Andy Tranfaglia, 23, who has Fragile X syndrome, rides a horse with his mother, Katie Clapp.

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Researchers say they have found a drug that can help people with the genetic condition called Fragile X syndrome. That finding is raising hopes that similar drugs could also help some people with autism. The discovery was published in the journal "Science Translational Medicine." And as NPR's Jon Hamilton reports, it came about with the help of a couple whose son was born with Fragile X more than 20 years ago.

JON HAMILTON, BYLINE: When Katie Clapp and Michael Tranfaglia learned that their son Andy had Fragile X, they started a foundation called FRAXA. Fragile X causes a wide range of intellectual and social problems, including many that are similar to those found in autism. Katie Clapp says the goal of their foundation was simple: Fund research that would lead to a treatment for their son. She says that goal is now in sight.

KATIE CLAPP: Back in 1994, we knew exactly what we were aiming for. And it's gotten closer and closer, little by little.

HAMILTON: Research funded, in part, by FRAXA led to the discovery that Fragile X disrupts a system that regulates connections in the brain. And that discovery eventually led to drugs with the potential to fix the problem, including a drug called arbaclofen. A team from Rush University and the University of California-Davis wanted to know whether arbaclofen could help people with Fragile X overcome their tendency to avoid social interactions. So they tried the drug on 63 children and adults with the syndrome, and it worked.

Becky Zorovic is a physician whose son Anders was in the trial and continues to take arbaclofen. She says before the treatment, Anders was terrified by things like birthday parties.

DR. BECKY ZOROVIC: We hadn't been to many parties because he would have such a tantrum about not wanting to go that after 20 minutes, or a half-hour, of refusing to go and screaming, and starting to hit and kick and bite, we would say, OK, fine - you know - we don't have to go to the birthday party.

HAMILTON: But Zorovic says recently, she was able to get Anders to at least take a look at a friend's pool party.

ZOROVIC: After 10, 15 minutes, he was in the pool and stayed for two hours. So he was able to overcome it, to get to that point where he was able to have a good time.

HAMILTON: Arbaclofen appears to work by tamping down overactive brain signals that can make it hard to navigate social interactions. Mark Bear is a researcher at MIT, who made some of the crucial early discoveries about how Fragile X affects the brain. He is also a co-founder of Seaside Therapeutics, which makes arbaclofen. Bear predicts the drug will help some people with autism because they have similar problems with social interactions.

MARK BEAR: It would be, I think, unrealistic to expect that this drug would be uniformly beneficial to all people that have an autism diagnosis. But I think we can still be quite optimistic that it will be a benefit to a subset of those patients. And right now, we don't know how large that subset is.

HAMILTON: For people with Fragile X, there are now several experimental drugs in trials. But so far, that hasn't helped Katie Clapp, the woman who started a foundation nearly two decades ago, to find a treatment for her child. She says she's been unable to enroll her son Andy in any studies near their home, which is not far from Boston.

CLAPP: Andy is now 23 years old, and we are so eager to get him started in one of these trials.

HAMILTON: But Katie Clapp says she has no regrets about her efforts over the past 20 years.

CLAPP: Even though we still have to wait for our son to begin to participate, I feel just absolutely thrilled that this result is out, and that the trials are proceeding. So it's made all the work worthwhile.

HAMILTON: And she thinks it won't be long before at least some of the new drugs are on the market, and available to all people with Fragile X.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.