A reliable and stable method for the determination of foretinib in human plasma by LC-MS/MS: Application to metabolic stability investigation and excretion rate

Foretinib (GSK1363089) is a multiple receptor tyrosine kinases inhibitor. In this study, a reliable, fast liquid chromatography-tandem mass spectrometric method was described for assaying foretinib in plasma, urine, and rat liver microsome samples. Simple extraction procedure by protein preciptation with acetonitrile was implemented for foretinib and brigatinib (internal standard) analysis. Chromatographic resolution of analytes was achieved on C₁₈ column with the help of isocratic mobile phase. The binary mobile phase consisted of 60% ammonium formate (10 mM, pH 4.2) and 40% acetonitrile at a flow rate of 0.25 mL/min. Run time was 3 min, and both foretinib and brigatinib were eluted within 0.74 and 1.95 min; they were detected in positive ion mode utilizing multiple reactions monitoring mode. Linearity of the proposed method ranged from 5 to 500 ng/mL (r²≥ 0.9993) in the human plasma. Lower limit of quantification and detection were 6.0 and 1.8 ng/mL, respectively. Intraday and interday precision and accuracy were 0.16 to 1.67 % and -2.39 to -0.52 %. In vitro half-life and intrinsic clearance were 24.93 min and 6.56 mL/min/kg, respectively. Literature review showed that no previous studies have been proposed for the analytical quantification of foretinib in human plasma or its metabolic stability. The established method was also applied to estimate the rate of foretinib excretion in rat urine. The developed method can be used for foretinib pharmacokinetic applications.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones (potent inhibitors of 11β-HSD2 and 11β-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11β-hydroxy-progesterone, and 3α,5α-tetrahydro-11β-hydroxy-progesterone strongly inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

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.

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.

[Significance of urinary uracil measurement following administration of DPD inhibitory fluoropyrimidine(DIF)products]

Individual differences in 5-FU metabolism are mainly attributed to individual differences in the activity of DPD, an enzyme that can metabolize more than 85% of 5-FU. Because urinary uracil is a reflection of DPD activity, it is measured to predict and prevent the occurrence of side effects caused by pyrimidine-type chemotherapeutic agents. From urinary uracil values measured in 84 gastrointestinal cancer patients, 0-60 mmol/g.creatinine was set as a standard. In patients whose urinary uracil values exceeded the standard, 5-FU tended to be accumulated when S-1, a DIF product, was administered and side effects, such as anorexia, vomiting and diarrhea occurred immediately after the start of S-1 administration. If an appropriate DIF product is selected and its dosage set based on the patient's urinary uracil value, the occurrence of side effects would be reduced. Subsequently, a continuation of medication would be possible.

Metabolism and excretion of the dipeptidyl peptidase 4 inhibitor [14C]sitagliptin in humans

The metabolism and excretion of [(14)C]sitagliptin, an orally active, potent and selective dipeptidyl peptidase 4 inhibitor, were investigated in humans after a single oral dose of 83 mg/193 muCi. Urine, feces, and plasma were collected at regular intervals for up to 7 days. The primary route of excretion of radioactivity was via the kidneys, with a mean value of 87% of the administered dose recovered in urine. Mean fecal excretion was 13% of the administered dose. Parent drug was the major radioactive component in plasma, urine, and feces, with only 16% of the dose excreted as metabolites (13% in urine and 3% in feces), indicating that sitagliptin was eliminated primarily by renal excretion. Approximately 74% of plasma AUC of total radioactivity was accounted for by parent drug. Six metabolites were detected at trace levels, each representing <1 to 7% of the radioactivity in plasma. These metabolites were the N-sulfate and N-carbamoyl glucuronic acid conjugates of parent drug, a mixture of hydroxylated derivatives, an ether glucuronide of a hydroxylated metabolite, and two metabolites formed by oxidative desaturation of the piperazine ring followed by cyclization. These metabolites were detected also in urine, at low levels. Metabolite profiles in feces were similar to those in urine and plasma, except that the glucuronides were not detected in feces. CYP3A4 was the major cytochrome P450 isozyme responsible for the limited oxidative metabolism of sitagliptin, with some minor contribution from CYP2C8.

Characterization of Two Cyclic Metabolites of Sitagliptin

Two novel metabolites of the dipeptidyl peptidase inhibitor sitagliptin (MK-0431, (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)-butan-2-amine), were identified after purification from dog urine. The metabolites (referred to as M2 and M5) were characterized by hydrogen/deuterium exchange tandem mass spectrometry and NMR spectroscopy nuclear Overhauser effect experiments as the cis and trans stereoisomers formed by cyclization of the primary amino group with the alpha carbon of the piperazine ring, following oxidative desaturation.

Disposition of the dipeptidyl peptidase 4 inhibitor sitagliptin in rats and dogs

The pharmacokinetics, metabolism, and excretion of sitagliptin [MK-0431; (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine], a potent dipeptidyl peptidase 4 inhibitor, were evaluated in male Sprague-Dawley rats and beagle dogs. The plasma clearance and volume of distribution of sitagliptin were higher in rats (40-48 ml/min/kg, 7-9 l/kg) than in dogs ( approximately 9 ml/min/kg, approximately 3 l/kg), and its half-life was shorter in rats, approximately 2 h compared with approximately 4 h in dogs. Sitagliptin was absorbed rapidly after oral administration of a solution of the phosphate salt. The absolute oral bioavailability was high, and the pharmacokinetics were fairly dose-proportional. After administration of [(14)C]sitagliptin, parent drug was the major radioactive component in rat and dog plasma, urine, bile, and feces. Sitagliptin was eliminated primarily by renal excretion of parent drug; biliary excretion was an important pathway in rats, whereas metabolism was minimal in both species in vitro and in vivo. Approximately 10 to 16% of the radiolabeled dose was recovered in the rat and dog excreta as phase I and II metabolites, which were formed by N-sulfation, N-carbamoyl glucuronidation, hydroxylation of the triazolopiperazine ring, and oxidative desaturation of the piperazine ring followed by cyclization via the primary amine. The renal clearance of unbound drug in rats, 32 to 39 ml/min/kg, far exceeded the glomerular filtration rate, indicative of active renal elimination of parent drug.

Mass balance study of [14C] rabeprazole following oral administration in healthy subjects

The study was designed to determine the excretion balance of radiolabeled rabeprazole in urine and feces and to examine the metabolite profile in plasma, urine and feces after a single oral dose of [14C] rabeprazole, preceded by once daily dose of rabeprazole for 7 days. Six healthy subjects were enrolled in this study. The study was a single-center, open-label, multiple-dose, mass-balance study. Each subject received a single 20 mg dose of rabeprazole tablet for 7 days followed by the administration of 20 mg of [14C] rabeprazole as an oral solution after an overnight fast on Day 8. After oral dosing of [14C] rabeprazole, the mean Cmax of total radioactivity was 1,080 +/- 215 ng equivalent/ml with 0.33 +/- 0.13 hours of the mean tmax. The apparent elimination half-life of total [14C] radioactivity was 12.6 +/- 3.4 hours. The total [14C] recovery in urine and feces was 99.8 +/-0.7% by 168 hours after oral administration of [14C] rabeprazole, and mean cumulative [14C] radioactivity excreted in urine was 90.0 +/- 1.7% by 168 hours and 79.8 +/- 2.5% of the radioactivity was excreted in urine within 24 hours. Excretion via feces added to the total by 9.8%. The major radioactive component in the early plasma samples was rabeprazole, however the thioether and thioether carboxylic acid metabolites were the main radioactive components in the later plasma sample. These results support the previous finding that the substantial contribution of the non-enzymatic thioether pathway minimizes the effect of CYP2C19 polymorphism on the inter-individual variation ofplasma clearance of rabeprazole compared with other PPIs. Low levels of the sulfone metabolite were detected only in early plasma samples. No rabeprazole was detected in any urine and feces samples. The main radioactive components in urine were thioether carboxylic acid and mercapturic acid conjugate metabolites, and in the feces, the thioether carboxylic acid metabolite. The administration of [14C] rabeprazole was safe as evidenced by the lack of serious adverse events and the fact that all observed events were mild in intensity. [14C] rabeprazole was rapidly absorbed after oral administration and mostly excreted in urine.

