ML289 (VU0463597) is a potent, selective, and CNS-penetrant mGlu3 (IC50=0.66 μM) negative allosteric modulator. ML289 displays >15-fold selectivity over mGlu2 and is inactive against mGlu5[1]. ML289 is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.