Permeability characteristics of novel aldose reductase inhibitors using rat jejunum in vitro

The aim of this study was to estimate in vivo permeability and bioavailability of epalrestat and newly synthesized compounds with possible therapeutic activity as aldose enzyme inhibitors (ARIs). For this purpose permeability in vitro using rat jejunum mounted in side-by-side diffusion cells was determined. Tested substances were found to be low and moderately permeable and some of them were also substrates for efflux transporters. It was shown, that the higher efflux for some derivatives was due to MRP-2, but not Pgp involvement. Tested ARIs do not share the same efflux transporter with epalrestat, the only ARI currently on the market in Japan. The most permeable compound, a 2,6-difluoro-4-pyrrol-1ylphenol derivative, is not a substrate for efflux transporters and would therefore be the most promising lead compound for further investigation of potent ARIs.

Distribution, metabolism, and excretion of the anti-angiogenic compound SU5416

SU5416, 3-(3,5-dimethyl-1H-pyrrol-2-ylmethylene)-1,3-dihydro-indol-2-one, is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinase, Flk-1/KDR (fetal liver kinase 1/kinase insert domain-containing receptor), also known as VEGF receptor 2 (VEGFR2). It was the first VEGFR2 inhibitor to enter clinical trials for the treatment of colorectal and non-small cell lung cancers. Pre-clinical evaluation of SU5416 included studies related to the distribution, metabolism and excretion of this compound. These studies have provided information useful in understanding the disposition and metabolism of the indolinone class of chemicals, which has not been studied previously with therapeutic intent. The lessons we learned from SU5416 have been successfully applied in developing next generation indolinone compounds targeting tumor angiogenesis.

Sunitinib malate for the treatment of solid tumours: a review of current clinical data

Receptor tyrosine kinases (RTKs) play important roles in the regulation of cellular growth, and mutated or overexpressed RTKs have been implicated in various human cancers. Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor with antitumour and antiangiogenic activity that recently received approval from the FDA for the treatment of advanced renal cell carcinoma and of gastrointestinal stromal tumours after disease progression on or intolerance to imatinib mesilate therapy. Sunitinib has also demonstrated promising clinical activity in the treatment of other advanced solid tumours. The present review provides an updated summary of emerging clinical experience with this promising new anticancer agent.

Pharmacokinetics of atorvastatin and its hydroxy metabolites in rats and the effects of concomitant rifampicin single doses: relevance of first-pass effect from hepatic uptake transporters, and intestinal and hepatic metabolism

Pharmacokinetic coadministration experiments with atorvastatin (ATV) and rifampicin (RIF) in rats were performed to investigate the potential involvement of hepatic uptake transporters, Oatps (organic anion-transporting polypeptides), during hepatic drug elimination, as an in vivo extension of our recently published cellular and isolated perfused liver studies. ATV was administered orally (10 mg/kg) and intravenously (2 mg/kg) to rats in the absence and presence of a single intravenous dose of RIF (20 mg/kg), and pharmacokinetic parameters were compared between control and RIF-treatment groups. RIF markedly increased the plasma concentrations of ATV and its metabolites when ATV was administered orally. The area under the plasma concentration-time curve (AUC(0-infinity)) for ATV also increased significantly after intravenous dosing of ATV with RIF, but the extent was much less than that observed for oral ATV dosing. Significant increases in plasma levels were observed for both metabolites as well. The 7-fold higher AUC ratio of metabolites to parent drug following oral versus intravenous ATV dosing suggests that ATV undergoes extensive gut metabolism. Both hepatic and intestinal metabolism contribute to the low oral bioavailability of ATV in rats. In the presence of RIF, the liver metabolic extraction was significantly reduced, most likely because of RIF's inhibition on Oatp-mediated uptake, which leads to reduced hepatic amounts of parent drug for subsequent metabolism. Gut extraction was also significantly reduced, but we were unable to elucidate the mechanism of this effect because intravenous RIF caused gut changes in availability. These studies reinforce our hypothesis that hepatic uptake is a major contributor to the elimination of ATV and its metabolites in vivo.

