Antonio D’Avolio

New HPLC-MS method for the simultaneous quantification of the antileukemia drugs imatinib, dasatinib, and nilotinib in human plasma.

A new method using high performance liquid chromatography coupled with electrospray mass spectrometry is described for the quantification of plasma concentration of tyrosine kinase inhibitors imatinib, dasatinib and nilotinib. A simple protein precipitation extraction procedure was applied on 250 microl of plasma aliquots. Chromatographic separation of drugs and Internal Standard (quinoxaline) was achieved with a gradient (acetonitrile and water + formic acid 0.05%) on a C18 reverse phase analytical column with 20min of analytical run, at flow rate of 1 ml/min. Mean intra-day and inter-day precision for all compounds were 4.3 and 11.4%; mean accuracy was 1.5%; extraction recovery ranged within 95 and 114%. Calibration curves ranged from 10,000 to 62.5 ng/ml. The limit of quantification was set at 78.1 ng/ml for imatinib and at 62.5 ng/ml for dasatinib and nilotinib. This novel developed methodology allows a specific, sensitive and reliable simultaneous determination of the three tyrosine kinase inhibitors imatinib, dasatinib and nilotinib in a single chromatographic run, useful for drugs estimation in plasma of patients affected by chronic myeloid leukemia.

HPLC–MS method for the quantification of nine anti-HIV drugs from dry plasma spot on glass filter and their long term stability in different conditions

A bioanalytical method for the determination of most commonly prescribed protease inhibitors (saquinavir, atazanavir, amprenavir, darunavir, lopinavir and ritonavir) and non-nucleoside reverse transcriptase inhibitors (etravirine, efavirenz and nevirapine) was developed, modifying our previous HPLC-MS chromatographic run, validated and a complete short and long term stability evaluation was carried out. One hundred microlitres of plasma were distributed on a collection glass paper filter (Glass-Microfibre from Sartorius), then the filter underwent thermal treatment, both for drying and for HIV inactivation, and stored at room temperature, 4 degrees C and -20 degrees C. The analytes were extracted from the filter disc using tert-butylmethylether with basic pH, after the addition of the internal standards quinoxaline. The extract was dried, reconstituted and the chromatographic separation was performed on a reversed-phase C-18 column (150 mm x 2.0 mm) and the analytes were quantified using a single quadrupole mass spectrometer. The method was validated considering the concentration ranges encountered in clinical trials and the routine clinical practice. The assay was linear over the concentration ranges tested. Accuracies ranged from 92.1% to 111.9% and intra-day and inter-day relative standard deviation for all quality control levels ranged from 0.2 to 12.9 and 3.1 to 14.4, respectively. Analytes in dried plasma spots were stable for longer time when dried/inactivation step was carried out before storage compared to samples not dried/inactivated before the analysis. The dried/inactivation step allows shipment of samples at room temperature without any risks, therefore the developed and validated method enables an easy and cheap sample shipment for therapeutic drug monitoring and pharmacokinetic studies.

A HPLC–MS method for the simultaneous quantification of fourteen antiretroviral agents in peripheral blood mononuclear cell of HIV infected patients optimized using medium corpuscular volume evaluation

A sensitive and accurate high performance liquid chromatography-mass spectrometric (HPLC-MS) method for the intracellular determination of 14 antiretroviral drugs in peripheral blood mononuclear cells (PBMCs) for HIV+ patients was validated. PBMCs are isolated by Ficoll density gradient centrifugation and cells count and the relative mean volume is performed with a Coulter(®) instrument. Extraction of drugs from PBMCs pellets was obtained with methanol:water (70:30, v/v), with quinoxaline added as internal standard, after a sonication step. Supernatant was dried and then dissolved in water/acetonitrile (60/40, v/v), before injection into a 2.1 mm×150 mm Atlantis(®) T3 3μ column. Chromatographic separations were performed using a gradient program with a mixture of water (0.05% formic acid), as mobile phase A and acetonitrile (0.05% formic acid), as mobile phase B. Analytes quantification was performed by electro-spray ionisation-single quadrupole mass spectrometry using the selected ion recording (SIR) detection mode. The positive ionization was used for the HIV protease inhibitors (PIs) indinavir, saquinavir, nelfinavir, nelfinavir M8 metabolite, amprenavir, darunavir, atazanavir, ritonavir, lopinavir, tipranavir, the integrase inhibitor (II) raltegravir and the non-nucleoside reverse transcriptase inhibitors (NNRTIs) nevirapine and etravirine, while the negative ionization is applied for efavirenz. The calibration curves were built using blank PBMCs spiked with antiretroviral drugs at concentrations ranging from 0.1 to 32 ng/mL (1-320 ng/mL for tipranavir) and fitted to a quadratic regression model weighted by 1/X. The mean extraction recovery for all PIs, II and NNRTIs was always above 82%. The method was precise, with a range of intra/inter-day percent standard deviation within 2.6-14.8%, and accurate with mean of percent coefficient of variation (CV%) from nominal values -7.85 to +9.7%. Each drug concentration evaluated was expressed in ng/mL and optimized using each patient medium corpuscolar volume and cell number. This analytical method is routinely used in our clinical research center for the assessment of intracellular levels of all PIs, raltegravir and NNRTIs commercially available at present.

