Metabolite profiling and enzyme reaction phenotyping of luseogliflozin, a sodium-glucose cotransporter 2 inhibitor, in humans.

1. To understand the clearance mechanism of luseogliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, we investigated its human metabolite profile and metabolic enzymes responsible for the primary metabolic pathways in human using reaction phenotyping. 2. Sixteen metabolites of luseogliflozin were found in human plasma and/or urine and their structural information indicated that the drug was metabolized via multiple metabolic pathways. The primary metabolic pathways involve (1) O-deethylation to form M2 and subsequent glucuronidation to form M12, (2) ω-hydroxylation at ethoxy group to form M3 followed by oxidation to form the corresponding carboxylic acid metabolite (M17) and (3) direct glucuronidation to form M8. 3. The reaction phenotyping studies indicated that the formation of M2 was mainly mediated by cytochrome P450 (CYP) 3A4/5, and subsequently M12 formation was catalyzed by UGT1A1, UGT1A8 and UGT1A9. The formation of M3 was mediated by CYP4A11, CYP4F2 and CYP4F3B, and the further oxidation of M3 to M17 was mediated by alcohol dehydrogenase and aldehyde dehydrogenase. The formation of M8 was catalyzed by UGT1A1. 4. These results demonstrate that luseogliflozin is metabolized through multiple pathways, including CYP-mediated oxidation and glucuronidation, in human.

A Strategy for assessing potential drug-drug interactions of a concomitant agent against a drug absorbed via an intestinal transporter in humans.

A strategy for assessing potential drug-drug interactions (DDIs) based on a simulated intestinal concentration is described. The proposed prediction method was applied to the DDI assessment of luseogliflozin, a novel antidiabetic drug, against miglitol absorbed via the intestinal sodium-glucose cotransporter 1 (SGLT1). The method involves four steps: collection of physicochemical and pharmacokinetic parameters of luseogliflozin for use in a computer simulation; evaluation of the validity of these parameters by verifying the goodness of fit between simulated and observed plasma profiles; simulation of the intestinal luseogliflozin concentration-time profile using the Advanced Compartment Absorption and Transit (ACAT) model in a computer program and estimation of the time spent above a value 10-fold higher than the IC50 value (TAIC) for SGLT1; and evaluation of the DDI potential of luseogliflozin by considering the percentage of TAIC against the miglitol Tmax (time for Cmax) value (TAIC/Tmax). An initial attempt to prove the validity of this method was performed in rats. The resulting TAIC/Tmax in rats was 32%, suggesting a low DDI potential of luseogliflozin against miglitol absorption. The validity was then confirmed using an in vivo interaction study in rats. In humans, luseogliflozin was expected to have no DDI potential against miglitol absorption, since the TAIC/Tmax in humans was lower than that in rats. This prediction was proven, as expected, in a clinical interaction study. In conclusion, the present strategy based on a simulation of the intestinal concentration-time profile using dynamic modeling would be useful for assessing the clinical DDI potential of a concomitant agent against drugs absorbed via an intestinal transporter.

A sensitive and selective method for the quantitative analysis of miglitol in rat plasma using unique solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.

A sensitive, selective and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of miglitol in rat plasma. The sample preparation procedures involved protein precipitation and unique solid-phase extraction, which efficiently removed sources of ion suppression and column degradation interference present in the plasma. Chromatographic separation was achieved on an amide column using 10 mmol/L CH3 COONH4 and CH3 CN:CH3 OH (90:10, v/v) as the mobile phase under gradient conditions. Detection was performed using tandem mass spectrometry equipped with an electrospray ionization interface in positive ion mode.The selected reaction monitoring transitions for miglitol and a stable isotope-labeled internal standard were m/z 208 → m/z 146 and m/z 212 → m/z 176, respectively. The correlation coefficients of the calibration curves ranged from 0.9984 to 0.9993 over a concentration range of 0.5-100 ng/mL plasma. The quantification limit of the proposed method was more than 10 times lower than those of previously reported LC-MS/MS methods. The novel method was successfully validated and applied to a pharmacokinetic study in rats.

A surrogate analyte method to determine D-serine in mouse brain using liquid chromatography-tandem mass spectrometry.

A bioanalytical method for determining endogenous d-serine levels in the mouse brain using a surrogate analyte and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. [2,3,3-(2)H]D-serine and [(15)N]D-serine were used as a surrogate analyte and an internal standard, respectively. The surrogate analyte was spiked into brain homogenate to yield calibration standards and quality control (QC) samples. Both endogenous and surrogate analytes were extracted using protein precipitation followed by solid phase extraction. Enantiomeric separation was achieved on a chiral crown ether column with an analysis time of only 6 min without any derivatization. The column eluent was introduced into an electrospray interface of a triple-quadrupole mass spectrometer. The calibration range was 1.00 to 300 nmol/g, and the method showed acceptable accuracy and precision at all QC concentration levels from a validation point of view. In addition, the brain d-serine levels of normal mice determined using this method were the same as those obtained by a standard addition method, which is time-consuming but is often used for the accurate measurement of endogenous substances. Thus, this surrogate analyte method should be applicable to the measurement of d-serine levels as a potential biomarker for monitoring certain effects of drug candidates on the central nervous system.

