RESEARCH ARTICLEOpen Access
Open-label add-on treatment trial of minocycline
in fragile X syndrome
Carlo Paribello1*, Leeping Tao1, Anthony Folino1, Elizabeth Berry-Kravis2, Michael Tranfaglia3, Iryna M Ethell4,
Douglas W Ethell4,5
Background: 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. 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.
Methods: Twenty 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.
Results: The 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).
Conclusions: Results 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 registration: ClinicalTrials.gov Open-Label Trial NCT00858689.
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 . It is also associated with a range of learning
disabilities, neurological problems such as seizures ,
and behavioural difficulties. For many individuals with
FXS, their behavioural difficulties result in severe pro-
blems within the family and community, particularly in
the form of agitation, temper outbursts, hyperactivity,
and aggression [3,4].
In 1991 the gene responsible for FXS was identified
and named Fragile X Mental Retardation-1 (FMR1) 
FMR1 is located toward the end of the long arm of the
X chromosome at Xq27.3. Most FXS cases are the result
of an unstable trinucleotide repeat (CGG) expansion in
the 5’-untranslated region of FMR1. When of sufficient
size, these expansions cause promoter methylation and
gene silencing, resulting in the absence of, or reduced
levels of FMR1 mRNA and FMRP (the protein product
of FMR1). FMRP is an RNA binding protein that
* Correspondence: email@example.com
1Surrey Place Centre, Toronto, Ontario, Canada
Full list of author information is available at the end of the article
Paribello et al. BMC Neurology 2010, 10:91
© 2010 Paribello et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
associates with actively translating ribosomes in dendrites
[6,7]. That discovery led to the hypothesis that FMRP
regulates synapse-relevant protein synthesis, which may
affect synapses in an activity-dependent manner [8,9].
FMRP deficiency would therefore alter synaptic plasticity
and account for the cognitive and behavioural impair-
ments associated with FXS [10,11]. Measures of cogni-
tion, including IQ, correlate with lymphocyte levels of
FMRP in blood in both males and females affected by
FXS [12-14]. Functional MRI (fMRI) studies have shown
that lymphocyte levels of FMRP also correlate with brain
metabolism during tasks involving math calculations,
working memory and response inhibition [15-17].
It has been hypothesized that the absence of FMRP
disrupts regulation of group 1 metabotropic glutamate
receptor (mGluR and mGluR5)-dependent translation in
dendrites . The defects in dendritic spine maturation
that have been found in the brains of patients with Fra-
gile X suggest that these structures may represent an
anatomical and physiological basis for the cognitive defi-
cits associated with this disorder [18,19].
The treatment of patients with Fragile X syndrome
often requires a variety of psychopharmacological and
behavioural approaches [20-22]. Although a variety of
medications can be helpful in FXS, only lithium has
been studied as a potential targeted intervention based
on molecular abnormalities seen in the FX drosophila
and mouse models . Lithium was found to reduce
mGluR-activated translation and reversed phenotypes in
the dfxr mutant fly and fmr1 knockout mouse.
Investigation into the developmental effects of matrix
metalloproteinases (MMPs) on hippocampal neurons
has shown that MMPs can influence dendritic spine
development and hence synaptic stability . Recent
findings have suggested that the MMP-inhibiting activity
of minocycline may provide specific benefits in the
treatment of FXS. Minocycline has been found to inhibit
the activity of matrix metallo-proteinase-9 (MMP-9),
which is elevated in the hippocampus of fmr1 KO mice
and may be partially responsible for the immature den-
dritic spine profile of hippocampal neurons . Mino-
cycline treatment of fmr1 KO mice rescued the spine
phenotype in fmr1 KO hippocampal neurons, both in
vitro and in vivo. Minocycline treated fmr1 KO mice
also performed significantly better in the elevated plus-
maze, a cognitive performance test that measures activ-
ity and anxiety.
