Pharmacokinetics of glycerol phenylbutyrate in pediatric patients 2 months to 2 years of age with urea cycle disorders.

INTRODUCTION: Glycerol phenylbutyrate (GPB) is approved in the US and EU for the chronic management of patients ≥2 months of age with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. GPB is a pre-prodrug, hydrolyzed by lipases to phenylbutyric acid (PBA) that upon absorption is beta-oxidized to the active nitrogen scavenger phenylacetic acid (PAA), which is conjugated to glutamine (PAGN) and excreted as urinary PAGN (UPAGN). Pharmacokinetics (PK) of GPB were examined to see if hydrolysis is impaired in very young patients who may lack lipase activity. METHODS: Patients 2 months to <2 years of age with UCDs from two open label studies (n = 17, median age 10 months) predominantly on stable doses of nitrogen scavengers (n = 14) were switched to GPB. Primary assessments included traditional plasma PK analyses of PBA, PAA, and PAGN, using noncompartmental methods with WinNonlin™. UPAGN was collected periodically throughout the study up to 12 months. RESULTS: PBA, PAA and PAGN rapidly appeared in plasma after GPB dosing, demonstrating evidence of GPB cleavage with subsequent PBA absorption. Median concentrations of PBA, PAA and PAGN did not increase over time and were similar to or lower than the values observed in older UCD patients. The median PAA/PAGN ratio was well below one over time, demonstrating that conjugation of PAA with glutamine to form PAGN did not reach saturation. Covariate analyses indicated that age did not influence the PK parameters, with body surface area (BSA) being the most significant covariate, reinforcing current BSA based dosing recommendations as seen in older patients. CONCLUSION: These observations demonstrate that UCD patients aged 2 months to <2 years have sufficient lipase activity to adequately convert the pre-prodrug GPB to PBA. PBA is then converted to its active moiety (PAA) providing successful nitrogen scavenging even in very young children.

Safety and efficacy of glycerol phenylbutyrate for management of urea cycle disorders in patients aged 2months to 2years.

INTRODUCTION: Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with protein restriction and/or amino acid supplementation alone. Limited data exist on the use of nitrogen conjugation agents in very young patients. METHODS: Seventeen patients (15 previously on other nitrogen scavengers) with all types of UCDs aged 2months to 2years were switched to, or started, GPB. Retrospective data up to 12months pre-switch and prospective data during initiation of therapy were used as baseline measures. The primary efficacy endpoint of the integrated analysis was the successful transition to GPB with controlled ammonia (<100µmol/L and no clinical symptoms). Secondary endpoints included glutamine and levels of other amino acids. Safety endpoints included adverse events, hyperammonemic crises (HACs), and growth and development. RESULTS: 82% and 53% of patients completed 3 and 6months of therapy, respectively (mean 8.85months, range 6days-18.4months). Patients transitioned to GPB maintained excellent control of ammonia and glutamine levels. There were 36 HACs in 11 patients before GPB and 11 in 7 patients while on GPB, with a reduction from 2.98 to 0.88 episodes per year. Adverse events occurring in at least 10% of patients while on GPB were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash/papule. CONCLUSION: GPB was safe and effective in UCD patients aged 2months to 2years. GPB use was associated with good short- and long-term control of ammonia and glutamine levels, and the annualized frequency of hyperammonemic crises was lower during the study than before the study. There was no evidence for any previously unknown toxicity of GPB.

Quantitation of phenylbutyrate metabolites by UPLC-MS/MS demonstrates inverse correlation of phenylacetate:phenylacetylglutamine ratio with plasma glutamine levels.