Kinesin spindle protein (KSP) inhibitors. Part 3: Synthesis and evaluation of phenolic 2,4-diaryl-2,5-dihydropyrroles with reduced hERG binding and employment of a phosphate prodrug strategy for aqueous solubility

2,4-Diaryl-2,5-dihydropyrroles have been discovered to be novel, potent and water-soluble inhibitors of KSP, an emerging therapeutic target for the treatment of cancer. A potential concern for these basic KSP inhibitors (1 and 2) was hERG binding that can be minimized by incorporation of a potency-enhancing C2 phenol combined with neutral N1 side chains. Aqueous solubility was restored to these, and other, non-basic inhibitors, through a phosphate prodrug strategy.

Effect of food on the pharmacokinetics of sunitinib malate (SU11248), a multi-targeted receptor tyrosine kinase inhibitor: results from a phase I study in healthy subjects

The effect of food on the oral bioavailability of sunitinib malate (SU11248, an oral, multi-targeted tyrosine kinase inhibitor with anti-angiogenic and anti-tumor activities) was assessed in a randomized open-label, two-way crossover study. A 50-mg dose of SU11248 was administered to 16 healthy subjects after a 10-h fast in one period and after a high-fat, high-calorie meal in the other period. The 90% confidence intervals (CIs) for maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) were within the 80-125% bioequivalence range, indicating the absence of a food effect. SU11248 exposure increased slightly in the fed compared with the fasted state (ratios of fed/fasted geometric least square means: Cmax 104%, AUC0-last and AUC0-infinity both 112%). There was a delay in the formation/absorption of the active metabolite SU12662 in the fed state (mean Cmax decreased 23%), but exposure remained unaffected (90% CIs for AUC0-last and AUC0-infinity were within 80-125%). These results indicate that SU11248 can be administered with or without food.

Phase I and pharmacologic study of PKI166, an epidermal growth factor receptor tyrosine kinase inhibitor, in patients with advanced solid malignancies

PURPOSE

This phase I study was conducted to assess the tolerability, pharmacokinetics, and antitumor activity of the oral, selective epidermal growth factor receptor tyrosine kinase inhibitor PKI166 in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

PKI166 was first given once daily continuously and in the second part of the study once daily for 2 weeks every 4 weeks to establish the maximum tolerated dose (MTD). Ten additional patients were studied at MTD to acquire additional safety information and characterize the effect of food intake on PKI166 pharmacokinetics. Pharmacokinetics of PKI166 were characterized after single and multiple doses at all dose levels.

RESULTS

Fifty-four patients received a total of one hundred sixteen 28-day cycles of PKI166. Dose-limiting transaminase elevations were observed in two of seven and two of eight patients using 50 and 100 mg PKI166 continuously. In the second part with PKI166 once daily for 2 weeks every 4 weeks, MTD was set at 750 mg. Dose-limiting toxicity consisted of diarrhea, skin rash, and transaminase elevations. Pharmacokinetic analysis revealed fast absorption, a linear dose-response relationship without drug accumulation after multiple doses. At MTD, no significant influence of food intake on PKI166 pharmacokinetics was observed. Stable disease for more than two cycles was observed in 11 patients.

CONCLUSIONS

PKI166 given once daily for 2 weeks every 4 weeks is well tolerated with linear pharmacokinetics, compatible with once daily dosing, and without significant effect of food intake on absorption. The recommended dose for further studies is 750 mg once daily for 2 weeks every 4 weeks.

Multiple transporters affect the disposition of atorvastatin and its two active hydroxy metabolites: application of in vitro and ex situ systems

Atorvastatin (ATV) is primarily metabolized by CYP3A in the liver to form two active hydroxy metabolites. Therefore, the sequential transport system governed by hepatic uptake and efflux transporters is important for the drug disposition and metabolism. Here, we assessed the interaction of ATV with hepatic uptake transporter organic anion transporting polypeptide (Oatp) and efflux transporter multidrug resistance associated protein 2 (MRP2/Mrp2) in vitro and ex situ using the isolated perfused rat liver (IPRL). Rifampicin (RIF) was chosen as an inhibitor for Oatp in both uptake and IPRL studies. Its inhibitory effects on MRP2 and metabolism were also tested using MRP2-overexpressing cells and rat microsomes, respectively. Our results indicate that RIF effectively inhibits the Oatp-mediated uptake of ATV and its metabolites. Inhibition on MRP2-mediated efflux of ATV was also observed at a high RIF concentration. Compared with ATV alone in the IPRL, the area under the curve(s) (AUC) of ATV was significantly increased by RIF, whereas the AUC of both metabolites were also increased in a concentration-dependent manner. However, the extent of metabolism was significantly reduced, as reflected by the reduced amounts of metabolites detected in RIF-treated livers. In conclusion, inhibition of Oatp-mediated uptake seems to be the major determinant for interaction between ATV and RIF. Metabolites of ATV were subject to Oatp-mediated uptake as well, suggesting that they undergo a similar disposition pathway as the parent drug. These data emphasize the relevance of uptake transporter as being one of the major players in hepatic drug elimination, even for substrates that undergo metabolism.

