Tomohiro Honda

Daiichi Sankyo, Parsippany, New Jersey, United States

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Publications (7)23.43 Total impact

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    ABSTRACT: Analyses using electrophoresis with accelerator mass spectrometry revealed that in vivo bioactivated radiolabeled troglitazone and flutamide, both known to be hepatotoxic in humans, bound nonspecifically to a variety of microsomal and cytosolic proteins in livers from chimeric mice with humanized liver. Unlike those of radiolabeled diazepam (rarely hepatotoxic) and previously reported 5-n-butyl-pyrazolo[1,5-a]pyrimidine (limited hepatotoxicity), some troglitazone and flutamide binding proteins were located in the top right area in a zone analysis, representing high covalent binding contents and high target protein concentrations. Among a variety of liver microsomal proteins bound, the binding target proteins of troglitazone and flutamide with the highest covalent binding contents (in terms of pmol equivalent/µg target protein) were 17-hydroxysteroid dehydrogenase and 3-hydroxysteroid dehydrogenase, respectively. Troglitazone and flutamide were activated to reactive metabolites and apparently bound to different target proteins in livers from chimeric mice with humanized liver. The highest covalent binding contents for troglitazone was higher than that for flutamide under the present conditions. These results indicate that drug metabolism mediated by humanized livers (leading to binding in vivo) in combination with a zone analysis of covalent binding contents/target protein concentration data could be a good tool for evaluating the relationship between the nonspecific protein binding behavior of medicines and potential hepatotoxicity in humans. Thus, testing whether protein binding data of new medicines are unbalanced with respect to deviation from an inverse relationship or the presence of data points in the high covalent binding/high protein concentration zone might be an important concept in evaluating hepatotoxic potential.
    Toxicol. Res. 09/2014;
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    ABSTRACT: We report herein the synthesis and structure-activity relationships (SAR) of a series of benzyl ether compounds as an S1P1 receptor modulator. From our SAR studies, the installation of substituents onto the central benzene ring of 2a was revealed to potently influence the S1P1 and S1P3 agonistic activities, in particular, an ethyl group on the 2-position afforded satisfactory S1P1/S1P3 selectivity. These changes of the S1P1 and S1P3 agonistic activities caused by the alteration of substituents on the 2-position were reasonably explained by a docking study using an S1P1 X-ray crystal structure and S1P3 homology modeling. We found that compounds 2b and 2e had a potent in vivo immunosuppressive efficacy along with acceptable S1P1/S1P3 selectivity, and confirmed that these compounds had less in vivo bradycardia risk through the evaluation of heart rate change after oral administration of the compounds (30mg/kg, p.o.) in rats.
    Bioorganic & Medicinal Chemistry 05/2014; · 2.90 Impact Factor
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    ABSTRACT: (2R,3R,4R)-4-hydroxy-2-(hydroxymethyl)pyrrolidin-3-yl 4-O-(6-deoxy-β-D-glucopyranosyl)-α-D-glucopyranoside, CS-1036, which is an α-amylase inhibitor, exhibited a biphasic and sustained elimination with a long t1/2 (18.4-30.0 hours) in rats and monkeys, but exhibited a short t1/2 (3.7-7.9 hours) in humans. To clarify the species differences in the t1/2, the plasma protein binding of CS-1036 was evaluated by ultrafiltration. A concentration-dependent and saturable plasma protein binding of CS-1036 was observed in rats and monkeys with the dissociation rate constant (KD) of 8.95 and 27.2 nM and the Bmax of 52.8 and 22.1 nM, respectively. By the assessments of the recombinant amylase and the immunoprecipitation, the major binding protein of CS-1036 in rats was identified as salivary amylase (KD; 5.64 nM). CS-1036 also showed a concentration-dependent and saturable binding to human salivary and pancreatic amylase with similar binding affinity to rats. However, the protein binding of CS-1036 was constant in human plasma (≤10.2%) due to the lower serum amylase level compared to animals. From the calculation of the fu in the plasma based on in vitro KD and Bmax, the dose-dependent increase in the fu after oral administration is speculated to lead a dose-dependent increase in the CL, and a high AUC/dose at the lower doses such as 0.3 mg/kg in rats.
