Drug-drug interaction potential of antitumor acridine agent C-1748: The substrate of UDP-glucuronosyltransferases 2B7, 2B17 and the inhibitor of 1A9 and 2B7.

BACKGROUND: The compound 9-(2'-hydroxyethylamino)-4-methyl-1-nitroacridine (C-1748), the promising antitumor agent developed in our laboratory was determined to undergo phase I metabolic pathways. The present studies aimed to know its biotransformation with phase II enzymes - UDP-glucuronosyltransferases (UGTs) and its potential to be engaged in drug-drug interactions arising from the modulation of UGT activity.

METHODS: UGT-mediated transformations with rat liver (RLM), human liver (HLM), and human intestine (HIM) microsomes and with 10 recombinant human isoenzymes were investigated. Studies on the ability of C-1748 to inhibit UGT were performed with HLM, HT29 colorectal cancer cell homogenate and the selected recombinant UGT isoenzymes. The reactions were monitored using HPLC-UV/Vis method and the C-1748 metabolite structure was determined with ESI-TOF-MS/MS analysis.

RESULTS: Pseudo-molecular ion (m/z 474.1554) and the experiment with β-glucuronidase indicated that O-glucuronide of C-1748 was formed in the presence of microsomal fractions. This reaction was selectively catalyzed by UGT2B7 and 2B17. High inhibitory effect of C-1748 was shown towards isoenzyme UGT1A9 (IC50 =39.7μM) and significant but low inhibitory potential was expressed in HT29 cell homogenate (IC50 =84.5μM). The mixed-type inhibition mechanism (Ki =17.0μM;Ki '=81.0μM), induced by C-1748 was observed for recombinant UGT1A9 glucuronidation, whereas HT29 cell homogenate resulted in noncompetitive inhibition (Ki =94.6μM).

CONCLUSIONS: The observed UGT-mediated metabolism of C-1748 and its ability to inhibit UGT activity should be considered as the potency for drug resistance and drug-drug interactions in the prospective multidrug therapy.