In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist

John R. Atack, Karen A. Maubach, Keith A. Wafford, Desmond O'Connor, A. David Rodrigues, David C. Evans, F. David Tattersall, Mark S. Chambers, Angus M. MacLeod, Wai Si Eng, Christine Ryan, Eric Hostetler, Sandra M. Sanabria, Raymond E. Gibson, Stephen Krause, H. Donald Burns, Richard J. Hargreaves, Nancy G B Agrawal, Ruth M. McKernan, M. Gail MurphyKevin Gingrich, Gerard R. Dawson, Donald G. Musson, Kevin J. Petty

Research output: Contribution to journalArticle

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Abstract

3-tert-Butyl-7-(5-methylisoxazol-3-yl)-2-(1-methyl-1H-1,2, 4-triazol-5-ylmethoxy)-pyrazolo[1,5-d][1,2,4]triazine (MRK-016) is a pyrazolotriazine with an affinity of between 0.8 and 1.5 nM for the benzodiazepine binding site of native rat brain and recombinant human α1-, α2-, α3-, and α5-containing GABAA receptors. It has inverse agonist efficacy selective for the α5 subtype, and this α5 inverse agonism is greater than that of the prototypic α5-selective compound 3-(5-methylisoxazol-3-yl)-6-[(1-methyl-1,2,3- triazol-4-hdyl)methyloxy]-1,2,4-triazolo[3,4-a]phthalazine (α5IA). Consistent with its greater α5 inverse agonism, MRK-016 increased long-term potentiation in mouse hippocampal slices to a greater extent than α5IA. MRK-016 gave good receptor occupancy after oral dosing in rats, with the dose required to produce 50% occupancy being 0.39 mg/kg and a corresponding rat plasma EC50 value of 15 ng/ml that was similar to the rhesus monkey plasma EC50 value of 21 ng/ml obtained using [ 11C]flumazenil positron emission tomography. In normal rats, MRK-016 enhanced cognitive performance in the delayed matching-to-position version of the Morris water maze but was not anxiogenic, and in mice it was not proconvulsant and did not produce kindling. MRK-016 had a short half-life in rat, dog, and rhesus monkey (0.3-0.5 h) but had a much lower rate of turnover in human compared with rat, dog, or rhesus monkey hepatocytes. Accordingly, in human, MRK-016 had a longer half-life than in preclinical species (∼3.5 h). Although it was well tolerated in young males, with a maximal tolerated single dose of 5 mg corresponding to an estimated occupancy in the region of 75%, MRK-016 was poorly tolerated in elderly subjects, even at a dose of 0.5 mg, which, along with its variable human pharmacokinetics, precluded its further development.

Original languageEnglish (US)
Pages (from-to)470-484
Number of pages15
JournalJournal of Pharmacology and Experimental Therapeutics
Volume331
Issue number2
DOIs
StatePublished - Nov 2009

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GABA-A Receptors
Macaca mulatta
Half-Life
Dogs
Flumazenil
Maximum Tolerated Dose
In Vitro Techniques
MRK 016
Long-Term Potentiation
Benzodiazepines
Positron-Emission Tomography
Hepatocytes
Pharmacokinetics
Binding Sites
Water
Brain

ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

Cite this

In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist. / Atack, John R.; Maubach, Karen A.; Wafford, Keith A.; O'Connor, Desmond; Rodrigues, A. David; Evans, David C.; Tattersall, F. David; Chambers, Mark S.; MacLeod, Angus M.; Eng, Wai Si; Ryan, Christine; Hostetler, Eric; Sanabria, Sandra M.; Gibson, Raymond E.; Krause, Stephen; Burns, H. Donald; Hargreaves, Richard J.; Agrawal, Nancy G B; McKernan, Ruth M.; Murphy, M. Gail; Gingrich, Kevin; Dawson, Gerard R.; Musson, Donald G.; Petty, Kevin J.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 331, No. 2, 11.2009, p. 470-484.

