Potent 5-lipoxygenase Inhibitor Research Articles

Retrograde trafficking of both Golgi complex and TGN markers to the ER induced by nordihydroguaiaretic acid and cyclofenil diphenol.

Previous studies have shown that the Golgi stack and the trans-Golgi network (TGN) may play a role in capturing escaped resident endoplasmic reticulum (ER) proteins, and directing their retrograde transport back to that organelle. Whether this retrograde movement represents a highly specific or more generalized membrane trafficking pathway is unclear. To better understand both the retrograde and anterograde trafficking pathways of the secretory apparatus, we examined more closely the in vivo effects of two structurally unrelated compounds, the potent lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA), and the non-steroidal estrogen cyclofenil diphenol (CFD), both of which are known to inhibit secretion. In the presence of these compounds, transport of vesicular stomatitis virus G membrane glycoprotein from the ER to the Golgi complex, and from the TGN to the cell surface, was inhibited potently and rapidly. Surprisingly, we found that NDGA and CFD stimulated the rapid, but not concomitant, retrograde movement of both Golgi stack and TGN membrane proteins back to the ER until both organelles were morphologically absent from cells. Both NDGA- and CFD-stimulated TGN and Golgi retrograde membrane trafficking were inhibited by microtubule depolymerizing agents and energy poisons. Removal of NDGA and CFD resulted in the complete, but not concomitant, reformation of both Golgi stacks and their closely associated TGN compartments. These studies suggest that NDGA and CFD unmask a generalized bulk recycling pathway to the ER for both Golgi and TGN membranes and, further, that NDGA and CFD are useful for investigating the molecular mechanisms that control the formation and maintenance of both the Golgi stack proper and the TGN.

Studies on 5-lipoxygenase inhibitors. II. Discovery, optical resolution and enantioselective synthesis of FR110302, a highly potent non-redox type 5-lipoxygenase inhibitor.

A novel series of 2,2-dialkyl-5-(2-quinolylmethoxy)-1,2,3, 4-tetrahydro-1-naphthols was synthesized and evaluated as 5-lipoxygenase (5-LO) inhibitors. Systematic optimization led to identification of several highly potent non-redox type 5-LO inhibitors with nanomolar IC50s as racemic mixtures. Optical resolution of racemate 50 indicated that its 5-LO inhibitory activity was enantiospecific and due to the (+)-enantiomer. An efficient synthetic route to the (+)-enantiomers via asymmetric reduction of tetralone intermediates was established. The best compound, (+)-2,2-dibutyl-5-(2-quinolylmethoxy)-1,2,3,4-tetrahydro-1-naphtho l (FR110302, (+)-50), showed potent inhibitory activity against leukotriene (LT) biosynthesis by intact neutrophiles in rats (IC50 4.9 nM) and in humans (IC50 40 nM). Furthermore oral administration of FR110302 significantly inhibited neutrophil migration in the rat air pouch model at 1 mg/kg.

Substituted (pyridylmethoxy)naphthalenes as potent and orally active 5-lipoxygenase inhibitors; synthesis, biological profile, and pharmacokinetics of L-739,010.

