Safety, pharmacokinetics, and changes in bone metabolism associated with zoledronic acid treatment in Japanese patients with primary osteoporosis

Although once-yearly intravenous administration of zoledronic acid has been reported to inhibit bone resorption and increase bone mineral density, no studies have evaluated its effectiveness in treating osteoporosis in Japanese patients. Therefore, the purpose of this study was to investigate the pharmacokinetics and assess the safety of and changes in bone metabolism associated with zoledronic acid treatment in Japanese patients with primary osteoporosis. This was a single-administration study with a single-blind parallel-group design. The study participants were 24 Japanese patients with primary osteoporosis. The patients were divided into two groups, with each group receiving a single injection of zoledronic acid (4 or 5 mg). Pharmacokinetics and urinary excretion were then compared, and drug-related adverse events and changes in the levels of bone turnover markers were assessed at 12 months. Mean plasma concentrations of zoledronic acid peaked in both groups immediately after administration, and decreased to 1% or less of peak levels after 24 h. Noncompartmental analysis revealed that C _max and the area under the curve from time zero to infinity increased in proportion to the dose. The levels of bone resorption and formation markers decreased from day 15 and from 3 months after administration respectively, and suppression of these markers remained constant for the entire study period. No serious adverse events were reported. There was no large difference between the 4- and 5-mg groups in terms of pharmacokinetics, changes in the levels of bone turnover markers, and safety profiles. This study demonstrated acceptable pharmacokinetics and changes in bone metabolism associated with zoledronic acid treatment in female Japanese osteoporosis patients. Both the 4-mg dose and the 5-mg dose demonstrated acceptable safety and sustained antiresorptive effects for the duration of the study.

Plasma profile of cimicoxib in sheep after oral administration at two different rates

Sheep are often subjected to painful procedures and thus they need to be treated with analgesics. Nevertheless, knowledges about pharmacokinetic features of these drugs in this species are poor. The aim of this study was to evaluate plasma behaviour of cimicoxib in sheep after a single oral administration at two different dose rates (4 and 6 mg/kg). Maximum plasma concentrations of cimicoxib were equal to 273.78 (median value; range 189.00-567.32) and 565.01 (range 308.27-822.59) ng/mL after treatment with 4 and 6 mg/kg, respectively. The time of maximum concentration (Tmax) was achieved between 4 and 10 hours following treatment at the lower dose, and between 6 and 10 hours after the administration of the higher dose, with one sheep achieving the concentration peak at 0.75 hours. The slow absorption and the great individual variability in plasma concentration, probably due to ruminal effects, suggest that cimicoxib is not suitable for oral treatment in sheep.

A simple and rapid UHPLC-MS/MS method for the quantitation of the dual aurora kinase A/B inhibitor SCH-1473759 in murine plasma

The Aurora kinase family facilitates cell division through various processes and is overexpressed in a wide variety of human cancers, leading to aneuploidy. For that reason, these enzymes are currently targets of a rising class of anticancer drugs, with some molecules already in therapeutic use. In this study, a new UHPLC-MS/MS method was developed and validated to quantitate a new pan Aurora kinase inhibitor still in preclinical development, SCH-1473759. This bioanalytical method employed a liquid-liquid extraction from plasma using ethyl acetate before evaporation. Calibration range encompassed 0.5-2500ng/mL. The inter- and intra-day accuracy and precision were assessed over five quality control levels; all within limits required by the FDA guidelines. Assay applicability was demonstrated in a first-in-animals study with oral administration, where the maximum plasma concentration (34ng/mL) occurred at 1h, the half-life (1h) was consistent with a previous IV study, and oral bioavailability was poor (F=0.002).

18F-FLT PET/CT imaging in patients with advanced solid malignancies treated with axitinib on an intermittent dosing regimen

PURPOSE

This study utilizes FLT PET/CT imaging to characterize changes in tumor cell proliferation and vasculature during intermittent treatment with VEGR-TKI axitinib.

