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Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane

Exemestane (EXE) is an aromatase inhibitor used for the prevention and treatment of estrogen receptor–positive breast cancer. Although the known major metabolic pathway for EXE is reduction to form the active 17β-dihydro-EXE (17β-DHE) and subsequent glucuronidation to 17β-hydroxy-EXE-17-O-β-D-glucur...

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Autores principales: Luo, Shaman, Chen, Gang, Truica, Cristina I., Baird, Cynthia C., Xia, Zuping, Lazarus, Philip
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The American Society for Pharmacology and Experimental Therapeutics 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333658/
https://www.ncbi.nlm.nih.gov/pubmed/30257855
http://dx.doi.org/10.1124/dmd.118.081166
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author Luo, Shaman
Chen, Gang
Truica, Cristina I.
Baird, Cynthia C.
Xia, Zuping
Lazarus, Philip
author_facet Luo, Shaman
Chen, Gang
Truica, Cristina I.
Baird, Cynthia C.
Xia, Zuping
Lazarus, Philip
author_sort Luo, Shaman
collection PubMed
description Exemestane (EXE) is an aromatase inhibitor used for the prevention and treatment of estrogen receptor–positive breast cancer. Although the known major metabolic pathway for EXE is reduction to form the active 17β-dihydro-EXE (17β-DHE) and subsequent glucuronidation to 17β-hydroxy-EXE-17-O-β-D-glucuronide (17β-DHE-Gluc), previous studies have suggested that other major metabolites exist for exemestane. In the present study, a liquid chromatography–mass spectrometry (LC-MS) approach was used to acquire accurate mass data in MS(E) mode, in which precursor ion and fragment ion data were obtained simultaneously to screen novel phase II EXE metabolites in urine specimens from women taking EXE. Two major metabolites predicted to be cysteine conjugates of EXE and 17β-DHE by elemental composition were identified. The structures of the two metabolites were confirmed to be 6-methylcysteinylandrosta-1,4-diene-3,17-dione (6-EXE-cys) and 6-methylcysteinylandrosta-1,4-diene-17β-hydroxy-3-one (6-17β-DHE-cys) after comparison with their chemically synthesized counterparts. Both underwent biosynthesis in vitro in three stepwise enzymatic reactions, with the first involving glutathione conjugation. The cysteine conjugates of EXE and 17β-DHE were subsequently quantified by liquid chromatography–mass spectrometry in the urine and matched plasma samples of 132 subjects taking EXE. The combined 6-EXE-cys plus 6-17β-DHE-cys made up 77% of total EXE metabolites in urine (vs. 1.7%, 0.14%, and 21% for EXE, 17β-DHE, and 17β-DHE-Gluc, respectively) and 35% in plasma (vs. 17%, 12%, and 36% for EXE, 17β-DHE, and 17β-DHE-Gluc, respectively). Therefore, cysteine conjugates of EXE and 17β-DHE appear to be major metabolites of EXE in both urine and plasma.
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spelling pubmed-73336582020-07-13 Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane Luo, Shaman Chen, Gang Truica, Cristina I. Baird, Cynthia C. Xia, Zuping Lazarus, Philip Drug Metab Dispos Articles Exemestane (EXE) is an aromatase inhibitor used for the prevention and treatment of estrogen receptor–positive breast cancer. Although the known major metabolic pathway for EXE is reduction to form the active 17β-dihydro-EXE (17β-DHE) and subsequent glucuronidation to 17β-hydroxy-EXE-17-O-β-D-glucuronide (17β-DHE-Gluc), previous studies have suggested that other major metabolites exist for exemestane. In the present study, a liquid chromatography–mass spectrometry (LC-MS) approach was used to acquire accurate mass data in MS(E) mode, in which precursor ion and fragment ion data were obtained simultaneously to screen novel phase II EXE metabolites in urine specimens from women taking EXE. Two major metabolites predicted to be cysteine conjugates of EXE and 17β-DHE by elemental composition were identified. The structures of the two metabolites were confirmed to be 6-methylcysteinylandrosta-1,4-diene-3,17-dione (6-EXE-cys) and 6-methylcysteinylandrosta-1,4-diene-17β-hydroxy-3-one (6-17β-DHE-cys) after comparison with their chemically synthesized counterparts. Both underwent biosynthesis in vitro in three stepwise enzymatic reactions, with the first involving glutathione conjugation. The cysteine conjugates of EXE and 17β-DHE were subsequently quantified by liquid chromatography–mass spectrometry in the urine and matched plasma samples of 132 subjects taking EXE. The combined 6-EXE-cys plus 6-17β-DHE-cys made up 77% of total EXE metabolites in urine (vs. 1.7%, 0.14%, and 21% for EXE, 17β-DHE, and 17β-DHE-Gluc, respectively) and 35% in plasma (vs. 17%, 12%, and 36% for EXE, 17β-DHE, and 17β-DHE-Gluc, respectively). Therefore, cysteine conjugates of EXE and 17β-DHE appear to be major metabolites of EXE in both urine and plasma. The American Society for Pharmacology and Experimental Therapeutics 2018-12 2018-12 /pmc/articles/PMC7333658/ /pubmed/30257855 http://dx.doi.org/10.1124/dmd.118.081166 Text en Copyright © 2018 The Author(s). http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the CC BY Attribution 4.0 International license (http://creativecommons.org/licenses/by/4.0/) .
spellingShingle Articles
Luo, Shaman
Chen, Gang
Truica, Cristina I.
Baird, Cynthia C.
Xia, Zuping
Lazarus, Philip
Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title_full Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title_fullStr Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title_full_unstemmed Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title_short Identification and Quantification of Novel Major Metabolites of the Steroidal Aromatase Inhibitor, Exemestane
title_sort identification and quantification of novel major metabolites of the steroidal aromatase inhibitor, exemestane
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333658/
https://www.ncbi.nlm.nih.gov/pubmed/30257855
http://dx.doi.org/10.1124/dmd.118.081166
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