Yoo-Seong Jeong

Kinetics of the Absorption, Distribution, Metabolism, and Excretion of Lobeglitazone, a Novel Activator of Peroxisome Proliferator-Activated Receptor Gamma in Rats

This study was performed to determine biopharmaceutical properties of lobeglitazone (LB), a novel thiazolidinedione-based activator of peroxisome proliferator-activated receptor gamma, in rats. In parallel artificial membrane permeability assay and Madin-Darby canine kidney (MDCK) cell permeability assays of LB, the activator was found to interact with multidrug-resistance protein 1 (MDR1) and OATP1B1. The concentration resulting in 50% inhibition value for LB in MDR1 expressing MDCK cells was approximately 12.5 ± 3.61 μM. LB had adequate stability (i.e., 56% remaining at 0.5 h) in rat liver microsomes. A cytochrome P450 (CYP) inhibitory potency study indicated that LB is primarily interacted with CYP1A2, 2C9, and 2C19. In rats, LB appeared to be readily absorbed after an oral administration (an absolute bioavailability of ∼95%). Following intravenous administration, LB exhibited linear pharmacokinetics in the dose range of 0.5-2 mg/kg. The primary distribution site was the liver but it was also distributed to heart, lungs, and fat tissue. The excretion of LB to the urine, bile, feces, and intestine was insignificant (i.e., <10% of the dose) in rats. These observations suggest that, despite the fact that it interacts with some drug transporters and metabolizing enzymes, the pharmacokinetics of LB were linear with a high oral bioavailability.

Specific Inhibition of the Distribution of Lobeglitazone to the Liver by Atorvastatin in Rats: Evidence for a Rat Organic Anion Transporting Polypeptide 1B2–Mediated Interaction in Hepatic Transport

Cytochrome P450 enzymes and human organic anion transporting polypeptide (OATP) 1B1 are reported to be involved in the pharmacokinetics of lobeglitazone (LB), a new peroxisome proliferator–activated receptor γ agonist. Atorvastatin (ATV), a substrate for CYP3A and human OATP1B1, is likely to be coadministered with LB in patients with the metabolic syndrome. We report herein on a study of potential interactions between LB and ATV in rats. When LB was administered intravenously with ATV, the systemic clearance and volume of distribution at steady state for LB remained unchanged (2.67 ± 0.63 ml/min per kg and 289 ± 20 ml/kg, respectively), compared with that of LB without ATV (2.34 ± 0.37 ml/min per kg and 271 ± 20 ml/kg, respectively). Although the tissue-to-plasma partition coefficient (Kp) of LB was not affected by ATV in most major tissues, the liver Kp for LB was decreased by ATV coadministration. Steady-state liver Kp values for three levels of LB were significantly decreased as a result of ATV coadministration. LB uptake was inhibited by ATV in rat OATP1B2-overexpressing Madin–Darby canine kidney cells and in isolated rat hepatocytes in vitro. After incorporating the kinetic parameters for the in vitro studies into a physiologically based pharmacokinetics model, the characteristics of LB distribution to the liver were consistent with the findings of the in vivo study. It thus appears that the distribution of LB to the liver is mediated by the hepatic uptake of transporters such as rat OATP1B2, and carrier-mediated transport is involved in the liver-specific drug–drug interaction between LB and ATV in vivo.

Quantification of EC-18, a synthetic monoacetyldiglyceride (1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol), in rat and mouse plasma by liquid-chromatography/tandem mass spectrometry

&NA; EC‐18 (i.e., 1‐palmitoyl‐2‐linoleoyl‐3‐acetyl‐rac‐glycerol), an active ingredient in Rockpid®, has been reported to be useful in controlling various types of inflammations, particularly those caused by neutropenia. Although this product was originally approved as a functional food in Korea, it is currently in phase II clinical trials for use in managing the severe chemotherapy‐induced neutropenia in patients with advanced breast cancer who are receiving intermediate febrile neutropenia risk chemotherapy. The objective of this study was to develop a rapid, sensitive method for the determination of EC‐18 in rat and mouse plasma and to evaluate the applicability of the assay in pharmacokinetic studies. EC‐18 was extracted with MeOH from rat and mouse plasma samples, and the extract directly introduced onto an LC–MS/MS system. The analyte and EC‐18‐d3, an internal standard, were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 635.4 → 355.4 for EC‐18 and 638.4 → 338.4 for the internal standard, respectively. The lower limit of quantification (LLOQ) was determined at 50 ng/mL, with an acceptable linearity in the range from 50 to 10,000 ng/mL (r > 0.999) for both matrices. Validation parameters such as accuracy, precision, dilution, recovery, matrix effects and stability were found to be within the acceptance criteria of the assay validation guidelines, indicating that the assay is applicable for estimating EC‐18 in concentrations in the range examined. EC‐18 was readily determined in plasma samples for periods of up to 8 h following an intravenous bolus injection of 1 mg/kg in rats and at 5 mg/kg in mice, respectively, and up to 24 h following the oral administration of 2000 mg/kg in mice. The findings indicate that the current analytical method is applicable for pharmacokinetic studies of EC‐18 in small animals. HighlightsLC–MS/MS assay of EC‐18 was developed/validated in plasma samples from rats/mice.A simple sample preparation and a short LC run‐time.Current assay applicable to pharmacokinetic studies of EC‐18 in rats/mice.

