Basmisanil (INN) (developmental code names RG-1662, RO5186582) is a highly selective inverse agonist/negative allosteric modulator of α5 subunit-containing GABAA receptors which is under development by Roche for the treatment of cognitive impairment associated with Down syndrome. The phase II trials were recently terminated due to lack of efficacy. This outcome suggests either that the α5-NAM was insufficiently effective to restore neuronal plasticity or alternatively that the hypothesis of excessive GABAergic inhibition obstructing neuronal plasticity does not extend to individuals with DS.

MRK-016 is a selective inverse agonist of GABA receptor alpha-5 subunit. It was shown; that in animal models this compound has effect effects on depression.

RO 15-4513 is a high-affinity benzodiazepine ligand which acts as a partial inverse agonist at recombinant diazepam-sensitive (DS) benzodiazepine α1-, α2-, α3- and α5-GABAA receptors, developed by Hoffmann–La Roche in the 1980s. Ro 15-4513 reverses the sedating and anticonflict effects of alcohol, and can, therefore, be used as an antidote to the acute impairment caused by alcohol. In non-food or fluid-deprived rats, orally self-administering 10% alcohol in an operant situation, Ro 15-4513 resulted in a dose-dependent suppression of alcohol intake. The use of Ro 15-4513 would appear to be limited by the fact that the compound is proconvulsant. Ro 15-4513 has been found to induce seizures in mice undergoing ethanol withdrawal. However, it is a potentially powerful tool with which to investigate the neuropsychopharmacology of alcohol. Labelling Ro15-4513 with carbon-11 leads to the possibility of its use in PET imaging of the brain. The specificity of the compound to a small number of GABA receptor sub-types leads to the generation, with accurate modeling, of detailed images with well-defined limbic and cortical structures. These images can be useful in quantitatively analyzing conditions such as addiction, that is known to be, at least in part, associated with the GABAergic system.

MRK-409 (MK-0343) is a subtype-selective GABA(A) partial agonist that occupies the benzodiazepine site of GABA(A) receptors. MK-0343 was designed to be a less sedating anxiolytic, based on reduced efficacy at the alpha-1 subtype and significant efficacy at alpha -2 and alpha-3 subtypes of the GABA(A) receptor. MRK-409 binds to alpha-1, 2, 3 and 5-containing human recombinant GABA(A) receptors with comparable high affinity (0.21-0.40 nM). However, MRK-409 has greater agonist efficacy at the alpha-3 compared with alpha-1 subtypes. MRK-409 exhibited anxiolytic and non-sedating properties in different rodent and primate models of unconditioned and conditioned models of anxiety but produced sedation in man at relatively low levels of GABA(A) receptor occupancy (∼10%). It was suggested that the sedation with MRK-409 was due to the partial agonist efficacy of that compound at the alpha-1 subtype. Although MRK-409 (MK-0343) reached clinical studies its development had to be stopped due to sedative effects in humans demonstrated that more preclinical efforts are needed to identify compounds with improved selectivity.

L-822179 is a triazolophthalazine that selectively attenuates the effects of GABA at GABA(A) receptors containing an alpha5 subunit. It is an orally active, functionally selective compound, which enhances cognition in animals without anxiogenic or convulsant effects. The dose-limiting adverse event of L-822179 is dizziness and/or light-headedness. L-822179 does not improve cognitive performance in the elderly; indeed the dose of 4 mg actually significantly impairs performance. In this regard, it could therefore be considered that this study is a failed trial in so far as the positive control, lorazepam, does not show the anticipated effect.

L-822179 is a triazolophthalazine that selectively attenuates the effects of GABA at GABA(A) receptors containing an alpha5 subunit. It is an orally active, functionally selective compound, which enhances cognition in animals without anxiogenic or convulsant effects. The dose-limiting adverse event of L-822179 is dizziness and/or light-headedness. L-822179 does not improve cognitive performance in the elderly; indeed the dose of 4 mg actually significantly impairs performance. In this regard, it could therefore be considered that this study is a failed trial in so far as the positive control, lorazepam, does not show the anticipated effect.