Metabolic Profile of FYX-051 (4-(5-Pyridin-4-yl-1H-[1,2,4]triazol-3-yl)pyridine-2-carbonitrile) in the Rat, Dog, Monkey, and Human: Identification of N-Glucuronides and N-Glucosides

FYX-051, 4-(5-pyridin-4-yl-1H-[1,2,4]triazol-3-yl)pyridine-2-carbonitrile, is a novel xanthine oxidoreductase inhibitor that can be used for the treatment of gout and hyperuricemia. We examined the metabolism of FYX-051 in rats, dogs, monkeys, and human volunteers after the p.o. administration of this inhibitor. The main metabolites in urine were pyridine N-oxide in rats, triazole N-glucoside in dogs, and triazole N-glucuronide in monkeys and humans, respectively. Furthermore, N-glucuronidation and N-glucosidation were characterized by two types of conjugation: triazole N(1)- and N(2)-glucuronidation and N(1)- and N(2)-glucosidation, respectively. N(1)- and N(2)-glucuronidation was observed in each species, whereas N(1)- and N(2)-glucosidation was mainly observed in dogs. With regard to the position of conjugation, N(1)-conjugation was predominant; this resulted in a considerably higher amount of N(1)-conjugate in each species than N(2)-conjugate. The present results indicate that the conjugation reaction observed in FYX-051 metabolism is unique, i.e., N-glucuronidation and N-glucosidation occur at the same position of the triazole ring, resulting in the generation of four different conjugates in mammals. In addition, a urinary profile of FYX-051 metabolites in monkeys and humans was relatively similar; triazole N-glucuronides were mainly excreted in urine.

Disposition of [14C]Ruboxistaurin in Humans

Ruboxistaurin is a potent and specific inhibitor of the beta isoforms of protein kinase C (PKC) that is being developed for the treatment of diabetic microvascular complications. The disposition of [(14)C]ruboxistaurin was determined in six healthy male subjects who received a single oral dose of 64 mg of [(14)C]ruboxistaurin in solution. There were no clinically significant adverse events during the study. Whole blood, urine, and feces were collected at frequent intervals after dosing. Metabolites were profiled by high performance liquid chromatography with radiometric detection. The total mean recovery of the radioactive dose was approximately 87%, with the majority of the radioactivity (82.6 +/- 1.1%) recovered in the feces. Urine was a minor pathway of elimination (4.1 +/- 0.3%). The major route of ruboxistaurin metabolism was to the N-desmethyl ruboxistaurin metabolite (LY338522), which has been shown to be active and equipotent to ruboxistaurin in the inhibition of PKC(beta). In addition, multiple hydroxylated metabolites were identified by liquid chromatography-mass spectrometry in all matrices. Pharmacokinetics were conducted for both ruboxistaurin and LY338522 (N-desmethyl ruboxistaurin, 1). These moieties together accounted for approximately 52% of the radiocarbon measured in the plasma. The excreted radioactivity was profiled using radiochromatography, and approximately 31% was structurally characterized as ruboxistaurin or N-desmethyl ruboxistaurin. These data demonstrate that ruboxistaurin is metabolized primarily to N-desmethyl ruboxistaurin (1) and multiple other oxidation products, and is excreted primarily in the feces.

Cholinesterase inhibition based determination of pancuronium bromide in biological samples

Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine. Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten's constant K(M)=0.40 mmol/L, maximal reaction rate V(max)=52.2 micromol/L min, inhibition constant K(i)=0,56 micromol/L and IC(50)=1.31 micromol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20-68.25 nmol/L, which corresponds to the real sample concentrations from 0.328 to 2.730 micromol/L. The method detection and quantification limits were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70, 29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15-7.45%. Accuracy was examined by standard addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery. The method has good sensitivity, accuracy, precision and it is suitable for clinical practice.

In vivo metabolism of [14C]ruboxistaurin in dogs, mice, and rats following oral administration and the structure determination of its metabolites by liquid chromatography/mass spectrometry and NMR spectroscopy

Ruboxistaurin (LY333531), a potent and isoform-selective protein kinase C beta inhibitor, is currently undergoing clinical trials as a therapeutic agent for the treatment of diabetic microvascular complications. The present study describes the disposition and metabolism of [14C]ruboxistaurin following administration of an oral dose to dogs, mice, and rats. The study revealed that ruboxistaurin was highly metabolized in all species. Furthermore, the results from the bile duct-cannulated study revealed that ruboxistaurin was well absorbed in rats. The primary route of excretion of ruboxistaurin and its metabolites was through feces in all species. The major metabolite detected consistently in all matrices for all species was the N-desmethyl metabolite 1, with the exception of rat bile, in which hydroxy N-desmethyl metabolite 5 was detected as the major metabolite. Other significant metabolites detected in dog plasma were 2, 3, 5, and 6 and in mouse plasma 2, 5, and 19. The structures of the metabolites were proposed by tandem mass spectrometry with the exception of 1, 2, 3, 5, and 6, which were additionally confirmed either by direct comparison with authentic standards or by nuclear magnetic resonance spectroscopy. To assist identification by nuclear magnetic resonance spectroscopy, metabolites 3 and 5 were produced via biotransformation using recombinant human CYP2D6 and, likewise, metabolite 6 and compound 4 (regioisomer of 3 which did not correlate to metabolites found in vivo) were produced using a microbe, Mortierella zonata. The unambiguous identification of metabolites enabled the proposal of clear metabolic pathways of ruboxistaurin in dogs, mice, and rats.

Involvement of marinobufagenin in a rat model of human preeclampsia

BACKGROUND

Preeclampsia is a potentially devastating disorder of hypertension in pregnancy for which there is currently no definitive treatment short of delivery. The bufadienolide, marinobufagenin (MBG), an inhibitor of Na(+)/K(+) ATPase, has been found to be elevated in extracellular fluid volume-expanded hypertensive patients, a condition similar to preeclampsia. Thus, these studies sought to examine the role of MBG in our rat model of preeclampsia.

METHODS AND RESULTS

Pregnant female rats were injected intraperitoneally with deoxycorticosterone acetate (DOCA) and given 0.9% saline as drinking water for the duration of their pregnancy. Urinary MBG was measured using a DELFIA immunoassay. Blood pressure was measured via the tail-cuff method. Injections of anti-MBG antibody were given intraperitoneally or intravenously to hypertensive pregnant rats. MBG was given intraperitoneally to pregnant rats. Uterine arterioles were dissected free and their diameters were measured before and after perfusion of MBG, ouabain, or digoxin. MBG was found to be elevated in the pregnant + DOCA + saline (PDS) rats compared to normal pregnant animals. In addition, when PDS rats were injected with anti-MBG antibody, there was a subsequent reduction in blood pressure. Administration of MBG in normal pregnant rats caused an elevation in blood pressure equivalent to the PDS model. Also, uterine vessel measurements showed an increased vasoconstrictive reactivity to MBG in the PDS animals vs. the normal pregnant controls; while no changes were observed with perfusion of digoxin or ouabain at the same concentration.

CONCLUSION

These results suggest a relationship between MBG and a syndrome in rats resembling preeclampsia. Armed with these promising results, it would seem logical to further examine the role of MBG in human preeclampsia.

Simplex optimization of the variables affecting the micelle-stabilized room temperature phosphorescence of 6-methoxy-2-naphthylacetic acid and its kinetic determination in human urine

This article reports the kinetic determination of 6-methoxy-2-naphthylacetic acid (6-MNA), the major metabolite of nabumetone, from micelle-stabilized room temperature phosphorescence (MS-RTP) measurements made by using the stopped-flow mixing technique. This methodology allows one to determine analytes in complex matrices without the need for a tedious separation process. It also shortens analysis times substantially. The proposed method uses simplex methodology to optimize the chemical and instrumental variables affecting the phosphorescence. It was applied to the determination of 6-MNA in human urine. The maximum phosphorescence signal is obtained within only 10 s after the sample is prepared. The maximum slope of the kinetic curve, which corresponds to the maximum rate of the phosphorescence development, is measured at lambda(ex)=273 nm and lambda(em)=516 nm. Least-squares regression was used to fit experimental data, and the detection limit, repeatability, and standard deviation for replicate samples were determined.

Development and validation of a liquid chromatography and tandem mass spectrometry method for determination of roscovitine in plasma and urine samples utilizing on-line sample preparation

Roscovitine, a purine analogue that selectively inhibits cyclin-dependent kinases, has been considered as a potential anti-tumor drug. The determination of roscovitine in plasma and urine was performed using microextraction in packed syringe as on-line sample preparation method with liquid chromatography and tandem mass spectrometry. The sampling sorbent utilized was polystyrene polymer. 2H3-lidocaine was used as internal standard. The limit of detection for roscovitine was as low as 0.5 ng/mL and the lower limit of quantification was 1.0 ng/mL. The accuracy and precision values of quality control samples were between +/-15% and < or =11%, respectively. The calibration curve was obtained within the concentration range 0.5-2000 ng/mL in both plasma and urine. The regression correlation coefficients for plasma and urine samples were > or =0.999 for all runs. The present method is miniaturized and fully automated and can be used for pharmacokinetic and pharmacodynamic studies.

Pharmacokinetic model of R-roscovitine and its metabolite in healthy male subjects

OBJECTIVE

To characterize the pharmacokinetics of R-roscovitine, a novel cyclin-dependent kinase inhibitor, and its carboxylate metabolite in man.

