A strategy of employing aminoheterocycles as amide mimics to identify novel, potent and bioavailable soluble epoxide hydrolase inhibitors

Replacing the oxidation-sensitive triaminoaryl chemotype of problematic KV 7 channel openers: Exploration of a nicotinamide scaffold

K_V 7 channel openers have proven their therapeutic value in the treatment of pain as well as epilepsy and, moreover, they hold the potential to expand into additional indications with unmet medical needs. However, the clinically validated but meanwhile discontinued K_V 7 channel openers flupirtine and retigabine bear an oxidation-sensitive triaminoraryl scaffold, which is suspected of causing adverse drug reactions via the formation of quinoid oxidation products. Here, we report the design and synthesis of nicotinamide analogs and related compounds that remediate the liability in the chemical structure of flupirtine and retigabine. Optimization of a nicotinamide lead structure yielded analogs with excellent K_V 7.2/3 opening activity, as evidenced by EC₅₀ values approaching the single-digit nanomolar range. On the other hand, weighted K_V 7.2/3 opening activity data including inactive compounds allowed for the establishment of structure-activity relationships and a plausible binding mode hypothesis verified by docking and molecular dynamics simulations.

Structure-activity relationship studies of benzothiazole-phenyl analogs as multi-target ligands to alleviate pain without affecting normal behavior

Soluble epoxide hydrolase (sEH) and fatty acid amide hydrolase (FAAH) are potential targets for several diseases. Previous studies have reported that concomitant selective inhibition of sEH and FAAH produced antinociception effects in an animal model of pain. However, the co-administration of a selective sEH inhibitor and a selective FAAH inhibitor might produce serious side effects due to drug-drug interactions that could complicate drug development in the long term. Thus, discovering dual sEH/FAAH inhibitors, single small molecules that can simultaneously inhibit both sEH and FAAH, would be a significant accomplishment in the medicinal chemistry field. Herein, we report the synthesis and biological evaluation of benzothiazole-phenyl-based analogs as potential dual sEH/FAAH inhibitors. This work represents a follow-up structure-activity relationship (SAR) and metabolic-stability studies of our best dual sEH/FAAH inhibitor identified previously, as well as in vivo evaluation of its effects on voluntary locomotor behavior in rats. Our SAR study indicates that trifluoromethyl groups on the aromatic rings are well tolerated by the targeted enzymes when placed at the ortho and para positions; however, they, surprisingly, did not improve metabolic stability in liver microsomes. Our behavioral studies indicate that doses of dual sEH/FAAH inhibitors that alleviate pain do not depress voluntary behavior in naïve rats, which is a common side effect of currently available analgesic drugs (e.g., opioids). Thus, dual sEH/FAAH inhibitors may be a safe and effective approach to treat pain.

Small Molecule Soluble Epoxide Hydrolase Inhibitors in Multitarget and Combination Therapies for Inflammation and Cancer

The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors.

Preparation and evaluation of soluble epoxide hydrolase inhibitors with improved physical properties and potencies for treating diabetic neuropathic pain

Soluble epoxide hydrolase (sEH), a novel therapeutic target for neuropathic pain, is a largely cytosolic enzyme that degrades epoxy-fatty acids (EpFAs), an important class of lipid signaling molecules. Many inhibitors of sEH have been reported, and to date, the 1,3-disubstituted urea has the highest affinity reported for the sEH among the central pharmacophores evaluated. An earlier somewhat water soluble sEH inhibitor taken to the clinic for blood pressure control had mediocre potency (both affinity and kinetics) and a short in vivo half-life. We undertook a study to overcome these difficulties, but the sEH inhibitors carrying a 1,3-disubstituted urea often suffer poor physical properties that hinder their formulation. In this report, we described new strategies to improve the physical properties of sEH inhibitors with a 1,3-disubstituted urea while maintaining their potency and drug-target residence time (a complementary in vitro parameter) against sEH. To our surprise, we identified two structural modifications that substantially improve the potency and physical properties of sEH inhibitors carrying a 1,3-disubstituted urea pharmacophore. Such improvements will greatly facilitate the movement of sEH inhibitors to the clinic.

