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Pharmacokinetic Study of Phenylbutyrate and Ursodoxicoltaurine in Adults with Renal 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 investigation includes individuals with reduced kidney function, known as renal impairment, and compares them with healthy volunteers. The medication being examined is AMX0035, an oral powder that provides two active substances: sodium phenylbutyrate, which helps the body remove excess nitrogen, and ursodoxicoltaurine, which supports cell health. Both components are taken by mouth and are intended to be studied for how they behave in people with different levels of kidney function.

The primary aim is to assess the pharmacokinetic profile of these substances and their main breakdown products, meaning how the body absorbs, distributes, processes, and eliminates them. Participants will receive one initial dose followed by several daily doses, with blood and urine samples collected to measure drug levels. Safety monitoring includes routine laboratory tests, vital‑sign checks, and an ECG to record heart activity, while any side effects are recorded throughout the study period.

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

    Baseline Screening and Assessments

    After joining the study, you will undergo a series of baseline assessments to confirm eligibility. This includes a review of your medical history, a physical examination, and collection of blood and urine samples.

    Additional safety checks such as an electrocardiogram (ECG, a test that records the heart's electrical activity) and measurement of vital signs (blood pressure, pulse, temperature) will be performed.

    These evaluations establish a reference point for comparing later results.

  2. Step 2

    Single Dose Administration

    You will receive a single dose of the study medication, AMX0035, in the form of an oral powder.

    The dose is 8 g and will be taken by mixing the powder with water as instructed by the study staff.

    Following this dose, blood and urine samples will be collected at scheduled times to measure how the drug and its metabolites appear in your body. This part of the study evaluates the pharmacokinetic (PK) characteristics, which describe how the medication is absorbed, distributed, metabolized, and eliminated.

  3. Step 3

    Multiple Dose Administration

    After the single‑dose phase, you will begin a multiple‑dose period in which you take AMX0035 repeatedly according to the study schedule.

    Each dose remains 8 g of oral powder, taken as directed (for example, once daily, if specified by the study team).

    Blood and urine samples will be collected after several doses to assess the drug’s behavior with repeated exposure.

  4. Step 4

    Ongoing Safety Monitoring

    Throughout the study, you will have regular safety checks, including repeat blood tests, ECGs, and vital‑sign measurements.

    Any side effects you experience will be recorded as treatment‑emergent adverse events (TEAEs), which are simply side effects that occur after you start the medication.

  5. Step 5

    Final Assessment and Study Completion

    At the end of the dosing period, a final set of blood and urine samples will be taken, along with a concluding ECG and vital‑sign check.

    These final measurements are compared with the baseline data to complete the evaluation of the medication’s safety and pharmacokinetic profile.

    After the final assessments, the study participation is concluded.

Who can join the trial?

13 criteria

  • Be able to understand the study information and sign a written consent form.
  • Be willing and able to follow the study visits, procedures, and both verbal and written instructions.
  • Be between 18 and 80 years old.
  • Weigh at least 50 kg and have a Body Mass Index (BMI) between 18 and 30 kg/m² (BMI is a calculation that relates weight to height).
  • Be a non‑smoker or a light smoker (no more than 5 cigarettes per day). Healthy volunteers must have never smoked or not smoked in the past 2 years.
  • Have a resting pulse (heart rate) while sitting that is between 50 and 100 beats per minute during the screening visit.
  • If you have kidney problems, your kidney function must have been stable (no more than a 20% change in eGFR) for at least 3 months before screening. eGFR is a lab estimate of how well the kidneys filter blood, calculated with the CKD‑EPI formula.
  • All participants must have negative screening tests for HIV, hepatitis B surface antigen (HBsAg), hepatitis C antibody (anti‑HCV), and syphilis (RPR/VDRL).
  • Healthy volunteers must have normal results on a physical exam, vital signs, blood chemistry, blood counts, and urine tests at screening.
  • Female participants who could become pregnant must have a negative pregnancy test at screening and again right before the first dose, and must agree to use a double‑barrier method of contraception (e.g., condom plus diaphragm). Hormonal birth control cannot be used for 30 days before the study starts or during the study. Women who are at least two years post‑menopausal or surgically sterile are not considered to have child‑bearing potential.
  • Male participants must agree to use a double‑barrier method of contraception throughout the study.
  • All participants must be willing to follow the specific dietary and lifestyle restrictions described in the study protocol.
  • Healthy volunteers should match the age, weight, and sex distribution of the kidney‑impaired groups as closely as possible.