METHOD

Twelve healthy male subjects received single oral doses of 50, 100, 200, 400 or 800 mg in a hierarchical 3-period, 6-sequence crossover design. One dose was given after breakfast, the others under fasting conditions. R-roscovitine and the carboxylate metabolite were measured in plasma and urine. A 2-compartment model for R-roscovitine with 1 compartment for the metabolite and a component for first-pass extraction was adequate. Protein binding was calculated from plasma and urine data.

RESULTS

R-roscovitine undergoes nonsaturatable first-pass extraction, rapid metabolism, exhibits high nonsaturated protein binding, is slowly absorbed from the GI tract and is rapidly and extensively distributed into tissues. The slow release of the molecule from tissue determines the apparent terminal half-life. Food delays the absorption and slows down the absorption rate but does not influence bioavailability. The formation rate of the carboxylate is a determinant of the plasma concentrations of this metabolite. It has low protein binding, limited tissue distribution and a renal clearance reflecting with good water solubility.

CONCLUSION

The compartmental analysis clarified important pharmacokinetic aspects relevant for the clinical development of the compound.

Compositional analyses of a human menopausal gonadotrophin preparation extracted from urine (menotropin). Identification of some of its major impurities

Recently, a highly purified human menopausal gonadotrophin preparation (HMG) was launched. The composition and purity of this HMG (Menopur); Ferring Pharmaceuticals) with a claimed 1:1 ratio of FSH and LH was determined. Three gonadotrophins were observed: FSH, LH and human chorionic gonadotrophin (HCG). The immunoactivity for HCG was three-fold higher than the immunoactivity for LH. Because of the longer half-life of HCG as compared with LH, about 95% of the in-vivo LH-receptor-mediated bioactivity is attributable to the presence of HCG. This is substantiated by biochemical analyses. To the best of the authors' knowledge, this relatively high amount of HCG can only be explained by assuming the addition of HCG from external sources, which is a well established practice for standardization purposes. In addition to gonadotrophins, a number of other proteins were detected. The amount of these impurities, as determined by reversed-phase high-performance liquid chromatography on a peak-area basis, is at least 30%. Therefore, it is concluded that this HMG preparation contains at most 70% gonadotrophins. Via a proteomics approach three major impurities were identified: leukocyte elastase inhibitor, protein C inhibitor, and zinc-alpha(2)-glycoprotein. On the basis of the results obtained in this study, a comparison is made with recombinant FSH.

Pharmacokinetics and pharmacodynamics of BIA 3-202, a novel COMT inhibitor, during first administration to humans

OBJECTIVE

To determine the tolerability, pharmacodynamics and pharmacokinetics of single oral doses of BIA 3-202, a novel catechol-O-methyltransferase (COMT) inhibitor, in healthy male volunteers.

METHODS

Single increasing oral doses of BIA 3-202 (10, 30, 50, 100, 200, 400 and 800mg) were administered under fasting conditions to seven sequential groups of nine subjects, under a double-blind, randomised, placebo-controlled design. In an additional group of eight subjects (group 8), a single dose of BIA 3-202 400mg was administered on two occasions, once under fasting conditions and once with a high-fat meal, under an open-label, two-way crossover design.

RESULTS

BIA 3-202 was well tolerated at all doses tested. Most adverse events were mild in severity and their incidence was similar between BIA 3-202 and placebo. Maximum plasma concentrations (C(max)) of BIA 3-202 were attained at 0.5-2.5h (t(max)) and thereafter declined with an apparent terminal half-life (t(1/2)) of 1.5-5h. Over the dose range of 10-800mg, there was an approximately dose-proportional increase in the area under the plasma concentration-time curve (AUC) values of BIA 3-202: for a dose level increase in the ratio 3.0:1.7:2.0:2.0:2.0:2.0, AUC increased in the ratio 3.1:1.7:1.9:2.2:2.1:1.7. Plasma concentrations of the O-methylated derivative, BIA 3-270, increased markedly less than predicted from a proportional relationship: for a dose level increase in the ratio 1:80, AUC(0-t )increased in the ratio 1:5. In most subjects, the t(max) of BIA 3-270 was attained at the last sampling time and, therefore, t(1/2 )could not be estimated. Urine assays showed that less than 1% of the total dose administered was excreted in urine as BIA 3-202. Urine concentrations of BIA 3-270 were below the limit of quantification. In group 8, the rate and extent of systemic availability (t(max), AUC and C(max)) of BIA 3-202 and BIA 3-270 after a high-fat meal were similar to those under fasting conditions. Inhibition of COMT activity in erythrocytes reached maximum levels at 2-2.5h post dose, with sustained inhibition up to approximately 4-6 hours, returning to baseline by about 16 hours.

CONCLUSION

BIA 3-202 was well tolerated at single 10-800mg oral doses and presented dose-proportional kinetics. It effectively inhibited COMT activity and the presence of food did not affect its pharmacokinetics or COMT inhibitory activity. The results provide a basis for further clinical studies with BIA 3-202.

Liquid chromatographic method for detection and quantitation of STI-571 and its main metabolite N-desmethyl-STI in plasma, urine, cerebrospinal fluid, culture medium and cell preparations

An isocratic online-enrichment HPLC-assay was developed allowing for the simple and fast separation and quantitation of STI-571 and its main metabolite N-desmethyl-STI (N-DesM-STI) in plasma, urine, cerebrospinal fluid (CSF), culture media and cell preparations in various concentrations using UV-detection at 260 nm. The analytical procedure consists of an online concentration of STI-571 and N-DesM-STI in the HPLC system followed by the elution on a ZirChrom-PBD analytical column. Time of analysis is 40 min including the enrichment time of 5 min. The detection limit is 10 ng/ml in plasma, CSF, culture medium (RPMI) and 25 ng/ml in urine for both STI-571 and N-DesM-STI. The intra-day precision, as expressed by the coefficient of variation (CV), in plasma samples ranges between 1.74 and 8.60% for STI-571 and 1.45 and 8.87% for N-DesM-STI. The corresponding values for urine measurements are 2.17-7.54% (STI-571) and 1.31-9.51% (N-DesM-STI). The inter-day precision analyzed over a 7-month time period was 8.31% (STI-571) or 6.88% (N-DesM-STI) and 16.45% (STI-571) or 14.83% (N-DesM-STI) for a concentration of 1000 ng/ml in plasma and 750 ng/ml in urine, respectively. Moreover, we demonstrate that with an alternative, but more time and labor consuming sample preparation and the implementation of electrochemical detection, a detection limit < 10 ng/ml can be achieved. The method described was used to perform pharmacokinetic measurements of STI-571 and N-desmethyl-STI in patient samples and for kinetic measurements of intracellular STI-571 and N-DesM-STI following in vitro incubation.

Quantitative determination of circulating and urinary asymmetric dimethylarginine (ADMA) in humans by gas chromatography–tandem mass spectrometry as methyl ester tri(N-pentafluoropropionyl) derivative

Asymmetric dimethylarginine (ADMA; N(G),N(G)-dimethyl-L-arginine) is the most important endogenous inhibitor of nitric oxide synthase and a potential risk factor for cardiovascular diseases. This article describes a gas chromatographic-tandem mass spectrometric (GC-tandem MS) method for the accurate quantification of ADMA in human plasma or serum and urine using de novo synthesized [2H(3)]-methyl ester ADMA (d(3)Me-ADMA) as the internal standard. Aliquots (100 microl) of plasma/serum ultrafiltrate or native urine and of aqueous solutions of synthetic ADMA (1 microM for plasma and serum; 20 microM for urine) are evaporated to dryness. The residue from plasma/serum ultrafiltrate or urine is treated with a 100 microl aliquot of 2M HCl in methanol, whereas the residue of the ADMA solution is treated with a 100 microl aliquot of 2M HCl in tetradeuterated methanol. Methyl esters are prepared by heating for 60 min at 80 degrees C. After cooling to room temperature, the plasma or urine sample is combined with the d(3)Me-ADMA sample, the mixture is evaporated to dryness, the residue treated with a solution of pentafluoropropionic (PFP) anhydride in ethyl acetate (1:4, v/v) and the sample is incubated for 30 min at 65 degrees C. Solvent and reagents are evaporated under a stream of nitrogen gas, the residue is treated with a 200 microl aliquot of 0.4M borate buffer, pH 8.5, and toluene (0.2 ml for plasma, 1 ml for urine). Reaction products are extracted by vortexing for 1 min, the toluene phase is decanted, and a 1 microl aliquot is injected into the GC-tandem MS instrument. Quantitation is performed by selected reaction monitoring (SRM) of the common product ion at m/z 378 which is produced by collision-induced dissociation of the ions at m/z 634 for endogenous ADMA and m/z 637 for d(3)Me-ADMA. In plasma and urine of healthy humans ADMA was measured at concentrations of 0.39+/-0.06 microM (n=12) and 3.4+/-1.1 micromol/mmol creatinine (n=9), respectively. The limits of detection and quantitation of the method are approximately 10 amol and 320 pM of d(3)Me-ADMA, respectively.

