Absolute Bioavailability of Imatinib (Glivec®) Orally versus Intravenous Infusion

The purpose of this study was to investigate the absolute bioavailability of a single oral dose of imatinib (Glivec), 400 mg (capsules vs. oral solution), compared with imatinib, 100 mg (intravenous [i.v.] infusion), in healthy subjects. Twelve subjects received a single treatment in each treatment period: a 400-mg oral dose of imatinib in capsule form or as a solution or a 100-mg i.v. infusion of imatinib. Plasma imatinib concentrations were measured following each treatment; pharmacokinetic parameters and absolute bioavailability were determined. Absolute bioavailability values (compared with i.v. infusion) for the imatinib capsule and oral solution were 98.3% and 97.2%, respectively. Both the rate and extent of imatinib absorption, as measured by C(max), partial AUC, and total AUC, were similar for the oral solution and the imatinib capsule intended for the market. The 400-mg oral dose of imatinib, as a capsule or a solution, was completely absorbed and was almost completely bioavailable (> 97%).

Ceruloplasmin is an endogenous inhibitor of myeloperoxidase

Myeloperoxidase is a neutrophil enzyme that promotes oxidative stress in numerous inflammatory pathologies. It uses hydrogen peroxide to catalyze the production of strong oxidants including chlorine bleach and free radicals. A physiological defense against the inappropriate action of this enzyme has yet to be identified. We found that myeloperoxidase oxidized 75% of the ascorbate in plasma from ceruloplasmin knock-out mice, but there was no significant loss in plasma from wild type animals. When myeloperoxidase was added to human plasma it became bound to other proteins and was reversibly inhibited. Ceruloplasmin was the predominant protein associated with myeloperoxidase. When the purified proteins were mixed, they became strongly but reversibly associated. Ceruloplasmin was a potent inhibitor of purified myeloperoxidase, inhibiting production of hypochlorous acid by 50% at 25 nm. Ceruloplasmin rapidly reduced Compound I, the Fe(V) redox intermediate of myeloperoxidase, to Compound II, which has Fe(IV) in its heme prosthetic groups. It also prevented the fast reduction of Compound II by tyrosine. In the presence of chloride and hydrogen peroxide, ceruloplasmin converted myeloperoxidase to Compound II and slowed its conversion back to the ferric enzyme. Collectively, our results indicate that ceruloplasmin inhibits myeloperoxidase by reducing Compound I and then trapping the enzyme as inactive Compound II. We propose that ceruloplasmin should provide a protective shield against inadvertent oxidant production by myeloperoxidase during inflammation.

A method for direct assessment of tissue-nonspecific alkaline phosphatase (TNAP) inhibitors in blood samples

Tissue nonspecific alkaline phosphatase (TNAP) is one of four human alkaline phosphatases (AP), a family of exocytic enzymes that catalyze hydrolysis of phospho-monoesters in bone, liver, kidney, and various other tissues. Overexpression of TNAP gives rise to excessive bone and soft tissue mineralization, including blood vessel calcification. Our prior screening campaigns have found several leads against this attractive therapeutic target using in vitro assay with a recombinant enzyme; these compounds were further optimized using medicinal chemistry approaches. To prioritize compounds for their use in animal models, we have designed and developed a biomarker assay for in situ detection of TNAP activity within human and mouse blood samples at physiological pH. This assay is suitable for screening compounds in 1,536-well plates using blood plasma from different mammalian species. The user may choose from two different substrates based on the need for greater assay simplicity or sensitivity.

Asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, interacts with gastric oxidative metabolism and enhances stress-induced gastric lesions

Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase known to exert vasoconstriction of vascular bed. The elevation of ADMA has been considered as the cardiovascular risk factor associated with hyperlipidemia, hypercholesterolemia and metabolic syndrome. ADMA is produced by the action of dimethylarginine dimethylaminohydrolase (DDAH), which hydrolyzes ADMA to L-citrulline and dimethylamine. Previous studies have shown that endogenous NO plays an important role in the mechanism of gastric mucosal defense, but the role of ADMA in the pathogenesis of serious clinical entity, such as the acute gastric mucosal injury induced by stress has been little studied. In present study, we determined the effect of intragastric (i.g.) pretreatment with ADMA applied in graded doses ranging from 0.1 up to 20 mg/kg on gastric mucosal lesions induced by 3.5 h of water immersion and restraint stress (WRS). The number of gastric lesions was determined by planimetry and the gastric blood flow (GBF) was assessed by laser Doppler technique. The malondialdehyde and 4-hydroxynonenal (MDA+4-HNE) concentration, as an index of oxygen radical-lipid peroxidation was assessed in the gastric mucosa in rats exposed to WRS with or without ADMA administration. Proinflammatory cytokines IL-1β, TNF-α, superoxide dismutase (SOD) and glutathione peroxidase (GPx) mRNAs in the gastric mucosa and plasma levels of ADMA, IL-1β and TNF-α were analyzed by RT-PCR and ELISA, respectively. The exposure of rats to WRS for 3.5 h produced acute gastric lesions accompanied by a significant rise in the plasma ADMA levels and a significant fall in the GBF, an increase in MDA+4-HNE concentrations and the significant increase in the expression and release of IL-1β and TNF-α. The pretreatment with ADMA, applied i.g. 30 min before WRS dose-dependently, aggravated WRS damage and this effect was accompanied by a further significant fall in the GBF. The ADMA induced exacerbation of WRS lesions and the accompanying rise in the plasma ADMA levels and the fall in GBF were significantly attenuated by concurrent treatment with glyceryl trinitrate (GTN) (10 mg/kg i.g.) in the presence of ADMA. Administration of ADMA resulted in a significant decrease in the expression of SOD and GPx mRNAs and the up-regulation of mRNA for IL-1β and TNF-α followed by an increase in these plasma cytokine levels as compared to respective values observed in vehicle-pretreated animals. We conclude that 1) ADMA could be implicated in the mechanism of WRS-induced ulcerogenesis, 2) ADMA exacerbates WRS-induced gastric lesions due to enhancement in neutrophil dependent lipid peroxidation and overexpression and release of proinflammatory cytokines IL-1β and TNF-α and a potent depletion of antioxidative enzymes SOD and GPx expression and activity.

High tea and vegetable consumption is associated with low ADMA generation in older healthy subjects

Asymmetric dimethylarginine (ADMA) has been recognized as a marker of cardiovascular risk. We sought to investigate whether consumption of tea, coffee, fruit or vegetables is associated with ADMA. In 148 consecutive apparently healthy subjects (104 men and 44 women aged 40 to 70), daily tea, coffee, fruit and vegetable consumption was ascertained by questionnaire. Plasma ADMA, symmetric dimethylarginine (SDMA), and l-arginine levels were measured by high-performance liquid chromatography. Median tea and coffee consumption was 2 cups/d, while vegetable and fruit intake was 152 (120-179)g/d and 120 (108-134)g/d, respectively. Median plasma ADMA, SDMA and arginine were 0.47 (0.43-0.53)μmol/L, 0.59 (0.54-0.66)μmol/L and 86 (68-101)μmol/L, respectively. ADMA correlated inversely with tea (r = -0.70, P < .0001) and vegetable consumption (r = -0.50, P < .0001) even after adjustment for age, sex, body mass index, smoking status, and potential dietary and biochemical parameters. No association between ADMA and fruit consumption was found. ADMA correlated positively with coffee intake (r = 0.37, P < .0001), although these associations were less potent after adjustment for dietary factors. Higher tea and vegetable intake is associated with lower plasma ADMA levels in healthy middle-aged subjects.

Esterase inhibitors as ester-containing drug stabilizers and their hydrolytic products: potential contributors to the matrix effects on bioanalysis by liquid chromatography/tandem mass spectrometry

RATIONALE

Esterase inhibitors are widely used to stabilize ester-containing drugs in biological matrices for quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays. These co-existing inhibitors could cause matrix effects on bioanalysis and jeopardize the assay performance. We therefore developed an LC/MS/MS methodology to monitor the fate of inhibitors and evaluate their matrix effects, which is described in this study.

METHODS

Human plasma containing 20 mM of diisopropylfluorophosphate (DFP), paraoxon, eserine, phenylmethylsulfonyl fluoride (PMSF) or 2-thenoyltrifluoroacetone (TTFA) was extracted by liquid-liquid extraction (LLE) and analyzed by an LC/MS/MS assay for BMS-068645 (a model drug) with additional pre-optimized selected reaction monitoring (SRM) transitions using positive/negative electrospray ionization (ESI) mode for each inhibitor. Hydrolytic products were characterized by product ion or neutral loss scan LC/MS/MS analysis. The matrix effect contribution from each inhibitor was evaluated by post-column infusion of BMS-068645.

RESULTS

In the extracted samples by LLE, SRM chromatograms revealed the presence of paraoxon, eserine and TTFA with peak intensity of >2.50E08. Three DFP hydrolytic products, diisopropyl phosphate (DP), triisopropyl phosphate (TP) and DP dimer, and one PMSF hydrolytic product, phenymethanesulfonic acid (PMSA), were identified in the extracted samples. In post-column infusion profiles, ion suppression or enhancement was observed in the retention time regions of eserine (~10% suppression), paraoxon (~70% enhancement) and DP dimer (~20% suppression).

CONCLUSIONS

The SRM transitions described here make it possible to directly monitor the inhibitors and their hydrolytic products. In combination with post-column infusion, this methodology provides a powerful tool to routinely monitor the matrix effects-causing inhibitors, so that their matrix effects on the bioanalysis can be evaluated and minimized.

