Development of orally active oxytocin antagonists: studies on 1-(1-[4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxy]-2- methoxybenzoyl]piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one (L-372,662) and related pyridines

Oxytocin and vasopressin signaling in health and disease

Neurohypophysial peptides are ancient and evolutionarily highly conserved neuropeptides that regulate many crucial physiological functions in vertebrates and invertebrates. The human neurohypophysial oxytocin/vasopressin (OT/VP) signaling system with its four receptors has become an attractive drug target for a variety of diseases, including cancer, pain, cardiovascular indications, and neurological disorders. Despite its promise, drug development faces hurdles, including signaling complexity, selectivity and off-target concerns, translational interspecies differences, and inefficient drug delivery. In this review we dive into the complexity of the OT/VP signaling system in health and disease, provide an overview of relevant pharmacological probes, and discuss the latest trends in therapeutic lead discovery and drug development.

Carriebowlinol, an antimicrobial tetrahydroquinolinol from an assemblage of marine cyanobacteria containing a novel taxon

A combined biodiversity- and bioassay-guided natural products discovery approach was used to explore new groups of marine cyanobacteria for novel secondary metabolites with ecologically relevant bioactivities. Phylogenetic analysis of cyanobacterial collections from Belize revealed a new taxon not previously well explored for natural products. The new alkaloid 5-hydroxy-4-(chloromethyl)-5,6,7,8-tetrahydroquinoline (1), named carriebowlinol, and the known compound lyngbic acid (2) were isolated from a nonpolar extract and identified by NMR and MS techniques. Compounds 1 and 2 inhibited the growth of pathogenic and saprophytic marine fungi, and 1 inhibited the growth of marine bacteria, suggesting an antimicrobial ecological function.

The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.

Novel oxytocin receptor agonists and antagonists: a patent review (2002 - 2013)

INTRODUCTION

Oxytocin is a nine amino acid cyclic peptide hormone with a high degree of uterotonic activity. The oxytocin receptor (Oxtr) is most strongly expressed in the uterus and mammary gland, but can also be found in regions of the brain, showing a neurotransmitter-like activity. The Oxtr knockout mice have no obvious defects in fertility or sexual behavior, but display aberrant social behavior. All of these suggest that Oxtr may become an important therapeutic target for the treatment of a wide range of conditions.

AREAS COVERED

This article will highlight the significant progress that has been made in the discovery and development of Oxtr agonists and antagonists in the patent literature between January 2002 and May 2013.

EXPERT OPINION

In the past decade, cumulative evidence supports the idea that activation of the Oxtr can have a positive effect upon human cognition and social behavior. The authors suggest that new agonists and antagonists may play an important role in the treatment of disorders such as anxiety, autism or schizophrenia. It may even be that older Oxtr agonists and antagonists, which were used to overcome labor-related dysfunction, may also have a significant impact on human social behavior.

REVIEW: Oxytocin: Crossing the bridge between basic science and pharmacotherapy

Is oxytocin the hormone of happiness? Probably not. However, this small nine amino acid peptide is involved in a wide variety of physiological and pathological functions such as sexual activity, penile erection, ejaculation, pregnancy, uterus contraction, milk ejection, maternal behavior, osteoporosis, diabetes, cancer, social bonding, and stress, which makes oxytocin and its receptor potential candidates as targets for drug therapy. In this review, we address the issues of drug design and specificity and focus our discussion on recent findings on oxytocin and its heterotrimeric G protein‐coupled receptor OTR. In this regard, we will highlight the following topics: (i) the role of oxytocin in behavior and affectivity, (ii) the relationship between oxytocin and stress with emphasis on the hypothalamo–pituitary–adrenal axis, (iii) the involvement of oxytocin in pain regulation and nociception, (iv) the specific action mechanisms of oxytocin on intracellular Ca²⁺ in the hypothalamo neurohypophysial system (HNS) cell bodies, (v) newly generated transgenic rats tagged by a visible fluorescent protein to study the physiology of vasopressin and oxytocin, and (vi) the action of the neurohypophysial hormone outside the central nervous system, including the myometrium, heart and peripheral nervous system. As a short nine amino acid peptide, closely related to its partner peptide vasopressin, oxytocin appears to be ideal for the design of agonists and antagonists of its receptor. In addition, not only the hormone itself and its binding to OTR, but also its synthesis, storage and release can be endogenously and exogenously regulated to counteract pathophysiological states. Understanding the fundamental physiopharmacology of the effects of oxytocin is an important and necessary approach for developing a potential pharmacotherapy.