Research output: Contribution to journalArticle

Atack, JR, Maubach, KA, Wafford, KA, O'Connor, D, Rodrigues, AD, Evans, DC, Tattersall, FD, Chambers, MS, MacLeod, AM, Eng, WS, Ryan, C, Hostetler, E, Sanabria, SM, Gibson, RE, Krause, S, Burns, HD, Hargreaves, RJ, Agrawal, NGB, McKernan, RM, Murphy, MG, Gingrich, K, Dawson, GR, Musson, DG & Petty, KJ 2009, 'In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist', Journal of Pharmacology and Experimental Therapeutics, vol. 331, no. 2, pp. 470-484. https://doi.org/10.1124/jpet.109.157636
Atack, John R. ; Maubach, Karen A. ; Wafford, Keith A. ; O'Connor, Desmond ; Rodrigues, A. David ; Evans, David C. ; Tattersall, F. David ; Chambers, Mark S. ; MacLeod, Angus M. ; Eng, Wai Si ; Ryan, Christine ; Hostetler, Eric ; Sanabria, Sandra M. ; Gibson, Raymond E. ; Krause, Stephen ; Burns, H. Donald ; Hargreaves, Richard J. ; Agrawal, Nancy G B ; McKernan, Ruth M. ; Murphy, M. Gail ; Gingrich, Kevin ; Dawson, Gerard R. ; Musson, Donald G. ; Petty, Kevin J. / In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist. In: Journal of Pharmacology and Experimental Therapeutics. 2009 ; Vol. 331, No. 2. pp. 470-484.
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title = "In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist",
abstract = "3-tert-Butyl-7-(5-methylisoxazol-3-yl)-2-(1-methyl-1H-1,2, 4-triazol-5-ylmethoxy)-pyrazolo[1,5-d][1,2,4]triazine (MRK-016) is a pyrazolotriazine with an affinity of between 0.8 and 1.5 nM for the benzodiazepine binding site of native rat brain and recombinant human α1-, α2-, α3-, and α5-containing GABAA receptors. It has inverse agonist efficacy selective for the α5 subtype, and this α5 inverse agonism is greater than that of the prototypic α5-selective compound 3-(5-methylisoxazol-3-yl)-6-[(1-methyl-1,2,3- triazol-4-hdyl)methyloxy]-1,2,4-triazolo[3,4-a]phthalazine (α5IA). Consistent with its greater α5 inverse agonism, MRK-016 increased long-term potentiation in mouse hippocampal slices to a greater extent than α5IA. MRK-016 gave good receptor occupancy after oral dosing in rats, with the dose required to produce 50{\%} occupancy being 0.39 mg/kg and a corresponding rat plasma EC50 value of 15 ng/ml that was similar to the rhesus monkey plasma EC50 value of 21 ng/ml obtained using [ 11C]flumazenil positron emission tomography. In normal rats, MRK-016 enhanced cognitive performance in the delayed matching-to-position version of the Morris water maze but was not anxiogenic, and in mice it was not proconvulsant and did not produce kindling. MRK-016 had a short half-life in rat, dog, and rhesus monkey (0.3-0.5 h) but had a much lower rate of turnover in human compared with rat, dog, or rhesus monkey hepatocytes. Accordingly, in human, MRK-016 had a longer half-life than in preclinical species (∼3.5 h). Although it was well tolerated in young males, with a maximal tolerated single dose of 5 mg corresponding to an estimated occupancy in the region of 75{\%}, MRK-016 was poorly tolerated in elderly subjects, even at a dose of 0.5 mg, which, along with its variable human pharmacokinetics, precluded its further development.",
author = "Atack, {John R.} and Maubach, {Karen A.} and Wafford, {Keith A.} and Desmond O'Connor and Rodrigues, {A. David} and Evans, {David C.} and Tattersall, {F. David} and Chambers, {Mark S.} and MacLeod, {Angus M.} and Eng, {Wai Si} and Christine Ryan and Eric Hostetler and Sanabria, {Sandra M.} and Gibson, {Raymond E.} and Stephen Krause and Burns, {H. Donald} and Hargreaves, {Richard J.} and Agrawal, {Nancy G B} and McKernan, {Ruth M.} and Murphy, {M. Gail} and Kevin Gingrich and Dawson, {Gerard R.} and Musson, {Donald G.} and Petty, {Kevin J.}",
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TY - JOUR

T1 - In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)- 2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor α5 subtype-selective inverse agonist

AU - Atack, John R.

AU - Maubach, Karen A.

AU - Wafford, Keith A.

AU - O'Connor, Desmond

AU - Rodrigues, A. David

AU - Evans, David C.

AU - Tattersall, F. David

AU - Chambers, Mark S.

AU - MacLeod, Angus M.

AU - Eng, Wai Si

AU - Ryan, Christine

AU - Hostetler, Eric

AU - Sanabria, Sandra M.

AU - Gibson, Raymond E.

AU - Krause, Stephen

AU - Burns, H. Donald

AU - Hargreaves, Richard J.

AU - Agrawal, Nancy G B

AU - McKernan, Ruth M.

AU - Murphy, M. Gail

AU - Gingrich, Kevin

AU - Dawson, Gerard R.

AU - Musson, Donald G.

AU - Petty, Kevin J.

PY - 2009/11

Y1 - 2009/11

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