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

Distinct from previously reported urea and amide inhibitors of soluble epoxide hydrolase (sEH), a novel class of inhibitors were rationally designed based on the X-ray structure of this enzyme and known amide inhibitors. The structure–activity relationship (SAR) study was focused on improving the sEH inhibitory activity. Aminobenzisoxazoles emerged to be the optimal series, of which a potent human sEH inhibitor 7t was identified with a good pharmacokinetics (PK) profile. The strategy of employing aminoheterocycles as amide replacements may represent a general approach to develop mimics of known hydrolase or protease inhibitors containing an amide moiety.     

Acidic Nonsteroidal Anti-inflammatory Drugs Inhibit Rat Brain Fatty Acid Amide Hydrolase in a pH-dependent Manner

Previous studies have demonstrated that fatty acid amide hydrolase, the enzyme responsible for the metabolism of anandamide, is inhibited by the acidic non-steroidal anti-inflammatory drug (NSAID) ibuprofen with a potency that increases as the assay pH is reduced. Here we show that (R) -, (S) - and (R, S) -flurbiprofen, indomethacin and niflumic acid show similar pH-dependent shifts in potency to that seen with ibuprofen. Thus, (S) -flurbiprofen inhibited 2 μM [3 H]anandamide metabolism with IC 50 values of 13 and 50 μM at assay pH values of 6 and 8, respectively. In contrast, the neutral compound celecoxib was a weak fatty acid amide hydrolase inhibitor and showed no pH dependency (IC 50 values ~300 μM at both assay pH). The cyclooxygenase-2-selective inhibitors nimesulide and SC-58125 did not inhibit fatty acid amide hydrolase activity at either pH. The data are consistent with the conclusion that the non-ionised forms of the acidic NSAIDs are responsible for the inhibition of fatty acid amide hydrolase.     

A reduced-amide inhibitor of Pin1 binds in a conformation resembling a twisted-amide transition state

The mechanism of the cell cycle regulatory peptidyl prolyl isomerase (PPIase), Pin1, was investigated using reduced-amide inhibitors designed to mimic the twisted-amide transition state. Inhibitors, R-pSer-Ψ[CH(2)N]-Pro-2-(indol-3-yl)ethylamine, 1 [R = fluorenylmethoxycarbonyl (Fmoc)] and 2 (R = Ac), of Pin1 were synthesized and bioassayed. Inhibitor 1 had an IC(50) value of 6.3 μM, which is 4.5-fold better for Pin1 than our comparable ground-state analogue, a cis-amide alkene isostere-containing inhibitor. The change of Fmoc to Ac in 2 improved aqueous solubility for structural determination and resulted in an IC(50) value of 12 μM. The X-ray structure of the complex of 2 bound to Pin1 was determined to 1.76 ? resolution. The structure revealed that the reduced amide adopted a conformation similar to the proposed twisted-amide transition state of Pin1, with a trans-pyrrolidine conformation of the prolyl ring. A similar conformation of substrate would be destabilized relative to the planar amide conformation. Three additional reduced amides, with Thr replacing Ser and l- or d-pipecolate (Pip) replacing Pro, were slightly weaker inhibitors of Pin1.     

Acidic nonsteroidal anti-inflammatory drugs inhibit rat brain fatty acid amide hydrolase in a pH-dependent manner

Previous studies have demonstrated that fatty acid amide hydrolase, the enzyme responsible for the metabolism of anandamide, is inhibited by the acidic non-steroidal anti-inflammatory drug (NSAID) ibuprofen with a potency that increases as the assay pH is reduced. Here we show that (R)-, (S)- and (R,S)-flurbiprofen, indomethacin and niflumic acid show similar pH-dependent shifts in potency to that seen with ibuprofen. Thus, (S)-flurbiprofen inhibited 2 microM [3H]anandamide metabolism with IC50 values of 13 and 50 microM at assay pH values of 6 and 8, respectively. In contrast, the neutral compound celecoxib was a weak fatty acid amide hydrolase inhibitor and showed no pH dependency (IC50 values approximately 300 microM at both assay pH). The cyclooxygenase-2-selective inhibitors nimesulide and SC-58125 did not inhibit fatty acid amide hydrolase activity at either pH. The data are consistent with the conclusion that the non-ionised forms of the acidic NSAIDs are responsible for the inhibition of fatty acid amide hydrolase.     

