In Vitro and Clinical Evaluations of the Drug-Drug Interaction Potential of a Metabotropic Glutamate 2/3 Receptor Agonist Prodrug with Intestinal Peptide Transporter 1

ABSTRACT Despite peptide transporter 1 (PEPT1) being responsible for the bioavailability for a variety of drugs, there has been little study of its potential involvement in drug-drug interactions. Pomaglumetad methionil, a metabotropic glutamate 2/3 receptor agonist prodrug, utilizes PEPT1 to enhance absorption and bioavailability. In vitro studies were conducted to guide the decision to conduct a clinical drug interaction study and to inform the clinical study design. In vitro investigations determined the prodrug (LY2140023 monohydrate) is a substrate of PEPT1 with K m value of approximately 30 mM, whereas the active moiety (LY404039) is not a PEPT1 substrate. In addition, among the eight known PEPT1 substrates evaluated in vitro, valacyclovir was the most potent inhibitor (IC 50 = 0.46 mM) of PEPT1-mediated uptake of the prodrug. Therefore, a clinical drug interaction study was conducted to evaluate the potential interaction between the prodrug and valacyclovir in healthy subjects. No effect of coadministration was observed on the pharmacokinetics of the prodrug, valacyclovir, or either of their active moieties. Although in vitro studies showed potential for the prodrug and valacyclovir interaction via PEPT1, an in vivo study showed no interaction between these two drugs. PEPT1 does not appear to easily saturate because of its high capacity and expression in the intestine. Thus, a clinical interaction at PEPT1 is unlikely even with a compound with high affinity for the transporter

Metabolism, Excretion and pharmacokinetics of duloxetine in healthy human subjects. The American Society for Pharmacology and Experimental Therapeutics, 31(9

This article is available online at http://dmd.aspetjournals.org ABSTRACT: Duloxetine is a potent and balanced dual inhibitor of serotonin and norepinephrine reuptake being investigated for the treatment of depression and urinary incontinence. The disposition of duloxetine was studied in four healthy human subjects after a single 20.2-mg (100.6 Ci) oral dose of [ 14 C]duloxetine in an enteric-coated tablet. The mean total recovery of radioactivity (؎ S.E.M.) after 312 h was 90.5% (؎0.4%) with 72.0% (؎1.1%) excreted in the urine. Duloxetine was extensively metabolized to numerous metabolites primarily excreted into the urine in the conjugated form. The major biotransformation pathways for duloxetine involved oxidation of the naphthyl ring at either the 4-, 5-, or 6-positions followed by further oxidation, methylation, and/or conjugation. The major metabolites found in plasma were glucuronide conjugates of the following: 4-hydroxy duloxetine (M6), 6-hydroxy-5-methoxy duloxetine (M10), 4, 6-dihydroxy duloxetine (M9), and a sulfate conjugate of 5-hydroxy-6-methoxy duloxetine (M7). The major metabolites found in plasma were also found in the urine, but the urine contained many additional metabolites. In addition to duloxetine, 4-hydroxy duloxetine (M14) and an unidentified polar metabolite were observed in feces. Following [ 14 C]duloxetine administration, C max was reached at a median of 6 h for both duloxetine and total radioactivity. Duloxetine accounted for less than 3% of the circulating radioactivity based on mean area under the curve values. The elimination half-life of total radioactivity (120 h) was substantially longer than that of duloxetine (10.3 h)