HPLC assay and pharmacokinetic study of atorvastatin in beagle dogs after oral administration of atorvastatin self-microemulsifying drug delivery system

A specific and accurate reversed-phase HPLC with UV detection was developed for the assay of atorvastatin in beagle dog plasma. Indomethacin was used as the internal standard. Atorvastatin was extracted by protein precipitation, the extracts were injected into a Kromasil C8 column (150 mm x 4.6 mm, 5 microm) with UV wavelength set at 270 nm. The mobile phase consisted of acetonitrile:0.1 mol/L ammonium acetate buffer (pH 4.0) (65:35% v/v) at a flow rate of 1.0 ml/min. The column was at ambient temperature (25 degrees C). The injection volume was 25 microl. The blank plasma did not interfere with the determination of atorvastatin and indomethacin. A good linear relationship was obtained between the peak area ratio of atorvastatin to indomethacin and the concentration of atorvastatin over the range of 0.05 to 2.5 microg/mL. The limit of quantification was 25 ng/mL, the limit of detection was 8 ng/ml. The total chromatographic analysis time was within 9 min. The method is accurate, precise and fast for the assay of atorvastatin in plasma following oral administration of an atorvastatin SMEDDS to healthy beagle dogs.

An open-label, crossover study of the pharmacokinetics of Insoluble Drug Delivery®-MicroParticle fenofibrate in combination with atorvastatin, simvastatin, and extended-release niacin in healthy volunteers

BACKGROUND

Fenofibrate has been prescribed concomitantly with other lipid-lowering agents as a treatment for dyslipidemia. However, combination therapy, particularly a statin-fibrate combination, may be associated with an increased risk of myopathy, although this risk appears to be less with fenofibrate than with other fibrates.

OBJECTIVE

The objective of this study was to determine the effect of administering a single dose of atorvastatin, simvastatin, or extended-release (ER) niacin on the pharmacokinetics and safety of a single dose of fenofibrate Insoluble Drug Delivery-MicroParticle (IDD-P).

METHODS

This was an open-label, single-center,randomized, 4-treatment, 4-period crossover study in healthy adult volunteers. Subjects were randomized to 1 of 4 treatment sequences, administered 1 week apart, that included all 4 of the following treatments: 1 IDD-P fenofibrate 160-mg tablet alone; 1 IDD-P fenofibrate 160-mg tablet plus 1 atorvastatin 10-mg tablet; 1 IDD-P fenofibrate 160-mg tablet plus 1 simvastatin 10-mg tablet; and 1 IDD-P fenofibrate 160-mg tablet plus 1 ER niacin 500-mg tablet. Blood samples for pharmacokinetic analysis were obtained immediately before and up to 72 hours after administration during each of the 4 treatment periods. If the 90% CI for the log-transformed parameter was between 0.80 and 1.25, and the 90% CI for the nontransformed parameter was between 0.80 and 1.20, then the absence of a clinically significant drug interaction was assumed. However, the absence of a drug interaction was not to be ruled out if one or more of the CIs exceeded the boundary, provided the CI included 1.00.