Dioxabicyclooctanyl naphthalenenitriles have been reported as a class of potent and nonredox 5-lipoxygenase (5-LO) inhibitors. These bicyclo derivatives were shown to be metabolically more stable than their tetrahydropyranyl counterparts but were not well orally absorbed. Replacement of the phenyl ring in the naphthalenenitrile 1 by a pyridine ring leads to the potent and orally absorbed inhibitor 3g (L-739,010, 2-cyano-4-(3-furyl)-7-[[6-[3-(3-hydroxy-6,8-dioxabicyclo[3.2.1] octanyl)]-2-pyridyl]methoxy]naphthalene). Compound 3g inhibits 5-HPETE production by human 5-LO and LTB4 biosynthesis by human PMN leukocytes and human whole blood (IC50S of 20, 1.6, and 42 nM, respectively). Derivative 3g is orally active in the rat pleurisy model (inhibition of LTB4, ED50 = 0.3 mg/kg) and in the anesthetized dog model (inhibition of ex vivo whole blood LTB4 and urinary LTE4, ED50 = 0.45 and 0.23 microgram/kg/min, respectively, i.v. infusion). In addition, 3g shows excellent functional activity against ovalbumin-induced dyspnea in rats (60% inhibition at 0.5 mg/kg, 4 h pretreatment) and Ascaris-induced bronchoconstriction in conscious sheep (50% and > 85% inhibition in early and late phases, respectively at 2.5 micrograms/kg/min, i.v. infusion) and, more particularly in the conscious antigen sensitive squirrel monkey model (53% inhibition of the increase in RL and 76% in the decrease of Cdyn, at 0.1 mg/kg, po). In rats and dogs, 3g presents excellent pharmacokinetics (estimated half-lives of 5 and 16 h, respectively) and bioavailabilities (26% and 73% when dosed as its hydrochloride salt at doses of 20 and 10 mg/kg, respectively, in methocel suspension). Based on its overall biological profile, compound 3g has been selected for preclinical animal toxicity studies.

N-(5-substituted) thiophene-2-alkylsulfonamides as potent inhibitors of 5-lipoxygenase

Compound 4k N-[5-(4-fluoro)phenoxythien-2-yl]methanesulfonamide is representative of a new class of potent inhibitors of 5-lipoxygenase (5-LO). These versatile compounds exhibit dose-dependent inhibition of 5-LO with IC 50s ranging from 20–100 nM in the rat basophilic leukemia (RBL-1) cell homogenate assay and submicromolar IC 50s in both the RBL-1 and human peripheral blood leukocyte (PBL) whole cell assays. Compound 4k also showed significant anti-inflammatory activity in the adjuvant arthritic rat at an oral dose of 3 mg/kg.

Inhibition of LTB4 biosynthesis in situ by CGS 23885, a potent 5-lipoxygenase inhibitor, correlates with its pleural fluid concentrations in an experimentally induced rat pleurisy model.

An intrapleural injection of carrageenan in rats induced LTB4 and LTC4/D4/E4 biosynthesis, exudate formation, and cellular influx in the pleural cavity. An injection of calcium ionophore (A23187, 100 nmol) 16-18 h after carrageenan injection augmented leukotriene biosynthesis and exudate formation, but not cellular influx. The carrageenan-induced pleurisy model modifid by A23187 administration was used to study the oral effect of CGS 23885 (N-hydroxy-N-[(6-phenoxy-2H-1-benzopyran-3-yl)-methyl]urea), a potent 5-lipoxygenase (5-LO) inhibitor, on inflammatory parameters. CGS 23885 dose-dependently (1 to 30 mg/kg) inhibited the enhanced LTB4 and LTC4/D4/E4 (1 to 10 mg/kg) biosynthesis, but had no effect on enhanced exudate formation. An inhibitory effect of CGS 23885 of small magnitude on cellular influx due to carrageenan stimulation was seen at 30 mg/kg. The concentrations of CGS 23885 in the pleural fluid were dose-related, and a positive correlation (r2=0.989) between pleural fluid concentration of LTB4 and CGS 23885 was observed. The results confirm that CGS 23885 is a specific, orally active 5-LO inhibitor which can achieve concentrations in the pleural cavity sufficient to inhibit production of LTB4 and LTC4/D4/E4 in an ongoing inflammatory response.

