Experimental Drug Shows Promise Reversing Intellectual Disability

No cognitive differences seen between normal mice and fragile X models treated with Nutlin-3.

In a recent study, mice missing the FMRP protein were able to create memories after taking an experimental cancer drug, Nutlin-3, for 2 weeks.

The study, published by Science Translational Medicine, used mice models to mimic the condition fragile X, which is caused by a genetic mutation. The condition results in the deletion of FMRP, which is essential to memory formation.

Researchers were initially able to detail the steps in the chain reaction that starts with the deletion of FMRP and ends with mice that cannot form memories. Nutlin-3 could potentially block this reaction.

Nutlin-3 is currently in a phase 1 trial for retinoblastoma and was able to prevent the last stage of the chain reaction by a mutation in the FMRP gene.

According to the study, memory capacities were the same in normal mice and fragile X models treated with Nutlin-3. Researchers then tested the mice models on curiosity.

"We placed two objects in an enclosure and let the mice run around," said study author Xinyu Zhao, PhD said. "Mice are naturally curious, so they explore and sniff each one. We take them out after 10 minutes, replace one object with a different one, wait 24 hours and put the mouse back in. If the mouse has normal learning ability, it will recognize the new object and spend more time with it. Mice without the FMRP gene don't remember the old object, so they spend a similar amount of time on each one."

According to the study, the test was conducted by different researchers who were not aware which mouse was treated with Nutlin-3 and which was the control.

"First author Yue Li, a postdoctoral researcher at Waisman, ran the test and sent the video to Michael Stockton, an undergraduate working on the project, but he had no idea which mouse was which," said Dr. Zhao. "It was fantastic to see such clear data."

The dosage used in the trial was only 10% of the proposed dose for cancer chemotherapy. Researchers said the mice looked happy and healthy.

"There are many hurdles. Among the many questions that need to be answered is how often the treatment would be needed. Still, we've drawn back the curtain on fragile X a bit, and that makes me optimistic,” Dr. Zhao concluded.