ABSTRACT
Agonism of the 5-HT2C receptor represents one of the most well-studied and clinically proven mechanisms for pharmacological weight reduction. Selectivity over the closely related 5-HT2A and 5-HT2B receptors is critical as their activation has been shown to lead to undesirable side effects and major safety concerns. In this communication, we report the development of a new screening paradigm that utilizes an active site mutant D134A (D3.32) 5-HT2C receptor to identify atypical agonist structures. We additionally report the discovery and optimization of a novel class of nonbasic heterocyclic amide agonists of 5-HT2C. SAR investigations around the screening hits provided a diverse set of potent agonists at 5-HT2C with high selectivity over the related 5-HT2A and 5-HT2B receptor subtypes. Further optimization through replacement of the amide with a variety of five- and six-membered heterocycles led to the identification of 6-(1-ethyl-3-(quinolin-8-yl)-1H-pyrazol-5-yl)pyridazin-3-amine (69). Oral administration of 69 to rats reduced food intake in an ad libitum feeding model, which could be completely reversed by a selective 5-HT2C antagonist.
Subject(s)
Arginine/analogs & derivatives , Flavones/chemistry , Receptor, Serotonin, 5-HT2C/metabolism , Serotonin 5-HT2 Receptor Agonists/chemistry , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics , Animals , Arginine/chemical synthesis , Arginine/chemistry , Arginine/pharmacology , Brain/metabolism , Caco-2 Cells , Cell Membrane Permeability , Feeding Behavior/drug effects , Flavones/chemical synthesis , Flavones/pharmacology , HEK293 Cells , Humans , Male , Membranes, Artificial , Mice, Knockout , Microsomes, Liver/metabolism , Mutation , Rats, Sprague-Dawley , Receptor, Serotonin, 5-HT2A/metabolism , Receptor, Serotonin, 5-HT2B/metabolism , Receptor, Serotonin, 5-HT2C/genetics , Serotonin 5-HT2 Receptor Agonists/chemical synthesis , Serotonin 5-HT2 Receptor Agonists/pharmacokinetics , Serotonin 5-HT2 Receptor Agonists/pharmacology , Structure-Activity RelationshipABSTRACT
The metabotropic glutamate receptor 5 (mGluR5) is an attractive target for the treatment of schizophrenia due to its role in regulating glutamatergic signaling in association with the N-methyl-d-aspartate receptor (NMDAR). We describe the synthesis of 1H-pyrazolo[3,4-b]pyridines and their utility as mGluR5 positive allosteric modulators (PAMs) without inherent agonist activity. A facile and convergent synthetic route provided access to a structurally diverse set of analogues that contain neither the aryl-acetylene-aryl nor aryl-methyleneoxy-aryl elements, the predominant structural motifs described in the literature. Binding studies suggest that members of our new chemotype do not engage the receptor at the MPEP and CPPHA mGluR5 allosteric sites. SAR studies culminated in the first non-MPEP site PAM, 1H-pyrazolo[3,4-b]pyridine 31 (BMT-145027), to improve cognition in a preclinical rodent model of learning and memory.
ABSTRACT
The muscarinic acetylcholine receptor subtype 1 (M1) receptors play an important role in cognition and memory, and are considered to be attractive targets for the development of novel medications to treat cognitive impairments seen in schizophrenia and Alzheimer's disease. Indeed, the M1 agonist xanomeline has been shown to produce beneficial cognitive effects in both Alzheimer's disease and schizophrenia patients. Unfortunately, the therapeutic utility of xanomeline was limited by cholinergic side effects (sweating, salivation, gastrointestinal distress), which are believed to result from nonselective activation of other muscarinic receptor subtypes such as M2 and M3. Therefore, drug discovery efforts targeting the M1 receptor have focused on the discovery of compounds with improved selectivity profiles. Recently, allosteric M1 receptor ligands have been described, which exhibit excellent selectivity for M1 over other muscarinic receptor subtypes. In the current study, the following three compounds with mixed agonist/positive allosteric modulator activities that are highly functionally selective for the M1 receptor were tested in rats, dogs, and cynomologous monkeys: (3-((1S,2S)-2-hydrocyclohexyl)-6-((6-(1-methyl-1H-pyrazol-4-yl)pyridin-3-yl)methyl)benzo[h]quinazolin-4(3H)-one; 1-((4-cyano-4-(pyridin-2-yl)piperidin-1-yl)methyl)-4-oxo-4H-quinolizine-3-carboxylic acid; and (R)-ethyl 3-(2-methylbenzamido)-[1,4'-bipiperidine]-1'-carboxylate). Despite their selectivity for the M1 receptor, all three compounds elicited cholinergic side effects such as salivation, diarrhea, and emesis. These effects could not be explained by activity at other muscarinic receptor subtypes, or by activity at other receptors tested. Together, these results suggest that activation of M1 receptors alone is sufficient to produce unwanted cholinergic side effects such as those seen with xanomeline. This has important implications for the development of M1 receptor-targeted therapeutics since it suggests that dose-limiting cholinergic side effects still reside in M1 receptor selective activators.
