BACKGROUND: We studied the interaction of oxaliplatin derivatives involving cytotoxic adenine-based cyclin-dependent kinase inhibitors, with human liver microsomal cytochrome P450. METHODS AND RESULTS: The activities of 9 human liver microsomal CYP forms (CYPs 1A2, 7-ethoxyresorufin O-deethylation; 2A6, coumarin 7-hydroxylation; 2B6, 7-ethoxy-4-(trifluoromethyl) coumarin O-deethylation; 2C8, luciferin-6´ methyl ether demethylation; 2C9, diclofenac 4´-hydroxylation, 6´-deoxyluciferin hydroxylation; 2C19, (S)-mephenytoin 4´-hydroxylation; 2D6, bufuralol 1´-hydroxylation, 2E1, chlorzoxazone 6-hydroxylation; 3A4, testosterone 6β-hydroxylation, luciferin-6´ benzyl ether debenzylation) were tested using HPLC, fluorescence and luminescence product detection. At 100 µM platinum(II) oxalato complex concentration, CYP inhibition was in general 25%-50%, except for the CYP3A4 form which showed roughly twice the inhibition (72%-95%). At low complex concentration (10 µM), the difference in inhibition of CYP3A4 and other forms was even more pronounced. Dixon and Lineweaver-Burk plots indicated a partially noncompetitive mechanism of CYP3A4 inhibition. CONCLUSIONS: The tested complexes significantly inhibit human liver microsomal CYP3A4 activity even at clinically relevant concentrations. This could be a serious drawback for the use of these compounds in clinical practice.

Department of Medical Chemistry and Biochemistry Faculty of Medicine and Dentistry Palacky University Olomouc

Department of Pharmacology Faculty of Medicine and Dentistry Palacky University Olomouc

Institute of Molecular and Translational Medicine Faculty of Medicine and Dentistry Palacky University Olomouc Czech Republic

Regional Centre of Advanced Technologies and Materials Department of Analytical Chemistry Faculty of Science Palacky University Olomouc

Regional Centre of Advanced Technologies and Materials Department of Inorganic Chemistry Faculty of Science Palacky University Olomouc

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