Development and validation of an HPLC-MS/MS analytical method for quantitative analysis of TCBA-TPQ, a novel anticancer makaluvamine analog, and application in a pharmacokinetic study in rats.

We have recently designed and synthesized several novel iminoquinone anticancer agents that have entered preclinical development for the treatment of human cancers. Herein we developed and validated a quantitative HPLC-MS/MS analytical method for one of the lead novel anticancer makaluvamine analog, TCBA-TPQ, and conducted a pharmacokinetic study in laboratory rats. Our results indicated that the HPLC-MS/MS method was precise, accurate, and specific. Using this method, we carried out in vitro and in vivo evaluations of the pharmacological properties of TCBA-TPQ and plasma pharmacokinetics in rats. Our results provide a basis for future preclinical and clinical development of this promising anticancer marine analog.

Relationship Between Sunitinib Pharmacokinetics and Administration Time: Preclinical and Clinical Evidence.

BACKGROUND AND OBJECTIVE: Circadian rhythms may influence the pharmacokinetics of drugs. This study aimed to elucidate whether the pharmacokinetics of the orally administered drug sunitinib are subject to circadian variation. METHODS: We performed studies in male FVB-mice aged 8-12 weeks, treated with single-dose sunitinib at six dosing times. Plasma and tissue samples were obtained for pharmacokinetic analysis and to monitor messenger RNA (mRNA) expression of metabolizing enzymes and drug transporters. A prospective randomized crossover study was performed in which patients took sunitinib once daily at 8 a.m., 1 p.m., and 6 p.m at three subsequent courses. Patients were blindly randomized into two groups, which determined the sequence of the sunitinib dosing time. The primary endpoint in both studies was the difference in plasma area under the concentration-time curve (AUC) of sunitinib and its active metabolite SU12662 between dosing times. RESULTS: Sunitinib and SU12662 plasma AUC in mice followed an ~12-h rhythm as a function of administration time (p ≤ 0.04). The combined AUC from time zero to 10 h (AUC10) was 14-27 % higher when sunitinib was administered at 4 a.m. and 4 p.m. than at 8 a.m. and 8 p.m. Twenty-four-hour rhythms were seen in the mRNA levels of drug transporters and metabolizing enzymes. In 12 patients, sunitinib trough concentrations (C trough) were higher when the drug was taken at 1 p.m. or 6 p.m. than when taken at 8 a.m. (C trough-1 p.m. 66.0 ng/mL; C trough-6 p.m. 58.9 ng/mL; C trough-8 a.m. 50.7 ng/mL; p = 0.006). The AUC was not significantly different between dosing times. CONCLUSIONS: Our results indicate that sunitinib pharmacokinetics follow an ~12-h rhythm in mice. In humans, morning dosing resulted in lower C trough values, probably resulting from differences in elimination. This can have implications for therapeutic drug monitoring.

The influence of the time-of-day administration of the drug on the pharmacokinetics of sunitinib in rabbits.

OBJECTIVES: At present it is known that the adjustment of the anticancer therapy to the circadian rhythms in tissues reduces the toxicity of the treatment. Chronotherapy also increases the efficacy of the anticancer treatment, which has been proved for many drugs. Sunitinib is a tyrosine kinase inhibitor, which is broadly used for the treatment of numerous cancers. The aim of the study was a comparison of the concentrations and pharmacokinetics of sunitinib after a single administration to rabbits at 08:00 (control group) and 20:00. Additionally, the effect of sunitinib on glucose levels was investigated. MATERIALS AND METHODS: The research was carried out on two groups of rabbits: I08:00, a group with the drug administered at 08:00 (n=8) and II20:00, a group with the drug administered at 20:00 (n=8). The rabbits were treated with sunitinib at an oral dose of 25 mg. Plasma concentrations of sunitinib and its metabolite (SU12662) were measured with a validated HPLC method with UV detection. RESULTS: The comparison of the sunitinib Cmax and AUC0-t in the group with sunitinib administered at 20:00 with the control group gave the ratios of 2.20 (90% confidence interval (CI) (2.17; 2.22) and 1.64 (1.61; 1.68), respectively. Statistically significant differences between the groups under analysis were revealed for Cmax (p < 0.0001), AUC0-t (p = 0.0079), AUC0-∞ (p = 0.0149), and tmax (p = 0.0085). The mean glycemia drop was higher in group I08:00. than in group II20:00 (22.7% vs. 14.3%; p = 0.0622). The glycemia values returned to the initial values in 24 h after the administration of the drug in both groups. CONCLUSIONS: The research proved a significant influence of the time-of-day administration on the pharmacokinetics of sunitinib.