RESULTS

Twenty healthy subjects were enrolled. Sixteen (80%) of the subjects were male and 17 (85%) were black; mean (SD) age was 35 (9.3) years. The mean C(max), AUC from the time of administration to the last quantifiable concentration (AUC(0-t)), and AUC from the time of administration to infinity (AUC(0-infinity)) were 5%, 6%, and 2% lower, respectively, with IDD-P fenofibrate plus atorvastatin than with IDD-P fenofibrate alone; the mean C(max), AUC(0-t), and AUC(0-infinity) were 6% lower, and 10% and 9% higher, respectively, with IDD-P fenofibrate plus simvastatin than with IDD-P fenofibrate alone; and the mean C(max), AUC(0-t), and AUC(0-infinity) were 12%, 6%, and 5% lower, respectively, with IDD-P fenofibrate plus ER niacin than with IDD-P fenofibrate alone. The 90% CIs surrounding the mean ratios for AUC(0-infinity) and AUC(0-infinity) for all 3 comparisons were between 0.80 and 1.25, suggesting the absence of a drug interaction for these parameters. For C(max), an absence of a drug interaction was observed between concomitantly administered IDD-P fenofibrate and both atorvastatin and simvastatin; absence of drug interaction was not found for IDD-P fenofibrate plus ER niacin. All treatments were well tolerated; headache was the most common adverse event (AE) (10%). One subject with creatinine kinase levels of 1300 IU/L (>6 times the upper limit of normal) at baseline experienced a seizure approximately 12 to approximately 13 hours after administration of IDD-P fenofibrate plus atorvastatin; this serious AE was deemed to be possibly related to study drug.

CONCLUSIONS

Concomitant administration of a single dose of either atorvastatin or simvastatin had no significant effect on the pharmacokinetics of a single dose of IDD-P fenofibrate. A drug interaction between concomitantly administered single doses of IDD-P fenofibrate and ER niacin could not be ruled out.

Phase I clinical and pharmacological evaluation of the multi-tyrosine kinase inhibitor SU006668 by chronic oral dosing

SU006668, an oral inhibitor of vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and fibroblast growth factor receptor (FGFR), was administered in fed conditions to 24 patients with advanced solid cancer at 100, 200 and 300 mg/m(2) b.i.d. Dose escalation was discontinued because the maximum tolerated dose was defined at 400 mg/m(2) b.i.d in a concomitant trial. The drug was generally well tolerated although two patients presented possibly drug-related dose-limiting toxicities (pericardial effusion and thrombocytopenia). SU006668 had a non-linear pharmacokinetic profile characterized by AUC and Cmax decreasing from day 1 to day 28 in all patients at all tested doses; a lower apparent bioavailability on day 28 compared to day 1; and a significant concomitant increase of the urinary metabolites. These findings are in agreement with the presence of saturable absorption and metabolic induction. The peculiar pharmacokinetics and >99% protein binding discouraged further clinical development of oral SU006668 in humans.

A single-pill combination of amlodipine besylate and atorvastatin calcium

This review describes the clinical profile and rationale for the development of a single-pill formulation of the calcium channel blocker amlodipine besylate, a blood pressure-lowering agent with pleiotropic effects, and atorvastatin calcium, a statin with lipid-lowering as well as pleiotropic anti-atherosclerotic properties. Amlodipine and atorvastatin have been demonstrated in numerous clinical trials to be highly effective in lowering blood pressure and low-density lipoprotein cholesterol (LDL-C). Furthermore, both amlodipine and atorvastatin have been demonstrated to reduce cardiovascular events in a broad range of patients. The amlodipine/atorvastatin single pill has been shown to improve patients' achievement of national guideline-recommended blood pressure and lipid target levels and exhibits a safety profile consistent with its parent compounds. The combination pill is available in formulations appropriate for administration across therapeutic dose ranges targeted to a wide variety of hypertensive patients with additional risk factors and differing degrees of cardiovascular risk, or with manifest cardiovascular disease. Single-pill amlodipine/atorvastatin has the potential to improve the management of hypertensive patients with additional cardiovascular risk factors, especially dyslipidemia, by reducing pill burden and prescription costs. This potential has important implications because hypertensive patients with additional risk factors represent a large proportion of those at risk for cardiovascular events.

