Drug Development

Despite extensive drug development efforts, efficacious treatment options for Alzheimer's Disease (AD) are still lacking. Studies identified the α5-containing GABAA receptor (α5-GABAAR) as essential for the regulation of cognitive function and a promising therapeutic target. GL-II-73, a positive allosteric modulator at the α5-GABAAR, showed efficacy at reversing working memory deficits and neuronal shrinkage induced by amyloid load in preclinical models. However, its mechanism of action through the benzodiazepine-binding pocket of the α5-GABAARs remains to be demonstrated. This project proposes to show the requirement of positive allosteric modulation of GL-II-73 at the α5-GABAARs in the regulation of cognitive functions in a double transgenic mouse model of AD. We hypothesize that, following chronic treatment, the drug-sensitive strain will show improved cognitive performance compared to the drug-insensitive strain, despite both groups having amyloid pathology.

5xFAD mice were bred with α5-KI (Knock-in) mice to generate double transgenic animals. Four-to-five-month-old double transgenic mice were used, which show amyloid deposition (5xFAD) and insensitivity to drug binding in the benzodiazepine-binding pocket. Double transgenic animals and their wild-type littermates (n=12/group, 50% female) underwent three weeks of drug treatment (GL-II-73, 30 mg/kg), administered through drinking water. Y-maze alternation task and Morris Water Maze were conducted to assess working memory and spatial cognition.

Drug-sensitive mice receiving GL-II-73 showed better cognitive performance than the control group in both Morris Water Maze and Y-Maze alternation task, while such facilitation was not observed in the drug-insensitive mice.

Our findings demonstrated that the effects of GL-II-73 are mediated by allosteric modulation of the benzodiazepine-binding site of α5-GABAARs, as expected, specifically at improving working memory and spatial cognition.