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MRM-3379 for males with Fragile X Syndrome (BLOOM)

Randomized, Double-Blind, Placebo-Controlled, Phase 2 Study of MRM-3379 in Male Participants With Fragile X Syndrome

Phase 2 Interventional Mirum Pharmaceuticals, Inc. · NCT07209462

This trial will test three doses of the oral drug MRM-3379 in males with Fragile X Syndrome aged 16–45 (placebo-controlled), with a parallel open-label group for ages 13–15.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment60 (estimated)
Ages13 Years to 45 Years
SexMale
SponsorMirum Pharmaceuticals, Inc. Industry-sponsored
Locations15 sites (Phoenix, Arizona and 14 other locations)
Trial IDNCT07209462 on ClinicalTrials.gov

What this trial studies

BLOOM is a multicenter, double-blind, randomized, placebo-controlled Phase 2 trial testing three dose levels of MRM-3379 over 12 weeks to characterize safety and tolerability in male participants with molecularly confirmed Fragile X Syndrome. Males aged 16–45 are randomized to low, middle, high dose or placebo, while a separate open-label cohort enrolls males 13–15. Participants must meet weight and BMI criteria, be able to swallow tablets, complete NIH Toolbox tasks (PVT and ORRT), and have a consistent caregiver available for visits. Exploratory measures are collected to provide proof-of-concept data on whether MRM-3379 can improve FXS symptoms.

Who should consider this trial

Good fit: Ideal candidates are males aged 16–45 with genetically confirmed Fragile X (≥200 CGG repeats), weighing ≥30 kg with BMI 18–36, who can swallow tablets, complete NIH Toolbox tasks, and have a consistent caregiver; males 13–15 may be eligible for the open-label cohort.

Not a fit: Females, individuals outside the 13–45 age range, those with significant unrelated medical conditions, or those unable to swallow capsules or complete required cognitive tasks are unlikely to be eligible or benefit.

Why it matters

Potential benefit: If successful, MRM-3379 could provide an oral treatment that improves behavioral and cognitive symptoms in people with Fragile X Syndrome.

How similar studies have performed: PDE4 modulation has shown cognitive and behavioral benefits in preclinical FXS models, but clinical evidence in Fragile X patients is limited, so this approach is relatively novel in patients.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Willing and able to provide signed informed consent/assent. Where local regulations permit inclusion of participants deemed unable to provide informed consent, a legally authorized representative must provide informed consent on the participant's behalf, and the participant must provide assent if applicable.
* Male, 13-45 years of age (inclusive)
* Weight ≥30 kg and BMI between 18 and 36 kg/m2 (inclusive) at the screening visit
* Diagnosis of FXS with a molecular genetic ≥200 CGG repetitions .
* Able to perform the PVT and ORRT of the NIH-TCB
* Have a consistent caregiver(s) who is willing and able to be present regularly and reliably with the participant
* Able to swallow tablets or capsules

Exclusion Criteria:

History of or current medical condition other than FXS and related issues that would place the participant at higher risk from study participation

Where this trial is running

Phoenix, Arizona and 14 other locations

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Fragile X SyndromeFXSFMRPhosphodiesterase 4PDE4
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.