A Simple Liquid Chromatography Tandem Mass Spectrometry Method for Quantitation of Plasma Busulfan

Liquid Chromatography-Tandem Mass Spectrometry Method for the Quantification of Plasma Busulfan

Busulfan is an alkylating agent and functions as a myeloablative and anti-leukemic chemotherapy drug. It is widely used with cyclophosphamide for conditioning patients undergoing bone marrow transplantation for myeloid leukemia. Studies have shown that the busulfan plasma concentration correlates better with clinical efficacy and toxicity than the patient's administered dosage. Low concentrations predispose to disease recurrence and even graft rejection, and higher concentrations can increase the risk of hepatic toxicity. As a result, dosing levels can vary significantly from patient to patient. Therapeutic drug monitoring (TDM) of busulfan plasma concentration guides the dosage adjustment to optimally achieve complete bone marrow ablation while minimizing the dosage-dependent toxicity. The quick and precise (precision <10%) UPLC-MS/MS method described here for monitoring plasma busulfan levels between 50 ng/mL and 5000 ng/mL involves the addition of an organic solvent and deuterated internal standard (busulfan d-8) followed by a liquid-liquid extraction, injection of the extract onto a C18 column, and analysis by multiple reaction monitoring (MRM) in ESI-positive mode.

PEG 400 Ion Suppression in Busulfan Detection by High-Performance Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Busulfan (Bu), an alkylating agent commonly used in chemotherapy and transplantation, exhibits high intraindividual pharmacokinetic variability and possible time-dependent variations in clearance, which complicate therapeutic drug monitoring. Numerous analytical methods have been developed to reduce analysis time and facilitate timely decision-making regarding treatment changes; however, the validation procedures rarely involve analysis of potentially interfering excipients. Macrogol 400 (PEG 400) should be considered as a possible interfering agent in the detection of plasma Bu levels, especially as an ionization suppressor.

METHODS

Six intravenous formulations of Bu were compared with identify at least 1 common excipient (PEG 400). During the 176 therapeutic drug monitoring analyses of Bu, one of the PEG 400 specific mass-to-charge ratio transitions was determined using an instrumental method. After coelution with Bu and its internal standard (Bu-d8) was confirmed, all analyses were repeated using a different experimental setup free of ion suppression induced by PEG. The concentration-time profile of PEG 400 was also analyzed.

RESULTS

The area under the curve obtained from the 2 data sets was compared and analyzed using Lin concordance correlation coefficient and Bland-Altman plot analysis. The results from the 2 analytical methods were comparable: PEG 400 negatively affected the Bu-d8 coefficient of variation but not the Bu/Bu-d8 ratio.

CONCLUSIONS

The possible interference of PEG 400 should be thoroughly investigated, especially with respect to analytical methods that cannot be supported by correction of the stable isotopically labeled internal standard analog.

Rapid and accurate method for quantifying busulfan in plasma samples by isocratic liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Objectives

Administration of busulfan is extending rapidly as a part of a conditioning regimen in patients undergoing hematopoietic stem cell transplantation (HSCT). Monitoring blood plasma levels of busulfan is recommended for identifying the optimal dose in patients and for minimizing toxicity. The aim of this research was to validate a simple, rapid, and cost-effective analytical tool for measuring busulfan in human plasma that would be suitable for routine clinical use. This novel tool was based on liquid chromatography coupled to mass spectrometry.

Methods

Human plasma samples were prepared using a one-step protein precipitation protocol. These samples were then resolved by isocratic elution in a C18 column. The mobile phase consisted 2 mM ammonium acetate and 0.1% formic acid dissolved in a 30:70 ratio of methanol/water. Busulfan-d8 was used as the internal standard.

Results

The run time was optimized at 1.6 min. Standard curves were linear from 0.03 to 5 mg/L. The coefficient of variation (%CV) was less than 8%. The accuracy of this method had an acceptable bias that fell within 85-115% range. No interference between busulfan and the interfering compound hemoglobin, lipemia, or bilirubin not even at the highest concentrations of compound was tested. Neither carryover nor matrix effects were observed using this method. The area under the plasma drug concentration-time curves obtained for 15 pediatric patients who received busulfan therapy prior to HSCT were analyzed and correlated properly with the administered doses.

Conclusions

This method was successfully validated and was found to be robust enough for therapeutic drug monitoring in a clinical setting.

