Plasmodium falciparum is responsible for most of the cases of malaria and its resistance to established antimalarial drugs is a major issue. Thus, new chemotherapies are needed to fight the emerging multi-drug resistance of P. falciparum malaria, like choline analogues targeting plasmodial phospholipidic metabolism. Here we describe the synthesis of amidoxime derivatives as prodrug candidates of reverse-benzamidines and hybrid compounds able to mimic choline, as well as the design of a new series of asymmetrical bis-cationic compounds. Bioconversion studies were conducted on amidoximes in asymmetrical series and showed that amidoxime prodrug strategy could be applied on C-alkylamidine moieties, like benzamidines and that N-substituents did not alter the bioconversion of amidoximes. The antimalarial activity of the three series of compounds was evaluated in vitro against P. falciparum and in vivo against P. vinckei petteri in mice.

Mycophenolate mofetil (MMF) is an important immunosuppressant used in renal transplantation, and mycophenolic acid (MPA) is the active component released from the ester prodrug MMF. The objective of this study was to investigate the population pharmacokinetics of mycophenolic acid (MPA) following oral administration of MMF in Chinese adult renal transplant recipients and to identify factors that explain MPA pharmacokinetic variability. Pharmacokinetic data for MPA and covariate information were retrospectively collected from 118 patients (79 patients were assigned to the group for building the population pharmacokinetic model, while 39 patients were assigned to the validation group). Population pharmacokinetic data analysis was performed using the NONMEM software. The pharmacokinetics of MPA was best described by a two-compartment model with a first-order absorption rate with no lag time. Body weight and serum creatinine level were positively correlated with apparent clearance (CL/F). The polymorphism in uridine diphosphate glucuronosyltransferase gene, UGT2B7 , significantly explained the interindividual variability in the initial volume of distribution (V 1 /F). The estimated population parameters (and interindividual variability) were CL/F 18.3 L/h (34.2%) and V 1 /F 27.9 L (21.3%). The interoccasion variability was 13.7%. These population pharmacokinetic data have significant clinical value for the individualization of MMF therapy in Chinese adult renal transplant patients.

One of the main reasons for the inefficiency of multicenter randomized clinical trials (RCTs) in depression is the excessively high level of placebo response. The aim of this work was to propose a novel methodology to analyze RCTs based on the assumption that centers with high placebo response are less informative than the other centers for estimating the 'true' treatment effect (TE). A linear mixed-effect modeling approach for repeated measures (MMRM) was used as a reference approach. The new method for estimating TE was based on a nonlinear longitudinal modeling of clinical scores (NLMMRM). NLMMRM estimates TE by associating a weighting factor to the data collected in each center. The weight was defined by the posterior probability of detecting a clinically relevant difference between active treatment and placebo at that center. Data from five RCTs in depression were used to compare the performance of MMRM with NLMMRM. The results of the analyses showed an average improvement of ~15% in the TE estimated with NLMMRM when the center effect was included in the analyses. Opposite results were observed with MMRM: TE estimate was reduced by ~4% when the center effect was considered as covariate in the analysis. The novel NLMMRM approach provides a tool for controlling the confounding effect of high placebo response, to increase signal detection and to provide a more reliable estimate of the 'true' TE by controlling false negative results associated with excessively high placebo response.

