Efflux Transport Is an Important Determinant of Ethinylestradiol Glucuronide and Ethinylestradiol Sulfate Pharmacokinetics

Abraham

Alberts

et al. 2013

Self Cite

LY2090314 (3-[9-fluoro-2-(piperidin-1-ylcarbonyl)-1,2,3,4-tetrahydro [1,4] diazepino [6,7,1-hi]indol-7-yl]-4-imidazo[1,2-a]pyridin-3-yl-1H-pyrrole-2,5-dione) is an intravenous glycogen synthase kinase-3 inhibitor in oncology trials. Drug disposition was characterized after intravenous infusion of [ 14 C]LY2090314 to rats and dogs, and was related to available clinical data. LY2090314 exhibited high clearance (approximating hepatic blood flow) and a moderate volume of distribution (∼1-2 l/kg) resulting in rapid elimination (half-life ∼0.4, 0.7, and 1.8-3.4 hours in rats, dogs, and humans, respectively). Scaled clearance from liver microsomes accurately predicted perfusion-limited clearance across species. LY2090314 was cleared by extensive metabolism, and the numerous metabolites were rapidly excreted into feces via bile (69-97% of dose; 62-93% within 0-24 hours); urinary recovery of drug-related material was low (£3% of dose). Despite extensive metabolism, in rats and humans the parent compound was the sole identifiable drug-related moiety in plasma. Even in Mdr1a-, Bcrp-, and Mrp2-knockout rats, LY2090314 metabolites did not appear in circulation, and their urinary excretion was not enhanced, because the hypothesized impaired biliary excretion of metabolites in the absence of these canalicular transporters was not observed. Canine metabolite disposition was generally similar, with the notable exception of dog-unique LY2090314 glucuronide. This conjugate was formed in the dog liver and was preferentially excreted into the blood, where it accounted for the majority of circulating radioactivity at later times, and was predominantly recovered in urine (16% of dose). In conclusion, LY2090314 was rapidly cleared by extensive metabolism with negligible circulating metabolite exposures due to biliary excretion of metabolites into feces with no apparent intestinal reabsorption.

Section: Discussionmentioning

confidence: 99%

Pharmacokinetics, Metabolism, and Excretion of the Glycogen Synthase Kinase-3 Inhibitor LY2090314 in Rats, Dogs, and Humans: A Case Study in Rapid Clearance by Extensive Metabolism with Low Circulating Metabolite Exposure

Abraham

Alberts

et al. 2013

Self Cite

“…Livers were prepared for perfusion by cannulation of the bile duct, portal vein (inflow), and inferior vena cava above the liver (outflow) as previously described (Zamek-Gliszczynski et al, 2011). After acclimation, livers were perfused in a single-pass manner with Krebs-Henseleit buffer containing 5 mM taurocholate (30 ml/min; 0-30 minutes with 10 mM metformin and drug-free 30-60 minutes).…”

Section: Methodsmentioning

confidence: 99%

Metformin Sinusoidal Efflux from the Liver Is Consistent with Negligible Biliary Excretion and Absence of Enterohepatic Cycling

Bao

Day

et al. 2013

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Although metformin hepatic distribution is critical to pharmacological activity, the drug is cleared by urinary excretion. Metformin hepatobiliary disposition was studied in rodents representative of clinical pharmacokinetics to elucidate why metformin is not appreciably eliminated in bile. On average, 1.0% 6 0.1% of the metformin oral dose was present in the liver (liver/plasma ratio = 4.5 6 0.6) over a pharmacologically relevant dose and time range in mice (10-300 mg/kg; 1.5-2.5 hours; T max = 1.4 6 0.5; bioavailability > 59%). Distribution to the kidneys was not markedly higher, which contained 0.87% 6 0.08% of the oral dose (kidney/plasma ratio = 11.9 6 1.1). However, only 0.11% 6 0.02% of the intravenous and bioavailable oral dose was recovered in bile, suggesting that biliary excretion is not the only route of clearance for hepatic metformin. Consistent with negligible biliary excretion, pharmacokinetics were unaffected by bile duct cannulation, proving the effective absence of enterohepatic cycling. In single-pass liver perfusion studies, 2.4% 6 0.3% of the perfused metformin dose was distributed to the liver, which underwent >300-fold greater sinusoidal than biliary excretion during the subsequent drug-free washout perfusion (74.0% 6 39.3% versus 0.222% 6 0.003% recovery of hepatic metformin in perfusate versus bile, respectively). These studies demonstrate that despite similar magnitude of metformin liver and kidney distribution, metformin biliary excretion is negligible due to predominant sinusoidal efflux from the liver.

“…Although detailed absorption, distribution, metabolism, and excretion (ADME) experiments can be conducted in knockout mice (Tian et al, 2007;Zamek-Gliszczynski et al, 2011;Higgins et al, 2012), rats are practically advantageous and more relevant as the most often used nonclinical species in drug development. SAGE Mdr1a, Bcrp, and Mrp2 knockout rats (SAGE Labs, Inc., St. Louis, MO) were recently commercialized in the Sprague-Dawley strain, which is commonly used in toxicology, pharmacokinetic, distribution, and excretion studies.…”

Section: Introductionmentioning

confidence: 99%

Minor Compensatory Changes in SAGE Mdr1a (P-gp), Bcrp, and Mrp2 Knockout Rats Do Not Detract from Their Utility in the Study of Transporter-Mediated Pharmacokinetics

Goldstein

Paulman

et al. 2013

Self Cite

Mdr1a-, Bcrp-, and Mrp2-knockout rats are a more practical species for absorption, distribution, metabolism, and excretion (ADME) studies than murine models and previously demonstrated expected alterations in the pharmacokinetics of various probe substrates. At present, gene expression and pathology changes were systematically studied in the small intestine, liver, kidney, and brain tissue from male SAGE Mdr1a, Bcrp, and Mrp2 knockout rats versus wild-type Sprague-Dawley controls. Gene expression data supported the relevant knockout genotype. As expected, Mrp2 knockout rats were hyperbilirubinemic and exhibited upregulation of hepatic Mrp3. Overall, few alterations were observed within 112 ADME-relevant genes. The two potentially most consequential changes were upregulation of intestinal carboxylesterase in Mdr1a knockouts and catechol-O-methyltransferase in all tissues of Bcrp knockout rats. Previously reported upregulation of hepatic Mdr1b P-glycoprotein in proprietary Wistar Mdr1a knockout rats was not observed in the SAGE counterpart investigated herein. Relative liver and kidney weights were 22-53% higher in all three knockouts, with microscopic increases in hepatocyte size in Mdr1a and Mrp2 knockout rats and glomerular size in Bcrp and Mrp2 knockouts. Increased relative weight of clearing organs is quantitatively consistent with reported increases in the clearance of drugs that are not substrates of the knocked-out transporter. Overall, SAGE knockout rats demonstrated modest compensatory changes, which do not preclude their general application to study transporter-mediated pharmacokinetics. However, until future studies elucidate the magnitude of functional change, caution is warranted in rare instances of extensive metabolism by catechol-O-methyltransferase in Bcrp knockouts and intestinal carboxylesterase in Mdr1a knockout rats, specifically for molecules with free catechol groups and esters subject to gutwall hydrolysis.