Effect of potential amine prodrugs of selective neuronal nitric oxide synthase inhibitors on blood–brain barrier penetration

Several prodrug approaches were taken to mask amino groups in two potent and selective neuronal nitric oxide synthase (nNOS) inhibitors containing either a primary or secondary amino group to lower the charge and improve blood–brain barrier (BBB) penetration. The primary amine was masked as an azide and the secondary amine as an amide or carbamate. The azide was not reduced to the amine under a variety of in vitro and ex vivo conditions. Despite the decrease in charge of the amino group as an amide and as carbamates, BBB penetration did not increase. It appears that the uses of azides as prodrugs for primary amines or amides and carbamates as prodrugs for secondary amines are not universally effective for CNS applications.     

叠氮水杨酰胺类化合物对呼吸链琥珀酸-细胞色素c还原酶的抑制作用

合成了３－叠氮基－Ｎ－正癸烷基水杨酰胺和５－叠氮基－Ｎ－正癸烷基水杨酰胺并检测了它们对呼吸链酶系从琥珀酸到细胞色素ｃ段电子传递活性的抑制作用．两种化合物对琥珀酸－泛醌还原酶的抑制能力基本相同,而５位叠氮基取代物对泛醌－细胞色素ｃ还原酶的抑制能力较３位叠氮基取代物为强．它们与泛醌反应抑制剂３－硝基－Ｎ－正癸烷基水杨酰胺相比较,其抑制性质基本相似,只是抑制能力较后者为弱     

Heteroaromatic-aminomethyl quinolones: potent and selective iNOS inhibitors

The overproduction of nitric oxide during the biological response to inflammation by the nitric oxide synthase (NOS) enzymes have been implicated in the pathology of many diseases. By removal of the amide core from uHTS-derived quinolone 4, a new series highly potent heteroaromatic-aminomethyl quinolone iNOS inhibitors 8 were identified. SAR studies led to identification of piperazine 22 and pyrimidine 32, both of which reduced plasma nitrates following oral dosing in a mouse lipopolysaccharide challenge assay.     

Structure- and property-based design of factor Xa inhibitors: pyrrolidin-2-ones with acyclic alanyl amides as P4 motifs

Structure-based drug design was exploited in the synthesis of 3-(6-chloronaphth-2-ylsulfonyl)aminopyrrolidin-2-one-based factor Xa (fXa) inhibitors, incorporating an alanylamide P4 group with acyclic tertiary amide termini. Optimized hydrophobic contacts of one amide substituent in P4 were complemented by hydrophobicity-modulating features in the second, producing potent fXa inhibitors including examples with excellent anticoagulant properties.     

Synthesis and evaluation of piperidine urea derivatives as efficacious 11β-hydroxysteroid dehydrogenase type 1 inhibitors in diabetic ob/ob mice

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) has attracted considerable attention as a potential target for the treatment of diabetes and metabolic syndrome. Herein we report the design, synthesis and efficacy evaluation of novel amide and urea 11β-HSD1 inhibitors. Structure-activity relationship studies led to the identification of 10c, which was efficacious in a diabetic ob/ob mouse model and reduced fasting and non-fasting blood glucose levels after ip dosing.     

