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Pharmacokinetic Study of Phenylbutyrate and Ursodoxicoltaurine (AMX0035) in Adults with Liver Impairment and Healthy Volunteers

Verified siteInvestigationalNo placebo
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What is this trial about?

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

The study involves people who have hepatic impairment and people with normal liver function. All participants will receive an oral powder called AMX0035, which contains two active substances: phenylbutyrate and ursodoxicoltaurine. The medication is taken by mouth in a dose of 8 grams each day.

The purpose of the study is to evaluate how the body processes (absorbs, distributes, breaks down, and removes) these substances and their main breakdown products after a single dose and after several days of dosing. Participants will stay in the clinic for a short period, take the medication as directed, and provide blood and urine samples at scheduled times so researchers can track the levels of the drug and its metabolites. Simple safety checks, such as blood tests, heart rhythm monitoring, and vital‑sign measurements, will also be performed.

Throughout the study, any unwanted effects will be recorded, and the overall safety of the medication will be assessed by comparing results between the group with liver impairment and the group with normal liver function.

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

    Enrollment and Baseline Assessments

    After agreeing to join the study, you sign an informed consent form and provide basic health information.

    You undergo initial safety tests, including a blood draw, an electrocardiogram (ECG) to check heart rhythm, and measurements of blood pressure and pulse.

  2. Step 2

    Single Dose Administration

    You receive one oral dose of AMX0035 powder, 8 g, which you mix with water and swallow as instructed.

    Following the dose, blood and urine samples are taken at several time points to measure how the drug and its components—phenylbutyrate and ursodoxicoltaurine—are processed by your body.

  3. Step 3

    Multiple Dose Phase

    You take the same 8 g oral dose of AMX0035 each day for the period defined by the study protocol.

    Blood and urine samples are collected each day to continue tracking drug levels and metabolism.

    You are asked to record any new symptoms or side effects that occur during this period.

  4. Step 4

    Safety Monitoring

    Throughout the study, regular safety checks are performed, including repeat blood tests, ECGs, and vital‑sign measurements.

    Any side effects, referred to as treatment‑emergent adverse events (TEAEs), are documented and evaluated by the study team.

  5. Step 5

    Study Completion and Final Evaluation

    At the end of the dosing period, a final set of blood and urine samples is taken.

    The last safety assessments are performed, and the study data are compiled before the study is closed.

Who can join the trial?

13 criteria

  • Ability to understand the study and provide written consent.
  • Willingness and ability to follow the study procedures, visit schedule, and verbal or written instructions.
  • Age between 18 and 80 years.
  • Minimum body weight of 50 kg and a Body Mass Index (BMI) of at least 18 and less than 30 kg/m² (BMI is a measure of weight relative to height).
  • Normal physical examination, vital signs, blood chemistry, blood count, and urinalysis, plus negative tests for anti‑HIV, hepatitis B surface antigen (HBsAg), hepatitis C antibody (anti‑HCV), and syphilis (RPR/VDRL). For participants with liver impairment, these labs must be normal except for changes caused by the liver disease.
  • Female participants who could become pregnant must have a negative pregnancy test at screening and again before the first dose, must use a double barrier method of contraception, and cannot use hormonal birth control for 30 days before and during the study. Women who are post‑menopausal for two years or surgically sterile are exempt.
  • Male participants must use a double barrier method of contraception throughout the study.
  • Must be a non‑smoker or light smoker (fewer than 5 cigarettes per day). Healthy volunteers must be non‑smokers (never smoked or not smoked in the past 2 years).
  • Must agree to follow the dietary and lifestyle restrictions outlined by the study.
  • Must have a sitting pulse rate between 50 and 100 beats per minute at the screening visit.
  • For participants with liver impairment: must have chronic liver disease or cirrhosis confirmed by at least one of the following—liver biopsy showing cirrhosis, CT or ultrasound showing hepatic fibrosis, physical‑exam findings, or liver‑spleen scan changes.
  • Must have stable cirrhosis and meet at least one of the following: clinical signs such as enlarged liver or spleen, mild fluid buildup in the abdomen, yellow skin (jaundice), mild leg swelling, spider‑like skin marks, etc.; or laboratory signs such as elevated liver enzymes (ALT, AST, alkaline phosphatase), high bilirubin, low albumin, low platelet count, or prolonged prothrombin time. Severity is often assessed with the Child‑Pugh criteria.
  • May have or not have a Transjugular Intrahepatic Portosystemic Shunt (TIPS) (a procedure that helps blood flow around a diseased liver).