Urea cycle disorders (UCDs) are genetic conditions characterized by nitrogen accumulation in the form of ammonia and caused by defects in the enzymes required to convert ammonia to urea for excretion. UCDs include a spectrum of enzyme deficiencies, namely n-acetylglutamate synthase deficiency (NAGS), carbamoyl phosphate synthetase I deficiency (CPS1), ornithine transcarbamylase deficiency (OTC), argininosuccinate lyase deficiency (ASL), citrullinemia type I (ASS1), and argininemia (ARG). Currently, sodium phenylbutyrate and glycerol phenylbutyrate are primary medications used to treat patients with UCDs, and long-term monitoring of these compounds is critical for preventing drug toxic levels. Therefore, a fast and simple ultra-performance liquid chromatography (UPLC-MS/MS) method was developed and validated for quantification of phenylbutyrate (PB), phenylacetate (PA), and phenylacetylglutamine (PAG) in plasma and urine. The separation of all three analytes was achieved in 2min, and the limits of detection were <0.04µg/ml. Intra-precision and inter-precision were <8.5% and 4% at two quality control concentrations, respectively. Average recoveries for all compounds ranged from 100% to 106%. With the developed assay, a strong correlation between PA and the PA/PAG ratio and an inverse correlation between PA/PAG ratio and plasma glutamine were observed in 35 patients with confirmed UCDs. Moreover, all individuals with a ratio ≥0.6 had plasma glutamine levels<1000µmol/l. Our data suggest that a PA/PAG ratio in the range of 0.6-1.5 will result in a plasma glutamine level<1000µmol/l without reaching toxic levels of PA.

Bioanalytical method development for quantification of ulifloxacin, fenbufen and felbinac in rat plasma by solid-phase extraction (SPE) and HPLC with PDA detection.

A procedure based on solid-phase extraction (SPE) followed by high performance liquid chromatography (HPLC) with PDA detection has been developed for the analysis of multiple drugs in rat plasma. The analytes evaluated were ulifloxacin, fenbufen and felbinac. Eight different solid phase extraction cartridges were tested to evaluate their applicability for the isolation of drugs from rat plasma. Comparison were recovery of different drugs and reproducibility. The samples were analyzed by HPLC using a Kinetex C18 EVO column and acetonitrile-10mM ammonium acetate-methanol as the mobile phase under gradient elution conditions. SPE combined with HPLC-PDA allowed the determination of drugs over a linear range of 0.05-15 µg/mL for ulifloxacin while 0.5-50 µg/mL for felbinac and fenbufen, with limit of detection at 0.05 for ulifloxacin and 0.5 for felbinac and fenbufen. Bond Elut Plexa sorbent was found to provide the most effective clean-up, removing the greatest amount of interfering substance and simultaneously ensuring analyte recoveries higher than 93.54% with relative standard deviation (RSD) <10%. The method was applied with good accuracy and precision in the determination of ulifloxacin, fenbufen and felbinac in rat plasma obtained from rats treated with selected drugs. This method permits its application to pharmacokinetic and pharmacodynamic studies of these analytes and will facilitate detailed investigations on the interactions between new fluoroquinolones and fenbufen.

Self-rated health in Brazilian adults and elderly: Data from the National Household Sample Survey 2008 / Percepción de la salud en adultos y ancianos brasileños: datos de la Encuesta Nacional de Hogares 2008

Objective. To investigate prevalence of poor self-rated health and its association with individual and household-level characteristics among adults and elderly in Brazil. Materials and methods. Cross-sectional study with Brazilian National Household Sample Survey 2008 (n=257 816). Crude and multilevel-adjusted Poisson regression models were fitted. Results. After adjusted analysis, poor self-rated health was significantly associated with higher household income, living alone, not having piped water nor garbage collection, lower education, not having health insurance, female sex, higher age, being a current or previous smoker, physical inactivity, having chronic diseases, having physical impairment. Subjects living in rural areas also had higher prevalence of poor self-rated health. The factors most strongly associated with the outcome were physical impairment and reporting three or more chronic diseases. Conclusions. Socioeconomic, health related behaviors, and physical health were associated with poor self-rated health.

Objetivo. Investigar la prevalencia de la percepción negativa de salud y su asociación con características individuales a nivel de los hogares en adultos y adultos mayores de Brasil. Material y métodos. Estudio transversal con datos de la Encuesta Nacional de Hogares de 2008 (n=257 816). Se estimaron modelos de regresión de Poisson multinivel crudos y ajustados. Resultados. Después del análisis ajustado, la autopercepción negativa de salud se asoció significativamente con mayor ingreso, vivir solo, no tener agua corriente ni recolección de basura, baja educación, carecer de seguro de salud, sexo femenino, mayor edad, tabaquismo, inactividad física, enfermedades crónicas y deterioro físico. Los habitantes de zonas rurales también tuvieron mayor prevalencia de percepción negativa. Los factores más fuertemente asociados fueron impedimento físico y presentación de tres o más enfermedades crónicas. Conclusiones. Factores socioeconómicos, comportamientos relacionados con la salud y salud física se asociaron con la percepción negativa.

