Gender differences in pharmacokinetics of perfluoropentanoic acid using non-linear mixed-effect modeling in rats.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been used in various industrial applications for many years. Long-chain PFASs are ubiquitous in wildlife and are reported to have a long elimination half-life in biological systems. Moreover, significant gender difference exists in the elimination of PFASs, where less is eliminated in male than in female. Recently, PFASs manufacturers and agencies have tried to replace the use of long-chain PFASs with short-chain PFASs, since they are expected to exhibit less bioaccumulation potential. Nevertheless, the potential risk and the pharmacokinetic (PK) characteristics of the short-chain PFASs still remain unknown. This study aims to fill the knowledge gap on short-chain PFASs, perfluoropentanoic acid (PFPeA), in terms of its PK properties using non-linear mixed-effect modeling and to explore gender differences in rats. Animal studies were carried out following oral or intravenous administration of PFPeA in male and female rats at a dose of 0.5-10 mg/kg. Plasma, urine, feces and nine tissues were collected and analyzed using ultra-performance liquid chromatography-tandem mass spectrometry. PK findings revealed that the clearance and the inter-compartmental clearance were 1.75 and 3.12 times higher in female rats than in male rats, respectively. According to the result, PFPeA is eliminated more rapidly in female rats than in male rats. Also, the tissue distribution study confirmed that distribution characteristics exhibited gender difference. This study provides scientific evidence for conducting further investigation into short-chain PFASs, biomonitoring plans and decision making regarding human health risk assessment.

Isovalerylshikonin, a new resistance-modifying agent from Arnebia euchroma, supresses antimicrobial resistance of drug-resistant Staphylococcus aureus.

Antimicrobial resistance is the greatest threat to the treatment of bacterial infectious diseases. The development of resistance-modifying agents (RMAs) represents a promising strategy to mitigate the spread of bacterial antimicrobial resistance. In this study, a natural product, isovalerylshikonin (IVS), was isolated from Arnebia euchroma, a traditional Chinese medicine herb, that exhibited marginal antibacterial activity against drug-resistant Staphylococcus aureus RN4220, with a minimum inhibitory concentration (MIC) of 16 mg/L. In addition, a synergistic effect between IVS and streptomycin (STM) was detected by the microdilution antimicrobial chequerboard assay, with a reduction in the MIC of STM by up to 16-fold against strain RN4220. A bacterial ethidium bromide efflux assay and reverse transcription PCR were performed to investigate the synergistic mechanism. IVS significantly inhibited bacterial efflux and expression of msrA mRNA in vitro. A murine peritonitis/sepsis model was employed to test the in vivo synergistic activity of IVS and STM. IVS synergistically decreased bacterial counts with STM in peritoneal, spleen and liver tissue and increased mouse survival with STM in 7 days. The acute toxicity of IVS was tested and the 50% lethal dose (LD50) of IVS with a single exposure was 2.584 g/kg in mice. Overall, IVS, a low-toxicity RMA, exhibited synergistic antibacterial activities in vitro and in vivo against drug-resistant S. aureus. The effects were mediated by suppression of msrA mRNA expression and reduced bacterial efflux. In addition, these data support that IVS is a potential RMA against microbial resistance caused by the MsrA efflux pump.

Novel Highly Potent and Metabolically Resistant Oxoeicosanoid (OXE) Receptor Antagonists That Block the Actions of the Granulocyte Chemoattractant 5-Oxo-6,8,11,14-Eicosatetraenoic Acid (5-oxo-ETE).

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a potent lipid mediator that induces tissue eosinophilia via the selective OXE receptor (OXE-R), which is an attractive therapeutic target in eosinophilic diseases. We previously identified indole OXE-R antagonists that block 5-oxo-ETE-induced primate eosinophil activation. Although these compounds possess good oral absorption, their plasma levels decline rapidly due to extensive oxidation of their hexyl side chain. We have now succeeded in dramatically increasing antagonist potency and resistance to metabolism by replacing the hexyl group with phenylpentyl or phenylhexyl side chains. Compared with our previous lead compound S-230, our most potent antagonist, S-C025, has an IC50 (120 pM) over 80 times lower and a substantially longer plasma half-life. A single major metabolite, which retains antagonist activity (IC50, 690 pM) and has a prolonged lifetime in plasma was observed. These new highly potent OXE-R antagonists may provide a novel strategy for the treatment of eosinophilic disorders like asthma.

