Discovery and SAR development of 2-(phenylamino) imidazolines as prostacyclin receptor antagonists [corrected

On the basis of screening hits (1a,b), a series of selective, high affinity prostacyclin receptor antagonists was developed. The optimized lead compound 25d [(4,5-dihydro-1H-imidazol-2-yl)-[4-(4-isopropoxybenzyl)phenyl]amine] had analgesic activity in the rat.     

Quinoxalin-2-carboxamides: synthesis and pharmacological evaluation as serotonin type-3 (5-HT3) receptor antagonists

A series of quinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT(3) receptor antagonists and synthesized by condensing the carboxylic group of quinoxalin-2-carboxylic acid with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole. The structures of the synthesized compounds were confirmed by physical and spectroscopic data. The carboxamides were evaluated for their 5-HT(3) receptor antagonisms in longitudinal muscle-myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methy-5-HT. All the synthesized compounds showed 5-HT(3) receptor antagonism, (4-benzylpiperazin-1-yl)(quinoxalin-2-yl)methanone was the most potent compound among this series.     

Quinoxalin-2-carboxamides: synthesis and pharmacological evaluation as serotonin type-3 (5-HT3) receptor antagonists

A series of quinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT₃ receptor antagonists and synthesized by condensing the carboxylic group of quinoxalin-2-carboxylic acid with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole. The structures of the synthesized compounds were confirmed by physical and spectroscopic data. The carboxamides were evaluated for their 5-HT₃ receptor antagonisms in longitudinal muscle-myenteric plexus preparation from guinea pig ileum against 5-HT₃ agonist, 2-methy-5-HT. All the synthesized compounds showed 5-HT₃ receptor antagonism, (4-benzylpiperazin-1-yl)(quinoxalin-2-yl)methanone was the most potent compound among this series.     

N-(2-alkylaminoethyl)-4-(1,2,4-oxadiazol-5-yl)piperazine-1-carboxamides as highly potent smoothened antagonists

Smoothened (Smo) antagonists are emerging as new therapies for the treatment of neoplasias with aberrantly reactivated hedgehog (Hh) signaling pathway. A novel series of 4-[3-(quinolin-2-yl)-1,2,4-oxadiazol-5-yl]piperazinyl ureas as smoothened antagonists was recently described, herein the series has been further optimized through the incorporation of a basic amine into the urea. This development resulted in identification of some exceptionally potent smoothened antagonists with low serum shifts, however, reductive ring opening on the 1,2,4-oxadiazole in rats limits the applicability of these compounds in in vivo studies.     

4-(2-pyridyl)piperazine-1-carboxamides: potent vanilloid receptor 1 antagonists

A series of 4-(2-pyridyl)piperazine-1-carboxamide analogues based on the lead compound 1 was synthesized and evaluated for VR1 antagonist activity in capsaicin-induced (CAP) and pH (5.5)-induced (pH) FLIPR assays in a rat VR1-expressing HEK293 cell line. Potent VR1 antagonists were identified through SAR studies. From these studies, 18 was found to be very potent in the in vitro assay [IC(50)=4.8 nM (pH) and 35 nM (CAP)] and orally available in rat (F%=15.1).     

Discovery and evaluation of spirocyclic derivatives as antagonists of the neuropeptide Y5 receptor

A novel series of spirocyclic derivatives was synthesized and evaluated as NPY Y5R antagonists for the treatment of obesity. Cis and trans analogs 7a and 8a were equipotent in a Y5R binding assay (K(i)'s ≤ 1 nM) and displayed good stability in human and rat liver microsome preparations. Compound 7a failed to demonstrate weight loss activity in a diet-induced obese (DIO) rat model at unbound drug levels in the brain that exceeded the Y5R K(i) value by 25-fold over a 24-h time-period.     

Tetrahydropyridine-4-carboxamides as novel, potent transient receptor potential vanilloid 1 (TRPV1) antagonists

A series of 1,2,3,6-tetrahydropyridyl-4-carboxamides, exemplified by 6, have been synthesized and evaluated for in vitro TRPV1 antagonist activity, and in vivo analgesic activity in animal pain models. The tetrahydropyridine 6 is a novel TRPV1 receptor antagonist that potently inhibits receptor-mediated Ca2+ influx in vitro induced by several agonists, including capsaicin, N-arachidonoyldopamine (NADA), and low pH. This compound penetrates the CNS and shows potent anti-nociceptive effects in a broad range of animal pain models upon oral dosing due in part to its ability to antagonize both central and peripheral TRPV1 receptors. The SAR leading to the discovery of 6 is presented in this report.     

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.     

Discovery of 4-(dimethylamino)quinazolines as potent and selective antagonists for the melanin-concentrating hormone receptor 1

A series of 4-(dimethylamino)quinazoline based antagonists of the melanin-concentrating hormone receptor 1 (MCH-R1) is described. This series was derived from a lead compound, AR129330, identified by HTS of a GPCR-directed library using a functional assay with a constitutively activated (CART) form of the receptor. The preliminary optimization resulted in the identification of compounds 20, 21, and 23.     

Substituted indole-5-carboxamides and -acetamides as potent nonpeptide GnRH receptor antagonists.

The 2-aryltryptamine class of GnRH receptor antagonists has been modified to incorporate carboxamide and acetamide substituents at the indole 5-position. With either a phenol or methanesulfonamide terminus on the N-aralkyl side chain, potent binding affinity to the GnRH receptor was achieved. A functional assay for GnRH antagonism was even more sensitive to structural modification and revealed a strong preference for branched tertiary amides.     