Pulmonary delivery of the 5-lipoxygenase inhibitor, Abbott-85761, in beagle dogs

Abbott-85761 is a potent 5-lipoxygenase inhibitor which is currently under investigation for the treatment of asthma. With a primary objective of targeting this compound to the lung and reducing systemic exposure, studies were undertaken to assess its lung delivery from a metered-dose inhalation (MDI) aerosol. Pulmonary absorption characteristics of Abbott-85761 from an intratracheally (I.T.) instilled aqueous solution at doses of 0.25, 0.50 and 0.75 mg/kg were ascertained. Using tracheostomized beagle dogs, and a parallel three-way crossover study design, the I.T. results were compared with equivalent doses of intravenously (I.V.) administered drug. Plasma drug concentrations were analyzed using a reverse-phase HPLC assay. Despite limited aqueous solubility, Abbott-85761 was rapidly absorbed from the lung after I.T. instillation, with complete absorption occurring within 15–30 min after dosing. A linear dose proportionality as a function of AUC was observed for I.V. as well as I.T. treatments, with pulmonary bioavailability approximating 80%. The MDI formulation contained 10 mg/ml drug in tetrafluoroethane (HFC-134a). In vitro tests for functional performance (dispersion quality, dose delivery, content uniformity and particle size) revealed a homogeneous, physically stable and a nearly monodispersed formulation. In vivo bioavailability studies were thus conducted using a three-way crossover study design, evaluating 0.5 mg/kg aerosolized Abbott-85761 and equivalent oral and I.V. dosages of the drug. Results demonstrated that the aerosol formulation was slowly absorbed from the lung. Plasma T max was approximately 7 h with pulmonary bioavailability about 40% compared to I.V. administration. The results are discussed in the context of formulation effects and delivery technique on pulmonary absorption of A-85761.

Effects of TMK-688 a potent 5-lipoxygenase inhibitor, on dual-phase asthmatic response in conscious guinea pigs sensitized with ovalbumin

ABSTRACT We evaluated the anti-asthmatic effects and mechanism of action of TMK-688, a potent 5-lipoxygenase inhibitor, on the dual-phase asthmatic response and on airway inflammation in conscious guinea pigs sensitized with ovalbumin (OA). TMK-688 inhibited both the immediate and the late asthmatic response (LAR) after administration of a single oral dose of 3.2 or 10 mg/kg 2 h before OA challenge. Pretreatment with TMK-688 also inhibited airway hyperresponsiveness to acetylcholine. The increase in eosinophils in bronchoalveolar lavage fluid and the production of reactive oxygen, an index of cell activation during LAR, was also suppressed by TMK-688. These findings suggest the following inhibitory mechanism of LAR by TMK-688: (i) a reduction of eosinophil accumulation in airways; (ii) the inhibition of the immediate asthmatic response; (iii) the inhibition of airway hyperresponsiveness; and (iv) the suppression of the generation of reactive oxygen from bronchoalveolar lavage cells.

Studies on 5-lipoxygenase inhibitors. Synthesis of and structure--activity relationship in p-hydroxyarylalkenylbenzoazoles

In a previous paper we reported that 2-(p-hydroxyarylbutadienyl)benzoxazoles are highly potent 5-lipoxygenase inhibitors. We synthesized their ethenyl homologues and benzothiazole derivatives, and evaluated their 5-lipoxygenase inhibitory activity in vitro with cell-free rat basophilic leukemia (RBL-1). In most cases the replacement of benzoxazolyl with benzothiazolyl resulted in an enhancement of the activity. All compounds with butadienyl spacers tested herein exhibited strong inhibitory activities. While most of the ethenyl homologues showed weaker activities than their corresponding butadienyl homologues, some ethenyl compounds in the benzothiazole derivatives were found to be as potent as their corresponding butadienyl homologues. The inhibitory activity was also affected by the variation in the p-hydroxyaryl functionality.

Benzophenanthridine alkaloids of Chelidonium majus; I. Inhibition of 5- and 12-lipoxygenase by a non-redox mechanism.