Who cannot join the trial?

18 criteria

  • Allergy (hypersensitivity) to the study drug AMX0035, any of its ingredients, or related substances.
  • Having a serious ongoing disease such as heart disease, high blood pressure, cancer, diabetes, liver disease, hormone problems, breathing problems, gut problems, blood disorders, or severe mental illness.
  • Blood pressure that is too high or too low at screening (systolic ≥ 140 mmHg or ≤ 100 mmHg, diastolic ≥ 100 mmHg or ≤ 60 mmHg; for some kidney participants the limits are even stricter: systolic ≥ 160 mmHg or ≤ 100 mmHg, diastolic ≥ 100 mmHg or ≤ 60 mmHg).
  • Significant abnormal results on an ECG (a test that records the heart’s electrical activity).
  • Current acute stomach or intestinal symptoms (such as nausea, vomiting, or diarrhea) or a diagnosis of irritable bowel syndrome (IBS) based on specific criteria.
  • History of alcohol or drug abuse within the past 5 years.
  • Positive test for alcohol, cocaine, methadone, barbiturates, amphetamines, benzodiazepines, cannabis, opiates, or PCP (a type of illegal drug).
  • Participation in another clinical study using an experimental drug that required frequent blood draws within the last 30 days (or longer if the drug stays in the body for a long time).
  • Blood or plasma donation within the past 2 months (60 days for kidney‑impaired participants).
  • Consumption of caffeine‑containing products, Seville oranges, grapefruit, or alcohol within the specified time before dosing (caffeine/oranges/grapefruit within 48 hours; alcohol within 72 hours).
  • Any other health condition that could affect how the study drug is absorbed, distributed, broken down, or removed from the body (except the kidney condition being studied).
  • Being employed by, or a family member of, anyone who works at the research site where the study is conducted.
  • Use of any medication (including over‑the‑counter drugs) within 14 days (or longer based on the drug’s elimination half‑life) before the study, unless the medication is required for treatment of the kidney condition.
  • Requirement to continue any prescribed medication that affects the central nervous system or mood during the study.
  • Severe allergies or multiple bad reactions to medicines such as penicillin or cephalosporin.
  • Inability to give informed consent or to communicate with the study staff as needed.
  • Current breastfeeding.
  • Clinically significant infection or inflammation at the time of screening.
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Investigated drugs

AMX0035 is an oral powder that combines two active ingredients: phenylbutyrate and ursodoxicoltaurine. In this study, the medicine is given to people with reduced kidney function and to healthy volunteers so researchers can see how the body absorbs, distributes, and clears these substances after one dose and after taking the medicine for several days. The goal is to understand the behavior of both components and their breakdown products, which helps determine safe and effective use of the combination in patients with kidney problems.

What is already known about the treatment

AMX0035 - AMX0035 is taken by mouth as a powder that is mixed with water. It is an investigational drug that is currently being studied in clinical trials and is not yet approved for routine medical use. The product is being tested in people with kidney function problems and in healthy volunteers to help the body remove waste chemicals. It works by combining phenylbutyrate, which helps clear excess nitrogen, with ursodoxicoltaurine, which supports liver and cell health, and is classified as a combination metabolic‑modulating therapy.

Investigated diseases

  • Renal impairment

    A condition in which the kidneys lose their ability to filter blood efficiently. It often begins with a mild reduction in glomerular filtration rate and can progress to moderate and severe stages over time. As the disease advances, waste products and fluid may accumulate in the body. The decline in kidney function can affect the balance of electrolytes and acids. Patients may experience changes in urine output and increased need for medical monitoring.

  • Normal renal function

    Refers to kidneys that filter blood at a normal rate and maintain fluid, electrolyte, and waste balance. This state remains stable without progressive loss of filtration capacity. The body efficiently removes metabolic waste and excess substances. No accumulation of toxins occurs, and urine production follows typical patterns. Individuals maintain overall metabolic homeostasis.

Trial detailsLast updated 15 Nov 2026
Age18+ yearsPhasePhase ITrial ID2023-504393-37-00Protocol codeA35-015Estimated enrolment32 patientsSponsorAmylyx Pharmaceuticals EMEA B.V.

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