METHODS

Patients with metastatic solid malignancies underwent 3-week treatment cycles with axitinib (7 and 5 mg BID for safety and pharmacodynamic cohorts, respectively). Cycles consisted of 2 weeks of treatment (dosing period) followed by a 1-week treatment break (washout period). Patients in the pharmacodynamic cohort had up to six FLT PET/CT scans (three scans in each cycle 1 and cycle 3) and had plasma VEGF concentrations measured at imaging timepoints. Changes in tumor SUVs and VEGF within and across drug cycles were investigated.

RESULTS

Eight patients enrolled in the safety cohort where it was determined 7 mg axitinib was not tolerable due to severe adverse events, including three patients who experienced significant hypertension and thrombovascular effects. Sixteen patients enrolled in the pharmacodynamic cohort demonstrated significant decreases in SUVs and increases in VEGF during dosing periods. This was followed by significant increases in SUVs and decreases in VEGF during drug washout periods. No significant differences in SUVs or VEGF were found when comparing cycle 1 with cycle 3. A mixed effects model demonstrated significant negative correlation between SUV and VEGF.

CONCLUSIONS

Response to axitinib included diminished FLT uptake during dosing periods followed by increased FLT uptake during drug washout periods. These changes were not different when comparing treatment cycle 1 versus cycle 3, suggesting that the pharmacodynamic effect of intermittent axitinib is similar across multiple drug cycles.

Validated LC-MS/MS Method for the Quantification of Ponatinib in Plasma: Application to Metabolic Stability

In the current work, a rapid, specific, sensitive and validated liquid chromatography tandem mass-spectrometric method was developed for the quantification of ponatinib (PNT) in human plasma and rat liver microsomes (RLMs) with its application to metabolic stability. Chromatographic separation of PNT and vandetanib (IS) were accomplished on Agilent eclipse plus C18 analytical column (50 mm × 2.1 mm, 1.8 μm particle size) maintained at 21±2°C. Flow rate was 0.25 mLmin^-1 with run time of 4 min. Mobile phase consisted of solvent A (10 mM ammonium formate, pH adjusted to 4.1 with formic acid) and solvent B (acetonitrile). Ions were generated by electrospray (ESI) and multiple reaction monitoring (MRM) was used as basis for quantification. The results revealed a linear calibration curve in the range of 5–400 ngmL^-1 (r² ≥ 0.9998) with lower limit of quantification (LOQ) and lower limit of detection (LOD) of 4.66 and 1.53 ngmL^-1 in plasma, 4.19 and 1.38 ngmL^-1 in RLMs. The intra- and inter-day precision and accuracy in plasma ranged from1.06 to 2.54% and -1.48 to -0.17, respectively. Whereas in RLMs ranged from 0.97 to 2.31% and -1.65 to -0.3%. The developed procedure was applied for quantification of PNT in human plasma and RLMs for study metabolic stability of PNT. PNT disappeared rapidly in the 1st 10 minutes of RLM incubation and the disappearance plateaued out for the rest of the incubation. In vitro half-life (t_1/2) was 6.26 min and intrinsic clearance (CL_in) was 15.182± 0.477.

An open-label investigation into drug-drug interactions between multiple doses of daclatasvir and single-dose cyclosporine or tacrolimus in healthy subjects

Background and Objective

Chronic hepatitis C virus (HCV) infection is a major cause of liver transplantation. Drug–drug interactions (DDIs) with cyclosporine and tacrolimus hindered the use of first-generation protease inhibitors in transplant recipients. The current study investigated DDIs between daclatasvir—a pan-genotypic HCV NS5A inhibitor with clinical efficacy in multiple regimens (including all-oral)—and cyclosporine or tacrolimus in healthy subjects.

Methods

Healthy fasted subjects (aged 18–49 years; body mass index 18–32 kg/m²) received single oral doses of cyclosporine 400 mg on days 1 and 9, and daclatasvir 60 mg once daily on days 4–11 (group 1, n = 14), or a single oral dose of tacrolimus 5 mg on days 1 and 13, and daclatasvir 60 mg once daily on days 8–19 (group 2, n = 14). Blood samples for pharmacokinetic analysis [by liquid chromatography with tandem mass spectrometry (LC–MS/MS)] were collected on days 1 and 9 for cyclosporine (72 h), on days 1 and 13 for tacrolimus (168 h) and on days 8 and 9 (group 1) or on days 12 and 13 (group 2) for daclatasvir (24 h). Plasma concentrations were determined by validated LC–MS/MS methods.

