Identification of Uridine 5'-Diphosphate-Glucuronosyltransferases Responsible for the Glucuronidation of Mirabegron, a Potent and Selective β3-Adrenoceptor Agonist, in Human Liver Microsomes

Eur J Drug Metab Pharmacokinet. 2018 Jun;43(3):301-309. doi: 10.1007/s13318-017-0450-x.

Abstract

Background and objectives: Mirabegron is cleared by multiple mechanisms, including drug-metabolizing enzymes. One of the most important clearance pathways is direct glucuronidation. In humans, M11 (O-glucuronide), M13 (carbamoyl-glucuronide), and M14 (N-glucuronide) have been identified, of which M11 is one of the major metabolites in human plasma. The objective of this study was to identify the uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT) isoform responsible for the direct glucuronidation of mirabegron using human liver microsomes (HLMs) and recombinant human UGTs (rhUGTs).

Methods: Reaction mixtures contained 1-1000 μM mirabegron, 8 mM MgCl2, alamethicin (25 μg/mL), 50 mM Tris-HCl buffer (pH 7.5), human liver microsome (HLM) or rhUGT (1.0 mg protein/mL), and 2 mM UDP-glucuronic acid in a total volume of 200 μL for 120 min at 37 °C. HLMs from 16 individuals were used for the correlation study, and mefenamic acid and propofol were used for the inhibition study.

Results: Regarding M11 formation, rhUGT2B7 showed high activity among the rhUGTs tested (11.3 pmol/min/mg protein). This result was supported by the correlation between M11 formation activity and UGT2B7 marker enzyme activity (3-glucuronidation of morphine, r 2 = 0.330, p = 0.020) in individual HLMs; inhibition by mefenamic acid in pooled HLMs (IC50 = 22.8 μM); and relatively similar K m values between pooled HLMs and rhUGT2B7 (1260 vs. 486 μM). Regarding M13 and M14 formation, rhUGT1A3 and rhUGT1A8 showed high activity among the rhUGTs tested, respectively.

Conclusions: UGT2B7 is the main catalyst of M11 formation in HLMs. Regarding M13 and M14 formation, UGT1A3 and UGT1A8 are strong candidates for glucuronidation, respectively.

MeSH terms

  • Acetanilides / pharmacology*
  • Adrenergic Agonists / pharmacology*
  • Glucuronides / metabolism*
  • Glucuronosyltransferase / metabolism*
  • Humans
  • Kinetics
  • Metabolic Clearance Rate / drug effects
  • Microsomes, Liver / drug effects
  • Microsomes, Liver / metabolism*
  • Morphine / metabolism
  • Receptors, Adrenergic / metabolism*
  • Recombinant Proteins / metabolism
  • Thiazoles / pharmacology*

Substances

  • Acetanilides
  • Adrenergic Agonists
  • Glucuronides
  • Receptors, Adrenergic
  • Recombinant Proteins
  • Thiazoles
  • Morphine
  • Glucuronosyltransferase
  • UDP-glucuronosyltransferase, UGT1A8
  • mirabegron