A phase I dose escalation study of AT9283, a small molecule inhibitor of aurora kinases, in patients with advanced solid malignancies

BACKGROUND

AT9283 is an inhibitor of aurora kinases A and B with antitumor activity in preclinical models. This a First in Human phase I study assessed the safety, tolerability, pharmacokinetic and pharmacodynamic properties and preliminary efficacy of AT9283.

PATIENTS AND METHODS

Patients with advanced tumors received AT9283 as a continuous central venous infusion over 3 days in cohorts of three to six patients starting at 1.5 mg/m(2)/day (equivalent to 4.5 mg/m(2)/72 h). The oral bioavailability of AT9283 was assessed in a cohort of seven patients. Pharmacodynamic analysis of biomarkers included phosphorylation of histone H3 on serine 10, proliferating cell nuclear antigen, Ki67, M30 and M65 in skin and plasma.

RESULTS

Forty patients were included in all analyses. AT9283 was generally well tolerated with main toxic effects of reversible dose-related myelosuppression, gastrointestinal disturbance, fatigue and alopecia. The dose-limiting toxicity of AT9283 was grade 3 febrile neutropenia in two patients at 36 mg/m(2)/72 h and the maximum tolerated dose (MTD) was established at 27 mg/m(2)/72 h. Systemic exposure was dose proportional. The mean oral bioavailability of a 0.9 mg/m(2) dose was 29.4% (range 11.2%-36.7%). Pharmacodynamic analyses indicated antiproliferative and apoptotic activity of AT9283. Four patients with esophageal, non-small-cell lung cancer (n = 2) and colorectal cancer demonstrated RECIST stable disease ≥ 6 months.

CONCLUSION

AT9283 was well tolerated up to the MTD of 27 mg/m(2)/72 h. AT9283 is currently assessed in phase II trials.

Ranolazine improves cardiac diastolic dysfunction through modulation of myofilament calcium sensitivity

RATIONALE

Previously, we demonstrated that a deoxycorticosterone acetate (DOCA)-salt hypertensive mouse model produces cardiac oxidative stress and diastolic dysfunction with preserved systolic function. Oxidative stress has been shown to increase late inward sodium current (I(Na)), reducing the net cytosolic Ca(2+) efflux.

OBJECTIVE

Oxidative stress in the DOCA-salt model may increase late I(Na), resulting in diastolic dysfunction amenable to treatment with ranolazine.

METHODS AND RESULTS

Echocardiography detected evidence of diastolic dysfunction in hypertensive mice that improved after treatment with ranolazine (E/E':sham, 31.9 ± 2.8, sham+ranolazine, 30.2 ± 1.9, DOCA-salt, 41.8 ± 2.6, and DOCA-salt+ranolazine, 31.9 ± 2.6; P=0.018). The end-diastolic pressure-volume relationship slope was elevated in DOCA-salt mice, improving to sham levels with treatment (sham, 0.16 ± 0.01 versus sham+ranolazine, 0.18 ± 0.01 versus DOCA-salt, 0.23 ± 0.2 versus DOCA-salt+ranolazine, 0.17 ± 0.0 1 mm Hg/L; P<0.005). DOCA-salt myocytes demonstrated impaired relaxation, τ, improving with ranolazine (DOCA-salt, 0.18 ± 0.02, DOCA-salt+ranolazine, 0.13 ± 0.01, sham, 0.11 ± 0.01, sham+ranolazine, 0.09 ± 0.02 seconds; P=0.0004). Neither late I(Na) nor the Ca(2+) transients were different from sham myocytes. Detergent extracted fiber bundles from DOCA-salt hearts demonstrated increased myofilament response to Ca(2+) with glutathionylation of myosin binding protein C. Treatment with ranolazine ameliorated the Ca(2+) response and cross-bridge kinetics.

CONCLUSIONS

Diastolic dysfunction could be reversed by ranolazine, probably resulting from a direct effect on myofilaments, indicating that cardiac oxidative stress may mediate diastolic dysfunction through altering the contractile apparatus.

Ingestion of proteoglycan fraction from shark cartilage increases serum inhibitory activity against matrix metalloproteinase-9 and suppresses development of N-nitrosobis(2-oxopropyl)amine-induced pancreatic duct carcinogenesis in hamster

A water extract of shark cartilage was fractionated into acidic and basic fractions by preparative isoelectric focusing on the basis of the amphoteric nature of samples. The acidic fraction was further fractionated into ethanol-soluble and -precipitate fractions. After the carcinogenesis treatment using N-nitrosobis(2-oxopropyl)amine, hamsters received a diet containing each fraction or purified chondroichin sulfate to give 0.4% (w/w) for 50 days. Only administration of the acidic ethanol-precipitate-fraction-containing diet significantly increased serum inhibitory activity against matrix metalloproteinase (MMP)-9 and reduced the number of adenocarcinomas in the pancreatic duct. The active fraction predominantly consisted of chondroichin sulfate-containing proteoglycan. However, the purified chondroichin sulfate had no significant activity. These results suggest that the protein moiety of the proteoglycan might be involved in the increase of serum inhibitory activity against MMP-9 and suppression of pancreatic carcinogenesis in hamster.

