Still, he added, this line of research is very promising.
"There are now multiple clinical trials underway of mGluR5 antagonists in individuals with Fragile X syndrome," Veenstra-VanderWeele said. "Many of us hope that these medications will help not only those who have autism spectrum disorder due to Fragile X syndrome but some people within the larger group of those with [autism spectrum disorder] not due to a well-understood cause. Of course, that hope hasn't yet been tested."
He said this new study is "an exciting hint that the mGluR5 hypothesis may extend outside of Fragile X Syndrome." If that's true, he said, it could potentially point to a role for this receptor in the biology underlying repetitive behavior and social interaction.
Experts noted that many cases of autism likely involve more than excessive glutamate signaling. Even in the mice, GRN-529 helped with certain symptoms, but not with all. For instance, the mice still didn't communicating normally.
Pfizer's Smith said GRN-529 is not being considered for clinical trials. Pfizer declined to give any more details about future research into GRN-529 or other glutamate-inhibiting drugs.
The U.S. National Institutes of Health has more on autism.
SOURCES: Daniel Smith, Ph.D., senior research scientist, Pfizer Worldwide Research and Development, Groton, Conn.; Robert Ring, Ph.D., vice president, translational research, Autism Speaks; Baltazar Gomez-Mancilla, executive director, translational medici
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