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Study of Pembrolizumab for Progressive Multifocal Leukoencephalopathy in Immunocompromised Patients Without HIV

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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 disease called Progressive Multifocal Leukoencephalopathy (PML), which affects the brain and is found in patients with weakened immune systems. The study is specifically for those who are immunocompromised but do not have HIV and are not taking certain medications for chronic inflammatory diseases. The treatment being tested in this trial is a medication called Pembrolizumab, which is given as an injection into a vein. Pembrolizumab is a type of protein that helps the immune system fight diseases.

The purpose of this study is to see if Pembrolizumab can help reduce the amount of a virus called JCV in the fluid around the brain and spinal cord, known as cerebrospinal fluid (CSF). The study will monitor patients over a period of time to check if the virus levels decrease. Participants will receive regular check-ups and tests to track their progress and the effects of the treatment. These tests include measuring the virus levels in the CSF and assessing neurological health using scales like the NIH Stroke Scale and the Modified Rankin Scale, which help evaluate the impact of the disease on daily activities and overall neurological function.

Throughout the study, the health and safety of participants will be closely monitored. The trial will also look at any side effects or adverse events that may occur during the treatment. The study aims to provide valuable information on whether Pembrolizumab can be an effective treatment for PML in patients with compromised immune systems, potentially offering a new option for managing this challenging condition.

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

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria such as age, diagnosis of progressive multifocal leukoencephalopathy (PML), and presence of JC virus (JCV) in the cerebrospinal fluid (CSF).

    Informed consent is required, either from the patient or a surrogate if the patient is unable to consent.

  2. Step 2

    Treatment initiation

    The treatment involves the administration of pembrolizumab, which is given intravenously. The specific dosage and frequency are determined by the study protocol.

  3. Step 3

    Monitoring and assessments

    Regular monitoring includes lumbar punctures to measure JCV viral load in the CSF at the start of the study (D0) and at months 1, 2, and 3 (M1, M2, M3).

    Neurological status is assessed using the NIH Stroke Scale at M1, M2, M3, M6, and M12.

    The degree of disability or dependence is measured using the Modified Rankin Scale and the Glasgow Outcome Scale Extended at the same intervals.

  4. Step 4

    Evaluation of outcomes

    The primary outcome is the reduction of JCV viral load in the CSF, with at least one negative result during the M0 to M3 period.

    Secondary outcomes include the evolution of JCV viral load, any repositivation of JCV, and the occurrence of adverse events.

  5. Step 5

    Completion of study

    The study is expected to conclude by September 2027, with ongoing assessments and data collection throughout the study period.

Who can join the trial?

5 criteria

  • Must be **18 years old** or older.
  • Must have a **definite diagnosis of PML** (a specific brain infection) for less than 2 months, as per the American Academy of Neurology.
  • Must have the **JCV virus** present in the **cerebrospinal fluid (CSF)**, which is the fluid around the brain and spine, from the most recent sample.
  • Must have **signed informed consent**, either by the patient or a representative if the patient is unable to consent.
  • For women who can have children: Must have a **negative pregnancy test** and agree to use **highly effective birth control methods** for 8 months, which includes 6 months after the end of the experimental treatment.

Who cannot join the trial?

1 criterion

  • Patients who have a weakened immune system due to a condition that cannot be easily reversed. This does not include patients with **HIV** or those taking certain medications for long-term inflammatory diseases.
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Investigated drugs

Pembrolizumab is a medication used in this clinical trial to treat progressive multifocal leukoencephalopathy (PML) in patients who have weakened immune systems but do not have HIV. The main goal of using Pembrolizumab in this study is to see if it can help reduce the amount of JCV virus in the cerebrospinal fluid of these patients. Pembrolizumab works by helping the immune system fight against the virus, potentially improving the condition of patients with PML.

What is already known about the treatment

Pembrolizumab – Pembrolizumab is administered as an intravenous infusion, typically given in a clinical setting. It is currently being studied for its effectiveness in treating progressive multifocal leukoencephalopathy (PML) in immunocompromised patients who do not have HIV and are not receiving biologics for chronic inflammatory diseases. The medication works by blocking a specific protein on immune cells, which helps the immune system attack cancer cells more effectively. Pembrolizumab is classified as an immune checkpoint inhibitor and is well-documented in medical literature for its use in various cancers.

Investigated diseases

Progressive Multifocal Leukoencephalopathy (PML) – Progressive Multifocal Leukoencephalopathy is a rare and serious brain infection caused by the John Cunningham virus (JCV). It primarily affects individuals with weakened immune systems, leading to the destruction of the white matter in the brain. The disease progresses as the virus attacks the cells that produce myelin, the protective covering of nerve cells, resulting in neurological symptoms. These symptoms can include weakness, vision problems, impaired speech, and cognitive difficulties. As the disease advances, it can lead to severe disability. PML is not typically associated with patients who have HIV or those receiving biologics for chronic inflammatory diseases, as these conditions are more manageable.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-503520-31-00Protocol codeAPHP211001Estimated enrolment33 patientsSponsorAssistance Publique Hopitaux De Paris

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