The benzophenanthridine alkaloids sanguinarine and chelerythrine of Chelidonium majus, L. (Papaveraceae), are potent inhibitors of 5-lipoxygenase in polymorphonuclear leukocytes and 12-lipoxygenase in mouse epidermis, while the activity of soybean lipoxygenase is not influenced. The extract of the herb of Ch.majus also inhibits the 5-LO enzyme. Chelidonine, which cannot form pseudobases, is inactive against LO enzymes. Pro- and antioxidant actions of benzophenanthridine alkaloids can be excluded from the lack of deoxyribose degradation, reactivity against free radicals and inhibition of lipid peroxidation, suggesting that the inhibitory effects against LO enzymes appear to be due to specific enzyme interaction rather than a nonspecific redox mechanism.

Polymorphism and Crystallization Behavior of Abbott-79175, a Second-Generation 5-Lipoxygenase Inhibitor

The crystal polymorphism of Abbott-79175, a potent second-generation 5-lipoxygenase inhibitor, has been studied. Crystallization from an ethyl acetate/heptane system in which moisture content was not controlled and from an ethanol/water system produced a crystal form I, which by differential scanning calorimetry, thermogravimetric analysis, and Karl Fischer analysis was likely a hemihydrate. This hemihydrate form of the compound was demonstrated to reversibly dehydrate/hydrate with the use of low heat and vacuum followed by exposure to water vapor (100% relative humidity). The dehydrated version of I was designated IA. However, it was shown that a relative humidity approaching 100% was required for the water to re-enter the crystal structure. X-ray powder diffraction and solid state 13C NMR data on polycrystalline samples crystallized from seven single organic solvents suggested two nonsolvated forms of the compound, II and III. The heptane addition rate to a dry ethyl acetate solution of the drug was shown to greatly affect the crystal habit, the crystallite size, and specific surface area upon its precipitation. Solution calorimetry of forms I, IA, and II showed that I had the most endothermic heat of solution, with IA and II having lower values. Initial dissolution rates of compressed disks of these forms in water showed rates of IA>II ≈ I. Considering all data, including evidence of conversion of II to I in aqueous suspension, it is suggested that the relative thermodynamic stability (at least when water was present) in decreasing order is I>II>IA, although I and II are similar energetically. The lower terminal dissolution rate for form IA was due to, in part, conversion to the less soluble Form I.

The effect of a selective 5-lipoxygenase inhibitor, zileuton, on tissue damage in acute colonic inflammation in rats.

Though the mechanism of tissue damage induced by colonic inflammation in ulcerative colitis is unknown, it has been established that the inflammatory mediator and potent neutrophil (PMN) chemotaxin, leukotriene B4(LTB4), is present in elevated amounts in the inflamed mucosa. The unique role of 5-lipoxygenase in the production of leukotrienes has made it a target for inhibition. This study used a rat model of acute colonic inflammation induced by a single IP injection of Mitomycin-C to test the efficacy of a specific and potent 5-lipoxygenase inhibitor zileuton in the treatment of colonic inflammation. We hypothesized that after inducing colitis in rats with mitomycin-C, the administration of oral zileuton would inhibit leukotriene production, thus preventing PMN infiltration and subsequent tissue damage. Zileuton decreased colonic tissue damage as measured by Histological score. However, zileuton did not significantly decrease neutrophil infiltration measured by mucosal PMN or myeloperoxidase (MPO) levels. Although zileuton was successful in significantly decreasing the frequency of severe colitis in our model, the fact that the decrease in PMN count and MPO level was not statistically significant suggests that another mechanism may be involved in its anti-inflammatory effect.

Dioxabicyclooctanyl naphthalenenitriles as nonredox 5-lipoxygenase inhibitors: structure-activity relationship study directed toward the improvement of metabolic stability.

