Discovery of novel biaryl heterocyclic EP1 receptor antagonists

We describe the generation of novel EP(1) receptor antagonists by investigation of thiophene isosteres. In addition, we disclose preliminary in vitro and in vivo DMPK for selected compounds.     

2,3-Diarylthiophenes as selective EP1 receptor antagonists

The synthesis and the EP(1) receptor binding affinity of 2,3-diarylthiophene derivatives are described. The evaluation of the structure-activity relationship (SAR) in this series led to the identification of compounds 4, 7, and 12a, which exhibit high affinity for the human EP(1) receptor and a selectivity greater than 100-fold against the EP(2), EP(3), EP(4), DP, FP, and IP receptors and greater than 25-fold versus the TP receptor. These three antagonists present good pharmacokinetics in rats and significant differences in the way they are distributed in the brain.     

Discovery of new chemical leads for selective EP1 receptor antagonists

A series of 4-([2-[alkyl(phenylsulfonyl)amino]phenoxy]methyl)benzoic acids were identified as functional PGE(2) antagonists with selectivity for the EP1 receptor subtype starting from a chemical lead 1, which was found while screening our in-house compound library. Discovery of the optimized analogs 21-23 is presented here and structure-activity relationships (SAR) are also discussed.     

Identification of novel glycine sulfonamide antagonists for the EP1 receptor

A high-throughput screen targeting the EP(1) receptor identified non-acidic glycine sulfonamide derivative 2a with a pK(i) of 6.2. Analogue synthesis allowed a thorough investigation of the structure-activity relationship (SAR) and led to a 100-fold increase in recombinant potency.     

Structure-activity relationships of 1,5-biaryl pyrroles as EP1 receptor antagonists

The preliminary SAR of a series of novel 1,5-biaryl pyrrole EP1 receptor antagonists derived from compound 1 is described. Replacement of the benzyl group of 1 with isosteric groups was investigated. The most effective replacement was found to be the isobutyl group. The cyclopentylmethyl and cyclohexylmethyl groups were also effective benzyl replacements. The cyclohexylmethyl derivative 19 demonstrated the lowest metabolic clearance within this series. In addition, several high affinity substituted benzyl analogues were also identified. Compound 39 was found to have good bioavailability in rats and demonstrated efficacy in the established FCA preclinical model of inflammatory pain with a calculated ED50 of 9.2mg/kg.     

Discovery of heteroaryl sulfonamides as new EP1 receptor selective antagonists

4-({2-[Isobutyl(phenylsulfonyl)amino]-5-(trifluoromethyl)phenoxy}methyl)benzoic acid (1) is a functional PGE2 antagonist selective for EP1 receptor subtype. Analogs of 1, in which the phenyl-sulfonyl moiety has been replaced with more hydrophilic heteroarylsulfonyl moieties, exhibited more optimized antagonist activity, while some of them showed in vivo antagonist activity. Structure-activity relationship (SAR) studies are also presented.     

Identification of novel pyrazole acid antagonists for the EP1 receptor

The discovery, synthesis and structure-activity relationship (SAR) of a novel series of EP1 receptor antagonists is described. Pyrazole acid 4, identified from a chemical array, had desirable physicochemical properties, an excellent in vitro microsomal inhibition and cytochrome P450 (CYP450) profile and good exposure levels in blood. This compound had an ED50 of 1.3 mg/kg in a rat pain model. A range of more potent analogues in the in vitro assay was identified using efficient array chemistry. These EP1 antagonists have potential as agents in the treatment of PGE2 mediated pain.     

Optimization of sulfonamide derivatives as highly selective EP1 receptor antagonists

A series of 4-[(2-{isobutyl[(5-methyl-2-furyl)sulfonyl]amino}phenoxy)methyl]benzoic acids and 4-({2-[isobutyl(1,3-thiazol-2-ylsulfonyl)amino]phenoxy}methyl)benzoic acids were synthesized and evaluated for their EP receptor affinities and EP1 receptor antagonist activities. Further structural optimization was carried out to reduce inhibitory activity against hepatic cytochrome P450 isozymes, which could represent a harmful potential drug interaction. Selected compounds were also evaluated for their binding affinities to hTP, hDP, mFP, and hIP, and for their hEP1 receptor antagonist activities. The results of structure-activity relationship studies are also presented.     

Non-acidic pyrazole EP1 receptor antagonists with in vivo analgesic efficacy

Replacement of the carboxylic acid group in a series of previously described methylene-linked pyrazole EP(1) receptor antagonists led to the discovery of amide, reversed amide and carbamate derivatives. Two compounds, 10a and 10b, were identified as brain penetrant compounds and both demonstrated efficacy in the CFA model of inflammatory pain.     