High-dose supplementation with natural α-tocopherol does neither alter the pharmacodynamics of atorvastatin nor its phase I metabolism in guinea pigs.

It has been hypothesized in the literature that intake of high-dosage vitamin E supplements might alter the expression of cytochrome P(450) enzymes (CYP), particularly CYP3A4, which may lead to adverse nutrient-drug interactions. Because previously published studies reported conflicting findings, we investigated the pharmacodynamics of the lipid-lowering drug atorvastatin (ATV), a CYP3A4 substrate, in response to high-dose α-tocopherol (αT) feeding and determined protein expression and activities of relevant CYP. Groups of ten female Dunkin-Hartley guinea pigs were fed a control (5% fat) or a high-fat control diet (HFC; 21% fat, 0.15% cholesterol) or the HFC diet fortified with αT (250 mg/kg diet), ATV (300 mg/kg diet) or both ATV+αT for 6 weeks. Relative to control, HFC animals had increased serum cholesterol concentrations, which were significantly reduced by ATV. High-dose αT feeding in combination with ATV (ATV+αT), albeit not αT feeding alone (αT), significantly lowered serum cholesterol relative to HFC, but did not alter the cholesterol-lowering activity of the drug compared to the ATV treated guinea pigs. Protein expression of CYP3A4, CYP4F2, CYP20A1 and OATP C was similar in all groups. Accordingly, no differences in plasma concentrations of phase I metabolites of ATV were observed between the ATV and ATV+αT groups. In conclusion, feeding guinea pigs high-doses of αT for 6 weeks did neither alter the hepatic expression of CYP, nor the pharmacodynamics and metabolism of ATV. High-dose αT intake is thus unlikely to change the efficacy of drugs metabolized by CYP enzymes, particularly by CYP3A4.

Evidence for therapeutic drug monitoring of targeted anticancer therapies.

Therapeutic drug monitoring (TDM) provides valuable guidance for dose adjustment of antibiotics, immunosuppressives, antiepileptics, and other drugs, but its use for traditional anticancer therapies has been limited. Perhaps the most important obstacle is the impractical requirement of multiple blood samples to adequately define systemic exposure of drugs that have a short elimination half-life and are given by intermittent intravenous injections. However, the newer targeted anticancer therapies have different pharmacokinetic (PK) and dosing characteristics compared with traditional cytotoxic drugs, making it possible to estimate the steady-state drug exposure with a single trough-level measurement. Recent evidence indicates that certain PK parameters, including trough levels, are correlated with clinical outcomes for many of these agents, including imatinib, sunitinib, rituximab, and cetuximab. Although the current evidence is insufficient to mandate TDM in routine practice, a concerted investigation should be encouraged to determine whether the steady-state trough measurements of targeted agents will have a practical place in the clinical care of patients with cancer.

Assessment of exposure of metabolites in preclinical species and humans at steady state from the single-dose radiolabeled absorption, distribution, metabolism, and excretion studies: a case study.

The exposure of a drug candidate and its metabolites in humans and preclinical species during drug development needs to be determined to ensure that the safety of drug-related components in humans is adequately assessed in the standard toxicology studies. The in vivo radiolabeled studies in preclinical species and human volunteers provide the total fate of the drug-derived radioactivity including the relative abundance of metabolites. Here, we describe how the single-dose radiolabeled human studies could provide the exposure of circulating metabolites at steady state using a case study of an extensively metabolized drug, lixivaptan. After an oral dose of [(14)C]lixivaptan to humans, a total of nine metabolites were detected in the systemic circulation; eight of them exceeded 10% of the parent exposure (2-41% of total radioactivity). The plasma samples were profiled for all subjects at each time point by high-performance liquid chromatography, and metabolites were quantified using a radioactive detector. On the basis of single-dose area under the concentration-time curve (AUC) values, exposure of six human metabolites was greater at least in one preclinical species used in toxicology evaluation. On the basis of the t(1/2) of lixivaptan and two major metabolites from a single dose in humans, their AUC and C(max) values were simulated at the steady state. The simulated exposure (C(max) and AUC) values of parent drug and the two most abundant metabolites were similar to those from a 7-day clinical study obtained using a validated liquid chromatography-mass spectrometry assay, suggesting that a well designed single-dose radiolabeled human study can help in addressing the metabolites in safety testing-related issues.