Electrochemically controlled release of dexamethasone from conducting polymer polypyrrole coated electrode

Chronic recordings from micromachined neural electrode arrays often fail a few weeks after implantation primarily due to the formation of an astro-glial sheath around the implant. We propose a drug delivery system, from conducting polymer (CP) coatings on the electrode sites, to modulate the inflammatory implant-host tissue reaction. In this study, polypyrrole (PPy) based coatings for electrically controlled and local delivery of the ionic form of an anti-inflammatory drug, dexamethasone (Dex), was investigated. The drug was incorporated in PPy via electropolymerization of pyrrole and released in PBS using cyclic voltammetry (CV). FTIR analysis of the surface showed the presence of Dex and polypyrrole on the coated electrode. The thickness of the coated film was estimated to be approximately 50 nm by ellipsometry. We are able to release 0.5 mug/cm(2) Dex in 1 CV cycle and a total of almost 16 mug/cm(2) Dex after 30 CV cycles. In vitro studies and immunocytochemistry on murine glial cells suggest that the released drug lowers the count of reactive astrocytes to the same extent as the added drug. In addition, the released drug is not toxic to neurons as seen by healthy neuronal viability in the released drug treated cells.

Safety, pharmacokinetic, and antitumor activity of SU11248, a novel oral multitarget tyrosine kinase inhibitor, in patients with cancer

PURPOSE

To establish the safety, pharmacokinetics, and recommended dose of sunitinib, a novel oral multitargeting tyrosine kinase inhibitor with antiangiogenic and antitumor properties, in patients with advanced malignancies.

PATIENTS AND METHODS

Sunitinib was given orally for 4 weeks every 6 weeks.

RESULTS

Twenty-eight patients received doses ranging from 15 to 59 mg/m2 (ranging from 50 mg every other day to 150 mg/d). Dose-limiting toxicities reported at the maximum-tolerated doses > or = 75 mg/d were reversible grade 3 fatigue, grade 3 hypertension, and grade 2 bullous skin toxicity. Therefore, the recommended dose was 50 mg/d. At this dose, the main adverse effects were sore mouth, edema, and thrombocytopenia. Hair discoloration and yellow coloration of the skin were observed at doses > or = 50 mg/d. Pharmacokinetic data indicate that potentially active target plasma concentrations > or = 50 ng/mL can be achieved with moderate interpatient variability and a long half-life compatible with a single daily dosing. Six objective responses were observed in three renal cell carcinomas, one neuroendocrine tumor, one stromal tumor, and one unknown primary adenocarcinoma patient. At higher doses (> or = 75 mg/d), tumor responses were often associated with reduced intratumoral vascularization and central tumor necrosis, eventually resulting in organ perforation or fistula.

CONCLUSION

At the dose of 50 mg/d (4 weeks on, 2 weeks off), sunitinib displays manageable toxicity. Antitumor activity supports further studies in patients with renal cell carcinoma, gastrointestinal, neuroendocrine, and stromal tumors. Future studies may consider including prospective imaging techniques such as high frequency ultrasound to monitor tumor density.

A Phase I study of the angiogenesis inhibitor SU5416 (semaxanib) in solid tumours, incorporating dynamic contrast MR pharmacodynamic end points

SU5416 (Z-3-[(2,4-dimethylpyrrol-5-yl)methylidenyl]-2-indolinone; semaxanib) is a small molecule inhibitor of the vascular endothelial growth factor receptor (VEGFR2). A Phase I dose escalation study was performed. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used as a pharmacodynamic assessment tool. In all, 27 patients were recruited. SU5416 was administered twice weekly by fixed rate intravenous infusion. Patients were treated in sequential cohorts of three patients at 48, 65, 85 110 and 145 mg m-2. A further dose level of 190 mg m-2 after a 2-week lead in period at a lower dose was completed; thereafter, the cohort at 145 mg m-2 was expanded. SU5416 showed linear pharmacokinetics to 145 mg m-2 with a large volume of distribution and rapid clearance. A significant degree of interpatient variability was seen. SU5416 was well tolerated, by definition a maximum-tolerated dose was not defined. No reproducible changes were seen in DCE-MRI end points. Serial assessments of VEGF in a cohort of patients treated at 145 mg m-2 did not show a statistically significant treatment-related change. Parallel assessments of the impact of SU5416 on coagulation profiles in six patients showed a transient effect within the fibrinolytic pathway. Clinical experience showed that patients who had breaks of therapy longer than a week could not have treatment reinitiated at a dose of 190 mg m-2 without unacceptable toxicity. The 145 mg m-2 dose level is thus the recommended dose for future study.

