Development and validation of a UHPLC-MS/MS bioanalytical method to quantify in plasma the analgesic candidate PT-31 following a preliminary pharmacokinetic study in rats.

A selective and sensitive UHPLC-MS/MS bioanalytical method to determine PT-31, an analgesic drug candidate, in rat plasma was developed and validated. Analyses were performed using a UHPLC-MS/MS system equipped with an electrospray ionization interface operating in the positive ionization mode using a C18 reversed-phase column with a mobile phase of water:acetonitrile (68:31, v/v) containing 0.1% acetic acid eluting in a gradient mode with a flow rate of 0.3 mL/min. Plasma samples were deproteinized with cold acetonitrile containing 0.01% TFA (1:2, v/v) and 50 µL of the supernatant were injected into the system. PT-31 and phenytoin (internal standard) retention times were roughly 1.0 and 1.5 min, respectively. Linear standard curves were plotted for the 0.01-10 µg/mL concentration range, with a coefficient of determination > 0.99. The method's precision was over 88%. Maximum intra- and inter-day relative standard deviations were 14.6% and 11.6%, respectively. Interfering substances were not detected in the chromatogram, indicating that the method was specific. PT-31 stability was assessed under different temperature and storage settings. The method was used to characterize PT-31 plasma pharmacokinetics following administration of 5 mg/kg i.v. to Wistar rats. Therefore, the method described is sensitive, linear, precise and specific enough to determine PT-31 in preclinical pharmacokinetic investigations. Copyright © 2015 John Wiley & Sons, Ltd.

Identification of carboxylesterases expressed in rat intestine and effects of their hydrolyzing activity in predicting first-pass metabolism of ester prodrugs.

Carboxylesterases (CESs) located in the intestine play an unique role in the absorption of many drugs especially ester prodrugs. In order to determine the expression and hydrolyzing activity of CESs isozymes (CES1 and CES2) located in rat intestine, the activities of CES1 and CES2 were evaluated by the intestinal S9 incubation with imidapril and irinotecan (CPT-11), the substrates of CES1 and CES2, respectively. The distribution characteristics of CES1, CES2, Pregnane X Receptor (PXR) and Constitutive Androstane Receptor were analyzed by real-time polymerase chain reaction (RT-PCR) or Western blot. Imidaprilat metabolized from imidapril by CES1 was too low to be detected in rat intestinal S9 fractions, while there was little and even no expression of CES1 mRNA in intestinal segments. In contrast, Vmax values for CPT-11 diminished gradually from proximal to distal segments within the rat intestine which was consistent with the mRNA expression level of CES2. These results indicated that CES2 represents the major CESs isoform in the rat complete intestine and decreased from duodenum to colon, whereas the expression of CES1 was too low to influence the metabolism of ester prodrugs. The expression of PXR and CAR decreased slightly along the entire intestine on both mRNA and protein levels which indicated that PXR and CAR may be one of the major factors which contribute to the expression of CES1 and CES2. Thus, the knowledge about the characteristic and site-specific expression of CES1 and CES2 in rat intestine will help to predict the oral bioavailability of ester prodrugs.

Identification and characterization of in vitro and in vivo fidarestat metabolites: Toxicity and efficacy evaluation of metabolites.

The progression of diabetic complications can be prevented by inhibition of aldose reductase and fidarestat considered to be highly potent. To date, metabolites of the fidarestat, toxicity, and efficacy are unknown. Therefore, the present study on characterization of hitherto unknown in vitro and in vivo metabolites of fidarestat using liquid chromatography-electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) is undertaken. In vitro and in vivo metabolites of fidarestat have been identified and characterized by using LC/ESI/MS/MS and accurate mass measurements. To identify in vivo metabolites, plasma, urine, and feces samples were collected after oral administration of fidarestat to Sprague-Dawley rats, whereas for in vitro metabolites, fidarestat was incubated in human S9 fraction, human liver microsomes, and rat liver microsomes. Furthermore, in silico toxicity and efficacy of the identified metabolites were evaluated. Eighteen metabolites have been identified. The main in vitro phase I metabolites of fidarestat are oxidative deamination, oxidative deamination and hydroxylation, reductive defluroniation, and trihydroxylation. Phase II metabolites are methylation, acetylation, glycosylation, cysteamination, and glucuronidation. Docking studies suggest that oxidative deaminated metabolite has better docking energy and conformation that keeps consensus with fidarestat whereas the rest of the metabolites do not give satisfactory results. Aldose reductase activity has been determined for oxidative deaminated metabolite (F-1), and it shows an IC50 value of 0.44 µM. The major metabolite, oxidative deaminated, did not show any cytotoxicity in H9C2, HEK, HEPG2, and Panc1 cell lines. However, in silico toxicity, the predication result showed toxicity in skin irritation and ocular irritancy SEV/MOD versus MLD/NON (v5.1) model for fidarestat and its all metabolites. In drug discovery and development research, it is distinctly the case that the potential for pharmacologically active metabolites must be considered. Thus, the active metabolites of fidarestat may have an advantage as drug candidates as many drugs were initially observed as metabolites.