Effects of Ginkgo biloba extracts on pharmacokinetics and efficacy of atorvastatin based on plasma indices.

Ginkgo biloba extract (GBE) is one of the most widely used herbal medicines in the world. It is often administered in combination with statins to treat diseases, especially some nervous system disorders. We aimed to investigate the influences of GBE on pharmacokinetics and efficacy of atorvastatin, which are currently unclear. Sixteen volunteers received a single oral dose of 40 mg atorvastatin, followed by a wash-out period of at least 5 days. Then the volunteers took 360 mg GBE daily for 14 days, followed by a single dose of 40 mg atorvastatin. Serial blood samples obtained over a period of 48 h after atorvastatin ingestion were subjected to determination of atorvastatin plasma concentrations and markers of cholesterol synthesis (lathosterol) and cholesterol absorption (sitosterol). With GBE administration, AUC0₋48, AUC(0-∞) and C(max) of atorvastatin were reduced by 14.27% (p = 0.005), 10.00% (p = 0.03) and 28.93% (p = 0.002), respectively; Vd/F and CL/F of atorvastatin were increased by 31.95% (p = 0.017) and 6.48% (p = 0.044). After 14 days of treatment, GBE has no significant effects on cholesterol-lowering efficacy of atorvastatin. This study suggests that GBE slightly decreases the plasma atorvastatin concentrations, but has no meaningful effect on the cholesterol-lowering efficacy of atorvastatin.

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.

Definitive diagnosis of hepatic sinusoidal obstruction syndrome induced by pyrrolizidine alkaloids.

OBJECTIVE: Hepatic sinusoidal obstruction syndrome (HSOS) induced by a Chinese medicinal herb Tusanqi is increasingly being reported in recent years. The aim of the study was to investigate the possibility of using blood pyrrole-protein adducts test as a confirmatory diagnostic method. METHODS: Patients with HSOS according to international diagnostic criteria associated with Tusanqi from January 2006 to August 2010 in Zhongshan Hospital Fudan University were included and clinical features were collected. Pyrrole-protein adducts in blood sample were determined with ultra performance liquid chromatography-mass spectrometry (UPLC-MS) while pyrrolizidine alkaloids (PAs) in available herbal preparations were analyzed by high performance liquid chromatography-ultraviolet (HPLC-UV). RESULTS: Five patients (age 41-72 years, median age 54 years, all women) were included. Ascites (5/5), jaundice (5/5) and hepatomegaly (4/5) were common manifestations. The imaging features were diffused, patchy hepatic enhancement, periportal edema and ascites. Pathology ascertained that blood flow was obstructive at the site of sinusoid. PAs (Seneionine and seneciphylline) were identified in all the three available herbal preparations ingested by the HSOS patients. Pyrrole-protein adducts were unequivocally found in all the five blood samples. Two patients recovered, two developed chronic illness and one died due to liver failure and hepatic encephalopathy. CONCLUSIONS: The detection of blood pyrrole-protein adducts using a UPLC-MS approach is a specific, reliable, unambiguous and confirmatory test for HSOS induced by PA, and should be used together with the conventional HSOS clinical diagnostic criteria for the definitive diagnosis of PA-induced HSOS.

The effect of the newly developed angiotensin receptor II antagonist fimasartan on the pharmacokinetics of atorvastatin in relation to OATP1B1 in healthy male volunteers.

OBJECTIVE: Interactions between coadministered drugs may unfavorably affect pharmacokinetics. This study evaluated whether fimasartan, an angiotensin receptor II antagonist, affected the pharmacokinetics of atorvastatin. METHODS: A randomized, open-label, 2-period, 2-sequence, crossover, multiple-dosing study was conducted with 24 healthy male volunteers. Twelve subjects received 80-mg atorvastatin once daily for 7 days; later, they received 80-mg atorvastatin with 240-mg fimasartan for 7 days. Twelve other subjects received the same drugs in the opposite sequence. Blood samples were collected scheduled intervals for 24 hours after the last dosing to determine plasma concentrations of atorvastatin acid, atorvastatin lactone, 2-hydroxy atorvastatin acid, and 2-hydroxy atorvastatin lactone. RESULTS: Compared with atorvastatin alone, coadministration of fimasartan and atorvastatin increased the atorvastatin acid mean (95% confidence interval) maximum concentration (Cmax,ss) by 1.89-fold (1.49-2.39) and the area under the concentration curve (AUCτ,ss) by 1.19-fold (0.96-1.48). Fimasartan also increased the mean 2-hydroxy atorvastatin acid Cmax,ss and AUCτ,ss by 2.45-fold (1.80-3.35) and 1.42-fold (1.09-1.85), respectively. The Cmax,ss and AUCτ,ss of the lactone forms of atorvastatin showed smaller changes than those observed for the acidic forms. CONCLUSION: We showed that fimasartan raised plasma atorvastatin concentrations. In vitro tests suggested that this effect may have been mediated by fimasartan inhibition of organic anion-transporting polypeptide 1B1.

