Differences in Cytochrome P450 Forms Involved in the Metabolism ofN,N-Dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]ethylamine monohydrochloride (NE-100), a Novel Sigma Ligand, in Human Liver and Intestine

Abstract

This article is available online at http://dmd.aspetjournals.org ABSTRACT:N,N-Dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]ethylamine monohydrochloride (NE-100) has been developed to treat subjects with schizophrenia. This drug is mainly excreted in the form of oxidative metabolites. In the present study, identification of P450 forms involved in the metabolism was carried out using human livers and intestinal microsomes (HLM and HIM). Eadie-Hofstee plots for NE-100 disappearance in HLM were biphasic, thus indicating the involvement of at least two P450 forms. The metabolism of NE-100 was mediated with recombinant CYP1A1, CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. A significant correlation was observed between activities of NE-100 metabolism and dextromethorphan Odemethylation (a specific activity for CYP2D6) or testosterone 6␤-hydroxylation (a specific activity for CYP3A4) in HLM. The activity of NE-100 metabolism was inhibited by approximately 80% by an anti-CYP2D6 antibody and only by quinidine among the P450-selective inhibitors at a low substrate concentration (0.1 M). In contrast, with a high substrate concentration (10 M), the activity was inhibited by an anti-CYP3A4 antibody and by ketoconazole. On the other hand, in HIM, the Eadie-Hofstee plots for NE-100 disappearance were monophasic, and the metabolism was strongly inhibited by an anti-CYP3A4 antibody and by ketoconazole but not by other inhibitors used. These results strongly suggest that NE-100 has different profiles regarding metabolism between liver and intestine. During absorption, NE-100 is mainly metabolized by CYP3A4 in the intestine and thereafter by CYP2D6 in the liver in the presence of therapeutic doses.

Metabolism of N,N-Dipropyl-2-[4-Methoxy-3-(2-Phenyl-Ethoxy)-Phenyl]-Ethyl-Amine-Monohydrochloride (NE-100), A Novel Sigma Ligand: Contribution of Cytochrome P450 Forms Involved in the Formation of Individual Metabolites in Human Liver and Small Intestine

“…However, CYP2D6 and CYP3A4 were predominant forms involved in NE-100 metabolism in the liver and in the small intestine, respectively. 3) These data support the possibility that NE-100 receives the considerableˆrst pass eŠect in the small intestine. In the previous study, however, we were unable to quantify individual metabolites and metabolism of NE-100 was monitored by substrate disappearance.…”

“…Formation activities of each metabolite in HLM were compared with phenacetin O-deethylation (CYP1A1 W 2), coumarin 7-hydroxylation (CYP2A6), 7-ethoxy 4-tri‰uomethyl coumarin O-deethlation (CYP2B6), omeprazole 5-hydroxylation (CYP2C19), dextrometrophan 6-hydroxylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1), testosterone 6 bhydroxylation (CYP3A4) and lauric acid v-hydroxylation activity (CYP4A11), using microsomes obtained from 28 individual human livers as described previously. 3) Immunoinhibition study: The inhibitory eŠects of monoclonal anti-CYP2D6 and anti-CYP3A4 antibodies on the formation of the metabolite were assessed using HLM. After preincubation with HLM (0.2 mgW mL) and an antibody on ice for 15 min, the reaction was carried out by adding NE-100 (0.1, 1 and 10 mM) at 379 Cfor5, 10 and 15 min, respectively.…”

“…Concentration of inhibitors used and reaction procedures were based on our descriptions given elsewhere. 3) Data analysis: Assuming one-or two-enzyme models as described by Nakajima et al, 19) kinetic data of enzyme, Km and Vmax values (Km1 and Vmax1 for high a‹nity component, Km2 and Vmax2 for low a‹nity component) for formation of each metabolite were estimated using residual analysis on Eadie-Hofstee plots based on visual inspection. Intrinsic clearance (CLint) wascalculatedasratiooftheVmax to the Km.…”

“…1,2) We have reported that the clinical eŠective level (concentration) of NE-100 required for therapy of schizophrenic subjects might be low due to high a‹nity for sigma receptor. 3) In pre-clinical pharmacokinetic experiments, NE-100 rapidly disappeared from the in vitro rat intestinal loop and bioavailability of NE-100 after oral administration to rats was low (unpublished data). Metabolites of NE-100 were detected only as high polarity compounds in rat plasma and urine, and dog plasma.…”

“…These data suggested that CYP2D6 as a high-a‹nity enzyme and CYP3A4 as a low-a‹nity enzyme play an important role in NE-100 disappearance in HLM and in HIM, respectively. 3) The contribution of these CYP forms for primary metabolites of NE-100 remained to be quantitatively predicted. CYP2D6 accounts for only 2z of the total CYP content in the liver, but it is involved in 30z metabolism of clinically relevant drugs.…”