Synthesis, SAR and evaluation of [1,4']-bipiperidinyl-4-yl-imidazolidin-2-one derivatives as novel CCR5 antagonists.

Elaboration of our previously disclosed spiropiperidine template led to the development of a series of novel CCR5 antagonists. Results of SAR exploration and preliminary lead characterization are described.

Different inhibitory effects in rat and human carboxylesterases.

In vitro inhibition studies on drug-metabolizing enzyme activity are useful for understanding drug-drug interactions and for drug development. However, the profile of the inhibitory effects of carboxylesterase (CES) activity has not been fully investigated concerning species and tissue differences. In the present study, we measured the inhibitory effects of 15 drugs and 1 compound on CES activity using liver and jejunum microsomes and cytosol in human and rat. In addition, the inhibition constant (K(i) values) and patterns were determined for the compounds exhibiting strong inhibition. Hydrolysis of imidapril and irinotecan hydrochloride (CPT-11) is catalyzed mainly by CES1 and CES2, respectively. In the inhibition study, imidaprilat formation from imidapril in human liver was strongly inhibited by nordihydroguaiaretic acid (NDGA) and procainamide. The inhibition profile and pattern were similar in human liver and rat liver. The compounds showing potent inhibition were similar between liver and jejunum. The K(i) value of NDGA (K(i) = 13.3 +/- 1.5 microM) in human liver microsomes was 30-fold higher than that in rat liver microsomes (K(i) = 0.4 +/- 0.0 microM). On the other hand, 7-ethyl-10-hydroxycamptothecin (SN-38) formation from CPT-11 was not inhibited except by carvedilol, manidipine, and physostigmine. The K(i) value of physostigmine (K(i) = 0.3 +/- 0.0 microM) in human jejunum cytosol was 10-fold lower than that in rat jejunum cytosol (K(i) = 3.1 +/- 0.4 microM) and was similar to that for manidipine. The present study clarified the species differences in CES inhibition. These results are useful for the development of prodrugs.

Improving Relative Bioavailability of Oral Imidazolidinedione by Reducing Particle Size Using Homogenization and Ultra-Sonication.

Particle size is an important determinant of gastrointestinal absorption of compounds administrated orally. The present study evaluates the effect of a reduction in particle size assessed by homogenization, sonication, and homogenization plus sonication on the bioavailability of imidazolidinedione (IZ), an antimalarial compound with known causal prophylactic activity and radical cure of relapsing malaria. Formulations were administrated intragastrically to mice, and blood samples were collected for LC-MS/MS analysis. The homogenization method manually decreased particle size with minimal variance, resulting in a mean particle diameter of 42.22 µm, whereas the probe sonication method evenly distributed pulses of sound to break apart particles, resulting in a mean diameter of 1.50 µm. Homogenization plus sonication resulted in a mean particle diameter of 1.44 µm, which was similar to that of the sonication method alone. The compound suspensions did not show a significant difference in mean particle size between the different vehicles. The sonically engineered microparticle delivers high sonic energy to the suspension leads to faster breakdown and stabilizing of the micronized particles when compared with homogenizer. The bioavailability of the small particle IZ formulation was 100%, compared to the 55.79% relative bioavailability of IZ with larger particle size. These initial data clearly show that a reduction in particle size of orally administered IZ with probe sonication could significantly increase bioavailability in rodent animals that is affected by a high first-pass effect.

Study of the in vitro metabolic profile of a new α2-adrenergic agonist in rat and human liver microsomes by using liquid chromatography-multiple-stage mass spectrometry and nuclear magnetic resonance.

