Trial of Minocycline to Treat Children With Fragile X Syndrome

This is a single center study at the UC Davis MIND Institute in patients age 3.5-16 years of
age with fragile X syndrome (FXS), funded by a National Fragile X Foundation Grant. It is a
controlled trial of minocycline, an antibiotic commonly used in children for infection or
for treatment of neurodegenerative disorders. We are investigating its use in FXS because it
lowers matrix metalloproteinase 9 (MMP9) levels, which are high in FXS, and it also
strengthens brain connections in the animal models of FXS. We hypothesize that minocycline
will likely be helpful for language, behavior and/or cognition in fragile X patients.

The aim of this study is to carry out a double-blind placebo controlled trial of minocycline
treatment in children with FXS who are 3.5 to 16 years of age. At baseline, we will assess
behavior and perceptual and cognitive development. After the children have been treated for
3 months with either minocycline or placebo, they undergo the same baseline testing. They
will then cross over and be treated for a second 3 months. We will carry out testing again
at the end of the second 3 month period. We will also assess the side effects of minocycline
treatment throughout the study.