These new findings in the mouse model of FXS and
our new understanding of the neurobiology of FXS have
suggested that the benefits of minocycline treatment
should be evaluated across a broad range of cognitive
and behavioural measures in adolescents and adults
with FXS. This pilot study was initiated to test the con-
cept that minocycline is a specific molecular targeted
treatment for FXS that will display beneficial effects on
disruptive behaviour and possibly other associated
features of FXS via a reduction in MMP-9 activity.
Research Design and Methods
The overall design for this study was an open-label, add-
on pilot trial of minocycline in participants with FXS,
including adolescents and young adults. Twenty subjects
with FXS were enrolled and after baseline testing, they
were started on an 8-week treatment course of minocy-
cline added on to any other medications being adminis-
tered at the time of enrollment. Trial length for this
acute treatment period was chosen for several reasons.
Firstly, the time course of FXS response to minocycline is
not certain and some studies which measured aggression
while using a treatment duration of less than 8 weeks,
were unable to detect drug-placebo differences that did
become apparent in trials of longer duration. Further-
more, shorter trial durations tend to be more vulnerable
to positive expectation bias, as seen for example in the
clinical trial using amantadine to treat autism .
It was anticipated that minocycline may be beneficial for
affected individuals of all ages and this trial included
both males and females affected with FXS between 13
and 35 years of age. Adolescents and young adults were
included because this is an age group that often presents
with impairing problems, with aggression, agitation, and
mood instability. The use of minocycline during tooth
development (last half of pregnancy, infancy and child-
hood under the age of 13 years) may cause permanent
tooth discolouration (yellow-grey-brown), so this trial
did not include patients under the age of 13.
Subjects were recruited from the FXS Clinic at Surrey
Place Centre or were self-referred after learning about
the study from the Fragile X Research Foundation of
Canada website or Newsletter. Individuals enrolled must
have met at least a Clinical Global Impressions-Severity
Scale (CGI-S) rating of moderate impairment (score of 4
or higher) so that the risk of exposing them to a medi-
cation was justified by a moderate level of behaviour dif-
ficulty. No changes in psychoactive medications were
allowed during the 8-week treatment period. Each sub-
ject was required to be in good physical health as deter-
mined by the screening procedures described below.
Inclusion criteria included (1) diagnosis of FXS by
clinical evaluation and confirmed by FMR1-DNA testing
with presence of full mutation or mosaicism for the full
mutation. Prior DNA test reports were accepted, when
available (2) age between 13 to 35 years inclusive at the
time of informed consent, (3) male or female, (4) CGI-
Severity Score of at least 4, indicative of moderate or
Paribello et al. BMC Neurology 2010, 10:91
Page 2 of 9
greater severity of behavioural problems, (5) a score of 9
or more on the Aberrant Behaviour Checklist - Irritabil-
ity Scale (top 50th %-tile), (6) availability of parent and/
or caregiver for all clinic visits and assessments, (7)
English language fluency and reading level of 6th grade
or greater in one caregiver (8) stable doses of psychoac-
tive medications for at least 8 weeks prior to entry into
the study, and (9) for those subjects with a seizure dis-
order, a stable regimen of anticonvulsants for at least
four months prior to entry into the study.
Subjects were excluded from participation if they had
(1) a known allergy to minocycline or tetracycline, (2)
kidney disease or elevated renal function tests, (3) liver
disease or elevated liver function tests, (4) neutropenia,
anemia, or thrombocytopenia, (5) history of systemic
lupus erythematosus or screening anti-nuclear antibody
(ANA) titre of > 1:40, as minocycline may cause a lupus-
like reaction, (6) individuals who did not have a parent or
caregiver who was willing to participate in the clinic vis-
its, (7) individuals who were pregnant or at risk of
becoming pregnant, specifically sexually active females
were excluded. (8) Presence of persistent psychotic symp-
toms (9) subjects with symptom severity judged to likely
endanger personal safety or the safety of others or which
would preclude co-operation for necessary tests.
