Imidazoacridinone antitumor agent C-1311 as a selective mechanism-based inactivator of human cytochrome P450 1A2 and 3A4 isoenzymes.
BACKGROUND
5-Diethylaminoethylamino-8-hydroxyimidazoacridinone (C-1311), a promising antitumor agent that is also active against autoimmune diseases, was determined to be a selective inhibitor of the cytochrome P450 (CYP) 1A2 and 3A4 isoenzymes. Therefore, C-1311 might modulate the effectiveness of other drugs used in multidrug therapy. The present work aimed to identify the mechanism of the observed C-1311-mediated inactivation of CYP1A2 and CYP3A4.


METHODS
The inactivation experiments were performed in vitro using the human recombinant CYP1A2 and CYP3A4 (Bactosomes). CYP isoenzyme activities were determined using the CYP-specific reactions, 7-ethoxycoumarin O-deethylation (CYP1A2) and testosterone 6β-hydroxylation (CYP3A4). The concentrations of CYP-specific substrates and their metabolites formed by CYP isoenzymes were measured by RP-HPLC with UV-Vis detection.


RESULTS
The inhibition of CYPs by C-1311 was time-, concentration- and NADPH-dependent, which suggested a mechanism-based mode of action. Using a 10-fold dilution method and potassium ferricyanide we demonstrated the irreversible nature of the inhibition. In addition, the inhibition was attenuated by the presence of alternate substrates (alternative active site ligands) but not by a nucleophilic trapping agent (glutathione) or a reactive oxygen scavenger (catalase), which further supported a mechanism-based action. Substrate depletion partition ratios of 299 and 985 were calculated for the inactivation of CYP1A2 and CYP3A4, respectively.


CONCLUSIONS
Our results indicated that C-1311 is a potent mechanism-based inactivator of CYP1A2 and CYP3A4. This finding provided new insights into the mechanism of C-1311 antitumor action, particularly in relation to potential pharmacokinetic drug-drug interactions between C-1311 and/or its derivatives and the substrates of CYP isoforms.
Department of Pharmaceutical Technology and Biochemistry, Chemical Faculty, Gdańsk University of Technology, Gdańsk, Poland. Electronic address: agnieszka.potega@pg.gda.pl.
Agnieszka
A
Potęga
Department of Pharmaceutical Technology and Biochemistry, Chemical Faculty, Gdańsk University of Technology, Gdańsk, Poland. Electronic address: basia_look@wp.pl.
Barbara
B
Fedejko-Kap
Department of Pharmaceutical Technology and Biochemistry, Chemical Faculty, Gdańsk University of Technology, Gdańsk, Poland. Electronic address: zofia.mazerska@pg.gda.pl.
Zofia
Z
Mazerska
D000609:Aminoacridines / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors
D000609:Aminoacridines; D000970:Antineoplastic Agents; D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes; D002374:Catalase; C504573:CYP1A2 protein, human; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D005978:Glutathione; C098965:C 1311
Antitumor agent; C-1311; Cytochrome P450 isoenzymes; Drug–drug interactions; Mechanism-based inhibition