In Vitro Mechanistic Study of the Distribution of Lascufloxacin into Epithelial Lining Fluid.

The present study aimed to clarify the mechanism underlying the high distribution of lascufloxacin in epithelial lining fluid (ELF). Involvement of transporters was examined by transcellular transport across Calu-3 and transporter-overexpressing cells; the binding of lascufloxacin to ELF components was examined by an organic solvent-water partitioning system that employed pulmonary surfactant and phospholipids. Transcellular transport across the transporter-overexpressing cells indicated lascufloxacin to be a substrate of both P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP); therefore, its transport across Calu-3 cells was inhibited by P-gp and BCRP inhibitors. However, permeability and efflux ratios of lascufloxacin were similar to those of the other quinolones with relatively low ELF distribution, indicating the existence of another mechanism for lascufloxacin distribution in ELF. Amongst pulmonary surfactants, which are a primary component of ELF, lascufloxacin preferentially bound to phosphatidylserine (PhS) from several phospholipids, and the binding was significantly greater than that for other quinolones. This binding was saturable with two apparent classes of binding sites and inhibited by some weakly basic drugs, indicating the presence of an ionic bond. In conclusion, the results of this study suggest that the binding of lascufloxacin to PhS in the pulmonary surfactant is the major mechanism of the high distribution of lascufloxacin in the ELF.

Organic Anion Transporting Polypeptide 1a4 is Responsible for the Hepatic Uptake of Cardiac Glycosides in Mice.

Among organic anion transporting polypeptide (Oatp) family transporters expressed in the rodent liver, such as Oatp1a1, Oatp1a4, Oatp1b2, and Oatp2b1, Oatp1a4 has a unique character to recognize neutral cardiac glycosides as a substrate in addition to organic anions. The relative contribution of Oatp1a4 to the substrate uptake into hepatocytes has not been clarified. In this study, we investigated the importance of Oatp1a4 in the hepatic uptake of its substrate drugs using Slco1a4-/- mice. The hepatic mRNA expression of Slco1a4 was decreased significantly in Slco1a4-/- mice, whereas no differences were seen in other hepatic transporters between wild-type and Slco1a4-/- mice. We determined the plasma concentrations and liver-to-plasma concentration ratios (Kp,liver) of Oatp1a4 substrates, including ouabain, digoxin, BQ-123, fexofenadine, rosuvastatin, pravastatin, nafcillin, and telmisartan, after continuous intravenous infusion. The plasma concentrations of ouabain and rosuvastatin were 2.1-fold and 1.7-fold higher in Slco1a4-/- mice, and Kp,liver of ouabain and digoxin were 13.4-fold and 4.3-fold lower in Slco1a4-/- mice, respectively. Furthermore, the biliary clearance of ouabain and digoxin with regard to plasma concentration were 21.9-fold and 4.1-fold lower in Slco1a4-/- mice, respectively, accompanied with a marked reduction in their Kp,liver, whereas the systemic clearance of ouabain, but not digoxin, was reduced significantly in Slco1a4-/- mice. These results suggest that Oatp1a4 plays a major role in the hepatic accumulation of cardiac glycosides in mice.

The Prediction of the Relative Importance of CYP3A/P-glycoprotein to the Nonlinear Intestinal Absorption of Drugs by Advanced Compartmental Absorption and Transit Model.

Intestinal CYP3A and P-glycoprotein (P-gp) decrease the intestinal absorption of substrate drugs. Since substrate specificity of CYP3A often overlaps that of P-gp, and estimation of their saturability in the intestine is difficult, dose-dependent FaFg (fraction of the administered drugs that reach the portal blood) of substrate drugs and the relative importance of CYP3A and P-gp have not been clarified in many cases. Thus, we tried to establish the universal methodology for predicting the in vivo absorption of several CYP3A and/or P-gp substrates from in vitro assays. One of the key points is to set up the scaling factor (SF), correcting the difference between the observed in vivo clearance and the predicted clearance from in vitro data. The SFs of Vmax for CYP3A (SFCYP3A) and P-gp (SFP-gp) were simultaneously optimized to explain the FaFg of CYP3A and/or P-gp substrate drugs. The best predictability of FaFg was achieved when considering both SFCYP3A and SFP-gp The simulation also clarified the relative importance of CYP3A and P-gp in determining FaFg In particular, the nonlinear intestinal absorption of verapamil was caused by the saturation of intestinal CYP3A, whereas that of quinidine was governed by the saturation of both CYP3A and P-gp. In addition, the dose-dependent FaFg of selective and dual CYP3A and/or P-gp substrates was well predicted. We therefore propose a methodology for predicting the FaFg of drugs using a mathematical model with optimized SFCYP3A and SFP-gp Our methodology is applicable to in vitro-in vivo extrapolation of intestinal absorption, even if absolute in vivo functions of enzymes/transporters are unclear.