Informed written consent was obtained from either the
subject or the parent prior to participation. Assent from
the subject was obtained in every case in which the sub-
ject was not his own legal guardian and had sufficient
cognitive ability to agree to participate. The study was
approved by the Research Ethics Board at Surrey Place
All subjects had a baseline medical evaluation, which
included detailed history, medication review, review of
FXS test results, a physical exam and screening blood
tests, including a CBC, BUN, creatinine, ALT, AST,
ANA to assess medical health. Female patients also had
a serum Beta HCG level done. The Aberrant Behaviour
Checklist (ABC-C) was completed by the caregiver,
along with the visual analog scale for behaviour (VAS).
The Clinical Global Impression - Severity (CGI-S) scale
for severity of behavioural dysfunction was completed
by the PI (CP).
All subjects were given minocycline capsules to be taken
orally on a BID basis to minimize gastric upset. In order
to determine the optimum effective dose, all subjects
were randomly assigned to either a low-dose group or a
high-dose group. Subjects in the low-dose group
received 50 mg of minocycline BID. Subjects in the
high-dose group were started on 50 mg of minocycline
BID but had their dose increased to 100 mg BID at the
2 week follow-up visit. These are standard doses used in
general practice and were used in this trial because
there is already a well established safety and side-effect
profile at these doses. Any subjects who were unable to
tolerate the higher dose would have been allowed to
continue at the lower dose. However, none of the parti-
cipants in this study required a dosage adjustment
during the 8 week treatment period.
Safety, Compliance and Adverse Event Monitoring
Initial blood tests for safety monitoring included a com-
plete blood count (CBC), blood urea nitrogen (BUN),
creatinine, ALT, aspartate aminotransferase (AST),
ANA, and pregnancy testing for women of childbearing
potential. The CBC, ALT, AST, BUN, creatinine and
ANA levels were measured again in 8 weeks. Outcome
measures were conducted at baseline and at 8 weeks.
A clinical visit occurred at enrolment, baseline, 2 weeks,
4 weeks, and 8 weeks. Compliance was checked at each
clinic visit with a direct query for any missed doses.
A medication dose tracking sheet was given to the par-
ent or caregiver to document the date and time of every
dose given. At each clinic visit a capsule count was done
on each medication bottle. At each visit, subjects and
families with less than an average of 90% compliance up
to that date were counselled about the importance of
taking the minocycline as dosed. Anyone with 80% or
less compliance required discussion with the PI about
continued study participation.
Assessment of Adverse Events
Caretakers were questioned regarding health problems,
intercurrent illnesses and concomitant medications at
each clinic visit. Any adverse event was documented
regarding time it occurred, duration, severity and whether
it was considered related to the minocycline or not.
At each visit the caregiver was asked to fill out a side
effects questionnaire that consisted of 34 items includ-
ing sedation, energy level, chest pain, nausea, vomiting,
bowel and bladder problems, fever, rash, joint pains and
swelling, infections and changes in teeth or skin colour,
headaches or visual disturbances. These items cover all
of the known side effects of minocycline.
Primary Outcome Measure
Aberrant Behaviour Checklist-Community (ABC-C)
Our main outcome measure was the ABC Irritability
subtest score because previous experience with patients
in this population suggested that it would be the most
sensitive to the benefits of minocycline. The ABC Irrit-
ability subscale was used as the primary outcome mea-
sure and was expected to support the theory that
minocycline is a specific molecular targeted treatment for
Paribello et al. BMC Neurology 2010, 10:91
Page 3 of 9
FXS that will display beneficial effects on disruptive beha-
viour and possibly other associated features of FXS. This
theory would be supported by an improvement in the
irritability score after 8 weeks of minocycline treatment.
