A Phase 2 Study of MZE782 Safety, Tolerability, and Efficacy in Adults with Phenylketonuria

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What is this study about?

Phenylketonuria is a rare inherited condition in which the body cannot properly break down an amino‑acid called phenylalanine, causing it to build up in the blood. High levels of this substance can affect brain function over time. The study is testing an oral tablet called MZE782, given at a dose of 480 mg once daily, to see whether it can lower blood phenylalanine levels and be safe to use in adults who have this condition.

The purpose of the study is to evaluate how the medication changes blood phenylalanine concentrations and to assess its safety and tolerability. Participants will be randomly assigned to receive either the study drug or a matching placebo tablet for several weeks, with regular clinic visits for blood tests and basic health checks to monitor any side effects. The study period includes an initial four‑week double‑blind phase followed by additional follow‑up visits up to about three months after treatment starts.

1 baseline visit and screening

you will attend an initial clinic visit after joining the study. during this visit, the study team will confirm that you have phenylketonuria and that your plasma phe level is above 600 μmol/l. blood samples will be taken to measure your baseline phe level and to assess your overall health. you will also receive information about the study procedures and what is expected of you.

2 randomization and start of study medication

based on the screening results, you will be randomly assigned to receive either mze782 or a placebo. the assignment is double‑blind, meaning that neither you nor the study staff will know which tablet you receive. you will be given a supply of tablets that contain 480 mg of the study drug (or an identical inactive tablet). the tablets are taken by mouth and are film‑coated.

3 daily medication intake (4‑week treatment period)

you will take one tablet each day for four weeks. the tablet should be swallowed with water and taken at the same time each day, unless the study staff provides a different schedule. the treatment period lasts for the first four weeks of the study.

4 clinic visits during the 4‑week treatment period

you will return to the clinic at the end of week 2, week 3, and week 4. at each visit, blood will be drawn to measure plasma phe levels and to check for any changes in safety parameters such as vital signs, laboratory tests, and a 12‑lead ecg. any symptoms or side effects you experience should be reported to the study staff at these visits.

5 follow‑up monitoring after the treatment period

after the four‑week treatment period, you will continue to be monitored without taking study medication. additional clinic visits are scheduled for week 8, week 10, and week 13. during these visits, blood samples will be collected to assess plasma phe levels over the longer term, and safety assessments will be repeated. you will also be asked about any adverse events that may have occurred since the last visit.

6 final study visit and end of participation

the last visit occurs at week 13. a final set of blood tests, safety evaluations, and a review of your overall experience in the study will be performed. after this visit, your participation in the trial is complete.

Who Can Join the Study?

Be between 18 and 75 years old when you sign the consent form.
Weigh at least 40 kg (about 88 lb).
Have a clinical diagnosis of PKU (a genetic condition that makes it hard for the body to break down the amino‑acid phenylalanine).
Have had at least one phenylalanine (Phe) test in the last 9 months (a dried blood spot test is acceptable).
For the primary groups, your average plasma Phe level from two tests taken at least 7 days apart must be higher than 600 µmol/L.
For the primary groups, you must also have at least one documented plasma Phe result over 600 µmol/L in the past 2 years.
If you are in the exploratory group, you must be on a stable dose of a BH4 agent (such as sapropterin or sepiapterin) for at least 12 weeks before screening and stay on the same dose during the study.
If you are in the exploratory group, your average plasma Phe from two tests at least 7 days apart must be higher than 360 µmol/L, and you need at least one documented level over 360 µmol/L in the past 2 years.
Be willing and able to keep a consistent total protein intake from regular foods and any prescribed medical foods, and to record your diet in a diary when asked.
If you take medication for attention‑deficit/hyperactivity disorder, depression, or other psychiatric conditions, the dose must have been stable and the condition well‑controlled for at least 3 months before screening.
If you have previously used pegvaliase, sapropterin, or sepiapterin, you must stop these medicines during screening and not use them again until after a specific study visit. Required washout periods are at least 14 days for sapropterin or sepiapterin and at least 28 days for pegvaliase.
If you have previously taken LNAAs (large neutral amino acids), you must stop them during screening and wait at least 2 days before the first Phe test.
Female participants who could become pregnant must have a negative pregnancy test at the screening visit and another negative test on Day 1 before receiving the study drug.
All participants must have negative test results for hepatitis B core antibody, hepatitis B surface antigen, hepatitis C antibody, and HIV antibody at screening (those with certain positive results may be allowed if further testing shows no active infection).
Male participants must agree to avoid donating sperm and to use contraception (a condom with a partner who is also using a highly effective method) or to remain abstinent for the study period and for 90 days after the last dose.
Female participants must not be pregnant or breastfeeding and must either use an accepted highly effective contraceptive method, be non‑childbearing, or practice abstinence; they must also agree not to donate eggs for 90 days after the last dose.
Be willing and able to follow all study procedures and to give signed informed consent.

