N-{4-chloro-2-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]phenyl}-2-hydroxybenzamide

CPPHA is a positive allosteric modulator of metabotropic glutamate receptor 5 (mGluR5) that potentiates human and rat mGluR5 activation by glutamate, 3,5-DHPG , and quisqualate (EC₅₀s = 0.316-0.5 and 0.634-1.16 μM for human and rat mGluR5, respectively). It is selective for mGluR5 over other mGluRs but exhibits submicromolar activity at PDE6, δ- and κ-opioid receptors, and the ether-a-go-go related gene (ERG) potassium channel (K_is = 500, 352, 474, and 813 nM, respectively). CPPHA potentiates 3,5-DHPG-induced NMDA currents in CA1 pyramidal cells and the depolarization of rat subthalamic nucleus (STN) neurons.