Whole-body pharmacokinetics of HDAC inhibitor drugs, butyric acid, valproic acid and 4-phenylbutyric acid measured with carbon-11 labeled analogs by PET.

The fatty acids, n-butyric acid (BA), 4-phenylbutyric acid (PBA) and valproic acid (VPA, 2-propylpentanoic acid) have been used for many years in the treatment of a variety of CNS and peripheral organ diseases including cancer. New information that these drugs alter epigenetic processes through their inhibition of histone deacetylases (HDACs) has renewed interest in their biodistribution and pharmacokinetics and the relationship of these properties to their therapeutic and side effect profiles. In order to determine the pharmacokinetics and biodistribution of these drugs in primates, we synthesized their carbon-11 labeled analogues and performed dynamic positron emission tomography (PET) in six female baboons over 90 min. The carbon-11 labeled carboxylic acids were prepared by using (11)CO2 and the appropriate Grignard reagents. [(11)C]BA was metabolized rapidly (only 20% of the total carbon-11 in plasma was parent compound at 5 min post injection) whereas for VPA and PBA 98% and 85% of the radioactivity were the unmetabolized compound at 30 min after their administration respectively. The brain uptake of all three carboxylic acids was very low (<0.006%ID/cc, BA>VPA>PBA), which is consistent with the need for very high doses for therapeutic efficacy. Most of the radioactivity was excreted through the kidneys and accumulated in the bladder. However, the organ biodistribution between the drugs differed. [(11)C]BA showed relatively high uptake in spleen and pancreas whereas [(11)C]PBA showed high uptake in liver and heart. Notably, [(11)C]VPA showed exceptionally high heart uptake possibly due to its involvement in lipid metabolism. The unique biodistribution of each of these drugs may be of relevance in understanding their therapeutic and side effect profile including their teratogenic effects.

A randomized controlled trial to evaluate the effects of high-dose versus low-dose of arginine therapy on hepatic function tests in argininosuccinic aciduria.

OBJECTIVE: To compare the effects of combinatorial therapy with low-dose arginine and a nitrogen scavenging agent (sodium phenylbutyrate) vs. monotherapy with high-dose arginine on liver function tests in patients with argininosuccinic aciduria (ASA). STUDY DESIGN: Twelve patients with ASA were enrolled in a double-blind, placebo-controlled, cross-over study design. Subjects were randomized to receive either a low-dose of arginine therapy (100 mg · kg(-1) · d(-1)) combined with sodium phenylbutyrate (500 mg · kg(-1) · d(-1)) (LDA arm) or a high-dose of arginine alone (500 mg · kg(-1) · d(-1)) (HDA arm) for one week. At the end of one week of therapy, liver function tests were assessed and metabolite fluxes were measured using a multi-tracer stable isotope protocol. RESULTS: Plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), and measures of synthetic functions of the liver were the primary outcomes. Subjects had significantly increased levels of argininosuccinate (P<0.03) and AST levels (P<0.01) after treatment with high-dose arginine. In the subset of subjects with elevated AST or ALT, treatment with high-dose of arginine was associated with further increases in plasma levels of both aminotransferases. Whereas subjects had increased arginine and citrulline flux with high-dose arginine therapy, the glutamine flux was not different between the two treatment arms. The synthetic liver functions as assessed by prothrombin time, INR, and coagulation factor levels were not different between the HDA and LDA arms. CONCLUSIONS: Administering higher doses of arginine in subjects with ASA results in increases in AST and ALT levels, especially in the subset of patients with elevated baseline aminotransferases. Hence, low-dose arginine sufficient to normalize arginine levels in plasma combined with nitrogen scavenging therapy should be considered as a therapeutic option for treatment of ASA in patients with elevations of hepatic aminotransferases.

Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders.

