Metabolism of a new antiepileptic drug, N-methyl-tetramethylcyclopropanecarboxamide, and anticonvulsant activity of its metabolites.
N-methyl-tetramethylcyclopropanecarboxamide (MTMCD) is a new antiepileptic drug (AED) structurally related to valproic acid (VPA) that has a broad spectrum of anticonvulsant activity including models of therapy-resistant epilepsy. The purpose of this study was to identify in vivo metabolites of MTMCD that could contribute to its anticonvulsant efficacy. The metabolism of MTMCD was studied in mice, in human liver microsomes (HLM), and in recombinant human CYP isoforms with focus on formation of the hydroxylation product, N-hydroxymethyl-tetramethylcyclopropanecarboxamide (OH-MTMCD) and the N-demethylation product tetramethylcyclopropanecarboxamide (TMCD). The anticonvulsant activity of MTMCD's metabolites was evaluated in the maximal electroshock (MES), subcutaneous metrazole (s.c. Met), and in the 6Hz model in mice. In mice, OH-MTMCD was identified as a phase I metabolite of MTMCD and detected in plasma and brain after administration of MTMCD. In human liver microsomes MTMCD was biotransformed to OH-MTMCD but not to TMCD. Chemical inhibition studies suggested that MTMCD hydroxylation is mainly mediated by CYP 2A6 and CYP 2C19, which was confirmed using cDNA-expressed P450 isozymes. OH-MTMCD was a broad-spectrum anticonvulsant and possessed significant anticonvulsant activity in mouse models of partial and generalized seizures (ED50 values 75-220mg/kg), but was less potent than MTMCD. As OH-MTMCD was also present at lower concentrations than MTMCD in mouse brain, it is likely that MTMCD itself and not one of its metabolites is responsible for its activity in therapy-resistant epilepsy.
Isoherranen
Nina
N
Department of Pharmaceutics, School of Pharmacy, Hebrew University of Jerusalem, Jerusalem, Israel.
Levy
René H
RH
Yagen
Boris
B
Woodhead
José H
JH
White
H Steve
HS
Bialer
Meir
M
D000577:Amides / Q000737:chemistry / Q000378:metabolism* / Q000627:therapeutic use; D000818:Animals; D000927:Anticonvulsants / Q000737:chemistry / Q000378:metabolism* / Q000627:therapeutic use; D001189:Aryl Hydrocarbon Hydroxylases; D001522:Behavior, Animal / Q000187:drug effects; D001711:Biotransformation; D001921:Brain / Q000187:drug effects; D001923:Brain Chemistry / Q000502:physiology; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003521:Cyclopropanes / Q000737:chemistry / Q000378:metabolism* / Q000627:therapeutic use; D065637:Cytochrome P-450 CYP2A6; D065731:Cytochrome P-450 CYP2C19; D004305:Dose-Response Relationship, Drug; D004597:Electroshock / Q000009:adverse effects; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D006899:Mixed Function Oxygenases; D010433:Pentylenetetrazole; D012640:Seizures / Q000139:chemically induced / Q000188:drug therapy; D014635:Valproic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use
C116673:2,2,3,3-tetramethylcyclopropane carboxamide; D000577:Amides; D000927:Anticonvulsants; D003521:Cyclopropanes; D014635:Valproic Acid; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065637:Cytochrome P-450 CYP2A6; D065731:Cytochrome P-450 CYP2C19; D010433:Pentylenetetrazole