Title:Effect of Saccharolactone on CYP-mediated Metabolism of Xenobiotics
Volume: 16
Issue: 2
Author(s): Dayanidhi Behera*, Pankaj Jain, Vishwanath Kurawattimath and Nagaraj Gowda
Affiliation:
- Department of Drug Metabolism and Pharmacokinetics, Glenmark Pharmaceuticals Limited, Glenmark Research Centre, MIDC Mahape, Navi-Mumbai, Maharashtra, India
Keywords:
Cytochrome P450 (CYP), UDP-glucuronosyltransferases (UGT), metabolism, human liver microsomes, saccharolactone, β-glucuronidase, CYP inhibition.
Abstract:
Background: Saccharolactone is used as a β-glucuronidase inhibitor in in vitro microsomal
and recombinant uridine diphosphoglucuronosyl transferases (rUGTs) incubations to enhance
glucuronide pathway and, thereby, formation of glucuronide metabolites. We investigated
its effect on CYP mediated metabolism of drugs (compound-174, phenacetin and quinidine) using
human liver microsomes (HLM) supplemented with Phase-1 and Phase-2 co-factors.
Methods: Compounds were incubated in HLM supplemented with co-factors to assess Phase-1
(NADPH) and Phase-2 (NADPH, alamethicin, saccharolactone and UDPGA) metabolism. CYP
phenotype assay for compound-174 was conducted in HLM (± 1-ABT) and human recombinant
CYP isoforms. CYP inhibition profile of saccharolactone was also generated in HLM.
Results: The metabolism of compound-174, phenacetin and quinidine in HLM significantly decreased
in reactions containing additional components like alamethicin, saccharolactone and UDPGA
and indicated that the addition of saccharolactone inhibited the metabolism. Phenacetin and
quinidine are known substrates of CYP1A2 and CYP3A4 isoforms. The metabolism of compound-
174 was significantly inhibited in the presence of 1-ABT in HLM, and CYP3A4 and
CYP2C8 isoforms were found to be the predominant isoforms responsible for its metabolism. Further
evaluation of CYP inhibition in HLM indicated saccharolactone to be a strong inhibitor of
CYP1A2, 2D6, 3A4 and 2C8 isoforms with IC50 values of less than 4 mM.
Conclusion: The findings indicated that saccharolactone being a strong inhibitor of CYP1A2,
2D6, 3A4 and 2C8 isoforms (IC50 < 4 mM), resulted in significant inhibition of the metabolism of
compound-174, phenacetin and quinidine in HLM and caution should be exercised in using it with
proper titration of the concentrations.