Subject(s)
Muscarinic Agonists/metabolism , Muscarinic Agonists/pharmacology , Receptor, Muscarinic M1/agonists , Receptor, Muscarinic M1/metabolism , Animals , CHO Cells , Cricetinae , Cricetulus , Dogs , Dose-Response Relationship, Drug , Humans , Macaca fascicularis , Male , Mice , Rats , Rats, Sprague-DawleyABSTRACT
The continued evolution of our understanding of G protein-coupled receptor (GPCR) signaling has revealed new opportunities for drug discovery. Specifically, biased agonism at GPCRs and allosteric modulation of GPCRs both represent emerging areas of GPCR biology that hold promise for the development of novel GPCR-targeted therapeutics that may provide greater therapeutic efficacy and/or improved side-effect profiles. To obtain initial chemical leads, high-throughput screening (HTS) of a large compound library for the desired activity is often deployed during the early stages of a discovery program. The identification of allosteric modulators, in particular, poses significant challenges for HTS. We describe several HTS protocols designed for the identification of GPCR ligands, with a particular focus on the identification of allosteric modulators.
Subject(s)
Drug Evaluation, Preclinical/methods , High-Throughput Screening Assays/methods , Receptors, G-Protein-Coupled/chemistry , Receptors, G-Protein-Coupled/metabolism , Allosteric Regulation/drug effects , Calcium/metabolism , Cell Line , Receptors, G-Protein-Coupled/agonistsABSTRACT
Depression is a serious illness that affects millions of patients. Current treatments are associated with a number of undesirable side effects. Neurokinin 1 receptor (NK1R) antagonists have recently been shown to potentiate the antidepressant effects of serotonin-selective reuptake inhibitors (SSRIs) in a number of animal models. Herein we describe the optimization of a biaryl chemotype to provide a series of potent dual NK1R antagonists/serotonin transporter (SERT) inhibitors. Through the choice of appropriate substituents, the SERT/NK1R ratio could be tuned to afford a range of target selectivity profiles. This effort culminated in the identification of an analog that demonstrated oral bioavailability, favorable brain uptake, and efficacy in the gerbil foot tap model. Ex vivo occupancy studies with compound 58 demonstrated the ability to maintain NK1 receptor saturation (>88% occupancy) while titrating the desired level of SERT occupancy (11-84%) via dose selection.
Subject(s)
Biphenyl Compounds/chemistry , Biphenyl Compounds/pharmacology , Neurokinin-1 Receptor Antagonists/chemistry , Neurokinin-1 Receptor Antagonists/pharmacology , Selective Serotonin Reuptake Inhibitors/chemistry , Selective Serotonin Reuptake Inhibitors/pharmacology , Animals , Antidepressive Agents/chemistry , Antidepressive Agents/pharmacokinetics , Antidepressive Agents/pharmacology , Biphenyl Compounds/pharmacokinetics , Brain/drug effects , Brain/metabolism , Depression/drug therapy , Depression/metabolism , Gerbillinae , Humans , Neurokinin-1 Receptor Antagonists/pharmacokinetics , Serotonin/metabolism , Serotonin Plasma Membrane Transport Proteins/metabolism , Selective Serotonin Reuptake Inhibitors/pharmacokineticsABSTRACT
Modulating GPR88 activity is suggested to have therapeutic utility in the treatment of CNS disorders, such as schizophrenia. This Letter will describe the discovery and SAR development of a class of potent GPR88 agonists.
