Renaud Respaud

Population pharmacokinetics of ceftriaxone in critically ill septic patients: a reappraisal

AIMS To investigate the population pharmacokinetics of ceftriaxone in critically ill patients suffering from sepsis, severe sepsis or septic shock. METHODS Blood samples were collected at preselected times in 54 adult patients suffering from sepsis, severe sepsis or septic shock in order to determine ceftriaxone concentrations using high-performance liquid chromatography-ultraviolet detection. The pharmacokinetics of ceftriaxone were assessed on two separate occasions for each patient: on the second day of ceftriaxone therapy and 48 h after catecholamine withdrawal in patients with septic shock, or on the fifth day in patients with sepsis. The population pharmacokinetics of ceftriaxone were studied using nonlinear mixed effects modelling. RESULTS The population estimates (interindividual variability; coefficient of variation) for ceftriaxone pharmacokinetics were: a clearance of 0.88 l h(-1) (49%), a mean half-life of 9.6 h (range 0.83-28.6 h) and a total volume of distribution of 19.5 l (range 6.48-35.2 l). The total volume of distribution was higher than that generally found in healthy individuals and increased with the severity of sepsis. However, the only covariate influencing the ceftriaxone pharmacokinetics was creatinine clearance. Dosage simulations showed that the risk of ceftriaxone concentrations dropping below the minimum inhibitory concentration threshold was low. CONCLUSIONS Despite the wide interpatient variability of ceftriaxone pharmacokinetic parameters, our results revealed that increasing the ceftriaxone dosage when treating critically ill patients is unnecessary. The risk of ceftriaxone concentrations dropping below the minimum inhibitory concentration threshold is limited to patients with high glomerular filtration rates or infections with high minimum inhibitory concentration pathogens (>1 mg l(-1)).

Nebulization as a delivery method for mAbs in respiratory diseases

Introduction: The pulmonary route is not invasive and can be used to target drugs directly to the lungs, limiting the exposure of secondary organs. It is, thus, an attractive alternative to the intravenous route, for the delivery of mAbs, which display limited transfer from blood into the lungs. Areas covered: This review provides an overview of the pharmacological properties of antibody-based treatments, describes those for respiratory diseases and discusses preclinical/clinical results of aerosolized antibody-based therapeutics. The advantages and limitations of aerosol devices and the formulation for the administration of aerosolized mAbs are also detailed. Expert opinion: Overall, the inhalation of mAbs for therapeutic purposes is both appropriate and feasible. The size and structure of the biotherapeutic molecule are important properties to be taken into account when trying to achieve long-term retention. Mesh nebulizers currently appear to be the most appropriate devices for the safe delivery of large amounts of active mAb into the lungs. mAbs should be formulated so as to prevent their degradation and possible immunogenicity. General guidelines can be given for mAb aerosolization, but the formulation and device combination should be adapted for each therapeutic and clinical application.

Effect of formulation on the stability and aerosol performance of a nebulized antibody

Most monoclonal antibodies (mAbs) are administered to patients intravenously to ensure high bioavailability as rapidly as possible. The airways, however, are an attractive delivery route for mAbs for the treatment of lung diseases, making it possible to increase their concentration in the target organ while limiting their systemic passage. Several challenges must be overcome for translation into clinical practice. For example, the drug and device must be paired for the efficient and reliable deposition of a pharmacologically active and safe mAb in the lung region of interest. Mesh nebulizers appear to be the most effective aerosol-producing devices for delivering large amounts of biopharmaceutical while limiting protein instability during nebulization. We used metrological and analytic methods to analyze the effect of both antibody concentration and surfactant addition on aerosol performance and antibody integrity. These two factors had a limited effect on aerosol performance, but affected antibody aggregation. The addition of surfactants to antibody formulations at concentrations appropriate for lung administration markedly reduced the formation of medium or large aggregates, as shown by dynamic light scattering and fluorescence microscopy. Aggregation was also dependent on the type of mesh nebulizer, highlighting the need to optimize drug and device together.