Blood Pb and δ-ALAD inhibition in cattle and sheep from a Pb-polluted mining area

The effects of Pb pollution on cattle and sheep raised in an ancient mining area were studied through the use of blood Pb (PbB) levels and δ-aminolevulinic acid dehydratase (δ-ALAD) activity. Lead levels in livestock blood from the mining area (n=110) were significantly elevated when compared to the controls (n=79). In 91.4% of cattle (n=58) and 13.5% of sheep (n=52) sampled in the mining area, PbB levels corresponded to subclinical exposure (6-35 μg/dl). Two young cattle (<2 years) from the mining area (n=5) had PbB levels indicative of clinical poisoning (>35 μg/dl). Elevated PbB was also accompanied by δ-ALAD activity inhibition in blood, which confirms that measurable effects of Pb poisoning were taking place. Observed PbB levels suggest that a potential risk to human consumers of beef from the Pb polluted areas may also exist, as has been shown previously for game meat from the same mining area.

A nonclinical safety and pharmacokinetic evaluation of N6022: a first-in-class S-nitrosoglutathione reductase inhibitor for the treatment of asthma

S-nitrosoglutathione reductase is the primary enzyme responsible for the metabolism of S-nitrosoglutathione (GSNO), the body's main source of bioavailable nitric oxide. Through its catabolic activity, GSNO reductase (GSNOR) plays a central role in regulating endogenous S-nitrosothiol levels and protein S-nitrosation-based signaling. By inhibiting GSNOR, we aim to increase pulmonary GSNO and induce bronchodilation while reducing inflammation in lung diseases such as asthma. To support the clinical development of N6022, a first-in-class GSNOR inhibitor, a 14-day toxicology study was conducted. Sprague-Dawley rats were given 2, 10 or 50 mg/kg/day N6022 via IV administration. N6022 was well tolerated at all doses and no biologically significant adverse findings were noted in the study up to 10 mg/kg/day. N6022-related study findings were limited to the high dose group. One male rat had mild hepatocellular necrosis with accompanying increases in ALT and AST and several male animals had histological lung assessments with a slight increase in foreign body granulomas. Systemic exposure was greater in males than females and saturation of plasma clearance was observed in both sexes in the high dose group. Liver was identified as the major organ of elimination. Mechanistic studies showed dose-dependent effects on the integrity of a rat hepatoma cell line.

Robust central reduction of amyloid-β in humans with an orally available, non-peptidic β-secretase inhibitor

According to the amyloid cascade hypothesis, cerebral deposition of amyloid-β peptide (Aβ) is critical for Alzheimer's disease (AD) pathogenesis. Aβ generation is initiated when β-secretase (BACE1) cleaves the amyloid precursor protein. For more than a decade, BACE1 has been a prime target for designing drugs to prevent or treat AD. However, development of such agents has turned out to be extremely challenging, with major hurdles in cell penetration, oral bioavailability/metabolic clearance, and brain access. Using a fragment-based chemistry strategy, we have generated LY2811376 [(S)-4-(2,4-difluoro-5-pyrimidin-5-yl-phenyl)-4-methyl-5,6-dihydro-4H-[1,3]thiazin-2-ylamine], the first orally available non-peptidic BACE1 inhibitor that produces profound Aβ-lowering effects in animals. The biomarker changes obtained in preclinical animal models translate into man at doses of LY2811376 that were safe and well tolerated in healthy volunteers. Prominent and long-lasting Aβ reductions in lumbar CSF were measured after oral dosing of 30 or 90 mg of LY2811376. This represents the first translation of BACE1-driven biomarker changes in CNS from preclinical animal models to man. Because of toxicology findings identified in longer-term preclinical studies, this compound is no longer progressing in clinical development. However, BACE1 remains a viable target because the adverse effects reported here were recapitulated in LY2811376-treated BACE1 KO mice and thus are unrelated to BACE1 inhibition. The magnitude and duration of central Aβ reduction obtainable with BACE1 inhibition positions this protease as a tractable small-molecule target through which to test the amyloid hypothesis in man.

