treatment with PTC923. At the end of treatment in Part 1, the mean change in blood Phe levels over the 14-day treatment period for all participants will be assessed against their pretreatment (baseline) blood Phe level. Participants ≥2 years of age who experience a <15% reduction in blood Phe levels will be classified as non-responsive and participation in the study will be terminated. Participants (≥2 years of age) who experience a ≥15% reduction in blood Phe levels will continue into Part 2. Participants <2 years of age who experience ≥15% reduction in blood Phe levels will be offered the option to enroll directly into an open-label extension Study PTC923-MD-004-PKU. Participants <2 years of age who experience a <15% reduction in blood Phe levels will be classified as nonresponsive, and participation in the study will be terminated. Following the minimum 14-day PTC923 washout period, all eligible participants will be randomized in Part 2 to receive either PTC923 or placebo. After 6 weeks of treatment with either PTC923 or placebo, participants will be offered the option to enter an open-label extension Study PTC923-MD-004-PKU (NCT05166161).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Uncontrolled blood Phe level ≥360 μmol/L on current therapy anytime during screening and uncontrolled blood Phe level ≥360 μmol/L on current therapy when taking the average of the 3 most recent Phe levels from the participant's medical history (inclusive of the screening value).
  • Clinical diagnosis of phenylketonuria with hyperphenylalaninemia (HPA) documented by past medical history of at least 2 blood Phe measurements ≥600 μmol/L.
  • Women of childbearing potential must have a negative pregnancy test at screening and agree to abstinence or the use of at least one highly effective form of contraception for the duration of the study, and for up to 90 days after the last dose of study drug.
  • Males who are sexually active with women of childbearing potential who have not had a vasectomy must agree to use a barrier method of birth control during the study and for up to 90 days after the last dose of study drug. Males must also refrain from sperm donations during this time period.
  • Willing to continue current diet unchanged while participating in the study.

Exclusion criteria

  • 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 tetrahydrobiopterin (BH4) or sepiapterin.
  • Current participation in any other investigational drug study or use of any investigational agent within 30 days prior to screening.
  • Any clinically significant laboratory abnormality as determined by the investigator.
  • 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 sponsor, 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]) and/or under care of a nephrologist.
  • Any abnormal physical examination and/or laboratory findings indicative of signs or symptoms of renal disease, including calculated GFR <60 mL/min/1.73 square meter (m^2).
  • Requirement for concomitant treatment with any drug known to inhibit folate synthesis (for example, methotrexate).
  • Confirmed diagnosis of a primary BH4 deficiency as evidenced by biallelic pathogenic mutations in 6-pyruvoyltetrahydropterin synthase, recessive guanosine-5'-triphosphate (GTP) cyclohydrolase I, sepiapterin reductase, quinoid dihydropteridine reductase, or pterin-4-alpha-carbinolamine dehydratase genes.
  • Major surgery within the prior 90 days of screening.
  • Concomitant treatment with BH4 supplementation (for example, sapropterin dihydrochloride, KUVAN) or pegvaliase-pqpz (PALYNZIQ).
  • Unwillingness to washout from BH4 supplementation (for example, sapropterin dihydrochloride, KUVAN) or pegvaliase-pqpz (PALYNZIQ)

Treatment and study plan

PTC923

Drug

PTC923 powder for oral use will be suspended in water or apple juice prior to administration.

Placebo

Drug

Placebo matching to PTC923

Primary outcomes

  1. Part 2 Double-blind Phase: Mean Change From Baseline in Blood Phenylketonuria (Phe) Level to Weeks 5 and 6 (Averaged Over a 2-week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 5 and 6 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window. Least square (LS) mean and standard error (SE) were calculated using mixed model repeated measures (MMRM) method.

  2. Part 2 Double-blind Phase: Percent Change From Baseline in Blood Phe Level to Weeks 5 and 6 (Averaged Over a 2-week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 5 and 6 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window. LS mean and SE were calculated using MMRM method.

Secondary outcomes

  1. Part 2 Double-blind Phase: Percentage of Participants With Baseline Phe Levels ≥600 μmol/L Who Achieved Phe Levels <600 μmol/L in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Weeks 5 and 6 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window.

  2. Part 2 Double-blind Phase: Percentage of Participants With Baseline Phe Levels ≥360 μmol/L Who Achieved Phe Levels <360 μmol/L in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Weeks 5 and 6 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window.

