A highly selective non-competitive antagonist for the metabotropic glutamate mGlu5 receptor subtype; displays an IC50 value of 0.3 μM at hmGlu5, compared with > 100 μM at hmGlu1b, hmGlu2, hmGlu6, hmGlu7 and hmGlu8. Centrally active upon systemic administration in vivo. Positive allosteric modulator at mGlu4 receptors. MW (observed): 195.26.