Development of a prodrug of hydantoin based TACE inhibitor.

Our research on hydantoin based TNF-α converting enzyme (TACE) inhibitors led to fused bi-heteroaryl hydantoin series that demonstrate sub-nanomolar potency (Ki) as well as excellent activity in human whole blood (hWBA). However, lead compound 2 posed some formulation challenges which prevented it for further development. A prodrug approach was investigated to address this issue. The pivalate prodrug 3 can be formulated as stable neutral form and demonstrated improved DMPK properties when compared with parent compound.

Carcinogenicity assessment of the pan-caspase inhibitor, emricasan, in Tg.rasH2 mice.

Emricasan, formerly IDN-6556, is a small molecule currently being evaluated in clinical trials to reduce hepatic injury and liver fibrosis. Since emricasan is an irreversible pan-caspase inhibitor that potently inhibits caspase-mediated apoptosis and inflammation, its carcinogenic potential was evaluated in a humanized mouse model. Tg.rasH2 mice received LabDiet formulated with 0, 10, 25, and 75mg/kg/day of emricasan, for 26weeks. At terminal sacrifice, blood was collected for clinical pathology analysis and tissues were collected, processed, and evaluated microscopically. There were no treatment related deaths or overt signs of toxicity for the duration of the study. There was no evidence of a carcinogenic effect in the peripheral blood leukocyte counts. Liver microgranulomas, which are background lesions, were slightly increased, especially in males. Increases in the incidence of the activated germinal centers were seen in the spleens and mesenteric lymph nodes of males and females, and in the mandibular lymph nodes of male mice. Atrophy of ovaries and testicular degeneration were also seen in emricasan treated animals. Although several non-neoplastic lesions were observed, there was no evidence of emricasan-related tumor formation in any tissue. In addition, the non-neoplastic lesions were not considered pre-neoplastic. Thus, emricasan is not considered carcinogenic.

Synthesis, Radiolabeling, and Biological Evaluation of (R)- and (S)-2-Amino-5-[(18)F]fluoro-2-methylpentanoic Acid ((R)-, (S)-[(18)F]FAMPe) as Potential Positron Emission Tomography Tracers for Brain Tumors.

A novel (18)F-labeled α,α-disubstituted amino acid-based tracer, 2-amino-5-[(18)F]fluoro-2-methylpentanoic acid ([(18)F]FAMPe), has been developed for brain tumor imaging with a longer alkyl side chain than previously reported compounds to increase brain availability via system L amino acid transport. Both enantiomers of [(18)F]FAMPe were obtained in good radiochemical yield (24-52% n = 8) and high radiochemical purity (>99%). In vitro uptake assays in mouse DBT gliomas cells revealed that (S)-[(18)F]FAMPe enters cells partly via sodium-independent system L transporters and also via other nonsystem A transport systems including transporters that recognize glutamine. Biodistribution and small animal PET/CT studies in the mouse DBT model of glioblastoma showed that both (R)- and (S)-[(18)F]FAMPe have good tumor imaging properties with the (S)-enantiomer providing higher tumor uptake and tumor to brain ratios. Comparison of the SUVs showed that (S)-[(18)F]FAMPe had higher tumor to brain ratios compared to (S)-[(18)F]FET, a well-established system L substrate.

Exploring the roles of UGT1A1 and UGT1A3 in oral clearance of GSK2190915, a 5-lipoxygenase-activating protein inhibitor.

Pharmacokinetic variability in drug exposure is a concern for all compounds in development including those for the treatment of asthma and other respiratory disorders. Substantial variability in the oral clearance of GSK2190915, a 5-lipoxygenase-activating protein inhibitor that attenuates the production of leukotriene B4 and cysteinyl leukotrienes, is largely unaccounted for by clinical variables. A study of 41 patients, 78% (32/41) of whom were non-Hispanic whites, with mild to moderate asthma identified an association of UGT1A1*28 and UGT1A3*2 with the oral clearance of GSK2190915 (P=3.8×10⁻4 and 1.2×10⁻5, respectively). However, in a subsequent replication study of 403 non-Hispanic white patients with asthma, we failed to observe a statistically significant association between oral clearance of GSK2190915 and either UGT1A1*28 or UGT1A3*2 (P>0.05). Therefore, genetic effects that could explain the systemic exposure level variability of GSK2190915 were not identified.