Quantitative analysis of dipeptidyl peptidase inhibitor P32/98 and its main metabolite in rat, dog, mouse, monkey, human plasma and human urine using liquid chromatography–tandem mass spectrometry: application to pharmacokinetic evaluation

A sensitive, specific and robust assay was developed for the simultaneous determination of the oral antidiabetic drug candidate P32/98 and its main metabolite P57/99 in different biological fluids using LC-MS/MS in the atmospheric pressure chemical ionization (APCI) positive mode. Both analytes were isolated from the biological matrices by solid phase extraction using a strong cation exchanger. This assay was successfully cross-validated for rat, dog, mouse, monkey, human plasma and human urine. The pre-study validation results, as well as the in-study quality control (QC) data obtained, demonstrate the feasibility of the assay for pharmacokinetic evaluation of the compounds in different species and confirm the robustness of the assay for routine use.

Altering cortisol level does not change the pleasurable effects of methamphetamine in humans

Preclinical studies have linked corticosteroid secretion and levels with drug self-administration by animals. In a double-blind, cross-over study, subjective, physiological, and endocrine responses to intravenous doses of methamphetamine 0.5 mg/kg or placebo were assessed in eight methamphetamine-experienced subjects after three cortisol-modifying premedication conditions: augmenting cortisol level with oral hydrocortisone 50 mg, blocking cortisol response with the corticosteroid synthesis inhibitor metyrapone 1500 mg orally, or no premedication. Although the pharmacologic manipulations produced the expected hormonal changes, subjective response to the methamphetamine showed few differences. Diminishing cortisol response by pharmacologic blockade did not alter the pleasurable effects of methamphetamine. Hydrocortisone did increase self-reported 'bad drug effect' and decreased craving after saline placebo relative to the period following methamphetamine. Metyrapone was associated with significant premature ventricular complexes in two subjects during methamphetamine administration and may not be safe for those who use methamphetamine.

LC-MS/MS determination of a farnesyl transferase inhibitor in human plasma and urine

To support clinical pharmacokinetic studies in cancer patients, sensitive and specific methods for measuring 4-[1-(4-cyanobenzyl)-5-imidazolylmethyl]-1-(3-chlorophenyl) piperazinone (I), a farnesyl transferase inhibitor (FTI), in human plasma and urine were developed and validated. The methods are based on high-performance liquid chromatography (HPLC) with atmospheric pressure chemical ionization (APCI) and tandem mass spectrometric (MS/MS) detection in the positive ion mode using a heated nebulizer interface. Drug and internal standard were isolated from plasma or basified urine using automated solid-phase extraction on cyano cartridges. The organic extracts were dried, reconstituted in aqueous acetonitrile and injected into the system. Chromatographic separation of I and internal standard (IS) was achieved using a BDS Hypersil C8 analytical column, with a mobile phase consisting of acetonitrile:methanol:water (50:4:46) and trifluoroacetic acid (0.05%) at a flow rate of 0.6 ml/min. MS/MS detection was performed on a PE-Sciex API 300 tandem mass spectrometer operated in selected reaction monitoring mode. The parent-->product ions monitored were m/z 406-->195 for analyte I and m/z 448-->195 for the internal standard. Unusual in this method is that quantitation is accomplished using a secondary product ion, m/z 195, of drug I and IS. The assays were validated over the concentration range of 0.5-1000 ng/ml (1.2 nM to 2.5 microM, respectively) in plasma, and 2.5-500 ng/ml (6.2 nM to 1.23 microM) in urine. Accuracy was within +/-10% of nominal concentration at all levels in urine, and all but the lowest standard in plasma (+/-14% at 0.5 ng/ml). Intraday precision (expressed as coefficients of variation, CVs) for standard replicates and interday precision for quality control (QC) samples were less than 8% at all concentrations in both matrices. Detailed descriptions of the extraction procedure and analytical methodology used in the assay of I in plasma and urine are presented. This procedure may have utility in the quantitation of other imidazole-based FTIs with cyanobenzyl substructures.

Pentostatin pharmacokinetics and dosing recommendations in patients with mild renal impairment

PURPOSE

The purpose of this study was to determine the pharmacokinetic parameters of pentostatin in renally impaired patients in order to establish dosing guidelines for this population.

METHODS

Pentostatin doses were administered as 15-min intravenous infusions to patients based on their measured creatinine clearance (CLcr) as follows. Patients with normal renal function (NRF), defined as CLcr >60 ml/min, received 4 mg/m(2) repeated every14 days. Patients with impaired renal function (IRF) included those with CLcr 41-60 ml/min who received 3 mg/m(2) and those with CLcr 21-40 ml/min who received 2 mg/m(2), also repeated every 14 days. Heparinized plasma samples were collected during drug infusion and out through 96 h after dosing, except in two patients in whom sampling was extended to 144 h after dosing. Urine sampling extended to 96 h after dosing, and all samples were analyzed by a validated enzyme immunoassay for pentostatin concentrations.

RESULTS

Enrolled in the study were 13 patients (7 IRF and 6 NRF), of whom 12 contributed samples for pharmacokinetic analysis. Median baseline CLcr values were 71.5 ml/min for NRF patients and 44 ml/min for IRF patients. Following the end of intravenous infusion, pentostatin plasma concentrations declined biexponentially with time. In some patients there was a transient increase in pentostatin equivalents 2 to 4 h after dosing. There was a good correlation between measured CLcr and pentostatin total plasma clearance. The AUC(0- infinity ) values seen in IRF patients, at lower doses, were within the range of the AUC(0- infinity ) values seen in patients with normal CLcr. Toxicities observed in the two groups of patients were similar.

CONCLUSIONS

The pentostatin doses used in the study appear to be appropriate for administration to cancer patients with varying degrees of renal impairment.

Down-regulation of rat organic cation transporter rOCT2 by 5/6 nephrectomy

BACKGROUND

In rat kidneys, the organic ion transporters rOCT1, rOCT2, rOAT1 and rOAT3 are considered to mediate the basolateral uptake of various ionic compounds. However, their changes in chronic renal failure (CRF) are poorly understood. The present study examined the renal handling of organic ions and the expression of these transporters under CRF.

METHODS

5/6 Nephrectomized rats were used as the animal model of CRF. Renal handlings of cimetidine and paraaminohippuric acid (PAH) were examined by in vivo experiments. rOAT1, rOAT3, rOCT1 and rOCT2 expressions were determined by Western blotting.

RESULTS

The tubular secretion rates of both PAH and cimetidine were markedly decreased in CRF rats. Although the distribution rates of PAH into the kidney cortex and medulla, and of cimetidine into the kidney cortex were maintained, the distribution rate of cimetidine into the kidney medulla was significantly decreased in CRF rats. The expression level of the rOCT2 protein was markedly depressed in CRF rats, but those of rOCT1, rOAT1 and rOAT3 were maintained. In addition, the plasma concentration of testosterone, a regulator of rOCT2 expression, was significantly reduced by CRF. Both the renal clearance of cimetidine and rOCT2 expression were recovered by the exogenous administration of testosterone in CRF rats.

CONCLUSIONS

The levels of urinary excretion of cationic drugs, especially substrates for rOCT2, were reduced under CRF partly due to the reduced expression of rOCT2, and the lowered plasma level of testosterone was suggested to be responsible for the depressed rOCT2 expression in CRF.

Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, suppresses the growth of carcinogen-induced mammary tumors

Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, has been shown to inhibit the development of N-methylnitrosourea (NMU)-induced rat mammary tumors when fed in the diet continuously for the duration of the carcinogenic process. The present study was designed to determine whether the inhibitory effects of SAHA occur during the initiation process or at subsequent stages in the carcinogenic process. In addition, animals with established NMU tumors were administered SAHA to determine whether SAHA could inhibit the continued growth of established mammary tumors. It was found that SAHA fed at 900 ppm in the diet inhibited tumor yields when administered from 14 days prior to NMU administration to termination (-14 to +130) and from +14 and +28 days to termination. However, SAHA had no effect on tumor yields when administered from -14 to +14 or from -14 to +50 days and then returned to the control diets for the remainder of the experimental period (130 days). These results indicate that the inhibitory effects of SAHA are not exerted at the initiation phase of NMU-induced mammary tumorigenesis and appear, instead, to inhibit the subsequent stages in tumor development. Of most interest was the ability of SAHA to inhibit the growth of established mammary tumors. Administration of SAHA in the diet at 900 ppm resulted in significant inhibition of established tumor growth. Thirty-two percent of SAHA-treated tumors exhibited partial regression compared to 12% of controls, growth was stabilized in 24% of treated tumors compared to 12% of controls while 11% exhibited complete regression compared to 0% of controls. Collectively, SAHA-treated tumors exhibited a 7-fold reduction in growth compared to untreated tumors over the test period. The results of this animal model study indicate that SAHA, when fed in the diet, serves as both a chemopreventive and chemotherapeutic agent in the absence of any detectable side effects.

