Chronic pharmacological inhibition of mGluR5 reversed established FXS phenotypes in adult Fmr1KO mice (Michalon et al., 2012), and a single dose, open-label clinical trial of the mGluR5 antagonist fenobam improved prepulse inhibition in adult FXS patients (Berry-Kravis et al., 2009); however, earlier intervention may show improved efficacy. The gene discussed is GRM5; the disease is fragile X syndrome.