In Vitro and In Vivo Metabolism of a Selective δ-Opioid Receptor

Abstract

ABSTRACT:4-({4-[(2-Hydroxy-ethyl)-methyl-carbamoyl]-phenyl}-quinolin-8-ylmethylene)-1-thiazol-4-ylmethyl-piperidinium (compound I) is a selective agonist of ␦-opioid receptor developed for the treatment of depressive and anxiety disorders. The in vitro biotransformation studies using rat, dog, and human hepatocytes showed that the metabolites detected in human hepatocytes were also found in either rat or dog hepatocytes. M1 (N-dealkylation), M2 (Ndemethylation), and M4 (carboxylic acid metabolite) were major phase I metabolites observed in all three species. Human CYP3A4/5 isoenzymes were identified to be the primary enzymes responsible for the formation of M1 and M2 in human liver microsomes. After single oral administration of [ 14 C]compound I, the major elimination route for [ 14 C]compound I and its metabolites in rat was through feces with 92.9% recovery. The results from the bile duct-cannulated study revealed that a minimum of 51% of administered dose was absorbed in rats. The pharmacokinetic analysis using unlabeled parent drug showed that compound I was rapidly absorbed and exhibited a mean apparent terminal half-life of approximately 2.7 h. A total of 15 metabolites of compound I were detected and profiled in rat urine, bile, and feces. In rat bile, compound I accounted for <1.5% of the excreted dose, suggesting that compound I underwent extensive metabolism before elimination. The structures of metabolites were elucidated by highresolution tandem mass spectrometry. M1, M4, and M6 were the most abundant metabolites observed in rat bile. Only a low level of parent [ 14 C]compound I was observed in rat plasma.

Current applications of high-resolution mass spectrometry in drug metabolism studies

“…Thevis et al [32], who accomplished an MA of lower than 3 ppm for the period of analysis, observed ppm errors between −2.0 and −0.2 for the protonated molecules and between −1.2 and 4.7 ppm for the product ions after HCD without any lock masses. Similar data were published by Guo et al [24] showing ppm errors between 1.4 and 3.1 ppm using a resolution of 15,000 on an LTQ-OT studying the metabolism of a selective delta-opioid receptor agonist. The additional use of lock masses can enhance MA.…”

“…The first group uses mainly IT-based mass spectrometers such as OT-or TOF-based detectors for metabolite and structure elucidation. Guo et al [24] used an IT-OT for the identification of metabolites of the selective δ-opioid receptor agonist 4-([4-[(2-hydroxyethyl)methylcarbamoyl]phenyl] quinolin-8-yl-methylene)-1-thiazol-4-yl-methylpiperidinium in hepatocyte samples. Liu et al [18] used LC coupled with IT-TOF for studying the metabolism of olaquindox in rat liver microsomes and structural elucidation of metabolites.…”

“…Human urine was used as well [3-5, 15, 29-34]. Rarely, other biosamples are used such as calf serum [35], dog hepatocytes [24], equine urine and plasma [36], and canine S9 mix [33].…”

“…Other in vitro models include microbiological transformation in wastewater [23], hepatocytes [24], or heterologously expressed cytochrome P450 isozymes [17]. In vivo metabolism is mainly investigated in rat specimens such as urine [3-5, 21, 24-28], bile [16,24,25,27], feces [21,24,25,27], and/or plasma [16,21]. Human urine was used as well [3-5, 15, 29-34].…”

Characterization of Metabolites of Leonurine (SCM-198) in Rats after Oral Administration by Liquid Chromatography/Tandem Mass Spectrometry and NMR Spectrometry

“…Plasma samples were prepared by centrifugation of blood samples at 3000 ×g for 10 min. Plasma samples were pooled in a time proportional manner to obtain a 0 to 4 h representative pooled sample for each rat [23]. An aliquot of 0.3 mL of pooled plasma sample was mixed vigorously with 1 mL of acetonitrile-methanol (v/v, 2 : 1) and then centrifuged at 10,000 ×g for 10 min to remove protein.…”