Pharmacodynamic and clinical endpoints for functional colonic disorders: statistical considerations.

BACKGROUND: Intra- and inter-subject coefficients of variation (COV) of scintigraphic colonic transit (SCT) are well characterized. SCT response to therapy predicts clinical efficacy of experimental medications in lower functional gastrointestinal disorders (FGID). AIM: To compare COVs for bowel function with pharmacodynamic (PD) colonic transit geometric center (GC) as endpoints in lower FGID studies. METHODS: We evaluated data from placebo arm of 9 phase IIA, parallel-group, clinical trials of PD effects of linaclotide, dexloxiglumide, renzapride, elobixibat, ROSE 010, and chenodeoxycholate in lower FGID with constipation, and pexacerafont, VSL#3, and colesevelam in lower FGID with diarrhea. Patients completed daily diaries for at least 7 days of stool frequency, consistency (7-point Bristol Stool Form Scale), and ease of passage (7-point scale from manual disimpaction to incontinence). Seventeen patients received placebo in 2 separate studies allowing assessment of intra-patient COVs. We calculated sample sizes required to demonstrate a 30 % effect size for colonic transit, stool frequency, consistency and ease of passage for patients with lower FGID with constipation and, separately, diarrhea. RESULTS: COV(inter) from 87 patients and COV(intra) from 17 patients are reported. Generally, COV(intra) is somewhat greater than COV(inter). The COVs for PD endpoints are lower than for clinical endpoints; however, clinically relevant effects can be identified with modest (~50 %) increases in the sample size using parallel-group design studies. CONCLUSION: Phase IIA studies that incorporate clinical and PD endpoints are feasible in lower FGID associated with constipation or diarrhea. Crossover design would require lower sample size for most endpoints compared to parallel-group studies.

Pharmacodynamics, pharmacokinetics and safety of GSK2190915, a novel oral anti-inflammatory 5-lipoxygenase-activating protein inhibitor.

AIM: To assess the pharmacokinetics, pharmacodynamics, safety and tolerability of the 5-lipoxygenase-activating protein inhibitor, GSK2190915, after oral dosing in two independent phase I studies, one in Western European and one in Japanese subjects, utilizing different formulations. METHOD: Western European subjects received single (50-1000 mg) or multiple (10-450 mg) oral doses of GSK2190915 or placebo in a dose-escalating manner. Japanese subjects received three of four GSK2190915 doses (10-200 mg) plus placebo once in a four period crossover design. Blood samples were collected for GSK2190915 concentrations and blood and urine were collected to measure leukotriene B4 and leukotriene E4, respectively, as pharmacodynamic markers of drug activity. RESULTS: There was no clear difference in adverse events between placebo and active drug-treated subjects in either study. Maximum plasma concentrations of GSK2190915 and area under the curve increased in a dose-related manner and mean half-life values ranged from 16-34 h. Dose-dependent inhibition of blood leukotriene B4 production was observed and near complete inhibition of urinary leukotriene E4 excretion was shown at all doses except the lowest dose. The EC50 values for inhibition of LTB4 were 85 nM and 89 nM in the Western European and Japanese studies, respectively. CONCLUSION: GSK2190915 is well-tolerated with pharmacokinetics and pharmacodynamics in Western European and Japanese subjects that support once daily dosing for 24 h inhibition of leukotrienes. Doses of ≥50 mg show near complete inhibition of urinary leukotriene E4 at 24 h post-dose, whereas doses of ≥150 mg are required for 24 h inhibition of blood LTB4.

PET imaging-based evaluation of hepatobiliary transport in humans with (15R)-11C-TIC-Me.