Interaction of green tea polyphenol epigallocatechin-3-gallate with sunitinib: potential risk of diminished sunitinib bioavailability.

Sunitinib, a novel oral multi-targeted tyrosine kinase inhibitor for patients with metastatic renal cell carcinoma (mRCC) and advanced gastrointestinal stromal tumor, has a good prospect for clinical application and is being investigated for the potential therapy of other tumors. We observed the phenomenon that drinking tea interfered with symptom control in an mRCC patient treated with sunitinib and speculated that green tea or its components might interact with sunitinib. This study was performed to investigate whether epigallocatechin-3-gallate (EGCG), the major constituent of green tea, interacted with sunitinib. The interaction between EGCG and sunitinib was examined in vitro and in vivo. (1)H nuclear magnetic resonance ((1)H-NMR) spectroscopy and mass spectrometry (MS) were used to analyze the interaction between these two molecules and whether a new compound was formed. Solutions of sunitinib and EGCG were intragastrically administered to rats to investigate whether the plasma concentrations of sunitinib were affected by EGCG. In this study, we noticed that a precipitate was formed when the solutions of sunitinib and EGCG were mixed under both neutral and acidic conditions. (1)H-NMR spectra indicated an interaction between EGCG and sunitinib, but no new compound was observed by MS. Sticky semisolid contents were found in the stomachs of sunitinib and EGCG co-administrated mice. The AUC(0-∞) and C (max) of plasma sunitinib were markedly reduced by co-administration of EGCG to rats. Our study firstly showed that EGCG interacted with sunitinib and reduced the bioavailability of sunitinib. This finding has significant practical implications for tea-drinking habit during sunitinib administration.

Pneumatosis intestinalis associated with treatment of cancer patients with the vascular growth factor receptor tyrosine kinase inhibitors sorafenib and sunitinib.

Recently, pneumatosis intestinalis has been described in patients receiving bevacizumab, a monoclonal antibody to VEGF-A. Pneumatosis intestinalis is a condition characterized by subserosal and submucosal gas-filled cysts in the gastrointestinal tract. We report on pneumatosis intestinalis in patients receiving oral anti-VEGF agents. Patients shared the following characteristics: long-term (> 4 months) exposure to anti-VEGF agents, lack of other factors predisposing to pneumatosis intestinalis, and lack of recent surgical intervention. Taken together, these observations suggest that pneumatosis intestinalis is a probable class-effect of anti-VEGF agents.

Therapeutic Drug Monitoring of the new targeted anticancer agents imatinib, nilotinib, dasatinib, sunitinib, sorafenib and lapatinib by LC tandem mass spectrometry.