A potent synthetic α2-adrenergic agonist called PT-31, (3-(2-chloro-6-fluorobenzyl)-imidazolidine-2,4-dione), was recently detected as a potential drug to be used as an adjuvant drug to treat chronic pain. The excellent pharmacological property of PT-31 highlights the importance in elucidating its metabolism, which could provide valuable information about its metabolite profile for further pharmacokinetics studies and additionally to estimate the impact of its metabolites on the efficacy, safety and elimination of PT-31. In this work, the study of the in vitro metabolism of PT-31 was initially carried out by using a liquid chromatography coupled to ion trap multiple-stage mass spectrometer (LC-IT-MSn) and a hybrid triple quadrupole/linear ion trap mass spectrometer (LC-QTrap). The production of at least three unknown oxidative metabolites was observed. Structural identification of the unknown metabolites was carried out by combination of LC-MS experiments, including selected reaction monitoring (SRM) and multi-stage full scan experiments. Further analysis of 1H-NMR led to the structural confirmation of the major metabolite. The results indicated that PT-31 was metabolized by a hydroxylation reaction in the imidazolidine-2,4-dione ring in rat and human liver microsomes, producing the metabolite 3-(2-chloro-6-fluorobenzyl)-5-hydroxyimidazolidine-2,4-dione in rat liver microsomes. A carbon hydroxylation onto the benzyl ring, produced two other minor metabolites of the PT-31 in rat liver microsomes.

Functional polymorphisms in carboxylesterase1A2 (CES1A2) gene involves specific protein 1 (Sp1) binding sites.

Carboxylesterase 1 (CES1) is involved in metabolic activation of a variety of prodrugs into active derivatives and plays an important role in pharmacokinetics. We previously reported that a single nucleotide polymorphism (SNP), -816A/C of the CES1A2 gene associates with the responsiveness to an angiotensin-converting enzyme (ACE) inhibitor, imidapril, whose activity is achieved by CES1. To identify relevant functional polymorphisms, we re-sequenced the CES1A2 promoter region ( approximately 1kb) in 100 Japanese hypertensive patients. Altogether 10 SNPs and one insertion/deletion (I/D) were identified, among which seven SNPs and one I/D residing between -62 and -32 were in almost complete linkage disequilibrium (D'=1.00, r2=0.97). They consisted a minor and a major haplotype, the allele frequencies of which were 22% and 74%, respectively. The minor haplotype possessed two putative Sp1 binding sites while the major haplotype did not have any Sp1 binding site. The minor haplotype had a higher transcription and Sp1 binding activities than the major haplotype, invitro. The original -816A/C was in high linkage disequilibrium with these haplotypes (D'=0.92, r2=0.85), and well agreed with the efficacy of imidapril medication. These results suggest that the Sp1 binding site variation in the CES1A2 promoter is functional, and are good candidates for the pharmacogenetic studies of CES1-activated drugs.

Clearance of imidapril, an Angiotensin-converting enzyme inhibitor, during hemodialysis in hypertensive renal failure patients: comparison with quinapril and enalapril.

The dialyzability of imidaprilat, an active metabolite of the angiotensin-converting enzyme (ACE) inhibitor imidapril, was determined and compared with those of enalaprilat and quinaprilat in hypertensive patients on chronic hemodialysis. Imidapril (5 mg/d, n = 6), enalapril (2.5 mg/d, n = 6), or quinapril (2.5 mg/d, n = 6) was given for at least 8 weeks prior to the trial. During dialysis, enalaprilat, but not imidaprilat or quinaprilat, concentrations in both sides decreased significantly. Compared to enalaprilat, the dialyzabilities of imidaprilat and quinaprilat were significantly lower (dialyzer clearance [mL/min/m(2)]: enalaprilat, 41.8 +/- 7.4; imidaprilat, 19.0 +/- 7.8; quinaprilat, 8.9 +/- 1.3). The dialyzabilities of the 3 drugs were negatively correlated with their respective protein-binding rates. During hemodialysis, blood pressure did not change significantly in any group. These results suggest that imidapril provides good blood pressure control without a large fluctuation of drug concentration in hypertensive patients undergoing chronic hemodialysis.

Topical aldose reductase inhibitor formulations for effective lens drug delivery in a rat model for sugar cataracts.

