3-Urea-1-(phenylmethyl)-pyridones as novel, potent, and selective EP3 receptor antagonists.

A series of 3-urea-1-(phenylmethyl)-pyridones was discovered as novel EP(3) antagonists via high-throughput screening and subsequent optimization. The synthesis, structure-activity relationships, and optimization of the initial hit that resulted in potent and selective EP(3) receptor antagonists such as 11g are described.

Discovery of novel aminothiadiazole amides as selective EP(3) receptor antagonists.

This Letter discloses a series of 2-aminothiadiazole amides as selective EP(3) receptor antagonists. SAR optimization resulted in compounds with excellent functional activity in vitro. In addition, efforts to optimize DMPK properties in the rat are discussed. These efforts have resulted in the identification of potent, selective EP(3) receptor antagonists with excellent DMPK properties suitable for in vivo studies.

Synthesis and SAR of amino acid-derived heterocyclic progesterone receptor full and partial agonists.

Two classes of amino acid-derived heterocyclic progesterone receptor ligands were developed to address the metabolic issues posed by the dimethyl amide functionality of the lead compound (1). The tetrazole-derived ligands behaved as potent partial agonists, while the 1,2,4-triazole ligands behaved as potent full agonists.

Potent and selective small-molecule human urotensin-II antagonists with improved pharmacokinetic profiles.

Lead compound 1 was successfully redesigned to provide compounds with improved pharmacokinetic profiles for this series of human urotensin-II antagonists. Replacement of the 2-pyrrolidinylmethyl-3-phenyl-piperidine core of 1 with a substituted N-methyl-2-(1-pyrrolidinyl)ethanamine core as in compound 7 resulted in compounds with improved oral bioavailability in rats. The relationship between stereochemistry and selectivity for hUT over the kappa-opioid receptor was also explored.

An excitatory role for peripheral EP3 receptors in bladder afferent function.

The excitatory roles of EP3 receptors at the peripheral afferent nerve innervating the rat urinary bladder have been evaluated by using the selective EP3 antagonist (2E)-3-[1-[(2,4-dichlorophenyl)methyl]-5-fluoro-3-methyl-1H-indol-7-yl]-N-[(4,5-dichloro-2-thienyl)sulfonyl]-2-propenamide (DG-041). The bladder rhythmic contraction model and a bladder pain model measuring the visceromotor reflex (VMR) to urinary bladder distension (UBD) have been used to evaluate DG-041 in female rats. In addition, male rats [spontaneously hypertensive rat (SHR), Wistar-Kyoto (WKY), and Sprague-Dawley (SD)] were anesthetized with pentobarbital sodium, and primary afferent fibers in the L6 dorsal root were isolated for recording the inhibitory response to UBD following intravenous injection of DG-041. Intravenous injection of DG-041 (10 mg/kg), a peripherally restricted EP3 receptor antagonist, significantly reduced the frequency of bladder rhythmic contraction and inhibited the VMR response to bladder distension. The magnitude of reduction of the VMR response was not different in the different strains of rats (SD, SHR, and WKY). Furthermore, quantitative characterization of the mechanosensitive properties of bladder afferent nerves in SHR, WKY, and SD rats did not show the SHR to be supersensitive to bladder distension. DG-041 selectively attenuated responses of mechanosensitive afferent nerves to UBD, with strong suppression on the slow-conducting, high-threshold afferent fibers, with equivalent activity in the three strains. We conclude that sensitization of afferent nerve activity was not one of the mechanisms of bladder hypersensitivity in SHR. EP3 receptors are involved in the regulation of bladder micturition and bladder nociception at the peripheral level.

Development of potent and selective small-molecule human Urotensin-II antagonists.

This work describes the development of potent and selective human Urotensin-II receptor antagonists starting from lead compound 1, (3,4-dichlorophenyl)methyl{2-oxo-2-[3-phenyl-2-(1-pyrrolidinylmethyl)-1-piperidinyl]ethyl}amine. Several problems relating to oral bioavailability, cytochrome P450 inhibition, and off-target activity at the kappa opioid receptor and cardiac sodium channel were addressed during lead development. hUT binding affinity relative to compound 1 was improved by more than 40-fold in some analogs, and a structural modification was identified which significantly attenuated both off-target activities.

Use of a variably sensitive selected reaction monitoring method to extend the linear dynamic range for quantitative high-performance liquid chromatography/tandem mass spectrometry.