EAPB0503, belonging to the imidazo[1,2-a]quinoxaline series, is an anticancer drug with antitumoral activity against a variety of tumors. Previous studies have shown that this drug undergoes demethylation and oxygenation reactions. In this paper, liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was employed to assess the structures of unknown oxygenated metabolites of EAPB0503. EAPB0503 and its identified demethylated metabolites, EAPB0502 and EAPB0603, were incubated with human, rat, dog and mouse liver microsomes, as well as human, rat and dog hepatocytes. After separation on a C8 analytical column with a gradient elution of acetonitrile-formate buffer, positive ESI-MS/MS experiments were performed. To facilitate metabolite identification, the detailed fragmentation pathways of the parent compounds were first studied using high-resolution MS/MS. Additional hydrogen/deuterium exchange LC-MS/MS experiments were used to support the identification and structural characterization of metabolites. Four hydroxylated metabolites were identified: M'4 and its demethylated derivative M'1 (OH in ortho position on the phenyl substituent in position 1), and M'6 and its demethylated derivative M'3 (OH on the imidazole ring at the C2 position). Three phase II metabolites (Met A, EAPB0602 glucuronide; Met B, M'4 glucuronide; Met C, EAPB0603 glucuronide) were also evidenced. Elucidation of the metabolite structures was performed by comparing the chromatographic behaviors (changes in retention times), by measuring the molecular masses (mass increment), by studying the MS2 spectral patterns of metabolites with those of parent drugs and for M'1 and M'4 by co-analysis with synthetic standards. The results of the present study provided important structural information relating to the metabolism of EAPB0503. (C) 2013 Elsevier B.V. All rights reserved.

Objective: to develop a population pharmacokinetic model taking into account blood losses during and after orthopedic surgery in adult hemophilia A patients receiving infusion of coagulation factor VIII, and to evaluate the influence of potential covariates. Methods: Factor VIII pharmacokinetic parameters were calculated from 24 patients. Among them, 7 were HIV+. The observations were analyzed with the mixed-effects compartment pharmacokinetic package NONMEM and the first-order conditional estimation method. To evaluate the stability and robustness of the final model the bootstrap method was used. Results: During the model-building process, central volume of distribution (V 1 ) was related to body weight (P = 0.0263) and viral status (P = 0.0078). Moreover, the peripheral volume of distribution was related to body weight (P=0.0362). In the final model, only the viral status was significant for V 1 when compared with the base model. Posterior predictive checks and robustness analysis showed that the model adequately described the pharmacokinetic parameters. The HIV covariate accounted for 29.8% of the unexplained variation across patients for V 1 . V 1 increased by 33.3% in HIV+ patients compared to HIV- patients. Conclusion: A population pharmacokinetic model taking into account blood losses during and after orthopedic surgery was developed. The 33.3% increase in V 1 observed in HIV+ patients explained the need for higher doses in these patients.

The aim of this study was to determine the stability of ready-to-use temsirolimus infusion solutions under different storage conditions. Solutions were prepared in polypropylene containers by adding temsirolimus injection to 0.9% sodium chloride infusion to reach a final concentration of 100mg/L. The following storage conditions were tested: (i) 4oC in the refrigerator; (ii) 20oC under room light exposure and light protection; and (iii) outdoor temperature with sunlight exposure. Moreover, stress testing was performed on drug substance at 20oC under ultraviolet (UV) radiation (365nm). A stability-indicating high-performance liquid chromatography (HPLC) method with UV detection was developed for this analysis. Precision was below 4% and accuracy ranged from 97 to 102%. The lower limit of quantitation was 0.1mg/L. The degradation products produced after UV light exposure were detected upon further analysis by mass spectrometry detection. The stability of temsirolimus is light and temperature dependent. After storage at 20oC with room light exposure, the rate of degradation was around 0.25%/h; after 1day, 92.5% of the initial temsirolimus concentration was recovered. When protected from light, at 4 and 20oC, losses were decelerated; the decrease in drug concentration was 1.0 and 1.56% per day, respectively. Under daylight exposure, a substantial decrease in drug concentration was observed; after 1h, losses were higher than 10%. Exposed to UV light, half of the drug was lost after 45min. In conclusion, temsirolimus 100mg/L in infusion polypropylene bags containing 0.9% sodium chloride was chemically stable when protected from light for 4 and 3days at 4 and 20oC, respectively.

