Discovery and structure-activity relationships study of positive allosteric modulators of the M3 muscarinic acetylcholine receptor.

The M3 muscarinic acetylcholine receptor (mAChR) is a member of the family of mAChRs, which are associated with a variety of physiological functions including the contraction of various smooth muscle tissues, stimulation of glandular secretion, and regulation of a range of cholinergic processes in the central nerve system. We report here the discovery and a comprehensive structure--activity relationships (SARs) study of novel positive allosteric modulators (PAMs) of the M3 mAChR through a high throughput screening (HTS) campaign. Compound 9 exhibited potent in vitro PAM activity towards the M3 mAChR and significant enhancement of muscle contraction in a concentration-dependent manner when applied to isolated smooth muscle strips of rat bladder. Compound 9 also showed excellent subtype selectivity over other subtypes of mAChRs including M1, M2, and M4 mAChRs, and moderate selectivity over the M5 mAChR, indicating that compound 9 is an M3-preferring M3/M5 dual PAM. Moreover, compound 9 displayed acceptable pharmacokinetics profiles after oral dosing to rats. These results suggest that compound 9 may be a promising chemical probe for the M3 mAChR for further investigation of its pharmacological function both in vitro and in vivo.

Expression and functional analysis of citrus carotene hydroxylases: unravelling the xanthophyll biosynthesis in citrus fruits.

BACKGROUND: Xanthophylls are oxygenated carotenoids and fulfill critical roles in plant growth and development. In plants, two different types of carotene hydroxylases, non-heme di-iron and heme-containing cytochrome P450, were reported to be involved in the biosynthesis of xanthophyll. Citrus fruits accumulate a high amount of xanthophylls, especially ß,ß-xanthophylls. To date, however, the roles of carotene hydroxylases in regulating xanthophyll content and composition have not been elucidated. RESULTS: In the present study, the roles of four carotene hydroxylase genes (CitHYb, CitCYP97A, CitCYP97B, and CitCYP97C) in the biosynthesis of xanthophyll in citrus fruits were investigated. Phylogenetic analysis showed that the four citrus carotene hydroxylases presented in four distinct clusters which have been identified in higher plants. CitHYb was a non-heme di-iron carotene hydroxylase, while CitCYP97A, CitCYP97B, and CitCYP97C were heme-containing cytochrome P450-type carotene hydroxylases. Gene expression results showed that the expression of CitHYb increased in the flavedo and juice sacs during the ripening process, which was well consistent with the accumulation of ß,ß-xanthophyll in citrus fruits. The expression of CitCYP97A and CitCYP97C increased with a peak in November, which might lead to an increase of lutein in the juice sacs during the ripening process. The expression level of CitCYP97B was much lower than that of CitHYb, CitCYP97A, and CitCYP97C in the juice sacs during the ripening process. Functional analysis showed that the CitHYb was able to catalyze the hydroxylation of the ß-rings of ß-carotene and α-carotene in Escherichia coli BL21 (DE3) cells. Meanwhile, when CitHYb was co-expressed with CitCYP97C, α-carotene was hydroxylated on the ß-ring and ε-ring sequentially to produce lutein. CONCLUSIONS: CitHYb was a key gene for ß,ß-xanthophyll biosynthesis in citrus fruits. CitCYP97C functioned as an ε-ring hydroxylase to produce lutein using zeinoxanthin as a substrate. The results will contribute to elucidating xanthophyll biosynthesis in citrus fruits, and provide new strategies to improve the nutritional and commercial qualities of citrus fruits.

Synthesis and structure-activity relationships of amide derivatives of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetic acid as selective arginine vasopressin V2 receptor agonists.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives was synthesized, and their structure-activity relationships were examined in order to identify potent and selective arginine vasopressin V(2) receptor agonists. Attempts to substitute other chemical groups in place of the 2-pyridilmethyl moiety of 1a led to the discovery that potent V(2) binding affinity could be obtained with a wide range of functional groups. This structural tolerance allowed for the manipulation of other attributes, such as selectivity against V(1a) receptor affinity or avoidance of the undesirable inhibition of cytochrome P450 (CYP), without losing potent affinity for the V(2) receptor. Some representative compounds obtained in this study were also found to decrease urine volume in awake rats.