Results

Daclatasvir did not affect the pharmacokinetic parameters of cyclosporine or tacrolimus, and tacrolimus did not affect the pharmacokinetic parameters of daclatasvir. Co-administration of cyclosporine resulted in a 40 % increase in the area under the concentration–time curve of daclatasvir but did not affect its maximum observed concentration.

Conclusion

On the basis of these observations in healthy subjects, no clinically relevant DDIs between daclatasvir and cyclosporine or tacrolimus are anticipated in liver transplant recipients infected with HCV; dose adjustments during co-administration are unlikely to be required.

Long-term exposure of rabbits to imidaclorpid as quantified in blood induces genotoxic effect

The present in-vivo study focuses on the genotoxic effect of the neonicotinoid pesticide imidacloprid (IMI) in rabbits. The purpose of the study was to establish a possible relationship between exposure to the pesticide (dose and duration) and genotoxicity. Furthermore, an analytical method for the simultaneous determination of IMI and its major metabolite 6-chloronicotinic acid (6-ClNA) in blood was developed and validated. The isolation of the two analytes from blood was performed by liquid-liquid extraction with dichloromethane. Analysis was performed by Liquid Chromatography - Atmospheric Pressure Chemical Ionization - Mass Spectrometry (LC-APCI-MS). The method was applied on the determination of IMI and 6-ClNA in serum samples obtained from rabbits fed with the insecticide at two low doses. Furthermore, parameters of genotoxicity and cytotoxicity were evaluated by measuring binucleated cells with micronuclei (BNMN), micronuclei (MN) and the Cytokinesis Block Proliferation Index (CBPI), in lymphocytes of exposed rabbits. The results revealed a genotoxic effect of IMI for both exposed groups. There were statistically significant differences in the frequencies of BNMN and MN between control and exposed groups but there was no dose-dependence, neither time-dependence of the genotoxic effect for the administered doses. This is the first time that long term exposure to IMI in rabbits was studied for the determination of its genotoxic effect. The genotoxic effect of IMI as it is depicted by the current study is in accordance with previous studies.

Population pharmacokinetic-pharmacodynamic modelling of 24-h diastolic ambulatory blood pressure changes mediated by axitinib in patients with metastatic renal cell carcinoma

BACKGROUND

Increased blood pressure (BP) is commonly observed in patients treated with vascular endothelial growth factor pathway inhibitors, including axitinib. Ambulatory BP monitoring (ABPM) and pharmacokinetic data were collected in a randomised, double-blind phase II study of axitinib with or without dose titration in previously untreated patients with metastatic renal cell carcinoma.

OBJECTIVE

Aims of these analyses were to (1) develop a population pharmacokinetic-pharmacodynamic model for describing the relationship between axitinib exposure and changes in diastolic BP (dBP) and (2) simulate changes in dBP with different axitinib dosing regimens.

METHODS

We employed a three-stage modelling approach, which included development of (1) a baseline 24-h ABPM model, (2) a pharmacokinetic model from serial and sparse pharmacokinetic data, and (3) an indirect-response, maximum-effect (Emax) model to evaluate the exposure-driven effect of axitinib on dBP. Simulations (N = 1,000) were performed using the final pharmacokinetic-pharmacodynamic model to evaluate dBP changes on days 4 and 15 of treatment with different axitinib doses.

RESULTS

Baseline ABPM data from 62 patients were best described by 24-h mean dBP and two cosine terms. The final indirect-response Emax model showed good agreement between observed 24-h ABPM data and population and individual predictions. The maximum increase in dBP was 20.8 %, and the axitinib concentration at which 50 % of the maximal increase in dBP was reached was 12.4 ng/mL.

CONCLUSION

Our model adequately describes the relationship between axitinib exposure and dBP increases. Results from these analyses may potentially be applied to infer dBP changes in patients administered axitinib at nonstandard doses.

