Yoshihiro Kawabata

Acotiamide hydrochloride (Z-338), a new selective acetylcholinesterase inhibitor, enhances gastric motility without prolonging QT interval in dogs: Comparison with cisapride, itopride and mosapride

Acotiamide hydrochloride (acotiamide; N-[2-[bis(1-methylethyl) amino]ethyl]-2-[(2-hydroxy-4,5-dimethoxybenzoyl) amino] thiazole-4-carboxamide monohydrochloride trihydrate, Z-338) has been reported to improve meal-related symptoms of functional dyspepsia in clinical studies. Here, we examined the gastroprokinetic effects of acotiamide and its antiacetylcholinesterase activity as a possible mechanism of action in conscious dogs. Acotiamide increased postprandial gastric motor activity in conscious dogs with chronically implanted force transducers and, like itopride, mosapride, and cisapride, exhibited gastroprokinetic activity in these dogs. Furthermore, acotiamide improved clonidine-induced hypomotility and delayed gastric emptying. Acotiamide-enhanced postprandial gastroduodenal motility was suppressed completely by pretreatment with atropine, a muscarinic receptor antagonist. In in vitro studies, acotiamide enhanced acetylcholine- but not carbachol-induced contractile responses of guinea pig gastric antrum strips. Moreover, like itopride and neostigmine, acotiamide inhibited recombinant human and canine stomach-derived acetylcholinesterase (AChE) activity in vitro. The mode of the AChE inhibitory action of acotiamide was selective and reversible. Unlike itopride or mosapride, acotiamide showed no affinity for dopamine D2 or serotonin 5-HT4 receptors. With regard to cardiovascular side effects, unlike cisapride, acotiamide did not affect myocardial monophasic action potential duration, QT interval, or corrected QT interval in anesthetized dogs. These results suggest that acotiamide stimulates gastric motility in vivo by inhibiting AChE activity without affecting QT interval. Acotiamide thus represents a beneficial new drug for the treatment of functional dyspepsia involving gastric motility dysfunction, with differences from other prokinetic agents.

Acotiamide hydrochloride (Z-338) enhances gastric motility and emptying by inhibiting acetylcholinesterase activity in rats.

In clinical trials, acotiamide hydrochloride (acotiamide: Z-338) has been reported to be useful in the treatment of functional dyspepsia. Here, we investigated the effects of acotiamide on gastric contraction and emptying activities in rats in comparison with itopride hydrochloride (itopride) and mosapride citrate (mosapride). We also examined in vitro the compounds inhibitory effect on acetylcholinesterase (AChE) activity derived from rat stomach. In in vivo studies, acotiamide (30 and 100mg/kg s.c.) and itopride (100mg/kg s.c.) markedly enhanced normal gastric antral motility in rats. In gastric motility dysfunction models, acotiamide (100mg/kg s.c.) and itopride (100mg/kg s.c.) improved both gastric antral hypomotility and the delayed gastric emptying induced by clonidine, an α(2)-adrenoceptor agonist. In contrast, mosapride (10mg/kg s.c.) had no effect on these models. Like the AChE inhibitors itopride (30 mg/kg s.c.) and neostigmine (10 μg/kg s.c.), acotiamide (10mg/kg s.c.) also clearly enhanced gastric body contractions induced by electrical stimulation of the vagus, which were abolished by atropine and hexamethonium, whereas mosapride (3 and 10mg/kg s.c.) did not. In in vitro studies, acotiamide concentration-dependently inhibited rat stomach-derived AChE activity (IC(50)=2.3 μmol/l). In addition, stomach tissue concentrations of acotiamide after administration at 10mg/kg s.c. were sufficient to produce inhibition of AChE activity in rat stomach. These results suggest that acotiamide stimulates gastric motility and improves gastric motility dysfunction in rats by inhibiting AChE activity, and may suggest a role for acotiamide in improving gastric motility dysfunction in patients with functional dyspepsia.

