Fenobam is a selective, orally active, and non-competitive mGluR5 antagonist acting at an allosteric modulatory site (Kd values are 54 and 31 nM for rat and human recombinant mGlu5 receptors, respectively). Fenobam displays inverse agonist activity which blocks the mGlu5 receptor basal activity with an IC50 of 84 nM. Fenobam exerts anxiolytic activity[1][2].
References:
[1]. Porter RH, et al. Fenobam: a clinically validated nonbenzodiazepine anxiolytic is a potent, selective, and noncompetitive mGlu5 receptor antagonist with inverse agonist activity. J Pharmacol Exp Ther. 2005 Nov;315(2):711-21.
[2]. Laura F, et al. The Metabotropic Glutamate Receptor 5 Negative Allosteric Modulator Fenobam: Pharmacokinetics, Side Effects, and Analgesic Effects in Healthy Human Subjects.bioRxiv 391383;