PURPOSE: In the topical delivery of drugs to the lens, drug retention on the eye surface is considered to be important because increased retention on the ocular surface should lead to increased ocular absorption of a drug through the cornea into the aqueous humor and subsequently the lens. The aim of this study was to investigate whether increasing the viscosity of a topical aldose reductase inhibitor suspension increases the lenticular bioavailability of the inhibitor and whether such a formulation can arrest sugar cataract formation. METHODS: Five topical suspensions of 3% 2-methylsorbinil (2-MS) were prepared using (1) hydroxypropyl methylcellulose (HPMC, 0.5% w/v), (2) xanthan gum (0.5% w/v), (3) gellan gum (0.5% w/v), (4) carbopol (0.25% w/v), and (5) carbopol (0.25% w/v)--hydroxypropyl methylcellulose (HPMC) (0.25% w/v). Viscosity measurements were conducted with a viscometer. Lenticular levels of 2-MS were determined in the lenses from young Sprague Dawley rats receiving 1 drop of selected topical suspension twice-daily for 7 days. The efficacy of the suspensions to arrest sugar cataract formation was evaluated by administering the suspensions for 21 days to similar rats fed a diet containing 50% galactose. Lens changes were examined by portable slit lamp following mydriasis. RESULTS: Lenticular levels of 2-MS was highest in rats administered suspensions containing 0.25% carbopol + 0.25% HPMC as vehicles followed by 0.5% gellan gum, 0.5% HPMC, 0.25% carbopol, and 0.5% xanthan gum. All untreated rats fed a 50% galactose diet developed hypermature cataracts within 15 days; however, none of the topical treated rats demonstrated cortical vacuole formation after 21 days of galactose feeding. CONCLUSIONS: In the suspensions examined, no direct relationship between the lenticular drug levels of 2-MS and either viscosity or pH of the vehicles were observed. The observed arrest of sugar cataract formation indicated that therapeutically adequate lenticular levels of 2-MS were provided by all topical suspensions.

Population Pharmacokinetic Modeling of JNJ-53718678, a Novel Fusion Inhibitor for the Treatment of Respiratory Syncytial Virus: Results from a Phase I, Double-Blind, Randomized, Placebo-Controlled First-in-Human Study in Healthy Adult Subjects.

BACKGROUND: JNJ-53718678 is a potent small-molecule inhibitor of the F-glycoprotein-mediated complex membrane fusion process of the respiratory syncytial virus. Here, we report the pharmacokinetics, the population pharmacokinetic modeling, and the safety and tolerability of JNJ-53718678 from the first-in-human, double-blind, randomized, placebo-controlled phase I study. METHODS: Healthy subjects were randomized (6:3) into five single-dose groups (25-1000 mg) or three multiple-dose groups [250 mg every 24 h (q24h), 500 mg q24h, 250 mg every 12 h; fed conditions for 8 days] to receive JNJ-53718678 or placebo. Blood and urine samples were collected at several timepoints up to 72 h after intake of JNJ-53718678 and analyzed using validated liquid chromatography-mass spectrometry methods. A population pharmacokinetic model was developed and validated. RESULTS: Peak plasma concentrations of JNJ-53718678 increased with increasing single (159 ± 54.9 to 6702 ± 1733 ng/mL) and multiple (on day 8, 1528 ± 256 to 2655 ± 591 ng/mL) doses. Steady-state conditions were reached on day 2 of the 8-day dosing regimen. Less than 4% of JNJ-53718678 was excreted in urine across all dose groups. Mean exposure of JNJ-53718678 was 7% lower in the fed state compared with the fasted state at the same dose. A two-compartment model with first-order absorption with parallel linear and non-linear elimination best described the pharmacokinetics of JNJ-53718678. No covariate effects were observed. CONCLUSIONS: A population pharmacokinetic model that describes the concentration data well with good precision of all parameter estimates was developed and validated. JNJ-53718678 was well tolerated at all single and multiple doses studied.

Associations between CYP11B2 gene polymorphisms and the response to angiotensin-converting enzyme inhibitors.