A method has been devised with the capacity to extend the linear dynamic range of a triple quadrupole mass spectrometer operated in the selected reaction monitoring (SRM) mode of analysis. This extended range experiment can be realized by simultaneously acquiring variably sensitive data, via collision energy adjustment, for the same precursor-to-product ion transition within a single SRM method. While this method can be applied universally to many different study types without any detrimental effect to the analysis or throughput, it was applied herein to acquire and quantify, within a single analysis, the concentrations of GSK-A in a multiple-dose rodent study, that previously required a dilution scheme. Using this methodology, the linear dynamic range of GSK-A was increased over traditional methods by nearly two orders of magnitude, from 2.00-10,000 ng/mL to 0.500-100,000 ng/mL.

Development of dihydropyridone indazole amides as selective Rho-kinase inhibitors.

Rho kinase (ROCK1) mediates vascular smooth muscle contraction and is a potential target for the treatment of hypertension and related disorders. Indazole amide 3 was identified as a potent and selective ROCK1 inhibitor but possessed poor oral bioavailability. Optimization of this lead resulted in the discovery of a series of dihydropyridones, exemplified by 13, with improved pharmacokinetic parameters relative to the initial lead. Indazole substitution played a critical role in decreasing clearance and improving oral bioavailability.

Evaluation of evaporative light-scattering detection for metabolite quantification without authentic analytical standards or radiolabel.

Development of a sensitive and specific technique for the quantitation of drug metabolites without the use of synthetic analytical standards or radiolabel would represent a major advance in preliminary route of metabolism screening in drug discovery. In this study, the ability of evaporative light-scattering detection (ELSD) to quantify metabolites of 7-ethoxycoumarin (EC) was evaluated. Because ELSD operates as a mass detector, the complex nature of in vitro-derived samples from hepatocyte incubations resulted in an inability to detect the analytes of interest in this matrix using ELSD. Additionally, the gradient nature of the analysis required to temporally separate ethoxycoumarin from its metabolites and matrix components interfered with the ELSD response. Furthermore, using less-complex contrived mixtures, ELSD demonstrated insufficient sensitivity (limit of detection of 1000-10,000 ng/mL) and an inconsistent inter-analyte response. Together, the limitations outlined in these experiments demonstrate that ELSD is at present an inadequate technique for generating semi-quantitative data on metabolites in drug discovery.

In vitro metabolic fate of a novel structural class: evidence for the formation of a reactive intermediate on a benzothiophene moiety.

The characterization of the metabolic pathways of new chemical entities with a special emphasis on detecting potentially reactive metabolites is increasingly being performed early in the drug discovery process. In the present study, the preliminary in vitro metabolic routes of a series of novel 2-substituted benzothiophene-containing discovery molecules were determined in fresh and cryopreserved hepatocyte suspensions. The objectives of this investigation were: (1) to use systematic LC/MS and LC/MS/MS analyses to provide a preliminary characterization of the in vitro metabolism of these compounds, with a particular focus on metabolites potentially arising from reactive intermediates, and (2) to identify potential lead molecules not associated with such metabolic pathways. This benzothiophene-containing series of compounds was characterized by the formation of five metabolites, at least two of which (dihydrodiol formation and glutathione adduct of the dihydrohydroxyl) were indicative of the formation of a reactive arene oxide intermediate. Tandem mass spectral analysis of the metabolites formed from a variety of structurally similar compounds demonstrated this reactive arene oxide intermediate to form on the 2-substituted benzothiophene moiety. Substitution of the benzothiophene with other functional groups eliminated these potentially toxic metabolites. The data presented here demonstrate the utility of performing metabolic route screens early in the drug discovery process prior to lengthy and costly radiolabeled studies, and furthermore, implicate a 2-substituted benzothiophene moiety as a substrate for formation of a reactive arene oxide intermediate.

Separating vesicle fusion and exocytosis in hypertonic conditions.

The existence of an osmotic gradient between the vesicular contents of chromaffin and mast cells and the extracellular fluid plays a key role in the exocytotic process. Altering this gradient by elevating the external buffer osmolarity allows for the inhibition of exocytosis from cells and isolation and identification of prespike current events upon stimulation using cyclic voltammetry. Subsequent replacement of the osmotic gradient leads to release of the contents from fused vesicles.