HPLC–MS method for the simultaneous quantification of the antileukemia drugs imatinib, dasatinib and nilotinib in human peripheral blood mononuclear cell (PBMC)

A new method using high performance liquid chromatography coupled with electrospray mass spectrometry is described for the quantification of PBMC concentration of tyrosine kinase inhibitors imatinib, dasatinib and nilotinib. A simple PBMC isolation and extraction procedure were applied on 10-14 mL of blood aliquots. Chromatographic separation of drugs and Internal Standard (quinoxaline) was achieved with a gradient (acetonitrile and water+formic acid 0.05%) on a C18 reverse phase analytical column with 25 min of analytical run, at flow rate of 0.25 mL/min. Mean intra- and inter-day precision for all compounds were 8.76 and 12.20%; mean accuracy was -3.86%; extraction recovery ranged within 79 and 91%. Calibration curves ranged from 50.0 to 0.25 ng. The limit of quantification was set at 0.25 ng for all the analyzed drugs. This novel developed methodology allows a specific, sensitive and reliable simultaneous intracellular determination of the three tyrosine kinase inhibitors imatinib, dasatinib and nilotinib in a single chromatographic run, useful for drugs estimation in PBMC of patients affected by chronic myeloid leukemia.

Glycopeptide Bone Penetration in Patients with Septic Pseudoarthrosis of the Tibia

Background and objective: In the treatment of bone infections, a major determinant of the clinical response is the active drug concentration at the infected site. Because of the high prevalence of meticillin (methicillin)-resistant staphylococci and enterococci, glycopeptides are widely used for the treatment of bone and joint infections, but data on their penetration into human bone are lacking. The aim of our study was to measure vancomycin and teicoplanin concentrations in infected human bone under steady-state conditions and verify their relationship with inflammatory markers, patient demographic characteristics and pharmacodynamic microbiological markers.Methods and patients: Twenty-seven adult orthopaedic patients undergoing surgical debridement for septic pseudoarthrosis of the tibia and receiving either intravenous vancomycin (Vancocina® 1 g twice daily) or teicoplanin (Targosid® 10 mg/kg/day) were studied from January 2004 to January 2008. Plasma and bone specimens were simultaneously collected during surgery for pharmacokinetic and microbiological assays at a variable interval after antimicrobial administration. Bone samples were dissected into cortical and cancellous bone, cleaned of soft tissues, crushed and eluted into phosphate buffer. Necrotic samples and sequestra were not analysed.Plasma and bone antimicrobial concentrations were measured by a validated method of high-performance liquid chromatography with UV detection, and bone/plasma concentration ratios were calculated. Cortical and cancellous bone area under the concentration-time curve (AUC) over 24 hours (AUC24) values were measured by the linear-log trapezoidal rule, using WinNonlin® software, and were compared with the minimum inhibitory concentrations (MICs) of the infecting agents.Results: For vancomycin, the mean ± SD concentrations were 2.66 ± 1.2 mg/L in cortical bone and 11.53 ± 7.8 mg/L in cancellous bone (corresponding to 20.67% and 89.39% of intraoperative plasma concentrations), and the mean ± SD tissue AUC24 values were 55.15 ± 25.26 h · mg/L for cortical bone and 299.16 ± 299.54 h · mg/L for cancellous bone. For teicoplanin, the mean ± SD concentrations were 2.01 ± 1.7 and 7.51 ± 7.0 mg/L in cortical and cancellous bone, respectively (12.35% and 48.6% of intraoperative plasma concentrations), and the mean ± SD teicoplanin tissue AUC24 values were 34.08 ± 23.6 h · mg/L and 155.17 ± 132.8 h · mg/L for cortical bone and cancellous bone, respectively. The mean vancomycin AUC24/MIC ratios were 215.02 for plasma, 47.14 for cortical bone and 268.95 for cancellous bone. The mean teicoplanin AUC24/MIC ratios were 336.48, 36.27 and 197.21 for plasma, cortical bone and cancellous bone, respectively.Conclusions: Bone penetration of both glycopeptides ranged from poor (<15%) to satisfactory (15–30%) in the cortical compartment, while it was far higher into the highly vascularized cancellous tissue. Vancomycin bone penetration was slightly higher than with teicoplanin, but the difference was not statistically significant. Higher bone concentrations were observed with higher inflammatory markers, possibly as a result of increased vascularization and vascular permeability under inflammatory conditions. Bone concentrations over the MIC and AUC/MIC ratios suggested that both glycopeptides achieve a satisfactory pharmacokinetic exposure in the cancellous bone, as far as Gram-positive pathogens are concerned. On the other hand, cortical bone exposure was suboptimal in most patients. Furthermore, as antimicrobial penetration may be affected by impaired blood supply, the role of radical surgical removal of purulent and necrotic tissues appears to be essential in order to shorten treatment duration and to reduce the risk of treatment failure.