Estimation of the minimum permeability coefficient in rats for perfusion-limited tissue distribution in whole-body physiologically-based pharmacokinetics

&NA; The objective of the current study was to determine the minimum permeability coefficient, Symbol, needed for perfusion‐limited distribution in PBPK. Two expanded kinetic models, containing both permeability and perfusion terms for the rate of tissue distribution, were considered: The resulting equations could be simplified to perfusion‐limited distribution depending on tissue permeability. Integration plot analyses were carried out with theophylline in 11 typical tissues to determine their apparent distributional clearances and the model‐dependent permeabilities of the tissues. Effective surface areas were calculated for 11 tissues from the tissue permeabilities of theophylline and its PAMPA Symbol. Tissue permeabilities of other drugs were then estimated from their PAMPA Symbol and the effective surface area of the tissues. The differences between the observed and predicted concentrations, as expressed by the sum of squared log differences with the present models were at least comparable to or less than the values obtained using the traditional perfusion‐limited distribution model for 24 compounds with diverse PAMPA Symbol values. These observations suggest that the use of a combination of the proposed models, PAMPA Symbol and the effective surface area can be used to reasonably predict the pharmacokinetics of 22 out of 24 model compounds, and is potentially applicable to calculating the kinetics for other drugs. Assuming that the fractional distribution parameter of 80% of the perfusion rate is a reasonable threshold for perfusion‐limited distribution in PBPK, our theoretical prediction indicates that the pharmacokinetics of drugs having an apparent PAMPA Symbol of 1 × 10−6 cm/s or more will follow the traditional perfusion‐limited distribution in PBPK for major tissues in the body. Symbol. No captoin available. Graphical abstract Figure. No caption available.

Identification of metabolites of MDR-1339, an inhibitor of β-amyloid protein aggregation, and kinetic characterization of the major metabolites in rats

HighlightsIdentification of ten metabolites (i.e., 7 Phase 1 + 3 Phase 2) of MDR‐1339 in rats.Proposal for the major metabolic pathways to be CYP3A4, 2B6 and 2C9.Simultaneous quantification of MDR‐1339 and its major metabolite M1 and M2.Formation of M1 accounted for ˜19.7% of the total MDR‐1339 elimination in rats. ABSTRACT We previously reported that MDR‐1339, an inhibitor of &bgr;‐amyloid protein aggregation, was likely to be eliminated by biotransformation in rats. The objective of this study was to determine the chemical identity of metabolites derived from this aggregate inhibitor and to characterize the kinetics of formation of these metabolites in rats. Using high performance liquid chromatography coupled with mass spectrometry with a hybrid triple quadrupole‐linear ion trap, 7 metabolites and 1 potential metabolic intermediate were identified in RLM incubations containing MDR‐1339. In addition to these, 3 glucuronide metabolites were detected in urine samples from rats receiving a 10 mg/kg oral dose of MDR‐1339. When the kinetics of the formation of two major metabolites, M1 and M2, were analyzed assuming simple Michaelis‐Menten kinetics, the Vmax and Km values were found to be 0.459 ± 0.0196 nmol/min/mg protein and 28.3 ± 3.07 &mgr;M for M1, and 0.101 ± 0.00537 nmol/min/mg protein and 14.7 ± 2.37 &mgr;M for M2, respectively. When chemically synthesized M1 and M2 were individually administered to rats intravenously at the dose of 5 mg/kg respectively, the volume of distribution and elimination clearance were determined to be 4590 ± 709 mL/kg and 68.4 ± 5.60 mL/min/kg for M1 and 15300 ± 8110 mL/kg and 98.0 ± 19.5 mL/min/kg for M2, respectively. When MDR‐1339 was intravenously administered to rats at a dose of 5 mg/kg, the parent drug and M1 were readily detected for periods of up to 6 h after the administration, but M2 was observed only from 2 to 4 h. A standard moment analysis indicates that the formation clearance of M1 is 6.01 mL/min/kg, suggesting that 19.7% of the MDR‐1339 dose was eliminated in rats. These observations indicate that the hepatic biotransformation of MDR‐1339 results in the formation of at least 10 metabolites and that M1 is the major metabolite derived from this aggregation inhibitor in rats.

Novel Hypoxia-Inducible Factor 1α (HIF-1α) Inhibitors for Angiogenesis-Related Ocular Diseases: Discovery of a Novel Scaffold via Ring-Truncation Strategy

Ocular diseases featuring pathologic neovascularization are the leading cause of blindness, and anti-VEGF agents have been conventionally used to treat these diseases. Recently, regulating factors upstream of VEGF, such as HIF-1α, have emerged as a desirable therapeutic approach because the use of anti-VEGF agents is currently being reconsidered due to the VEGF action as a trophic factor. Here, we report a novel scaffold discovered through the complete structure-activity relationship of ring-truncated deguelin analogs in HIF-1α inhibition. Interestingly, analog 6i possessing a 2-fluorobenzene moiety instead of a dimethoxybenzene moiety exhibited excellent HIF-1α inhibitory activity, with an IC50 value of 100 nM. In particular, the further ring-truncated analog 34f, which showed enhanced HIF-1α inhibitory activity compared to analog 2 previously reported by us, inhibited in vitro angiogenesis and effectively suppressed hypoxia-mediated retinal neovascularization. Importantly, the heteroatom-substituted benzene ring as a key structural feature of analog 34f was identified as a novel scaffold for HIF-1α inhibitors that can be used in lieu of a chromene ring.