[Preparation and evaluation of self-microemulsifying drug delivery systems containing atorvastatin]

AIM

To prepare self-microemulsifying drug delivery system (SMEDDS) containing atorvastatin,and decrease its size to improve the solubility in the stomach. And to study the effect of the resultant microemulsion in reducing the presystemic clearance in the gastrointestinal mucosa and hepatic first-pass metabolism, improving the oral bioavailability, and reducing side effect and expenditure.

METHODS

Pseudoternary phase diagrams were used to evaluate the self-microemulsification existence area. The HPLC analyses in vitro and in vivo were set up. Solubility in various vehicles was determined. The self-microemulsification efficiency was assessed, such as self-microemulsification time, stability, particle size and zeta potential. SMEDDS containing atorvastatin, non-ionic surfactant and lipid were prepared. Droplet size/distributions and zeta potential of the resultant microemulsion were determined. Photos were taken with transmission electron microscope. Oral bioavailability was studied on prepared SMEDDS hard capsules and compared with that of the conventional tablet in Beagle dogs in vivo.

RESULTS

The optimal formulations had wide microemulsion existent field and had good self-microemulsifying efficiency. Droplet size was within 100 nm and showed Gaussian distribution. After oral administration of SMEDDS capsules and the conventional tablet to fasted Beagle dogs, the Cmax from SMEDDS was greater than that of the conventional tablet. AUC from zero to 24 h of SMEDDS was about 1.5-fold higher than that of the conventional tablet. Oral bioavailability of atorvastatin SMEDDS was greater than that of the conventional tablet.

CONCLUSION

The results indicated the potential use of SMEDDS for the delivery of atorvastatin to increase its oral bioavailability.

A phase I Study with oral SU5416 in patients with advanced solid tumors: A drug inducing its clearance

Vascular endothelial growth factor (VEGF) is a potent stimulant of angiogenesis. SU5416, is a small molecule tyrosine kinase inhibitor, and a potent inhibitor of VEGF-mediated Flk-1 receptor signaling. Intravenous agent SU5416 has shown evidence of biological activity against a variety of tumor types. The current intravenous dosing regimen is not optimal for long-term administration, which is needed for optimal efficacy. The aim of this study was to evaluate the safety profile and pharmacokinetics of a Nanocrystal Colloidal Dispersion (NCD) SU5416 formulation in humans. Patients with advanced and/or metastatic solid organ tumors were included in the trial; various SU5416 regimens were tested for tolerability, safety and were evaluated concerning pharmacokinetics. The results of this study indicate that induction of clearance after oral dosing of NCD SU5416 in humans occurs and is greater than following i.v. administration. It has been confirmed that SU5416 is a high clearance compound, also as an oral NCD formulation. The NCD formulation was well tolerated, but no effective drug serum levels could be achieved. These data help to understand the ADME (Absorption, Distribution, Metabolism, Excretion) properties of indoline chemical class compounds. The lessons learned should be applied in the development of next generation indoline anti-angiogenic and anti-tumor compounds.

A simple and rapid HPLC method for the determination of atorvastatin in human plasma with UV detection and its application to pharmacokinetic studies

A rapid and sensitive high-performance liquid chromatographic method for the determination of atorvastatin (CAS 134523-00-5) in plasma was developed in this study. Atorvastatin was isolated from plasma using protein precipitation by acetonitrile. Diltiazem (CAS 33286-22-5) was used as internal standard. The chromatographic conditions were as follows: analytical 125 x 4 mm (i.d.) Nucleosil C8 column (5 microm particle size), mobile phase consisting of sodium dihydrogen phosphate buffer-acetonitrile (60:40, v/v) adjusted to pH 5.5 at a flow rate of 1.5 ml/min, UV detection at 245 nm. The detection limit for atorvastatin in plasma was 1 ng ml(-1). The calibration curve was linear over the concentration range 20-800 ng ml(-1). The recovery was complete. The inter-day and intra-day assay coefficients of variation were found to be less than 7%. The present validated method was successfully used for pharmacokinetic studies of atorvastatin in human subjects.

