Prediction of differences in in vivo oral clearance of N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]ethylamine monohydrochloride (NE-100) between extensive and poor metabolizers from in vitro metabolic data in human liver microsomes lacking CYP2D6 activity and recombinant CYPs

Abstract

1. It has previously been reported that N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride (NE-100) was predominantly metabolized by cytochrome P450 (CYP) 2D6 in human liver microsomes (HLM). In the present study, the contribution of CYP forms involved in the formation of the major metabolites of NE-100 in human liver lacking CYP2D6 activity (PM-HLM) has been predicted by use of in vitro kinetic data on recombinant CYPs microsomes (rCYPs).

2. In PM-HLM, NE-100 is predicted to be metabolized to N-despropyl-NE-100 (NE-098), p-hydroxy-NE-100 (NE-152) and m-hydroxyl-NE-100 (NE-163), but not to O-demethy-NE-100 (NE-125), which is a major metabolite in pooled human liver microsomes (EM-HLM). The relative activity factor approach assumed that NE-098 formation is predominantly catalysed by CYP3A4 and CYP2C9 and the NE-152 + 163mix (a mixture of two hydroxylated metabolites, NE-152 and NE-163) formation is only catalysed by CYP3A4.

3. The predicted contribution rates of CYP3A4 and CYP2C9 for NE-098 formation were 58.1 and 34.6%, respectively, in PM-HLM. These predicted results were strongly supported by kinetic and inhibition studies using PM-HLM. The intrinsic clearance of NE-100 predicted from rCYPs (the predicted CL_{int-HLM-total}) corresponded to those observed from EM- and PM-HLM (the observed CL_int-HLM).

4. The in vivo oral clearance (CL_oral) of NE-100 in extensive metabolizers and poor metabolizers of CYP2D6 was predicted to be 50 times higher in extensive metabolizers than poor metabolizers using in vitro–in vivo scaling method based on the dispersion model. These data suggest that polymorphism of CYP2D6 might greatly affect NE-100 metabolism in vivo.