A comparison of quantitative NMR and radiolabelling studies of the metabolism and excretion of Statil (3-(4-bromo-2-fluorobenzyl)-4-oxo-3H-phthalazin-1-ylacetic acid) in the rat

The identification and quantitation of the metabolites of Statil in rat bile and urine were investigated by 1H- and 19F-NMR spectroscopy and liquid scintillation counting. Male Wistar rats received a single oral dose of 100 mg/kg of radiolabelled Statil. Statil is known to produce glucuronide conjugates which are predominantly excreted into the bile in male rats. The complex multiphasic matrix of bile has been shown to make identification of the resonances by 1H-NMR spectroscopy very difficult as Statil appeared to be micellar bound giving rise to very broad signals. This not only impaired unambiguous signal characterisation but also quantification. The partial separation by SPEC-(1)H-NMR spectroscopy enabled the disruption of the micellar matrices and hence enabled the identification of Statil predominantly as aglycone, and to a lesser extent as glucuronide conjugate. In addition, minor acyl migration products of Statil glucuronide could also be detected as they were separated during the SPEC-process. 19F-NMR spectroscopic measurements on whole bile confirmed their presence as a number of overlapped signals could be observed. The selectivity, simplicity and signal dispersion characteristic of 19F-NMR spectroscopy also enabled the calculation of dose related recoveries of Statil related material in the bile and urine samples without the need for a radiolabel. The aim of this work was to investigate the usefulness and limitations of NMR spectroscopy of intact bile and urine as a means of quantifying levels of drug metabolites. The results obtained from NMR spectroscopy are compared with those obtained using scintillation techniques. Scintillation counting yields unequivocal quantification results, provided the label is preserved in metabolites as has been the case here. In general, quantification by 19F-NMR results similar to those obtained by scintillation counting (in agreement within about 20%). However, discrepancies have been observed with very small and broad 19F-NMR signals in bile. Nevertheless, 19F-NMR spectroscopy of bile is a rapid and facile method for assessing metabolite levels of fluorinated drugs.

Glutathione and mercapturic acid conjugates of sulofenur and their activity against a human colon cancer cell line

Sulofenur is one of the diarylsulfonylureas developed as an anticancer agent. Sulofenur possesses a broad spectrum of activity in several solid tumor models and has undergone extensive clinical trials based on its impressive preclinical activity. However, the clinical response of sulofenur has been disappointing because of the side effect of anemia. Furthermore, the anticancer mechanism of sulofenur and its diarylsulfonylurea analogs still remains unknown. Elucidation of the metabolic fates of sulofenur may help to delineate the mechanism and provide information to guide the structural modification for more potent anticancer agents with less side effects. We have identified a glutathione conjugate and a mercapturic acid conjugate from sulofenur-dosed rats with the aid of liquid chromatography/mass spectrometry. The fraction of the dose of sulofenur as the glutathione conjugate in the dosed-rat bile over 5 h was 0.12 +/- 0.03%, and the mercapturic acid conjugate in urine over 24 h was 1.4 +/- 0.7%. Protein binding of the glutathione conjugate and mercapturic acid conjugate was determined to be 20 +/- 3 and 84 +/- 2%, respectively, as opposed to >99% of sulofenur. The high protein binding of sulofenur requires a higher than in vitro dose, which is believed to cause the side effect of anemia. The significance of this metabolic pathway is that both conjugates were found to be glutathione reductase inhibitors and to possess anticancer activity comparable to sulofenur against human colon adenocarcinoma GC(3)/c1 cells, a sulofenur-sensitive cell line. These conjugates may serve as new leads for the development of novel anticancer agents.

Chiral pharmacokinetics and inversion of enantiomers of a new quinoxaline topoisomerase IIbeta poison in the rat

XK469 (NSC 697887; (+/-)-2-[4-(7-chloro-2-quinoxaliny)oxy]phenoxy propionic acid), an analog of the herbicide Assure, which possesses antitumor activity, especially against murine solid tumors and human xenografts, has recently been found to be the first topoisomerase IIbeta poison. Both R(+) and S(-) isomers are cytotoxic, although the R-isomer is more potent. Using a chiral high-performance liquid chromatography assay, pharmacokinetics of R(+)-, S(-)-, and (+/-)-XK469 in Fischer-344 rats were investigated following their separate i.v. administrations. S(-)-XK469 was found to be predominantly converted to the R-isomer in circulation when the S-isomer was administered either alone or as a racemic mixture. No trace of the S-isomer was found in circulation or in urine or feces, following the R-isomer administration, up to 72 h. In the rat, the plasma concentration-time profiles for both isomers follow a two-compartment pharmacokinetics with the mean t(1/2beta) for the R-isomer of 24.7 h being significantly longer than 4.2 h, the mean t(1/2beta) for the S-isomer. The mean total clearance of the S-isomer was over 200-fold more rapid than that of the R-isomer, and the major clearance route of the S-enantiomer was inversion to its antipode, as estimated by the fractional formation clearance of R(+)-XK469 of 0.93. Protein binding for both enantiomers was in the range of 95 to 98%. Urinary and fecal elimination in 72 h as the intact drug were 7 to 10% and 8% of the administered dose, respectively, either administered as the individual enantiomers or as a racemate. Cumulative biliary elimination in 7 h was about 3% of the dose. No evidence of enantiomeric interaction at the pharmacokinetic level was detected.

Metabolism and urinary excretion of a new quinoline anticancer drug, TAS-103, in humans

1. TAS-103, a novel condensed quinoline derivative, has been developed as an anticancer drug targeting topoisomerases I and II. 2. The purpose of the present study was to characterize the metabolism and urinary excretion of TAS-103 after the intravenous infusion of a single dose to patients in Phase I clinical trials. 3. Five metabolites were detected using high-performance liquid chromatography (HPLC) photodiode array and a precursor scan by liquid chromatography mass spectrometry mass spectrometry (LC/MS/MS). 4. Structures of the five metabolites were determined using the results of enzymatic hydrolysis and the analysis of production mass spectra obtained by LC/MS/MS, and by comparing HPLC retention times and UV, mass and production mass spectra of authentic standards. 5. The metabolites were identified as demethyl-TAS-103 glucuronide (DM-TAS-103-G), TAS-103 glucuronide (TAS-103-G), TAS-103 glucuronide N-oxide (NO-TAS-103-G), demethyl-TAS-103 (DM-TAS-103) and TAS-103 N-oxide (NO-TAS-103). 6. The mean total amount of TAS-103 and TAS-103-G in urine was only 6.03% of the dose, suggesting that urine is not the main elimination route. TAS-103 was extensively metabolized, and a small percentage of the parent drug (0.41%) was found in urine.

Inhibitors of the hyaluronidases

The inhibitors of hyaluronidase present in mammalian sera, first described half a century ago, have remained uncharacterized. Because of increased interest in hyaluronidases and their hyaluronan substrate, a study of these inhibitors was undertaken recently. The predominant serum inhibitor is magnesium-dependent and is eliminated by protease or chondroitinase digestion, and by heat. Kinetics of inhibition are similar against hyaluronidases from testis, snake and bee venom. The inhibitor has no effect on Streptomyces hyaluronidase; indicating inhibition is not through protection of the hyaluronan substrate. Circulating inhibition levels are increased in mice following carbon tetrachloride or interleukin-1 injection, inducers of the acute-phase response. Reverse hyaluronan gel zymography reveals a predominant band of 120 kDa relative molecular size. Additional studies indicate that the inhibitor resembles a member of the Kunitz type inter-alpha-inhibitor family. Inhibition of hyaluronidase activity is observed using purified inter-alpha-inhibitor and is reversed by antibodies specific for inter-alpha-inhibitor. This molecule, found in the hyaluronan-rich cumulus mass surrounding mammalian ova and the pericellular coat of fibroblasts and mesothelial cells, may function to stabilize such matrices by protecting against hyaluronidase degradation. Turnover of circulating hyaluronan is extraordinarily rapid, with a half-life of two to five min. Prompt increases in levels of serum hyaluronan occur in patients with shock, septicemia or massive burns, increases that may be partly attributed to suppression by these acute phase reactants of the constant and rapid rates of hyaluronan degradation by hyaluronidase. A literature survey of other hyaluronidase inhibitors is also presented.