Naphthalenic lignan lactone 3a (L-702,539), a potent and selective 5-lipoxygenase (5-LO) inhibitor, is extensively metabolized at two different sites: the tetrahydropyran and the lactone rings. Early knowledge of the metabolic pathways triggered and directed a structure-activity relationship study aimed toward the improvement of metabolic stability in this series. The best modifications discovered, i.e., replacement of the lactone ring by a nitrile group, replacement of the tetrahydropyran ring by a 6,8-dioxabicyclo[3.2.1]octanyl moiety, and replacement of the pendant phenyl ring by a 3-furyl ring, were incorporated in a single molecule to produce inhibitor 9ac (L-708,780). Compound 9ac inhibits the oxidation of arachidonic acid to 5-hydroperoxy-eicosatetraenoic acid by 5-LO (IC50 = 190 nM) and the formation of leukotriene B4 in human polymorphonuclear leukocytes (IC50 = 3 nM) as well as in human whole blood (IC50 = 150 nM). The good inhibitory profile shown by naphthalenenitrile 9ac is accompanied by an improved resistance to oxidative metabolism. In addition, 9ac is orally active in the functional model of antigen-induced bronchoconstriction in allergic squirrel monkeys (95% inhibition at 0.1 mg/kg).

Inhibition of Sardine Flesh Lipoxygenase by a New Antioxidant from Aspergillus terreus.

A new antioxidant and potent lipoxygenase (LOX) inhibitor, NC3B, was isolated from the fungus Aspergillus terreus and identified as 1, 3-dihydro-7-methyl-4, 5, 6-trihydroxy-isobenzofuran. Under weight gain method conditions with methyl linoleate as a substrate, NC3B was a stronger antioxidant than tocopherol (Toc) and acted as a weak Toc synergist during the autoxidation of methyl linoleate. NC3B significantly inhibited the oxidation of linoleic acid by sardine flesh LOX and caused reduction in oxygen uptake by the substrate.

Thiopyranol[2,3,4-c,d]indoles as inhibitors of 5-lipoxygenase, 5-lipoxygenase-activating protein, and leukotriene C4 synthase.

The attachment of an arylacetic or benzoic acid moiety to the thiopyrano[2,3,4-c,d]indole nucleus results in compounds which are highly potent and selective 5-lipoxygenase (5-LO) inhibitors. These compounds are structurally simpler than previous compounds of similar potency in that they contain a single chiral center. From the data presented, 2-[[1-(3-chlorobenzyl)-4-methyl-6-[(5-phenylpyridin-2-yl)methoxy]- 4, 5-dihydro-1H-thiopyrano[2,3,4-c,d]indol-2-yl]methoxy]-phenylacetic acid, 14b, was shown to inhibit 5-hydroperoxyeicosatetraenoic acid (5-HPETE) production by human 5-LO (IC50 of 18 nM). The acid 14b is highly selective as an inhibitor of 5-LO activity when compared to the inhibition of ram seminal vesicle cyclooxygenase (IC50 > 5 microM) or human leukocyte leukotriene A4 (LTA4) hydrolase (IC50 > 20 microM). In addition, 14b was inactive in a 5-lipoxygenase-activating protein (FLAP) binding assay at 10 microM. In vivo studies showed that 14b is bioavailable in rat and functionally active in the hyperreactive rat model of antigen-induced dyspnea (74% inhibition at 0.5 mk/kg po; 2 h pretreatment). In the conscious squirrel monkey model of asthma, 14b showed excellent functional activity at 0.1 mg/kg against antigen-induced bronchoconstriction (94% inhibition of the increase in RL and 100% inhibition in the decrease in Cdyn; n = 4). Resolution of this compound gave (-)-14b, the most potent enantiomer (IC50 = 10 nM in the human 5-LO assay), which was shown to possess the S configuration at the chiral center by X-ray crystallographic analysis of an intermediate. Subsequent studies on the aryl thiopyrano[2,3,4-c,d]indole series of inhibitors led to the discovery of potent dual inhibitors of both FLAP and 5-LO, the most potent of which is 2-[[1-(4-chlorobenzyl)-4-methyl-6-(quinolin-2-ylmethoxy)-4, 5-dihydro-1H-thiopyrano[2,3,4-c,d]indol-2-yl]methoxy]phenylacetic acid, 19. Acid 19 has an IC50 of 100 nM for the inhibition of 5-HPETE production by human 5-LO and is active in a FLAP binding assay with an IC50 of 32 nM. Furthermore, thiopyrano[2,3,4-c,d]indoles such as 1 and 14b are capable of inhibiting the LTC4 synthase reaction in a dose dependent manner (IC50s of 11 and 16 microM, respectively, compared to that of LTC2 at 1.2 microM) in contrast to other, structurally distinct 5-LO inhibitors. It has also been observed that the thiopyrano[2,3,4-c,d]indole class of compounds strongly promotes the translocation of 5-LO from the cytosol to a membrane fraction in the presence or absence of the ionophore A23187.(ABSTRACT TRUNCATED AT 400 WORDS)

