ABSTRACT
Herein we report on the structure-based discovery of a C-2 hydroxyethyl moiety which provided consistently high levels of selectivity for JAK1 over JAK2 to the imidazopyrrolopyridine series of JAK1 inhibitors. X-ray structures of a C-2 hydroxyethyl analogue in complex with both JAK1 and JAK2 revealed differential ligand/protein interactions between the two isoforms and offered an explanation for the observed selectivity. Analysis of historical data from related molecules was used to develop a set of physicochemical compound design parameters to impart desirable properties such as acceptable membrane permeability, potent whole blood activity, and a high degree of metabolic stability. This work culminated in the identification of a highly JAK1 selective compound (31) exhibiting favorable oral bioavailability across a range of preclinical species and robust efficacy in a rat CIA model.
Subject(s)
Antirheumatic Agents/chemical synthesis , Heterocyclic Compounds, 3-Ring/chemical synthesis , Imidazoles/chemical synthesis , Janus Kinase 1/antagonists & inhibitors , Janus Kinase 2/antagonists & inhibitors , Pyridines/chemical synthesis , Pyrroles/chemical synthesis , Administration, Oral , Animals , Antirheumatic Agents/chemistry , Antirheumatic Agents/pharmacology , Arthritis, Experimental/drug therapy , Arthritis, Experimental/etiology , Biological Availability , Cell Membrane Permeability , Collagen , Crystallography, X-Ray , Dogs , Haplorhini , Heterocyclic Compounds, 3-Ring/chemistry , Heterocyclic Compounds, 3-Ring/pharmacology , Humans , Imidazoles/chemistry , Imidazoles/pharmacology , Isoenzymes/antagonists & inhibitors , Isoenzymes/chemistry , Janus Kinase 1/chemistry , Janus Kinase 2/chemistry , Madin Darby Canine Kidney Cells , Microsomes, Liver/metabolism , Models, Molecular , Molecular Structure , Pyridines/chemistry , Pyridines/pharmacology , Pyrroles/chemistry , Pyrroles/pharmacology , Rats , StereoisomerismABSTRACT
The identification of a novel series of 7,8,9,10-tetrahydro-(7,10-ethano)-1,2,4-triazolo[3,4-a]phthalazines as GABA(A)alpha5 inverse agonists, which have both binding and functional (efficacy) selectivity for the benzodiazepine binding site of alpha5- over alpha1-, alpha2-, and alpha3-containing GABA(A) receptor subtypes, is described. Binding selectivity was determined to a large part by the degree of planarity of the fused ring system whereas functional selectivity was dependent on the nature of the heterocycle at the 3-position of the triazolopyridazine ring. 3-Furan and 5-methylisoxazole were shown to be optimal for GABA(A)alpha5 functional selectvity. 3-(5-Methylisoxazol-3-yl)-6-(2-pyridyl)methyloxy-1,2,4-triazolo[3,4-a]phthalazine (43) was identified as a full inverse agonist at the GABA(A)alpha5 subtype with functional selectivity over the other GABA(A) receptor subtypes and good oral bioavailability.