Mechanism for distribution of acotiamide, a novel gastroprokinetic agent for the treatment of functional dyspepsia, in rat stomach

The novel gastroprokinetic agent acotiamide improves gastric motility by inhibiting acetylcholinesterase activity in stomach; however, the mechanism of distribution of acotiamide from blood to stomach has not been clarified. Here, the tissue distribution of acotiamide was investigated in rats. The tissue-to-plasma concentration ratio (K(p,app,in vivo)) for stomach decreased from 4.1 to 2.4 mL/g of tissue at steady state with increasing plasma concentrations, whereas the K(p,app,in vivo) for skeletal muscle was much lower and constant, regardless of the concentration of acotiamide in plasma. In vitro binding to stomach tissue protein exhibited a linear profile, with a predicted K(p,app,in vitro) of 2.2 from free fractions under linear conditions. Therefore, protein binding to stomach tissue might only play a limited role in the stomach distribution of acotiamide. The influx permeability (f (u,b) × PS(inf,app)) in the stomach exhibited dose-dependent saturation at the lowest range of examined blood unbound concentrations of acotiamide, whereas that in skeletal muscle exhibited only minimal dose dependence. In addition, the unbound concentration ratio of stomach to plasma (2.8) at steady state was markedly higher than unity. Taken together, these results suggest that carrier-mediated concentrative uptake processes play an important role in the distribution of acotiamide to the stomach but not skeletal muscle.

Polaprezinc, a zinc compound, is distributed to the lingual epithelium and increases its zinc concentration in zinc-deficient rats.

AIMSnTo clarify the mechanism underlying the effect of polaprezinc on hypogeusia, we investigated the uptake of polaprezinc by the tongue in rats.nnnMAIN METHODSnRats were fed a zinc-sufficient (Zn(+)) or zinc-deficient (Zn(-)) diet. After 4weeks on the Zn(-) diet, polaprezinc (1, 3, or 10mg/kg) or [(65)Zn] polaprezinc (10mg/kg) was administered orally once a day. The zinc concentration or the (65)Zn radioactivity of the tongue was measured by inductively-coupled plasma mass spectrometry or gamma counting, respectively. In addition, the distribution of (65)Zn in the tongue was analyzed by microautoradiography and the proliferative activity of taste bud cells was measured from the uptake of 5-bromo-2-deoxyuridine.nnnKEY FINDINGSnThe zinc concentration of the lingual epithelium, but not the whole tongue, was markedly decreased in Zn(-) rats compared with Zn(+) rats. After administration of polaprezinc to Zn(-) rats at doses of 1, 3, and 10mg/kg, the zinc concentration in the lingual epithelium increased significantly from 85+/-4 to 105+/-7 (p<0.05), 120+/-3 (p<0.001), and 124+/-3 (p<0.001) microg/g, respectively. After administration of [(65)Zn] polaprezinc, the (65)Zn radioactivity of the tongue and serum were higher in Zn(-) rats than in Zn(+) rats. (65)Zn was mainly detected in the epithelium on microautoradiograms of the tongue in Zn(-) rats. In addition, polaprezinc (3 and 10mg/kg) improved the reduced proliferation of taste bud cells due to zinc deficiency.nnnSIGNIFICANCEnPolaprezinc is distributed to the lingual epithelium and restores its zinc concentration in Zn(-) rats resulting in improvement of cellular functions, especially proliferation.

Concentration dependence of 5-aminosalicylic acid pharmacological actions in intestinal mucosa after oral administration of a pH-dependent formulation.

Asacol, a medication that delivers delayed release 5-aminosalicylic acid (5-ASA), is a useful therapeutic agent for inflammatory bowel disease (IBD), but the relationship between its pharmacological actions and intestinal concentrations has not been studied in detail. Therefore, our aim was to assess 5-ASAs pharmacological actions as a function of its concentration at its target site. We first evaluated 5-ASAs release profiles in vitro by the paddle method and found that Asacol starts to release 5-ASA at pH ≥ 7. Orally administered Asacol pharmacokinetic parameters were evaluated in dogs. Asacols T(max) was much longer than that of the time-dependent release 5-ASA formulation. We also determined 5-ASAs distribution in the intestinal mucosa and found that it is effectively delivered there by Asacol. These results indicated that Asacol released 5-ASA in a pH-dependent manner, resulting in efficient delivery to the large intestine. We also compared the mucosal 5-ASA concentrations with the IC(50) values for scavenging free radicals or suppressing LTB(4) production. The 5-ASA concentration in the large intestine was higher than IC(50) values necessary to suppress inflammatory processes. We also report the release characteristics of Asacol and the targeted delivery of 5-ASA to affected sites in IBD patients.

