Trial results
AI generated results summary. Written by an AI model from the official source data and checked on a sample basis. It can contain mistakes, so confirm anything important against the original source. How we use AI
According to the results reported on ClinicalTrials.gov, this trial (NCT05099640) tested a medicine called sepiapterin in people with phenylketonuria (PKU) — a condition where the body cannot properly break down a substance called phenylalanine (Phe), which can build up in the blood. The trial ran in two parts. In Part 1, 157 participants received sepiapterin for 14 days; 111 completed this stage. Those who showed a blood Phe reduction of at least 30% during Part 1 were then eligible for Part 2, a 6-week randomised stage where 56 participants received sepiapterin and 54 received a placebo (a dummy treatment with no active ingredient). The trial's main goal was to measure changes in blood Phe levels. The reported data shows that, for the main outcome measured at weeks 5 and 6 of Part 2, participants in the sepiapterin group had an average blood Phe level that was about 416 units (μmol/L) lower than their starting level, representing a decrease of around 63%. In the placebo group over the same period, blood Phe levels were largely unchanged, with the reported data showing an average decrease of about 20 units and a change of less than 1%. For the secondary outcomes, the reported data shows that among participants whose starting Phe levels were above 600 μmol/L, about 93% of the sepiapterin group reached levels below that threshold by weeks 5–6, compared with 30% in the placebo group. Among those starting above 360 μmol/L, about 84% of the sepiapterin group reached levels below that point, compared with around 9% in the placebo group. These are the results as reported to ClinicalTrials.gov. They are not medical advice — always discuss what they mean for you with your doctor.
View full results on ClinicalTrials.gov ↗ · Read the linked publication on PubMed (PMID 41363942) ↗
These are the results as reported to ClinicalTrials.gov, not medical advice. Verify independently with the trial site and discuss what they mean for you with your doctor.
Phase 3 Phenylketonuria Trial, Completed
Who may be able to join
AI generated eligibility summary. Written by an AI model from the official source data and checked on a sample basis. It can contain mistakes, so confirm anything important against the original source. How we use AI
Who might be able to join this trial:
- Your blood phenylalanine (Phe) levels must be 360 or above (on a specific measurement scale) both at the screening visit and on average across your three most recent test results.
- You must have a confirmed diagnosis of phenylketonuria (PKU), with at least two past blood tests showing Phe levels of 600 or above.
- If you are a woman who could become pregnant, you must have a negative pregnancy test at the start of the study and agree to use at least one highly effective form of birth control throughout the study and for 90 days after your last dose.
- If you are a man who is sexually active with a woman who could become pregnant and have not had a vasectomy, you must agree to use a barrier method of contraception (such as condoms) during the study and for 90 days after your last dose, and avoid donating sperm during this time.
- You must be willing to keep your current diet exactly the same while taking part in the study.
Who may not be able to join:
- You have a digestive or stomach condition (such as irritable bowel syndrome, inflammatory bowel disease, chronic gastritis, or peptic ulcers) that could affect how your body absorbs the study drug.
- You have had certain types of stomach or digestive surgery in the past (such as gastric bypass, stomach removal, or a related procedure).
- You have had an allergic reaction or bad response to a substance called tetrahydrobiopterin (BH4) or sepiapterin in the past.
- You are currently taking part in another clinical trial or have taken an experimental drug within the last 30 days.
- You have any significant abnormal results on laboratory tests, as decided by the study doctor.
- You are pregnant, breastfeeding, or planning to become pregnant.
- You have a serious mental health condition (such as major depression) that is not currently being managed with treatment, and which the study doctor feels could interfere with your participation or put you at risk.
- You have a history of kidney problems or reduced kidney function (confirm with trial site), or are currently under the care of a kidney specialist.
- Your physical examination or lab tests show any signs of kidney disease or reduced kidney function.
- You are currently taking a medication known to block the body's use of folate (for example, methotrexate).
- You have been diagnosed with a specific inherited condition called a "primary BH4 deficiency" caused by certain known gene mutations (confirm with trial site).
- You have had major surgery within the 90 days before the screening visit.
- You are currently taking a BH4 supplement such as sapropterin dihydrochloride (KUVAN) or a treatment called pegvaliase-pqpz (PALYNZIQ).
- You are unwilling to stop taking KUVAN or PALYNZIQ before joining the study.
Important: Always verify eligibility with the trial site directly before applying.
Based on publicly available eligibility criteria from ClinicalTrials.gov. Verify directly with the trial site before acting. This is not medical advice.
Contact this trial
Australian sites
Contact details sourced from ClinicalTrials.gov. Verify directly with the trial site before attending.
GP referral letter
Print a one-page summary to share with your doctor.
Trial details
Where this trial is recruiting
3 site(s) in Australia. Confirm current status and contact details directly with the trial site.
Primary endpoints
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; 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
Can't join this trial?
Data last synced from ClinicalTrials.gov: 28 July 2026. Trial status can change. Always verify current status directly with the trial site before making any decision.