Optimization of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin V2 receptor agonists and discussion of their binding modes.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives were optimized to achieve potent agonistic activity, both in vitro and in vivo, for the arginine vasopressin V(2) receptor, resulting in the eventual discovery of compound 1g. Molecular modeling of compound 1g with V(2) receptor was also examined to evaluate the binding mode of this series of compounds.

Preparation of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives as novel arginine vasopressin V(2) receptor agonists.

The present work describes the discovery of novel series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin (AVP) V(2) receptor agonists. By replacing the amide juncture in YM-35278 with a direct ring connection gave compound 10a, which acts as a V(2) receptor agonist. These studies provided the potent, orally active non-peptidic V(2) receptor agonists 10a and 10j.

Recent patenting activities in the discovery and development of vasopressin V2 receptor agonists.

INTRODUCTION: Vasopressin V(2) agonists are well known as effective therapies in the treatment of central diabetes insipidus and nocturnal enuresis. Furthermore, given their mode of action, these particular agonists have more recently been considered, in both the pharmaceutical industry and in academia, as viable therapies for urological conditions such as nocturia. AREAS COVERED: For the past 10 years, significant progress has been made in the discovery and development of vasopressin V(2) agonists. This article provides the reader with information on the recent progress in the discovery and development of these compounds based on patents published from 2002 onward. Specifically, the article looks at the discovery of new non-peptide agonists as well as well as novel formulations of the vasopressin V(2) agonist desmopressin. EXPERT OPINION: The V(2) receptor is currently one of the hottest therapeutic targets investigated for the treatment of urinary disorders such as nocturia and central diabetes. Over the past 10 years, significant progress has been made in the discovery and development of vasopressin V(2) receptor agonists, for the treatment of these disorders. The author anticipates that these agonists will be launched to market in the not-too-distant future.

Synthesis and structure-activity relationships of 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives as a novel class of NCX inhibitors: a QSAR study.

The sodium-calcium exchanger (NCX) transports Na+ and Ca2+ ions, and controls the Ca2+ concentration in myocytes. Calcium overload is induced via activation of reverse NCX, and is responsible for reperfusion injury in heart failure. Hence, NCX is an attractive target for prevention and treatment of reperfusion arrhythmias, myocardial contracture, and necrosis. We have synthesized a series of 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives, and evaluated their inhibitory activity against the reverse and forward modes of NCX. N-(3-Aminobenzyl)-6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide (8) was shown to be a potent inhibitor of reverse NCX activity, with an IC50 value of 0.24 microM. A QSAR study showed that inhibition of reverse NCX activity by 6-{4-[(3-fluorobenzyl)oxy]phenoxy}nicotinamide derivatives is multiply dependent on the hydrophobicity (pi) and the shape (B(iv)) of the substituent at the 3-position of the phenyl ring.

Discovery of an N-(2-aminopyridin-4-ylmethyl)nicotinamide derivative: a potent and orally bioavailable NCX inhibitor.

Ca(2+) overload in myocardial cells is responsible for arrhythmia. Sodium-calcium exchanger (NCX) inhibitors are more effective than sodium-hydrogen exchanger (NHE) inhibitors with regard to modulation of Ca(2+) overload, because NCX inhibitors can directly inhibit the influx of Ca(2+) into cells. NCX is an attractive target for the treatment of heart failure and ischemia-reperfusion. We have designed and synthesized a series of N-(2-aminopyridin-4-ylmethyl)nicotinamide derivatives, based on compound 5. We have discovered a novel NCX inhibitor (23 h) with an IC(50) value of 0.12 microM against reverse NCX. The inhibitory activities of our NCX inhibitors against cytochrome P450 were also evaluated. The effects on heart failure and the pharmacokinetic profile of compound 23 h are discussed.