UNLABELLED: It is well accepted that drug transporters play a pivotal role in hepatobiliary excretion of anionic drugs, in which drug-drug interactions and genetic polymorphisms are known to cause variations. However, PET probes for in vivo functional characterization of these transporters have not been established yet. We used PET to investigate hepatic uptake and subsequent canalicular efflux of (11)C-labeled (15R)-16-m-tolyl-17,18,19,20-tetranorisocarbacyclin methyl ester [(15R)-(11)C-TIC-Me)] in healthy subjects. METHODS: Serial PET scans of the abdominal region in healthy male subjects were obtained with or without the organic anion-transporting polypeptide (OATP) inhibitor rifampicin after intravenous injection of (15R)-(11)C-TIC-Me as a radiotracer. Venous blood samples and PET images were obtained at frequent intervals up to 30 min after administration of the PET tracer. Dynamic imaging data were evaluated by integration plots of data collected for 2-10 min and for 10-30 min after tracer administration for the determination of tissue uptake clearance and biliary efflux clearance, respectively. RESULTS: After rapid hydrolysis in blood, the acid form-(11)C-labeled (15R)-16-m-tolyl-17,18,19,20-tetranorisocarbacyclin [(15R)-(11)C-TIC]-accumulated in the liver (37% of the dose by 17 min), and the radioactivity was then excreted into the bile (6.2% by 30 min). Rifampicin (600 mg by mouth), a potent OATP inhibitor, significantly reduced the radioactivity excreted into the bile (by 44%) by inhibiting both uptake (by 45%) and subsequent canalicular efflux (by 62%). (15R)-(11)C-TIC is an in vitro substrate of OATP1B1 and OATP1B3, and clinically relevant concentrations of rifampicin inhibited uptake by OATP1B1 and OATP1B3. These results demonstrated that in humans, (15R)-(11)C-TIC-associated radioactivity is excreted into the bile by organic anion transport systems. CONCLUSION: We demonstrated that PET image analysis with (15R)-(11)C-TIC-Me is useful for investigating variations in OATP function in the human hepatobiliary transport system.

5-Lipoxygenase-activating protein (FLAP) inhibitors. Part 4: development of 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxypyridin-3-yl)benzyl]-5-(5-methylpyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethylpropionic acid (AM803), a potent, oral, once daily FLAP inhibitor.

The potent 5-lipoxygenase-activating protein (FLAP) inhibitor 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxypyridin-3-yl)benzyl]-5-(5-methylpyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethylpropionic acid 11cc is described (AM803, now GSK2190915). Building upon AM103 (1) (Hutchinson et al. J. Med Chem.2009, 52, 5803-5815; Stock et al. Bioorg. Med. Chem. Lett. 2010, 20, 213-217; Stock et al. Bioorg. Med. Chem. Lett.2010, 20, 4598-4601), SAR studies centering around the pyridine moiety led to the discovery of compounds that exhibit significantly increased potency in a human whole blood assay measuring LTB(4) inhibition with longer drug preincubation times (15 min vs 5 h). Further studies identified 11cc with a potency of 2.9 nM in FLAP binding, an IC(50) of 76 nM for inhibition of LTB(4) in human blood (5 h incubation) and excellent preclinical toxicology and pharmacokinetics in rat and dog. 11cc also demonstrated an extended pharmacodynamic effect in a rodent bronchoalveolar lavage (BAL) model. This compound has successfully completed phase 1 clinical studies in healthy volunteers and is currently undergoing phase 2 trials in asthmatic patients.

Chronic treatment with a novel γ-secretase modulator, JNJ-40418677, inhibits amyloid plaque formation in a mouse model of Alzheimer's disease.

BACKGROUND AND PURPOSE: γ-Secretase modulators represent a promising therapeutic approach for Alzheimer's disease (AD) because they selectively decrease amyloid ß 42 (Aß42), a particularly neurotoxic Aß species that accumulates in plaques in the brains of patients with AD. In the present study, we describe the in vitro and in vivo pharmacological properties of a potent novel γ-secretase modulator, 2-(S)-(3,5-bis(4-(trifluoromethyl)phenyl)phenyl)-4-methylpentanoic acid (JNJ-40418677). EXPERIMENTAL APPROACH: The potency and selectivity of JNJ-40418677 for Aß reduction was investigated in human neuroblastoma cells, rat primary neurones and after treatment with single oral doses in non-transgenic mouse brains. To evaluate the effect of JNJ-40418677 on plaque formation, Tg2576 mice were treated from 6 until 13 months of age via the diet. KEY RESULTS: JNJ-40418677 selectively reduced Aß42 secretion in human neuroblastoma cells and rat primary neurones, but it did not inhibit Notch processing or formation of other amyloid precursor protein cleavage products. Oral treatment of non-transgenic mice with JNJ-40418677 resulted in an excellent brain penetration of the compound and a dose- and time-dependent decrease of brain Aß42 levels. Chronic treatment of Tg2576 mice with JNJ-40418677 reduced brain Aß levels, the area occupied by plaques and plaque number in a dose-dependent manner compared with transgenic vehicle-treated mice. CONCLUSIONS AND IMPLICATIONS: JNJ-40418677 selectively decreased Aß42 production, showed an excellent brain penetration after oral administration in mice and lowered brain Aß burden in Tg2576 mice after chronic treatment. JNJ-40418677 therefore warrants further investigation as a potentially effective disease-modifying therapy for AD.

