Investigations into the metabolism of two novel neuroprotective agents by human cytochrome P450 enzymes

(-)-Deprenyl, an antiParkinson drug, demonstrates neuroprotective efficacy in several models of neurotoxicity, but has the disadvantage of being metabolized to the potential neurotoxins(-)methamphetamine and (-)-amphetamine. Two novel analogues of (-)-deprenyl which would not be metabolized to amphetamines, N-methyl,N-propargyl-beta-phenylethylamine (MPPE) and N-methyl,N-propargylphentermine (MPPT), have been synthesized in our laboratories and have demonstrated neuroprotection. Rapid and sensitive analytical methods for the proposed metabolites of MPPE and MPPT were developed and applied to metabolism studies using human liver microsomes (HLMs) and cDNA-expressed individual human cytochrome P450 (CYP) enzymes. HLM panel studies demonstrated that both drugs are metabolized in similar patterns to (-)-deprenyl, and the rates of formation of the primary metabolites, N-methylphenylethylamine, N-propargylphenylethylamine, N-methylphentermine and N-propargylphentermine were determined. HLM panels were also used to demonstrate metabolism of the primary metabolites to secondary metabolites. Both N-methylphentermine and N-propargylphentermine were metabolized to phentermine, but only N-propargylphenylethylamine was metabolized to phenylethylamine (PEA).;A fluorogenic screen established interactions of MPPE and MPPT and their metabolites with individual CYP enzymes. The CYP enzymes inhibited strongly by MPPE or MPPT were investigated further to determine if they catalyzed the metabolism of the drugs to the primary metabolites. The effects of CYPs 2B6, 2C19 and 2D6 on metabolism of MPPE, MPPT and (-)-deprenyl were quite different. CYP2B6 catalyzed N-demethylation and N-depropargylation of all three compounds, though at significantly different rates; CYP2C19 catalyzed N-demethylation of all three compounds but N-depropargylation of only MPPT; and CYP2D6 catalyzed N-depropargylation of both (-)-deprenyl and MPPE but only catalyzed N-demethylation of (-)-deprenyl.;These studies resulted in the development of sensitive, rapid assays for metabolites and characterized the metabolism of the novel neuroprotective agents MPPE and MPPT. The data obtained demonstrate that CYP-mediated metabolism of N-propargylphenylethylamines can be affected markedly by simple chemical modifications such as removal or addition of a methyl group at the side chain alpha carbon. Such information will be very useful in future studies in vivo on the metabolism and drug-drug interactions involving MPPE and MPPT.