Characterization of the binding of the novel compound GT-002 to GABAA receptors in the mammalian brain : Development and validation of a radioligand binding assay. A comparative study to Flumazenil

Abstract: Gamma-Amino butyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system (CNS) and inhibits the neurotransmission by targeting the ionotropic transmembrane GABAA receptor. Modulators of the GABAA receptor targets the allosteric binding sites and modifies the GABA effect and these sites acts as superior drug targets within psychopharmacology.   Gabather AB has developed the novel compound GT-002 that is known to target the receptor and cause a behavioral effect in rodents. This project characterized the binding of the lead compound GT-002 to GABAA receptor in mammalian brain tissue by development and validation of a radioligand binding assay. In the assay a comparative evaluation was performed using the benzodiazepine (BZ) antagonist Flumazenil (FLU).   All experiments were performed using GABAA receptors originating from porcine and mouse brain tissue membrane, where no significant difference between the mammals was displayed. GT-002 binds with higher affinity and associates faster than FLU to the receptor and implies a two-binding site model. GT-002 displaced FLU and no tested competitive analytes targeting various modulatory sites of the receptor displaced GT-002, implying independent binding of GT-002 and allosterically impacts the BZ binding site.