Development and validation of a liquid chromatography-tandem mass spectrometric method for the quantification of 5-thio-d-glucose in rat and human plasma.

A highly selective, sensitive, and robust liquid chromatography-tandem mass spectrometric method for the determination of 5-thio-d-glucose concentrations in rat and human plasma was developed and validated. The sample preparation procedure involved protein precipitation and solid phase extraction, which efficiently removed sources of interference present in the plasma. Chromatographic separation was obtained using an NH(2)-column with distilled water and acetonitrile as the mobile phase under gradient conditions. Detection was performed using tandem mass spectrometry equipped with an electrospray ionization interface in negative ion mode. The selected reaction monitoring (SRM) transitions for 5-thio-d-glucose and an internal standard (5-thio-d-glucose-(13)C(6)) were m/z 195→m/z 105 and m/z 201→m/z 108, respectively. The correlation coefficients of the calibration curves ranged from 0.9997 to 0.9999 over a concentration range from 10 to 3000ng/mL plasma. The validated method was successfully applied to a pharmacokinetic study in rats.

(2S,4S)-4-Fluoro-1-{[(2-hydroxy-1,1-dimethylethyl)amino]acetyl}-pyrrolidine-2-carbonitrile monobenzenesulfonate (TS-021) is a selective and reversible dipeptidyl peptidase IV inhibitor.

The incretin hormone glucagon-like peptide-1 (GLP-1) has significant roles in the regulation of postprandial glucose metabolism, and the active form of GLP-1 is rapidly degraded by dipeptidyl peptidase (DPP)-IV. Therefore, DPP-IV inhibition is a promising approach for the treatment of type 2 diabetes. In the present study, we investigated the character of a DPP-IV inhibitor, TS-021, (2S, 4S)-4-fluoro-1-{[(2-hydroxy-1,1-dimethylethyl)amino]acetyl}-pyrrolidine-2-carbonitrile monobenzenesulfonate both in vitro and in vivo. TS-021 inhibits DPP-IV activity in human plasma with an IC(50) value of 5.34nM. In kinetics experiments, TS-021 had a relatively higher dissociation rate constant, with a k(off) value of 1.09×10(-3)s, despite exhibiting a potent human plasma DPP-IV inhibition activity with a K(i) value of 4.96nM. TS-021 exhibited significant inhibition selectivity against DPP-8 (>600 fold), DPP-9 (>1200 fold) and other peptidases examined (>15,000 fold). In normal rats, dogs and monkeys, a single oral dose of TS-021 exhibited favorable pharmacokinetic profiles. In Zucker fatty (fa/fa) rats, a rat model of obesity and impaired glucose tolerance, the oral administration of TS-021 resulted in the suppression of plasma DPP-IV activity and an increase in the active form of GLP-1. Furthermore, TS-021 exhibited a significant improvement in glucose tolerance by increasing the plasma insulin level during oral glucose tolerance tests at doses of 0.02-0.5mg/kg. These results suggest that TS-021 is a selective and reversible dipeptidyl peptidase IV inhibitor and has excellent characteristics as an oral anti-diabetic agent for postprandial hyperglycemia in patients with impaired glucose tolerance or type 2 diabetes.

Differentiation between isomeric oxidative metabolites of a piperidine-containing drug by liquid chromatography-tandem mass spectrometry with stable-isotope tracer technique.

This report describes the application of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to differentiation of hydroxylations and N-oxidations and of two different aliphatic hydroxylations in the investigation of the metabolism of pibutidine hydrochloride, a novel H2 antagonist, the structure of which includes a piperidine ring. Pibutidine metabolites in urine samples from adult male volunteers after oral administration of pibutidine hydrochloride were separated by reversed-phase LC and ionized using an electrospray ionization (ESI) interface. A hydroxylated form of pibutidine was distinguished from the N-oxide by comparison of their product ion spectra, although their mass-to-charge ratios of protonated molecules were identical. Further, two hydroxylated compounds were present in rat microsomal incubation mixtures with pibutidine. The distinction between their positions of hydroxylation (beta- and gamma-carbon hydroxylation) on the piperidine ring was studied using [piperidine-2H10] pibutidine as incubation substrate. The production of the beta-hydroxylated form was accompanied by the elimination of three 2H, resulting from a mechanism including the formation of iminium/enamine. The participation of the iminium ion intermediate in the beta-hydroxylation was confirmed by the observation that a cyanide adduct of pibutidine was formed instead of the beta-hydroxylated form when another incubation was performed in the presence of cyanide.