A simple HPLC-UV method was developed to determine the stability of ready-to-use eribulin solutions under different storage conditions. The developed method was validated with respect to linearity, accuracy, precision and ruggedness. The following admixtures were prepared: 3-mL polypropylene syringes at concentration of 440 μg/mL and multilayer laminate polyolefin containers containing 0.9% sodium chloride (50 mL) at concentrations of 15.4 and 43.3 μg/mL. The open-vial stability of eribulin was also evaluated. The following storage conditions were tested: 4 °C in the refrigerator; 20 °C under room light exposure; and 20 °C with light-protection. The drug was also subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The retention time of eribulin was 4.9 min. Admixtures of eribulin solutions in vials, syringes or polyolefin bags at clinically relevant concentrations were physically compatible and chemically stable for at least 14 days at 4 °C in the refrigerator and at 20 °C with or without any protection against light. Degradation was only found to occur under oxidation conditions.

Blood oxygenation is a fundamental factor in optimising muscular activity. Enhancement of oxygen delivery to tissues is associated with a substantial improvement in athletic performance, particularly in endurance sports. Progress in medical research has led to the identification of new chemicals for the treatment of severe anaemia. Effective and promising molecules have been created and sometimes used for doping purposes. The aim of this review is to present methods, and drugs, known to be (or that might be) used by athletes to increase oxygen transport in an attempt to improve endurance capacity. These methods and drugs include: (i) blood transfusion; (ii) endogenous stimulation of red blood cell production at altitude, or using hypoxic rooms, erythropoietins (EPOs), EPO gene therapy or EPO mimetics; (iii) allosteric effectors of haemoglobin; and (iv) blood substitutes such as modified haemoglobin solutions and perfluorochemicals. Often, new chemicals are used before safety tests have been completed and athletes are taking great health risks. Such new chemicals have also created the need for new instrumental strategies in doping control laboratories, but not all of these chemicals are detectable. Further progress in analytical research is necessary.

The purpose of this paper is: (i) to compare recombinant human erythropoietin (rHuEPO) pharmacokinetics in athletes and healthy individuals; and (ii) to report pharmacokinetic/pharmacodynamic (PK/PD) studies performed in athletes. Effect parameters in PK/PD studies included:.(i) red blood cell variables (haematocrit, reticulocyte count); and (ii) markers of iron metabolism (serum soluble transferrin receptors [sTfR], ferritin [fr] and sTfR : fr ratio). To understand the choice of these markers, we first performed a brief review of the pharmacological effects of rHuEPO. Few studies have been conducted in healthy individuals and there are minimal references concerning pharmacokinetics in athletes. A 'flip-flop' phenomenon was noted after subcutaneous administration. The pharmacokinetics appeared linear from 50-1000 U/kg, but this linearity was not observed at the lowest dose of 10 U/kg. A negative-feedback loop of endogenous erythropoietin production occurred at the end of treatment. The half-life of the terminal part of the curves seemed to be slightly higher in athletes (36-42 vs 32 hours) than in untrained individuals and total clearance tended to be greater (17.5 vs 6.5 mL/h/kg).In conclusion, more investigations are needed to better understand the relationship between rHuEPO administration and changes in haematological and iron-metabolism parameters in athletes, particularly after chronic low-dose administration of rHuEPO.

The present study was conducted to assess the structures of the main unknown oxygenated metabolites of EAPB0203. The first step was to assign all the (1)H and (13)C NMR of both EAPB0203 and its demethylated metabolite (EAPB0202) to the corresponding atoms in their molecular structures and to elucidate the fragmentation pathways for the [M + H](+) ions of these compounds using high-resolution mass spectrometry (MS). MS/MS spectra showed that both protonated molecules possessing an even number of electrons were unexpectedly losing radicals such as H(•), CH(3)(•), or even C(7)H(7)(•) giving stable radical cations. In vitro metabolism studies were investigated in rat and dog liver microsomes and in the filamentous fungus Cunninghamella elegans. Structural elucidation of six oxygenated metabolites was performed based on the following: (i) their fragmentation pathways in liquid chromatography-MS/MS (LC-MS/MS) analyses; (ii) comparison of their changes in their molecular masses and fragment ions with those of the parent drugs; and (iii) the results of online H/D exchange experiments that provided additional evidence in differentiating hydoxylated metabolites from N-oxides. Structures of the metabolites were elucidated by LC-MS/MS and comparison with synthetic standards; structures of these standards were confirmed using one- and two-dimensional (1)H NMR spectroscopies.