The ABC is a global behaviour checklist implemented for
the measurement of drug and other treatment effects in
cognitively impaired individuals. It is made up of five
empirically derived dimensions including irritability,
lethargy/withdrawal, inappropriate speech, hyperactivity,
and stereotypic behaviour based on 58 items that
describe various behavioural problems. The ABC was
validated on 509 (moderate to profound) cognitively
impaired residents (M = 26 years old, SD = 14.5, ages
6 and up). Spearman correlation coefficients for subscales
were very high, from .96 to .99, and test-retest reliability
is good . The 15-item Irritability Scale includes ques-
tions about aggression, self-injury, tantrums, agitation,
and unstable mood on a scale of 0 to 45 with higher
scores indicating greater severity. This scale has been
successfully used in previous medication studies in chil-
dren with autism  and in patients with FXS and in a
controlled trial of ampakine CX516 in FXS . All ABC
subscales showed good reliability when used by parents
and caregivers of individuals with FXS to assess beha-
viour in the CX516 study, and yielded intraclass correla-
tion coefficient (ICC) values of 0.7-0.9.
Secondary Outcome Measures
Subscales of the ABC-C
Secondary outcome measures were the other subscales of
the ABC-C including the Lethargy (score range 0 - 48),
Hyperactivity (score range 0 - 48), Stereotypy (score range
0 -21), and Inappropriate Speech (score range 0 -12)
Visual Analog Scale (VAS)
This methodology involves a parent-defined target beha-
viour and has been utilized and validated in the RUPP
clinical trials particularly for the risperidone studies in
autism [28,30]. The parent or caretaker chooses a beha-
viour target symptom, such as tantrums or aggression.
This allows the problems that are of concern to parents
and the family to be targeted in the trial. The use of this
methodology was originally described by Arnold et al
 and subsequently utilized in studies of ADHD
symptoms [32,33]. In this study the family chose a target
symptom at baseline and then continued with that
symptom throughout the eight weeks of the study. The
caregiver described the symptom including frequency,
duration, time spent on it and intensity, interference in
daily function or family life and other consequences.
These responses were documented in a written format.
We asked the caregiver to mark on a visual analogue
scale (VAS), a 10 centimetre line, where the symptom
lies from worst ever to no problem at all.
In the RUPP 8 week controlled trial of risperidone in
autism the Parent Defined Target Symptom Scale was a
valid measure of outcome and correlated (Pearson r)
with the Irritability subscale of the ABC at 0.64 and
with the CGI-I at 0.75 . The Parent Target Symptom
score demonstrated a significant difference between ris-
peridone and placebo at weeks 4 and 8 . The VAS
with the Parent Target Symptom score was used for
participants with FXS in the CX516 study. The visual
analogue scale showed good reliability when used by
parents and caregivers of individuals with FXS to assess
behaviour in the CX516 study with an ICC value of 0.8.
Clinical Global Impressions Scale-Severity (CGI-S) and
This scale is commonly used in drug studies because it
allows the clinician to utilize the history from the par-
ents or caretaker and incorporate it into a clinical rating
first for severity and then for the clinical follow up of
the patient. In the initial evaluation of each participant,
we used the CGI-S to judge the severity of the symp-
toms requiring a rating of moderate or higher for inclu-
sion in the study. In the follow up clinical visits we used
the CGI-I. This 7- point scale is a well validated mea-
sure of clinical global impression of improvement that
the clinician fills out after considering all the available
new information on the participant including the parent
history, the examination in clinic, reports from the
school and other sources .
Data were analyzed for change at 8 weeks treatment
from baseline for all safety and outcome measures.
A series of paired samples t-test were conducted on all
outcome measures and mean group change and stan-
dard deviations were determined for all measures for
which sufficient data existed from both assessments.
Analysis involving the ABC-C assessed pre-post differ-
ences across the 5 separate subscales and the Total
Behaviour Problems. To address the issue of multiple
comparisons, Bonferroni correction procedures were
used for all analyses involving the ABC-C scores .
More specifically, since analysis involving the ABC-C
included 5 separate comparisons, a more conservative
level of significance was calculated by dividing the origi-
nal significance value (.05) by the number of simulta-
neous tests conducted (5), to yield a new significance
value of .01. Distributions were within the normal range,
as indicated by skewness and kurtosis across variables.
Due to the exploratory nature of the investigation,
participants were randomly assigned to a low dose or
high dose group to assess if there could be a dose
response effect. These results were assessed using a ser-
ies of repeated measures analysis of variance (ANOVA).
