Further Characterization of the Metabolism of Desloratadine and Its Cytochrome P450 and UDP-glucuronosyltransferase Inhibition Potential: Identification of Desloratadine as a Relatively Selective UGT2B10 Inhibitor
Abstract:Desloratadine (Clarinex), the major active metabolite of loratadine (Claritin), is a nonsedating antihistamine used for the treatment of seasonal allergies and hives. Previously we reported that the formation of 3-hydroxydesloratadine, the major human metabolite of desloratadine, involves three sequential reactions, namely N-glucuronidation by UGT2B10 followed by 3-hydroxylation by CYP2C8 followed by deconjugation (rapid, nonenzymatic hydrolysis of the N-glucuronide). In this study we assessed the perpetrator … Show more
“…3 demonstrate that UGT2B10 is responsible for .90% of cotinine N-glucuronidation by HLM, making this compound a convenient, readily available UGT2B10 substrate probe. Moreover, compared with many other UGT enzyme-selective substrate probes, cotinine does not bind to BSA Consistent with the recent report of Kazmi et al (2015b), desloratadine was shown to be a moderately selective inhibitor of UGT2B10 (Fig. 2B).…”
Section: Discussionsupporting
confidence: 71%
“…2B; (Supplemental Table 2). In general, the inhibition observed in this study for desloratadine (10 mM) is in good agreement to that reported by Kazmi et al (2015b) for hepatically expressed UGT enzymes, except UGT2B4, which was not investigated by these authors.…”
supporting
confidence: 80%
“…of parameter fit) IC 50 value was 214 6 2.9 mM. Consistent with the recent report of Kazmi et al (2015b), desloratadine potently inhibited UGT2B10 (IC 50 3.86 6 0.05 mM). IC 50 values for other hepatically expressed UGT enzymes ranged from 18.9 6 0.10 mM for UGT2B4 to 271 6 7.6 mM for UGT1A6 ( Fig.…”
supporting
confidence: 76%
“…It should be noted that the extent of cotinine N-glucuronidation observed with 10 mM desloratadine is broadly consistent with IC 50 for desloratadine (;4 mM) reported in Table 2. Consistent with competitive inhibition by desloratadine (Kazmi et al, 2015b), greater and lesser inhibition occurred at cotinine concentrations below and above the K m , respectively. Collectively, the data indicate that cotinine is a selective substrate of human liver microsomal UGT2B10.…”
mentioning
confidence: 53%
“…In particular, desloratadine has been reported to be a relatively selective and potent competitive inhibitor of UGT2B10, with a K i of 1.3 mM (Kazmi et al, 2015b). Nicotine has also been employed as an inhibitor of UGT2B10 in vitro, although the UGT enzyme inhibition selectivity of this compound is incompletely characterized (Zhou et al, 2010).…”
Although there is evidence for an important role of UGT2B10 in the N-glucuronidation of drugs and other xenobiotics, the inhibitor selectivity of this enzyme is poorly understood. This study sought primarily to characterize the inhibition selectivity of UGT2B10 by UDP-glucuronosyltransferase (UGT) enzyme-selective inhibitors used for reaction phenotyping, and 34 antidepressant and antipsychotic drugs that contain an amine functional group. Initial studies demonstrated that cotinine is a highly selective substrate of human liver microsomal UGT2B10. The kinetics of cotinine N-glucuronidation by recombinant UGT and human liver microsomes (6 bovine serum albumin) were consistent with the involvement of a single enzyme. Of the UGT enzyme-selective inhibitors employed for reaction phenotyping, only the UGT2B4/7 inhibitor fluconazole reduced recombinant UGT2B10 activity to an appreciable extent. The majority of antidepressant and antipsychotic drugs screened for effects on UGT2B10 inhibited enzyme activity with IC 50 values <100 mM. The most potent inhibition was observed with the tricyclic antidepressants amitriptyline and doxepin and the tetracyclic antidepressant mianserin, and the structurally related compounds desloratadine and loratadine. Molecular modeling using a ligand-based approach indicated that hydrophobic and charge interactions are involved in inhibitor binding, whereas spatial features influence the potency of UGT2B10 inhibition. Respective mean K i,u (6 S.D.) values for amitriptyline, doxepin, and mianserin inhibition of human liver microsomal UGT2B10 were 0.61 6 0.05, 0.95 6 0.18, and 0.43 6 0.01 mM. In vitro-in vivo extrapolation indicates that these drugs may perpetrate inhibitory drug-drug interactions when coadministered with compounds that are cleared predominantly by UGT2B10.
