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

Biochem Pharmacol. 2017 08 15;138:107-118

Authors: Chourey S, Ye Q, Reddy CN, Cossette C, Gravel S, Zeller M, Slobodchikova I, Vuckovic D, Rokach J, Powell WS

Abstract

We have developed a selective indole antagonist (230) targeting the OXE receptor for the potent eosinophil chemoattractant 5-oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid), that may be useful for the treatment of eosinophilic diseases such as asthma. In previous studies we identified ?2-oxidation of the hexyl side chain of racemic 230 as a major metabolic route in monkeys, but also obtained evidence for another pathway that appeared to involve hydroxylation of the hexyl side chain close to the indole. The present study was designed to investigate the metabolism of the active S-enantiomer of 230 (S230) and to identify the novel hydroxy metabolite and its chirality. Following oral administration, S230 rapidly appeared in the blood along with metabolites formed by a novel and highly stereospecific a-hydroxylation pathway, resulting in the formation of aS-hydroxy-S230. The chirality of a-hydroxy-S230 was determined by the total synthesis of the relevant diastereomers. Of the four possible diastereomers of a-hydroxy-230 only aS-hydroxy-S230 has significant OXE receptor antagonist activity and only this diastereomer was found in significant amounts in blood following oral administration of S230. Other novel metabolites of S230 identified in plasma by LC-MS/MS were aS,?2-dihydroxy-S230 and glucuronides of S230 and ?2-hydroxy-S230. Thus the alkyl side chain of S230, which is essential for its antagonist activity, is also the major target of the metabolic enzymes that terminate its antagonist activity. Modification of this side chain might result in the development of related antagonists with improved metabolic stability and efficacy.

PMID: 28476332 [PubMed - indexed for MEDLINE]