Heteroaryl urea inhibitors of fatty acid amide hydrolase: Structure–mutagenicity relationships for arylamine metabolites

Mild and efficient synthesis and base-promoted rearrangement of novel isoxazolo[4,5-b]pyridines

An efficient method for the synthesis of isoxazolo[4,5-b]pyridines has been developed on the basis of readily available 2-chloro-3-nitropyridines via the intramolecular nucleophilic substitution of the nitro group as a key step. The previously unknown base-promoted Boulton-Katritzky rearrangement of isoxazolo[4,5-b]pyridine-3-carbaldehyde arylhydrazones into 3-hydroxy-2-(2-aryl[1,2,3]triazol-4-yl)pyridines was observed.

Accessing three-dimensional molecular diversity through benzylic C-H cross-coupling

Pharmaceutical and agrochemical discovery efforts rely on robust methods for chemical synthesis that rapidly access diverse molecules1,2. Cross-coupling reactions are the most widely used synthetic methods3, but these methods typically form bonds to C(sp2)-hybridized carbon atoms (e.g., amide coupling, biaryl coupling) and lead to a prevalence of "flat" molecular structures with suboptimal physicochemical and topological properties4. Benzylic C(sp3)-H cross-coupling methods offer an appealing strategy to address this limitation by directly forming bonds to C(sp3)-hybridized carbon atoms, and emerging methods exhibit synthetic versatility that rivals conventional cross-coupling methods to access products with drug-like properties. Here, we use a virtual library of >350,000 benzylic ethers and ureas derived from benzylic C-H cross-coupling to test the widely held view that coupling at C(sp3)-hybridized carbon atoms affords products with improved three-dimensionality. The results show that the conformational rigidity of the benzylic scaffold strongly influences the product dimensionality. Products derived from flexible scaffolds often exhibit little or no improvement in three-dimensionality, unless they adopt higher energy conformations. This outcome introduces an important consideration when designing routes to topologically diverse molecular libraries. The concepts elaborated herein are validated experimentally through an informatics-guided synthesis of selected targets and the use of high-throughput experimentation to prepare a library of three-dimensional products that are broadly distributed across drug-like chemical space.

From Synthetic Simplified Marine Metabolite Analogues to New Selective Allosteric Inhibitor of Aurora B Kinase

Significant inhibition of Aurora B was achieved by the synthesis of simplified fragments of benzosceptrins and oroidin belonging to the marine pyrrole-2-aminoimidazoles metabolites isolated from sponges. Evaluation of kinase inhibition enabled the discovery of a synthetically accessible rigid acetylenic structural analogue EL-228 (1), whose structure could be optimized into the potent CJ2-150 (37). Here we present the synthesis of new inhibitors of Aurora B kinase, which is an important target for cancer therapy through mitosis regulation. The biologically oriented synthesis yielded several nanomolar inhibitors. The optimized compound CJ2-150 (37) showed a non-ATP competitive allosteric mode of action in a mixed-type inhibition for Aurora B kinase. Molecular docking identified a probable binding mode in the allosteric site "F" and highlighted the key interactions with the protein. We describe the improvement of the inhibitory potency and specificity of the novel scaffold as well as the characterization of the mechanism of action.

Heteroarylureas with fused bicyclic diamine cores as inhibitors of fatty acid amide hydrolase

A series of mechanism-based heteroaryl urea fatty acid amide hydrolase (FAAH) inhibitors with fused bicyclic diamine cores is described. In contrast to compounds built around a piperazine core, most of the fused bicyclic diamine bearing analogs prepared exhibited greater potency against rFAAH than the human enzyme. Several compounds equipotent against both species were identified and profiled in vivo.

Three-Dimensional Quantitative Structure-Activity Relationships (3D-QSAR) on a Series of Piperazine-Carboxamides Fatty Acid Amide Hydrolase (FAAH) Inhibitors as a Useful Tool for the Design of New Cannabinoid Ligands

Fatty Acid Amide Hydrolase (FAAH) is one of the main enzymes responsible for endocannabinoid metabolism. Inhibition of FAAH increases endogenous levels of fatty acid ethanolamides such as anandamide (AEA) and thus consitutes an indirect strategy that can be used to modulate endocannabinoid tone. In the present work, we present a three-dimensional quantitative structure-activity relationships/comparative molecular similarity indices analysis (3D-QSAR/CoMSIA) study on a series of 90 reported irreversible inhibitors of FAAH sharing a piperazine-carboxamide scaffold. The model obtained was extensively validated (q² = 0.734; r² = 0.966; r²_m = 0.723). Finally, based on the information derived from the contour maps we designed a series of 10 new compounds with high predicted FAAH inhibition (predicted pIC₅₀ of the best-proposed compounds = 12.196; 12.416).

Discovery of a Potent, Selective T-type Calcium Channel Blocker as a Drug Candidate for the Treatment of Generalized Epilepsies

We report here the discovery and pharmacological characterization of N-(1-benzyl-1H-pyrazol-3-yl)-2-phenylacetamide derivatives as potent, selective, brain-penetrating T-type calcium channel blockers. Optimization focused mainly on solubility, brain penetration, and the search for an aminopyrazole metabolite that would be negative in an Ames test. This resulted in the preparation and complete characterization of compound 66b (ACT-709478), which has been selected as a clinical candidate.

