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

Abstract

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 230 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 230 is a potent antagonist of the OXE receptor in monkey eosinophils. Pharmacokinetic studies revealed that 230 appears rapidly in the blood following oral administration. Using chemically synthesized standards, we identified the major microsomal and plasma metabolites of 230 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.

In vivo α-hydroxylation of a 2-alkylindole antagonist of the OXE receptor for the eosinophil chemoattractant 5-oxo-6,8,11,14-eicosatetraenoic acid in monkeys

“…2F) displayed major ions at m/z 274 (loss of H 2 O), 248 (loss of CO 2 ), 206 (loss of CH 2 =CH-CH 2 -CO 2 H due to a McLafferty rearrangement), and 180. Both the MS 2 and MS 3 spectra of x and y are identical to those that we previously reported for d and e [4], confirming the identities of these metabolites as α-OH- 230 diastereomers.…”

“…2D). We previously showed [4] that d and e have identical mass spectra, with [M-H] − ions consistent with monohydroxy metabolites of 230 and MS 2 fragmentation patterns showing a single major ion at m/z 292 corresponding to loss of the alkyl side chain, which was consistent with the MS 3 fragmentation pattern of this ion. In the present study we examined the mass spectral fragmentation of x and y derived from authentic α-OH- 230 .…”

“…Plasma samples were thawed and diluted by the addition of MeOH (2 volumes), followed by addition of the internal standard (1 μg 5-(5-chloro-1-methyl-2-(5-methylhexyl)-1H-indol-3-yl)-3-methyl-5-oxopentanoate; identical to 230 except that it contains an isoheptyl group instead of a hexyl group; synthesized as previously described [4]). After storing overnight at −80 °C the samples were thawed and centrifuged.…”

“…The formation of 5-oxo-ETE is regulated by the availability of the cofactor NADP + , which is normally present at very low intracellular concentrations, but is dramatically elevated under conditions of oxidative stress, activation of the respiratory burst, and cell death [3]. 5-Oxo-ETE is a potent activator of human and monkey [4] eosinophils and is the only 5-lipoxygenase product with potent chemoattractant effects for these cells [5]. It acts via the selective OXE receptor, which is highly expressed on eosinophils and to a lesser extent on neutrophils and macrophages [6].…”

“…In an initial study we investigated the pharmacokinetics and metabolism of racemic 230 , as at the time that the study was initiated we did not have a procedure for the synthesis of sufficient amounts of the pure S-enantiomer. We found that 230 is a potent OXE receptor antagonist in vitro in monkeys and that it rapidly appears in the blood, along with a number of metabolites, following oral administration [4]. Chiral analysis of 230 recovered from the blood revealed that the S-enantiomer was depleted more rapidly than the R-enantiomer.…”