Treatment of autism spectrum disorders: neurotransmitter signaling pathways involved in motivation and reward as therapeutic targets

BACKGROUND

There is a growing body of literature describing the etiology of autism spectrum disorders (ASD). Some of the targets suggested belong to neurochemical transmitter pathways implicated in the behavior and motivation reward pathway.

OBJECTIVE

To examine data linking potential targets to ASD and the feasibility of developing drugs targeting these pathways. While the inhibitors are mostly being developed for other indications, it is beneficial to examine them to determine the responsiveness of the targets to small-molecule modulation.

METHODS

A search in Medline and Scifinder for articles concerning relevant targets in the context of ASD and their relation to the reward signaling pathway.

RESULTS

There is evidence suggesting that behaviors controlled by these targets are related to behaviors exhibited by individuals with ASD. The targets appear to be involved in neurotransmitter pathways controlling motivation and reward, further implicating this system in ASD. Sufficient research has been conducted to identify lead compounds for discovering agents for treatment of ASD.

Discovery of a novel A2B adenosine receptor antagonist as a clinical candidate for chronic inflammatory airway diseases

Recently, we have reported a series of new 1,3-symmetrically (R 1 = R 3) substituted xanthines ( 3 and 4) which have high affinity and selectivity for the human adenosine A 2B receptors (hA(2B)-AdoR). Unfortunately, this class of compounds had poor pharmacokinetic properties. This prompted us to investigate the effect of differential alkyl substitution at the N-1 and N-3 positions ( N 1-R not equal to N 3-R) on A(2B)-AdoR affinity and selectivity; we had the dual objectives of enhancing affinity and selectivity for the A(2B)-AdoR, as well as improving oral bioavailability. This effort has led to the discovery of compound 62, that displayed high affinity and selectivity for the hA(2B)-AdoR (K(i) = 22 nM). In addition, compound 62 showed high functional potency in inhibiting the accumulation of cyclic adenosine monophosphate induced by 5'- N-ethylcarboxamidoadenosine in HEK-A(2B)-AdoR and NIH3T3 cells with K(B) values of 6 and 2 nM, respectively. In a single ascending-dose phase I clinical study, compound 62 had no serious adverse events and was well tolerated.

Use of a novel and highly selective oxytocin receptor antagonist to characterize uterine contractions in the rat

Spontaneous and induced uterine contractions in the rat were found to be inhibited by a novel and selective oxytocin receptor antagonist GSK221149A (3R,6R)-3-Indan-2-yl-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-morpholin-4-yl-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2,5-piperazinedione. GSK221149A displayed nanomolar affinity (K(i) = 0.65 nM) for human recombinant oxytocin receptors with >1,400-fold selectivity over human V1a, V1b, and V2 receptors. GSK221149A had similar affinity (K(i) = 4.1 nM) and selectivity for native oxytocin receptors from rat and produced a functional, competitive block of oxytocin-induced contractions in isolated rat myometrial strips with a pA(2) value of 8.18. Intravenous administration of GSK221149A produced a dose-dependent decrease in oxytocin-induced uterine contractions in anesthetized rats with an ID(50) = 0.27 +/- 0.60 mg/kg (corresponding plasma concentrations were 88 ng/ml). Oral administration of GSK221149A (5 mg/kg) was effective in inhibiting oxytocin-induced uterine contractions after single and multiple (4-day) dosing. Spontaneous uterine contractions in late-term pregnant rats (19-21 days gestation) were significantly reduced by intravenous administration of 0.3 mg/kg of GSK221149A. These results provide further evidence that selective oxytocin receptor antagonism may offer an effective treatment for preterm labor.

Possible dynamic anchor points in a benzoxazinone derivative-human oxytocin receptor system--a molecular docking and dynamics calculation

In this study, we performed a molecular docking and dynamics simulation for a benzoxazinone-human oxytocin receptor system to determine the possible hydrophobic and electrostatic interaction points in the dynamic complex. After the homology modeling, the ligand was docked into the putative active using AutoDock 3.05. After the application of energetic and structural filters, the complexes obtained were further refined with a simulated annealing protocol (AMBER8) to remove steric clashes. Three complexes were selected for subjection to the molecular dynamics simulation (5 ns), and the results on the occurrence of average anchor points showed a stable complex between the benzoxazinone derivative and the receptor. The complex could be used as a good starting point for further analysis with site-directed mutagenesis, or further computational research.