Kinetics of degradation in aqueous solution of Abbott-79175, a potent second generation 5-lipoxygenase inhibitor

The degradation kinetics of Abbott-79175 in aqueous solution have been studied as a function of pH. Concentration/time plots indicated a pseudo-first order nature of reactions throughout the pH range studied. Additionally, the effects of temperature, ionic strength, and buffer concentration have been examined. From multiple temperature experiments, Arrhenius and activation parameters were calculated. Furthermore, it was determined that upon ionization, Abbott-79175 degradation proceeded independently of ionic strength. These data in addition to the plateau-like nature of the pH-rate constant profile above pH 10 suggest a lack of participation of hydroxide ion during the reaction. This behavior in the neutral and alkaline regions was qualitatively very similar to that of zileuton, a 5-lipoxygenase inhibitor in phase III clinical trials. In addition to allowing the determination of the buffer independent rate constants, kinetic studies as a function of buffer concentration allowed in some of the systems the deduction of which buffer species were catalytic. A multi-parameter model was fitted to the pH buffer independent rate constant data using non-linear regression. This modeling yielded parameters such as the microscopic rate constants and the p K a under the aforementioned conditions. From the pH-rate constant profile, Abbott-79175 was found to be more labile than zileuton throughout the pH range studied. This difference was greater than three orders of magnitude at pH 1. Such acid lability produced a pH profile which had a much narrower region of maximum stability.

Synthesis, antioxidant properties, biological activity and molecular modelling of a series of chalcogen analogues of the 5-lipoxygenase inhibitor DuP 654

2-Phenylsulfenyl- ( 1b), 2-phenylselenenyl- ( 1c) and 2-phenyltellurenyl-1-naphthol ( 1d) were prepared and their antioxidative properties evaluated in comparison with 2-benzyl-1-naphthol ( 1a; DuP 654). 2-Phenyltellurenyl-1-naphthol had a significantly lower (1.00 V versus SCE) oxidation potential than the other three compounds (1.24, 1.27 and 1.25 V, respectively, versus SCE for compounds 1a, 1b and 1c) as determined by cyclic voltammetry. In contrast to the other materials, compound 1d was able to catalyze the reduction of hydrogen peroxide in the presence of thiols as stoichiometric reducing agents. The organotellurium compound was also the most efficient inhibitor of azo-initiated peroxidation of linoleic acid in a two-phase model system. Ab initio geometry optimization at the 3–21G( ∗) level revealed infinitesimal changes in the molecular conformations of the carbon, sulfur, selenium and tellurium analogues. As judged by their ability to inhibit stimulated LTB 4 biosynthesis in human neutrophils, compounds 1a-1d all turned out to be highly potent 5-lipoxygenase inhibitors with IC 50-values ranging from 0.40 μM for 2-benzyl-1-naphthol ( 1a) to 0.063 μM for 2-phenyltellurenyl-1-naphthol ( 1d).