Effects of cytochrome P450 1A substrate (difloxacin) on enzyme gene expression and pharmacokinetics in crucian carp (hybridized Prussian carp)

Cytochrome P450s (CYPs) play a prominent role in drug metabolism and biotransformation which are distributed in liver of aquatic animals. However, limited information is available about CYP genes involved in drug metabolism in fish. In the present study, we explore CYP1A characterization for DIF metabolism. Firstly, we cloned and characterized the full-length cDNA sequence of a CYP1A gene from crucian carp (hybridized Prussian carp), the predicted protein sequence for CYP1A comprise 496 amino acids. The heme-binding region of the CYP1A, encompassing the amino acid sequence GLGKRRCIG, which is identical to the same region of other homologues. Secondly, we studied the difloxacin (DIF) kinetics and the effects of DIF on their corresponding CYP1A mRNA levels in liver of crucian carp. CYP1A1 mRNA expression was analyzed by real-time PCR, and DIF concentration was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). Results showed that the concentration of DIF in liver reached its peak (67.70 mg kg(-1)) at 0.5h, while the CYP1A1 gene expression was at the lowest point. CYP1A mRNA was down-regulated by 6.5 mg ml(-1) DIF in the liver of crucian carp. Thus, our work confirmed that DIF is both the substrate and inhibitor of CYP1A. The information provided a model for the potential utility of gene expression analysis and drug metabolization in fish.

Increase of CSF tyrosine and impaired serotonin turnover in tyrosinemia type I

OBJECTIVE

Psychomotor impairment has been described in hypertyrosinemia types II and III (HT III). Only recently cognitive deficits have also been reported in hypertyrosinemia type I (HT I). The pathogenic mechanisms responsible are unknown. Since implementation of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC, Nitisinone (Swedish Orphan International)) in the treatment of HT I, plasma tyrosine elevation is a common finding as known from the other hypertyrosinemias.

PATIENTS AND METHODS

With elevated tyrosine as suspected pathogenic factor in the development of cognitive deficits, we here investigated tyrosine in the cerebrospinal fluid (CSF) and serotonergic and dopaminergic neurotransmitter levels in three patients with HT I during long-term treatment with Nitisinone. In addition, Nitisinone concentrations in plasma and CSF were measured. We also assessed psychomotor and cognitive development by standardized test systems and brain morphology by magnetic resonance imaging.

RESULTS

All patients presented with high tyrosine concentrations in CSF correlating with increased plasma tyrosine levels and a reduced CSF serotonin turnover. MRI revealed no structural abnormalities in the brain. All patients presented with either impaired cognitive development or behavioural abnormalities.

CONCLUSIONS

We here outline the need to further study the exact pathogenic mechanisms responsible for the neurotransmitter changes observed in HT type I in order to possibly prevent cognitive dysfunction. Nitisinone has significantly improved outcome and quality of life in HT type I; however, it is also accompanied by elevated plasma and CSF tyrosine. Further studies are essential to identify the necessary dietary tyrosine restriction and the optimal Nitisinone dose.

[Determination of nabumetone and 6-methoxy-2-naphthylacetic acid in plasma using HPLC with UV and MS detection]

The study aimed to establish and validate an analytical method for the determination of nabumetone and 6-methoxy-2-naphthylacetic acid (6-MNA) in human plasma after a single therapeutic dose of the drug. Two methods based on HPLC with UV and MS detection were compared. Optimal results in sample preparation were achieved using solid phase extraction. The recovery reached approximately 84% and 86-90% for nabumetone and 6-MNA, respectively. A reverse C18 column was used for HPLC separation of the analytes. The limit of UV detection was 50 nM and 0.1 microM for 6-MNA and nabumetone, respectively. The limit of MS detection was 1 microM and 0.5 microM for 6-MNA and nabumetone, respectively. Precision ranged between 4.2-14.4% and 4.6-8.5% using UV and MS detection for nabumetone, respectively. The respective values for 6-MNA were 2.4-12.5% and 2.1-9.4%. Accuracy ranged between 93.4-109.6% in UV detection and 86.2-107.9% using UV and MS detection for nabumetone, respectively. The respective values for 6-MNA were 87.8-107.4% and 86.3-106.4%. The method was subsequently applied to determine the pharmacokinetic parameters of nabumetone and 6-MNA in a group of 24 healthy volunteers.

[High digoxin serum levels in an elderly patient for the endogenous digoxin-like immunoreactive substances. A case report]

Digoxin is typically prescribed in the treatment of heart failure. Its limited therapeutic range requires systematic monitoring of plasmatic concentration through immunoreactive tests. Laboratory results, however, can be altered by the presence of digoxin-like immunoreactive factors (DLIF) which are released in all clinical conditions involving volemic expansion.

CASE REPORT

An 86-year-old woman arrived in emergency with severe dyspnoea, atrial flutter and a medical history of ischemic cardiopathy. The patient was treated with ACE inhibitor, furosemide, spironolactone and digoxin. The first lab test for digoxin showed levels of digoxin of 7.05 ng/ml. Although the patient did not show any clinical evidence of digital intoxication nor was she treated with drugs which might interfere with digoxin kinetics and even if she had markers of renal function within clinical limits, digoxin was suspended and a treatment was initiated with 0.9% NaCl solution and furosemide. The second lab test showed levels of digoxin of 8.38 ng/ml. A possible interference of DLIF with immunoreactive tests was therefore assumed.