The SAR of 4-substituted (6,6-bicyclic) piperidine cathepsin S inhibitors

A series of competitive, reversible cathepsin S (CatS) inhibitors was investigated. An earlier disclosure detailed the discovery of the 4-(2-keto-1-benzimidazolinyl)-piperidin-1-yl moiety as an effective replacement for the 4-arylpiperazin-1-yl group found in our screening hit. Continued investigation into replacements for the 4-aryl piperazine resulted in the identification of potentially useful CatS inhibitors with enzymatic and cellular activity similar to that of JNJ 10329670 as disclosed in a previous publication.

The 3D Structure of the Binding Pocket of the Human Oxytocin Receptor for Benzoxazine Antagonists, Determined by Molecular Docking, Scoring Functions and 3D-QSAR Methods

Molecular docking and 3D-QSAR studies were performed to determine the binding mode for a series of benzoxazine oxytocin antagonists taken from the literature. Structural hypotheses were generated by docking the most active molecule to the rigid receptor by means of AutoDock 3.05. The cluster analysis yielded seven possible binding conformations. These structures were refined by using constrained simulated annealing, and the further ligands were aligned in the refined receptor by molecular docking. A good correlation was found between the estimated deltaG(bind) and the pKi values for complex F. The Connolly-surface analysis, CoMFA and CoMSIA models q2(CoMFA) = 0.653, q2(CoMSA) = 0.630 and r2(pred,CoMFA) = 0.852 , r2(pred,CoMSIA) = 0.815) confirmed the scoring function results. The structural features of the receptor-ligand complex and the CoMFA and CoMSIA fields are in closely connected. These results suggest that receptor-ligand complex F is the most likely binding hypothesis for the studied benzoxazine analogs.

Recent pharmacological advances in the treatment of preterm membrane rupture, labour and delivery

Preterm delivery (before 37 completed weeks of gestation) is the major determinant of infant mortality. In women with a previous preterm birth associated with bacterial vaginosis, prophylactic antibiotics (e.g., metronidazole) reduce the risk of preterm birth and low birth weight. Trichomonas vaginalis increases the risk of preterm delivery, but metronidazole is not beneficial for this and may even be detrimental. Antibiotic use (e.g., erythromycin) prolongs pregnancy in late premature rupture and has health benefits for the neonate. However, antibiotics are probably not useful in preterm labour. Intramuscular 17alpha-progesterone and vaginal progesterone reduce the rate of preterm labour in high-risk pregnancies, including previous spontaneous preterm delivery. Magnesium sulfate, beta2-adrenoceptor agonists and the oxytocin-receptor antagonist, atosiban, are effective in reducing uterine contractions short-term, but there is little evidence that this leads to improved outcomes for the neonate. However, tocolysis with calcium-channel blockers does seem to lead to better outcomes for the neonate. Fetal side effects, such as ductus arteriosus constriction and impaired renal function, are associated with the inhibition of prostaglandin synthesis with indomethacin. New approaches and more effective drugs are required in the treatment of preterm delivery.

A Gly/Ala switch contributes to high affinity binding of benzoxazinone-based non-peptide oxytocin receptor antagonists

Non-peptide antagonists of the oxytocin receptor (OTR) have been developed to prevent pre-term labour. The benzoxazinone-based antagonists L-371,257 and L-372,662 display pronounced species-dependent pharmacology with respect to selectivity for the OTR over the V(1a) vasopressin receptor. Examination of receptor sequences from different species identified Ala(318) in helix 7 of the human OTR as a candidate discriminator required for high affinity binding. The mutant receptor [A318G]OTR was engineered and characterised using ligands representing many different chemical classes. Of all the ligands investigated, only the benzoxazinone-based antagonists had decreased affinity for [A318G]OTR. Molecular modelling revealed that Ala(318) provides a direct hydrophobic contact with a methoxy group of L-371,257 and L-372,662.