UNLABELLED: We have analyzed pharmacokinetic data for glycerol phenylbutyrate (also GT4P or HPN-100) and sodium phenylbutyrate with respect to possible dosing biomarkers in patients with urea cycle disorders (UCD). STUDY DESIGN: These analyses are based on over 3000 urine and plasma data points from 54 adult and 11 pediatric UCD patients (ages 6-17) who participated in three clinical studies comparing ammonia control and pharmacokinetics during steady state treatment with glycerol phenylbutyrate or sodium phenylbutyrate. All patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate or sodium phenylbutyrate in a cross over fashion and underwent 24-hour blood samples and urine sampling for phenylbutyric acid, phenylacetic acid and phenylacetylglutamine. RESULTS: Patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate ranging from 1.5 to 31.8 g/day and of sodium phenylbutyrate ranging from 1.3 to 31.7 g/day. Plasma metabolite levels varied widely, with average fluctuation indices ranging from 1979% to 5690% for phenylbutyric acid, 843% to 3931% for phenylacetic acid, and 881% to 1434% for phenylacetylglutamine. Mean percent recovery of phenylbutyric acid as urinary phenylacetylglutamine was 66.4 and 69.0 for pediatric patients and 68.7 and 71.4 for adult patients on glycerol phenylbutyrate and sodium phenylbutyrate, respectively. The correlation with dose was strongest for urinary phenylacetylglutamine excretion, either as morning spot urine (r = 0.730, p < 0.001) or as total 24-hour excretion (r = 0.791 p<0.001), followed by plasma phenylacetylglutamine AUC(24-hour), plasma phenylacetic acid AUC(24-hour) and phenylbutyric acid AUC(24-hour). Plasma phenylacetic acid levels in adult and pediatric patients did not show a consistent relationship with either urinary phenylacetylglutamine or ammonia control. CONCLUSION: The findings are collectively consistent with substantial yet variable pre-systemic (1st pass) conversion of phenylbutyric acid to phenylacetic acid and/or phenylacetylglutamine. The variability of blood metabolite levels during the day, their weaker correlation with dose, the need for multiple blood samples to capture trough and peak, and the inconsistency between phenylacetic acid and urinary phenylacetylglutamine as a marker of waste nitrogen scavenging limit the utility of plasma levels for therapeutic monitoring. By contrast, 24-hour urinary phenylacetylglutamine and morning spot urine phenylacetylglutamine correlate strongly with dose and appear to be clinically useful non-invasive biomarkers for compliance and therapeutic monitoring.

Determination of phenylbutyric acid and its metabolite phenylacetic acid in different tissues of mouse by liquid chromatography with tandem mass spectrometry and its application in drug tissue distribution.

Endoplasmic reticulum (ER) stress is associated with various human diseases. Phenylbutyric acid (PBA) is a well-known chemical chaperone that regulates ER stress. The main objective of this study was to develop a simple, rapid, and sensitive method for the simultaneous determination of phenylbutyric acid and its metabolite, phenylacetic acid (PAA). A LC-MS/MS analysis using negative electrospray ionization was used. Samples were analyzed by multiple reaction monitoring (MRM) in 15 min of total run time, using d11-PBA and d7-PAA as internal standards. The limit of quantification was 1 µg/g for tissue and 0.8 µg/mL for plasma. Recoveries for plasma and tissues were higher than 81% for both PBA and PAA. The inter-day and intra-day accuracy and precision were within ±15%. We then further successfully validated this method by applying it to determine the tissue distribution of PBA and its metabolite PAA after i.p. injection of PBA at a dose of 500 mg/kg in mice. The maximum concentrations of PBA and PAA in plasma and tissues were seen at 15 min and 45 min, respectively. The PBA plasma concentration was 15-fold higher than the concentration in the kidney, whereas the PAA plasma concentration was 6-fold higher than the concentration in the liver. The area under the curve decreased in the order of plasma > kidney > liver > heart > muscle > lung for PBA and plasma > liver > kidney > heart > muscle > lung for PAA. The tissue to plasma ratio ranged from 0.007 to 0.063 for PBA and 0.016 to 0.109 for PAA. In summary, the LC-ESI-MS method developed in this study is simple, sensitive and reliable.

Simultaneous LC-MS/MS determination of phenylbutyrate, phenylacetate benzoate and their corresponding metabolites phenylacetylglutamine and hippurate in blood and urine.