Association of ITPA polymorphisms rs6051702/rs1127354 instead of rs7270101/rs1127354 as predictor of ribavirin-associated anemia in chronic hepatitis C treated patients

Functional variants rs7270101 and rs1127354 of inosine triphosphatase (ITPA) were recently found to protect against ribavirin (RBV)-induced hemolytic anemia. However, no definitive data are yet available on the role of no functional rs6051702 polymorphism. Since a simultaneous evaluation of the three ITPA SNPs for hemolytic anemia has not yet been investigated, we aimed to understand the contribution of each SNPs and its potential clinical use to predict anemia in HCV treated patients. A retrospective analysis included 379 HCV treated patients. The ITPA variants rs6051702, rs7270101 and rs1127354 were genotyped and tested for association with achieving anemia at week 4. We also investigated, using multivariate logistic regression, the impact of each single and paired associated polymorphism on anemia onset. All SNPs were associated with Hb decrease. The carrier of at least one variant allele in the functional ITPA SNPs was associated with a lower decrement of Hb, as compared to patients without a variant allele. In multivariate logistic regression analyses the carrier of a variant allele in the rs6051702/rs1127354 association (OR=0.11, p=1.75×10(-5)) and Hb at baseline (OR=1.51, p=1.21×10(-4)) were independently associated with protection against clinically significant anemia at week 4. All ITPA polymorphisms considered were shown to be significantly associated with anemia onset. A multivariate regression model based on ITPA genetic polymorphisms was developed for predicting the risk of anemia. Considering the characterization of pre-therapy anemia predictors, rs6051702 SNP in association to rs1127354 is more informative in order to avoid this relevant adverse event.

Development and validation of a new UPLC-PDA method to quantify linezolid in plasma and in dried plasma spots

Linezolid is an oxazolidinone antibiotic used for the treatment of pneumonia and uncomplicated and complicated skin and soft tissues infections caused by Gram positive bacteria. It is also used as second line agent in multi-drug resistant tuberculosis. Therapeutic drug monitoring (TDM) of linezolid represents a valid tool in clinical practice to optimize therapy, especially in critically ill patients. Spreading of TDM is mainly limited by high costs shipment and lack of laboratories that offer a TDM service. To overcome these problems, the use of dried plasma spots or dried blood spots is increasing. The aim of this work was to develop and validate a new chromatographic method to analyze linezolid in plasma and in dried plasma spots and to evaluate the correlation between the two extraction methods. Linezolid extraction from plasma and from dried plasma spots was obtained using acetonitrile. Quinoxaline was used as internal standard. Analysis was performed by an ultra performance liquid chromatography (UPLC) system coupled with photo diode array (PDA) detector, at 254nm. Both analytical methods were linear (r(2)>0.999) over the calibration range of 30-0.117mg/L. Limit of quantification and limit of detection were 0.117mg/L and 0.058mg/L, respectively. Intra and inter-day precision (R.S.D.%) and accuracy (%) were <15%. Long term stability of linezolid in dried plasma spots showed absence of degradation at room temperature (20-25°C) and at 4°C, for at least one month. Linear regression analysis confirmed that the two methods of extraction have good correlation. Thus they are suited for TDM of linezolid and for pharmacokinetic studies.

Influence of the CYP2B6 polymorphism on the pharmacokinetics of mitotane.

