As an expansion of a CGG repeat in the 5'-UTR of the fragile X mental retardation 1 gene leads to the up-regulation of metabotropic glutamate receptor 5-mediated signaling, an international research team sought to determine "whether a receptor subtype-selective inhibitor of mGluR5, AFQ056, improves the behavioral symptoms of FXS in a randomized, double-blind, two-treatment, two-period, crossover study of 30 male FXS patients aged 18 to 35 years." In Science Translational Medicine this week, the team reports that "seven patients with full FMR1 promoter methylation and no detectable