Antimalarial activities and pharmacokinetics of the bis-alkylamidine, M64, and its amidoxime, M64-AH, and O-methylsulfonate, M64-S-Me, derivatives were investigated. M64 and M64-S-Me had the most potent activity against the Plasmodium falciparum growth (IC(50)<12nM). The three compounds can clear the Plasmodium vinckei infection in mice (ED(50)<10mg/kg). A liquid chromatography-mass spectrometry method was validated to simultaneously quantify M64 and M64-AH in human and rat plasma. M64 is partially metabolized to M64-monoamidoxime and M64-monoacetamide by rat and mouse liver microsomes. The amidoxime M64-AH undergoes extensive metabolism forming M64, M64-monoacetamide, M64-diacetamide and M64-monoamidoxime. Strong interspecies differences were observed. The pharmacokinetic profiles of M64, M64-AH and M64-S-Me were studied in rat after intravenous and oral administrations. M64 is partially metabolized to M64-AH; while M64-S-Me is rapidly and totally converted to M64 and M64-AH. M64-AH is mostly oxidized to the inactive M64-diacetamine while its N-reduction to the efficient M64 is a minor metabolic pathway. Oral dose of M64-AH was well absorbed (38%) and converted to M64 and M64-diacetamide. This study generated substantial information about the properties of this class of antimalarial drugs. Other routes of synthesis will be explored to prevent oxidative transformation of the amidoxime and to favour the N-reduction.

BACKGROUNDNalbuphine is an opioid analgesic agent widely used for control of mild-to-severe pain. However, limited data are available on the pharmacokinetics of this drug in children. The aim of this study was to characterize the population pharmacokinetics of nalbuphine in patients with ages ranging from 1 to 11 yr and to identify patient characteristics partially explaining inter-individual variability in nalbuphine pharmacokinetic parameters.METHODSTwenty-two children were included in this study. They received nalbuphine after surgery by continuous infusion (loading dose, 0.2 mg kg(-1) over 10 min followed by continuous infusion of 0.8 mg kg(-1) over 24 h). If pain relief was not adequate, 0.1 mg kg(-1) bolus doses were allowed in 10 min. Eleven blood samples were collected per patient. The data were analysed by non-linear mixed-effect modelling with the use of a two-compartment structural model.RESULTSTwenty patients completed the study. In the final model, the parameter values were standardized for a body weight of 70 kg using an allometric model. Population parameter estimates were: clearance 130 litre h(-1) 70 kg(-1), inter-compartment clearance 75.6 litre h(-1) 70 kg(-1), central volume of distribution 210 litre 70 kg(-1), and peripheral volume of distribution 151 litre 70 kg(-1). In the children of this study, total clearance expressed in litre h(-1) kg(-1) decreased significantly with increasing age and the elimination half-life significantly increased.CONCLUSIONSThe allometric power model developed in this study best reflected the data and may be useful for dose adjustment.

Objective. Peritoneal spread is an adverse outcome in ovarian cancer. Despite clinical efficiency, intraperitoneal (i.p.) chemotherapy after cytoreductive surgery is associated with high systemic and local toxicity. Two polymer-drug delivery systems (P-HYD1-DOX and P-HYD2-DOX) were developed for i.p. administration by conjugating doxorubicin (DOX) to a poly(L-Lysine citramide) polymer carrier with a hydrazone-based degradable spacer. The aim of this study was to assess the antitumoral efficacy of these two conjugates in a xenograft model of human ovarian carcinomatosis.Methods. Peritoneal carcinomatosis was generated in athymic mice by i.p. injection of SKOV3-Luc cells. Free DOX, P-HYD1-DOX and P-HYD2-DOX solutions were administered i.p. at the same dose of 10 mg/kg (DOX eq.). For each treatment, tumor load and therapeutic efficacy were compared to untreated mice and assessed by bioluminescence imaging and survival rates. Toxicity profiles in each group and biodistribution of P-HYD2-DOX after i.p. administration were also determined.Results. P-HYD-1-DOX and P-HYD-2-DOX demonstrated significant antitumoral efficacy against peritoneal carcinomatosis. Compared to untreated group. P-HYD1-DOX improved median survival times from 58 to 105 days. For P-HYD2-DOX, median survival was not reached after a follow-up of 120 clays. Bioluminescence showed high efficacy of P-HYD-2-DOX compared to free DOX but the difference was not significant. Biodistribution study confirmed that free and active DOX were successively released from P-HYD2-DOX in vivo. P-HYD-DOX conjugates were well tolerated by mice after i.p. injection.Conclusion. P-HYD-DOX conjugates demonstrated significant activity against peritoneal carcinomatosis in a xenograft model of ovarian carcinomatosis and their ability to release active DOX in i.p. deposits and tumor. These features are of clinical interest for i.p. administration in the treatment of ovarian peritoneal carcinomatosis after cytoreductive surgery. (C) 2011 Elsevier Inc. All rights reserved.