Radiosynthesis of novel pitavastatin derivative ([18 F]PTV-F1) as a tracer for hepatic OATP using a one-pot synthetic procedure.

Pitavastatin is an antihyperlipidemic agent, a potent inhibitor of 3-hydroxymethyl-glutaryl-CoA reductase, which is selectively taken up into the liver mainly via hepatic organic anion transporting polypeptide 1B1 (OATP1B1). OATP1B1 can accept a variety of organic anions, and previous reports indicated that it is responsible for the hepatic clearance of several clinically used anionic drugs. Therefore, the pharmacokinetics and the hepatic distribution of pitavastatin provide an insight into the function of OATP1B1 in humans. For the development of the in vivo evaluation of OATP1B1 function by positron emission tomography imaging, we designed a novel [18 F]pitavastatin derivative ([18 F]PTV-F1), in which a [18 F]fluoroethoxy group is substituted for the [18 F]fluoro group of [18 F]pitavastatin, with the aim of convenient radiolabeling protocol and high radiochemical yield. In vitro studies suggested that transport activities of PTV-F1 mediated by OATP1B1 and OATP1B3 were very similar to those of pitavastatin and PTV-F1 was metabolically stable in human liver microsomes. In the radiosynthesis of [18 F]PTV-F1 from the tosylate precursor, nucleophilic fluorination and subsequent deprotection were performed using a one-pot procedure. [18 F]PTV-F1 was obtained with a radiochemical yield of 45% ± 3% (n = 3), and the operating time for the radiosynthesis of [18 F]PTV-F1 is very short (30 minutes) compared with [18 F]pitavastatin.

Importance of free water in controlling granule and tablet properties in a novel granulation method, green fluidized bed granulation (GFBG).

In the pharmaceutical field, green fluidized bed granulation (GFBG) is a novel and eco-friendly manufacturing technology used to produce desired granules via simple blending and spraying steps at ambient temperature using a standard fluidized bed granulator. However, the relations between water content and granule and tablet qualities have not yet been elucidated for GFBG. The purpose of this study was to elucidate the influence of different water quantities used in the GFBG process on granule and tablet qualities. In addition, results from the GFBG process were compared with those from the moisture-activated dry granulation (MADG) process. In terms of tablet tensile strength and disintegration time, GFBG had a wider acceptable range for added water quantity (2.0-5.0%) than did MADG. For all added water quantities, the GFBG granules were within the upper limit of water activity (a surrogate of free water amount), which was 0.61 for tensile strength and 0.55 for disintegration time. The air flow in the GFBG process may have reduced the excess free water on the granules during the absorption process. It was concluded that as compared with MADG, GFBG may be a more robust process for manufacturing granules and tablets with superior properties.

Development of pH-Independent Drug Release Formulation Using Lipocalin-Type Prostaglandin D Synthase.

The purpose of this study was to develop a pH-independent drug release formulation using lipocalin-type prostaglandin D synthase, a member of the lipocalin superfamily, with the function of forming complexes together with various small lipophilic molecules. Dipyridamole, a poorly water-soluble drug, showing a pH-dependent solubility profile, was used as the model drug. The solubilization of dipyridamole was achieved by a simple complex formulation method with lipocalin-type prostaglandin D synthase. The complex formulation was produced successfully by spray drying, and the obtained powder formulation showed complete dissolution in fasted-state simulated gastric fluid (pH, 1.6) and phosphate-buffered solution (pH, 6.8). In addition, the potential stability of the complex formulation was assessed, and the dissolution profile of the produced powder at pH 6.8 was maintained after 4-week storage under several storage conditions. Furthermore, a pharmacokinetic study using hypochlorhydria model rats was performed to verify the improvement of the intestinal absorption behavior, and eventually the complex formulation overcame the problematic absorption profile of dipyridamole in the elevated gastric pH conditions. These results, taken together, demonstrate that the use of this well-designed drug-delivery carrier is feasible for the development of pH-independent drug release formulations.

Tocilizumab, a humanized anti-IL-6R antibody, as an emerging therapeutic option for rheumatoid arthritis: molecular and cellular mechanistic insights.