Assessing the risk to green sturgeon from application of imidacloprid to control burrowing shrimp in Willapa Bay, Washington--Part II: controlled exposure studies

The activities of 2 species of burrowing shrimp have a negative impact on the growth and survival of oysters reared on intertidal mudflats in Willapa Bay and Grays Harbor, Washington (USA). To maintain viable harvests, oyster growers proposed the application of the neonicotinoid insecticide imidacloprid onto harvested beds for the control of burrowing shrimp. In test applications, water column concentrations of imidacloprid were relatively low and dissipated rapidly. The foraging activities of the green sturgeon (listed in the US Endangered Species Act) could result in exposure to higher, more sustained imidacloprid concentrations within sediment porewater and from the consumption of contaminated shrimp. Controlled experiments were conducted using surrogate white sturgeon to determine acute and chronic effect concentrations, to examine overt effects at more environmentally realistic concentrations and durations of exposure, and to assess chemical depuration. The 96-h median lethal concentration was 124 mg L(-1) , and the predicted 35-d no-observed-adverse-effect concentration was 0.7 mg L(-1) . No overt effects were observed following environmentally relevant exposures. Imidacloprid half-life in plasma was greater than 32 h. Measured concentrations of imidacloprid in porewater were significantly lower than the derived acute and chronic effect concentrations for white sturgeon. Exposure risk quotients were calculated using the effect concentrations and estimated environmental exposure. The resulting values were considerably below the level of concern for direct effects from either acute or chronic exposure to an endangered species.

The advanced glycation end product methylglyoxal-derived hydroimidazolone-1 and early signs of atherosclerosis in childhood diabetes

BACKGROUND

Advanced protein glycation is an important mechanism for the development of late diabetic complications including atherosclerosis. Methylglyoxal-derived hydroimidazolone-1 is the most abundant advanced glycation end product in human plasma.

AIM

To investigate the relationship between methylglyoxal-derived hydroimidazolone-1 and early signs of atherosclerosis in children and adolescents with type 1 diabetes and healthy controls.

METHODS

A total of 314 diabetes patients aged 8-18 years were compared with 120 healthy controls. Serum methylglyoxal-derived hydroimidazolone-1 was measured by immunoassay. Atherosclerosis was evaluated by assessing carotid intima-media thickness by ultrasound, arterial stiffness by Young's modulus and inflammation by C-reactive protein.

RESULTS

Methylglyoxal-derived hydroimidazolone-1 was significantly increased in the diabetes group compared with controls, 155.3 (standard deviation (SD) = 41.0) versus 143.0 (SD = 35.1) U/mL, p = 0.003, as was C-reactive protein, median 0.51 (0.27, 1.83) versus 0.31 (0.19, 0.67) mg/L, p < 0.001. There was no significant difference between the groups regarding carotid intima-media thickness or Young's modulus. Multiple regression analysis showed a significant positive association between methylglyoxal-derived hydroimidazolone-1 and C-reactive protein in the diabetes group.

CONCLUSION

Serum levels of methylglyoxal-derived hydroimidazolone-1 in diabetes patients are increased and associated with low-grade inflammation, but not yet arterial stiffness or wall thickness. This indicates that methylglyoxal-derived hydroimidazolone-1 may be important in the early phase of the accelerated atherosclerotic process in diabetes.

[EVALUATION OF THE PHARMACOKINETIC INTERACTION OF AFOBAZOLE WITH CYP2C9 ENZYME DRUG SUBSTRATE OF CYTOCHROME P450]

We have studied the pharmacokinetics of drug-marker of cytochrome P450 isoenzyme CYP2C9 (losartan) and its metabolite E-3174 after subchronic oral administration of afobazole in doses 5 and 25 mg/kg in rats. The metabolic ratio (MR) of E-3174/Losartan was calculated. The pharmacokinetic parameters of losartan and its metabolite on the background of 4-day afabazole administration 5 mg/kg dose were not significantly different from analogous values calculated for the control group of rats. Therefore, afobazole in the effective anxiolytic dose did not change the MR value of metabolized P450 isoform. A five-fold dose increase in the afobazole dose led to significant difference in pharmacokinetic parameters, including A UC0-t, Cmax, Kel, t1/2el, MRT, CL/F, and Vd/F of losartan and AUC0-T, Cmax, and Tmax of E-3174. These findings are indicative of the induction of CYP2C9 isoenzyme by afobazole.

