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Efficacy and Safety Study of STX209 (Arbaclofen) for the Treatment of Social Withdrawal in Children With Fragile X Syndrome (Harbor-C)

This study has been completed.
Information provided by (Responsible Party):
Seaside Therapeutics, Inc. Identifier:
First received: March 28, 2011
Last updated: July 30, 2013
Last verified: July 2013
There will be four study periods: Screening (up to 14 days in length), the Treatment Period (8 weeks), the Withdrawal Period (22 days), and Follow-up Period (up to 31 days). Subjects will be randomized to receive either STX209 (5 mg twice daily [BID], 10 mg BID or 10 mg three times daily [TID]) or placebo. Efficacy,safety and tolerability assessments will be performed periodically

Condition Intervention Phase
Fragile X Syndrome Drug: arbaclofen Drug: Placebo Phase 3

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
Official Title: A Randomized, Double-Blind, Placebo-Controlled, Fixed-Dose Study of the Efficacy, Safety, and Tolerability of STX209 (Arbaclofen) Administered for the Treatment of Social Function in Children With Fragile X Syndrome

Resource links provided by NLM:

Further study details as provided by Seaside Therapeutics, Inc.:

Primary Outcome Measures:
  • Aberrant Behavior Checklist-Lethargy Social Withdrawal subscale [ Time Frame: at 8 weeks of treatment ]
    This is a single subscale of the aberrant behavior checklist entitiled Lethargy Social Withdrawal

Enrollment: 172
Study Start Date: June 2011
Primary Completion Date: June 2013 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: STX209 5 mg BID Drug: arbaclofen
5 mg bid
Other Name: R-baclofen, STX209
Active Comparator: STX209 10 mg BID Drug: arbaclofen
10 mg bid
Other Name: R-baclofen, STX209
Active Comparator: STX209 10 mg TID Drug: arbaclofen
10 mg tid
Other Name: R-baclofen, STX209
Placebo Comparator: Placebo Drug: Placebo


Ages Eligible for Study:   5 Years to 11 Years   (Child)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Molecular documentation of the full FMR1 mutation
  • Current pharmacological treatment regimen has been stable for at least 4 weeks prior to Screening.
  • Subjects with a history of seizure disorder must currently be receiving treatment with antiepileptics and must have been seizure free for 6 months, or must be seizure free for 3 years if not currently receiving antiepileptics.
  • If the subject is already receiving stable non-pharmacologic educational, behavioral, and/or dietary interventions, participation in these programs must have been continuous during the 2 months prior to Screening

Exclusion Criteria:

  • Subjects with any condition, including alcohol and drug abuse, which might interfere with the conduct of the study, confound interpretation of the study results, or endanger their own well-being.
  • Subjects who plan to initiate or change pharmacologic or non-pharmacologic interventions during the course of the study.
  • Subjects who have taken another investigational drug within the last 30 days.
  • Subjects who are not able to take oral medications
  Contacts and Locations
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Please refer to this study by its identifier: NCT01325220

  Show 28 Study Locations
Sponsors and Collaborators
Seaside Therapeutics, Inc.
Study Director: Paul Wang, M.D. Seaside Therapeutics, Inc.
  More Information

Responsible Party: Seaside Therapeutics, Inc. Identifier: NCT01325220     History of Changes
Other Study ID Numbers: 209FX302
Study First Received: March 28, 2011
Last Updated: July 30, 2013

Additional relevant MeSH terms:
Mental Retardation, X-Linked
Fragile X Syndrome
Pathologic Processes
Intellectual Disability
Neurobehavioral Manifestations
Neurologic Manifestations
Nervous System Diseases
Sex Chromosome Disorders
Chromosome Disorders
Congenital Abnormalities
Genetic Diseases, Inborn
Genetic Diseases, X-Linked
Heredodegenerative Disorders, Nervous System processed this record on September 21, 2017