Who cannot join the trial?

23 criteria

  • Known hypersensitivity (allergy) to the study drug AMX0035, any of its ingredients, or its inactive components (excipients).
  • Any other health condition that could change how the drug is absorbed, spread, broken down, or removed from the body, except the liver problems being studied.
  • Use of any other medicines (including over‑the‑counter drugs) within the past 14 days, unless the medicine is needed for the liver disease being studied.
  • Employment by, or being a family member of an employee at, the research site where the study is conducted.
  • Inability to give informed consent or communicate with the study staff because of a condition that affects thinking or communication.
  • Currently breast‑feeding.
  • A worsening of liver blood test results (serum bilirubin or prothrombin time) by more than 50% in the past three months.
  • Bleeding in the stomach or esophagus from varices or ulcers within the past six months.
  • Severe fluid buildup in the abdomen (ascites) or around the lungs (pleural effusion).
  • Feverish illness within five days before the first dose if there is visible fluid buildup (ascites).
  • Serious heart disease (e.g., heart attack or stroke in the last year), other major organ disease, extreme obesity, or severe malnutrition.
  • Blood pressure that is too high or too low at screening (for healthy volunteers: systolic ≥ 140 mmHg or ≤ 100 mmHg, diastolic ≥ 100 mmHg or ≤ 60 mmHg; for liver‑impaired participants: systolic ≥ 160 mmHg or ≤ 100 mmHg, diastolic ≥ 100 mmHg or ≤ 60 mmHg).
  • Significant abnormalities on an electrocardiogram (ECG), a test that records the heart’s electrical activity.
  • Active infection or inflammation at the time of screening.
  • Current stomach or intestinal symptoms such as nausea, vomiting, diarrhea, or a diagnosis of irritable bowel syndrome (IBS) defined by regular abdominal pain and changes in stool.
  • History of alcohol or drug abuse within the past five years.
  • Positive test for illegal or prescription drugs (e.g., cocaine, methadone, barbiturates, amphetamines, benzodiazepines, cannabis, opiates, PCP) or alcohol at screening.
  • Participation in another clinical trial using an experimental drug that required frequent blood draws within the past 30 days (or longer, depending on the drug’s half‑life).
  • Blood or plasma donation within the past two months (or 60 days for liver‑impaired participants).
  • Consumption of caffeine‑containing products, Seville oranges, grapefruit, or alcohol within 48–72 hours before dosing.
  • Need to continue taking any medication during the study (except those required for the liver condition).
  • Use of centrally active or psychoactive agents (drugs that affect the brain) within 28 days before starting the study.
  • History of severe allergies or multiple bad reactions to medicines, such as penicillin or cephalosporin antibiotics.
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Investigated drugs

AMX0035 is an oral powder that combines two active ingredients, phenylbutyrate and ursodoxicoltaurine. In this study, participants take the powder to help researchers understand how the body absorbs, distributes, and clears these substances when the liver is healthy or when it has reduced function. By measuring the levels of the original ingredients and their breakdown products, the trial aims to see how liver problems might change the way the medication works and is processed. This information can guide safe and effective dosing for people with liver impairment.

What is already known about the treatment

AMX0035 - AMX0035 is taken orally as a powder that is mixed with water and swallowed. It is an approved orphan drug mainly used for a rare neurodegenerative disease and is being studied for safety in people with liver problems. The product combines sodium phenylbutyrate, which helps remove toxic waste by converting it into easier‑to‑excrete compounds, with ursodoxicoltaurine, which protects cells by stabilizing the outer layer of mitochondria. It belongs to the class of metabolic modulators and bile‑acid derivatives.

Investigated diseases

Hepatic impairment - Hepatic impairment is a condition in which the liver’s ability to perform its normal functions is reduced. It can result from chronic liver disease, viral infection, alcohol use, or metabolic disorders. The condition is classified by severity—mild, moderate, and severe—reflecting the extent of loss of liver function. As impairment worsens, the liver becomes less able to process toxins, produce proteins, and regulate blood clotting. Progressive loss can lead to accumulation of waste products in the blood and further damage to liver tissue.
Trial detailsLast updated 15 Nov 2026
Age18+ yearsPhasePhase ITrial ID2023-504397-38-00Protocol codeA35-016Estimated enrolment32 patientsSponsorAmylyx Pharmaceuticals EMEA B.V.

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