Measuring human cytochrome P4503A4 (CYP3A4)

摘要

Monoclonal antibodies have been developed to human cytochrome P450 3A4 (CYP3A4) and cytochrome P450 2C9 (CYP2C9) by the fusion of myeloma tumor cells with isolated B-lymphocytes from spleens of mice immunized with baculovirus-expressed human CYP3A4 and human CYP2C9, respectively. The MAb specific for CYP3A4 is both a potent inhibitor of CYP3A4-catalyzed metabolism of numerous compounds (greater than 98%) and a strong binder of CYP3A4 antigen by immunoblot. The MAb for CYP3A4 cross-reacts to a less extent with CYP3A5 and CYP3A7, a fetal liver CYP3A enzyme, but not with any other human CYPs (e.g., 1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 2E1). In addition, the MAb for CYP3A4 inhibits testosterone 6β-hydroxylase activity in Rhesus monkey liver microsomes. The MAbs for CYP2C9 are very powerful inhibitors of CYP2C8/9 activity and strong binders of the enzymes on Westernblot and, further, exhibit no cross-reaction towards any of the other P450 subfamily members. Based on these features, these antibodies can be very useful tools for assessing the role of CYP3A4/5, or CYP2C9/8, respectively, in the metabolism of various compounds.