Preclinical Characterization of the FAAH Inhibitor JNJ-42165279

The pre-clinical characterization of the aryl piperazinyl urea inhibitor of fatty acid amide hydrolase (FAAH) JNJ-42165279 is described. JNJ-42165279 covalently inactivates the FAAH enzyme, but is highly selective with regard to other enzymes, ion channels, transporters, and receptors. JNJ-42165279 exhibited excellent ADME and pharmacodynamic properties as evidenced by its ability to block FAAH in the brain and periphery of rats and thereby cause an elevation of the concentrations of anandamide (AEA), oleoyl ethanolamide (OEA), and palmitoyl ethanolamide (PEA). The compound was also efficacious in the spinal nerve ligation (SNL) model of neuropathic pain. The combination of good physical, ADME, and PD properties of JNJ-42165279 supported it entering the clinical portfolio.

Establishing best practise in the application of expert review of mutagenicity under ICH M7

The ICH M7 guidelines for the assessment and control of DNA reactive (mutagenic) impurities in pharmaceuticals allows for the consideration of in silico predictions in place of in vitro studies. This represents a significant advance in the acceptance of (Q)SAR models and has resulted from positive interactions between modellers, regulatory agencies and industry with a shared purpose of developing effective processes to minimise risk. This paper discusses key scientific principles that should be applied when evaluating in silico predictions with a focus on accuracy and scientific rigour that will support a consistent and practical route to regulatory submission.

Discovery libraries targeting the major enzyme classes: the serine hydrolases

Two libraries of modestly reactive ureas containing either electron-deficient acyl anilines or acyl pyrazoles were prepared and are reported as screening libraries for candidate serine hydrolase inhibitors. Within each library is a small but powerful subset of compounds that serve as a chemotype fragment screening library capable of subsequent structural diversification. Elaboration of the pyrazole-based ureas provided remarkably potent irreversible inhibitors of fatty acid amide hydrolase (FAAH, apparent Ki=100-200 pM) complementary to those previously disclosed enlisting electron-deficient aniline-based ureas.

Reductive Amination of Acetals by Anilines in the Presence of Triethylsilane and Iodine

A mild and efficient method for N-alkylation of aromatic amines with various acetals such as aryl, alkyl, cyclic and acyclic acetals was developed. A number of aromatic amines bearing electron-donating or electron-withdrawing substituents were directly alkylated by acetals with excellent yields. The method uses a catalytic amount of I2 and triethylsilane as the hydride source without a metal present. Monoalkylation with excellent chemoselectivity was observed.

Design, synthesis, crystallographic studies, and preliminary biological appraisal of new substituted triazolo[4,3-b]pyridazin-8-amine derivatives as tankyrase inhibitors

Searching for selective tankyrases (TNKSs) inhibitors, a new small series of 6,8-disubstituted triazolo[4,3-b]piridazines has been synthesized and characterized biologically. Structure-based optimization of the starting hit compound NNL (3) prompted us to the discovery of 4-(2-(6-methyl-[1,2,4]triazolo[4,3-b]pyridazin-8-ylamino)ethyl)phenol (12), a low nanomolar selective TNKSs inhibitor working as NAD isostere as ascertained by crystallographic analysis. Preliminary biological data candidate this new class of derivatives as a powerful pharmacological tools in the unraveling of TNKS implications in physiopathological conditions.

Design, synthesis, and characterization of α-ketoheterocycles that additionally target the cytosolic port Cys269 of fatty acid amide hydrolase

A series of α-ketooxazoles incorporating electrophiles at the C5 position of the pyridyl ring of 2 (OL-135) and related compounds were prepared and examined as inhibitors of fatty acid amide hydrolase (FAAH) that additionally target the cytosolic port Cys269. From this series, a subset of the candidate inhibitors exhibited time-dependent FAAH inhibition and noncompetitive irreversible inactivation of the enzyme, consistent with the targeted Cys269 covalent alkylation or addition, and maintained or enhanced the intrinsic selectivity for FAAH versus other serine hydrolases. A preliminary in vivo assessment demonstrates that these inhibitors raise endogenous brain levels of anandamide and other FAAH substrates upon intraperitoneal (i.p.) administration to mice, with peak levels achieved within 1.5–3 h, and that the elevations of the signaling lipids were maintained >6 h, indicating that the inhibitors effectively reach and remain active in the brain, inhibiting FAAH for a sustained period.

Latest advances in the discovery of fatty acid amide hydrolase inhibitors

INTRODUCTION

Fatty acid amide hydrolase (FAAH) is the major catabolic enzyme of the endocannabinoid N-arachidonoylethanolamine (anandamide) that, with different degrees of efficiency, also hydrolyzes other endogenous fatty acid ethanolamides. FAAH is increasingly being considered a relevant therapeutic target, especially in models of inflammatory pain. The opportunity to selectively increase the endocannabinoid tone only in those tissues where such an enhancement can be beneficial might result in a therapeutic benefit with more limited side effects, compared to the use of direct agonists of anandamide-binding receptors. Thus the research for selective FAAH inhibitors has become a hot topic in current drug discovery.

AREAS COVERED

This review highlights the advances in the development of different compounds belonging to different chemical families that have been proposed as FAAH inhibitors. Several classes of inhibitors have been reported so far, and they may be classified into two major classes: reversible and irreversible compounds. These inhibitors are reviewed herein with an emphasis on their potency and selectivity.

EXPERT OPINION

In recent years, tremendous efforts have been made to develop the FAAH inhibitors, and consequently many novel chemical templates have been discovered. It is still a major challenge to identify the first inhibitor of FAAH suitable for clinical exploitation that satisfies the requirements of potency, selectivity versus proteins related to anandamide activity as well as other potential off-targets, reversibility versus irreversibility, and efficacy toward rat versus human FAAH.