GRM5 and fragile X syndrome: Although mGluR5 negative modulators are not currently available for treatment of humans with FXS, during recent high throughput lead-finding screens, Porter et al17 discovered that fenobam is a high potency and highly selective mGluR5 antagonist, comparable to MPEP, with no relevant effects on a panel of 86 central nervous system (CNS) receptors assayed in a commercial receptor binding screen, including other mGluRs.