ATP-Dependent Transport of a Novel Thromboxane A2 Receptor Antagonist, [2-(4-Chlorophenylsulfonylaminomethyl)-Indan-5-yl]Acetate (Z-335) and Its Xenobiotic Taurine Conjugate (Z-335-Tau) by Rat Bile Canalicular Membrane Vesicles

AbstractPurpose. The characteristics of bile canalicular transport processes for xenobiotic taurine conjugates have not yet been clarified. To elucidate the biliary excretion characteristics of xenobiotic taurine conjugates, we investigated the transport of a novel thromboxane A2 receptor antagonist, Z-335, and its taurine conjugate (Z-335-Tau) across the bile canalicular membrane.nMethods. We examined the uptake of Z-335 and Z-335-Tau by isolated bile canalicular membrane vesicles (CMVs) from Sprague Dawley and Eisai-hyperbilirubinemic rats (EHBRs) which EHBRs have a hereditary defect of canalicular multidrug resistance-associated protein 2 (Mrp2) function. Also, the in vitro and in vivo kinetics of Z-335-Tau uptake and excretion were compared.nResults. Z-335 uptake by CMVs from normal rats exhibited marked ATP-dependence, whereas ATP-dependent uptake of Z-335 into CMVs from EHBRs was not observed. In contrast, Z-335-Tau uptake into CMVs from both normal rats and EHBRs was ATP dependent. The initial uptake velocity was concentration-dependent, with an in vitro Michaelis constant for initial uptake of 189 μM, which was similar to the in vivo value.nConclusions. The biliary excretion of Z-335 involves Mrp2, whereas that of Z-335-Tau involves active transport systems that remain intact in EHBRs and show marked ATP dependence, which ATP-dependent transport is involved in the biliary excretion of Z-335-Tau in vivo.

Pharmacokinetics, pharmacodynamics, safety, and tolerability of intravenous ferric carboxymaltose: a dose-escalation study in Japanese volunteers with iron-deficiency anemia

Iron-deficiency anemia (IDA) is the most common form of anemia. Iron replacement therapy is an effective treatment, but oral and previously available intravenous (IV) formulations in Japan have disadvantages such as side effects, immunogenic reactions, low dose per tablet/vial, and the need for continuous administration. Ferric carboxymaltose (FCM), which overcomes these limitations, is widely used as an IV iron preparation outside of Japan. In this single-center, open-label, single-dose escalation study, we investigated the pharmacokinetics (PK), pharmacodynamics (PD), safety, and tolerability of FCM in Japanese subjects. Twenty-four Japanese IDA patients, diagnosed by hemoglobin, serum ferritin, and transferrin saturation, were assigned in equal groups to the 100, 500, 800, and 1000xa0mg iron dose arms. All subjects completed the study without important protocol deviations. Mean total serum iron concentrations showed a rapid, dose-dependent increase after FCM injection, reaching a maximum within 1xa0h. Mean reticulocyte counts significantly increased in all arms, suggesting improved hematopoietic function. Fourteen of 24 subjects experienced adverse events, but these were neither serious nor led to drug interruption. The PK/PD and safety profiles were similar in Japanese and European subjects. Ferric carboxymaltose is safe for administration in Japanese patients with IDA.