Subject(s)
Amides/pharmacology , Amines/pharmacology , Central Nervous System Diseases/drug therapy , Drug Discovery , Receptors, G-Protein-Coupled/agonists , Amides/chemical synthesis , Amides/chemistry , Amines/chemical synthesis , Amines/chemistry , Dose-Response Relationship, Drug , Humans , Molecular Structure , Structure-Activity RelationshipABSTRACT
Small molecule modulators of GPR88 activity (agonists, antagonists, or modulators) are of interest as potential agents for the treatment of a variety of psychiatric disorders including schizophrenia. A series of phenylglycinol and phenylamine analogs have been prepared and evaluated for their GPR88 agonist activity and pharmacokinetic (PK) properties.
Subject(s)
Amines/pharmacology , Drug Design , Ethanolamines/pharmacology , Receptors, G-Protein-Coupled/agonists , Amines/chemical synthesis , Amines/chemistry , Dose-Response Relationship, Drug , Ethanolamines/chemical synthesis , Ethanolamines/chemistry , HEK293 Cells , Humans , Molecular Structure , Structure-Activity RelationshipABSTRACT
A series of 4-bicyclic heteroaryl 1,2,3,4-tetrahydroisoquinoline inhibitors of the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT) was discovered. The synthesis and structure-activity relationship (SAR) of these triple reuptake inhibitors (TRIs) will be discussed. Compound 10i (AMR-2), a very potent inhibitor of SERT, NET, and DAT, showed efficacy in the rat forced-swim and mouse tail suspension models with minimum effective doses of 0.3 and 1 mg/kg (po), respectively. At efficacious doses in these assays, 10i exhibited substantial occupancy levels at the three transporters in both rat and mouse brain. The study of the metabolism of 10i revealed the formation of a significant active metabolite, compound 13.
ABSTRACT
Comprehensive structure activity relationship (SAR) studies were conducted on a focused screening hit, 2-(methylthio)-3-(phenylsulfonyl)-4H-pyrido[1,2-a]pyrimidin-4-imine (1, IC50: 4.0 nM), as 5-HT6 selective antagonists. Activity was improved some 2-4 fold when small, electron-donating groups were added to the central core as observed in 19, 20 and 26. Molecular docking of key compounds in a homology model of the human 5-HT6 receptor was used to rationalize our structure-activity relationship (SAR) findings. In pharmacokinetic experiments, compound 1 displayed good brain uptake in rats following intra-peritoneal administration, but limited oral bioavailability.
Subject(s)
Alzheimer Disease/drug therapy , Imines/pharmacokinetics , Receptors, Serotonin/therapeutic use , Animals , Humans , Imines/pharmacology , Molecular Docking Simulation , Rats , Structure-Activity RelationshipABSTRACT
Cyclopentylamine 4 was identified as a potent dual NK1R antagonist-SERT inhibitor. This compound demonstrated significant oral activity in the gerbil forced swimming test, suggesting that dual NK1R antagonists-SERT inhibitors may be useful in treating depression disorders.
Subject(s)
Cyclopentanes/chemistry , Neurokinin-1 Receptor Antagonists/chemistry , Receptors, Neurokinin-1/chemistry , Selective Serotonin Reuptake Inhibitors/chemistry , Serotonin Plasma Membrane Transport Proteins/chemistry , Administration, Oral , Animals , Crystallography, X-Ray , Cyclopentanes/chemical synthesis , Cyclopentanes/pharmacology , Drug Evaluation, Preclinical , Gerbillinae , Humans , Molecular Conformation , Motor Activity/drug effects , Neurokinin-1 Receptor Antagonists/metabolism , Neurokinin-1 Receptor Antagonists/pharmacology , Protein Binding , Receptors, Neurokinin-1/metabolism , Serotonin Plasma Membrane Transport Proteins/metabolism , Selective Serotonin Reuptake Inhibitors/chemical synthesis , Selective Serotonin Reuptake Inhibitors/pharmacologyABSTRACT
This report describes the synthesis, structure-activity relationships and activity of piperidine, homopiperidine, and azocane derivatives combining NK1 receptor (NK1R) antagonism and serotonin reuptake transporter (SERT) inhibition. Our studies culminated in the discovery of piperidine 2 and homopiperidine 8 as potent dual NK1R antagonists-SERT inhibitors. Compound 2 demonstrated significant activity in the gerbil forced swimming test, suggesting that dual NK1R antagonists-SERT inhibitors may be useful in treating depression disorders.