Soluble Epoxide Hydrolase Inhibition for Ocular Diseases: Vision for the Future

Ocular diseases cause visual impairment and blindness, imposing a devastating impact on quality of life and a substantial societal economic burden. Many such diseases lack universally effective pharmacotherapies. Therefore, understanding the mediators involved in their pathophysiology is necessary for the development of therapeutic strategies. To this end, the hydrolase activity of soluble epoxide hydrolase (sEH) has been explored in the context of several eye diseases, due to its implications in vascular diseases through metabolism of bioactive epoxygenated fatty acids. In this mini-review, we discuss the mounting evidence associating sEH with ocular diseases and its therapeutic value as a target. Substantial data link sEH with the retinal and choroidal neovascularization underlying diseases such as wet age-related macular degeneration, retinopathy of prematurity, and proliferative diabetic retinopathy, although some conflicting results pose challenges for the synthesis of a common mechanism. sEH also shows therapeutic relevance in non-proliferative diabetic retinopathy and diabetic keratopathy, and sEH inhibition has been tested in a uveitis model. Various approaches have been implemented to assess sEH function in the eye, including expression analyses, genetic manipulation, pharmacological targeting of sEH, and modulation of certain lipid metabolites that are upstream and downstream of sEH. On balance, sEH inhibition shows considerable promise for treating multiple eye diseases. The possibility of local delivery of inhibitors makes the eye an appealing target for future sEH drug development initiatives.

Prospective for cytochrome P450 epoxygenase cardiovascular and renal therapeutics

Therapeutics for arachidonic acid pathways began with the development of non-steroidal anti-inflammatory drugs that inhibit cyclooxygenase (COX). The enzymatic pathways and arachidonic acid metabolites and respective receptors have been successfully targeted and therapeutics developed for pain, inflammation, pulmonary and cardiovascular diseases. These drugs target the COX and lipoxygenase pathways but not the third branch for arachidonic acid metabolism, the cytochrome P450 (CYP) pathway. Small molecule compounds targeting enzymes and CYP epoxy-fatty acid metabolites have evolved rapidly over the last two decades. These therapeutics have primarily focused on inhibiting soluble epoxide hydrolase (sEH) or agonist mimetics for epoxyeicosatrienoic acids (EET). Based on preclinical animal model studies and human studies, major therapeutic indications for these sEH inhibitors and EET mimics/analogs are renal and cardiovascular diseases. Novel small molecules that inhibit sEH have advanced to human clinical trials and demonstrate promise for cardiovascular diseases. Challenges remain for sEH inhibitor and EET analog drug development; however, there is a high likelihood that a drug that acts on this third branch of arachidonic acid metabolism will be utilized to treat a cardiovascular or kidney disease in the next decade.

Synthesis of substituted fluorobenzimidazoles as inhibitors of 5-lipoxygenase and soluble epoxide hydrolase for anti-inflammatory activity

A new series of 4-((5-fluoro-6-(substituted)-1H-benzo[d]imidazol-2-ylthio)methyl)-benzoic acids 4a-o and 2-(5-fluoro-6-(substituted)-1H-benzo[d]imidazol-2-ylthio)-2-methylpropanoic acids 8a-e were synthesized, and their inhibitory potencies against soluble epoxide hydrolase (sEH) and 5-lipoxygenase (5-LOX) were investigated. These molecules were designed based on the combination of 5-LOX and sEH pharmacophores, resulting in hybrid analogs with potent sEH and 5-LOX inhibitory activity. Compound 4g showed remarkable activity with IC₅₀ values of less than 1 μM (0.9 μM) against 5-LOX, while compound 4k displayed promising activity against sEH with IC₅₀  ≤ 1 μM (0.7 μM). These compounds were evaluated for their in vivo potential using the carrageenan-induced rat paw edema assay. Based on the obtained results, the structure-activity relationship was established and a correlation between the activities was observed. Compounds 4f, 4g, 4k, 4n, and 8e showed potent anti-inflammatory activity and significant inhibition of edema (64.13, 67.39, 66.30, 65.21, and 58.69%, respectively) at a dose of 100 mg/kg, comparable to the standard drug ibuprofen (70.65%) at 3 h.