N-Oxide analogs of WAY-100635: new high affinity 5-HT1A receptor antagonists

WAY-100635 [N-(2-(1-(4-(2-methoxyphenyl)piperazinyl)ethyl))-N-(2-pyridinyl)cyclohexanecarboxamide] 1 and its O-desmethyl derivative DWAY 2 are well-known high affinity 5-HT(1A) receptor antagonists, which when labeled with carbon-11 (beta+; t(1/2) = 20.4 min) in the carbonyl group are effective radioligands for imaging brain 5-HT(1A) receptors with positron emission tomography (PET). In a search for new 5-HT(1A) antagonists with different pharmacokinetic and metabolic properties, the pyridinyl N-oxide moiety was incorporated into analogs of 1 and 2. NOWAY 3, in which the pyridinyl ring of 1 was oxidized to the pyridinyl N-oxide, was prepared via nucleophilic substitution of 2-[4-(2-methoxyphenyl)piperazin-1-yl]ethylamine on 2-chloropyridine-N-oxide followed by acylation with cyclohexanecarbonyl chloride. 6Cl-NOWAY 4, a more lipophilic (pyridinyl-6)-chloro derivative of 3, was prepared by treating 1-(2-methoxyphenyl)-4-(2-(2-(6-bromo)aminopyridinyl-N-oxide)ethyl)piperazine with cyclohexanecarbonyl chloride for acylation and concomitant chloro for bromo substitution. NEWWAY 5, in which the 2-hydroxy-phenyl group of 2 is replaced with a 2-pyridinyl N-oxide group with the intention of mimicking the topology of 2, was prepared in five steps from 2-(chloroacetylamino)pyridine. N-Oxides 3-5 were found to be high affinity antagonists at 5-HT(1A) receptors, with 3 having the highest affinity and a Ki value (0.22 nM) comparable to that of 1 (0.17 nM). By calculation the lipophilicity of 3 (LogP = 1.87) is lower than that of 1 by 1.25 LogP units while TLC and reverse phase HPLC indicate that 3 has slightly lower lipophilicity than 1. On the basis of these encouraging findings, the N-oxide 3 was selected for labeling with carbon-11 in its carbonyl group and for evaluation as a radioligand with PET. After intravenous injection of [carbonyl-11C]3 into cynomolgus monkey there was very low uptake of radioactivity into brain and no PET image of brain 5-HT(1A) receptors was obtained. Either 3 inadequately penetrates the blood-brain barrier or it is excluded from brain by an active efflux mechanism. Rapid deacylation of 3 was not apparent in vivo; in cynomolgus monkey plasma radioactive metabolites of [carbonyl-11C]3 appeared less rapidly than from the radioligands [carbonyl-11C]1 and [carbonyl-11C]2, which are known to be primarily metabolized by deacylation. Ligand 3 may have value as a new pharmacological tool, but not as a radioligand for brain imaging.

Synthesis and evaluation of fluorine-substituted 1H-pyrrolo[2,3-b]pyridine derivatives for dopamine D4 receptor imaging

Seven fluorine-substituted 1H-pyrrolo[2,3-b]pyridine derivatives were synthesized based on a lead ligand, 3-[[4-(4-iodophenyl)piperazin-1-yl]-methyl]-1H-pyrrolo[2,3-b]pyridine (L-750,667) and evaluated as potential dopamine D(4) receptor imaging agents by positron emission tomography (PET). Binding affinities of these ligands for the dopamine D(2), D(3), and D(4) receptor subtypes were measured in vitro. Most ligands showed high and selective binding for the D(4) receptor. Ligand 7 had high affinity for the D(4) receptor, whereas ligands 1, 2, and 6 showed high selectivity for the D(4) receptor. LogP values were calculated for the ligands in this series and ligand 6 had the lowest lipophilicity. (18)F-labeled ligand 7 demonstrated a uniform regional brain distribution and a rapid washout in mice, probably due to nonspecific binding. Based on their in vitro binding properties and calculated logP values, ligand 6 appears to have the most promise for dopamine D(4) receptor imaging.

Design, synthesis, and biological activity of non-amidine factor Xa inhibitors containing pyridine N-oxide and 2-carbamoylthiazole units

Based on the both of results for X-ray studies of tetrahydrothiazolopyridine derivative 1c and FXV673, we synthesized a series of thiazol-5-ylpyridine derivatives containing pyridine N-oxide and 2-carbamoylthiazole units to optimize the S4 binding element. N-Oxidation of thiazol-5-ylpyridine increased the anti-fXa activity more than 10-fold independent on the position of N-oxide. The 4-pyridine N-oxide derivatives 3a and 3d excelled over the tetrahydrothiazolopyridine 1b in potency. 2-Methylpyridine N-oxide 3d exhibited 49-fold selectivity over thrombin. Our modeling study proposed a binding mode that the pyridine N-oxide ring of 3a stuck into the "cation hole" , and the oxide anion of 3a occupied in the almost same space to that of FXV673. From observations of the SAR and modeling studies, we suggested the possibilities that the formation of hydrogen bond with the oxide anion in the "cation hole" and the affinity of cationic pyridine ring to S4 subsite were responsible for increase in anti-fXa activity.

