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Study on Brain Activity in Treatment-Resistant Depression Using [18F]MC225 for Patients with Depression

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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 treatment-resistant depression, a form of depression that does not improve after trying at least two different antidepressant treatments. The study will use a special imaging technique called positron emission tomography (PET) to look at changes in a protein called p-glycoprotein in the brain. The medication used in this study is a solution for injection known by its code name [18F]MC225. This medication acts as a radiotracer, which means it helps to highlight certain areas of the brain during the PET scan.

The purpose of the study is to understand how p-glycoprotein is involved in treatment-resistant depression by comparing its activity in people with this condition to those whose depression responds to treatment. Participants will receive an injection of [18F]MC225, and then undergo a PET scan to measure how the radiotracer is distributed in the brain. This will help researchers see if there are differences in p-glycoprotein activity between the two groups.

The study will take place over a period of time, during which participants will be asked to come in for the PET scan and possibly other assessments related to their depression. The information gathered from this study could provide valuable insights into why some people with depression do not respond to standard treatments and help in developing better treatment strategies in the future.

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, participants will be required to provide written informed consent. This is a document that confirms understanding of the study and agreement to participate.

    Participants must meet certain criteria, including being between 18 and 65 years old, having a diagnosis of major depressive disorder, and having at least five years of education.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to confirm eligibility. This includes verifying the diagnosis of treatment-resistant depression, which means having tried at least two antidepressant treatments without success.

    Participants will also need to demonstrate the ability to complete imaging procedures, which are an essential part of the study.

  3. Step 3

    Imaging procedure

    Participants will undergo a PET/CT scan, a type of imaging test that helps to visualize brain activity.

    A special substance called [18F]MC225 will be used during the scan. This is a solution for injection that helps to highlight certain areas of the brain.

  4. Step 4

    Administration of [18F]MC225

    The [18F]MC225 solution will be administered through an intravenous injection. This means it will be injected directly into a vein.

    The dosage and frequency of the injection will be determined by the study team and will be explained to participants before the procedure.

  5. Step 5

    Follow-up assessments

    After the imaging procedure, participants will have follow-up assessments to monitor any changes in brain activity.

    These assessments will help to compare brain activity between those with treatment-resistant depression and those who respond to treatment.

  6. Step 6

    Completion of the study

    The study is expected to continue until April 15, 2027. Participants will be informed about the duration of their involvement.

    Upon completion, participants may receive information about the study's findings and any potential implications for their treatment.

Who can join the trial?

6 criteria

  • Age between 18 and 65 years old
  • Diagnosis of MDD (Major Depressive Disorder) according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5)
  • At least 5 years of education
  • Ability to complete imaging procedures
  • For subjects with TRD (Treatment-Resistant Depression): Must have a current TRD, which means not responding to at least two previous antidepressant treatments that were given in the right dose and for a sufficient time. Non-response means the treatment did not lead to the disappearance of symptoms. The treatments should not include antidepressants that are known not to be affected by P-gp (a protein that affects drug transport in the brain)
  • Ability to provide written informed consent

Who cannot join the trial?

5 criteria

  • Patients who are not within the specified age range for the study.
  • Patients who are not diagnosed with depression.
  • Patients who are part of a vulnerable population, which means groups that might need special protection or care.
  • Patients who are not able to undergo a PET/CT scan, which is a type of imaging test that helps doctors see how the organs and tissues inside your body are functioning.
  • Patients who cannot safely receive the radiotracer [18F]MC225, a special substance used in the imaging test to help see certain activities in the brain.
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Investigated drugs

[18F]MC225 is a special type of medication used in this study to help doctors see how a protein called P-glycoprotein (P-gp) is working in the brain. This medication is not used to treat depression directly. Instead, it is used as a tool to take pictures of the brain using a scan called PET/CT. By looking at these pictures, doctors can understand if P-gp is working differently in people who have depression that doesn't get better with regular treatments compared to those whose depression does improve with treatment. This helps researchers learn more about why some people don't respond to depression treatments and could lead to better ways to help them in the future.

What is already known about the treatment

[18F]MC225 – This medication is administered as a radiotracer through an injection, typically used in PET/CT scans to study brain activity. Currently, it is being researched in clinical trials to understand its role in treatment-resistant depression. The main therapeutic indication is to evaluate the activity of a protein called P-glycoprotein (P-gp) in the brain, which may affect how depression treatments work. At the molecular level, [18F]MC225 helps visualize P-gp activity by binding to it, allowing researchers to see how much of the radiotracer is taken up in the brain. It is classified as a radiopharmaceutical, which means it is a radioactive compound used for diagnosis or research in medicine.

Investigated diseases

Depression – Depression is a mental health disorder characterized by persistent feelings of sadness, hopelessness, and a lack of interest or pleasure in activities. It can affect a person's thoughts, behavior, feelings, and sense of well-being. The progression of depression can vary, with some individuals experiencing a single episode, while others may have recurrent episodes over time. Symptoms can include changes in appetite, sleep disturbances, fatigue, difficulty concentrating, and feelings of worthlessness or guilt. The severity and duration of symptoms can differ among individuals, and the condition can impact daily functioning and quality of life.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-508303-20-01Protocol codeP-gp-TRDEstimated enrolment44 patientsSponsorFondazione Policlinico Universitario Agostino Gemelli IRCCS

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).