Chemical Proteomics Reveals Soluble Epoxide Hydrolase as a Therapeutic Target for Ocular Neovascularization

The standard-of-care therapeutics for the treatment of ocular neovascular diseases like wet age-related macular degeneration (AMD) are biologics targeting vascular endothelial growth factor signaling. There are currently no FDA approved small molecules for treating these blinding eye diseases. Therefore, therapeutic agents with novel mechanisms are critical to complement or combine with existing approaches. Here, we identified soluble epoxide hydrolase (sEH), a key enzyme for epoxy fatty acid metabolism, as a target of an antiangiogenic homoisoflavonoid, SH-11037. SH-11037 inhibits sEH in vitro and in vivo and docks to the substrate binding cleft in the sEH hydrolase domain. sEH levels and activity are up-regulated in the eyes of a choroidal neovascularization (CNV) mouse model. sEH is overexpressed in human wet AMD eyes, suggesting that sEH is relevant to neovascularization. Known sEH inhibitors delivered intraocularly suppressed CNV. Thus, by dissecting a bioactive compound's mechanism, we identified a new chemotype for sEH inhibition and characterized sEH as a target for blocking the CNV that underlies wet AMD.

A convenient one-pot synthesis of N-substituted amidoximes and their application toward 1,2,4-oxadiazol-5-ones

The first direct one-pot approach for the synthesis of N-substituted amidoximes from secondary amides or the intermediate amides has been developed. Through the Ph₃P–I₂-mediated dehydrative condensation, a variety of N-aryl and N-alkyl amidoximes (R¹(C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> NOH)NHR², where R¹ or R² = aryl, alkyl, or benzyl) were readily afforded under mild conditions and short reaction times. The synthetic application of the obtained amidoximes has also been demonstrated through the formation of 1,2,4-oxadiazolones via base-mediated carbonylative cyclization with 1,1′-carbonyldiimidazole.

Ph₃P–I₂ mediated one-pot synthesis of N-substituted amidoximes via imidoyl iodide was developed. The synthesis of 1,2,4-oxadiazol-5-ones was also demonstrated.

Discovery of enantioselectivity of urea inhibitors of soluble epoxide hydrolase

Soluble epoxide hydrolase (sEH) hydrolyzes epoxyeicosatrienoic acids (EETs) in the metabolic pathway of arachidonic acid and has been considered as an important therapeutic target for chronic diseases such as hypertension, diabetes and inflammation. Although many urea derivatives are known as sEH inhibitors, the enantioselectivity of the inhibitors is not highlighted in spite of the stereoselective hydrolysis of EETs by sEH. In an effort to explore the importance of enantioselectivity in the urea scaffold, a series of enantiomers with the stereocenter adjacent to the urea nitrogen atom were prepared. The selectivity of enantiomers of 1-(α-alkyl-α-phenylmethyl)-3-(3-phenylpropyl)ureas showed wide range differences up to 125 fold with the low IC50 value up to 13 nM. The S-configuration with planar phenyl and small alkyl groups at α-position is crucial for the activity and selectivity. However, restriction of the free rotation of two α-groups with indan-1-yl or 1,2,3,4-tetrahydronaphthalen-1-yl moiety abolishes the selectivity between the enantiomers, despite the increase in activity up to 13 nM. The hydrophilic group like sulfonamido group at para position of 3-phenylpropyl motif of 1-(α-alkyl-α-phenylmethyl-3-(3-phenylpropyl)urea improves the activity as well as enantiomeric selectivity. All these ureas are proved to be specific inhibitor of sEH without inhibition against mEH.

Novel soluble epoxide hydrolase inhibitors with a dihydropyrimidinone scaffold: design, synthesis and biological evaluation

Amide non-urea derivatives with a dihydropyrimidinone ring as a novel secondary pharmacophore against the sEH enzyme were designed, synthesized and biologically evaluated.

Inhibition of soluble epoxide hydrolase by fulvestrant and sulfoxides

The soluble epoxide hydrolase (sEH) is a key enzyme in the metabolism of epoxy-fatty acids, signaling molecules involved in numerous biologies. Toward finding novel inhibitors of sEH, a library of known drugs was tested for inhibition of sEH. We found that fulvestrant, an anticancer agent, is a potent (KI=26 nM) competitive inhibitor of sEH. From this observation, we found that alkyl-sulfoxides represent a new kind of pharmacophore for the inhibition of sEH.