Fast and reliable quantification of busulfan in blood plasma using two-channel liquid chromatography tandem mass spectrometry: Validation of assay performance in the presence of drug formulation excipients

A fast and reliable method based on two-channel liquid chromatography coupled to tandem mass spectrometry was developed and successfully validated for quantification of busulfan. The drug vehicle polyethylene glycol 400 was quantified simultaneously in patient samples. The sample preparation consisted of simple protein precipitation using a mixture of methanol and zinc sulphate containing busulfan-d8 as internal standard. Chromatographic separation was performed on a short biphenyl column (30 mm × 3.0 mm, 5 μm particles) using a step gradient from 30 % to 85 % methanol, ensuring co-elution of the analyte and internal standard. Quantification was performed using the mass transition of 264.1 > 151.1 for busulfan and 272.1 > 159.1 for the internal standard. Using only 20 μL of plasma sample, the lower limit of quantification was 25 ng/mL. Signal to noise ratio at the lower limit of quantification exceeded 300. The assay performance was not adversely affected by matrix effects originating from drug formulation excipients or other sample components. The coefficient of variation was ≤4 % and the mean accuracy 101-108 % across the calibration range 25-5 000 ng/mL. Chromatographic run time was 2 min and 8 s, allowing an effective run-time of 1 min and 10 s when using two alternating LC-channels. The assay has been implemented in routine practice with accreditation according to the ISO 15189 standard, and performs well in external quality control assessments. We present for the first time that shortly after an IV infusion of busulfan, the plasma levels of polyethylene glycol 400 may be in the range of 400-800 mg/L. The presence of these levels of detergent in patient samples may have detrimental effects on assay performance in LC-MS/MS, not limited to busulfan assays. This may be a concern for any LC-MS/MS analysis performed on samples collected within the first 24 h after an IV infusion of busulfan.

A rapid HPLC-MS/MS method for determining busulfan in hemolytic samples from children with hematopoietic stem cell transplantation

A rapid and sensitive method for the quantitative detection of busulfan (BU) in children's hemolytic samples by HPLC-tandem mass spectrometry (MS/MS) was established. In this study, the sample preparation procedure involved a one-step protein precipitation with acetonitrile (ACN) solution, and the HPLC-MS/MS method used Hypersil GOLD C₁₈ . The mobile phase consisted of 10 mM ammonium acetate solution (containing 0.1% formic acid) and ACN with a flow rate of 0.4 mL/min. Multiple reaction monitoring modes were used for quantitative analysis and the ion pairs of BU and BU-d8 were m/z 263.9 → 150.9 and 272.0 → 159.0, respectively. BU had a good linearity in the range of 0.01-10 μg mL^-1 . The intra- and inter-day relative error was between -7.21% and 8.26%, and the coefficient of variation was less than 12.64%. The average extraction recovery rate in plasma samples was 99.76% ± 6.53%, and the matrix in normal plasma and hemolyzed plasma had no significant effect on the detection results. Normal and hemolytic samples could maintain good stability at 4, 25 and -40°C. As a result, this method is particularly suitable for determining BU in hemolytic samples from children with hematopoietic stem cell transplantation (HSCT), and this study provides the methodological basis for further research on the pharmacokinetics of BU in children with HSCT.

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

Design and Testing of an EHR-Integrated, Busulfan Pharmacokinetic Decision Support Tool for the Point-of-Care Clinician

Background: Busulfan demonstrates a narrow therapeutic index for which clinicians routinely employ therapeutic drug monitoring (TDM). However, operationalizing TDM can be fraught with inefficiency. We developed and tested software encoding a clinical decision support tool (DST) that is embedded into our electronic health record (EHR) and designed to streamline the TDM process for our oncology partners.

Methods: Our development strategy was modeled based on the features associated with successful DSTs. An initial Requirements Analysis was performed to characterize tasks, information flow, user needs, and system requirements to enable push/pull from the EHR. Back-end development was coded based on the algorithm used when manually performing busulfan TDM. The code was independently validated in MATLAB using 10,000 simulated patient profiles. A 296-item heuristic checklist was used to guide design of the front-end user interface. Content experts and end-users (n = 28) were recruited to participate in traditional usability testing under an IRB approved protocol.

Results: Decision support software was developed to systematically walk the point-of-care clinician through the TDM process. The system is accessed through the EHR which transparently imports all of the requisite patient data. Data are visually inspected and then curve fit using a model-dependent approach. Quantitative goodness-of-fit are converted to single tachometer where “green” alerts the user that the model is strong, “yellow” signals caution and “red” indicates that there may be a problem with the fitting. Override features are embedded to permit application of a model-independent approach where appropriate. Simulations are performed to target a desired exposure or dose as entered by the clinician and the DST pushes the user approved recommendation back into the EHR. Usability testers were highly satisfied with our DST and quickly became proficient with the software.

Conclusions: With early and broad stake-holder engagement we developed a clinical DST for the non-pharmacologist. This tools affords our clinicians the ability to seamlessly transition from patient assessment, to pharmacokinetic modeling and simulation, and subsequent prescription order entry.