Metabolism and pharmacokinetics of a potent N -acylindole antagonist of the OXE receptor for the eosinophil chemoattractant 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) in rats and monkeys

We previously identified the indole 264 as a potent in vitro antagonist of the human OXE receptor that mediates the actions of the powerful eosinophil chemoattractant 5-oxo-ETE. No antagonists of this receptor are currently commercially available or are being tested in clinical studies. The lack of a rodent ortholog of the OXE receptor has hampered progress in this area because of the unavailability of commonly used mouse or rat animal models. In the present study, we examined the feasibility of using the cynomolgus monkey as an animal model to investigate the efficacy of orally administered 264 in future in vivo studies. We first confirmed that 264 is active in monkeys by showing that it is a potent inhibitor of 5-oxo-ETE-induced actin polymerization and chemotaxis in granulocytes. The major microsomal metabolites of 264 were identified by cochromatography with authentic chemically synthesized standards and LC-MS/MS as its ω2-hydroxy and ω2-oxo derivatives, formed by ω2-oxidation of its hexyl side chain. Small amounts of ω1-oxidation products were also identified. None of these metabolites have substantial antagonist potency. High levels of 264 appeared rapidly in the blood following oral administration to both rats and monkeys, and declined to low levels by 24 h. As with microsomes, its major plasma metabolites in monkeys were ω2-oxidation products. We conclude that the monkey is a suitable animal model to investigate potential therapeutic effects of 264. This, or a related compound with diminished susceptibility to ω2-oxidation, could be a useful therapeutic agent in eosinophilic disorders such as asthma

Targeting the OXE receptor with a selective antagonist inhibits allergen‐induced pulmonary inflammation in non‐human primates

Background and purposeThe 5-lipoxygenase product, 5-oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid), is a potent chemoattractant for eosinophils and neutrophils. However, little is known about its pathophysiological role because of the lack of a rodent ortholog of the oxoeicosanoid (OXE) receptor. The present study aimed to determine whether the selective OXE receptor antagonist S-Y048 can inhibit allergen-induced pulmonary inflammation in a monkey model of asthma.Experimental approachMonkeys sensitized to house dust mite antigen (HDM) were treated with either vehicle or S-Y048 prior to challenge with aerosolized HDM, and bronchoalveolar (BAL) fluid was collected 24 h later. After 6 weeks, animals that had initially been treated with vehicle received S-Y048 and vice versa for animals initially treated with S-Y048. Eosinophils and neutrophils in BAL and lung tissue samples were evaluated, as well as mucus-containing cells in bronchi.Key resultsHDM significantly increased the numbers of eosinophils, neutrophils, and macrophages in BAL fluid 24 h after challenge. These responses were all significantly inhibited by S-Y048, which also reduced the numbers of eosinophils and neutrophils in lung tissue 24 h after challenge with HDM. S-Y048 also significantly reduced the numbers of bronchial epithelial cells staining for mucin and MUC5AC after antigen challenge.Conclusion and implicationsThis study provides the first evidence that 5-oxo-ETE may play an important role in inducing allergen-induced pulmonary inflammation and could also be involved in regulating MUC5AC in goblet cells. OXE receptor antagonists such as S-Y048 may useful therapeutic agents in asthma and other eosinophilic as well as neutrophilic diseases

Inhibition of allergen‐induced dermal eosinophilia by an oxoeicosanoid receptor antagonist in non‐human primates