Positron emission tomography studies using (15R)-16-m-[11C]tolyl-17,18,19,20-tetranorisocarbacyclin methyl ester for the evaluation of hepatobiliary transport.

A quantitative positron emission tomography (PET) methodology was developed for in vivo kinetic analysis of hepatobiliary transport. Serial abdominal PET scans were performed on normal and multidrug resistance-associated protein 2 (Mrp2)-deficient rats after intravenous injection of (15R)-16-m-[(11)C]tolyl-17,18,19,20-tetranorisocarbacyclin methyl ester (15R-[(11)C] TIC-Me) as a radiotracer. 15R-[(11)C]TIC-Me was rapidly converted to its acid form in blood within 10 s. PET scans revealed that 15R-[(11)C]TIC was localized mainly in the liver within 5 min of injection. By 90 min, total radioactivity in bile of Mrp2-deficient rats was significantly reduced compared with controls. Metabolite analysis by thin-layer chromatography autoradiography showed that 15R-[(11)C]TIC is converted to at least three metabolites (M1, M2, and M3), and M2 and M3 are the major metabolites in plasma and bile, respectively. Hepatic uptake clearance of total radioactivity in normal rats was close to the hepatic blood flow rate and slightly higher than that in Mrp2-deficient rats. The intrinsic canalicular efflux clearance of M3 (CL(int,bile,M3)) in Mrp2-deficient rats was decreased to 12% of controls, whereas clearance of M2 was moderately decreased (54%). An in vitro transport assay detected ATP-dependent uptake of both M2 and M3 by rat Mrp2-expressing membrane vesicles. These results demonstrated that M3 is excreted primarily into the bile by Mrp2 in normal rats. We conclude that PET studies using 15R-[(11)C]TIC-Me could be useful for in vivo analyses of Mrp2-mediated hepatobiliary transport.

Pharmacology of AM803, a novel selective five-lipoxygenase-activating protein (FLAP) inhibitor in rodent models of acute inflammation.

We evaluated the in vivo pharmacological properties of AM803 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxy-pyridin-3-yl)-benzyl]-5-(5-methyl-pyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethyl-propionic acid, a selective five-lipoxygenase-activating protein (FLAP) inhibitor, using rat and mouse models of acute inflammation. Oral administration of AM803 (1 mg/kg) resulted in sustained inhibition of ex vivo ionophore-challenged whole blood LTB4 biosynthesis with >90% inhibition for up to 12 h and an EC50 of approximately 7 nM. When rat lungs were challenged in vivo with calcium-ionophore, AM803 inhibited LTB4 and cysteinyl leukotriene (CysLT) production with ED50s of 0.12 mg/kg and 0.37 mg/kg, respectively. The inhibition measured 16 h following a single oral dose of 3 mg/kg was 86% and 41% for LTB4 and CysLTs, respectively. In an acute inflammation setting, AM803 dose-dependently reduced LTB4, CysLTs, plasma protein extravasation and neutrophil influx induced by peritoneal zymosan injection. Finally, AM803 increased survival time in mice exposed to a lethal intravenous injection of platelet activating factor (PAF). The magnitude of effect was similar to that of an inhibitor of five-lipoxygenase (5-LO) and LTA4 hydrolase but superior to a leukotriene CysLT1 receptor antagonist. In summary, AM803 is a novel, potent and selective FLAP inhibitor that has excellent pharmacodynamic properties in vivo and is effective in animal models of acute inflammation and in a model of lethal shock.

Evaluation of stereoselective anticonvulsant, teratogenic, and pharmacokinetic profile of valnoctylurea (capuride): a chiral stereoisomer of valproic acid urea derivative.

