An LC-MS Assay with Isocratic Separation and On-line Solid Phase Extraction to Improve the Routine Therapeutic Drug Monitoring of Busulfan in Plasma

UPLC-Tandem Mass Spectrometry for Quantification of Busulfan in Human Plasma: Application to Therapeutic Drug Monitoring

Busulfan (Bu) is an alkylating agent commonly used in preparative regimens for hematologic malignant and non-malignant patients undergoing hematopoietic stem cell transplantation (HSCT). The objective of the present study was to develop an UPLC-MS/MS method for quantification of Bu in human plasma. A total of 55 patients with hematologic malignancies (n = 34) and non- malignancies (n = 21) received myeloablative Bu therapy prior to HSCT. A tandem mass spectrometric method was developed and validated to quantify Bu levels in these patients. The method was fully validated over the concentration range of 25–2000 ng/mL (r > 0.99). The assay method demonstrated good precision and accuracy. Stability studies indicated that the drug was stable in various conditions. Incurred sample reanalysis findings were within acceptable ranges (<15% of the nominal concentration). Based on the 1^st dose AUC results, one third of hematologic malignant patients and half of non-malignant patients needed dose adjustment. However, in subsequent doses (5^th, 9^th, and 13^th), 77%, 82% and 82%, respectively, of hematologic malignant patients and 71%, 67% and 86%, respectively, of non-malignant patients achieved the target range of Bu AUC. The suitability of the developed method for routine TDM of Bu in HSCT patients was demonstrated. The study suggests that the pharmacokinetic profile of Bu varies in both groups.

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.

A rapid and simple LC-MS/MS method for personalized busulfan dosing in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT)

BACKGROUND

Busulfan is commonly used as a conditioning regimen before hematopoietic stem cell transplantation (HSCT). There is a big inter-individual variability in busulfan exposure and the narrow therapeutic index, especially in pediatric population. Therefore, to achieve therapeutic efficacy and safety concurrently, personalized busulfan dosing, guided by pharmacokinetic study with serial plasma samples, is needed a few hours afterwards.

METHODS

A fast, sensitive, and accurate method for busulfan measurement was developed, validated, and implemented with liquid-chromatography-mass spectrometry (HPLC-MS/MS). The sample preparation procedure involves only protein precipitation and dilution, and the HPLC-MS/MS method takes 3 min/sample. The assay was linear from 10 ng/ml to 7500 ng/ml (R² = 0.99). Recoveries were above 90%. The precision was determined at 3 levels (30, 300 and 4000 ng/ml): the intra-day variability (%CV) ranged from 1.4% to 2.5% (n = 20); the inter-day variability ranged from 2.2% to 5.5% (n = 20). The accuracy of the HPLC-MS/MS test was evaluated with an old HPLC-fluorescence method (n = 84), and a Correlation Coefficient (R) of 0.99 was observed.

CONCLUSIONS

The analytical performance of the assay allows for timely dose adjustment and has been implemented in clinical service for better clinical outcome.