Autism May Benefit from Potential Fragile X Syndrome Drug
A search for a drug that can treat fragile X syndrome has led to the discovery of a compound that may benefit more than individuals with this form of intellectual disability. Researchers suggest their study results may also help people who have autism spectrum disorder.
New drug could be first for fragile X and autism
Fragile X syndrome is a genetic condition associated with intellectual, behavioral, and learning challenges along with various physical traits. Males are more likely to be affected by fragile X syndrome than are females, and the condition is generally more severe as well.
According to the National Fragile X Foundation, studies suggest that 15 to 33 percent of children with fragile X syndrome also have autism. Conversely, an estimated 2 to 6 percent of children with autism are diagnosed with fragile X syndrome.
People with fragile X syndrome who also have autism may have a lower IQ than individuals with the syndrome who do not have autism. Fragile X syndrome is also the main known single-gene cause of autism.
This relationship between fragile X syndrome and autism is an interesting factor to consider in light of the new study by researchers at Rush University Medical Center and the University of California, Davis MIND Institute.
Basically, the authors reported that an investigational compound called STX209 (aka arbaclofen) improved symptoms in patients with fragile X syndrome as well as those with autism or significant social deficits such as poor eye contact and severe shyness, which are core features of autism.
Arbaclofen is a chemical with the ability to combine with a receptor in the brain to trigger a physiologic reaction usually seen with a naturally occurring substance. In this case, arbaclofen combines with the neurotransmitter gamma-amino butyric acid (GABA), which has been found in low levels in the brains of mouse models of fragile X syndrome.
Low GABA is believed to have a key role in the social withdrawal and social anxiety demonstrated by people with fragile X syndrome. Other characteristics of fragile X syndrome in males can include moderate learning disabilities to severe intellectual disabilities, autism and autistic behaviors, sensory disorders, increased risk for aggression, hand-biting, hand flapping, and attention deficit disorder (ADD). Females usually have milder intellectual and behavioral disabilities and symptoms.
In the new double-blind, crossover study, 56 individuals ranging in age from 6 to 39 years were given either arbaclofen (10 mg twice daily for younger patients and three times for adults) or placebo in a double-blind manner for six weeks, then crossed over. Drug use was tapered down over a one- to two-week period.
The authors reported that participants improved in the three most challenging behaviors, but there was no improvement for irritability. Overall, the findings of this first-of-its-kind study suggest arbaclofen may effectively treat social withdrawal and problem behaviors in individuals with fragile X syndrome and those with autism as well.
Arbaclofen and autism
Parents of children with autism may be interested to know that a search of the government's website on clinical trials reveals three phase 2 trials currently underway that involve use of the drug in autism spectrum disorder. Anyone interested in learning more can visit the clinical trials website.
One trial is by invitation only and is examining use of arbaclofen for irritability. Another is active but not recruiting and is looking at how the drug affects social withdrawal in individuals with autism spectrum disorder, while the status of the third trial is "unknown," and is a preliminary study of the drug's safety and tolerability.
Berry-Kravis EM et al. Effects of STX209 (Arbaclofen) on neurobehavioral function in children and adults with fragile X syndrome: a randomized, controlled, phase 2 trial. Science Translational Medicine 2012; 4(152): 152ra172
National Fragile X Foundation