PURPOSE: The purpose of this study was to evaluate the stereoselective anticonvulsant activity, neurotoxicity, pharmacokinetics, and teratogenic potential of two stereoisomers of valnoctylurea (VCU), a central nervous system (CNS)-active urea derivative of valnoctic acid, which is a constitutional isomer of valproic acid (VPA). METHODS: VCU stereoisomers (2S,3S)-VCU and (2R,3S)-VCU were synthesized. Their anticonvulsant activity was determined and compared to VPA and racemic-VCU in rats utilizing the maximal electroshock seizure (MES) and the subcutaneous pentylenetetrazole (scMet) tests. Neurotoxicity was determined in rats using the positional sense test, muscle tone test, and gait and stance test. The induction of neural tube defects (NTDs) by VCU stereoisomers was evaluated in a mouse strain highly susceptible to VPA-induced teratogenicity. The pharmacokinetics of VCU was studied in a stereoselective manner following intraperitoneal (i.p.) administration to rats. RESULTS: (2S,3S)-VCU and (2R,3S)-VCU median effective dose ED(50) values were 29 mg/kg [95% confidence interval (CI) = 8-60 mg/kg] and 42 mg/kg (95% CI = 36-51 mg/kg) (MES) and 22 mg/kg (95% CI = 13-51 mg/kg) and 12 mg/kg (95%CI = 7-21 mg/kg) (scMet), respectively. (2S,3S)-VCU was more potent and had a wider safety margin (p < 0.05), defined as the protective index (PI = TD(50)/ED(50)), at both the MES (PI > 17) and scMet (PI > 23) tests than racemic-VCU or (R,S)-VCU (PI = 2.8 and 9.9, respectively). VCU stereoisomers caused NTDs at doses >4 times that of their anticonvulsant ED(50) values. At a dose of 112 mg/kg, (2R,3S)-VCU was nonteratogenic and less embryotoxic than its stereoisomer (2S,3S)-VCU. No stereoselective pharmacokinetics was observed following intraperitoneal dosing of racemic-VCU to rats. VCU was mainly eliminated by metabolism with a half-life of 2 h. CONCLUSIONS: VCU anticonvulsant activity and wide PI values make it a potential candidate for development as a new, potent antiepileptic drug (AED).

Orally-administered caspase inhibitor PF-03491390 is retained in the liver for prolonged periods with low systemic exposure, exerting a hepatoprotective effect against alpha-fas-induced liver injury in a mouse model.

In a mouse model of alpha-Fas-induced acute liver injury, the orally-administered caspase inhibitor PF-03491390 (formerly named IDN-6556) was retained in the liver for prolonged periods with a low systemic exposure. Reductions in the elevated plasma levels of alanine aminotransferase (ALT) revealed that the retention of PF-03491390 in the liver exerted a hepatoprotective effect, even when pre-administered to mice 4 h before alpha-Fas insult. Prolonged retention of PF-03491390 in the liver after oral administration has the benefit of low systemic exposure, making this a beneficial agent for the treatment of liver diseases.

Pharmacokinetic profile of dexloxiglumide.

