Premium
Characterization of human cytochrome P450 mediated bioactivation of amodiaquine and its major metabolite N‐desethylamodiaquine
Author(s) -
Zhang Yongjie,
Vermeulen Nico P. E.,
Commandeur Jan N. M.
Publication year - 2017
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/bcp.13148
Subject(s) - metabolite , chemistry , glutathione , cytochrome p450 , microsome , cyp3a4 , biochemistry , enzyme , stereochemistry
Aims Oxidative bioactivation of amodiaquine (AQ) by cytochrome P450s to a reactive quinoneimine is considered as an important mechanism underlying its idiosyncratic hepatotoxicity. However, because internal exposure to its major metabolite N‐desethylamodiaquine (DEAQ) is up to 240‐fold higher than AQ, bioactivation of DEAQ might significantly contribute to covalent binding. The aim of the present study was to compare the kinetics of bioactivation of AQ and DEAQ by human liver microsomes (HLM) and to characterize the CYPs involved in bioactivation of AQ and DEAQ. Methods Glutathione was used to trap reactive metabolites formed in incubations of AQ and DEAQ with HLM and recombinant human cytochrome P450s (hCYPs). Kinetics of bioactivation of AQ and DEAQ in HLM and involvement of hCYPs were characterized by measuring corresponding glutathione conjugates (AQ‐SG and DEAQ‐SG) using a high‐performance liquid chromatography method. Results Bioactivation of AQ and DEAQ in HLM both exhibited Michaelis–Menten kinetics. For AQ bioactivation, enzyme kinetical parameters were K m , 11.5 ± 2.0 μmol l –1 , V max , 59.2 ± 3.2 pmol min −1 mg −1 and CL int , 5.15 μl min −1 mg −1 . For DEAQ, parameters for bioactivation were K m , 6.1 ± 1.3 μmol l –1 , V max , 5.5 ± 0.4 pmol min −1 mg −1 and CL int 0.90 μl min −1 mg −1 . Recombinant hCYPs and inhibition studies with HLM showed involvement of CYP3A4, CYP2C8, CYP2C9 and CYP2D6 in bioactivation. Conclusions The major metabolite DEAQ is likely to be quantitatively more important than AQ with respect to hepatic exposure to reactive metabolites in vivo . High expression of CYP3A4, CYP2C8, CYP2C9, and CYP2D6 may be risk factors for hepatotoxicity caused by AQ‐therapy.