MATERIALS AND METHODS

The patient's serum was ultrafiltered and centrifugated to remove possible DLIF; subsequently, the measurement of digoxin levels was repeated. As a result, the digoxin level decreased to 0.25 ng/ml.

CONCLUSIONS

DLIF increase in several diseases, including heart failure, end-stage renal disease, pre-eclampsy and acromegaly. High digoxin levels in a patient who does not show any symptoms of digital intoxication should lead to suspect the presence of these factors and to preventively determine DLIF in serum so as not to incur the risk of suspending an important treatment like digoxin in heart failure.

Effect of food on the pharmacokinetic profile of etamicastat (BIA 5-453)

BACKGROUND

Etamicastat is a novel, potent, and reversible peripheral dopamine-β-hydroxylase inhibitor that has been administered orally at doses up to 600 mg once daily for 10 days to male healthy volunteers and appears to be well tolerated.

OBJECTIVE

The aim of this study was to investigate the effect of food on the pharmacokinetics of etamicastat.

MATERIAL AND METHODS

A single-center, open-label, randomized, two-way crossover study in 12 healthy male subjects was performed. Subjects were administered a single dose of etamicastat 200 mg following either a standard high-fat and high-calorie content meal (test) or 10 hours of fasting (reference). The statistical method for testing the effect of food on the pharmacokinetic parameters of interest was based upon the 90% confidence interval (CI) for the test/reference geometric mean ratio (GMR). The parameters of interest were maximum plasma concentration (C(max)), area under the plasma concentration-time curve (AUC) from time zero to the last measurable concentration (AUC(last)), and AUC from time zero to infinity (AUC(∞)). Bioequivalence was assumed when the 90% CI fell within the recommended acceptance interval (80, 125).

RESULTS

Etamicastat C(max), AUC(last), and AUC(∞) were 229 ng/mL, 1856 ng · h/mL, and 2238 ng · h/mL, respectively, following etamicastat in the fasting, and 166 ng/mL, 1737 ng · h/mL, and 2119 ng · h/mL, respectively, following etamicastat in the fed condition. Etamicastat test/reference GMR was 72.27% (90% CI 64.98, 80.38) for C(max), 93.59% (90% CI 89.28, 98.11) for AUC(last), and 96.47% (90% CI 91.67, 101.53) for AUC(∞). Time to C(max) was prolonged by the presence of food (p < 0.001). The C(max), AUC(last), and AUC(∞) values of the inactive metabolite BIA 5-961 were 275 ng/mL, 1827 ng · h/mL, and 2009 ng · h/mL, respectively, in the fasting, and 172 ng/mL, 1450 ng · h/mL, and 1677 ng · h/mL, respectively, in the fed condition. BIA 5-961 test/reference GMR was 62.42% (90% CI 56.77, 68.63) for C(max), 79.41% (90% CI 56.77, 68.63) for AUC(last), and 83.47% (90% CI 76.62, 90.93) for AUC(∞). A total of six mild to moderate unspecific adverse events were reported by four subjects. There was no clinically significant abnormality in laboratory assessments.

CONCLUSION

Etamicastat was well tolerated. The C(max) of etamicastat decreased 28% following oral administration of etamicastat in the presence of food, while AUC remained within the pre-defined acceptance interval. The delay in absorption and decrease in peak exposure of etamicastat is not clinically significant, and therefore etamicastat could be administered without regard to meals.

TRIAL REGISTRATION

EudraCT No. 2007-006530-33.

Alteration in the plasma concentration of a DAAO inhibitor, 3-methylpyrazole-5-carboxylic acid, in the ketamine-treated rats and the influence on the pharmacokinetics of plasma D-tryptophan

A determination method for 3-methylpyrazole-5-carboxylic acid (MPC), an inhibitor of D-amino acid oxidase (DAAO), in rat plasma was developed by using high-performance liquid chromatography-mass spectrometry (LC-MS). The structural isomer of MPC, 3-methylpyrazole-4-carboxylic acid, was used as an internal standard, and the intra- and inter-day accuracies and precisions were satisfactory for the determination of plasma MPC.Next, the LC-MS method was applied to determine the plasma MPC concentration in ketamine (Ket)-treated rats after intraperitoneal administration of MPC (5.0 or 50 mg·kg(-1)). The C(max) value of plasma MPC concentration in the Ket-treated rats was significantly higher than that in the control group when a high dose of MPC (50 mg·kg(-1)) was administered. In addition, it was found that plasma D-tryptophan (D-Trp) concentration in Ket-treated rats administered D-Trp was not significantly increased by MPC, suggesting that the DAAO-inhibitory effect of MPC is attenuated in Ket-treated rats.