Triazole-linked reduced amide isosteres: an approach for the fragment-based drug discovery of anti-Alzheimer's BACE1 inhibitors

In the course of a β-site APP-cleaving enzyme 1 (BACE1) inhibitor discovery project an in situ synthesis/screening protocol was employed to prepare 120 triazole-linked reduced amide isostere inhibitors. Among these compounds, four showed modest (single digit micromolar) BACE1 inhibition. Our ligand design was based on a potent reduced amide isostere 1, wherein the P₂ amide moiety was replaced with an anti-1,2,3-triazole unit. Unfortunately, this replacement resulted in a 1000-fold decrease in potency. Docking studies of triazole-linked reduced amide isostere A3Z10 and potent oxadiazole-linked tertiary carbinamine 2a with BACE1 suggests that the docking poses of A3Z10 and 2a in the active sites are quite similar, with one exception. In the docked structures the placement of the protonated amine that engages D228 differs considerably between 2a and A3Z10. This difference could account for the lower BACE1 inhibition potency of A3Z10 and related compounds relative to 2a.     

Systematic evaluation of amide bioisosteres leading to the discovery of novel and potent thiazolylimidazolidinone inhibitors of SCD1 for the treatment of metabolic diseases

Several five- and six-membered heterocycles were introduced to replace the C2-position amide bond of the original 2-aminothiazole-based hit compound 5. Specifically, replacement of the amide bond with an imidazolidinone moiety yielded a novel and potent thiazolylimidazolidinone series of SCD1 inhibitors. XEN723 (compound 22) was identified after optimization of the thiazolylimidazolidinone series. This compound demonstrated a 560-fold improvement in in vitro potency and reduced plasma desaturation indices in a dose dependent manner, with an EC₅₀ of 4.5 mg/kg.     

Aza-peptide epoxides: potent and selective inhibitors of Schistosoma mansoni and pig kidney legumains (asparaginyl endopeptidases)

Aza-peptide epoxides are a new class of irreversible cysteine protease inhibitors. Derivatives containing a P1 aza-asparagine residue are specific for Schistosoma mansoni and pig kidney legumains, which are clan CD cysteine proteases. The inhibitors have second-order rate constants of up to 10(4) M(-1) s(-1) with pig kidney legumain and IC50 values as low as 45 nM with S. mansoni legumain. The most potent epoxides contain an ester moiety with S,S stereochemistry attached to the epoxide. Interestingly, amide and amino acid derivatives of the epoxysuccinate moiety were not inhibitors of legumain, while disubstituted amide derivatives are quite potent. The inhibitors have little or no inhibitory activity with other proteases such as caspases, chymotrypsin, papain, cathepsin B, granzyme B, and various aspartyl proteases.     

α-Ketoheterocycle inhibitors of fatty acid amide hydrolase: Exploration of conformational constraints in the acyl side chain

A series of α-ketooxazoles containing heteroatoms embedded within conformational constraints in the C2 acyl side chain of 2 (OL-135) were synthesized and evaluated as inhibitors of fatty acid amide hydrolase (FAAH). The studies reveal that the installation of a heteroatom (O) in the conformational constraint is achievable, although the potency of these novel derivatives is reduced slightly relative to 2 and the analogous 1,2,3,4-tetrahydronaphthalene series. Interestingly, both enantiomers (R and S) of the candidate inhibitors bearing a chiral center adjacent to the electrophilic carbonyl were found to effectively inhibit FAAH.     

New ketomethylene inhibitor analogues: synthesis and assessment of structural determinants for N-domain selective inhibition of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase containing two homologous domains. While the C-domain plays a major role in blood pressure regulation, the N-domain hydrolyzes the antifibrotic agent N-acetyl-Ser-Asp-Lys-Pro. Thus, N-domain selective (N-selective) inhibitors could be useful in the treatment of conditions relating to excessive tissue fibrosis. New keto-ACE analogues were designed that contained functionalities considered important for N-selective inhibitor RXP407 binding, namely, a P(2) Asp, N-acetyl group, and C-terminal amide. Such functionalities were incorporated to assess the structural determinants for N-selective binding in a novel inhibitor template. Inhibitors containing a C-terminal amide and modified P(2)' group were poor inhibitors of the N-domain, with several of these displaying improved inhibition of the C-domain. Molecules with both a C-terminal amide and P(2) Asp were also poor inhibitors and not N-selective. Compounds containing a free C-terminus, a P(2) Asp and protecting group displayed a change of more than 1000-fold N-selectivity compared with the parent molecule. Molecular docking models revealed interaction of these P(2) groups with S(2) residues Tyr369 and Arg381. This study emphasizes the importance of P(2) functionalities in allowing for improved N-selective binding and provides further rationale for the design of N-selective inhibitors, which could be useful in treating tissue fibrosis.     