Identification of the aromatase inhibitor aminoglutethimide in urine by gas chromatography/mass spectrometry

Aminoglutethimide is used therapeutically as an aromatase inhibitor in the treatment of metastatic breast cancer in post-menopausal women. For doping purposes, aminoglutethimide may be used for treatment of adverse effects of an extensive abuse of anabolic androgenic steroids (gynaecomastia) and to increase the testosterone concentration and stimulation of testosterone biosynthesis. The use of aromatase inhibitors has been prohibited for male athletes since September 1, 2001. The purpose of this study was to develop methods for the identification of the parent compound or its main metabolite and the inclusion of this information into established screening procedures in doping analysis. An excretion study was conducted using oral application of one single therapeutic dose (500 mg) of Orimeten. The analysis was performed by gas chromatography/mass spectrometry (GC/MS). Aminoglutethimide is excreted almost totally as unconjugated parent compound and is detectable by different screening procedures for up to 165 h. Most suitable for the detection of aminoglutethimide is the screening procedure for heavy volatile nitrogen-containing drugs ('Screening 2'). However, since only competition samples are analysed in that screening procedure, the additional inclusion of aminoglutethimide in the screening procedure for anabolic androgenic agents ('Screening 4') is recommended. Full mass spectra and diagnostic ions for the analysis of aminoglutethimide are presented.

Urinary metabolites of genistein administered orally to rats

In a study on the metabolism of flavonoids, the isoflavone genistein was administered orally to rats. Urine samples were collected and treated with beta-glucuronidase and arylsulfatase. Genistein and its metabolites, 4',5,7-trihydroxyisoflavanone (M1), 4',7-dihydroxyisoflavan (M2), and p-ethylphenol (M3) were isolated from the urine following treatment with enzymes. The structures of M1, M2, and M3 were determined on the basis of chemical and spectral data.

Pharmacokinetics and metabolism of formestane in breast cancer patients

Formestane (Lentaron(R), 4-hydroxyandrostenedione) is a steroidal aromatase inhibitor used for treatment of advanced breast cancer. Clinically, it is administered as a depot form once fortnightly by intramuscular (i.m.) injection. To investigate the pharmacokinetics, bioavailability and metabolism of the drug, seven patients received single 250 mg i.m. doses of commercial formestane on Days 0, 21, 35, 49 and 63 of this trial. On Day 63, three of the patients received an additional single intravenous (i.v.) pulse dose of 1 mg of 14C-labelled formestane. The plasma kinetics after i.m. dosing confirmed a sustained release of formestane from the site of injection. Within 24-48 h of the first dose, the circulating drug reached a C(max) of 48.0+/-20.9 nmol/l (mean+/-S.D.; N=7). At the end of the dosing interval, after 14 days, the plasma concentration was still at 2.3+/-1.8 nmol/l. The kinetic variables did not significantly change during prolonged treatment. Intramuscular doses appear to be fully bioavailable. Following i.v. injection of 14C-formestane, the unchanged drug disappeared rapidly from plasma, the terminal elimination half-life being 18+/-2 min (N=3). Plasma clearance, CL was 4.2+/-1.3 l/(h kg) and the terminal distribution volume V(z) was 1.8+/-0.5 l/kg. The drug is mainly eliminated by metabolism, renal excretion of metabolites accounting for 95% of dose. The excretory balance of 14C-compounds in urine and faeces totals up to 98.9+/-0.8% of the i.v. dose after 168 h. The 14C-compounds in plasma and urine were separated by HPLC, and three major metabolites were submitted to structural analysis by MS, NMR and UV spectroscopy. One of the metabolites is the direct 4-O-glucuronide of formestane. The other two represent 3-O-sulfates of the exocons 3beta,4beta-dihydroxy-5alpha-androstane-17-one and 3alpha,4beta-dihydroxy-5alpha-androstane-17-one, their ratio being 7:3. These exocons are formed by stereoselective 3-keto reduction, accompanied by reduction of the 4,5-enol function. The exocons do not inhibit human placental aromatase activity in vitro.

Pharmacokinetics of mycophenolic acid after mycophenolate mofetil administration in liver transplant patients treated with tacrolimus

The pharmacokinetics of mycophenolic acid (MPA) was studied after oral administration of mycophenolate mofetil (MMF) in 8 liver transplant patients. The mean (+/- SD) maximum MPA plasma concentration of 10.6 (+/- 7.5) mg/ml was achieved within 0.5 to 5 hours. The mean (+/- SD) steady-state area under the plasma concentration versus time curve (AUC(0-12)) was 40 (+/- 30.9) mg/ml/h. The mean (+/- SD) half-life was 5.8 (+/- 3.8) hours. There was poor correlation between trough blood concentrations of tacrolimus (r = -0.004) or serum creatinine (r = 0.689) with MPA AUC, while the serum bilirubin concentrations correlated (r = 0.743) well with MPA AUC, suggesting impairment in MPA conjugation in patients with liver dysfunction. The mean (+/- SD) ratio of the AUC of mycophenolic acid glucuronide (MPAG) to MPA was 64 (+/- 84), which correlated significantly with serum creatinine (r = 0.72) but not with serum bilirubin concentrations (r = 0.309), indicating accumulation of MPAG in patients with renal dysfunction. In 7 primary liver transplant patients on the same dose of MMF, the trough plasma concentrations of MPA during the first week of therapy ranged from < 0.3 to 1.5 microg/ml. The MPA concentrations increased by several folds during the next few weeks, which correlates well with increases in serum albumin concentrations. Changes in albumin appear to partially contribute to the variations in the pharmacokinetics of MPA in liver transplant patients.

Determination of sphinganine, sphingosine and Sa/So ratio in urine of humans exposed to dietary fumonisin B1

Fumonisin B1 (FB1) is an inhibitor of sphinganine N-acyltransferase and the increase in the sphinganine/ sphingosine (Sa/So) ratio in urine or serum has been proposed as a biomarker to evaluate exposure to fumonisins. The objectives of this study were to (1) develop a liquid chromatographic method sufficiently sensitive to determine the low concentration of free Sa in male human urine, and (2) analyse So and Sa in human urine and monitor the Sa/So ratio in urine of humans exposed to FB1 in corn diets over 1 month. The liquid chromatographic method involved isolation from human urine of exfoliated cells followed by an extraction of free sphingoid bases and their separation and quantification by high performance liquid chromatography. The detection limits for So and Sa were 0.15 ng/ml in female urine (2 ml used) and 0.005 ng/ ml in male urine (60 ml used). Twenty-eight healthy adult volunteers consumed for 1 month a normal diet containing their homegrown corn potentially contaminated with FB1. Immediately preceding the start of the test, morning urine samples for the determination of So and Sa were collected from each person, and the corn samples used in cooking were obtained from each family for the determination of FB1. At the end of the test period, morning-urine samples were collected from each person and analysed again. The daily FB1 intakes were estimated and used to assess the relationship between them and the urinary Sa/So ratios in humans exposed to dietary FB1 over 1 month. All the homegrown corn samples contained FB1 ranging from 0.08 to 41.1 mg/kg, and the estimated daily FB1 intakes ranged from 0.4 to 740 microg/kg b.w./day. The 1-month monitoring results suggest that sphingolipid metabolism of humans could be affected by FB1 intake, the urinary Sa/So ratio may be useful for evaluating FB1 exposure when the contamination of FB1 is high, and that males are more sensitive to FB1 disruption of sphingolipid metabolism than females.

Studies on the possible mechanisms of protective activity against alpha-amanitin poisoning by aucubin

Aucubin, an iridoid glucoside, was investigated to determine whether it has a stimulating effect on alpha-amanitin excretion in alpha-amanitin intoxicated rats, and whether there is binding activity to calf thymus DNA. High-performance liquid chromatography (HPLC) analysis of alpha-amanitin in rat urine allowed quantitative measurement of the alpha-amanitin concentration with a detection limit of 50 ng/ml. In this system, a group treated with both alpha-amanitin and aucubin showed that alpha-amanitin was excreted about 1.4 times faster than in the alpha-amanitin only treated group. Our previous results showed that the toxicity of alpha-amanitin is due to specific inhibition of RNA polymerase activity and the resultant blockage of the synthesis of certain RNA species in the nucleus. However, no significant activity change on RNA polymerase from Hep G2 cells was observed when aucubin was treated with alpha-amanitin at any concentration tested. Nevertheless, aucubigenin inhibited both DNA polymerase (IC50, 80.5 microg/ml) and RNA polymerase (IC50, 135.0 microg/ml) from the Hep G2 cells. The potential of both alpha-amanitin and aucubin to interact with DNA were examined by spectrophotometric analysis. Alpha-Amanitin showed no significant binding capacity to calf thymus DNA, but aucubin was found to interact with DNA, and the apparent binding constant (Kapp) and apparent number of binding sites per DNA phosphate (Bapp) were 0.45 x 10(4) M(-1) and 1.25, respectively.