SSR126768A (4-chloro-3-[(3R)-(+)-5-chloro-1-(2,4-dimethoxybenzyl)-3-methyl-2-oxo-2,3-dihydro-1H-indol-3-yl]-N-ethyl-N-(3-pyridylmethyl)-benzamide, hydrochloride): a new selective and orally active oxytocin receptor antagonist for the prevention of preterm labor

4-chloro-3-[(3R)-(+)-5-chloro-1-(2,4-dimethoxybenzyl)-3-methyl-2-oxo-2,3-dihydro-1H-indol-3-yl]-N-ethyl-N-(3-pyridylmethyl)benzamide, hydrochloride (SSR126768A), a new potent and selective, orally active oxytocin (OT) receptor antagonist was characterized in several biochemical and pharmacological models. In binding studies, SSR126768A showed nanomolar affinity for rat and human recombinant and native OT receptors (K(i) = 0.44 nM) and exhibited much lower affinity for V(1a), V(1b), and V(2) receptors. In addition, it did not interact with a large number of other receptors, enzymes, and ion channels (1 microM). In autoradiographic experiments performed on at-term human pregnant uterus sections, SSR126768A dose dependently displaced [I(125)]d(CH(2))(5)[Tyr(Me)(2), Thr(4), Orn(8) (125)I-Tyr-NH(2)(9)]VT in situ labeling to OT receptors highly expressed in these tissues. In functional studies, SSR126768A behaved as a full antagonist and potently antagonized OT-induced intracellular Ca(2+) increase (K(i) = 0.50 nM) and prostaglandin release (K(i) = 0.45 nM) in human uterine smooth muscle cells. In rat isolated myometrium, OT-induced uterine contractions were competitively antagonized by SSR126768A (pA(2) = 8.47). Similarly, in human pregnant myometrial strips, SSR126768A inhibited the contractile uterine response to OT. In conscious telemetrated rats, oral administration of SSR126768A (1-10 mg/kg) produced a competitive inhibition of the dose response to OT on uterine contractions up to 24 h at 3 mg/kg p.o.; no tachyphylaxis was observed after 4-day repeated treatment. Finally, SSR126768A (30 mg/kg p.o.) significantly delayed parturition in pregnant rats in labor similar to ritodrine (10 mg/kg p.o.). Thus, SSR126768A is a potent, highly selective, orally active OT receptor antagonist with a long duration of action. This molecule could find therapeutic application as a tocolytic agent for acute and chronic oral management of preterm labor.

Pharmacokinetic optimization of 3-amino-6-chloropyrazinone acetamide thrombin inhibitors. Implementation of P3 pyridine N-oxides to deliver an orally bioavailable series containing P1 N-benzylamides

In this manuscript we demonstrate that a modification principally directed toward the improvement of the aqueous solubility (i.e., introduction a P3 pyridine N-oxide) of the previous lead compound afforded a new series of potent orally bioavailable P1 N-benzylamide thrombin inhibitors. An expedited investigation of the P1 SAR with respect to oral bioavailability, plasma half-life, and human liver microsome stability revealed 5 as the best candidate for advanced evaluation.

Identification of potent and selective oxytocin antagonists. Part 1: indole and benzofuran derivatives

Studies to discover novel, potent and selective oxytocin antagonists are reported. Combinatorial libraries designed to find novel replacements of fragments of oxytocin antagonist L-371,257, identified pyrimidine, thiazole, indole and benzofuran as potential alternatives to the benzoic acid moiety of L-371,257. Additional investigations identified indole and benzofuran derivatives with potent oxytocin antagonist activity.

Optimization of metabolic stability as a goal of modern drug design

Metabolism and other pharmacokinetic (PK) studies have always played a critical role in helping to optimize the bioavailability and duration of action of new drugs thereby increasing their success rate. With the advent of automated combinatorial synthesis, high-throughput pharmacological testing, and the ability to create extensive databases in the past decade, drug discovery has undergone an amazing evolution. With the increased throughput of drug discovery, metabolism and other PK studies have evolved to keep pace. Often called "early ADME" studies, these studies are characterized by parallel processing and higher throughput than before. This article focuses on a particular class of early ADME (absorption, distribution mechanism, and excretion) studies known as "metabolic stability" studies. The theoretical basis for metabolic stability and its relationship to the concept of metabolic intrinsic clearance is briefly presented. Some key relationships between structure and metabolism are summarized. Several case studies from recent medicinal chemistry literature are reviewed to exemplify how metabolic stability studies influenced drug design and led to improvements in bioavailability and half-life. Finally, future trends in drug metabolism and analytical chemistry and how they may influence metabolic stability studies are reviewed.

