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An Alzheimer's Drug May Boost Cognition In People With Fragile X Syndrome

Fragile X syndrome involves changes in the X chromosome, as pictured in the four columns of chromosomes starting on the left. The fifth column, on the far right, shows two normal X chromosomes.
Richard J. Green/Science Source
Fragile X syndrome involves changes in the X chromosome, as pictured in the four columns of chromosomes starting on the left. The fifth column, on the far right, shows two normal X chromosomes.

An experimental drug intended for Alzheimer's patients seems to improve both language and learning in adults with Fragile X syndrome.

The drug, called BPN14770, increased cognitive scores by about 10% in 30 adult males after 12 weeks, a team reports in the journal Nature Medicine.

That is enough to change the lives of many people with Fragile X, says Mark Gurney, CEO of Tetra Therapeutics, developer of the medicine.

"People with Fragile X with an IQ of 40 are typically living with their parents or in an institutional setting," Gurney says. "With an IQ of 50, in some cases they're able to ride the bus, they're able to hold a job with some assistance and they're able to function better in their community."

But it will take a much larger study to know whether the drug is as good as it seems, says Mark Bear, Picower professor of neuroscience at the Massachusetts Institute of Technology.

"This study is certainly not definitive, but it's encouraging," he says.

Fragile X syndrome is a genetic disorder that affects about 1 in 4,000 males and a smaller proportion of females. It is the most common inherited cause of intellectual disabilities and autism.

The idea of treating Fragile X with an Alzheimer's drug came from Gurney after he learned that both conditions affect a substance called cyclic AMP that helps transmit messages inside cells.

Tetra had been developing BPN14770 as an Alzheimer's drug that worked by manipulating cyclic AMP, "so we thought there was a strong possibility that this drug might be effective in Fragile X," Gurney says.

He contacted FRAXA, a foundation that has been funding research on the disorder since the mid-1990s. The foundation arranged to have Tetra's drug tested in animals; then it agreed to fund the study in people.

The apparent success comes seven years after two other promising drugs for Fragile X did not pan out when tested in people.

The positive result "makes up for some of the devastation of years ago when we had such high-profile failures," says Katie Clapp, one of FRAXA's founders.

Clapp says the results also give her new hope for her son Andy Tranfaglia, who is 31 and has Fragile X syndrome.

"The incredible thing about the results of this trial are that they were able to show that learning improved," Clapp says.

In some previous studies, drugs that produced dramatic results in mice failed to act the same way in people, says Dr. Michael Tranfaglia, who is Clapp's husband and a co-founder of FRAXA.

With BNP14770, "we saw an almost perfect translation of these findings we saw in the mice into the human condition," he says.

At least one promising drug candidate may have failed because people developed a tolerance to it, Tranfaglia says.

"The one thing we know with [BPN14770] is that the longer you're on it, the better you do," he says. "It just keeps on working better and better."

If the new drug's effectiveness is confirmed in adults, it is likely to be even more successful in children, Bear says.

"Fragile X can be conceptualized as a derailment of normal brain maturation," Bear says. "So the earlier we can get in there and correct the course of development, the more dramatic will be the improvement."

Tetra Therapeutics is working with its parent company, Japanese drugmaker Shionogi, to launch a much larger study of the new drug this summer.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.
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