ABSTRACT
Pyrazolines 7-10 were designed as novel CB(1) receptor antagonists, which exhibited improved turbidimetric aqueous solubilities. On the basis of their extended CB(1) antagonist pharmacophore, hybrid molecules exhibiting cannabinoid CB(1) receptor antagonistic as well as acetylcholinesterase (AChE) inhibiting activities were designed. The target compounds 12, 13, 20, and 21 are based on 1 (tacrine) as the AChE inhibitor (AChEI) pharmacophore and two different CB(1) antagonistic pharmacophores. The imidazole-based 20 showed high CB(1) receptor affinity (48 nM) in combination with high CB(1)/CB(2) receptor subtype selectivity (>20-fold) and elicited equipotent AChE inhibitory activity as 1. Molecular modeling studies revealed the presence of a binding pocket in the AChE enzyme which nicely accommodates the CB(1) pharmacophores of the target compounds 12, 13, 20, and 21.
Subject(s)
Acetylcholinesterase/chemistry , Cholinesterase Inhibitors/chemical synthesis , Cholinesterase Inhibitors/pharmacology , Drug Design , Receptor, Cannabinoid, CB1/antagonists & inhibitors , Receptor, Cannabinoid, CB2/antagonists & inhibitors , Tacrine/analogs & derivatives , Tacrine/chemistry , Animals , CHO Cells , Cannabinoids/metabolism , Cells, Cultured , Cholinesterase Inhibitors/chemistry , Cricetinae , Cricetulus , Crystallography, X-Ray , Humans , Kidney/cytology , Kidney/drug effects , Models, Molecular , Molecular Structure , Protein Conformation , Structure-Activity Relationship , Tacrine/chemical synthesis , Tacrine/pharmacologyABSTRACT
Series of thiazoles, triazoles, and imidazoles were designed as bioisosteres, based on the 1,5-diarylpyrazole motif that is present in the potent CB(1) receptor antagonist rimonabant (SR141716A, 1). A number of target compounds was synthesized and evaluated in cannabinoid (hCB(1) and hCB(2)) receptor assays. The thiazoles, triazoles, and imidazoles elicited in vitro( )()CB(1) antagonistic activities and in general exhibited considerable CB(1) vs CB(2) receptor subtype selectivities, thereby demonstrating to be cannabinoid bioisosteres of the original diarylpyrazole class. Some key representatives in the imidazole series showed potent pharmacological in vivo activities after oral administration in both a CB agonist-induced hypotension model and a CB agonist-induced hypothermia model. Molecular modeling studies showed a close three-dimensional structural overlap between the key compound 62 and rimonabant. A structure-activity relationship (SAR) study revealed a close correlation between the biological results in the imidazole and pyrazole series.
Subject(s)
Imidazoles/chemical synthesis , Piperidines/chemistry , Piperidines/chemical synthesis , Pyrazoles/chemistry , Receptor, Cannabinoid, CB1/antagonists & inhibitors , Thiazoles/chemical synthesis , Triazoles/chemical synthesis , Administration, Oral , Animals , CHO Cells , Cricetinae , Cricetulus , Cyclohexanols/antagonists & inhibitors , Hypotension/chemically induced , Hypothermia/chemically induced , Imidazoles/chemistry , Imidazoles/pharmacology , Mice , Models, Molecular , Molecular Conformation , Piperidines/pharmacology , Pyrazoles/pharmacology , Radioligand Assay , Rats , Receptor, Cannabinoid, CB1/agonists , Receptor, Cannabinoid, CB2/drug effects , Rimonabant , Stereoisomerism , Structure-Activity Relationship , Thiazoles/chemistry , Thiazoles/pharmacology , Triazoles/chemistry , Triazoles/pharmacologyABSTRACT
A series of novel 3,4-diarylpyrazolines was synthesized and evaluated in cannabinoid (hCB(1) and hCB(2)) receptor assays. The 3,4-diarylpyrazolines elicited potent in vitro CB(1) antagonistic activities and in general exhibited high CB(1) vs CB(2) receptor subtype selectivities. Some key representatives showed potent pharmacological in vivo activities after oral dosing in both a CB agonist-induced blood pressure model and a CB agonist-induced hypothermia model. Chiral separation of racemic 67, followed by crystallization and an X-ray diffraction study, elucidated the absolute configuration of the eutomer 80 (SLV319) at its C(4) position as 4S. Bioanalytical studies revealed a high CNS-plasma ratio for the development candidate 80. Molecular modeling studies showed a relatively close three-dimensional structural overlap between 80 and the known CB(1) receptor antagonist rimonabant (SR141716A). Further analysis of the X-ray diffraction data of 80 revealed the presence of an intramolecular hydrogen bond that was confirmed by computational methods. Computational models and X-ray diffraction data indicated a different intramolecular hydrogen bonding pattern in the in vivo inactive compound 6. In addition, X-ray diffraction studies of 6 revealed a tighter intermolecular packing than 80, which also may contribute to its poorer absorption in vivo. Replacement of the amidine -NH(2) moiety with a -NHCH(3) group proved to be the key change for gaining oral biovailability in this series of compounds leading to the identification of 80.