Pro-inflammatory cytokines play a major role in the initiation and maintenance of joint inflammation and destruction in rheumatoid arthritis (RA). The therapeutic success of biologics targeting tumour necrosis factor-alpha (TNF-α), interleukin-1 (IL-1) and interleukin (IL)-6 receptor (IL-6R) has broadened the treatment options for RA. These agents have potential overlapping and discriminating biologic effects, as well as different pharmacological features. Tocilizumab (TCZ) is a humanized monoclonal antibody that binds and neutralizes IL-6R, resulting in the inhibition of various IL-6-mediated biological activities, including inflammation-related, immunomodulatory and tissue/matrix remodelling effects. Randomized, double-blind, controlled phase III studies and a number of early clinical observational studies have shown that treatment with TCZ results in rapid and sustained improvement in the signs and symptoms of RA among different patient populations. These studies have established the efficacy and safety of TCZ. Here, we review the pleiotropic functions of IL-6 and how it impinges on many aspects of RA pathogenesis, and highlight the clinical experience to date with TCZ as an emerging new treatment option for RA.

Direct and rapid genotyping of SLCO1B1 388A>G and 521T>C in human blood specimens using the SmartAmp-2 method.

Organic anion-transporting polypeptide (OATP) 1B1, encoded by the solute carrier organic anion transporter family member 1B1 (SLCO1B1) gene, mediates the active uptake of various organic anions into hepatocytes and determines their hepatic clearances as the first step in the detoxification pathway. Previous reports indicated that alterations in its function by drug-drug interactions or genetic polymorphisms affect the pharmacokinetics of the substrate drugs. In the present study, we developed a method to genotype SLCO1B1 388A>G (rs2306283) and 521>C (rs4149056), which significantly affect the clinical pharmacokinetics and subsequent side effects such as myopathy caused by statins, OATP1B1 substrates in humans. We used a small aliquot of blood and the isothermal Smart Amplification Process version 2 (SmartAmp-2), which could complete the genotyping of 388A>G and 521T>C within 60 min. The genotypes of 101 genomic DNA samples and blood samples assessed by SmartAmp-2 matched perfectly to those determined previously by the conventional PCR-SSCP method. The SmartAmp-2 method enables the rapid identification of the 388A>G and 521T>C genotypes, saving time and effort in the genomic DNA preparation in clinical practice. This method will be useful for evaluating and predicting altered pharmacological and toxicological effects of substrate drugs caused by SLCO1B1 polymorphisms.

Predicting drug-drug interactions involving the inhibition of intestinal CYP3A4 and P-glycoprotein.

Recently, interest has grown in drug-drug interactions (DDIs) involving the inhibition of intestinal CYP3A4, P-glycoprotein (P-gp), and other drug efflux transporters. The criteria for intestinal DDIs are described in the draft guidances of the US Food and Drug Administration (FDA) and European Medicines Agency (EMA). Substrate drugs with small fraction absorbed (Fa) and/or low intestinal availability (Fg) as a result of intestinal efflux transport and metabolism are important as "victim" drugs because these substrates are likely to show considerable interactions. The susceptibility of a victim drug to intestinal interactions can be evaluated from its FaFg. In this review, methods for estimating the FaFg of substrate drugs are discussed. The nonlinear pharmacokinetics of substrate drugs caused by the saturation of intestinal CYP3A4/P-gp is also discussed. The methods for predicting intestinal DDIs caused by inhibitor drugs are then summarized. Because the prediction accuracy of intestinal DDIs also depends on the inhibition constant (Ki) estimated in in vitro studies, these in vitro methods of estimating Ki are also discussed. Standardized methods for predicting intestinal DDIs have not yet been established. Further studies are required to establish more accurate and standardized prediction methods.

Muscle reflection human computer model in wheelchairs traveling in motor vehicles.

In this study, a human motion computer model in a wheelchair was developed to evaluate the effectiveness of a seatbelt for disabled people traveling in a motor vehicle. The human model was composed of two rigid links and three masses. This model was characterized with muscle reflection defined by Hill's equation. A sudden stop experiment by using a carriage on which a wheelchair was fixed with a subject was performed to obtain the human muscle parameters and to evaluate the model. Volunteer subjects including disabled people participated in the experiment. The motion and muscle activity of a subject wearing a seatbelt were simulated by this model. The muscle reflection of disabled people was stronger than that of normal people in the case of not using a seatbelt, but in the case of using a seatbelt the muscle reflection of disabled people was similarly weak with normal people. The result of computer simulation showed that a seatbelt is more important for disabled people than for normal people.