Mg. Shou et al., Use of inhibitory monoclonal antibodies to assess the contribution of cytochromes P450 to human drug metabolism, EUR J PHARM, 394(2-3), 2000, pp. 199-209
Three inhibitory monoclonal antibodies specific to cytochrome P450 3A4/5 (C
YP3A3/5), CYP2C8/9/19 and CYP2E1, respectively, were used to assess the con
tribution of the P450s to the metabolism of seven substrates in liver micro
somes from 18 human donors, as measured by monoclonal antibody inhibition p
henotyping of the substrate conversion to product(s). Metabolism of seven s
ubstrates by recombinant cytochromes P450 and human liver microsomes was pe
rformed in the presence of monoclonal antibodies and their metabolites were
analyzed by high-performance liquid chromatography (HPLC) or gas chromatog
raphy-mass spectrophotometry (GC-MS) to measure the magnitude of inhibition
. Our results showed that CYP3A4/5 contributes to testosterone 6 beta-hydro
xylation, taxol phenol formation, diazepam 3-hydroxylation, diazepam N-deme
thylation, and aflatoxin B1 3-hydroxylation in human liver by 79.2%, 81.5%,
73.2%, 34.5% and 80%, respectively. CYP2E1 contributes to chlorzoxazone 6-
hydroxylation, p-nitroanisole O-demethylation, and toluene hydroxylation by
45.8%, 27.7% and 44.2% respectively, and CYP2C8/9/19 contribute to diazepa
m N-demethylation by 30.6%. The additive contribution (75.3%) of human CYP3
A and CYP2C to diazepam N-demethylation was also observed in the presence o
f both anti-CYP3A4/5 and anti-CYP2C8/9/19 monoclonal antibodies. The contri
bution of individual P450s to the specific metabolic reaction in human live
r varies greatly in the individual donors and the substrates examined. Thus
, inhibitory monoclonal antibodies could play a unique role in defining the
single or subfamily of cytochrome P450 that is responsible for the metabol
ism of specific drugs. (C) 2000 Elsevier Science B.V. All rights reserved.