Pulmonary bioavailability and absorption characteristics of the 5-lipoxygenase inhibitor, Abbott-79175, in beagle dogs

The pulmonary bioavailability and absorption characteristics of two aerosol suspensions of a potent 5-lipoxygenase inhibitor, Abbott-79175, containing different dispersants (formulations B and C) were investigated using an intravenous (i.v.) formulation of the drug as a reference. A reverse-phase HPLC assay was used to analyze drug concentrations in serial blood samples taken after drug administration to groups of nine tracheostomized dogs. Both formulations demonstrated fast onset of drug absorption from the lung which lasted for about 9 h. Data stripping yielded absolute bioavailabilities of 57.8 (± 25.7) and 68.4 (± 22.8)% for formulations B and C, respectively. Analysis of variance (ANOVA) yielded sources of variation in each data set thus providing a means for comparisons. Moment analysis and deconvolution (PCDCON and RSTRIP) using i.v. data as the unit impulse response enabled estimation of drug absorption from the formulations for each animal. The apparent absorption of aerosolized drug from the lungs was found to fit first-order kinetics ( k 1 = 0.083 and 0.093 h −1 for formulations B and C, respectively). The results also suggested involvement of particle dissolution phenomenon as potential rate-limiting step in the absorption process (e.g., cube-root model: k 1 3 = 0.023 and 0.026 h −1 for formulations B and C, respectively). Hence, it appears that particle dissolution as well as membrane transport may be rate determining processes in the absorption of Abbott-79175 from the airways.

Determination of a new 5-lipoxygenase inhibitor, zileuton, and its inactive N-dehydroxylated metabolite in plasma by high performance liquid chromatography.

A rapid and sensitive assay was developed for the measurement of plasma concentrations of zileuton racemate, a potent inhibitor of 5-lipoxygenase. Zileuton and its inactive N-dehydroxylated metabolite were extracted from human, monkey, and rat plasma by use of a solid-phase extraction column (Analytichem Bond Elut). The compounds were then separated by reverse-phase high performance liquid chromatography (HPLC) on a Supelcosil LC-18 column and quantified on the basis of ultraviolet absorption at 260nm relative to an internal standard. The extraction recovery of zileuton, as determined by HPLC assay, was 77.9 +/- 1.7%. Recovery of the metabolite was 85.8 +/- 0.7%. Calibration curves for both compounds were linear over the zileuton concentration range 0.01 to 10.0 mg/L (correlation coefficients > 0.987), while the intra- and interassay coefficients of variation were < 15.6%. In practice, > 97% of blinded daily spiked control samples for zileuton and > 90% of those for the metabolite were within 10% of their target concentrations.

A novel series of highly potent 5-lipoxygenase inhibitors; 2-aryldienylbenzoxazoles

A series of 2-(4-arylbutadienyl)benzoxazole derivatives and an oxazolopyridine derivative were prepared and their 5-lipoxygenase inhibitory activities were evaluated. A number of compounds showed 50 % inhibition in the range of 10 −8 ≈10 −7 M.

(6,7-Diaryldihydropyrrolizin-5-yl)acetic acids, a novel class of potent dual inhibitors of both cyclooxygenase and 5-lipoxygenase.

A novel class of nonantioxidant dual inhibitors of both CO and 5-LO is described. The balance between the activity against CO and 5-LO can be shifted by modifying the substitution pattern of the phenyl moiety at the 6-position of the pyrrolizine ring. Structure-activity relationships are discussed. Compound 3e with a 4-Cl substituent (IC50 = 0.21 microM (CO); 0.18 microM (5-LO)) and 3n with a 4-OCH3 substituent (IC50 = 0.1 microM (CO); 0.24 microM (5-LO)) are the most potent and well-balanced dual inhibitors of both enzymes. The inhibition of CO was determined in a bovine thrombocyte intact cell assay and that of 5-LO using intact bovine PMNL. Compound 3e was also investigated in human cells.