OBJECTIVE: Our objective was to investigate the association between the -344C/T or A6547G polymorphism of the aldosterone synthase gene and the blood pressure response to angiotensin-converting enzyme inhibitors in a hypertensive cohort. METHODS: After a 2-week single-blind placebo run-in period, either benazepril or imidapril was administered for 6 weeks to 509 patients with mild to moderate essential hypertension. Polymerase chain reaction combined with restriction enzyme digestion was used to detect the 2 polymorphisms. The achieved changes in systolic and diastolic blood pressure were analyzed for their association with genotypes at the aldosterone synthase gene loci. RESULTS: Regarding the -344C/T polymorphism, we observed the CC genotype in 53 patients (10.4%), the CT genotype in 204 (40.1%), and the TT genotype in 252 (49.5%). After 6 weeks of treatment, the reductions in diastolic blood pressure were significantly greater in patients carrying the TT or CT genotype compared with those carrying the CC genotype (9.1+/-7.0 mm Hg or 8.9+/-7.0 mm Hg versus 5.1+/-7.3 mm Hg, respectively; P=.001, ANOVA). Regarding the A6547G polymorphism, we observed the AA genotype in 19 patients (3.7%), the AG genotype in 184 (36.2%), and the GG genotype in 306 (60.1%). There were no significant differences in the blood pressure reductions after treatment among the 3 genotype groups, and there was no interaction between it and the -344C/T polymorphism. Stepwise multiple regression analysis showed that the significant predictors of diastolic blood pressure reduction at 6 weeks were baseline diastolic blood pressure (P<.001), -344C/T genotype (P=.007), and sex (P=.033). CONCLUSIONS: The -344C/T variant, but not the A6547G variant, of the aldosterone synthase gene may be a determinant of the blood pressure response to angiotensin-converting enzyme inhibitors in hypertensive patients.

Bioactivation and hepatotoxicity of nitroaromatic drugs.

Certain drugs containing a nitroaromatic moiety (e.g., tolcapone, nimesulide, nilutamide, flutamide, nitrofurantoin) have been associated with organ-selective toxicity including rare cases of idiosyncratic liver injury. What they have in common is the potential for multistep nitroreductive bioactivation (6-electron transfer) that produces the potentially hazardous nitroanion radical, nitroso intermediate, and N-hydroxy derivative. These intermediates have been associated with increased oxidant stress and targeting of nucleophilic residues on proteins and nucleic acids. However, other mechanisms including the formation of oxidative metabolites and mitochondrial liability, as well as inherent toxicokinetic properties, also determine the drugs' overall potency. Therefore, structural modification not only of the nitro moiety but also of ring substituents can greatly reduce toxicity. Novel concepts have revealed that, besides the classical microsomal nitroreductases, cytosolic and mitochondrial enzymes including nitric oxide synthase can also bioactivate certain nitroarenes (nilutamide). Furthermore, animal models of silent mitochondrial dysfunction have demonstrated that a mitochondrial oxidant stress posed by certain nitroaromatic drugs (nimesulide) can produce significant mitochondrial injury if superimposed on a genetic mitochondrial abnormality. Finally, there may be mechanisms for all nitroaromatic drugs that do not involve bioactivation of the nitro group, e.g., AHR interactions with flutamide. Taken together, the focus of research on the hepatic toxicity of nitroarene-containing drugs has shifted over the past years from the identification of the reactive intermediates generated during the bioreductive pathway to the underlying biomechanisms of liver injury. Most likely one of the next paradigm shifts will include the identification of determinants of susceptibility to nitroaromatic drug-induced hepatotoxicity.

Imidapril in heart failure.

Angiotensin-converting enzyme (ACE) inhibitors improve the prognosis in mild, moderate and severe heart failure, as well as preventing the onset of heart failure in patients with chronic asymptomatic left-ventricular dysfunction and in those with reduced ejection fraction after myocardial infarction (MI). Imidapril is a long-acting ACE inhibitor that is rapidly converted in the liver to its active metabolite, imidaprilat. Maximum plasma concentrations of imidapril and imidaprilat are achieved after 2 and 5-6 hours, respectively, with corresponding elimination half-lives of 1.1-2.5 and 10-19 hours. Imidapril is used in the treatment of hypertension, chronic heart failure, acute MI and diabetic nephropathy. In patients with mild-to-moderate chronic heart failure, imidapril 10 mg once-daily increased exercise time and physical working capacity, decreased plasma atrial natriuretic peptide and brain natriuretic peptide levels and reduced blood pressure. It also improved left ventricular ejection fraction, being significantly more effective than bisoprolol, in patients with acute MI. Imidapril is well tolerated and preliminary studies suggest it has an advantage over captopril and enalapril in terms of a lower incidence of cough. In conclusion, imidapril is a well-investigated versatile ACE inhibitor for the treatment of a range of cardiovascular diseases.

