Abstract
BackgroundFragile X syndrome (FXS) is a disorder characterized by a variety of disabilities, including cognitive deficits, attention-deficit/hyperactivity disorder, autism, and other socio-emotional problems. It is hypothesized that the absence of the fragile X mental retardation protein (FMRP) leads to higher levels of matrix metallo-proteinase-9 activity (MMP-9) in the brain. Minocycline inhibits MMP-9 activity, and alleviates behavioural and synapse abnormalities in fmr1 knockout mice, an established model for FXS. This open-label add-on pilot trial was conducted to evaluate safety and efficacy of minocycline in treating behavioural abnormalities that occur in humans with FXS.MethodsTwenty individuals with FXS, ages 13-32, were randomly assigned to receive 100 mg or 200 mg of minocycline daily. Behavioural evaluations were made prior to treatment (baseline) and again 8 weeks after daily minocycline treatment. The primary outcome measure was the Aberrant Behaviour Checklist-Community Edition (ABC-C) Irritability Subscale, and the secondary outcome measures were the other ABC-C subscales, clinical global improvement scale (CGI), and the visual analog scale for behaviour (VAS). Side effects were assessed using an adverse events checklist, a complete blood count (CBC), hepatic and renal function tests, and antinuclear antibody screen (ANA), done at baseline and at 8 weeks.ResultsThe ABC-C Irritability Subscale scores showed significant improvement (p < 0.001), as did the VAS (p = 0.003) and the CGI (p < 0.001). The only significant treatment-related side effects were minor diarrhea (n = 3) and seroconversion to a positive ANA (n = 2).ConclusionsResults from this study demonstrate that minocycline provides significant functional benefits to FXS patients and that it is well-tolerated. These findings are consistent with the fmr1 knockout mouse model results, suggesting that minocycline modifies underlying neural defects that account for behavioural abnormalities. A placebo-controlled trial of minocycline in FXS is warranted.Trial registrationClinicalTrials.gov Open-Label Trial NCT00858689.
Highlights
Fragile X syndrome (FXS) is a disorder characterized by a variety of disabilities, including cognitive deficits, attention-deficit/hyperactivity disorder, autism, and other socio-emotional problems
Functional MRI studies have shown that lymphocyte levels of fragile X mental retardation protein (FMRP) correlate with brain metabolism during tasks involving math calculations, working memory and response inhibition [15,16,17]
Minocycline treated fmr1 KO mice performed significantly better in the elevated plusmaze, a cognitive performance test that measures activity and anxiety
Summary
Fragile X syndrome (FXS) is a disorder characterized by a variety of disabilities, including cognitive deficits, attention-deficit/hyperactivity disorder, autism, and other socio-emotional problems. Minocycline inhibits MMP-9 activity, and alleviates behavioural and synapse abnormalities in fmr knockout mice, an established model for FXS. Fragile X Syndrome (FXS) is the most common known inherited form of intellectual disability and autism, with an estimated prevalence of about 1/4000 males and females [1]. It is associated with a range of learning disabilities, neurological problems such as seizures [2], and behavioural difficulties. Measures of cognition, including IQ, correlate with lymphocyte levels of FMRP in blood in both males and females affected by FXS [12,13,14]. Functional MRI (fMRI) studies have shown that lymphocyte levels of FMRP correlate with brain metabolism during tasks involving math calculations, working memory and response inhibition [15,16,17]
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