Determination of atorvastatin in human serum by reversed-phase high-performance liquid chromatography with UV detection

A rapid and sensitive high-performance liquid chromatographic method was validated and described for determination of atorvastatin in human serum. Following liquid-liquid extraction of the drug and an internal standard (sodium diclofenac), chromatographic separation was accomplished using C18 analytical column with a mobile phase consisting of sodium phosphate buffer (0.05 M, pH 4.0) and methanol (33:67, v/v). Atorvastatin and the internal standard were detected by ultraviolet absorbance at 247 nm. The average recoveries of the drug and internal standard were 95 and 80%, respectively. The lower limits of detection and quantification were 1 and 4 ng/ml, respectively, and the calibration curves were linear over a concentration range of 4-256 ng/ml of atorvastatin in human serum. The analysis performance was studied and the method was applied in a randomized cross-over bioequivalence study of two different atorvastatin preparations in 12 healthy volunteers.

A phase I surrogate endpoint study of SU6668 in patients with solid tumors

PURPOSE

To evaluate the biologic effects of SU6668 in patients with solid tumors using comprehensive measures of pharmacokinetics (PK), functional imaging, and tissue correlative studies.

EXPERIMENTAL DESIGN

Eligible patients with tumors accessible for core needle biopsy were treated with SU6668 at doses of 200 or 400 mg/m(2)/day. Functional computed tomography (CT) scan and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were performed at baseline and repeated 4 weeks and 12 weeks after treatment for analysis of tumor angiogenesis. The PK was analyzed using a high-performance liquid chromatography assay. Tumor specimens obtained via core needle biopsy at baseline and 4 weeks later were analyzed for the biologic effects of SU6668.

RESULTS

Six of a total of seven patients received treatment for at least 3 months and underwent comprehensive correlative studies, including PK, imaging, and tissue biopsy. Functional CT showed that five of six patients had decreased blood flow in tumors in response to treatment, and DCE-MRI results indicated significant change of area under the signal intensity vs. time curve (AUC) and/or maximum slope (maximum rate of signal intensity change) in two of four patients evaluated with this technique. PK studies showed that the mean apparent oral clearance (Cl(oral)) measured on day 1 was 6.3 +/- 2.7 L/hr/m(2), yielding a mean AUC of 16.6 +/- 4.3 mg/L.hr. By day 22, the Cl(oral) was 40% more than that observed on day 1.

CONCLUSION

It is feasible to evaluate the biologic effects of antiangiogenic agents using comprehensive surrogate measures.

Dose-Finding Study of the Multitargeted Tyrosine Kinase Inhibitor SU6668 in Patients with Advanced Malignancies

PURPOSE

SU6668 is a tyrosine kinase inhibitor which targets platelet-derived growth factor receptor-beta, fibroblast growth factor receptor-1, vascular endothelial growth factor receptor-2, and KIT. We did a phase I study to define the maximum tolerated dose and to assess the pharmacokinetics of SU6668 administered orally thrice daily with food.

PATIENTS AND METHODS

Patients with histologically proven, advanced, and progressive solid tumors were included at a starting dose level of 400 mg/m2 thrice daily. The early onset of dose-limiting toxicities (DLT) required dose reductions to 100 and 200 mg/m2 thrice daily. Pharmacokinetics was done on days 1, 28, and 56.

RESULTS

Sixteen patients were included. Two of the first three patients developed DLTs, which consisted of grade 4 fatigue and grade 3 serositis-like pains. Six patients at dose level 100 mg/m2 thrice daily experienced no DLT. At dose level 200 mg/m2 thrice daily, two out of seven patients experienced DLTs consisting of grade 3 abdominal pain, grade 4 anorexia and grade 3 nausea/vomiting. Increasing doses resulted in a disproportional increase in area under the curve and C(max) (peak plasma concentration). Both variables, however, decreased significantly on days 28 and 56 compared with day 1 (P < 0.05). No objective responses were observed. Acute phase response, probably mediated by interleukin-6, was observed in serial blood samples.

CONCLUSIONS

The maximum tolerated dose of SU6668 given orally, thrice daily under fed conditions, is 100 mg/m2. Because of the low plasma levels reached at this dose level, the efficacy of SU6668 as a single agent is not to be expected.