Fenobam sulfate inhibits cocaine-taking and cocaine-seeking behavior in rats: implications for addiction treatment in humans

RATIONALE

The metabotropic glutamate receptor subtype 5 (mGluR5) has been reported to be critically involved in drug reward and addiction. Because the mGluR5 negative allosteric modulators (NAMs) 2-methyl-6-(phenylethynyl)pyridine (MPEP) and 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine (MTEP) significantly inhibit addictivelike behaviors of cocaine and other drugs of abuse in experimental animals, it has been suggested that mGluR5 NAMs may have translational potential for treatment of addiction in humans. However, neither MPEP nor MTEP have been evaluated in humans due to their off-target actions and rapid metabolism.

OBJECTIVES

Herein, we evaluate a potential candidate for translational addiction research: a new sulfate salt formulation of fenobam, a selective mGluR5 NAM that has been investigated in humans.

RESULTS

In rats, fenobam sulfate had superior pharmacokinetics compared to the free base, with improved maximal plasma concentration (C max) and longer half life. Oral (p.o.) administration of fenobam sulfate (30 or 60 mg/kg) inhibited intravenous (i.v.) cocaine self-administration, cocaine-induced reinstatement of drug-seeking behavior, and cocaine-associated cue-induced cocaine-seeking behavior in rats. Fenobam sulfate also inhibited p.o. sucrose self-administration and sucrose-induced reinstatement of sucrose-seeking behavior, but had no effect on locomotion.

CONCLUSIONS

This study provides additional support for the role of mGluR5 signaling in cocaine addiction and suggests that fenobam sulfate may have translational potential in medication development for the treatment of cocaine addiction in humans.

Analysis of the potential effect of ponatinib on the QTc interval in patients with refractory hematological malignancies

Purpose

Cardiac dysfunction, particularly QT interval prolongation, has been observed with tyrosine kinase inhibitors approved to treat chronic myeloid leukemia. This study examines the effects of ponatinib on cardiac repolarization in patients with refractory hematological malignancies enrolled in a phase 1 trial.

Methods

Electrocardiograms (ECGs) were collected at 3 dose levels (30, 45, and 60 mg) at 6 time points. Electrocardiographic parameters, including QTc interval, were measured, and 11 morphological analyses were conducted. Central tendency analyses of ECG parameters were performed using time-point and time-averaged approaches. All patients with at least 2 baseline ECGs and 1 on-treatment ECG were included in the analyses. Patients with paired ECGs and plasma samples were included in the pharmacokinetic/pharmacodynamic analysis to examine the relationship between ponatinib plasma concentration and change from baseline in QT intervals.

Results

Thirty-nine patients at the 30-, 45-, and 60-mg dose levels were included in the central tendency and morphological analyses. There was no significant effect on cardiac repolarization, as evidenced by non-clinically significant mean QTcF changes from baseline of −10.9, −3.6, and −5.0 ms for the 30-, 45-, and 60-mg dose levels, respectively. The morphological analysis revealed 2 patients with atrial fibrillation and 2 with T wave inversion. Seventy-five patients were included in the pharmacokinetic/pharmacodynamic analysis across all dose levels. The slope of the relationship for QTcF versus plasma ponatinib concentration was not positive (−0.0171), indicating no exposure–effect relationship.

Conclusions

Ponatinib is associated with a low risk of QTc prolongation in patients with refractory hematological malignancies.