We retrospectively analyzed amikacin pharmacokinetics in 19 critically ill patients who received amikacin intravenously. Fourteen subjects (577 serum amikacin concentrations, 167 urine measurements) were studied to obtain data for population modeling, while 5 patients (267 serum amikacin concentrations, 68 urine measurements) were studied for the assessment of predictive performance. The population analysis was performed using serum and urine amikacin measurements; the renal clearance of amikacin was expressed as a function of creatinine clearance. A two-compartment model was fitted to the population data by using NONMEM. The population characteristics of the pharmacokinetic parameters (fixed and random effects) were estimated using the FOCE method. The population pharmacokinetic parameters with the interindividual variability (CV%) were as follows: slope (0.254, 126%) and intercept (3 l/h, 59.6%) of the linear model which relate the amikacin renal clearance to the creatinine clearance, initial volume of distribution (17.11, 22.2%), intercompartment clearance (5.22 l/h, 104%), steady state volume of distribution (55.2 l, 64.1%) and urinary elimination (67.5%, 36.3%). The Bayesian approach developed in this study accurately predicts amikacin concentrations in serum and urine and allows for the estimation of amikacin pharmacokinetic parameters, minimizing the risk of bias in the prediction.

The objective of the present study was to develop a selective and sensitive liquid chromatography-mass spectrometry (LC-MS) method for the simultaneous quantitation of capecitabine, 5′-deoxy-5-fluorocytidine (5′-DFCR), 5′-deoxy-5-fluorouridine (5′-DFUR), 5-fluorouracil (5-FU), and 5-fluorodihydrouracil (5-FUH2) in human plasma. Chromatography was performed on an Atlantis dC18 column with a mobile phase consisting of 1% formic acid in acetonitrile and 1% formic acid in water gradient elution. 5-fluorocytosine (5-FC) was used as internal standard. LC-MS data were acquired in SIM mode at m/z 130 for 5-FC, m/z 131 for 5-FU, m/z 133 for 5-FUH2, m/z 246 for 5′-DFCR, m/z 247 for 5′-DFUR, and m/z 360 for capecitabine. The drug/internal standard peak area ratios were linked via quadratic relationships to concentrations (100–10000 μg/L for 5-FU; 50–10000 μg/L for 5-FUH2; and 25–10000 μg/L for 5′-DFCR, 5′-DFUR, and capecitabine). The analysis of blank matrices from different donors showed the absence of interfering endogenous components at the retention times of the analytes. No evidence of matrix effect was observed. The method was precise (precision, 0.2–8.3%) and accurate (recovery, 99–104%). Mean extraction efficiencies >89% for each analyte were obtained. The lower limits of quantitation were 25 μg/L for capecitabine, 5′-DFCR, and 5′-DFUR; 50 μg/L for 5-FUH2; and 100 μg/L for 5-FU. This method was successfully used to investigate plasma concentrations of capecitabine and its metabolites in a pharmacokinetic study carried out in patients with metastatic solid tumors receiving oral administration of capecitabine (1600 to 3420 mg according to the patient) twice a day.