ABSTRACT
PURPOSE: E6201 is a natural product-inspired novel inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-1 (MEK1) and other kinases and is currently under development as an anticancer (parenteral administration) and antipsoriasis agent (topical application). In vitro and in vivo preclinical studies were performed to characterize the pharmacokinetics of E6201. Allometric scaling was applied to predict human pharmacokinetics of E6201. METHODS: In vitro metabolism studies for CYP induction and CYP inhibition were conducted using human hepatocytes and microsomes, respectively. Metabolic stability using microsomes and protein-binding studies using pooled plasma were performed for mice, rats, dogs, and human. Pharmacokinetics of E6201 and its isomeric metabolite, ER-813010, in mice, rats, and dogs was determined following single IV administration of E6201 at three dose levels. Bioanalysis was performed using LC/MS/MS. Pharmacokinetic parameters were determined using non-compartmental analysis, and allometric scaling with a two-compartment model was used to predict E6201 pharmacokinetics in humans. RESULTS: E6201 showed high plasma protein binding (>95%), and metabolic stability half-life ranged from 36 to 89 min across species. In vitro CYP inhibition (CYP1A2, 2C9, 2C19, 2D6, 2E1, and 3A) and CYP induction (CYP1A, 3A, 2C9, and 2C19) suggested no inhibitory or induction effect on the tested human CYPs up to 10 µM of E6201. Pharmacokinetics of E6201 in mice, rats, and dogs was characterized by mean clearance ranging from 3.45 to 10.92 L/h/kg, distribution volume ranging from 0.63 to 13.09 L/kg, and elimination half-life ranging from 0.4 to 1.6 h. ER-813010 was detected in all species with metabolite to parent exposure ratio (AUC(R)) ranging from 3.1 to 33.4% and exhibited fast elimination (<3 h). The allometry predicted high clearance and large volume of distribution of E6201 in humans and was in general in good agreement with the observed first human subject pharmacokinetics. CONCLUSIONS: E6201 exhibited high clearance, high to moderate distribution, and fast elimination in preclinical species. In vitro results suggested that E6201 has low risk of drug-drug interactions due to CYP inhibition and induction in humans. In the first-in-man study, E6201 exhibited high clearance, which was well predicted by allometric scaling.
Subject(s)
Cytochrome P-450 Enzyme Inhibitors , Lactones/pharmacokinetics , MAP Kinase Kinase 1/antagonists & inhibitors , Animals , Chromatography, Liquid , Dogs , Drug Evaluation, Preclinical , Half-Life , Humans , Lactones/administration & dosage , Male , Mice , Mice, Inbred BALB C , Microsomes, Liver , Protein Binding , Rats , Rats, Sprague-Dawley , Species Specificity , Tandem Mass Spectrometry , Tissue DistributionABSTRACT
E2101 or N-methyl-[1-[1-(2-fluorophenethyl)piperidine-4-yl]-1H-indol-6-yl] acetamide, an antagonist of 5-hydroxytryptamine receptor subtypes 1A and 2, is currently under development for the potential treatment of skeletal muscle associated spasticity. Here we characterized the in vitro metabolism of E2101 using human liver enzymes including human liver microsomal preparations, human liver S9 fractions, and individual forms of recombinant cytochromes P450 (P450s). Our results showed that E2101 was metabolized by P450s to form monohydroxylated (M1 and M2), dihydroxylated (M3), and N-dealkylated metabolites (M4). The structures of these major microsomal metabolites were proposed based on LC/MS/MS analyses. All four metabolites, M1-M4, were formed by CYP3A4. Metabolites, M1, M2, and M4, were also formed by CYP2C19 and M2 and M3 by CYP2D6. The potential P450 inhibition and induction of E2101 were also evaluated. E2101 was determined to be a competitive inhibitor of CYP2C19 and CYP2D6 with K(i) of 15 and 48 microM, respectively, as determined by both Dixon plots and simultaneously nonlinear regression analyses. Induction of major P450 expression was not detected immunochemically after 72-h exposure to 10 or 50 microM E2101 in primary hepatocyte cultures obtained from three subjects. Taken together, E2101 is expected to metabolically interact with major human P450 enzymes including CYP2C19, CYP2D6, and CYP3A4, and a low risk of drug-drug interaction would be anticipated in clinical studies.
