Arbaclofen Continues Clinical Trials for Treatment of Social Withdrawal in Autism


As of today, there are thirteen clinical trials in various stages of completion listed by the US National Institutes of Health for the use of a new drug known as arbaclofen, or STX209. Several studies are recruiting participants to evaluate the efficacy of the drug in autism spectrum disorders (ASD), including those with Fragile X syndrome. The experimental treatment is also being studied in other conditions, such as Multiple Sclerosis and Gastroesophageal Reflux Disease.

STX209 is an orally-administered GABA-B agonist. According to Autism Speaks Chief Science Officer Geraldine Dawson PhD, the drug acts by stimulating the release of GABA (Gamma-Amino Butyric Acid), a neurotransmitter in the central nervous system. GABA inhibits the release of glutamate, an excitatory neurotransmitter, for which an overabundance negatively affects the ability of neurons to communicate with each other (synaptic functioning). Other conditions, such as anxiety disorders, Parkinson’s syndrome, and addiction, have been linked to low GABA activity.

More on Novel Drug for Fragile X Could Treat Disorder Cause Instead of Symptoms

Some of the first studies of arbaclofen have been conducted in patients with Fragile X syndrome, a genetic condition that is caused by a change in a gene known as FMR1 which normally is needed to make the brain grow properly. Fragile X is the most common form of inherited intellectual disability in boys and can be a cause of autism or related disorders. In those Phase 2 trials, arbaclofen has been shown to decrease social withdrawal and improve adaptive social function.


In July 2011, Seaside Therapeutics, the pharmaceutical company that created and is testing STX209, announced that 25 sites across the nation will be involved in a new clinical trial to involve approximately 150 ASD patients between the ages of 5 and 21. Participants in the 22-week Phase 2b study will be randomized to receive either arbaclofen or a placebo.

More on Autistic Persons Have Strong Abilities that are Underestimated

A smaller, Phase 2a study conducted at 8 sites and involving 32 children showed significant positive behavioral outcomes, including improved scores on the Aberrant Behavior Checklist-Irritability Score (ABC-I) and on the ABC-Social Withdrawal Scale. The most common adverse events were agitation, irritability, fatigue, psychomotor hyperactivity, insomnia and diarrhea. Most resolved without dose changes, but one serious adverse effect did occur during down-titration of the medication.

“There are currently no FDA-approved therapeutics to treat the core symptoms of autism spectrum disorders, creating a vast unmet need for the millions of individuals and their families affected by this condition in the US and EU alone,” said Randall L. Carpenter, M.D., President and Chief Executive Officer of Seaside Therapeutics. “(We) are truly excited about the prospect of helping patients and their families achieve an improved quality of life.”

References Include:
Seaside Therapeutics
Autism Speaks
International Meeting for Autism Research: Effects of STX209 (arbaclofen) on Social and Communicative Function In ASD: Results of An 8-Week Open-Label Trial