Influence of coadministration on the pharmacokinetics of azimilide dihydrochloride and digoxin.

The influence of coadministration on digoxin and azimilide pharmacokinetics/pharmacodynamics was assessed in a randomized, 3-way crossover study in 18 healthy men. Serial blood and urine samples were obtained for azimilide and digoxin quantitation. Treatment effects on pharmacokinetics were assessed using analysis of variance. The relationship between azimilide blood concentrations and QT(c) prolongation was characterized by an E(max) model. Effects of coadministration on pharmacodynamics were assessed using a mechanistic-based inhibition model. Azimilide pharmacokinetics was unaffected by digoxin, except for a 36% increase in CL(r) (P = .0325), with no change in CL(o). Digoxin pharmacokinetics was unaffected by azimilide, except for a 21% increase in C(max) (P = .0176) and a 10% increase in AUC(tau) (P = .0121). Digoxin coadministration increased the apparent EC(50) with no effect on E(max), consistent with competitive inhibition (K(i) = 0.899 ng/mL). The pharmacokinetic and pharmacodynamic changes observed upon coadministration were small and are not expected to be clinically important.

The metabolic profile of azimilide in man: in vivo and in vitro evaluations.

The metabolic fate of azimilide in man is unusual as it undergoes a cleavage in vivo resulting in the formation of two classes of structurally distinct metabolites. During a metabolite profiling study conducted in human volunteers to assess the contribution of all pathways to the clearance of (14)C-azimilide, greater than 82% of radioactivity was recovered in urine (49%-58%) and feces (33%). Urine, feces, and plasma were profiled for metabolites. A cleaved metabolite, 4-chloro-2-phenyl furoic acid was present at high concentration in plasma (metabolite/parent AUC ratio approx. 4), while other plasma metabolites, azimilide N-oxide (metabolite/parent AUC ratio 0.001), and a cleaved hydantoin metabolite (metabolite/parent AUC ratio = 0.3) were present at lower concentrations than azimilide. In urine, the cleaved metabolites were the major metabolites, (> 35% of the dose) along with phenols (as conjugates, 7%-8%), azimilide N-oxide (4%-10%), a butanoic acid metabolite (2%-3%), and desmethyl azimilide (2%). A limited investigation of fecal metabolites indicated that azimilide (3%-5%), desmethyl azimilide (1%-3%), and the butanoic acid metabolite (< 1%) were present. Contributing pathways for metabolism of azimilide, identified through in vitro and in-vivo studies, were CYPs 1A1 (est. 28%), 3A4/5 (est. 20%), 2D6 (< 1%), FMO (est. 14%), and cleavage (35%). Enzyme(s) involved in the cleavage of azimilide were not identified.

LC-MS determination and bioavailability study of imidapril hydrochloride after the oral administration of imidapril tablets in human volunteers.

The purpose of the present study was to develop a standard protocol for imidapril hydrochloride bioequivalence testing. For this reason, a specific LC-MS method was developed and validated for the determination of imidapril in human plasma. A solid-phase extraction cartridge, Sep-pak C18, was used to extract imidapril and ramipril (an internal standard) from deproteinized plasma. The compounds were separated using a XTerra MS C18 column (3.5 microm, 2.1 x 150 mm) and acetonitrile-0.1% formic acid (67:33, v/v) adjusted to pH 2.4 by 2 mmol/L ammonium formic acid, as mobile phase at 0.3 mL/min. Imidapril was detected as m/z 406 at a retention time of ca. 2.3 min, and ramipril as m/z 417 at ca. 3.6 min. The described method showed acceptable specificity, linearity from 0.5 to 100 ng/mL, precision (expressed as a relative standard deviation of less than 15%), accuracy, and stability. The plasma concentration-versus-time curves of eight healthy male volunteers administered a single dose of imidapril (10 mg), gave an AUC12hr of imidapril of 121.48 +/- 35.81 ng mL(-1) h, and Cmax and Tmax values of 32.59 +/- 9.76 ng/mL and 1.75 +/- 0.27 h. The developed method should be useful for the determination of imidapril in plasma with sufficient sensitivity and specificity in bioequivalence study.

Design, synthesis and biological evaluation of novel 5-oxo-2-thioxoimidazolidine derivatives as potent androgen receptor antagonists.