Urinary elimination of coproporphyrins is dependent on ABCC2 polymorphisms and represents a potential biomarker of MRP2 activity in humans.

MRP2 encoded by ABCC2 gene is involved in the secretion of numerous drugs and endogenous substrates. Patients with Dubin-Johnson syndrome due to mutation in ABCC2 gene have elevated urinary coproporphyrin ratio (UCP I/(I + III)). Here we investigated whether this ratio could serve as a biomarker of MRP2 function. Phenotype-genotype relationships were studied in 74 healthy subjects by measuring individual UCP I/(I + III) ratio obtained on 24-hour urine and by analyzing five common SNPs in ABCC2 gene. The UCP I/(I + III) ratio varied from 14.7% to 46.0% in our population. Subjects with 3972TT genotype had a higher ratio (P = .04) than those carrying the C allele. This higher UCP I/(I + III) ratio was correlated with a higher level of isomer I excretion. This study provides a proof of concept that UCP I/(I + III) ratio can be used as a biomarker of MRP2 function in clinical studies as it provides quantitative information about the in vivo activity of MRP2 in a given patient.

Development of an ion-pairing reversed-phase liquid chromatography method using a double detection analysis (UV and evaporative light scattering detection) to monitor the stability of Alimta®-pemetrexed preparations: Identification and quantification of l-glutamic acid as a potential degradation product

A new method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the determination of L-glutamic acid, a potential degradation product of pemetrexed, and for the quantification of pemetrexed itself. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 μm (150 mm x 4.6 mm). The mobile phase was 1 mM tridecafluoroheptanoic acid in aqueous solution and acetonitrile under gradient elution mode. L-Glutamic acid was detected by ELSD, and pemetrexed by UV at 254 nm. Good resolution was achieved between pemetrexed and L-glutamic acid. The HPLC method was validated according to SFSTP and ICH guidelines, and applied the accuracy profile procedure with a five-level validation experimental design. For pemetrexed, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains for L-glutamic acid (0.005-0.025 mg/mL) and pemetrexed (0.4-0.6 mg/mL) and shown to provide a very effective method.

Quantification of coproporphyrin isomers I and III in urine by HPLC and determination of their ratio for investigations of Multidrug Resistance Protein 2 (MRP2) function in humans

We describe here the development of a high-performance liquid chromatography (HPLC) method for quantitative determination of the ratio of isomers I and III of urinary coproporphyrin [the UCP I/(I+III) ratio], which is used for the diagnosis of Dubin-Johnson syndrome (DJS). This technique could also be used for research applications, such as investigations of the function of Multidrug Resistance Protein 2 (MRP2) in humans. Chromatographic separation was achieved on a reverse-phase C18 Symmetry((R)) column (5microm; 4.8mmx250mm), using a mobile phase consisting of a mixture of acetonitrile and acetate buffer (0.015M, pH 4), with fluorescence detection based on excitation at 365nm and emission at 624nm. The method was validated over a concentration range of 10-400nmol/l for UCP I and 30-560nmol/l for UCP III, yielding calibration curves with correlation coefficients greater than 0.998. The lower limit of quantification (LLOQ) was 7nmol/l for UCP I and 10nmol/l for UCP III. Inter- and intra-day precision (CV<5%) and accuracy (95-99%) complied with ICH guidelines. We also demonstrated that samples could be stored for 3 days at +4 degrees C and for 12 months at -20 degrees C with no change in UCP ratio (CV<5%), providing a basis for storage recommendations for future clinical studies based on this analysis. Our method is simple, rapid and universal and is suitable for quantitative determinations of each isomer and their ratio for routine and research purposes.

Increment in Drug Loading on an Antibody-Drug Conjugate Increases Its Binding to the Human Neonatal Fc Receptor in Vitro.