Combined therapy with atorvastatin and calcineurin inhibitors: no interactions with tacrolimus

Increased systemic exposure to statins and consequent risk for complications has been reported in patients concomitantly treated with cyclosporin A (CsA). This has been ascribed to inhibition of drug catabolism by cytochrome P450 3A4 (CYP3A4) or drug transport by P-glycoprotein (PGP) and organic anion transporting polypeptide (OATP1B1). It is not known whether the combination of statins and tacrolimus (Tac) also suffers from this drawback. Therefore, a pharmacokinetic study of atorvastatin and its metabolites was performed in 13 healthy volunteers after 4 days' treatment, and after short (12 h) concomitant exposure to CsA and Tac. A complementary assessment of overall CYP, and hepatic and intestinal CYP3A4+PGP activity was performed after each treatment episode and compared to baseline (no drugs). Systemic exposure to atorvastatin acid and its metabolites was significantly increased when administered with CsA. In contrast, intake of Tac did not have any impact on atorvastatin pharmacokinetics. Concomitantly, a profound decrease of hepatic and intestinal PGP and an increase of intestinal CYP3A4 were noted with CsA, whereas no effect was seen after atorvastatin therapy with or without Tac. Based on these findings treatment with Tac appears a safer option for patients needing a combination of statins and calcineurin inhibitors.

A proof-of-principle pharmacokinetic, pharmacodynamic, and clinical study with purine nucleoside phosphorylase inhibitor immucillin-H (BCX-1777, forodesine)

The discovery of purine nucleoside phosphorylase (PNP) deficiency and T lymphocytopenia suggested that inhibition of this enzyme could serve as a therapeutic target. Inhibitors of PNP failed until structure-based synthesis of immucillin-H (BCX-1777, forodesine), a transition-state analog of PNP. The picomolar potency for PNP, T cell-selective cytotoxicity, and animal studies provided the rationale for use of forodesine in T-cell malignancies. Five patients were treated with an intravenous infusion of forodesine (40 mg/m2) on day 1; treatment continued on day 2; forodesine was administered every 12 hours for an additional 8 doses. Plasma and cellular pharmacokinetics and pharmaco-dynamics were investigated. Median peak level of forodesine (5.4 microM) was achieved at the end of infusion. This level was sufficient to increase plasma 2'-deoxyguanosine (dGuo) concentrations in all patients. Intracellular deoxyguanosine triphosphate (dGTP) increased by 2- to 40-fold in 4 of 5 patients (8 of 9 courses) and correlated with antileukemia activity in 4 patients. However, objective responses were not observed. This was the first clinical study in humans to demonstrate the plasma pharmacokinetics and the pharmacodynamic effectiveness of the PNP inhibitor, forodesine; however, regrowth of leukemia cells in the blood and marrow after course 1 suggested that a different therapeutic schedule should be considered for future studies.

A literature search on pharmacokinetic drug interactions of statins and analysis of how such interactions are reflected in package inserts in Japan

BACKGROUND AND OBJECTIVES

Statins (HMG-CoA reductase inhibitors) are one of the most widely prescribed classes of drugs throughout the world, because of their excellent cholesterol-lowering effect and overall safety profile except for rare but fatal rhabdomyolysis arising either directly or indirectly by pharmacokinetic interactions with certain other drugs. As package inserts in pharmaceuticals are the primary source of information for health care providers, we carried out a literature search to examine how crucial information was provided in package inserts of five statins approved in Japan (simvastatin, atorvastatin, fluvastatin, pravastatin and pitavastatin).

METHODS

A MEDLINE search from 1996 to June 2004 was carried out to identify studies on clinical pharmacokinetic drug interactions for the five statins. We mainly collected information on area under plasma concentration (AUC) following co-administration of statins with other drugs. The current package inserts used in Japan were obtained from the website of the Pharmaceutical and Medical Device Agency whereas USA package inserts were obtained from the Food and Drug Administration website.

RESULTS

The majority of package inserts listed the drugs that interacted with statins with most describing the risk of rhabdomyolysis because of the possibility of increases in blood concentration. However, quantitative information such as change in AUC was provided in only a few cases. Instructions for dosage adjustment are seldom provided in the Japanese package inserts. USA package inserts list almost identical drug interactions as the Japanese package inserts, although they contain more quantitative data, especially for typical cytochrome P450 (CYP) inhibitors.

CONCLUSION

All pharmacokinetic drug interactions including relevant quantitative data for potential effectors and details on mechanisms of interaction need to be given in package inserts as soon as the information becomes available, to ensure safe and proper use of the drugs concerned. Including such information in the package insert will be an extremely valuable aid for health care providers.