title: Metabolism of sirolimus in the presence or absence of cyclosporine by genotyped human liver microsomes and recombinant cytochromes P450 3A4 and 3A5.
abstract: Sirolimus is an immunosuppressive drug currently used alone or in combination with cyclosporine. Both drugs undergo extensive metabolism by the CYP 3A enzymes. This study aimed at comparing the activity of recombinant CYP (rCYP) 3A4 and 3A5 toward sirolimus, investigating the effect of cyclosporine on the metabolic rate of these two cytochromes P450 (P450s), as well as the impact of the CYP 3A5*3 polymorphism on that of human liver microsomes (HLMs). Two distinct approaches were used; i.e., the measurement of (1) hydroxy-sirolimus and desmethyl-sirolimus production, and (2) sirolimus depletion by the in vitro half-life method. rCYP 3A5 exhibited a lower intrinsic clearance (CL(int)) for both hydroxylation (0.11 versus 0.24 microl/pmol P450/min) and depletion of sirolimus (0.64 versus 2.36 microl/pmol P450/min) than rCYP 3A4. Similar CL(int) values for hydroxylation, demethylation, and depletion were found when comparing a pool of HLMs carrying at least one CYP 3A5*1 (active) allele with a pool of HLMs not expressing CYP 3A5. This was further confirmed for sirolimus depletion using individual microsome preparations (p = 0.42). A deeper inhibitory effect of cyclosporine on the CL(int) of sirolimus depletion was found for rCYP 3A4 than for rCYP 3A5 (i.e., -44% versus -8% at 0.62 microM, 750 microg/l cyclosporine), and sirolimus metabolism was slightly less inhibited for HLMs expressing CYP 3A5 than not (-38% versus -56%). In the absence of cyclosporine, the CYP 3A5*3 polymorphism may not influence significantly sirolimus metabolism at the hepatic level. However, strong CYP 3A4 inhibition by cyclosporine could unveil the influence of this polymorphism.
authors.affiliation: Laboratoire de Pharmacologie Médicale, EA 3838 DEXO, Facultéde Médecine, 2 rue du Dr Marcland, 87025 Limoges, France. nicolas.picard@unilim.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Picard
authors.forename: Nassim
authors.initials: N
authors.lastname: Djebli
authors.forename: François-Ludovic
authors.initials: FL
authors.lastname: Sauvage
authors.forename: Pierre
authors.initials: P
authors.lastname: Marquet
mesh_terms: D016572:Cyclosporine / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D005838:Genotype; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D011994:Recombinant Proteins / Q000378:metabolism; D020123:Sirolimus / Q000378:metabolism*
chemical_list: D007166:Immunosuppressive Agents; D011994:Recombinant Proteins; D016572:Cyclosporine; D003577:Cytochrome P-450 Enzyme System; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D020123:Sirolimus