So far, the research indicates the drugs will only be effective for one form of autism that is caused by a mutation of a gene on the X chromosome, a condition known as fragile X syndrome.
The exact cause of the disorder remains elusive but it has been linked to a variety of genes, including the fragile X mutation that can lead to both mental retardation and autism. The mutation is thought to lead to mental problems because it causes hyperactivity of a brain protein called metabotropic glutamate receptor 5 (mGluR5) that normally plays a role in learning and memory.
A team led by Bear wondered if reducing levels of mGluR5 protein could restore normal brain function. The researchers used a combination of genetic engineering and selective breeding to produce a line of mice that had both the fragile X mutation and toned down levels of the mGluR5 protein in their brain. The intent was to get an idea of what would happen when the protein was suppressed using a drug in human patients.
In a finding that the researchers described as “remarkable” the mice — which should have had mental retardation and autism-like symptoms due to the fragile X mutation — instead showed near-normal brain function and memory.
Pill in the works
That was exciting in and of it, because it indicated that blocking the mGluR5 protein could lead to improvements in some forms of autism and mental retardation. But Bear said the even more provocative implication is that a compound that does just that already exists. A few years ago, he founded Seaside Therapeutics, a small pharmaceutical firm in
Randall Carpenter,
Outside researchers also were enthusiastic about the potential of the compound.
“It seems very promising indeed,” said Matthew Belmonte, a neuroscientist at
Not everyone is on board, however. Sophia Colamarino, a neurobiologist and vice president of research for the advocacy group Autism Speaks, which helped fund Bear's research, said the finding “give us hope” that this could be a viable strategy for treating autism, but she added that it's too early to tell whether STX107 will improve autistic behaviors in people. The drug could reduce mGluR5 levels, but autism is such a complex disease, this may not be enough to restore normal behavior in patients, Colamarino said.
Two other drugs in the works
If the drug does fail, there still may be hope for patients and their families. The Fragile X Research Foundation (FRAXA), which co-funded STX107 research, is supporting investigations involving two other drugs that block the same protein Lithium, Fenobam.
“We believe that drugs which block mGluR5 have enormous potential for the treatment of fragile X and related developmental disorders, including many cases of autism,” said Katie Clapp, president and executive director of FRAXA.
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