Who Cannot Join the Study?

Has any health problem that the doctor believes could interfere with the study results, make the medication unsafe, or make it hard for you to follow the study schedule.
Has a disorder of how the body uses the vitamin BH4 (a rare metabolic condition).
Is currently breastfeeding or plans to breastfeed while in the study.
Plans to become pregnant (for women) or to help a woman become pregnant (for men) during the study or within 90 days after the last dose.
Had cancer in the past two years, except for certain skin cancers, early‑stage cervical cancer, or early‑stage prostate cancer that were successfully treated.
Has a history of vasculitis or other autoimmune/inflammatory diseases that affect blood vessels.
Shows a high level of C‑reactive protein (CRP) or fibrinogen (both are blood markers of inflammation) that suggests an active inflammatory condition, unless the doctor confirms the rise is temporary and it returns to normal after retesting.
Has an abnormal heart test (ECG) showing a corrected QT interval (QTcF) longer than 450 milliseconds or a known history of a prolonged QT interval (which can affect heart rhythm).
Has a low kidney function result: an estimated glomerular filtration rate based on cystatin C (eGFRcys) less than 45 mL/min/1.73 m² (a measure of how well the kidneys filter blood).
Has a total bilirubin level (a substance that indicates liver function) at or above 1.5 times the normal upper limit, unless the increase is due to Gilbert syndrome (a mild, harmless liver condition) and other liver tests are normal.
Has liver enzymes called aspartate transaminase (AST) or alanine transaminase (ALT) at or above twice the normal upper limit, unless the doctor thinks the rise is temporary (for example, after intense exercise) and can retest.
Has had an organ transplant (such as a kidney, liver, or heart) or a bone‑marrow transplant.
Is currently abusing alcohol or other substances, as judged by the doctor.
Has taken any other experimental (investigational) drug within the past 30 days or within five half‑lives of that drug (the time it takes for half of the drug to leave the body), whichever period is longer.
Is allergic (has hypersensitivity) to MZE782 or any of its ingredients.
Cannot swallow pills or tolerate oral medication.
Has donated more than 50 mL of blood or plasma in the past 30 days, or more than 500 mL in the past 60 days.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country
Centre Hospitalier Regional Universitaire De Tours	Tours	France
University Medical Center Hamburg-Eppendorf	Hamburg	Germany
Universitair Medisch Centrum Groningen	Groningen	The Netherlands
Hopital Beaujon	Clichy	France

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
France	Not yet recruiting	01.10.2026
Germany	Not yet recruiting	01.10.2026
The Netherlands	Not yet recruiting	01.10.2026

Trial locations

MZE782 is an experimental oral tablet being studied as a possible treatment for adults with phenylketonuria (PKU). In the trial, participants take the tablet by mouth. The drug is designed to help lower the amount of phenylalanine, a protein building block that builds up to harmful levels in people with PKU. By reducing phenylalanine in the blood, the medication aims to improve safety and overall health for those with the condition. The study is checking how well the tablet works, how safe it is, and whether people can tolerate it without serious side effects.

Phenylketonuria – Phenylketonuria is a genetic condition where the body cannot break down the amino acid phenylalanine. It is present from birth and continues throughout life. As phenylalanine accumulates in the blood, it can affect brain function. Over time, high levels may cause reduced mental development and learning difficulties. The condition requires ongoing monitoring of blood phenylalanine levels.

Trial ID:

2026-525622-37-01

Protocol code:

MZE782-201

Trial Phase:

Therapeutic exploratory (Phase II)

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A Phase 2 Study of MZE782 Safety, Tolerability, and Efficacy in Adults with Phenylketonuria

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?