But now that dogma is being challenged, said study co-author Daniel Smith, a senior research scientist at Pfizer Worldwide Research and Development.
Studies have suggested that some genes involved with autism play a role in the formation of brain synapses throughout childhood, and even into adulthood. That has led researchers to hunt for compounds that could alter how those genes function.
In Fragile X, for example, research suggests that excessive glutamate signaling may underlie the condition, and clinical trials are already underway by Novartis, Seaside Therapeutics and Roche to test other compounds that inhibit glutamate activity, Ring said.
"Because Fragile X symptoms overlap with autism symptoms, we hypothesized this same mechanism might affect autism patients from populations other than Fragile X," Smith said.
In an accompanying journal editorial, Baltazar Gomez-Mancilla, executive director of translational medicine neuroscience at Novartis, wrote that GRN-529 reduced repetitive behavior and partially reversed lack of sociability in a mouse model of autism.
And yet this is only "early stage, preclinical research" that will help advance the understanding of molecular mechanisms involving the mGluR5 receptor and generate more avenues for research, Gomez-Mancilla said.
"It is too early to speculate as to whether or not autism spectrum disorders can be reversed by small molecules," Gomez-Mancilla said.
Gomez-Mancilla wrote that this trial and previous work on mGluR5 inhibitors support further clinical trials. If the trials show the drugs are effective, a major question would be whether children should receive the drugs when diagnosed or if adults would also benefit.
Dr. Jeremy Veenstra-VanderWeele, an assistant professor of psychiatry, pediatrics and pharmacology at Vanderbilt University in Nashville, Tenn.,
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