Identification of cytochrome P4503A as the major subfamily responsible for the metabolism of roquinimex in man.
1. Roquinimex, a novel immunomodulator, is metabolized in liver microsomes from mouse and rat via cytochrome P450s to four hydroxylated and two demethylated metabolites (R1-6). The study investigated which cytochrome P450 enzyme(s) is responsible for the metabolism of roquinimex in man. 2. Enzyme kinetic analysis demonstrated an apparent Km = 1.28-7.00 mM and Vmax = 50-159 pmol x mg(-1) microsomal protein x min(-1) for the primary metabolites in human liver microsomes. The sum of Cl(int) for the primary pathways was 0.167 microl x mg(-1) microsomal protein x min(-1). 3. A correlation between the formation rate of R1-6 and 6beta-hydroxylation of testosterone was obtained within a panel of liver microsomes from 11 individuals (r2 = 0.72-0.97). Furthermore, significant inhibition (>90%) of roquinimex primary metabolism was demonstrated by ketoconazole and troleandomycin, specific inhibitors of CYP3A4 as well as with anti-CYP3A4 antibodies. Moreover, a similar metabolite pattern was produced from roquinimex by incubation with cDNA-expressed CYP3A4 as by human liver microsomes. 4. In conclusion, these data indicate a major role for CYP3A4 in the formation of roquinimex primary metabolites in human liver microsomes.
Tuvesson
H
H
Pharmacokinetics and Metabolism, Active Biotech Research AB, Lund, Sweden. helen.tuvesson@activebiotech.com
Wienkers
L C
LC
Gunnarsson
P O
PO
Seidegård
J
J
Persson
R
R
D000906:Antibodies / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D006801:Humans; D006900:Hydroxylation; D006912:Hydroxyquinolines / Q000378:metabolism*; D007654:Ketoconazole / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism; D014217:Troleandomycin / Q000494:pharmacology
D000906:Antibodies; D065607:Cytochrome P-450 Enzyme Inhibitors; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D006912:Hydroxyquinolines; C045282:roquinimex; D013739:Testosterone; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D007654:Ketoconazole