Background and purpose5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), acting via the OXE receptor, is unique among 5-lipoxygenase products in its ability to directly induce human eosinophil migration, suggesting its involvement in eosinophilic diseases. To address this hypothesis, we synthesized selective indole-based OXE receptor antagonists. Because rodents lack an OXE receptor orthologue, we sought to determine whether these antagonists could attenuate allergen-induced skin eosinophilia in sensitized monkeys.Experimental approachIn a pilot study, cynomolgus monkeys with environmentally acquired sensitivity to Ascaris suum were treated orally with the "first-generation" OXE antagonist 230 prior to intradermal injection of 5-oxo-ETE or Ascaris extract. Eosinophils were evaluated in punch biopsy samples taken 6 or 24 hr later. We subsequently treated captive-bred rhesus monkeys sensitized to house dust mite (HDM) allergen with a more recently developed OXE antagonist, S-Y048, and evaluated its effects on dermal eosinophilia induced by either 5-oxo-ETE or HDM.Key resultsIn a pilot experiment, both 5-oxo-ETE and Ascaris extract induced dermal eosinophilia in cynomolgus monkeys, which appeared to be reduced by 230. Subsequently, we found that the related OXE antagonist S-Y048 is a highly potent inhibitor of 5-oxo-ETE-induced activation of rhesus monkey eosinophils in vitro and has a half-life in plasma of about 6 hr after oral administration. S-Y048 significantly inhibited eosinophil infiltration into the skin in response to both intradermally administered 5-oxo-ETE and HDM.Conclusions and implications5-Oxo-ETE may play an important role in allergen-induced eosinophilia. Blocking its effects with S-Y048 may provide a novel therapeutic approach for eosinophilic diseases

Inhibition of allergen‐induced dermal eosinophilia by an oxoeicosanoid receptor antagonist in non‐human primates

Background and purpose5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), acting via the OXE receptor, is unique among 5-lipoxygenase products in its ability to directly induce human eosinophil migration, suggesting its involvement in eosinophilic diseases. To address this hypothesis, we synthesized selective indole-based OXE receptor antagonists. Because rodents lack an OXE receptor orthologue, we sought to determine whether these antagonists could attenuate allergen-induced skin eosinophilia in sensitized monkeys.Experimental approachIn a pilot study, cynomolgus monkeys with environmentally acquired sensitivity to Ascaris suum were treated orally with the "first-generation" OXE antagonist 230 prior to intradermal injection of 5-oxo-ETE or Ascaris extract. Eosinophils were evaluated in punch biopsy samples taken 6 or 24 hr later. We subsequently treated captive-bred rhesus monkeys sensitized to house dust mite (HDM) allergen with a more recently developed OXE antagonist, S-Y048, and evaluated its effects on dermal eosinophilia induced by either 5-oxo-ETE or HDM.Key resultsIn a pilot experiment, both 5-oxo-ETE and Ascaris extract induced dermal eosinophilia in cynomolgus monkeys, which appeared to be reduced by 230. Subsequently, we found that the related OXE antagonist S-Y048 is a highly potent inhibitor of 5-oxo-ETE-induced activation of rhesus monkey eosinophils in vitro and has a half-life in plasma of about 6 hr after oral administration. S-Y048 significantly inhibited eosinophil infiltration into the skin in response to both intradermally administered 5-oxo-ETE and HDM.Conclusions and implications5-Oxo-ETE may play an important role in allergen-induced eosinophilia. Blocking its effects with S-Y048 may provide a novel therapeutic approach for eosinophilic diseases

Role of Metal Ion in Specific Recognition of Pyrophosphate Ion under Physiological Conditions and Hydrolysis of the Phosphoester Linkage by Alkaline Phosphatase

Complexes synthesized from Zn­(II), Cu­(II), and Cd­(II), using a dipicolyl amine derivative (<b>L</b>), showed unique specificity toward pyrophosphate ion (PPi or P₄O₇^4–) among all other common anionic analytes, including different biologically significant phosphate ion (PO₄^3–, H₂PO₄^2–) or phosphate-ion-based nucleotides, such as AMP, ADP, ATP, and CTP. However, the relative affinities of PPi toward these three metal complexes were found to vary and follow the order <i>K</i>_a^{<b>L.Zn</b>–PPi} > are given in units of _a^{<b>L.Cu</b>–PPi} ≥ <i>K</i>_a^{<b>L.Cd</b>–PPi}. Luminescence responses of the receptor <b>L</b> were substantial on binding to Zn²⁺ and Cd²⁺, while relatively a much smaller luminescence response was observed in the presence of Cu²⁺. Luminescence responses of <b>L.M</b>–PPi (<b>M</b> is Zn²⁺, Cd²⁺, and Cu²⁺) were further modified on binding to the PPi ion. This could be utilized for quantitative detection of PPi in physiological condition as well as for developing a real time “turn-on” (for <b>L.Zn</b> and <b>L.Cu</b>) and “turn-off” (for <b>L.Cd</b>) fluorescence assay for evaluating the enzymatic activity of alkaline phosphatase (ALP). Experimental results revealed how the subtle differences in the binding affinities between PPi and M in <b>L.M</b> (<b>M</b> is Zn²⁺, Cd²⁺, and Cu²⁺), could influence the cleavage of the phosphoester linkage in PPi by ALP. The DFT calculations further revealed that the hydrolytic cleavage of the metal ion coordinated phosphoester bond is kinetically faster than that for free PPi and thus, rationalized the observed difference in the cleavage of the phosphoester bond by an important mammalian enzyme such as ALP in the presence of different metal complexes

