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A study to evaluate the safety of MRM-3379 in men with Fragile X Syndrome

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What is this trial about?

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

This study focuses on individuals with Fragile X Syndrome, a genetic condition that can cause various developmental and cognitive challenges. The research aims to evaluate the safety and how well the body tolerates a new experimental drug called MRM-3379.

Participants in this study will be assigned to receive either MRM-3379, which is taken as a hard capsule by oral use, or a placebo. This is a double-blind study, meaning that neither the participants nor the researchers know who is receiving the active medication or the placebo during the course of the trial. The study will monitor how the body processes the drug and observe any side effects that may occur.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Study participation

    You will receive either the test medication, known as mrm-3379, or a placebo, which is an inactive substance that contains no medicine.

    The mrm-3379 is provided in the form of a hard capsule to be taken by oral use (swallowed by mouth).

  2. Step 2

    Safety and efficacy monitoring

    The study monitors how well the body tolerates the mrm-3379 and tracks any treatment-emergent adverse events, which are any unwanted medical side effects that occur during the treatment period.

    The study also tracks if any participant must stop taking the medication due to adverse events, or unfavorable medical occurrences.

  3. Step 3

    Evaluation of cognitive changes

    Changes in crystallized cognition, which refers to learned knowledge and skills, are evaluated using specific tests: the picture vocabulary test (identifying images) and the oral reading recognition test (reading words aloud).

    A clinician global impression-change scale is used to record the overall clinical improvement or change observed by the healthcare provider.

  4. Step 4

    Blood concentration analysis

    The pharmacokinetic properties are studied, which means measuring how the body processes the medicine. this involves checking the plasma concentrations, or the amount of medicine in the blood, to see how much mrm-3379 and its metabolites (the substances the body creates after breaking down the medicine) are present when the levels become stable.

Who can join the trial?

8 criteria

  • You must be a male between the ages of 13 and 45 years old.
  • You must have a diagnosis of Fragile X Syndrome, which is a genetic condition, and have a specific genetic test result showing 200 or more CGG repetitions (this refers to a repeated pattern of DNA code in your genes).
  • You must weigh at least 30 kilograms.
  • Your Body Mass Index (a measure of body weight relative to height) must be at least 18 but less than 36.
  • You or your legal representative must be willing and able to sign an informed consent form, which is a document that explains all the details and risks of the study before you agree to join.
  • If you cannot provide consent yourself, a legally authorized representative (a person allowed by law to make decisions for you) must sign for you, and you must provide assent (your personal agreement to participate).
  • You must have a regular caregiver (a person who looks after you) who is willing and able to be with you consistently.
  • You must be able to swallow tablets or capsules (medicine in pill form).

Who cannot join the trial?

1 criterion

  • You cannot participate if you have a medical condition (a health problem or illness) other than Fragile X Syndrome or issues directly related to it that could make participating in this study more dangerous for you.
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Investigated drugs

MRM-3379 is an experimental medication taken by mouth in capsule form. This study is testing how safe and well the body tolerates this drug in men with Fragile X Syndrome.

What is already known about the treatment

  • Placebo for MRM-3379

    This is an inactive substance that looks like the actual study drug but contains no medicinal ingredients. It is administered orally in capsule form to act as a control group during the clinical trial. Because it has no active component, it does not work on any biological processes or treat any specific medical conditions.

  • MRM-3379

    This experimental medication is taken by mouth in the form of a hard capsule. It is currently being studied in clinical trials to determine if it can help treat Fragile X Syndrome, a genetic condition. This substance is classified as an investigational drug that works by targeting specific molecular pathways to address the underlying issues of the disorder.

Investigated diseases

Fragile X Syndrome - This is a genetic condition caused by a change in a specific gene on the X chromosome. It primarily affects how the brain develops and functions. The condition often leads to various developmental delays and challenges with learning. Individuals may also experience differences in social behavior and communication skills. As the person grows, these developmental and behavioral characteristics typically persist throughout their life.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-523738-21-00Protocol code​​ENV-202​Estimated enrolment69 patientsSponsorMirum Pharmaceuticals Inc.

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