Inborn errors of urea metabolism result in hyperammonemia. Treatment of urea cycle disorders can effectively lower plasma ammonium levels and results in survival in the majority of patients. Available medications for treating urea cycle disorders include sodium benzoate (BA), sodium phenylacetate (PAA), and sodium phenylbutyrate (PBA) and are given to provide alternate routes for disposition of waste nitrogen excretion. In this study, we develop and validate a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of benzoic acid, phenylacetic acid, phenylbutyric acid, phenylacetylglutamine, and hippuric acid in plasma and urine from children with inborn errors of urea synthesis. Plasma extracts and diluted urine samples were injected on a reverse-phase column and identified and quantified by selected reaction monitoring (SRM) in negative ion mode. Deuterated analogues served as internal standards. Analysis time was 7 min. Assay precision, accuracy, and linearity and sample stability were determined using enriched samples. Quantification limits of the method were 100 ng/ml (0.3-0.8 µmol/L) for all analytes, and recoveries were >90%. Inter- and intraday relative standard deviations were <10%. Our newly developed LC-MS/MS represents a robust, sensitive, and rapid method that allows simultaneous determination of the five compounds in plasma and urine.

Phase 2 comparison of a novel ammonia scavenging agent with sodium phenylbutyrate in patients with urea cycle disorders: safety, pharmacokinetics and ammonia control.

UNLABELLED: Glycerol phenylbutyrate (glyceryl tri (4-phenylbutyrate)) (GPB) is being studied as an alternative to sodium phenylbutyrate (NaPBA) for the treatment of urea cycle disorders (UCDs). This phase 2 study explored the hypothesis that GPB offers similar safety and ammonia control as NaPBA, which is currently approved as adjunctive therapy in the chronic management of UCDs, and examined correlates of 24-h blood ammonia. METHODS: An open-label, fixed sequence switch-over study was conducted in adult UCD patients taking maintenance NaPBA. Blood ammonia and blood and urine metabolites were compared after 7 days (steady state) of TID dosing on either drug, both dosed to deliver the same amount of phenylbutyric acid (PBA). RESULTS: Ten subjects completed the study. Adverse events were comparable for the two drugs; 2 subjects experienced hyperammonemic events on NaPBA while none occurred on GPB. Ammonia values on GPB were approximately 30% lower than on NaPBA (time-normalized AUC=26.2 vs. 38.4 micromol/L; Cmax=56.3 vs. 79.1 micromol/L; not statistically significant), and GPB achieved non-inferiority to NaPBA with respect to ammonia (time-normalized AUC) by post hoc analysis. Systemic exposure (AUC(0-24)) to PBA on GPB was 27% lower than on NaPBA (540 vs. 739 microgh/mL), whereas exposure to phenylacetic acid (PAA) (575 vs. 596 microg h/mL) and phenylacetylglutamine (PAGN) (1098 vs. 1133 microg h/mL) were similar. Urinary PAGN excretion accounted for approximately 54% of PBA administered for both NaPBA and GPB; other metabolites accounted for <1%. Intact GPB was generally undetectable in blood and urine. Blood ammonia correlated strongly and inversely with urinary PAGN (r=-0.82; p<0.0001) but weakly or not at all with blood metabolite levels. CONCLUSIONS: Safety and ammonia control with GPB appear at least equal to NaPBA. Urinary PAGN, which is stoichiometrically related to nitrogen scavenging, may be a useful biomarker for both dose selection and adjustment for optimal control of venous ammonia.

The safety, tolerability, pharmacokinetics, and pharmacodynamics of single oral doses of RO5068760, an MEK inhibitor, in healthy volunteers: assessment of target suppression.

