Functional and binding kinetic studies make a distinction between OX1 and OX2 orexin receptor antagonists.
In this work the pharmacology and the receptor kinetics of the following orexin receptor antagonists SB-649868, ACT-078573, JNJ-10397049, MK-6096 and Roche-Cp were evaluated at human OX(1) and OX(2) orexin receptors by using functional and receptor binding assays. Kinetic analysis of the unlabeled ligands was carried out by indirect measurement according to the Motulski and Mahan's method as opposed to the direct measure by using labeled test compounds. All compounds antagonized orexin-A-induced inositol 1 phosphate (IP1) accumulation with the following pK(B) values: SB-649868 (OX(1)=9.67; OX(2)=9.64), ACT-078573 (OX(1)=8.44; OX(2)=9.02), JNJ-10397049 (OX(1)=5.97; OX(2)=8.35), MK-6096 (OX(1)=9.13; OX(2)=9.79) and Roche-Cp (OX(1)=7.18; OX(2)=8.83). They displaced the [(3)H]ACT-078573 receptor binding with the following pK(i) values: SB-649868 (OX(1)=9.27; OX(2)=8.91), ACT-078573 (OX(1)=7.80; OX(2)=9.12), JNJ-10397049 (OX(1)=5.18; OX(2)=8.10), MK-6096 (OX(1)=8.39; OX(2)=8.90) and Roche-Cp (OX(1)=6.65; OX(2)=8.54). From dissociation kinetic studies using [(3)H]ACT-078573, the calculated long half-life, (t(½)) supported the non-surmountability profile of SB-649868 (t(½)=35.91min) at OX(1) orexin receptor. Similarly, the long or moderately long t(½) values for ACT-078573 at OX(2) orexin receptor (t(½)=69.71min), MK-6096 (t(½)=17.70min), SB-649868 (t(½)=8.09min) and Roche-Cp (t(½)=5.79min) sustained their non-surmountable profile. JNJ-10397049 showed short t(½) values at both receptor subtypes (OX(1)t(½)=0.19min; OX(2)t(½)=0.60min) with surmountable antagonism.
Neurosciences Centre of Excellence for Drug Discovery, GlaxoSmithKline, Medicines Research Centre, 37135 Verona, Italy.
Stefania
S
Faedo
Elisabetta
E
Perdonà
Marinella
M
Antolini
Romano
R
di Fabio
Emilio
E
Merlo Pich
Mauro
M
Corsi
D000081:Acetamides / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001572:Benzofurans / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004146:Dioxanes / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007546:Isoquinolines / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D064446:Orexin Receptors; D010671:Phenylurea Compounds / Q000378:metabolism / Q000494:pharmacology; D010880:Piperidines / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011743:Pyrimidines / Q000378:metabolism / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D018013:Receptors, Neuropeptide / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism / Q000494:pharmacology
D000081:Acetamides; D001572:Benzofurans; D004146:Dioxanes; D007546:Isoquinolines; C524573:JNJ 10397049; C573816:MK-6096; C557781:N-((1-((5-(4-fluorophenyl)-2-methyl-4-thiazolyl)carbonyl)-2-piperidinyl)methyl)-4-benzofurancarboxamide; D064446:Orexin Receptors; D010671:Phenylurea Compounds; D010880:Piperidines; D011743:Pyrimidines; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D013844:Thiazoles; C519150:almorexant