A series of novel highly active androgen receptor (AR) antagonists containing spiro-4-(5-oxo-3-phenyl-2-thioxoimidazolidin-1-yl)-2-(trifluoromethyl)benzonitrile core was designed based on the SAR studies available from the reported AR antagonists and in silico modeling. Within the series, compound (R)-6 (ONC1-13B) and its related analogues, including its active N-dealkylated metabolite, were found to be the most potent molecules with the target activity (IC50, androgen-sensitive human PCa LNCaP cells) in the range of 59-80 nM (inhibition of PSA production). The disclosed hits were at least two times more active than bicalutamide, nilutamide and enzalutamide within the performed assay. Several compounds were classified as partial agonists. Hit-compounds demonstrated benefit pharmacokinetic profiles in rats. Comparative SAR and 3D molecular docking studies were performed for the hit compounds elucidating the observed differences in the binding potency.

Down-regulation of carboxylesterases 1 and 2 plays an important role in prodrug metabolism in immunological liver injury rats.

Liver plays a central role in xenobiotics metabolism, thus affecting the in vivo disposition and therapeutic effects of drugs. Carboxylesterases (CESs), with the main isoforms CES1 and CES2, are important in the metabolism of ester-type prodrugs. However, influences of immunological liver injury on the activity of CES remain undefined. In the present study, we demonstrated treatment with lipopolysaccharide (LPS) suppressed the activities of CES1 and CES2. The decreased activities of CES1 and CES2 were preliminarily assessed by the hydrolysis assay for their common substrate p-nitrophenyl acetate (PNPA) with rat hepatic microsomal enzyme. Subsequently, RT-PCR results showed that the levels of CES1 mRNA and mRNA of CES2 (AB010635) and CES2 (AY034877) in the model group were significantly lower than those of the normal control group (P<0.05). Western blot results showed that the expressions of CES1 and CES2 proteins were decreased (P<0.05). To further clarify the effects of LPS on the metabolic activities of CESs, pharmacokinetic studies were performed in rats by utilizing imidapril and irinotecan (CPT-11) as the specific substrates for CES1 and CES2, respectively. After treatment with LPS, AUC0-∞ and Cmax of imidaprilat were decreased from 2084.86±340.66ng·h(-1)·mL(-1) and 234.66±68.85ng·mL(-1) to 983.87±315.34ng·h(-1)·mL(-1) and 113.1±19.69ng·mL(-1) (P<0.05), respectively. Moreover, AUC0-∞ and Cmax of SN-38 were decreased from 8100±918.6ng·h(-1)·mL(-1) and 144.67±20.28ng·mL(-1) to 3270±500.5ng·h(-1)·mL(-1) and 56.19±10.38ng·mL(-1) (P<0.05), respectively. In summary, immunological liver injury remarkably attenuated the expressions and metabolic activities of CES1 and CES2, which may be associated with the regulatory effects of cytokines under inflammation.

Recent developments in cardiovascular drug therapy: treatment of atrial arrhythmias with new class III drugs and beyond.

Despite recent advances in non-pharmacologic approaches antiarrhythmic drugs still play a dominant role in the treatment of cardiac arrhythmias. Large randomized controlled clinical trials have pointed out the importance of a proper benefit to risk evaluation in various patient subsets. This led to a continuous decline in the use of sodium channel blockers due to their possible proarrhythmic effects particularly in patients with reduced left ventricular function and ischemic heart disease. On the contrary, beta-blockers and more complex class III compounds such as sotalol and amiodarone have been prescribed increasingly. However, side effects commonly observed boosted the development of agents with simpler ion channel-blockade and less adverse reactions. In this review newer so-called "pure" class III agents will be discussed. Their common mechanism of action is an antifibrillatory effect both on the atrial and ventricular level. Clinically, they are used in the chemical cardioversion and the prevention of atrial fibrillation or atrial flutter as well as for the maintenance of sinus rhythm after its successful restoration. This report contains a detailed analysis of the pharmacokinetics, results of clinical studies and implications regarding the use in daily practice for three distinct compounds: ibutilide, dofetilide and azimilide. As efficacy is still limited their current and future role in hybrid therapies combining drug therapy with alternative treatment modalities (catheter ablation, pacemakers and implantable cardioverter defibrillators) is discussed. In addition, an outlook for a future drug design implementing changes in electrically remodeled atrial tissue will be given.