RO5068760, a substituted hydantoin, represents a new class of potent, highly selective, non-adenosine triphosphate (ATP)-competitive MEK1/2 inhibitors. The study aimed to determine the safety/tolerability, pharmacokinetics, and pharmacodynamics of single ascending doses of RO5068760 in human healthy volunteers. All participants received a single dose followed by 48 hours of pharmacokinetics, pharmacodynamics, and safety/tolerability assessments. The pharmacodynamics were measured by changes in ERK phosphorylation (pERK) in peripheral blood mononuclear cells, ex vivo stimulated by phorbol 12-myristate 13-acetate (PMA). Forty-eight participants received 6 doses (50, 100, 200, 400, 600, 800 mg). RO5068760 was well tolerated up to 800 mg. There were no clinically significant safety findings, including laboratory, electrocardiogram, ophthalmological assessment, and fecal occult blood tests. Of the total 13 adverse events (n = 12), 11 were mild, 2 were moderate, and none were severe, and only 5 were considered by the investigator as possibly related to treatment. RO5068760 was absorbed with a t(max), of 2 hours. Disposition appeared to be biphasic with a terminal elimination t(1/2) of 5 to 9 hours. The variability was moderate to high, ranging from 38% to 62% for C(max) and 41% to 69% AUC. Within the dose range tested, pERK inhibition was relatively modest with a mean maximal pERK suppression of 55%.

Preclinical in vivo evaluation of efficacy, pharmacokinetics, and pharmacodynamics of a novel MEK1/2 kinase inhibitor RO5068760 in multiple tumor models.

Targeting the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway represents a promising anticancer strategy. Recently, we have reported a novel class of potent and selective non-ATP-competitive MEK1/2 inhibitors with a unique structure and mechanism of action. RO5068760 is a representative of this class showing significant efficacy in a broad spectrum of tumors with aberrant mitogen-activated protein kinase pathway activation. To understand the relationship between systemic exposures and target (MEK1/2) inhibition as well as tumor growth inhibition, the current study presents a detailed in vivo characterization of efficacy, pharmacokinetics, and pharmacodynamics of RO5068760 in multiple xenograft tumor models. For inhibition of MEK1/2 as measured by the phosphorylated ERK levels, the estimated EC(50)s in plasma were 1.36 micromol/L (880 ng/mL) and 3.35 micromol/L (2168 ng/mL) in LOX melanoma and HT-29 colorectal cancer models, respectively. A similar EC(50) (1.41 micromol/L or 915 ng/mL) was observed in monkey peripheral blood lymphocytes. To achieve tumor growth inhibition (>or=90%), an average plasma drug concentration of 0.65 or 5.23 micromol/L was required in B-RafV600E or K-Ras mutant tumor models, respectively, which were remarkably similar to the IC(90) values (0.64 or 4.1 micromol/L) determined in vitro for cellular growth inhibition. With equivalent in vivo systemic exposures, RO5068760 showed superior efficacy in tumors harboring B-RafV600E mutation. The plasma concentration time profiles indicate that constant p-ERK suppression (>50%) may not be required for optimal efficacy, especially in highly responsive tumors. This study may facilitate future clinical trial design in using biochemical markers for early proof of mechanism and in selecting the right patients and optimal dose regimen.

Identification of phenylbutyrate-generated metabolites in Huntington disease patients using parallel liquid chromatography/electrochemical array/mass spectrometry and off-line tandem mass spectrometry.

Oral sodium phenylbutyrate (SPB) is currently under investigation as a histone deacetylation (HDAC) inhibitor in Huntington disease (HD). Ongoing studies indicate that symptoms related to HD genetic abnormalities decrease with SPB therapy. In a recently reported safety and tolerability study of SPB in HD, we analyzed overall chromatographic patterns from a method that employs gradient liquid chromatography with series electrochemical array, ultraviolet (UV), and fluorescence (LCECA/UV/F) for measuring SPB and its metabolite phenylacetate (PA). We found that plasma and urine from SPB-treated patients yielded individual-specific patterns of approximately 20 metabolites that may provide a means for the selection of subjects for extended trials of SPB. The structural identification of these metabolites is of critical importance because their characterization will facilitate understanding the mechanisms of drug action and possible side effects. We have now developed an iterative process with LCECA, parallel LCECA/LCMS, and high-performance tandem MS for metabolite characterization. Here we report the details of this method and its use for identification of 10 plasma and urinary metabolites in treated subjects, including indole species in urine that are not themselves metabolites of SPB. Thus, this approach contributes to understanding metabolic pathways that differ among HD patients being treated with SPB.

Metabolite identification using a nanoelectrospray LC-EC-array-MS integrated system.