The effect of a single gavage dose of fumonisin B(1) on the sphinganine and sphingosine levels in vervet monkeys

This is the first report of sphinganine (Sa) and sphingosine (So) levels determined in serum and urine of vervet monkeys (Cercopithecus aethiops) dosed with pure fumonisin B(1) (FB(1)). Initially, experimental vervet monkeys were given a single gavage dose of either 1 or 10 mg FB(1) /kg body weight. Blood and urine were sampled daily and on day seven the monkeys were terminated and the kidneys and livers harvested. In a subsequent experiment, other vervet monkeys were similarly dosed and blood and urine samples were collected over a 50-day period. In the high-dose monkeys the serum Sa/So ratio, as well as levels of serum cholesterol and liver function enzymes, increased during the first week after dosing and remained elevated for several weeks thereafter. The urinary Sa/So ratio and the serum renal function indicators showed a more rapid response and a correspondingly more rapid return to pre-dosing levels. In the low-dose monkeys serum Sa and the Sa/So ratio were the only parameters to increase above the control levels. The Sa/So ratio in liver and kidney tissue showed an elevation over controls in a dose-dependent manner. The serum Sa/So ratio was exclusively elevated above the control levels in the low- and high-dose monkeys and seems more relevant as a marker for fumonisin exposure than any of the other indicators.

Metabolism of [(14)C]omapatrilat, a sulfhydryl-containing vasopeptidase inhibitor in humans

Omapatrilat, a potent vasopeptidase inhibitor, is currently under development for the treatment of hypertension and congestive heart failure. This study describes the plasma profile along with isolation and identification of urinary metabolites of omapatrilat from subjects dosed orally with 50 mg of [(14)C]omapatrilat. Only a portion of the radioactivity in plasma was unextractable (40-43%). Prominent metabolites identified in plasma were S-methyl omapatrilat, acyl glucuronide of S-methyl omapatrilat, and S-methyl (S)-2-thio-3-phenylpropionic acid. Omapatrilat accounted for less than 3% of the radioactivity. However, after dithiothreitol reduction all of the radioactivity was extractable and was characterized to be omapatrilat and its hydrolysis product (S)-2-thio-3-phenylpropionic acid, both apparently bound to proteins via reversible disulfide bonds. Urinary profile of radioactivity showed no parent compound but the presence of several metabolites that can be grouped into three categories. 1) Three metabolites, accounting for 56% of the urinary radioactivity, resulted from the hydrolysis of the exocyclic amide bond of omapatrilat. Two metabolites were diastereomers of S-methyl sulfoxide of (S)-2-thio-3-phenylpropionic acid, and the third was the acyl glucuronide of S-methyl (S)-2-thio-3-phenylpropionic acid. 2) One disulfide, identified as the L-cysteine mixed disulfide of omapatrilat, accounted for 8% of the radioactivity in the urine. 3) Five metabolites, derived from omapatrilat, accounted for 30% of the radioactivity in the urine. Two of these metabolites were mixtures of diastereomers of S-methyl sulfoxide of omapatrilat and the third was the S-methyl omapatrilat ring sulfoxide. The other two metabolites were S-methyl omapatrilat and its acyl glucuronide. These results indicate that omapatrilat undergoes extensive metabolism in humans.

A cutaneous full-thickness liquid sulfur mustard burn model in weanling swine: clinical pathology and urinary excretion of thiodiglycol

Sulfur mustard (bis(2-chloroethyl)sulfide, HD) is a well-known blistering chemical warfare agent. We have developed a cutaneous full-thickness HD burn model in weanling pigs for efficacy testing of candidate treatment regimens. This report addresses clinical pathology findings and the urinary excretion profile of a major HD metabolite (thiodiglycol, TDG) in this model. Six female Yorkshire pigs were exposed to HD liquid on the ventral surface for 2 h, generating six 3-cm diameter full-thickness dermal lesions per pig. Blood samples were collected throughout a 7-day observation period for hematology and serum chemistry examinations. Urine was collected in metabolism cages. Routine urinalysis was performed and the urine analyzed for TDG using gas chromatography/mass spectrometry. Examination of clinical pathology parameters revealed subtle HD-related changes that are suggestive of a mild hemolytic episode. No other signs of clinically significant systemic toxicities were noted, including bone marrow suppression. Thiodiglycol was detected at the earliest time point tested (6-8 h post-exposure) at levels ranging from 0.66 to 4.98 microg ml(-1) with a mean of 2.14 microg ml(-1). Thiodiglycol concentrations were the highest for half of the animals at this earliest time point and at 24-48 h for the others. By the evening of day 3, the mean level had reached 50 ng ml(-1). Mean levels remained 10-40 ng ml(-1) for the remainder of the 7-day observation period, with the highest individual concentration noted during this period of 132 ng ml(-1). Our results are in general agreement with the TDG excretion profiles previously described for rodent models and humans. Urinary excretion of absorbed HD in our weanling pig wound healing model appears to follow the same pattern as is seen in other laboratory animals models. In general, urinary excretion of TDG appears to peak within the first 1-4 days following exposure, with detectable levels after 1 week. Relatively high urinary TDG levels may thus indicate agent exposure within the previous 96 h. Low levels significantly above natural background levels may indicate either exposure to low levels of agent or exposure that occurred more than 4 days prior to collection of the sample.

Use of directly coupled ion-exchange liquid chromatography-mass spectrometry and liquid chromatography-nuclear magnetic resonance spectroscopy as a strategy for polar metabolite identification

Ion-exchange LC-MS and LC-NMR have been successfully used to identify a novel N-acetyl metabolite of a highly polar drug candidate [2-(ethanimidoylamino)ethyl]sulfonyl alanine (GW273629) under development as a therapeutic agent. This has been achieved using a simple HPLC method without the need for complicated and time consuming pre- or post-column derivatisation. Ion-exchange chromatography using simple ionic strength buffer and organic solvent mobile phases, as applied here, should be suitable for the analysis of other charged polar species. Optimisation of the system described could result in the development of a rational generic HPLC approach specifically designed for the characterisation of polar drug molecules and their metabolites.

Inhibitors of Na-K-ATPase in human urine: effects of ouabain-like factors and of vanadium-diascorbate on calcium mobilization in rat vascular smooth muscle cells: comparison with the effects of ouabain, angiotensin II, and arginine-vasopressin

Endogenous ouabain-like factors (OLF) may play a role in the pathogenesis of volume-dependent hypertension by raising intracellular free calcium ([Ca2+]i) as a consequence of inhibition of the sodium pump. In previous studies we described the presence of two low molecular (Mr approximately equals 400) inhibitors of Na-K-ATPase in human urine, ie, a more polar OLF-1 and a more apolar OLF-2. We subsequently identified the active compound in OLF-2 as vanadium (V(IV))-diascorbate (Mr 416). OLF-1, OLF-2, and V-diascorbate inhibited dose-dependently porcine Na-K-ATPase in vitro. In the present study we investigated the effects of urinary OLF-1, OLF-2, and V-diascorbate on calcium mobilization, ie, on [Ca2+]i in cultured rat vascular smooth muscle (VSM) cells in comparison to the effects of ouabain, angiotensin II (A II), and arginine-vasopressin (AVP). [Ca2+]i was determined by the fura-2 method. OLF-1 and OLF-2 (each approximately equals 10(-4) mol/L), obtained as single spots by thin-layer chromatography, produced a rise in [Ca2+]i in VSM cells from 45 +/- 7 to 99 +/- 22 and from 48 +/- 9 to 92 +/- 2 nmol/L (each n = 5; P < .05), respectively, after 3 min. V-diascorbate also increased [Ca2+]i slowly and dose-dependently, eg, from 56 +/- 14 to 102 +/- 15 nmol/L at a concentration of 10(-6) mol/L (n = 5; P < .05) after 3 min. A similar slow rise in [Ca2+]i from 53 +/- 10 to 185 +/- 3 nM (n = 5; P < .05) after 3 min was found with ouabain (10(-6) mol/L). As standard vasoconstrictor, All (10(-8) mol/L) rapidly increased [Ca2+]i from 23 +/- 4 to 846 +/- 50 nmol/L (n = 7; P < .01) within 30 sec. This effect was enhanced to 1,389 +/- 161 nM (n = 7; P < .01) when VSM cells were preincubated with V-diascorbate (10(-6) mol/L) for 10 min. AVP (10(-7) mol/L) also rapidly increased [Ca2+]i to 418 +/-11 nmol/L within 30 sec (n = 7; P < .01). This effect was enhanced in the presence of OLF-2 (approximately equals 10(-4) mol/L) or ouabain (10(-6) mol/L) to 523 +/- 14 and 560 +/- 19 nmol/L, respectively (each n = 7); P < .01). The calcium channel blocker verapamil, the intracellular calcium release blocker TMB-8, and the unselective cation channel blocker Ni2+ partly blunted the A II- or AVP-induced rise in [Ca2+]i and prevented the OLF-2- and V-diascorbate-induced increase in [Ca2+]i. Thus, OLF-1, OLF-2 and V-diascorbate, the active component of OLF-2, reveal effects similar to those of ouabain on [Ca2+]i in VSM cells, ie, they produce a slow rise in [Ca2+]i subsequent to inhibition of the sodium pump. The physiologic and pathologic roles of these and additional OLF in body fluid and blood pressure regulation and in hypertension have yet to be evaluated.