    Drug metabolism and disposition: the biological fate of chemicals 12/2013; · 3.74 Impact Factor
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    ABSTRACT: (2R,3R,4R)-4-hydroxy-2-(hydroxymethyl)pyrrolidin-3-yl 4-O-(6-deoxy-β-D-glucopyranosyl)-α-D-glucopyranoside (CS-1036) is a potent inhibitor of pancreatic and salivary α-amylase. After oral administration of [14C]CS-1036 to rats, the radioactivity was still detectable up to 7-14 days post-dose in various tissues, and its terminal phase in plasma could be explained neither by the exposure of CS-1036 nor its major metabolite M1. The slow elimination of radioactivity in various tissues was hypothesized to be caused by covalent binding to macromolecules or utilization for biogenic components. To assess the utilization for biogenic components, amino acid analysis of plasma proteins and lipid analysis of adipose tissue were conducted after repeated oral administration of [14C]CS-1036 by high-performance liquid chromatography and accelerated mass spectrometry, and by thin layer chromatography and liquid chromatography/mass spectrometry, respectively. In amino acid analysis, glutamic acid, aspartic acid, alanine and proline were identified as major radioactive amino acids, and radioactive non-essential amino acids occupied 76.0% of the radioactivity. In lipid analysis, a part of the radioactive lipids were identified as the fatty acids constituting the neutral lipids by lipase-hydrolysis. The radioactive fatty acids from neutral lipids were identified as palmitic acid, oleic acid and 8,11,14-eicosatrienoic acid. Intestinal flora was involved in CS-1036 metabolism, and also is indicated to be involved in the production of small molecule metabolites, which are the sources for amino acids and fatty acids, from [14C]CS-1036. In conclusion, radioactivity derived from [14C]CS-1036 was incorporated as the constituents of amino acids of plasma proteins and fatty acids of neutral lipids.
    Drug metabolism and disposition: the biological fate of chemicals 03/2013; · 3.74 Impact Factor
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    ABSTRACT: The absorption, metabolism and excretion of (2R,3R,4R)-4-hydroxy-2-(hydroxymethyl)pyrrolidin-3-yl 4-O-(6-deoxy-β-D-glucopyranosyl)-α-D-glucopyranoside (CS-1036), a novel and potent pancreatic and salivary α-amylase inhibitor, were evaluated in F344/DuCrlCrlj rats and cynomolgus monkeys. The total body clearance and volume of distribution of CS-1036 were low (2.67-3.44 ml/min/kg and 0.218-0.237 l/kg for rats and 2.25-2.84 ml/min/kg and 0.217-0.271 l/kg for monkeys). After intravenous administration of [(14)C]CS-1036 to rats and monkeys, radioactivity was mainly excreted into urine (77.2% for rats and 81.1% for monkeys). After oral administration, most of the radioactivity was recovered from feces (80.28% for rats and 88.13% for monkeys) with a low oral bioavailability (1.73-2.44% for rats and 0.983%-1.20% for monkeys). In rats, intestinal secretion is suggested to be involved in the fecal excretion as a minor component because the fecal excretion after intravenous administration was observed (15.66%) and the biliary excretion was almost negligible. Although intestinal flora was involved in CS-1036 metabolism, CS-1036 was the main component in feces (70.3% for rats and 48.7% for monkeys) and in the intestinal contents (33-68% for rats up to 2 h post-dose) after oral administration. In Zucker diabetic fatty rats, CS-1036 showed a suppressive effect on plasma glucose elevation after starch loading with a 50% effective dose at 0.015 mg/kg. In summary, CS-1036 showed optimal pharmacokinetic profiles: low oral absorption and favorable stability in gastrointestinal lumen, resulting in suppression of postprandial hyperglycemia by α-amylase inhibition.