Physiologically-Based Pharmacokinetic and Pharmacodynamic Modeling for the Inhibition of Acetylcholinesterase by Acotiamide, A Novel Gastroprokinetic Agent for the Treatment of Functional Dyspepsia, in Rat Stomach

PurposeAcotiamide, a gastroprokinetic agent used to treat functional dyspepsia, is transported to at least two compartments in rat stomach. However, the role of these stomach compartments in pharmacokinetics and pharmacodynamics of acotiamide remains unclear. Thus, the purpose of this study was to elucidate the relationship of the blood and stomach concentration of acotiamide with its inhibitory effect on acetylcholinesterase (AChE).MethodsConcentration profiles of acotiamide and acetylcholine (ACh) were determined after intravenous administration to rats and analyzed by physiologically-based pharmacokinetic and pharmacodynamic (PBPK/PD) model containing vascular space, precursor pool and deep pool of stomach.ResultsAcotiamide was eliminated from the blood and stomach in a biexponential manner. Our PBPK/PD model estimated that acotiamide concentration in the precursor pool exceeded 2xa0μM at approximately 2xa0h after administration. Acotiamide inhibited AChE activity in vitro with a 50% inhibitory concentration of 1.79xa0μM. ACh reached the maximum concentration at 2xa0h after administration.ConclusionsOur PBPK model well described the profile of acotiamide and ACh concentration in the stomach in the assumption that acotiamide was distributed by carrier mediated process and inhibited AChE in the precursor pool of stomach. Thus, Acotiamide in the precursor pool plays an important role for producing the pharmacological action.

Verification of a false positive in a two-year rat carcinogenicity study using dual control groups

There is sometimes controversy over whether or not statistically significant responses produced in carcinogenicity studies have biologically significance. Ambiguous results from our previous two-year oral carcinogenicity study on acotiamide hydrochloride hydrate (acotiamide-HH), a prokinetic drug for functional dyspepsia, in rats made it unclear whether the drug may exhibit uterine carcinogenicity. To check this finding, we performed a second long-term carcinogenicity study using two identical control groups to more accurately evaluate uterine carcinogenesis by considering the incidence of spontaneous neoplasms. Female Fischer 344 rats were divided into three groups: the two control groups (control 1 and 2) were administered vehicle (0.5% w/v methylcellulose) and the acotiamide-HH-treated group was administered 2,000 mg/kg/day of acotiamide-HH by oral gavage for two years. Among all groups, the incidence of endometrial adenocarcinoma (EmA) was highest in the control 2 group, followed by the acotiamide-HH-treated group and the control 1 group. Moreover, acotiamide-HH did not affect the incidence of precursor lesions of EmA. In cases where an ambiguous difference is observed, the use of two control groups allows for a more informed interpretation of the findings in the drug-treated groups. The outcomes in this study strongly support the hypothesis that the increase in EmA in rats treated with acotiamide-HH in our previous study is unrelated to administration of the drug.

Distribution of acotiamide, an orally active acetylcholinesterase inhibitor, into the myenteric plexus of rat and dog stomachs

AIMSnAcotiamide is the first-in-class drug for the treatment of functional dyspepsia. Although pharmacological and therapeutic actions of acotiamide are thought to be derived from its inhibitory effects on acetylcholinesterase (AChE), whether the concentration of acotiamide at the site of action is sufficient to inhibit AChE remains unclear. Since major site of acotiamide action is thought to be the cholinergic nerve terminals in gastric myenteric plexus, we studied the distribution of [(14)C]acotiamide into gastric myenteric plexus.nnnMAIN METHODSnDistribution of [(14)C]acotiamide was evaluated using macro- and micro-autoradiography in rats and dogs.nnnKEY FINDINGSnThe results of macro-autoradiography showed the concentration of radioactivity was 27.9μM in rat stomach, which was 12 times higher than IC50 of acotiamide for rat AChE. Being different from rats, the distribution of radioactivity in the muscular layer was distinguishable from that in the mucosal layer in dog stomach. The concentration of radioactivity in the muscular layer of dog stomach (1.41μM) was approximately two-times lower than those in the mucosal layer, however, it was approximately 1.2 times higher than IC50 of acotiamide for dog AChE. The results of micro-autoradiography also showed the radioactivity distributed homogenously in the muscular layer of rat stomach, suggesting the concentration of radioactivity around the ganglion of myenteric plexus is similar to that in the muscular layer of stomach.nnnSIGNIFICANCEnThese findings suggest acotiamide distributes to the myenteric plexus of stomach, a putative site of acotiamide action, with adequate concentrations to inhibit AChE, in both of rat and dog stomachs.