Subject(s)
Neurokinin-1 Receptor Antagonists/chemistry , Neurokinin-1 Receptor Antagonists/pharmacology , Piperidines/chemistry , Piperidines/pharmacology , Selective Serotonin Reuptake Inhibitors/chemistry , Selective Serotonin Reuptake Inhibitors/pharmacology , Antidepressive Agents/chemistry , Antidepressive Agents/pharmacology , Astrocytes/cytology , Astrocytes/drug effects , Cell Line , HEK293 Cells , Humans , Piperidines/chemical synthesis , Receptors, Neurokinin-1/metabolism , Serotonin Plasma Membrane Transport Proteins/biosynthesis , Serotonin Plasma Membrane Transport Proteins/genetics , Selective Serotonin Reuptake Inhibitors/chemical synthesis , Structure-Activity RelationshipABSTRACT
High throughput screening led to the identification of a novel series of quinolone α7 nicotinic acetylcholine receptor (nAChR) agonists. Optimization of an HTS hit (1) led to 4-phenyl-1-(quinuclidin-3-ylmethyl)quinolin-2(1H)-one, which was found to be potent and selective. Poor brain penetrance in this series was attributed to transporter-mediated efflux, which was in turn due to high pKa. A novel 4-fluoroquinuclidine significantly lowered the pKa of the quinuclidine moiety, reducing efflux as measured by a Caco-2 assay.
Subject(s)
Nicotinic Agonists/chemistry , Quinolones/chemistry , Receptors, Nicotinic/chemistry , Animals , Caco-2 Cells , Drug Evaluation, Preclinical , Humans , Kinetics , Nicotinic Agonists/chemical synthesis , Nicotinic Agonists/metabolism , Quinolones/chemical synthesis , Quinolones/metabolism , Rats , Receptors, Nicotinic/metabolism , Structure-Activity Relationship , alpha7 Nicotinic Acetylcholine ReceptorABSTRACT
A series of substituted pyridines, ether linked to a phenylpiperidine core were optimized for dual NK(1)/SERT affinity. Optimization based on NK(1)/SERT binding affinities, and minimization of off-target ion channel activity lead to the discovery of compound 44. In vivo evaluation of 44 in the gerbil forced swim test (a depression model), and ex-vivo NK(1)/SERT receptor occupancy data support the potential of a dual acting compound for the treatment of depression.
Subject(s)
Depression/drug therapy , Drug Design , Neurokinin-1 Receptor Antagonists , Pyridines/chemical synthesis , Serotonin Antagonists , Animals , Disease Models, Animal , Gerbillinae , Inhibitory Concentration 50 , Molecular Structure , Pyridines/chemistry , Pyridines/therapeutic use , Serotonin Antagonists/chemical synthesis , Serotonin Antagonists/chemistry , Serotonin Antagonists/therapeutic useABSTRACT
In recent years, the increased use of cell-based functional assays for G protein-coupled receptors in high-throughput screening has enabled the design of robust assays to identify allosteric modulators (AMs) in addition to the more traditional orthosteric agonists and antagonists. In this article, the authors describe a screening format able to identify all ligand types using a triple-add assay that measures changes in cytosolic calcium concentration with three separate additions and reads in the same assay plate. This triple-add assay captures more small molecule ligand types than previously described assay formats without a significant increase in screening cost. Finally, the customizability of the triple-add assay to suit the needs of various AM screening programs is demonstrated.
