Cytochrome P-450 3A enzymes are responsible for biotransformation of FK506 and rapamycin in man and rat
Sattler, M.; Guengerich, F.P.; Yun, C.H.; Christians, U.; Sewing, K.F.
Drug Metabolism and Disposition the Biological Fate of Chemicals 20(5): 753-761
1992
ISSN/ISBN: 0090-9556 PMID: 1385058 Document Number: 397121
The hepatic cytochrome P-450 responsible for metabolism of the structurally related macrolides FK506 and rapamycin in humans was identified using in vitro studies. FK506 and rapamycin metabolism was significantly correlated with nifedipine oxidation in human liver microsomes of eight different individuals. Immunoinhibition with anti-P450 3A4 abolished almost all FK506 and rapamycin metabolite formation. Inactivation of P450 3A4 by incubation of human liver microsomes with triacetyl oleandomycin (50 microM) or gestodene (10 microM) inhibited metabolism of FK506 and rapamycin. In liver microsomes from dexamethasone-treated rats FK506 and rapamycin metabolism was increased compared to liver microsomes from uninduced, phenobarbital-, or 3-methylcholanthrene-induced rats. FK506 and rapamycin were metabolized by reconstituted recombinant human liver P450 3A4. It is concluded that in human and rat liver FK506 and rapamycin are metabolized primarily by cytochrome P-450 3A4.