For this analysis the independent variables were dose
Paribello et al. BMC Neurology 2010, 10:91
Page 4 of 9
(high dose vs. low dose) and time (baseline vs.8 week
follow-up). Consistent with previous analysis, the depen-
dent variables included all subscales of the ABC-C, CGI,
and VAS. Also, 10 participants were enrolled in the
study while currently taking other types of medication.
In order to assess potential drug interaction effects, a
series of repeated measures ANOVA were conducted.
For this analysis, the independent variables were medi-
cation group (Minocycline only group vs. Minocycline
plus additional medication(s) group) and time (baseline
vs. 8 week follow-up). Consistent with previous analysis
the ABC-C, CGI, and VAS served as the dependent
Twenty subjects were enrolled into the study and started
on minocycline. One subject dropped out of the study
after four weeks of treatment due to side effects. Nine-
teen subjects completed the minocycline treatment pro-
tocol for the full 8 week treatment period. Demographic
characteristics of the study population are shown in
Safety and Adverse Events
There were no clinically significant changes in blood
chemistries including liver functions, creatinine, BUN,
or blood counts during the eight week treatment period.
However, two participants developed an asymptomatic
seroconversion of their ANA, both exhibiting a 1/80
titre with a nucleolar pattern.
There was no significant change in heart rate, blood
pressure or weight for any study subject. Adverse events
observed during the treatment period are shown in
Table 2. There were no serious adverse events. Dizziness
was reported by 4 subjects, diarrhea by 3 subjects, slee-
piness and headache each reported by 2 subjects. The
adverse events reported were transient, mild or moder-
ate in intensity, and only one subject withdrew from the
trial after four weeks of treatment because of flu-like
symptoms that we could not definitely attribute to the
use of minocycline. Of the two individuals who had
seizures while on minocycline, one had no change in
seizure frequency or severity from the period prior to
starting minocycline and was therefore considered unre-
lated to minocycline treatment. The second had three
minor petit mal seizures over a three day period, com-
pared to four seizures over the one year period prior to
starting the minocycline. It was concluded that the
minocycline was an unlikely cause of these seizures.
There was significant improvement in behaviour across
the cohort as measured by 4 out of the 5 subscale scores
of the ABC-C during the period of minocycline treat-
ment (Table 3). These included the irritability subscore
(primary outcome measure) as well as the stereotypy,
hyperactivity and inappropriate speech subscales. The
lethargy subscore was the only area that did not show a
significant change. The CGI also showed statistically sig-
nificant improvement with only one subject remaining
unchanged, and no subjects getting worse. Mean
improvement in the CGI rating of 1.61 corresponded to
a mild-to-moderate overall improvement. Likewise, the
VAS showed significant improvement in 12 of the 19
subjects in parent-defined behaviours, while 6 remained
unchanged and 1 became worse. The parent-defined
behaviours included attention deficit, perseveration,
anxiety, self-injurious behaviour, abnormal vocalizations,
mood swings, social avoidance and repetitive behaviour.
No significant differences were found on any of the out-
come measures between the high dose and low dose
groups, and this raises the possibility of a placebo effect.
Furthermore, participants taking additional medications
did not differ on any of the outcome measures com-
pared to those taking only minocycline.