Antibody-drug conjugates, such as brentuximab vedotin (BTXv), are an innovative category of monoclonal antibodies. BTXv is bioconjugated via the chemical reduction of cysteine residues involved in disulfide bonds. Species of BTXv containing zero, two, four, six, or eight vedotin molecules per antibody coexist in the stock solution. We investigated the influence of drug loading on the binding of the antibody to FcRn, a major determinant of antibody pharmacokinetics in humans. We developed a hydrophobic interaction chromatography (HIC) method for separating the different species present in the stock solution of BTXv, and we purified and characterized the collected species before use. We assessed the binding of these different species to FcRn in a cellular assay based on flow cytometry and surface plasmon resonance. HIC separated the different species of BTXv and allowed their collection at adequate levels of purity. Physicochemical characterization showed that species with higher levels of drug loading tended to form more aggregates. FcRn binding assays showed that the most conjugated species, particularly those with saturated loading, interacted more strongly than unconjugated BTXv with the FcRn.

Screening the low molecular weight fraction of human serum using ATR-IR spectroscopy

Vibrational spectroscopic techniques can detect small variations in molecular content, linked with disease, showing promise for screening and early diagnosis. Biological fluids, particularly blood serum, are potentially valuable for diagnosis purposes. The so-called Low Molecular Weight Fraction (LMWF) contains the associated peptidome and metabolome and has been identified as potentially the most relevant molecular population for disease-associated biomarker research. Although vibrational spectroscopy can deliver a specific chemical fingerprint of the samples, the High Molecular Weight Fraction (HMWF), composed of the most abundant serum proteins, strongly dominates the response and ultimately makes the detection of minor spectral variations a challenging task. Spectroscopic detection of potential serum biomarkers present at relatively low concentrations can be improved using pre-analytical depletion of the HMWF. In the present study, human serum fractionation by centrifugal filtration was used prior to analysis by Attenuated Total Reflection infrared spectroscopy. Using a model sample based on glycine spiked serum, it is demonstrated that the screening of the LMWF can be applied to quantify blinded concentrations up to 50 times lower. Moreover, the approach is easily transferable to different bodily fluids which would support the development of more efficient and suitable clinical protocols exploring vibrational spectroscopy based ex-vivo diagnostic tools. Revealing serum LMWF for spectral serological diagnostic applications.

Inhaled phage therapy: a promising and challenging approach to treat bacterial respiratory infections

ABSTRACT Introduction: Bacterial respiratory tract infections (RTIs) are increasingly difficult to treat due to evolving antibiotic resistance. In this context, bacteriophages (or phages) are part of the foreseen alternatives or combination therapies. Delivering phages through the airways seems more relevant to accumulate these natural antibacterial viruses in proximity to their bacterial host, within the infectious site. Areas covered: This review addresses the potential of phage therapy to treat RTIs and discusses preclinical and clinical results of phages administration in this context. Recent phage formulation and aerosolization attempts are also reviewed, raising technical challenges to achieve efficient pulmonary deposition via inhalation. Expert opinion: Overall, the inhalation of phages as antibacterial treatment seems both clinically relevant and technically feasible. Several crucial points still need to be investigated, such as phage product pharmacokinetics and immunogenicity. Furthermore, given phage-specific features, appropriate regulatory and manufacturing guidelines will need to be defined. Finally, randomized controlled clinical trials should be carried out to establish phage therapy’s clinical positioning in the antimicrobial arsenal against RTIs.

A stability-indicating, ion-pairing, reversed-phase liquid chromatography method for studies of daunorubicin degradation in i.v. infusion fluids

A new stability-indicating method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the quantification of daunorubicin. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 μm (150 mm × 4.6 mm). The mobile phase was 6.2mM nonafluoropentanoic acid in aqueous solution and acetonitrile under isocratic elution mode. The drug was subjected to oxidation, basic and acid hydrolysis to apply stress conditions. Good resolution was achieved between daunorubicin, related products and all degradation products in an overall analytical run time of approximately 16 min with the parent compound daunorubicin eluting at approximately 8 min. The method was fully validated according to ICH guidelines and SFSTP protocols in terms of accuracy, precision, specificity and linearity. For daunorubicin, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains daunorubicin (0.25-0.45 mg/mL) and shown to provide a very effective method. Physical and chemical stability study was carried out on daunorubicin preparation in our hospital centralized pharmacy unit.