Subject(s)
Calcium Signaling/physiology , High-Throughput Screening Assays/methods , Receptors, G-Protein-Coupled/physiology , Allosteric Regulation/physiology , Animals , CHO Cells , Cricetinae , Cricetulus , Humans , Ligands , Protein Binding/physiologyABSTRACT
Once considered a pharmacological curiosity, allosteric modulation of seven transmembrane domain G-protein-coupled receptors (GPCRs) has emerged as a potentially powerful means to affect receptor function for therapeutic purposes. Allosteric modulators, which interact with binding sites topologically distinct from the orthosteric ligand binding sites, can potentially provide improved selectivity and safety, along with maintenance of spatial and temporal aspects of GPCR signaling. Accordingly, drug discovery efforts for GPCRs have increasingly focused on the identification of allosteric modulators. This review is devoted to an examination of the strategies, challenges, and opportunities for high-throughput screening for allosteric modulators of GPCRs, with particular focus on the identification of positive allosteric modulators.
Subject(s)
Allosteric Regulation/physiology , Drug Discovery/methods , Receptors, G-Protein-Coupled/chemistry , Receptors, G-Protein-Coupled/metabolism , Allosteric Regulation/drug effects , Allosteric Site/drug effects , Allosteric Site/physiology , Animals , Drug Discovery/trends , Humans , LigandsABSTRACT
A series of novel oxime carbamates have been identified as potent inhibitors of the key regulatory enzyme of the endocannabinoid signaling system, fatty acid amide hydrolase (FAAH). In this Letter, the rationale behind the discovery and the biological evaluations of this novel class of FAAH inhibitors are presented. Both in vitro and in vivo results of selected targets are discussed, along with inhibition kinetics and molecular modeling studies.(1).
Subject(s)
Amidohydrolases/antagonists & inhibitors , Carbamates/chemistry , Drug Discovery/methods , Oximes/chemistry , Oximes/pharmacology , Amidohydrolases/physiology , Animals , Cannabinoid Receptor Modulators/physiology , Carbamates/metabolism , Carbamates/pharmacology , Cell Line , Crystallography, X-Ray , Humans , Oximes/metabolism , Protein Binding/physiology , Protein Structure, Tertiary , Rats , Signal Transduction/drug effects , Signal Transduction/physiologyABSTRACT
A series of hybrid molecules containing the cyclopropylmethylamino side chain found in homotryptamine (1S,2S)-2c and an isosteric heteroaryl or naphthyl core were prepared and their binding affinities for the human serotonin transporter determined. The most potent isosteres were CN-substituted naphthalenes. These results demonstrate that isosteric aromatic cores which lack an H-bond donor site may be substituted for the indole nucleus without substantial loss in hSERT binding.
Subject(s)
Heterocyclic Compounds/chemistry , Heterocyclic Compounds/pharmacology , Selective Serotonin Reuptake Inhibitors/chemistry , Selective Serotonin Reuptake Inhibitors/pharmacology , Tryptamines/chemistry , Dopamine Plasma Membrane Transport Proteins/antagonists & inhibitors , Dopamine Plasma Membrane Transport Proteins/metabolism , Heterocyclic Compounds/chemical synthesis , Humans , Inhibitory Concentration 50 , Molecular Conformation , Norepinephrine Plasma Membrane Transport Proteins/antagonists & inhibitors , Norepinephrine Plasma Membrane Transport Proteins/metabolism , Selective Serotonin Reuptake Inhibitors/chemical synthesis , Structure-Activity RelationshipABSTRACT