“…3 demonstrate that UGT2B10 is responsible for .90% of cotinine N-glucuronidation by HLM, making this compound a convenient, readily available UGT2B10 substrate probe. Moreover, compared with many other UGT enzyme-selective substrate probes, cotinine does not bind to BSA Consistent with the recent report of Kazmi et al (2015b), desloratadine was shown to be a moderately selective inhibitor of UGT2B10 (Fig. 2B).…”
Section: Discussionsupporting
confidence: 71%
“…2B; (Supplemental Table 2). In general, the inhibition observed in this study for desloratadine (10 mM) is in good agreement to that reported by Kazmi et al (2015b) for hepatically expressed UGT enzymes, except UGT2B4, which was not investigated by these authors.…”
supporting
confidence: 80%
“…of parameter fit) IC 50 value was 214 6 2.9 mM. Consistent with the recent report of Kazmi et al (2015b), desloratadine potently inhibited UGT2B10 (IC 50 3.86 6 0.05 mM). IC 50 values for other hepatically expressed UGT enzymes ranged from 18.9 6 0.10 mM for UGT2B4 to 271 6 7.6 mM for UGT1A6 ( Fig.…”
supporting
confidence: 76%
“…It should be noted that the extent of cotinine N-glucuronidation observed with 10 mM desloratadine is broadly consistent with IC 50 for desloratadine (;4 mM) reported in Table 2. Consistent with competitive inhibition by desloratadine (Kazmi et al, 2015b), greater and lesser inhibition occurred at cotinine concentrations below and above the K m , respectively. Collectively, the data indicate that cotinine is a selective substrate of human liver microsomal UGT2B10.…”
mentioning
confidence: 53%
“…In particular, desloratadine has been reported to be a relatively selective and potent competitive inhibitor of UGT2B10, with a K i of 1.3 mM (Kazmi et al, 2015b). Nicotine has also been employed as an inhibitor of UGT2B10 in vitro, although the UGT enzyme inhibition selectivity of this compound is incompletely characterized (Zhou et al, 2010).…”
Although there is evidence for an important role of UGT2B10 in the N-glucuronidation of drugs and other xenobiotics, the inhibitor selectivity of this enzyme is poorly understood. This study sought primarily to characterize the inhibition selectivity of UGT2B10 by UDP-glucuronosyltransferase (UGT) enzyme-selective inhibitors used for reaction phenotyping, and 34 antidepressant and antipsychotic drugs that contain an amine functional group. Initial studies demonstrated that cotinine is a highly selective substrate of human liver microsomal UGT2B10. The kinetics of cotinine N-glucuronidation by recombinant UGT and human liver microsomes (6 bovine serum albumin) were consistent with the involvement of a single enzyme. Of the UGT enzyme-selective inhibitors employed for reaction phenotyping, only the UGT2B4/7 inhibitor fluconazole reduced recombinant UGT2B10 activity to an appreciable extent. The majority of antidepressant and antipsychotic drugs screened for effects on UGT2B10 inhibited enzyme activity with IC 50 values <100 mM. The most potent inhibition was observed with the tricyclic antidepressants amitriptyline and doxepin and the tetracyclic antidepressant mianserin, and the structurally related compounds desloratadine and loratadine. Molecular modeling using a ligand-based approach indicated that hydrophobic and charge interactions are involved in inhibitor binding, whereas spatial features influence the potency of UGT2B10 inhibition. Respective mean K i,u (6 S.D.) values for amitriptyline, doxepin, and mianserin inhibition of human liver microsomal UGT2B10 were 0.61 6 0.05, 0.95 6 0.18, and 0.43 6 0.01 mM. In vitro-in vivo extrapolation indicates that these drugs may perpetrate inhibitory drug-drug interactions when coadministered with compounds that are cleared predominantly by UGT2B10.
Employment of transient expression of foreign genes for bioconversion of pharmaceutically valuable low-molecular-weight compounds, including plant secondary metabolites, is an enticing trend still scantily explored in plant biotechnology. In the present work, an efficient protocol for rapid assessment of synthetic and plant-derived metabolites as potential substrates for human P450s (CYP2D6 and CYP3A4) via Agrobacterium-mediated transient expression in Nicotiana benthamiana is put forth. Animal P450s with broad substrate specificity are promising candidates for transformation of diverse metabolites. The efficiency of P450s in heterologous surroundings is not always satisfactory and depends on the availability of an associated electron-transfer enzyme. Plants represent an attractive assortment of prospective hosts for foreign P450s expression. The optimal composition of genetic blocks providing the highest transient expression efficiency is designed, an effective substrate administration scheme is validated, and biological activity of the investigated P450s against loratadine and several indole alkaloids with different molecular scaffold structures is tested. A novel indole alkaloid, 11-hydroxycorynanthine, is isolated from N. benthamiana plants transiently expressing CYP2D6 and supplemented with corynanthine, and its structure was elucidated. The proposed technique might be of value in realization of combinatorial biosynthesis concept comprising the junction of heterologous enzymes and substrates in different metabolic surroundings.
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