P-Glycoprotein, Multidrug-Resistance Associated Protein 2, Cyp3a, and Carboxylesterase Affect the Oral Availability and Metabolism of Vinorelbine

Abstract

We investigated the interactions of the anticancer drug vinorelbine with drug efflux transporters and cytochrome P450 3A drug-metabolizing enzymes. Vinorelbine was transported by human multidrug-resistance associated protein (MRP) 2, and Mrp2 knockout mice displayed increased vinorelbine plasma exposure after oral administration, suggesting that Mrp2 limits the intestinal uptake of vinorelbine. Using P-glycoprotein (Pgp), Cyp3a-, and P-gp/Cyp3a knockout mice, we found that the absence of P-gp or Cyp3a resulted in increased vinorelbine plasma exposure, both after oral and intravenous administration. Surprisingly, P-gp/Cyp3a knockout mice displayed markedly lower vinorelbine plasma concentrations than wild-type mice upon intravenous administration but higher concentrations upon oral administration. This could be explained by highly increased formation of 4Ј-O-deacetylvinorelbine, an active vinorelbine metabolite, especially in P-gp/Cyp3a knockout plasma. Using wild-type and Cyp3a knockout liver microsomes, we found that 4Ј-O-deacetylvinorelbine formation was 4-fold increased in Cyp3a knockout liver and was not mediated by Cyp3a or other cytochrome P450 enzymes. In vitro incubation of vinorelbine with plasma revealed that vinorelbine deacetylation in Cyp3a and especially in P-gp/Cyp3a knockout mice but not in P-gp-deficient mice was strongly up-regulated. Metabolite formation in microsomes and plasma could be completely inhibited with the nonspecific carboxylesterase (CES) inhibitor bis(4-nitrophenyl) phosphate and partly with the CES2-specific inhibitor loperamide, indicating that carboxylesterase Ces2a, which was appropriately up-regulated in Cyp3a and especially in P-gp/Cyp3a knockout liver was responsible for the 4ЈO-deacetylvinorelbine formation. Such compensatory upregulation can complicate the interpretation of knockout mouse data. Nonetheless, P-gp, Mrp2, Cyp3a, and Ces2a clearly restricted vinorelbine availability in mice. Variation in activity of their human homologs may also affect vinorelbine pharmacokinetics in patients.

OATP1A/1B Transporters Affect Irinotecan and SN-38 Pharmacokinetics and Carboxylesterase Expression in Knockout and Humanized Transgenic Mice

“…A recent study tested the impact of a few microsomal enzyme inducers on the mouse Ces enzymes, but it did not find a substantial effect on the mRNA expression levels of the Ces1 subfamily (34). Interestingly, we recently also observed Ces1 upregulation in P-gp-and Cyp3a-deficient mice similar to that in Oatp1a/1b knockout mice (41). This suggests that when normal detoxification processes of endogenous and/or dietary-derived components are reduced (by knockout of transporters or metabolizing enzymes), Ces1 upregulation can occur.…”

P-Glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain and Blood Disposition of the mTOR Inhibitor Everolimus (Afinitor) in Mice

“…As Ces1b is hardly expressed in mouse liver (28,29), the substantially expressed carboxylesterase Ces1c is the most likely candidate everolimus-binding protein in plasma. A range of other esterases, including Ces2e, Ces3a, Aadac, and Pon1, 2, and 3, were not upregulated in Abcb1a/ 1b À/À mice (27), and thus unlikely to be involved in everolimus protection in the knockout strains studied here.…”

“…À/À , and Abcb1a/1b;Abcg2 À/À mice While trying to identify the nature of the everolimusstabilizing plasma protein, we discovered in an independent study that a range of carboxylesterase enzymes was highly upregulated in, among others, Abcb1a/1b À/À mice (27). As some carboxylesterases synthesized in the liver can be abundant in mouse plasma, perhaps one or more of these plasma carboxylesterases could tightly bind everolimus.…”

Cytochrome P450 in Cancer Susceptibility and Treatment

“…Recently, interactions of the anticancer drug vinorelbine with CYP450 3A were investigated using P-gp/Cyp3a knockout mice [362]. The absence of Cyp3a alone or the combined absence of P-gp and Cyp3a resulted in increased plasma concentration of 2.2-and 3.4-fold, respectively.…”