Subject(s)
GABA-A Receptor Agonists , Isoxazoles/chemical synthesis , Phthalazines/chemical synthesis , Triazoles/chemical synthesis , Administration, Oral , Animals , Binding Sites , Biological Availability , Cell Line , Female , Humans , Isoxazoles/chemistry , Isoxazoles/pharmacology , Male , Maze Learning/drug effects , Oocytes/drug effects , Oocytes/physiology , Patch-Clamp Techniques , Phthalazines/chemistry , Phthalazines/pharmacokinetics , Phthalazines/pharmacology , Protein Subunits/agonists , Radioligand Assay , Rats , Structure-Activity Relationship , Triazoles/pharmacokinetics , Triazoles/pharmacology , Xenopus laevisABSTRACT
Nonselective inverse agonists at the gamma-aminobutyric acid(A) (GABA-A) benzodiazepine binding site have cognition-enhancing effects in animals but are anxiogenic and can precipitate convulsions. Herein, we describe novel GABA-A alpha5 subtype inverse agonists leading to the identification of 16 as an orally active, functionally selective compound that enhances cognition in animals without anxiogenic or convulsant effects. Compounds of this type may be useful in the symptomatic treatment of memory impairment associated with Alzheimer's disease and related dementias.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/chemical synthesis , GABA-A Receptor Agonists , Nootropic Agents/chemical synthesis , Phthalazines/chemical synthesis , Triazoles/chemical synthesis , Animals , Binding, Competitive , Biological Availability , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Convulsants/chemical synthesis , Convulsants/chemistry , Convulsants/pharmacology , Dogs , Humans , Macaca mulatta , Mice , Nootropic Agents/chemistry , Nootropic Agents/pharmacology , Oocytes/metabolism , Patch-Clamp Techniques , Phthalazines/chemistry , Phthalazines/pharmacology , Radioligand Assay , Rats , Receptors, GABA-A/physiology , Structure-Activity Relationship , Triazoles/chemistry , Triazoles/pharmacology , Xenopus laevisABSTRACT
In pursuit of a GABA(A) alpha5-subtype-selective inverse agonist to enhance cognition, a series of 6,7-dihydro-2-benzothiophen-4(5H)-ones has been identified as a novel class of GABA(A) receptor ligands. These thiophenes have higher binding affinity for the GABA(A) alpha5 receptor subtype compared to the GABA(A) alpha1, alpha2, and alpha3 subtypes, and several analogues exhibit high GABA(A) alpha5 receptor inverse agonism. 6,6-Dimethyl-3-(2-hydroxyethyl)thio-1-(thiazol-2-yl)-6,7-dihydro-2-benzothiophen-4(5H)-one (43) has been identified as a full inverse agonist at the GABA(A) alpha5 receptor and is functionally selective over the other major GABA(A) receptor subtypes. 43 readily penetrates into the CNS to give selective occupancy of GABA(A) alpha5 receptors. In addition, 43 enhances cognitive performance in rats in the delayed 'matching-to-place' Morris water maze test-a hippocampal-dependent memory task-without the convulsant or proconvulsant activity associated with nonselective, GABA(A) receptor inverse agonists.
Subject(s)
Cognition/drug effects , GABA Agonists/chemical synthesis , Nootropic Agents/chemical synthesis , Receptors, GABA-A/drug effects , Thiazoles/chemical synthesis , Thiophenes/chemical synthesis , Animals , Brain/metabolism , Cell Line , Female , GABA Agonists/adverse effects , GABA Agonists/pharmacology , Hippocampus/physiology , Humans , In Vitro Techniques , Ligands , Male , Maze Learning/drug effects , Memory/drug effects , Mice , Nootropic Agents/adverse effects , Nootropic Agents/pharmacology , Oocytes/drug effects , Oocytes/physiology , Patch-Clamp Techniques , Protein Subunits , Radioligand Assay , Rats , Seizures/chemically induced , Structure-Activity Relationship , Thiazoles/adverse effects , Thiazoles/pharmacology , Thiophenes/adverse effects , Thiophenes/pharmacology , Xenopus laevisABSTRACT
A new synthetic approach to tricyclic pyridones bearing a fused seven-membered ring is described. These compounds exhibit atropisomerism and exist in enantiomeric forms. Chiral HPLC separation of the enantiomers has allowed the rates of racemization to be measured and hence the free energy barrier for flipping the seven-membered ring to be deduced. Introduction of a further element of planar chirality leads to diastereomeric atropisomerism. The rate of interconversion of the diastereomers has been quantified by 2D EXSY NMR spectroscopy allowing a full description of the conformational dynamics of the system.
Subject(s)
Combinatorial Chemistry Techniques , Pyridones/chemical synthesis , Algorithms , Chromatography, High Pressure Liquid , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Conformation , Molecular Structure , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Nonselective inverse agonists at the benzodiazepine binding site on the GABA-A chloride ion channel enhance cognitive performance in animals but cannot be used in the treatment of cognitive disorders because of anxiogenic and convulsant side effects. We have identified a novel series of GABA-A alpha5 receptor ligands during our search for alpha5 receptor inverse agonists as potential cognition enhancers. In particular, 6,6-dimethyl-3-(2-hydroxyethyl)thio-1-(thiazol-2-yl)-6,7-dihydro-2-benzothiophen-4(5H)-one (26) has been identified as a functionally selective GABA-A alpha5 inverse agonist.