Species differences in oral bioavailability of methotrexate between rats and monkeys

The contributions of incomplete absorption and a first-pass effect to the low bioavailability (BA) of methotrexate (MTX) were evaluated pharmacokinetically in rats and monkeys which respectively have a lower and higher aldehyde oxidase (AO) activity than humans. Plasma concentration profiles of MTX in rats showed linear and nonlinear pharmacokinetics respectively after intravenous (i.v.) and oral dosing of 0.1, 0.5 or 2.5 mg/kg MTX. In rats, most of the dose was excreted as the parent compound into bile and urine after i.v. dosing of 0.5 mg/kg MTX, while the radioactivity was largely eliminated in expired air after oral dosing of 0.5 mg/kg 14C-MTX. Elimination in expired air fell markedly following antibiotics treatment. 7-Hydroxymethotrexate (7-OH-MTX), formed from MTX by AO, was detected in monkey plasma after i.v. and oral dosing of 0.5 mg/kg MTX, but not in rat plasma. The ratio of the cumulative urinary excretion of 7-OH-MTX to MTX in monkeys was higher after oral dosing than after i.v. dosing. The low BA in rats (10% at 0.5 mg/kg) was shown to be mainly due to incomplete absorption, including limited absorption and degradation to 2,4-diamino-N10-methylpteroic acid (DAMPA) and glutamic acid (Glu) by the carboxypeptidase of intestinal bacteria. The low BA in monkeys (5% at 0.5 mg/kg) was shown to be mainly due to the extensive first-pass effect, including metabolism to 7-OH-MTX.

Automated quantitative determination of the new renin inhibitor CGP 60536 by high-performance liquid chromatography

A fully automated high-performance liquid chromatography method with fluorescence detection for the determination of the renin inhibitor CGP 60536 in animal and human plasma and urine has been developed and validated. After addition of an internal standard, the compounds were automatically extracted from 400 microl of plasma or urine with methyl alcohol-acetic acid (99:1, v/v) on 100-mg Bond-Elut CN cartridges using the Gilson ASPEC system. The on-line chromatographic separation was performed on a LiChrospher 100 RP8 5-microm particle size packed analytical column (25x0.4 cm I.D.). The mobile phase consisted of acetonitrile-0.01 M potassium dihydrogenphosphate (65:35, v/v) at a flow-rate of 0.8 ml/min. The analytes were detected using a fluorescence detector at excitation and emission wavelengths of 280 and 330 nm, respectively. The limit of quantitation was established at 4.5 ng/ml in plasma (accuracy 106% and precision 1%), and 9.0 ng/ml in urine (accuracy 101% and precision 13%). The method was applied to the investigation of the pharmacokinetics of CGP 60536.

Phenolphthalein metabolite inhibits catechol-O-methyltransferase-mediated metabolism of catechol estrogens: a possible mechanism for carcinogenicity

Phenolphthalein (PT), used in over-the-counter laxatives, has recently been identified as a multisite carcinogen in rodents, but the molecular species responsible for the carcinogenicity is not known. A catechol metabolite of PT, hydroxyphenolphthalein (PT-CAT), was recently identified and may be the molecular species responsible for at least part of the toxicity/carcinogenicity of PT. We hypothesize that PT-CAT inhibits the enzyme catechol-O-methyltransferase (COMT) and therefore potentiates genotoxicity by either PT-CAT itself or the endogenous catechol estrogens (CEs) in susceptible tissues. The present studies were conducted to determine the effects of PT treatment and PT-CAT itself on the COMT-mediated metabolism of 4- and 2-hydroxyestradiol both in vitro and in vivo. Female mice were treated with PT (50 mg/kg/d) for 21 days and then euthanized. PT-CAT concentration in urine reached plateau levels by 7 days of exposure. An O-methylated metabolite of PT-CAT was detected in feces. In vitro experiments demonstrated that PT treatment resulted in an increase in free CEs, which are normally cleared by COMT and a concurrent decrease in the capacity of hepatic catechol clearance by COMT. In vitro, PT-CAT was a substrate of COMT, with kinetic properties within the range measured with endogenous substrates. PT-CAT was an extremely potent mixed-type inhibitor of the O-methylation of the catechol estrogens, with 90-300 nM IC50s. The above data, when taken together, suggest that chronic administration of PT may enhance metabolic redox cycling of both PT-CAT and the catechol estrogens and this, in turn, may contribute to PT-induced tumorigenesis.

Endogenous inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 do not explain abnormal cortisol metabolism in polycystic ovary syndrome

OBJECTIVE

The aetiology of enhanced adrenal androgen secretion in polycystic ovary syndrome is poorly understood. Previous reports suggest that enhanced peripheral metabolism of cortisol results in decreased negative feedback suppression of ACTH secretion, either by enhanced inactivation of cortisol by 5alpha-reductase or impaired reactivation of cortisol by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). Endogenous inhibitors of hepatic 11beta-HSD1 can be extracted from urine. We have tested the hypothesis that these are increased in patients with polycystic ovary syndrome.

DESIGN

A case-control study.

PATIENTS

57 patients with polycystic ovary syndrome and 27 healthy control women.

MEASUREMENTS

Aliquots from 24 h urine samples were extracted with Sep-Paks and incubated with rat liver microsomes in which 11beta-HSD1 activity was quantified by conversion of 3H-corticosterone to 3H-11-dehydrocorticosterone.

RESULTS

Inhibition of 11beta-HSD1 activity was not different in extracts from patients compared with controls (40.8 +/- 18.9 arbitrary units in patients vs. 42.7 +/- 16.6 in controls, mean (+/- SEM, P > 0.60) and did not correlate with ratios of cortisol metabolites in urine or with body mass index.

CONCLUSIONS

The altered cortisol metabolism in polycystic ovarian syndrome, which is consistent with impaired 11beta-HSD1 activity, cannot be accounted for by increased production of measurable endogenous inhibitors of this enzyme.

Biotransformation of the xanthine oxidase inhibitor BOF-4272 and its metabolites in the liver and by the intestinal flora in rat

1. BOF-4272, (+/-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one), is a new drug intended for the treatment of hyperuricaemia. 2. This paper describes the detailed biotransformation of BOF-4272 and its metabolites in the liver and by the intestinal flora in rat. 3. Only the sulphoxide metabolite (M6) was detected in plasma in small amounts after the intravenous administration of M4 (hydroxy-BOF-4272) and in culture medium after the addition of M4. 4. Only M3 (the sulphide metabolite of M4) was detected in faeces, and its amount was approximately 50% of the administered dose within 1 day after the intravenous administration of M4. 5. These findings suggest that M4, which is excreted in the bile, is metabolized mainly to M3 (the corresponding sulphide of M4) by the intestinal flora in rat, whereas little M4 is metabolized to the sulphoxide (M6) in the rat liver. 6. M2, which is the demethylated form of BOF-4269, was detected in faeces after the oral administration of BOF-4272 to rat in which the common bile duct was cannulated, suggesting that BOF-4272 is metabolized to BOF-4269 and then to M2 by the intestinal flora. 7. These findings suggest that in rat the sulphoxide of BOF-4272 and its metabolites are demethylated and reduced by the intestinal flora, with other types of biotransformation occurring in the liver.

Metabolic pathways and pharmacokinetics of BOF-4272, a sulfoxide-containing drug, in the dog: in vivo and in vitro studies

BOF-4272, (+/-)-8-(3-methoxy-4- phenylsulfinylphenyl)pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one, is a new drug intended for the treatment of hyperuricemia. This report describes the detailed metabolic pathways of BOF-4272 in the dog. The metabolic pathways were investigated using the metabolites found in plasma, urine, and feces after intravenous or oral administration of BOF-4272, as well as the metabolites found in the liver S9 incubation mixture after the addition of BOF-4272 or BOF-4269. BOF-4269 (the sulfide metabolite of BOF-4272) was the only metabolite detected in plasma and feces after the intravenous or oral administration of BOF-4272. BOF-4269 was detected in dog plasma after a lag time following the oral administration of BOF-4272, and the Cmax and AUC0-t of BOF-4269 were higher in fed dogs than in fasted dogs after the oral administration of BOF-4272. A small amount of BOF-4269 was detected in dog plasma immediately after the intravenous administration of BOF-4272. Only BOF-4276 (the sulfone metabolite of BOF-4272) was detected in the S9 incubation mixture after the addition of BOF-4272. Mainly BOF-4272 was detected and small amounts of BOF-4276 and M-1 (the hydroxy metabolite of BOF-4269) were detected in the S9 incubation mixture after the addition of BOF-4269. These findings suggest that BOF-4272 is mainly metabolized to BOF-4269 by the intestinal flora in dogs, whereas little of this drug is metabolized to BOF-4269 in the dog liver. In conclusion, this work has allowed us to formulate the proposed metabolic pathways of BOF-4272 in the dog.