Influence of Azimilide on CYP2C19-Mediated Metabolism

The purpose of this study was to assess the influence of multiple-dose oral administration of azimilide dihydrochloride on CYP2C19-mediated metabolism. A two-period, randomized crossover study was conducted in 40 healthy male subjects who were phenotyped as extensive CYP2C19 metabolizers. Oral doses of placebo or 125 mg of azimilide dihydrochloride were administered every 12 hours for 3 days, followed by every 24 hours for 5 days; 20 mg omeprazole was coadministered on Day 8. Blood or plasma samples were obtained over 24 hours and analyzed for azimilide or omeprazole/5-hydroxyomeprazole using high-performance liquid chromatography with tandem mass spectrometry. Data were analyzed using "noncompartmental" analysis. Azimilide blood concentrations observed in this study were similar to those previously observed at steady state in patients. Based on AUC(m)/AUC(p) for omeprazole, azimilide does not significantly inhibit CYP2C19-mediated metabolism (90% confidence interval [CI] = 104%-111%). For 5-hydroxyomeprazole, no significant changes in pharmacokinetics were observed. For omeprazole, a statistically significant decrease ( approximately 12%) was observed for AUC. However, this change was small and is not expected to be clinically important since the CI was contained within those used to establish bioequivalence. These results indicate that azimilide does not inhibit CYP2C19-mediated metabolism. Since this isozyme had the lowest in vitro IC(50) values for the cytochrome P450s most commonly involved with the metabolism of drugs (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4), azimilide-related drug interactions mediated via these isozymes are not anticipated.

Pharmacokinetics of CS-866, a New Angiotensin II Receptor Blocker, in Healthy Subjects

CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.

Orteronel (TAK-700), a novel non-steroidal 17,20-lyase inhibitor: effects on steroid synthesis in human and monkey adrenal cells and serum steroid levels in cynomolgus monkeys

Surgical or pharmacologic methods to control gonadal androgen biosynthesis are effective approaches in the treatment of a variety of non-neoplastic and neoplastic diseases. For example, androgen ablation and its consequent reduction in circulating levels of testosterone is an effective therapy for advanced prostate cancers. Unfortunately, the therapeutic effectiveness of this approach is often temporary because of disease progression to the 'castration resistant' (CRPC) state, a situation for which there are limited treatment options. One mechanism thought to be responsible for the development of CRPC is extra-gonadal androgen synthesis and the resulting impact of these residual extra-gonadal androgens on prostate tumor cell proliferation. An important enzyme responsible for the synthesis of extra-gonadal androgens is CYP17A1 which possesses both 17,20-lyase and 17-hydroxylase catalytic activities with the 17,20-lyase activity being key in the androgen biosynthetic process. Orteronel (TAK-700), a novel, selective, and potent inhibitor of 17,20-lyase is under development as a drug to inhibit androgen synthesis. In this study, we quantified the inhibitory activity and specificity of orteronel for testicular and adrenal androgen production by evaluating its effects on CYP17A1 enzymatic activity, steroid production in monkey adrenal cells and human adrenal tumor cells, and serum levels of dehydroepiandrosterone (DHEA), cortisol, and testosterone after oral dosing in castrated and intact male cynomolgus monkeys. We report that orteronel potently suppresses androgen production in monkey adrenal cells but only weakly suppresses corticosterone and aldosterone production; the IC(50) value of orteronel for cortisol was ~3-fold higher than that for DHEA. After single oral dosing, serum levels of DHEA, cortisol, and testosterone were rapidly suppressed in intact cynomolgus monkeys. In castrated monkeys treated twice daily with orteronel, suppression of DHEA and testosterone persisted throughout the treatment period. In both in vivo models and in agreement with our in vitro data, suppression of serum cortisol levels following oral dosing was less than that seen for DHEA. In terms of human CYP17A1 and human adrenal tumor cells, orteronel inhibited 17,20-lyase activity 5.4 times more potently than 17-hydroxylase activity in cell-free enzyme assays and DHEA production 27 times more potently than cortisol production in human adrenal tumor cells, suggesting greater specificity of inhibition between 17,20-lyase and 17-hydroxylase activities in humans vs monkeys. In summary, orteronel potently inhibited the 17,20-lyase activity of monkey and human CYP17A1 and reduced serum androgen levels in vivo in monkeys. These findings suggest that orteronel may be an effective therapeutic option for diseases where androgen suppression is critical, such as androgen sensitive and CRPC.