The treatment of some cancer patients has shifted from traditional, non-specific cytotoxic chemotherapy to chronic treatment with molecular targeted therapies. Imatinib mesylate, a selective inhibitor of tyrosine kinases (TKIs) is the most prominent example of this new era and has opened the way to the development of several additional TKIs, including sunitinib, nilotinib, dasatinib, sorafenib and lapatinib, in the treatment of various hematological malignancies and solid tumors. All these agents are characterized by an important inter-individual pharmacokinetic variability, are at risk for drug interactions, and are not devoid of toxicity. Additionally, they are administered for prolonged periods, anticipating the careful monitoring of their plasma exposure via Therapeutic Drug Monitoring (TDM) to be an important component of patients' follow-up. We have developed a liquid chromatography-tandem mass spectrometry method (LC-MS/MS) requiring 100 microL of plasma for the simultaneous determination of the six major TKIs currently in use. Plasma is purified by protein precipitation and the supernatant is diluted in ammonium formate 20 mM (pH 4.0) 1:2. Reverse-phase chromatographic separation of TKIs is obtained using a gradient elution of 20 mM ammonium formate pH 2.2 and acetonitrile containing 1% formic acid, followed by rinsing and re-equilibration to the initial solvent composition up to 20 min. Analyte quantification, using matrix-matched calibration samples, is performed by electro-spray ionization-triple quadrupole mass spectrometry by selected reaction monitoring detection using the positive mode. The method was validated according to FDA recommendations, including assessment of extraction yield, matrix effects variability (<9.6%), overall process efficiency (87.1-104.2%), as well as TKIs short- and long-term stability in plasma. The method is precise (inter-day CV%: 1.3-9.4%), accurate (-9.2 to +9.9%) and sensitive (lower limits of quantification comprised between 1 and 10 ng/mL). This is the first broad-range LC-MS/MS assay covering the major currently in-use TKIs. It is an improvement over previous methods in terms of convenience (a single extraction procedure for six major TKIs, reducing significantly the analytical time), sensitivity, selectivity and throughput. It may contribute to filling the current knowledge gaps in the pharmacokinetics/pharmacodynamics relationships of the latest TKIs developed after imatinib and better define their therapeutic ranges in different patient populations in order to evaluate whether a systematic TDM-guided dose adjustment of these anticancer drugs could contribute to minimize the risk of major adverse reactions and to increase the probability of efficient, long lasting, therapeutic response.

Effects of vitamin D supplementation in atorvastatin-treated patients: a new drug interaction with an unexpected consequence.

The objective of this study was to determine vitamin D supplementation effects on concentrations of atorvastatin and cholesterol in patients. Sixteen patients (8 men, 8 women; 10 Caucasians, 4 African Americans, 1 Hispanic, 1 Asian), aged 63 +/- 11 years (mean +/- SD, weight 92 +/- 31 kg) on atorvastatin (45 +/- 33 mg/day) were studied with and without supplemental vitamin D (800 IU/day for 6 weeks). Levels of vitamin D (1,25-dihydroxy(OH) and 25 OH-metabolites), atorvastatin (parent, OH-acid metabolites, lactone, and lactone metabolites), and cholesterol (total, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol) were determined at 0.5, 3, and 10 h after dosing. Vitamin D supplementation increased vitamin D-25-OH metabolites (P < 0.0001) without increased 1,25-dihydroxy vitamin D. Atorvastatin and active metabolite concentrations (P < 0.001) as well as LDL-cholesterol and total-cholesterol levels (97 +/- 28 mg/dl vs. 83 +/- 30 and 169 +/- 35 mg/dl vs. 157 +/- 37, P < 0.005) were lower during vitamin D supplementation. The conclusion of the study is that vitamin D supplementation lowers atorvastatin and active metabolite concentrations yet has synergistic effects on cholesterol concentrations.

A preliminary study of atorvastatin plasma concentrations in critically ill patients with sepsis.

OBJECTIVE: A lack of published pharmacokinetic data on statins in sepsis has prompted concerns about their safety and toxicity. This study determined single dose pharmacokinetics of Atorvastatin administered orally to acutely ill patients. DESIGN, SETTING AND PARTICIPANTS: A prospective open label study conducted in a tertiary referral centre on 5 healthy volunteers, 5 acutely ill patients admitted to the medical ward and a heterogeneous cohort of 25 critically ill patients admitted to an intensive care unit. INTERVENTION: All participants received a single oral dose of 20 mg of atorvastatin. MEASUREMENT AND RESULTS: Plasma pharmacokinetics of atorvastatin as measured by maximal plasma concentration (Cmax) and area under the curve (AUC) (0-24 h). Critically ill patients with sepsis had a significantly higher Cmax and AUC as compared to healthy volunteers [110.5(86.5) vs. 5.9(2.50) ng/ml, p < 0.01 and 1,051(810) vs. 67(48) ng h/ml (p < 0.0001)], respectively. Atorvastatin concentrations in the plasma of critically ill patients with sepsis remained supratherapeutic for up to 20 h after a single dose. The AUC was significantly higher for those patients on concomitant CYP 450 inhibitor therapy as compared to those patients not on inhibitors (1,518 +/- 793 vs. 584 +/- 540 ng h/ml, p = 0.0260). CONCLUSIONS: Very high plasma concentrations were achieved in intensive care patients with sepsis. This can only be partly explained by altered metabolism of atorvastatin. Further investigations are essential to better describe the pharmacokinetics of statins in various groups of critically ill patients. Caution should be exercised prior to adopting high dose regimens in patients with severe sepsis.