Two Potent OXE‑R Antagonists: Assignment of Stereochemistry

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is formed by the oxidation of 5-hydroxy-6<i>E</i>,8<i>Z</i>,11<i>Z</i>,14<i>Z</i>-eicosatetraenoic acid (5-HETE), which is a major metabolite of enzymatic oxidation of arachidonic acid (AA). 5-Oxo-ETE is the most potent lipid chemoattractant for human eosinophils. Its actions are mediated by the selective OXE receptor, which is therefore an attractive target in eosinophilic diseases such as allergic rhinitis and asthma. Recently, we have reported two excellent OXE receptor antagonists that have IC₅₀ values at low nanomolar concentrations. Each of these antagonists has a chiral center, and the isolation of the individual enantiomers by chiral high-performance liquid chromatography (HPLC) revealed that in each case one enantiomer is over 300 times more potent than the other. To unambiguously assign the stereochemistry of these enantiomers and to provide access to larger amounts of the active compounds for biological testing, we report here their total synthesis

Novel Highly Potent and Metabolically Resistant Oxoeicosanoid (OXE) Receptor Antagonists That Block the Actions of the Granulocyte Chemoattractant 5‑Oxo-6,8,11,14-Eicosatetraenoic Acid (5-oxo-ETE)

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a potent lipid mediator that induces tissue eosinophilia via the selective OXE receptor (OXE-R), which is an attractive therapeutic target in eosinophilic diseases. We previously identified indole OXE-R antagonists that block 5-oxo-ETE-induced primate eosinophil activation. Although these compounds possess good oral absorption, their plasma levels decline rapidly due to extensive oxidation of their hexyl side chain. We have now succeeded in dramatically increasing antagonist potency and resistance to metabolism by replacing the hexyl group with phenylpentyl or phenylhexyl side chains. Compared with our previous lead compound <b><i>S</i>-230</b>, our most potent antagonist, <b><i>S</i>-C025</b>, has an IC₅₀ (120 pM) over 80 times lower and a substantially longer plasma half-life. A single major metabolite, which retains antagonist activity (IC₅₀, 690 pM) and has a prolonged lifetime in plasma was observed. These new highly potent OXE-R antagonists may provide a novel strategy for the treatment of eosinophilic disorders like asthma

Pharmacokinetics and Metabolism of Selective Oxoeicosanoid (OXE) Receptor Antagonists and Their Effects on 5‑Oxo-6,8,11,14-eicosatetraenoic Acid (5-Oxo-ETE)-Induced Granulocyte Activation in Monkeys

The potent eosinophil chemoattractant 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a 5-lipoxygenase product that acts via the selective OXE receptor, which is present in many species, but not rodents. We previously reported that the indole <b>230</b> is a potent human OXE receptor antagonist. The objective of the present study was to determine whether the monkey would be a suitable animal model to investigate its pharmaceutical potential. We found that monkey leukocytes synthesize and respond to 5-oxo-ETE and that <b>230</b> is a potent antagonist of the OXE receptor in monkey eosinophils. Pharmacokinetic studies revealed that <b>230</b> appears rapidly in the blood following oral administration. Using chemically synthesized standards, we identified the major microsomal and plasma metabolites of <b>230</b> as products of ω2-hydroxylation of the alkyl side chain. These studies demonstrate that the monkey is a promising animal model to investigate the drug potential of OXE receptor antagonists