Peptidyl-prolyl isomerase inhibitors

Designed peptidyl-prolyl isomerase (PPIase) inhibitors of Pin1, cyclophilin (CyP), and FK506 binding protein (FKBP) are reviewed. Emphasis is placed on the design, structure, and biological activity of the inhibitors. While CyP and FKBP inhibitors have been explored fairly thoroughly, inhibitors of the relatively new Pin1 cell cycle regulator are in their infancy. Ligands designed for Pin1 and CyP have primarily been ground state analogues: alkenes and bicyclic compounds. For FKBP, more of the focus has been on analogues of bonds at the reactive center, the prolyl amide, because of the idea that the alpha-ketoamide of FK506 is an analogue of the twisted amide in the transition state.     

N-arylaminonitriles as bioavailable peptidomimetic inhibitors of cathepsin B

To improve the pharmacokinetics of a previously reported series of dipeptidyl nitrile cathepsin B inhibitors, the P(2)-P(3) amide group was replaced with an arylamine. Further optimization of this template resulted in highly potent and selective inhibitors with excellent oral availability.     

Inhibition of Candida albicans secreted aspartic protease by a novel series of peptidomimetics,also active on the HIV-1 protease

Nineteen reduced amide, monohydroxy- or dihydroxyethylene-based transition-state peptidomimetics, known to be good inhibitors of the aspartic protease of HIV-1, were tested against a secreted aspartic protease (Sap2), purified from the culture medium of a virulent strain of Candida albicans. Ten of these compounds exhibited IC(50)s against Sap2 lower than 15 microM; the best inhibitor, Kyn-Val-Phe-Psi[OH-OH]-Phe-Val-Kyn, when added to the C. albicans culture, repressed the hydrolysis of bovine serum albumin (BSA), contained in the culture medium, and inhibited the growth of the fungus.     

Structure–activity relationships of substituted oxyoxalamides as inhibitors of the human soluble epoxide hydrolase

We explored both structure–activity relationships among substituted oxyoxalamides used as the primary pharmacophore of inhibitors of the human sEH and as a secondary pharmacophore to improve water solubility of inhibitors. When the oxyoxalamide function was modified with a variety of alkyls or substituted alkyls, compound 6 with a 2-adamantyl group and a benzyl group was found to be a potent sEH inhibitor, suggesting that the substituted oxyoxalamide function is a promising primary pharmacophore for the human sEH, and compound 6 can be a novel lead structure for the development of further improved oxyoxalamide or other related derivatives. In addition, introduction of substituted oxyoxalamide to inhibitors with an amide or urea primary pharmacophore produced significant improvements in inhibition potency and water solubility. In particular, the N,N,O-trimethyloxyoxalamide group in amide or urea inhibitors (26 and 31) was most effective among those tested for both inhibition and solubility. The results indicate that substituted oxyoxalamide function incorporated into amide or urea inhibitors is a useful secondary pharmacophore, and the resulting structures will be an important basis for the development of bioavailable sEH inhibitors.     

Amino acids as substrate for the reduction of tellurite by cells ofProteus vulgaris

Potassium tellurite was reduced more rapidly inProteus vulgaris cells in the presence of glycine, lysine, methionine, ornithine, glutamic acid and leucine. Reduction was probably bound to the activity of L-amino acid oxidases. Tellurite probably acted as an acceptor of hydrogen from reduced flavin adenine dinucleotide (FAD). Nicotine amide dinucleotide (NAD) also significantly stimulated reduction. Reduction was sensitive to SH-group inhibitors and party to KCN. Oxygen competed with the tellurite. The optimum pH was 6.7 and 7.3. Reduction did not take place in cells whose inner structure was injured.