A novel approach to the parallel coupling of normal-bore high-performance liquid chromatography (LC) with electrochemical-array detection (EC-array) and nanoelectrospray mass spectrometry (MS), based on the use of a nanosplitting interface, is described where both detectors are utilized at their optimal detection mode for parallel configuration. The dual detection platform was shown to maintain full chromatographic integrity with retention times and peak widths at half-height between the EC-array and MS displaying high reproducibility with relative standard deviations of <2%. Detection compatibility between the two detectors at the part per billion level injected on-column was demonstrated using selected metabolites representative of the diversity typically encountered in physiological systems. Metabolites were detected with equal efficiency whether neat or in serum, demonstrating the system's ability to handle biological samples with limited sample cleanup and reduced concern for biological matrix effects. Direct quantification of known analytes from the EC-array signal using Faraday's law can eliminate the need for isotopically labeled internal standards. The system was successfully applied to the detection and characterization of metabolites of phenylbutyrate from serum samples of Huntington's disease patients in an example that illustrates the complementarity of the dual detection nanoelectrospray LC-EC-array-MS system.

Oral sodium phenylbutyrate in patients with recurrent malignant gliomas: a dose escalation and pharmacologic study.

We determined the maximum tolerated dose (MTD), toxicity profile, pharmacokinetic parameters, and preliminary efficacy data of oral sodium phenylbutyrate (PB) in patients with recurrent malignant gliomas. Twenty-three patients with supratentorial recurrent malignant gliomas were enrolled on this dose escalation trial. Four dose levels of PB were studied: 9, 18, 27, and 36 g/day. Data were collected to assess toxicity, response, survival, and pharmacokinetics. All PB doses of 9, 18, and 27 g/day were well tolerated. At 36 g/day, two of four patients developed dose-limiting grade 3 fatigue and somnolence. At the MTD of 27 g/day, one of seven patients developed reversible grade 3 somnolence. Median survival from time of study entry was 5.4 months. One patient had a complete response for five years, and no partial responses were noted, which yielded an overall response rate of 5%. Plasma concentrations of 706, 818, 1225, and 1605 muM were achieved with doses of 9, 18, 27, and 36 g/day, respectively. The mean value for PB clearance in this patient population was 22 liters/h, which is significantly higher than the 16 liters/h reported in patients with other malignancies who were not receiving P450 enzyme-inducing anticonvulsant drugs (P = 0.038). This study defines the MTD and recommended phase 2 dose of PB at 27 g/day for heavily pretreated patients with recurrent gliomas. The pharmacology of PB appears to be affected by concomitant administration of P450-inducing anticonvulsants.

Resolution of indobufen enantiomers by capillary zone electrophoresis. Pharmacokinetic studies of human serum.

A direct and stereospecific method was worked out to quantify indobufen enantiomers in human serum using capillary zone electrophoresis (CZE). The indobufen enantiomers and (+)-S-ketoprofen (internal standard, IS) were separated in a fused silica capillary, filled with heptakis 2,3,6-tri-O-methyl-beta-cyclodextrin as a chiral selector in a buffer of pH 5.0. Indobufen enantiomers and other non-steroidal anti-inflammatory drugs: flurbiprofen, ketoprofen and (+)-S-naproxen were also separated during one analytical run. UV absorbances of indobufen enantiomers were measured at 282 nm. Influence of temperature on resolution of the enantiomers, and the electrophoretic parameters: electrophoretic (muep) and electroosmotic (muEOF) mobilities were also determined. Validation of the method was carried out. Calibration curves of indobufen enantiomers were linear in the range of 0.2-20.0 microg/ml. Percent recovery of both enantiomers from acidified serum was calculated after extraction with methylene chloride. Intra- and inter-day measurement precision and accuracy were below 15.0%. Limits of quantitation and detection were also estimated. The elaborated method was tested in vivo after administration of a single dose of 200 mg rac-indobufen tablets to healthy volunteers. Calculated parameters confirmed usefulness of the method in human pharmacokinetic studies on indobufen enantiomers. The direct CZE method can provide an alternative to HPLC, where enantiomers used to be derivatised before determination.

Pharmacokinetics and cerebrospinal fluid penetration of phenylacetate and phenylbutyrate in the nonhuman primate.