Metabotropic glutamate receptor 5 antagonism with fenobam: examination of analgesic tolerance and side effect profile in mice

BACKGROUND

The metabotropic glutamate receptor 5 noncompetitive antagonist fenobam is analgesic in rodents. Future development of fenobam as an analgesic in humans will require a favorable long-term treatment profile and a lack of significant deleterious side effects. This study aimed to determine whether tolerance to fenobam's analgesic effects developed over 14 days and to assess for side effects in mice.

METHODS

Mouse models of pain, locomotor behavior, and coordination were used. Fenobam or vehicle (n = 8 or 11 per group) was administered for 14 days, and analgesic tolerance to fenobam was assessed using the formalin test. Histopathologic examination, hematology, and clinical chemistry analysis after 14-day fenobam administration were also assessed (n = 12 or 9). The effects of fenobam on locomotor activity were assessed in the open field and elevated zero maze (n = 8 or 7). Coordination was assessed using ledge crossing and vertical pole descent tasks (n = 11 or 10).

RESULTS

Tolerance to fenobam's analgesic effect did not develop after 14 days. Chronic fenobam administration resulted in statistically significantly less weight gain compared with vehicle control subjects, but did not cause any physiologically or statistically significant hematologic abnormalities, altered organ function, or abnormal histopathology of the liver, brain, or testes. Fenobam administration resulted in a metabotropic glutamate receptor 5-dependent increase in exploratory behavior but does not impair motor coordination at analgesic doses.

CONCLUSIONS

Analgesic tolerance to repeat fenobam dosing does not develop. Chronic dosing of up to 14 days is well tolerated. Fenobam represents a promising candidate for the treatment of human pain conditions.

Liquid chromatographic method for the simultaneous determination of eprosartan and hydrochlorothiazide in tablets and human plasma

A new, specific, and sensitive RP-HPLC method was developed for the simultaneous determination of eprosartan (EPR) and hydrochlorothiazide (HCT). Good chromatographic separation was achieved using a 250 x 4.6 mm id, 5 microm particle size Symmetry C18 column. The mobile phase acetonitrile-0.1 M phosphate buffer (35+65, v/v), pH 4.5, was pumped at a flow rate of 1 mL/min, with UV detection at 275 nm. The method showed good linearity in the ranges of 0.5-50 and 0.1-10 microg/mL, with LOD of 0.06 and 0.02 microg/mL and LOQ of 0.20 and 0.08 microg/mL for EPR and HCT, respectively. The proposed method was successfully applied for the analysis of the studied drugs in their synthetic mixture and co-formulated tablets. The method was further extended to the in vitro and in vivo determination of the two drugs in spiked and real human plasma. Interference likely to be encountered from the co-administered drugs was studied.

Determination of fenticonazole enantiomers by LC-ESI-MS/MS and its application to pharmacokinetic studies in female rats

A simple, rapid, and specific high-performance liquid chromatograph coupled with a tandem mass spectrometry method has been developed and validated for the determination of fenticonazole (CAS 72479-26-6) enantiomers in rat plasma. Simple protein precipitation by acetonitrile was utilized for extracting analytes from the plasma samples. Chromatography separation was performed on a C18 analytical column (150 mm x 2.0 mm, 5 microm) with a mobile phase consisting of methanol-10 mM aqueous ammonium acetate (adjusted to pH 3.5 with acetic acid) (90:10, v/v) at a flow rate of 0.2 ml/min. Detection was carried out on a triple quadrupole mass spectrometer equipped with electrospray ionization (ESI) source, and operated in multiple-reaction monitoring (MRM) mode. The calibration curves were linear over the range 0.5 -200 ng/ml (r > 0.99). The relative recoveries of R-(-)-fenticonazole and its enantiomer were better than 85%. The intra- and inter-day precisions (R.S.D.%) and deviations of the assay accuracies were less than 10%. This newly developed and validated method was successfully applied to pharmacokinetic studies after administration at a single dose of 20 mg/ kg R-(-)-fenticonazole nitrate and its enantiomer to female rats per vagina. The Cmax value of S-(+)-fenticonazole was greater than that of R-(-)-fenticonazole by 1.36-fold, whereas, the t(1/2) beta and MRT values of R-(-)-fenticonazole were longer than those of its enantiomer by 1.95- and 1.24-fold. The results indicated that S-(+)-fenticonazole was faster in absorption and elimination in female rat. But, the Tmax and AUC(0-12) values for each of fenticonazole enantiomers were not significantly different.