Serum asymmetric dimethylarginine levels in normotensive obese individuals

BACKGROUND

Obesity is associated with an increased risk of developing insulin resistance, hyperinsulinemia, glucose intolerance, dyslipidemia, hypertension, premature atherosclerosis, and coronary artery disease. This study is designed to compare serum asymmetric dimethylarginine (ADMA) levels between obese individuals and controls.

MATERIAL/METHODS

Fifty volunteers, 30 obese (13 men; mean age, 40±11 years) and 20 healthy controls (13 men; mean age, 44±10 years) were enrolled to this study. Measurement of ADMA was accomplished by high performance liquid chromatography.

RESULTS

The mean body mass index of the obese group was significantly higher than that of the control group (35±4 vs 26±3 kg/m2; P=.001). The mean waist circumference of the obese subjects was also significantly higher compared with controls (111±11 vs 93±10 cm; P=.001). No significant difference was found concerning age, sex, blood pressures, and biochemistry parameters. Serum ADMA levels were significantly higher in obese individuals compared with healthy controls (5.4±3.3 vs 3.1±1.8 µmol/L; P=.006). A weak but significant correlation was identified between serum ADMA concentration and the waist circumference (r=0.282, P=.047).

CONCLUSIONS

The results of the present study demonstrated that serum ADMA levels of normotensive obese individuals were significantly higher than healthy controls. Increased ADMA concentrations observed only in the obese group were deemed to be important regarding the development future of cardiovascular disease in the future.

A lipase inhibitor monoterpene and monoterpene glycosides from Monarda punctata

An 80% acetone extract of Monarda punctata showed an inhibitory effect on lipase activity in isolated mouse plasma in vitro and carvacrol was obtained as the active constituent. It had an IC₅₀ value of 4.07 mM invitro and suppressed elevations in blood triacylglycerol levels in olive oil-loaded mice. Furthermore, from the whole plant, 22 compounds were isolated. Six monoterpene glycosides, a flavone glucuronide, and other known compounds were identified based on the results of spectroscopic analyses.

Effect of CYP2C19 genotypes on the pharmacokinetic/pharmacodynamic relationship of rabeprazole after a single oral dose in healthy Chinese volunteers

AIMS

To explore the pharmacokinetic/pharmacodynamic relationship of rabeprazole and the role of CYP2C19 genotypes after a single oral dose in healthy Chinese volunteers by a population approach.

METHODS

Plasma concentration time profile data and intragastric pH values of 19 genotyped healthy male adults after a single oral dose of rabeprazole in an open label randomized fashion were used for this population analysis. Simulation technology was performed to examine the rabeprazole response in subjects with different CYP2C19 genotypes to further investigate the effect of acid inhibition.

RESULTS

The pharmacokinetics of rabeprazole was characterized by a two-compartment model with first order absorption and with an absorption lag-time. The results show that clearance of rabeprazole was affected by CYP2C19 genotypes (average clearances of homEM, hetEM, and PM were 13.9, 11.5, and 8.74 L·h(-1) respectively). An effect compartment with a sigmoidal Emax model was considered more rational for analyzing the relationship between rabeprazole concentrations and intragastric pH values. Simulated results suggest that rabeprazole 20 mg once daily for PMs is sufficient, but might be administered more frequently for other genotypes in treating gastro-esophageal reflux disease.

CONCLUSION

The CYP2C19 genotype played a considerable role in the pharmacokinetic characteristics of rabeprazole, and this might need to be taken into account for clinical use.

Liquid chromatography-tandem mass spectrometric assay for the quantitation in human plasma of the novel indenoisoquinoline topoisomerase I inhibitors, NSC 743400 and NSC 725776

Topoisomerase I (Topo I) is a recognized target for ovarian, lung, and colorectal cancer therapy. The FDA-approved camptothecin (CPT) Topo I inhibitors, topotecan and irinotecan are labile and their effects are rapidly reversible. The indenoisoquinoline topoisomerase I inhibitors, NSC 743400 and NSC 725776, have been developed as a new generation of Topo I inhibitors and are being advanced to clinical evaluation. To support the clinical development of NSC 743400 and NSC 725776, we developed and validated, according to FDA guidelines, LC-MS/MS assays for the sensitive, accurate and precise quantitation of NSC 743400 and NSC 725776 in 0.2 mL human plasma. After ethyl acetate extraction, separation was achieved with a Synergi Polar RP column and a gradient of 0.1% formic acid in acetonitrile:water. NSC 743400 and NSC 725776 eluted at approximately 3 min, and the total run time was 14 min. Detection consisted of electrospray, positive-mode ionization mass spectrometry. Between 3 and 1000 ng/mL, accuracy was 96.9-108.2% for NSC 743400 and 95.1-106.7% for NSC 725776, and precision was <11.4% for NSC 743400 and <5.9% for NSC 725776. Extraction recovery was >80% for both analytes, and ion suppression ranged from -46.7 to 5.7%. The use of isotopically labeled internal standards and a wash phase at the end of the run were necessary to achieve adequate assay performance. Protein binding in human plasma as assessed by equilibrium dialysis showed both indenoisoquinolines to be more than 98% protein bound.