  3. Part 2 Double-blind Phase: Mean Change From Baseline in Blood Phe Level at Each 2-Week Period (Averaged Over Each 2-Week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 1 and 2, Weeks 3 and 4, and Weeks 5 and 6 (average of each 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean levels at Weeks 1 and 2, Weeks 3 and 4, and Weeks 5 and 6 were calculated as the average of blood Phe levels collected during the Week 1-2, Week 3-4, and Week 5-6 analysis visit windows, respectively.

  4. Part 2 Double-blind Phase: Percent Change From Baseline in Blood Phe Level at Each 2-Week Period (Averaged Over Each 2-Week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 1 and 2, Weeks 3 and 4, and Weeks 5 and 6 (average of each 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean levels at Weeks 1 and 2, Weeks 3 and 4, and Weeks 5 and 6 were calculated as the average of blood Phe levels collected during the Week 1-2, Week 3-4, and Week 5-6 analysis visit windows, respectively.

  5. Part 1 Open-label Run-in Phase: Plasma Concentration of Tetrahydrobiopterin (BH4) and Sepiapterin

    Time frame: Predose, 0.5, 1, 2, 4, 6, 8, and 24 hours postdose at Day 1; 2 and 6 hours postdose at Day 14

  6. Part 2 Double-blind Phase: Plasma Concentration of BH4 and Sepiapterin

    Time frame: Predose and 4 hours postdose at Days 1, 14, 28, and 42

  7. Part 1 Open-label Run-in Phase: Area Under the Concentration-time Curve From Time 0 to 24 Hours Postdose (AUC0-24h) of Sepiapterin and BH4 Following the First Dose of Sepiapterin at 60 mg/kg

    Time frame: 0 to 24 hours postdose at Day 1

  8. Number of Participants With Treatment-emergent Adverse Events (TEAEs)

    Time frame: Baseline up to Day 42

    An adverse event (AE) was as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. TEAEs were considered:

    • Part 1 TEAEs, which included all AEs occurring after first dose in Part 1 but before first dose in Part 2;
    • Part 2 TEAEs, which included all AEs after first randomized dose in Part 2. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Other outcomes

  1. Part 2 Double-blind Phase: Mean Change From Baseline in Blood Phe Level to Weeks 5 and 6 (Averaged Over a 2-week Period) in Classical PKU Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 5 and 6 (average of the 2-week period)

    Classical PKU participants: Participants with severe forms of PKU, typically very high blood Phe levels (>1200 μmol/L). Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window. LS mean and SE were calculated using MMRM method.

  2. Part 2 Double-blind Phase: Percent Change From Baseline in Blood Phe Level to Weeks 5 and 6 (Averaged Over a 2-week Period) in Classical PKU Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline, Weeks 5 and 6 (average of the 2-week period)

    Classical PKU participants: Participants with severe forms of PKU, typically very high blood Phe levels (>1200 μmol/L). Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 2, and mean level at Weeks 5 and 6 was calculated as the average of blood Phe levels collected during the Week 5-6 analysis visit window. LS mean and SE were calculated using MMRM method.

  3. Part 1 Open-label Run-in Phase: Mean Change From Baseline (Part 1) in Blood Phe Level to Weeks 1 and 2 (Averaged Over a 2-week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline (Part 1), Weeks 1 and 2 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 1 Open-label Run-in Phase, and mean level at Weeks 1 and 2 was calculated as the average of blood Phe levels collected during the Week 1-2 analysis visit window. LS mean and SE were calculated using MMRM method.

  4. Part 1 Open-label Run-in Phase: Percent Change From Baseline (Part 1) in Blood Phe Level to Weeks 1 and 2 (Averaged Over a 2-week Period) in Participants With Phe Reduction From Baseline ≥30% During Part 1

    Time frame: Baseline (Part 1), Weeks 1 and 2 (average of the 2-week period)

    Baseline was defined as the average of Day -1 and Day 1 predose blood Phe levels in Part 1 Open-label Run-in Phase, and mean level at Weeks 1 and 2 was calculated as the average of blood Phe levels collected during the Week 1-2 analysis visit window. LS mean and SE were calculated using MMRM method.

Sponsors and collaborators

Lead sponsor

PTC Therapeutics

Industry

Registry information

Official study title

A Phase 3 Study of PTC923 in Subjects With Phenylketonuria

Important dates

Study start
2021
Primary completion
2023
Study completion
2023
First posted
Oct 29, 2021
Registry last updated
Jan 10, 2024

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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