At the end of 8 weeks of treatment, subjects were
offered ongoing treatment with follow up through an
extension study for 1 year. At 8 weeks, eighteen families
independently reported an improvement in some level
of functioning and elected to continue the one year
extension. One participant did not continue beyond 4
Table 1 Demographic Data for Subject Cohort in Open-
Label Treatment Study of Minocycline in FXS
Mean +/- SD (range)18 +/- 5
Range13 to 32
Home with family20
Number of concomitant psychoactive
Two or more6
Type of concomitant psychoactive
Paribello et al. BMC Neurology 2010, 10:91
Page 5 of 9
weeks of treatment because of the limiting gastrointest-
inal side effects, and the other chose to leave the trial
after 8 weeks because the parents did not feel there had
been any significant benefit to treatment with the mino-
cycline and did not want to continue with the follow up
The results of this pilot open-label trial suggest that
minocycline has positive effects on behavioural symptoms
in individuals with FXS. Significance was reached for the
primary endpoint, change in the ABC-C Irritability Sub-
scale, as well as five out of six secondary outcome mea-
sures. If, as hypothesized for this study, minocycline
targets an underlying molecular defect in FXS, then it
would be expected to improve multiple areas of dysfunc-
tion and this is suggested by our data. Lethargy was the
only area that did not show any statistically significant
Positive responses were distributed across the age
range of the study cohort, suggesting that both adoles-
cents and adults with FXS can benefit from minocyline
treatment. Beneficial effects of minocycline in this small
cohort did not seem to relate strongly to dose, although
it is possible that such relationships would emerge in a
larger treatment cohort. Also, since this trial of minocy-
cline was adjunctive or add-on therapy, half of the sub-
jects were on other medications to manage their
Table 2 Adverse Events During Minocycline Treatment Period
Relationship to Minocycline Treatment
1Time period in weeks such that 0-4 represents the first 4 weeks of treatment and 4+ represents the time between 4 weeks and 8 weeks.
2Total events is the total number of events that occurred during the treatment period.
3Total subjects is the total number of subjects experiencing the event (some subjects had an event more than once).
Table 3 Baseline Scores and Group Change in Behaviour after Treatment with Minocycline for 8 weeks
Baseline Group8 Week Group Group Meanp1
MeasureMean +/- SDMean +/- SDChange+/- SD
19.327.6734.40 18.4815.5820.25 .003
Stereotypy7.95 5.34 3.793.07-4.163.34<.001
Hyperactivity17.42 10.4311.117.06-6.32 7.67.002
Inappropriate speech7.424.00 4.792.68-2.633.13.002
Total70.2626.03 38.9017.78 -31.37 23.21<.001
1 Significance with Bonferroni correction applied.
2 Negative values indicate a positive change.
Paribello et al. BMC Neurology 2010, 10:91
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behavioural dysfunction and even though doses were
not changed, it is possible that interactions between
minocycline and these medications could have contribu-
ted to the minocycline response. Although there
appeared to be statistically significant pre-post treatment
differences on measures of irritability and lethargy as a
function of medication, these differences were not sig-
nificant when the Bonferroni correction methods were
applied and a more conservative significance value (i.e.,
p = 0.01) was applied. Furthermore, the size of the
cohort was too small to draw any conclusions regarding
the interaction with different classes of psychoactive
medications that the participants were taking.
All subjects were in a consistent educational or work
program throughout the 8 weeks in the trial. Although
environmental factors could have contributed to the
minocycline response, and minor environmental changes
would be difficult to control, there were no substantial
changes in programming, family environment or living
setting during the treatment period for any subject.
Dizziness and diarrhea were the most commonly
reported side effects during this trial. Symptoms of slee-
piness, headache, fatigue, nausea and pruritus were
other complaints occurring infrequently during treat-
ment in this cohort that may represent side effects of
minocycline in FXS. Of particular note however, were
the asymptomatic seroconversions to a positive ANA in
2 trial subjects. Neither of these subjects had any rheu-
matologic or constitutional symptoms but they were not
allowed to continue the trial beyond 8 weeks. At least
15 cases of minocycline-induced lupus-like symptoms
have been reported in the literature . A retrospective
cohort study of patients with development of rheumato-
logic symptoms while receiving minocycline showed
that a substantial proportion of children with minocy-
cline-induced autoimmunity can develop chronic symp-
toms with the potential for significant morbidity .
Physicians who prescribe minocycline should be aware
of its propensity for inducing potentially serious autoim-
mune phenomena. Other potential risks, such as the
prolonged use of an antibiotic, will have to be weighed
against the possible benefits of using minocycline to
treat patients with FXS. However, minocycline is already
indicated for long-term use to treat acne. Adolescents
with acne are frequently treated with minocycline for
periods of months or years, and this drug has proven to
be very well tolerated [38,39].