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.

A fully validated method for the determination of vardenafil in blood using gas chromatography/mass spectrometry

Vardenafil (VDN) is one of the three commercially available phosphodiesterase type 5 inhibitors and it is mainly used in the treatment of erectile dysfunction. A sensitive and specific gas chromatography/mass spectrometry (GC/MS) method for the determination of VDN in blood has been developed and validated. Sample preparation included solid-phase extraction and derivatization with N-methyl-N-tert-butyldimethylsilyl-trifluoroacetamide (MTBSTFA) and 1% tert-butyldimethylsilylchloride (TBDMSCl). Protriptyline was used as the internal standard for this assay. Limits of detection and quantification for VDN were 0.70 and 2.00 µg/l, respectively. The calibration curves were linear within the dynamic range 2.00-200.0 µg/l with a correlation coefficient higher than 0.991. Absolute recovery ranged from 88.6% to 95.7% for the analyte of interest at three quality control levels. Intra- and inter-day accuracy was found to be between - 6.1% to 10.8% and - 9.3% to 11.6%, respectively, whereas intra- and inter-day precision was < 7.8% and 9.7%, correspondingly. The proposed method is the first fully validated GC/MS method for the determination of VDN in blood samples and it can be used in routine every day analysis by clinical and forensic laboratories for pharmacokinetic studies, for therapeutic drug level monitoring or for the investigation of related forensic cases. A few blood samples analyzed using the developed method is reported herein to demonstrate the suitability of the method.

A pharmacokinetic/pharmacodynamic model for a platelet activating factor antagonist based on data arising from Phase I studies

A nonlinear mixed-effects modelling approach was used to analyse pharmacokinetic and pharma-codynamic data from two Phase I studies of a platelet activating factor (PAF) antagonist under development for the treatment of seasonal allergic rhinitis. Data for single-dose (8 subjects) and multiple-dose (9 subjects) administration were available for analysis with a program based on an EM algorithm. Pharmacokinetic analyses of plasma drug concentrations were performed using a biexponential model with first-order absorption. PAF response data were modelled with a hyperbolic Emax model. The drug showed nonlinear pharmacokinetics, with the clearance decreasing from 46.0 to 27.1 L h−1 over a dose range of 160–480 mg. There was an apparent dose dependency within the C50 (concentration producing 50% of the maximum effect) but at higher doses most of the data was above the estimated C50 and when the data was analysed simultaneously a value of 17.57 ng mL−1 was obtained for C50, with considerable intersubject variability (103%). Consistent results were obtained from the two studies and the population and individual pharmacodynamic parameter estimates from the analyses provided predicted responses that were in good agreement with the observed data. The results were used to simulate a 320-mg twice-daily dosing regimen.

Effect of rifampin on the pharmacokinetics of Axitinib (AG-013736) in Japanese and Caucasian healthy volunteers

PURPOSE

Axitinib, a potent and selective inhibitor of vascular endothelial growth factor receptors 1, 2, 3, is metabolized by cytochrome P450 3A4 and glucuronidation. This study evaluated the effect of rifampin, a potent inducer of drug-metabolizing enzymes, on axitinib plasma pharmacokinetics. Equal numbers of Japanese and Caucasian subjects were enrolled to assess the potential differences in axitinib pharmacokinetics between the two ethnicities.

METHODS

Forty healthy volunteers were randomized to receive 5 mg axitinib alone and with 600 mg rifampin.

RESULTS

Rifampin expectedly decreased AUCinf and Cmax of axitinib (geometric mean reduced by 79 and 71%, respectively). However, differences in axitinib pharmacokinetics were not observed between Japanese and Caucasian subjects (geometric mean ratios for axitinib treatment alone for AUCinf and Cmax were 103 and 96%).

CONCLUSIONS

The results support a common axitinib starting dose in both populations. Potent inducers of drug-metabolizing enzymes reduce axitinib exposure and dose adjustments may be needed for optimal efficacy.