Dexloxiglumide is a potent and selective cholecystokinin type 1 (CCK1) receptor antagonist currently under development in a variety of diseases affecting the gastrointestinal tract such as gastro-oesophageal reflux disease, irritable bowel syndrome (IBS), functional dyspepsia, constipation and gastric emptying disorders. In female patients with constipation-predominant IBS, clinical efficacy has been demonstrated following administration of dexloxiglumide 200 mg three times daily. Dexloxiglumide is rapidly and extensively absorbed after single oral administration in humans with an absolute bioavailability of 48%. The incomplete bioavailability is due to both incomplete absorption and hepatic first-pass effect. Following multiple-dose administration of 200 mg three times daily, the accumulation is predictable, indicating time-independent pharmacokinetics. In addition, dexloxiglumide pharmacokinetics are dose-independent after both single and repeated oral three-times-daily doses in the dose range 100-400 mg. Dexloxiglumide absorption window extends from the jejunum to the colon and the drug is a substrate and a weak inhibitor of P-glycoprotein and multidrug resistance protein 1. Plasma protein binding of dexloxiglumide is 94-98% and the drug has a moderate to low volume of distribution in humans. Systemic clearance of dexloxiglumide is moderate and cytochrome P450 (CYP) 3A4/5 and CYP2C9 have been implicated in the metabolism of dexloxiglumide to produce O-demethyl dexloxi-glumide. This metabolite is further oxidised to dexloxiglumide carboxylic acid. These two major metabolites (accounting for up to 50% of dexloxiglumide elimination) have been identified. However, in human plasma the unchanged drug represents the major (up to 91%) component of the metabolic profile. The parent drug is believed to be the major contributor to the efficacy of the compound, since its major metabolites are pharmacologically inactive. In addition, the drug is a single isomer chiral drug (eutomer) that does not undergo chiral inversion into its pharmacologically inactive enantiomer (distomer). After oral administration of (14)C-dexloxiglumide, radioactivity is mainly excreted in bile and in faeces (74% of dose) with much lower excretion in urine (20% of dose). Renal excretion of unchanged dexloxiglumide is low (7% of dose in urine and faeces, 1% of dose in urine) and is dose-independent in the dose range 100-400 mg. As the kidney is a minor contributor to the elimination of dexloxiglumide and/or its metabolites in humans, the pharmacokinetics of the drug should not be affected in patients with renal insufficiency. The pharmacokinetics of dexloxiglumide are also not affected by age, sex and administration with a high-fat breakfast. Mild and moderate liver impairment do not affect the pharmacokinetics of dexloxiglumide but severe liver impairment causes increases in systemic exposure to dexloxiglumide and O-demethyl dexloxiglumide. Thus, the drug should be prescribed with caution in patients with severe hepatic impairment even though no dose adjustment is warranted. The results of different drug interaction studies have indicated that no clinically relevant metabolic and concomitant drug-drug interactions are expected during the clinical use of dexloxiglumide.

Novel selective inhibitors of neutral endopeptidase for the treatment of female sexual arousal disorder. Synthesis and activity of functionalized glutaramides.

Female sexual arousal disorder (FSAD) is a highly prevalent sexual disorder affecting up to 40% of women. We describe herein our efforts to identify a selective neutral endopeptidase (NEP) inhibitor as a potential treatment for FSAD. The rationale for this approach, together with a description of the medicinal chemistry strategy, lead compounds, and SAR investigations are detailed. In particular, the strategy of starting with the clinically precedented selective NEP inhibitor, Candoxatrilat, and targeting low molecular weight and relatively polar mono-carboxylic acids is described. This led ultimately to the prototype development candidate R-13, for which detailed pharmacology and pharmacokinetic parameters are presented.(1)

Effect of azole antifungals ketoconazole and fluconazole on the pharmacokinetics of dexloxiglumide.

AIMS: Dexloxiglumide is a new CCK(1) receptor antagonist under investigation for treatment of functional gastrointestinal disorders and is metabolized by CYP3A4 and CYP2C9. The objectives of these two separate randomized, two-period, two-treatment crossover studies were to investigate the effects of steady-state ketoconazole, a model CYP3A4 inhibitor (Study 1), and steady-state fluconazole, a model CYP2C9 inhibitor (Study 2), on the pharmacokinetics of dexloxiglumide in healthy subjects. METHODS: Plasma samples were analysed for dexloxiglumide and its primary metabolites: O-demethyl dexloxiglumide (ODM; Study 1 and 2) and dexloxiglumide carboxylic acid (DCA; Study 2). RESULTS: Following ketoconazole coadministration, dexloxiglumide C(max) increased by 32% (90% confidence intervals (CI) 112-154), with unchanged ODM C(max); AUC of dexloxiglumide and ODM increased by 36% (90% CI 124-140 and 128-142, respectively). No changes were observed in dexloxiglumide or ODM t((1/2)). Fluconazole coadministration caused a 77% increase (90% CI 154-204) in dexloxiglumide C(max), no change in ODM C(max) and a 32% decrease (90% CI 62-75) in DCA C(max). Fluconazole coadministration resulted in a 2.5-fold increase (90% CI 235-267) in dexloxiglumide AUC, 40% increase (90% CI 136-156) in ODM AUC and an 18% decrease (90% CI 82-94) in DCA AUC. The t((1/2)) of all three analytes increased by approximately 2-fold with fluconazole coadministration (P-value < 0.05). CONCLUSIONS: Ketoconazole caused a minimal increase while fluconazole caused a moderate increase in dexloxiglumide systemic exposure with no change in the adverse event profile of dexloxiglumide.