A sensitive and practical LC-MS/MS method for the determination of mizoribine in human serum and its bioequivalence study on Chinese healthy volunteers

A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed and validated for the determination of mizoribine in human serum using thiamphenicol as internal standard (IS). The serum samples of mizoribine were precipitated with acetonitrile and separated by HPLC on a reversed phase C18 column with a mobile phase of 0.1% ammonium acetate water solution-methanol (47:53, v/v). Mizoribine and IS were detected in the multiple reaction monitoring mode with precursor/product ion transitions of m/z 258.2/126.0 and 354.1/185.2, respectively. The calibration curves were linear over the range of 0.02-2 microg mL(-1) for mizoribine. The limit of quantification (LOQ) was 0.02 microg mL(-1) with acceptable precision and accuracy. The validated method was successfully applied for the evaluation of a bioequivalence study on Chinese healthy volunteers. The main pharmacokinetics parameters after oral administration of 100 mg mizoribine test or reference formulation were as follows: Cmax (1.00 +/- 0.21), (1.00 +/- 0.22) microg mL(-1); AUC(0-infinity) (6.72 +/- 1.39), (6.48 +/- 1.44) microg h mL(-1); t1/2 (2.77 +/- 0.26), (2.66 +/- 0.29) h; tmax (2.95 +/- 0.78), (2.84 +/- 0.50) h.

Pharmacokinetics, disposition, and metabolism of [14C]-nebicapone in humans

OBJECTIVE

This study investigated the absorption, distribution, metabolism and excretion (ADME) of nebicapone [BIA 3-202; 1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone], a reversible catechol-O-methyltransferase (COMT) inhibitor, in 4 healthy male subjects.

METHODS

This was a single center, open, non-placebo-controlled, single-group, and a single 200 mg dose study of [(14)C]-nebicapone (2.5 MBq). Blood, urine and faeces were collected up to 264 hours post-dose.

RESULTS

Collectively more than 22 metabolites were identified in plasma, urine and faeces, with 3-O-nebicapone-glucuronide (BIA 3-476) identified as the major metabolite. Plasma concentration-time profiles of [(14)C]-nebicapone demonstrated T(max) (h) 1.25+/-0.65, t(1/2) (h) 134.55+/-25.67, C(max) (ng-eq/g) 19647.02+/-4930.20, AUC(0-t) (h.ng-eq/g) 161735.51+/-9224.66, AUC(0-infinity) (h.ng-eq/g) 199603.30+/-16854.08, and for whole blood T(max) 1.00+/-0.41, t(1/2) 32.98+/-22.82, AUC(0-t) 35539.23+/-13664.87, AUC(0-infinity) 36970.64+/-14559.17. Plasma pharmacokinetics of nebicapone demonstrated T(max) (h) 1.00+/-0.41, t(1/2) (h) 2.34+/-0.51; C(max) (ng-eq/g) 12650.00+/-2898.85, AUC(0-t) (h.ng-eq/g) 18719.96+/-734.18, AUC(0-infinity) (h.ng-eq/g) 18392.12+/-753.81; BIA 3-476 demonstrated T(max) 1.25+/-0.50, t(1/2) 3.47+/-0.68; C(max) 15250+/-2563.20, AUC(0-t) 53810.61+/-7358.81, AUC(0-infinity) 54541.21+/-7135.70; 3-O-methyl-nebicapone (BIA 3-270) demonstrated T(max) 21.01+/-6.01, t(1/2) 103.43+/-6.01; C(max) 286.25+/-20.48, AUC(0-t) 27641.89+/-4569.99, AUC(0-infinity) 36968.12+/-4294.42.

CONCLUSIONS

Nebicapone and BIA 3-476 accounted for most early phase circulating nebicapone-derived moieties, have limited circulating cell association, peak concentrations shortly after dosing, and short body residence. In longer terminal half-life phases low concentrations of BIA 3-270 predominate. While about 70% of the dose was eliminated in the urine as BIA 3-476, < 1% of the dose was excreted as unchanged nebicapone. Faecal excretion accounted for 17.3% administered dose. On average, the total recovery of 88.6% of the radioactivity suggested no worrisome retention of drug derived material following a single 200 mg administration of nebicapone to healthy volunteers. The treatment was very well tolerated with no reported adverse events.