Discovery of 5-hydroxyalkyl-4-phenylpyridines as a new class of glucagon receptor antagonists

5-Hydroxyalkyl-4-phenylpyridines have been identified as a novel class of glucagon antagonists with potential utility for the treatment of diabetes. A lead structure with moderate activity was discovered through a high throughput screening assay. Structure-activity relationships led to the discovery of a potent antagonist, IC(50)=0.11 microM, more than 60-fold improvement over the lead structure.     

The discovery of novel indole-2-carboxamides as cannabinoid CB(1) receptor antagonists

The discovery and structure-activity relationship of a novel series of indole-2-carboxamide antagonists of the cannabinoid CB(1) receptor is disclosed. Compound 26i was found to be a high potency, selective cannabinoid CB(1) antagonist.     

Synthesis and evaluation of 4- and 5-pyridazin-3-one phenoxypropylamine analogues as histamine-3 receptor antagonists

A novel series of 4-pyridazin-3-one and 5-pyridazin-3-one analogues were designed and synthesized as H(3)R antagonists. Structure-activity relationship revealed the 5-pyridazin-3-ones 8a and S-methyl 8b had excellent human and rat H(3)R affinities, and acceptable pharmacokinetic properties. In vivo evaluation of 8a showed potent activity in the rat dipsogenia model and robust wake-promoting activity in the rat EEG/EMG model.     

Discovery and pharmacological profile of new hydrophilic 5-HT4 receptor antagonists

The synthesis and pharmacological data of some new and potent hydrophilic 5-HT₄ receptor antagonists are described. Propanediol derivative 25 was identified as a potent antagonist with low affinity for the hERG potassium channel and promising pharmacokinetics.     

Discovery of new anti-depressants from structurally novel 5-HT3 receptor antagonists: design, synthesis and pharmacological evaluation of 3-ethoxyquinoxalin-2-carboxamides

A novel series of 3-ethoxyquinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT₃ receptor antagonist using ligand-based approach. The desired carboxamides were synthesized from the key intermediate, 3-ethoxyquinoxalin-2-carboxylic acid by coupling with appropriate amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The 5-HT₃ receptor antagonism was evaluated in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT₃ agonist, 2-methy-5-HT, which was expressed in the form of pA₂ values. Compound 6h (3-ethoxyquinoxalin-2-yl)(4-methylpiperazin-1-yl)methanone was found to be the most active compound, which expressed a pA₂ value of 7.7. In forced swim test, the compounds with higher pA₂ value exhibited good anti-depressant-like activity and compounds with lower pA₂ value failed to show activity as compared to the vehicle-treated group.     

Discovery and evaluation of N-(triazin-1,3,5-yl) phenylalanine derivatives as VLA-4 integrin antagonists

SAR studies aimed at improving the rate of clearance of a series of VLA-4 integrin antagonists by the introduction of a 1,3,5-triazine as an amide isostere are described.     

Discovery of 1-(1,3,5-triazin-2-yl)piperidine-4-carboxamides as inhibitors of soluble epoxide hydrolase

1-(1,3,5-Triazin-yl)piperidine-4-carboxamide inhibitors of soluble epoxide hydrolase were identified from high through-put screening using encoded library technology. The triazine heterocycle proved to be a critical functional group, essential for high potency and P450 selectivity. Phenyl group substitution was important for reducing clearance, and establishing good oral exposure. Based on this lead optimization work, 1-[4-methyl-6-(methylamino)-1,3,5-triazin-2-yl]-N-{[[4-bromo-2-(trifluoromethoxy)]-phenyl]methyl}-4-piperidinecarboxamide (27) was identified as a useful tool compound for in vivo investigation. Robust effects on a serum biomarker, 9, 10-epoxyoctadec-12(Z)-enoic acid (the epoxide derived from linoleic acid) were observed, which provided evidence of robust in vivo target engagement and the suitability of 27 as a tool compound for study in various disease models.     

Discovery of a series of aryl-N-(3-(alkylamino)-5-(trifluoromethyl)phenyl)benzamides as TRPA1 antagonists

We describe the discovery and advancement of a novel series of TRPA1 antagonist having an aryl-N-(3-(alkylamino)-5-(trifluoromethyl)phenyl)benzamide scaffold. The physical and in vitro DMPK profiles are discussed.     

Syntheses and biological evaluation of 5-(piperidin-1-yl)-3-phenyl-pentylsulfones as CCR5 antagonists

Cellular proliferation of HIV-1 requires the cooperative assistance of both the CCR5 and CD4 receptors. Our medicinal chemistry efforts in this area have resulted in the identification of N-alkyl piperidine sulfones as CCR5 antagonists. These compounds display potent binding and show antiviral properties in HIV-1 spread cell-based assays.     

Discovery of 2-(3,5-difluoro-4-methylsulfonaminophenyl)propanamides as potent TRPV1 antagonists

A series of A-region analogues of 2-(3-fluoro-4-methylsufonamidophenyl) propanamide 1 were investigated as TRPV1 antagonists. The analysis of structure-activity relationship indicated that a fluoro group at the 3- (or/and) 5-position and a methylsulfonamido group at the 4-position were optimal for antagonism of TRPV1 activation by capsaicin. The most potent antagonist 6 not only exhibited potent antagonism of activation of hTRPV1 by capsaicin, low pH and elevated temperature but also displayed highly potent antagonism of activation of rTRPV1 by capsaicin. Further studies demonstrated that antagonist 6 blocked the hypothermic effect of capsaicin in vivo, consistent with its in vitro mechanism, and it showed promising analgesic activity in the formalin animal model.