An imidazopyridine is a nitrogen containing heterocycle that is also a class of drugs that contain this same chemical substructure. In general, they are GABAA receptor agonists, however recently proton pump inhibitors, aromatase inhibitors, NSAIDs and other classes of drugs in this class have been developed as well. Despite usually being similar to them in effect, they are not chemically related to benzodiazepines. As such, GABAA-agonizing imidazopyridines, pyrazolopyrimidines, and cyclopyrrones are sometimes grouped together and referred to as "nonbenzodiazepines." Imidazopyridines include:
Bretazenil (Ro16-6028) is an imidazopyrrolobenzodiazepine anxiolytic drug which is derived from the benzodiazepine family, and was invented in 1988. It is most closely related in structure to the GABA antagonist flumazenil, although its effects are somewhat different. It is classified as a high-potency benzodiazepine due to its high affinity binding to benzodiazepine binding sites where it acts as a partial agonist. Its profile as a partial agonist and preclinical trial data suggests that it may have a reduced adverse effect profile. In particular bretazenil has been proposed to cause a less strong development of tolerance and withdrawal syndrome. Bretazenil differs from traditional 1,4-benzodiazepines by being a partial agonist and because it binds to α1, α2, α3, α4, α5 and α6 subunit containing GABAA receptor benzodiazepine receptor complexes. 1,4-benzodiazepines bind only to α1, α2, α3 and α5GABAA benzodiazepine receptor complexes.
Pagoclone is an anxiolytic agent from the cyclopyrrolone family, related to better-known drugs such as the sleeping medication zopiclone. It was synthesized by a French team working for Rhone-Poulenc & Rorer S.A. Pagoclone belongs to the class of nonbenzodiazepines, which have similar effects to the older benzodiazepine group, but with quite different chemical structures. It was never commercialised.
Panadiplon (U-78875) is an anxiolytic drug with a novel chemical structure that is not closely related to other drugs of this type. It has a similar pharmacological profile to the benzodiazepine family of drugs, but with mainly anxiolytic properties and relatively little sedative or amnestic effect, and so is classified as a nonbenzodiazepine anxiolytic.
QH-II-66 (QH-ii-066) is a sedative drug which is a benzodiazepine derivative. It produces some of the same effects as other benzodiazepines, but is much more selective than most other drugs of this class and so produces somewhat less sedation and ataxia than other related drugs such as diazepam and triazolam, although it still retains anticonvulsant effects.
L-838,417 is an anxiolytic drug used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. The compound was developed by Merck, Sharp and Dohme.
SL651498 is an anxiolytic and anticonvulsant drug used in scientific research, with a chemical structure most closely related to β-carboline derivatives such as abecarnil and gedocarnil. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
SX-3228 is a sedative and hypnotic drug used in scientific research. It has similar effects to sedative-hypnotic benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine hypnotic.
Adipiplon (NG2-73) is an anxiolytic drug developed by Neurogen Corporation. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
ABT-418 is a drug developed by Abbott, that has nootropic, neuroprotective and anxiolytic effects, and has been researched for treatment of both Alzheimer's disease and ADHD. It acts as an agonist at neural nicotinic acetylcholine receptors, subtype-selective binding with high affinity to the α4β2, α7/5-HT3, and α2β2 nicotinic acetylcholine receptors but not α3β4 receptors ABT-418 was reasonably effective for both applications and fairly well tolerated, but produced some side effects, principally nausea, and it is unclear whether ABT-418 itself will proceed to clinical development or if another similar drug will be used instead.
Tracazolate (ICI-136,753) is an anxiolytic drug which is used in scientific research. It is a pyrazolopyridine derivative, most closely related to pyrazolopyrimidine drugs such as zaleplon, and is one of a structurally diverse group of drugs known as the nonbenzodiazepines which act at the same receptor targets as benzodiazepines but have distinct chemical structures.
SB-205384 is an anxiolytic drug. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
ELB-139 (LS-191,811) is an anxiolytic drug with a novel chemical structure, which is used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
NS-2710 (LS-193,970) is an anxiolytic drug with a novel chemical structure, developed by the small pharmaceutical company NeuroSearch. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. NS-2710 is a potent but non-selective partial agonist at GABAA receptors, although with little efficacy at the α1 subtype and more at α2 and α3. It has anxiolytic effects comparable to chlordiazepoxide, and while it is a less potent anticonvulsant than the related drug NS-2664, it has a much longer duration of action, and similarly to other α2/α3-preferring partial agonists produces little sedative effects or physical dependence.
TPA-023 (MK-0777) is an anxiolytic drug with a novel chemical structure, which is used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. It is a subtype-selective, mixed allosteric modular at the benzodiazepine location on GABAA receptors, where it acts as a partial agonist at the α2 and α3 subtypes, but as a silent antagonist at α1 and α5 subtypes. It has primarily anxiolytic and anticonvulsant effects in animal tests, but with no sedative effects even at 50 times the effective anxiolytic dose.
TP-13 is an anxiolytic drug with a novel chemical structure, which is used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. It is a subtype-selective partial agonist at GABAA receptors, binding selectively to GABAA receptor complexes bearing α2 and α3 subunits. It has modest anticonvulsant activity although less than that of diazepam, and its main effect is likely to be selective anxiolytic action, as seen with other related α2/3-preferring agonists such as L-838,417.
Biphenylindanone A is a research agent which acts as a potent and selective positive allosteric modulator for the group II metabotropic glutamate receptor subtype mGluR2.
Baicalein (5,6,7-trihydroxyflavone) is a flavone, a type of flavonoid, originally isolated from the roots of Scutellaria baicalensis and Scutellaria lateriflora. It is also reported in Oroxylum indicum and Thyme. It is the aglycone of baicalin. Baicalein is one of the active ingredients of Sho-Saiko-To, which is a Chinese classic herbal formula, and listed in Japan as Kampo medicine. As a Chinese herbal supplement, it is believed to enhance liver health.
SH-053-R-CH3-2′F is a drug used in scientific research which is a benzodiazepine derivative. It produces some of the same effects as other benzodiazepines, but is much more subtype-selective than most other drugs of this class, having high selectivity, binding affinity and efficacy at the α5 subtype of the GABAA receptor. This gives much tighter control of the effects produced, and so while SH-053-R-CH3-2′F retains sedative and anxiolytic effects, it does not cause ataxia at moderate doses. SH-053-R-CH3-2′F also blocks the nootropic effects of the α5-selective inverse agonist PWZ-029, so amnesia is also a likely side effect.
NS-11394 is a drug which acts as a subtype-selective positive allosteric modulator at GABAA receptors, with selectivity for the α3 and α5 subtypes. It has been researched as an analgesic for use in chronic or neuropathic pain.
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