Abstract
(R)-N-{1-[3-(4-Ethoxy-phenyl)-4-oxo-3,4-dihydro-pyrido[2,3-d]-pyrimidin-2-yl]-ethyl}-N-pyridin-3-yl-methyl-2-(4-trifluoromethoxyphenyl)-acetamide (AMG 487) is a potent and selective orally bioavailable chemokine (C-X-C motif) receptor 3 (CXCR3) antagonist that displays dose- and time-dependent pharmacokinetics in human subjects after multiple oral dosing. Although AMG 487 exhibited linear pharmacokinetics on both days 1 and 7 at the 25-mg dose, dose- and time-dependent kinetics were evident at the two higher doses. Nonlinear kinetics were more pronounced after multiple dosing. Area under the plasma concentration-time curve from 0 to 24 h [AUC(0–24 h)] increased 96-fold with a 10-fold increase in dose on day 7 compared with a 28-fold increase in AUC(0–24 h) on day 1. These changes were correlated with time- and dose-dependent decreases in the metabolite to parent plasma concentrations, suggesting that these changes result from a decrease in the oral clearance (CL) of AMG 487 (e.g., intestinal/hepatic first-pass metabolism and systemic CL). The biotransformation of AMG 487 is dependent on CYP3A and results in the formation of two primary metabolites, a pyridyl N-oxide AMG 487 (M1) and an O-deethylated AMG 487 (M2). One of these metabolites, M2, undergoes further metabolism by CYP3A. M2 has also been demonstrated to inhibit CYP3A in a competitive (Ki = 0.75 μM) manner as well as via mechanism-based inhibition (unbound KI = 1.4 μM, kinact = 0.041 min–1). Data from this study implicate M2-mediated CYP3A mechanism-based inhibition as the proximal cause for the time-dependent pharmacokinetics of AMG 487. However, the sequential metabolism of M2, nonlinear AMG 487 pharmacokinetics, and the inability to accurately determine the role of intestinal AMG 487 metabolism complicates the correlation between M2 plasma concentrations and the time-dependent AMG 487 pharmacokinetic changes.
Footnotes
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Parts of this work were previously presented as follows: Tonn GR, Wong SG, Wong SC, Ye Q, Schneider M, Ma J, Jiang B, Kersey K, Floren LC, Berry K, et al. (2006) An inhibitory metabolite implicated in the time-dependent increase in AMG 487 exposures in healthy human subjects following multiple oral dosing. 14th North American Meeting of the International Society for the Study of Xenobiotics; 2006 Oct 22–26; Rio Grande, Puerto Rico. International Society for the Study of Xenobiotics, Washington, DC.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.108.021931.
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ABBREVIATIONS: AMG 487, (R)-N-{1-[3-(4-ethoxy-phenyl)-4-oxo-3,4-dihydro-pyrido[2,3-d]pyrimidin-2-yl]-ethyl}-N-pyridin-3-yl-methyl-2-(4-trifluoromethoxy-phenyl)-acetamide; AUC, area under the plasma concentration-time curve; MBI, mechanism based inhibition; DDI, drug-drug interaction; LC, liquid chromatography; MS/MS, tandem mass spectrometry; ACN, acetonitrile; HLM, human liver microsome; P450, cytochrome P450; IS, internal standard; OH, hydroxy; TDI, time-dependent inhibition.
- Received April 18, 2008.
- Accepted December 16, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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