A class of bisarylimidazole derivatives are identified as potent inhibitors of the enzyme fatty acid amide hydrolase (FAAH). Compound 17 (IC(50)=2 nM) dose-dependently (0.1-10mg/kg, iv) potentiates the effects of exogenous anandamide (1 mg/kg, iv) in a rat thermal escape test (Hargreaves test), and shows robust antinociceptive activity in animal models of persistent (formalin test) and neuropathic (Chung model) pain. Compound 17 (20 mg/kg, iv) demonstrates activity in the formalin test that is comparable to morphine (3mg/kg, iv), and is dose-dependently inhibited by the CB1 antagonist SR141716A. In the Chung model, compound 17 shows antineuropathic effects similar to high-dose (100 mg/kg) gabapentin. FAAH inhibition shows potential utility for the clinical treatment of persistent and neuropathic pain.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Analgesics/pharmacology , Enzyme Inhibitors/pharmacology , Imidazoles/pharmacology , Pain Measurement/drug effects , Amines/pharmacology , Analgesics/administration & dosage , Animals , Cyclohexanecarboxylic Acids/pharmacology , Dose-Response Relationship, Drug , Enzyme Inhibitors/administration & dosage , Gabapentin , Humans , Imidazoles/chemistry , Mice , Mice, Knockout , Morphine/pharmacology , Pain Measurement/methods , Piperidines/antagonists & inhibitors , Piperidines/metabolism , Pyrazoles/antagonists & inhibitors , Pyrazoles/metabolism , Rats , Receptor, Cannabinoid, CB1/antagonists & inhibitors , Receptor, Cannabinoid, CB1/metabolism , Rimonabant , gamma-Aminobutyric Acid/pharmacologyABSTRACT
BACKGROUND: Aripiprazole (7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butoxy}-3,4-dihydro-2(1H)-quinolinone) is a novel antipsychotic with a mechanism of action that differs from current typical and atypical antipsychotics. Aripiprazole interacts with a range of receptors, including serotonin [5-hydroxytryptamine (5-HT)] and dopamine receptors. MATERIALS AND METHODS: This study examined aripiprazole's interactions with 5-HT systems in vitro and in vivo to further clarify its pharmacologic properties. RESULTS: Aripiprazole produced increases in [(35)S]GTPgammaS binding to rat hippocampal membranes. Its potency (pEC(50) = 7.2) was similar to that of ziprasidone (7.1) and greater than that of 5-HT (6.7) and buspirone (6.4), a 5-HT(1A)-receptor partial agonist, whereas its intrinsic activity was similar to that of ziprasidone and buspirone. The stimulatory effect of aripiprazole was blocked by WAY-100635, a 5-HT(1A)-receptor antagonist. In in vivo electrophysiology studies, aripiprazole produced a dose-related reduction in the firing rate of 5-HT-containing dorsal raphe neurons in rats, which was both prevented and reversed by WAY-100635 administration. Aripiprazole showed a high affinity for human 5-HT(1A) receptors (K (i) = 4.2 nM) using parietal cortex membrane preparations. In membranes from cells expressing human recombinant receptors, aripiprazole bound with high affinity to 5-HT(2A) receptors (K (i) = 3.4 nM), moderate affinity to 5-HT(2C) (K (i) = 15 nM) and 5-HT(7) (K (i) = 39 nM) receptors, and low affinity to 5-HT(6) receptors (K (i) = 214 nM) and 5-HT transporter (K (i) = 98 nM). In addition, aripiprazole potently blocked 5-HT(2A)-receptor-mediated increases in intracellular Ca(2+) levels in a rat pituitary cell line (IC(50) = 11 nM). DISCUSSION: These results support a partial agonist activity for aripiprazole at 5-HT(1A) receptors in vitro and in vivo, and suggest important interactions with other 5-HT-receptor subtypes. This receptor activity profile may contribute to the antipsychotic activity of aripiprazole in humans.
Subject(s)
Antipsychotic Agents/pharmacology , Piperazines/pharmacology , Quinolones/pharmacology , Receptor, Serotonin, 5-HT1A/metabolism , Receptor, Serotonin, 5-HT2A/metabolism , Animals , Aripiprazole , CHO Cells , Calcium/metabolism , Cell Line , Cricetinae , Cricetulus , Dose-Response Relationship, Drug , Drug Interactions , Electrophysiology , Hippocampus/drug effects , Hippocampus/metabolism , Humans , Male , Neurons/drug effects , Neurons/physiology , Radioligand Assay , Raphe Nuclei/cytology , Raphe Nuclei/drug effects , Raphe Nuclei/physiology , Rats , Rats, Sprague-Dawley , Serotonin 5-HT1 Receptor Agonists , Serotonin 5-HT1 Receptor Antagonists , Serotonin 5-HT2 Receptor Agonists , Serotonin 5-HT2 Receptor Antagonists , Serotonin Antagonists/pharmacology , Serotonin Plasma Membrane Transport Proteins/metabolism , Serotonin Receptor Agonists/pharmacologyABSTRACT
(E)-3-(Benzenesulfonyl)-2-(methylsulfanyl)pyrido[1,2-a]pyrimidin-4-ylidenamine (7) was found to be a potent and selective 5-HT(6) antagonist. A one-step synthesis of this compound is described.