A Study of Experimental Treatment With Metformin for Fragile X Syndrome

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"Learn if Metformin may be helpful for language, behavior problems, and obesity / excessive appetite in patients with Fragile X Syndrome."
Age: 6 to 25 years old
Healthy Volunteers: No
Keywords: fragile x syndrome, metformin, genetic diseases, mental retardation
Type: Drug study, Phase 2, 3
60 Participants
This research will study the use of the medication Metformin. It will be used in patients with Fragile X syndrome (FXS). The study team wants to find out if it can help language, behavior problems, and obesity / excessive appetite.
This study requires

If you decide to take part in this study, you or your child will receive either metformin or placebo for 4 months.

You will complete assessments and questionnaires at three separate visits to the MIND Institute. These will occur at: - screening / baseline visit - checkup at 2 months - final follow-up visit at 4 months

A physician will also conduct a physical and neurological exam at every visit. You will discuss of any side effects of the study drug as well as any medical issues the subject may be having.

At every visit, a fasting blood draw will take place to ensure patient safety and to perform exploratory biomarker studies. The total amount of blood drawn at each blood draw will be about 8 teaspoons or less. Urine collection will also be attempted at every visit. This will be for biomarker studies, urinalysis, and pregnancy testing if applicable. At baseline only, a small skin biopsy will be obtained from the back of the shoulder. The team will utilize a small punch biopsy after numbing the skin with lidocaine to minimize discomfort..

For those subjects able to swallow capsules, study drug will be provided in capsule form. For those subjects unable to swallow capsules, liquid study drug may be available. A 2-month supply of the study drug will be dispensed at the baseline visit. Another 2-month supply will be dispensed at the 2-month visit at the MIND Institute.

Between visits to the MIND Institute, we will call you weekly during the first month. They will monitor side effects and medication changes and ensure proper dosing with the study medication. The Week 4 (1-month) phone call will be conducted by the study physician. We will call you once more at Week 12 (halfway between your 2-month and 4-month visits).

Randomization to metformin or placebo will be carried out by the UC Davis pharmacy. You will have an equal (50%) chance of being given each treatment, which is like flipping a coin. Neither you nor the study doctor will know or choose which treatment you are getting at any point during the study. You will receive the same treatment for the full duration of the study.

Who can participate

Inclusion criteria:

  • Molecular genetic confirmation of the full FMR1 mutation or mosaicism.
  • Males and non-pregnant, non-lactating females age 6 to 25 years, inclusive.
  • Ability of subject and/or caregiver to understand, read, write, and speak English fluently to complete study-related materials.
  • IQ ≤ 75 as measured by the Leiter-III at screening.
  • Participant is able to speak at least occasional 3-word phrases.
  • Participant and parent/caregiver are willing to participate in the protocol and able to attend the clinic regularly and reliably.
  • Stable concomitant medication dose and dosing regimen for at least 4 weeks prior to the screening/baseline visit, and the intention to maintain a stable regimen of allowed concomitant medications for the full duration of the study.
  • Stable behavioral/educational treatments for at least 4 weeks prior to the screening/baseline visit.
  • Sexually active women of childbearing potential must be using a medically acceptable method of birth control for the duration of the study and have a negative urine pregnancy test collected at the initial screening/baseline visit.
  • For participants who are not their own legal guardian, the parent/legal authorized representative is able to understand and sign an informed consent to participate in the study.

Exclusion criteria:

  • Non-cooperation or inability to follow through with the study protocol.
  • Life-threatening medical problem or other major systemic illness that compromises health or safety and/or would interfere with the study.
  • History of intolerable adverse events with metformin.
  • Current or recent metformin treatment (within the past year).
  • Body mass index (BMI) less than 2 standard deviations for age.
  • Serum creatinine > 1.4 mg/dl (female) or > 1.5 mg/dl (male) at screening.
  • History of metabolic acidosis or a condition with lactic acidosis.
  • Severe B12 deficiency.
  • Pregnancy at screening or unwillingness to use acceptable method of birth control, if applicable.
Benefits and risks of participating

We cannot promise any benefits to you or others from your taking part in this research. We cannot guarantee this medicine will help you. This study will teach us more about how to help individuals who have fragile X syndrome.


You or your child may have side effects while in this study. Everyone taking part in the study will be watched carefully for any side effects. However, the investigator may not know all the side effects or risks. Side effects may be mild or serious. Most side effects go away soon after you stop taking the study drug.

You should talk to the researcher team about any side effects you have while taking part in the study.
You will not be compensated for taking part in this study.
Study duration and period
We expect that you will be in this research study for 4 months.
Recruitment period
From Dec. 20, 2017
UC Davis MIND Institute
2825 50th Street
Sacramento, CA 95817
Research Topic
  • Fragile X Syndrome
  • Fragile X Mental Retardation Syndrome
  • Mental Retardation, X Linked
  • Genetic Diseases, X-Linked
  • Trinucleotide Repeat Expansion
  • Fra(X) Syndrome
  • Intellectual Disability
  • FXS
  • Neurobehavioral Manifestations
  • Sex Chromosome Disorders

Have any questions or want to learn more? Leave your contact details below and the research team will reach out to you.


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