Anti-infective and herbicidal activity of N-substituted 2-aminobenzothiazoles

In this study, a series of N-substituted 2-aminobenzothiazoles was prepared according to a recently developed method. Twelve compounds were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Primary in vitro screening of the discussed compounds was also performed against fungal, bacterial and mycobacterial species. The biological activities of some compounds were comparable or higher than the standards phenoxymethylpenicillin or pyrazinamide. The most effective compounds demonstrated insignificant toxicity against the human monocytic leukemia THP-1 cell line. For all compounds, the structure-activity relationships are discussed.

Impact of soluble epoxide hydrolase and epoxyeicosanoids on human health

The presence of epoxyeicosatrienoic acids (EETs) in tissues and their metabolism by soluble epoxide hydrolase (sEH) to 1,2-diols were first reported 30 years ago. However, appreciation of their importance in cell biology and physiology has greatly accelerated over the past decade with the discovery of metabolically stable inhibitors of sEH, the commercial availability of EETs, and the development of analytical methods for the quantification of EETs and their diols. Numerous roles of EETs in regulatory biology now are clear, and the value of sEH inhibition in various animal models of disease has been demonstrated. Here, we review these results and discuss how the pharmacological stabilization of EETs and other natural epoxy-fatty acids could lead to possible disease therapies.

1-Alkyl-5-((di)alkylamino) tetrazoles: building blocks for peptide surrogates

An approach to the synthesis of 1-alkyl-5-((di)alkylamino)tetrazoles by nucleophilic substitution in 1-alkyl-5-sulfonyltetrazoles with anions generated from the primary or secondary amines was developed. Tolerance of the method to the presence of some functional groups (i.e., protected amine) in both components of the reaction was demonstrated. Obtained tetrazoles are promising building blocks for the design of peptide surrogates, in particular, for replacement approaches of alkyl urea derivatives.

1-(1-acetyl-piperidin-4-yl)-3-adamantan-1-yl-urea (AR9281) as a potent, selective, and orally available soluble epoxide hydrolase inhibitor with efficacy in rodent models of hypertension and dysglycemia

1-(1-Acetyl-piperidin-4-yl)-3-adamantan-1-yl-urea 14a (AR9281), a potent and selective soluble epoxide hydrolase inhibitor, was recently tested in a phase 2a clinical setting for its effectiveness in reducing blood pressure and improving insulin resistance in pre-diabetic patients. In a mouse model of diet induced obesity, AR9281 attenuated the enhanced glucose excursion following an intraperitoneal glucose tolerance test. AR9281 also attenuated the increase in blood pressure in angiotensin-II-induced hypertension in rats. These effects were dose-dependent and well correlated with inhibition of the sEH activity in whole blood, consistent with a role of sEH in the observed pharmacology in rodents.

Soluble epoxide hydrolase inhibitors: a patent review

IMPORTANCE OF THE FIELD

Soluble epoxide hydrolase (sEH) inhibitors have been shown to effectively increase the levels of epoxyeicosatrienoic acids and reduce the levels of dihydroxyeicosatrienoic acids, which may be translated to therapeutic potentials for multiple disease indications. It has been claimed that sEH inhibitors can be used to treat hypertension, diabetes, stroke, dyslipidemia, pain, immunological disorders, eye diseases, neurological diseases and other indications.

AREAS COVERED IN THIS REVIEW

A comprehensive synopsis of patent literature on sEH inhibitors is provided.

WHAT THE READER WILL GAIN

A total of more than 100 patent publications describing multiple classes of sEH inhibitors are analyzed. These include amides, ureas, thioamides, thioureas, carbamates, acyl hydrazones, chalcone oxdies, etc. In addition to selected in vitro and in vivo data of representative sEH inhibitors, a wide range of proposed applications of sEH inhibitors are also summarized.

TAKE HOME MESSAGE

Several sEH inhibitors with potent in vitro and in vivo target inhibition appear promising, including one Phase II clinical candidate. The clinical evaluation will be critical to assess the proclaimed therapeutic utility of sEH inhibition.

Substituted pyrazoles as novel sEH antagonist: investigation of key binding interactions within the catalytic domain

A novel series of pyrazole sEH inhibitors is reported. Lead optimization efforts to replace the aniline core are also described. In particular, 2-pyridine, 3-pyridine and pyridazine analogs are potent sEH inhibitors with favorable CYP3A4 inhibitory and microsomal stability profiles.