Identification and optimization of novel 1,3,4-oxadiazole EP1 receptor antagonists

A novel series of oxadiazole EP1 receptor antagonists was identified by replacing the amide of a known glycine sulfonamide derivative with a 1,3,4-oxadiazole. Optimization of the substitution patterns on the three aromatic rings led to the identification of high affinity EP1 receptor antagonists. The derivative with highest affinity displayed a binding IC50 of 2.5 nM (pIC50 8.6).     

Non-imidazole heterocyclic histamine H3 receptor antagonists

Continued exploration of the SAR around the lead imidazopyridine histamine H(3) antagonist 1 has led to the discovery of several related series of heterocyclic histamine H(3) antagonists. The synthesis and SAR of indolizine, indole and pyrazolopyridine based compounds are now described.     

Discovery of a novel series of nonacidic benzofuran EP1 receptor antagonists

We describe the discovery and optimization of a novel series of benzofuran EP₁ antagonists, leading to the identification of 26d, a novel nonacidic EP₁ antagonist which demonstrated efficacy in preclinical models of chronic inflammatory pain.     

Discovery of novel, non-acidic 1,5-biaryl pyrrole EP1 receptor antagonists

Replacement of the carboxylic acid group in a series of previously described 1,5-biaryl pyrrole EP1 receptor antagonists led to the discovery of various novel non-acidic antagonists. Several analogues displayed high binding affinity and high binding efficiency indices.     

Discovery of brain penetrant, soluble, pyrazole amide EP1 receptor antagonists

We describe the discovery of a series of pyrazole amide EP₁ receptor antagonists with good aqueous solubility and CNS penetration. In order to achieve solubility we investigated the incorporation of a basic group in the region of the molecule previously occupied by a carboxylic acid, which was known to be a key element of the pharmacophore. This study led to the identification of compounds such as 4h, 4j and 10b which demonstrated brain-to-blood ratios of 0.8:1–2.0:1 in addition to good solubility and metabolic stability.     

Novel thioamide derivatives as neutral CB1 receptor antagonists

A novel class of cannabinoid-1 (CB1) receptor antagonists for the treatment of obesity is presented. The carboxamide linker in a set of 5,6-diaryl-pyrazine-2-amide derivatives was transformed into the corresponding thioamide, by using a one-pot synthesis. The structural series of thioamides not only showed retained CB1 potency (below 10 nM), but also showed improved solubility. In addition, the neutral antagonist 2c significantly reduced body weight in cafeteria diet obese mice.     

Novel heterocycles as selective alpha1-adrenergic receptor antagonists

A novel series of aryl piperazine substituted heterocycles has been synthesized and identified as antagonists of the alpha1a-adrenergic receptor (alpha1a-AR), which has been implicated in benign prostatic hyperplasia (BPH). These compounds selectively inhibit binding to the alpha1a-AR with K(i)s as low as 2.1 nM.     

Novel arylpiperazines as selective alpha1-adrenergic receptor antagonists

A novel series of arylpiperazines has been synthesized and identified as antagonists of alpha1a adrenergic receptor (alpha1a-AR) implicated in benign prostatic hyperplasia. These compounds selectively bind to membrane bound alpha1a-AR with K(i)s as low as 0.66 nM. As such, these potentially represent a viable treatment for BPH without the side effects associated with known alpha1-adrenergic antagonists.     

Discovery of a novel indole series of EP1 receptor antagonists by scaffold hopping

We describe the medicinal chemistry approach that generated a novel indole series of EP(1) receptor antagonists. The SAR of this new template was evaluated and culminated in the identification of compound 12g which demonstrated in vivo efficacy in a preclinical model of inflammatory pain.     

Novel substituted tetrahydrotriazaacenaphthylene derivatives as potent CRF1 receptor antagonists

Corticotropin-releasing factor (CRF), a 41 amino acid peptide neurohormone synthesised by specific hypothalamic nuclei in the brain, is implicated in stress-related function. Antagonism of CRF(1) receptors is an attractive therapeutic approach for the treatment of depression and anxiety. Unsaturated tetrahydrotriazaacenaphthylenes of general structure 3 have been identified as potent and selective CRF(1) receptor antagonists with a suitable oral pharmacokinetic profile.     

Novel pyrrolidine melanin-concentrating hormone receptor 1 antagonists with reduced hERG inhibition

We discovered novel pyrrolidine MCHR1 antagonist 1 possessing moderate potency. Profiling of pyrrolidine 1 demonstrated that it was an inhibitor of the hERG channel. Investigation of the structure-activity relationship of this class of pyrrolidines allowed us to optimize the MCHR1 potency and decrease the hERG inhibition. Increasing the acidity of the amide proton by converting the benzamide in lead 1 to an anilide provided single digit nanomolar MCHR1 antagonists while replacing the dimethoxyphenyl ring of 1 with alkyl groups possessing increased polarity dramatically reduced the hERG inhibition.