    Drug metabolism and disposition: the biological fate of chemicals 02/2013; · 3.74 Impact Factor
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    ABSTRACT: CS-0777 is a selective sphingosine 1-phosphate (S1P) receptor 1 modulator with potential benefits in the treatment of autoimmune diseases, including multiple sclerosis. CS-0777 is a prodrug that requires phosphorylation to an active S1P analog, similar to the first-in-class S1P receptor modulator FTY720 (fingolimod). We sought to identify the kinase(s) involved in phosphorylation of CS-0777, anticipating sphingosine kinase (SPHK) 1 or 2 as likely candidates. Unlike kinase activity for FTY720, which is found predominantly in platelets, CS-0777 kinase activity was found mainly in red blood cells (RBCs). N,N-Dimethylsphingosine, an inhibitor of SPHK1 and -2, did not inhibit CS-0777 kinase activity. We purified CS-0777 kinase activity from human RBCs by more than 10,000-fold using ammonium sulfate precipitation and successive chromatography steps, and we identified fructosamine 3-kinase (FN3K) and fructosamine 3-kinase-related protein (FN3K-RP) by mass spectrometry. Incubation of human RBC lysates with 1-deoxy-1-morpholinofructose, a competitive inhibitor of FN3K, inhibited ∼10% of the kinase activity, suggesting FN3K-RP is the principal kinase responsible for activation of CS-0777 in blood. Lysates from HEK293 cells overexpressing FN3K or FN3K-RP resulted in phosphorylation of CS-0777 and structurally related molecules but showed little kinase activity for FTY720 and no kinase activity for sphingosine. Substrate preference was highly correlated among FN3K, FN3K-RP, and rat RBC lysates. FN3K and FN3K-RP are known to phosphorylate sugar moieties on glycosylated proteins, but this is the first report that these enzymes can phosphorylate hydrophobic xenobiotics. Identification of the kinases responsible for CS-0777 activation will permit a better understanding of the pharmacokinetics and pharmacodynamics of this promising new drug.
    Journal of Biological Chemistry 07/2011; 286(28):24765-24775. · 4.65 Impact Factor
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    ABSTRACT: CS-0777 is a selective sphingosine 1-phosphate (S1P) receptor 1 modulator with potential benefits in the treatment of autoimmune diseases, including multiple sclerosis. CS-0777 is a prodrug that requires phosphorylation to an active S1P analog, similar to the first-in-class S1P receptor modulator FTY720 (fingolimod). We sought to identify the kinase(s) involved in phosphorylation of CS-0777, anticipating sphingosine kinase (SPHK) 1 or 2 as likely candidates. Unlike kinase activity for FTY720, which is found predominantly in platelets, CS-0777 kinase activity was found mainly in red blood cells (RBCs). N,N-Dimethylsphingosine, an inhibitor of SPHK1 and -2, did not inhibit CS-0777 kinase activity. We purified CS-0777 kinase activity from human RBCs by more than 10,000-fold using ammonium sulfate precipitation and successive chromatography steps, and we identified fructosamine 3-kinase (FN3K) and fructosamine 3-kinase-related protein (FN3K-RP) by mass spectrometry. Incubation of human RBC lysates with 1-deoxy-1-morpholinofructose, a competitive inhibitor of FN3K, inhibited ∼10% of the kinase activity, suggesting FN3K-RP is the principal kinase responsible for activation of CS-0777 in blood. Lysates from HEK293 cells overexpressing FN3K or FN3K-RP resulted in phosphorylation of CS-0777 and structurally related molecules but showed little kinase activity for FTY720 and no kinase activity for sphingosine. Substrate preference was highly correlated among FN3K, FN3K-RP, and rat RBC lysates. FN3K and FN3K-RP are known to phosphorylate sugar moieties on glycosylated proteins, but this is the first report that these enzymes can phosphorylate hydrophobic xenobiotics. Identification of the kinases responsible for CS-0777 activation will permit a better understanding of the pharmacokinetics and pharmacodynamics of this promising new drug.
    Journal of Biological Chemistry 05/2011; 286(28):24765-75. · 4.65 Impact Factor