Structure-activity relationship investigations of a potent and selective benzodiazepine oxytocin antagonist

We have investigated the structure-activity relationships of the 1- and 3-substituents and replacements of the 5-phenyl group of GW405212X 1, a potent selective oxytocin antagonist. The effect of these modifications on oxytocin binding antagonism and on pharmacokinetic parameters is reported.

Pharmacologic characterization of the oxytocin receptor in human uterine smooth muscle cells

[(3)H]-oxytocin was used to characterize the oxytocin receptor found in human uterine smooth muscle cells (USMC). Specific binding of [(3)H]-oxytocin to USMC plasma membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with an apparent equilibrium dissociation constant (K(d)) of 0.76 nM and a maximum receptor density (B(max)) of 153 fmol mg(-1) protein. The Hill coefficient (n(H)) did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Competitive inhibition of [(3)H]-oxytocin binding showed that oxytocin and vasopressin (AVP) receptor agonists and antagonists displaced [(3)H]-oxytocin in a concentration-dependent manner. The order of potencies for peptide agonists and antagonists was: oxytocin>[Asu(1,6)]-oxytocin>AVP= atosiban>d(CH(2))(5)Tyr(Me)AVP>[Thr(4),Gly(7)]-oxytocin>dDAVP, and for nonpeptide antagonists was: L-371257>YM087>SR 49059>OPC-21268>SR 121463A>OPC-31260. Oxytocin significantly induced concentration-dependent increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) and hyperplasia in USMC. The oxytocin receptor antagonists, atosiban and L-371257, potently and concentration-dependently inhibited oxytocin-induced [Ca(2+)](i) increase and hyperplasia. In contrast, the V(1A) receptor selective antagonist, SR 49059, and the V(2) receptor selective antagonist, SR 121463A, did not potently inhibit oxytocin-induced [Ca(2+)](i) increase and hyperplasia. The potency order of antagonists in inhibiting oxytocin-induced [Ca(2+)](i) increase and hyperplasia was similar to that observed in radioligand binding assays. In conclusion, these data provide evidence that the high-affinity [(3)H]-oxytocin binding site found in human USMC is a functional oxytocin receptor coupled to [Ca(2+)](i) increase and cell growth. Thus human USMC may prove to be a valuable tool in further investigation of the physiologic and pathophysiologic roles of oxytocin in the uterus. British Journal of Pharmacology (2000) 129, 131 - 139

Nonpeptidic ligands for peptide and protein receptors

The first potent nonpeptidic ligands for somatostatin, luteinizing hormone-releasing hormone, glucagon and bradykinin receptors have been reported. Nonpeptidic clinical candidates have been identified or are currently under study for substance P, bradykinin, endothelin, growth hormone secretagogue, angiotensin, vasopressin, motilin and cholecystokinin. Design, screening, combinatorial chemistry and classical medicinal chemistry all played important roles in these advances.

Nonpeptide oxytocin antagonists: analogs of L-371,257 with improved potency

Structure-activity studies on the oxytocin antagonist 1 (L-371,257; Ki = 9.3 nM) have led to the identification of a related series of compounds containing an ortho-trifluoroethoxyphenylacetyl core which are orally bioavailable and have significantly improved potency in vitro and in vivo, e.g., compound 8 (L-374,943; Ki = 1.4 nM).

Recent advances in the therapeutic management of preterm labour

Preterm labour and delivery pose an increasing problem to the obstetrician. Improvements in tocolysis with the recent introduction of new therapeutic targeting strategies, and a reappraisal of the safety and relative efficacy of some older compounds, have led to a tendency away from prescribing beta-sympathomimetic agents. Infection prophylaxis and promotion of fetal lung maturity are deemed advantageous, but treatment protocols have not been clarified. This review examines the important publications of the past year in these areas.

Nonpeptide oxytocin antagonists: potent, orally bioavailable analogs of L-371,257 containing a 1-R-(pyridyl)ethyl ether terminus

Structure-activity studies on the oxytocin antagonist 1 (L-371,257) have identified a new series of high affinity, receptor-selective OT antagonists in which the N-acetyl-4-piperidinyl ether terminus in 1 has been replaced with a 1-(aryl)ethoxy group.