ABSTRACT
The disclosed 3-phenyl-5-isothiazole carboxamides are potent allosteric antagonists of mGluR1 with generally good selectivity relative to the related group 1 receptor mGluR5. Pharmacokinetic properties of a member of this series (1R,2R)-N-(3-(4-methoxyphenyl)-4-methylisothiazol-5-yl)-2-methylcyclopropanecarboxamide (14) are good, showing acceptable plasma and brain exposure after oral dosing. Oral administration of isothiazole 14 gave robust activity in the formalin model of persistent pain which correlated with CNS receptor occupancy.
Subject(s)
Amides/chemical synthesis , Analgesics/chemical synthesis , Excitatory Amino Acid Antagonists/chemical synthesis , Pain/drug therapy , Receptors, Metabotropic Glutamate/antagonists & inhibitors , Thiazoles/chemical synthesis , Administration, Oral , Amides/administration & dosage , Amides/pharmacokinetics , Analgesics/administration & dosage , Analgesics/pharmacokinetics , Animals , Biological Availability , Brain/metabolism , Excitatory Amino Acid Antagonists/administration & dosage , Excitatory Amino Acid Antagonists/pharmacokinetics , Humans , Pain/metabolism , Pain Measurement , Rats , Rats, Sprague-Dawley , Receptors, Metabotropic Glutamate/metabolism , Stereoisomerism , Structure-Activity Relationship , Thiazoles/administration & dosage , Thiazoles/pharmacokineticsABSTRACT
Homologation and cyclization back to the chiral methine of compound 3 yields achiral 4,4-disubstituted piperidine privileged structures (e.g., 8a) useful in the construction of melanocortin 4 receptor (MC4R) ligands. The piperidine nitrogen was replaced with carbon, oxygen, sulfur, and sulfone with minor erosion of binding. The methyl cyclohexane substituent was the most potent while significant affinity was still seen for smaller lipophilic groups such as ethyl.
Subject(s)
Piperazines/chemical synthesis , Piperazines/metabolism , Receptor, Melanocortin, Type 4/metabolism , Binding Sites , Carbon/chemistry , Cyclohexanes/chemistry , Ligands , Oxygen/chemistry , Receptor, Melanocortin, Type 4/antagonists & inhibitors , Structure-Activity Relationship , Sulfones/chemistry , Sulfur/chemistryABSTRACT
A series of benzylic piperazines (e.g., 4 and 5) attached to an 'address element', the dipeptide H-D-Tic-D-p-Cl-Phe-OH, 3 has been identified as ligands for the melanocortin subtype-4 receptor (MC4R). We describe herein the structure-activity relationship (SAR) studies on the N-terminal residue of the 'address element'. Several novel dipeptides and reduced dipeptides with high MC4R binding affinities and selectivity emerged from this SAR study.
Subject(s)
Dipeptides/chemical synthesis , Dipeptides/pharmacology , Receptor, Melanocortin, Type 4/drug effects , Dipeptides/chemistry , Ligands , Molecular Structure , Piperazines/chemistry , Protein Binding , Receptor, Melanocortin, Type 4/chemistry , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Replacement of the aryl piperazine moiety in compound 1 with a variety of substituted benzylic piperazines (6) yields compounds that afford melanocortin receptor 4 (MCR4) activity. Analogs with ortho substitution on the aromatic ring afforded the highest affinity. Resolution of the stereocenter of the benzylic piperazine based privileged structure revealed that the R-enantiomer was more active.
Subject(s)
Benzene Derivatives/chemistry , Benzene Derivatives/metabolism , Piperazines/chemistry , Piperazines/metabolism , Receptors, Melanocortin/metabolism , Ligands , Molecular Structure , Piperazine , Receptors, Melanocortin/antagonists & inhibitors , Structure-Activity RelationshipABSTRACT
Substitution of the aryl sulfonamide moiety contained in MC4 agonist 1 with bicyclic heterocycles and aminotetralines produced compounds with MC4 activity. The heterocycles represent alternative privileged structures to that contained in 1. Compounds in which the polar group of the privileged structure was displayed in an endocyclic fashion were not as active as the parent agonist 1, while those with an exocyclic polar group afforded activity competitive with 1.
Subject(s)
Indoles/pharmacology , Quinolines/pharmacology , Receptors, Melanocortin/drug effects , Tetrahydronaphthalenes/pharmacology , Humans , Indoles/chemistry , Indoles/metabolism , Ligands , Molecular Structure , Quinolines/chemistry , Quinolines/metabolism , Receptors, Melanocortin/metabolism , Tetrahydronaphthalenes/chemistry , Tetrahydronaphthalenes/metabolismABSTRACT
The melanocortin receptors have been implicated as potential targets for a number of important therapeutic indications, including inflammation, sexual dysfunction, and obesity. We identified compound 1, an arylpiperazine attached to the dipeptide H-d-Tic-d-p-Cl-Phe-OH, as a novel melanocortin subtype-4 receptor (MC4R) agonist through iterative directed screening of nonpeptidyl G-protein-coupled receptor biased libraries. Structure-activity relationship (SAR) studies demonstrated that substitutions at the ortho position of the aryl ring improved binding and functional potency. For example, the o-isopropyl-substituted compound 29 (K(i) = 720 nM) possessed 9-fold better binding affinity compared to the unsubstituted aryl ring (K(i) = 6600 nM). Sulfonamide 39 (K(i) = 220 nM) fills this space with a polar substituent, resulting in a further 2-fold improvement in binding affinity. The most potent compounds such as the diethylamine 44 (K(i) = 60 nM) contain a basic group at this position. Basic heterocycles such as the imidazole 50 (K(i) = 110 nM) were similarly effective. We also demonstrated good oral bioavailability for sulfonamide 39.