Discerning the Mauve factor, Part 2.

"Mauve Factor" was once mistaken for kryptopyrrole but is the hydroxylactam of hemopyrrole, hydroxyhemopyrrolin-2-one (HPL). Treatment with nutrients--particularly vitamin B6 and zinc--reduces urinary excretion of HPL and improves diverse neurobehavioral symptoms in subjects with elevated urinary HPL. Heightened HPL excretion classically associates with emotional stress, which in turn is known to associate with oxidative stress. For this review, markers for nutritional status and for oxidative stress were examined in relationship to urinary HPL. In cohorts with mixed diagnoses, 24-hour urinary HPL correlated negatively with vitamin B6 activity and zinc concentration in red cells (P < .0001). Above-normal HPL excretion corresponded to subnormal vitamin B6 activity and subnormal zinc with remarkable consistency. HPL correlated inversely with plasma GSH and red-cell catalase, and correlated directly with plasma nitric oxide (P < .0001). Thus, besides implying proportionate needs for vitamin B6 and zinc, HPL is a promising biomarker for oxidative stress. HPL is known to cause non-erythroid heme depression, which lowers zinc, increases nitric oxide, and increases oxidative stress. Administration of prednisone reportedly provoked HPL excretion in animals. Since adrenocorticoid (and catecholamine) stress hormones mediate intestinal permeability, urinary HPL was examined in relationship to urinary indicans, presumptive marker for intestinal permeability. Urinary HPL associated with higher levels ofindicans (P < .0001). Antibiotics reportedly reduce HPL in urine, suggesting an enterobic role in production. Potentially, gut is reservoir for HPL or its precursor, and stress-related changes in intestinal permeability mediate systemic and urinary concentrations.

A rapid and sensitive LC-MS/MS assay to quantify yonkenafil in rat plasma with application to preclinical pharmacokinetics studies.

A novel method for the quantitation of yonkenafil, a new synthetic phosphodiesterase V inhibitor, in rat plasma using high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed. The analyte and internal standard (diazepam) were extracted from plasma (100 microl) by liquid-liquid extraction and separated on a C18 column using 10mM ammonium acetate buffer: methanol (15:85, v/v) as mobile phase in a run time of 3.0 min. The detector was a Q-trap mass spectrometer with an ESI interface operating in the multiple reaction monitoring (MRM) mode. The assay was linear over the concentration range 1.0-1000 ng/ml with a limit of detection of 0.20 ng/ml. Intra- and inter-day precision (as relative standard deviation) were both within 8.45% with good accuracy. The method was successfully applied to a preclinical pharmacokinetic study of yonkenafil in rat after sublingual, oral and intravenous administration. The results demonstrate that the sublingual route gives a higher bioavailablity than the oral route and may represent a useful alternative route of yonkenafil administration.

Discerning the Mauve Factor, Part 1.

"Mauve Factor" was once mistaken for kryptopyrrole but is the hydroxylactam of hemopyrrole, hydroxyhemopyrrolin-2-one (HPL). Treatment with nutrients--particularly vitamin B6 and zinc--reduces urinary excretion of HPL and improves diverse neurobehavioral symptoms in subjects with elevated urinary HPL. Heightened HPL excretion classically associates with emotional stress, which in turn is known to associate with oxidative stress. For this review, markers for nutritional status and for oxidative stress were examined in relationship to urinary HPL. In cohorts with mixed diagnoses, 24-hour urinary HPL correlated negatively with vitamin B6 activity and zinc concentration in red cells (P < .0001). Above-normal HPL excretion corresponded to subnormal vitamin B6 activity and subnormal zinc with remarkable consistency. HPL correlated inversely with plasma glutathione and red-cell catalase, and correlated directly with plasma nitric oxide (P < .0001). Thus, besides implying proportionate needs for vitamin B6 and zinc, HPL is a promising biomarker for oxidative stress. HPL is known to cause non-erythroid heme depression, which lowers zinc, increases nitric oxide, and increases oxidative stress. Administration of prednisone reportedly provoked HPL excretion in animals. Since adrenocorticoid (and catecholamine) stress hormones mediate intestinal permeability, urinary HPL examined in relationship to urinary indicans, presumptive marker for intestinal permeability. Urinary HPL associated with higher levels of indicans (P < .0001). Antibiotics reportedly reduce HPL in urine, suggesting an enterobic role in production. Potentially, gut is a reservoir for HPL or its precursor, and stress-related changes in intestinal permeability mediate systemic and urinary concentrations.