INTRODUCTION: Phenylbutyrate (PB) and its metabolite phenylacetate (PA) demonstrate anticancer activity in vitro through promotion of cell differentiation, induction of apoptosis through the p21 pathway, inhibition of histone deacetylase, and in the case of PB, direct cytotoxicity. We studied the pharmacokinetics, metabolism, and cerebrospinal fluid (CSF) penetration of PA and PB after intravenous (i.v.) administration in the nonhuman primate. METHODS: Three animals received 85 mg/kg PA and 130 mg/kg PB as a 30-min infusion. Blood and CSF samples were obtained at 15, 30, 35, 45, 60 or 75 min, and at 1.5, 2.5, 3.5, 5.5, 6.5, 8.5, 10.5 and 24.5 h after the start of the infusion. Plasma was separated immediately, and plasma and CSF were frozen until HPLC analysis was performed. RESULTS: After i.v. PA administration, the plasma area under the concentration-time curve (AUC) of PA (median +/- SD) was 82 +/- 16 mg/ml.min, the CSF AUC was 24 +/- 7 mg/ml.min, clearance (Cl) was 1 +/- 0.3 ml/min per kg, and the AUCCSF:AUCplasma ratio was 28 +/- 19%. After i.v. PB administration, the plasma PB AUC was 19 +/- 3 mg/ml.min, the CSF PB AUC was 8 +/- 11 mg/ml.min, the PB Cl was 7 +/- 1 ml/min per kg, and the AUCCSF:AUCplasma ratio was 41 +/- 47%. The PA plasma AUC after i.v. PB administration was 50 +/- 9 mg/ml.min, the CSF AUC was 31 +/- 24 mg/ml.min, and the AUCCSF:AUCplasma ratio was 53 +/- 46%. CONCLUSIONS: These data indicate that PA and PB penetrate well into the CSF after i.v. administration. There may be an advantage to administration of PB over PA, since the administration of PB results in significant exposure to both active compounds. Clinical trials to evaluate the activity of PA and PB in pediatric central nervous system tumors are in progress.

Steady-state pharmacokinetics of indobufen enantiomers in patients with obliterative atherosclerosis.

Steady-state pharmacokinetics of indobufen (INDB) enantiomers administered as racemic INDB (rac-INDB) tablets and bleeding time were studied in patients. Two-hundred mg INDB tablets (Ibustrin) were administered twice daily for 7 days to obliterative atherosclerosis patients. Enantiospecific reversed phase (RP) HPLC with UV detection (lambda = 275 nm) was used for determination of INDB enantiomers in serum of patients. The ratio AUCR:AUCS equalled 1.7 +/- 0.2 as a result of higher (-)-R-enantiomer serum levels. The (+)-S-enantiomer was more rapidly eliminated (oral clearance, Cl = 1.1 +/- 0.3 L/h) than its (-)-R-antipode (Cl = 0.7 +/- 0.2 L/h). Therefore, the mean steady/state levels of (-)/R/enantiomer (13.5 +/- 3.8 mg/L) exceeded those of its (+)-S-enantiomer (7.8 +/- 1.8 mg/L). Furthermore, half-life (t1/2) was significantly shorter for (+)-S-INDB (t1/2 = 4.5 +/- 1.2 h as compared to (-)-R-INDB (t1/2 = 7.4 +/- 2.4 h). However, no significant differences were observed in the respective Vd values. The bleeding time of patients was not significantly extended. The above pharmacokinetic data provide a rationale for potential future replacement of INDB racemic tablets with tablets of its (+)-S-enantiomer.

Determination of nonsteroidal anti-inflammatory drugs in biological fluids by automatic on-line integration of solid-phase extraction and capillary electrophoresis.

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biological samples (human urine and serum) using solid-phase extraction coupled on-line to capillary electrophoresis is proposed. Automatic pretreatment is carried out by using a continuous flow system operating simultaneously with the capillary electrophoresis equipment, to which it is linked via a laboratory-made mechanical arm. This integrated system is controlled by an electronic interface governed via a program developed in GWBasic. Capillary electrophoresis is conducted by using a separation buffer consisting of 20 mM NaHPO4, 20 mM beta-cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degrees C. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 microg mL(-1). Automatic clean-up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these compounds is between 71.1 and 109.7 microg mL(-1) (RSD 2.0-7.7%) for urine samples and from 77.2 to 107.1 microg mL(-1) (RSD 3.5-7.1%) for serum samples.