There are a number of limitations to this study, speci-
fically the small size of the cohort treated and the open-
label design, which allows for potential placebo effect
and rater bias. Use of a second rater and inter-rater
reliability comparisons would have helped improve the
validity of these measures. Furthermore, the usage of
the ABC and CGI assessments are also limited in this
disorder, partly because of the difficulty defining the
underlying basis to the externalizing behaviours and
partly because assessment of these individuals is difficult
in itself because of the dynamic behavioural issues.
However, there have been relatively few clinical drug
trials in patients with fragile X, and these tools appear
to be the best available outcome measures at this time.
The concept motivating this study was to extend to a
human population the findings that minocycline can
normalize the phenotype seen in the mouse model for
FXS. In that regard the trial was aimed at targeting an
underlying molecular defect in FXS as a mode of treat-
ing the behavioural phenotype in humans. Theoretically,
minocycline should act by inhibiting excessive MMP
activity, which is known to be involved in normal synap-
tic structure and function , and is excessively trans-
lated due to the lack of normal translational repression
by FMRP. Furthermore, minocycline is not thought to
possess any significant intrinsic anxiolytic or psychotro-
pic properties, though two recent studies in schizophre-
nic subjects suggest that it may augment the effect of
antipsychotics [41,42]. Yet minocycline treatment
resulted in significant improvements across a broad
range of behaviours seen in FXS, with only one trial par-
ticipant receiving concomitant antipsychotic medication.
While these results could be due to a placebo effect, the
findings suggest that minocycline may be targeting an
underlying molecular defect in this disorder and the
results of this trial are consistent with the positive
effects of minocycline in the mouse model of FXS.
The results of this study are consistent with the concept
that modulation of excessive MMP production would be
helpful in FXS, and suggest that a placebo-controlled
trial of minocycline in FXS should be done as a next
step to confirm effectiveness, before generally recom-
mending minocycline treatment to individuals with FXS.
While adverse events would not be expected to be a
limiting problem in such a controlled trial, screening of
ANA titres with follow-up during the treatment period
would be recommended to avoid potential cases of min-
ocycline induced autoimmunity. This pilot study serves
as an example to demonstrate the translation of infor-
mation from basic science and animal model research to
the clinical treatment of a neurodevelopmental disorder.
This study was supported by a grant from the FRAXA Research Foundation
and the Fragile X Research Foundation of Canada. We would also like to
thank Barry Isaacs, Ph. D., Director, Research and Evaluation at Surrey Place
Centre for his guidance and assistance.
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1Surrey Place Centre, Toronto, Ontario, Canada.2Departments of Pediatrics,
Neurological Sciences, Biochemistry, Rush University Medical Center,
Chicago, IL, USA.3FRAXA Research Foundation, Newburyport, MA, USA.
4Biomedical Sciences, University of California, Riverside, CA, USA.5Biomedical
Sciences, Western University of Health Sciences, Pomona, CA, USA.
CP participated in the design of the study, submitted all trial applications,
conducted the medical assessments of the subjects, and drafted the
manuscript. LT participated in trial coordination and assisted with medical
assessments of the trial subjects. AF conducted the behavioural and
cognitive assessments of the subjects, and performed the statistical analysis
on the data. EBK participated in the design of the study. MT conceived of
the study, and participated in its design. IME conducted the preclinical
studies on the fmr1 knockout mouse. DWE conducted the preclinical studies
on the fmr1 knockout mouse. All authors have read and approved the final
The authors declare that they have no competing interests.
Received: 10 April 2010 Accepted: 11 October 2010
Published: 11 October 2010
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Paribello et al. BMC Neurology 2010, 10:91
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The pre-publication history for this paper can be accessed here:
Cite this article as: Paribello et al.: Open-label add-on treatment trial of
minocycline in fragile X syndrome. BMC Neurology 2010 10:91.
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