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Study on the Effects of Glycerol Phenylbutyrate in Patients with Corticobasal Syndrome

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What is this trial about?

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

This clinical trial is focused on studying a condition known as corticobasal syndrome (CBS). CBS is a rare neurological disorder that affects movement and cognitive functions. The study will explore the effects of a treatment called glycerol phenylbutyrate (GPB), which is administered as an oral liquid. The purpose of the study is to assess whether GPB can help reduce levels of a protein called neurofilament light chain (NfL) in patients with CBS. NfL is a marker that can indicate nerve cell damage.

Participants in the study will be randomly assigned to receive either GPB or a placebo, which is a substance with no active medication. The study will last for 26 weeks, during which time participants will take the treatment orally. Throughout the study, researchers will monitor the safety and tolerability of GPB, as well as any changes in NfL levels. The study is designed to be double-blind, meaning neither the participants nor the researchers will know who is receiving GPB or the placebo, to ensure unbiased results.

In addition to monitoring NfL levels, the study will also observe any changes in clinical scales that measure movement and cognitive abilities. These scales help researchers understand how the treatment might be affecting the symptoms of CBS. The study aims to provide valuable insights into the potential benefits of GPB for individuals living with corticobasal syndrome.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria such as age, medical condition, and medication history.

    Participants must be 18 years or older and diagnosed with corticobasal syndrome (CBS) or related conditions.

    Participants should not have regularly consumed glycerol phenylbutyrate in the last 6 months.

  2. Step 2

    Initial assessment

    An initial assessment is conducted to establish baseline measurements.

    This includes a physical and neurological examination, as well as basic clinical chemistry tests.

  3. Step 3

    Medication administration

    Participants receive either glycerol phenylbutyrate or a placebo in a double-blind manner, meaning neither the participant nor the researchers know which treatment is being administered.

    The medication is provided as an oral liquid, known as RAVICTI, with a concentration of 1.1 g/ml.

    The treatment period lasts for 26 weeks.

  4. Step 4

    Regular monitoring

    Throughout the 26-week period, participants undergo regular monitoring to assess the safety and tolerability of the treatment.

    This includes checking vital signs such as blood pressure, heart rate, and temperature, as well as conducting physical and neurological examinations.

  5. Step 5

    Evaluation of treatment effects

    The primary goal is to evaluate the effect of glycerol phenylbutyrate on reducing neurofilament light chain (NfL) levels in the blood.

    Secondary assessments involve changes in clinical scales related to movement disorders and quality of life.

  6. Step 6

    Completion of the study

    At the end of the 26-week period, a final assessment is conducted to compare the results between those who received glycerol phenylbutyrate and those who received the placebo.

    The study aims to determine the efficacy, safety, and tolerability of the treatment.

Who can join the trial?

7 criteria

  • Must be **18 years or older**.
  • Must have a diagnosis of **Corticobasal Syndrome (CBS)** or **Progressive Supranuclear Palsy-CBS**.
  • Must not have regularly used **glycerol phenylbutyrate** in the last 6 months.
  • Must be able to understand all information provided and give full informed consent.
  • Must be willing and able to follow the procedures of the clinical trial.
  • Women who can have children must not be breastfeeding, must be surgically sterile or using a highly effective birth control method, and must have a negative pregnancy test. If using hormonal birth control, it must be combined with a barrier method like a male condom. Acceptable birth control methods include implants, injectables, combined oral contraceptives, hormonal intrauterine devices (IUDs), sexual abstinence, or having a partner who has had a vasectomy. Unacceptable methods include periodic abstinence, withdrawal, spermicides only, and the lactational amenorrhea method. Female and male condoms should not be used together.
  • Must have a stable medication routine for at least 1 month before starting the trial and should not need to change it during the 26-week treatment period. This includes medications for Parkinsonism (like Levodopa and Dopamine-Agonists) and other central nervous system (CNS) active substances, such as antidepressants and antidementia drugs.

Who cannot join the trial?

4 criteria

  • Patients who are not diagnosed with Corticobasal Syndrome (CBS) cannot participate. CBS is a rare brain disorder that affects movement and thinking.
  • Patients who are not within the specified age range cannot participate. The age range is typically defined by the study, but it is not specified here.
  • Patients who are part of a vulnerable population may not be eligible. Vulnerable populations can include groups like children, pregnant women, or those with certain disabilities.
  • Patients who do not meet other specific health criteria set by the study may be excluded. These criteria are not detailed here.
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Investigated drugs

Glycerol Phenylbutyrate (GPB) is being studied to see if it can lower the levels of a protein called neurofilament light chain (NfL) in patients with corticobasal syndrome (CBS). The trial aims to determine if this medication is effective, safe, and well-tolerated over a period of 26 weeks.

What is already known about the treatment

Glycerol Phenylbutyrate – This medication is administered orally and is currently being studied in clinical trials for its potential effects on corticobasal syndrome (CBS). It is in the phase II stage of research, focusing on its ability to reduce neurofilament light chain (NfL) levels, which are associated with nerve cell damage. The main therapeutic indication for glycerol phenylbutyrate is to manage CBS symptoms by potentially lowering NfL levels. At the molecular level, it works by modulating metabolic pathways that may influence the production or clearance of NfL. It is classified pharmacologically as a nitrogen-binding agent, traditionally used in the management of urea cycle disorders.

Investigated diseases

Corticobasal Syndrome – Corticobasal Syndrome is a progressive neurological disorder characterized by movement difficulties, cognitive impairment, and muscle stiffness. It often begins with symptoms on one side of the body, such as tremors or muscle rigidity, and can progress to affect both sides. As the disease advances, individuals may experience problems with coordination, speech, and swallowing. Cognitive changes can include difficulties with memory, problem-solving, and language. The progression of symptoms can vary widely among individuals, making it a complex condition to manage.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-516897-31-00Protocol codePROFIL-2088-SIM-0032Estimated enrolment32 patientsSponsorKlinikum der Technischen Universitaet Muenchen (TUM Klinikum)

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