Objective The aim of this study was to assess the potential impact of the pharmacogenetic variability of CYP2B6 and ABCB1 genes on the pharmacokinetics of mitotane. Methods A retrospective analysis was carried out on 27 patients with adrenocortical carcinoma on postoperative adjunctive mitotane. CYP2B6 and ABCB1 polymorphisms were genotyped and tested for an association with plasma trough concentration after 3, 6, 9, and 12 months of therapy. Results Patients with the GT/TT genotype had higher mitotane plasma concentrations compared with patients with GG at 3 months (14.80 vs. 8.01 &mgr;g/ml; P=0.008) and 6 months (17.70 vs. 9.75 &mgr;g/ml; P=0.015). Multivariate logistic regression analysis showed that only the CYP2B6 rs3745274GT/TT genotype (odds ratio=10.7; P=0.017) was a predictor of mitotane plasma concentrations of at least 14 µg/ml after 3 months of treatment. Mitotane concentrations were not influenced by the polymorphisms of the ABCB1 gene. Conclusion Evaluation of the CYP2B6 polymorphism enabled prediction of the individual response to adjuvant mitotane treatment.

A UPLC-MS/MS method for the simultaneous plasma quantification of all isomeric forms of the new anti-HCV protease inhibitors boceprevir and telaprevir.

HCV infection affects over 170 milions people in the world. Up to now standard-of-care therapy consisted in ribavirin plus interferon-α 2a or 2b. Recently, two new Direct Acting Antivirals (DAA), inhibitors of NS3 HCV protease, have been developed and approved for the routine use on HCV genotype 1 infected patients: boceprevir and telaprevir. Protease inhibitors show complex pharmacokinetics (strong metabolism of both drugs by CYP3A and drug interactions), they require a TID dosage and, furthermore, they are present in plasma patients in two different isomeric forms. In this work, we developed and validated an UPLC-tandem mass spectrometry assay method capable of monitoring the telaprevir and boceprevir concentrations in plasma, discriminating each isomer of both drugs. Blank plasma used for Standards and QCs preparation, was obtained from blood of healthy donors. The calibration curves for each isomer of telaprevir and boceprevir were linear in a range from 46.87 ng/mL to 6000 ng/mL and from 23.43 to 3000 ng/mL, respectively (mean r(2)>0.998 for all analytes). QCs at three different concentration were prepared: High, Medium and Low. Each Standard, QC and patient sample was treated with a protein precipitation protocol with a solution containing acidified acetonitrile and Internal Standard (6,7-Dimethyl-2,3-di(2-pyridyl)quinoxaline). An aliquot of supernatant was diluted and then directly analyzed by reverse-phase UPLC-MS/MS. Accuracy (mean 98.47%), intra-day (mean <5.21%) and inter-day (mean <7.57%) precision for telaprevir and boceprevir quality controls fitted all FDA guidelines. All compounds resulted stable in our method conditions and the extraction procedure showed a recovery near to 100%. Finally, we tested this method by monitoring plasma concentrations in 9 HCV+ patients, for each triple combined therapy, with good results. The observed median ratio between S and R isomers for boceprevir and telaprevir were 1.22 (IQR 1.10-1.33) and 1.52 (IQR 1.21-1.67), respectively. The use of this simple assay method could be an important tool for management of HCV-1 DAAs treated patients.

Development and validation of a useful HPLC-UV method for quantification of total and phosphorylated-ribavirin in blood and erythrocytes of HCV+ patients.

Ribavirin-induced hemolytic anemia is the main cause of discontinuation of the combination therapy with alpha-interferon-2b and ribavirin for the treatment of hepatitis C virus (HCV) infection. The determination of intracellular ribavirin levels in blood, including the levels of its phosphorylated metabolites, might be useful for predicting ribavirin-induced anemia, which could be caused by the accumulation of these molecules within the erythrocytes. In this work, we simplified and validated a previously developed assay method, to make it suitable for routine monitoring of cellular ribavirin. Whole blood diluted with a five-fold volume of ice-cold distilled underwent a process of acid phosphatase digestion to convert phosphorylated ribavirin metabolites to free ribavirin. The resulting mixture, spiked with an internal standard, was treated with a protein precipitation protocol in acetonitrile, followed by reverse-phase high-performance liquid chromatography analysis. The calibration curve for ribavirin levels in whole blood was linear at concentrations from 625 to 320,000 ng/mL (r(2)=0.998). Accuracy, intra-day and inter-day precision for ribavirin and phosphorylated-ribavirin quality controls were all below 9.0%. We tested this method by monitoring blood ribavirin concentrations in 13 HCV+ patients, receiving alpha interferon-plus ribavirin combination therapy.