In vitro phase I cytochrome P450 metabolism, permeability and pharmacokinetics of SB639, a novel histone deacetylase inhibitor in preclinical species.

In vitro liver microsomal stability, permeability, pharmacokinetics (PK) and oral bioavailability of SB639, a novel HDACi (Histone Deacetylase inhibitor), were determined. The in vitro metabolism was examined in mouse, rat, dog and human liver microsomes. The permeability and efflux potential of SB639 were determined using Caco-2 cell monolayers. To determine pharmacokinetics and oral bioavailability, blood samples were drawn at pre-determined intervals up to 24 h post-dose after single intravenous (i.v.) or oral (p.o.) administration of SB639 to mouse or rat. The concentrations of SB639 in plasma samples were determined by a validated LC-MS/MS method. In vitro liver microsomal stability data revealed that SB639 was stable in human and dog liver microsomes, unstable in mouse and rat liver microsomes. The Caco-2 data has shown that SB639 is highly permeable with an apparent permeability of 3.01.10(-6) cm/s at 10 microM. After oral administration, maximum concentrations of SB639 were achieved within 0.5 h of post dose. Following i.v. administration, the concentration of SB639 declined in a bi-exponential fashion with terminal elimination half-life of 1.67 h for mice and 1.12 h for rats. The systemic clearance and volume of distribution of SB639 in mice were 15.8 l/h/kg and 38 l/kg, respectively, while the respective values in rats were 3.84 l/h/kg and 3.67 l/kg. Elimination half-life in rats ranged between 1.12-2.26 h. Absolute oral bioavailability of SB639 in mouse and rat was 13% and 10%, respectively. In conclusion, the superior potency, physicochemical and PK properties of SB639 compared to the recently FDA approved drug Zolinza (Suberoylanilide hydroxamic acid or Vorinostat) in the preclinical setting makes it a potential clinical candidate.

Study of a novel indolin-2-ketone compound Z24 induced hepatotoxicity by NMR-spectroscopy-based metabonomics of rat urine, blood plasma, and liver extracts.

Antiangiogenic compound has been believed to be an ideal drug in the current cancer biological therapy, but the angiogenesis inhibitors suffer setback for unknown toxicity now. A novel synthetic indolin-s-ketone small molecular compound, 3Z-3-[((1)H-pyrrol-2-yl)-methylidene]-1-(1-piperidinylmethyl)-1,3-2H-indol-2-one (Z24) can inhibit angiogenesis in new blood vessels. The hepatotoxicity effects of Z24 oral administration (dosed at 60, 130 and 200 mg/kg) have been investigated in female Wistar rats by using metabonomic analysis of (1)H NMR spectra of urine, plasma and liver extracts, as well as by clinical chemistry analysis, liver histopathology and electron micrographs examination. The (1)H NMR spectra of the biofluids were analyzed visually and via pattern recognition by using principal component analysis. The metabonomic trajectory analysis on the time-related hepatotoxicity of Z24 was carried out based on the (1)H NMR spectra of urine samples, which were collected daily predose and postdose over an 8-day period. Urinary excretion of citrate, lactate, 2-oxo-glutarate and succinate increased following Z24 dosing. Increased plasma levels of lactate, TMAO and lipid were observed, with concomitant decrease in the level of glucose and phosphatidylcholine. Metabolic profiling on aqueous soluble extracts of liver tissues with the high dose level of Z24 showed an increase in lactate and glutamine, together with a decrease in glucose, glycogen and choline. On the other hand, studies on lipid soluble extracts of liver tissues with the high dose level of Z24 showed increased level in lipid triglycerides and decreased level in unsaturated fatty acids and phosphatidylcholine. Moreover, the most notable effect of Z24 on the metabolism was the reduction in the urinary levels of creatinine and TMAO and the increase in acetate, citrate, succinate and 2-oxo-glutamate with time dependence. The results indicate that in rats Z24 inhibits mitochondrial function through altering the energy and lipid metabolism, which results in the accumulation of free fatty acids and lactate because of the lack of aerobic respiration. These data show that the metabonomic approach represents a promising new technology for the toxicological mechanism study.